Electron gun controlled smart structure

DOEpatents

Martin, Jeffrey W.; Main, John Alan; Redmond, James M.; Henson, Tammy D.; Watson, Robert D.

2001-01-01

Disclosed is a method and system for actively controlling the shape of a sheet of electroactive material; the system comprising: one or more electrodes attached to the frontside of the electroactive sheet; a charged particle generator, disposed so as to direct a beam of charged particles (e.g. electrons) onto the electrode; a conductive substrate attached to the backside of the sheet; and a power supply electrically connected to the conductive substrate; whereby the sheet changes its shape in response to an electric field created across the sheet by an accumulation of electric charge within the electrode(s), relative to a potential applied to the conductive substrate. Use of multiple electrodes distributed across on the frontside ensures a uniform distribution of the charge with a single point of e-beam incidence, thereby greatly simplifying the beam scanning algorithm and raster control electronics, and reducing the problems associated with "blooming". By placing a distribution of electrodes over the front surface of a piezoelectric film (or other electroactive material), this arrangement enables improved control over the distribution of surface electric charges (e.g. electrons) by creating uniform (and possibly different) charge distributions within each individual electrode. Removal or deposition of net electric charge can be affected by controlling the secondary electron yield through manipulation of the backside electric potential with the power supply. The system can be used for actively controlling the shape of space-based deployable optics, such as adaptive mirrors and inflatable antennae.

Estimation of electrical conductivity distribution within the human head from magnetic flux density measurement.

PubMed

Gao, Nuo; Zhu, S A; He, Bin

2005-06-07

We have developed a new algorithm for magnetic resonance electrical impedance tomography (MREIT), which uses only one component of the magnetic flux density to reconstruct the electrical conductivity distribution within the body. The radial basis function (RBF) network and simplex method are used in the present approach to estimate the conductivity distribution by minimizing the errors between the 'measured' and model-predicted magnetic flux densities. Computer simulations were conducted in a realistic-geometry head model to test the feasibility of the proposed approach. Single-variable and three-variable simulations were performed to estimate the brain-skull conductivity ratio and the conductivity values of the brain, skull and scalp layers. When SNR = 15 for magnetic flux density measurements with the target skull-to-brain conductivity ratio being 1/15, the relative error (RE) between the target and estimated conductivity was 0.0737 +/- 0.0746 in the single-variable simulations. In the three-variable simulations, the RE was 0.1676 +/- 0.0317. Effects of electrode position uncertainty were also assessed by computer simulations. The present promising results suggest the feasibility of estimating important conductivity values within the head from noninvasive magnetic flux density measurements.

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

Visualization of Electrical Field of Electrode Using Voltage-Controlled Fluorescence Release

PubMed Central

Jia, Wenyan; Wu, Jiamin; Gao, Di; Wang, Hao; Sun, Mingui

2016-01-01

In this study we propose an approach to directly visualize electrical current distribution at the electrode-electrolyte interface of a biopotential electrode. High-speed fluorescent microscopic images are acquired when an electric potential is applied across the interface to trigger the release of fluorescent material from the surface of the electrode. These images are analyzed computationally to obtain the distribution of the electric field from the fluorescent intensity of each pixel. Our approach allows direct observation of microscopic electrical current distribution around the electrode. Experiments are conducted to validate the feasibility of the fluorescent imaging method. PMID:27253615

The Role of Additional Pulses in Electropermeabilization Protocols

PubMed Central

Suárez, Cecilia; Soba, Alejandro; Maglietti, Felipe; Olaiz, Nahuel; Marshall, Guillermo

2014-01-01

Electropermeabilization (EP) based protocols such as those applied in medicine, food processing or environmental management, are well established and widely used. The applied voltage, as well as tissue electric conductivity, are of utmost importance for assessing final electropermeabilized area and thus EP effectiveness. Experimental results from literature report that, under certain EP protocols, consecutive pulses increase tissue electric conductivity and even the permeabilization amount. Here we introduce a theoretical model that takes into account this effect in the application of an EP-based protocol, and its validation with experimental measurements. The theoretical model describes the electric field distribution by a nonlinear Laplace equation with a variable conductivity coefficient depending on the electric field, the temperature and the quantity of pulses, and the Penne's Bioheat equation for temperature variations. In the experiments, a vegetable tissue model (potato slice) is used for measuring electric currents and tissue electropermeabilized area in different EP protocols. Experimental measurements show that, during sequential pulses and keeping constant the applied voltage, the electric current density and the blackened (electropermeabilized) area increase. This behavior can only be attributed to a rise in the electric conductivity due to a higher number of pulses. Accordingly, we present a theoretical modeling of an EP protocol that predicts correctly the increment in the electric current density observed experimentally during the addition of pulses. The model also demonstrates that the electric current increase is due to a rise in the electric conductivity, in turn induced by temperature and pulse number, with no significant changes in the electric field distribution. The EP model introduced, based on a novel formulation of the electric conductivity, leads to a more realistic description of the EP phenomenon, hopefully providing more accurate predictions of treatment outcomes. PMID:25437512

A quasi-static model of global atmospheric electricity. I - The lower atmosphere

NASA Technical Reports Server (NTRS)

Hays, P. B.; Roble, R. G.

1979-01-01

A quasi-steady model of global lower atmospheric electricity is presented. The model considers thunderstorms as dipole electric generators that can be randomly distributed in various regions and that are the only source of atmospheric electricity and includes the effects of orography and electrical coupling along geomagnetic field lines in the ionosphere and magnetosphere. The model is used to calculate the global distribution of electric potential and current for model conductivities and assumed spatial distributions of thunderstorms. Results indicate that large positive electric potentials are generated over thunderstorms and penetrate to ionospheric heights and into the conjugate hemisphere along magnetic field lines. The perturbation of the calculated electric potential and current distributions during solar flares and subsequent Forbush decreases is discussed, and future measurements of atmospheric electrical parameters and modifications of the model which would improve the agreement between calculations and measurements are suggested.

Experimental results for 2D magnetic resonance electrical impedance tomography (MR-EIT) using magnetic flux density in one direction.

PubMed

Birgül, Ozlem; Eyüboğlu, B Murat; Ider, Y Ziya

2003-11-07

Magnetic resonance electrical impedance tomography (MR-EIT) is an emerging imaging technique that reconstructs conductivity images using magnetic flux density measurements acquired employing MRI together with conventional EIT measurements. In this study, experimental MR-EIT images from phantoms with conducting and insulator objects are presented. The technique is implemented using the 0.15 T Middle East Technical University MRI system. The dc current method used in magnetic resonance current density imaging is adopted. A reconstruction algorithm based on the sensitivity matrix relation between conductivity and only one component of magnetic flux distribution is used. Therefore, the requirement for object rotation is eliminated. Once the relative conductivity distribution is found, it is scaled using the peripheral voltage measurements to obtain the absolute conductivity distribution. Images of several insulator and conductor objects in saline filled phantoms are reconstructed. The L2 norm of relative error in conductivity values is found to be 13%, 17% and 14% for three different conductivity distributions.

Experimental characterization of intrapulse tissue conductivity changes for electroporation.

PubMed

Neal, Robert E; Garcia, Paulo A; Robertson, John L; Davalos, Rafael V

2011-01-01

Cells exposed to short electric pulses experience a change in their transmembrane potential, which can lead to increased membrane permeability of the cell. When the energy of the pulses surpasses a threshold, the cell dies in a non-thermal manner known as irreversible electroporation (IRE). IRE has shown promise in the focal ablation of pathologic tissues. Its non-thermal mechanism spares sensitive structures and facilitates rapid lesion resolution. IRE effects depend on the electric field distribution, which can be predicted with numerical modeling. When the cells become permeabilized, the bulk tissue properties change, affecting this distribution. For IRE to become a reliable and successful treatment of diseased tissues, robust predictive treatment planning methods must be developed. It is vital to understand the changes in tissue properties undergoing the electric pulses to improve numerical models and predict treatment volumes. We report on the experimental characterization of these changes for kidney tissue. Tissue samples were pulsed between plate electrodes while intrapulse voltage and current data were measured to determine the conductivity of the tissue during the pulse. Conductivity was then established as a function of the electric field to which the tissue is exposed. This conductivity curve was used in a numerical model to demonstrate the impact of accounting for these changes when modeling electric field distributions to develop treatment plans.

Innovative methodology for electrical conductivity measurements and metal partition in biosolid pellets

NASA Astrophysics Data System (ADS)

Jordan, Manuel Miguel; Rincón-Mora, Beatriz; Belén Almendro-Candel, María; Navarro-Pedreño, José; Gómez-Lucas, Ignacio; Bech, Jaume

2017-04-01

Use of biosolids to improve the nutrient content in a soil is a common practice. The obligation to restore abandoned mine and the correct application of biosolids is guaranteed by the legislation on waste management, biosolids and soil conservation (Jordán et al. 2008). The present research was conducted to determine electrical conductivity in dry wastes (pellets) using a innovative methodology (Camilla and Jordán, 2009). On the other hand, the present study was designed to examine the distribution of selected heavy metals in biosolid pellets, and also to relate the distribution patterns of these metals. In this context, heavy metal concentrations were studied in biosolid pellets under different pressures. Electrical conductivity measurements were taken in biosolid pellets under pressures on the order of 50 to 150 MPa and with currents of 10-15 A. Measurements of electrical conductivity and heavy metal content for different areas (H1, H2, and H3) were taken. Total content of metals was determined following microwave digestion and analysed by ICP/MS. Triplicate portions were weighed in polycarbonate centrifuge tubes and sequentially extracted. The distribution of chemical forms of Cd, Ni, Cr, and Pb in the biosolids was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible, and residual forms. The residual, reducible, and carbonate-sorbed forms were dominant. Higher Cr and Ni content were detected in pellets made with biosolids from the H3. The highest Cd and Ni values were detected in the H2. The trends of the conductivity curves were similar for the sludge from the isolation surface (H1) and for the mesophilous area (H2). In the case of the thermophilous area (H3), the electrical conductivity showed extremely high values. This behaviour was similar in the case of the Cr and Ni content. However, in the case of Cd and Pb, the highest values were detected in the H2. This experiment could be useful for establishing a general rule for taking measurements of electrical conductivity and heavy metals in biosolid pellets and other types of dry wastes. References Camilla S, Jordán MM (2009) Electrical conductivity measurements in sewage sludge pellets: innovative techniques for environmental management. J Hazard Mater 168:1260-1263 Jordán, MM, Rincón-Mora, B; Almendro, MB (2015). Heavy metal distribution and electrical conductivity measurements in biosolid pellets. J, Soils and Sediments, 16 1176-118

Integration of piezo-capacitive and piezo-electric nanoweb based pressure sensors for imaging of static and dynamic pressure distribution.

PubMed

Jeong, Y J; Oh, T I; Woo, E J; Kim, K J

2017-07-01

Recently, highly flexible and soft pressure distribution imaging sensor is in great demand for tactile sensing, gait analysis, ubiquitous life-care based on activity recognition, and therapeutics. In this study, we integrate the piezo-capacitive and piezo-electric nanowebs with the conductive fabric sheets for detecting static and dynamic pressure distributions on a large sensing area. Electrical impedance tomography (EIT) and electric source imaging are applied for reconstructing pressure distribution images from measured current-voltage data on the boundary of the hybrid fabric sensor. We evaluated the piezo-capacitive nanoweb sensor, piezo-electric nanoweb sensor, and hybrid fabric sensor. The results show the feasibility of static and dynamic pressure distribution imaging from the boundary measurements of the fabric sensors.

Electrically conductive composite material

DOEpatents

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

1989-05-23

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

Electrically conductive composite material

DOEpatents

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

1988-06-20

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

Electrically conductive composite material

DOEpatents

Clough, Roger L.; Sylwester, Alan P.

1989-01-01

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

Anatomically informed mesoscale electrical impedance spectroscopy in southern pine and the electric field distribution for pin-type electric moisture metres

Treesearch

Samuel L. Zelinka; Alex C. Wiedenhoeft; Samuel V. Glass; Flavio Ruffinatto

2015-01-01

Electrical impedance spectra of wood taken at macroscopic scales below the fibre saturation point have led to inferences that the mechanism of charge conduction involves a percolation phenomenon. The pathways responsible for charge conduction would necessarily be influenced by wood structure at a variety of sub-macroscopic scales – at a mesoscale – but these questions...

The relation between temperature distribution for lung RFA and electromagnetic wave frequency dependence of electrical conductivity with changing a lung's internal air volumes.

PubMed

Yamazaki, Nozomu; Watanabe, Hiroki; Lu, Xiaowei; Isobe, Yosuke; Kobayashi, Yo; Miyashita, Tomoyuki; Fujie, Masakatsu G

2013-01-01

Radio frequency ablation (RFA) for lung cancer has increasingly been used over the past few years because it is a minimally invasive treatment. As a feature of RFA for lung cancer, lung contains air during operation. Air is low thermal and electrical conductivity. Therefore, RFA for this cancer has the advantage that only the cancer is coagulated, and it is difficult for operators to control the precise formation of coagulation lesion. In order to overcome this limitation, we previously proposed a model-based robotic ablation system using finite element method. Creating an accurate thermo physical model and constructing thermal control method were a challenging problem because the thermal properties of the organ are complex. In this study, we measured electromagnetic wave frequency dependence of lung's electrical conductivity that was based on lung's internal air volumes dependence with in vitro experiment. In addition, we validated the electromagnetic wave frequency dependence of lung's electrical conductivity using temperature distribution simulator. From the results of this study, it is confirmed that the electromagnetic wave frequency dependence of lung's electrical conductivity effects on heat generation of RFA.

