Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

NASA Astrophysics Data System (ADS)

Costall, A.; Harris, B.; Pigois, J. P.

2018-05-01

Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole-dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.

Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

NASA Astrophysics Data System (ADS)

Costall, A.; Harris, B.; Pigois, J. P.

2018-07-01

Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole-dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.

Scenario Evaluator for Electrical Resistivity Survey Pre-modeling Tool

EPA Science Inventory

Geophysical tools have much to offer users in environmental, water resource, and geotechnical fields; however, techniques such as electrical resistivity imaging (ERI) are often oversold and/or overinterpreted due to a lack of understanding of the limitations of the techniques, su...

Geophysical imaging of root-zone, trunk, and moisture heterogeneity.

PubMed

Attia Al Hagrey, Said

2007-01-01

The most significant biotic and abiotic stress agents of water extremity, salinity, and infection lead to wood decay and modifications of moisture and ion content, and density. This strongly influences the (di-)electrical and mechanical properties and justifies the application of geophysical imaging techniques. These are less invasive and have high resolution in contrast to classical methods of destructive, single-point measurements for inspecting stresses in trees and soils. This review presents some in situ and in vivo applications of electric, radar, and seismic methods for studying water status and movement in soils, roots, and tree trunks. The electrical properties of a root-zone are a consequence of their moisture content. Electrical imaging discriminates resistive, woody roots from conductive, soft roots. Both types are recognized by low radar velocities and high attenuation. Single roots can generate diffraction hyperbolas in radargrams. Pedophysical relationships of water content to electrical resistivity and radar velocity are established by diverse infiltration experiments in the field, laboratory, and in the full-scale 'GeoModel' at Kiel University. Subsurface moisture distributions are derived from geophysical attribute models. The ring electrode technique around trunks images the growth ring structure of concentric resistivity, which is inversely proportional to the fluid content. Healthy trees show a central high resistivity within the dry heartwood that strongly decreases towards the peripheral wet sapwood. Observed structural deviations are caused by infection, decay, shooting, or predominant light and/or wind directions. Seismic trunk tomography also differentiates between decayed and healthy woods.

Choice of reconstructed tissue properties affects interpretation of lung EIT images.

PubMed

Grychtol, Bartłomiej; Adler, Andy

2014-06-01

Electrical impedance tomography (EIT) estimates an image of change in electrical properties within a body from stimulations and measurements at surface electrodes. There is significant interest in EIT as a tool to monitor and guide ventilation therapy in mechanically ventilated patients. In lung EIT, the EIT inverse problem is commonly linearized and only changes in electrical properties are reconstructed. Early algorithms reconstructed changes in resistivity, while most recent work using the finite element method reconstructs conductivity. Recently, we demonstrated that EIT images of ventilation can be misleading if the electrical contrasts within the thorax are not taken into account during the image reconstruction process. In this paper, we explore the effect of the choice of the reconstructed electrical properties (resistivity or conductivity) on the resulting EIT images. We show in simulation and experimental data that EIT images reconstructed with the same algorithm but with different parametrizations lead to large and clinically significant differences in the resulting images, which persist even after attempts to eliminate the impact of the parameter choice by recovering volume changes from the EIT images. Since there is no consensus among the most popular reconstruction algorithms and devices regarding the parametrization, this finding has implications for potential clinical use of EIT. We propose a program of research to develop reconstruction techniques that account for both the relationship between air volume and electrical properties of the lung and artefacts introduced by the linearization.

Static resistivity image of a cubic saline phantom in magnetic resonance electrical impedance tomography (MREIT).

PubMed

Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyeong; Kwon, Ohin; Seo, Jin Keun; Baek, Woon Sik

2003-05-01

In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.

Electrical Imaging of Infiltration in Agricultural Soils on Long Island, New York

NASA Astrophysics Data System (ADS)

Lampousis, A.; Kenyon, P. M.; Sanwald, K.; Steiner, N.

2007-12-01

High resolution electrical resistivity imaging of vadose zone infiltration experiments was conducted on agricultural soils by the City College and Graduate Center of CUNY, in cooperation with Cornell University's Agricultural Stewardship Program and Long Island Horticultural Research and Extension Center (LIHREC) in Riverhead, New York. Measurements were made in active vineyards with a commercial resistivity imaging system, using a half- meter electrode spacing. Soils considered were Riverhead sandy loam (RdA), Haven loam (HaA), and Bridgehampton silty loam (BgA). The Riverhead and Haven soils are the most common types found on eastern Long Island. The Bridgehampton is considered the most fertile. Soil samples and measurements of soil compaction were collected at the same time as the geophysical measurements. In addition, remote sensing data were obtained for the three sites and processed to produce normalized difference vegetation index (NDVI) data to evaluate potential correlations between vegetation vigor, soil texture and water migration patterns. Applications of this study include continuous water content monitoring in high value cash crops (precision agriculture). Changes in electrical resistivity during infiltration are clearly visible at all three locations. Preliminary analysis of the results shows correlations of baseline resistivity with particle size distributions and correlations between changes in resistivity during infiltration and soil compaction data. Time-lapse electrical images of the three sites will also be compared with published properties for these soils, including particle size distribution, saturated hydraulic conductivity, available water capacity, and surface texture.

Improved Geologic Interpretation of Non-invasive Electrical Resistivity Imaging from In-situ Samples

NASA Astrophysics Data System (ADS)

Mucelli, A.; Aborn, L.; Jacob, R.; Malusis, M.; Evans, J.

2016-12-01

Non-invasive geophysical techniques are useful in characterizing the subsurface geology without disturbing the environment, however, the ability to interpret the subsurface is enhanced by invasive work. Since geologic materials have electrical resistivity values it allows for a geologic interpretation to be made based on variations of electrical resistivity measured by electrical resistivity imaging (ERI). This study focuses on the pre-characterization of the geologic subsurface from ERI collected adjacent to the Montandon Marsh, a wetland located near Lewisburg, PA within the West Branch of the Susquehanna River watershed. The previous invasive data, boreholes, indicate that the subsurface consists of limestone and shale bedrock overlain with sand and gravel deposits from glacial outwash and aeolian processes. The objective is to improve our understanding of the subsurface at this long-term hydrologic research site by using excavation results, specifically observed variations in geologic materials and electrical resistivity laboratory testing of subsurface samples. The pre-excavation ERI indicated that the shallow-most geologic material had a resistivity value of 100-500 ohm-m. In comparison, the laboratory testing indicated the shallow-most material had the same range of electrical resistivity values depending on saturation levels. The ERI also showed that there was an electrically conductive material, 7 to 70 ohm-m, that was interpreted to be clay and agreed with borehole data, however, the excavation revealed that at this depth range the geologic material varied from stratified clay to clay with cobbles to weathered residual clay. Excavation revealed that the subtle variations in the electrical conductive material corresponded well with the variations in the geologic material. We will use these results to reinterpret previously collected ERI data from the entire long-term research site.

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.

MT2D Inversion to Image the Gorda Plate Subduction Zone

NASA Astrophysics Data System (ADS)

Lubis, Y. K.; Niasari, S. W.; Hartantyo, E.

2018-04-01

The magnetotelluric method is applicable for studying complicated geological structures because the subsurface electrical properties are strongly influenced by the electric and magnetic fields. This research located in the Gorda subduction zone beneath the North American continental plate. Magnetotelluric 2D inversion was used to image the variation of subsurface resistivity although the phase tensor analysis shows that the majority of dimensionality data is 3D. 19 MT sites were acquired from EarthScope/USArray Project. Wepresent the image of MT 2D inversion to exhibit conductivity distribution from the middle crust to uppermost asthenosphere at a depth of 120 kilometers. Based on the inversion, the overall data misfit value is 3.89. The Gorda plate subduction appears as a high resistive zone beneath the California. Local conductive features are found in the middle crust downward Klamath Mountain, Bonneville Lake, and below the eastern of Utah. Furthermore, mid-crustal is characterized by moderately resistive. Below the extensional Basin and Range province was related to highly resistive. The middle crust to the uppermost asthenosphere becomes moderately resistive. We conclude that the electrical parameters and the dimensionality of datain the shallow depth(about 22.319 km) beneath the North American platein accordance with surface geological features.

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.

Electrical resistance tomography during in-situ trichloroethylene remediation at the Savannah River Site

NASA Astrophysics Data System (ADS)

Daily, W.; Ramirez, A.

1995-04-01

Electrical resistance tomography was used to monitor in-situ remediation processes for removal of volatile organic compounds from subsurface water and soil at the Savannah River Site near Aiken, South Carolina. This work was designed to test the feasibility of injecting a weak mixture of methane in air as a metabolic carbon source for natural microbial populations which are capable of trichloroethylene degradation. Electrical resistance tomograms were constructed of the subsurface during the test to provide detailed images of the process. These images were made using an iterative reconstruction algorithm based on a finite element forward model and Newton-type least-squares minimization. Changes in the subsurface resistivity distribution were imaged by a pixel-by-pixel subtraction of images taken before and during the process. This differential tomography removed all static features of formation resistivity but clearly delineated dynamic features induced by remediation processes. The air-methane mixture was injected into the saturated zone and the intrained air migration paths were tomographically imaged by the increased resistivity of the path as air displaced formation water. We found the flow paths to be confined to a complex three-dimensional network of channels, some of which extended as far as 30 m from the injection well. These channels were not entirely stable over a period of months since new channels appeared to form with time. Also, the resistivity of the air injection paths increased with time. In another series of tests, resistivity images of water infiltration from the surface support similar conclusions about the preferential permeability paths in the vadose zone. In this case, the water infiltration front is confined to narrow channels which have a three-dimensional structure. Here, similar to air injection in the saturated zone, the water flow is controlled by local variations in formation permeability. However, temporal changes in these channels are minor, indicating that the permeable paths do not seem to be modified by continued infiltration.

Potential of electrical resistivity tomography and muon density imaging to study spatio-temporal variations in the sub-surface

NASA Astrophysics Data System (ADS)

Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

2015-04-01

We explore the capacity of electrical resistivity tomography and muon density imaging to detect spatio-temporal variations of the medium surrounding a regional fault crossing the underground platform of Tournemire (Aveyron, France). The studied Cernon fault is sub-vertical and intersects perpendicularly the tunnel of Tournemire and extends to surface. The fault separates clay and limestones layers of the Dogger from limestones layers of the Lias. The Cernon fault presents a thickness of a ten of meters and drives water from an aquifer circulating at the top of the Dogger clay layer to the tunnel. An experiment combining electrical resistivity imaging and muon density imaging was setup taking advantage of the tunnel presence. 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 in order to acquire data in transmission across the massif to better cover the sounded medium. Electrical resistivity is particularly sensitive to water presence in the medium and thus carry information on the main water flow paths and on the pore space saturation. At the same time a muon sensor was placed in the tunnel under the fault region to detect muons coming from the sky after their crossing of the rock medium. Since the muon flux is attenuated as function of the quantity of matter crossed, muons flux measurements supply information on the medium average density along muons paths. The sensor presents 961 angles of view so measurements performed from one station allows a comparison of the muon flux temporal variations along the fault as well as in the medium surrounding the fault. As the water saturation of the porous medium fluctuates through time the medium density might indeed present sensible variations as shown by gravimetric studies. During the experiment important rainfalls occurred leading variations of the medium properties affecting density and electrical resistivity physical parameters. We show with data sets acquired before and after an important rainfall event how muon density and electrical resistivity imaging may complementary characterize variations of the medium properties. The development of such innovative experiments for hydrogeophysical studies presents then the ability to supply new information on fluid dynamics in the sub-surface.

Electrical resistivity tomography for studying liquefaction induced by the May 2012 Emilia-Romagna earthquake (Mw = 6.1, northern Italy)

NASA Astrophysics Data System (ADS)

Giocoli, A.; Quadrio, B.; Bellanova, J.; Lapenna, V.; Piscitelli, S.

2014-04-01

This work shows the result of an electrical resistivity tomography (ERT) survey carried out for imaging and characterizing the shallow subsurface affected by the coseismic effects of the Mw = 6.1 Emilia-Romagna (northern Italy) earthquake that occurred on 20 May 2012. The most characteristic coseismic effects were ground failure, lateral spreading and liquefaction that occurred extensively along the paleo-Reno River in the urban areas of San Carlo and Mirabello (southwestern portion of Ferrara Province). In total, six electrical resistivity tomographies were performed and calibrated with surface geological surveys, exploratory boreholes and aerial photo interpretations. This was one of first applications of the electrical resistivity tomography method in investigating coseismic liquefaction.

Application of Electrical Resistivity Imaging for Engineering Site Investigation. A Case Study on Prospective Hospital Site, Varamin, Iran

NASA Astrophysics Data System (ADS)

Amini, Amin; Ramazi, Hamidreza

2016-12-01

The article addresses the application of electrical resistivity imaging for engineering site investigation in Pishva Hospital, Varamin, Iran. Some aqueduct shafts exist in the study area backfilled by loose materials. The goals of this study are to detect probable aqueduct tunnels and their depth, investigate filling quality in the shafts as well as connection(s) between them. Therefore, three profiles were surveyed by dipoledipole electrode array. Also, to investigate the potentially anomalous areas more accurately, five additional resistivity profiles were measured by a Combined Resistivity Sounding-Profiling array (CRSP). According to the results of 2-D inversion modelling, a main aqueduct tunnel was detected beneath the central part of the site. Finally, the resistivity pattern of the detected aqueduct system passing the investigated area was provided using the obtained results.

New Electrical Resistivity Tomography approach for karst cave characterization: Castello di Lepre karst cave (Marsico Nuovo, Southern Italy).

NASA Astrophysics Data System (ADS)

Guerriero, Merilisa; Capozzoli, Luigi; De Martino, Gregory; Perciante, Felice; Gueguen, Erwan; Rizzo, Enzo

2017-04-01

Geophysical methods are commonly applied to characterize karst cave. Several geophysical method are used such as electrical resistivity tomography (ERT), gravimetric prospecting (G), ground penetrating radar (GPR) and seismic methods (S), in order to provide information on cave geometry and subsurface geological structure. In detail, in some complex karst systems, each geophysical method can only give partial information if used in normal way due to a low resolution for deep target. In order to reduce uncertainty and avoid misinterpretations based on a normal use of the electrical resistivity tomography method, a new ERT approach has been applied in karst cave Castello di Lepre (Marsico Nuovo, Basilicata region, Italy) located in the Mezo-Cenozoic carbonate substratum of the Monti della Maddalena ridge (Southern Appenines). In detail, a cross-ERT acquisition system was applied in order to improve the resolution on the electrical resistivity distribution on the surrounding geological structure of a karst cave. The cross-ERT system provides a more uniform model resolution vertically, increasing the resolution of the surface resistivity imaging. The usual cross-ERT is made by electrode setting in two or more borehole in order to acquire the resistivity data distribution. In this work the cross-ERT was made between the electrodes located on surface and along a karst cave, in order to obtain an high resolution of the electrical resistivity distributed between the cave and the surface topography. Finally, the acquired cross-ERT is potentially well-suited for imaging fracture zones since electrical current flow in fractured rock is primarily electrolytic via the secondary porosity associated with the fractures.

Contactless Electroluminescence Imaging for Cell and Module Characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Steve

2015-06-14

Module performance can be characterized by imaging using baseline and periodic images to track defects and degradation. Both thermal images, which can be acquired during sunny operating conditions, and photoluminescence images, which could be acquired at night, can be collected without electrical connection. Electroluminescence (EL) images, which are useful to detect many types of defects such as cracks, interconnect and solder faults, and resistances, have typically required electrical connection to drive current in the cells and modules. Here, a contactless EL imaging technique is proposed, which provides an EL image without the need for electrical connection to drive current throughmore » the module. Such EL imaging has the capability to be collected at night without disruption to daytime power generation.« less

Electrical resistivity tomography for studying liquefaction induced by the May 2012 Emilia-Romagna earthquake (Mw = 6.1, North Italy)

NASA Astrophysics Data System (ADS)

Giocoli, A.; Quadrio, B.; Bellanova, J.; Lapenna, V.; Piscitelli, S.

2013-10-01

This work shows the result of an Electrical Resistivity Tomography survey carried out for imaging and characterizing the shallow subsurface affected by the coseismic effects of the Mw = 6.1 Emilia-Romagna (North Italy) earthquake occurred on 20 May 2012. The most characteristic coseismic effects were ground failure, lateral spreading and liquefaction that occurred extensively along the paleo-Reno river in the urban areas of San Carlo, a hamlet of Sant'Agostino municipality, and of Mirabello (south-western portion of the Ferrara Province). Totally, six Electrical Resistivity Tomography were performed and calibrated with surface geological surveys, exploratory borehole and aerial photo interpretations. This was one of the first applications of the Electrical Resistivity Tomography method in investigating coseismic liquefaction.

Forensic Assessment on Ground Instability Using Electrical Resistivity Imaging (ERI)

NASA Astrophysics Data System (ADS)

Hazreek, Z. A. M.; Azhar, A. T. S.; Aziman, M.; Fauzan, S. M. S. A.; Ikhwan, J. M.; Aishah, M. A. N.

2017-02-01

Electrical resistivity imaging (ERI) was used to evaluate the ground settlement in local scale at housing areas. ERI and Borehole results were used to interpret the condition of the problematic subsurface profile due to its differential stiffness. Electrical resistivity of the subsurface profile was measured using ABEM SAS4000 equipment set. ERI results using electrical resistivity anomaly on subsurface materials resistivity shows the subsurface profile exhibited low (1 - 100 Ωm) and medium (> 100 Ωm) value (ERV) representing weak to firm materials. The occurrences of soft to medium cohesive material (SPT N value = 2 - 7) and stiff cohesive material (SPT N ≥ 8) in local scale has created inconsistency of the ground stability condition. Moreover, it was found that a layer of organic decayed wood (ERV = 43 ˜ 29 Ωm & SPT N = 15 ˜ 9) has been buried within the subsurface profile thus weaken the ground structure and finally promoting to the ground settlement. The heterogeneous of the subsurface material presented using integrated analysis of ERI and borehole data enabled ground settlement in this area to be evaluated. This is the major factor evaluating ground instability in the local scale. The result was applicable to assist in planning a strategy for sustainable ground improvement of local scale in fast, low cost, and large data coverage.

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, 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.

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.

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. © 2015, National Ground Water Association.

Mapping reversible photoswitching of molecular-resistance fluctuations during the conformational transformation of azobenzene-terminated molecular switches.

PubMed

Cho, Duckhyung; Yang, Myungjae; Shin, Narae; Hong, Seunghun

2018-06-07

We report a direct mapping and analysis of electrical noise in azobenzene-terminated molecular monolayers, revealing reversible photoswitching of the molecular-resistance fluctuations in the layers. In this work, a conducting atomic force microscope combined with a homemade spectrum analyzer was used to image electrical current and noise at patterned self-assembled monolayers (SAMs) of azobenzene-terminated molecular wires on a gold substrate. We analyzed the current and noise imaging data to obtain maps of molecular resistances and amount of mean-square fluctuations in the resistances of the regions of trans-azobenzene and a cis/trans-azobenzene mixture. We revealed that the fluctuations in the molecular resistances in the SAMs were enhanced after the trans-to-cis isomerization, while the resistances were reduced. This result could be attributed to enhanced disorders in the molecular arrangements in the cis-SAMs. Furthermore, we observed that the changes in the resistance fluctuations were reversible with respect to repeated trans-to-cis and cis-to-trans isomerizations, indicating that the effects originated from reversible photoswitching of the molecular structures rather than irreversible damages of the molecules. These findings provide valuable insights into the electrical fluctuations in photoswitchable molecules, which could be utilized in further studies on molecular switches and molecular electronics in general. © 2018 IOP Publishing Ltd.

Assessment of errors in static electrical impedance tomography with adjacent and trigonometric current patterns.

PubMed

Kolehmainen, V; Vauhkonen, M; Karjalainen, P A; Kaipio, J P

1997-11-01

In electrical impedance tomography (EIT), difference imaging is often preferred over static imaging. This is because of the many unknowns in the forward modelling which make it difficult to obtain reliable absolute resistivity estimates. However, static imaging and absolute resistivity values are needed in some potential applications of EIT. In this paper we demonstrate by simulation the effects of different error components that are included in the reconstruction of static EIT images. All simulations are carried out in two dimensions with the so-called complete electrode model. Errors that are considered are the modelling error in the boundary shape of an object, errors in the electrode sizes and localizations and errors in the contact impedances under the electrodes. Results using both adjacent and trigonometric current patterns are given.

Electrical Resistivity Imaging for Long-Term Monitoring of Contaminant Degradation

EPA Science Inventory

The results from this experiment strongly suggest that the resistivity changes seen are the results of the biodegradation of the oil. This conclusion was further supported by the results of the microcosm experiment. These results demonstrate the utility of the resistivity method ...

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.

Kirchhoff and Ohm in action: solving electric currents in continuous extended media

NASA Astrophysics Data System (ADS)

Dolinko, A. E.

2018-03-01

In this paper we show a simple and versatile computational simulation method for determining electric currents and electric potential in 2D and 3D media with arbitrary distribution of resistivity. One of the highlights of the proposed method is that the simulation space containing the distribution of resistivity and the points of external applied voltage are introduced by means of digital images or bitmaps, which easily allows simulating any phenomena involving distributions of resistivity. The simulation is based on the Kirchhoff’s laws of electric currents and it is solved by means of an iterative procedure. The method is also generalised to account for media with distributions of reactive impedance. At the end of this work, we show an example of application of the simulation, consisting in reproducing the response obtained with the geophysical method of electric resistivity tomography in presence of soil cracks. This paper is aimed at undergraduate or graduated students interested in computational physics and electricity and also researchers involved in the area of continuous electric media, which could find a simple and powerful tool for investigation.

Surface property detection apparatus and method

DOEpatents

Martens, J.S.; Ginley, D.S.; Hietala, V.M.; Sorensen, N.R.

1995-08-08

Apparatus and method for detecting, determining, and imaging surface resistance corrosion, thin film growth, and oxide formation on the surface of conductors or other electrical surface modification. The invention comprises a modified confocal resonator structure with the sample remote from the radiating mirror. Surface resistance is determined by analyzing and imaging reflected microwaves; imaging reveals anomalies due to surface impurities, non-stoichiometry, and the like, in the surface of the superconductor, conductor, dielectric, or semiconductor. 4 figs.

Characterizing soil erosion potential using electrical resistivity imaging : final report.

DOT National Transportation Integrated Search

2017-04-01

The erosion rate, or erodibility, of soil depends on many soil characteristics including: plasticity, : water content, grain size, percent clay, compaction, and shear strength. Many of these characteristics also : influence soil in situ bulk electric...

Characterizing soil erosion potential using electrical resistivity imaging : technical summary.

DOT National Transportation Integrated Search

2017-04-01

The erosion rate, or erodibility, of soil depends on many soil characteristics : including: plasticity, water content, grain size, percent clay, compaction, and shear : strength. Many of these characteristics also influence soil in situ bulk electric...

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. © 2015, National Ground Water Association.

Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vecchiola, Aymeric; Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis; Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau

An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10more » decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes.« less

Accurate modeling and inversion of electrical resistivity data in the presence of metallic infrastructure with known location and dimension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy C.; Wellman, Dawn M.

2015-06-26

Electrical resistivity tomography (ERT) has been widely used in environmental applications to study processes associated with subsurface contaminants and contaminant remediation. Anthropogenic alterations in subsurface electrical conductivity associated with contamination often originate from highly industrialized areas with significant amounts of buried metallic infrastructure. The deleterious influence of such infrastructure on imaging results generally limits the utility of ERT where it might otherwise prove useful for subsurface investigation and monitoring. In this manuscript we present a method of accurately modeling the effects of buried conductive infrastructure within the forward modeling algorithm, thereby removing them from the inversion results. The method ismore » implemented in parallel using immersed interface boundary conditions, whereby the global solution is reconstructed from a series of well-conditioned partial solutions. Forward modeling accuracy is demonstrated by comparison with analytic solutions. Synthetic imaging examples are used to investigate imaging capabilities within a subsurface containing electrically conductive buried tanks, transfer piping, and well casing, using both well casings and vertical electrode arrays as current sources and potential measurement electrodes. Results show that, although accurate infrastructure modeling removes the dominating influence of buried metallic features, the presence of metallic infrastructure degrades imaging resolution compared to standard ERT imaging. However, accurate imaging results may be obtained if electrodes are appropriately located.« less

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.

Three-dimensional forward solver and its performance analysis for magnetic resonance electrical impedance tomography (MREIT) using recessed electrodes.

PubMed

Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyoung; Kwon, Ohin; Seo, Jin Keun; Lee, June-Yub; Baek, Woon Sik

2003-07-07

In magnetic resonance electrical impedance tomography (MREIT), we try to reconstruct a cross-sectional resistivity (or conductivity) image of a subject. When we inject a current through surface electrodes, it generates a magnetic field. Using a magnetic resonance imaging (MRI) scanner, we can obtain the induced magnetic flux density from MR phase images of the subject. We use recessed electrodes to avoid undesirable artefacts near electrodes in measuring magnetic flux densities. An MREIT image reconstruction algorithm produces cross-sectional resistivity images utilizing the measured internal magnetic flux density in addition to boundary voltage data. In order to develop such an image reconstruction algorithm, we need a three-dimensional forward solver. Given injection currents as boundary conditions, the forward solver described in this paper computes voltage and current density distributions using the finite element method (FEM). Then, it calculates the magnetic flux density within the subject using the Biot-Savart law and FEM. The performance of the forward solver is analysed and found to be enough for use in MREIT for resistivity image reconstructions and also experimental designs and validations. The forward solver may find other applications where one needs to compute voltage, current density and magnetic flux density distributions all within a volume conductor.

Electrical Imaging of Roots and Trunks

NASA Astrophysics Data System (ADS)

Al Hagrey, S.; Werban, U.; Meissner, R.; Ismaeil, A.; Rabbel, W.

2005-05-01

We applied geoelectric and GPR techniques to analyze problems of botanical structures and even processes, e.g., mapping root zones, internal structure of trunks, and water uptake by roots. The dielectric nature of root zones and trunks is generally a consequence of relatively high moisture content. The electric method, applied to root zones, can discriminate between old, thick, isolated roots (high resistivity) and the network of young, active, and hydraulically conductive zones (low resistivity). Both types of roots show low radar velocity and a strong attenuation caused by the dominant effect of moisture (high dielectric constant) on the electromagnetic wave propagation. Single root branches could be observed in radargrams by their reflection and diffraction parabolas. We have perfected the inversion method for perfect and imperfect cylindrical objects, such as trunks, and developed a new multielectrodes (needle or gel) ring array for fast applications on living trees and discs. Using synthetic models we tested the technique successfully and analyzed it as a function of total electrode number and configuration. Measurements at a trunk show a well established inverse relationship between the imaged resistivity and the moisture content determined from cores. The central resistivity maximum of healthy trees strongly decreases toward the rim. This agrees with the moisture decrease to the outside where active sap flow processes take place. Branching, growth anomalies (new or old shoots) and meteorological effects (sunshine and wind direction) lead to deviations of the concentric electric structure. The strongest anomalies are related to infections causing wet, rotting spots or cavities. The heartwood resistivity is highest in olive and oak trunks, intermediate in young fruit trees and lowest in cork oak trunks that are considered to be anomalously wet. Compared to acoustic tomography our electric technique shows a better resolution in imaging internal ring structures where moisture is the most dominating factor. We conclude that our imaging resistivity technique is applicable for investigating or controlling the botanical and physical conditions of endangered trees (health inspection) and capable to monitor dynamic processes of sap flow if adequate tracers are used.

Real-time imaging of cerebral infarction in rabbits using electrical impedance tomography.

PubMed

Yang, Bin; Shi, Xuetao; Dai, Meng; Xu, Canhua; You, Fushen; Fu, Feng; Liu, Ruigang; Dong, Xiuzhen

2014-02-01

To investigate the possible use of electrical impedance tomography (EIT) in monitoring focal cerebral infarction in a rabbit model. A model of focal cerebral infarction was established in eight New Zealand rabbits using a photochemical method without craniectomy. Focal cerebral infarction was confirmed by histopathological examination. Intracranial impedance variation was measured using 16 electrodes placed in a circle on the scalp. EIT images were obtained using a damped least-squares reconstruction algorithm. The average resistivity value (ARV) of the infarct region on EIT images was calculated to quantify relative resistivity changes. A symmetry index was calculated to evaluate the relative difference in resistivity between the two sides of the cerebrum. EIT images and ARV curves showed that impedance changes caused by cerebral infarction increased linearly with irradiation time. A difference in ARV was found between measurements taken before and after infarct induction. Focal cerebral infarction can be monitored by EIT in the proposed animal model. The results are sufficiently encouraging that the authors plan to extend this study to humans, after further technical improvements.

Detection of Potential Shallow Aquifer Using Electrical Resistivity Imaging (ERI) at UTHM Campus, Johor Malaysia

NASA Astrophysics Data System (ADS)

Izzaty Riwayat, Akhtar; Nazri, Mohd Ariff Ahmad; Hazreek Zainal Abidin, Mohd

2018-04-01

In recent years, Electrical Resistivity Imaging (ERI) has become part of important method in preliminary stage as to gain more information in indicate the hidden water in underground layers. The problem faces by engineers is to determine the exact location of groundwater zone in subsurface layers. ERI seen as the most suitable tools in exploration of groundwater as this method have been applied in geotechnical and geo-environment investigation. This study was conducted using resistivity at UTHM campus to interpret the potential shallow aquifer and potential location for borehole as observation well. A Schlumberger array was setup during data acquisition as this array is capable in imaging deeper profile data and suitable for areas with homogeneous layer. The raw data was processed using RES2DINV software for 2D subsurface image. The result obtained indicate that the thickness of shallow aquifer for both spread line varies between 7.5 m to 15 m. The analysis of rest raw data using IP showed that the chargeability parameter is equal to 0 which strongly indicated the presence of groundwater aquifer in the study area.

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.

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.

Identification of different geologic units using fuzzy constrained resistivity tomography

NASA Astrophysics Data System (ADS)

Singh, Anand; Sharma, S. P.

2018-01-01

Different geophysical inversion strategies are utilized as a component of an interpretation process that tries to separate geologic units based on the resistivity distribution. In the present study, we present the results of separating different geologic units using fuzzy constrained resistivity tomography. This was accomplished using fuzzy c means, a clustering procedure to improve the 2D resistivity image and geologic separation within the iterative minimization through inversion. First, we developed a Matlab-based inversion technique to obtain a reliable resistivity image using different geophysical data sets (electrical resistivity and electromagnetic data). Following this, the recovered resistivity model was converted into a fuzzy constrained resistivity model by assigning the highest probability value of each model cell to the cluster utilizing fuzzy c means clustering procedure during the iterative process. The efficacy of the algorithm is demonstrated using three synthetic plane wave electromagnetic data sets and one electrical resistivity field dataset. The presented approach shows improvement on the conventional inversion approach to differentiate between different geologic units if the correct number of geologic units will be identified. Further, fuzzy constrained resistivity tomography was performed to examine the augmentation of uranium mineralization in the Beldih open cast mine as a case study. We also compared geologic units identified by fuzzy constrained resistivity tomography with geologic units interpreted from the borehole information.

Electric field tomography for contactless imaging of resistivity in biomedical applications.

PubMed

Korjenevsky, A V

2004-02-01

The technique of contactless imaging of resistivity distribution inside conductive objects, which can be applied in medical diagnostics, has been suggested and analyzed. The method exploits the interaction of a high-frequency electric field with a conductive medium. Unlike electrical impedance tomography, no electric current is injected into the medium from outside. The interaction is accompanied with excitation of high-frequency currents and redistribution of free charges inside the medium leading to strong and irregular perturbation of the field's magnitude outside and inside the object. Along with this the considered interaction also leads to small and regular phase shifts of the field in the area surrounding the object. Measuring these phase shifts using a set of electrodes placed around the object enables us to reconstruct the internal structure of the medium. The basics of this technique, which we name electric field tomography (EFT), are described, simple analytical estimations are made and requirements for measuring equipment are formulated. The realizability of the technique is verified by numerical simulations based on the finite elements method. Results of simulation have confirmed initial estimations and show that in the case of EFT even a comparatively simple filtered backprojection algorithm can be used for reconstructing the static resistivity distribution in biological tissues.

Passive, Highly-Sensitive, Room-Temperature Magnetic Field Sensors and Arrays for Detection and Imaging of Hidden Threats in Urban Environments

DTIC Science & Technology

2012-07-01

units made from the various sensors. This was because the different types of ME laminates have different electrical properties ( resistance and...DC resistance of a sensor (Rdc) 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT: SAR 18. NUMBER OF PAGES 338 19a. NAME OF...3.3.6. Electric -field tuning effect ..................................................................70 A.3.4. Dielectric loss noise reduction

Exploratory study on the methodology of fast imaging of unilateral stroke lesions by electrical impedance asymmetry in human heads.

PubMed

Ma, Jieshi; Xu, Canhua; Dai, Meng; You, Fusheng; Shi, Xuetao; Dong, Xiuzhen; Fu, Feng

2014-01-01

Stroke has a high mortality and disability rate and should be rapidly diagnosed to improve prognosis. Diagnosing stroke is not a problem for hospitals with CT, MRI, and other imaging devices but is difficult for community hospitals without these devices. Based on the mechanism that the electrical impedance of the two hemispheres of a normal human head is basically symmetrical and a stroke can alter this symmetry, a fast electrical impedance imaging method called symmetrical electrical impedance tomography (SEIT) is proposed. In this technique, electrical impedance tomography (EIT) data measured from the undamaged craniocerebral hemisphere (CCH) is regarded as reference data for the remaining EIT data measured from the other CCH for difference imaging to identify the differences in resistivity distribution between the two CCHs. The results of SEIT imaging based on simulation data from the 2D human head finite element model and that from the physical phantom of human head verified this method in detection of unilateral stroke.

Exploratory Study on the Methodology of Fast Imaging of Unilateral Stroke Lesions by Electrical Impedance Asymmetry in Human Heads

PubMed Central

Xu, Canhua; Dai, Meng; You, Fusheng; Shi, Xuetao

2014-01-01

Stroke has a high mortality and disability rate and should be rapidly diagnosed to improve prognosis. Diagnosing stroke is not a problem for hospitals with CT, MRI, and other imaging devices but is difficult for community hospitals without these devices. Based on the mechanism that the electrical impedance of the two hemispheres of a normal human head is basically symmetrical and a stroke can alter this symmetry, a fast electrical impedance imaging method called symmetrical electrical impedance tomography (SEIT) is proposed. In this technique, electrical impedance tomography (EIT) data measured from the undamaged craniocerebral hemisphere (CCH) is regarded as reference data for the remaining EIT data measured from the other CCH for difference imaging to identify the differences in resistivity distribution between the two CCHs. The results of SEIT imaging based on simulation data from the 2D human head finite element model and that from the physical phantom of human head verified this method in detection of unilateral stroke. PMID:25006594

The instantaneous apparent resistivity tensor: a visualization scheme for LOTEM electric field measurements

NASA Astrophysics Data System (ADS)

Caldwell, T. Grant; Bibby, Hugh M.

1998-12-01

Long-offset transient electromagnetic (LOTEM) data have traditionally been represented as early- and late-time apparent resistivities. Time-varying electric field data recorded in a LOTEM survey made with multiple sources can be represented by an `instantaneous apparent resistivity tensor'. Three independent, coordinate-invariant, time-varying apparent resistivities can be derived from this tensor. For dipolar sources, the invariants are also independent of source orientation. In a uniform-resistivity half-space, the invariant given by the square root of the tensor determinant remains almost constant with time, deviating from the half-space resistivity by a maximum of 6 per cent. For a layered half-space, a distance-time pseudo-section of the determinant apparent resistivity produces an image of the layering beneath the measurement profile. As time increases, the instantaneous apparent resistivity tensor approaches the direct current apparent resistivity tensor. An approximate time-to-depth conversion can be achieved by integrating the diffusion depth formula with time, using the determinant apparent resistivity at each instant to represent the resistivity of the conductive medium. Localized near-surface inhomogeneities produce shifts in the time-domain apparent resistivity sounding curves that preserve the gradient, analogous to static shifts seen in magnetotelluric soundings. Instantaneous apparent resistivity tensors calculated for 3-D resistivity models suggest that profiles of LOTEM measurements across a simple 3-D structure can be used to create an image that reproduces the main features of the subsurface resistivity. Where measurements are distributed over an area, maps of the tensor invariants can be made into a sequence of images, which provides a way of `time slicing' down through the target structure.

Microscopic histological characteristics of soft tissue sarcomas: analysis of tissue features and electrical resistance.

PubMed

Tosi, A L; Campana, L G; Dughiero, F; Forzan, M; Rastrelli, M; Sieni, E; Rossi, C R

2017-07-01

Tissue electrical conductivity is correlated with tissue characteristics. In this work, some soft tissue sarcomas (STS) excised from patients have been evaluated in terms of histological characteristics (cell size and density) and electrical resistance. The electrical resistance has been measured using the ex vivo study on soft tissue tumors electrical characteristics (ESTTE) protocol proposed by the authors in order to study electrical resistance of surgical samples excised by patients in a fixed measurement setup. The measurement setup includes a voltage pulse generator (700 V, 100 µs long at 5 kHz, period 200 µs) and an electrode with 7 needles, 20 mm-long, with the same distance arranged in a fixed hexagonal geometry. In the ESTTE protocol, the same voltage pulse sequence is applied to each different tumor mass and the corresponding resistance has been evaluated from voltage and current recorded by the equipment. For each tumor mass, a histological sample of the volume treated by means of voltage pulses has been taken for histological analysis. Each mass has been studied in order to identify the sarcoma type. For each histological sample, an image at 20× or 40× of magnification was acquired. In this work, the electrical resistance measured for each tumor has been correlated with tissue characteristics like the type, size and density of cells. This work presents a preliminary study to explore possible correlations between tissue characteristics and electrical resistance of STS. These results can be helpful to adjust the pulse voltage intensity in order to improve the electrochemotherapy efficacy on some histotype of STS.

Assessment of the Efficiency of Consolidation Treatment through Injections of Expanding Resins by Geotechnical Tests and 3D Electrical Resistivity Tomography

PubMed Central

2015-01-01

The design and execution of consolidation treatment of settled foundations by means of injection of polyurethane expanding resins require a proper investigation of the state of the foundation soil, in order to better identify anomalies responsible for the instability. To monitor the injection process, a procedure has been developed, which involves, in combination with traditional geotechnical tests, the application of a noninvasive, geophysical technique based on the electrical resistivity, which is strongly sensitive to presence of water or voids. Three-dimensional electrical resistivity tomography is a useful tool to produce effective 3D images of the foundation soils before, during, and after the injections. The achieved information allows designing the consolidation scheme and monitoring its effects on the treated volumes in real time. To better understand the complex processes induced by the treatment and to learn how variations of resistivity accompany increase of stiffness, an experiment was carried out in a full-scale test site. Injections of polyurethane expanding resin were performed as in real worksite conditions. Results confirm that the experimented approach by means of 3D resistivity imaging allows a reliable procedure of consolidation, and geotechnical tests demonstrate the increase of mechanical stiffness. PMID:26167521

Pulsed infrared thermography for assessment of ultrasonic welds

NASA Astrophysics Data System (ADS)

McGovern, Megan E.; Rinker, Teresa J.; Sekol, Ryan C.

2018-03-01

Battery packs are a critical component in electric vehicles. During pack assembly, the battery cell tab and busbar are ultrasonically welded. The properties of the welds ultimately affect battery pack durability. Quality inspection of these welds is important to ensure durable battery packs. Pack failure is detrimental economically and could also pose a safety hazard, such as thermal runaway. Ultrasonic welds are commonly checked by measuring electrical resistance or auditing using destructive mechanical testing. Resistance measurements are quick, but sensitive to set-up changes. Destructive testing cannot represent the entire weld set. It is possible for a weak weld to satisfy the electrical requirement check, because only sufficient contact between the tabs and busbar is required to yield a low resistance measurement. Laboratory techniques are often not suitable for inline inspection, as they may be time-consuming, use couplant, or are only suitable for coupons. The complex surface geometry also poses difficulties for conventional nondestructive techniques. A method for inspection of ultrasonic welds is proposed using pulsed infrared thermography to identify discrepant welds in a manufacturing environment. Thermal measurements of welds were compared to electrical and mechanical measurements. The heat source distribution was calculated to obtain thermal images with high temporal and spatial resolution. All discrepant welds were readily identifiable using two thermographic techniques: pixel counting and the gradient image. A positive relationship between pixel count and mechanical strength was observed. The results demonstrate the potential of pulsed thermography for inline inspection, which can complement, or even replace, conventional electrical resistance measurements.

Inversion of quasi-3D DC resistivity imaging data using artificial neural networks

NASA Astrophysics Data System (ADS)

Neyamadpour, Ahmad; Wan Abdullah, W. A. T.; Taib, Samsudin

2010-02-01

The objective of this paper is to investigate the applicability of artificial neural networks in inverting quasi-3D DC resistivity imaging data. An electrical resistivity imaging survey was carried out along seven parallel lines using a dipole-dipole array to confirm the validation of the results of an inversion using an artificial neural network technique. The model used to produce synthetic data to train the artificial neural network was a homogeneous medium of 100Ωm resistivity with an embedded anomalous body of 1000Ωm resistivity. The network was trained using 21 datasets (comprising 12159 data points) and tested on another 11 synthetic datasets (comprising 6369 data points) and on real field data. Another 24 test datasets (comprising 13896 data points) consisting of different resistivities for the background and the anomalous bodies were used in order to test the interpolation and extrapolation of network properties. Different learning paradigms were tried in the training process of the neural network, with the resilient propagation paradigm being the most efficient. The number of nodes, hidden layers, and efficient values for learning rate and momentum coefficient have been studied. Although a significant correlation between results of the neural network and the conventional robust inversion technique was found, the ANN results show more details of the subsurface structure, and the RMS misfits for the results of the neural network are less than seen with conventional methods. The interpreted results show that the trained network was able to invert quasi-3D electrical resistivity imaging data obtained by dipole-dipole configuration both rapidly and accurately.

Electrical Resistance Based Damage Modeling of Multifunctional Carbon Fiber Reinforced Polymer Matrix Composites

NASA Astrophysics Data System (ADS)

Hart, Robert James

In the current thesis, the 4-probe electrical resistance of carbon fiber-reinforced polymer (CFRP) composites is utilized as a metric for sensing low-velocity impact damage. A robust method has been developed for recovering the directionally dependent electrical resistivities using an experimental line-type 4-probe resistance method. Next, the concept of effective conducting thickness was uniquely applied in the development of a brand new point-type 4-probe method for applications with electrically anisotropic materials. An extensive experimental study was completed to characterize the 4-probe electrical resistance of CFRP specimens using both the traditional line-type and new point-type methods. Leveraging the concept of effective conducting thickness, a novel method was developed for building 4-probe electrical finite element (FE) models in COMSOL. The electrical models were validated against experimental resistance measurements and the FE models demonstrated predictive capabilities when applied to CFRP specimens with varying thickness and layup. These new models demonstrated a significant improvement in accuracy compared to previous literature and could provide a framework for future advancements in FE modeling of electrically anisotropic materials. FE models were then developed in ABAQUS for evaluating the influence of prescribed localized damage on the 4-probe resistance. Experimental data was compiled on the impact response of various CFRP laminates, and was used in the development of quasi- static FE models for predicting presence of impact-induced delamination. The simulation-based delamination predictions were then integrated into the electrical FE models for the purpose of studying the influence of realistic damage patterns on electrical resistance. When the size of the delamination damage was moderate compared to the electrode spacing, the electrical resistance increased by less than 1% due to the delamination damage. However, for a specimen with large delamination extending beyond the electrode locations, the oblique resistance increased by 30%. This result suggests that for damage sensing applications, the spacing of electrodes relative to the size of the delamination is important. Finally CT image data was used to model 3-D void distributions and the electrical response of such specimens were compared to models with no voids. As the void content increased, the electrical resistance increased non-linearly. The relationship between void content and electrical resistance was attributed to a combination of three factors: (i) size and shape, (ii) orientation, and (iii) distribution of voids. As a whole, the current thesis provides a comprehensive framework for developing predictive, resistance-based damage sensing models for CFRP laminates of various layup and thickness.

Electrical Resistivity Imaging Below Nuclear Waste Tank Farms at the Hanford Site

NASA Astrophysics Data System (ADS)

Rucker, D. F.; Levitt, M. T.

2006-12-01

The Hanford Site, a Department of Energy nuclear processing facility in eastern Washington, contains a complex series of radiological liquid waste disposal and storage facilities. The primary method of interim storage is the use of large single-shelled steel tanks with capacities of up to 3790 m3 (1 million gallons). The tanks are organized below ground into tank farms, with about 12 tanks per farm. The liquid waste within the tanks is primarily comprised of inorganic salts with minor constituents of heavy metals and radiological metals. The electrical properties of the radiological waste are significantly different to that of the surrounding engineered fill and native geologic formations. Over the past 60 years since the earliest tanks have been in use, many have been known to leak. An electrical resistivity survey was conducted within a tank farm to map the extent of the plumes resulting from historic leaks. Traditional surface-based electrical resistivity surveys resulted in unusable data due to the significant subsurface infrastructure that included a network of delivery pipes, wells, fences, and electrical discharge sources . HGI adapted the resistivity technique to include the site infrastructure as transceivers to augment data density and geometry. The results show a distribution of low resistivity values within the farm in areas that match known historic leak sites. The addition of site infrastructure as sensors demonstrates that the electrical resistivity technique can be used in highly industrial sites.

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.

Marine electrical resistivity imaging of submarine groundwater discharge: Sensitivity analysis and application in Waquoit Bay, Massachusetts, USA

USGS Publications Warehouse

Henderson, Rory; Day-Lewis, Frederick D.; Abarca, Elena; Harvey, Charles F.; Karam, Hanan N.; Liu, Lanbo; Lane, John W.

2010-01-01

Electrical resistivity imaging has been used in coastal settings to characterize fresh submarine groundwater discharge and the position of the freshwater/salt-water interface because of the relation of bulk electrical conductivity to pore-fluid conductivity, which in turn is a function of salinity. Interpretation of tomograms for hydrologic processes is complicated by inversion artifacts, uncertainty associated with survey geometry limitations, measurement errors, and choice of regularization method. Variation of seawater over tidal cycles poses unique challenges for inversion. The capabilities and limitations of resistivity imaging are presented for characterizing the distribution of freshwater and saltwater beneath a beach. The experimental results provide new insight into fresh submarine groundwater discharge at Waquoit Bay National Estuarine Research Reserve, East Falmouth, Massachusetts (USA). Tomograms from the experimental data indicate that fresh submarine groundwater discharge may shut down at high tide, whereas temperature data indicate that the discharge continues throughout the tidal cycle. Sensitivity analysis and synthetic modeling provide insight into resolving power in the presence of a time-varying saline water layer. In general, vertical electrodes and cross-hole measurements improve the inversion results regardless of the tidal level, whereas the resolution of surface arrays is more sensitive to time-varying saline water layer.

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.

Monitoring groundwater-surface water interaction using time-series and time-frequency analysis of transient three-dimensional electrical resistivity changes

USGS Publications Warehouse

Johnson, Timothy C.; Slater, Lee D.; Ntarlagiannis, Dimitris; Day-Lewis, Frederick D.; Elwaseif, Mehrez

2012-01-01

Time-lapse resistivity imaging is increasingly used to monitor hydrologic processes. Compared to conventional hydrologic measurements, surface time-lapse resistivity provides superior spatial coverage in two or three dimensions, potentially high-resolution information in time, and information in the absence of wells. However, interpretation of time-lapse electrical tomograms is complicated by the ever-increasing size and complexity of long-term, three-dimensional (3-D) time series conductivity data sets. Here we use 3-D surface time-lapse electrical imaging to monitor subsurface electrical conductivity variations associated with stage-driven groundwater-surface water interactions along a stretch of the Columbia River adjacent to the Hanford 300 near Richland, Washington, USA. We reduce the resulting 3-D conductivity time series using both time-series and time-frequency analyses to isolate a paleochannel causing enhanced groundwater-surface water interactions. Correlation analysis on the time-lapse imaging results concisely represents enhanced groundwater-surface water interactions within the paleochannel, and provides information concerning groundwater flow velocities. Time-frequency analysis using the Stockwell (S) transform provides additional information by identifying the stage periodicities driving groundwater-surface water interactions due to upstream dam operations, and identifying segments in time-frequency space when these interactions are most active. These results provide new insight into the distribution and timing of river water intrusion into the Hanford 300 Area, which has a governing influence on the behavior of a uranium plume left over from historical nuclear fuel processing operations.

Dissolution-Enlarged Fractures Imaging Using Electrical Resistivity Tomography (ERT)

NASA Astrophysics Data System (ADS)

Siami-Irdemoosa, Elnaz

In recent years the electrical imaging techniques have been largely applied to geotechnical and environmental investigations. These techniques have proven to be the best geophysical methods for site investigations in karst terrain, particularly when the overburden soil is clay-dominated. Karst is terrain with a special landscape and distinctive hydrological system developed by dissolution of rocks, particularly carbonate rocks such as limestone and dolomite, made by enlarging fractures into underground conduits that can enlarge into caverns, and in some cases collapse to form sinkholes. Bedding planes, joints, and faults are the principal structural guides for underground flow and dissolution in almost all karstified rocks. Despite the important role of fractures in karst development, the geometry of dissolution-enlarged fractures remain poorly unknown. These features are characterized by an strong contrast with the surrounding formations in terms of physical properties, such as electrical resistivity. Electrical resistivity tomography (ERT) was used as the primary geophysical tool to image the subsurface in a karst terrain in Greene County, Missouri. Pattern, orientation and density of the joint sets were interpreted from ERT data in the investigation site. The Multi-channel Analysis of Surface Wave (MASW) method and coring were employed to validate the interpretation results. Two sets of orthogonal visually prominent joints have been identified in the investigation site: north-south trending joint sets and west-east trending joint sets. However, most of the visually prominent joint sets are associated with either cultural features that concentrate runoff, natural surface drainage features or natural surface drainage.

Nanometer-scale surface potential and resistance mapping of wide-bandgap Cu(In,Ga)Se2 thin films

NASA Astrophysics Data System (ADS)

Jiang, C.-S.; Contreras, M. A.; Mansfield, L. M.; Moutinho, H. R.; Egaas, B.; Ramanathan, K.; Al-Jassim, M. M.

2015-01-01

We report microscopic characterization studies of wide-bandgap Cu(In,Ga)Se2 photovoltaic thin films using the nano-electrical probes of scanning Kelvin probe force microscopy and scanning spreading resistance microscopy. With increasing bandgap, the potential imaging shows significant increases in both the large potential features due to extended defects or defect aggregations and the potential fluctuation due to unresolvable point defects with single or a few charges. The resistance imaging shows increases in both overall resistance and resistance nonuniformity due to defects in the subsurface region. These defects are expected to affect open-circuit voltage after the surfaces are turned to junction upon device completion.

EIT images of ventilation: what contributes to the resistivity changes?

PubMed

Zhang, Jie; Patterson, Robert P

2005-04-01

One promising application of electrical impedance tomography (EIT) is the monitoring of pulmonary ventilation and edema. Using three-dimensional (3D) finite difference human models as virtual phantoms, the factors that contribute to the observed lung resistivity changes in the EIT images were investigated. The results showed that the factors included not only tissue resistivity or vessel volume changes, but also chest expansion and tissue/organ movement. The chest expansion introduced artifacts in the center of the EIT images, ranging from -2% to 31% of the image magnitude. With the increase of simulated chest expansion, the percentage contribution of chest expansion relative to lung resistivity change in the EIT image remained relatively constant. The averaged resistivity changes in the lung regions caused by chest expansion ranged from 0.65% to 18.31%. Tissue/organ movement resulted in an increased resistivity in the lung region and in the center anterior region of EIT images. The increased resistivity with inspiration observed in the heart region was caused mainly by a drop in the heart position, which reduced the heart area at the electrode level and was replaced by the lung tissue with higher resistivity. This study indicates that for the analysis of EIT, data errors caused by chest expansion and tissue/organ movement need to be considered.

Evaluation of physico-mechanical properties of clayey soils using electrical resistivity imaging technique

NASA Astrophysics Data System (ADS)

Kibria, Golam

Resistivity imaging (RI) is a promising approach to obtaining continuous profile of soil subsurface. This method offers simple technique to identify moisture variation and heterogeneity of the investigated area. However, at present, only qualitative information of subsurface can be obtained using RI. A study on the quantification of geotechnical properties has become important for rigorous use of this method in the evaluation of geohazard potential and construction quality control of landfill liner system. Several studies have been performed to describe electrical resistivity of soil as a function of pore fluid conductivity and surface conductance. However, characterization tests on pore water and surface charge are not typically performed in a conventional geotechnical investigation. The overall objective of this study is to develop correlations between geotechnical parameters and electrical resistivity of soil, which would provide a mean to estimate geotechnical properties from RI. As a part of the study, multiple regression analyses were conducted to develop practically applicable models correlating resistivity with influential geotechnical parameters. The soil samples considered in this study were classified as highly plastic clay (CH) and low plasticity clay (CL) according to Unified Soil Classification System (USCS). Based on the physical tests, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) analysis, kaolinite was identified as the dominant mineral with some traces of magnesium, calcium, potassium, and iron. Electrical resistivity tests were conducted on compacted clays and undisturbed samples under varied geotechnical conditions. The experimental results indicated that the degree of saturation substantially influenced electrical resistivity. Electrical resistivity decreased as much as 11 times from initial value for the increase of degree of saturation from 23 to 100% in the laboratory tests on compacted clays. In case of undisturbed soil samples, resistivity decreased as much as sixteen fold (49.4 to 3.2 Ohm-m) for an increase of saturation from 31 to 100%. Furthermore, the resistivity results were different for the specimens at a specific degree of saturation because of varied surface activity and isomorphous substitution of clayey soils. In addition to physical properties, compressibility of clays was correlated with electrical conductivity. Based on the investigation, it was determined that the electrical conductivity vs. pressure curves followed similar trends as e vs. logp curves. Multiple linear regression (MLR) models were developed for compacted and undisturbed samples using statistical analysis software SAS (2009). During model development, degree of saturation and CEC were selected as independent variables. The proposed models were validated using experimental results on a different set of samples. Moreover, the applicability of the models in the determination of degrees of saturation was evaluated using field RI tests.

Long-term ERT monitoring of biogeochemical changes of an aged hydrocarbon contamination.

PubMed

Caterina, David; Flores Orozco, Adrian; Nguyen, Frédéric

2017-06-01

Adequate management of contaminated sites requires information with improved spatio-temporal resolution, in particular to assess bio-geochemical processes, such as the transformation and degradation of contaminants, precipitation of minerals or changes in groundwater geochemistry occurring during and after remediation procedures. Electrical Resistivity Tomography (ERT), a geophysical method sensitive to pore-fluid and pore-geometry properties, permits to gain quasi-continuous information about subsurface properties in real-time and has been consequently widely used for the characterization of hydrocarbon-impacted sediments. However, its application for the long-term monitoring of processes accompanying natural or engineered bioremediation is still difficult due to the poor understanding of the role that biogeochemical processes play in the electrical signatures. For in-situ studies, the task is further complicated by the variable signal-to-noise ratio and the variations of environmental parameters leading to resolution changes in the electrical images. In this work, we present ERT imaging results for data collected over a period of two years on a site affected by a diesel fuel contamination and undergoing bioremediation. We report low electrical resistivity anomalies in areas associated to the highest contaminant concentrations likely due transformations of the contaminant due to microbial activity and accompanying release of metabolic products. We also report large seasonal variations of the bulk electrical resistivity in the contaminated areas in correlation with temperature and groundwater level fluctuations. However, the amplitude of bulk electrical resistivity variations largely exceeds the amplitude expected given existing petrophysical models. Our results suggest that the variations in electrical properties are mainly controlled by microbial activity which in turn depends on soil temperature and hydrogeological conditions. Therefore, ERT can be suggested as a promising tool to track microbial activity during bioremediation even though further research is still needed to completely understand the bio-geochemical processes involved and their impact on electrical signatures. Copyright © 2017 Elsevier B.V. All rights reserved.

Long-term ERT monitoring of biogeochemical changes of an aged hydrocarbon contamination

NASA Astrophysics Data System (ADS)

Caterina, David; Flores Orozco, Adrian; Nguyen, Frédéric

2017-06-01

Adequate management of contaminated sites requires information with improved spatio-temporal resolution, in particular to assess bio-geochemical processes, such as the transformation and degradation of contaminants, precipitation of minerals or changes in groundwater geochemistry occurring during and after remediation procedures. Electrical Resistivity Tomography (ERT), a geophysical method sensitive to pore-fluid and pore-geometry properties, permits to gain quasi-continuous information about subsurface properties in real-time and has been consequently widely used for the characterization of hydrocarbon-impacted sediments. However, its application for the long-term monitoring of processes accompanying natural or engineered bioremediation is still difficult due to the poor understanding of the role that biogeochemical processes play in the electrical signatures. For in-situ studies, the task is further complicated by the variable signal-to-noise ratio and the variations of environmental parameters leading to resolution changes in the electrical images. In this work, we present ERT imaging results for data collected over a period of two years on a site affected by a diesel fuel contamination and undergoing bioremediation. We report low electrical resistivity anomalies in areas associated to the highest contaminant concentrations likely due transformations of the contaminant due to microbial activity and accompanying release of metabolic products. We also report large seasonal variations of the bulk electrical resistivity in the contaminated areas in correlation with temperature and groundwater level fluctuations. However, the amplitude of bulk electrical resistivity variations largely exceeds the amplitude expected given existing petrophysical models. Our results suggest that the variations in electrical properties are mainly controlled by microbial activity which in turn depends on soil temperature and hydrogeological conditions. Therefore, ERT can be suggested as a promising tool to track microbial activity during bioremediation even though further research is still needed to completely understand the bio-geochemical processes involved and their impact on electrical signatures.

Imaging Neuronal Seal Resistance on Silicon Chip using Fluorescent Voltage-Sensitive Dye

PubMed Central

Braun, Dieter; Fromherz, Peter

2004-01-01

The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and by imaging the voltage change across the attached cell membrane with a fluorescent voltage-sensitive dye. The phase map of voltage change was fitted with a planar core-coat conductor model using the sheet resistance as a free parameter. For nerve cells from rat brain on polylysine as well as for HEK293 cells and MDCK cells on fibronectin we find a similar sheet resistance of 10 MΩ. Taking into account the independently measured distance of 50 nm between chip and membrane for these cells, we obtain a specific resistance of 50 Ωcm that is indistinguishable from bulk electrolyte. On the other hand, the sheet resistance for erythrocytes on polylysine is far higher, at ∼1.5 GΩ. Considering the distance of 10 nm, the specific resistance in the narrow cleft is enhanced to 1500 Ωcm. We find this novel optical method to be a convenient tool to optimize the interface between cells and chips for bioelectronic devices. PMID:15298937

Imaging neuronal seal resistance on silicon chip using fluorescent voltage-sensitive dye.

PubMed

Braun, Dieter; Fromherz, Peter

2004-08-01

The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and by imaging the voltage change across the attached cell membrane with a fluorescent voltage-sensitive dye. The phase map of voltage change was fitted with a planar core-coat conductor model using the sheet resistance as a free parameter. For nerve cells from rat brain on polylysine as well as for HEK293 cells and MDCK cells on fibronectin we find a similar sheet resistance of 10 MOmega. Taking into account the independently measured distance of 50 nm between chip and membrane for these cells, we obtain a specific resistance of 50 Omegacm that is indistinguishable from bulk electrolyte. On the other hand, the sheet resistance for erythrocytes on polylysine is far higher, at approximately 1.5 GOmega. Considering the distance of 10 nm, the specific resistance in the narrow cleft is enhanced to 1500 Omegacm. We find this novel optical method to be a convenient tool to optimize the interface between cells and chips for bioelectronic devices.

Electrical Tomography for seismic hazard monitoring: state-of-the-art and future challenges.

NASA Astrophysics Data System (ADS)

Lapenna, Vincenzo; Piscitelli, Sabatino

2010-05-01

The Self-Potential (passive) and DC resistivity (active) methods have been considered for a long period as ancillary and/or secondary tools in geophysical exploration, simplified procedures for data processing and purely qualitative techniques for data inversion were the main drawbacks. Recently, innovative algorithms for tomographic data inversion, new models for describing the electrokinetic phenomena associated to the subsurface fluid migration and modern technologies for the field surveying have rapidly transformed these geoelectrical methods in powerful tools for geo-hazard monitoring. These technological and methodological improvements disclose the way for a wide spectra of interesting and challenging applications: mapping of the water content in landslide bodies; identification of fluid and gas emissions in volcanic areas; search of earthquake precursors. In this work we briefly resume the current start-of-the-art and analyse the new applications of the Electrical Tomography in the seismic hazard monitoring. An overview of the more interesting results obtained in different worldwide areas (i.e. Mediterranean Basin, California, Japan) is presented and discussed. To-date, combining novel techniques for data inversion and new strategies for the field data acquisition is possible to obtain high-resolution electrical images of complex geological structures. One of the key challenges for the near-future will be the integration of active (DC resistivity) and passive (Self-Potential) measurements for obtaining 2D, 3D and 4D electrical tomographies able to follow the spatial and temporal dynamics of electrical parameters (i.e. resistivity, self-potential). This approach could reduce the ambiguities related to the interpretation of anomalous SP signals in seismic active areas and their applicability for short-term earthquake prediction. The resistivity imaging can be applied for illuminating the fault geometry, while the SP imaging is the key instrument for capturing the fingerprints of the electrokinetic phenomena potentially generated in focal regions.

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.

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.

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.

General Approach for Rock Classification Based on Digital Image Analysis of Electrical Borehole Wall Images

NASA Astrophysics Data System (ADS)

Linek, M.; Jungmann, M.; Berlage, T.; Clauser, C.

2005-12-01

Within the Ocean Drilling Program (ODP), image logging tools have been routinely deployed such as the Formation MicroScanner (FMS) or the Resistivity-At-Bit (RAB) tools. Both logging methods are based on resistivity measurements at the borehole wall and therefore are sensitive to conductivity contrasts, which are mapped in color scale images. These images are commonly used to study the structure of the sedimentary rocks and the oceanic crust (petrologic fabric, fractures, veins, etc.). So far, mapping of lithology from electrical images is purely based on visual inspection and subjective interpretation. We apply digital image analysis on electrical borehole wall images in order to develop a method, which augments objective rock identification. We focus on supervised textural pattern recognition which studies the spatial gray level distribution with respect to certain rock types. FMS image intervals of rock classes known from core data are taken in order to train textural characteristics for each class. A so-called gray level co-occurrence matrix is computed by counting the occurrence of a pair of gray levels that are a certain distant apart. Once the matrix for an image interval is computed, we calculate the image contrast, homogeneity, energy, and entropy. We assign characteristic textural features to different rock types by reducing the image information into a small set of descriptive features. Once a discriminating set of texture features for each rock type is found, we are able to discriminate the entire FMS images regarding the trained rock type classification. A rock classification based on texture features enables quantitative lithology mapping and is characterized by a high repeatability, in contrast to a purely visual subjective image interpretation. We show examples for the rock classification between breccias, pillows, massive units, and horizontally bedded tuffs based on ODP image data.

Probing the frontal deformation zone of the Chihshang Fault with boreholes and high-resolution electrical resistivity imaging methods: A case study at the Dapo site in eastern Taiwan

NASA Astrophysics Data System (ADS)

Chang, Ping-Yu; Huang, Wen-Jeng; Chen, Chien-Chih; Hsu, Han-lun; Yen, I.-Chin; Ho, Gong-Ruei; Lee, Jian-Cheng; Lu, Shih-Ting; Chen, Po-Tsun

2018-06-01

Not only direct fault ruptures but also later mass movement may result in complicated frontal deformation of the faults. Consequently, the deformation front or the contacts between the unconsolidated materials from the hanging wall and footwall of the thrust fault may indicate the toe of the mass movement instead of the actual fault zone. In this study, we used a combination of surface electrical resistivity imaging methods and borehole records in order to investigate the geometries of the structures in the frontal deformation zone of the Chihshang Fault at the Dapo elementary school. From the cores, we observed three different geological components at the Dapo site: the conductive Lichi mélange of the hanging wall, the colluvial gravels and the underlying fluvial-gravel layer at the footwall. The resistivity images from two parallel survey lines reveal that the position where the fault trace was thought to be is actually the toe of the slumping body's surface ruptures consisting of materials from the Lichi mélange. On the basis of the resistivity images, we also found that the actual fault plane is located on the southeastern side of the resistivity survey line near the hilltop. As a result, we conclude that mass movement induced by the inter-seismic creeping, not direct faulting, is the main factor affecting the frontal deformation zone of the Chihshang fault at the Dapo site.