Response of ionospheric electric fields at mid-low latitudes during sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2015-06-01

Using in situ observations from the Republic of China Satellite-1 spacecraft, we investigated the time response and local time dependence of the ionospheric electric field at mid-low latitudes associated with geomagnetic sudden commencements (SCs) that occurred from 1999 to 2004. We found that the ionospheric electric field variation associated with SCs instantaneously responds to the preliminary impulse (PI) signature on the ground regardless of spacecraft local time. Our statistical analysis also supports the global instant transmission of electric field from the polar region. In contrast, the peak time detected in the ionospheric electric field is earlier than that of the equatorial geomagnetic field (~20 s before in the PI phase). Based on the ground-ionosphere waveguide model, this time lag can be attributed to the latitudinal difference of ionospheric conductivity. However, the local time distribution of the initial excursion of ionospheric electric field shows that dusk-to-dawn ionospheric electric fields develop during the PI phase. Moreover, the westward electric field in the ionosphere, which produces the preliminary reverse impulse of the geomagnetic field on the dayside feature, appears at 18-22 h LT where the ionospheric conductivity beyond the duskside terminator (18 h LT) is lower than on the dayside. The result of a magnetohydrodynamic simulation for an ideal SC shows that the electric potential distribution is asymmetric with respect to the noon-midnight meridian. This produces the local time distribution of ionospheric electric fields similar to the observed result, which can be explained by the divergence of the Hall current under nonuniform ionospheric conductivity.

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

EPA Science Inventory

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

Electron transport and electron energy distributions within the wurtzite and zinc-blende phases of indium nitride: Response to the application of a constant and uniform electric field

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

Siddiqua, Poppy; Hadi, Walid A.; Salhotra, Amith K.

2015-03-28

Within the framework of an ensemble semi-classical three-valley Monte Carlo electron transport simulation approach, we critically contrast the nature of the electron transport that occurs within the wurtzite and zinc-blende phases of indium nitride in response to the application of a constant and uniform electric field. We use the electron energy distribution and its relationship with the electron transport characteristics in order to pursue this analysis. For the case of zinc-blende indium nitride, only a peak corresponding to the electrons within the lowest energy conduction band valley is observed, this peak being seen to broaden and shift to higher energiesmore » in response to increases in the applied electric field strength, negligible amounts of upper energy conduction band valley occupancy being observed. In contrast, for the case of wurtzite indium nitride, in addition to the aforementioned lowest energy conduction band valley peak in the electron energy distribution, and its broadening and shifting to higher energies in response to increases in the applied electric field strength, beyond a certain critical electric field strength, 30 kV/cm for the case of this particular material, upper energy conduction band valley occupancy is observed, this occupancy being further enhanced in response to further increases in the applied electric field strength. Reasons for these results are provided. The potential for device consequences is then commented upon.« less

Three Dimensional Distribution of Sensitive Field and Stress Field Inversion of Force Sensitive Materials under Constant Current Excitation.

PubMed

Zhao, Shuanfeng; Liu, Min; Guo, Wei; Zhang, Chuanwei

2018-02-28

Force sensitive conductive composite materials are functional materials which can be used as the sensitive material of force sensors. However, the existing sensors only use one-dimensional electrical properties of force sensitive conductive materials. Even in tactile sensors, the measurement of contact pressure is achieved by large-scale arrays and the units of a large-scale array are also based on the one-dimensional electrical properties of force sensitive materials. The main contribution of this work is to study the three-dimensional electrical properties and the inversion method of three-dimensional stress field of a force sensitive material (conductive rubber), which pushes the application of force sensitive material from one dimensional to three-dimensional. First, the mathematical model of the conductive rubber current field distribution under a constant force is established by the effective medium theory, and the current field distribution model of conductive rubber with different geometry, conductive rubber content and conductive rubber relaxation parameters is deduced. Secondly, the inversion method of the three-dimensional stress field of conductive rubber is established, which provides a theoretical basis for the design of a new tactile sensor, three-dimensional stress field and space force based on force sensitive materials.

Experimental research of gas shale electrical properties by NMR and the combination of imbibition and drainage

NASA Astrophysics Data System (ADS)

Dong, Xu; Sun, Jianmeng; Li, Jun; Gao, Hui; Liu, Xuefeng; Wang, Jinjie

2015-08-01

Gas shale has shown considerable force in gas production worldwide, but little attention has been paid to its electrical properties, which are essential for reservoir evaluation and differentiating absorbed gas and free gas. In this study, experiments are designed to research water saturation establishment methods and electrical properties of gas shale. Nuclear magnetic resonance (NMR) with short echo space (TE) is used to identify water saturation and distribution of saturated pores which contribute to the conductivity. The experimental results indicate that NMR with shorter TE can estimate porosity and fluid distribution better than NMR with longer TE. A full range of water saturation is established by the combination of new-type spontaneous imbibition and semi-permeable plate drainage techniques. Spontaneous imbibition gains water saturation from 0% to near irreducible water saturation, and, semi-permeable plate drainage desaturates from 100% to irreducible water saturation. The RI-Sw curve shows a nonlinear relationship, and can be divided into three parts with different behaviors. The comparative analysis of transverse relaxation time (T2) distribution and RI-Sw curves, indicates that free water, and water trapped by capillarity in the non-clay matrix, differ in terms of electrical conductivity from water absorbed in clay. The new experiments prove the applicability of imbibition, drainage and NMR in investigating electrical properties of gas shale and differentiating fluid distribution which makes contribution to conductivity.

Quantum Electronic Solids

DTIC Science & Technology

2012-03-07

signal processing with smaller sizes and unique properties Nanoelectronics: NTs, graphene, diamond, SiC for sensing, logic & memory storage 3...synthesized i-n graphene heterojunctions 19 DISTRIBUTION A: Approved for public release; distribution is unlimited. Electrical Properties of...boundaries in polycrystalline samples Polycrystalline graphene can have similar (as much as 90%) electrical properties (conductance and mobility

Investigation of the electric field distribution in the human brain based on MRI and EEG data

NASA Astrophysics Data System (ADS)

Kistenev, Yu. V.; Borisov, A. V.; Knyazkova, A. I.; Shapovalova, A. V.; Ilyasova, E. E.; Sandykova, E. A.

2018-04-01

This work is devoted to the development of the approach to restoration of the spatial-temporal distribution of electric field in the human brain. This field was estimated from the model derived from the Maxwell's equations with boundary conditions corresponding to electric potentials at the EEG electrodes, which are located on the surface of the head according to the standard "10-20" scheme. The MRI data were used for calculation of the spatial distribution of the electrical conductivity of biotissues in the human brain. The study of the electric field distribution using our approach was carried out for the healthy child and the child with autism. The research was carried out using the equipment of the Tomsk Regional Common Use Center of Tomsk State University.

Impact of electric vehicles on the IEEE 34 node distribution infrastructure

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

Jiang, Zeming; Shalalfel, Laith; Beshir, Mohammed J.

With the growing penetration of the electric vehicles to our daily life owing to their economic and environmental benefits, there will be both opportunities and challenges to the utilities when adopting plug-in electric vehicles (PEV) to the distribution network. In this study, a thorough analysis based on real-world project is conducted to evaluate the impacts of electric vehicles infrastructure on the grid relating to system load flow, load factor, and voltage stability. IEEE 34 node test feeder was selected and tested along with different case scenarios utilizing the electrical distribution design (EDD) software to find out the potential impacts tomore » the grid.« less

Impact of electric vehicles on the IEEE 34 node distribution infrastructure

DOE PAGES

Jiang, Zeming; Shalalfel, Laith; Beshir, Mohammed J.

2014-10-01

With the growing penetration of the electric vehicles to our daily life owing to their economic and environmental benefits, there will be both opportunities and challenges to the utilities when adopting plug-in electric vehicles (PEV) to the distribution network. In this study, a thorough analysis based on real-world project is conducted to evaluate the impacts of electric vehicles infrastructure on the grid relating to system load flow, load factor, and voltage stability. IEEE 34 node test feeder was selected and tested along with different case scenarios utilizing the electrical distribution design (EDD) software to find out the potential impacts tomore » the grid.« less

Node-node correlations and transport properties in scale-free networks

NASA Astrophysics Data System (ADS)

Obregon, Bibiana; Guzman, Lev

2011-03-01

We study some transport properties of complex networks. We focus our attention on transport properties of scale-free and small-world networks and compare two types of transport: Electric and max-flow cases. In particular, we construct scale-free networks, with a given degree sequence, to estimate the distribution of conductances for different values of assortative/dissortative mixing. For the electric case we find that the distributions of conductances are affect ed by the assortative mixing of the network whereas for the max-flow case, the distributions almost do not show changes when node-node correlations are altered. Finally, we compare local and global transport in terms of the average conductance for the small-world (Watts-Strogatz) model

Determination of water saturation using gas phase partitioning tracers and time-lapse electrical conductivity measurements

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

Johnson, Timothy C.; Oostrom, Martinus; Truex, Michael J.

2013-05-21

Water saturation is an important indicator of contaminant distribution and plays a governing role in contaminant transport within the vadose zone. Understanding the water saturation distribution is critical for both remediation and contaminant flux monitoring in unsaturated environments. In this work we propose and demonstrate a method of remotely determining water saturation levels using gas phase partitioning tracers and time-lapse bulk electrical conductivity measurements. The theoretical development includes the partitioning chemistry for the tracers we demonstrate (ammonia and carbon dioxide), as well as a review of the petrophysical relationship governing how these tracers influence bulk conductivity. We also investigate methodsmore » of utilizing secondary information provided by electrical conductivity breakthrough magnitudes induced by the tracers. We test the method on clean, well characterized, intermediate-scale sand columns under controlled conditions. Results demonstrate the capability to predict partitioning coefficients and accurately monitor gas breakthrough curves along the length of the column according to the corresponding electrical conductivity response, leading to accurate water saturation estimates. This work is motivated by the need to develop effective characterization and monitoring techniques for contaminated deep vadose zone environments, and provides a proof-of-concept toward uniquely characterizing and monitoring water saturation levels at the field scale and in three-dimensions using electrical resistivity tomography.« less

Using electrical impedance tomography to map subsurface hydraulic conductivity

DOEpatents

Berryman, James G.; Daily, William D.; Ramirez, Abelardo L.; Roberts, Jeffery J.

2000-01-01

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

Using Rouse-Fowler model to describe radiation-induced electrical conductivity of nanocomposite materials

NASA Astrophysics Data System (ADS)

Dyuryagina, N. S.; Yalovets, A. P.

2017-05-01

Using the Rouse-Fowler (RF) model this work studies the radiation-induced electrical conductivity of a polymer nanocomposite material with spherical nanoparticles against the intensity and exposure time of gamma-ray, concentration and size of nanoparticles. The research has found the energy distribution of localized statesinduced by nanoparticles. The studies were conducted on polymethylmethacrylate (PMMA) with CdS nanoparticles.

Discharge current distribution in stratified soil under impulse discharge

NASA Astrophysics Data System (ADS)

Eniola Fajingbesi, Fawwaz; Shahida Midi, Nur; Elsheikh, Elsheikh M. A.; Hajar Yusoff, Siti

2017-06-01

The mobility of charge particles traversing a material defines its electrical properties. Soil (earth) have long been the universal grounding before and after the inception of active ground systems for electrical appliance purpose due to it semi-conductive properties. The soil can thus be modelled as a single material exhibiting semi-complex inductive-reactive impedance. Under impulse discharge such as lightning strikes to soil this property of soil could result in electric potential level fluctuation ranging from ground potential rise/fall to electromagnetic pulse coupling that could ultimately fail connected electrical appliance. In this work we have experimentally model the soil and lightning discharge using point to plane electrode setup to observe the current distribution characteristics at different soil conductivity [mS/m] range. The result presented from this research indicate above 5% shift in conductivity before and after discharge which is significant for consideration when dealing with grounding designs. The current distribution in soil have also be successfully observed and analysed from experimental result using mean current magnitude in relation to electrode distance and location, current density variation with depth all showing strong correlation with theoretical assumptions of a semi-complex impedance material.

Training Needs Assessment of Technical Skills in Managers of Tehran Electricity Distribution Company

ERIC Educational Resources Information Center

Koohi, Amir Hasan; Ghandali, Fatemeh; Dehghan, Hasan; Ghandali, Najme

2016-01-01

Current dissertation has been conducted in order to investigate and detect training needs of the mangers (top and middle) in Tehran Electricity Distribution Company. Research method is applied kind based on its purpose. Due to data collection method, this query is descriptive-survey type. Statistical population in this study is all of managers in…

Effect of iron content on the electrical conductivity of perovskite and magnesiowuestite assemblages at lower mantle conditions

NASA Technical Reports Server (NTRS)

Li, Xiaoyuan; Jeanloz, Raymond

1991-01-01

The electrical conductivity of (Mg/0.76/Fe/0.24/)SiO3 perovskite and of an assemblage of (Mg/0.89/Fe/0.11/)SiO3 perovskite + (Mg/0.70/Fe/0.30/)O magnesiowiestite was measured at pressures of 45-80 GPa and temperatures from 295 to 3600 K. The apparent activation energy for electrical conduction is 0.24 (+ or - 0.10) eV for the perovskite and 0.20 (+ or - 0.08) eV for the perovskite + magnesiowuestite assemblage. Comparing present results with those derived previously for Fe-poor samples, it is found that the electrical conductivities of both the silicate perovskite and the perovskite + magnesiowuestite assemblage depend strongly on iron content. Thus, the electrical conductivity distribution inside the earth could provide an important constraint in modeling the composition of the lower mantle.

ENERGY EFFICIENCY AND ENVIRONMENTALLY FRIENDLY DISTRIBUTED ENERGY STORAGE BATTERY

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

LANDI, J.T.; PLIVELICH, R.F.

2006-04-30

Electro Energy, Inc. conducted a research project to develop an energy efficient and environmentally friendly bipolar Ni-MH battery for distributed energy storage applications. Rechargeable batteries with long life and low cost potentially play a significant role by reducing electricity cost and pollution. A rechargeable battery functions as a reservoir for storage for electrical energy, carries energy for portable applications, or can provide peaking energy when a demand for electrical power exceeds primary generating capabilities.

Reduction technique of drop voltage and power losses to improve power quality using ETAP Power Station simulation model

NASA Astrophysics Data System (ADS)

Satrio, Reza Indra; Subiyanto

2018-03-01

The effect of electric loads growth emerged direct impact in power systems distribution. Drop voltage and power losses one of the important things in power systems distribution. This paper presents modelling approach used to restructrure electrical network configuration, reduce drop voltage, reduce power losses and add new distribution transformer to enhance reliability of power systems distribution. Restructrure electrical network was aimed to analyse and investigate electric loads of a distribution transformer. Measurement of real voltage and real current were finished two times for each consumer, that were morning period and night period or when peak load. Design and simulation were conduct by using ETAP Power Station Software. Based on result of simulation and real measurement precentage of drop voltage and total power losses were mismatch with SPLN (Standard PLN) 72:1987. After added a new distribution transformer and restructrured electricity network configuration, the result of simulation could reduce drop voltage from 1.3 % - 31.3 % to 8.1 % - 9.6 % and power losses from 646.7 watt to 233.29 watt. Result showed, restructrure electricity network configuration and added new distribution transformer can be applied as an effective method to reduce drop voltage and reduce power losses.

A new theoretical formulation of coupling thermo-electric breakdown in LDPE film under dc high applied fields

NASA Astrophysics Data System (ADS)

Boughariou, F.; Chouikhi, S.; Kallel, A.; Belgaroui, E.

2015-12-01

In this paper, we present a new theoretical and numerical formulation for the electrical and thermal breakdown phenomena, induced by charge packet dynamics, in low-density polyethylene (LDPE) insulating film under dc high applied field. The theoretical physical formulation is composed by the equations of bipolar charge transport as well as by the thermo-electric coupled equation associated for the first time in modeling to the bipolar transport problem. This coupled equation is resolved by the finite-element numerical model. For the first time, all bipolar transport results are obtained under non-uniform temperature distributions in the sample bulk. The principal original results show the occurring of very sudden abrupt increase in local temperature associated to a very sharp increase in external and conduction current densities appearing during the steady state. The coupling between these electrical and thermal instabilities reflects physically the local coupling between electrical conduction and thermal joule effect. The results of non-uniform temperature distributions induced by non-uniform electrical conduction current are also presented for several times. According to our formulation, the strong injection current is the principal factor of the electrical and thermal breakdown of polymer insulating material. This result is shown in this work. Our formulation is also validated experimentally.

Study on temperature distribution effect on internal charging by computer simulation

NASA Astrophysics Data System (ADS)

Yi, Zhong

2016-07-01

Internal charging (or deep dielectric charging) is a great threaten to spacecraft. Dielectric conductivity is an important parameter for internal charging and it is sensitive to temperature. Considering the exposed dielectric outside a spacecraft may experience a relatively large temperature range, temperature effect can't be ignored in internal charging assessment. We can see some reporters on techniques of computer simulation of internal charging, but the temperature effect has not been taken into accounts. In this paper, we realize the internal charging simulation with consideration of temperature distribution inside the dielectric. Geant4 is used for charge transportation, and a numerical method is proposed for solving the current reservation equation. The conductivity dependences on temperature, radiation dose rate and intense electric field are considered. Compared to the case of uniform temperature, the internal charging with temperature distribution is more complicated. Results show that temperature distribution can cause electric field distortion within the dielectric. This distortion refers to locally considerable enlargement of electric field. It usually corresponds to the peak electric field which is critical for dielectric breakdown judgment. The peak electric field can emerge inside the dielectric, or appear on the boundary. This improvement of internal charging simulation is beneficial for the assessment of internal charging under multiple factors.

3D imaging of soil apparent electrical conductivity from VERIS data using a 1D spatially constrained inversion algorithm

NASA Astrophysics Data System (ADS)

Jesús Moral García, Francisco; Rebollo Castillo, Francisco Javier; Monteiro Santos, Fernando

2016-04-01

Maps of apparent electrical conductivity of the soil are commonly used in precision agriculture to indirectly characterize some important properties like salinity, water, and clay content. Traditionally, these studies are made through an empirical relationship between apparent electrical conductivity and properties measured in soil samples collected at a few locations in the experimental area and at a few selected depths. Recently, some authors have used not the apparent conductivity values but the soil bulk conductivity (in 2D or 3D) calculated from measured apparent electrical conductivity through the application of an inversion method. All the published works used data collected with electromagnetic (EM) instruments. We present a new software to invert the apparent electrical conductivity data collected with VERIS 3100 and 3150 (or the more recent version with three pairs of electrodes) using the 1D spatially constrained inversion method (1D SCI). The software allows the calculation of the distribution of the bulk electrical conductivity in the survey area till a depth of 1 m. The algorithm is applied to experimental data and correlations with clay and water content have been established using soil samples collected at some boreholes. Keywords: Digital soil mapping; inversion modelling; VERIS; soil apparent electrical conductivity.

Influence of electrical boundary conditions on profiles of acoustic field and electric potential of shear-horizontal acoustic waves in potassium niobate plates.

PubMed

Kuznetsova, I E; Nedospasov, I A; Kolesov, V V; Qian, Z; Wang, B; Zhu, F

2018-05-01

The profiles of an acoustic field and electric potential of the forward and backward shear-horizontal (SH) acoustic waves of a higher order propagating in X-Y potassium niobate plate have been theoretically investigated. It has been shown that by changing electrical boundary conditions on a surface of piezoelectric plates, it is possible to change the distributions of an acoustic field and electric potential of the forward and backward acoustic waves. The dependencies of the distribution of a mechanical displacement and electrical potential over the plate thickness for electrically open and electrically shorted plates have been plotted. The influence of a layer with arbitrary conductivity placed on a one or on the both plate surfaces on the profiles under study, phase and group velocities of the forward and backward acoustic waves in X-Y potassium niobate has been also investigated. The obtained results can be useful for development of the method for control of a particle or electrical charge movement inside the piezoelectric plates, as well a sensor for definition of the thin film conductivity. Copyright © 2018 Elsevier B.V. All rights reserved.

NREL Establishes New Center for Distributed Power

Science.gov Websites

Establishes New Center for Distributed Power Changing Electricity Market Demands Greater , smaller-scale generation facilities. That concept, known as "distributed power," will be Energy Laboratory (NREL). The Distributed Energy Resources Center at NREL will conduct research and

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...

Enhancement of Electrical Conductivity in Multicomponent Nanocomposites.

NASA Astrophysics Data System (ADS)

Ni, Xiaojuan; Hui, Chao; Su, Ninghai; Liu, Feng

To date, very limited theoretical or numerical analyses have been carried out to understand the electrical percolation properties in multicomponent nanocomposite systems. In this work, a disk-stick percolation model was developed to investigate the electrical percolation behavior of an electrically insulating matrix reinforced with one-dimensional (1D) and two-dimensional (2D) conductors via Monte Carlo simulation. The effective electrical conductivity was evaluated through Kirchhoff's current law by transforming it into an equivalent resistor network. The percolation threshold, equivalent resistance and conductivity were obtained from the distribution of nodal voltages by solving a system of linear equations with Gaussian elimination method. The effects of size, aspect ratio, relative concentration and contact patterns of 1D/2D inclusions on conductivity performance were examined. Our model is able to predict the electrical percolation threshold and evaluate the conductivity for hybrid systems with multiple components. The results suggest that carbon-based nanocomposites can have a high potential for applications where favorable electrical properties and low specific weight are required. We acknowledge the financial support from DOE-BES (No. DE-FG02-04ER46148).

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.

Ionic Conductivity, Structural Deformation and Programmable Anisotropy of DNA Origami in Electric Field

PubMed Central

Li, Chen-Yu; Hemmig, Elisa A.; Kong, Jinglin; Yoo, Jejoong; Hernández-Ainsa, Silvia

2015-01-01

The DNA origami technique can enable functionalization of inorganic structures for single-molecule electric current recordings. Experiments have shown that several layers of DNA molecules—a DNA origami plate— placed on top of a solid-state nanopore is permeable to ions. Here, we report a comprehensive characterization of the ionic conductivity of DNA origami plates by means of all-atom molecular dynamics (MD) simulations and nanocapillary electric current recordings. Using the MD method, we characterize the ionic conductivity of several origami constructs, revealing the local distribution of ions, the distribution of the electrostatic potential and contribution of different molecular species to the current. The simulations determine the dependence of the ionic conductivity on the applied voltage, the number of DNA layers, the nucleotide content and the lattice type of the plates. We demonstrate that increasing the concentration of Mg2+ ions makes the origami plates more compact, reducing their conductivity. The conductance of a DNA origami plate on top of a solid-state nanopore is determined by the two competing effects: bending of the DNA origami plate that reduces the current and separation of the DNA origami layers that increases the current. The latter is produced by the electro-osmotic flow and is reversible at the time scale of a hundred nanoseconds. The conductance of a DNA origami object is found to depend on its orientation, reaching maximum when the electric field aligns with the direction of the DNA helices. Our work demonstrates feasibility of programming the electrical properties of a self-assembled nanoscale object using DNA. PMID:25623807

Ionic conductivity, structural deformation, and programmable anisotropy of DNA origami in electric field.

PubMed

Li, Chen-Yu; Hemmig, Elisa A; Kong, Jinglin; Yoo, Jejoong; Hernández-Ainsa, Silvia; Keyser, Ulrich F; Aksimentiev, Aleksei

2015-02-24

The DNA origami technique can enable functionalization of inorganic structures for single-molecule electric current recordings. Experiments have shown that several layers of DNA molecules, a DNA origami plate, placed on top of a solid-state nanopore is permeable to ions. Here, we report a comprehensive characterization of the ionic conductivity of DNA origami plates by means of all-atom molecular dynamics (MD) simulations and nanocapillary electric current recordings. Using the MD method, we characterize the ionic conductivity of several origami constructs, revealing the local distribution of ions, the distribution of the electrostatic potential and contribution of different molecular species to the current. The simulations determine the dependence of the ionic conductivity on the applied voltage, the number of DNA layers, the nucleotide content and the lattice type of the plates. We demonstrate that increasing the concentration of Mg(2+) ions makes the origami plates more compact, reducing their conductivity. The conductance of a DNA origami plate on top of a solid-state nanopore is determined by the two competing effects: bending of the DNA origami plate that reduces the current and separation of the DNA origami layers that increases the current. The latter is produced by the electro-osmotic flow and is reversible at the time scale of a hundred nanoseconds. The conductance of a DNA origami object is found to depend on its orientation, reaching maximum when the electric field aligns with the direction of the DNA helices. Our work demonstrates feasibility of programming the electrical properties of a self-assembled nanoscale object using DNA.

Thermally Stimulated Currents in Nanocrystalline Titania

PubMed Central

Bruzzi, Mara; Mori, Riccardo; Baldi, Andrea; Cavallaro, Alessandro; Scaringella, Monica

2018-01-01

A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO2. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5–630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 1014–1018 cm−3, associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies. PMID:29303976

Thermally Stimulated Currents in Nanocrystalline Titania.

PubMed

Bruzzi, Mara; Mori, Riccardo; Baldi, Andrea; Carnevale, Ennio Antonio; Cavallaro, Alessandro; Scaringella, Monica

2018-01-05

A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO₂. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5-630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 10 14 -10 18 cm -3 , associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies.

Electrical resistance tomography from measurements inside a steel cased borehole

DOEpatents

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

2000-01-01

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

Electrically actuatable doped polymer flakes and electrically addressable optical devices using suspensions of doped polymer flakes in a fluid host

DOEpatents

Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Marshall, Kenneth L.; Kosc, Tanya Z.