Electrical Resistivity Imaging of Saltwater and Freshwater Along the Coast of Monterey Bay

NASA Astrophysics Data System (ADS)

Knight, R. J.; Pidlisecky, A.; Moran, T.; Goebel, M.

2014-12-01

A coastal region represents a dynamic interface where the processes of saltwater intrusion and freshwater flow create complex spatial and temporal changes in water chemistry. These changes in water chemistry affect both human use of coastal groundwater aquifers and the functioning of coastal ecosystems. Mapping out the subsurface distribution of saltwater and freshwater is a critical step in predicting, and managing, changes in water chemistry in coastal regions. Our research is focused on California's Monterey Bay region where agriculturally-intensive land meets the sensitive marine environment of the Monterey Bay National Marine Sanctuary. Along the coast of Monterey Bay extensive groundwater extraction (groundwater provides more than 80% of the area's water supply) has led to saltwater intrusion into aquifers at various locations. To date, the mapping of saltwater intrusion has relied on measurements of changing water chemistry in monitoring wells. But it is challenging with wells to capture the spatially complex hydrostratigraphy resulting from changing depositional environments and numerous faulting events. We suggest that geophysical methods be used to map and monitor the distribution of saltwater and freshwater by acquiring non-invasive, high-resolution continuous images of the subsurface. In a pilot study conducted over the past four years, we used electrical resistivity imaging to successfully identify regions of saltwater and freshwater 150 m below sea level along a 7 km stretch of the southern Monterey Bay coast. We employed large-offset electrical resistance tomography using a 96-electrode system with an overall array length of 860 m. The results showed excellent agreement with measurements in nearby monitoring wells. The large-scale image provided by the geophysical measurements revealed the hydrostratigraphic controls on the spatial distribution of the saltwater/freshwater interface. In October 2014 we will expand this study, using large-offset electrical resistance tomography to image to a depth of 300 m along a 40 km stretch of the Monterey Bay coast. The acquisition of this continuous dataset will provide an improved understanding of the biophysical and human factors controlling the processes of saltwater intrusion and freshwater flow in this coastal region.

Determination of consolidation properties using electrical resistivity

NASA Astrophysics Data System (ADS)

Kibria, Golam; Hossain, Sahadat; Khan, Mohammad Sadik

2018-05-01

Electrical conductivity is an indirect method used to evaluate pore-structures and their influence on macro and microscale behavior of soils. Although this method can provide useful information about the consolidation properties of soil samples, insufficient studies have been conducted to identify correlations between electrical and consolidation properties. The current study presents electrical resistivity responses of clayey samples at different consolidation stages. The consolidation properties of four soil specimens were measured in conjunction with electrical conductivity. Scanning electron microscope (SEM) analyses were performed on soil samples before and after consolidation to identify the changes in fabric morphology due to the application of loads. It was observed that the electrical conductivity of samples decreased with the increase of pressure, and the trends of variations were similar to e vs. logP curves. Although a linear correlation exists between electrical conductivity and void ratio, the relationship depends on the structural changes in clay particles. Therefore, changes in fabric structures were analyzed using SEM images, and results showed that the aspect ratio of the particles increased as much as 18.3% after consolidation. Based on the investigation, the coefficient of consolidations and one-dimensional strain were determined using electrical resistivity measurements.

Quantification of blood volume by electrical impedance tomography using a tissue-equivalent phantom.

PubMed

Sadleir, R; Fox, R

1998-11-01

An in vivo electrical impedance tomography (EIT) system was designed to accurately estimate quantities of intra-peritoneal blood in the abdominal cavity. For this it is essential that the response is relatively independent of the position of the high conductivity anomaly (blood) in the body. The sensitivity of the system to the introduction of blood-equivalent resistivity anomalies was assessed by using a cylindrical tissue-equivalent phantom. It was found that a satisfactorily uniform response of the system in both radial (transverse) and axial (longitudinal) directions in the phantom could be achieved by filtering resistivity profile images obtained by EIT measurement, and by using extended electrodes to collect data. Post-processing of single impedance images gave rise to a quantity denoted the resistivity index. A filter was then used to remove the remaining radial variation of the resistivity index. It was calculated by evaluating the resistivity index of a number of theoretically calculated images, and constructing a correction filter similar to those used to remove lens imperfections, such as coma, in optical components. The 30% increase in the resistivity index observed when an anomaly was moved to the maximum extent allowed by the filter calculation (0.75 of the phantom radius) was reduced by the filter to 6%. A study of the axial dependence observed in the resistivity index using electrodes extended in the axial direction by +/-5 cm found that the variation in resistivity index with axial position was about half of that observed using small circular electrodes similar to those used in the Sheffield mark I system.

Electric Imaging through Evolution, a Modeling Study of Commonalities and Differences

PubMed Central

Pedraja, Federico; Aguilera, Pedro; Caputi, Angel A.; Budelli, Ruben

2014-01-01

Modeling the electric field and images in electric fish contributes to a better understanding of the pre-receptor conditioning of electric images. Although the boundary element method has been very successful for calculating images and fields, complex electric organ discharges pose a challenge for active electroreception modeling. We have previously developed a direct method for calculating electric images which takes into account the structure and physiology of the electric organ as well as the geometry and resistivity of fish tissues. The present article reports a general application of our simulator for studying electric images in electric fish with heterogeneous, extended electric organs. We studied three species of Gymnotiformes, including both wave-type (Apteronotus albifrons) and pulse-type (Gymnotus obscurus and Gymnotus coropinae) fish, with electric organs of different complexity. The results are compared with the African (Gnathonemus petersii) and American (Gymnotus omarorum) electric fish studied previously. We address the following issues: 1) how to calculate equivalent source distributions based on experimental measurements, 2) how the complexity of the electric organ discharge determines the features of the electric field and 3) how the basal field determines the characteristics of electric images. Our findings allow us to generalize the hypothesis (previously posed for G. omarorum) in which the perioral region and the rest of the body play different sensory roles. While the “electrosensory fovea” appears suitable for exploring objects in detail, the rest of the body is likened to a “peripheral retina” for detecting the presence and movement of surrounding objects. We discuss the commonalities and differences between species. Compared to African species, American electric fish show a weaker field. This feature, derived from the complexity of distributed electric organs, may endow Gymnotiformes with the ability to emit site-specific signals to be detected in the short range by a conspecific and the possibility to evolve predator avoidance strategies. PMID:25010765

Electric imaging through evolution, a modeling study of commonalities and differences.

PubMed

Pedraja, Federico; Aguilera, Pedro; Caputi, Angel A; Budelli, Ruben

2014-07-01

Modeling the electric field and images in electric fish contributes to a better understanding of the pre-receptor conditioning of electric images. Although the boundary element method has been very successful for calculating images and fields, complex electric organ discharges pose a challenge for active electroreception modeling. We have previously developed a direct method for calculating electric images which takes into account the structure and physiology of the electric organ as well as the geometry and resistivity of fish tissues. The present article reports a general application of our simulator for studying electric images in electric fish with heterogeneous, extended electric organs. We studied three species of Gymnotiformes, including both wave-type (Apteronotus albifrons) and pulse-type (Gymnotus obscurus and Gymnotus coropinae) fish, with electric organs of different complexity. The results are compared with the African (Gnathonemus petersii) and American (Gymnotus omarorum) electric fish studied previously. We address the following issues: 1) how to calculate equivalent source distributions based on experimental measurements, 2) how the complexity of the electric organ discharge determines the features of the electric field and 3) how the basal field determines the characteristics of electric images. Our findings allow us to generalize the hypothesis (previously posed for G. omarorum) in which the perioral region and the rest of the body play different sensory roles. While the "electrosensory fovea" appears suitable for exploring objects in detail, the rest of the body is likened to a "peripheral retina" for detecting the presence and movement of surrounding objects. We discuss the commonalities and differences between species. Compared to African species, American electric fish show a weaker field. This feature, derived from the complexity of distributed electric organs, may endow Gymnotiformes with the ability to emit site-specific signals to be detected in the short range by a conspecific and the possibility to evolve predator avoidance strategies.

Shallow subsurface imaging of the Piano di Pezza active normal fault (central Italy) by high-resolution refraction and electrical resistivity tomography coupled with time domain electromagnetic data

NASA Astrophysics Data System (ADS)

Villani, Fabio; Tulliani, Valerio; Fierro, Elisa; Sapia, Vincenzo; Civico, Riccardo

2015-04-01

The Piano di Pezza fault is the north-westernmost segment of the >20 km long Ovindoli-Pezza active normal fault-system (central Italy). Although existing paleoseismic data document high vertical Holocene slip rates (~1 mm/yr) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time by means of high-resolution seismic and electrical resistivity tomography coupled with time domain electromagnetic (TDEM) measurements the shallow subsurface of a key section of the Piano di Pezza fault. Our surveys cross a ~5 m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing some Late Holocene alluvial fans. We provide 2-D Vp and resistivity images which clearly show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. We can estimate the dip (~50°) and the Holocene vertical displacement of the master fault (~10 m). We also recognize in the hangingwall some low-velocity/low-resistivity regions that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of several paleo-earthquakes older than the Late Holocene events previously recognized by paleoseismic trenching. Conversely, due to the limited investigation depth of seismic and electrical tomography, the estimation of the cumulative amount of Pleistocene throw is hampered. Therefore, to increase the depth of investigation, we performed 7 TDEM measurements along the electrical profile using a 50 m loop size both in central and offset configuration. The recovered 1-D resistivity models show a good match with 2-D resistivity images in the near surface. Moreover, TDEM inversion results indicate that in the hangingwall, ~200 m away from the surface fault trace, the carbonate pre-Quaternary basement may be found at ~90-100 m depth. The combined approach of electrical and seismic data coupled with TDEM measurements provides a robust constraint to the Piano di Pezza fault cumulative offset. Our data are useful for better reconstructing the deep structural setting of the Piano di Pezza basin and assessing the role played by extensional tectonics in its Quaternary evolution.

Monitoring Shallow Subsurface CO2 Migration using Electrical Imaging Technique, Pilot Site in Brazil

NASA Astrophysics Data System (ADS)

Oliva, A.; Chang, H. K.; Moreira, A.

2013-12-01

Carbon Capture and Geological Sequestration (CCGS or CCS) is one of the main technological strategies targeting Greenhouse Gases (GHG) emissions reduction, with special emphasis on carbon dioxide (CO2) coming from industrial sources. CCGS integrates the so called Carbon Management Strategies, as indicated by the Intergovernmental Panel on Climate Change (IPCC), and is the basis of main technical route likely to enable substantial emission reduction in a safe, quick and cost-effective way. Currently one of the main challenges in the area of CO2 storage research is to grant the development, testing and validation of accurate and efficient measuring, monitoring and verification (MMV) techniques to be deployed at the final storage site, targeting maximum storage efficiency at the minimal leakage risk levels. The implementation of the first CO2 MMV field lab in Brazil, located in Florianópolis, Santa Catarina state, offered an excellent opportunity for running controlled release experiments in a real open air environment. The purpose of this work is to present the results of a time lapse monitoring experiment of CO2 migration in both saturated and unsaturated sand-rich sediments, using electrical imaging technique. The experiment covered an area of approximately 6300 m2 and CO2 was continuously injected at depth of 8 m, during 12 days, at an average rate of 90 g/ day, totalizing 1080 g of injected CO2. 2D and 3D electrical images using Wenner array were acquired daily during 13 consecutive days. Comparison of post injection electrical imaging results with pre injection images shows change in resistivity values consistent with migration pathways of CO2. A pronounced increase in resistivity values (up to ~ 500 ohm.m) with respect to the pre-injection values occurs in the vicinity of the injection well. Background values of 530 ohm.m have changed to 1118 ohm.m, right after injection. Changes in resistivity values progressively diminish outward of the well, following groundwater flow path.

In vivo imaging of twist drill drainage for subdural hematoma: a clinical feasibility study on electrical impedance tomography for measuring intracranial bleeding in humans.

PubMed

Dai, Meng; Li, Bing; Hu, Shijie; Xu, Canhua; Yang, Bin; Li, Jianbo; Fu, Feng; Fei, Zhou; Dong, Xiuzhen

2013-01-01

Intracranial bleeding is one of the most severe medical emergencies in neurosurgery. Early detection or diagnosis would largely reduce the rate of disability and mortality, and improve the prognosis of the patients. Electrical Impedance Tomography (EIT) can non-invasively image the internal resistivity distribution within a human body using a ring of external electrodes, and is thus a promising technique to promptly detect the occurrence of intracranial bleedings because blood differs from other brain tissues in resistivity. However, so far there is no experimental study that has determined whether the intracranial resistivity changes in humans could be repeatedly detected and imaged by EIT. Hence, we for the first time attempt to clinically validate this by in vivo imaging the influx and efflux of irrigating fluid (5% dextrose in water, D5W) during the twist-drill drainage operation for the patients with subdural hematoma (SDH). In this study, six patients (four male, two female) with subacute or chronic SDH received the surgical operation in order to evacuate the hematoma around subdural region, and EIT measurements were performed simultaneously on each patient's head. The results showed that the resistivity significantly increased on the corresponding position of EIT images during the influx of D5W and gradually decreased back to baseline during the efflux. In the quantitative analysis, the average resistivity values demonstrated the similar results and had highly linear correlation (R(2) = 0.93 ± 0.06) with the injected D5W volumes, as well as the area of the resistivity gain(R(2) = 0.94 ± 0.05). In conclusion, it was clinically validated that intracranial resistivity changes in humans were detectable and quantifiable by the EIT method. After further technical improvements, EIT has the great potential of being a routine neuroimaging tool for early detection of intracranial bleedings.

In Vivo Imaging of Twist Drill Drainage for Subdural Hematoma: A Clinical Feasibility Study on Electrical Impedance Tomography for Measuring Intracranial Bleeding in Humans

PubMed Central

Xu, Canhua; Yang, Bin; Li, Jianbo; Fu, Feng; Fei, Zhou; Dong, Xiuzhen

2013-01-01

Intracranial bleeding is one of the most severe medical emergencies in neurosurgery. Early detection or diagnosis would largely reduce the rate of disability and mortality, and improve the prognosis of the patients. Electrical Impedance Tomography (EIT) can non-invasively image the internal resistivity distribution within a human body using a ring of external electrodes, and is thus a promising technique to promptly detect the occurrence of intracranial bleedings because blood differs from other brain tissues in resistivity. However, so far there is no experimental study that has determined whether the intracranial resistivity changes in humans could be repeatedly detected and imaged by EIT. Hence, we for the first time attempt to clinically validate this by in vivo imaging the influx and efflux of irrigating fluid (5% dextrose in water, D5W) during the twist-drill drainage operation for the patients with subdural hematoma (SDH). In this study, six patients (four male, two female) with subacute or chronic SDH received the surgical operation in order to evacuate the hematoma around subdural region, and EIT measurements were performed simultaneously on each patient’s head. The results showed that the resistivity significantly increased on the corresponding position of EIT images during the influx of D5W and gradually decreased back to baseline during the efflux. In the quantitative analysis, the average resistivity values demonstrated the similar results and had highly linear correlation (R2 = 0.93±0.06) with the injected D5W volumes, as well as the area of the resistivity gain(R2 = 0.94±0.05). In conclusion, it was clinically validated that intracranial resistivity changes in humans were detectable and quantifiable by the EIT method. After further technical improvements, EIT has the great potential of being a routine neuroimaging tool for early detection of intracranial bleedings. PMID:23372808

Scenario Evaluator for Electrical Resistivity survey pre-modeling tool

USGS Publications Warehouse

Terry, Neil; Day-Lewis, Frederick D.; Robinson, Judith L.; Slater, Lee D.; Halford, Keith J.; Binley, Andrew; Lane, John W.; Werkema, Dale D.

2017-01-01

Geophysical tools have much to offer users in environmental, water resource, and geotechnical fields; however, techniques such as electrical resistivity imaging (ERI) are often oversold and/or overinterpreted due to a lack of understanding of the limitations of the techniques, such as the appropriate depth intervals or resolution of the methods. The relationship between ERI data and resistivity is nonlinear; therefore, these limitations depend on site conditions and survey design and are best assessed through forward and inverse modeling exercises prior to field investigations. In this approach, proposed field surveys are first numerically simulated given the expected electrical properties of the site, and the resulting hypothetical data are then analyzed using inverse models. Performing ERI forward/inverse modeling, however, requires substantial expertise and can take many hours to implement. We present a new spreadsheet-based tool, the Scenario Evaluator for Electrical Resistivity (SEER), which features a graphical user interface that allows users to manipulate a resistivity model and instantly view how that model would likely be interpreted by an ERI survey. The SEER tool is intended for use by those who wish to determine the value of including ERI to achieve project goals, and is designed to have broad utility in industry, teaching, and research.

Combined application of vertical electrical sounding and 2D electrical resistivity imaging for geothermal groundwater characterization: Hammam Sayala hot spring case study (NW Tunisia)

NASA Astrophysics Data System (ADS)

Chabaane, Achref; Redhaounia, Belgacem; Gabtni, Hakim

2017-10-01

The following work is an attempt to enhance and optimize the potential exploitation of the Hammam Sayala thermal spring (NW Tunisia). This hot spring is located at 10 km of South-western Béja city, with higher temperature values around 42 °C and a low discharge value of about 1 l s-1. The geological and structural settings of the study area are complex and associated with faults and Triassic intruded salt and evaporate. An integrated geophysical approach using Electrical Resistivity Tomography (ERT), Induced Polarization (IP) and Vertical Electrical Sounding (VES) techniques can provide a high-resolution subsurface image of the principal geothermal plume and associated pathways. These data were used to determine and understand the mechanisms responsible of the rise of hot water flowing out onto the surface. Our results add new information of the hydrothermal system's context in Hammam Sayala area, which can help to create a therapeutic center opening new perspectives in the Béja region and to encourage regional thermal tourism development.

Imaging and characterizing root systems using electrical impedance tomography

NASA Astrophysics Data System (ADS)

Kemna, A.; Weigand, M.; Kelter, M.; Pfeifer, J.; Zimmermann, E.; Walter, A.

2011-12-01

Root architecture, growth, and activity play an essential role regarding the nutrient uptake of roots in soils. While in recent years advances could be achieved concerning the modeling of root systems, measurement methods capable of imaging, characterizing, and monitoring root structure and dynamics in a non-destructive manner are still lacking, in particular at the field scale. We here propose electrical impedance tomography (EIT) for the imaging of root systems. The approach takes advantage of the low-frequency capacitive electrical properties of the soil-root interface and the root tissue. These properties are based on the induced migration of ions in an externally applied electric field and give rise to characteristic impedance spectra which can be measured by means of electrical impedance spectroscopy. The latter technique was already successfully applied in the 10 Hz to 1 MHz range by Ozier-Lafontaine and Bajazet (2005) to monitor root growth of tomato. We here apply the method in the 1 mHz to 45 kHz range, requiring four-electrode measurements, and demonstrate its implementation and potential in an imaging framework. Images of real and imaginary components of complex electrical conductivity are computed using a finite-element based inversion algorithm with smoothness-constraint regularization. Results from laboratory measurements on rhizotrons with different root systems (barley, rape) show that images of imaginary conductivity delineate the spatial extent of the root system under investigation, while images of real conductivity show a less clear response. As confirmed by numerical simulations, the latter could be explained by the partly compensating electrical conduction properties of epidermis (resistive) and inner root cells (conductive), indicating the limitations of conventional electrical resistivity tomography. The captured spectral behavior exhibits two distinct relaxation processes with Cole-Cole type signatures, which we interpret as the responses of the soil-root interface (phase peak in the range of 10 Hz) and the root tissue (phase peak above 10 kHz). Importantly, our measurements prove an almost linear relationship between root mass and the electrical polarizability associated with the low-frequency relaxation, suggesting the potential of the method to quantify root structural parameters. In future studies we will in particular investigate a hypothesized relationship between time constant and effective root radius. Based on our results, we believe that spectral EIT, by combining the spatial resolution benefits of a tomographic method with the diagnostic capability of spectroscopy, can be developed into a valuable tool for imaging, characterizing, and monitoring root systems both at laboratory and field scales.

Time-lapse electrical resistivity imaging of the thermally affected zone of a Borehole Thermal Energy Storage system near Torino (Northern Italy)

NASA Astrophysics Data System (ADS)

Giordano, N.; Arato, A.; Comina, C.; Mandrone, G.

2017-05-01

A Borehole Thermal Energy Storage living lab was built up nearby Torino (Northern Italy). This living lab aims at testing the ability of the alluvial deposits of the north-western Po Plain to store the thermal energy collected by solar thermal panels and the efficiency of energy storage systems in this climatic context. Different monitoring approaches have been tested and analyzed since the start of the thermal injection in April 2014. Underground temperature monitoring is constantly undertaken by means of several temperature sensors located along the borehole heat exchangers and within the hydraulic circuit. Nevertheless, this can provide only pointwise information about underground temperature distribution. For this reason, a geophysical approach is proposed in order to image the thermally affected zone (TAZ) caused by the heat injection: surface electrical resistivity measurements were carried out with this purpose. In the present paper, results of time-lapse acquisitions during a heating day are reported with the aim of imaging the thermal plume evolution within the subsoil. Resistivity data, calibrated on local temperature measurements, have shown their potentiality in imaging the heated plume of the system and depicting its evolution throughout the day. Different types of data processing were adopted in order to face issues mainly related to a highly urbanized environment. The use of apparent resistivity proved to be in valid agreement with the results of different inversion approaches. The inversion processes did not significantly improve the qualitative and quantitative TAZ imaging in comparison to the pseudo-sections. This suggested the usefulness of apparent resistivity data alone for a rough monitoring of TAZ in this kind of applications.

The use of the multiple-gradient array for geoelectrical resistivity and induced polarization imaging

NASA Astrophysics Data System (ADS)

Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.

2014-12-01

The use of most conventional electrode configurations in electrical resistivity survey is often time consuming and labour intensive, especially when using manual data acquisition systems. Often, data acquisition teams tend to reduce data density so as to speed up field operation thereby reducing the survey cost; but this could significantly degrade the quality and resolution of the inverse models. In the present work, the potential of using the multiple-gradient array, a non-conventional electrode configuration, for practical cost effective and rapid subsurface resistivity and induced polarization mapping was evaluated. The array was used to conduct 2D resistivity and time-domain induced polarization imaging along two traverses in a study site at Ota, southwestern Nigeria. The subsurface was characterised and the main aquifer delineated using the inverse resistivity and chargeability images obtained. The performance of the multiple-gradient array was evaluated by correlating the 2D resistivity and chargeability images with those of the conventional Wenner array as well as the result of some soundings conducted along the same traverses using Schlumberger array. The multiple-gradient array has been found to have the advantage of measurement logistics and improved image resolution over the Wenner array.

[Research on respiration course of human at different postures by electrical impedance tomography].

PubMed

Chen, Xiaoyan; Wu, Jun; Wang, Huaxiang; Li, Da

2010-10-01

In this paper, the respiration courses of human at different postures are reconstructed by electrical impedance tomography (EIT). Conjugate gradient least squares (CGLS) algorithm is applied to reconstruct the resistivity distribution during respiration courses, and the EIT images taken from human at flat lying, left lying, right lying, sitting and prone postures are reconstructed and compared. The relative changes of the resistivity in region of interest (ROI) are analyzed to evidence the influences caused by different postures. Results show that the changes in postures are the most influential factors for the reconstructions, and the EIT images vary with the postures. In human at flat-lying posture, the left and right lungs have larger pulmonary ventilation volume simultaneously, and the EIT-measured data are of lower variability.

Use of electromagnetic-terrain conductivity and DC-resistivity profiling techniques for bedrock characterization at the 15th-of-May City extension, Cairo, Egypt

NASA Astrophysics Data System (ADS)

Aly, Said A.; Farag, Karam S. I.; Atya, Magdy A.; Badr, Mohamed A. M.

2018-06-01

A joint multi-spacing electromagnetic-terrain conductivity meter and DC-resistivity horizontal profiling survey was conducted at the anticipated eastern extensional area of the 15th-of-May City, southeastern Cairo, Egypt. The main objective of the survey was to highlight the applicability, efficiency, and reliability of utilizing such non-invasive surface techniques in a field like geologic mapping, and hence to image both the vertical and lateral electrical resistivity structures of the subsurface bedrock. Consequently, a total of reliable 6 multi-spacing electromagnetic-terrain conductivity meter and 7 DC-resistivity horizontal profiles were carried out between August 2016 and February 2017. All data sets were transformed-inverted extensively and consistently in terms of two-dimensional (2D) electrical resistivity smoothed-earth models. They could be used effectively and inexpensively to interpret the area's bedrock geologic sequence using the encountered consecutive electrically resistive and conductive anomalies. Notably, the encountered subsurface electrical resistivity structures, below all surveying profiles, are correlated well with the mapped geological faults in the field. They even could provide a useful understanding of their faulting fashion. Absolute resistivity values were not necessarily diagnostic, but their vertical and lateral variations could provide more diagnostic information about the layer lateral extensions and thicknesses, and hence suggested reliable geo-electric earth models. The study demonstrated that a detailed multi-spacing electromagnetic-terrain conductivity meter and DC-resistivity horizontal profiling survey can help design an optimal geotechnical investigative program, not only for the whole eastern extensional area of the 15th-of-May City, but also for the other new urban communities within the Egyptian desert.

High-resolution electrical resistivity and aeromagnetic imaging reveal the causative fault of the 2009 Mw 6.0 Karonga, Malawi earthquake

NASA Astrophysics Data System (ADS)

Kolawole, F.; Atekwana, E. A.; Laó-Dávila, D. A.; Abdelsalam, M. G.; Chindandali, P. R.; Salima, J.; Kalindekafe, L.

2018-05-01

Seismic events of varying magnitudes have been associated with ruptures along unknown or incompletely mapped buried faults. The 2009 Mw 6.0 Karonga, Malawi earthquake caused a surface rupture length of 14-18 km along a single W-dipping fault [St. Mary Fault (SMF)] on the hanging wall of the North Basin of the Malawi Rift. Prior to this earthquake, there was no known surface expression or knowledge of the presence of this fault. Although the earthquake damage zone is characterized by surface ruptures and coseismic liquefaction-induced sand blows, the origin of the causative fault and the near-surface structure of the rupture zone are not known. We used high-resolution aeromagnetic and electrical resistivity data to elucidate the relationship between surface rupture locations and buried basement structures. We also acquired electrical resistivity tomography (ERT) profiles along and across the surface rupture zone to image the near-surface structure of the damaged zone. We applied mathematical derivative filters to the aeromagnetic data to enhance basement structures underlying the rupture zone and surrounding areas. Although several magnetic lineaments are visible in the basement, mapped surface ruptures align with a single 37 km long, 148°-162°—striking magnetic lineament, and is interpreted as the ruptured normal fault. Inverted ERT profiles reveal three regional geoelectric layers which consist of 15 m thick layer of discontinuous zones of high and low resistivity values, underlain by a 27 m thick zone of high electrical resistivity (up to 100 Ω m) and a basal layer of lower resistivity (1.0-6.0 Ω m) extending from 42 m depth downwards (the maximum achieved depth of investigation). The geoelectric layers are truncated by a zone of electrical disturbance (electrical mélange) coinciding with areas of coseismic surface rupturing and sediment liquefaction along the ruptured. Our study shows that the 2009 Karonga earthquake was associated with the partial rupture of the buried SMF, and illuminates other potential seismogenic buried faults within the Karonga area of the North Basin. Although our electrical surveys were conducted 6 yr after the 2009 Karonga earthquake, we observe that near-surface lenses of electrically conductive sediments imaged by our ERT profiles, coincide with zones of coseismic surface rupture and liquefaction sand blows. We suggest that the presence of these preserved near-surface lenses of potentially water-saturated sand pose potential hazard in the event of a future earthquake in the area. In addition, our ERT profiles reveal structures that could represent relics of previous earthquake events along the SMF. In addition, our study demonstrates that the integration of ERT and aeromagnetic data can be very useful in illuminating seismogenic buried faults, thereby significantly improving seismic hazard analysis in tectonically active areas.

Real-time 4D electrical resistivity imaging of tracer transport within an energically stimulated fracture zone

NASA Astrophysics Data System (ADS)

Johnson, T. C.

2016-12-01

Hydraulic fracture stimulation is used extensively in the subsurface energy sector to improve access between energy bearing formations and production boreholes. However, large uncertainties exist concerning the location and extent of stimulated fractures, and concerning the behavior of flow within those fractures. This uncertainty often results in significant risks, including induced seismicity and contamination of potable groundwater aquifers. Time-lapse electrical resistivity tomography (ERT) is a proven method of imaging fluid flow within fracture networks, by imaging the change in bulk conductivity induced by the presence of an electrically anomalous tracer within the fracture. In this work we demonstrate characterization and flow monitoring of a stimulated fracture using real-time four-dimensional ERT imaging within an unsaturated rhyolite formation. After stimulation, a conductive tracer was injected into the fracture zone. ERT survey data were continuously and autonomously collected, pre-processed on site, submitted to an off-site high performance computing system for inversion, and returned to the field for inspection. Surveys were collected at approximately 12 minute intervals. Data transmission and inversion required approximately 2 minutes per survey. The time-lapse imaging results show the dominant flow-paths within the stimulated fracture zone, thereby revealing the location and extent of the fracture, and the behavior of tracer flow within the fracture. Ultimately real-time imaging will enable site operators to better understand stimulation operations, and control post-stimulation reservoir operations for optimal performance and environmental protection.

A role for ion implantation in quantum computing

NASA Astrophysics Data System (ADS)

Jamieson, David N.; Prawer, Steven; Andrienko, Igor; Brett, David A.; Millar, Victoria

2001-04-01

We propose to create arrays of phosphorus atoms in silicon for quantum computing using ion implantation. Since the implantation of the ions is essentially random, the yield of usefully spaced atoms is low and therefore some method of registering the passage of a single ion is required. This can be accomplished by implantation of the ions through a thin surface layer consisting of resist. Changes to the chemical and/or electrical properties of the resist will be used to mark the site of the buried ion. For chemical changes, the latent damage will be developed and the atomic force microscope (AFM) used to image the changes in topography. Alternatively, changes in electrical properties (which obviate the need for post-irradiation chemical etching) will be used to register the passage of the ion using scanning tunneling microscopy (STM), the surface current imaging mode of the AFM. We address the central issue of the contrast created by the passage of a single ion through resist layers of PMMA and C 60.

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

Time-lapse electrical resistivity investigations for imaging the grouting injection in shallow subsurface cavities.

PubMed

Farooq, Muhammad; Park, Samgyu; 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.

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.

Conductive contact area estimation for carbon nanotube via interconnects using secondary-electron imaging

NASA Astrophysics Data System (ADS)

Abe, Yusuke; Suzuki, Makoto; Vyas, Anshul; Yang, Cary Y.

2018-01-01

A major challenge for carbon nanotube (CNT) to become a viable replacement of copper and tungsten in the next-generation on-chip via interconnects is the high contact resistance between CNT and metal electrodes. A first step in meeting this challenge is an accurate characterization of via contact resistance. In this paper, the scanning electron microscope (SEM) image contrast at low landing energy is employed to estimate the conductive CNT area inside vias. The total conductive CNT area inside each via is deduced using SEM image with 0.1 keV landing energy and a specified threshold brightness, yielding via resistance versus CNT area behavior, which correlates well with electrical nanoprobing measurements of via resistance. Monte Carlo simulation of secondary electron generation lends further support for our analysis and suggests that the residue covering the CNT does not affect the conduction across the contact for residue thickness below 1 nm. This imaging and analysis technique can add much value to CNT via interconnect contact characterization.

Understanding the conductive channel evolution in Na:WO3-x-based planar devices

NASA Astrophysics Data System (ADS)

Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

2015-03-01

An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07545e

Dynamic imaging in electrical impedance tomography of the human chest with online transition matrix identification.

PubMed

Moura, Fernando Silva; Aya, Julio Cesar Ceballos; Fleury, Agenor Toledo; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez

2010-02-01

One of the electrical impedance tomography objectives is to estimate the electrical resistivity distribution in a domain based only on electrical potential measurements at its boundary generated by an imposed electrical current distribution into the boundary. One of the methods used in dynamic estimation is the Kalman filter. In biomedical applications, the random walk model is frequently used as evolution model and, under this conditions, poor tracking ability of the extended Kalman filter (EKF) is achieved. An analytically developed evolution model is not feasible at this moment. The paper investigates the identification of the evolution model in parallel to the EKF and updating the evolution model with certain periodicity. The evolution model transition matrix is identified using the history of the estimated resistivity distribution obtained by a sensitivity matrix based algorithm and a Newton-Raphson algorithm. To numerically identify the linear evolution model, the Ibrahim time-domain method is used. The investigation is performed by numerical simulations of a domain with time-varying resistivity and by experimental data collected from the boundary of a human chest during normal breathing. The obtained dynamic resistivity values lie within the expected values for the tissues of a human chest. The EKF results suggest that the tracking ability is significantly improved with this approach.

Novel laboratory methods for determining the fine scale electrical resistivity structure of core

NASA Astrophysics Data System (ADS)

Haslam, E. P.; Gunn, D. A.; Jackson, P. D.; Lovell, M. A.; Aydin, A.; Prance, R. J.; Watson, P.

2014-12-01

High-resolution electrical resistivity measurements are made on saturated rocks using novel laboratory instrumentation and multiple electrical voltage measurements involving in principle a four-point electrode measurement but with a single, moving electrode. Flat, rectangular core samples are scanned by varying the electrode position over a range of hundreds of millimetres with an accuracy of a tenth of a millimetre. Two approaches are tested involving a contact electrode and a non-contact electrode arrangement. The first galvanic method uses balanced cycle switching of a floating direct current (DC) source to minimise charge polarisation effects masking the resistivity distribution related to fine scale structure. These contacting electrode measurements are made with high common mode noise rejection via differential amplification with respect to a reference point within the current flow path. A computer based multifunction data acquisition system logs the current through the sample and voltages along equipotentials from which the resistivity measurements are derived. Multiple measurements are combined to create images of the surface resistivity structure, with variable spatial resolution controlled by the electrode spacing. Fine scale sedimentary features and open fractures in saturated rocks are interpreted from the measurements with reference to established relationships between electrical resistivity and porosity. Our results successfully characterise grainfall lamination and sandflow cross-stratification in a brine saturated, dune bedded core sample representative of a southern North Sea reservoir sandstone, studied using the system in constant current, variable voltage mode. In contrast, in a low porosity marble, identification of open fracture porosity against a background very low matrix porosity is achieved using the constant voltage, variable current mode. This new system is limited by the diameter of the electrode that for practical reasons can only be reduced to between 0.5 and 0.75 mm. Improvements to this resolution may be achieved by further reducing the electrode footprint to 0.1 mm × 0.1 mm using a novel high-impedance, non-contact potential probe. Initial results with this non-contact electric potential sensor indicate the possibility for generating images with grain-scale resolution.

High-throughput electrical characterization for robust overlay lithography control

NASA Astrophysics Data System (ADS)

Devender, Devender; Shen, Xumin; Duggan, Mark; Singh, Sunil; Rullan, Jonathan; Choo, Jae; Mehta, Sohan; Tang, Teck Jung; Reidy, Sean; Holt, Jonathan; Kim, Hyung Woo; Fox, Robert; Sohn, D. K.

2017-03-01

Realizing sensitive, high throughput and robust overlay measurement is a challenge in current 14nm and advanced upcoming nodes with transition to 300mm and upcoming 450mm semiconductor manufacturing, where slight deviation in overlay has significant impact on reliability and yield1). Exponentially increasing number of critical masks in multi-patterning lithoetch, litho-etch (LELE) and subsequent LELELE semiconductor processes require even tighter overlay specification2). Here, we discuss limitations of current image- and diffraction- based overlay measurement techniques to meet these stringent processing requirements due to sensitivity, throughput and low contrast3). We demonstrate a new electrical measurement based technique where resistance is measured for a macro with intentional misalignment between two layers. Overlay is quantified by a parabolic fitting model to resistance where minima and inflection points are extracted to characterize overlay control and process window, respectively. Analyses using transmission electron microscopy show good correlation between actual overlay performance and overlay obtained from fitting. Additionally, excellent correlation of overlay from electrical measurements to existing image- and diffraction- based techniques is found. We also discuss challenges of integrating electrical measurement based approach in semiconductor manufacturing from Back End of Line (BEOL) perspective. Our findings open up a new pathway for accessing simultaneous overlay as well as process window and margins from a robust, high throughput and electrical measurement approach.

Improving Powder Magnetic Core Properties via Application of Thin, Insulating Silica-Nanosheet Layers on Iron Powder Particles

PubMed Central

Ishizaki, Toshitaka; Nakano, Hideyuki; Tajima, Shin; Takahashi, Naoko

2016-01-01

A thin, insulating layer with high electrical resistivity is vital to achieving high performance of powder magnetic cores. Using layer-by-layer deposition of silica nanosheets or colloidal silica over insulating layers composed of strontium phosphate and boron oxide, we succeeded in fabricating insulating layers with high electrical resistivity on iron powder particles, which were subsequently used to prepare toroidal cores. The compact density of these cores decreased after coating with colloidal silica due to the substantial increase in the volume, causing the magnetic flux density to deteriorate. Coating with silica nanosheets, on the other hand, resulted in a higher electrical resistivity and a good balance between high magnetic flux density and low iron loss due to the thinner silica layers. Transmission electron microscopy images showed that the thickness of the colloidal silica coating was about 700 nm, while that of the silica nanosheet coating was 30 nm. There was one drawback to using silica nanosheets, namely a deterioration in the core mechanical strength. Nevertheless, the silica nanosheet coating resulted in nanoscale-thick silica layers that are favorable for enhancing the electrical resistivity. PMID:28336835

Dynamic electrical impedance imaging with the interacting multiple model scheme.

PubMed

Kim, Kyung Youn; Kim, Bong Seok; Kim, Min Chan; Kim, Sin; Isaacson, David; Newell, Jonathan C

2005-04-01

In this paper, an effective dynamical EIT imaging scheme is presented for on-line monitoring of the abruptly changing resistivity distribution inside the object, based on the interacting multiple model (IMM) algorithm. The inverse problem is treated as a stochastic nonlinear state estimation problem with the time-varying resistivity (state) being estimated on-line with the aid of the IMM algorithm. In the design of the IMM algorithm multiple models with different process noise covariance are incorporated to reduce the modeling uncertainty. Simulations and phantom experiments are provided to illustrate the proposed algorithm.

Spatially distributed characterization of hyporheic solute transport during baseflow recession in a headwater mountain stream using electrical geophysical imaging

Treesearch

Adam S. Ward; Michael N. Gooseff; Michael Fitzgerald; Thomas J. Voltz; Kamini Singha

2014-01-01

The transport of solutes along hyporheic flowpaths is recognized as central to numerous biogeochemical cycles, yet our understanding of how this transport changes with baseflow recession, particularly in a spatially distributed manner, is limited. We conducted four steady-state solute tracer injections and collected electrical resistivity data to characterize hyporheic...

Near-surface high resolution imaging of a metallogenic zone in the northern fringe of Dalma volcanics in eastern India using electrical resistivity tomography

NASA Astrophysics Data System (ADS)

Adhikari, P. K.; Srivastava, Shalivahan; Maurya, Ved P.; Tripathi, Anurag; Singh, Roshan K.; Bage, Ashish K.

2017-06-01

Electrical resistivity tomography (ERT) is a useful tool to map near-surface conducting anomalies. The detailed ERT survey was taken over an already defined conducting zone on a regional scale through a magnetotelluric (MT) survey, in order to provide better resolution of the subsurface structure within the study area. The survey lines were carried out crossing the delineated conducting zone through MT giving a dense coverage over the area. The ERT survey were carried out along 15 lines covering an area of ~1 km2 with a line spacing of ~50 m in the northern fringe of the Dalma volcanics (DVs). The study utilised the 61-channel cum 64-electrode resistivity equipment, FlashRES-Universal ERT multi-electrode data acquisition system, developed by ZZ Resistivity Imaging, Australia. Data has been acquired both through conventional arrays i.e. Wenner, Schlumberger and ZZ unconventional arrays. Inversion of the data set have been performed using 2.5D finite element conjugate gradient algorithm after performing the quality check. Resistivity models along all the lines were obtained using Wenner, Schlumberger and combination of Wenner, Schlumberger and ZZ arrays. Resistivity models resolved four major zones: (1) resistivity less than 1 Ωm (2) resistivity 1-10 Ωm (3) resistivity 10-100 Ωm and (4) resistivity more than 100 Ωm . The resistivity results corroborate well with the geological succession from the drilling data. The conducting zones with resistivity values ranging from 1-10 Ωm correlates with the Lower Dalma volcanics while the Upper Dalma volcanics corresponds to the regions with resistivity values of less than 1 Ωm. The Upper Dalma volcanics corresponds to the metallogeny while the depth to the top of the ore body is ~25 m.

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.

Electrical conductivity imaging using gradient B, decomposition algorithm in magnetic resonance electrical impedance tomography (MREIT).

PubMed

Park, Chunjae; Kwon, Ohin; Woo, Eung Je; Seo, Jin Keun

2004-03-01

In magnetic resonance electrical impedance tomography (MREIT), we try to visualize cross-sectional conductivity (or resistivity) images of a subject. We inject electrical currents into the subject through surface electrodes and measure the z component Bz of the induced internal magnetic flux density using an MRI scanner. Here, z is the direction of the main magnetic field of the MRI scanner. We formulate the conductivity image reconstruction problem in MREIT from a careful analysis of the relationship between the injection current and the induced magnetic flux density Bz. Based on the novel mathematical formulation, we propose the gradient Bz decomposition algorithm to reconstruct conductivity images. This new algorithm needs to differentiate Bz only once in contrast to the previously developed harmonic Bz algorithm where the numerical computation of (inverted delta)2Bz is required. The new algorithm, therefore, has the important advantage of much improved noise tolerance. Numerical simulations with added random noise of realistic amounts show the feasibility of the algorithm in practical applications and also its robustness against measurement noise.

Dust Accumulation on Mars

NASA Technical Reports Server (NTRS)

2005-01-01

Since landing on Mars a year ago, NASA's pair of six-wheeled geologists have been constantly exposed to martian winds and dust. As a result, the Spirit rover has gradually experienced a slight decline in power as a thin layer of dust has accumulated on the solar panels, blocking some of the sunlight that is converted to electricity. In this enlarged image of a postage-stamp-size (3-centimeter-square, 1.2-inch-square) portion of one of Spirit's solar panels, a fine layer of martian dust coats electrical connections and metal surfaces. Individual silt grains or clumps of dust are visible where sediment has accumulated in crevices between solar cells and circuits. The upper right half of the image shows the edge of one of the rover's solar cells. The lower left half shows electrical wires bonded with silicon adhesive to the underlying composite surface; the circular abrasions are the result of sanding by hand on Earth. The braided wire is connected to a thermocouple used to measure temperature based on electrical resistance. Spirit took this image with its microscopic imager on martian day, or sol, 350 (Dec. 26, 2004).

Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

NASA Astrophysics Data System (ADS)

Song, Xizi; Xu, Yanbin; Dong, Feng

2017-04-01

Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results.

Resolving Large Pre-glacial Valleys Buried by Glacial Sediment Using Electric Resistivity Imaging (ERI)

NASA Astrophysics Data System (ADS)

Schmitt, D. R.; Welz, M.; Rokosh, C. D.; Pontbriand, M.-C.; Smith, D. G.

2004-05-01

Two-dimensional electric resistivity imaging (ERI) is the most exciting and promising geological tool in geomorphology and stratigraphy since development of ground-penetrating radar. Recent innovations in 2-D ERI provides a non-intrusive mean of efficiently resolving complex shallow subsurface structures under a number of different geological scenarios. In this paper, we test the capacity of ERI to image two large pre-late Wisconsinan-aged valley-fills in central Alberta and north-central Montana. Valley-fills record the history of pre-glacial and glacial sedimentary deposits. These fills are of considerable economical value as groundwater aquifers, aggregate resources (sand and gravel), placers (gold, diamond) and sometime gas reservoirs in Alberta. Although the approximate locations of pre-glacial valley-fills have been mapped, the scarcity of borehole (well log) information and sediment exposures make accurate reconstruction of their stratigraphy and cross-section profiles difficult. When coupled with borehole information, ERI successfully imaged three large pre-glacial valley-fills representing three contrasting geological settings. The Sand Coulee segment of the ancestral Missouri River, which has never been glaciated, is filled by electrically conductive pro-glacial lacustrine deposits over resistive sandstone bedrock. By comparison, the Big Sandy segment of the ancestral Missouri River valley has a complex valley-fill composed of till units interbedded with glaciofluvial gravel and varved clays over conductive shale. The fill is capped by floodplain, paludal and low alluvial fan deposits. The pre-glacial Onoway Valley (the ancestral North Saskatchewan River valley) is filled with thick, resistive fluvial gravel over conductive shale and capped with conductive till. The cross-sectional profile of each surveyed pre-glacial valley exhibits discrete benches (terraces) connected by steep drops, features that are hard to map using only boreholes. Best quality ERI results were obtained along the Sand Coulee and Onoway transects where the contrast between the bedrock and valley-fill was large and the surficial sediment was homogeneous. The effects of decreasing reliability with depth, 3-D anomalies, principles of equivalence and suppression, and surface inhomogeneity on the image quality are discussed.

A new method for electric impedance imaging using an eddy current with a tetrapolar circuit.

PubMed

Ahsan-Ul-Ambia; Toda, Shogo; Takemae, Tadashi; Kosugi, Yukio; Hongo, Minoru

2009-02-01

A new contactless technique for electrical impedance imaging, using an eddy current managed along with the tetrapolar circuit method, is proposed. The eddy current produced by a magnetic field is superimposed on a constant current that is normally used in the tetrapolar circuit method, and thus is used to control the current distribution in the body. By changing the current distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.

A method for recording resistance changes non-invasively during neuronal depolarization with a view to imaging brain activity with electrical impedance tomography.

PubMed

Gilad, Ori; Ghosh, Anthony; Oh, Dongin; Holder, David S

2009-05-30

Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. The principle is that current remains in the extracellular space at rest but passes into the intracellular space during depolarization through open ion channels. As current passes into the intracellular space across the capacitance of cell membranes at higher frequencies, applied current needs to be below 100 Hz. A method is presented for its measurement with subtraction of the contemporaneous evoked potentials which occur in the same frequency band. Neuronal activity is evoked by stimulation and resistance is recorded from the potentials resulting from injection of a constant current square wave at 1 Hz with amplitude less than 25% of the threshold for stimulating neuronal activity. Potentials due to the evoked activity and the injected square wave are removed by subtraction. The method was validated with compound action potentials in crab walking leg nerve. Resistance changes of -0.85+/-0.4% (mean+/-SD) occurred which decreased from -0.97+/-0.43% to -0.46+/-0.16% with spacing of impedance current application electrodes from 2 to 8 mm but did not vary significantly with applied currents of 1-10 microA. These tallied with biophysical modelling, and so were consistent with a genuine physiological origin. This method appears to provide a reproducible and artefact free means for recording resistance changes during neuronal activity which could lead to the long-term goal of imaging of fast neural activity in the brain.

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 water plume as occurred in the homogeneous agricultural soils, the location of the infiltrated water seems to be highly influenced by the soil heterogeneity, and the water front is scattered into discontinuous layers and travels in additional directions. The geophysical results during infiltration correlate well with soil compaction data. It follows that the ERI method can be used as a proxy for soil compaction and water content variations in agricultural applications. In a natural environment, ERI successfully maps the tree root zone of mature trees. Applications include continuous water content monitoring in high value cash crops, such as viticulture (precision agriculture).

Characterizing Uncertainty In Electrical Resistivity Tomography Images Due To Subzero Temperature Variability

NASA Astrophysics Data System (ADS)

Herring, T.; Cey, E. E.; Pidlisecky, A.

2017-12-01

Time-lapse electrical resistivity tomography (ERT) is used to image changes in subsurface electrical conductivity (EC), e.g. due to a saline contaminant plume. Temperature variation also produces an EC response, which interferes with the signal of interest. Temperature compensation requires the temperature distribution and the relationship between EC and temperature, but this relationship at subzero temperatures is not well defined. The goal of this study is to examine how uncertainty in the subzero EC/temperature relationship manifests in temperature corrected ERT images, especially with respect to relevant plume parameters (location, contaminant mass, etc.). First, a lab experiment was performed to determine the EC of fine-grained glass beads over a range of temperatures (-20° to 20° C) and saturations. The measured EC/temperature relationship was then used to add temperature effects to a hypothetical EC model of a conductive plume. Forward simulations yielded synthetic field data to which temperature corrections were applied. Varying the temperature/EC relationship used in the temperature correction and comparing the temperature corrected ERT results to the synthetic model enabled a quantitative analysis of the error of plume parameters associated with temperature variability. Modeling possible scenarios in this way helps to establish the feasibility of different time-lapse ERT applications by quantifying the uncertainty associated with parameter(s) of interest.

Rock classification based on resistivity patterns in electrical borehole wall images

NASA Astrophysics Data System (ADS)

Linek, Margarete; Jungmann, Matthias; Berlage, Thomas; Pechnig, Renate; Clauser, Christoph

2007-06-01

Electrical borehole wall images represent grey-level-coded micro-resistivity measurements at the borehole wall. Different scientific methods have been implemented to transform image data into quantitative log curves. We introduce a pattern recognition technique applying texture analysis, which uses second-order statistics based on studying the occurrence of pixel pairs. We calculate so-called Haralick texture features such as contrast, energy, entropy and homogeneity. The supervised classification method is used for assigning characteristic texture features to different rock classes and assessing the discriminative power of these image features. We use classifiers obtained from training intervals to characterize the entire image data set recovered in ODP hole 1203A. This yields a synthetic lithology profile based on computed texture data. We show that Haralick features accurately classify 89.9% of the training intervals. We obtained misclassification for vesicular basaltic rocks. Hence, further image analysis tools are used to improve the classification reliability. We decompose the 2D image signal by the application of wavelet transformation in order to enhance image objects horizontally, diagonally and vertically. The resulting filtered images are used for further texture analysis. This combined classification based on Haralick features and wavelet transformation improved our classification up to a level of 98%. The application of wavelet transformation increases the consistency between standard logging profiles and texture-derived lithology. Texture analysis of borehole wall images offers the potential to facilitate objective analysis of multiple boreholes with the same lithology.

Dynamic Properties of Electrotonic Coupling between Cells of Early Xenopus Embryos

PubMed Central

DiCaprio, R. A.; French, A. S.; Sanders, E. J.

1974-01-01

Frequency response functions were measured between the cells of Xenopus laevis embryos during the first two cleavage stages. Linear systems theory was then used to produce electronic models which account for the electrical behavior of the systems. Coupling between the cells may be explained by models which have simple resistive elements joining each cell to its neighbors. The vitelline, or fertilization, membrane which surrounds the embryos has no detectable resistance to the passage of electric current. The electrical properties of the four-cell embryo can only be explained by the existence of individual junctions linking each pair of cells. This arrangement suggests that electrotonic coupling is important in the development of the embryos, at least until the four-cell stage. ImagesFIGURE 5FIGURE 14FIGURE 15 PMID:19431351

Electrical resistance tomography to monitor unsaturated moisture flow in cementitious materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hallaji, Milad; Seppänen, Aku; Pour-Ghaz, Mohammad, E-mail: mpourghaz@ncsu.edu

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 tomore » show approximately the shape and position of the water front even if the flow is nonuniform.« less

Imaging of electrical response of NiO x under controlled environment with sub-25-nm resolution

DOE PAGES

Jacobs, Christopher B.; Ievlev, Anton V.; Collins, Liam F.; ...

2016-07-19

The spatially resolved electrical response of rf-sputtered polycrystalline NiO x films composed of 40 nm crystallites was investigated under different relative humidity levels (RH). The topological and electrical properties (surface potential and resistance) were characterized using Kelvin probe force microscopy (KPFM) and conductive scanning probe microscopy at 0%, 50%, and 80% relative humidity with sub 25nm resolution. The surface potential of NiO x decreased by about 180 mV and resistance decreased in a nonlinear fashion by about 2 G when relative humidity was increased from 0% to 80%. The dimensionality of surface features obtained through autocorrelation analysis of topological, surfacemore » potential and resistance maps increased linearly with increased relative humidity as water was adsorbed onto the film surface. Spatially resolved surface potential and resistance of the NiO x films were found to be heterogeneous, with distinct features that grew in size from about 60 nm to 175 nm between 0% and 80% RH levels, respectively. Here, we find that the changes in the heterogeneous character of the NiO films are consistent through the topological, surface potential, and resistance measurements, suggesting that the nanoscale surface potential and resistance properties converge with the mesoscale properties as water is adsorbed onto the NiO x film.« less

Monitoring subterraneous water regime at the new Ain Shams university campus in Al-Obour city (northeast of Cairo-Egypt) using both azimuthal very low frequency-electromagnetic and DC-resistivity sounding techniques

NASA Astrophysics Data System (ADS)

Farag, Karam S. I.; Abd El-Aal, Mohamed H.; Garamoon, Hassan K. F.

2018-07-01

A joint azimuthal very low frequency-electromagnetic (VLF-EM) and DC-resistivity sounding survey was conducted at the new Ain Shams university campus in Al-Obour city, northwest of Cairo, Egypt. The main objective of the survey was to highlight the applicability and reliability of such non-invasive surface techniques in mapping and monitoring both the vertical and lateral electrical conductivity structures of waterlogged areas, by subterraneous water accumulations, at the campus site. Consequently, a total of 743 azimuthal VLF-EM and 4 DC-resistivity soundings were carried out in June, 2011, 2012 and 2013. The data were interpreted extensively and consistently in terms of two-dimensional (2D) transformed EM equivalent current-density and stitched inverted electrical resistivity models, without using any geological a-priori information. They could be used effectively to image the local anomalous lower electrical resistivity (higher EM equivalent current-density) structures and their near-surface spreading with time, due to the excessive accumulations of subterraneous water at the campus site. The study demonstrated that a regional azimuthal VLF-EM and DC-resistivity sounding survey could help design an optimal dewatering program for the whole city, at greatly reduced execution time.

Analysis of electroluminescence images in small-area circular CdTe solar cells

NASA Astrophysics Data System (ADS)

Bokalič, Matevž; Raguse, John; Sites, James R.; Topič, Marko

2013-09-01

The electroluminescence (EL) imaging process of small area solar cells is investigated in detail to expose optical and electrical effects that influence image acquisition and corrupt the acquired image. An approach to correct the measured EL images and to extract the exact EL radiation as emitted from the photovoltaic device is presented. EL images of circular cadmium telluride (CdTe) solar cells are obtained under different conditions. The power-law relationship between forward injection current and EL emission and a negative temperature coefficient of EL radiation are observed. The distributed Simulation Program with Integrated Circuit Emphasis (SPICE®) model of the circular CdTe solar cell is used to simulate the dark J-V curve and current distribution under the conditions used during EL measurements. Simulation results are presented as circularly averaged EL intensity profiles, which clearly show that the ratio between resistive parameters determines the current distribution in thin-film solar cells. The exact resistance values for front and back contact layers and for CdTe bulk layer are determined at different temperatures, and a negative temperature coefficient for the CdTe bulk resistance is observed.

Analysis and comparison of magnetic sheet insulation tests

NASA Astrophysics Data System (ADS)

Marion-Péra, M. C.; Kedous-Lebouc, A.; Cornut, B.; Brissonneau, P.

1994-05-01

Magnetic circuits of electrical machines are divided into coated sheets in order to limit eddy currents. The surface insulation resistance of magnetic sheets is difficult to evaluate because it depends on parameters like pressure and covers a wide range of values. Two methods of measuring insulation resistance are analyzed: the standardized 'Franklin device' and a tester developed by British Steel Electrical. Their main drawback is poor local repeatability. The Franklin method allows better quality control of industrial process because it measures only one insulating layer at a time. It also gives more accurate images of the distribution of possible defects. Nevertheless, both methods lead to similar classifications of insulation efficiency.

Geoelectrical Tomography for landslide monitoring: state-of-the-art and future challenges.

NASA Astrophysics Data System (ADS)

Lapenna, V.; Perrone, A.; Piscitelli, S.

2011-12-01

Recently, novel algorithms for tomographic data inversion, robust models for describing the hydrogeophysical processes and new sensor networks for the field data acquisition have rapidly transformed the geoelectrical methods in a powerful and cost-effective tool for geo-hazard monitoring. These technological and methodological improvements disclose the way for a wide spectra of interesting and challenging applications in geo-hazards monitoring: reconstruction of landslide geometry; identification of fluid and gas uprising in volcanic areas; electrical imaging of seismic faults etc.. We briefly resume the current state-of-the-art of the geoelectrical methods in landslide monitoring and introduce new and emerging applications of the geoelectrical tomographic methods. An overview of the more interesting results obtained in different areas of Italian territory affected by wide and diffuse hydrogeological instability phenomena will be presented and discussed. We will focus the attention to some recent results obtained in the frame of national and international projects (Morfeo, Eurorisk/Preview, DORIS). One of the key challenges for the future will be the integration of active (Resistivity) and passive (Self-Potential) measurements for obtaining 2D, 3D and 4D (time-lapse) electrical tomographies able to follow the spatial and temporal dynamics of electrical parameters (i.e. resistivity, self-potential) inside the landslide body. The resistivity imaging can be applied for illuminating the sliding surfaces and for mapping the time-dependent changes of water content in vadose zones, while the Self Potential imaging could give a significant contribute for delineating the groundwater circulation patterns and to the early identification of triggering factors.

Contact inspection of Si nanowire with SEM voltage contrast

NASA Astrophysics Data System (ADS)

Ohashi, Takeyoshi; Yamaguchi, Atsuko; Hasumi, Kazuhisa; Ikota, Masami; Lorusso, Gian; Horiguchi, Naoto

2018-03-01

A methodology to evaluate the electrical contact between nanowire (NW) and source/drain (SD) in NW FETs was investigated with SEM voltage contrast (VC). The electrical defects were robustly detected by VC. The validity of the inspection result was verified by TEM physical observations. Moreover, estimation of the parasitic resistance and capacitance was achieved from the quantitative analysis of VC images which were acquired with different scan conditions of electron beam (EB). A model considering the dynamics of EB-induce charging was proposed to calculate the VC. The resistance and capacitance can be determined by comparing the model-based VC with experimentally obtained VC. Quantitative estimation of resistance and capacitance would be valuable not only for more accurate inspection, but also for identification of the defect point.

Micro-electro-fluidic grids for nematodes: a lens-less, image-sensor-less approach for on-chip tracking of nematode locomotion.

PubMed

Liu, Peng; Martin, Richard J; Dong, Liang

2013-02-21

This paper reports on the development of a lens-less and image-sensor-less micro-electro-fluidic (MEF) approach for real-time monitoring of the locomotion of microscopic nematodes. The technology showed promise for overcoming the constraint of the limited field of view of conventional optical microscopy, with relatively low cost, good spatial resolution, and high portability. The core of the device was microelectrode grids formed by orthogonally arranging two identical arrays of microelectrode lines. The two microelectrode arrays were spaced by a microfluidic chamber containing a liquid medium of interest. As a nematode (e.g., Caenorhabditis elegans) moved inside the chamber, the invasion of part of its body into some intersection regions between the microelectrodes caused changes in the electrical resistance of these intersection regions. The worm's presence at, or absence from, a detection unit was determined by a comparison between the measured resistance variation of this unit and a pre-defined threshold resistance variation. An electronic readout circuit was designed to address all the detection units and read out their individual electrical resistances. By this means, it was possible to obtain the electrical resistance profile of the whole MEF grid, and thus, the physical pattern of the swimming nematode. We studied the influence of a worm's body on the resistance of an addressed unit. We also investigated how the full-frame scanning and readout rates of the electronic circuit and the dimensions of a detection unit posed an impact on the spatial resolution of the reconstructed images of the nematode. Other important issues, such as the manufacturing-induced initial non-uniformity of the grids and the electrotaxic behaviour of nematodes, were also studied. A drug resistance screening experiment was conducted by using the grids with a good resolution of 30 × 30 μm(2). The phenotypic differences in the locomotion behaviours (e.g., moving speed and oscillation frequency extracted from the reconstructed images with the help of software) between the wild-type (N2) and mutant (lev-8) C. elegans worms in response to different doses of the anthelmintic drug, levamisole, were investigated. The locomotive parameters obtained by the MEF grids agreed well with those obtained by optical microscopy. Therefore, this technology will benefit whole-animal assays by providing a structurally simple, potentially cost-effective device capable of tracking the movement and phenotypes of important nematodes in various microenvironments.

Three-dimensional electrical impedance tomography based on the complete electrode model.

PubMed

Vauhkonen, P J; Vauhkonen, M; Savolainen, T; Kaipio, J P

1999-09-01

In electrical impedance tomography an approximation for the internal resistivity distribution is computed based on the knowledge of the injected currents and measured voltages on the surface of the body. It is often assumed that the injected currents are confined to the two-dimensional (2-D) electrode plane and the reconstruction is based on 2-D assumptions. However, the currents spread out in three dimensions and, therefore, off-plane structures have significant effect on the reconstructed images. In this paper we propose a finite element-based method for the reconstruction of three-dimensional resistivity distributions. The proposed method is based on the so-called complete electrode model that takes into account the presence of the electrodes and the contact impedances. Both the forward and the inverse problems are discussed and results from static and dynamic (difference) reconstructions with real measurement data are given. It is shown that in phantom experiments with accurate finite element computations it is possible to obtain static images that are comparable with difference images that are reconstructed from the same object with the empty (saline filled) tank as a reference.

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

NASA Astrophysics Data System (ADS)

Campanyà, Joan; Ogaya, Xènia; Jones, Alan G.; Rath, Volker; Vozar, Jan; Meqbel, Naser

2016-12-01

As a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in 2-D and 3-D environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomalies surrounding the acquisition site. This behaviour complicates the characterization of the electrical resistivity distribution of the subsurface, particularly in complex areas. In this manuscript we assess the main advantages of complementing the standard MT impedance tensor (Z) data with interstation horizontal magnetic tensor (H) and geomagnetic transfer function (T) data in constraining the subsurface in a 3-D environment beneath a MT profile. Our analysis was performed using synthetic responses with added normally distributed and scattered random noise. The sensitivity of each type of data to different resistivity anomalies was evaluated, showing that the degree to which each site and each period is affected by the same anomaly depends on the type of data. A dimensionality analysis, using Z, H and T data, identified the presence of the 3-D anomalies close to the profile, suggesting a 3-D approach for recovering the electrical resistivity values of the subsurface. Finally, the capacity for recovering the geoelectrical structures of the subsurface was evaluated by performing joint inversion using different data combinations, quantifying the differences between the true synthetic model and the models from inversion process. Four main improvements were observed when performing joint inversion of Z, H and T data: (1) superior precision and accuracy at characterizing the electrical resistivity values of the anomalies below and outside the profile; (2) the potential to recover high electrical resistivity anomalies that are poorly recovered using Z data alone; (3) improvement in the characterization of the bottom and lateral boundaries of the anomalies with low electrical resistivity; and (4) superior imaging of the horizontal continuity of structures with low electrical resistivity. These advantages offer new opportunities for the MT method by making the results from a MT profile in a 3-D environment more convincing, supporting the possibility of high-resolution studies in 3-D areas without expending a large amount of economical and computational resources, and also offering better resolution of targets with high electrical resistivity.

Detecting defective electrical components in heterogeneous infra-red images by spatial control charts

NASA Astrophysics Data System (ADS)

Jamshidieini, Bahman; Fazaee, Reza

2016-05-01

Distribution network components connect machines and other loads to electrical sources. If resistance or current of any component is more than specified range, its temperature may exceed the operational limit which can cause major problems. Therefore, these defects should be found and eliminated according to their severity. Although infra-red cameras have been used for inspection of electrical components, maintenance prioritization of distribution cubicles is mostly based on personal perception and lack of training data prevents engineers from developing image processing methods. New research on the spatial control chart encouraged us to use statistical approaches instead of the pattern recognition for the image processing. In the present study, a new scanning pattern which can tolerate heavy autocorrelation among adjacent pixels within infra-red image was developed and for the first time combination of kernel smoothing, spatial control charts and local robust regression were used for finding defects within heterogeneous infra-red images of old distribution cubicles. This method does not need training data and this advantage is crucially important when the training data is not available.