2010-05-11

Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, the non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.

Evaluation of Soft Tissue Sarcoma Tumors Electrical Conductivity Anisotropy Using Diffusion Tensor Imaging for Numerical Modeling on Electroporation.

PubMed

Ghazikhanlou-Sani, K; Firoozabadi, S M P; Agha-Ghazvini, L; Mahmoodzadeh, H

2016-06-01

There is many ways to assessing the electrical conductivity anisotropy of a tumor. Applying the values of tissue electrical conductivity anisotropy is crucial in numerical modeling of the electric and thermal field distribution in electroporation treatments. This study aims to calculate the tissues electrical conductivity anisotropy in patients with sarcoma tumors using diffusion tensor imaging technique. A total of 3 subjects were involved in this study. All of patients had clinically apparent sarcoma tumors at the extremities. The T1, T2 and DTI images were performed using a 3-Tesla multi-coil, multi-channel MRI system. The fractional anisotropy (FA) maps were performed using the FSL (FMRI software library) software regarding the DTI images. The 3D matrix of the FA maps of each area (tumor, normal soft tissue and bone/s) was reconstructed and the anisotropy matrix was calculated regarding to the FA values. The mean FA values in direction of main axis in sarcoma tumors were ranged between 0.475-0.690.  With assumption of isotropy of the electrical conductivity, the FA value of electrical conductivity at each X, Y and Z coordinate axes would be equal to 0.577. The gathered results showed that there is a mean error band of 20% in electrical conductivity, if the electrical conductivity anisotropy not concluded at the calculations. The comparison of FA values showed that there is a significant statistical difference between the mean FA value of tumor and normal soft tissues (P<0.05). DTI is a feasible technique for the assessment of electrical conductivity anisotropy of tissues.  It is crucial to quantify the electrical conductivity anisotropy data of tissues for numerical modeling of electroporation treatments.

Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication.

PubMed

Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

2014-03-19

Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices.

Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication

PubMed Central

Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

2014-01-01

Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices. PMID:24642903

Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication

NASA Astrophysics Data System (ADS)

Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

2014-03-01

Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices.

A novel approach to model hydraulic and electrical conductivity in fractal porous media

NASA Astrophysics Data System (ADS)

Ghanbarian, B.; Daigle, H.; Sahimi, M.

2014-12-01

Accurate prediction of conductivity in partially-saturated porous media has broad applications in various phenomena in porous media, and has been studied intensively since the 1940s by petroleum, chemical and civil engineers, and hydrologists. Many of the models developed in the past are based on the bundle of capillary tubes. In addition, pore network models have also been developed for simulating multiphase fluid flow in porous media and computing the conductivity in unsaturated porous media. In this study, we propose a novel approach using concepts from the effective-medium approximation (EMA) and percolation theory to model hydraulic and electrical conductivity in fractal porous media whose pore-size distributions exhibit power-law scaling. In our approach, the EMA, originally developed for predicting electrical conductivity of composite materials, is used to predict the effective conductivity, from complete saturation to some intermediate water content that represents a crossover point. Below the crossover water content, but still above a critical saturation (percolation threshold), a universal scaling predicted by percolation theory, a power law that expresses the dependence of the conductivity on the water content (less a critical water saturation) with an exponent of 2, is invoked to describe the effective conductivity. In order to evaluate the accuracy of the approach, experimental data were used from the literature. The predicted hydraulic conductivities for most cases are in excellent agreement with the data. In a few cases the theory underestimates the hydraulic conductivities, which correspond to porous media with very broad pore-size distribution in which the largest pore radius is more than 7 orders of magnitude greater than the smallest one. The approach is also used to predict the saturation dependence of the electrical conductivity for experiments in which capillary pressure data are available. The results indicate that the universal scaling of the electrical conductivity is valid from the percolation threshold all the way up to the complete saturation point. Our results confirm those reported previously by Ewing and Hunt (2006) who argued that the electrical conductivity should follow universal scaling over the entire range of saturation.

Gravimetric water distribution assessment from geoelectrical methods (ERT and EMI) in municipal solid waste landfill.

PubMed

Dumont, Gaël; Pilawski, Tamara; Dzaomuho-Lenieregue, Phidias; Hiligsmann, Serge; Delvigne, Frank; Thonart, Philippe; Robert, Tanguy; Nguyen, Frédéric; Hermans, Thomas

2016-09-01

The gravimetric water content of the waste material is a key parameter in waste biodegradation. Previous studies suggest a correlation between changes in water content and modification of electrical resistivity. This study, based on field work in Mont-Saint-Guibert landfill (Belgium), aimed, on one hand, at characterizing the relationship between gravimetric water content and electrical resistivity and on the other hand, at assessing geoelectrical methods as tools to characterize the gravimetric water distribution in a landfill. Using excavated waste samples obtained after drilling, we investigated the influences of the temperature, the liquid phase conductivity, the compaction and the water content on the electrical resistivity. Our results demonstrate that Archie's law and Campbell's law accurately describe these relationships in municipal solid waste (MSW). Next, we conducted a geophysical survey in situ using two techniques: borehole electromagnetics (EM) and electrical resistivity tomography (ERT). First, in order to validate the use of EM, EM values obtained in situ were compared to electrical resistivity of excavated waste samples from corresponding depths. The petrophysical laws were used to account for the change of environmental parameters (temperature and compaction). A rather good correlation was obtained between direct measurement on waste samples and borehole electromagnetic data. Second, ERT and EM were used to acquire a spatial distribution of the electrical resistivity. Then, using the petrophysical laws, this information was used to estimate the water content distribution. In summary, our results demonstrate that geoelectrical methods represent a pertinent approach to characterize spatial distribution of water content in municipal landfills when properly interpreted using ground truth data. These methods might therefore prove to be valuable tools in waste biodegradation optimization projects. Copyright © 2016 Elsevier Ltd. All rights reserved.

The influence of the dispersion method on the electrical properties of vapor-grown carbon nanofiber/epoxy composites

PubMed Central

2011-01-01

The influence of the dispersion of vapor-grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/Epoxy composites has been studied. A homogenous dispersion of the VGCNF does not imply better electrical properties. In fact, it is demonstrated that the most simple of the tested dispersion methods results in higher conductivity, since the presence of well-distributed nanofiber clusters appears to be a key factor for increasing composite conductivity. PACS: 72.80.Tm; 73.63.Fg; 81.05.Qk PMID:21711873

Estimates of olivine-basaltic melt electrical conductivity using a digital rock physics approach

NASA Astrophysics Data System (ADS)

Miller, Kevin J.; Montési, Laurent G. J.; Zhu, Wen-lu

2015-12-01

Estimates of melt content beneath fast-spreading mid-ocean ridges inferred from magnetotelluric tomography (MT) vary between 0.01 and 0.10. Much of this variation may stem from a lack of understanding of how the grain-scale melt geometry influences the bulk electrical conductivity of a partially molten rock, especially at low melt fraction. We compute bulk electrical conductivity of olivine-basalt aggregates over 0.02 to 0.20 melt fraction by simulating electric current in experimentally obtained partially molten geometries. Olivine-basalt aggregates were synthesized by hot-pressing San Carlos olivine and high-alumina basalt in a solid-medium piston-cylinder apparatus. Run conditions for experimental charges were 1.5 GPa and 1350 °C. Upon completion, charges were quenched and cored. Samples were imaged using synchrotron X-ray micro-computed tomography (μ-CT). The resulting high-resolution, 3-dimensional (3-D) image of the melt distribution constitutes a digital rock sample, on which numerical simulations were conducted to estimate material properties. To compute bulk electrical conductivity, we simulated a direct current measurement by solving the current continuity equation, assuming electrical conductivities for olivine and melt. An application of Ohm's Law yields the bulk electrical conductivity of the partially molten region. The bulk electrical conductivity values for nominally dry materials follow a power-law relationship σbulk = Cσmeltϕm with fit parameters m = 1.3 ± 0.3 and C = 0.66 ± 0.06. Laminar fluid flow simulations were conducted on the same partially molten geometries to obtain permeability, and the respective pathways for electrical current and fluid flow over the same melt geometry were compared. Our results indicate that the pathways for flow fluid are different from those for electric current. Electrical tortuosity is lower than fluid flow tortuosity. The simulation results are compared to existing experimental data, and the potential influence of volatiles and melt films on electrical conductivity of partially molten rocks is discussed.

In vivo mapping of current density distribution in brain tissues during deep brain stimulation (DBS)

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-01-01

New methods for in vivo mapping of brain responses during deep brain stimulation (DBS) are indispensable to secure clinical applications. Assessment of current density distribution, induced by internally injected currents, may provide an alternative method for understanding the therapeutic effects of electrical stimulation. The current flow and pathway are affected by internal conductivity, and can be imaged using magnetic resonance-based conductivity imaging methods. Magnetic resonance electrical impedance tomography (MREIT) is an imaging method that can enable highly resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In the current study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The current density maps of three canine brains were calculated from the measured magnetic flux density data. The absolute current density values of brain tissues, including gray matter, white matter, and cerebrospinal fluid were compared to assess the active regions during DBS. The resulting current density in different tissue types may provide useful information about current pathways and volume activation for adjusting surgical planning and understanding the therapeutic effects of DBS.

Determinants of the electric field during transcranial direct current stimulation.

PubMed

Opitz, Alexander; Paulus, Walter; Will, Susanne; Antunes, Andre; Thielscher, Axel

2015-04-01

Transcranial direct current stimulation (tDCS) causes a complex spatial distribution of the electric current flow in the head which hampers the accurate localization of the stimulated brain areas. In this study we show how various anatomical features systematically shape the electric field distribution in the brain during tDCS. We constructed anatomically realistic finite element (FEM) models of two individual heads including conductivity anisotropy and different skull layers. We simulated a widely employed electrode montage to induce motor cortex plasticity and moved the stimulating electrode over the motor cortex in small steps to examine the resulting changes of the electric field distribution in the underlying cortex. We examined the effect of skull thickness and composition on the passing currents showing that thinner skull regions lead to higher electric field strengths. This effect is counteracted by a larger proportion of higher conducting spongy bone in thicker regions leading to a more homogenous current over the skull. Using a multiple regression model we could identify key factors that determine the field distribution to a significant extent, namely the thicknesses of the cerebrospinal fluid and the skull, the gyral depth and the distance to the anode and cathode. These factors account for up to 50% of the spatial variation of the electric field strength. Further, we demonstrate that individual anatomical factors can lead to stimulation "hotspots" which are partly resistant to electrode positioning. Our results give valuable novel insights in the biophysical foundation of tDCS and highlight the importance to account for individual anatomical factors when choosing an electrode montage. Copyright © 2015 Elsevier Inc. All rights reserved.

Magneto-acousto-electrical Measurement Based Electrical Conductivity Reconstruction for Tissues.

PubMed

Zhou, Yan; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

2018-05-01

Based on the interaction of ultrasonic excitation and magnetoelectrical induction, magneto-acousto-electrical (MAE) technology was demonstrated to have the capability of differentiating conductivity variations along the acoustic transmission. By applying the characteristics of the MAE voltage, a simplified algorithm of MAE measurement based conductivity reconstruction was developed. With the analyses of acoustic vibration, ultrasound propagation, Hall effect, and magnetoelectrical induction, theoretical and experimental studies of MAE measurement and conductivity reconstruction were performed. The formula of MAE voltage was derived and simplified for the transducer with strong directivity. MAE voltage was simulated for a three-layer gel phantom and the conductivity distribution was reconstructed using the modified Wiener inverse filter and Hilbert transform, which was also verified by experimental measurements. The experimental results are basically consistent with the simulations, and demonstrate that the wave packets of MAE voltage are generated at tissue interfaces with the amplitudes and vibration polarities representing the values and directions of conductivity variations. With the proposed algorithm, the amplitude and polarity of conductivity gradient can be restored and the conductivity distribution can also be reconstructed accurately. The favorable results demonstrate the feasibility of accurate conductivity reconstruction with improved spatial resolution using MAE measurement for tissues with conductivity variations, especially suitable for nondispersive tissues with abrupt conductivity changes. This study demonstrates that the MAE measurement based conductivity reconstruction algorithm can be applied as a new strategy for nondestructive real-time monitoring of conductivity variations in biomedical engineering.

Experimental characterization and numerical modeling of tissue electrical conductivity during pulsed electric fields for irreversible electroporation treatment planning.

PubMed

Neal, Robert E; Garcia, Paulo A; Robertson, John L; Davalos, Rafael V

2012-04-01

Irreversible electroporation is a new technique to kill cells in targeted tissue, such as tumors, through a nonthermal mechanism using electric pulses to irrecoverably disrupt the cell membrane. Treatment effects relate to the tissue electric field distribution, which can be predicted with numerical modeling for therapy planning. Pulse effects will change the cell and tissue properties through thermal and electroporation (EP)-based processes. This investigation characterizes these changes by measuring the electrical conductivity and temperature of ex vivo renal porcine tissue within a single pulse and for a 200 pulse protocol. These changes are incorporated into an equivalent circuit model for cells and tissue with a variable EP-based resistance, providing a potential method to estimate conductivity as a function of electric field and pulse length for other tissues. Finally, a numerical model using a human kidney volumetric mesh evaluated how treatment predictions vary when EP- and temperature-based electrical conductivity changes are incorporated. We conclude that significant changes in predicted outcomes will occur when the experimental results are applied to the numerical model, where the direction and degree of change varies with the electric field considered.