Development of an Arduino-based electrical impedance tomography system with application to dam internal erosion detection

NASA Astrophysics Data System (ADS)

Masi, Matteo; Ferdos, Farzad; Losito, Gabriella; Solari, Luca

2016-04-01

Electrical Impedance Tomography (EIT) is a technique for the imaging of the electrical properties of conductive materials. In EIT, the spatial distribution of the electrical resistivity or electrical conductivity within a domain is reconstructed using measurements made with electrodes placed at the boundaries of the domain. Data acquisition is typically made by applying an electrical current to the object under investigation using a set of electrodes, and measuring the developed voltage between the other electrodes. The tomographic image is then obtained using an inversion algorithm. This work describes the implementation of a simple and low cost 3D EIT measurement system suitable for laboratory-scale studies. The system was specifically developed for the time-lapse imaging of soil samples subjected to erosion processes during laboratory tests. The tests reproduce the process of internal erosion of soil particles by water flow within a granular media; this process is one of the most common causes of failure of earthen levees and embankment dams. The measurements needed strict requirements of speed and accuracy due to the varying time scale and magnitude of these processes. The developed EIT system consists of a PC which controls I/O cards (multiplexers) through the Arduino micro-controller, an external current generator, a digital acquisition device (DAQ), a power supply and the electrodes. The ease of programming of the Arduino interface greatly helped the implementation of custom acquisition software, increasing the overall flexibility of the system and the creation of specific acquisition schemes and configurations. The system works with a multi-electrode configuration of up to 48 channels but it was designed to be upgraded to an arbitrary large number of electrodes by connecting additional multiplexer cards (> 96 electrodes). The acquisition was optimized for multi-channel measurements so that the overall time of acquisition is dramatically reduced compared to the single channel instrumentation. The accuracy and operation were tested under different conditions. The results from preliminary tests show that the system is able to clearly identify objects discriminated by different resistivity. Furthermore, measurements carried out during internal erosion simulations demonstrate that even small variations in the electrical resistivity can be captured and these changes can be related to the erosion processes.

Analysis and interpretation of electrical resistivity tomography data of alluvial aquifer of Tamanrasset Southern Algeria

NASA Astrophysics Data System (ADS)

Zeddouri, Aziez; Elkheir, Abderrahmane Ben; Hadj-Said, Samia; Taupin, Jean-Denis; Leduc, Christian; Patris, Nicholas

2018-05-01

A groundwater exploration work in the Tamanrasset region in southern Algeria was started in August 2016 to assess the water reserves in the hydrogeological system related to the Oued Tamanrasset underflow water table which overcomes a volcanic basement. Five (05) electrical resistivity tomography (ERT) surveys were conducted in Tamanrasset area by using ABEM Terrameter LS system. the low electrical contrast between wet alluvium and water saturated alterites makes difficult the electrical response interpretation. to overcome the difficulties of interpretation of ERT profiles, field investigations, laboratory tests and software simulations, were carried out in order to clearly identify the structure of the hydrogeological system. The experimental investigation of the electrical characteristics of the alluvium as a function of water saturation was carried by the use of two devices (Wenner α and Schlumberger). Samples true resistivity values varies between 50 Ω.m for a 100% saturated sample and 1250 Ω.m for a 25% saturation sample. The interpretation of the measurements by the RES2DINV software made it possible to give 2D images of the subsoil up to a depth of 50 m. the electrical contrast between the bedrock and the overlying formations made it possible to identify it, however, it was difficult to distinguish alterites from alluvium. A methodology combining piezometric survey, geo-electrical measurements and field observations improves the interpretation of electrical tomography profiles and the application of the ERT method for accurate characterization of water resources in the Tamanrasset region.

Joint application of GPR and electrostatic resistivity to assess mixed pavement condition

NASA Astrophysics Data System (ADS)

Chouteau, M.; Camerlynck, C.; Kaouane, C.

2009-05-01

In planning maintenance and rehabilitation of paved streets it is of first importance to gather internal structure information to establish a diagnostic. We investigate the potential of the GPR and of the capacitively-coupled resistivity array profiling techniques to map the geometry and the defects present at various depths in streets with mixed pavement. GPR is excellent at delineating boundaries of material with contrasting electrical properties whereas the resistivity array is needed to determine the nature and quality of the imaged material. Thicknesses of asphalt and concrete can be continuously determined. Defects such as cracks, delaminations, voids and former repairs can be mapped. Quality of the concrete slab can be assessed by resistivity. The performances of the two techniques are demonstrated first using numerical modeling and imaging of typical pavement defects. Resistivity and GPR data were collected along a few streets in Montreal using a 1GHz GPR smart cart and a compact 2-receiver dipole resistivity system. Streets were selected to demonstrate the responses to different pavement defects. The results allow to show the performance and limitations of present systems. In particular, it is shown that multiple configuration arrays and real-time imaging for the resistivity pulled array are needed. For the arrays we investigate some designs and for the real-time imaging a technique based on Kalman filtering was developed.

Monitoring electrical properties for improving the lithological and hydrological characterization of landslides

NASA Astrophysics Data System (ADS)

Malet, J. P.; Gance, J.; Lajaunie, M.; Gallistl, J.; Denchik, N.; Flores Orozco, A.; Ottowitz, D.; Supper, R.; Sailhac, P.; Gautier, S.; Schmutz, M.

2017-12-01

Imaging water flows in landslides is of critical importance as the distribution of pore-fluid pressures controls the dynamics (acceleration, deceleration) of the material. Detecting and imaging water is a difficult task, not only because of the complex topography and the small dimensions of the geological structures, but also because the landslide material consists of unsaturated porous and heterogeneous fractured media, leading to multi-scale water-flow properties. Further, these properties can change in time, in relation to temperature, rainfall and biological forcings. Electrical properties are relevant proxies of the sub-surface hydrological properties. In order to image water in landslide bodies, we propose to combine multi-frequency electrical and electromagnetic measurements using campaigns or permanent instruments, and surface/boreole investigations, installed on several unstable slopes in France. To evaluate the information gained from electrical properties for different geological conditions, we discuss electrical and electro-magnetic imaging results for data collected at four different landslides located in France (Super-Sauze and La Valette in the South East Alps, Lodève lin the southern border of the Massif Central Massif, and Séchilienne in the North French Alps). Time-lapse electrical DC resistivity observations, complex electrical conductivity (conduction and polarization/chargeability) measured by IP imaging methods, and controlled-source electromagnetic (CS-AMT) methods are discussed. Imaging results demonstrate an improved lithological characterization of the landslide structures (delineation of the sliding planes, identification of the fractures, discrimination of clay lenses with enhanced resolution); further, water infiltration within the soil matrix and/or the fractures is discriminated allowing better modelling of the hydrological regime of the landslides at the slope scale. This research is conducted in the frame of the project HYDROSLIDE - Hydrogeophysical Monitoring of Clay-Rich Landslides funded by the Austrian Science Fund (FWF) and the French Research Agency (ANR).

Hierarchical Bayesian method for mapping biogeochemical hot spots using induced polarization imaging

DOE PAGES

Wainwright, Haruko M.; Flores Orozco, Adrian; Bucker, Matthias; ...

2016-01-29

In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this work, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys andmore » drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.« less

An electrical impedance tomography (EIT) multi-electrode needle-probe device for local assessment of heterogeneous tissue impeditivity.

PubMed

Meroni, Davide; Maglioli, Camilla Carpano; Bovio, Dario; Greco, Francesco G; Aliverti, Andrea

2017-07-01

Electrical Impedance Tomography (EIT) is an image reconstruction technique applied in medicine for the electrical imaging of living tissues. In literature there is the evidence that a large resistivity variation related to the differences of the human tissues exists. As a result of this interest for the electrical characterization of the biological samples, recently the attention is also focused on the identification and characterization of the human tissue, by studying the homogeneity of its structure. An 8 electrodes needle-probe device has been developed with the intent of identifying the structural inhomogeneities under the surface layers. Ex-vivo impeditivity measurements, by placing the needle-probe in 5 different patterns of fat and lean porcine tissue, were performed, and impeditivity maps were obtained by EIDORS open source software for image reconstruction in electrical impedance. The values composing the maps have been analyzed, pointing out a good tissue discrimination, and the conformity with the real images. We conclude that this device is able to perform impeditivity maps matching to reality for position and orientation. In all the five patterns presented is possible to identify and replicate correctly the heterogeneous tissue under test. This new procedure can be helpful to the medical staff to completely characterize the biological sample, in different unclear situations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wainwright, Haruko M.; Flores Orozco, Adrian; Bucker, Matthias

In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this work, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys andmore » drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.« less

Hydrogeological modeling constraints provided by geophysical and geochemical mapping of a chlorinated ethenes plume in northern France

NASA Astrophysics Data System (ADS)

Razafindratsima, Stephen; Guérin, Roger; Bendjoudi, Hocine; de Marsily, Ghislain

2014-09-01

A methodological approach is described which combines geophysical and geochemical data to delineate the extent of a chlorinated ethenes plume in northern France; the methodology was used to calibrate a hydrogeological model of the contaminants' migration and degradation. The existence of strong reducing conditions in some parts of the aquifer is first determined by measuring in situ the redox potential and dissolved oxygen, dissolved ferrous iron and chloride concentrations. Electrical resistivity imaging and electromagnetic mapping, using the Slingram method, are then used to determine the shape of the pollutant plume. A decreasing empirical exponential relation between measured chloride concentrations in the water and aquifer electrical resistivity is observed; the resistivity formation factor calculated at a few points also shows a major contribution of chloride concentration in the resistivity of the saturated porous medium. MODFLOW software and MT3D99 first-order parent-daughter chain reaction and the RT3D aerobic-anaerobic model for tetrachloroethene (PCE)/trichloroethene (TCE) dechlorination are finally used for a first attempt at modeling the degradation of the chlorinated ethenes. After calibration, the distribution of the chlorinated ethenes and their degradation products simulated with the model approximately reflects the mean measured values in the observation wells, confirming the data-derived image of the plume.

Near real-time imaging of molasses injections using time-lapse electrical geophysics at the Brandywine DRMO, Brandywine, Maryland

NASA Astrophysics Data System (ADS)

Versteeg, R. J.; Johnson, T.; Major, B.; Day-Lewis, F. D.; Lane, J. W.

2010-12-01

Enhanced bioremediation, which involves introduction of amendments to promote biodegradation, increasingly is used to accelerate cleanup of recalcitrant compounds and has been identified as the preferred remedial treatment at many contaminated sites. Although blind introduction of amendments can lead to sub-optimal or ineffective remediation, the distribution of amendment throughout the treatment zone is difficult to measure using conventional sampling. Because amendments and their degradation products commonly have electrical properties that differ from those of ambient soil, time-lapse electrical geophysical monitoring has the potential to verify amendment emplacement and distribution. In order for geophysical monitoring to be useful, however, results of the injection ideally should be accessible in near real time. In August 2010, we demonstrated the feasibility of near real-time, autonomous electrical geophysical monitoring of amendment injections at the former Defense Reutilization and Marketing Office (DRMO) in Brandywine, Maryland. Two injections of about 1000 gallons each of molasses, a widely used amendment for enhanced bioremediation, were monitored using measurements taken with borehole and surface electrodes. During the injections, multi-channel resistance data were recorded; data were transmitted to a server and processed using a parallel resistivity inversion code; and results in the form of time-lapse imagery subsequently were posted to a website. This process occurred automatically without human intervention. The resulting time-lapse imagery clearly showed the evolution of the molasses plume. The delay between measurements and online delivery of images was between 45 and 60 minutes, thus providing actionable information that could support decisions about field procedures and a check on whether amendment reached target zones. This experiment demonstrates the feasibility of using electrical imaging as a monitoring tool both during amendment emplacement and post-injection to track amendment distribution, geochemical breakdown, and other remedial effects.

Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography.

PubMed

Zhang, Jie; Patterson, Robert

2010-08-01

Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 +/- 13 years, 78 +/- 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC--end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Omega cm to 1583 Omega cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method.

An alternative methodology for the analysis of electrical resistivity data from a soil gas study

NASA Astrophysics Data System (ADS)

Johansson, Sara; Rosqvist, Hâkan; Svensson, Mats; Dahlin, Torleif; Leroux, Virginie

2011-08-01

The aim of this paper is to present an alternative method for the analysis of resistivity data. The methodology was developed during a study to evaluate if electrical resistivity can be used as a tool for analysing subsurface gas dynamics and gas emissions from landfills. The main assumption of this study was that variations in time of resistivity data correspond to variations in the relative amount of gas and water in the soil pores. Field measurements of electrical resistivity, static chamber gas flux and weather data were collected at a landfill in Helsingborg, Sweden. The resistivity survey arrangement consisted of nine lines each with 21 electrodes in an investigation area of 16 ×20 m. The ABEM Lund Imaging System provided vertical and horizontal resistivity profiles every second hour. The data were inverted in Res3Dinv using L1-norm-based optimization method with a standard least-squares formulation. Each horizontal soil layer was then represented as a linear interpolated raster model. Different areas underneath the gas flux measurement points were defined in the resistivity model of the uppermost soil layer, and the vertical extension of the zones could be followed at greater depths in deeper layer models. The average resistivity values of the defined areas were calculated and plotted on a time axis, to provide graphs of the variation in resistivity with time in a specific section of the ground. Residual variation of resistivity was calculated by subtracting the resistivity variations caused by the diurnal temperature variations from the measured resistivity data. The resulting residual resistivity graphs were compared with field data of soil moisture, precipitation, soil temperature and methane flux. The results of the study were qualitative, but promising indications of relationships between electrical resistivity and variations in the relative amount of gas and water in the soil pores were found. Even though more research and better data quality is necessary for verification of the results presented here, we conclude that this alternative methodology of working with resistivity data seems to be a valuable and flexible tool for this application.

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

NASA Astrophysics Data System (ADS)

Revil, A.; Karaoulis, M.; Johnson, T.; Kemna, A.

2012-06-01

Low-frequency geoelectrical methods include mainly self-potential, resistivity, and induced polarization techniques, which have potential in many environmental and hydrogeological applications. They provide complementary information to each other and to in-situ measurements. The self-potential method is a passive measurement of the electrical response associated with the in-situ generation of electrical current due to the flow of pore water in porous media, a salinity gradient, and/or the concentration of redox-active species. Under some conditions, this method can be used to visualize groundwater flow, to determine permeability, and to detect preferential flow paths. Electrical resistivity is dependent on the water content, the temperature, the salinity of the pore water, and the clay content and mineralogy. Time-lapse resistivity can be used to assess the permeability and dispersivity distributions and to monitor contaminant plumes. Induced polarization characterizes the ability of rocks to reversibly store electrical energy. It can be used to image permeability and to monitor chemistry of the pore water-minerals interface. These geophysical methods, reviewed in this paper, should always be used in concert with additional in-situ measurements (e.g. in-situ pumping tests, chemical measurements of the pore water), for instance through joint inversion schemes, which is an area of fertile on-going research.

Maxwell-Wagner relaxation in electrical imaging.

PubMed

Korjenevsky, A V

2005-04-01

The electric field tomography (EFT) method exploits interaction of high-frequency electric field with an inhomogeneous conductive medium without contact with the electrodes. The interaction is accompanied by a high-frequency redistribution of free charges inside the medium and leads to small and regular phase shifts of the field in the area surrounding an object. Such a kind of phenomenon is referred to as the Maxwell-Wagner relaxation. Measuring the perturbations of the field using the set of electrodes placed around the object enables us to reconstruct the internal structure of the medium, generally the spatial distribution of a nonlinear combination of permittivity and resistivity. In the case of biomedical applications the result of measurements is determined mainly by the resistivity of the tissues. Three-dimensional simulation based on the finite element method has demonstrated the feasibility of the technique.

Electrical resistivity characterization of anisotropy in the Biscayne Aquifer.

PubMed

Yeboah-Forson, Albert; Whitman, Dean

2014-01-01

Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28-electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E-W/SE-NW beneath the ridge and E-W/SW-NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo-groundwater flow in the Biscayne Aquifer. © 2013, National Ground Water Association.

Spatial and temporal variations of thaw layer thickness and its controlling factors identified using time-lapse electrical resistivity tomography and hydro-thermal modeling

NASA Astrophysics Data System (ADS)

Tran, Anh Phuong; Dafflon, Baptiste; Bisht, Gautam; Hubbard, Susan S.

2018-06-01

Quantitative understanding of controls on thaw layer thickness (TLT) dynamics in the Arctic peninsula is essential for predictive understanding of permafrost degradation feedbacks to global warming and hydrobiochemical processes. This study jointly interprets electrical resistivity tomography (ERT) measurements and hydro-thermal numerical simulation results to assess spatiotemporal variations of TLT and to determine its controlling factors in Barrow, Alaska. Time-lapse ERT measurements along a 35-m transect were autonomously collected from 2013 to 2015 and inverted to obtain soil electrical resistivity. Based on several probe-based TLT measurements and co-located soil electrical resistivity, we estimated the electrical resistivity thresholds associated with the boundary between the thaw layer and permafrost using a grid search optimization algorithm. Then, we used the obtained thresholds to derive the TLT from all soil electrical resistivity images. The spatiotemporal analysis of the ERT-derived TLT shows that the TLT at high-centered polygons (HCPs) is smaller than that at low-centered polygons (LCPs), and that both thawing and freezing occur earlier at the HCPs compared to the LCPs. In order to provide a physical explanation for dynamics in the thaw layer, we performed 1-D hydro-thermal simulations using the community land model (CLM). Simulation results showed that air temperature and precipitation jointly govern the temporal variations of TLT, while the topsoil organic content (SOC) and polygon morphology are responsible for its spatial variations. When the topsoil SOC and its thickness increase, TLT decreases. Meanwhile, at LCPs, a thicker snow layer and saturated soil contribute to a thicker TLT and extend the time needed for TLT to freeze and thaw. This research highlights the importance of combination of measurements and numerical modeling to improve our understanding spatiotemporal variations and key controls of TLT in cold regions.

Electrical resistivity tomography determines the spatial distribution of clay layer thickness and aquifer vulnerability, Kandal Province, Cambodia

NASA Astrophysics Data System (ADS)

Uhlemann, Sebastian; Kuras, Oliver; Richards, Laura A.; Naden, Emma; Polya, David A.

2017-10-01

Despite being rich in water resources, many areas of South East Asia face difficulties in securing clean water supply. This is particularly problematic in regions with a rapidly growing population. In this study, the spatial variability of the thickness of a clay layer, controlling surface - groundwater interactions that affect aquifer vulnerability, was investigated using electrical resistivity tomography (ERT). Data were acquired along two transects, showing significant differences in the imaged resistivities. Borehole samples were analyzed regarding particle density and composition, and linked to their resistivity. The obtained relationships were used to translate the field electrical resistivities into lithologies. Those revealed considerable variations in the thickness of the clay layer, ranging from 0 m up to 25 m. Geochemical data, highlighting zones of increased ingress of surface water into the groundwater, confirmed areas of discontinuities in the clay layer, which act as preferential flow paths. The results may guide urban planning of the Phnom Penh city expansion, in order to supply the growing population with safe water. The presented approach of using geophysics to estimate groundwater availability, accessibility, and vulnerability is not only applicable to Kandal Province, Cambodia, but also to many other areas of fast urbanization in South East Asia and beyond.

Quantitative impact of hydrothermal alteration on electrical resistivity in geothermal systems from a joint analysis of laboratory measurements and borehole data in Krafla area, N-E Iceland

NASA Astrophysics Data System (ADS)

Lévy, Léa; Páll Hersir, Gylfi; Flóvenz, Ólafur; Gibert, Benoit; Pézard, Philippe; Sigmundsson, Freysteinn; Briole, Pierre

2016-04-01

Rock permeability and fluid temperature are the two most decisive factors for a successful geothermal drilling. While those parameters are only measured from drilling, they might be estimated on the basis of their impact on electrical resistivity that might be imaged from surface soundings, for example through TEM (Transient Electro Magnetic) down to one km depth. The electrical conductivity of reservoir rocks is the sum of a volume term depending on fluid parameters and a surface term related to rock alteration. Understanding the link between electrical resistivity and geothermal key parameters requires the knowledge of hydrothermal alteration and its petrophysical signature with the Cation Exchange Capacity (CEC). Fluid-rock interactions related to hydrothermal circulation trigger the precipitation of alteration minerals, which are both witnesses of the temperature at the time of reaction and new paths for the electrical current. Alteration minerals include zeolites, smectites, chlorites, epidotes and amphiboles among which low temperatures parageneses are often the most conductive. The CEC of these mineral phases contributes to account for surface conductivity occuring at the water-rock interface. In cooling geothermal systems, these minerals constitute in petrophysical terms and from surface electrical conduction a memory of the equilibrium phase revealed from electrical probing at all scales. The qualitative impact of alteration minerals on resistivity structure has been studied over the years in the Icelandic geothermal context. In this work, the CEC impact on pore surfaces electrical conductivity is studied quantitatively at the borehole scale, where several types of volcanic rocks are mixed together, with various degrees of alteration and porosity. Five boreholes located within a few km at the Krafla volcano, Northeast Iceland, constitute the basis for this study. The deepest and reference hole, KJ-18, provides cuttings of rock and logging data down to 2215 m depth; CEC measurements performed on cuttings show. KH-1 and KH-3 have cores and logs in the top 200 m only. Boreholes KH-5 and KH-6 sample cores with higher temperature alteration minerals down to 600 m. Together, these 4 shallow holes cover the diversity of rock types and alterations facies found in KJ-18. The petrophysical calibration obtained from cores will then be upscaled to log data analysis in KJ-18: porosity, formation factor, permeability, acoustic velocity, electrical surface conduction at different temperatures and CEC. This research is supported by the IMAGE FP7 EC project (Integrated Methods for Advanced Geothermal Exploration, grant agreement No. 608553).

Get the LED Out.

ERIC Educational Resources Information Center

Jewett, John W., Jr.

1991-01-01

Describes science demonstrations with light-emitting diodes that include electrical concepts of resistance, direct and alternating current, sine wave versus square wave, series and parallel circuits, and Faraday's Law; optics concepts of real and virtual images, photoresistance, and optical communication; and modern physics concepts of spectral…

A Laboratory Approach Relating Complex Resistivity Observations to Flow and Transport in Saturated and Unsaturated Hydrologic Regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martins, S A; Daily, W D; Ramirez, A L

2002-01-31

Subsurface imaging technology, such as electric resistance tomography (ERT), is rapidly improving as a means for characterizing some soil properties of the near-surface hydrologic regime. While this information can be potentially useful in developing hydrologic models of the subsurface that are required for contaminant transport investigations, an image alone of the subsurface soil regime gives little or no information about how the site will respond to groundwater flow or contaminant transport. In fact, there is some question that tomographic imaging of soils alone can even provide meaningful values of hydraulic properties, such as the permeability structure, which is critical tomore » estimates of contaminant transport at a site. The main objective of this feasibility study was to initiate research on electrical imaging not just as a way to characterize the soil structure by mapping different soil types at a site but as a means of obtaining quantitative information about how a site will respond hydrologically to an infiltration event. To this end, a scaled system of electrode arrays was constructed that simulates the subsurface electrode distribution used at the LLNL Vadose Zone Observatory (VZO) where subsurface imaging of infiltration events has been investigated for several years. The electrode system was immersed in a 10,000-gallon tank to evaluate the fundamental relationship between ERT images and targets of a given volume that approximate infiltration-induced conductivity anomalies. With LDRD funds we have explored what can be initially learned about porous flow and transport using two important electrical imaging methods--electric resistance tomography (ERT) and electric impedance tomography (EIT). These tomographic methods involve passing currents (DC or AC) between two electrodes within or between electrode arrays while measuring the electric potential at the remaining electrodes. With the aid of a computer-based numerical inversion scheme, the potentials are used to solve for the electrical conductivity distribution in the region bounded by the electrode arrays. Groundwater movement resulting from a leak or surface spill will produce measurable conductivity changes that have been imaged using ERT or EIT. The kind of laboratory scale experiments supported by this work will help us to better understand the connection between imaged conductivity anomalies and the groundwater or contaminant flow that causes them. This work will also help to demonstrate the feasibility or value of doing lab experiments in imaging that can be applied to interpreting field-scale experiments. A secondary objective of this study was to initiate a collaboration with researchers at the Rensselaer Polytechnic Institute (RPI; Troyl NY) who are also participants in the newly created NSF Center for Subsurface Imaging and Sensing Systems (CenSSIS) which is managed in part by RPI. During the course of this study C.R. Carrigan and W. Daily visited the electromagnetic imaging lab at RPI to initiate discussions on subsurface imaging technology with Professors David Isaacson, Jon Newell, Gary Salunier and their research graduate students. A major goal of CenSSIS is to promote collaborations among researchers with imaging backgrounds in different disciplines (geosciences, biomedical, civil engineering and biomedical) that will lead to new solutions of common subsurface imaging problems. The geophysical test section constructed for this study included electrode arrays that resemble biomedical array distributions. Comparing images of the same target produced with the 4-array geophysical approach and with the biomedical imaging approach will help us to better understand differences and advantages that are characteristic of the two imaging methods. Our initial interactions with the researchers at RPI concluded that this was a viable problem to consider. The support for this subsequent research will come from a 3-year Office of Basic Energy Sciences (BES) proposal that has just received funding. This feasibility study contributed positively to the successful review and ultimately to the award of this BES funding. A letter (Appendix) from Professor Michael Silevitch, Director of CenSSIS, to Dr. Rokaya Al-Ayat, Director of the LLNL Science & Technology Office, acknowledges the contribution of this LDRD study to obtaining the Basic Energy Science grant that will fund further work in this area.« less

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.

In situ detection of tree root distribution and biomass by multi-electrode resistivity imaging.

PubMed

Amato, Mariana; Basso, Bruno; Celano, Giuseppe; Bitella, Giovanni; Morelli, Gianfranco; Rossi, Roberta

2008-10-01

Traditional methods for studying tree roots are destructive and labor intensive, but available nondestructive techniques are applicable only to small scale studies or are strongly limited by soil conditions and root size. Soil electrical resistivity measured by geoelectrical methods has the potential to detect belowground plant structures, but quantitative relationships of these measurements with root traits have not been assessed. We tested the ability of two-dimensional (2-D) DC resistivity tomography to detect the spatial variability of roots and to quantify their biomass in a tree stand. A high-resolution resistivity tomogram was generated along a 11.75 m transect under an Alnus glutinosa (L.) Gaertn. stand based on an alpha-Wenner configuration with 48 electrodes spaced 0.25 m apart. Data were processed by a 2-D finite-element inversion algorithm, and corrected for soil temperature. Data acquisition, inversion and imaging were completed in the field within 60 min. Root dry mass per unit soil volume (root mass density, RMD) was measured destructively on soil samples collected to a depth of 1.05 m. Soil sand, silt, clay and organic matter contents, electrical conductivity, water content and pH were measured on a subset of samples. The spatial pattern of soil resistivity closely matched the spatial distribution of RMD. Multiple linear regression showed that only RMD and soil water content were related to soil resistivity along the transect. Regression analysis of RMD against soil resistivity revealed a highly significant logistic relationship (n = 97), which was confirmed on a separate dataset (n = 67), showing that soil resistivity was quantitatively related to belowground tree root biomass. This relationship provides a basis for developing quick nondestructive methods for detecting root distribution and quantifying root biomass, as well as for optimizing sampling strategies for studying root-driven phenomena.

Innovative computational tools for reducing exploration risk through integration of water-rock interactions and magnetotelluric surveys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Joseph

2017-04-20

Mapping permeability distributions in geothermal reservoirs is essential for reducing the cost of geothermal development. To avoid the cost and sampling bias of measuring permeability directly through drilling, we require remote methods of imaging permeability such as geophysics. Electrical resistivity (or its inverse, conductivity) is one of the most sensitive geophysical properties known to reflect long range fluid interconnection and thus the likelihood of permeability. Perhaps the most widely applied geophysical methods for imaging subsurface resistivity is magnetotellurics (MT) due to its relatively great penetration depths. A primary goal of this project is to confirm through ground truthing at existingmore » geothermal systems that MT resistivity structure interpreted integratively is capable of revealing permeable fluid pathways into geothermal systems.« less

Understanding the conductive channel evolution in Na:WO(3-x)-based planar devices.

PubMed

Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

2015-04-14

An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO(3-x)) films on a soda-lime glass substrate, from which Na(+) diffuses into the WO(3-x) films during the deposition. The entire process of Na(+) migration driven by an alternating electric field is visualized in the Na-doped WO(3-x) films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na(+) mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.

Non-invasive imaging and assessment of active karst features in proximity to paved roadways.

DOT National Transportation Integrated Search

2014-02-01

In an effort to better understand and define the lateral and vertical extent of active karst features in immediate proximity to paved : MoDOT roadways in Springfield Missouri, MS&T will acquire electrical resistivity tomography (ERT) data. The intent...

Conductivity of laser printed copper structures limited by nano-crystal grain size and amorphous metal droplet shell

NASA Astrophysics Data System (ADS)

Winter, Shoshana; Zenou, Michael; Kotler, Zvi

2016-04-01

We present a study of the morphology and electrical properties of copper structures which are printed by laser induced forward transfer from bulk copper. The percentage of voids and the oxidation levels are too low to account for the high resistivities (~4 to 14 times the resistivity of bulk monocrystalline copper) of these structures. Transmission electron microscope (TEM) images of slices cut from the printed areas using a focused ion beam (FIB) show nano-sized crystal structures with grain sizes that are smaller than the electron free path length. Scattering from such grain boundaries causes a significant increase in the resistivity and can explain the measured resistivities of the structures. The TEM images also show a nano-amorphous layer (~5 nm) at the droplet boundaries which also contributes to the overall resistivity. Such morphological characteristics are best explained by the ultrafast cooling rate of the molten copper droplets during printing.

Deep electrical resistivity structure of northwestern Costa Rica

NASA Astrophysics Data System (ADS)

Brasse, H.; Kapinos, G.; Mütschard, L.; Alvarado, G. E.; Worzewski, T.; Jegen, M.

2009-01-01

First long-period magnetotelluric investigations were conducted in early 2008 in northwestern Costa Rica, along a profile that extends from the coast of the Pacific Ocean, traverses the volcanic arc and ends currently at the Nicaraguan border. The aim of this study is to gain insight into the electrical resistivity structure and thus fluid distribution at the continental margin where the Cocos plate subducts beneath the Caribbean plate. Preliminary two-dimensional models map the only moderately resistive mafic/ultramafic complexes of the Nicoya Peninsula (resistivity of a few hundred Ωm), the conductive forearc and the backarc basins (several Ωm). Beneath the backarc basin the data image a poor conductor in the basement with a clear termination in the south, which may tentatively be interpreted as the Santa Elena Suture. The volcanic arc shows no pronounced anomaly at depth, but a moderate conductor underlies the backarc with a possible connection to the upper mantle. A conductor at deep-crustal levels in the forearc may reflect fluid release from the downgoing slab.

Resistance of domain walls created by means of a magnetic force microscope in transversally magnetized epitaxial Fe wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassel, C.; Stienen, S.; Roemer, F. M.

2009-07-20

Magnetic domain walls are created in a controllable way in transversally magnetized epitaxial Fe wires on GaAs(110) by approaching a magnetic force microscope (MFM) tip. The electrical resistance-change due to the addition of these domain walls is measured. The anisotropic magnetoresistance as well as the intrinsic domain wall resistance contribute to the resistance-change. The efficiency of this procedure is proven by MFM images, which are obtained subsequent to the domain wall creation at a larger sample-to-probe distance. The contribution of the anisotropic magnetoresistance is calculated using micromagnetic calculations, thus making it possible to quantify the intrinsic domain wall resistance.

Model study of imaging myocardial infarction by intracardiac electrical impedance tomography.

PubMed

Li, Ying; Rao, Liyun; Ling, Yuesheng; He, Renjie; Khoury, Dirar S

2008-01-01

Electrical impedance tomography (EIT) detects tissue composition inside a medium by determining its resistive properties, and uses various electrode configurations to pass a small electric current and measure corresponding potential. We investigated the feasibility of reconstructing scarred tissue inside the heart wall by employing EIT on the basis of a catheter carrying a plurality of electrodes and placed inside the blood-filled heart cavity. We built a computer model of the biological medium, and reconstructed the resistivity distribution using the finite element method and Tikhonov regularization. The results established the successful implementation of the numeric methods and the possibility of localizing and quantifying scarred myocardium. Novel application of EIT from inside the heart cavity could be useful during catheterization and may complement other diagnostic modalities. Further research is necessary to assess the impact of several factors on the accuracy of the reconstruction and include number of electrodes, catheter location, and scar size.

Real-time imaging of subarachnoid hemorrhage in piglets with electrical impedance tomography.

PubMed

Dai, Meng; Wang, Liang; Xu, Canhua; Li, Lianfeng; Gao, Guodong; Dong, Xiuzhen

2010-09-01

Subarachnoid hemorrhage (SAH) is one of the most severe medical emergencies in neurosurgery. Early detection or diagnosis would significantly reduce the rate of disability and mortality, and improve the prognosis of the patients. Although the present medical imaging techniques generally have high sensitivity to identify bleeding, the use of an additional, non-invasive imaging technique capable of continuously monitoring SAH is required to prevent contingent bleeding or re-bleeding. In this study, electrical impedance tomography (EIT) was applied to detect the onset of SAH modeled on eight piglets in real time, with the subsequent process being monitored continuously. The experimental SAH model was introduced by one-time injection of 5 ml fresh autologous arterial blood into the cisterna magna. Results showed that resistivity variations within the brain caused by the added blood could be detected using the EIT method and may be associated not only with the resistivity difference among brain tissues, but also with variations of cerebrospinal fluid dynamics. In conclusion, EIT has unique potential for use in clinical practice to provide invaluable real-time neuroimaging data for SAH after the improvement of electrode design, anisotropic realistic modeling and instrumentation.

Inner structure of the Puy de Dôme volcano: cross-comparison of geophysical models (ERT, gravimetry, muon imaging)

NASA Astrophysics Data System (ADS)

Portal, A.; Labazuy, P.; Lénat, J.-F.; Béné, S.; Boivin, P.; Busato, E.; Cârloganu, C.; Combaret, C.; Dupieux, P.; Fehr, F.; Gay, P.; Laktineh, I.; Miallier, D.; Mirabito, L.; Niess, V.; Vulpescu, B.

2013-01-01

Muon imaging of volcanoes and of geological structures in general is actively being developed by several groups in the world. It has the potential to provide 3-D density distributions with an accuracy of a few percent. At this stage of development, comparisons with established geophysical methods are useful to validate the method. An experiment has been carried out in 2011 and 2012 on a large trachytic dome, the Puy de Dôme volcano, to perform such a comparison of muon imaging with gravimetric tomography and 2-D electrical resistivity tomography. Here, we present the preliminary results for the last two methods. North-south and east-west resistivity profiles allow us to model the resistivity distribution down to the base of the dome. The modelling of the Bouguer anomaly provides models for the density distribution within the dome that are directly comparable with the results from the muon imaging. Our ultimate goal is to derive a model of the dome using the joint interpretation of all sets of data.

Carbon nanotube film interlayer for strain and damage sensing in composites during dynamic compressive loading

NASA Astrophysics Data System (ADS)

Wu, A. S.; Na, W.-J.; Yu, W.-R.; Byun, J.-H.; Chou, T.-W.

2012-11-01

A major challenge in the damage assessment of materials under dynamic, high strain rate loading lies in the inability to apply most health monitoring methodologies to the analysis and evaluation of damage incurred on short timescales. Here, we present a resistance-based sensing method utilizing an electrically conductive carbon nanotube film in a fiberglass/vinyl ester composite. This method reveals that applied strain and damage in the form of matrix cracking and delamination give rise to electrical resistance increases across the composite specimen; these can be measured in real-time during high strain rate loading. Damage within the composite specimens is confirmed through pre- and post-mortem x-ray micro computed tomography imaging.

PFLOTRAN-E4D: A parallel open source PFLOTRAN module for simulating time-lapse electrical resistivity data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy C.; Hammond, Glenn E.; Chen, Xingyuan

Time-lapse electrical resistivity tomography (ERT) is finding increased application for remotely monitoring processes occurring in the near subsurface in three-dimensions (i.e. 4D monitoring). However, there are few codes capable of simulating the evolution of subsurface resistivity and corresponding tomographic measurements arising from a particular process, particularly in parallel and with an open source license. Herein we describe and demonstrate an electrical resistivity tomography module for the PFLOTRAN subsurface flow and reactive transport simulation code, named PFLOTRAN-E4D. The PFLOTRAN-E4D module operates in parallel using a dedicated set of compute cores in a master-slave configuration. At each time step, the master processesmore » receives subsurface states from PFLOTRAN, converts those states to bulk electrical conductivity, and instructs the slave processes to simulate a tomographic data set. The resulting multi-physics simulation capability enables accurate feasibility studies for ERT imaging, the identification of the ERT signatures that are unique to a given process, and facilitates the joint inversion of ERT data with hydrogeological data for subsurface characterization. PFLOTRAN-E4D is demonstrated herein using a field study of stage-driven groundwater/river water interaction ERT monitoring along the Columbia River, Washington, USA. Results demonstrate the complex nature of subsurface electrical conductivity changes, in both the saturated and unsaturated zones, arising from river stage fluctuations and associated river water intrusion into the aquifer. Furthermore, the results also demonstrate the sensitivity of surface based ERT measurements to those changes over time.« less

PFLOTRAN-E4D: A parallel open source PFLOTRAN module for simulating time-lapse electrical resistivity data

DOE PAGES

Johnson, Timothy C.; Hammond, Glenn E.; Chen, Xingyuan

2016-09-22

Time-lapse electrical resistivity tomography (ERT) is finding increased application for remotely monitoring processes occurring in the near subsurface in three-dimensions (i.e. 4D monitoring). However, there are few codes capable of simulating the evolution of subsurface resistivity and corresponding tomographic measurements arising from a particular process, particularly in parallel and with an open source license. Herein we describe and demonstrate an electrical resistivity tomography module for the PFLOTRAN subsurface flow and reactive transport simulation code, named PFLOTRAN-E4D. The PFLOTRAN-E4D module operates in parallel using a dedicated set of compute cores in a master-slave configuration. At each time step, the master processesmore » receives subsurface states from PFLOTRAN, converts those states to bulk electrical conductivity, and instructs the slave processes to simulate a tomographic data set. The resulting multi-physics simulation capability enables accurate feasibility studies for ERT imaging, the identification of the ERT signatures that are unique to a given process, and facilitates the joint inversion of ERT data with hydrogeological data for subsurface characterization. PFLOTRAN-E4D is demonstrated herein using a field study of stage-driven groundwater/river water interaction ERT monitoring along the Columbia River, Washington, USA. Results demonstrate the complex nature of subsurface electrical conductivity changes, in both the saturated and unsaturated zones, arising from river stage fluctuations and associated river water intrusion into the aquifer. Furthermore, the results also demonstrate the sensitivity of surface based ERT measurements to those changes over time.« less

Aquifer Characterization and Groundwater Potential Evaluation in Sedimentary Rock Formation

NASA Astrophysics Data System (ADS)

Ashraf, M. A. M.; Yusoh, R.; Sazalil, M. A.; Abidin, M. H. Z.

2018-04-01

This study was conducted to characterize the aquifer and evaluate the ground water potential in the formation of sedimentary rocks. Electrical resistivity and drilling methods were used to develop subsurface soil profile for determining suitable location for tube well construction. The electrical resistivity method was used to infer the subsurface soil layer by use of three types of arrays, namely, the pole–dipole, Wenner, and Schlumberger arrays. The surveys were conducted using ABEM Terrameter LS System, and the results were analyzed using 2D resistivity inversion program (RES2DINV) software. The survey alignments were performed with maximum electrode spreads of 400 and 800 m by employing two different resistivity survey lines at the targeted zone. The images were presented in the form of 2D resistivity profiles to provide a clear view of the distribution of interbedded sandstone, siltstone, and shale as well as the potential groundwater zones. The potential groundwater zones identified from the resistivity results were confirmed using pumping, step drawdown, and recovery tests. The combination among the three arrays and the correlation between the well log and pumping test are reliable and successful in identifying potential favorable zones for obtaining groundwater in the study area.

Shielded piezoresistive cantilever probes for nanoscale topography and electrical imaging

NASA Astrophysics Data System (ADS)

Yang, Yongliang; Ma, Eric Yue; Cui, Yong-Tao; Haemmerli, Alexandre; Lai, Keji; Kundhikanjana, Worasom; Harjee, Nahid; Pruitt, Beth L.; Kelly, Michael; Shen, Zhi-Xun

2014-04-01

This paper presents the design and fabrication of piezoresistive cantilever probes for microwave impedance microscopy (MIM) to enable simultaneous topographic and electrical imaging. Plasma enhanced chemical vapor deposited Si3N4 cantilevers with a shielded center conductor line and nanoscale conductive tip apex are batch fabricated on silicon-on-insulator wafers. Doped silicon piezoresistors are integrated at the root of the cantilevers to sense their deformation. The piezoresistive sensitivity is 2 nm for a bandwidth of 10 kHz, enabling topographical imaging with reasonable speed. The aluminum center conductor has a low resistance (less than 5 Ω) and small capacitance (˜1.7 pF) to ground; these parameters are critical for high sensitivity MIM imaging. High quality piezoresistive topography and MIM images are simultaneously obtained with the fabricated probes at ambient and cryogenic temperatures. These new piezoresistive probes remarkably broaden the horizon of MIM for scientific applications by operating with an integrated feedback mechanism at low temperature and for photosensitive samples.

Sustainability of bridge foundations using electrical resistivity imaging and induced polarization to support transportation safety.

DOT National Transportation Integrated Search

2014-04-01

As of September 2007, there were 67,240 U.S. bridges in the National Bridge Inventory classified as having unknown : foundations (FHWA 2008). The bridges spanning rivers are of critical importance due to the risks of potential scour. In fact, it is :...

Surface geophysical methods for characterising frozen ground in transitional permafrost landscapes

USGS Publications Warehouse

Briggs, Martin A.; Campbell, Seth; Nolan, Jay; Walvoord, Michelle Ann; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D.; Lane, John W.

2017-01-01

The distribution of shallow frozen ground is paramount to research in cold regions, and is subject to temporal and spatial changes influenced by climate, landscape disturbance and ecosystem succession. Remote sensing from airborne and satellite platforms is increasing our understanding of landscape-scale permafrost distribution, but typically lacks the resolution to characterise finer-scale processes and phenomena, which are better captured by integrated surface geophysical methods. Here, we demonstrate the use of electrical resistivity imaging (ERI), electromagnetic induction (EMI), ground penetrating radar (GPR) and infrared imaging over multiple summer field seasons around the highly dynamic Twelvemile Lake, Yukon Flats, central Alaska, USA. Twelvemile Lake has generally receded in the past 30 yr, allowing permafrost aggradation in the receded margins, resulting in a mosaic of transient frozen ground adjacent to thick, older permafrost outside the original lakebed. ERI and EMI best evaluated the thickness of shallow, thin permafrost aggradation, which was not clear from frost probing or GPR surveys. GPR most precisely estimated the depth of the active layer, which forward electrical resistivity modelling indicated to be a difficult target for electrical methods, but could be more tractable in time-lapse mode. Infrared imaging of freshly dug soil pit walls captured active-layer thermal gradients at unprecedented resolution, which may be useful in calibrating emerging numerical models. GPR and EMI were able to cover landscape scales (several kilometres) efficiently, and new analysis software showcased here yields calibrated EMI data that reveal the complicated distribution of shallow permafrost in a transitional landscape.

System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography

PubMed Central

Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

2016-01-01

A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz–960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images. PMID:27463715

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malin, Peter E.; Shalev, Eylon; Onacha, Stepthen A.

In this final report, we discuss both theoretical and applied research resulting from our DOE project, ICEKAP 2004: A Collaborative Joint Geophysical Imaging Project at Krafla and IDDP. The abstract below begins with a general discussion of the problem we addressed: the location and characterization of “blind” geothermal resources using microearthquake and magnetotelluric measurements. The abstract then describes the scientific results and their application to the Krafla geothermal area in Iceland. The text following this abstract presents the full discussion of this work, in the form of the PhD thesis of Stephen A. Onacha. The work presented here was awardedmore » the “Best Geophysics Paper” at the 2005 Geothermal Resources Council meeting, Reno. This study presents the modeling of buried fault zones using microearthquake and electrical resistivity data based on the assumptions that fluid-filled fractures cause electrical and seismic anisotropy and polarization. In this study, joint imaging of electrical and seismic data is used to characterize the fracture porosity of the fracture zones. P-wave velocity models are generated from resistivity data and used in locating microearthquakes. Fracture porosity controls fluid circulation in the hydrothermal systems and the intersections of fracture zones close to the heat source form important upwelling zones for hydrothermal fluids. High fracture porosity sites occur along fault terminations, fault-intersection areas and fault traces. Hydrothermal fault zone imaging using resistivity and microearthquake data combines high-resolution multi-station seismic and electromagnetic data to locate rock fractures and the likely presence fluids in high temperature hydrothermal systems. The depths and locations of structural features and fracture porosity common in both the MT and MEQ data is incorporated into a joint imaging scheme to constrain resistivity, seismic velocities, and locations of fracture systems. The imaging of the fault zones is constrained by geological, drilling, and geothermal production data. The objective is to determine interpretation techniques for evaluating structural controls of fluid circulation in hydrothermal systems. The conclusions are: • directions of MT polarization and anisotropy and MEQ S-splitting correlate. Polarization and anisotropy are caused by fluid filled fractures at the base of the clay cap. •Microearthquakes occur mainly on the boundary of low resistivity within the fracture zone and high resistivity in the host rock. Resistivity is lowest within the core of the fracture zone and increases towards the margins of the fracture zone. The heat source and the clay cap for the hydrothermal have very low resistivity of less than 5Ωm. •Fracture porosity imaged by resistivity indicates that it varies between 45-5% with most between 10-20%, comparable to values from core samples in volcanic areas in Kenya and Iceland. For resistivity values above 60Ωm, the porosity reduces drastically and therefore this might be used as the upper limit for modeling fracture porosity from resistivity. When resistivity is lower than 5Ωm, the modeled fracture porosity increases drastically indicating that this is the low resistivity limit. This is because at very low resistivity in the heat source and the clay cap, the resistivity is dominated by ionic conduction rather than fracture porosity. •Microearthquakes occur mainly above the heat source which is defined by low resistivity at a depth of 3-4.5 km at the Krafla hydrothermal system and 4-7 km in the Longonot hydrothermal system. •Conversions of S to P waves occur for microearthquakes located above the heat source within the hydrothermal system. Shallow microearthquakes occur mainly in areas that show both MT and S-wave anisotropy. •S-wave splitting and MT anisotropy occurs at the base of the clay cap and therefore reflects the variations in fracture porosity on top of the hydrothermal system. •In the Krafla hydrothermal system in Iceland, both MT polarization and MEQ splitting directions align with zones that have high fracture porosity below the clay cap. These zones coincide with fault zones trending in the NNE-SSW and NW-SE directions in otherwise uniform volcanic rocks and laterally continuous geology. The NW-SE orientation is parallel to the regional shear fractures while the NNE-SSW trending polarizations align parallel to rift zone fracture swarms. This suggest that correlations between MT polarizations and MEQ splitting may be related to fluid filled fractures. •In areas of high resistivity (60Ωm), the P-wave velocity approaches that of the rock matrix. •S-wave splitting polarization is determined from measurements of angles of rotation to get the optimum direction of polarization. •The use of MEQ and resistivity for imaging fractures requires that the MEQ data acquisition system be located close to the fracture zone.« less

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 concentration in water may be neglected during the sewage of macro voids as it corresponds to a small quantity of water for the studied samples. Soil solid components are generally electrical insulators, the conduction of electrical current only lies on two phenomenon occurring in water : (i) volume conduction controlled by the electrolyte concentration in water and the geometrical characteristics of macro voids network ; (ii) surface conduction controlled by the double diffuse layer that depends on the solid-liquid interactions, the specific surface of clay minerals and the geometry of particles contacts. For the water contained in macro voids the preeminent phenomenon seems to be volume conduction while for the water contained in micro voids, it seems to be surface conduction. This hypothesis satisfyingly explains the shape of the electrical resistivity versus water content curves obtained for three different oxisols with clayey, clayey-sandy and sandy-clayey texture. [1] Archie G.E. 1942. The electrical resistivity log as an aid in determining some reservoirs characteristics. Trans. AIME, 146, 54-67. [2] Braudeau E. et al. 1999. New device and method for soil shrinkage curve measurement and characterization. S.S.S.A.J., 63(3), 525-535.

Offset-electrode profile acquisition strategy for electrical resistivity tomography

NASA Astrophysics Data System (ADS)

Robbins, Austin R.; Plattner, Alain

2018-04-01

We present an electrode layout strategy that allows electrical resistivity profiles to image the third dimension close to the profile plane. This "offset-electrode profile" approach involves laterally displacing electrodes away from the profile line in an alternating fashion and then inverting the resulting data using three-dimensional electrical resistivity tomography software. In our synthetic and field surveys, the offset-electrode method succeeds in revealing three-dimensional structures in the vicinity of the profile plane, which we could not achieve using three-dimensional inversions of linear profiles. We confirm and explain the limits of linear electrode profiles through a discussion of the three-dimensional sensitivity patterns: For a homogeneous starting model together with a linear electrode layout, all sensitivities remain symmetric with respect to the profile plane through each inversion step. This limitation can be overcome with offset-electrode layouts by breaking the symmetry pattern among the sensitivities. Thanks to freely available powerful three-dimensional resistivity tomography software and cheap modern computing power, the requirement for full three-dimensional calculations does not create a significant burden and renders the offset-electrode approach a cost-effective method. By offsetting the electrodes in an alternating pattern, as opposed to laying the profile out in a U-shape, we minimize shortening the profile length.

Integrated electromagnetic (EM) and Electrical Resistivity Tomography (ERT) geophysical studies of environmental impact of Awotan dumpsite in Ibadan, southwestern Nigeria

NASA Astrophysics Data System (ADS)

Osinowo, Olawale Olakunle; Falufosi, Michael Oluseyi; Omiyale, Eniola Oluwatosin

2018-04-01

This study attempts to establish the level of contamination caused by the decomposition of wastes by defining the lateral distribution and the vertical limit of leachate induced zone of anomalous conductivity distribution within the subsurface through the analyses of Electromagnetic (EM) and Electrical Resistivity Tomography (ERT) data, generated from the integrated geophysical survey over Awotan landfill dumpsite, in Ibadan, southwest Nigeria. Nine (9) EM and ERT profiles each were established within and around the Awotan landfill site. EM data were acquire at 5 m station interval using 10 m, 20 m and 40 m inter-coil spacings, while ERT stations were occupied at 2 m electrode spacing using dipole-dipole electrode configuration. The near perfect agreement between the two sets of data generated from the EM and ERT surveys over the Awotan landfill site as well as the subsurface imaging ability of these geophysical methods to delineate the region of elevated contamination presented in the form of anomalously high apparent ground conductivity and low subsurface resistivity distribution, suggest the importance of integrating electromagnetic and electrical resistivity investigation techniques for environmental studies and more importantly for selecting appropriate landfill dump site location such with ability to retain the generated contaminants and thus prevent environmental pollution.

Comparison of Compressed Sensing Algorithms for Inversion of 3-D Electrical Resistivity Tomography.

NASA Astrophysics Data System (ADS)

Peddinti, S. R.; Ranjan, S.; Kbvn, D. P.

2016-12-01

Image reconstruction algorithms derived from electrical resistivity tomography (ERT) are highly non-linear, sparse, and ill-posed. The inverse problem is much severe, when dealing with 3-D datasets that result in large sized matrices. Conventional gradient based techniques using L2 norm minimization with some sort of regularization can impose smoothness constraint on the solution. Compressed sensing (CS) is relatively new technique that takes the advantage of inherent sparsity in parameter space in one or the other form. If favorable conditions are met, CS was proven to be an efficient image reconstruction technique that uses limited observations without losing edge sharpness. This paper deals with the development of an open source 3-D resistivity inversion tool using CS framework. The forward model was adopted from RESINVM3D (Pidlisecky et al., 2007) with CS as the inverse code. Discrete cosine transformation (DCT) function was used to induce model sparsity in orthogonal form. Two CS based algorithms viz., interior point method and two-step IST were evaluated on a synthetic layered model with surface electrode observations. The algorithms were tested (in terms of quality and convergence) under varying degrees of parameter heterogeneity, model refinement, and reduced observation data space. In comparison to conventional gradient algorithms, CS was proven to effectively reconstruct the sub-surface image with less computational cost. This was observed by a general increase in NRMSE from 0.5 in 10 iterations using gradient algorithm to 0.8 in 5 iterations using CS algorithms.

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.

Using electrical resistivity tomography to assess the effectiveness of managed aquifer recharge in a salinized coastal aquifer.

PubMed

García-Menéndez, Olga; Ballesteros, Bruno J; Renau-Pruñonosa, Arianna; Morell, Ignacio; Mochales, Tania; Ibarra, Pedro I; Rubio, Félix M

2018-01-27

Over 40 years, the detrital aquifer of the Plana de Castellón (Spanish Mediterranean coast) has been subjected to seawater intrusion because of long dry periods combined with intensive groundwater exploitation. Against this backdrop, a managed artificial recharge (MAR) scheme was implemented to improve the groundwater quality. The large difference between the electrical conductivity (EC) of the ambient groundwater (brackish water due to marine intrusion) and the recharge water (freshwater) meant that there was a strong contrast between the resistivities of the brackish water saturated zone and the freshwater saturated zone. Electrical resistivity tomography (ERT) can be used for surveying similar settings to evaluate the effectiveness of artificial recharge schemes. By integrating geophysical data with lithological information, EC logs from boreholes, and hydrochemical data, we can interpret electrical resistivity (ER) with groundwater EC values and so identify freshwater saturated zones. Using this approach, ERT images provided a high-resolution spatial characterization and an accurate picture of the shape and extent of the recharge plume of the MAR site. After 5 months of injection, a freshwater plume with an EC of 400-600 μS/cm had formed that extended 400 m in the W-E direction, 250 m in the N-S direction, and to a depth of 40 m below piezometric level. This study also provides correlations between ER values with different lithologies and groundwater EC values that can be used to support other studies.

Resolution Study of Marine CSEM Imaging of Subduction Zones

NASA Astrophysics Data System (ADS)

Gustafson, C.; Key, K.

2016-12-01

Marine controlled source electromagnetic (CSEM) data allow us to image seafloor electrical resistivity from which we can constrain the porosity and fluid content of the subsurface. In subduction zones, CSEM data can be used to constrain geologic structure, hydrogeology and fluid-tectonic processes. The scales of features we are interested in recovering with CSEM data range from large-scale features such as the incoming tectonic plate and subducting slab, to the narrow dipping plate boundary interface where slip occurs, to thin faults that cut the overriding forearc crust and shallow fluid seeps and mounds on the seafloor. Thus electrical structure is expected to vary on scales ranging from scales of meters to tens of kilometers. CSEM data collected by Scripps at the Middle America Trench in 2010 is the first and to-date the only application of the method for studying a subduction zone. The results from this pioneering data set highlight the types of new discoveries that are possible with CSEM data, such as imaging conductive bending faults and a water-rich channel of subducting sediments. In this work we explore the magnitude and scale of 2D resistivity structures that can be resolved with CSEM data through a suite of synthetic inversion studies. We build resistivity models that are representative of various known and hypothesized subduction zone plate boundary structures. We generate synthetic noisy data for these models and invert them using the freely available MARE2DEM inversion code. We compare the recovered models to the original models in order to determine which resistivity structures may be successfully identified using CSEM. We explore the potential effects of receiver spacing, frequency bandwidth and system noise levels on the ability of CSEM to recover these different subduction zone structures.

Assessment of local hydraulic properties from electrical resistivity tomography monitoring of a three-dimensional synthetic tracer test experiment

NASA Astrophysics Data System (ADS)

Camporese, M.; Cassiani, G.; Deiana, R.; Salandin, P.

2011-12-01

In recent years geophysical methods have become increasingly popular for hydrological applications. Time-lapse electrical resistivity tomography (ERT) represents a potentially powerful tool for subsurface solute transport characterization since a full picture of the spatiotemporal evolution of the process can be obtained. However, the quantitative interpretation of tracer tests is difficult because of the uncertainty related to the geoelectrical inversion, the constitutive models linking geophysical and hydrological quantities, and the a priori unknown heterogeneous properties of natural formations. Here an approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique is applied to assess the spatial distribution of hydraulic conductivity K by incorporating time-lapse cross-hole ERT data. Electrical data consist of three-dimensional cross-hole ERT images generated for a synthetic tracer test in a heterogeneous aquifer. Under the assumption that the solute spreads as a passive tracer, for high Peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity. The assimilation of the electrical conductivity 4D images allows updating of the hydrological state as well as the spatial distribution of K. Thus, delineation of the tracer plume and estimation of the local aquifer heterogeneity can be achieved at the same time by means of this interpretation of time-lapse electrical images from tracer tests. We assess the impact on the performance of the hydrological inversion of (i) the uncertainty inherently affecting ERT inversions in terms of tracer concentration and (ii) the choice of the prior statistics of K. Our findings show that realistic ERT images can be integrated into a hydrological model even within an uncoupled inverse modeling framework. The reconstruction of the hydraulic conductivity spatial distribution is satisfactory in the portion of the domain directly covered by the passage of the tracer. Aside from the issues commonly affecting inverse models, the proposed approach is subject to the problem of the filter inbreeding and the retrieval performance is sensitive to the choice of K prior geostatistical parameters.

Resistivity profiling for mapping gravel layers that may control contaminant migration at the Amargosa Desert Research Site, Nevada

USGS Publications Warehouse

Lucius, Jeffrey E.; Abraham, Jared D.; Burton, Bethany L.

2008-01-01

Gaseous contaminants, including CFC 113, chloroform, and tritiated compounds, move preferentially in unsaturated subsurface gravel layers away from disposal trenches at a closed low-level radioactive waste-disposal facility in the Amargosa Desert about 17 kilometers south of Beatty, Nevada. Two distinct gravel layers are involved in contaminant transport: a thin, shallow layer between about 0.5 and 2.2 meters below the surface and a layer of variable thickness between about 15 and 30 meters below land surface. From 2003 to 2005, the U.S. Geological Survey used multielectrode DC and AC resistivity surveys to map these gravel layers. Previous core sampling indicates the fine-grained sediments generally have higher water content than the gravel layers or the sediments near the surface. The relatively higher electrical resistivity of the dry gravel layers, compared to that of the surrounding finer sediments, makes the gravel readily mappable using electrical resistivity profiling. The upper gravel layer is not easily distinguished from the very dry, fine-grained deposits at the surface. Two-dimensional resistivity models, however, clearly identify the resistive lower gravel layer, which is continuous near the facility except to the southeast. Multielectrode resistivity surveys provide a practical noninvasive method to image hydrogeologic features in the arid environment of the Amargosa Desert.

Use of electrical imaging and distributed temperature sensing methods to characterize surface water–groundwater exchange regulating uranium transport at the Hanford 300 Area, Washington

USGS Publications Warehouse

Slater, Lee D.; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D.; Mwakanyamale, Kisa; Versteeg, Roelof J.; Ward, Andy; Strickland, Christopher; Johnson, Carole D.; Lane, John W.

2010-01-01

We explored the use of continuous waterborne electrical imaging (CWEI), in conjunction with fiber‐optic distributed temperature sensor (FO‐DTS) monitoring, to improve the conceptual model for uranium transport within the Columbia River corridor at the Hanford 300 Area, Washington. We first inverted resistivity and induced polarization CWEI data sets for distributions of electrical resistivity and polarizability, from which the spatial complexity of the primary hydrogeologic units was reconstructed. Variations in the depth to the interface between the overlying coarse‐grained, high‐permeability Hanford Formation and the underlying finer‐grained, less permeable Ringold Formation, an important contact that limits vertical migration of contaminants, were resolved along ∼3 km of the river corridor centered on the 300 Area. Polarizability images were translated into lithologic images using established relationships between polarizability and surface area normalized to pore volume (Spor). The FO‐DTS data recorded along 1.5 km of cable with a 1 m spatial resolution and 5 min sampling interval revealed subreaches showing (1) temperature anomalies (relatively warm in winter and cool in summer) and (2) a strong correlation between temperature and river stage (negative in winter and positive in summer), both indicative of reaches of enhanced surface water–groundwater exchange. The FO‐DTS data sets confirm the hydrologic significance of the variability identified in the CWEI and reveal a pattern of highly focused exchange, concentrated at springs where the Hanford Formation is thickest. Our findings illustrate how the combination of CWEI and FO‐DTS technologies can characterize surface water–groundwater exchange in a complex, coupled river‐aquifer system.

Survey Plan For Characterization of the Subsurface Underlying the National Aeronautics and Space Administration's Marshall Space Flight Center in Huntsville, Alabama. Volume 1 and 2

NASA Technical Reports Server (NTRS)

1996-01-01

Topic considered include: survey objectives; technologies for non-Invasive imaging of subsurface; cost; data requirements and sources; climatic condition; hydrology and geology; chemicals; magnetometry; electrical(resistivity, potential); optical-style imaging; reflection/refraction seismics; gravitometry; photo-acoustic activation;well drilling and borehole analysis; comparative assessment matrix; ground sensors; choice of the neutron sources; logistic of operations; system requirements; health and safety plans.

Electrical structures in the northwest margin of the Junggar basin: Implications for its late Paleozoic geodynamics

NASA Astrophysics Data System (ADS)

Zhang, Sheng; Xu, Yixian; Jiang, Li; Yang, Bo; Liu, Ying; Griffin, W. L.; Luo, Yong; Huang, Rong; Zhou, Yong; Zhang, Liangliang

2017-10-01

Recent geological, geochemical and geophysical data have inclined to support the presence of a remnant Paleozoic oceanic lithosphere beneath the Western Junggar, southwestern Chinese Altaids. However, regional high-resolution geophysical data have been rarely deployed to image its geometry, making it difficult to trace its evolution and final geodynamic setting. Presently, two magnetotelluric (MT) profiles are deployed across the northwest margin of the Junggar basin and the southern Darbut belt to image the electrical structure of the crust and lithospheric mantle. High-quality data at 102 sites and the quasi-2D indications of phase tensor skew angles and impedance phase ellipses for relatively short periods (up to 500 s) allow us to invert the two profile data by a 2-D scheme. The resistivity cross-section of a NW-SE striking LINE2 sheds light on a fossil intraoceanic subduction system, and reveals the Miaoergou intrusions as a bowl-like pluton, indicating that the multi-phase intrusions primarily formed in a post-collisional setting. The resistivity cross-section of striking NE-SW LINE1 reveals a possible oceanic slab with relatively lower resistivity underlying the low-resistivity sedimentary strata and high-resistivity mélange. Given that the profile of LINE1 cuts the out-rise zone of a subducted slab developed during the late Paleozoic, the 2-D resistivity model may thus represent the zone that have experienced heterogeneous deformation, reflecting subduction with barrier variation parallel to the ancient trench. Moreover, as shown in previous results, the new MT data also illustrate that the Darbut Fault is a thin-skinned structure, which has been erased at depths during the subsequent magmatism.

High-resolution resistivity imaging of marine gas hydrate structures by combined inversion of CSEM towed and ocean-bottom receiver data

NASA Astrophysics Data System (ADS)

Attias, Eric; Weitemeyer, Karen; Hölz, Sebastian; Naif, Samer; Minshull, Tim A.; Best, Angus I.; Haroon, Amir; Jegen-Kulcsar, Marion; Berndt, Christian

2018-06-01

We present high-resolution resistivity imaging of gas hydrate pipe-like structures, as derived from marine controlled-source electromagnetic (CSEM) inversions that combine towed and ocean-bottom electric field receiver data, acquired from the Nyegga region, offshore Norway. Two-dimensional CSEM inversions applied to the towed receiver data detected four new prominent vertical resistive features that are likely gas hydrate structures, located in proximity to a major gas hydrate pipe-like structure, known as the CNE03 pockmark. The resistivity model resulting from the CSEM data inversion resolved the CNE03 hydrate structure in high resolution, as inferred by comparison to seismically constrained inversions. Our results indicate that shallow gas hydrate vertical features can be delineated effectively by inverting both ocean-bottom and towed receiver CSEM data simultaneously. The approach applied here can be utilised to map and monitor seafloor mineralisation, freshwater reservoirs, CO2 sequestration sites and near-surface geothermal systems.

Rheological and electrical properties of hybrid nanocomposites of epoxy resins filled with graphite nanoplatelets and carbon black.

PubMed

Truong, Quang-Trung; Lee, Seon-Suk; Lee, Dai-Soo

2011-02-01

Graphite nanoplatelets (GNP) were prepared by microwave irradiation of natural graphites intercalated with ferric chloride in nitromethane (GIC). Intercalated structure of GIC was confirmed by X-ray diffraction patterns. SEM images of GIC after microwave irradiation showed the exfoliation of GIC, the formation of GNPs. Hybrid nanocomposites of bisphenol-A type epoxy resins filled with GNP and a conductive carbon black (CB) were prepared and rheological and electrical properties of the nanocomposites were investigated. Viscosity and electrical surface resistivity of the nanocomposites showed minima at certain mixtures of GNP and CB in the epoxy resins.

Investigation of electrical and optical properties of low temperature titanium nitride grown by rf-magnetron sputtering

NASA Astrophysics Data System (ADS)

Sosnin, D.; Kudryashov, D.; Mozharov, A.

2017-11-01

Titanium nitride is a promising material due to its low resistivity, high hardness and chemical inertness. Titanium nitride (TiN) can be applied as an ohmic contact for n-GaN and rectifying contact for p-GaN and also as a part of perovskite solar cell. A technology of TiN low temperature reactive rf-magnetron sputtering has been developed. Electrical and optical properties of titanium nitride were studied as a function of the rf-power and gas mixture composition. Reflectance and transmittance spectra were measured. Cross-section and surface SEM image were obtained. 250 nm thin films of TiN with a resistivity of 23.6 μOm cm were obtained by rf-magnetron sputtering at low temperature.

Influence of carbon nanoparticle modification on the mechanical and electrical properties of epoxy in small volumes.

PubMed

Leopold, Christian; Augustin, Till; Schwebler, Thomas; Lehmann, Jonas; Liebig, Wilfried V; Fiedler, Bodo

2017-11-15

The influence of nanoparticle morphology and filler content on the mechanical and electrical properties of carbon nanoparticle modified epoxy is investigated regarding small volumes. Three types of particles, representing spherical, tubular and layered morphologies are used. A clear size effect of increasing true failure strength with decreasing volume is found for neat and carbon black modified epoxy. Carbon nanotube (CNT) modified epoxy exhibits high potential for strength increase, but dispersion and purity are critical. In few layer graphene modified epoxy, particles are larger than statistically distributed defects and initiate cracks, counteracting any size effect. Different toughness increasing mechanisms on the nano- and micro-scale depending on particle morphology are discussed based on scanning electron microscopy images. Electrical percolation thresholds in the small volume fibres are significantly higher compared to bulk volume, with CNT being found to be the most suitable morphology to form electrical conductive paths. Good correlation between electrical resistance change and stress strain behaviour under tensile loads is observed. The results show the possibility to detect internal damage in small volumes by measuring electrical resistance and therefore indicate to the high potential for using CNT modified polymers in fibre reinforced plastics as a multifunctional, self-monitoring material with improved mechanical properties. Copyright © 2017. Published by Elsevier Inc.

Electrical Characteristics CuFe2O4 Thick Film Ceramics Made with Different Screen Size Utiizing Fe2O3 Nanopowder Derived from Yarosite for NTC Thermistor

NASA Astrophysics Data System (ADS)

Wiendartun, Syarif, Dani Gustaman

2010-10-01

Fabrication of CuFe2O4 thick film ceramics utilizing Fe2O3 derived from yarosite using screen printing technique for NTC thermistor has been carried out. Effect of thickness variation due to different size of screen (screen 225; 300 and 375 mesh) has been studied. X-ray diffraction analyses (XRD) was done to know crystal structure and phases formation. SEM analyses was carried out to know microstructure of the films. Electrical properties characterization was done through measurement of electrical resistance at various temperatures (room temperature to 100° C). The XRD data showed that the films crystalize in tetragonal spinel. The SEM images showed that the screen with the smaller of the hole size, made the grain size was bigger. Electrical data showed that the larger the screen different size thickness variation (mesh), the larger the resistance, thermistor constant and sensitivity. From the electrical characteristics data, it was known that the electrical characteristics of the CuFe2O4 thick film ceramics followed the NTC characteristic. The value of B and RRT of the produced CuFe2O4 ceramics namely B = 3241-3484 K and RRT = 25.6-87.0 M Ohm, fitted market requirement.

PFLOTRAN-E4D: A parallel open source PFLOTRAN module for simulating time-lapse electrical resistivity data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy C.; Hammond, Glenn E.; Chen, Xingyuan

Time-lapse electrical resistivity tomography (ERT) is finding increased application for remotely monitoring processes occurring in the near subsurface in three-dimensions (i.e. 4D monitoring). However, there are few codes capable of simulating the evolution of subsurface resistivity and corresponding tomographic measurements arising from a particular process, particularly in parallel and with an open source license. Herein we describe and demonstrate an electrical resistivity tomography module for the PFLOTRAN subsurface simulation code, named PFLOTRAN-E4D. The PFLOTRAN-E4D module operates in parallel using a dedicated set of compute cores in a master-slave configuration. At each time step, the master processes receives subsurface states frommore » PFLOTRAN, converts those states to bulk electrical conductivity, and instructs the slave processes to simulate a tomographic data set. The resulting multi-physics simulation capability enables accurate feasibility studies for ERT imaging, the identification of the ERT signatures that are unique to a given process, and facilitates the joint inversion of ERT data with hydrogeological data for subsurface characterization. PFLOTRAN-E4D is demonstrated herein using a field study of stage-driven groundwater/river water interaction ERT monitoring along the Columbia River, Washington, USA. Results demonstrate the complex nature of changes subsurface electrical conductivity, in both the saturated and unsaturated zones, arising from water table changes and from river water intrusion into the aquifer. The results also demonstrate the sensitivity of surface based ERT measurements to those changes over time. PFLOTRAN-E4D is available with the PFLOTRAN development version with an open-source license at https://bitbucket.org/pflotran/pflotran-dev .« less

PFLOTRAN-E4D: A parallel open source PFLOTRAN module for simulating time-lapse electrical resistivity data

NASA Astrophysics Data System (ADS)

Johnson, Timothy C.; Hammond, Glenn E.; Chen, Xingyuan

2017-02-01

Time-lapse electrical resistivity tomography (ERT) is finding increased application for remotely monitoring processes occurring in the near subsurface in three-dimensions (i.e. 4D monitoring). However, there are few codes capable of simulating the evolution of subsurface resistivity and corresponding tomographic measurements arising from a particular process, particularly in parallel and with an open source license. Herein we describe and demonstrate an electrical resistivity tomography module for the PFLOTRAN subsurface flow and reactive transport simulation code, named PFLOTRAN-E4D. The PFLOTRAN-E4D module operates in parallel using a dedicated set of compute cores in a master-slave configuration. At each time step, the master processes receives subsurface states from PFLOTRAN, converts those states to bulk electrical conductivity, and instructs the slave processes to simulate a tomographic data set. The resulting multi-physics simulation capability enables accurate feasibility studies for ERT imaging, the identification of the ERT signatures that are unique to a given process, and facilitates the joint inversion of ERT data with hydrogeological data for subsurface characterization. PFLOTRAN-E4D is demonstrated herein using a field study of stage-driven groundwater/river water interaction ERT monitoring along the Columbia River, Washington, USA. Results demonstrate the complex nature of subsurface electrical conductivity changes, in both the saturated and unsaturated zones, arising from river stage fluctuations and associated river water intrusion into the aquifer. The results also demonstrate the sensitivity of surface based ERT measurements to those changes over time. PFLOTRAN-E4D is available with the PFLOTRAN development version with an open-source license at https://bitbucket.org/pflotran/pflotran-dev.

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.

An electrical-heating and self-sensing shape memory polymer composite incorporated with carbon fiber felt

NASA Astrophysics Data System (ADS)

Gong, Xiaobo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2016-03-01

Shape memory polymers (SMPs) have the ability to adjust their stiffness, lock a temporary shape, and recover the permanent shape upon imposing an appropriate stimulus. They have found their way into the field of morphing structures. The electrically Joule resistive heating of the conductive composite can be a desirable stimulus to activate the shape memory effect of SMPs without external heating equipment. Electro-induced SMP composites incorporated with carbon fiber felt (CFF) were explored in this work. The CFF is an excellent conductive filler which can easily spread throughout the composite. It has a huge advantage in terms of low cost, simple manufacturing process, and uniform and tunable temperature distribution while heating. A continuous and compact conductive network made of carbon fibers and the overlap joints among them was observed from the microscopy images, and this network contributes to the high conductive properties of the CFF/SMP composites. The CFF/SMP composites can be electrical-heated rapidly and uniformly, and its’ shape recovery effect can be actuated by the electrical resistance Joule heating of the CFF without an external heater. The CFF/SMP composite get higher modulus and higher strength than the pure SMP without losing any strain recovery property. The high dependence of temperature and strain on the electrical resistance also make the composite a good self-sensing material. In general, the CFF/SMP composite shows great prospects as a potential material for the future morphing structures.

Optimal irradiance for sintering of inkjet-printed Ag electrodes with a 532nm CW laser

NASA Astrophysics Data System (ADS)

Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Moon, Seung Jae

2013-09-01

Industrial solar cell fabrication generally adopts printing process to deposit the front electrodes, which needs additional heat treatment after printing to enhance electrical conductivity. As a heating method, laser irradiation draws attention not only because of its special selectivity, but also because of its intense heating to achieve high electric conductivity which is essential to reduce ohmic loss of solar cells. In this study, variation of electric conductivity was examined with laser irradiation having various beam intensity. 532 nm continuous wave (CW) laser was irradiated on inkjet-printed silver lines on glass substrate and electrical resistance was measured in situ during the irradiation. The results demonstrate that electric conductivity varies nonlinearly with laser intensity, having minimum specific resistance of 4.1 x 10-8 Ωm at 529 W/cm2 irradiation. The results is interesting because the specific resistance achieved by the present laser irradiation was about 1.8 times lower than the best value obtainable by oven heating, even though it was still higher by 2.5 times than that of bulk silver. It is also demonstrated that the irradiation time, needed to finish sintering process, decreases with laser intensity. The numerical simulation of laser heating showed that the optimal heating temperature could be as high as 300 oC for laser sintering, while it was limited to 250 oC for oven sintering. The nonlinear response of sintering with heating intensity was discussed, based on the results of FESEM images and XRD analysis.

Combined 2-D Electrical Resistivity and Self Potential Survey to Investigate the Pattern of the Watukosek Fault System Around the Lusi Eruption Site, Indonesia.

NASA Astrophysics Data System (ADS)

Mazzini, A.; Husein, A.; Mauri, G.; Lupi, M.; Hadi, S.; Kemna, A.

2015-12-01

The Lusi mud eruption is located in the Sidoarjo area, Indonesia and is continuously erupting hot mud since its birth in May 2006. A comprehensive combined electrical resistivity and self-potential (SP) survey was performed in the 7 km2 area inside the Lusi embankment that had been built to contain the erupted mud and to prevent flooding of the surrounding roads and settlements. The goal of the geophysical survey is to map the near-surface occurrence of the Watukosek fault system, upon which LUSI resides, delineate its spatial pattern and monitor its development. We completed six lines of measurements combining resistivity measurement using Wenner configuration and SP measurements using roll-along technique. Three subparallel lines were located either to the north and to the south of the main crater. Each line was approximately W-E oriented extending for ~1.26 km. The surveyed regions consist of dried mud breccia (containing clayey-silty-sandy admixture with clast up to ~ 10 cm in size). The thickness of the dry walkable mud is approximately 2-3 m and the deeper layer consist of water saturated mud that could be vulnerable to a liquefaction scenario in case of significant seismic activity in the region. The resistivity data were inverted into 2-D resistivity images with a maximum exploration depth of almost 200 m. The resistivity images consistently reveal a region of about 300 m in width (between 30-90 m depth) characterized by anomalous resistivities, which are lower than the value observed in the surounding area. The position of these anomalies is also supported by the SP data, which suggests that their origin is related to fluid flow path in the subsurface. Thus the combined resistivity and SP results allow inference of an improved model of the Watukosek fault system.

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 characteristic slow-spreading features at the surface. We have conducted marine magnetotelluric (MT) surveys at the southern Mariana in 2010 and at the Eastern Lau in 2009-2010. We obtained 10 ocean bottom electro-magnetometer (OBEM) data from a 130 km length MT transect across the southern Mariana spreading axis at 13 N, while we obtained 2 OBEM data and 11 ocean bottom magnetometer data from two 160 km length MT transects across the Eastern Lau spreading axes at 19.7 S and 21.3 S. After calculation of MT response functions and their correction for topographic distortion, two-dimensional electrical resistivity structures will be derived using an inversion algorithm. At this meeting, first we will show the resistivity structure images of the upper mantle beneath these spreading axes. Then, these structure images will be compared to identify differences in the mantle dynamics and the melt supply beneath the back-arc spreading system related to the subducting slab.

Shallow subsurface imaging of the Piano di Pezza active normal fault (central Italy) by high-resolution refraction and electrical resistivity tomography coupled with time-domain electromagnetic data

NASA Astrophysics Data System (ADS)

Villani, Fabio; Tulliani, Valerio; Sapia, Vincenzo; Fierro, Elisa; Civico, Riccardo; Pantosti, Daniela

2015-12-01

The Piano di Pezza fault is the central section of the 35 km long L'Aquila-Celano active normal fault-system in the central Apennines of Italy. Although palaeoseismic data document high Holocene vertical slip rates (˜1 mm yr-1) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time the shallow subsurface of a key section of the main Piano di Pezza fault splay by means of high-resolution seismic and electrical resistivity tomography coupled with time-domain electromagnetic soundings (TDEM). Our surveys cross a ˜5-m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing Holocene alluvial fans. We provide 2-D Vp and resistivity images, which show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. Our data indicate that the upper fault termination has a sub-vertical attitude, in agreement with palaeoseismological trench evidence, whereas it dips ˜50° to the southwest in the deeper part. We recognize some low-velocity/low-resistivity regions in the fault hangingwall that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of some Holocene palaeo-earthquakes. We estimate a ˜13-15 m throw of this fault splay since the end of the Last Glacial Maximum (˜18 ka), leading to a 0.7-0.8 mm yr-1 throw rate that is quite in accordance with previous palaeoseismic estimation of Holocene vertical slip rates. The 1-D resistivity models from TDEM soundings collected along the trace of the electrical profile significantly match with 2-D resistivity images. Moreover, they indicate that in the fault hangingwall, ˜200 m away from the surface fault trace, the pre-Quaternary carbonate basement is at ˜90-100 m depth. We therefore provide a minimal ˜150-160 m estimate of the cumulative throw of the Piano di Pezza fault system in the investigated section. We further hypothesize that the onset of the Piano di Pezza fault activity may date back to the Middle Pleistocene (˜0.5 Ma), so this is a quite young active normal fault if compared to other mature normal fault systems active since 2-3 Ma in this portion of the central Apennines.

Three-Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System

NASA Astrophysics Data System (ADS)

Gresse, Marceau; Vandemeulebrouck, Jean; Byrdina, Svetlana; Chiodini, Giovanni; Revil, André; Johnson, Timothy C.; Ricci, Tullio; Vilardo, Giuseppe; Mangiacapra, Annarita; Lebourg, Thomas; Grangeon, Jacques; Bascou, Pascale; Metral, Laurent

2017-11-01

The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3-D, high-resolution, electrical resistivity tomography of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of 0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a 10 m thick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.

Near surface geophysical techniques on subsoil contamination: laboratory experiments

NASA Astrophysics Data System (ADS)

Capozzoli, Luigi; Giampaolo, Valeria; Rizzo, Enzo

2016-04-01

Hydrocarbons contamination of soil and groundwater has become a serious environmental problem, because of the increasing number of accidental spills caused by human activities. The starting point of any studies is the reconstruction of the conceptual site model. To make valid predictions about the flow pathways following by hydrocarbons compound is necessary to make a correct reconstruction of their characteristics and the environment in which they move. Near-surface geophysical methods, based on the study of electrical and electromagnetic properties, are proved to be very useful in mapping spatial distribution of the organic contaminants in the subsurface. It is well known, in fact, that electrical properties of the porous media are significantly influenced by hydrocarbons because, when contaminants enter the rock matrix, surface reaction occur between the contaminant and the soil grain surface. The main aim of this work is to investigate the capability of near-surface geophysical methods in mapping and monitoring spatial distribution of contaminants in a controlled setting. A laboratory experiment has been performed at the Hydrogeosite Laboratory of CNR-IMAA (Marsico Nuovo, PZ) where a box-sand has been contaminated by diesel. The used contaminant is a LNAPL, added to the sand through a drilled pipe. Contaminant behaviour and its migration paths have been monitored for one year by Electrical Resistivity measurements. In details, a Cross Borehole Electrical Resistivity Tomography techniques were used to characterize the contamination dynamics after a controlled hydrocarbon spillage occurring in the vadose zone. The approach with cross-borehole resistivity imaging provide a great advantage compared to more conventional surface electrical resistivity tomography, due to the high resolution at high depth (obviously depending on the depth of the well instrumented for the acquisition). This method has been shown to provide good information on the distribution of electrical properties of the subsoil at high depths and, in some cases, a detailed assessment of dynamic processes in the subsurface environment (Binley et al., 2002). Our study confirms the link between hydrocarbons contamination and geoelectrical signal and the capability of cross-hole electrical resistivity tomographies to realize a non-invasive characterization of LNAPL contamination of the media. Although, the electrical behaviour is much more complex and the relation with the contaminants depends also by time of investigation.

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.

Selective Laser Sintering of Conductive Inks for Inkjet Printing Based on Nanoparticle Compositions with Organic Silver Salts

NASA Astrophysics Data System (ADS)

Titkov, A. I.; Gadirov, R. M.; Nikonov, S. Yu.; Odod, A. V.; Solodova, T. A.; Kurtсevich, A. E.; Kopylova, T. N.; Yukhin, Yu. M.; Lyakhov, N. Z.

2018-02-01

Inkjet ink based on silver nanoparticles with sizes of 11.1 ± 2.4 nm has been developed. Test images are printed on a laboratory inkjet printer, followed by sintering the printed patterns with a diode laser having a wavelength of 453 nm. The structure and electrical properties of the resulting films are studied depending on the parameters of laser sintering. It is found that under optimal conditions, an electrically conductive film with a low resistivity of 12.2 μΩ· cm can be formed.

Route of steroid-activated macromolecules through nuclear pores imaged with atomic force microscopy.

PubMed

Oberleithner, H; Schäfer, C; Shahin, V; Albermann, L

2003-02-01

In eukaryotic cells, two concentric membranes, the nuclear envelope (NE), separate the nucleus from the cytoplasm. The NE is punctured by nuclear pore complexes (NPCs; molecular mass 120 MDa) that serve as regulated pathways for macromolecules entering and leaving the nuclear compartment. Transport across NPCs occurs through central channels. Such import and export of macromolecules through individual NPCs can be elicited in the Xenopus laevis oocyte by injecting the mineralocorticoid aldosterone and can be visualized with atomic force microscopy. The electrical NE resistance in intact cell nuclei can be measured in parallel. Resistance increases when macromolecules are engaged with the NPC. This article describe six observations made from these experiments and the conclusions that can be drawn from them. (i) A homogeneous population of macromolecules (approx. 100 kDa) attaches to the cytoplasmic face of the NPC 2 min after aldosterone injection. They are most likely to be aldosterone receptors. After a few minutes, they have disappeared. (ii) Large plugs (approx. molecular mass 1 MDa) appear in the central channels 20 min after hormone injection. They are most likely to be ribonucleoproteins exiting the nucleus. (iii) Electrical resistance measurements in isolated nuclei reveal transient electrical NE resistance peaks: an early (2 min) peak and a late (20 min) peak. Electrical peaks reflect macromolecule interaction with the NPC. (iv) Spironolactone blocks both the early and late peaks. This indicates that classic aldosterone receptors are involved in the pregenomic (early) and post-genomic (late) responses. (v) Actinomycin D and, independently, RNase A block the late electrical peak, confirming that plugs are genomic in nature. (vi) Intracellular calcium chelation blocks both early and late electrical peaks. Thus, the release of calcium from internal stores, which is known to be the first intracellular signal in response to aldosterone, is a prerequisite for the late genomic response.

Electrical Resistivity Measurement of Petroleum Coke Powder by Means of Four-Probe Method

NASA Astrophysics Data System (ADS)

Rouget, G.; Majidi, B.; Picard, D.; Gauvin, G.; Ziegler, D.; Mashreghi, J.; Alamdari, H.

2017-10-01

Carbon anodes used in Hall-Héroult electrolysis cells are involved in both electrical and chemical processes of the cell. Electrical resistivity of anodes depends on electrical properties of its constituents, of which carbon coke aggregates are the most prevalent. Electrical resistivity of coke aggregates is usually characterized according to the ISO 10143 standardized test method, which consists of measuring the voltage drop in the bed of particles between two electrically conducing plungers through which the current is also applied. Estimation of the electrical resistivity of coke particles from the resistivity of particle bed is a challenging task and needs consideration of the contribution of the interparticle void fraction and the particle/particle contact resistances. In this work, the bed resistivity was normalized by subtracting the interparticle void fraction. Then, the contact size was obtained from discrete element method simulation and the contact resistance was calculated using Holm's theory. Finally, the resistivity of the coke particles was obtained from the bed resistivity.

Leachate recirculation: moisture content assessment by means of a geophysical technique.

PubMed

Guérin, Roger; Munoz, Marie Laure; Aran, Christophe; Laperrelle, Claire; Hidra, Mustapha; Drouart, Eric; Grellier, Solenne

2004-01-01

Bioreactor technology is a waste treatment concept consisting in speeding up the biodegradation of landfilled waste by optimizing its moisture content through leachate recirculation. The measurement of variations in waste moisture content is critical in the design and control of bioreactors. Conventional methods such as direct physical sampling of waste reach their limits due to the interference with the waste matrix. This paper reviews geophysical measurements such as electrical direct current and electromagnetic slingram methods for measuring the electrical conductivity. Electrical conductivity is a property, which is linked to both moisture and temperature and can provide useful indications on the biodegradation environment in the waste mass. The study reviews three site experiments: a first experimentation shows the advantages (correlation between conductive anomaly and water seepage) but also the limits of geophysical interpretation; the two other sites allow the leachate recirculation to be tracked by studying the relative resistivity variation versus time from electrical 2D imaging. Even if some improvements are necessary to consider geophysical measurements as a real bioreactor monitoring tool, results are promising and could lead to the use of electrical 2D imaging in bioreactor designing.

Geophysical Responses of Hydrocarbon-impacted Zones at the Various Contamination Conditions

NASA Astrophysics Data System (ADS)

Kim, C.; Ko, K.; Son, J.; Kim, J.

2008-12-01

One controlled experiment and two field surveys were conducted to investigate the geoelectrical responses of hydrocarbon-contaminated zones, so called smeared zone, on the geophysical data at the hydrocarbon- contaminated sites with various conditions. One controlled physical model experiment with GPR using fresh gasoline and two different 3-D electrical resistivity investigations at the aged sites. One field site (former military facilities for arms maintenance) was mainly contaminated with lubricating oils and the other (former gas station) was contaminated with gasoline and diesel, respectively. The results from the physical model experiment show that GPR signals were enhanced when LNAPL was present as a residual saturation in the water-saturated system due to less attenuation of the electromagnetic energy through the soil medium of the hydrocarbon-impacted zone (no biodegradation), compared to when the medium was saturated with only water (no hydrocarbon impaction). In the former gas station site, 3-D resistivity results demonstrate that the highly contaminated zones were imaged with low resistivity anomalies since the biodegradation of petroleum hydrocarbons has been undergone for many years, causing the drastic increase in the TDS at the hydrocarbon-impacted zones. Finally, 3-D resistivity data obtained from the former military maintenance site show that the hydrocarbon-contaminated zones show high resistivity anomalies since the hydrocarbons such as lubricating oils at the contaminated soils were not greatly influenced by microbial degradation and has relatively well kept their original physical properties of high electrical resistivity. The results of the study illustrated that the hydrocarbon-impacted zones under various contamination conditions yielded various geophysical responses which include (1) enhanced GPR amplitudes at the fresh LNAPL (Gasoline to middle distillates) spill sites, (2) low electrical resistivity anomalies due to biodegradation at the aged LNAPL- impacted sites, and (3) high electrical resistivity anomalies at the fresh or aged sites contaminated with residual products of crude oils (lubricating oils). The study results also show that the geophysical methods, as a non-invasive sounding technique, can be effectively applied to mapping hydrocarbon-contaminated zones.

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.

Geophysical monitoring of simulated graves with resistivity, magnetic susceptibility, conductivity and GPR in Colombia, South America.

PubMed

Molina, Carlos Martin; Pringle, Jamie K; Saumett, Miguel; Evans, Gethin T

2016-04-01

In most Latin American countries there are significant numbers of both missing people and forced disappearances, ∼71,000 Colombia alone. Successful detection of buried human remains by forensic search teams can be difficult in varying terrain and climates. Three clandestine burials were simulated at two different depths commonly encountered in Latin America. In order to gain critical knowledge of optimum geophysical detection techniques, burials were monitored using: ground penetrating radar, magnetic susceptibility, bulk ground conductivity and electrical resistivity up to twenty-two months post-burial. Radar survey results showed good detection of modern 1/2 clothed pig cadavers throughout the survey period on 2D profiles, with the 250MHz antennae judged optimal. Both skeletonised and decapitated and burnt human remains were poorly imaged on 2D profiles with loss in signal continuity observed throughout the survey period. Horizontal radar time slices showed good anomalies observed over targets, but these decreased in amplitude over the post-burial time. These were judged due to detecting disturbed grave soil rather than just the buried targets. Magnetic susceptibility and electrical resistivity were successful at target detection in contrast to bulk ground conductivity surveys which were unsuccessful. Deeper burials were all harder to image than shallower ones. Forensic geophysical surveys should be undertaken at suspected burial sites. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Non-invasive Geophysical Surveys in Search of the Roman Temple of Augustus Under the Cathedral of Tarragona (Catalonia, Spain): A Case Study

NASA Astrophysics Data System (ADS)

Casas, Albert; Cosentino, Pietro L.; Fiandaca, Gianluca; Himi, Mahjoub; Macias, Josep M.; Martorana, Raffaele; Muñoz, Andreu; Rivero, Lluís; Sala, Roger; Teixell, Imma

2018-04-01

An integrated geophysical survey has been conducted at the Tarragona's Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner-Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.

Imaging Preferential Flow Pathways of Contaminants from Passive Acid Mine Drainage Mitigation Sites Using Electrical Resistivity

NASA Astrophysics Data System (ADS)

Kelley, N.; Mount, G.; Terry, N.; Herndon, E.; Singer, D. M.

2017-12-01

The Critical Zone represents the surficial and shallow layer of rock, air, water, and soil where most interactions between living organisms and the Earth occur. Acid mine drainage (AMD) resulting from coal extraction can influence both biological and geochemical processes across this zone. Conservative estimates suggest that more than 300 million gallons of AMD are released daily, making this acidic solution of water and contaminants a common issue in areas with legacy or current coal extraction. Electrical resistivity imaging (ERI) provides a rapid and minimally invasive method to identify and monitor contaminant pathways from AMD remediation systems in the subsurface of the Critical Zone. The technique yields spatially continuous data of subsurface resistivity that can be inverted to determine electrical conductivity as a function of depth. Since elevated concentrations of heavy metals can directly influence soil conductivity, ERI data can be used to trace the flow pathways or perhaps unknown mine conduits and transport of heavy metals through the subsurface near acid mine drainage sources. This study aims to examine preferential contaminant migration from those sources through substrate pores, fractures, and shallow mine workings in the near subsurface surrounding AMD sites in eastern Ohio and western Pennsylvania. We utilize time lapse ERI measures during different hydrologic conditions to better understand the variability of preferential flow pathways in relation to changes in stage and discharge within the remediation systems. To confirm ERI findings, and provide constraint to geochemical reactions occurring in the shallow subsurface, we conducted Inductively Coupled Plasma (ICP) spectrometry analysis of groundwater samples from boreholes along the survey transects. Through these combined methods, we can provide insight into the ability of engineered systems to contain and isolate metals in passive acid mine drainage treatment systems.

Absolute electrical impedance tomography (aEIT) guided ventilation therapy in critical care patients: simulations and future trends.

PubMed

Denaï, Mouloud A; Mahfouf, Mahdi; Mohamad-Samuri, Suzani; Panoutsos, George; Brown, Brian H; Mills, Gary H

2010-05-01

Thoracic electrical impedance tomography (EIT) is a noninvasive, radiation-free monitoring technique whose aim is to reconstruct a cross-sectional image of the internal spatial distribution of conductivity from electrical measurements made by injecting small alternating currents via an electrode array placed on the surface of the thorax. The purpose of this paper is to discuss the fundamentals of EIT and demonstrate the principles of mechanical ventilation, lung recruitment, and EIT imaging on a comprehensive physiological model, which combines a model of respiratory mechanics, a model of the human lung absolute resistivity as a function of air content, and a 2-D finite-element mesh of the thorax to simulate EIT image reconstruction during mechanical ventilation. The overall model gives a good understanding of respiratory physiology and EIT monitoring techniques in mechanically ventilated patients. The model proposed here was able to reproduce consistent images of ventilation distribution in simulated acutely injured and collapsed lung conditions. A new advisory system architecture integrating a previously developed data-driven physiological model for continuous and noninvasive predictions of blood gas parameters with the regional lung function data/information generated from absolute EIT (aEIT) is proposed for monitoring and ventilator therapy management of critical care patients.

A compressed sensing based 3D resistivity inversion algorithm for hydrogeological applications

NASA Astrophysics Data System (ADS)

Ranjan, Shashi; Kambhammettu, B. V. N. P.; Peddinti, Srinivasa Rao; Adinarayana, J.

2018-04-01

Image reconstruction from discrete electrical responses pose a number of computational and mathematical challenges. Application of smoothness constrained regularized inversion from limited measurements may fail to detect resistivity anomalies and sharp interfaces separated by hydro stratigraphic units. Under favourable conditions, compressed sensing (CS) can be thought of an alternative to reconstruct the image features by finding sparse solutions to highly underdetermined linear systems. This paper deals with the development of a CS assisted, 3-D resistivity inversion algorithm for use with hydrogeologists and groundwater scientists. CS based l1-regularized least square algorithm was applied to solve the resistivity inversion problem. Sparseness in the model update vector is introduced through block oriented discrete cosine transformation, with recovery of the signal achieved through convex optimization. The equivalent quadratic program was solved using primal-dual interior point method. Applicability of the proposed algorithm was demonstrated using synthetic and field examples drawn from hydrogeology. The proposed algorithm has outperformed the conventional (smoothness constrained) least square method in recovering the model parameters with much fewer data, yet preserving the sharp resistivity fronts separated by geologic layers. Resistivity anomalies represented by discrete homogeneous blocks embedded in contrasting geologic layers were better imaged using the proposed algorithm. In comparison to conventional algorithm, CS has resulted in an efficient (an increase in R2 from 0.62 to 0.78; a decrease in RMSE from 125.14 Ω-m to 72.46 Ω-m), reliable, and fast converging (run time decreased by about 25%) solution.

Saline tracer visualized with three-dimensional electrical resistivity tomography: Field-scale spatial moment analysis

USGS Publications Warehouse

Singha, Kamini; Gorelick, Steven M.

2005-01-01

Cross-well electrical resistivity tomography (ERT) was used to monitor the migration of a saline tracer in a two-well pumping-injection experiment conducted at the Massachusetts Military Reservation in Cape Cod, Massachusetts. After injecting 2200 mg/L of sodium chloride for 9 hours, ERT data sets were collected from four wells every 6 hours for 20 days. More than 180,000 resistance measurements were collected during the tracer test. Each ERT data set was inverted to produce a sequence of 3-D snapshot maps that track the plume. In addition to the ERT experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values. Using modified moment analysis of the electrical conductivity tomograms, the mass, center of mass, and spatial variance of the imaged tracer plume were estimated. Although the tomograms provide valuable insights into field-scale tracer migration behavior and aquifer heterogeneity, standard tomographic inversion and application of Archie's law to convert electrical conductivities to solute concentration results in underestimation of tracer mass. Such underestimation is attributed to (1) reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and (2) spatial smoothing (regularization) from tomographic inversion. The center of mass estimated from the ERT inversions coincided with that given by migration of the tracer plume using 3-D advective-dispersion simulation. The 3-D plumes seen using ERT exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well.

Electrical Methods: Resistivity Methods

EPA Pesticide Factsheets

Surface electrical resistivity surveying is based on the principle that the distribution of electrical potential in the ground around a current-carrying electrode depends on the electrical resistivities and distribution of the surrounding soils and rocks.

2D resistivity imaging and magnetic survey for characterization of thermal springs: A case study of Gergedi thermal springs in the northwest of Wonji, Main Ethiopian Rift, Ethiopia

NASA Astrophysics Data System (ADS)

Abdulkadir, Yahya Ali; Eritro, Tigistu Haile

2017-09-01

Electrical resistivity imaging and magnetic surveys were carried out at Gergedi thermal springs, located in the Main Ethiopian Rift, to characterize the geothermal condition of the area. The area is geologically characterized by alluvial and lacustrine deposits, basaltic lava, ignimbrites, and rhyolites. The prominent structural feature in this part of the Main Ethiopian Rift, the SW -NE trending structures of the Wonji Fault Belt System, crosse over the study area. Three lines of imaging data and numerous magnetic data, encompassing the active thermal springs, were collected. Analysis of the geophysical data shows that the area is covered by low resistivity response regions at shallow depths which resulted from saline moisturized soil subsurface horizon. Relatively medium and high resistivity responses resulting from the weathered basalt, rhyolites, and ignimbrites are also mapped. Qualitative interpretation of the magnetic data shows the presence of structures that could act as pathways for heat and fluids manifesting as springs and also characterize the degree of thermal alteration of the area. Results from the investigations suggest that the Gergedi thermal springs area is controlled by fault systems oriented parallel and sub-parallel to the main tectonic lines of the Main Ethiopian Rift.

Patient-Specific Detection of Cerebral Blood Flow Alterations as Assessed by Arterial Spin Labeling in Drug-Resistant Epileptic Patients

PubMed Central

Boscolo Galazzo, Ilaria; Storti, Silvia Francesca; Del Felice, Alessandra; Pizzini, Francesca Benedetta; Arcaro, Chiara; Formaggio, Emanuela; Mai, Roberto; Chappell, Michael; Beltramello, Alberto; Manganotti, Paolo

2015-01-01

Electrophysiological and hemodynamic data can be integrated to accurately and precisely identify the generators of abnormal electrical activity in drug-resistant focal epilepsy. Arterial Spin Labeling (ASL), a magnetic resonance imaging (MRI) technique for quantitative noninvasive measurement of cerebral blood flow (CBF), can provide a direct measure of variations in cerebral perfusion associated with the epileptic focus. In this study, we aimed to confirm the ASL diagnostic value in the identification of the epileptogenic zone, as compared to electrical source imaging (ESI) results, and to apply a template-based approach to depict statistically significant CBF alterations. Standard video-electroencephalography (EEG), high-density EEG, and ASL were performed to identify clinical seizure semiology and noninvasively localize the epileptic focus in 12 drug-resistant focal epilepsy patients. The same ASL protocol was applied to a control group of 17 healthy volunteers from which a normal perfusion template was constructed using a mixed-effect approach. CBF maps of each patient were then statistically compared to the reference template to identify perfusion alterations. Significant hypo- and hyperperfused areas were identified in all cases, showing good agreement between ASL and ESI results. Interictal hypoperfusion was observed at the site of the seizure in 10/12 patients and early postictal hyperperfusion in 2/12. The epileptic focus was correctly identified within the surgical resection margins in the 5 patients who underwent lobectomy, all of which had good postsurgical outcomes. The combined use of ESI and ASL can aid in the noninvasive evaluation of drug-resistant epileptic patients. PMID:25946055

Groundwater resources evaluation in calcareous limestone using geoelectrical and VLF-EM surveys (El Salloum Basin, Egypt)

NASA Astrophysics Data System (ADS)

Zarif, Fardous; Slater, Lee; Mabrouk, Mohamed; Youssef, Ahmed; Al-Temamy, Ayman; Mousa, Salah; Farag, Karam; Robinson, Judy

2018-01-01

Understanding and developing groundwater resources in arid regions such as El Salloum basin, along the northwestern coast of Egypt, remains a challenging issue. One-dimensional (1D) electrical sounding (ES), two-dimensional (2D) electrical resistivity imaging (ERI), and very low frequency electromagnetic (VLF-EM) measurements were used to investigate the hydrogeological framework of El Salloum basin with the aim of determining the potential for extraction of potable water. 1D resistivity sounding models were used to delineate geoelectric sections and water-bearing layers. 2D ERI highlighted decreases in resistivity with depth, attributed to clay-rich limestone combined with seawater intrusion towards the coast. A depth of investigation (DOI) index was used to constrain the information content of the images at depths up to 100 m. The VLF-EM survey identified likely faults/fractured zones across the study area. A combined analysis of the datasets of the 1D ES, 2D ERI, and VLF-EM methods identified potential zones of groundwater, the extent of seawater intrusion, and major hydrogeological structures (fracture zones) in El Salloum basin. The equivalent geologic layers suggest that the main aquifer in the basin is the fractured chalky limestone middle Miocene) south of the coastal plain of the study area. Sites likely to provide significant volumes of potable water were identified based on relatively high resistivity and thickness of laterally extensive layers. The most promising locations for drilling productive wells are in the south and southeastern parts of the region, where the potential for potable groundwater increases substantially.

Groundwater resources evaluation in calcareous limestone using geoelectrical and VLF-EM surveys (El Salloum Basin, Egypt)

NASA Astrophysics Data System (ADS)

Zarif, Fardous; Slater, Lee; Mabrouk, Mohamed; Youssef, Ahmed; Al-Temamy, Ayman; Mousa, Salah; Farag, Karam; Robinson, Judy

2018-06-01

Understanding and developing groundwater resources in arid regions such as El Salloum basin, along the northwestern coast of Egypt, remains a challenging issue. One-dimensional (1D) electrical sounding (ES), two-dimensional (2D) electrical resistivity imaging (ERI), and very low frequency electromagnetic (VLF-EM) measurements were used to investigate the hydrogeological framework of El Salloum basin with the aim of determining the potential for extraction of potable water. 1D resistivity sounding models were used to delineate geoelectric sections and water-bearing layers. 2D ERI highlighted decreases in resistivity with depth, attributed to clay-rich limestone combined with seawater intrusion towards the coast. A depth of investigation (DOI) index was used to constrain the information content of the images at depths up to 100 m. The VLF-EM survey identified likely faults/fractured zones across the study area. A combined analysis of the datasets of the 1D ES, 2D ERI, and VLF-EM methods identified potential zones of groundwater, the extent of seawater intrusion, and major hydrogeological structures (fracture zones) in El Salloum basin. The equivalent geologic layers suggest that the main aquifer in the basin is the fractured chalky limestone middle Miocene) south of the coastal plain of the study area. Sites likely to provide significant volumes of potable water were identified based on relatively high resistivity and thickness of laterally extensive layers. The most promising locations for drilling productive wells are in the south and southeastern parts of the region, where the potential for potable groundwater increases substantially.

Influence of vehicle resistance on transdermal iontophoretic delivery of acetylcholine and sodium nitroprusside in humans.

PubMed

Khan, Faisel; Newton, David J; Smyth, Emily C; Belch, Jill J F

2004-09-01

Iontophoresis is a valuable method of noninvasive drug delivery for assessment of skin microvascular function, but it is important to consider and minimize its potential nonspecific electrical effects on blood flow. The use of sodium chloride (NaCl) instead of water as the iontophoresis vehicle has been reported to reduce these effects because it has a lower electrical resistance. However, this argument may not be valid when an agonist is added to the vehicle because its resistance will be changed. The aim of our study was to determine whether there is a difference in resistance between water and NaCl when used as vehicles for iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). Four cumulative doses of each drug, dissolved in either water or NaCl, were delivered via iontophoresis to the forearm skin of 14 healthy volunteers. We measured the resulting blood flow responses by using laser-Doppler imaging and the voltage across the electrodes for each delivery as an index of resistance. For ACh and SNP, there were no significant differences between the voltages measured when either water or NaCl was used as the vehicle. However, the blood flow responses to both agonists were significantly lower with NaCl (ACh: 25% lower, P < 0.001; SNP: 15% lower, P = 0.019). The use of NaCl is therefore unlikely to decrease any nonspecific electrical effects, and it may in fact reduce the effective dose of drug delivered. Deionized water is a better iontophoresis vehicle for the assessment of microvascular function in skin when using ACh and SNP.

Geoelectrical investigation of oil contaminated soils in former underground fuel base: Borne Sulinowo, NW Poland

NASA Astrophysics Data System (ADS)

Zogala, B.; Dubiel, R.; Zuberek, W. M.; Rusin-Zogala, M.; Steininger, M.

2009-07-01

The survey has been carried out in the area of 0.23 km2 of the former military underground fuel base. The oil derivative products were observed in excavations and the laboratory tests confirmed the occurrence of hydrocarbons (>C12) in soils. The purpose of the survey was to determine the spatial extent of the contamination. The studied area is covered by postglacial sediments: sands, gravels and till. The first water table was observed at a depth of 10-12 m. The detailed electromagnetic measurements with Geonics EM31-MK2 conductivity meter were performed in the whole area of the former fuel base. Obtained results were elaborated statistically and the map of apparent electrical conductivity to a depth of 6 m was created. Many local low conductivity anomalies were observed. The measurements with Geonics EM34-3XL were performed along one A-A' profile and 1D electromagnetic modelling along with this profile was calculated to obtain the electrical conductivity cross-section to a depth of 30 m. Two-dimensional electrical resistivity imaging measurements were carried out along the same profile and the resistivity cross-section to a depth of 20 m was performed. Both conducivity and resistivity cross-sections show anomalous zones. The zones correlate with oil contaminated zones very well.

Electrical Resistivity of Wire Arc Sprayed Zn and Cu Coatings for In-Mold-Metal-Spraying

NASA Astrophysics Data System (ADS)

Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Hopmann, Ch; Ochotta, P.

2018-06-01

Electrical functionalities can be integrated into plastic parts by integrating thermally sprayed metal coatings into the non-conductive base material. Thermally sprayed conducting tracks for power and signal transmission are one example. In this case, the electrical resistance or resistivity of the coatings should be investigated. Therefore, the electrical resistivity of wire arc sprayed Zn and Cu coatings has been investigated. In case of Zn coatings, spray distance, gas pressure and wire diameter could be identified as significant influencing parameters on the electrical resistivity. In contrast, process gas, gas pressure and voltage do have a significant influence on the electrical resistivity of Cu coatings. Through the use of the In-Mold-Metal-Spraying method (IMMS), thermal degradation can be avoided by transferring thermally sprayed coating from a mold insert onto the plastic part. Therefore, the influence of the transfer process on the electrical resistance of the coatings has also been investigated.

Electrical and structural properties of Nb-doped TiO2 at different Nb concentrations deposited by spin coating technique

NASA Astrophysics Data System (ADS)

Saurdi, I.; Shafura, A. K.; Mamat, M. H.; Ishak, A.; Rusop, M.

2018-05-01

In this paper, the Nb-doped TiO2 films were deposited on glass substrate and their electrical and structural properties were investigated. The results revealed that the resistivity of Nb-doped TiO2 films of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.% were 2.78 × 105, 1.35 × 105 Ω.cm, 5.89 × 104 Ω.cm, 9.20 × 102 Ω.cm and 9.56 × 103 Ω.cm, respectively. Where, the lowest resistivity of 9.20 × 102 Ω.cm was obtained at 5at.% Nb-doped TiO2 films. The resistivity of Nb-doped TiO2 films decreases as the Nb concentration increased from 0 at.% to 5 at.%. However, the resistivity decrease at 7 at.% Nb-doped TiO2 films. Meanwhile, from the FESEM images the Nb-doped TiO2 films with 0 at.%, 1 at.%, 3 at.% and 5 at.% Nb had a rough and porous structures were observed. However, the Nb-doped TiO2 at 7 at.% has a agglomerated and denser structures.

Detection and quantification of intraperitoneal fluid using electrical impedance tomography.

PubMed

Sadleir, R J; Fox, R A

2001-04-01

A prototype electrical impedance tomography system was evaluated prior to its use for the detection of intraperitoneal bleeding, with the assistance of patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The system was sensitive enough to detect small amounts of dialysis fluid appearing in subtractive images over short time periods. Uniform sensitivity to blood appearing anywhere within the abdominal cavity was produced using a post-reconstructive filter that corrected for changes in apparent resistivity of anomalies with their radial position. The image parameter used as an indication of fluid quantity, the resistivity index, varied approximately linearly with the quantity of fluid added. A test of the system's response to the introduction of conductive fluid out of the electrode plane (when a blood-equivalent fluid was added to the stomach) found that the sensitivity of the system was about half that observed in the electrode plane. Breathing artifacts were found to upset quantitative monitoring of intraperitoneal bleeding, but only on time scales short compared with the fluid administration rate. Longer term breathing changes, such as those due to variations in the functional residual capacity of the lungs, should ultimately limit the sensitivity over long time periods.

Sinop Province, Şahintepesi Region, Bayraktepe Tumulus' Display With Electrical Resistivity Tomography

NASA Astrophysics Data System (ADS)

Yıldırım, Şahin; Ahmet Yüksel, Fethi; Avcı, Kerim; Ziya Görücü, Mahmut

2017-04-01

Paphlagonia is located on the Boztepe Foreland (Sinop Foreland) and its peninsula, which extends northwards along the coastal lane of the Black Sea. Sinop is at the northernmost tip of Turkey, in the middle of the Black Sea region. Archaeological excavations of the entire Sinop province have uncovered artifacts from the Bronze Age dating back to 3000 BC. Most ancient sources indicate that Mithridates is buried in Sinop. It is alleged that the Tumuli on the crest of the historical peninsula, called Boztepe in Sinop, could be the resting spot of Mithridates. There are three tumuli in this area known as Şahin Tepesi Mevkii (Şahin Hill Site). In order to determine the location of the burial chamber of the tomb, Electrical Resistivity Tomography (ERT) measurement methods were used, which is a geophysical method capable of three dimensional (3D) measurement and evaluation. In the area of the tumulus, measurements were made in a 57 electrode array using a 42 x 36 m (total 1512 m2) spread electrode pattern with 6m spacing. In the study, an AGI brand SuperString R1 Resistivity device and equipment were used. Resistivity data were interpreted using AGI Earthimag 3D software. From the geoelectric resistivity data, 2D and 3D images were obtained as a result of data processing. In the tumulus area smooth geometrical forms and individual high-amplitude anomalies were visualized, that could be attributed to structural remains and the presence of archaeological materials. These anomalies were plotted on the gridded location plan of the excavation area. Within the artificial hill forming the tumulus, with regards to the natural geological units, anomalies such as very high resistivity, linear elongations, angular rotations, curves, etc. (stone wall, hollow room) that are caused by architectural elements were observed. These geometrically shaped, very highly resistive, anomalies should be checked. Keywords: Sinope, Tumulus, Electrical Resistivity Tomography, Archaeo-geophysics

Electrical Resistance Tomography to Monitor Mitigation of Metal-Toxic Acid-Leachates Ruby Gulch Waste Rock Repository Gilt Edge Mine Superfund Site, South Dakota USA

NASA Astrophysics Data System (ADS)

Versteeg, R.; Heath, G.; Richardson, A.; Paul, D.; Wangerud, K.

2003-12-01

At a cyanide heap-leach open-pit mine, 15-million cubic yards of acid-generating sulfides were dumped at the head of a steep-walled mountain valley, with 30 inches/year precipitation generating 60- gallons/minute ARD leachate. Remediation has reshaped the dump to a 70-acre, 3.5:1-sloped geometry, installed drainage benches and runoff diversions, and capped the repository and lined diversions with a polyethylene geomembrane and cover system. Monitoring was needed to evaluate (a) long-term geomembrane integrity, (b) diversion liner integrity and long-term effectiveness, (c) ARD geochemistry, kinetics and pore-gas dynamics within the repository mass, and (d) groundwater interactions. Observation wells were paired with a 600-electrode resistivity survey system. Using near-surface and down-hole electrodes and automated data collection and post-processing, periodic two- and three-dimensional resistivity images are developed to reflect current and changed-conditions in moisture, temperature, geochemical components, and flow-direction analysis. Examination of total resistivity values and time variances between images allows direct observation of liner and cap integrity with precise identification and location of leaks; likewise, if runoff migrates from degraded diversion ditches into the repository zone, there is an accompanying and noticeable change in resistivity values. Used in combination with monitoring wells containing borehole resistivity electrodes (calibrated with direct sampling of dump water/moisture, temperature and pore-gas composition), the resistivity arrays allow at-depth imaging of geochemical conditions within the repository mass. The information provides early indications of progress or deficiencies in de-watering and ARD- mitigation that is the remedy intent. If emerging technologies present opportunities for secondary treatment, deep resistivity images may assist in developing application methods and evaluating the effectiveness of any reagents introduced into the repository mass to further effect changes in oxidation/reduction reactions.

Electrical contacts to thin layers of Bi2Sr2CaCu2O8+δ

NASA Astrophysics Data System (ADS)

Suzuki, Shota; Taniguchi, Hiroki; Kawakami, Tsukasa; Cosset-Cheneau, Maxen; Arakawa, Tomonori; Miyasaka, Shigeki; Tajima, Setsuko; Niimi, Yasuhiro; Kobayashi, Kensuke

2018-05-01

Thin layers of Bi2Sr2CaCu2O8+δ (Bi2212) were fabricated using the mechanical exfoliation technique. Good electrical contacts to the thin Bi2212 films with low contact resistance were realized by depositing Ag and Au electrodes onto the Bi2212 films and annealing them with an oxygen flow at 350 °C for 30 min. We observed cross-section images of the Bi2212 thin film device using a transmission electron microscope to characterize the diffusion of Ag and Au atoms into the Bi2212 thin film.

Conductive fabric seal

DOEpatents

Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

2017-04-04

Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

Conductive fabric seal

DOEpatents

Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

2015-10-13

Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

Formation of Bimolecular Membranes from Lipid Monolayers and a Study of Their Electrical Properties

PubMed Central

Montal, M.; Mueller, P.

1972-01-01

Bimolecular membranes are formed from two lipid monolayers at an air-water interface by the apposition of their hydrocarbon chains when an aperture in a Teflon partition separating two aqueous phases is lowered through the interface. Formation of the membrane is monitored by an increase of the electrical capacity, as measured with a voltage clamp. Electrical resistance of the unmodified membrane is analogous to that of conventional planar bilayers (black lipid membranes) prepared in the presence of a hydrocarbon solvent, i.e., 106-108 ohm cm2; the resistance can be lowered to values of 103 ohm cm2 by gramicidin, an antibiotic that modifies the conductance only when the membranes are of biomolecular thickness. In contrast to the resistance, there is a significant difference between the capacity of bilayers made from mono-layers and that of hydrocarbon-containing bilayers made by phase transition; the average values are 0.9 and 0.45 μF cm-2, respectively. The value of 0.9 μF cm-2 approximates that of biological membranes. Assuming a dielectric constant of 2.1 for the hydrocarbon region, the dielectric thickness, as calculated from a capacity of 0.9 μF cm-2, is 22 Å. This value is 6-10 Å smaller than the actual thickness of the hydrocarbon region of bilayers and cell membranes, as determined by x-ray diffraction. The difference may be due to a limited penetration of water into the hydrocarbon region near the ester groups that would lower the electrical resistance of this region and reduce the dielectric thickness. Asymmetric membranes have been formed by adjoining two lipid monolayers of different chemical composition. Images PMID:4509315

3D pore-type digital rock modeling of natural gas hydrate for permafrost and numerical simulation of electrical properties

NASA Astrophysics Data System (ADS)

Dong, Huaimin; Sun, Jianmeng; Lin, Zhenzhou; Fang, Hui; Li, Yafen; Cui, Likai; Yan, Weichao

2018-02-01

Natural gas hydrate is being considered as an alternative energy source for sustainable development and has become a focus of research throughout the world. In this paper, based on CT scanning images of hydrate reservoir rocks, combined with the microscopic distribution of hydrate, a diffusion limited aggregation (DLA) model was used to construct 3D hydrate digital rocks of different distribution types, and the finite-element method was used to simulate their electrical characteristics in order to study the influence of different hydrate distribution types, hydrate saturation and formation of water salinity on electrical properties. The results show that the hydrate digital rocks constructed using the DLA model can be used to characterize the microscopic distribution of different types of hydrates. Under the same conditions, the resistivity of the adhesive hydrate digital rock is higher than the cemented and scattered type digital rocks, and the resistivity of the scattered hydrate digital rock is the smallest among the three types. Besides, the difference in the resistivity of the different types of hydrate digital rocks increases with an increase in hydrate saturation, especially when the saturation is larger than 55%, and the rate of increase of each of the hydrate types is quite different. Similarly, the resistivity of the three hydrate types decreases with an increase in the formation of water salinity. The single distribution hydrate digital rock constructed, combined with the law of microscopic distribution and influence of saturation on the electrical properties, can effectively improve the accuracy of logging identification of hydrate reservoirs and is of great significance for the estimation of hydrate reserves.

Comparing Three-Dimensional Geophysical Models of Mount St. Helens

NASA Astrophysics Data System (ADS)

Creager, K. C.; Ulberg, C. W.; Vidale, J. E.; Levander, A.; Kiser, E.; Abers, G. A.; Crosbie, K.; Mann, M. E.; Moran, S. C.; Denlinger, R. P.; Thelen, W. A.; Hansen, S. M.; Schmandt, B.; Schultz, A.; Bowles-martinez, E.; Bedrosian, P.; Peacock, J.; Hill, G.

2017-12-01

The iMUSH project integrates active- and passive-source seismic experiments with magnetotelluric (MT) observations and petrology to better understand the structure and dynamics of the Mount St. Helens (MSH) magmatic system from the subducted plate to the surface. The geophysical experiments included a two-year, 70-element broadband array with 10-km station spacing within 50 km of the MSH edifice, 23 shots recorded by geophones at 6000 sites including 900 Nodal stations, and 147 wideband MT stations with 6-km nominal station spacing. We have determined 3-D models of P-wave, S-wave and P/S-wave velocity as well as 3-D electrical resistivity. Our models from independent data sets and methodologies exhibit remarkable similarity. A narrow low-VP and VS anomaly as well as a high VP/VS and conductivity anomaly is well imaged by nearly all methods at about 6-15 km beneath MSH and coincides with a previously inferred magma storage volume. The St. Helens seismic zone (SHZ), which cuts through MSH with a NNW-SSE orientation, coincides with a narrow, vertical, planar zone of high electrical conductivity and low VP from the near surface to 15 km depth where we lose resolution. The continental Moho shows strong reflectivity east of the SHZ, but is weak to non-existent to the west, perhaps because this marks the eastern edge of hydrous mineral stability in the cold mantle wedge. Farther north, a similar high-conductivity feature is imaged along the west Rainer seismic zone. High Vp/Vs and high electrical conductivity extend under the Indian Heaven volcanic field at depths of 5-15 km, potentially associated with regions of partial melt and/or fluids. Mid- to lower-crustal velocities are generally fast to the west of MSH, consistent with the presence of the accreted Siletz terrane, and slow to the east suggesting both a change in composition and higher temperatures. Moderate lower-crustal resistivity is also present to the east, and is consistent with a small degree of partial melt. Several plutons, including the Spirit Lake, Spud Mountain and Silver Star plutons, are clearly imaged as high wave speeds and high resistivity anomalies in the upper crust, while the Chehalis Basin and Morton Anticline exhibit very low wave speeds and extremely low resistivities, indicative of marine to transitional Tertiary sediments.

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-shifting effects of secondary roots of the two Juglans regia in differently inclined ambiences can be imaged using 3D ERT. The results of this study can yield a grasp about the dimension of root architecture of single trees by using non-invasive geophysical techniques and give evidence about how roots influence the soil mantle mechanically and hydrologically according to the spatial distribution of their coarse roots.

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 machining ZnO/Al2O3 ceramic.

A solid-state amorphous selenium avalanche technology for low photon flux imaging applications

PubMed Central

Wronski, M. M.; Zhao, W.; Reznik, A.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A.

2010-01-01

Purpose: The feasibility of a practical solid-state technology for low photon flux imaging applications was investigated. The technology is based on an amorphous selenium photoreceptor with a voltage-controlled avalanche multiplication gain. If this photoreceptor can provide sufficient internal gain, it will be useful for an extensive range of diagnostic imaging systems. Methods: The avalanche photoreceptor under investigation is referred to as HARP-DRL. This is a novel concept in which a high-gain avalanche rushing photoconductor (HARP) is integrated with a distributed resistance layer (DRL) and sandwiched between two electrodes. The avalanche gain and leakage current characteristics of this photoreceptor were measured. Results: HARP-DRL has been found to sustain very high electric field strengths without electrical breakdown. It has shown avalanche multiplication gains as high as 104 and a very low leakage current (≤20 pA∕mm2). Conclusions: This is the first experimental demonstration of a solid-state amorphous photoreceptor which provides sufficient internal avalanche gain for photon counting and photon starved imaging applications. PMID:20964217

Enhanced copper micro/nano-particle mixed paste sintered at low temperature for 3D interconnects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Y. Y.; Anantha, P.; Tan, C. S., E-mail: tancs@ntu.edu.sg

2016-06-27

An enhanced copper paste, formulated by copper micro- and nano-particles mixture, is reported to prevent paste cracking and obtain an improved packing density. The particle mixture of two different sizes enables reduction in porosity of the micro-paste and resolves the cracking issue in the nano-paste. In-situ temperature and resistance measurements indicate that the mixed paste has a lower densification temperature. Electrical study also shows a ∼12× lower sheet resistance of 0.27 Ω/sq. In addition, scanning electron microscope image analysis confirms a ∼50% lower porosity, which is consistent with the thermal and electrical results. The 3:1 (micro:nano, wt. %) mixed pastemore » is found to have the strongest synergistic effect. This phenomenon is discussed further. Consequently, the mixed paste is a promising material for potential low temperature 3D interconnects fabrication.« less

Influence of defect luminescence and structural modification on the electrical properties of Magnesium Doped Zinc Oxide Nanorods

NASA Astrophysics Data System (ADS)

Santoshkumar, B.; Biswas, Amrita; Kalyanaraman, S.; Thangavel, R.; Udayabhanu, G.; Annadurai, G.; Velumani, S.

2017-06-01

Magnesium doped zinc oxide nanorod arrays on zinc oxide seed layers were grown by hydrothermal method. X-ray diffraction (XRD) patterns revealed the growth orientation along the preferential (002) direction. The hexagonal morphology was revealed from the field emission scanning electron microscope (FESEM) images. The elemental composition of the samples was confirmed by energy dispersive x-ray analysis spectra (EDS) and mapping dots. Carrier concentration, resistivity and mobility of the samples were obtained by Hall measurements. I-V characteristic curve confirmed the increase in resistivity upon doping. Photoluminescence (PL) spectra exposed the characteristic of UV emission along with defect mediated visible emission in the samples. Electrochemical impedance spectroscopy and cyclic voltammetry were undertaken to study the charge transport property. Owing to the change in the structural parameters and defect concentration the electrical properties of the doped samples were altered.

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.

Forward problem studies of electrical resistance tomography system on concrete materials

NASA Astrophysics Data System (ADS)

Ang, Vernoon; Rahiman, M. H. F.; Rahim, R. A.; Aw, S. R.; Wahab, Y. A.; Thomas W. K., T.; Siow, L. T.

2017-03-01

Electrical resistance tomography (ERT) is well known as non-invasive imaging technique, inexpensive, radiation free, visualization measurements of the multiphase flows and frequently applied in geophysical, medical and Industrial Process Tomography (IPT) applications. Application of ERT in concrete is a new exploration field, which can be used in monitoring and detecting the health and condition of concrete without destroying it. In this paper, ERT model under the condition of concrete is studied in which the sensitivity field model is produced and simulated by using COMSOL software. The affects brought by different current injection values with different concrete conductivity are studied in detail. This study able to provide the important direction for the further study of inverse problem in ERT system. Besides, the results of this technique hopefully can open a new exploration in inspection method of concrete structures in order to maintain the health of the concrete structure for civilian safety.

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

NASA Astrophysics Data System (ADS)

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.

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.

Evaluating conducting network based transparent electrodes from geometrical considerations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Ankush; Kulkarni, G. U., E-mail: guk@cens.res.in

2016-01-07

Conducting nanowire networks have been developed as viable alternative to existing indium tin oxide based transparent electrode (TE). The nature of electrical conduction and process optimization for electrodes have gained much from the theoretical models based on percolation transport using Monte Carlo approach and applying Kirchhoff's law on individual junctions and loops. While most of the literature work pertaining to theoretical analysis is focussed on networks obtained from conducting rods (mostly considering only junction resistance), hardly any attention has been paid to those made using template based methods, wherein the structure of network is neither similar to network obtained frommore » conducting rods nor similar to well periodic geometry. Here, we have attempted an analytical treatment based on geometrical arguments and applied image analysis on practical networks to gain deeper insight into conducting networked structure particularly in relation to sheet resistance and transmittance. Many literature examples reporting networks with straight or curvilinear wires with distributions in wire width and length have been analysed by treating the networks as two dimensional graphs and evaluating the sheet resistance based on wire density and wire width. The sheet resistance values from our analysis compare well with the experimental values. Our analysis on various examples has revealed that low sheet resistance is achieved with high wire density and compactness with straight rather than curvilinear wires and with narrower wire width distribution. Similarly, higher transmittance for given sheet resistance is possible with narrower wire width but of higher thickness, minimal curvilinearity, and maximum connectivity. For the purpose of evaluating active fraction of the network, the algorithm was made to distinguish and quantify current carrying backbone regions as against regions containing only dangling or isolated wires. The treatment can be helpful in predicting the properties of a network simply from image analysis and will be helpful in improvisation and comparison of various TEs and better understanding of electrical percolation.« less

Evaluating conducting network based transparent electrodes from geometrical considerations

NASA Astrophysics Data System (ADS)

Kumar, Ankush; Kulkarni, G. U.

2016-01-01

Conducting nanowire networks have been developed as viable alternative to existing indium tin oxide based transparent electrode (TE). The nature of electrical conduction and process optimization for electrodes have gained much from the theoretical models based on percolation transport using Monte Carlo approach and applying Kirchhoff's law on individual junctions and loops. While most of the literature work pertaining to theoretical analysis is focussed on networks obtained from conducting rods (mostly considering only junction resistance), hardly any attention has been paid to those made using template based methods, wherein the structure of network is neither similar to network obtained from conducting rods nor similar to well periodic geometry. Here, we have attempted an analytical treatment based on geometrical arguments and applied image analysis on practical networks to gain deeper insight into conducting networked structure particularly in relation to sheet resistance and transmittance. Many literature examples reporting networks with straight or curvilinear wires with distributions in wire width and length have been analysed by treating the networks as two dimensional graphs and evaluating the sheet resistance based on wire density and wire width. The sheet resistance values from our analysis compare well with the experimental values. Our analysis on various examples has revealed that low sheet resistance is achieved with high wire density and compactness with straight rather than curvilinear wires and with narrower wire width distribution. Similarly, higher transmittance for given sheet resistance is possible with narrower wire width but of higher thickness, minimal curvilinearity, and maximum connectivity. For the purpose of evaluating active fraction of the network, the algorithm was made to distinguish and quantify current carrying backbone regions as against regions containing only dangling or isolated wires. The treatment can be helpful in predicting the properties of a network simply from image analysis and will be helpful in improvisation and comparison of various TEs and better understanding of electrical percolation.

Nanofabrication of insulated scanning probes for electromechanical imaging in liquid solutions

PubMed Central

Noh, Joo Hyon; Nikiforov, Maxim; Kalinin, Sergei V.; Vertegel, Alexey A.; Rack, Philip D.

2011-01-01

In this paper, the fabrication and electrical and electromechanical characterization of insulated scanning probes have been demonstrated in liquid solutions. The silicon cantilevers were sequentially coated with chromium and silicon dioxide, and the silicon dioxide was selectively etched at tip apex using focused electron beam induced etching (FEBIE) with XeF2 The chromium layer acted not only as the conductive path from the tip, but also as an etch resistant layer. This insulated scanning probe fabrication process is compatible with any commercial AFM tip and can be used to easily tailor the scanning probe tip properties because FEBIE does not require lithography. The suitability of the fabricated probes is demonstrated by imaging of standard topographical calibration grid as well as piezoresponse force microscopy (PFM) and electrical measurements in ambient and liquid environments. PMID:20702930

Electrode Models for Electric Current Computed Tomography

PubMed Central

CHENG, KUO-SHENG; ISAACSON, DAVID; NEWELL, J. C.; GISSER, DAVID G.