Transmission of electric fields due to distributed cloud charges in the atmosphere-ionosphere system

NASA Astrophysics Data System (ADS)

Paul, Suman; De, S. S.; Haldar, D. K.; Guha, G.

2017-10-01

The transmission of electric fields in the lower atmosphere by thunder clouds with a suitable charge distribution profile has been modeled. The electromagnetic responses of the atmosphere are presented through Maxwell's equations together with a time-varying source charge distribution. The conductivities are taken to be exponentially graded function of altitude. The radial and vertical electric field components are derived for isotropic, anisotropic and thundercloud regions. The analytical solutions for the total Maxwell's current which flows from the cloud into the ionosphere under DC and quasi-static conditions are obtained for isotropic region. We found that the effect of charge distribution in thunderclouds produced by lightning discharges diminishes rapidly with increasing altitudes. Also, it is found that time to reach Maxwell's currents a maximum is higher for higher altitudes.

Electrically and Thermally Conductive Low Density Polyethylene-Based Nanocomposites Reinforced by MWCNT or Hybrid MWCNT/Graphene Nanoplatelets with Improved Thermo-Oxidative Stability.

PubMed

Paszkiewicz, Sandra; Szymczyk, Anna; Pawlikowska, Daria; Subocz, Jan; Zenker, Marek; Masztak, Roman

2018-04-22

In this paper, the electrical and thermal conductivity and morphological behavior of low density polyethylene (LDPE)/multi-walled carbon nanotubes (MWCNTs) + graphene nanoplatelets (GNPs) hybrid nanocomposites (HNCs) have been studied. The distribution of MWCNTs and the hybrid of MWCNTs/GNPs within the polymer matrix has been investigated with scanning electron microscopy (SEM). The results showed that the thermal and electrical conductivity of the LDPE-based nanocomposites increased along with the increasing content of carbon nanofillers. However, one could observe greater improvement in the thermal and electrical conductivity when only MWCNTs have been incorporated. Moreover, the improvement in tensile properties and thermal stability has been observed when carbon nanofillers have been mixed with LDPE. At the same time, the increasing content of MWCNTs and MWCNTs/GNPs caused an increase in the melt viscosity with only little effect on phase transition temperatures.

Electrically and Thermally Conductive Low Density Polyethylene-Based Nanocomposites Reinforced by MWCNT or Hybrid MWCNT/Graphene Nanoplatelets with Improved Thermo-Oxidative Stability

PubMed Central

Pawlikowska, Daria; Subocz, Jan; Zenker, Marek; Masztak, Roman

2018-01-01

In this paper, the electrical and thermal conductivity and morphological behavior of low density polyethylene (LDPE)/multi-walled carbon nanotubes (MWCNTs) + graphene nanoplatelets (GNPs) hybrid nanocomposites (HNCs) have been studied. The distribution of MWCNTs and the hybrid of MWCNTs/GNPs within the polymer matrix has been investigated with scanning electron microscopy (SEM). The results showed that the thermal and electrical conductivity of the LDPE-based nanocomposites increased along with the increasing content of carbon nanofillers. However, one could observe greater improvement in the thermal and electrical conductivity when only MWCNTs have been incorporated. Moreover, the improvement in tensile properties and thermal stability has been observed when carbon nanofillers have been mixed with LDPE. At the same time, the increasing content of MWCNTs and MWCNTs/GNPs caused an increase in the melt viscosity with only little effect on phase transition temperatures. PMID:29690551

46 CFR 169.678 - Main distribution panels and switchboards.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Section 169.678 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Electrical Installations Operating at Potentials of 50 Volts Or...) Each switchboard must have front and, if accessible from the back, rear non-conducting hand rails...

46 CFR 169.678 - Main distribution panels and switchboards.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Section 169.678 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Electrical Installations Operating at Potentials of 50 Volts Or...) Each switchboard must have front and, if accessible from the back, rear non-conducting hand rails...

46 CFR 169.678 - Main distribution panels and switchboards.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Section 169.678 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Electrical Installations Operating at Potentials of 50 Volts Or...) Each switchboard must have front and, if accessible from the back, rear non-conducting hand rails...

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

Magnetoacoustic Tomography with Magnetic Induction for Electrical Conductivity based Tissue imaging

NASA Astrophysics Data System (ADS)

Mariappan, Leo

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

Highest recorded electrical conductivity and microstructure in polypropylene-carbon nanotubes composites and the effect of carbon nanofibers addition

NASA Astrophysics Data System (ADS)

Ramírez-Herrera, C. A.; Pérez-González, J.; Solorza-Feria, O.; Romero-Partida, N.; Flores-Vela, A.; Cabañas-Moreno, J. G.

2018-04-01

In the last decade, numerous investigations have been devoted to the preparation of polypropylene-multiwalled carbon nanotubes (PP/MWCNT) nanocomposites having enhanced properties, and in particular, high electrical conductivities (> 1 S cm-1). The present work establishes that the highest electrical conductivity in PP/MWCNT nanocomposites is limited by the amount of nanofiller content which can be incorporated in the polymer matrix, namely, about 20 wt%. This concentration of MWCNT in PP leads to a maximum electrical conductivity slightly lower than 8 S cm-1, but only by assuring an adequate combination of dispersion and spatial distribution of the carbon nanotubes. The realization of such an optimal microstructure depends on the characteristics of the production process of the PP/MWCNT nanocomposites; in our experiments, involving composite fabrication by melt mixing and hot pressing, a second re-processing cycle is shown to increase the electrical conductivity values by up to two orders of magnitude, depending on the MWCNT content of the nanocomposite. A modest increase of the highest electrical conductivity obtained in nanocomposites with 21.5 wt% MWCNT content has been produced by the combined use of carbon nanofibers (CNF) and MWCNT, so that the total nanofiller content was increased to 30 wt% in the nanocomposite with PP—15 wt% MWCNT—15 wt%CNF.

The best thermoelectric.

PubMed Central

Mahan, G D; Sofo, J O

1996-01-01

What electronic structure provides the largest figure of merit for thermoelectric materials? To answer that question, we write the electrical conductivity, thermopower, and thermal conductivity as integrals of a single function, the transport distribution. Then we derive the mathematical function for the transport distribution, which gives the largest figure of merit. A delta-shaped transport distribution is found to maximize the thermoelectric properties. This result indicates that a narrow distribution of the energy of the electrons participating in the transport process is needed for maximum thermoelectric efficiency. Some possible realizations of this idea are discussed. PMID:11607692

Technology survey of electrical power generation and distribution for MIUS application

NASA Technical Reports Server (NTRS)

Gill, W. L.; Redding, T. E.

1975-01-01

Candidate electrical generation power systems for the modular integrated utility systems (MIUS) program are described. Literature surveys were conducted to cover both conventional and exotic generators. Heat-recovery equipment associated with conventional power systems and supporting equipment are also discussed. Typical ranges of operating conditions and generating efficiencies are described. Power distribution is discussed briefly. Those systems that appear to be applicable to MIUS have been indicated, and the criteria for equipment selection are discussed.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

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

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

DOE PAGES

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

2016-11-30

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

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.

Electrical properties of lunar soil sample 15301,38

NASA Technical Reports Server (NTRS)

Olhoeft, G. R.; Frisillo, A. L.; Strangway, D. W.

1974-01-01

Electrical property measurements have been made on an Apollo 15 lunar soil sample in ultrahigh vacuum from room temperature to 827 C for the frequency spectrum from 100 Hz through 1 MHz. The dielectric constant, the total ac loss tangent, and the dc conductivity were measured. The dc conductivity showed no thermal hysteresis, but an irreversible (in vacuum) thermal effect was found in the dielectric loss tangent on heating above 700 C and during the subsequent cooling. This appears to be related to several effects associated with lunar glass above 700 C. The sample also showed characteristic low-frequency dispersion in the dielectric constant with increasing temperature, presumably due to Maxwell-Wagner intergranular effects. The dielectric properties may be fitted to a model involving a Cole-Cole frequency distribution that is relatively temperature-independent below 200 C and follows a Boltzmann temperature distribution with an activation energy of 2.5 eV above 200 C. The dc conductivity is fitted by an exponential temperature distribution and becomes the dominant loss above 700 C.

High temperature superconductor current leads

DOEpatents

Hull, John R.; Poeppel, Roger B.

1995-01-01

An electrical lead having one end for connection to an apparatus in a cryogenic environment and the other end for connection to an apparatus outside the cryogenic environment. The electrical lead includes a high temperature superconductor wire and an electrically conductive material distributed therein, where the conductive material is present at the one end of the lead at a concentration in the range of from 0 to about 3% by volume, and at the other end of the lead at a concentration of less than about 20% by volume. Various embodiments are shown for groups of high temperature superconductor wires and sheaths.

High temperature superconductor current leads

DOEpatents

Hull, J.R.; Poeppel, R.B.

1995-06-20

An electrical lead is disclosed having one end for connection to an apparatus in a cryogenic environment and the other end for connection to an apparatus outside the cryogenic environment. The electrical lead includes a high temperature superconductor wire and an electrically conductive material distributed therein, where the conductive material is present at the one end of the lead at a concentration in the range of from 0 to about 3% by volume, and at the other end of the lead at a concentration of less than about 20% by volume. Various embodiments are shown for groups of high temperature superconductor wires and sheaths. 9 figs.

Investigating the impact of visuohaptic simulations for the conceptual understanding of electric field for distributed charges

NASA Astrophysics Data System (ADS)

Shaikh, Uzma Abdul Sattar

The present study assessed the benefits of a multisensory intervention on the conceptual understanding of electric field for distributed charges in engineering and technology undergraduate students. A novel visuohaptic intervention was proposed, which focused on exploring the forces around the different electric field configurations for distributed charges namely point, infinitely long line and uniformly charged ring. The before and after effects of the visuohaptic intervention are compared, wherein the intervention includes instructional scaffolding. Three single-group studies were conducted to investigate the effect among three different populations: (a) Undergraduate engineering students, (b) Undergraduate technology students and (c) Undergraduate engineering technology students from a different demographic setting. The findings from the three studies suggests that the haptic modality intervention provides beneficial effects by allowing students to improve their conceptual understanding of electric field for distributed charges, although students from groups (b) and (c) showed a statistically significant increase in the conceptual understanding. The findings also indicate a positive learning perception among all the three groups.

Simulation of the Electrical Field in Equine Larynx to Optimize Functional Electrical Stimulation in Denervated Musculus Cricoarythenoideus Dorsalis

PubMed Central

Martinek, Johannes

2014-01-01

Distribution of the electrical field is very important to activate muscle and nerve cells properly. One therapeutic method to treat Recurrent Laryngeal Neuropathy (RLN) in horses can be performed by Functional Electrical Stimulation (FES). Current method to optimize the stimulation effect is to use implanted quadripolar electrodes to the musculus cricoarythenoideus dorsalis (CAD) and testing electrode configuration until best possible optimum is reached. For better understanding and finding of maximum possible activation of CAD a simulation model of the actual entire setting is currently in development. Therefore the geometric model is built from CT-data of a dissected larynx containing the quadripolar electrodes as well as fiducials for later data registration. The geometric model is the basis for a finite difference method containing of voxels with corresponding electrical conductivity of the different types of tissue due to threshold segmentation of the CT-data. Model validation can be done by the measurement of the 3D electrical potential distribution of a larynx positioned in an electrolytic tray. Finally, measured and calculated results have to be compared as well as further investigated. Preliminary results show, that changes of electrode as well as conductivity configuration leads to significant different voltage distributions and can be well presented by equipotential lines superimposed CT-slices – a Matlab graphical user interface visualizes the results in freely selectable slices of the 3D geometry. Voltage distribution along theoretically estimated fiber paths could be calculated as well as visualized. For further calculation of nerve or denervated muscle fiber activation and its optimization, real fiber paths have to be defined and referenced to the potential- and the CT-data. PMID:26913137

Analysis of electrophoresis performance

NASA Technical Reports Server (NTRS)

Roberts, G. O.

1984-01-01

The SAMPLE computer code models electrophoresis separation in a wide range of conditions. Results are included for steady three dimensional continuous flow electrophoresis (CFE), time dependent gel and acetate film experiments in one or two dimensions and isoelectric focusing in one dimension. The code evolves N two dimensional radical concentration distributions in time, or distance down a CFE chamber. For each time or distance increment, there are six stages, successively obtaining the pH distribution, the corresponding degrees of ionization for each radical, the conductivity, the electric field and current distribution, and the flux components in each direction for each separate radical. The final stage is to update the radical concentrations. The model formulation for ion motion in an electric field ignores activity effects, and is valid only for low concentrations; for larger concentrations the conductivity is, therefore, also invalid.

Random network model of electrical conduction in two-phase rock

NASA Astrophysics Data System (ADS)

Fuji-ta, Kiyoshi; Seki, Masayuki; Ichiki, Masahiro

2018-05-01

We developed a cell-type lattice model to clarify the interconnected conductivity mechanism of two-phase rock. We quantified electrical conduction networks in rock and evaluated electrical conductivity models of the two-phase interaction. Considering the existence ratio of conductive and resistive cells in the model, we generated natural matrix cells simulating a natural mineral distribution pattern, using Mersenne Twister random numbers. The most important and prominent feature of the model simulation is a drastic increase in the pseudo-conductivity index for conductor ratio R > 0.22. This index in the model increased from 10-4 to 100 between R = 0.22 and 0.9, a change of four orders of magnitude. We compared our model responses with results from previous model studies. Although the pseudo-conductivity computed by the model differs slightly from that of the previous model, model responses can account for the conductivity change. Our modeling is thus effective for quantitatively estimating the degree of interconnection of rock and minerals.

Theoretical and experimental studies of electric field distribution in N-polar GaN/AlGaN/GaN heterostructures

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

Gladysiewicz, M., E-mail: marta.gladysiewicz@pwr.edu.pl; Janicki, L.; Kudrawiec, R.

2015-12-28

Electric field distribution in N-polar GaN(channel)/AlGaN/GaN(buffer) heterostructures was studied theoretically by solving Schrodinger and Poisson equations in a self-consistent manner for various boundary conditions and comparing results of these calculations with experimental data, i.e., measurements of electric field in GaN(channel) and AlGaN layers by electromodulation spectroscopy. A very good agreement between theoretical calculations and experimental data has been found for the Fermi-level located at ∼0.3 eV below the conduction band at N-polar GaN surface. With this surface boundary condition, the electric field distribution and two dimensional electron gas concentration are determined for GaN(channel)/AlGaN/GaN(buffer) heterostructures of various thicknesses of GaN(channel) and AlGaNmore » layers.« less

Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

NASA Technical Reports Server (NTRS)

Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

1976-01-01

Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

Evaluation of the Atmospheric Boundary-Layer Electrical Variability

NASA Astrophysics Data System (ADS)

Anisimov, Sergey V.; Galichenko, Sergey V.; Aphinogenov, Konstantin V.; Prokhorchuk, Aleksandr A.

2017-12-01

Due to the chaotic motion of charged particles carried by turbulent eddies, electrical quantities in the atmospheric boundary layer (ABL) have short-term variability superimposed on long-term variability caused by sources from regional to global scales. In this study the influence of radon exhalation rate, aerosol distribution and turbulent transport efficiency on the variability of fair-weather atmospheric electricity is investigated via Lagrangian stochastic modelling. For the mid-latitude lower atmosphere undisturbed by precipitation, electrified clouds, or thunderstorms, the model is capable of reproducing the diurnal variation in atmospheric electrical parameters detected by ground-based measurements. Based on the analysis of field observations and numerical simulation it is found that the development of the convective boundary layer, accompanied by an increase in turbulent kinetic energy, forms the vertical distribution of radon and its decaying short-lived daughters to be approximately coincident with the barometric law for several eddy turnover times. In the daytime ABL the vertical distribution of atmospheric electrical conductivity tends to be uniform except within the surface layer, due to convective mixing of radon and its radioactive decay products. At the same time, a decrease in the conductivity near the ground is usually observed. This effect leads to an enhanced ground-level atmospheric electric field compared to that normally observed in the nocturnal stably-stratified boundary layer. The simulation showed that the variability of atmospheric electric field in the ABL associated with internal origins is significant in comparison to the variability related to changes in global parameters. It is suggested that vertical profiles of electrical quantities can serve as informative parameters on ABL turbulent dynamics and can even more broadly characterize the state of the environment.

The Effect of Precipitating Electrons and Ions on Ionospheric Conductance and Inner Magnetospheric Electric Fields 142106

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Hecht, J. H.; Evans, J. S.; Boyd, A. J.

2016-12-01

We investigate how scattering of electrons by waves and of ions by field-line curvature in the inner magnetosphere affect precipitating energy flux distributions and how the precipitating particles modify the ionospheric conductivity and electric potentials during magnetic storms. We examine how particle precipitation in the evening sector affects the development of the Sub-Auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector as well as the electric field in the morning sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating particle distributions and the electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are employed. Our description for the rate of ion scattering is more simplistic. We assume that the ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. We compare simulated trapped and precipitating electron/ion flux distributions with measurements from Van Allen Probes/MagEIS, POES and DMSP, respectively, to validate the particle loss models. DMSP observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons and ions on the SAPS and the inner magnetospheric electric field through the data-model comparisons.

Electrical conductivity of basaltic and carbonatite melt-bearing peridotites at high pressures: Implications for melt distribution and melt fraction in the upper mantle

NASA Astrophysics Data System (ADS)

Yoshino, Takashi; Laumonier, Mickael; McIsaac, Elizabeth; Katsura, Tomoo

2010-07-01

Electrical impedance measurements were performed on two types of partial molten samples with basaltic and carbonatitic melts in a Kawai-type multi-anvil apparatus in order to investigate melt fraction-conductivity relationships and melt distribution of the partial molten mantle peridotite under high pressure. The silicate samples were composed of San Carlos olivine with various amounts of mid-ocean ridge basalt (MORB), and the carbonate samples were a mixture of San Carlos olivine with various amounts of carbonatite. High-pressure experiments on the silicate and carbonate systems were performed up to 1600 K at 1.5 GPa and up to at least 1650 K at 3 GPa, respectively. The sample conductivity increased with increasing melt fraction. Carbonatite-bearing samples show approximately one order of magnitude higher conductivity than basalt-bearing ones at the similar melt fraction. A linear relationship between log conductivity ( σbulk) and log melt fraction ( ϕ) can be expressed well by the Archie's law (Archie, 1942) ( σbulk/ σmelt = Cϕn) with parameters C = 0.68 and 0.97, n = 0.87 and 1.13 for silicate and carbonate systems, respectively. Comparison of the electrical conductivity data with theoretical predictions for melt distribution indicates that the model assuming that the grain boundary is completely wetted by melt is the most preferable melt geometry. The gradual change of conductivity with melt fraction suggests no permeability jump due to melt percolation at a certain melt fraction. The melt fraction of the partial molten region in the upper mantle can be estimated to be 1-3% and ˜ 0.3% for basaltic melt and carbonatite melt, respectively.

Coherent radar estimates of high latitude field-aligned currents: the importance of conductance gradients

NASA Astrophysics Data System (ADS)

Kosch, M.; Nielsen, E.

Two bi-static VHF radar systems STARE and SABRE have been employed to estimate ionospheric electric field distributions in the geomagnetic latitude range 61 1 - 69 3 degrees over Scandinavia corresponding to the global Region 2 current system 173 days of data from all four radars have been analysed during the period 1982 to 1986 The average magnetic field-aligned currents have been computed as a function of the Kp and Ae indices using an empirical model of ionospheric Pedersen and Hall conductance taking into account conductance gradients The divergence of horizontal Pedersen currents and Hall conductance gradients have approximately the same importance for generating the Region 2 field-aligned currents Pedersen conductance gradients have a significant modifying effect A case study of field-aligned currents has been performed using the STARE radar system to obtain the instantaneous ionospheric electric field distribution in the vicinity of an auroral arc The instantaneous Hall conductance was estimated from the Scandinavian Magnetometer Array This study clearly shows that even for quiet steady state geomagnetic conditions conductance gradients are important modifiers of magnetic field-aligned currents

Geophysical data integration and conditional uncertainty analysis on hydraulic conductivity estimation

USGS Publications Warehouse

Rahman, A.; Tsai, F.T.-C.; White, C.D.; Carlson, D.A.; Willson, C.S.

2007-01-01

Integration of various geophysical data is essential to better understand aquifer heterogeneity. However, data integration is challenging because there are different levels of support between primary and secondary data needed to be correlated in various ways. This study proposes a geostatistical method to integrate the hydraulic conductivity measurements and electrical resistivity data to better estimate the hydraulic conductivity (K) distribution. The K measurements are obtained from the pumping tests and represent the primary data (hard data). The borehole electrical resistivity data from electrical logs are regarded as the secondary data (soft data). The electrical resistivity data is used to infer hydraulic conductivity values through the Archie law and Kozeny-Carman equation. A pseudo cross-semivariogram is developed to cope with the resistivity data non-collocation. Uncertainty in the auto-semivariograms and pseudo cross-semivariogram is quantified. The methodology is demonstrated by a real-world case study where the hydraulic conductivity is estimated in the Upper Chicot aquifer of Southwestern Louisiana. The groundwater responses by the cokriging and cosimulation of hydraulic conductivity are compared using analysis of variance (ANOVA). ?? 2007 ASCE.

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.

An Explosively Actuated Electrical Switch Using Kapton Insulation

DTIC Science & Technology

1993-03-01

ionization pin. This is consistent with a shock-induced conduction model because the conductivity is known to increase with pressure.5 The aluminum...34Shock Induced Electrical Activity in Polymeric Solids. A Mechanically Induced Bond Scission Model ," J. Phys. Chem., 83 (23), 1979, p. 3048. 9. Graham...NSWC, White Oak, MD. 6-2 NSWCDD/TR-92/124 DISTRIBUTION Copies Chief of Naval Research Attn: ONR1132P(R. Miller ) 1 ONT 20T (L. V. Schmidt) 1

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.

Ohmic Heating of an Electrically Conductive Food Package.

PubMed

Kanogchaipramot, Kanyawee; Tongkhao, Kullanart; Sajjaanantakul, Tanaboon; Kamonpatana, Pitiya

2016-12-01

Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post-process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3-D thermal-electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food. © 2016 Institute of Food Technologists®.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

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

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the filmmore » and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

DOE PAGES

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter; ...

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behavior, large changes in metal-insulator transition temperatures, or enhanced catalytic activity. Here in this paper, we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In 2O 3 films grown on ionically conducting Y 2O 3-stabilized ZrO 2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygenmore » vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behavior is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

Anisotropic conductivity imaging with MREIT using equipotential projection algorithm.

PubMed

Değirmenci, Evren; Eyüboğlu, B Murat

2007-12-21

Magnetic resonance electrical impedance tomography (MREIT) combines magnetic flux or current density measurements obtained by magnetic resonance imaging (MRI) and surface potential measurements to reconstruct images of true conductivity with high spatial resolution. Most of the biological tissues have anisotropic conductivity; therefore, anisotropy should be taken into account in conductivity image reconstruction. Almost all of the MREIT reconstruction algorithms proposed to date assume isotropic conductivity distribution. In this study, a novel MREIT image reconstruction algorithm is proposed to image anisotropic conductivity. Relative anisotropic conductivity values are reconstructed iteratively, using only current density measurements without any potential measurement. In order to obtain true conductivity values, only either one potential or conductivity measurement is sufficient to determine a scaling factor. The proposed technique is evaluated on simulated data for isotropic and anisotropic conductivity distributions, with and without measurement noise. Simulation results show that the images of both anisotropic and isotropic conductivity distributions can be reconstructed successfully.

The role of Hurst exponent on cold field electron emission from conducting materials: from electric field distribution to Fowler-Nordheim plots

PubMed Central

de Assis, T. A.

2015-01-01

This work considers the effects of the Hurst exponent (H) on the local electric field distribution and the slope of the Fowler-Nordheim (FN) plot when considering the cold field electron emission properties of rough Large-Area Conducting Field Emitter Surfaces (LACFESs). A LACFES is represented by a self-affine Weierstrass-Mandelbrot function in a given spatial direction. For 0.1 ≤ H < 0.5, the local electric field distribution exhibits two clear exponential regimes. Moreover, a scaling between the macroscopic current density () and the characteristic kernel current density (), , with an H-dependent exponent , has been found. This feature, which is less pronounced (but not absent) in the range where more smooth surfaces have been found (), is a consequence of the dependency between the area efficiency of emission of a LACFES and the macroscopic electric field, which is often neglected in the interpretation of cold field electron emission experiments. Considering the recent developments in orthodox field emission theory, we show that the exponent must be considered when calculating the slope characterization parameter (SCP) and thus provides a relevant method of more precisely extracting the characteristic field enhancement factor from the slope of the FN plot. PMID:26035290

Current density and catalyst-coated membrane resistance distribution of hydro-formed metallic bipolar plate fuel cell short stack with 250 cm2 active area

NASA Astrophysics Data System (ADS)

Haase, S.; Moser, M.; Hirschfeld, J. A.; Jozwiak, K.

2016-01-01

An automotive fuel cell with an active area of 250 cm2 is investigated in a 4-cell short stack with a current and temperature distribution device next to the bipolar plate with 560 current and 140 temperature segments. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this current scan shunt module. The applied fuel cell consists of bipolar plates constructed of 75-μm-thick, welded stainless-steel foils and a graphitic coating. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this module with a 6% deviation in in-plane conductivity. The current density distribution is evaluated up to 2.4 A cm-2. The entire cell's investigated volumetric power density is 4.7 kW l-1, and its gravimetric power density is 4.3 kW kg-1 at an average cell voltage of 0.5 V. The current density distribution is determined without influencing the operating cell. In addition, the current density distribution in the catalyst-coated membrane and its effective resistivity distribution with a finite volume discretisation of Ohm's law are evaluated. The deviation between the current density distributions in the catalyst-coated membrane and the bipolar plate is determined.