2016-01-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 Ω · cm were studied. Values of “effective” contact impedance z used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 Ω · cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an “effective” contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field. PMID:2777280

Electrode models for electric current computed tomography.

PubMed

Cheng, K S; Isaacson, D; Newell, J C; Gisser, D G

1989-09-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 omega.cm were studied. Values of "effective" contact impedance zeta used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 omega.cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an "effective" contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field.

Determination of Electrical Resistivity of Dry Coke Beds

NASA Astrophysics Data System (ADS)

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

2008-02-01

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 °C to 1600 °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 °C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.

Methods for calculating the electrode position Jacobian for impedance imaging.

PubMed

Boyle, A; Crabb, M G; Jehl, M; Lionheart, W R B; Adler, A

2017-03-01

Electrical impedance tomography (EIT) or electrical resistivity tomography (ERT) current and measure voltages at the boundary of a domain through electrodes. The movement or incorrect placement of electrodes may lead to modelling errors that result in significant reconstructed image artifacts. These errors may be accounted for by allowing for electrode position estimates in the model. Movement may be reconstructed through a first-order approximation, the electrode position Jacobian. A reconstruction that incorporates electrode position estimates and conductivity can significantly reduce image artifacts. Conversely, if electrode position is ignored it can be difficult to distinguish true conductivity changes from reconstruction artifacts which may increase the risk of a flawed interpretation. In this work, we aim to determine the fastest, most accurate approach for estimating the electrode position Jacobian. Four methods of calculating the electrode position Jacobian were evaluated on a homogeneous halfspace. Results show that Fréchet derivative and rank-one update methods are competitive in computational efficiency but achieve different solutions for certain values of contact impedance and mesh density.

Real-time imaging and detection of intracranial haemorrhage by electrical impedance tomography in a piglet model.

PubMed

Xu, C H; Wang, L; Shi, X T; You, F S; Fu, F; Liu, R G; Dai, M; Zhao, Z W; Gao, G D; Dong, X Z

2010-01-01

The aim of this study was to use electrical impedance tomography (EIT) to detect and image acute intracranial haemorrhage (ICH) in an animal model. Blood was infused into the frontal lobe of the brains of anaesthetized piglets and impedance was measured using 16 electrodes placed in a circle on the scalp. The EIT images were constructed using a filtered back-projection algorithm. The mean of all the pixel intensities within a region of interest--the mean resistivity value (MRV)--was used to evaluate the relative impedance changes in the target region. A symmetrical index (SI), reflecting the relative impedance on both sides of the brain, was also calculated. Changes in MRV and SI were associated with the injection of blood, demonstrating that EIT can successfully detect ICH in this animal model. The unique features of EIT may be beneficial for diagnosing ICH early in patients after cranial surgery, thereby reducing the risk of complications and mortality.

Induced polarization imaging of volcanoes

NASA Astrophysics Data System (ADS)

Revil, Andre; Soueid Ahmed, Abdellahi

2017-04-01

The first part of the presentation is related to the petrophysics of induced polarization of volcanic rocks. We described induced polarization of these rocks using a dynamic Stern layer model describing the polarization of the electrical double layer around the mineral grains. This model shows that the normalized chargeability and quadrature conductivity of volcanic rocks is sensitive to the cation exchange capacity (CEC) of these materials and therefore to their alteration. In the second part pf the presentation, we use a geostatistical inversion framework to image chargeability in 2.5D or in 3D. This new framework is benchmarked using synthetic data and data from various volcanoes (Kilaua, Furnas, Yellowstone). We show that chargeability tomography is very complementary to the now classical electrical resistivity tomography in order to image volcanic structures and to separate the conduction in the bulk pore network from interfacial effects such as surface conductivity. This approach appears to be promising as a first step toward joint inversion with seismic and gravity data.

Statistical theory and applications of lock-in carrierographic image pixel brightness dependence on multi-crystalline Si solar cell efficiency and photovoltage

NASA Astrophysics Data System (ADS)

Mandelis, Andreas; Zhang, Yu; Melnikov, Alexander

2012-09-01

A solar cell lock-in carrierographic image generation theory based on the concept of non-equilibrium radiation chemical potential was developed. An optoelectronic diode expression was derived linking the emitted radiative recombination photon flux (current density), the solar conversion efficiency, and the external load resistance via the closed- and/or open-circuit photovoltage. The expression was shown to be of a structure similar to the conventional electrical photovoltaic I-V equation, thereby allowing the carrierographic image to be used in a quantitative statistical pixel brightness distribution analysis with outcome being the non-contacting measurement of mean values of these important parameters averaged over the entire illuminated solar cell surface. This is the optoelectronic equivalent of the electrical (contacting) measurement method using an external resistor circuit and the outputs of the solar cell electrode grid, the latter acting as an averaging distribution network over the surface. The statistical theory was confirmed using multi-crystalline Si solar cells.

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

NASA Astrophysics Data System (ADS)

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

2010-04-01

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

Altered Landscapes and Groundwater Sustainability — Exploring Impacts with Induced Polarization, DC Resistivity, and Thermal Tracing

NASA Astrophysics Data System (ADS)

Eddy-Miller, C.; Caldwell, R.; Wheeler, J.; McCarthy, P.; Binley, A. M.; Constantz, J. E.; Stonestrom, D. A.

2009-12-01

Anthropogenically impacted landscapes constitute rising proportions of the Earth’s surface that are characterized by generally elevated nutrient and sediment loadings concurrent with increased consumptive water withdrawals. In recent years a growing number of hydraulically engineered riparian habitat restoration projects have attempted to ameliorate negative impacts of land use on groundwater-surface water systems resulting, e.g., from agricultural practices and urban development. Often the nature of groundwater-surface water interactions in pre- and minimally altered systems is poorly known, making it difficult to assess the impacts of land use and restoration projects on groundwater sustainability. Traditional assessments of surface water parameters (flow, temperature, dissolved oxygen, biotic composition, etc.) can be complemented by hydraulic and thermal measurements to better understand the important role played by groundwater-surface water interactions. Hydraulic and thermal measurements are usually limited to point samples, however, making non-invasive and spatially extensive geophysical characterizations an attractive additional tool. Groundwater-surface water interactions along the Smith River, a tributary to the Missouri River in Montana, and Fish Creek and Flat Creek, tributaries to the Snake River in Wyoming, are being examined using a combination of hydraulic measurements, thermal tracing, and electrical-property imaging. Ninety-two direct-current (DC) resistivity and induced polarization cross sections were obtained at stream transects covering a wide variety of hydrogeologic settings ranging from shallow bedrock to thick alluvial sequences, nature of groundwater-surface water interactions (always gaining, always losing, or seasonally varying) and anthropogenic impacts (minimal low-intensity agriculture to major landscape engineering, including channel reconstruction). DC resistivity and induced polarization delineated mutually distinct features related to hydraulic architecture. For example, induced polarization imaging resolved channel-edge muck deposits that are presumed to be sites of low hydraulic conductivity, chemical reduction, and metal accumulation. DC resistivity delineated bedrock-alluvium contacts and showed potential for tracking changes in salinization. While electrical properties cannot substitute for hydraulic and thermal data, the addition of relatively rapidly acquired, spatially extensive resistivity and induced polarization imaging offers synergistic opportunities for interpretive hydrologic investigations.

Integrated interpretation of helicopter and ground-based geophysical data recorded within the Okavango Delta, Botswana

NASA Astrophysics Data System (ADS)

Podgorski, Joel E.; Green, Alan G.; Kalscheuer, Thomas; Kinzelbach, Wolfgang K. H.; Horstmeyer, Heinrich; Maurer, Hansruedi; Rabenstein, Lasse; Doetsch, Joseph; Auken, Esben; Ngwisanyi, Tiyapo; Tshoso, Gomotsang; Jaba, Bashali Charles; Ntibinyane, Onkgopotse; Laletsang, Kebabonye

2015-03-01

Integration of information from the following sources has been used to produce a much better constrained and more complete four-unit geological/hydrological model of the Okavango Delta than previously available: (i) a 3D resistivity model determined from helicopter time-domain electromagnetic (HTEM) data recorded across most of the delta, (ii) 2D models and images derived from ground-based electrical resistance tomographic, transient electromagnetic, and high resolution seismic reflection/refraction tomographic data acquired at four selected sites in western and north-central regions of the delta, and (iii) geological details extracted from boreholes in northeastern and southeastern parts of the delta. The upper heterogeneous unit is the modern delta, which comprises extensive dry and freshwater-saturated sand and lesser amounts of clay and salt. It is characterized by moderate to high electrical resistivities and very low to low P-wave velocities. Except for images of several buried abandoned river channels, it is non-reflective. The laterally extensive underlying unit of low resistivities, low P-wave velocity, and subhorizontal reflectors very likely contains saline-water-saturated sands and clays deposited in the huge Paleo Lake Makgadikgadi (PLM), which once covered a 90,000 km2 area that encompassed the delta, Lake Ngami, the Mababe Depression, and the Makgadikgadi Basin. Examples of PLM sediments are intersected in many boreholes. Low permeability clay within the PLM unit seems to be a barrier to the downward flow of the saline water. Below the PLM unit, freshwater-saturated sand of the Paleo Okavango Megafan (POM) unit is distinguished by moderate to high resistivities, low P-wave velocity, and numerous subhorizontal reflectors. The POM unit is interpreted to be the remnants of a megafan based on the arcuate nature of its front and the semi-conical shape of its upper surface in the HTEM resistivity model. Moderate to high resistivity subhorizontal layers are consistent with this interpretation. The deepest unit is the basement with very high resistivity, high P-wave velocity, and low or complex reflectivity. The interface between the POM unit and basement is a prominent seismic reflector.

3-D interpretation of short-period magnetotelluric data at Furnas Volcano, Azores Islands

NASA Astrophysics Data System (ADS)

Hogg, C.; Kiyan, D.; Rath, V.; Byrdina, S.; Vandemeulebrouck, J.; Revil, A.; Viveiros, F.; Carmo, R.; Silva, C.; Ferreira, T.

2018-04-01

Accurate geophysical imaging of shallow subsurface features provides crucial constraints on understanding the dynamics of volcanic systems. At Furnas Volcano (Azores), intense circulation of volcanic fluids at depth leading to high CO2 outgassing and flank destabilization poses considerable threat to the local population. Presented is a novel 3-D electrical resistivity model developed from 39 magnetotelluric soundings that images the hydrothermal system of the Furnas Volcano to a depth of 1 km. The resistivity model images two conductive zones, one at 100 m and another at 500 m depth, separated by a resistive layer. The shallow conductor has conductivity less than 1 S m-1, which can be explained by clay mineral surface conduction with a mass fraction of at least 20 per cent smectite. The deeper conductor extends across the majority of the survey area. This deeper conductor is located at depths where smectite is generally replaced by chlorite and we interpret it as aqueous fluids near the boiling point and infer temperatures of at least 240 °C. The less conductive layer found between these conductors is probably steam-dominated, and coincides within the mixed-clay zone found in many volcanic hydrothermal systems.

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.

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.

A Geophysical Characterization & Monitoring Strategy for Determining Hydrologic Processes in the Hyporheic Corridor at the Hanford 300-Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slater, Lee; Day-Lewis, Frederick; Lane, John

2011-08-31

The primary objective of this research was to advance the prediction of solute transport between the Uranium contaminated Hanford aquifer and the Columbia River at the Hanford 300 Area by improving understanding of how fluctuations in river stage, combined with subsurface heterogeneity, impart spatiotemporal complexity to solute exchange along the Columbia River corridor. Our work explored the use of continuous waterborne electrical imaging (CWEI), in conjunction with fiber-optic distributed temperature sensor (FO-DTS) and time-lapse resistivity monitoring, to improve the conceptual model for how groundwater/surface water exchange regulates uranium transport. We also investigated how resistivity and induced polarization can be usedmore » to generate spatially rich estimates of the variation in depth to the Hanford-Ringold (H-R) contact between the river and the 300 Area Integrated Field Research Challenge (IFRC) site. Inversion of the CWEI datasets (a data rich survey containing {approx}60,000 measurements) provided predictions of the distributions of electrical resistivity and polarizability, from which the spatial complexity of the primary hydrogeologic units along the river corridor was reconstructed. Variation in the depth to the interface between the overlying coarse-grained, high permeability Hanford Formation and the underlying finer-grained, less permeable Ringold Formation, an important contact that limits vertical migration of contaminants, has been resolved along {approx}3 km of the river corridor centered on the IFRC site in the Hanford 300 Area. Spatial variability in the thickness of the Hanford Formation captured in the CWEI datasets indicates that previous studies based on borehole projections and drive-point and multi-level sampling likely overestimate the contributing area for uranium exchange within the Columbia River at the Hanford 300 Area. Resistivity and induced polarization imaging between the river and the 300 Area IFRC further imaged spatial variability in the depth to the Hanford-Ringold inland over a critical region where borehole information is absent, identifying evidence for a continuous depression in the H-R contact between the IFRC and the river corridor. Strong natural contrasts in temperature and specific conductance of river water compared to groundwater at this site, along with periodic river stage fluctuations driven by dam operations, were exploited to yield new insights into the dynamics of groundwater-surface water interaction. Whereas FO-DTS datasets have provided meter-scale measurements of focused groundwater discharge at the riverbed along the corridor, continuous resistivity monitoring has non-invasively imaged spatiotemporal variation in the resistivity inland driven by river stage fluctuations. Time series and time-frequency analysis of FO-DTS and 3D resistivity datasets has provided insights into the role of forcing variables, primarily daily dam operations, in regulating the occurrence of focused exchange at the riverbed and its extension inland. High amplitudes in the DTS and 3D resistivity signals for long periods that dominate the stage time series identify regions along the corridor where stage-driven exchange is preferentially focused. Our work has demonstrated how time-series analysis of both time-lapse resistivity and DTS datasets, in conjunction with resistivity/IP imaging of lithology, can improve understanding of groundwater-surface water exchange along river corridors, offering unique opportunities to connect stage-driven groundwater discharge observed with DTS on the riverbed to stage-driven groundwater and solute fluctuations captured with resistivity inland.« less

FINAL PROJECT REPORT: A Geophysical Characterization & Monitoring Strategy for Determining Hydrologic Processes in the Hyporheic Corridor at the Hanford 300-Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee Slater

2011-08-15

The primary objective of this research was to advance the prediction of solute transport between the Uranium contaminated Hanford aquifer and the Columbia River at the Hanford 300 Area by improving understanding of how fluctuations in river stage, combined with subsurface heterogeneity, impart spatiotemporal complexity to solute exchange along the Columbia River corridor. Our work explored the use of continuous waterborne electrical imaging (CWEI), in conjunction with fiber-optic distributed temperature sensor (FO-DTS) and time-lapse resistivity monitoring, to improve the conceptual model for how groundwater/surface water exchange regulates uranium transport. We also investigated how resistivity and induced polarization can be usedmore » to generate spatially rich estimates of the variation in depth to the Hanford-Ringold (H-R) contact between the river and the 300 Area Integrated Field Research Challenge (IFRC) site. Inversion of the CWEI datasets (a data rich survey containing ~60,000 measurements) provided predictions of the distributions of electrical resistivity and polarizability, from which the spatial complexity of the primary hydrogeologic units along the river corridor was reconstructed. Variation in the depth to the interface between the overlying coarse-grained, high permeability Hanford Formation and the underlying finer-grained, less permeable Ringold Formation, an important contact that limits vertical migration of contaminants, has been resolved along ~3 km of the river corridor centered on the IFRC site in the Hanford 300 Area. Spatial variability in the thickness of the Hanford Formation captured in the CWEI datasets indicates that previous studies based on borehole projections and drive-point and multi-level sampling likely overestimate the contributing area for uranium exchange within the Columbia River at the Hanford 300 Area. Resistivity and induced polarization imaging between the river and the 300 Area IFRC further imaged spatial variability in the depth to the Hanford-Ringold inland over a critical region where borehole information is absent, identifying evidence for a continuous depression in the H-R contact between the IFRC and the river corridor. Strong natural contrasts in temperature and specific conductance of river water compared to groundwater at this site, along with periodic river stage fluctuations driven by dam operations, were exploited to yield new insights into the dynamics of groundwater-surface water interaction. Whereas FO-DTS datasets have provided meter-scale measurements of focused groundwater discharge at the riverbed along the corridor, continuous resistivity monitoring has non-invasively imaged spatiotemporal variation in the resistivity inland driven by river stage fluctuations. Time series and time-frequency analysis of FO-DTS and 3D resistivity datasets has provided insights into the role of forcing variables, primarily daily dam operations, in regulating the occurrence of focused exchange at the riverbed and its extension inland. High amplitudes in the DTS and 3D resistivity signals for long periods that dominate the stage time series identify regions along the corridor where stage-driven exchange is preferentially focused. Our work has demonstrated how time-series analysis of both time-lapse resistivity and DTS datasets, in conjunction with resistivity/IP imaging of lithology, can improve understanding of groundwater-surface water exchange along river corridors, offering unique opportunities to connect stage-driven groundwater discharge observed with DTS on the riverbed to stage-driven groundwater and solute fluctuations captured with resistivity inland.« less

State Waste Discharge Permit Application: Electric resistance tomography testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 arealmore » 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.« less

3D printing scanning electron microscopy sample holders: A quick and cost effective alternative for custom holder fabrication.

PubMed

Meloni, Gabriel N; Bertotti, Mauro

2017-01-01

A simple and cost effective alternative for fabricating custom Scanning Electron Microscope (SEM) sample holders using 3D printers and conductive polylactic acid filament is presented. The flexibility of the 3D printing process allowed for the fabrication of sample holders with specific features that enable the high-resolution imaging of nanoelectrodes and nanopipettes. The precise value of the inner semi cone angle of the nanopipettes taper was extracted from the acquired images and used for calculating their radius using electrochemical methods. Because of the low electrical resistivity presented by the 3D printed holder, the imaging of non-conductive nanomaterials, such as alumina powder, was found to be possible. The fabrication time for each sample holder was under 30 minutes and the average cost was less than $0.50 per piece. Despite being quick and economical to fabricate, the sample holders were found to be sufficiently resistant, allowing for multiple uses of the same holder.

3D printing scanning electron microscopy sample holders: A quick and cost effective alternative for custom holder fabrication

PubMed Central

Bertotti, Mauro

2017-01-01

A simple and cost effective alternative for fabricating custom Scanning Electron Microscope (SEM) sample holders using 3D printers and conductive polylactic acid filament is presented. The flexibility of the 3D printing process allowed for the fabrication of sample holders with specific features that enable the high-resolution imaging of nanoelectrodes and nanopipettes. The precise value of the inner semi cone angle of the nanopipettes taper was extracted from the acquired images and used for calculating their radius using electrochemical methods. Because of the low electrical resistivity presented by the 3D printed holder, the imaging of non-conductive nanomaterials, such as alumina powder, was found to be possible. The fabrication time for each sample holder was under 30 minutes and the average cost was less than $0.50 per piece. Despite being quick and economical to fabricate, the sample holders were found to be sufficiently resistant, allowing for multiple uses of the same holder. PMID:28753638

Geoelectrical characterisation of basement aquifers: the case of Iberekodo, southwestern Nigeria

NASA Astrophysics Data System (ADS)

Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.

2018-03-01

Basement aquifers, which occur within the weathered and fractured zones of crystalline bedrocks, are important groundwater resources in tropical and subtropical regions. The development of basement aquifers is complex owing to their high spatial variability. Geophysical techniques are used to obtain information about the hydrologic characteristics of the weathered and fractured zones of the crystalline basement rocks, which relates to the occurrence of groundwater in the zones. The spatial distributions of these hydrologic characteristics are then used to map the spatial variability of the basement aquifers. Thus, knowledge of the spatial variability of basement aquifers is useful in siting wells and boreholes for optimal and perennial yield. Geoelectrical resistivity is one of the most widely used geophysical methods for assessing the spatial variability of the weathered and fractured zones in groundwater exploration efforts in basement complex terrains. The presented study focuses on combining vertical electrical sounding with two-dimensional (2D) geoelectrical resistivity imaging to characterise the weathered and fractured zones in a crystalline basement complex terrain in southwestern Nigeria. The basement aquifer was delineated, and the nature, extent and spatial variability of the delineated basement aquifer were assessed based on the spatial variability of the weathered and fractured zones. The study shows that a multiple-gradient array for 2D resistivity imaging is sensitive to vertical and near-surface stratigraphic features, which have hydrological implications. The integration of resistivity sounding with 2D geoelectrical resistivity imaging is efficient and enhances near-surface characterisation in basement complex terrain.

Estimates of in situ gas hydrate concentration from resistivity monitoring of gas hydrate bearing sediments during temperature equilibration

USGS Publications Warehouse

Riedel, M.; Long, P.E.; Collett, T.S.

2006-01-01

As part of Ocean Drilling Program Leg 204 at southern Hydrate Ridge off Oregon we have monitored changes in sediment electrical resistivity during controlled gas hydrate dissociation experiments. Two cores were used, each filled with gas hydrate bearing sediments (predominantly mud/silty mud). One core was from Site 1249 (1249F-9H3), 42.1 m below seafloor (mbsf) and the other from Site 1248 (1248C-4X1), 28.8 mbsf. At Site 1247, a third experiment was conducted on a core without gas hydrate (1247B-2H1, 3.6 mbsf). First, the cores were imaged using an infra-red (IR) camera upon recovery to map the gas hydrate occurrence through dissociation cooling. Over a period of several hours, successive runs on the multi-sensor track (includes sensors for P-wave velocity, resistivity, magnetic susceptibility and gamma-ray density) were carried out complemented by X-ray imaging on core 1249F-9H3. After complete equilibration to room temperature (17-18??C) and complete gas hydrate dissociation, the final measurement of electrical resistivity was used to calculate pore-water resistivity and salinities. The calculated pore-water freshening after dissociation is equivalent to a gas hydrate concentration in situ of 35-70% along core 1249F-9H3 and 20-35% for core 1248C-4X1 assuming seawater salinity of in situ pore fluid. Detailed analysis of the IR scan, X-ray images and split-core photographs showed the hydrate mainly occurred disseminated throughout the core. Additionally, in core 1249F-9H3, a single hydrate filled vein, approximately 10 cm long and dipping at about 65??, was identified. Analyses of the logging-while-drilling (LWD) resistivity data revealed a structural dip of 40-80?? in the interval between 40 and 44 mbsf. We further analyzed all resistivity data measured on the recovered core during Leg 204. Generally poor data quality due to gas cracks allowed analyses to be carried out only at selected intervals at Sites 1244, 1245, 1246, 1247, 1248, 1249, and 1252. With a few exceptions, data from these intervals yield low to no gas hydrate concentration, which corresponds to estimates from downhole resistivity logs. However, since the gas cracking may be the result of gas hydrate dissociation, this is a biased sampling. Cores that had contained some gas hydrate may have been excluded. ?? 2005 Elsevier B.V. All rights reserved.

Electrical conductivity of the Cascadia subduction zone and implications for the plate interface

NASA Astrophysics Data System (ADS)

Livelybrooks, D.; Bedrosian, P.; Egbert, G. D.; Key, K.; Schultz, A.; Parris, B. A.; Yang, B.; Bowles-martinez, E.

2016-12-01

The Magnetotelluric Observations of Cascadia using a Huge Array (MOCHA) experiment resulted in the collection of 146 amphibious, long-period magnetotelluric stations acquired between 2012 and 2014. These data, supplemented with the previously-acquired CAFÉ, EMSLAB, SWORMT and EarthScope (MT) Transportable Array stations, have been interpreted to provide electrical conductivity models of Cascadia spanning from the trench eastward through the Cascades, and extending to about 150km depth. We have a particular interest in understanding the roles electrically-conductive, aqueous fluids play in Cascadia subduction processes at or near the plate interface, thus inversions of data are predisposed to accommodate an initially-resistive (McCrory et al. 2014) slab. Beginning at the mantle wedge corner, 3-D inversions reveal significant, latitudinal variation in the conductivity, with enhanced conductivity at 47oN and south at 42oN. Two-dimensional inversions at 44.5oN allowing for a step discontinuity at the Moho give two distinct zones of conductance, one at the MWC tip (c.f. Furukowa, 2009) and another further down-dip, with a conductivity `plume' directed eastwards. At depths of between 20-25km we image a latitudinally-discontinuous resistive lower crust immediately overlying resistive subducted slab. This implies a lack of free fluids near the plate interface. Krogstad et al. (2016) have analyzed historic uplift data and can model the presence of an inboard `secondary locked zone' near 44.5oN. One explanation for both observations—a down-dip, `pinned interface' that is shielding the traditionally-modeled off-shore locked zone from stress accumulation, would explain the paucity of seismicity observed off the north-central Oregon coast during the four-year Cascadia Initiative. At coastal longitudes a narrow, supra-slab conductive zone is imaged at 22km depth with a southern termination at 45oN. It is notable that some researchers place the inboard boundary of the (mostly off-shore) seismogenic zone as moving eastward and on-shore beginning north of 45oN. The thinner Coast Range crust is imaged as generally more conductive north of 46oN, which is consistent with higher permeabilities ascribed to the Crescent formation.

Assessment of electrical resistivity imaging for pre-tunneling geological characterization - A case study of the Qingdao R3 metro line tunnel

NASA Astrophysics Data System (ADS)

Li, Shucai; Xu, Shan; Nie, Lichao; Liu, Bin; Liu, Rentai; Zhang, Qingsong; Zhao, Yan; Liu, Quanwei; Wang, Houtong; Liu, Haidong; Guo, Qin

2018-06-01

Water inrush during tunneling is a significant problem in the underground infrastructure construction. Electrical resistivity imaging (ERI) is a technique that can detect and characterize a water body in an open fracture or fault by exploiting the resistivity contrast that exists between the water body and the surrounding materials. ERI is an efficient method for pre-tunneling geological characterization. In this study, a case study is presented in which tunnel-face and borehole ERI (TBERI) is performed by using the probe hole to detect a water body during tunnel construction. The construction site is a metro line site, situated in the city of Qingdao, China. Unlike the traditional cross-hole observation mode, TBERI only use a single borehole. The installation of injection electrodes inside the probe hole and the installation of measuring electrodes on the tunnel face is proposed as the observation mode. Furthermore, a numerical simulation is carried out before the real field experiment, and the simulation results show that the TBERI is capable of detecting a deeply buried water body. In addition, the water body in the field case is also identified by TBERI. The water body appears as a strongly conductive anomaly relative to the background materials. This study highlights the respective strengths and weaknesses of the TBERI for pre-tunneling geological characterization. This method is a relatively rapid means of investigating the studied area. This study clearly demonstrates the suitability of TBERI in a tunneling scenario.

Geoelectric Monitoring of geological CO2 storage at Ketzin, Germany (CO2SINK project): Downhole and Surface-Downhole measurements

NASA Astrophysics Data System (ADS)

Kiessling, D.; Schuett, H.; Schoebel, B.; Krueger, K.; Schmidt-Hattenberger, C.; Schilling, F.

2009-04-01

Numerical models of the CO2 storage experiment CO2SINK (CO2 Storage by Injection into a Natural Saline Aquifer at Ketzin), where CO2 is injected into a deep saline aquifer at roughly 650 m depth, yield a CO2 saturation of approximately 50% for large parts of the plume. Archie's equation predicts an increase of the resistivity by a factor of approximately 3 to 4 for the reservoir sandstone, and laboratory tests on Ketzin reservoir samples support this prediction. Modeling results show that tracking the CO2 plume may be doable with crosshole resistivity surveys under these conditions. One injection well and two observation wells were drilled in 2007 to a depth of about 800 m and were completed with "smart" casings, arranged L-shaped with distances of 50 m and 100 m. 45 permanent ring-shaped steel electrodes were attached to the electrically insulated casings of the three Ketzin wells at 590 m to 735 m depth with a spacing of about 10 m. It is to our knowledge the deepest permanent vertical electrical resistivity array (VERA) worldwide. The electrodes are connected to the current power supply and data registration units at the surface through custom-made cables. This deep electrode array allows for the registration of electrical resistivity tomography (ERT) data sets at basically any desired repetition rate and at very low cost, without interrupting the injection operations. The installation of all 45 electrodes succeeded. The electrodes are connected to the electrical cable, and the insulated casing stood undamaged. Even after 2-odd years under underground conditions only 6 electrodes are in a critical state now, caused by corrosion effects. In the framework of the COSMOS project (CO2-Storage, Monitoring and Safety Technology), supported by the German "Geotechnologien" program, the geoelectric monitoring has been performed. The 3D crosshole time-laps measurements are taken using dipole-dipole configurations. The data was inverted using AGI EarthImager 3D to obtain 3D images of the true resistivity distribution in the reservoir, which reflects the extent of the CO2 plume. The resistivity data provide information about the saturation state of the reservoir independently of seismic methods. Base data sets have been measured prior to the CO2 injection; monitoring data sets are registered while CO2 is being injected. Using combined 3D surface-downhole measurements (realized in cooperation with University of Leipzig) we got in addition an indication for effects of anisotropy in CO2 migration. We present an overview of the electrode installation, first examples for baseline and monitoring datasets and the corresponding tomograms that show indications of the CO2 migration.

Electrical Characteristics CuFe{sub 2}O{sub 4} Thick Film Ceramics Made with Different Screen Size Utilizing Fe{sub 2}O{sub 3} Nanopowder Derived from Yarosite for NTC Thermistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiendartun,; Syarif, Dani Gustaman

2010-10-24

Fabrication of CuFe{sub 2}O{sub 4} thick film ceramics utilizing Fe{sub 2}O{sub 3} derived from yarosite using screen printing technique for NTC thermistor has been carried out. Effect of thickness variation due to different size of screen (screen 225; 300 and 375 mesh) has been studied. X-ray diffraction analyses (XRD) was done to know crystal structure and phases formation. SEM analyses was carried out to know microstructure of the films. Electrical properties characterization was done through measurement of electrical resistance at various temperatures (room temperature to 100 deg. C). The XRD data showed that the films crystalize in tetragonal spinel. Themore » SEM images showed that the screen with the smaller of the hole size, made the grain size was bigger. Electrical data showed that the larger the screen different size thickness variation (mesh), the larger the resistance, thermistor constant and sensitivity. From the electrical characteristics data, it was known that the electrical characteristics of the CuFe{sub 2}O{sub 4} thick film ceramics followed the NTC characteristic. The value of B and R{sub RT} of the produced CuFe{sub 2}O{sub 4} ceramics namely B = 3241-3484 K and R{sub RT} = 25.6-87.0 M Ohm, fitted market requirement.« less

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 machining ZnO/Al2O3 ceramic. PMID:25364912

Audiomagnetotelluric exploration across the Waíanae Range, Óahu, Hawaíi

NASA Astrophysics Data System (ADS)

Sigurdardottir, T. D.; Thomas, D. M.; Wallin, E.; Winchester, C.; Sinton, J. M.

2015-12-01

The audiomagnetotelluric (AMT) method is capable of providing direct evidence of a geothermal resource within the extinct Waíanae volcano, Óahu, Hawaíi. Geothermal systems are becoming an increasingly important energy source worldwide. With electric energy costs in Hawaíi the most expensive in the US (30.54 cents/kWh), it is important to investigate the potential of local geothermal resources. Slightly elevated temperature and chloride concentrations, measured in the 1970's at wells in the upper Lualualei Valley indicate the possibility of a geothermal resource. Previous geophysical investigations: self-potential, rotating quadripole resistivity, and shallow soil temperature surveys in the caldera measured low resistivity values. Resistivity is related to rock characteristics (e.g., porosity, saturation, salinity, temperature, chemistry, and the presence of weathered minerals). We are investigating the area further using the AMT method. We have collected profiles of AMT measurements across the Lualualei Valley and the Waíanae caldera boundary. Anthropogenic noise and access in this area is problematic. Electrical noise, originating from power lines along roads and very low frequency radio towers in the vicinity, add noise to the data. Limited access to sites on military lands inhibit data collection. However, preliminary results show that we have successfully imaged the expected higher resistivity values as our profiles cross the mountains bounding the caldera. As data continue to be collected across the Waíanae Caldera and Range and we begin modeling our data in two dimensions, we expect to be able to identify water table elevations, detect lateral variability between salt and fresh water saturation, estimate thickness of the freshwater lens and depth to the transition zone, image fault structures at the caldera boundary, and with enough sensitivity to conductivity, we can identify regions of elevated temperature.

Electrical condition monitoring method for polymers

DOEpatents

Watkins, Jr., Kenneth S.; Morris, Shelby J [Hampton, VA; Masakowski, Daniel D [Worcester, MA; Wong, Ching Ping [Duluth, GA; Luo, Shijian [Boise, ID

2008-08-19

An electrical condition monitoring method utilizes measurement of electrical resistivity of an age sensor made of a conductive matrix or composite disposed in a polymeric structure such as an electrical cable. The conductive matrix comprises a base polymer and conductive filler. The method includes communicating the resistivity to a measuring instrument and correlating resistivity of the conductive matrix of the polymeric structure with resistivity of an accelerated-aged conductive composite.

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.

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.

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.

Density Imaging of Puy de Dôme Volcano with Atmospheric Muons in French Massif Central as a Case Study for Volcano Muography

NASA Astrophysics Data System (ADS)

Carloganu, Cristina; Le Ménédeu, Eve

2016-04-01

High energy atmospheric muons have high penetration power that renders them appropriate for geophysical studies. Provided the topography is known, the measurement of the muon flux transmittance leads in an univoque way to 2D density mapping (so called radiographic images) revealing spatial and possibly also temporal variations. Obviously, several radiographic images could be combined into 3D tomographies, though the inverse 3D problem is generally ill-posed. The muography has a high potential for imaging remotely (from kilometers away) and with high resolution (better than 100 mrad2) volcanoes. The experimental and methodological task is however not straightforward since atmospheric muons have non trivial spectra that fall rapidly with muon energy. As shown in [Ambrosino 2015] successfully imaging km-scale volcanoes remotely requires state-of-the art, high-resolution and large-scale muon detectors. This contribution presents the geophysical motivation for muon imaging as well as the first quantitative density radiographies of Puy de Dôme volcano obtained by the TOMUVOL collaboration using a highly segmented muon telescope based on Glass Resistive Plate Chambers. In parallel with the muographic studies, the volcano was imaged through standard geophysical methods (gravimetry, electrical resistivity) [Portal 2013] allowing in depth comparisons of the different methods. Ambrosino, F., et al. (2015), Joint measurement of the atmospheric muon flux through the Puy de Dôme volcano with plastic scintillators and Resistive Plate Chambers detectors, J. Geophys. Res. Solid Earth, 120, doi:10.1002/2015JB011969 A. Portal et al (2013) , "Inner structure of the Puy de Dme volcano: cross-comparison of geophysical models (ERT, gravimetry, muon imaging)", Geosci. Instrum. Method. Data Syst., 2, 47-54, 2013

Scaling Effect on Unipolar and Bipolar Resistive Switching of Metal Oxides

PubMed Central

Yanagida, Takeshi; Nagashima, Kazuki; Oka, Keisuke; Kanai, Masaki; Klamchuen, Annop; Park, Bae Ho; Kawai, Tomoji

2013-01-01

Electrically driven resistance change in metal oxides opens up an interdisciplinary research field for next-generation non-volatile memory. Resistive switching exhibits an electrical polarity dependent “bipolar-switching” and a polarity independent “unipolar-switching”, however tailoring the electrical polarity has been a challenging issue. Here we demonstrate a scaling effect on the emergence of the electrical polarity by examining the resistive switching behaviors of Pt/oxide/Pt junctions over 8 orders of magnitudes in the areas. We show that the emergence of two electrical polarities can be categorised as a diagram of an electric field and a cell area. This trend is qualitatively common for various oxides including NiOx, CoOx, and TiO2-x. We reveal the intrinsic difference between unipolar switching and bipolar switching on the area dependence, which causes a diversity of an electrical polarity for various resistive switching devices with different geometries. This will provide a foundation for tailoring resistive switching behaviors of metal oxides. PMID:23584551

Subsurface imaging of an abandoned solid waste landfill site in Norman, Oklahoma

USGS Publications Warehouse

Zume, J.T.; Tarhule, A.; Christenson, S.

2006-01-01

Leachate plume emanating from an old unlined municipal landfill site near the city of Norman, Oklahoma, is discharging into the underlying alluvial aquifer. Subsurface imaging techniques, electrical resistivity tomography and electrical conductivity (EC) logging, were used on the site to detect and map the position of the leachate plume. Anomalous EC zones, delineated with the two methods, correlated with the occurrence of the plume detected by water chemistry analyses from multilevel monitoring wells. Specific conductance, a potential indicator of leachate contamination, ranged from 1861 to 7710 ??S/cm in contaminated zones and from 465 to 2180 ??S/cm in uncontaminated ground water. Results are in agreement with those from earlier studies that the leachate plume emerges from the landfill along preferential pathways. Additionally, there are indications that the leading edge of the plume has migrated, at least, 200 m away from the landfill in the direction of ground water flow. ?? 2006 National Ground Water Association.

Influence of multi-depositions on the final properties of thermally evaporated TlBr films

NASA Astrophysics Data System (ADS)

Destefano, N.; Mulato, M.

2010-12-01

Thallium bromide is a promising candidate material for photodetectors in medical imaging systems. This work investigates the structural, optical and electrical properties of thermally evaporated TlBr films. The main fabrication parameter is the number of depositions. The use of sequential runs is aimed to increase the thickness of the films, as necessary, for technological applications. We deposited films using one-four runs, that led to maximum thickness of about 50 μm. Crystallographic and morphological changes were observed with varying deposition runs. Nevertheless, the optical gap and electrical resistivity in the dark remained constant at about 2.85 eV and 10 9 Ω cm, respectively. Thicker samples have a larger ratio of photo-to-dark signal under medical X-ray exposure, with a larger linear region as a function of applied voltage. The results are discussed aiming at future technological applications in medical imaging.

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.

Electrical conduction of organic ultrathin films evaluated by an independently driven double-tip scanning tunneling microscope.

PubMed

Takami, K; Tsuruta, S; Miyake, Y; Akai-Kasaya, M; Saito, A; Aono, M; Kuwahara, Y

2011-11-02

The electrical transport properties of organic thin films within the micrometer scale have been evaluated by a laboratory-built independently driven double-tip scanning tunneling microscope, operating under ambient conditions. The two tips were used as point contact electrodes, and current in the range from 0.1 pA to 100 nA flowing between the two tips through the material can be detected. We demonstrated two-dimensional contour mapping of the electrical resistance on a poly(3-octylthiophene) thin films as shown below. The obtained contour map clearly provided an image of two-dimensional electrical conductance between two point electrodes on the poly(3-octylthiophene) thin film. The conductivity of the thin film was estimated to be (1-8) × 10(-6) S cm(-1). Future prospects and the desired development of multiprobe STMs are also discussed.

Time-lapse electric resistivity in a stressed mangrove forest to image the role of the root zone in porewater salt distribution

NASA Astrophysics Data System (ADS)

Downs, C. M.; Krauss, K.; Kruse, S.

2017-12-01

The movement and storage of porewater salts is poorly understood in mangrove forests with limited surface water exchange between the forest and neighboring lagoon. These mangroves are often the most stressed, and have the most unfavorable salinity balance that often transition to mortality during extreme drought. A time-lapse resistivity survey was conducted in a stressed mangrove forest over a diel period. Resistivity is sensitive to the entire soil volume, including fine roots. The objective was to image changes in porewater salinity structures around both mangrove trees, where roots can be a prolific contributor to soil volume, and a salt pan with little or no vegetation. Throughout the diel period, salt pan conductivities remained relatively constant. The most significant temporal changes occur in the root zone around mangrove trees. Particularly interesting is a drop in resistivity (increased conductivity) at sunset when transpiration from individual trees decreases (or even ceases), potentially identifying a cumulative concentration of salts around the mangrove root zone after a full day of transpiration. The resistivity gradient decreases immediately after its peak at sunset, potentially identifying the consequences of hydraulic redistribution in diluting soils surrounding trees immediately after transpiration ceases. This is quicker than expected, and may imply a very strong and rapid eco-hydrological connection in the tree-facilitated salinity balance essential to their survival under the most salinity-stressed environments. At sunrise, resistivity increases, further suggesting dilution of salts via hydraulic redistribution of fresh water from the tree into the upper soil layers, or suggests an accumulation of salts within roots when presumably less water is moving through the trees. Repeated electric resistivity arrays provide spatial and temporal information about these salts and contribute to an overall understanding of how stressed mangrove forests behave. The mangrove ecophysiology literature has suggested that such a balance should exist between tree water use and soil salinity concentration. Here, we document the diel pattern from the perspective of the soil for the first time, but need more surveys to develop conclusive ecosystem level impacts.

In-situ petrophysical properties of hotspot volcanoes. Results from ODP Leg 197, Detroit Seamount and HSDP II borehole, Hawaii

NASA Astrophysics Data System (ADS)

Kock, I.; Pechnig, R.; Buysch, A.; Clauser, C.

2003-04-01

During ODP Leg 197 an extensive logging program was run on Site 1203, Detroit Seamount. This seamount is part of the Emperor seamount chain, a continuation of the Hawaiian volcanic chain. Standard ODP/LDEO logging tool strings were used to measure porosity, density, resistivity, p- and s-wave velocities and gamma ray activity. The FMS-tool yielded detailed high resolution resistivity images of the borehole wall. By interpretation and statistical analysis of the logging parameters a petrophysical classification of the drilled rock content could be derived. The pillow lava recovered in the cores exhibits low porosity, low resistivity and high density. This indicates no or very little vesicles in the non-fractured rock unit. Compared to the pillow basalts, subaerial basalts show increasing porosity, gamma ray and potassium content and decreasing density, resistivity and velocity. A basalt with no or little vesicles and a basalt with average or many vesicles can clearly be distinguished. The volcaniclastics show lower resistivity, lower sonic velocities, higher porosities and lower densities than the basalts. Three different rock types can be distinguished within the volcaniclastics: Tuffs, resedimented tephra and breccia. The tuff shows medium porosity and density, low gamma ray and potassium content. The log responses from the resedimented tephra suggest that the tephra is more easily altered than the tuff. The log responses from the breccia lie between the tuff and tephra log responses, but the breccia can clearly be identified in the FMS borehole images. A similar rock content was found in the Hawaiian Scientific Drilling Project borehole. Gamma ray activity, electrical resistivity and sonic velocity were measured down to 2700 mbsl.. Compared to the 72-76 Ma old Detroit seamount basalts, the HSDP subaerial and submarine lava flows show a significant lower gamma ray activity, while sonic velocity and electrical resistivity are comparable. Deviations between the gamma ray activity might be due to the different primary compositions of the melt or to long lasting low temperature alteration. Investigations on this topic are in progress.

Application of 2D electrical resistivity imaging and cone penetration test (CPT) to assess the harzadous effect of near surface water on foundations in Lagos Nigeria

NASA Astrophysics Data System (ADS)

Adewoyin, O. O.; Joshua, E. O.; Akinyemi, M. L.; Omeje, M.; Joel, E. S.

2017-05-01

Adequate information on the condition of the subsurface is very important for site evaluation for engineering purposes. In this study two dimensional (2D) geoelectrical resistivity survey and cone penetration tests were conducted to study the hazardous effect of excess near surface water on the foundation of building in a reclaimed land located at Victoria Island area of Lagos State. The results of the inverted 2D geoelectrical resistivity data revealed three distinct geoelectrical layers characterized by low to moderate electrical resistivity of 2.23 and 129Ωm and 9.46 to 636Ωm respectively. The topsoil is characterized by wet sandy soil, which is underlain by sandy clay and banded at the below by a geologic formation of low resistivity which is suspected to be clay. The clay material may be responsible for the excess water retention observed in the area. The CPT method on the other hand revealed a geological formation of low resistance to penetration between 2-3 kg/cm2 from the topsoil to a depth of 7 m, which may be the effect of excess water in the near surface. This study revealed that the foundation of building may not be founded directly on the soil in any reclaimed land as this may result in collapse as a result of upward migration of water to the near surface.

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 resolution and current density close to the cutterhead.

Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary.

PubMed

Grayver, Alexander V; Schnepf, Neesha R; Kuvshinov, Alexey V; Sabaka, Terence J; Manoj, Chandrasekharan; Olsen, Nils

2016-09-01

The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals a ≈72-km-thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere.

Magnetocardiography with sensors based on giant magnetoresistance

NASA Astrophysics Data System (ADS)

Pannetier-Lecoeur, M.; Parkkonen, L.; Sergeeva-Chollet, N.; Polovy, H.; Fermon, C.; Fowley, C.

2011-04-01

Biomagnetic signals, mostly due to the electrical activity in the body, are very weak and they can only be detected by the most sensitive magnetometers, such as Superconducting Quantum Interference Devices (SQUIDs). We report here biomagnetic recordings with hybrid sensors based on Giant MagnetoResistance (GMR). We recorded magnetic signatures of the electric activity of the human heart (magnetocardiography) in healthy volunteers. The P-wave and QRS complex, known from the corresponding electric recordings, are clearly visible in the recordings after an averaging time of about 1 min. Multiple recordings at different locations over the chest yielded a dipolar magnetic field map and allowed localizing the underlying current sources. The sensitivity of the GMR-based sensors is now approaching that of SQUIDs and paves way for spin electronics devices for functional imaging of the body.

Optical, electrical, and photovoltaic properties of PbS thin films by anionic and cationic dopants

NASA Astrophysics Data System (ADS)

Cheraghizade, Mohsen; Jamali-Sheini, Farid; Yousefi, Ramin

2017-06-01

Lead sulfide (PbS) thin films were deposited by CVD method to examine the effects of anionic and cationic dopants on optical and electrical properties for photovoltaic applications. XRD diffractograms verified the formation of cubic phase of multicrystalline PbS thin films. FESEM images showed surface morphologies in nano-dimensions (rods and flowers). UV-Vis-NIR spectrum revealed absorbance in the visible and NIR regions for all samples, in which dopants decreased the intensity of absorbance. Se as an anionic dopant for PbS thin films increased electrical resistance, acceptor concentrations, and crystallite defects, and decreased flat-band voltage and depletion width. Finally, photovoltaic measurements indicated that Zn-doped PbS thin film, as a photovoltaic cell, exhibited higher conversion efficiency and external quantum efficiency (EQE).

Evolution of the electrical resistivity anisotropy during saline tracer tests: insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, D.; Jimenez-Martinez, J.; Legendre, R.; Le Borgne, T.; Meheust, Y.; Linde, N.

2017-12-01

The use of time-lapse electrical resistivity tomography has been largely developed in environmental studies to remotely monitor water saturation and contaminant plumes migration. However, subsurface heterogeneities, and corresponding preferential transport paths, yield a potentially large anisotropy in the electrical properties of the subsurface. In order to study this effect, we have used a newly developed geoelectrical milli-fluidic experimental set-up with a flow cell that contains a 2D porous medium consisting of a single layer of cylindrical solid grains. We performed saline tracer tests under full and partial water saturations in that cell by jointly injecting air and aqueous solutions with different salinities. The flow cell is equipped with four electrodes to measure the bulk electrical resistivity at the cell's scale. The spatial distribution of the water/air phases and the saline solute concentration field in the water phase are captured simultaneously with a high-resolution camera by combining a fluorescent tracer with the saline solute. These data are used to compute the longitudinal and transverse effective electrical resistivity numerically from the measured spatial distributions of the fluid phases and the salinity field. This approach is validated as the computed longitudinal effective resistivities are in good agreement with the laboratory measurements. The anisotropy in electrical resistivity is then inferred from the computed longitudinal and transverse effective resistivities. We find that the spatial distribution of saline tracer, and potentially air phase, drive temporal changes in the effective resistivity through preferential paths or barriers for electrical current at the pore scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical resistivity, especially for partially saturated conditions. Therefore, considering the electrical resistivity as a tensor could improve our understanding of transport properties from field-scale time-lapse ERT.

Electrical imaging of subsurface nanoparticle propagation for in-situ groundwater remediation

NASA Astrophysics Data System (ADS)

Flores Orozco, Adrián; Gallistl, Jakob; Schmid, Doris; Micic Batka, Vesna; Bücker, Matthias; Hofmann, Thilo

2017-04-01

Application of nanoparticles has emerged as a promising in situ remediation technology for the remediation of contaminated groundwater, particularly for areas difficult to access by other remediation techniques. The performance of nanoparticle injections, as a foremost step within this technology, is usually assessed through the geochemical analysis of soil and groundwater samples. This approach is not well suited for a real-time monitoring, and often suffers from a poor spatio-temporal resolution and only provides information from areas close to the sampling points. To overcome these limitations we propose the application of non-invasive Induced Polarization (IP) imaging, a geophysical method that provides information on the electrical properties of the subsurface. The analysis of temporal changes in the electrical images allows tracking the propagation of the injected nanoparticle suspension and detection of the induced bio-geochemical changes in the subsurface. Here, we present IP monitoring results for data collected during the injection of Nano-Goethite particles (NGP) used for simulation of biodegradation of a BTEX plume (i.e., benzene, toluene, ethylbenzene, and xylene) at the Spolchemie II site, CZ. Frequency-domain IP measurements were collected parallel to the groundwater flow direction and centred on the NGP injection point. Pre-injection imaging results revealed high electrical conductivities (> 10 S/m) and negligible polarization effects in the BTEX-contaminated part of the saturated zone (below 5 m depth). The apparently contradictory observation - BTEX compounds are poor electrical conductors - can be explained by the release of carbonic acids (a metabolic by-product of the biodegradation of hydrocarbons), which leads to an increase of the electrical conductivity. Post-injection images revealed a significant decrease (> 50%) of the electrical conductivity, with even larger changes in the proximity of the injection points, most likely due to the relatively high resistivity of the NGP suspension. This is in line with geochemical data from both the injected NGP suspension and the groundwater samples. Furthermore, temporal changes in the IP images are consistent with variations in total iron concentration in groundwater (a proxy for the NGP concentration) as well as in situ groundwater parameters, such as pH and oxidation-reduction potential. Our results demonstrate the applicability of IP imaging for the real-time monitoring of nanoparticle injection, as well as of the accompanying geochemical changes. Part of this research is funded by the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 309517.

Correlation of Resistivity Value with Geotechnical N-Value of Sedimentary Area in Nusajaya, Johor, Malaysia

NASA Astrophysics Data System (ADS)

Akip Tan, S. N. Mohd; Edy Tonnizam, M.; Saad, R.; Dan, M. F. Md; Nordiana, M. M.; Hazreek, Z. A. M.; Madun, A.

2018-04-01

Electrical resistivity survey and the geotechnical SPT blow counts (N-value) were carried out simultaneously on the tropically weathered sedimentary rock mass for an excavation project at Nusajaya, Johor, Malaysia. This study aims to determine subsurface profile by using 2D-resistivity methods and correlate with N-value derived from boring works. Four boreholes were investigated in five survey lines that revealed the site is underlain by moderately to completely weathered sandstone, clay, silt and shale. Data analysis from 2D-resistivity image shows that zones with high resistivity value generally have high N-value, and vice versa. Five zones have inversed the proportional relation between N-value and resistivity Ωm value due to different types of soil lithology. It indicates that 2D-resistivity is significance to detect bodies of anomalous materials or estimating the depth of bedrock. As a conclusion, the integration of geophysical and geotechnical analysis provides a promise approach to understand some relationship concerning the subsurface subsurface ground through the combination of 2D-resistivity and N-value.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 cokesmore » 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.« less

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder.

PubMed

Li, Jiaxiang; Li, Yunping; Wang, Zhongchang; Bian, Huakang; Hou, Yuhang; Wang, Fenglin; Xu, Guofu; Liu, Bin; Liu, Yong

2016-12-22

The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service.

Characterisation of electrical resistance for CMC Materials up to 1200 °C

NASA Astrophysics Data System (ADS)

Stäbler, T.; Böhrk, H.; Voggenreiter, H.

2017-12-01

Damage to thermal protection systems (TPS) during atmospheric re-entry is a severe safety issue, especially when considering re-usability of space transportation systems. There is a need for structural health monitoring systems and non-destructive inspection methods. However, damages are hard to detect. When ceramic matrix composites, in this case carbon fibre reinforced silicon carbide (C/C-SiC), are used as a TPS, the electrical properties of the present semiconductor material can be used for health monitoring, since the resistivity changes with damage, strain and temperature. In this work the electrical resistivity as a function of the material temperature is analysed eliminating effects of thermal electricity and the thermal coefficient of electrical resistance is determined. A sensor network is applied for locally and time resolved monitoring of the 300 mm x 120 mm x 3 mm panel shaped samples. Since the material is used for atmospheric re-entry it needs to be characterised for a wide range of temperatures, in this case as high as 1200 °C. Therefore, experiments in an inductively heated test bench were conducted. Firstly, a reference sample was used with thermocouples for characterising the temperature distribution across the sample surface. Secondly, electrical resistance under heat load was measured, time and spatially resolved. Results will be shown and discussed in terms of resistance dependence on temperature, thermal coefficient of electrical resistance, thermal electricity and electrical path orientation including an analysis on effective conducting cross section. Conversely, the thermal coefficient can also be used to determine the material temperature as a function of electrical resistance.

Using Electrical Resistivity Imaging to Evaluate Permanganate Performance During an In Situ Treatment of a RDX-Contaminated Aquifer

DTIC Science & Technology

2009-08-01

assess the performance of remedial efforts. These techniques are expensive and, by themselves, are effectively random samples guided by the training...technology should be further explored and developed for use in pre-amendment tracer tests and quantitative remedial assessments . 15. SUBJECT TERMS...and flow of injectate. Site assessment following groundwater remediation efforts typically involves discrete point sampling using wells or

Electrical resistivity imaging (ERI) and ground-penetrating radar (GPR) survey at the Giribaile site (upper Guadalquivir valley; southern Spain)

NASA Astrophysics Data System (ADS)

Martínez, J.; Rey, J.; Gutiérrez, L. M.; Novo, A.; Ortiz, A. J.; Alejo, M.; Galdón, J. M.

2015-12-01

The Giribaile archaeological site is one of the most important Iberian enclaves of the Alto Guadalquivir (Southern Spain). However, to date, only minimal excavation work has been performed at the site. Evaluation requires a preliminary, non-destructive general analysis to determine high-interest areas. This stage required a geophysical survey. Specifically, a 100 m2 grid was selected, where an initial campaign of nine electrical resistivity imaging (ERI) profiles was performed, where each profile was 111 m in length; these profiles were previously located using a detailed topographical survey. A total of 112 electrodes were used for each profile, spaced at 1 m apart with a Wenner-Schlumberger configuration. Secondly, 201 GPR profiles were created using a 500 MHz antenna. The 100 m long profiles were spaced 0.5 m apart and parallel to one another. The present research analyses the efficiency of each of these geophysical tools in supporting archaeological research. Using these methodologies, the position, morphology, and depth of different buried structures can be determined. 3D interpretation of the geophysical survey in 100 × 100 m grid allowed to differentiate structures square and rectangular, interesting buildings in a semicircle (interpreted as ovens) plus delineate different streets. From the geophysical survey follows the Carthaginian presence inside this ancient Iberian enclave.

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.

3D electromagnetic modelling of a TTI medium and TTI effects in inversion

NASA Astrophysics Data System (ADS)

Jaysaval, Piyoosh; Shantsev, Daniil; de la Kethulle de Ryhove, Sébastien

2016-04-01

We present a numerical algorithm for 3D electromagnetic (EM) forward modelling in conducting media with general electric anisotropy. The algorithm is based on the finite-difference discretization of frequency-domain Maxwell's equations on a Lebedev grid, in which all components of the electric field are collocated but half a spatial step staggered with respect to the magnetic field components, which also are collocated. This leads to a system of linear equations that is solved using a stabilized biconjugate gradient method with a multigrid preconditioner. We validate the accuracy of the numerical results for layered and 3D tilted transverse isotropic (TTI) earth models representing typical scenarios used in the marine controlled-source EM method. It is then demonstrated that not taking into account the full anisotropy of the conductivity tensor can lead to misleading inversion results. For simulation data corresponding to a 3D model with a TTI anticlinal structure, a standard vertical transverse isotropic inversion is not able to image a resistor, while for a 3D model with a TTI synclinal structure the inversion produces a false resistive anomaly. If inversion uses the proposed forward solver that can handle TTI anisotropy, it produces resistivity images consistent with the true models.

The Effect of MnO2 Content and Sintering Atmosphere on The Electrical Properties of Iron Titanium Oxide NTC Thermistors using Yarosite

NASA Astrophysics Data System (ADS)

Wiendartun; Gustaman Syarif, Dani

2017-02-01

The effect of MnO2 content and sintering atmosphere on the characteristics of Fe2TiO5 ceramics for Negative Thermal Coefficient (NTC) thermistors by using Fe2O3 derived from yarosite has been studied. The ceramics were produced by pressing a homogeneous mixture of Fe2O3, TiO2 and MnO2 (0-2.0 w/o) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1100-1200°C for 3 hours in air, O2 and N2 gas. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 30°C to 200°C. Microstructure and structural analyses were also carried out by using an scanning electron microscope (SEM) and x-ray diffraction (XRD). The XRD data showed that the pellets crystallize in orthorhombic. The presence of second phase could not be identified from the XRD analyses. The SEM images showed that the grain size of pellet ceramics increase with increasing of MnO2 addition, and the grains size of the ceramic sintered in oxygen gas is smaller than sintered in nitrogen gas. Electrical data showed that the value of room temperature resistance (RRT) tend to decrease with respect to the increasing of MnO2 addition and the pellet ceramics sintered in oxygen gas had the largest thermistor constant (B), activation energy (Ea), sensitivity (α) and room temperature resistance (RRT), compared to the sintered in nitrogen gas. From the electrical characteristics data, it was known that the electrical characteristics of the Fe2TiO5 pellet ceramics followed the NTC characteristic. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 2207-7145K). This can be applied as temperature sensor, and will fulfill the market requirement.

Three-dimensional internal structure of an entire alpine rockglacier, detected by Electrical Resistivity Imaging

NASA Astrophysics Data System (ADS)

Emmert, Adrian; Kneisel, Christof

2017-04-01

Uertsch rockglacier (46.61° N, 9.84°E, ca. 2500m asl.) is a tongue-shaped 300m x 100m landform at the head of a small high mountain valley in the Eastern Swiss Alps. Located at the lower end of possible permafrost existence, the rockglacier shows indications of permafrost decay although borehole temperature measurements exhibit an at least partly occurrence of permanently frozen subsurface conditions. To delimit the extent of the frozen area and to characterize subsurface structures, we performed three adjacent 3-D Electrical Resistivity Imaging (ERI) surveys consisting of data from altogether 138 merged 2-D profiles, covering nearly the entire rockglacier by an investigation area of more than 2.5 ha. More than 47000 data points of Wenner-Schlumberger and Dipol-Dipol electrode arrays grant sufficient data coverage. Ground-truthing was achieved through borehole temperature measurements and multiple comparative ground-penetrating radar (GPR) and seismic refraction tomography (SRT) surveys. Results show that the rockglacier today lacks a consistent permafrost table and only shows a patchy permafrost distribution. Several structures differing in geometry and electric resistivity show a complex pattern of ice-rich, ice-poor and ice-free areas. We could identify glacial influence in the root zone of the rockglacier, where a 3200m2 perennial surface ice field is visible. In a downslope direction, a shallow layer of high resistivity values, which is limited to the shallow subsurface, follows the ice field and indicates a genesis by refreezing meltwater. The central part of the rockglacier also shows traces of glacial interaction by the occurrence of a several meters thick buried ice patch in the shallow subsurface at a marginal position. Next to this position, in an area where longitudinal surface ridges are exposed, modelled resistivity values indicate frozen conditions with relatively low ice content, limited to the shallow subsurface. We assume that these structures are likely connected to permafrost creep processes. The frontal part of the rockglacier is affected by a strong ridge-and-furrow topography with arcuate ridge structures. Frozen conditions within these structures indicate an increase of ice content by thickening through compressive flow. Our study reflects the complexity of landform evolution for Uertsch rockglacier, where glacial and periglacial processes occur in close proximity. This emphasize the value of comprehensive 3-D investigations to assess the geometry and characteristics of larger subsurface structures.

Geotechnical studies for evaluation and limitations of environmental and engineering hazards that affect the economic infrastructure in Abha, Saudi Arabia

NASA Astrophysics Data System (ADS)

Shaaban, Fathy; Al-Salami, Ali E.

2014-12-01

Abha is the capital of Asir province in Saudi Arabia. It is situated 2200 meters (7200 ft) above the sea level in the fertile mountains of the south-western Saudi Arabia. One of the most important structures of this region is Abha dam that acts as a barrier that impounds water or underground streams thereby retaining the ground water of the region. With the passage of time, various environmental factors such as ground movement, wind and changes in temperature may have significant effect on these various structure factors and may lead to invisible cracks and other structural defects. Because the dams and tunnels are prone to sudden collapse, there is potential great risk to lives of the people and significant economic loss in this area. The use of the ground penetrating radar (GPR) and electric resistivity techniques is a non-invasive scan and could assess the conditions of various built structures as well as the earth beneath or surrounding it. So the GPR system with appropriate types of antennas (1.5 GH, 1 GH, 400 MH and 100 MH) and electrical resistivity in one dimension (VES) and two dimensions (electrical profiling and imaging) is used in this work. This work aims to investigate the dam structure, developing cracks or areas of increased moisture. Also to study the surrounding areas to detect seepage from pond that may affect nearby buildings and the dam itself. It reveals that, the depth of water bearing layer ranges from 2 m to 10 m, where the three geoelectric layers are present. The first layer has resistivity values ranging from 44 Ω m-1200 Ω m with thickness ranging from 3 m to 18 m that is interpreted as the wadi deposits. The second layer having resistivity values from 11 Ω m to 137 Ω m is interpreted as the water saturated in the fractured basements. The third layer of resistivity values ranging from 2200 Ω m to 90,000 Ω m is interpreted as dry, massive basements. The GPR results provided internal images of the slab, showing its morphology, areas of possible damage and changes to the structure, and the situation of the steel reinforcements. It showed the presence of different shapes of fractures and voids with the growing of moisture zones.

The Effect of Electrical Treatment on Cyclic Fatigue of NiTi Instruments

PubMed Central

Saghiri, Mohammad Ali; Asatourian, Armen; Garcia-Godoy, Franklin; Gutmann, James L.; Lotfi, Mehrdad; Sheibani, Nader

2016-01-01

Summary Dentists desire to use NiTi rotary instruments, which do not break inside the root canals of teeth, since the pieces from broken files are difficult to remove. The NiTi rotary instrument breakage is because of cyclic and torsional fatigue. Here the low-voltage (12 V) and high voltage (24 V) electrical treatments were used to enhance the cyclic fatigue of NiTi rotary instruments and increase their durability. In excremental groups, following electrical treatment samples of the NiTi instruments were rotated inside artificial root canals until they broke. Our results showed that electrical treatment with 12-V DC was effective in restoring NiTi instrument’s resistance to cyclic fatigue. The scanning electron microscopy images and fractograph of samples exposed to 12-V electrical treatment showed a more regular texture over the surface with less dimpling on fractured site. These patterns can improve the super elasticity of tested devices during rotational movement, and delay the NiTi instruments separation in root canal preparations. PMID:24798116

In-situ measurement system

DOEpatents

Lord, David E.

1983-01-01

A multipurpose in situ underground measurement system comprising a plurality of long electrical resistance elements in the form of rigid reinforcing bars, each having an open loop "hairpin" configuration of shorter length than the other resistance elements. The resistance elements are arranged in pairs in a unitized structure, and grouted in place in the underground volume. The electrical resistance of each element and the difference in electrical resistance of the paired elements are obtained, which difference values may be used in analytical methods involving resistance as a function of temperature. A scanner sequentially connects the resistance-measuring apparatus to each individual pair of elements. A source of heating current is also selectively connectable for heating the elements to an initial predetermined temperature prior to electrical resistance measurements when used as an anemometer.