Carbon nanotube-based bioceramic grafts for electrotherapy of bone.

PubMed

Mata, D; Horovistiz, A L; Branco, I; Ferro, M; Ferreira, N M; Belmonte, M; Lopes, M A; Silva, R F; Oliveira, F J

2014-01-01

Bone complexity demands the engineering of new scaffolding solutions for its reconstructive surgery. Emerging bone grafts should offer not only mechanical support but also functional properties to explore innovative bone therapies. Following this, ceramic bone grafts of Glass/hydroxyapatite (HA) reinforced with conductive carbon nanotubes (CNTs) - CNT/Glass/HA - were prepared for bone electrotherapy purposes. Computer-aided 3D microstructural reconstructions and TEM analysis of CNT/Glass/HA composites provided details on the CNT 3D network and further correlation to their functional properties. CNTs are arranged as sub-micrometric sized ropes bridging homogenously distributed ellipsoid-shaped agglomerates. This arrangement yielded composites with a percolation threshold of pc=1.5vol.%. At 4.4vol.% of CNTs, thermal and electrical conductivities of 1.5W·m(-1)·K(-1) and 55S·m(-1), respectively, were obtained, matching relevant requisites in electrical stimulation protocols. While the former avoids bone damaging from Joule's heat generation, the latter might allow the confinement of external electrical fields through the conductive material if used for in vivo electrical stimulation. Moreover, the electrically conductive bone grafts have better mechanical properties than those of the natural cortical bone. Overall, these highly conductive materials with controlled size CNT agglomerates might accelerate bone bonding and maximize the delivery of electrical stimulation during electrotherapy practices. © 2013.

Influence of anisotropic conductivity in the skull and white matter on transcranial direct current stimulation via an anatomically realistic finite element head model

NASA Astrophysics Data System (ADS)

Suh, Hyun Sang; Lee, Won Hee; Kim, Tae-Seong

2012-11-01

To establish safe and efficient transcranial direct current stimulation (tDCS), it is of particular importance to understand the electrical effects of tDCS in the brain. Since the current density (CD) and electric field (EF) in the brain generated by tDCS depend on various factors including complex head geometries and electrical tissue properties, in this work, we investigated the influence of anisotropic conductivity in the skull and white matter (WM) on tDCS via a 3D anatomically realistic finite element head model. We systematically incorporated various anisotropic conductivity ratios into the skull and WM. The effects of anisotropic tissue conductivity on the CD and EF were subsequently assessed through comparisons to the conventional isotropic solutions. Our results show that the anisotropic skull conductivity significantly affects the CD and EF distribution: there is a significant reduction in the ratio of the target versus non-target total CD and EF on the order of 12-14%. In contrast, the WM anisotropy does not significantly influence the CD and EF on the targeted cortical surface, only on the order of 1-3%. However, the WM anisotropy highly alters the spatial distribution of both the CD and EF inside the brain. This study shows that it is critical to incorporate anisotropic conductivities in planning of tDCS for improved efficacy and safety.

Numerical Computation of Electric Field and Potential Along Silicone Rubber Insulators Under Contaminated and Dry Band Conditions

NASA Astrophysics Data System (ADS)

Arshad; Nekahi, A.; McMeekin, S. G.; Farzaneh, M.

2016-09-01

Electrical field distribution along the insulator surface is considered one of the important parameters for the performance evaluation of outdoor insulators. In this paper numerical simulations were carried out to investigate the electric field and potential distribution along silicone rubber insulators under various polluted and dry band conditions. Simulations were performed using commercially available simulation package Comsol Multiphysics based on the finite element method. Various pollution severity levels were simulated by changing the conductivity of pollution layer. Dry bands of 2 cm width were inserted at the high voltage end, ground end, middle part, shed, sheath, and at the junction of shed and sheath to investigate the effect of dry band location and width on electric field and potential distribution. Partial pollution conditions were simulated by applying pollution layer on the top and bottom surface respectively. It was observed from the simulation results that electric field intensity was higher at the metal electrode ends and at the junction of dry bands. Simulation results showed that potential distribution is nonlinear in the case of clean and partially polluted insulator and linear for uniform pollution layer. Dry band formation effect both potential and electric field distribution. Power dissipated along the insulator surface and the resultant heat generation was also studied. The results of this study could be useful in the selection of polymeric insulators for contaminated environments.

Fourier analysis of polar cap electric field and current distributions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1984-01-01

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Mineral resource of the month: copper

USGS Publications Warehouse

,

2011-01-01

The article provides information on copper and its various uses. It was the first metal used by humans and is considered as one of the materials that played an important role in the development of civilization. It is a major industrial metal because of its low cost, availability, electrical conductivity, high ductility and thermal conductivity. Copper has long been used in the circuitry of electronics and the distribution of electricity and is now being used in silicon-based computer chips, solar and wind power generation, and coinage.

Field-aligned current sources in the high-latitude ionosphere

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1979-01-01

The paper determines the electric potential in a plane which is fed current from a pair of field-aligned current sheets. The ionospheric conductivity is modelled as a constant with an enhanced conductivity annular ring. It is shown that field-aligned current distributions are arbitrary functions of azimuth angle (MLT) and thus allow for asymmetric potential configurations over the pole cap. In addition, ionospheric surface currents are computed by means of stream functions. Finally, the discussion relates these methods to the electrical characteristics of the magnetosphere.

A Reconstruction Algorithm of Magnetoacoustic Tomography with Magnetic Induction for Acoustically Inhomogeneous Tissue

PubMed Central

Zhou, Lian; Zhu, Shanan

2014-01-01

Magnetoacoustic tomography with Magnetic Induction (MAT-MI) is a noninvasive electrical conductivity imaging approach that measures ultrasound wave induced by magnetic stimulation, for reconstructing the distribution of electrical impedance in biological tissue. Existing reconstruction algorithms for MAT-MI are based on the assumption that the acoustic properties in the tissue are homogeneous. However, the tissue in most parts of human body, has heterogeneous acoustic properties, which leads to potential distortion and blurring of small buried objects in the impedance images. In the present study, we proposed a new algorithm for MAT-MI to image the impedance distribution in tissues with inhomogeneous acoustic speed distributions. With a computer head model constructed from MR images of a human subject, a series of numerical simulation experiments were conducted. The present results indicate that the inhomogeneous acoustic properties of tissues in terms of speed variation can be incorporated in MAT-MI imaging. PMID:24845284

Integral gas seal for fuel cell gas distribution assemblies and method of fabrication

DOEpatents

Dettling, Charles J.; Terry, Peter L.

1985-03-19

A porous gas distribution plate assembly for a fuel cell, such as a bipolar assembly, includes an inner impervious region wherein the bipolar assembly has good surface porosity but no through-plane porosity and wherein electrical conductivity through the impervious region is maintained. A hot-pressing process for forming the bipolar assembly includes placing a layer of thermoplastic sealant material between a pair of porous, electrically conductive plates, applying pressure to the assembly at elevated temperature, and allowing the assembly to cool before removing the pressure whereby the layer of sealant material is melted and diffused into the porous plates to form an impervious bond along a common interface between the plates holding the porous plates together. The distribution of sealant within the pores along the surface of the plates provides an effective barrier at their common interface against through-plane transmission of gas.

Method of fabricating an integral gas seal for fuel cell gas distribution assemblies

DOEpatents

Dettling, Charles J.; Terry, Peter L.

1988-03-22

A porous gas distribution plate assembly for a fuel cell, such as a bipolar assembly, includes an inner impervious region wherein the bipolar assembly has good surface porosity but no through-plane porosity and wherein electrical conductivity through the impervious region is maintained. A hot-pressing process for forming the bipolar assembly includes placing a layer of thermoplastic sealant material between a pair of porous, electrically conductive plates, applying pressure to the assembly at elevated temperature, and allowing the assembly to cool before removing the pressure whereby the layer of sealant material is melted and diffused into the porous plates to form an impervious bond along a common interface between the plates holding the porous plates together. The distribution of sealant within the pores along the surface of the plates provides an effective barrier at their common interface against through-plane transmission of gas.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

Conventional ground survey of soil root zone salinity by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity, σb, in the field. This approach is faster and cheaper, and allows a more intensive surveying. Measurements of σb can be made either in situ or with remote devices. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on the Electrical Resistivity Tomography (ERT) techniques represent an alternative in respect to those traditional for soil salinity characterization. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from ERT sensors. The latter, in turn, depends on the specific depth distribution of the σb, as well as on the electrical configuration of the sensor used. With these premises, the main aim of this study is to estimate the vertical σb distribution starting from resistivity data series measured using the ERT method under different salinity conditions and using TDR data as ground-truth data for calibration and validation of the ERT sensor. This way, limited measured TDR data may be used for translating extensive ERT apparent electrical conductivity, σa, measurements to estimate depth-distributions of σb. These, in turn, may be translated to many σw values by applying the σw-σb-θ calibration relationship obtained in the laboratory by using the TDR probes. A field experiment was conducted in the Mediterranean Agronomic Institute (MAI) of Valenzano (Bari - Italy). The experiment consisted of three transects 30 m long and 4.2 width, cultivated with green bean and irrigated with three different salinity levels (1 dS/m, 3 dS/m, and 6 dS/m). Each transect consisted of seven rows equipped by a dripper irrigation system, which supplied a water flux of 2 l/h. As for the salt application, CaCl2 were dissolved in tap water, and subsequently siphoned into the irrigation system. For each transect, 24 regularly spaced monitoring sites (1 m apart) were selected for soil measurements, using different equipments: i) a TDR100, ii) an ERT apparatus in the Wenner configuration array. Overall, 17 measurement campaigns were carried out. Monitoring along transects also allowed to evaluate the role of different smaller and larger scale heterogeneities on the electrical conductivity measured by the two different sensors. Because of the different variability patterns and structure of the ERT and TDR data due to the different observation windows, a site-by-site comparison of the corresponding readings may not reveal the actual correlation between the σb values deduced by ERT measurements on one side and the TDR data on the other. In order to make TDR and ERT data actually comparable, we analyzed the effect of the different observation windows of the two sensors on the different spatial and temporal variability observed in the two data series. Specifically, the study assessed the potential of applying a Fourier's analysis to filter the original data series to extract the predominant, high-variance signal after removing the small- scale (high frequency) variance observed in the TDR data series.

Response of ionospheric electric fields at mid-low latitudes during geomagnetic sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2014-12-01

Geomagnetic sudden commencements (SCs) are known as one of the distinct magnetospheric disturbance phenomena triggered by solar wind disturbances. Many previous studies have focused on the generation mechanism of SCs by using in-situ observations and simulations. However, the global evolution of ionospheric electric fields has primarily been estimated from the ionospheric current. Although a few studies utilized electric field data from radar observations, the coverage is limited in time, and limited component of the electric field is obtained. In this study, we investigated the response and local time dependence of the ionospheric electric field at mid-low latitudes associated with 203 SCs occurred from 1999 to 2004 by the in-situ observation of the ROCSAT-1 spacecraft. We found that the ionospheric electric field associated with SCs instantaneously responds to geomagnetic fields regardless of spacecraft local time. Our statistical analysis also showed the instantaneous response of the electric field, which indicates the global instant transmission of the electric field from polar region. In contrast, peak times in the preliminary impulse (PI) and main impulse (MI) phases were different between the ionospheric electric field and equatorial geomagnetic field (20 sec in the PI phase). Based on a comparison to the ground-ionosphere waveguide model by Kikuchi [2014], this time lag is suggested to be due to the latitudinal difference of the ionospheric conductivity. After constructing the local time distribution of the SC amplitude, we found that the dayside feature was seen at 18-22 h even the ionospheric conductivity is lower than that at dayside. We performed a magnetohydrodynamic (MHD) simulation for an ideal SC. The result of the simulation showed that the electric potential distribution is asymmetric with respect to the noon-midnight meridian, which is similar to our observational result. It appears to result from the divergence of the Hall current under the non-uniform ionospheric conductivity near the terminator as well as the auroral region.

Computational Interpretation of the Relation Between Electric Field and the Applied Current for Cathodic Protection Under Different Conductivity Environments

NASA Astrophysics Data System (ADS)

Kim, Yong-Sang; Ko, Sang-Jin; Lee, Sangkyu; Kim, Jung-Gu

2018-03-01

An interpretation of the relation between the electric field and the applied current for cathodic protection is investigated using a boundary element method simulation. Also, a conductivity-difference environment is set for the interface influence. The variation of the potential distribution is increased with the increase of the applied current and the conductivity difference due to the rejection of the current at the interface. In the case of the electric field, the tendencies of the increasing rate and the applied currents are similar, but the interface influence is different according to the directional component and field type (decrease of E z and increases of E x and E y) due to the directional difference between the electric fields. Also, the change tendencies of the electric fields versus the applied current plots are affected by the polarization curve tendency regarding the polarization type (activation and concentration polarizations in the oxygen-reduction and hydrogen-reduction reactions). This study shows that the underwater electric signature is determined by the polarization behavior of the materials.