Non-volatile, solid state bistable electrical switch

NASA Technical Reports Server (NTRS)

Williams, Roger M. (Inventor)

1994-01-01

A bistable switching element is made of a material whose electrical resistance reversibly decreases in response to intercalation by positive ions. Flow of positive ions between the bistable switching element and a positive ion source is controlled by means of an electrical potential applied across a thermal switching element. The material of the thermal switching element generates heat in response to electrical current flow therethrough, which in turn causes the material to undergo a thermal phase transition from a high electrical resistance state to a low electrical resistance state as the temperature increases above a predetermined value. Application of the electrical potential in one direction renders the thermal switching element conductive to pass electron current out of the ion source. This causes positive ions to flow from the source into the bistable switching element and intercalate the same to produce a non-volatile, low resistance logic state. Application of the electrical potential in the opposite direction causes reverse current flow which de-intercalates the bistable logic switching element and produces a high resistance logic state.

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

DOT National Transportation Integrated Search

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, leav...

Thermal and electrical contact conductance studies

NASA Technical Reports Server (NTRS)

Vansciver, S. W.; Nilles, M.

1985-01-01

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

Study of electrical resistivity on the location and identification of contamination

NASA Astrophysics Data System (ADS)

McCarty, B. D.

1985-12-01

Electrical resistance studies were conducted in two laboratory models to determine electrical resistivity relationships and to use those defined relationships to identify contamination spikes. A good correlation was established between resistance data and the composition of leachate and copper spiked leachate gelatin blocks under study. The major variable that could not be eliminated from this study which had the greatest effect on data was moisture content. This thesis contains a review of the theory and field application of electrical resistivity, a description of the experimental approach used, and a summary of the data collected.

Characterization of real objects by an active electrolocation sensor

NASA Astrophysics Data System (ADS)

Metzen, Michael G.; Al Ghouz, Imène; Krueger, Sandra; Bousack, Herbert; von der Emde, Gerhard

2012-04-01

Weakly electric fish use a process called 'active electrolocation' to orientate in their environment and to localize objects based on their electrical properties. To do so, the fish discharge an electric organ which emits brief electrical current pulses (electric organ discharge, EOD) and in return sense the generated electric field which builds up surrounding the animal. Caused by the electrical properties of nearby objects, fish measure characteristic signal modulations with an array of electroreceptors in their skin. The fish are able to gain important information about the geometrical properties of an object as well as its complex impedance and its distance. Thus, active electrolocation is an interesting feature to be used in biomimetic approaches. We used this sensory principle to identify different insertions in the walls of Plexiglas tubes. The insertions tested were composed of aluminum, brass and graphite in sizes between 3 and 20 mm. A carrier signal was emitted and perceived with the poles of a commercial catheter for medical diagnostics. Measurements were performed with the poles separated by 6.3 to 55.3 mm. Depending on the length of the insertion in relation to the sender-receiver distance, we observed up to three peaks in the measured electric images. The first peak was affected by the material of the insertion, while the distance between the second and third peak strongly correlated with the length of the insertion. In a second experiment we tested whether various materials could be detected by using signals of different frequency compositions. Based on their electric images we were able to discriminate between objects having different resistive properties, but not between objects of complex impedances.

Determination of the electrical resistivity of vertically aligned carbon nanotubes by scanning probe microscopy

NASA Astrophysics Data System (ADS)

Ageev, O. A.; Il'in, O. I.; Rubashkina, M. V.; Smirnov, V. A.; Fedotov, A. A.; Tsukanova, O. G.

2015-07-01

Techniques are developed to determine the resistance per unit length and the electrical resistivity of vertically aligned carbon nanotubes (VA CNTs) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). These techniques are used to study the resistance of VA CNTs. The resistance of an individual VA CNT calculated with the AFM-based technique is shown to be higher than the resistance of VA CNTs determined by the STM-based technique by a factor of 200, which is related to the influence of the resistance of the contact of an AFM probe to VA CNTs. The resistance per unit length and the electrical resistivity of an individual VA CNT 118 ± 39 nm in diameter and 2.23 ± 0.37 μm in height that are determined by the STM-based technique are 19.28 ± 3.08 kΩ/μm and 8.32 ± 3.18 × 10-4 Ω m, respectively. The STM-based technique developed to determine the resistance per unit length and the electrical resistivity of VA CNTs can be used to diagnose the electrical parameters of VA CNTs and to create VA CNT-based nanoelectronic elements.

In memoriam: Dr. Gary A. Dudley (1952-2006) a modern pioneer in the study of muscle and resistance training.

PubMed

2007-02-01

Dr. Gary Alton Dudley was a modern pioneer in the study of muscle. His work encompassed almost 30 years of study with dramatic discoveries in the areas of muscle physiology, resistance training, and spinal cord injury and therapy. The greater understanding of muscle fiber changes with training, as well as novel experiments using magnetic resonance imaging and single fiber analyses, allowed for many discoveries in the areas of resistance training and detraining, the roles of electrical stimulation in training muscle, the compatibility of different exercise modes, and the characteristics of and treatment interventions for spinal cord injury. His work and insights will provide future investigators a knowledge base from which to work for both basic and applied research in muscle and exercise physiology.

Use of electrical resistivity to detect underground mine voids in Ohio : executive summary.

DOT National Transportation Integrated Search

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 ...

Geophysical Images of the Shallow Hydrothermal Degassing at Solfatara (Phlegrean Fields, Italy)

NASA Astrophysics Data System (ADS)

Byrdina, S.; Vandemeulebrouck, J.; Cardellini, C.; Chiodini, G.; Legaz, A.; Camerlynck, C.; Lebourg, T.

2014-12-01

We present the results of an electric resistivity tomography (ERT) survey, combined with mappings of diffuse carbon dioxide flux, ground temperature and self-potential (SP) at Solfatara, the most active crater of Phlegrean Fields. Solfatara is characterized by an intense carbon dioxide degassing, fumarole activity, and ground deformation. This ensemble of methods is applied to image the hydrothermal system of Solfatara, to understand the geometry of the fluid circulation, and to define the extension of the hydrothermal plume at a high enough resolution for a quantitative modeling. ERT inversion results show Solfatara as a globally conductive structure, with resistivity in the range 1-200 Ohmm. Broad negative anomaly of self-potential in the inner part of Solfatara with a minimum in the area of Bocca Grande suggests a significant downward flow of condensing liquid water. Comparison between spatial variations of resistivity and gas flux indicates that resistivity changes at depth are related to gas saturation and fluid temperature. These variations delineate two plume structures: a liquid-dominated conductive plume below Fangaia mud-pool and a gas-dominated plume below Bocca Grande fumarole. The geometry of the Fangaia liquid-saturated plume is also imaged by a high resolution 3-D resistivity model. In order to estimate the permeability, we propose a 2-D axis-symmetric numerical model coupling Richards's equation for fluid flow in conditions of partial saturation with the resistivity calculation as function of saturation only. Alternatively, we apply the Dupuit equation to estimate the permeability of the shallow layer. Using these two approaches, we obtain the permeability of the shallow layer below Fangaia which ranges between (2 - 4) 10-14 m 2.

An estimation of the electrical characteristics of planetary shallow subsurfaces with TAPIR antennas

NASA Astrophysics Data System (ADS)

Le Gall, A.; Reineix, A.; Ciarletti, V.; Berthelier, J. J.; Ney, R.; Dolon, F.; Corbel, C.

2006-06-01

In the frame of the NETLANDER program, we have developed the Terrestrial And Planetary Investigation by Radar (TAPIR) imaging ground-penetrating radar to explore the Martian subsurface at kilometric depths and search for potential water reservoirs. This instrument which is to operate from a fixed lander is based on a new concept which allows one to image the various underground reflectors by determining the direction of propagation of the reflected waves. The electrical parameters of the shallow subsurface (permittivity and conductivity) need to be known to correctly determine the propagation vector. In addition, these electrical parameters can bring valuable information on the nature of the materials close to the surface. The electric antennas of the radar are 35 m long resistively loaded monopoles that are laid on the ground. Their impedance, measured during a dedicated mode of operation of the radar, depends on the electrical parameters of soil and is used to infer the permittivity and conductivity of the upper layer of the subsurface. This paper presents an experimental and theoretical study of the antenna impedance and shows that the frequency profile of the antenna complex impedance can be used to retrieve the geoelectrical characteristics of the soil. Comparisons between a numerical modeling and in situ measurements have been successfully carried over various soils, showing a very good agreement.

Near-infrared imaging of water in human hair.

PubMed

Egawa, Mariko; Hagihara, Motofumi; Yanai, Motohiro

2013-02-01

The water content of hair can be evaluated by weighing, the Karl Fischer method, and from electrical properties. However, these methods cannot be used to study the distribution of water in the hair. Imaging techniques are required for this purpose. In this study, a highly sensitive near-infrared (NIR) imaging system was developed for evaluating water in human hair. The results obtained from NIR imaging and conventional methods were compared. An extended indium-gallium-arsenide NIR camera (detection range: 1100-2200 nm) and diffuse illumination unit developed in our laboratory were used to obtain a NIR image of hair. A water image was obtained using a 1950-nm interference filter and polarization filter. Changes in the hair water content with relative humidity (20-95% RH) and after immersion in a 7% (w/w) sorbitol solution were measured using the NIR camera and an insulation resistance tester. The changes in the water content after treatment with two types of commercially available shampoo were also measured using the NIR camera. As the water content increased with changes in the relative humidity, the brightness of the water image decreased and the insulation resistance decreased. The brightness in the NIR image of hair treated with sorbitol solution was lower than that in the image of hair treated with water. This shows the sorbitol-treated hair contains more water than water-treated hair. The sorbitol-treated hair had a lower resistance after treatment than before, which also shows that sorbitol treatment increases the water content. With this system, we could detect a difference in the moisturizing effect between two commercially available shampoos. The highly sensitive imaging system could be used to study water in human hair. Changes in the water content of hair depended on the relative humidity and treatment with moisturizer. The results obtained using the NIR imaging system were similar to those obtained using a conventional method. Our system could detect differences in the moisturizing effects of two commercially available shampoos. © 2012 John Wiley & Sons A/S.

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.

An experimental study on the thermal characteristics and heating effect of arc-fault from Cu core in residential electrical wiring fires

PubMed Central

Du, Jian-Hua; Zeng, Yi; Pan, Leng; Zhang, Ren-Cheng

2017-01-01

The characteristics of a series direct current (DC) arc-fault including both electrical and thermal parameters were investigated based on an arc-fault simulator to provide references for multi-parameter electrical fire detection method. Tests on arc fault behavior with three different initial circuit voltages, resistances and arc gaps were conducted, respectively. The influences of circuit conditions on arc dynamic image, voltage, current or power were interpreted. Also, the temperature rises of electrode surface and ambient air were studied. The results showed that, first, significant variations of arc structure and light emitting were observed under different conditions. A thin outer burning layer of vapor generated from electrodes with orange light was found due to the extremely high arc temperature. Second, with the increasing electrode gap in discharging, the arc power was shown to have a non monotonic relationship with arc length for constant initial circuit voltage and resistance. Finally, the temperature rises of electrode surface caused by heat transfer from arc were found to be not sensitive with increasing arc length due to special heat transfer mechanism. In addition, temperature of ambient air showed a large gradient in radial direction of arc. PMID:28797055

An experimental study on the thermal characteristics and heating effect of arc-fault from Cu core in residential electrical wiring fires.

PubMed

Du, Jian-Hua; Tu, Ran; Zeng, Yi; Pan, Leng; Zhang, Ren-Cheng

2017-01-01

The characteristics of a series direct current (DC) arc-fault including both electrical and thermal parameters were investigated based on an arc-fault simulator to provide references for multi-parameter electrical fire detection method. Tests on arc fault behavior with three different initial circuit voltages, resistances and arc gaps were conducted, respectively. The influences of circuit conditions on arc dynamic image, voltage, current or power were interpreted. Also, the temperature rises of electrode surface and ambient air were studied. The results showed that, first, significant variations of arc structure and light emitting were observed under different conditions. A thin outer burning layer of vapor generated from electrodes with orange light was found due to the extremely high arc temperature. Second, with the increasing electrode gap in discharging, the arc power was shown to have a non monotonic relationship with arc length for constant initial circuit voltage and resistance. Finally, the temperature rises of electrode surface caused by heat transfer from arc were found to be not sensitive with increasing arc length due to special heat transfer mechanism. In addition, temperature of ambient air showed a large gradient in radial direction of arc.

Applications of Synthetic Microchannel and Nanopore Systems

NASA Astrophysics Data System (ADS)

Hinkle, Thomas Preston

This thesis describes research conducted on the physics and applications of micro- and nanoscale ion-conducting channels. Making use of the nanoscale physics that takes place in the vicinity of charged surfaces, there is the possibility that nanopores, holes on the order of 1 nm in size, could be used to make complex integrated ionic circuits. For inspiration on what such circuits could achieve we only need to look to biology systems, immensely complex machines that at their most basic level require precise control of ions and intercellular electric potentials to function. In order to contribute to the ever expanding field of nanopore research, we engineered novel hybrid insulator-conductor nanopores that behave analagously to ionic diodes, which allow passage of current flow in one direction but severely limit the current in the opposite direction. The experiments revealed that surface polarization of the conducting material can induce the formation of an electrical double layer in the same way static surface charges can. Furthermore, we showed that the hybrid device behaved similar to an ionic diode, and could see potential use as a standard rectifying element in ionic circuits. Another application based on ion conducting channels is resistive pulse sensing, a single particle detection and characterization method. We present three main experiments that expand the capacity of resistive pulse sensing for particle characterization. First, we demonstrate how resistive pulse sensing in pores with longitudinal irregularities can be used to measure the lengths of individual nanoparticles. Then, we describe an entirely new hybrid approach to resistive pulse sensing, whereby the electrical measurements are combined with simultaneous optical imaging. The hybrid method allows for validation of the resistive pulse signals and will greatly contribute to their interpretability. We present experiments that explore some of the possibilities of the hybrid method. Then, building off the hybrid method we present experiments performed to measure single particle deformability with resistive pulse sensing. Using a novel microfluidic channel design, we were able to reproducibily induce bidirectional deformation of cells. We describe how these deformations could be detected with the resistive pulse signal alone, paving the way for resistive pulse sensing based cell deformability cytometers.

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 in kaolin clay normally had three kinds of effects including oil filling, coating, and bridging. Finally, a resistivity-based ANN model was established based on the database collected from the experiment data. The performance of the model was proved to be reasonably accepted, which puts forward a possible simple, economic, and effective tool to detect the oil content in contaminated clayey soils just with four basic parameters: wet density, dry density, measured moisture content, and electrical resistivity.

A spatially adaptive total variation regularization method for electrical resistance tomography

NASA Astrophysics Data System (ADS)

Song, Xizi; Xu, Yanbin; Dong, Feng

2015-12-01

The total variation (TV) regularization method has been used to solve the ill-posed inverse problem of electrical resistance tomography (ERT), owing to its good ability to preserve edges. However, the quality of the reconstructed images, especially in the flat region, is often degraded by noise. To optimize the regularization term and the regularization factor according to the spatial feature and to improve the resolution of reconstructed images, a spatially adaptive total variation (SATV) regularization method is proposed. A kind of effective spatial feature indicator named difference curvature is used to identify which region is a flat or edge region. According to different spatial features, the SATV regularization method can automatically adjust both the regularization term and regularization factor. At edge regions, the regularization term is approximate to the TV functional to preserve the edges; in flat regions, it is approximate to the first-order Tikhonov (FOT) functional to make the solution stable. Meanwhile, the adaptive regularization factor determined by the spatial feature is used to constrain the regularization strength of the SATV regularization method for different regions. Besides, a numerical scheme is adopted for the implementation of the second derivatives of difference curvature to improve the numerical stability. Several reconstruction image metrics are used to quantitatively evaluate the performance of the reconstructed results. Both simulation and experimental results indicate that, compared with the TV (mean relative error 0.288, mean correlation coefficient 0.627) and FOT (mean relative error 0.295, mean correlation coefficient 0.638) regularization methods, the proposed SATV (mean relative error 0.259, mean correlation coefficient 0.738) regularization method can endure a relatively high level of noise and improve the resolution of reconstructed images.

Crustal structure beneath Namche Barwa, eastern Himalayan syntaxis: New insights from three-dimensional magnetotelluric imaging

NASA Astrophysics Data System (ADS)

Lin, Changhong; Peng, Miao; Tan, Handong; Xu, Zhiqin; Li, Zhong-Hai; Kong, Wenxin; Tong, Tuo; Wang, Mao; Zeng, Weihua

2017-07-01

The eastern terminations of the Himalayan orogeny, named Namche Barwa, are considered a vital natural laboratory in the Tibetan plateau for geodynamics due to its distinctive geological and geomorphological characteristics. Magnetotelluric (MT) data measured at 83 sites around the Namche Barwa are imaged by three-dimensional (3-D) inversion to better reveal the crustal structure of the eastern Himalaya. The results show a complex and heterogeneous electrical structure beneath the Namche Barwa. The electrical conductors distributed in the middle and lower crust around the Namche Barwa provide additional evidence for the "crustal flow" model if they are considered as some parts of the flow in a relatively large-scale region. The near-surface resistivity model beneath the inner part of Namche Barwa conforms with the locations of hot spring and fluid inclusions, the brittle-ductile transition, and the 300°C-400°C isotherm from previous hydrothermal studies. Relatively resistive upper crust (>800 Ωm) is underlain by a more conductive middle to lower crust (<80 Ωm). The electrical characteristics of the thermal structure at shallow depth indicate an accumulation of hydrous melting, a localized conductive steep dipping zone for decompression melting consistent with the "tectonic aneurysm" model for explaining the exhumation mechanism of metamorphic rocks at Namche Barwa. The results also imply that both surface processes and local tectonic responses play a vital role in the evolution of Namche Barwa. An alternative hypothesis that the primary sustained heat source accounts for the local thermal-rheological structure beneath Namche Barwa is also discussed.

Experimental results on rock resistivity and its applications in monitoring and predicting natural disasters

NASA Astrophysics Data System (ADS)

Zhou, Jianguo; Zhu, Tao; Tang, Baolin

2017-04-01

There have been many earthquakes occurring in Chinese Mainland. These earthquakes, especially large earthquakes, often cause immeasurable loss. For instance, the 2008 Wenchuan Ms8.0 earthquake killed 70, 000 people and caused 17, 000 people missing. It is well known that this earthquake was not predicted. Why? Were there no precursors? After analyzing the geo-electrical resistivity recording at Chengdu station which is only about 36 km to the epicenter, we find that resistivity had changed abnormally very significantly along NE direction but no outstanding abnormal changes had been observed along NW direction before the earthquake. Perhaps this non-consistent changes result in that this earthquake was not predicted. However, in another standpoint, can another observation way be found to supplement the current geo-electrical resistivity observation in Chinese Mainland in order to improve the probability of catching the precursor? This motivates us to conduct experiments in lab and field. Apparent resistivity data are acquired along three common-midpoint measuring lines during the fixed-rate uniaxial compression on two sets of dry man-made samples and a Magnetite sample. We construct the relative resistivity change images (RRCIs). Our results indicate that all RRCIs show a trending change with stress: with the increase of stress, the resistivity-decreased region (RDR) in the RRCIs shrinks/expands, while the resistivity-increased region (RIR) expands/shrinks gradually, which is in agreement with the field experimental results of earthquake monitoring (Feng et al., 2001). Our results encourage us to conclude that the trending changes in RRCI with stress could probably become a useful indicator in monitoring and predicting earthquakes, volcanic eruptions and large-scale geologic movements. This work is supported by National Natural Science Foundation of China (NSFC, Grant 41574083).

In situ measurement system

DOEpatents

Lord, D.E.

1980-11-24

A multipurpose in situ underground measurement system comprising a plurality of long electrical resistance elements in the form of rigid reinforcing bars, each having an open loop hairpin configuration of shorter length than the other resistance elements. The resistance elements are arranged in pairs in a unitized structure, and grouted in place in the underground volume. Measurement means are provided for obtaining for each pair the electrical resistance of each element and the difference in electrical resistance of the paired elements, which difference values may be used in analytical methods involving resistance as a function of temperature. A scanner means sequentially connects the resistance-measuring apparatus to each individual pair of elements. A source of heating current is also selectively connectable for heating the elements to an initial predetermined temperature prior to electrical resistance measurements when used as an anemometer.

Experimental investigation into the coupling effects of magnetic field, temperature and pressure on electrical resistivity of non-oriented silicon steel sheet

NASA Astrophysics Data System (ADS)

Xiao, Lijun; Yu, Guodong; Zou, Jibin; Xu, Yongxiang

2018-05-01

In order to analyze the performance of magnetic device which operate at high temperature and high pressure, such as submersible motor, oil well transformer, the electrical resistivity of non-oriented silicon steel sheets is necessary for precise analysis. But the reports of the examination of the measuring method suitable for high temperature up to 180 °C and high pressure up to 140 MPa are few. In this paper, a measurement system based on four-probe method and Archimedes spiral shape measurement specimens is proposed. The measurement system is suitable for measuring the electrical resistivity of unconventional specimens under high temperature and high pressure and can simultaneously consider the influence of the magnetic field on the electrical resistivity. It can be seen that the electrical resistivity of the non-oriented silicon steel sheets will fluctuate instantaneously when the magnetic field perpendicular to the conductive path of the specimens is loaded or removed. The amplitude and direction of the fluctuation are not constant. Without considering the effects of fluctuations, the electrical resistivity of the non-oriented silicon steel sheets is the same when the magnetic field is loaded or removed. And the influence of temperature on the electrical resistivity of the non-oriented silicon steel sheet is still the greatest even though the temperature and the pressure are coupled together. The measurement results also show that the electrical resistivity varies linearly with temperature, so the temperature coefficient of resistivity is given in the paper.

Seasonal electrical resistivity surveys of a coastal bluff, Barter Island, North Slope Alaska

USGS Publications Warehouse

Swarzenski, Peter W.; Johnson, Cordell; Lorenson, Thomas; Conaway, Christopher H.; Gibbs, Ann E.; Erikson, Li; Richmond, Bruce M.; Waldrop, Mark P.

2016-01-01

Select coastal regions of the North Slope of Alaska are experiencing high erosion rates that can be attributed in part to recent warming trends and associated increased storm intensity and frequency. The upper sediment column of the coastal North Slope of Alaska can be described as continuous permafrost underlying a thin (typically less than 1–2 m) active layer that responds variably to seasonal thaw cycles. Assessing the temporal and spatial variability of the active layer and underlying permafrost is essential to better constrain how heightened erosion may impact material fluxes to the atmosphere and the coastal ocean, and how enhanced thaw cycles may impact the stability of the coastal bluffs. In this study, multi-channel electrical resistivity tomography (ERT) was used to image shallow subsurface features of a coastal bluff west of Kaktovik, on Barter Island, northeast Alaska. A comparison of a suite of paired resistivity surveys conducted in early and late summer 2014 provided detailed information on how the active layer and permafrost are impacted during the short Arctic summer. Such results are useful in the development of coastal resilience models that tie together fluvial, terrestrial, climatic, geologic, and oceanographic forcings on shoreline stability.

Investigation of Sm substitution on structural and superconducting properties of Y1Ba2-xSmxCu3O7-δ superconductors

NASA Astrophysics Data System (ADS)

Sharifzadegan, L.; Sedghi, H.

2018-07-01

In this work, samples of a nominal composition Y1 Ba2 - x Smx Cu3O7 - δ With Sm substitution (X = 0.00, 0.01, 0.03, 0.05) were prepared by the solid state reaction method. And the effect of substituting Sm instead of Ba was investigated on the structural and superconducting properties of the samples. Measurement of electrical resistance and critical temperature was done using 4-Probe connection method. Results indicate that Sm substitution affects the YBSCO superconducting samples, decrease the transition temperature of the superconductor and increases the special electrical resistance and the transition width. Also, XRD studies show that in all samples of the Y-123 phase, the formation and structure is orthorhombic. SEM images showed that the porosity in the samples increased with increasing Sm due to disruption in grain growth and instead, increase Sm in the samples cause decreasing the size of the grain.

Deconvolution of Voltage Sensor Time Series and Electro-diffusion Modeling Reveal the Role of Spine Geometry in Controlling Synaptic Strength.

PubMed

Cartailler, Jerome; Kwon, Taekyung; Yuste, Rafael; Holcman, David

2018-03-07

Most synaptic excitatory connections are made on dendritic spines. But how the voltage in spines is modulated by its geometry remains unclear. To investigate the electrical properties of spines, we combine voltage imaging data with electro-diffusion modeling. We first present a temporal deconvolution procedure for the genetically encoded voltage sensor expressed in hippocampal cultured neurons and then use electro-diffusion theory to compute the electric field and the current-voltage conversion. We extract a range for the neck resistances of 〈R〉=100±35MΩ. When a significant current is injected in a spine, the neck resistance can be inversely proportional to its radius, but not to the radius square, as predicted by Ohm's law. We conclude that the postsynaptic voltage cannot only be modulated by changing the number of receptors, but also by the spine geometry. Thus, spine morphology could be a key component in determining synaptic transduction and plasticity. Copyright © 2018 Elsevier Inc. All rights reserved.

Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

USGS Publications Warehouse

Peacock, Jared R.; Selway, Katherine

2016-01-01

The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

Corrosion resistant PEM fuel cell

DOEpatents

Fronk, Matthew Howard; Borup, Rodney Lynn; Hulett, Jay S.; Brady, Brian K.; Cunningham, Kevin M.

2011-06-07

A PEM fuel cell having electrical contact elements comprising a corrosion-susceptible substrate metal coated with an electrically conductive, corrosion-resistant polymer containing a plurality of electrically conductive, corrosion-resistant filler particles. The substrate may have an oxidizable metal first layer (e.g., stainless steel) underlying the polymer coating.

Corrosion resistant PEM fuel cell

DOEpatents

Fronk, Matthew Howard; Borup, Rodney Lynn; Hulett, Jay S.; Brady, Brian K.; Cunningham, Kevin M.

2002-01-01

A PEM fuel cell having electrical contact elements comprising a corrosion-susceptible substrate metal coated with an electrically conductive, corrosion-resistant polymer containing a plurality of electrically conductive, corrosion-resistant filler particles. The substrate may have an oxidizable metal first layer (e.g., stainless steel) underlying the polymer coating.

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

PubMed Central

Li, Jiaxiang; Li, Yunping; Wang, Zhongchang; Bian, Huakang; Hou, Yuhang; Wang, Fenglin; Xu, Guofu; Liu, Bin; Liu, Yong

2016-01-01

The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service. PMID:28004839

Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process.

PubMed

Blázquez, O; Martín, G; Camps, I; Mariscal, A; López-Vidrier, J; Ramírez, J M; Hernández, S; Estradé, S; Peiró, F; Serna, R; Garrido, B

2018-06-08

The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole-Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process

NASA Astrophysics Data System (ADS)

Blázquez, O.; Martín, G.; Camps, I.; Mariscal, A.; López-Vidrier, J.; Ramírez, J. M.; Hernández, S.; Estradé, S.; Peiró, F.; Serna, R.; Garrido, B.

2018-06-01

The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole‑Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

Two-dimensional finite element modelling of the neonatal head.

PubMed

Gibson, A; Bayford, R H; Holder, D S

2000-02-01

Electrical impedance tomography (EIT) could allow the early diagnosis of infant brain injury following birth asphyxia. The purpose of this work was to determine the effect of variations in skull, scalp or cerebrospinal fluid (CSF) resistivity, as these vary in clinical conditions and could degrade image quality. These factors were investigated using finite element models of the adult and neonatal head. The results suggest that there is a wide range over which the resistivity of the neonatal skull has little effect on the sensitivity to a central impedance change. The scalp and CSF appear to shunt current away from the brain; when their resistivity was decreased from normal values, this shunting effect increased and caused a decrease in sensitivity to a central resistance change. The resistivity of neonatal skull has not, to our knowledge, been directly measured and will anyway vary within and between individuals; this work suggests that EIT will be relatively insensitive to variations in neonatal skull impedance.

Designing and Implementation a Lab Testing Method for Power Cables Insulation Resistance According with STAS 10411-89, SR EN ISO/CEI/17025/2005

NASA Astrophysics Data System (ADS)

Dobra, R.; Pasculescu, D.; Marc, G.; Risteiu, M.; Antonov, A.

2017-06-01

Insulation resistance measurement is one of the most important tests required by standards and regulations in terms of electrical safety. Why these tests are is to prevent possible accidents caused by electric shock, damage to equipment or outbreak of fire in normal operating conditions of electrical cables. The insulation resistance experiment refers to the testing of electrical cable insulation, which has a measured resistance that must be below the imposed regulations. Using a microcontroller system data regarding the insulation resistance of the power cables is acquired and with SCADA software the test results are displayed.

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.

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.

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.

Restrictive loads powered by separate or by common electrical sources

NASA Technical Reports Server (NTRS)

Appelbaum, J.

1989-01-01

In designing a multiple load electrical system, the designer may wish to compare the performance of two setups: a common electrical source powering all loads, or separate electrical sources powering individual loads. Three types of electrical sources: an ideal voltage source, an ideal current source, and solar cell source powering resistive loads were analyzed for their performances in separate and common source systems. A mathematical proof is given, for each case, indicating the merit of the separate or common source system. The main conclusions are: (1) identical resistive loads powered by ideal voltage sources perform the same in both system setups, (2) nonidentical resistive loads powered by ideal voltage sources perform the same in both system setups, (3) nonidentical resistive loads powered by ideal current sources have higher performance in separate source systems, and (4) nonidentical resistive loads powered by solar cells have higher performance in a common source system for a wide range of load resistances.

Satellite Tidal Magnetic Signals Constrain Oceanic Lithosphere-Asthenosphere Boundary Earth Tomography with Tidal Magnetic Signals

NASA Technical Reports Server (NTRS)

Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.; Sabaka, Terence J.; Chandrasekharan, Manoj; Olsen, Niles

2016-01-01

The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. Here we use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals an Approximately 72 km thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere.

Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary

PubMed Central

Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.; Sabaka, Terence J.; Manoj, Chandrasekharan; Olsen, Nils

2016-01-01

The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals a ≈72-km-thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere. PMID:27704045

46 CFR 111.01-11 - Corrosion-resistant parts.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Corrosion-resistant parts. 111.01-11 Section 111.01-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-11 Corrosion-resistant parts. Each enclosure and part of electric...

46 CFR 111.01-11 - Corrosion-resistant parts.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Corrosion-resistant parts. 111.01-11 Section 111.01-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-11 Corrosion-resistant parts. Each enclosure and part of electric...

46 CFR 111.01-11 - Corrosion-resistant parts.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Corrosion-resistant parts. 111.01-11 Section 111.01-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-11 Corrosion-resistant parts. Each enclosure and part of electric...

46 CFR 111.01-11 - Corrosion-resistant parts.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Corrosion-resistant parts. 111.01-11 Section 111.01-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-11 Corrosion-resistant parts. Each enclosure and part of electric...

46 CFR 111.01-11 - Corrosion-resistant parts.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Corrosion-resistant parts. 111.01-11 Section 111.01-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-11 Corrosion-resistant parts. Each enclosure and part of electric...

Spaceborne electronic imaging systems

NASA Technical Reports Server (NTRS)

1971-01-01

Criteria and recommended practices for the design of the spaceborne elements of electronic imaging systems are presented. A spaceborne electronic imaging system is defined as a device that collects energy in some portion of the electromagnetic spectrum with detector(s) whose direct output is an electrical signal that can be processed (using direct transmission or delayed transmission after recording) to form a pictorial image. This definition encompasses both image tube systems and scanning point-detector systems. The intent was to collect the design experience and recommended practice of the several systems possessing the common denominator of acquiring images from space electronically and to maintain the system viewpoint rather than pursuing specialization in devices. The devices may be markedly different physically, but each was designed to provide a particular type of image within particular limitations. Performance parameters which determine the type of system selected for a given mission and which influence the design include: Sensitivity, Resolution, Dynamic range, Spectral response, Frame rate/bandwidth, Optics compatibility, Image motion, Radiation resistance, Size, Weight, Power, and Reliability.

Thermal-electrical properties and resistance stability of silver coated yarns

NASA Astrophysics Data System (ADS)

Li, Yafang; Liu, Hao; Li, Xiaojiu

2017-03-01

Thermal-electrical properties and resistance stability of silver yarns was researched to evaluate the performance be a heating element. Three samples of silver coated yarns with different linear density and electrical resistivity, which obtained by market. Silver coated yarns were placed at the high temperature condition for ageing. The electrical resistances of yarns were increased with the ageing process. The infrared photography instrument was used to measurement the temperature variation of silver coated yarns by applied different current on. The result shows that the temperature rise with the power increases.

Electrical Resistivity Measurements: a Review

NASA Astrophysics Data System (ADS)

Singh, Yadunath

World-wide interest on the use of ceramic materials for aerospace and other advanced engineering applications, has led to the need for inspection techniques capable of detecting unusually electrical and thermal anomalies in these compounds. Modern ceramic materials offer many attractive physical, electrical and mechanical properties for a wide and rapidly growing range of industrial applications; moreover specific use may be made of their electrical resistance, chemical resistance, and thermal barrier properties. In this review, we report the development and various techniques for the resistivity measurement of solid kind of samples.

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

Code of Federal Regulations, 2014 CFR

2014-07-01

... 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 electric... a minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and a relative humidity of 55 ±10...

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

Code of Federal Regulations, 2012 CFR

2012-07-01

... 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 electric... a minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and a relative humidity of 55 ±10...

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

Code of Federal Regulations, 2013 CFR

2013-07-01

... 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 electric... a minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and a relative humidity of 55 ±10...

Geochemical mapping in polluted floodplains using handheld XRF, geophysical imaging, and geostatistics

NASA Astrophysics Data System (ADS)

Hošek, Michal; Matys Grygar, Tomáš; Popelka, Jan; Kiss, Timea; Elznicová, Jitka; Faměra, Martin

2017-04-01

In the recent years researchers have enjoyed noticeable improvements of portable analytical and geophysical methods, which allow studying floodplain architecture and deciphering pollutant distribution more easily than ever before. Our area of interest was floodplain of the Ploučnice River, particularly a pollution hotspot in Boreček, severely impacted by U mining between the 1970s and late 1980s, in particular a "radioactive flood" in 1981. In the area, we used hand drill coring and in situ (field) analysis of so acquired sediments by handheld X-ray fluorescence spectrometer (XRF), which gave us information about depth profiles of pollutants (Ba, U, Zn) and the Al/Si and Zr/Rb ratios, i.e., proxies for sediment lithology. We found that spatial distribution of pollutants (control by depth and position in the floodplain) is apparently complex and discontinuous. In some places, contamination is buried by a couple decimetres of less polluted sediments, while in other places the peak pollution is near surface, apparently without a straightforward connection with the surface topography and the distance to the river channel. We thus examined the floodplain architecture, the internal structure of the floodplain using two geophysical methods. First of them, dipole electromagnetic profiling (DEMP, also denoted EMP, MP, or Slingram) quickly acquires average electric resistivity in top strata in selected areas, which was actually top 3 m with our particular instrument. Second, electric resistivity tomography (ERT) produces much more detailed information on resistivity with depth resolution of ca 0.5 m to the depth of ca 5 m in selected lines. ERT thus allows identifying boundaries of electric resistivity domains (sediment bodies) and DEMP their spatial distribution. Based on the obtained data, we divided the floodplain to five segments with specific topography, pollution characteristics, and electric resistivity. We suppose that those segments are lithogenetic floodplain units. Those findings must, however, be checked by sediment examination and analysis in selected points. We processed the crucial characteristics obtained by geochemical mapping, namely depth of maximum pollution, amount of contamination, and lithology (Al/Si and Zr/Rb ratios), using geostatistics. Moreover, some parts of floodplain were dated by optically stimulated luminescence (OSL) which revealed, that recycling of top decimetres of floodplain fine fill (silts) in Boreček site has proceeded relatively recently (in decades and centuries) as compared to deeper lying coarser (sandy) strata (millennia). The results of geochemical mapping show complexity of pollution hotspots and need of their integrated interpretation. Key words: Dipole electromagneting profilling, electric resistivity tomography, floodplain contamination, geochemical mapping

Histamine and thrombin modulate endothelial focal adhesion through centripetal and centrifugal forces.

PubMed Central

Moy, A B; Van Engelenhoven, J; Bodmer, J; Kamath, J; Keese, C; Giaever, I; Shasby, S; Shasby, D M

1996-01-01

We examined the contribution of actin-myosin contraction to the modulation of human umbilical vein endothelial cell focal adhesion caused by histamine and thrombin. Focal adhesion was measured as the electrical resistance across a cultured monolayer grown on a microelectrode. Actin-myosin contraction was measured as isometric tension of cultured monolayers grown on a collagen gel. Histamine immediately decreased electrical resistance but returned to basal levels within 3-5 min. Histamine did not increase isometric tension. Thrombin also immediately decreased electrical resistance, but, however, resistance did not return to basal levels for 40-60 min. Thrombin also increased isometric tension, ML-7, an inhibitor of myosin light chain kinase, prevented increases in myosin light chain phosphorylation and increases in tension development in cells exposed to thrombin. ML-7 did not prevent a decline in electrical resistance in cells exposed to thrombin. Instead, ML-7 restored the electrical resistance to basal levels in a shorter period of time (20 min) than cells exposed to thrombin alone. Also, histamine subsequently increased electrical resistance to above basal levels, and thrombin initiated an increase in resistance during the time of peak tension development. Hence, histamine and thrombin modulate endothelial cell focal adhesion through centripetal and centrifugal forces. PMID:8613524

Reconstructing the internal structure and long-term evolution of hazardous sinkholes combining trenching, electrical resistivity imaging (ERI) and ground penetrating radar (GPR)

NASA Astrophysics Data System (ADS)

Fabregat, Ivan; Gutiérrez, Francisco; Roqué, Carles; Comas, Xavier; Zarroca, Mario; Carbonel, Domingo; Guerrero, Jesús; Linares, Rogelio

2017-05-01

The approaches aimed at characterising specific damaging sinkholes have received limited attention compared with other ground instability phenomena (e.g. landslides). Moreover, the practicality of the trenching technique in combination with numerical dating and retro-deformation analysis for sinkhole site-investigations has been barely explored. This work illustrates the advantages of combining geomorphic mapping, electrical resistivity imaging (ERI), ground penetrating radar (GPR) and trenching for sinkhole characterisation and shows how the trenching technique contributes to fill significant gaps that neither geomorphic nor geophysical methods can address. Two large sinkholes (> 200 m long) related to the interstratal karstification of evaporites and generated by contrasting subsidence mechanisms (sagging, collapse) were investigated in the Fluvia Valley, NE Spain. Although GPR data may provide high resolution information on subsidence-related stratigraphic and structural features at shallow depth, the profiles acquired in the investigated sites with 100 MHz shielded and 40 MHz unshielded antennae provided limited insight into the internal geometry of the sinkholes due to reduced signal penetration related to the presence of conductive clayey material. The ERI sections satisfactorily imaged the general geometry of the sagging and collapse subsidence structures up to depths higher than 100 m and clearly captured the basal contact of the low-resistivity sinkhole fill in the sections with adequate layout and resolution. The trenches, despite their limited depth (ca. 5 m) allowed us to obtain valuable objective information on several key aspects of the subsidence phenomenon: (1) mechanisms (deformation style) and kinematics (progressive versus episodic); (2) limits of ground deformation; (3) temporal evolution (expansion versus contraction); (4) chronology and timing of most recent deformation phase; (5) rates of subsidence and sedimentation; and (6) the role played by subsidence in the development of lacustrine environments and the associated sedimentation patterns.

Geological modeling and infiltration pattern of a karstic system based upon crossed geophysical methods and image-guided inversion

NASA Astrophysics Data System (ADS)

Duran, Lea; Jardani, Abderrahim; Fournier, Matthieu; Massei, Nicolas

2015-04-01

Karstic aquifers represent an important part of the water resources worldwide. Though they have been widely studied on many aspects, their geological and hydrogeological modeling is still complex. Geophysical methods can provide useful subsurface information for the characterization and mapping of karstic systems, especially when not accessible by speleology. The site investigated in this study is a sinkhole-spring system, with small diameter conduits that run within a chalk aquifer (Norville, in Upper Normandy, France). This site was investigated using several geophysical methods: electrical tomography, self-potential, mise-à-la-masse methods, and electromagnetic method (EM34). Coupling those results with boreholes data, a 3D geological model of the hydrogeological basin was established, including tectonic features as well as infiltration structures (sinkhole, covered dolines). The direction of the karstic conduits near the main sinkhole could be established, and the major fault was shown to be a hydraulic barrier. Also the average concentration of dolines on the basin could be estimated, as well as their depth. At last, several hypotheses could be made concerning the location of the main conduit network between the sinkhole and the spring, using previous hydrodynamic study of the site along with geophysical data. In order to validate the 3D geological model, an image-guided inversion of the apparent resistivity data was used. With this approach it is possible to use geological cross sections to constrain the inversion of apparent resistivity data, preserving both discontinuities and coherences in the inversion of the resistivity data. This method was used on the major fault, enabling to choose one geological interpretation over another (fault block structure near the fault, rather than important folding). The constrained inversion was also applied on covered dolines, to validate the interpretation of their shape and depth. Key words: Magnetic and electrical methods, karstic system modeling; image-guided inversion

Transient Electromagnetic Modelling and Imaging of Thin Resistive Structures: Applications for Gas Hydrate Assessment

NASA Astrophysics Data System (ADS)

Swidinsky, Andrei

Gas hydrates are a solid, ice-like mixture of water and low molecular weight hydrocarbons. They are found under the permafrost and to a far greater extent under the ocean, usually at water depths greater than 300m. Hydrates are a potential energy resource, a possible factor in climate change, and a geohazard. For these reasons, it is critical that gas hydrate deposits are quantitatively assessed so that their concentrations, locations and distributions may be established. Due to their ice-like nature, hydrates are electrically insulating. Consequently, a method which remotely detects changes in seafloor electrical conductivity, such as marine controlled source electromagnetics (CSEM), is a useful geophysical tool for marine gas hydrate exploration. Hydrates are geometrically complex structures. Advanced electromagnetic modelling and imaging techniques are crucial for proper survey design and data interpretation. I develop a method to model thin resistive structures in conductive host media which may be useful in building approximate geological models of gas hydrate deposits using arrangements of multiple, bent sheets. I also investigate the possibility of interpreting diffusive electromagnetic data using seismic imaging techniques. To be processed in this way, such data must first be transformed into its non-diffusive, seismic-like counterpart. I examine such a transform from both an analytical and a numerical point of view, focusing on methods to overcome inherent numerical instabilities. This is the first step to applying seismic processing techniques to CSEM data to rapidly and efficiently image resistive gas hydrate structures. The University of Toronto marine electromagnetics group has deployed a permanent marine CSEM array offshore Vancouver Island, in the framework of the NEPTUNE Canada cabled observatory, for the purposes of monitoring gas hydrate deposits. In this thesis I also propose and examine a new CSEM survey technique for gas hydrate which would make use of the stationary seafloor transmitter already on the seafloor, along with a cabled receiver array, towed from a ship. I furthermore develop a modelling algorithm to examine the electromagnetic effects of conductive borehole casings which have been proposed to be placed in the vicinity of this permanent marine CSEM array, and make preliminary recommendations about their locations.

Imaging Saltwater Intrusion Along the Coast of Monterey Bay Using Long-Offset Electrical Resistivity Tomography

NASA Astrophysics Data System (ADS)

Goebel, M.; Knight, R. J.; Pidlisecky, A.

2016-12-01

Coastal regions represent a complex dynamic interface where saltwater intrusion moves seawater landward and groundwater discharge moves freshwater seaward. These processes can have a dramatic impact on water quality, affecting both humans and coastal ecosystems. The ability to map the subsurface distribution of fresh and salt water is a critical step in predicting and managing water quality in coastal regions. This is commonly accomplished using wells, which are expensive and provide point information, which may fail to capture the spatial complexity in subsurface conditions. We present an alternate method for acquiring data, long-offset Electrical Resistivity Tomography (ERT), which is non-invasive, cost effective, and can address the problem of poor spatial sampling. This geophysical method can produce continuous profiles of subsurface electrical resistivity to a depth of 300 m, with spatial resolution on the order of tens of meters. Our research focuses on the Monterey Bay region, where sustained groundwater extraction over the past century has led to significant saltwater intrusion. ERT was acquired along 40 kilometers of the coast using the roll along method, allowing for continuous overlap in data acquisition. Electrodes were spaced every 22.2 m, with a total of 81 electrodes along the 1.8 km active cable length. The data show a complex distribution of fresh and salt water, influenced by geology, groundwater pumping, recharge, and land-use. While the inverted ERT resistivity profiles correspond well with existing data sets and geologic interpretations in the region, the spatial complexity revealed through the ERT data goes beyond what is known from traditional data sources alone. This leads us to conclude that this form of data can be extremely useful in informing and calibrating groundwater flow models, making targeted management decisions, and monitoring changes in subsurface salinities over time.

Use Of Vertical Electrical Sounding Survey For Study Groundwater In NISSAH Region, SAUDI ARABIA

NASA Astrophysics Data System (ADS)

Alhenaki, Bander; Alsoma, Ali

2015-04-01

The aim of this research is to investigate groundwater depth in desert and dry environmental conditions area . The study site located in Wadi Nisah-eastern part of Najd province (east-central of Saudi Arabia), Generally, the study site is underlain by Phanerozoic sedimentary rocks of the western edge of the Arabian platform, which rests on Proterozoic basement at depths ranged between 5-8km. Another key objective of this research is to assess the water-table and identify the bearing layers structures study area by using Vertical Electrical Sounding (VES) 1D imaging technique. We have been implemented and acquired a sections of 315 meter vertical electrical soundings using Schlumberger field arrangements . These dataset were conducted along 9 profiles. The resistivity Schlumberger sounding was carried with half-spacing in the range 500 . The VES survey intend to cover several locations where existing wells information may be used for correlations. also location along the valley using the device Syscal R2 The results of this study concluded that there are at least three sedimentary layers to a depth of 130 meter. First layer, extending from the surface to a depth of about 3 meter characterized by dry sandy layer and high resistivity value. The second layer, underlain the first layer to a depth of 70 meter. This layer has less resistant compare to the first layer. Last layer, has low resistivity values of 20 ohm .m to a depth of 130 meter blow ground surface. We have observed a complex pattern of groundwater depth (ranging from 80 meter to 120 meter) which may reflect the lateral heterogeneity of study site. The outcomes of this research has been used to locate the suitable drilling locations.

[In vivo measurement of rabbits brain impedance frequency response and the elementary imaging of EIT].

PubMed

Wu, Xiaoming; Dong, Xiuzhen; Qin, Mingxin; Fu, Feng; Wang, Yuemin; You, Fusheng; Xiang, Haiyan; Liu, Ruigang; Shi, Xuetao

2003-03-01

The in vivo measurements of rabbit brain tissue impedance were taken under both normal and ischemic conditions by using two-electrode measurement method in the frequency range from 0.1 Hz to 1 MHz. The dynamic images about the resistivity of cerebral ischemia were reconstructed based on a 16-electrode system. The results of in vivo measurement showed that the ratio of impedance increased can be as high as 75% at frequencies lower than 10 Hz. In the range from 1 KHz to 1 MHz, the ratio showed a constant value of 15%. The electrical impedance tomography (EIT) images obtained suggested that the regions of impedance changes highly correspond to the position of ischemia. It is confirmed that the brain function changes caused by local deficiency of blood can be detected and imaged by EIT method.

Electrical resistivity structure of the Great Slave Lake shear zone, northwest Canada: implications for tectonic history

NASA Astrophysics Data System (ADS)

Yin, Yaotian; Unsworth, Martyn; Liddell, Mitch; Pana, Dinu; Craven, James A.

2014-10-01

Three magnetotelluric (MT) profiles in northwestern Canada cross the central and western segments of Great Slave Lake shear zone (GSLsz), a continental scale strike-slip structure active during the Slave-Rae collision in the Proterozoic. Dimensionality analysis indicates that (i) the resistivity structure is approximately 2-D with a geoelectric strike direction close to the dominant geological strike of N45°E and that (ii) electrical anisotropy may be present in the crust beneath the two southernmost profiles. Isotropic and anisotropic 2-D inversion and isotropic 3-D inversions show different resistivity structures on different segments of the shear zone. The GSLsz is imaged as a high resistivity zone (>5000 Ω m) that is at least 20 km wide and extends to a depth of at least 50 km on the northern profile. On the southern two profiles, the resistive zone is confined to the upper crust and pierces an east-dipping crustal conductor. Inversions show that this dipping conductor may be anisotropic, likely caused by conductive materials filling a network of fractures with a preferred spatial orientation. These conductive regions would have been disrupted by strike-slip, ductile deformation on the GSLsz that formed granulite to greenschist facies mylonite belts. The pre-dominantly granulite facies mylonites are resistive and explain why the GSLsz appears as a resistive structure piercing the east-dipping anisotropic layer. The absence of a dipping anisotropic/conductive layer on the northern MT profile, located on the central segment of the GSLsz, is consistent with the lack of subduction at this location as predicted by geological and tectonic models.

Hole-to-surface resistivity measurements.

USGS Publications Warehouse

Daniels, J.J.

1983-01-01

Hole-to-surface resistivity measurements over a layered volcanic tuff sequence illustrate procedures for gathering, reducing, and interpreting hole-to-surface resistivity data. The magnitude and direction of the total surface electric field resulting from a buried current source is calculated from orthogonal potential difference measurements for a grid of closely spaced stations. A contour map of these data provides a detailed map of the distribution of the electric field away from the drill hole. Resistivity anomalies can be enhanced by calculating the difference between apparent resistivities calculated from the total surface electric field and apparent resistivities for a layered earth model.-from Author

Hydrogeophysics in an Alpine Watershed: Lake O'Hara, Canadian Rocky Mountains

NASA Astrophysics Data System (ADS)

Bentley, L. R.; Hayashi, M.; Roy, J.

2007-05-01

Alpine watersheds are the headwaters of major rivers in western Canada and many other regions in the world. Consequently, understanding the storage, flow paths and timing of the release of water is an important aspect of water resources management. Recent studies have shown that groundwater stored in moraines, talus slopes and alpine meadows are important water reservoirs in the Canadian Rocky Mountains. A research program in the Lake O'Hara Research Basin, Yoho National Park is characterizing the hydrologic cycle within this alpine watershed. Bedrock topography, preferential flow paths and the internal structure of the subsurface play a fundamental role in determining the volume and timing of groundwater discharge. Geophysical methods are needed to help delineate the subsurface, because drilling is not an option. A preliminary survey using electrical resistivity imaging (ERI) was conducted in the summer of 2006. ERI profiles were run across a small wetland in an alpine meadow and over the nose of a glacial moraine. Much of the surfaces consisted of dry rock rubble and boulders, so contact resistance was at times as high as several hundred thousand ohms. To establish electrical contact, we drove spikes into sponges saturated with salt water that were forced into boulder contacts. Another enhanced contact strategy was to smear medical contact jell over boulder surfaces and connect an electrode to aluminum foil plastered onto the jell. The survey was conducted with an 800 V transmitter, a Wenner array and an electrode spacing of 2 to 5 m. Due to the resistive environment, currents as small as 1 mA produced measured potentials in the volt range. Due to the contact difficulties, some electrode locations were offset one or more meters from the preferred array location and this offset may cause some distortion in the inverted images. The data produced inversions with resistivity values ranging from 500 ohm-m to 100,000 ohm-m. The lowest resistivity values correspond to wetlands and the saturated outflow at the toe of the moraine. The highest resistivity values correspond to dry bolder fields at the surface of the moraine. Bedrock appears to be in the 10,000 to 40,0000 ohm-m range. Although interpretation ambiguities exist in some portion of the images, the wetland is seen to be on the order of 2 m deep and overlies bedrock. In the moraine, discrete zones of groundwater flow have been identified. These results are consistent with water chemistry results that indicate that groundwater discharging from the toe of the moraine comes from more than one source.

Superconducting thermoelectric generator

DOEpatents

Metzger, J.D.; El-Genk, M.S.

1998-05-05

An apparatus and method for producing electricity from heat is disclosed. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device. 4 figs.

Superconducting thermoelectric generator

DOEpatents

Metzger, J.D.; El-Genk, M.S.

1996-01-01

An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

Superconducting thermoelectric generator

DOEpatents

Metzger, John D.; El-Genk, Mohamed S.

1998-01-01

An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

Extremely high resolution 3D electrical resistivity tomography to depict archaeological subsurface structures

NASA Astrophysics Data System (ADS)

Al-Saadi, Osamah; Schmidt, Volkmar; Becken, Michael; Fritsch, Thomas

2017-04-01

Electrical resistivity tomography (ERT) methods have been increasingly used in various shallow depth archaeological prospections in the last few decades. These non-invasive techniques are very useful in saving time, costs, and efforts. Both 2D and 3D ERT techniques are used to obtain detailed images of subsurface anomalies. In two surveyed areas near Nonnweiler (Germany), we present the results of the full 3D setup with a roll-along technique and of the quasi-3D setup (parallel and orthogonal profiles in dipole-dipole configuration). In area A, a dipole-dipole array with 96 electrodes in a uniform rectangular survey grid has been used in full 3D to investigate a presumed Roman building. A roll-along technique has been utilized to cover a large part of the archaeological site with an electrode spacing of 1 meter and with 0.5 meter for a more detailed image. Additional dense parallel 2D profiles have been carried out in dipole-dipole array with 0.25 meter electrode spacing and 0.25 meter between adjacent profiles in both direction for higher- resolution subsurface images. We have designed a new field procedure, which used an electrode array fixed in a frame. This facilitates efficient field operation, which comprised 2376 electrode positions. With the quasi 3D imaging, we confirmed the full 3D inversion model but at a much better resolution. In area B, dense parallel 2D profiles were directly used to survey the second target with also 0.25 meter electrode spacing and profiles separation respectively. The same field measurement design has been utilized and comprised 9648 electrode positions in total. The quasi-3D inversion results clearly revealed the main structures of the Roman construction. These ERT inversion results coincided well with the archaeological excavation, which has been done in some parts of this area. The ERT result successfully images parts from the walls and also smaller internal structures of the Roman building.

Three-dimensional magnetotelluric axial anisotropic forward modeling and inversion

NASA Astrophysics Data System (ADS)

Cao, Hui; Wang, Kunpeng; Wang, Tao; Hua, Boguang

2018-06-01

Magnetotelluric (MT) data has been widely used to image underground electrical structural. However, when the significant axial resistivity anisotropy presents, how this influences three-dimensional MT data has not been resolved clearly yet. We here propose a scheme for three-dimensional modeling of MT data in presence of axial anisotropic resistivity, where the electromagnetic fields are decomposed into primary and secondary components. A 3D staggered-grid finite difference method is then used to resolve the resulting 3D governing equations. Numerical tests have completed to validate the correctness and accuracy of the present algorithm. A limited-memory Broyden-Fletcher-Goldfarb-Shanno method is then utilized to realize the 3D MT axial anisotropic inversion. The testing results show that, compared to the results of isotropic resistivity inversion, taking account the axial anisotropy can much improve the inverted results.

Photocurrent microscopy of contact resistance and charge carrier traps in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Liewald, C.; Reiser, D.; Westermeier, C.; Nickel, B.

2016-08-01

We use a pentacene transistor with asymmetric source drain contacts to test the sensitivity of scanning photocurrent microscopy (SPCM) for contact resistance and charge traps. The drain current of the device strongly depends on the choice of the drain electrode. In one case, more than 94% of the source drain voltage is lost due to contact resistance. Here, SPCM maps show an enhanced photocurrent signal at the hole-injecting contact. For the other bias condition, i.e., for ohmic contacts, the SPCM signal peaks heterogeneously along the channel. We argue from basic transport models that bright areas in SPCM maps indicate areas of large voltage gradients or high electric field strength caused by injection barriers or traps. Thus, SPCM allows us to identify and image the dominant voltage loss mechanism in organic field-effect transistors.

Relating the Electrical Resistance of Fresh Concrete to Mixture Proportions.

PubMed

Obla, K; Hong, R; Sherman, S; Bentz, D P; Jones, S Z

2018-01-01

Characterization of fresh concrete is critical for assuring the quality of our nation's constructed infrastructure. While fresh concrete arriving at a job site in a ready-mixed concrete truck is typically characterized by measuring temperature, slump, unit weight, and air content, here the measurement of the electrical resistance of a freshly cast cylinder of concrete is investigated as a means of assessing mixture proportions, specifically cement and water contents. Both cement and water contents influence the measured electrical resistance of a sample of fresh concrete: the cement by producing ions (chiefly K + , Na + , and OH - ) that are the main source of electrical conduction; and the water by providing the main conductive pathways through which the current travels. Relating the measured electrical resistance to attributes of the mixture proportions, such as water-cement ratio by mass ( w/c ), is explored for a set of eleven different concrete mixtures prepared in the laboratory. In these mixtures, w/c , paste content, air content, fly ash content, high range water reducer dosage, and cement alkali content are all varied. Additionally, concrete electrical resistance data is supplemented by measuring the resistivity of its component pore solution obtained from 5 laboratory-prepared cement pastes with the same proportions as their corresponding concrete mixtures. Only measuring the concrete electrical resistance can provide a prediction of the mixture's paste content or the product w*c ; conversely, when pore solution resistivity is also available, w/c and water content of the concrete mixture can be reasonably assessed.

Relating the Electrical Resistance of Fresh Concrete to Mixture Proportions

PubMed Central

Obla, K.; Hong, R.; Sherman, S.; Bentz, D.P.; Jones, S.Z.

2018-01-01

Characterization of fresh concrete is critical for assuring the quality of our nation’s constructed infrastructure. While fresh concrete arriving at a job site in a ready-mixed concrete truck is typically characterized by measuring temperature, slump, unit weight, and air content, here the measurement of the electrical resistance of a freshly cast cylinder of concrete is investigated as a means of assessing mixture proportions, specifically cement and water contents. Both cement and water contents influence the measured electrical resistance of a sample of fresh concrete: the cement by producing ions (chiefly K+, Na+, and OH-) that are the main source of electrical conduction; and the water by providing the main conductive pathways through which the current travels. Relating the measured electrical resistance to attributes of the mixture proportions, such as water-cement ratio by mass (w/c), is explored for a set of eleven different concrete mixtures prepared in the laboratory. In these mixtures, w/c, paste content, air content, fly ash content, high range water reducer dosage, and cement alkali content are all varied. Additionally, concrete electrical resistance data is supplemented by measuring the resistivity of its component pore solution obtained from 5 laboratory-prepared cement pastes with the same proportions as their corresponding concrete mixtures. Only measuring the concrete electrical resistance can provide a prediction of the mixture’s paste content or the product w*c; conversely, when pore solution resistivity is also available, w/c and water content of the concrete mixture can be reasonably assessed. PMID:29882546

KrF laser-induced OH fluorescence imaging in a supersonic combustion tunnel

NASA Technical Reports Server (NTRS)

Quagliaroli, T. M.; Laufer, G.; Hollo, S. D.; Krauss, R. H.; Whitehurst, R. B., III; Mcdaniel, J. C., Jr.

1992-01-01

Planar fluorescence images of OH in a continuous-flow, electrical-resistively heated, high enthalpy, hydrogen-air combustion tunnel, induced by a tunable KrF laser, were recorded. These images were compared to previously recorded fluorescence images induced by a doubled-dye laser under similar conditions. Images induced by the doubled-dye laser system demonstrated a severe distortion caused by absorption and fluorescence trapping. By contrast, images of the fluorescence induced by the tunable KrF laser retained the symmetry properties of the flow. Based on signal-to-noise ratio measurements the yield of the fluorescence induced by the doubled-dye laser is larger than the fluorescence yield induced by the KrF laser. The measurements in the present facility of OH fluorescence induced by the KrF laser were limited by the photon-statistical noise. Based 2 on this result, doubled-dye laser systems are recommended for OH imaging in small and OH lean (less than 10 exp 15/cu cm) facilities. KrF lasers should be selected otherwise.

Ab-initio study of liquid systems: Concentration dependence of electrical resistivity of binary liquid alloy Rb1-xCsx

NASA Astrophysics Data System (ADS)

Thakur, Anil; Sharma, Nalini; Chandel, Surjeet; Ahluwalia, P. K.

2013-02-01

The electrical resistivity (ρL) of Rb1-XCsX binary alloys has been made calculated using Troullier Martins ab-initio pseudopotentials. The present results of the electrical resistivity (ρL) of Rb1-XCsX binary alloys have been found in good agreement with the experimental results. These results suggest that ab-initio approach for calculating electrical resistivity is quite successful in explaining the electronic transport properties of binary Liquid alloys. Hence ab-initio pseudopotentials can be used instead of model pseudopotentials having problem of transferability.

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

PubMed

Trindade, I G; Fermento, R; Leitão, D; Sousa, J B

2009-07-01

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.

Electrical resistivity of liquid lanthanides using charge hard sphere system

NASA Astrophysics Data System (ADS)

Sonvane, Y. A.; Thakor, P. B.; Jani, A. R.

2013-06-01

In the present paper, we have studied electrical resistivity (ρ) of liquid lanthanides. To describe the structural information, the structure factor S(q) due to the charged hard sphere (CHS) reference systems is used along with our newly constructed model potential. To see the influence of exchange and correlation effect on the electrical resistivity (ρ) have used different local field correction functions like Hartree (H), Sarkar et al (S) and Taylor (T). Lastly we conclude that the proper choice of the model potential along with local field correction function plays a vital role to the study of the electrical resistivity (ρ).

MoisturEC: a new R program for moisture content estimation from electrical conductivity data

USGS Publications Warehouse

Terry, Neil; Day-Lewis, Frederick D.; Werkema, Dale D.; Lane, John W.

2018-01-01

Noninvasive geophysical estimation of soil moisture has potential to improve understanding of flow in the unsaturated zone for problems involving agricultural management, aquifer recharge, and optimization of landfill design and operations. In principle, several geophysical techniques (e.g., electrical resistivity, electromagnetic induction, and nuclear magnetic resonance) offer insight into soil moisture, but data‐analysis tools are needed to “translate” geophysical results into estimates of soil moisture, consistent with (1) the uncertainty of this translation and (2) direct measurements of moisture. Although geostatistical frameworks exist for this purpose, straightforward and user‐friendly tools are required to fully capitalize on the potential of geophysical information for soil‐moisture estimation. Here, we present MoisturEC, a simple R program with a graphical user interface to convert measurements or images of electrical conductivity (EC) to soil moisture. Input includes EC values, point moisture estimates, and definition of either Archie parameters (based on experimental or literature values) or empirical data of moisture vs. EC. The program produces two‐ and three‐dimensional images of moisture based on available EC and direct measurements of moisture, interpolating between measurement locations using a Tikhonov regularization approach.

Resistive foil edge grading for accelerator and other high voltage structures

DOEpatents

Caporaso, George J.; Sampayan, Stephen F.; Sanders, David M.

2014-06-10

In a structure or device having a pair of electrical conductors separated by an insulator across which a voltage is placed, resistive layers are formed around the conductors to force the electric potential within the insulator to distribute more uniformly so as to decrease or eliminate electric field enhancement at the conductor edges. This is done by utilizing the properties of resistive layers to allow the voltage on the electrode to diffuse outwards, reducing the field stress at the conductor edge. Preferably, the resistive layer has a tapered resistivity, with a lower resistivity adjacent to the conductor and a higher resistivity away from the conductor. Generally, a resistive path across the insulator is provided, preferably by providing a resistive region in the bulk of the insulator, with the resistive layer extending over the resistive region.

Evaluation of a high-resolution patient-specific model of the electrically stimulated cochlea

NASA Astrophysics Data System (ADS)

Cakir, Ahmet; Dwyer, Robert T.; Noble, Jack H.

2017-03-01

Cochlear implants (CIs) are considered standard treatment for patients who experience sensorineural hearing loss. Although these devices have been remarkably successful at restoring hearing, it is rare to achieve natural fidelity, and many patients experience poor outcomes. Our group has developed the first image-guided CI programming (IGCIP) technique where the positions of the electrodes are found in CT images and used to estimate neural activation patterns, which is unique information that audiologists can use to define patient-specific processor settings. In our current system, neural activation is estimated using only the distance from each electrode to the neural activation sites. This approach might be less accurate than using a high-resolution electro-anatomical model (EAM) of the electrically stimulated cochlea to perform physics-based estimation of neural activation. In this work, we propose a patientcustomized EAM approach where the EAM is spatially and electrically adapted to a patient-specific configuration. Spatial adaptation is done through non-rigid registration of the model with the patient CT image. Electrical adaptation is done by adjusting tissue resistivity parameters so that the intra-cochlear voltage distributions predicted by the model best match those directly measured for the patient via their implant. We demonstrated our approach for N=7 patients. We found that our approach results in mean percent differences between direct and simulated measurements of voltage distributions of 11%. In addition, visual comparison shows the simulated and measured voltage distributions are qualitatively in good agreement. This represents a crucial step toward developing and validating the first in vivo patient-specific cochlea EAMs.

Influence of tissue resistivities on neuromagnetic fields and electric potentials studied with a finite element model of the head.

PubMed

Haueisen, J; Ramon, C; Eiselt, M; Brauer, H; Nowak, H

1997-08-01

Modeling in magnetoencephalography (MEG) and electroencephalography (EEG) requires knowledge of the in vivo tissue resistivities of the head. The aim of this paper is to examine the influence of tissue resistivity changes on the neuromagnetic field and the electric scalp potential. A high-resolution finite element method (FEM) model (452,162 elements, 2-mm resolution) of the human head with 13 different tissue types is employed for this purpose. Our main finding was that the magnetic fields are sensitive to changes in the tissue resistivity in the vicinity of the source. In comparison, the electric surface potentials are sensitive to changes in the tissue resistivity in the vicinity of the source and in the vicinity of the position of the electrodes. The magnitude (strength) of magnetic fields and electric surface potentials is strongly influenced by tissue resistivity changes, while the topography is not as strongly influenced. Therefore, an accurate modeling of magnetic field and electric potential strength requires accurate knowledge of tissue resistivities, while for source localization procedures this knowledge might not be a necessity.

The effect of the geometry and material properties of a carbon joint produced by electron beam induced deposition on the electrical resistance of a multiwalled carbon nanotube-to-metal contact interface

NASA Astrophysics Data System (ADS)

Rykaczewski, Konrad; Henry, Matthew R.; Kim, Song-Kil; Fedorov, Andrei G.; Kulkarni, Dhaval; Singamaneni, Srikanth; Tsukruk, Vladimir V.

2010-01-01

Multiwall carbon nanotubes (MWNTs) are promising candidates for yielding next generation electrical and electronic devices such as interconnects and tips for conductive force microscopy. One of the main challenges in MWNT implementation in such devices is the high contact resistance of the MWNT-metal electrode interface. Electron beam induced deposition (EBID) of an amorphous carbon interface has previously been demonstrated to simultaneously lower the electrical contact resistance and improve the mechanical characteristics of the MWNT-electrode connection. In this work, we investigate the influence of process parameters, such as the electron beam energy, current, geometry, and deposition time, on the EBID-made carbon joint geometry and electrical contact resistance. The influence of the composition of the deposited material on its resistivity is also investigated. The relative importance of each component of the contact resistance and the limiting factor of the overall electrical resistance of a MWNT-based interconnect is determined through a combination of a model analysis and comprehensive experiments.

High Speed Imaging using Nanoprobe Arrays

DTIC Science & Technology

2010-06-23

Gotsmann and U. Dürig, Appl. Phys. Lett. 87, 194102 2005. 9 W. P. King, S. Saxena, B. A. Nelson, R. Pitchimani, and B. L. Weeks, Nano Lett. 6, 2145...microcantilevers with selective coatings has been applied as an artificial nose to recognize and characterize alcohol vapors either in a static mode...doped resistive heater. Fig. 4(c) shows a custom printed circuit board (PCB) to mount the array chip and a flexible ribbon cable for the electrical

Specific storage and hydraulic conductivity tomography through the joint inversion of hydraulic heads and self-potential data

NASA Astrophysics Data System (ADS)

Ahmed, A. Soueid; Jardani, A.; Revil, A.; Dupont, J. P.

2016-03-01

Transient hydraulic tomography is used to image the heterogeneous hydraulic conductivity and specific storage fields of shallow aquifers using time series of hydraulic head data. Such ill-posed and non-unique inverse problem can be regularized using some spatial geostatistical characteristic of the two fields. In addition to hydraulic heads changes, the flow of water, during pumping tests, generates an electrical field of electrokinetic nature. These electrical field fluctuations can be passively recorded at the ground surface using a network of non-polarizing electrodes connected to a high impedance (> 10 MOhm) and sensitive (0.1 mV) voltmeter, a method known in geophysics as the self-potential method. We perform a joint inversion of the self-potential and hydraulic head data to image the hydraulic conductivity and specific storage fields. We work on a 3D synthetic confined aquifer and we use the adjoint state method to compute the sensitivities of the hydraulic parameters to the hydraulic head and self-potential data in both steady-state and transient conditions. The inverse problem is solved using the geostatistical quasi-linear algorithm framework of Kitanidis. When the number of piezometers is small, the record of the transient self-potential signals provides useful information to characterize the hydraulic conductivity and specific storage fields. These results show that the self-potential method reveals the heterogeneities of some areas of the aquifer, which could not been captured by the tomography based on the hydraulic heads alone. In our analysis, the improvement on the hydraulic conductivity and specific storage estimations were based on perfect knowledge of electrical resistivity field. This implies that electrical resistivity will need to be jointly inverted with the hydraulic parameters in future studies and the impact of its uncertainty assessed with respect to the final tomograms of the hydraulic parameters.

Fully anisotropic 3-D EM modelling on a Lebedev grid with a multigrid pre-conditioner

NASA Astrophysics Data System (ADS)

Jaysaval, Piyoosh; Shantsev, Daniil V.; de la Kethulle de Ryhove, Sébastien; Bratteland, Tarjei

2016-12-01

We present a numerical algorithm for 3-D electromagnetic (EM) simulations in conducting media with general electric anisotropy. The algorithm is based on the finite-difference discretization of frequency-domain Maxwell's equations on a Lebedev grid, in which all components of the electric field are collocated but half a spatial step staggered with respect to the magnetic field components, which also are collocated. This leads to a system of linear equations that is solved using a stabilized biconjugate gradient method with a multigrid preconditioner. We validate the accuracy of the numerical results for layered and 3-D tilted transverse isotropic (TTI) earth models representing typical scenarios used in the marine controlled-source EM method. It is then demonstrated that not taking into account the full anisotropy of the conductivity tensor can lead to misleading inversion results. For synthetic data corresponding to a 3-D model with a TTI anticlinal structure, a standard vertical transverse isotropic (VTI) inversion is not able to image a resistor, while for a 3-D model with a TTI synclinal structure it produces a false resistive anomaly. However, if the VTI forward solver used in the inversion is replaced by the proposed TTI solver with perfect knowledge of the strike and dip of the dipping structures, the resulting resistivity images become consistent with the true models.

Dynamic underground stripping: steam and electric heating for in situ decontamination of soils and groundwater

DOEpatents

Daily, W.D.; Ramirez, A.L.; Newmark, R.L.; Udell, K.; Buetnner, H.M.; Aines, R.D.

1995-09-12

A dynamic underground stripping process removes localized underground volatile organic compounds from heterogeneous soils and rock in a relatively short time. This method uses steam injection and electrical resistance heating to heat the contaminated underground area to increase the vapor pressure of the contaminants, thus speeding the process of contaminant removal and making the removal more complete. The injected steam passes through the more permeable sediments, distilling the organic contaminants, which are pumped to the surface. Large electrical currents are also applied to the contaminated area, which heat the impermeable subsurface layers that the steam has not penetrated. The condensed and vaporized contaminants are withdrawn by liquid pumping and vacuum extraction. The steam injection and electrical heating steps are repeated as necessary. Geophysical imaging methods can be used to map the boundary between the hot, dry, contamination-free underground zone and the cool, damp surrounding areas to help monitor the dynamic stripping process. 4 figs.

Dynamic underground stripping: steam and electric heating for in situ decontamination of soils and groundwater

DOEpatents

Daily, William D.; Ramirez, Abelardo L.; Newmark, Robin L.; Udell, Kent; Buetnner, Harley M.; Aines, Roger D.

1995-01-01

A dynamic underground stripping process removes localized underground volatile organic compounds from heterogeneous soils and rock in a relatively short time. This method uses steam injection and electrical resistance heating to heat the contaminated underground area to increase the vapor pressure of the contaminants, thus speeding the process of contaminant removal and making the removal more complete. The injected steam passes through the more permeable sediments, distilling the organic contaminants, which are pumped to the surface. Large electrical currents are also applied to the contaminated area, which heat the impermeable subsurface layers that the steam has not penetrated. The condensed and vaporized contaminants are withdrawn by liquid pumping and vacuum extraction. The steam injection and electrical heating steps are repeated as necessary. Geophysical imaging methods can be used to map the boundary between the hot, dry, contamination-free underground zone and the cool, damp surrounding areas to help monitor the dynamic stripping process.

Induction heating apparatus and methods for selectively energizing an inductor in response to a measured electrical characteristic that is at least partially a function of a temperature of a material being heated

DOEpatents

Richardson, John G.; Morrison, John L.; Hawkes, Grant L.

2006-07-04

An induction heating apparatus includes a measurement device for indicating an electrical resistance of a material to be heated. A controller is configured for energizing an inductor in response to the indicated resistance. An inductor may be energized with an alternating current, a characteristic of which may be selected in response to an indicated electrical resistance. Alternatively, a temperature of the material may be indicated via measuring the electrical resistance thereof and a characteristic of an alternating current for energizing the inductor may be selected in response to the temperature. Energizing the inductor may minimize the difference between a desired and indicated resistance or the difference between a desired and indicated temperature. A method of determining a temperature of at least one region of at least one material to be induction heated includes correlating a measured electrical resistance thereof to an average temperature thereof.

Risk analysis and detection of thrombosis by measurement of electrical resistivity of blood.

PubMed

Sapkota, Achyut; Asakura, Yuta; Maruyama, Osamu; Kosaka, Ryo; Yamane, Takashi; Takei, Masahiro

2013-01-01

Monitoring of thrombogenic process is very important in ventricular assistance devices (VADs) used as temporary or permanent measures in patients with advanced heart failure. Currently, there is a lack of a system which can perform a real-time monitoring of thrombogenic activity. Electrical signals vary according to the change in concentration of coagulation factors as well as the distribution of blood cells, and thus have potential to detect the thrombogenic process in an early stage. In the present work, we have made an assessment of an instrumentation system exploiting the electrical properties of blood. The experiments were conducted using bovine blood. Electrical resistance tomography with eight-electrode sensor was used to monitor the spatio-temporal change in electrical resistivity of blood in thrombogenic and non-thrombogenic condition. Under non-thrombogenic condition, the resistivity was uniform across the cross-section and average resistivity monotonically decreased with time before remaining almost flat. In contrary, under thrombogenic condition, there was non-uniform distribution across the cross-section, and average resistivity fluctuated with time.

Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging

NASA Astrophysics Data System (ADS)

Alvarez, J.; Boutchich, M.; Kleider, J. P.; Teraji, T.; Koide, Y.

2014-09-01

The origin of the high leakage current measured in several vertical-type diamond Schottky devices is conjointly investigated by conducting probe atomic force microscopy and confocal micro-Raman/photoluminescence imaging analysis. Local areas characterized by a strong decrease of the local resistance (5-6 orders of magnitude drop) with respect to their close surrounding have been identified in several different regions of the sample surface. The same local areas, also referenced as electrical hot-spots, reveal a slightly constrained diamond lattice and three dominant Raman bands in the low-wavenumber region (590, 914 and 1040 cm-1). These latter bands are usually assigned to the vibrational modes involving boron impurities and its possible complexes that can electrically act as traps for charge carriers. Local current-voltage measurements performed at the hot-spots point out a trap-filled-limited current as the main conduction mechanism favouring the leakage current in the Schottky devices.

Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring

NASA Astrophysics Data System (ADS)

Watlet, Arnaud; Kaufmann, Olivier; Triantafyllou, Antoine; Poulain, Amaël; Chambers, Jonathan E.; Meldrum, Philip I.; Wilkinson, Paul B.; Hallet, Vincent; Quinif, Yves; Van Ruymbeke, Michel; Van Camp, Michel

2018-03-01

Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. In particular, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of 3 years at the Rochefort Cave Laboratory (RCL) site in south Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography (ERT) monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring and summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; and (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes.

The effect of temperature and moisture on electrical resistance, strain sensitivity and crack sensitivity of steel fiber reinforced smart cement composite

NASA Astrophysics Data System (ADS)

Teomete, Egemen

2016-07-01

Earthquakes, material degradations and other environmental factors necessitate structural health monitoring (SHM). Metal foil strain gages used for SHM have low durability and low sensitivity. These factors motivated researchers to work on cement based strain sensors. In this study, the effects of temperature and moisture on electrical resistance, compressive and tensile strain gage factors (strain sensitivity) and crack sensitivity were determined for steel fiber reinforced cement based composite. A rapid increase of electrical resistance at 200 °C was observed due to damage occurring between cement paste, aggregates and steel fibers. The moisture—electrical resistance relationship was investigated. The specimens taken out of the cure were saturated with water and had a moisture content of 9.49%. The minimum electrical resistance was obtained at 9% moisture at which fiber-fiber and fiber-matrix contact was maximum and the water in micro voids was acting as an electrolyte, conducting electrons. The variation of compressive and tensile strain gage factors (strain sensitivities) and crack sensitivity were investigated by conducting compression, split tensile and notched bending tests with different moisture contents. The highest gage factor for the compression test was obtained at optimal moisture content, at which electrical resistance was minimum. The tensile strain gage factor for split tensile test and crack sensitivity increased by decreasing moisture content. The mechanisms between moisture content, electrical resistance, gage factors and crack sensitivity were elucidated. The relations of moisture content with electrical resistance, gage factors and crack sensitivities have been presented for the first time in this study for steel fiber reinforced cement based composites. The results are important for the development of self sensing cement based smart materials.

Coatings for graphite fibers

NASA Technical Reports Server (NTRS)

Galasso, F. S.; Scola, D. A.; Veltri, R. D.

1980-01-01

Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

On the use of statistical methods to interpret electrical resistivity data from the Eumsung basin (Cretaceous), Korea

NASA Astrophysics Data System (ADS)

Kim, Ji-Soo; Han, Soo-Hyung; Ryang, Woo-Hun

2001-12-01

Electrical resistivity mapping was conducted to delineate boundaries and architecture of the Eumsung Basin Cretaceous. Basin boundaries are effectively clarified in electrical dipole-dipole resistivity sections as high-resistivity contrast bands. High resistivities most likely originate from the basement of Jurassic granite and Precambrian gneiss, contrasting with the lower resistivities from infilled sedimentary rocks. The electrical properties of basin-margin boundaries are compatible with the results of vertical electrical soundings and very-low-frequency electromagnetic surveys. A statistical analysis of the resistivity sections is tested in terms of standard deviation and is found to be an effective scheme for the subsurface reconstruction of basin architecture as well as the surface demarcation of basin-margin faults and brittle fracture zones, characterized by much higher standard deviation. Pseudo three-dimensional architecture of the basin is delineated by integrating the composite resistivity structure information from two cross-basin E-W magnetotelluric lines and dipole-dipole resistivity lines. Based on statistical analysis, the maximum depth of the basin varies from about 1 km in the northern part to 3 km or more in the middle part. This strong variation supports the view that the basin experienced pull-apart opening with rapid subsidence of the central blocks and asymmetric cross-basinal extension.

Electrical Impedance Tomography: a new study method for neonatal Respiratory Distress Syndrome?

PubMed Central

Chatziioannidis, I; Samaras, T; Nikolaidis, N

2011-01-01

Treatment of cardiorespiratory system diseases is a procedure that usually demands data collection on terms of the anatomy and the operation of the organs that are under study. Electrical Impedance Tomography (EIT) is an alternative approach, in comparison to existing techniques. With EIT electrodes are placed in the perimeter of the human body and images of the estimated organ are reconstructed, using the measurement of its impendence (or resistance) distribution and determining its alteration through time, while at the same time the patient is not exposed to ionizing radiation. Its clinical use presupposes the correct placement of the electrodes over the perimeter of the human body, the rapid data collection and electrical safety. It is a low cost technique and it is implemented near the patient. It is able to determine the distribution of ventilation, blood supply, diffused or localized lung defects, but it can also estimate therapeutic interventions or alteration to assisted ventilation of the neonate. EIT was developed at the beginning of the 1980s, but it has only recently begun to be implemented on neonates, and especially in the study of their respiratory system function. The low rate of image analysis is considered to be a drawback, but it is offset by the potential offered for the estimation of lungs' function (both under normal and pathological conditions), since ventilation and resistance are two quite similar concepts. In this review the most important studies about EIT are mentioned as a method of estimating respiratory distress syndrome in neonates. In terms of the above mentioned development, it is supposed that this technique will offer a great amount of help to the doctor in his / her estimations of the cardiorespiratory system and to his / her selection of the best intervening strategies. PMID:22435017

A field comparison of multiple techniques to quantify groundwater - surface-water interactions

USGS Publications Warehouse

González-Pinzón, Ricardo; Ward, Adam S; Hatch, Christine E; Wlostowski, Adam N; Singha, Kamini; Gooseff, Michael N.; Haggerty, Roy; Harvey, Judson; Cirpka, Olaf A; Brock, James T

2015-01-01

Groundwater–surface-water (GW-SW) interactions in streams are difficult to quantify because of heterogeneity in hydraulic and reactive processes across a range of spatial and temporal scales. The challenge of quantifying these interactions has led to the development of several techniques, from centimeter-scale probes to whole-system tracers, including chemical, thermal, and electrical methods. We co-applied conservative and smart reactive solute-tracer tests, measurement of hydraulic heads, distributed temperature sensing, vertical profiles of solute tracer and temperature in the stream bed, and electrical resistivity imaging in a 450-m reach of a 3rd-order stream. GW-SW interactions were not spatially expansive, but were high in flux through a shallow hyporheic zone surrounding the reach. NaCl and resazurin tracers suggested different surface–subsurface exchange patterns in the upper ⅔ and lower ⅓ of the reach. Subsurface sampling of tracers and vertical thermal profiles quantified relatively high fluxes through a 10- to 20-cm deep hyporheic zone with chemical reactivity of the resazurin tracer indicated at 3-, 6-, and 9-cm sampling depths. Monitoring of hydraulic gradients along transects with MINIPOINT streambed samplers starting ∼40 m from the stream indicated that groundwater discharge prevented development of a larger hyporheic zone, which progressively decreased from the stream thalweg toward the banks. Distributed temperature sensing did not detect extensive inflow of ground water to the stream, and electrical resistivity imaging showed limited large-scale hyporheic exchange. We recommend choosing technique(s) based on: 1) clear definition of the questions to be addressed (physical, biological, or chemical processes), 2) explicit identification of the spatial and temporal scales to be covered and those required to provide an appropriate context for interpretation, and 3) maximizing generation of mechanistic understanding and reducing costs of implementing multiple techniques through collaborative research.

Long-term autonomous resistivity monitoring of oil-contaminated sediments from the Deepwater Horizon spill

NASA Astrophysics Data System (ADS)

Heenan, J. W.; Slater, L. D.; Ntarlagiannis, D.; Atekwana, E. A.; Ross, C.; Nolan, J. T.; Atekwana, E. A.; Werkema, D. D.; Fathepure, B.

2012-12-01

We conducted a long-term electrical resistivity survey at Grand Terre 1 (GT1) Island off the coast of Louisiana, a site contaminated with crude oil associated with the April 2010 BP Deepwater Horizon oil spill. Electrical resistivity has proven sensitivity to biogeochemical processes associated with the biodegradation of hydrocarbons in the subsurface. However, most of these studies have been in freshwater environments and for aged spills. The BP Deepwater Horizon oil spill therefore provided an unprecedented opportunity to capture the early time biogeophysical signals resulting from the physical, chemical and microbial transformation of crude oil in highly saline environments. We used a multi-channel resistivity system powered by solar panels to obtain continuous measurements twice a day on both a surface array and two shallow borehole arrays. This system operated for approximately 1.5 years and provided a unique long-term dataset of resistivity changes. Temperature and specific conductance values for the shallow groundwater were continuously logged. . Resistivity changes likely associated with biodegradation processes were then isolated from these environmental factors by modeling. In addition, groundwater was sampled for geochemical analyses from wells installed at the study site and soil samples were collected for microbial analyses at several locations, including both contaminated and uncontaminated locations. Microcosms were set up to determine the biodegradation potential of indigenous populations, and microbial diversity analysis was used to determine microbial community composition. Surface and borehole resistivity arrays revealed an initial resistive anomaly co-located with the known contamination. Pixel time series analysis of an inverted time sequence of resistivity sections highlighted differing responses between contaminated and uncontaminated locations. The contaminated locations exhibit persistent resistivity decreases over time, whereas areas outside of the contaminated location exhibit relatively uniform resistivity or show clear evidence of seasonal effect. Temperature-corrected resistivity changes show no direct correlation with pore fluid specific conductance changes, suggesting that specific conductance changes (e.g. due to tides) have little influence on imaged resistivity structure. Microbial data suggest that resistivity changes within the contaminated location resulted from biodegradation, showing the presence of native populations capable of degrading aromatic hydrocarbons at salinities ranging from 6 to 15 % NaCl within the contaminated location. Aqueous geochemical measurements performed on samples from the site further indicate that at depth intervals coincident with the resistivity anomaly, marked increases in the concentration of dissolved inorganic carbon (DIC) were observed suggesting biodegradation of petroleum hydrocarbon although other DIC generating processes such as organic matter degradation coupled to sulfate and iron reduction were also prominent. This experiment demonstrates the potential viability of long-term autonomous electrical monitoring as a means of decreasing the frequency of more costly and invasive chemical analysis of natural attenuation.

The Nature and Subsurface Geometry of Late Holocene Coquina Rocks, Karaburun-Istanbul, NW Turkey

NASA Astrophysics Data System (ADS)

Ekinci, Y. L.; Demirci, A.; Erginal, A. E.; Kaya, H.; Ekinci, R.

2012-04-01

The so-called coquina defines moderately to hardly amalgamated shell debris by calcium carbonate cement. Even though its some depositional features are similar to intertidal beachrocks and carbonate-cemented dune rocks or eolianites, coquina occurs in shoal environments and is, in some cases, representative of tectonically uplifted coasts when it exposes remarkably above sea-level. In this study (supported financially by the Research Foundation of Çanakkale Onsekiz Mart University under project number COMUBAP: 2011/41), we discuss diagenetic features, radiocarbon age and subsurface geometry of coquina on Black Sea coast of Istanbul, NW Turkey, where such a Late Holocene occurrence has not been recorded so far. Having a visible thickness of 1 m, the coquina beds crop out on a slightly inclined wide beach formed mostly of shell fragments less than 5 cm in size. It contains calcite and aragonite as connective cement and broken or unbroken shells of Donacilla sp., Pecten glaucum and Ostrea edulis together with various foraminifera such as Elphidium macellum Ammonia compacta and coccolithophore Emiliania huxleyi. Radiocarbon ages from four bulk samples yielded calibrated ages ranging between 3.7 and 2.8 ka BP. Electrical resistivity tomography survey along three distinct transects perpendicular to the coastline were carried out in order to understand the thickness of coquina and its subsurface extensions along the beach. The apparent resistivity data were acquired along the survey lines of 21 electrodes with electrode spacing of 2 m, to give a total length of the line of 40 m. Dipole-dipole electrode configuration was used for 9 data levels. Topographic changes at the locations of each electrode points were determined by means of optical leveling technique for a more accurate calculation and interpretation. Apparent resistivity data were inverted by using 2D smoothness-constrained least squares algorithm. Similar electrical resistivity tomograms were obtained for three lines after the inversion process. The 2D resistivity images displayed a depth range of ~ 4.5 m and showed a strong resistivity contrast between coquina beach material (composed of shell fragments) and coquina rocks. Low resistivity values located at the northern lowermost part of tomograms point to seawater saturated material whilst the highest resistivity values indicate coquina beach material, having larger pore spaces between the grains. The northern uppermost parts of the tomograms, having a moderate resistivity range, mark the coquina rocks with a thickness of ~ 1-1.5 m. Additionally, the images also showed that the landward extension of the coquina rocks reaches ~ 22 m. Keywords: Coquina rocks, diagenetic features, radiocarbon age, subsurface geometry, İstanbul-Turkey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández-Rosales, E.; Cedeño, E.; Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Legaria 694, Colonia Irrigación, CP 11500, México, DF

In this work a combined thermoacoustic and thermoreflectance set-up was designed for imaging biased microelectronic circuits. In particular, it was used with polycrystalline silicon resistive tracks grown on a monocrystalline Si substrate mounted on a test chip. Thermoreflectance images, obtained by scanning a probe laser beam on the sample surface, clearly show the regions periodically heated by Joule effect, which are associated to the electric current distribution in the circuit. The thermoacoustic signal, detected by a pyroelectric/piezoelectric sensor beneath the chip, also discloses the Joule contribution of the whole sample. However, additional information emerges when a non-modulated laser beam ismore » focused on the sample surface in a raster scan mode allowing imaging of the sample. The distribution of this supplementary signal is related to the voltage distribution along the circuit.« less

An MRI-Compatible High Frequency AC Resistive Heating System for Homeothermic Maintenance in Small Animals

PubMed Central

Gomes, Ana L.; Kinchesh, Paul; Kersemans, Veerle; Allen, Philip D.; Smart, Sean C.

2016-01-01

Purpose To develop an MRI-compatible resistive heater, using high frequency alternating current (AC), for temperature maintenance of anaesthetised animals. Materials and Methods An MRI-compatible resistive electrical heater was formed from narrow gauge wire connected to a high frequency (10–100 kHz) AC power source. Multiple gradient echo images covering a range of echo times, and pulse-acquire spectra were acquired with the wire heater powered using high frequency AC or DC power sources and without any current flowing in order to assess the sensitivity of the MRI acquisitions to the presence of current flow through the heater wire. The efficacy of temperature maintenance using the AC heater was assessed by measuring rectal temperature immediately following induction of general anaesthesia for a period of 30 minutes in three different mice. Results Images and spectra acquired in the presence and absence of 50–100 kHz AC through the wire heater were indistinguishable, whereas DC power created field shifts and lineshape distortions. Temperature lost during induction of anaesthesia was recovered within approximately 20 minutes and a stable temperature was reached as the mouse’s temperature approached the set target. Conclusion The AC-powered wire heater maintains adequate heat input to the animal to maintain body temperature, and does not compromise image quality. PMID:27806062

Spatial Control of Photoacid Diffusion in Chemically Amplified Resist (CAR) via External Electric Field.

PubMed

Kim, Jinok; Yoo, Gwangwe; Park, Jin; Park, Jin-Hong

2018-09-01

We investigated the effect of an electric field-based post exposure bake (EF-PEB) process on photoacid diffusion and pattern formation. To investigate the control of photoacid diffusion experimentally, the EF-PEB processes was performed at various temperatures. Cross sectional images of various EF-PEB processed samples were obtained by scanning electron microscopy (SEM) after ion beam milling. In addition, we conducted a numerical analysis of photoacid distribution and diffusion with following Fick's second law and compared the experimental results with our theoretical model. The drift distance was theoretically predicted by multiplying drift velocity and EF-PEB time, and the experimental values were obtained by finding the difference in pattern depths of PEB/EFPEB samples. Finally, an EF-PEB temperature of 85 °C was confirmed as the optimum condition to maximize photoacid drift distance using the electric field.

Multiphoton imaging reveals that nanosecond pulsed electric fields collapse tumor and normal vascular perfusion in human glioblastoma xenografts.

PubMed

Bardet, Sylvia M; Carr, Lynn; Soueid, Malak; Arnaud-Cormos, Delia; Leveque, Philippe; O'Connor, Rodney P

2016-10-04

Despite the biomedical advances of the last century, many cancers including glioblastoma are still resistant to existing therapies leaving patients with poor prognoses. Nanosecond pulsed electric fields (nsPEF) are a promising technology for the treatment of cancer that have thus far been evaluated in vitro and in superficial malignancies. In this paper, we develop a tumor organoid model of glioblastoma and apply intravital multiphoton microscopy to assess their response to nsPEFs. We demonstrate for the first time that a single 10 ns, high voltage electric pulse (35-45 kV/cm), collapses the perfusion of neovasculature, and also alters the diameter of capillaries and larger vessels in normal tissue. These results contribute to the fundamental understanding of nsPEF effects in complex tissue environments, and confirm the potential of nsPEFs to disrupt the microenvironment of solid tumors such as glioblastoma.

Electric moisture meters for wood

Treesearch

William L. James

1988-01-01

Electric moisture meters for wood measure electric conductance (resistance) or dielectric properties, which vary fairly consistently with moisture content when it is less than 30 percent. The two major classes of electric moisture meters are the conductance (resistance) type and the dielectric type. Conductance-t ype meters use penetrating electrodes that measure in a...

van der Pauw's Theorem on Sheet Resistance

ERIC Educational Resources Information Center

Bolt, Michael

2017-01-01

The sheet resistance of a conducting material of uniform thickness is analogous to the resistivity of a solid material and provides a measure of electrical resistance. In 1958, L. J. van der Pauw found an effective method for computing sheet resistance that requires taking two electrical measurements from four points on the edge of a simply…

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. We made corrections according to the temperature profile and to volumetric water contents obtained previously on undisturbed samples. Corrected values tended to be superimposed on those obtained in the field. Then, we calculated the water content of the different reworked waste samples using the correlation between volumetric water content correlation and electrical resistivity and we compared this value to the one measured at the laboratory. Both values were correlated satisfactorily. In conclusion, we show that bulk electrical resistivity measurements are very promising to quantify water content in landfills if temperature can be estimated independently. In future applications, electrical resistivity tomography coupled with distributed temperature sensing could give important estimates of water content of the waste and thus helping in dealing with problematics such as boosting biodegradation and stabilization of the waste, reducing risks of soil and aquifers pollution, landfill mining, and controlled production of methane.

Stretchable Conductive Elastomers for Soldier Biosensing Applications: Final Report

DTIC Science & Technology

2016-03-01

public release; distribution is unlimited. 7 the electrical impedance tunability that we required. Representative data for resistance versus volume...Technology Directorate’s (VTD) electric field mediated morphing wing research effort. Fig. 5 Resistance values of EEG electrodes as a function of...extend the resistance range of the developed polymer EEG electrodes to potentially provide insight into defining an optimum electrical performance for

Indications of vigor loss after fire in Caribbean pine (Pinus caribaea) from electrical resistance measurements

Treesearch

T.E. Paysen; A.L. Koonce; E. Taylor; M.O. Rodriquez

2006-01-01

In May 1993, electrical resistance measurements were performed on trees in burned and unburned stands of Caribbean pine (Pinus caribaea Mor.) in north-eastern Nicaragua to determine whether tree vigor was affected by fire. An Osmose model OZ-67 Shigometer with digital readout was used to collect the sample electrical resistance data. Computer-...

Direct-current vertical electrical-resistivity soundings in the Lower Peninsula of Michigan

USGS Publications Warehouse

Westjohn, D.B.; Carter, P.J.

1989-01-01

Ninety-three direct-current vertical electrical-resistivity soundings were conducted in the Lower Peninsula of Michigan from June through October 1987. These soundings were made to assist in mapping the depth to brine in areas where borehole resistivity logs and water-quality data are sparse or lacking. The Schlumberger array for placement of current and potential electrodes was used for each sounding. Vertical electrical-resistivity sounding field data, shifted and smoothed sounding data, and electric layers calculated using inverse modeling techniques are presented. Also included is a summary of the near-surface conditions and depths to conductors and resistors for each sounding location.

Electrical resistivity tomography to monitor enhanced biodegradation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale.

PubMed

Masy, Thibaut; Caterina, David; Tromme, Olivier; Lavigne, Benoît; Thonart, Philippe; Hiligsmann, Serge; Nguyen, Frédéric

2016-01-01

Petroleum hydrocarbons (HC) represent the most widespread contaminants and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on the environment affected and is still difficult to predict a priori. In order to overcome these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was to isolate an electrical signal linked to an enhanced bacterial activity with ERT, in an aged HC-contaminated clay loam soil. To achieve this, a pilot tank was built to mimic field conditions. Compared to a first insufficient biostimulation phase, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600ppm) in 3months in the center of the contaminated zone, where pollutants were less bioavailable. In the meantime, lithological heterogeneities and microbial activities (growth and biosurfactant production) were successively discriminated by ERT images. In the future, this cost-effective technique should be more and more transferred to the field in order to monitor biodegradation processes and assist in selecting the most appropriate remediation technique. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermal Design and Characterization of Heterogeneously Integrated InGaP/GaAs HBTs

DOE PAGES

Choi, Sukwon; Peake, Gregory M.; Keeler, Gordon A.; ...

2016-04-21

Flip-chip heterogeneously integrated n-p-n InGaP/GaAs heterojunction bipolar transistors (HBTs) with integrated thermal management on wide-bandgap AlN substrates followed by GaAs substrate removal are demonstrated. Without thermal management, substrate removal after integration significantly aggravates self-heating effects, causing poor I–V characteristics due to excessive device self-heating. An electrothermal codesign scheme is demonstrated that involves simulation (design), thermal characterization, fabrication, and evaluation. Thermoreflectance thermal imaging, electrical-temperature sensitive parameter-based thermometry, and infrared thermography were utilized to assess the junction temperature rise in HBTs under diverse configurations. In order to reduce the thermal resistance of integrated devices, passive cooling schemes assisted by structural modification, i.e.,more » positioning indium bump heat sinks between the devices and the carrier, were employed. By implementing thermal heat sinks in close proximity to the active region of flip-chip integrated HBTs, the junction-to-baseplate thermal resistance was reduced over a factor of two, as revealed by junction temperature measurements and improvement of electrical performance. In conclusion, the suggested heterogeneous integration method accounts for not only electrical but also thermal requirements providing insight into realization of advanced and robust III–V/Si heterogeneously integrated electronics.« less

Electrical resistivity tomography to monitor enhanced biodegradation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale

NASA Astrophysics Data System (ADS)

Masy, Thibaut; Caterina, David; Tromme, Olivier; Lavigne, Benoît; Thonart, Philippe; Hiligsmann, Serge; Nguyen, Frédéric

2016-01-01

Petroleum hydrocarbons (HC) represent the most widespread contaminants and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on the environment affected and is still difficult to predict a priori. In order to overcome these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was to isolate an electrical signal linked to an enhanced bacterial activity with ERT, in an aged HC-contaminated clay loam soil. To achieve this, a pilot tank was built to mimic field conditions. Compared to a first insufficient biostimulation phase, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the center of the contaminated zone, where pollutants were less bioavailable. In the meantime, lithological heterogeneities and microbial activities (growth and biosurfactant production) were successively discriminated by ERT images. In the future, this cost-effective technique should be more and more transferred to the field in order to monitor biodegradation processes and assist in selecting the most appropriate remediation technique.

Imaging quantum transport using scanning gate microscopy

NASA Astrophysics Data System (ADS)

Hackens, Benoit

2014-03-01

Quantum transport in nanodevices is usually probed thanks to measurements of the electrical resistance or conductance, which lack the spatial resolution necessary to probe electron behaviour inside the devices. In this talk, we will show that scanning gate microscopy (SGM) yields real-space images of quantum transport phenomena inside archetypal mesoscopic devices such as quantum point contacts and quantum rings. We will first discuss the SGM technique, which is based on mapping the electrical conductance of a device as an electrically-biased sharp metallic tip scans in its vicinity. With SGM, we demonstrated low temperature imaging of the electron probability density and interferences in embedded mesoscopic quantum rings [B. Hackens et al., Nat. Phys. 2, 826 (2006)]. At high magnetic field, thanks to the SGM conductance maps, one can decrypt complex transport phenomena such as tunneling between quantum Hall edge state, either direct or through localized states [B. Hackens et al., Nat. Comm. 1, 39 (2010)]. Moreover, the technique also allows to perform local spectroscopy of electron transport through selected localized states [F. Martins et al., New J. of Phys. 15, 013049 (2013); F. Martins et al., Sci. Rep. 3, 1416 (2013)]. Overall, these examples show that scanning gate microscopy is a powerful tool for imaging charge carrier behavior inside devices fabricated from a variety of materials, and opens the way towards a more intimate manipulation of charge and quasiparticle transport. This work was performed in collaboration with F. Martins, S. Faniel, B. Brun, M. Pala, X. Wallart, L. Desplanque, B. Rosenow, T. Ouisse, H. Sellier, S. Huant and V. Bayot.

Low-temperature electrical resistivity of transition-metal carbides

NASA Astrophysics Data System (ADS)

Allison, C. Y.; Finch, C. B.; Foegelle, M. D.; Modine, F. A.

1988-10-01

The electrical resistivities of single crystals of ZrC 0.93, VC 0.88, NbC 0.95, and TaC 0.99 were measured from liquid helium temperature to 350 K. The Bloch-Gruneisen theory of electrical resistivity gives a good fit to the zirconium carbide and the vanadium carbide measurements. In contrast, the resistivities of the two superconducting crystals, tantalum carbide and niobium carbide, show excellent agreement with the Wilson model. The appropriate model appears to depend upon the superconducting properties of the crystals.

Atomic Migration Induced Crystal Structure Transformation and Core-Centered Phase Transition in Single Crystal Ge2Sb2Te5 Nanowires.

PubMed

Lee, Jun-Young; Kim, Jeong-Hyeon; Jeon, Deok-Jin; Han, Jaehyun; Yeo, Jong-Souk

2016-10-12

A phase change nanowire holds a promise for nonvolatile memory applications, but its transition mechanism has remained unclear due to the analytical difficulties at atomic resolution. Here we obtain a deeper understanding on the phase transition of a single crystalline Ge 2 Sb 2 Te 5 nanowire (GST NW) using atomic scale imaging, diffraction, and chemical analysis. Our cross-sectional analysis has shown that the as-grown hexagonal close-packed structure of the single crystal GST NW transforms to a metastable face-centered cubic structure due to the atomic migration to the pre-existing vacancy layers in the hcp structure going through iterative electrical switching. We call this crystal structure transformation "metastabilization", which is also confirmed by the increase of set-resistance during the switching operation. For the set to reset transition between crystalline and amorphous phases, high-resolution imaging indicates that the longitudinal center of the nanowire mainly undergoes phase transition. According to the atomic scale analysis of the GST NW after repeated electrical switching, partial crystallites are distributed around the core-centered amorphous region of the nanowire where atomic migration is mainly induced, thus potentially leading to low power electrical switching. These results provide a novel understanding of phase change nanowires, and can be applied to enhance the design of nanowire phase change memory devices for improved electrical performance.

A method to improve tree water use estimates by distinguishing sapwood from heartwood using Electrical Resistivity Tomography

NASA Astrophysics Data System (ADS)

Guyot, A.; Ostergaard, K.; Lenkopane, M.; Fan, J.; Lockington, D. A.

2011-12-01

Estimating whole-plant water use in trees requires reliable and accurate methods. Measuring sap velocity and extrapolating to tree water use is seen as the most commonly used. However, deducing the tree water use from sap velocity requires an estimate of the sapwood area. This estimate is the highest cause of uncertainty, and can reach more than 50 % of the uncertainty in the estimate of water use per day. Here, we investigate the possibility of using Electrical Resistivity Tomography to evaluate the sapwood area distribution in a plantation of Pinus elliottii. Electric resistivity tomographs of Pinus elliottii show a very typical pattern of electrical resistivity, which is highly correlated to sapwood and heartwood distribution. To identify the key factors controlling the variation of electrical resistivity, cross sections at breast height for ten trees have been monitored with electrical resistivity tomography. Trees have been cut down after the experiment to identify the heartwood/sapwood boundaries and to extract wood and sap samples. pH, electrolyte concentration and wood moisture content have then been analysed for these samples. Results show that the heartwood/sapwood patterns are highly correlated with electrical resistivity, and that the wood moisture content is the most influencing factor controlling the variability of the patterns. These results show that electric resistivity tomography could be used as a powerful tool to identify the sapwood area, and thus be used in combination with sapflow sensors to map tree water use at stand scale. However, if Pinus elliottii shows typical patterns, further work is needed to identify to see if there are species - specific characterictics as shown in previous works (, electrolyte gradients from the bark to the heartwood). Also, patterns of high resistivity in between needles positions, which are not correlated with either wood moisture content or sapwood, appear to be artifacts. Thus, inversion methods have also to be improved to take into account these measurements issues.

A geophysical system combining electrical resistivity and spontaneous potential for detecting, delineating, and monitoring slope stability.

DOT National Transportation Integrated Search

1991-01-01

Various geophysical electrical measuring techniques, i.e., spontaneous potential (SP) terrain conductivity meter (TCM), and conventional electrical resistivity/conductivity (ER), were tested to determine their effectiveness in detecting, delineating,...

Impact of small-scale saline tracer heterogeneity on electrical resistivity monitoring in fully and partially saturated porous media: Insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, Damien; Jiménez-Martínez, Joaquín; Legendre, Raphaël; Le Borgne, Tanguy; Méheust, Yves; Linde, Niklas

2018-03-01

Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele-Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical conductivity, especially for partially saturated conditions. We highlight how these phenomena contribute to the typically large apparent mass loss observed when conducting field-scale time-lapse ERT.

Tailings dams stability analysis using numerical modelling of geotechnical and geophysical data

NASA Astrophysics Data System (ADS)

Mihai, S.; Zlagnean, M.; Oancea, I.; Petrescu, A.

2009-04-01

Methods for monitoring seepage and detecting internal erosion are essential for the safety evaluation of embankment dams. Internal erosion is one of the major reasons for embankment dam failures, and there are thousands of large tailings dams and waste-rock dumps in the world that may pe considered as hotspots for environmental impact. In this research the geophysical survey works were performed on Cetatuia 2 tailings dam. Electrical resistivity imaging (ERI) method was able to detect spatially anomalous zones inside the embankment dam. These anomalies are the results of internal erosion phenomena which may progressing inside the dam and is difficult to detect by conventional methods. Data aquired by geophysical survey together with their interpretations were used in the numerical model for slope stability assessment. The final results show us the structural weakness induced by the presence of internal erosion elements especially for seismic loading case. This research methodology may be also available for tailings dam monitoring purposes. Electrical Rezistivity Imaging (ERI) was performed on Cetatuia 2 dam at the Uranium Milling Plant Feldioara, in order to map areas with lateral and vertical changes in resistivity. The electrodes are connected to an automated computer operated switch box that selects the 4 electrodes to be used. A computer controls the switch box and the measuring device, and runs a program that selects the electrodes, makes the measurement, and stores the measurement. For inversion processing procedures was used Res2Din software. The measured resistivity were plotted by the pseudo section contouring method. There are five resistivity pseudosections obtained from the Cetatuia 2 tailings dam during the october 2007 measurements. Four transversal profiles trans1 to trans4 are perpendicular to the berms and the longitudinal one long1 is placed along dam's crest. The high resistivities near the berms surfaces corresponds to unsaturated fill materials and the low resistivities near the crest correspond to water saturated material. The resistivities values greater then 80 ohm.m may be explained by some error obtained for that inversion model. Profiles trans3 and trans4 were measured on perpendicular directions to berm alignment and show two distinct zones. The upward low resistivities zone correspond to water saturated materials especially from the compacted clay dam's core and the downward high resistivities zone belongs to unsaturated fill materials. The boundary between high and low resistivity at the depth of about 5 to 7 meters shows the groundwater level. The continuation of the high resistivity zones towards the end of the profile trans3, which is different from other profiles is probably due to the presence of dry coarse materials in shallow depth correspondingly to sandy clay. The sand fractions from the clay matrix may be affected by internal erosional phenomena, due to seepage currents that overpassed the material critical gradient. In this case the relative high resistivities values were considered as a presumptive erosional pattern. This profile was considered for the slope stability finite element modelling. The profile long1 which is placed along dam's crest is the longest profiles and extends up to nearly 420 m. The boundary between high and low resistivity at the depth of about 4 to 8 meters shows the groundwater across the dam core. The central part of the profile (about meter 200) shows the same relative high resistivities that occurred on transversal profile trans3. Resistivity data was used for building the 3D electrical resistivity model. The water saturated materials have locations very close to dam's crest (resistivity values usually lower then 10 ohm.m) and on both dam's arms. The groundwater levels were confirmed by the piezometric measurements. Electrical Rezistivity Imaging method had the possibility to show the most important disturbant elements that in certain conditions may weak the dam's state of safety. This study considered the SSR (Shear Strength Reduction) technique for slope stability numerical modelling. In the SSR finite element technique, elasto-plastic strength is assumed for dam's materials and shear strengths are progressively reduced until collapse occurs. Numerical modelling was performed on the most critical profile choosed through analysis of geophysical and geotechnical informational volume achieved by insitu or in laboratory tests. Finite element analysis were considered in two situations: first, before geophysical investigations and second considering the whole informational of data achieved. Both situations were analysed in static and pseudo-static conditions. The factor of safety before geophysical investigations is high enough to describe a stable state of stability even for the seismic load. The total displacement distributions were modified by the presence of internal erosional element giving a high state of instability, especially for the pseudo-static case. These analysis using the finite element method prove the importance of structural disturbance elements that may occure inside the dam body produced by internal erosional processes.

Evaluation of groundwater potentiality survey in south Ataqa-northwestern part of Gulf of Suez by using resistivity data and site-selection modeling

NASA Astrophysics Data System (ADS)

Sultan, Sultan Awad; Essa, Khalid Sayed Ahmed Tawfik; Khalil, Mohamed Hassan; El-Nahry, Alaa Eldin Hassan; Galal, Alaa Nayef Hasan

2017-06-01

The integration between advanced techniques for groundwater exploration is necessary to manage and protect the vital resources. Direct current (DC) resistivity geoelectrical technique, Enhanced Thematic Mapper Landsat (ETM+) images and a geographic information system (GIS) are integrated to identify the groundwater potentiality in the study area. The interpretation of the one-dimensional (1-D) inversion of the acquired resistivity data are implemented for mapping the fresh to slightly brackish water aquifer. This number of vertical electric sounding is quite enough for different geologic mapping. The depth to the top of the ground water table (obtained from the existing Water well) and subsurface lithological information are used to calibrate the results of the resistivity data inversion. This research discussed how the integration between the geoelectrical parameters and hydrological data, could be used to determine the appropriate locations of dams construction and recommend the appropriate methods for management and rehabilitation of the aquifer.

Controlling the anomalous Hall effect by electric-field-induced piezo-strain in Fe40Pt60/(001)-Pb(Mg1/3Nb2/3)0.67Ti0.33O3 multiferroic heterostructures

NASA Astrophysics Data System (ADS)

Yang, Yuanjun; Yao, Yingxue; Chen, Lei; Huang, Haoliang; Zhang, Benjian; Lin, Hui; Luo, Zhenlin; Gao, Chen; Lu, Y. L.; Li, Xiaoguang; Xiao, Gang; Feng, Ce; Zhao, Y. G.

2018-01-01

Electric-field control of the anomalous Hall effect (AHE) was investigated in Fe40Pt60/(001)-Pb(Mg1/3Nb2/3)0.67Ti0.33O3 (FePt/PMN-PT) multiferroic heterostructures at room temperature. It was observed that a very large Hall resistivity change of up to 23.9% was produced using electric fields under a magnetic field bias of 100 Oe. A pulsed electric field sequence was used to generate nonvolatile strain to manipulate the Hall resistivity. Two corresponding nonvolatile states with distinct Hall resistivities were achieved after the electric fields were removed, thus enabling the encoding of binary information for memory applications. These results demonstrate that the Hall resistivity can be reversibly switched in a nonvolatile manner using programmable electric fields. Two remanent magnetic states that were created by electric-field-induced piezo-strain from the PMN-PT were attributed to the nonvolatile and reversible properties of the AHE. This work suggests that a low-energy-consumption-based approach can be used to create nonvolatile resistance states for spintronic devices based on electric-field control of the AHE.

Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

DOEpatents

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

2003-08-19

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.

Carbon nanotube modified probes for stable and high sensitivity conductive atomic force microscopy

NASA Astrophysics Data System (ADS)

Slattery, Ashley D.; Shearer, Cameron J.; Gibson, Christopher T.; Shapter, Joseph G.; Lewis, David A.; Stapleton, Andrew J.

2016-11-01

Conductive atomic force microscopy (C-AFM) is used to characterise the nanoscale electrical properties of many conducting and semiconducting materials. We investigate the effect of single walled carbon nanotube (SWCNT) modification of commercial Pt/Ir cantilevers on the sensitivity and image stability during C-AFM imaging. Pt/Ir cantilevers were modified with small bundles of SWCNTs via a manual attachment procedure and secured with a conductive platinum pad. AFM images of topography and current were collected from heterogeneous polymer and nanomaterial samples using both standard and SWCNT modified cantilevers. Typically, achieving a good current image comes at the cost of reduced feedback stability. In part, this is due to electrostatic interaction and increased tip wear upon applying a bias between the tip and the sample. The SWCNT modified tips displayed superior current sensitivity and feedback stability which, combined with superior wear resistance of SWCNTs, is a significant advancement for C-AFM.

Electrical Switching of Perovskite Thin-Film Resistors

NASA Technical Reports Server (NTRS)

Liu, Shangqing; Wu, Juan; Ignatiev, Alex

2010-01-01

Electronic devices that exploit electrical switching of physical properties of thin films of perovskite materials (especially colossal magnetoresistive materials) have been invented. Unlike some related prior devices, these devices function at room temperature and do not depend on externally applied magnetic fields. Devices of this type can be designed to function as sensors (exhibiting varying electrical resistance in response to varying temperature, magnetic field, electric field, and/or mechanical pressure) and as elements of electronic memories. The underlying principle is that the application of one or more short electrical pulse(s) can induce a reversible, irreversible, or partly reversible change in the electrical, thermal, mechanical, and magnetic properties of a thin perovskite film. The energy in the pulse must be large enough to induce the desired change but not so large as to destroy the film. Depending on the requirements of a specific application, the pulse(s) can have any of a large variety of waveforms (e.g., square, triangular, or sine) and be of positive, negative, or alternating polarity. In some applications, it could be necessary to use multiple pulses to induce successive incremental physical changes. In one class of applications, electrical pulses of suitable shapes, sizes, and polarities are applied to vary the detection sensitivities of sensors. Another class of applications arises in electronic circuits in which certain resistance values are required to be variable: Incorporating the affected resistors into devices of the present type makes it possible to control their resistances electrically over wide ranges, and the lifetimes of electrically variable resistors exceed those of conventional mechanically variable resistors. Another and potentially the most important class of applications is that of resistance-based nonvolatile-memory devices, such as a resistance random access memory (RRAM) described in the immediately following article, Electrically Variable Resistive Memory Devices (MFS-32511-1).

Optimization and performance comparison for galloping-based piezoelectric energy harvesters with alternating-current and direct-current interface circuits

NASA Astrophysics Data System (ADS)

Tan, Ting; Yan, Zhimiao; Lei, Hong

2017-07-01

Galloping-based piezoelectric energy harvesters scavenge small-scale wind energy and convert it into electrical energy. For piezoelectric energy harvesting with the same vibrational source (galloping) but different (alternating-current (AC) and direct-current (DC)) interfaces, general analytical solutions of the electromechanical coupled distributed parameter model are proposed. Galloping is theoretically proven to appear when the linear aerodynamic negative damping overcomes the electrical damping and mechanical damping. The harvested power is demonstrated as being done by the electrical damping force. Via tuning the load resistance to its optimal value for optimal or maximal electrical damping, the harvested power of the given structure with the AC/DC interface is maximized. The optimal load resistances and the corresponding performances of such two systems are compared. The optimal electrical damping are the same but with different optimal load resistances for the systems with the AC and DC interfaces. At small wind speeds where the optimal electrical damping can be realized by only tuning the load resistance, the performances of such two energy harvesting systems, including the minimal onset speeds to galloping, maximal harvested powers and corresponding tip displacements are almost the same. Smaller maximal electrical damping with larger optimal load resistance is found for the harvester with the DC interface when compared to those for the harvester with the AC interface. At large wind speeds when the maximal electrical damping rather than the optimal electrical damping can be reached by tuning the load resistance alone, the harvester with the AC interface circuit is recommended for a higher maximal harvested power with a smaller tip displacement. This study provides a method using the general electrical damping to connect and compare the performances of piezoelectric energy harvesters with same excitation source but different interfaces.

Fault Zone Resistivity Structure and Monitoring at the Taiwan Chelungpu Drilling Project from AMT data

NASA Astrophysics Data System (ADS)

Chiang, C.-W.; Unsworth, M. J.; Chen, C.-S.; Chen, C.-C.; Lin, A.-T.; Hsu, H.-L.

2009-04-01

The Chi-Chi earthquake occurred on September 21st, 1999 in the Western Foothills of central Taiwan. This Mw=7.6 earthquake produced a 90 km long surface rupture and caused severe damage across Taiwan. The coseismic displacement on the Chelungpu fault was one of the largest ever observed. The Taiwan Chelungpu drilling project (TCDP) began in 2003 and resulted in a 2,000 m well that recovered cores from the fault zone at A-hole and finished in 2005 with two boreholes (A-hole and B-hole) being completed. The Chelungpu fault that caused the Chi-Chi earthquake was observed in the core at a depth of 1,111 m (FAZ1111). Another fault zone (Sanyi Fault - FAZ1710) was observed at depths of 1,500~1,710 m. Since the electrical resistivity of rocks is sensitive to the presence of fluids, geophysical methods that remotely sense sub-surface resistivity, such as Magnetotellurics (MT), can be a powerful tool in investigating the fluid distribution in the shallow crust. The effectiveness of MT in imaging fault zones has been demonstrated by studies of the San Andreas Fault zone in California, the U.S. and elsewhere. In magnetotellurics, the depth of exploration increases as the signal frequency decreases. Thus for imaging shallow fault zone structure at the TCDP site, the higher frequency audio-magnetotelluric (AMT) method is the most suitable. In this paper, AMT data collected at the TCDP site from 2004 to 2006 are presented. Spatial and temporal variations are described and interpreted in terms of the tectonic setting. Audio-magnetotelluric (AMT) measurements were used to investigate electrical resistivity structure at the TCDP site from 2004~2006. These data show a geoelectric strike direction of N15°E to N30°E. Inversion and forward modeling of the AMT data were used to generate a 1-D resistivity model that has a prominent low resistivity zone (< 10 ohm-m) between depths of 1,100 and 1,500 m. When combined with porosity measurements, the AMT measurements imply that the ground water has a resistivity of 0.55 ohm-m at the depth of the fault zone. Time variations in the measured AMT data were observed from 2004~2005 with maximum changes of 43% in apparent resistivity and 18° in phase. The change in apparent resistivity is greatest in the 1,000~100 Hz frequency band. These frequencies are sensitive to the resistivity structure of the upper 500 m of the hanging wall of the Chelungpu Fault. The decrease in resistivity over time appears to be robust and could be caused by an increase in porosity and a re-distribution of the groundwater.

Forward modeling to investigate inversion artifacts resulting from time-lapse electrical resistivity tomography during rainfall simulations

NASA Astrophysics Data System (ADS)

Carey, Austin M.; Paige, Ginger B.; Carr, Bradley J.; Dogan, Mine

2017-10-01

Time-lapse electrical resistivity tomography (ERT) is commonly used as a minimally invasive tool to study infiltration processes. In 2014, we conducted field studies coupling variable intensity rainfall simulation with high-resolution ERT to study the real-time partitioning of rainfall into surface and subsurface response. The significant contrast in resistivity in the subsurface from large changes in subsurface moisture resulted in artifacts during the inversion process of the time-lapse ERT data collected using a dipole-dipole electrode array. These artifacts, which are not representative of real subsurface moisture dynamics, have been shown to arise during time-lapse inversion of ERT data and may be subject to misinterpretation. Forward modeling of the infiltration process post field experiments using a two-layer system (saprolite overlain by a soil layer) was used to generate synthetic datasets. The synthetic data were used to investigate the influence of both changes in volumetric moisture content and electrode configuration on the development of the artifacts identified in the field datasets. For the dipole-dipole array, we found that a decrease in the resistivity of the bottom layer by 67% resulted in a 50% reduction in artifact development. Artifacts for the seven additional array configurations tested, ranged from a 19% increase in artifact development (using an extended dipole-dipole array) to as much as a 96% decrease in artifact development (using a wenner-alpha array), compared to that of the dipole-dipole array. Moreover, these arrays varied in their ability to accurately delineate the infiltration front. Model results showed that the modified pole-dipole array was able to accurately image the infiltration zone and presented fewer artifacts for our experiments. In this study, we identify an optimal array type for imaging rainfall-infiltration dynamics that reduces artifacts. The influence of moisture contrast between the infiltrating water and the bulk subsurface material was characterized and shown to be a major factor in contributing to artifact development. Through forward modeling, this study highlights the importance of considering array type and subsurface moisture conditions when using time-lapse resistivity to obtain reliable estimates of vadose zone flow processes during rainfall-infiltration events.

2.5D transient electromagnetic inversion with OCCAM method

NASA Astrophysics Data System (ADS)

Li, R.; Hu, X.

2016-12-01

In the application of time-domain electromagnetic method (TEM), some multidimensional inversion schemes are applied for imaging in the past few decades to overcome great error produced by 1D model inversion when the subsurface structure is complex. The current mainstream multidimensional inversion for EM data, with the finite-difference time-domain (FDTD) forward method, mainly implemented by Nonlinear Conjugate Gradient (NLCG). But the convergence rate of NLCG heavily depends on Lagrange multiplier and maybe fail to converge. We use the OCCAM inversion method to avoid the weakness. OCCAM inversion is proven to be a more stable and reliable method to image the subsurface 2.5D electrical conductivity. Firstly, we simulate the 3D transient EM fields governed by Maxwell's equations with FDTD method. Secondly, we use the OCCAM inversion scheme with the appropriate objective error functional we established to image the 2.5D structure. And the data space OCCAM's inversion (DASOCC) strategy based on OCCAM scheme were given in this paper. The sensitivity matrix is calculated with the method of time-integrated back-propagated fields. Imaging result of example model shown in Fig. 1 have proven that the OCCAM scheme is an efficient inversion method for TEM with FDTD method. The processes of the inversion iterations have shown the great ability of convergence with few iterations. Summarizing the process of the imaging, we can make the following conclusions. Firstly, the 2.5D imaging in FDTD system with OCCAM inversion demonstrates that we could get desired imaging results for the resistivity structure in the homogeneous half-space. Secondly, the imaging results usually do not over-depend on the initial model, but the iteration times can be reduced distinctly if the background resistivity of initial model get close to the truthful model. So it is batter to set the initial model based on the other geologic information in the application. When the background resistivity fit the truthful model well, the imaging of anomalous body only need a few iteration steps. Finally, the speed of imaging vertical boundaries is slower than the speed of imaging the horizontal boundaries.

Electric moisture meters for wood

Treesearch

William L. James

1963-01-01

Common methods of measuring the moisture content of wood are described briefly, and a short historical account of the development of electric moisture meters is given. Electrical properties of wood are discussed briefly, and the basic operation of the resistance type and the radio- frequency types of moisture meter is outlined. Data relating the electrical resistance...

Effect of CFRC layers on the electrical properties and failure mode of RC beams strengthened with CFRC composites

NASA Astrophysics Data System (ADS)

Wu, Sigang; Dai, Hongzhe; Wang, Wei

2007-12-01

This paper designs an innovative reinforced concrete (RC) beam strengthened with carbon fiber reinforced concrete (CFRC) composites. Six groups of test beams, five with different degrees of strengthening, achieved by changing the location and the thickness of the CFRC layer, and one virgin RC beam, were tested in four-point bending over a span of 3000 mm. We investigate the effect of the CFRC layer on the flexural performance and the electrical properties of the designed beams. The test results indicate that the CFRC strengthened RC beam exhibits improved electrical properties as well as better mechanical performance. Also, the location and the thickness of the CFRC layer affect the initial electrical resistance and other electrical properties of the beam. Relationships between electrical resistance, loading, deflection and cracks show that the increase in the electrical resistance can be used to monitor the extent of damage to the designed beam. Based on this discovery, a new health monitoring technique for RC structures is produced by means of electrical resistance measurements.

Semiconductor bridge (SCB) igniter

DOEpatents

Bickes, Jr., Robert W.; Schwarz, Alfred C.

1987-01-01

In an explosive device comprising an explosive material which can be made to explode upon activation by activation means in contact therewith; electrical activation means adaptable for activating said explosive material such that it explodes; and electrical circuitry in operation association with said activation means; there is an improvement wherein said activation means is an electrical material which, at an elevated temperature, has a negative temperature coefficient of electrical resistivity and which has a shape and size and an area of contact with said explosive material sufficient that it has an electrical resistance which will match the resistance requirements of said associated electrical circuitry when said electrical material is operationally associated with said circuitry, and wherein said electrical material is polycrystalline; or said electrical material is crystalline and (a) is mounted on a lattice matched substrate or (b) is partially covered with an intimately contacting metallization area which defines its area of contact with said explosive material.

Resistive field structures for semiconductor devices and uses therof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marinella, Matthew; DasGupta, Sandeepan; Kaplar, Robert

The present disclosure relates to resistive field structures that provide improved electric field profiles when used with a semiconductor device. In particular, the resistive field structures provide a uniform electric field profile, thereby enhancing breakdown voltage and improving reliability. In example, the structure is a field cage that is configured to be resistive, in which the potential changes significantly over the distance of the cage. In another example, the structure is a resistive field plate. Using these resistive field structures, the characteristics of the electric field profile can be independently modulated from the physical parameters of the semiconductor device. Additionalmore » methods and architectures are described herein.« less

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.

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.

Rupture mechanism and seismotectonics of the Ms6.5 Ludian earthquake inferred from three-dimensional magnetotelluric imaging

NASA Astrophysics Data System (ADS)

Cai, Juntao; Chen, Xiaobin; Xu, Xiwei; Tang, Ji; Wang, Lifeng; Guo, Chunling; Han, Bing; Dong, Zeyi

2017-02-01

A three-dimensional (3-D) resistivity model around the 2014 Ms6.5 Ludian earthquake was obtained. The model shows that the aftershocks were mainly distributed in a shallow inverse L-shaped conductive angular region surrounded by resistive structures. The presences of this shallow conductive zone may be the key factor leading to the severe damage and surface rupture of the Ludian earthquake. A northwest trending local resistive belt along the Baogunao-Xiaohe fault interrupts the northeast trending conductive zone at the Zhaotong-Lianfeng fault zone in the middle crust, which may be the seismogenic structure of the main shock. Based on the 3-D electrical model, combining with GPS, thermal structure, and seismic survey results, a geodynamic model is proposed to interpret the seismotectonics, deep seismogenic background, and deformation characterized by a sinistral strike slip with a tensile component of the Ludian earthquake.

Simulation of variation of apparent resistivity in resistivity surveys using finite difference modelling with Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Aguirre, E. E.; Karchewski, B.

2017-12-01

DC resistivity surveying is a geophysical method that quantifies the electrical properties of the subsurface of the earth by applying a source current between two electrodes and measuring potential differences between electrodes at known distances from the source. Analytical solutions for a homogeneous half-space and simple subsurface models are well known, as the former is used to define the concept of apparent resistivity. However, in situ properties are heterogeneous meaning that simple analytical models are only an approximation, and ignoring such heterogeneity can lead to misinterpretation of survey results costing time and money. The present study examines the extent to which random variations in electrical properties (i.e. electrical conductivity) affect potential difference readings and therefore apparent resistivities, relative to an assumed homogeneous subsurface model. We simulate the DC resistivity survey using a Finite Difference (FD) approximation of an appropriate simplification of Maxwell's equations implemented in Matlab. Electrical resistivity values at each node in the simulation were defined as random variables with a given mean and variance, and are assumed to follow a log-normal distribution. The Monte Carlo analysis for a given variance of electrical resistivity was performed until the mean and variance in potential difference measured at the surface converged. Finally, we used the simulation results to examine the relationship between variance in resistivity and variation in surface potential difference (or apparent resistivity) relative to a homogeneous half-space model. For relatively low values of standard deviation in the material properties (<10% of mean), we observed a linear correlation between variance of resistivity and variance in apparent resistivity.

Subsurface Resistivity Structures in and Around Strike-Slip Faults - Electromagnetic Surveys and Drillings Across Active Faults in Central Japan -

NASA Astrophysics Data System (ADS)

Omura, K.; Ikeda, R.; Iio, Y.; Matsuda, T.

2005-12-01

Electrical resistivity is important property to investigate the structure of active faults. Pore fluid affect seriously the electrical properties of rocks, subsurface electrical resistivity can be an indicator of the existence of fluid and distribution of pores. Fracture zone of fault is expected to have low resistivity due to high porosity and small gain size. Especially, strike-slip type fault has nearly vertical fracture zone and the fracture zone would be detected by an electrical survey across the fault. We performed electromagnetic survey across the strike-slip active faults in central Japan. At the same faults, we also drilled borehole into the fault and did downhole logging in the borehole. We applied MT or CSAMT methods onto 5 faults: Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2), western Nagano Ohtaki area(1984 Nagano-ken seibu earthquake (M=6.8), the fault did not appeared on the surface), Neodani fault which appeared by the 1891 Nobi earthquake (M=8.0), Atera fault which seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9), Gofukuji fault that is considered to have activated about 1200 years ago. The sampling frequencies of electrical and magnetic field were 2 - 1024Hz (10 frequencies) for CSAMT survey and 0.00055 - 384Hz (40 frequencies) for MT survey. The electromagnetic data were processed by standard method and inverted to 2-D resistivity structure along transects of the faults. Results of the survey were compared with downhole electrical logging data and observational descriptions of drilled cores. Fault plane of each fault were recognized as low resistivity region or boundary between relatively low and high resistivity region, except for Gofukuji fault. As for Gofukuji fault, fault was located in relatively high resistivity region. During very long elapsed time from the last earthquake, the properties of fracture zone of Gofukuji fault might changed from low resistivity properties as observed for other faults. Downhole electrical logging data were consistent to values of resistivity estimated by electromagnetic survey for each fault. The existence of relatively low and high resistivity regions in 2-D structure from electromagnetic survey was observed again by downhole logging at the correspondent portion in the borehole. Cores recovered from depthes where the electrical logging showed low resistivity were hardly fractured and altered from host rock which showed high resistivity. Results of electromagnetic survey, downhole electrical logging and observation of drilled cores were consistent to each other. In present case, electromagnetic survey is useful to explore the properties of fault fracture zone. In the further investigations, it is important to explore relationships among features of resistivity structure and geological and geophysical situations of the faults.

Correlation of Electrical Resistance to CMC Stress-Strain and Fracture Behavior Under High Heat-Flux Thermal and Stress Gradients

NASA Technical Reports Server (NTRS)

Appleby, Matthew; Morscher, Gregory; Zhu, Dongming

2015-01-01

Because SiCSiC ceramic matrix composites (CMCs) are under consideration for use as turbine engine hot-section components in extreme environments, it becomes necessary to investigate their performance and damage morphologies under complex loading and environmental conditions. Monitoring of electrical resistance (ER) has been shown as an effective tool for detecting damage accumulation of woven melt-infiltrated SiCSiC CMCs. However, ER change under complicated thermo-mechanical loading is not well understood. In this study a systematic approach is taken to determine the capabilities of ER as a relevant non-destructive evaluation technique for high heat-flux testing, including thermal gradients and localized stress concentrations. Room temperature and high temperature, laser-based tensile tests were conducted in which stress-dependent damage locations were determined using modal acoustic emission (AE) monitoring and compared to full-field strain mapping using digital image correlation (DIC). This information is then compared with the results of in-situ ER monitoring, post-test ER inspection and fractography in order to correlate ER response to convoluted loading conditions and damage evolution.

Vanadium Oxide Thin Films Alloyed with Ti, Zr, Nb, and Mo for Uncooled Infrared Imaging Applications

NASA Astrophysics Data System (ADS)

Ozcelik, Adem; Cabarcos, Orlando; Allara, David L.; Horn, Mark W.

2013-05-01

Microbolometer-grade vanadium oxide (VO x ) thin films with 1.3 < x < 2.0 were prepared by pulsed direct-current (DC) sputtering using substrate bias in a controlled oxygen and argon environment. These films were systematically alloyed with Ti, Nb, Mo, and Zr using a second gun and radiofrequency (RF) reactive co-sputtering to probe the effects of the transition metals on the film charge transport characteristics. The results reveal that the temperature coefficient of resistance (TCR) and resistivity are unexpectedly similar for alloyed and unalloyed films up to alloy compositions in the ˜20 at.% range. Analysis of the film structures for the case of the 17% Nb-alloyed film by glancing-angle x-ray diffraction and transmission electron microscopy shows that the microstructure remains even with the addition of high concentrations of alloy metal, demonstrating the robust character of the VO x films to maintain favorable electrical transport properties for bolometer applications. Postdeposition thermal annealing of the alloyed VO x films further reveals improvement of electrical properties compared with unalloyed films, indicating a direction for further improvements in the materials.

Non-destructive reversible resistive switching in Cr doped Mott insulator Ca2RuO4: Interface vs bulk effects

NASA Astrophysics Data System (ADS)

Shen, Shida; Williamson, Morgan; Cao, Gang; Zhou, Jianshi; Goodenough, John; Tsoi, Maxim

2017-12-01

A non-destructive reversible resistive switching is demonstrated in single crystals of Cr-doped Mott insulator Ca2RuO4. An applied electrical bias was shown to reduce the DC resistance of the crystal by as much as 75%. The original resistance of the sample could be restored by applying an electrical bias of opposite polarity. We have studied this resistive switching as a function of the bias strength, applied magnetic field, and temperature. A combination of 2-, 3-, and 4-probe measurements provide a means to distinguish between bulk and interfacial contributions to the switching and suggests that the switching is mostly an interfacial effect. The switching was tentatively attributed to electric-field driven lattice distortions which accompany the impurity-induced Mott transition. This field effect was confirmed by temperature-dependent resistivity measurements which show that the activation energy of this material can be tuned by an applied DC electrical bias. The observed resistance switching can potentially be used for building non-volatile memory devices like resistive random access memory.

Modeling pore corrosion in normally open gold- plated copper connectors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Battaile, Corbett Chandler; Moffat, Harry K.; Sun, Amy Cha-Tien

2008-09-01

The goal of this study is to model the electrical response of gold plated copper electrical contacts exposed to a mixed flowing gas stream consisting of air containing 10 ppb H{sub 2}S at 30 C and a relative humidity of 70%. This environment accelerates the attack normally observed in a light industrial environment (essentially a simplified version of the Battelle Class 2 environment). Corrosion rates were quantified by measuring the corrosion site density, size distribution, and the macroscopic electrical resistance of the aged surface as a function of exposure time. A pore corrosion numerical model was used to predict bothmore » the growth of copper sulfide corrosion product which blooms through defects in the gold layer and the resulting electrical contact resistance of the aged surface. Assumptions about the distribution of defects in the noble metal plating and the mechanism for how corrosion blooms affect electrical contact resistance were needed to complete the numerical model. Comparisons are made to the experimentally observed number density of corrosion sites, the size distribution of corrosion product blooms, and the cumulative probability distribution of the electrical contact resistance. Experimentally, the bloom site density increases as a function of time, whereas the bloom size distribution remains relatively independent of time. These two effects are included in the numerical model by adding a corrosion initiation probability proportional to the surface area along with a probability for bloom-growth extinction proportional to the corrosion product bloom volume. The cumulative probability distribution of electrical resistance becomes skewed as exposure time increases. While the electrical contact resistance increases as a function of time for a fraction of the bloom population, the median value remains relatively unchanged. In order to model this behavior, the resistance calculated for large blooms has been weighted more heavily.« less

Oxidation Resistance, Electrical and Thermal Conductivity, and Spectral Emittance of Fully Dense HfB2 and ZrB2 with SiC, TaSi2, and LaB6 Additives

DTIC Science & Technology

2012-01-26

Resistance , Electrical and Thermal Conductivity, and Spectral Emittance of Fully Dense HfB2 and ZrB2 "With SiC, TaSi2, and LaB6 Additives Sb. GRANT NUMBER... RESISTANCE , ELECTRICAL AND THERMAL CONDUCTIVITY, AND SPECTRAL EMITTANCE OF FULLY DENSE HfB2 AND ZrB2 WITH SiC, TaSi2, AND LaB6 ADDITIVES Air Force Office...thickened regions with dry 220 grit SiC sandpaper so that a low- resistance electrical connection could be achieved. A handheld multimeter was used to measure

Hydrogeophysical imaging of deposit heterogeneity and groundwater chemistry changes during DNAPL source zone bioremediation.

PubMed

Chambers, J E; Wilkinson, P B; Wealthall, G P; Loke, M H; Dearden, R; Wilson, R; Allen, D; Ogilvy, R D

2010-10-21

Robust characterization and monitoring of dense nonaqueous phase liquid (DNAPL) source zones is essential for designing effective remediation strategies, and for assessing the efficacy of treatment. In this study high-resolution cross-hole electrical resistivity tomography (ERT) was evaluated as a means of monitoring a field-scale in-situ bioremediation experiment, in which emulsified vegetable oil (EVO) electron donor was injected into a trichloroethene source zone. Baseline ERT scans delineated the geometry of the interface between the contaminated alluvial aquifer and the underlying mudstone bedrock, and also the extent of drilling-induced physical heterogeneity. Time-lapse ERT images revealed major preferential flow pathways in the source and plume zones, which were corroborated by multiple lines of evidence, including geochemical monitoring and hydraulic testing using high density multilevel sampler arrays within the geophysical imaging planes. These pathways were shown to control the spatial distribution of the injected EVO, and a bicarbonate buffer introduced into the cell for pH control. Resistivity signatures were observed within the preferential flow pathways that were consistent with elevated chloride levels, providing tentative evidence from ERT of the biodegradation of chlorinated solvents. Copyright © 2010 S. Yamamoto. Published by Elsevier B.V. All rights reserved.

Electrical properties of materials for high temperature strain gage applications

NASA Technical Reports Server (NTRS)

Brittain, John O.

1989-01-01

A study was done on the electrical resistance of materials that are potentially useful as resistance strain gages at high temperatures under static strain conditions. Initially a number of binary alloys were investigated. Later, third elements were added to these alloys, all of which were prepared by arc melting. Several transition metals were selected for experimentation, most prepared as thin films. Difficulties with electrical contacts thwarted efforts to extend measurements to the targeted 1000 C, but results obtained did suggest ways of improving the electrical resistance characteristics of certain materials.

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

Safety Assessment of Multi Purpose Small Payload Rack(MSPR)

NASA Astrophysics Data System (ADS)

Mizutani, Yoshinobu; Takada, Satomi; Murata, Kosei; Ozawa, Daisaku; Kobayashi, Ryoji; Nakamura, Yasuhiro

2010-09-01

We are reporting summary of preliminary safety assessment for Multi Purpose Small Payload Rack(MSPR), which is one of the micro gravity experiment facilities that are being developed for the 2nd phase JEM utilization(JEM: Japanese Experiment Module) that will be launched on H-II Transfer Vehicle(HTV) 2nd flight in 2011. MSPR is used for multi-purpose micro-g experiment providing experimental spaces and work stations. MSPR has three experimental spaces; first, there is a space called Work Volume(WV) with capacity volume of approximately 350 litters, in which multiple resources including electricity, communication, and moving image functions can be used. Within this space, installation of devices can be done by simple, prompt attachment by Velcro and pins with high degree of flexibility. Second, there is Small Experiment Area(SEA), with capacity volume of approximately 70 litters, in which electricity, communication, and moving image functions can also be used in the same way as WV. These spaces protect experiment devices and specimens from contingent loads by the crewmembers. Third, there is Work Bench with area of 0.5 square meters, on which can be used for maintenance, inspection and data operations of installed devices, etc. This bench can be stored in the rack during contingency. Chamber for Combustion Experiment(CCE) that is planned to be installed in WV is a pressure-resistant experimental container that can be used to seal hazardous materials from combustion experiments. This CCE has double sealing design in chamber itself, which resist gas leakage under normal the temperature and pressure. Electricity, communication, moving image function can be used in the same way as WV. JAXA Phase 2 Safety Review Panel(SRP) has been held in April, 2010. For safety analysis of MSPR, hazards were identified based on Fault Tree Analysis methodology and then these hazards were classified into either eight ISS standard-type hazards or eight unique-type hazards that requires special controls based on ISS common safety assessment methodology. Safety evaluation results are reported in the Safety Assessment Report(SAR) 1). Regarding structural failure, unique hazards are especially evaluated considering not only the tolerance for launch load but also load by crewmembers or orbital loads. Regarding electrical shock, electricity design up to secondary power is evaluated in unique hazard from a view point of Electrical design suitable for high voltage(32VDC or more) circuit. Regarding rupture/leakage of pressure system, hazards of fuel supply line, waste line for combustion gas, and pressure system including CCE are evaluated. Also evaluation for contamination due to hazardous gas leakage from CCE is conducted. External propagation of fire from CCE is also evaluated. In this report, we will show the overview of the result of safety assessment and future plan toward critical design phase activity.

The electrical resistance of gold-capped chromium thin films

NASA Astrophysics Data System (ADS)

Ohashi, Masashi; Sawabu, Masaki; Ohashi, Kohei; Miyagawa, Masahiro; Maeta, Kae; Kubota, Takahide; Takanashi, Koki

2018-03-01

We studied the electrical resistance of polycrystalline chromium films capped by a gold layer. No anomaly was detected by resistance measurements of 10 nm thick film around room temperature, indicating that the antiferromagnetic interaction may be suppressed as decreasing the thickness of the chromium film. The sheet resistance Rs (T) curves differ from polycrystalline chromium films in previous studies because of the electrical current flows through a gold capping layer. On the other hand, the resistance drop is observed at T C = 1.15±0.05 K as that of polycrystalline chromium films in the previous report. It means that such resistance drop is not related to the chromium oxide layer on a polycrystalline chromium films. However, it is difficult to conclude that superconducting transition occurs because of the large residual resistance below the temperature where the resistance drop is observed.

Structural, optical and high pressure electrical resistivity studies of pure NiO and Cu-doped NiO nanoparticles

NASA Astrophysics Data System (ADS)

Marselin, M. Abila; Jaya, N. Victor

2016-04-01

In this paper, pure NiO and Cu-doped NiO nanoparticles are prepared by co-precipitation method. The electrical resistivity measurements by applying high pressure on pure NiO and Cu-doped NiO nanoparticles were reported. The Bridgman anvil set up is used to measure high pressures up to 8 GPa. These measurements show that there is no phase transformation in the samples till the high pressure is reached. The samples show a rapid decrease in electrical resistivity up to 5 GPa and it remains constant beyond 5 GPa. The electrical resistivity and the transport activation energy of the samples under high pressure up to 8 GPa have been studied in the temperature range of 273-433 K using diamond anvil cell. The temperature versus electrical resistivity studies reveal that the samples behave like a semiconductor. The activation energies of the charge carriers depend on the size of the samples.

Germanium Resistance Thermometer For Subkelvin Temperatures

NASA Technical Reports Server (NTRS)

Castles, Stephen H.

1993-01-01

Improved germanium resistance thermometer measures temperatures as small as 0.01 K accurately. Design provides large area for electrical connections (to reduce electrical gradients and increase sensitivity to changes in temperatures) and large heat sink (to minimize resistance heating). Gold pads on top and bottom of germanium crystal distribute electrical current and flow of heat nearly uniformly across crystal. Less expensive than magnetic thermometers or superconducting quantum interference devices (SQUID's) otherwise used.

The Development and Application of Simulative Insulation Resistance Tester

NASA Astrophysics Data System (ADS)

Jia, Yan; Chai, Ziqi; Wang, Bo; Ma, Hao

2018-02-01

The insulation state determines the performance and insulation life of electrical equipment, so it has to be judged in a timely and accurate manner. Insulation resistance test, as the simplest and most basic test of high voltage electric tests, can measure the insulation resistance and absorption ratio which are effective criterion of part or whole damp or dirty, breakdown, severe overheating aging and other insulation defects. It means that the electrical test personnel need to be familiar with the principle of insulation resistance test, and able to operate the insulation resistance tester correctly. At present, like the insulation resistance test, most of electrical tests are trained by physical devices with the real high voltage. Although this allows the students to truly experience the test process and notes on security, it also has certain limitations in terms of safety and test efficiency, especially for a large number of new staves needing induction training every year. This paper presents a new kind of electrical test training system based on the simulative device of dielectric loss measurement and simulative electrical testing devices. It can not only overcome the defects of current training methods, but also provide other advantages in economical efficiency and scalability. That makes it possible for the system to be allied in widespread.

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.

Electrical Conductivity Imaging Using Controlled Source Electromagnetics for Subsurface Characterization

NASA Astrophysics Data System (ADS)

Miller, C. R.; Routh, P. S.; Donaldson, P. R.

2004-05-01

Controlled Source Audio-Frequency Magnetotellurics (CSAMT) is a frequency domain electromagnetic (EM) sounding technique. CSAMT typically uses a grounded horizontal electric dipole approximately one to two kilometers in length as a source. Measurements of electric and magnetic field components are made at stations located ideally at least four skin depths away from the transmitter to approximate plane wave characteristics of the source. Data are acquired in a broad band frequency range that is sampled logarithmically from 0.1 Hz to 10 kHz. The usefulness of CSAMT soundings is to detect and map resistivity contrasts in the top two to three km of the Earth's surface. Some practical applications that CSAMT soundings have been used for include mapping ground water resources; mineral/precious metals exploration; geothermal reservoir mapping and monitoring; petroleum exploration; and geotechnical investigations. Higher frequency data can be used to image shallow features and lower frequency data are sensitive to deeper structures. We have a 3D CSAMT data set consisting of phase and amplitude measurements of the Ex and Hy components of the electric and magnetic fields respectively. The survey area is approximately 3 X 5 km. Receiver stations are situated 50 meters apart along a total of 13 lines with 8 lines bearing approximately N60E and the remainder of the lines oriented orthogonal to these 8 lines. We use an unconstrained Gauss-Newton method with positivity to invert the data. Inversion results will consist of conductivity versus depth profiles beneath each receiver station. These 1D profiles will be combined into a 3D subsurface conductivity image. We will include our interpretation of the subsurface conductivity structure and quantify the uncertainties associated with this interpretation.

Coaxial Electric Heaters

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

2008-01-01

Coaxial electric heaters have been conceived for use in highly sensitive instruments in which there are requirements for compact heaters but stray magnetic fields associated with heater electric currents would adversely affect operation. Such instruments include atomic clocks and magnetometers that utilize heated atomic-sample cells, wherein stray magnetic fields at picotesla levels could introduce systematic errors into instrument readings. A coaxial electric heater is essentially an axisymmetric coaxial cable, the outer conductor of which is deliberately made highly electrically resistive so that it can serve as a heating element. As in the cases of other axisymmetric coaxial cables, the equal magnitude electric currents flowing in opposite directions along the inner and outer conductors give rise to zero net magnetic field outside the outer conductor. Hence, a coaxial electric heater can be placed near an atomic-sample cell or other sensitive device. A coaxial electric heater can be fabricated from an insulated copper wire, the copper core of which serves as the inner conductor. For example, in one approach, the insulated wire is dipped in a colloidal graphite emulsion, then the emulsion-coated wire is dried to form a thin, uniform, highly electrically resistive film that serves as the outer conductor. Then the film is coated with a protective layer of high-temperature epoxy except at the end to be electrically connected to the power supply. Next, the insulation is stripped from the wire at that end. Finally, electrical leads from the heater power supply are attached to the exposed portions of the wire and the resistive film. The resistance of the graphite film can be tailored via its thickness. Alternatively, the film can be made from an electrically conductive paint, other than a colloidal graphite emulsion, chosen to impart the desired resistance. Yet another alternative is to tailor the resistance of a graphite film by exploiting the fact that its resistance can be changed permanently within about 10 percent by heating it to a temperature above 300 C. A coaxial heater, with electrical leads attached, that has been bent into an almost full circle for edge heating of a circular window is shown. (In the specific application, there is a requirement for a heated cell window, through which an optical beam enters the cell.)

Anatomy of a lava dome using muon radiography and electrical resistivity tomography

NASA Astrophysics Data System (ADS)

Lenat, J.

2011-12-01

For the TOMUVOL Collaboration Previous works (e.g. Tanaka et al., 2008) have demonstrated the capacity of muon radiography techniques to image the internal structure of volcanoes. The method is based on the attenuation of the flux of high energy atmospheric muons through a volcanic edifice, which is measured by a muon telescope installed at some distance from the volcano. The telescope is composed of three parallel matrices of detectors in order to record the angle of incidence of the muons. The aperture of the telescope and its resolution are determined by the distance between the matrices, their surface and their segmentation. TOMUVOL is a project, involving astroparticle and particle physicists and volcanologists, aimed at developing muon tomography of volcanoes. The ultimate goal is to construct autonomous, portable, remote controlled muon telescopes to study and monitor active volcanoes. A first experiment has been carried out on a large, 11000-year-old, trachytic dome, the Puy de Dôme, located in the French Central Massif. The telescope system is derived from particle physics experiments. The sensors are glass resistive plate chambers. The telescope has two 1 m2 and one 1/6 m2 planes. It is located 2 km away from the summit of Puy de Dôme (elevation 1465 m), at 868 m in elevation, Signals have been accumulated during several months. A high resolution LiDAR digital terrain model has been used in computing a density model of the dome, averaged along the path of the muons through the dome. In parallel, an electrical resistivity section of the dome has been obtained using a long (2.2 km) line of electrodes. The internal structure of the dome is thus described with two physical parameters (density and resistivity). This allows us to analyse jointly the results of the two types of measurements. At the time of writing, a new muon radiography campaign is being carried out from a different viewpoint. This is the first step towards a tomographic image of the volcano's internal structure. Reference: Tanaka, H. K. M., T. Nakano, S. Takahashi, J. Yoshida, M. Takeo, J. Oikawa, T. Ohminato, Y. Aoki, E. Koyama, H. Tsuji, H. Ohshima, T. Maekawa, H. Watanabe, and K. Niwa, Radiographic imaging below a volcanic crater floor with cosmic-ray muons, Am. J. Sci., 308, 843-850, 2008.

Structure-from-Motion (SfM) and Electrical Resistivity Tomography (ERT) evaluation of the Ohuka landslide, North Island, New Zealand

NASA Astrophysics Data System (ADS)

Brook, Martin; Bevan, David; Prebble, Warwick; Tunnicliffe, Jon; Richards, Nick

2017-04-01

Globally, slope failures cause many thousands of deaths per year and damage infrastructure, costing billions of dollars to repair. There is a clear need for efficient and affordable techniques that can assess and evaluate ongoing slope instability. Of particular importance when assessing and evaluating ongoing landslide deformation is the availability of high-resolution Digital Surface Models (DSMs). Here, we applied the Structure-from-Motion (SfM) approach to low-altitude aerial images collected by an unmanned aerial vehicle (UAV) at the Ohuka coastal landslide on the North Island of New Zealand. The SfM image-based approach was selected as a mapping tool in order to provide a rapid, cost-effective, and highly automated method, generating high-resolution topography and coregistered texture (colour) from an unstructured set of overlapping photographs taken from varying viewpoints. This overcomes many of the cost, time, and logistical limitations of LiDAR and other topographic surveying methods. The SfM photogrammetry was undertaken in conjunction with Electrical Resistivity Tomography (ERT) to image the subsurface and provide an interpretation of the hydrogeology, due to the technique's high sensitivity to lateral and vertical changes in moisture content. Landslide features include a large arcuate scarp, flanked by gullies, which indicate the lateral boundaries of initial slope failure. Other topographic features include a 200 m wide bench with uphill-facing scarps, pull-apart zones, and surface flows from ongoing reactivation. ERT has proved useful in imaging the near-surface moisture movement driving the landsliding processes. Failure mechanisms include block-sliding along a clay seam in the early-Miocene Koheroa siltstone, and weathered deposits of the c. 1 Ma Kidnappers tephra. Cyclic variation in moisture content and formation of perched water tables above clay and tephra seam aquitards plays a key role in reactivation.

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 interpretation. Geometry and location of ERT profiles on the Puy de Dôme volcano allow to compute 3D inversion models of the electrical resistivity distribution with a new inversion code. This code uses tetrahedrons to discretize the 3D model and uses also a conventional Gauss-Newton inversion scheme combined to an Occam regularisation to process the data. It allows to take into account all the data information and prevents the construction of 3D artefacts present in conventional 2D inversion results. Inversion results show a strong electrical resistivity heterogeneity of the entire dome. Underlying volcanic edifices are clearly identified below the lava dome. Generally speaking, the flanks of the volcano show high resistivity values, and the summit part is more conductive but also very heterogeneous.

An Integration of Geophysical Methods to Explore Buried Structures on the Bench and in the Field

NASA Astrophysics Data System (ADS)

Booterbaugh, A. P.; Lachhab, A.

2011-12-01

In the following study, an integration of geophysical methods and devices were implemented on the bench and in the field to accurately identify buried structures. Electrical resistivity and ground penetrating radar methods, including both a fabricated electrical resistivity apparatus and an electrical resistivity device were all used in this study. The primary goal of the study was to test the accuracy and reliability of the apparatus which costs a fraction of the price of a commercially sold resistivity instrument. The apparatus consists of four electrodes, two multimeters, a 12-volt battery, a DC to AC inverter and wires. Using this apparatus, an electrical current, is injected into earth material through the outer electrodes and the potential voltage is measured across the inner electrodes using a multimeter. The recorded potential and the intensity of the current can then be used to calculate the apparent resistivity of a given material. In this study the Wenner array, which consists of four equally spaced electrodes, was used due to its higher accuracy and greater resolution when investigating lateral variations of resistivity in shallow depths. In addition, the apparatus was used with an electrical resistivity device and a ground penetrating radar unit to explore the buried building foundation of Gustavus Adolphus Hall located on Susquehanna University Campus, Selinsgrove, PA. The apparatus successfully produced consistent results on the bench level revealing the location of small bricks buried under a soil material. In the summer of 2010, seventeen electrical resistivity transects were conducted on the Gustavus Adolphus site where and revealed remnants of the foundation. In the summer of 2011, a ground penetrating radar survey and an electrical resistivity tomography survey were conducted to further explore the site. Together these methods identified the location of the foundation and proved that the apparatus was a reliable tool for regular use on the bench and in the field.

Resistance probe for energetic particle dosimetry

DOEpatents

Wampler, W.R.

A probe for determining the energy and flux of particles in a plasma comprises a carbon film adapted to be exposed to the plasma, the film having an electrical resistance which is related to the number of particles impacting the film, contacts for passing an electrical current throught the film, and contacts for determining the electrical resistance of the film. An improved method for determining the energy or flux of particles in a plasma is also disclosed.

Resistance probe for energetic particle dosimetry

DOEpatents

Wampler, William R.

1988-01-01

A probe for determining the energy and flux of particles in a plasma comprises a carbon film adapted to be exposed to the plasma, the film havinmg an electrical resistance which is related to the number of particles impacting the film, contacts for passing an electrical current through the film, and contacts for determining the electrical resistance of the film. An improved method for determining the energy or flux of particles in a plasma is also disclosed.

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.

Low temperature resistivity studies of SmB6: Observation of two-dimensional variable-range hopping conductivity

NASA Astrophysics Data System (ADS)

Batkova, Marianna; Batko, Ivan; Gabáni, Slavomír; Gažo, Emil; Konovalova, Elena; Filippov, Vladimir

2018-05-01

We studied electrical resistance of a single-crystalline SmB6 sample with a focus on the region of the "low-temperature resistivity plateau". Our observations did not show any true saturation of the electrical resistance at temperatures below 3 K down to 70 mK. According to our findings, temperature dependence of the electrical conduction in a certain temperature interval above 70 mK can be decomposed into a temperature-independent term and a temperature-activated term that can be described by variable-range hopping formula for two-dimensional systems, exp [ -(T0 / T) 1 / 3 ]. Thus, our results indicate importance of hopping type of electrical transport in the near-surface region of SmB6.

Micromachined capacitive ultrasonic immersion transducer array

NASA Astrophysics Data System (ADS)

Jin, Xuecheng

Capacitive micromachined ultrasonic transducers (cMUTs) have emerged as an attractive alternative to conventional piezoelectric ultrasonic transducers. They offer performance advantages of wide bandwidth and sensitivity that have heretofore been attainable. In addition, micromachining technology, which has benefited from the fast-growing microelectronics industry, enables cMUT array fabrication and electronics integration. This thesis describes the design and fabrication of micromachined capacitive ultrasonic immersion transducer arrays. The basic transducer electrical equivalent circuit is derived from Mason's theory. The effects of Lamb waves and Stoneley waves on cross coupling and acoustic losses are discussed. Electrical parasitics such as series resistance and shunt capacitance are also included in the model of the transducer. Transducer fabrication technology is systematically studied. Device dimension control in both vertical and horizontal directions, process alternatives and variations in membrane formation, via etch and cavity sealing, and metalization as well as their impact on transducer performance are summarized. Both 64 and 128 element 1-D array transducers are fabricated. Transducers are characterized in terms of electrical input impedance, bandwidth, sensitivity, dynamic range, impulse response and angular response, and their performance is compared with theoretical simulation. Various schemes for cross coupling reduction is analyzed, implemented, and verified with both experiments and theory. Preliminary results of immersion imaging are presented using 64 elements 1-D array transducers for active source imaging.

MoisturEC: A New R Program for Moisture Content Estimation from Electrical Conductivity Data.

PubMed

Terry, Neil; Day-Lewis, Frederick D; Werkema, Dale; Lane, John W

2018-03-06

Noninvasive geophysical estimation of soil moisture has potential to improve understanding of flow in the unsaturated zone for problems involving agricultural management, aquifer recharge, and optimization of landfill design and operations. In principle, several geophysical techniques (e.g., electrical resistivity, electromagnetic induction, and nuclear magnetic resonance) offer insight into soil moisture, but data-analysis tools are needed to "translate" geophysical results into estimates of soil moisture, consistent with (1) the uncertainty of this translation and (2) direct measurements of moisture. Although geostatistical frameworks exist for this purpose, straightforward and user-friendly tools are required to fully capitalize on the potential of geophysical information for soil-moisture estimation. Here, we present MoisturEC, a simple R program with a graphical user interface to convert measurements or images of electrical conductivity (EC) to soil moisture. Input includes EC values, point moisture estimates, and definition of either Archie parameters (based on experimental or literature values) or empirical data of moisture vs. EC. The program produces two- and three-dimensional images of moisture based on available EC and direct measurements of moisture, interpolating between measurement locations using a Tikhonov regularization approach. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Sample support and resistivity imaging interpretation

NASA Astrophysics Data System (ADS)

Bentley, L. R.; Gharibi, M.

2003-04-01

Three-D Electrical Resistivity Imaging (ERI) is a powerful technique that can be used to improve site characterization. In order to integrate ERI with other site characterization measurements such as soil and water chemistry, it is necessary to understand the sample support of various data. We have studied a decommissioned sour gas processing plant which has experienced releases of glycol and amine. Ammonium and acetic acid are degradation products that cause elevated electrical conductivity (EC) in groundwater and soils.The site is underlain by glacial till that is fractured and has thin sand lenses. 3-D ERI inversion results, direct push tool EC and core EC from the same location are well correlated. However, groundwater EC from piezometer installations are poorly correlated with ERI EC. We hypothesize that the ERI, direct push and core EC are mainly meausuring relatively immobile pore water EC in the fine grain matrix. Piezometer water is derived from mobile groundwater that travels in preferred flow paths such as fractures and higher permeability sand lenses. Due to dewatering and other remediation efforts, the mobile groundwater can have a different chemistry, concentration and EC than the immobile pore water. Consequently, the sample support is different for the groundwater samples and the difference explains the poor correlation between ERI EC and groundwater sample EC. In this particular case, we have the potential to monitor the chemical evolution of the source areas, but cannot use ERI to monitor the chemical evolution of mobile groundwater.

Transfer of Wire Arc-Sprayed Metal Coatings onto Plastic Parts

NASA Astrophysics Data System (ADS)

Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Hopmann, Ch.; Ochotta, P.

2018-01-01

By means of In-Mold-Metal-Spraying (IMMS), metal coatings deposited by means of arc spraying process (ASP) can be transferred onto plastic parts during injection molding, thus realizing an efficient production of metallized plastic parts. Parts produced by means of IMMS can be used in electrical applications. In the current study, the electrical resistivity of coatings applied with different feedstock materials was determined. As a starting point, pressurized air is used as atomizing gas for ASP. In contrast to Zn coatings, Cu coatings applied with pressurized air exhibit a significantly higher electrical resistivity in comparison with massive material. One possible reason is the more pronounced oxidation of Cu particles during ASP. Therefore, N2 and a mixture of N2 and H2 were used as atomizing gas. As a result, the electrical resistivity of coatings applied by means of IMMS could be significantly reduced. Furthermore, standoff distance, current and pressure of the atomizing gas were varied to investigate the influence of these process parameters on the electrical resistivity of Zn coatings using a full factorial experiment design with center point. It can be observed that the electrical resistivity of the Zn coatings increases with decreasing current and increasing standoff distance and pressure.

Transfer of Wire Arc-Sprayed Metal Coatings onto Plastic Parts

NASA Astrophysics Data System (ADS)

Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Hopmann, Ch.; Ochotta, P.

2017-12-01

By means of In-Mold-Metal-Spraying (IMMS), metal coatings deposited by means of arc spraying process (ASP) can be transferred onto plastic parts during injection molding, thus realizing an efficient production of metallized plastic parts. Parts produced by means of IMMS can be used in electrical applications. In the current study, the electrical resistivity of coatings applied with different feedstock materials was determined. As a starting point, pressurized air is used as atomizing gas for ASP. In contrast to Zn coatings, Cu coatings applied with pressurized air exhibit a significantly higher electrical resistivity in comparison with massive material. One possible reason is the more pronounced oxidation of Cu particles during ASP. Therefore, N2 and a mixture of N2 and H2 were used as atomizing gas. As a result, the electrical resistivity of coatings applied by means of IMMS could be significantly reduced. Furthermore, standoff distance, current and pressure of the atomizing gas were varied to investigate the influence of these process parameters on the electrical resistivity of Zn coatings using a full factorial experiment design with center point. It can be observed that the electrical resistivity of the Zn coatings increases with decreasing current and increasing standoff distance and pressure.

Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruverman, Alexei; Tsymbal, Evgeny Y.; Eom, Chang-Beom

2017-05-03

This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modelingmore » of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.« less

The electrical resistivity and percolation threshold of MWCNTs/polymer composites filled with a few aligned carbonyl iron particles

NASA Astrophysics Data System (ADS)

Dong, Shuai; Wang, Xiaojie

2018-03-01

Conductive polymer composites (CPCs) consist of multi-walled carbon nanotubes (MWCNTs), a few carbonyl iron particles (CIPs) and polydimethylsiloxane (PDMS) are fabricated under a moderate magnetic field. The alignment of CIPs will change the structure of MWCNT network, and consequently the electrical properties of CPCs. The volume fraction of CIPs is fixed at 0.08 vol% at which CIPs will not directly participate in electric conduction. The electrical resistivity of CPCs and the changes of resistance versus strain are evaluated at various MWCNT volume fractions. The testing results show that a percolation threshold as low as 0.19 vol% is obtained due to the effect of aligned CIPs, comparing with 0.39 vol% of isotropic MWCNT/CIP/PDMS (prepared without magnetic field). Meanwhile, the anisotropic structure reduces the electrical resistivity by more than 80% when the MWCNT volume fractions is over the percolation threshold.

The effect of mechanical stress on electric resistance of nanographite-epoxy composites

NASA Astrophysics Data System (ADS)

Vovchenko, L.; Lazarenko, A.; Matzui, L.; Zhuravkov, A.

2012-03-01

The in-plane electric resistance Ra of composite materials (CMs) thermoexfoliated graphite(TEG)-epoxy resin(ED) under compression along compacting C-axis has been investigated by four-probe method. TEG content was 5-75 wt%. It was shown that specimens prepared by cold pressing are denser and reveal lower values of electric resistivity in comparison with specimens prepared by pouring. It was found that compression of the specimens leads to plastic deformation of specimens (εpl) and essential irreversible decrease of electric resistance during the first cycle of loading (up to 50 MPa), especially for the poured specimens with low density. Within the proposed model the contact resistance Rk between graphite particles in CM has been evaluated and it was shown that it increased with the decrease in TEG content in CM and depends on compacting method of CMs and the dispersity of graphite filler.

Conductive Textiles via Vapor-Phase Polymerization of 3,4-Ethylenedioxythiophene.

PubMed

Ala, Okan; Hu, Bin; Li, Dapeng; Yang, Chen-Lu; Calvert, Paul; Fan, Qinguo

2017-08-30

We fabricated electrically conductive textiles via vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) layers on cotton, cotton/poly(ethylene terephthalate) (PET), cotton/Lycra, and PET fabrics. We then measured the electrical resistivity values of such PEDOT-coated textiles and analyzed the effect of water treatment on the electrical resistivity. Additionally, we tested the change in the electrical resistance of the conductive textiles under cyclic stretching and relaxation. Last, we characterized the uniformity and morphology of the conductive layer formed on the fabrics using scanning electron microscopy and electron-dispersive X-ray spectroscopy.

Research on HOPE communication and data processing equipment

NASA Astrophysics Data System (ADS)

Yamamoto, Satoru; Kikuchi, Toshio

1992-08-01

An overview of the research on heat-resisting antenna is presented. Candidate heat-resisting antennas which were selected as the result of review on seven kinds of antenna are the antennas of micro strip, cavity, and horn types. Heat resistance characteristics of electric power supplying section (connectors) of heat-resisting antenna were studied. Heat cycling test and heat shock tests were conducted on the subject plugs and it was confirmed that they can be usable at - 80 C to + 200 C against - 65 C to + 125 C for the existing plugs. Fundamental electric data such as antenna pattern were acquired mating trial produced components simulating electric characteristics of heat-resisting antenna and trial-produced ceramic tiles.

Parallel Infrastructure Modeling and Inversion Module for E4D

DOE Office of Scientific and Technical Information (OSTI.GOV)

2014-10-09

Electrical resistivity tomography ERT is a method of imaging the electrical conductivity of the subsurface. Electrical conductivity is a useful metric for understanding the subsurface because it is governed by geomechanical and geochemical properties that drive subsurface systems. ERT works by injecting current into the subsurface across a pair of electrodes, and measuring the corresponding electrical potential response across another pair of electrodes. Many such measurements are strategically taken across an array of electrodes to produce an ERT data set. These data are then processed through a computationally demanding process known as inversion to produce an image of the subsurfacemore » conductivity structure that gave rise to the measurements. Data can be inverted to provide 2D images, 3D images, or in the case of time-lapse 3D imaging, 4D images. ERT is generally not well suited for environments with buried electrically conductive infrastructure such as pipes, tanks, or well casings, because these features tend to dominate and degrade ERT images. This reduces or eliminates the utility of ERT imaging where it would otherwise be highly useful for, for example, imaging fluid migration from leaking pipes, imaging soil contamination beneath leaking subusurface tanks, and monitoring contaminant migration in locations with dense network of metal cased monitoring wells. The location and dimension of buried metallic infrastructure is often known. If so, then the effects of the infrastructure can be explicitly modeled within the ERT imaging algorithm, and thereby removed from the corresponding ERT image. However,there are a number of obstacles limiting this application. 1) Metallic infrastructure cannot be accurately modeled with standard codes because of the large contrast in conductivity between the metal and host material. 2) Modeling infrastructure in true dimension requires the computational mesh to be highly refined near the metal inclusions, which increases computational demands. 3) The ERT imaging algorithm requires specialized modifications to accomodate high conductivty inclusions within the computational mesh. The solution to each of these challenges was implemented within E4D (formerly FERM3D), which is a parallel ERT imaging code developed at PNNL (IPID #30249). The infrastructure modeling module implement in E4D uses a method of decoupling the model at the metallic interface(s) boundaries, into several well posed sub-problems (one for each distinct metallicinclusion) that are subsequently solved and recombined to form the global solution. The approach is based on the immersed interface method, with has been applied for similar problems in other fields (e.g. semiconductor industry). Comparisons to analytic solutions have shown the results to be very accurate, addressing item 1 above. The solution is implemented about an unstructured mesh, which enables arbitrary shapes to be efficiently modelled, thereby addressing item 2 above. In addition, the algorithm is written in parallel and shows excellent scalability, which also addresses equation 2 above. Finally, because only the boundaries of metallic inclusions are modeled, there are no high conductivity cells within the modeling mesh, and the problem described by item 3 above is no longer applicable.« less

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

DOEpatents

Phelps, Amanda C [Malibu, CA; Kirby, Kevin K [Calabasas Hills, CA; Gregoire, Daniel J [Thousand Oaks, CA

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.

Concentration dependence of electrical resistivity of binary liquid alloy HgZn: Ab-initio study

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-06-01

The electrical resistivity of HgZn liquid alloy has been made calculated using Troullier and Martins ab-initio pseudopotential as a function of concentration. Hard sphere diameters of Hg and Zn are obtained through the inter-ionic pair potential have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. These results suggest that ab-initio approach for calculating electrical resistivity is quite successful in explaining the electronic transport properties of binary Liquid alloys.

Modeling the electrical resistance of gold film conductors on uniaxially stretched elastomeric substrates

NASA Astrophysics Data System (ADS)

Cao, Wenzhe; Görrn, Patrick; Wagner, Sigurd

2011-05-01

The electrical resistance of gold film conductors on polydimethyl siloxane substrates at stages of uniaxial stretching is measured and modeled. The surface area of a gold conductor is assumed constant during stretching so that the exposed substrate takes up all strain. Sheet resistances are calculated from frames of scanning electron micrographs by numerically solving for the electrical potentials of all pixels in a frame. These sheet resistances agree sufficiently well with values measured on the same conductors to give credence to the model of a stretchable network of gold links defined by microcracks.

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.

MOM3D method of moments code theory manual

NASA Technical Reports Server (NTRS)

Shaeffer, John F.

1992-01-01

MOM3D is a FORTRAN algorithm that solves Maxwell's equations as expressed via the electric field integral equation for the electromagnetic response of open or closed three dimensional surfaces modeled with triangle patches. Two joined triangles (couples) form the vector current unknowns for the surface. Boundary conditions are for perfectly conducting or resistive surfaces. The impedance matrix represents the fundamental electromagnetic interaction of the body with itself. A variety of electromagnetic analysis options are possible once the impedance matrix is computed including backscatter radar cross section (RCS), bistatic RCS, antenna pattern prediction for user specified body voltage excitation ports, RCS image projection showing RCS scattering center locations, surface currents excited on the body as induced by specified plane wave excitation, and near field computation for the electric field on or near the body.

Silicon switching transistor with high power and low saturation voltage

NASA Technical Reports Server (NTRS)

Stonebraker, E.; Stoneburner, D.; Ferree, H.

1973-01-01

Assembly of two individually encapsulated silicon-chip transistors produces silicon power-transistor that has low electrical resistance and low thermal impedance. Electrical resistance and thermal impedance are low because of short lead lengths, and external contact surfaces are plated to reduce resistance at interfaces.

Three-dimensional electrical impedance tomography: a topology optimization approach.

PubMed

Mello, Luís Augusto Motta; de Lima, Cícero Ribeiro; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez; Silva, Emílio Carlos Nelli

2008-02-01

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.

Evaluation of groundwater and soil pollution in a landfill area using electrical resistivity imaging survey.

PubMed

Ahmed, A M; Sulaiman, W N

2001-11-01

Landfills are sources of groundwater and soil pollution due to the production of leachate and its migration through refuse. This study was conducted in order to determine the extent of groundwater and soil pollution within and around the landfill of Seri Petaling located in the State of Selangor, Malaysia. The condition of nearby surface water was also determined. An electrical resistivity imaging survey was used to investigate the leachate production within the landfill. Groundwater geochemistry was carried out and chemical analysis of water samples was conducted upstream and downstream of the landfill. Surface water was also analyzed in order to determine its quality. Soil chemical analysis was performed on soil samples taken from different locations within and around the landfill in the vadose zone (unsaturated zone) and below the water table (in the soil saturated zone). The resistivity image along line L-L1 indicated the presence of large zones of decomposed waste bodies saturated with highly conducting leachate. Analysis of trace elements indicated their presence in very low concentrations and did not reflect any sign of heavy metal pollution of ground and surface water or of soil. Major ions represented by Na, K, and Cl were found in anomalous concentrations in the groundwater of the downstream bore hole, where they are 99.1%, 99.2%, and 99.4%, respectively, higher compared to the upstream bore hole. Electrical conductivity (EC) was also found in anomalous concentration downstream. Ca and Mg ions represent the water hardness (which is comparatively high downstream). There is a general trend of pollution towards the downstream area. Sulfates (SO4) and nitrates (NO3) are found in the area in low concentrations, even below the WHO standards for drinking water, but are significantly higher in the surface water compared to the groundwater. Phosphate (PO4) and nitrite (NO2), although present in low levels, are significantly higher at the downstream. There is no significant difference in the amount of fluoride (F) in the different locations. In the soil vadose zone, heavy metals were found to be in their typical normal ranges and within the background concentrations. Soil exchangeable bases were significantly higher in the soil saturated zone compared to the vadose zone, and no significant difference was obtained in the levels of inorganic pollutants. With the exception of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of Seri Petaling landfill soils were below the upper limits of baseline concentrations published from different sources.

Two different electrical properties can improve transoceanic cable-route mapping

USGS Publications Warehouse

Wynn, J.; McGinnis, T.

2001-01-01

Induced polarization (IP) measurements made in the marine environment were investigated to map and remotely characterize the top 6-10 meters of the seafloor. The continuous resistivity profiling with cone-penetrometer tests, providing important information to engineers planning transoceanic cable routes, was also described. The IP effect and resistivity were identified as the two electric properties to improve transoceanic cable-route mapping. The measurement of IP and resistivity was found to depend on electrical current.

Electrical Resistivity of Vanadium and Zirconium.

DTIC Science & Technology

1982-12-01

general agreement on the temperature depodeace of the electrical resistivity. There are little good data from 300 VI to 1200 K. The recommended values...liquid region, are based on the compromise between the only two data sets available. due to Seydel and Fucks [91 (data set 1) and to Gathers et al. (101...555-600 (1928). 8. Block. F., ’The Electrical Resistance Law at Low Temperatures,’ Z. Phys.. 12.208-14 (1930). -𔄃. Seydel, U. and Fucke , W

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 remarkable correlation with the image obtained from surface data but indicate that the electrically derived mass fraction of pure seawater could not be recovered due to the discrepancy between the in-situ and laboratory-derived petrophysical relationships. Inversion of hydrologic model parameters using the field ERT image was not possible due to the inadequacy of a 2D representation of the geology at the site. Using ERT-derived data to estimate hydrological parameters requires to address resolution loss issues and the non-stationarity of the petrophysical relationship. The first issue may be approached using objective criteria. The most crucial limitation, however, is probably the non-stationarity of the petrophysical relationship. This is currently being investigated using more realistic models based on geostatistical modeling (SGeMS) of the petrophysical properties of a coastal aquifer and for transient simulations.

Regional two-dimensional magnetotelluric profile in West Bohemia/Vogtland reveals deep conductive channel into the earthquake swarm region

NASA Astrophysics Data System (ADS)

Muñoz, Gerard; Weckmann, Ute; Pek, Josef; Kováčiková, Světlana; Klanica, Radek

2018-03-01

The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohře) Rift and the Mariánské Lázně fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublák and Hartoušov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Nový Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mýtina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Teplá-Barrandian zones, whose surface expression is located only a few kilometres away.

Electromagnetic constraints on a melt region beneath the central Mariana back-arc spreading ridge

NASA Astrophysics Data System (ADS)

Matsuno, Tetsuo; Evans, Rob L.; Seama, Nobukazu; Chave, Alan D.

2012-10-01

An electrical resistivity profile across the central Mariana subduction system shows high resistivity in the upper mantle beneath the back-arc spreading ridge where melt might be expected to exist. Although seismic data are equivocal on the extent of a possible melt region, the question arises as to why a 2-D magnetotelluric (MT) survey apparently failed to image any melt. We have run forward models and inversions that test possible 3-D melt geometries that are consistent with the MT data and results of other studies from the region, and that we use to place upper bounds on the possible extent of 3-D melt region beneath the spreading center. Our study suggests that the largest melt region that was not directly imaged by the 2-D MT data, but that is compatible with the observations as well as the likely effects of melt focusing, has a 3-D shape on a ridge-segment scale focused toward the spreading center and a resistivity of 100 Ω-m that corresponds to ˜0.1-˜1% interconnected silicate melt embedded in a background resistivity of ˜500 Ω-m. In contrast to the superfast spreading southern East Pacific Rise, the 3-D melt region suggests that buoyant mantle upwelling on a ridge-segment scale is the dominant process beneath the slow-spreading central Mariana back-arc. A final test considers whether the inability to image a 3-D melt region was a result of the 2-D survey geometry. The result reveals that the 2-D transect completed is useful to elucidate a broad range of 3-D melt bodies.

Monitoring a pilot CO2 injection experiment in a shallow aquifer using 3D cross-well electrical resistance tomography

NASA Astrophysics Data System (ADS)

Yang, X.; Lassen, R. N.; Looms, M. C.; Jensen, K. H.

2014-12-01

Three dimensional electrical resistance tomography (ERT) was used to monitor a pilot CO2 injection experiment at Vrøgum, Denmark. The purpose was to evaluate the effectiveness of the ERT method for monitoring the two opposing effects from gas-phase and dissolved CO2 in a shallow unconfined siliciclastic aquifer. Dissolved CO2 increases water electrical conductivity (EC) while gas phase CO2 reduce EC. We injected 45kg of CO2 into a shallow aquifer for 48 hours. ERT data were collected for 50 hours following CO2 injection. Four ERT monitoring boreholes were installed on a 5m by 5m square grid and each borehole had 24 electrodes at 0.5 m electrode spacing at depths from 1.5 m to 13 m. ERT data were inverted using a difference inversion algorithm for bulk EC. 3D ERT successfully detected the CO2 plume distribution and growth in the shallow aquifer. We found that the changes of bulk EC were dominantly positive following CO2 injection, indicating that the effect of dissolved CO2 overwhelmed that of gas phase CO2. The pre-injection baseline resistivity model clearly showed a three-layer structure of the site. The electrically more conductive glacial sand layer in the northeast region are likely more permeable than the overburden and underburden and CO2 plumes were actually confined in this layer. Temporal bulk EC increase from ERT agreed well with water EC and cross-borehole ground penetrating radar data. ERT monitoring offers a competitive advantage over water sampling and GPR methods because it provides 3D high-resolution temporal tomographic images of CO2 distribution and it can also be automated for unattended operation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC. LLNL IM release#: LLNL-PROC-657944.

Resistive spectroscopy coupled with non-contacting oscillator for detecting discontinuous-continuous transition of metallic films

NASA Astrophysics Data System (ADS)

Nakamura, N.; Ogi, H.

2017-09-01

In spectroscopic measurements, one measures responses of specimens to oscillating fields (including electric, magnetic, and stress fields) at different frequencies for characterizing the samples. In contrast, we develop spectroscopy where the response (loss) is measured by changing the electric resistance, named the resistive spectroscopy. In the resistive spectroscopy, an energy-loss peak appears when the resistance is changed. We here apply it for studying the morphological change of thin films. When a metallic material is deposited on a substrate, the morphological transition from discontinuous islands to the continuous film occurs. It accompanies a drastic change in the resistance of the deposited material because of the transition from an insulator to a conductor. We find that the energy-loss peak appears at the transition moment during deposition of Ag. The resistive spectroscopy we develop uses no electrodes; it adopts the electric field generated by a piezoelectric material vibrating at its resonant frequency beneath the substrate. It is observed that the full width at half maximum (FWHM) of the resonance shows the peak during the deposition for high resistance substrates. The FWHM peak fails to be found for low resistance substrates, but it appears when the resonance frequency is increased. We propose an electrical-circuit model for explaining these observations.

Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor.

PubMed

Jaafar, W M N Wan; Snyder, J E; Min, Gao

2013-05-01

An apparatus for measuring the Seebeck coefficient (α) and electrical resistivity (ρ) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring α and ρ of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C-100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 μVK(-1) (-12.5%) for the Seebeck coefficient and -0.4 μΩ cm (-4.6%) for the electrical resistivity, respectively.

Study on strength estimation of soil cement used in the embedded pile method by electrical resistivity measurement

NASA Astrophysics Data System (ADS)

Mochida, Y.; Sakurai, Y.; Indra, H.; Karimi, A. L.

2017-11-01

Problems caused by poor quality control and quality assurance of the pre-boring embedded pile construction, such as on domestic apartment house is still occurring nowadays. An adequate consideration for invisible risks inside or below the ground is important in pile foundation construction therefore the demand for advanced and reliable quality assurance is increase in the future. In this research, to understand the quality of the construction at early stage, the compressive strength of cement-soil mixture of pile construction after 28 days is estimated using electrical resistivity value of the mixture. More accurate measurement for electrical resistivity value is conducted by inserting the electrodes without using potassium chloride solution as a catalyst. The result showed that there is a certain tendency in the electric resistivity value at the early age regarding to the type of soil (sand, clay) mixed in. The most accurate estimation was achieved from the electric resistivity value at the first day and several days onwards, and from the compressive strength after 3 days.

Geophysical characterization of Range-Front Faults, Snake Valley, Nevada

USGS Publications Warehouse

Asch, Theodore H.; Sweetkind, Donald S.

2010-01-01

In September 2009, the U.S. Geological Survey, in cooperation with the National Park Service, collected audiomagnetotelluric (AMT) data along two profiles on the eastern flank of the Snake Range near Great Basin National Park to refine understanding of the subsurface geology. Line 1 was collected along Baker Creek, was approximately 6.7-km long, and recorded subsurface geologic conditions to approximately 800-m deep. Line 2, collected farther to the southeast in the vicinity of Kious Spring, was 2.8-km long, and imaged to depths of approximately 600 m. The two AMT lines are similar in their electrical response and are interpreted to show generally similar subsurface geologic conditions. The geophysical response seen on both lines may be described by three general domains of electrical response: (1) a shallow (mostly less than 100-200-m deep) domain of highly variable resistivity, (2) a deep domain characterized by generally high resistivity that gradually declines eastward to lower resistivity with a steeply dipping grain or fabric, and (3) an eastern domain in which the resistivity character changes abruptly at all depths from that in the western domain. The shallow, highly variable domain is interpreted to be the result of a heterogeneous assemblage of Miocene conglomerate and incorporated megabreccia blocks overlying a shallowly eastward-dipping southern Snake Range detachment fault. The deep domain of generally higher resistivity is interpreted as Paleozoic sedimentary rocks (Pole Canyon limestone and Prospect Mountain Quartzite) and Mesozoic and Cenozoic plutonic rocks occurring beneath the detachment surface. The range of resistivity values within this deep domain may result from fracturing adjacent to the detachment, the presence of Paleozoic rock units of variable resistivities that do not crop out in the vicinity of the lines, or both. The eastern geophysical domain is interpreted to be a section of Miocene strata at depth, overlain by Quaternary alluvial fill. These deposits lie east of a steeply east-dipping normal fault that cuts all units and has about 100 m of east-side-down offset.

Lead-free epitaxial ferroelectric material integration on semiconducting (100) Nb-doped SrTiO3 for low-power non-volatile memory and efficient ultraviolet ray detection

PubMed Central

Kundu, Souvik; Clavel, Michael; Biswas, Pranab; Chen, Bo; Song, Hyun-Cheol; Kumar, Prashant; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Sanghadasa, Mohan; Priya, Shashank

2015-01-01

We report lead-free ferroelectric based resistive switching non-volatile memory (NVM) devices with epitaxial (1-x)BaTiO3-xBiFeO3 (x = 0.725) (BT-BFO) film integrated on semiconducting (100) Nb (0.7%) doped SrTiO3 (Nb:STO) substrates. The piezoelectric force microscopy (PFM) measurement at room temperature demonstrated ferroelectricity in the BT-BFO thin film. PFM results also reveal the repeatable polarization inversion by poling, manifesting its potential for read-write operation in NVM devices. The electroforming-free and ferroelectric polarization coupled electrical behaviour demonstrated excellent resistive switching with high retention time, cyclic endurance, and low set/reset voltages. X-ray photoelectron spectroscopy was utilized to determine the band alignment at the BT-BFO and Nb:STO heterojunction, and it exhibited staggered band alignment. This heterojunction is found to behave as an efficient ultraviolet photo-detector with low rise and fall time. The architecture also demonstrates half-wave rectification under low and high input signal frequencies, where the output distortion is minimal. The results provide avenue for an electrical switch that can regulate the pixels in low or high frequency images. Combined this work paves the pathway towards designing future generation low-power ferroelectric based microelectronic devices by merging both electrical and photovoltaic properties of BT-BFO materials. PMID:26202946

Lead-free epitaxial ferroelectric material integration on semiconducting (100) Nb-doped SrTiO3 for low-power non-volatile memory and efficient ultraviolet ray detection.

PubMed

Kundu, Souvik; Clavel, Michael; Biswas, Pranab; Chen, Bo; Song, Hyun-Cheol; Kumar, Prashant; Halder, Nripendra N; Hudait, Mantu K; Banerji, Pallab; Sanghadasa, Mohan; Priya, Shashank

2015-07-23

We report lead-free ferroelectric based resistive switching non-volatile memory (NVM) devices with epitaxial (1-x)BaTiO3-xBiFeO3 (x = 0.725) (BT-BFO) film integrated on semiconducting (100) Nb (0.7%) doped SrTiO3 (Nb:STO) substrates. The piezoelectric force microscopy (PFM) measurement at room temperature demonstrated ferroelectricity in the BT-BFO thin film. PFM results also reveal the repeatable polarization inversion by poling, manifesting its potential for read-write operation in NVM devices. The electroforming-free and ferroelectric polarization coupled electrical behaviour demonstrated excellent resistive switching with high retention time, cyclic endurance, and low set/reset voltages. X-ray photoelectron spectroscopy was utilized to determine the band alignment at the BT-BFO and Nb:STO heterojunction, and it exhibited staggered band alignment. This heterojunction is found to behave as an efficient ultraviolet photo-detector with low rise and fall time. The architecture also demonstrates half-wave rectification under low and high input signal frequencies, where the output distortion is minimal. The results provide avenue for an electrical switch that can regulate the pixels in low or high frequency images. Combined this work paves the pathway towards designing future generation low-power ferroelectric based microelectronic devices by merging both electrical and photovoltaic properties of BT-BFO materials.

Effect of calcination environments and plasma treatment on structural, optical and electrical properties of FTO transparent thin films

NASA Astrophysics Data System (ADS)

Kafle, Madhav; Kapadi, Ramesh K.; Joshi, Leela Pradhan; Rajbhandari, Armila; Subedi, Deepak P.; Gyawali, Gobinda; Lee, Soo W.; Adhikari, Rajendra; Kafle, Bhim P.

2017-07-01

The dependence of the structural, optical and electrical properties of the FTO thin films on the film thickness (276 nm - 546 nm), calcination environment, and low temperature plasma treatment were examined. The FTO thin films, prepared by spray pyrolysis, were calcinated under air followed by either further heat treatment under N2 gas or treatment in low temperature atmospheric plasma. The samples before and after calcination under N2, and plasma treatment will be represented by Sair, SN2 and SPl, respectively, hereafter. The thin films were characterized by measuring the XRD spectra, SEM images, optical transmittance and reflectance, and sheet resistance of the films before and after calcination in N2 environment or plasma treatment. The presence of sharp and narrow multiple peaks in XRD spectra hint us that the films were highly crystalline (polycrystalline). The samples Sair with the thickness of 471 nm showed as high as 92 % transmittance in the visible range. Moreover, from the tauc plot, the optical bandgap Eg values of the Sair found to be noticeably lower than that of the samples SN2. Very surprisingly, the electrical sheet resistance (Rsh) found to decrease following the trend as Rshair > RshN2 > RshPl. The samples exposed to plasma found to possess the lowest RshPl (for film with thickness 546 nm, the RshPl was 17 Ω /sq.).

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

2017-01-01

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.

Electrical Resistivity Measurement of Cu and Zn on the Pressure-Dependent Melting Boundary

NASA Astrophysics Data System (ADS)

Secco, R. A.; Ezenwa, I.; Yong, W.

2016-12-01

Understanding how the core cools through heat conduction and modelling the geodynamo requires knowledge of the thermal and electrical conductivity of solid and liquid Fe and its relevant alloys at high pressures. It has been proposed that electrical resistivity of a pure metal is constant along its P-dependent melting boundary (Stacey and Anderson, PEPI, 2001). If confirmed, this invariant behavior could serve as a practical tool for low P studies to assess electrical resistivity of Earth's core. Since Earth's inner core boundary (ICB) is a melting boundary of mainly Fe, measurements of electrical resistivity of Fe at the melting boundary, under any P, would serve as a proxy for the resistivity at the ICB. A revised treatment (Stacey and Loper, PEPI, 2007) accounted for s-d scattering in transition metals with unfilled d-bands and limited the proposal to metals with electrons of the same type in filled d-band metals. To test this proposal, we made high P, T measurements of electrical resistivity of d-band filled Cu and Zn in solid and liquid states. Experiments were carried out in a 1000 ton cubic anvil press up to 5 GPa and 300K above melting temperatures. Two thermocouples placed at opposite ends of the wire sample served as T probes as well as 4-wire resistance electrodes in a switched circuit. A polarity switch was used to remove any bias voltage measurement using thermocouple legs. Electron microprobe analyses were used to check the compositions of the recovered samples. The expected resistivity decrease with P and increase with T were found and comparisons with 1atm data are in very good agreement. Within the error of measurement, the resistivity values of Cu decrease along the melting boundary while Zn appears to support the hypothesis of constant resistivity along the melting boundary.

Characterization of riverbed sediments hydraulic conductivity using slug tests and electrical resistivity tomography and induced polarization tomogrpahy.

NASA Astrophysics Data System (ADS)

Nguyen, F.; Benoit, S.; Gommers, K.; Ghysels, G.; Hermans, T.; Huysmans, M.

2017-12-01

Hydraulic conductivity of river sediments ranges from values smaller than 10-9 m/s to values higher than 10-2 m/s, with a dominance in values between 10-7 m/s and 10-3 m/s. Both horizontal hydraulic conductivity and vertical hydraulic conductivity show spatial variation in a riverbed. The spatial variation in hydraulic conductivity is due to the influence of the sedimentary and geomorphological environment as well as the method of determination, including scale, size and imprecision of the applied method. The characterization of the spatial variability of hydraulic conductivity in riverbeds is important because of its effect on the interaction between river and groundwater. These river - groundwater interactions influence water resource management, water quality and functioning of the riparian ecosystem. It is necessary in the simulation of 3D flow between river and aquifer near the interface and thus, it also determines contaminant transport and biogeochemical modelling in this riparian or hyporheic zone. Different processes occur in this specific zone such as transport, degradation, transformation, precipitation and sorption of substances, all dependent on hydraulic conductivity. Several methods exist to determine the hydraulic conductivity in river beds, both direct and indirect methods, from field to laboratory experiments or numerical modelling, but the uncertainty on obtained K values is often large because of the large variability of K. In the recent years, research has been performed on the usefulness of geophysical methods on rivers, in particular Electrical Resistivity Tomography (ERT) and Induced Polarization (IP). The implementation of ERT and IP in rivers provides a continuous image of the resistivity and chargeability of the subsurface, respectively, and can be used in several applications as proxies for hydraulic conductivity. This work reports and investigate a correlation between hydraulic conductivity measured by slug tests at an experimental site, and electrical resistivity, chargeability and normalized chargeability for riverbeds sediments.

Effect of nano-scale morphology on micro-channel wall surface and electrical characterization in lead silicate glass micro-channel plate

NASA Astrophysics Data System (ADS)

Cai, Hua; Li, Fangjun; Xu, Yanglei; Bo, Tiezhu; Zhou, Dongzhan; Lian, Jiao; Li, Qing; Cao, Zhenbo; Xu, Tao; Wang, Caili; Liu, Hui; Li, Guoen; Jia, Jinsheng

2017-10-01

Micro-channel plate (MCP) is a two dimensional arrays of microscopic channel charge particle multiplier. Silicate composition and hydrogen reduction are keys to determine surface morphology of micro-channel wall in MCP. In this paper, lead silicate glass micro-channel plates in two different cesium contents (0at%, 0.5at%) and two different hydrogen reduction temperatures (400°C,450°C) were present. The nano-scale morphology, elements content and chemical states of microporous wall surface treated under different alkaline compositions and reduction conditions was investigated by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), respectively. Meanwhile, the electrical characterizations of MCP, including the bulk resistance, electron gain and the density of dark current, were measured in a Vacuum Photoelectron Imaging Test Facility (VPIT).The results indicated that the granular phase occurred on the surface of microporous wall and diffuses in bulk glass is an aggregate of Pb atom derived from the reduction of Pb2+. In micro-channel plate, the electron gain and bulk resistance were mainly correlated to particle size and distribution, the density of dark current (DDC) went up with the increasing root-mean-square roughness (RMS) on the microporous wall surface. Adding cesiums improved the size of Pb atomic aggregation, lowered the relative concentration of [Pb] reduced from Pb2+ and decreased the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a less dark current. Increasing hydrogen reduction temperature also improved the size of Pb atomic aggregation, but enhanced the relative concentration of [Pb] and enlarged the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a larger dark current. The reasons for the difference of electrical characteristics were discussed.