Local structural behavior of PbZr0.5Ti0.5O3 during electric field application via in situ pair distribution function study

NASA Astrophysics Data System (ADS)

Zhao, Changhao; Hou, Dong; Chung, Ching-Chang; Yu, Yingying; Liu, Wenfeng; Li, Shengtao; Jones, Jacob L.

2017-11-01

The local structural behavior of PbZr0.5Ti0.5O3 (PZT 50/50) ceramics during application of an electric field was investigated using pair distribution function (PDF) analysis. In situ synchrotron total scattering was conducted, and the PDFs were calculated from the Fourier transform of the total scattering data. The PDF refinement of the zero-field data suggests a local-structure model with [001] Ti-displacement and negligible Zr-displacement. The directional PDFs at different field amplitudes indicate the bond-length distribution of the nearest Pb-B (B = Zr/Ti) pair changes significantly with the field. The radial distribution functions (RDFs) of a model for polarization rotation were calculated. The calculated and the experimental RDFs are consistent. This result suggests the changes in Pb-B bond-length distribution could be dominantly caused by polarization rotation. Peak fitting of the experimental RDFs was also conducted. The peak position trends with increasing field are mostly in agreement with the calculation result of the polarization rotation model. The area ratio of the peaks in the experimental RDFs also changed with field amplitude, indicating that Zr atoms have a detectable displacement driven by the electric field. Our study provides an experimental observation of the behaviors of PZT 50/50 under field at a local scale which supports the polarization rotation mechanism.

Lightweight electrically-powered flexible thermal laminate. [made of metal and nonconductive yarns

NASA Technical Reports Server (NTRS)

Dawn, F. S.; Sauers, D. G. (Inventor)

1978-01-01

Cross-layered woven or unwoven yarns are used to provide an active thermal control mechanism for spacecraft use. One set of yarns is composed of flexible electrically conductive metal fibers which are capable of being resistance heated by the application of voltage. Another set of yarns, nonconductive and flexible, provides mechanical strength and precludes the passage of electrical current between the metal yarns by virtue of the spacing between them. A lightweight, electrically nonconductive film is bonded to the cross-layered yarns to protect the metal yarns from the elements (minimize electrical shorts from moisture such as rain), to provide additional strength to the fabric, and to prevent conductive loss of heat in nonvacuum applications. The nonconductive film is metalized on its obverse side to provide a more uniform heat load distribution.

Steady-state protein focusing in carrier ampholyte based isoelectric focusing: Part I-Analytical solution.

PubMed

Shim, Jaesool; Yoo, Kisoo; Dutta, Prashanta

2017-03-01

The determination of an analytical solution to find the steady-state protein concentration distribution in IEF is very challenging due to the nonlinear coupling between mass and charge conservation equations. In this study, approximate analytical solutions are obtained for steady-state protein distribution in carrier ampholyte based IEF. Similar to the work of Svensson, the final concentration profile for proteins is assumed to be Gaussian, but appropriate expressions are presented in order to obtain the effective electric field and pH gradient in the focused protein band region. Analytical results are found from iterative solutions of a system of coupled algebraic equations using only several iterations for IEF separation of three plasma proteins: albumin, cardiac troponin I, and hemoglobin. The analytical results are compared with numerically predicted results for IEF, showing excellent agreement. Analytically obtained electric field and ionic conductivity distributions show significant deviation from their nominal values, which is essential in finding the protein focusing behavior at isoelectric points. These analytical solutions can be used to determine steady-state protein concentration distribution for experiment design of IEF considering any number of proteins and ampholytes. Moreover, the model presented herein can be used to find the conductivity, electric field, and pH field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Frequency characteristics of geomagnetic induction anomalies in Saurashtra region

NASA Astrophysics Data System (ADS)

Kumar, P. V. Vijaya; Rao, P. B. V. Subba; Rao, C. K.; Singh, A. K.; Rao, P. Rama

2017-10-01

Magnetovariational studies were carried out along four different EW profiles in Saurashtra region in different phases, during January 2007-March 2012. Transient geomagnetic field variations (X, Y horizontal field and Z vertical field components) recorded along these profiles are analyzed to infer the electrical conductivity distribution of the region. The vertical field transfer functions which depict the characteristics of electrical conductivity distribution are presented in the form of induction arrows. From the spatial distribution of these arrows, it is inferred that the sediments filling the offshore basins have more conductivity than those basins in Saurashtra region. Z/ H pseudo sections along the four profiles in conjunction with tectonics and other geophysical methods permit to infer that the conductivity anomaly in the eastern part of the profiles is associated with the crustal/lithosphere thinning. The possible cause for these anomalies may be explained in terms of partial melts associated with mafic intrusions, related to Deccan and pre-Deccan volcanism. High resistive block related to underplating mantle material has been reflected in 1D models of long period magnetotelluric data and its thickness reduces from west to east. Lithosphere-asthenosphere boundary varies from 80 to 100 km.

Electrical conductivity enhancement by boron-doping in diamond using first principle calculations

NASA Astrophysics Data System (ADS)

Ullah, Mahtab; Ahmed, Ejaz; Hussain, Fayyaz; Rana, Anwar Manzoor; Raza, Rizwan

2015-04-01

Boron doping in diamond plays a vital role in enhancing electrical conductivity of diamond by making it a semiconductor, a conductor or even a superconductor. To elucidate this fact, partial and total density of states has been determined as a function of B-content in diamond. Moreover, the orbital charge distributions, B-C bond lengths and their population have been studied for B-doping in pristine diamond thin films by applying density functional theory (DFT). These parameters have been found to be influenced by the addition of different percentages of boron atoms in diamond. The electronic density of states, B-C bond situations as well as variations in electrical conductivities of diamond films with different boron content and determination of some relationship between these parameters were the basic tasks of this study. Diamond with high boron concentration (∼5.88% B-atoms) showed maximum splitting of energy bands (caused by acceptor impurity states) at the Fermi level which resulted in the enhancement of electron/ion conductivities. Because B atoms either substitute carbon atoms and/or assemble at grain boundaries (interstitial sites) inducing impurity levels close to the top of the valence band. At very high B-concentration, impurity states combine to form an impurity band which accesses the top of the valence band yielding metal like conductivity. Moreover, bond length and charge distributions are found to decrease with increase in boron percentage in diamond. It is noted that charge distribution decreased from +1.89 to -1.90 eV whereas bond length reduced by 0.04 Å with increasing boron content in diamond films. These theoretical results support our earlier experimental findings on B-doped diamond polycrystalline films which depict that the addition of boron atoms to diamond films gives a sudden fall in resistivity even up to 105 Ω cm making it a good semiconductor for its applications in electrical devices.

Radiofrequency ablation: importance of background tissue electrical conductivity--an agar phantom and computer modeling study.

PubMed

Solazzo, Stephanie A; Liu, Zhengjun; Lobo, S Melvyn; Ahmed, Muneeb; Hines-Peralta, Andrew U; Lenkinski, Robert E; Goldberg, S Nahum

2005-08-01

To determine whether radiofrequency (RF)-induced heating can be correlated with background electrical conductivity in a controlled experimental phantom environment mimicking different background tissue electrical conductivities and to determine the potential electrical and physical basis for such a correlation by using computer modeling. The effect of background tissue electrical conductivity on RF-induced heating was studied in a controlled system of 80 two-compartment agar phantoms (with inner wells of 0.3%, 1.0%, or 36.0% NaCl) with background conductivity that varied from 0.6% to 5.0% NaCl. Mathematical modeling of the relationship between electrical conductivity and temperatures 2 cm from the electrode (T2cm) was performed. Next, computer simulation of RF heating by using two-dimensional finite-element analysis (ETherm) was performed with parameters selected to approximate the agar phantoms. Resultant heating, in terms of both the T2cm and the distance of defined thermal isotherms from the electrode surface, was calculated and compared with the phantom data. Additionally, electrical and thermal profiles were determined by using the computer modeling data and correlated by using linear regression analysis. For each inner compartment NaCl concentration, a negative exponential relationship was established between increased background NaCl concentration and the T2cm (R2= 0.64-0.78). Similar negative exponential relationships (r2 > 0.97%) were observed for the computer modeling. Correlation values (R2) between the computer and experimental data were 0.9, 0.9, and 0.55 for the 0.3%, 1.0%, and 36.0% inner NaCl concentrations, respectively. Plotting of the electrical field generated around the RF electrode identified the potential for a dramatic local change in electrical field distribution (ie, a second electrical peak ["E-peak"]) occurring at the interface between the two compartments of varied electrical background conductivity. Linear correlations between the E-peak and heating at T2cm (R2= 0.98-1.00) and the 50 degrees C isotherm (R2= 0.99-1.00) were established. These results demonstrate the strong relationship between background tissue conductivity and RF heating and further explain electrical phenomena that occur in a two-compartment system.

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

Aldridge, David F.; Bartel, Lewis C.

Program LETS calculates the electric current distribution (in space and time) along an electrically energized steel-cased geologic borehole situated within the subsurface earth. The borehole is modeled as an electrical transmission line that “leaks” current into the surrounding geology. Parameters pertinent to the transmission line current calculation (i.e., series resistance and inductance, shunt capacitance and conductance) are obtained by sampling the electromagnetic (EM) properties of a three-dimensional (3D) geologic earth model along a (possibly deviated) well track.

Analysis of electrical tomography sensitive field based on multi-terminal network and electric field

NASA Astrophysics Data System (ADS)

He, Yongbo; Su, Xingguo; Xu, Meng; Wang, Huaxiang

2010-08-01

Electrical tomography (ET) aims at the study of the conductivity/permittivity distribution of the interested field non-intrusively via the boundary voltage/current. The sensor is usually regarded as an electric field, and finite element method (FEM) is commonly used to calculate the sensitivity matrix and to optimize the sensor architecture. However, only the lumped circuit parameters can be measured by the data acquisition electronics, it's very meaningful to treat the sensor as a multi terminal network. Two types of multi terminal network with common node and common loop topologies are introduced. Getting more independent measurements and making more uniform current distribution are the two main ways to minimize the inherent ill-posed effect. By exploring the relationships of network matrixes, a general formula is proposed for the first time to calculate the number of the independent measurements. Additionally, the sensitivity distribution is analyzed with FEM. As a result, quasi opposite mode, an optimal single source excitation mode, that has the advantages of more uniform sensitivity distribution and more independent measurements, is proposed.

Experimental study to improve the focalization of a figure-eight coil of rTMS by using a highly conductive and highly permeable medium.

PubMed

Zhang, Shunqi; Yin, Tao; Liu, Zhipeng; Li, Ying; Jin, Jingna; Ma, Ren

2013-05-01

A method to improve the focalization of the repetitive transcranial magnetic stimulation figure-eight coil in a magnetic stimulation is presented in this paper. For the purpose of reducing the half width of the distribution curve, while improving the ratio of positive to negative electric field, a shield plate with a window and a magnetic conductor were adopted. The shield plate, which was made of highly conductive copper, focused the magnetic field into a smaller area. The magnetic inductor, which was made of highly permeable soft magnetic ferrite, strengthened the magnetic field. A group of experiments was conducted to validate the focalizing effect. Experimental results showed that the negative peak and the half width of the distribution curve reduced by using the shield plate and the magnetic conductor. Especially for to the Magstim 70 mm double coil, when the shield window was 30 × 60 mm, the ratio of positive to negative electric field could be increased 109%, while the half width of the distribution curve could be reduced about 55%.

Electrical conductivity imaging in the western Pacific subduction zone

NASA Astrophysics Data System (ADS)

Utada, Hisashi; Baba, Kiyoshi; Shimizu, Hisayoshi

2010-05-01

Oceanic plate subduction is an important process for the dynamics and evolution of the Earth's interior, as it is regarded as a typical downward flow of the mantle convection that transports materials from the near surface to the deep mantle. Recent seismological study showed evidence suggesting the transportation of a certain amount of water by subduction of old oceanic plate such as the Pacific plate down to 150-200 km depth into the back arc mantle. However it is not well clarified how deep into the mantle the water can be transported. The electromagnetic induction method to image electrical conductivity distribution is a possible tool to answer this question as it is known to be sensitive to the presence of water. Here we show recent result of observational study from the western Pacific subduction zone to examine the electrical conductivity distribution in the upper mantle and in the mantle transition zone (MTZ), which will provide implications how water distributes in the mantle. We take two kinds of approach for imaging the mantle conductivity, (a) semi-global and (b) regional induction approaches. Result may be summarized as follows: (a) Long (5-30 years) time series records from 8 submarine cables and 13 geomagnetic observatories in the north Pacific region were analyzed and long period magnetotelluric (MT) and geomagnetic deep sounding (GDS) responses were estimated in the period range from 1.7 to 35 days. These frequency dependent response functions were inverted to 3-dimensional conductivity distribution in the depth range between 350 and 850 km. Three major features are suggested in the MTZ depth such as, (1) a high conductivity anomaly beneath the Philippine Sea, (2) a high conductivity anomaly beneath the Hawaiian Islands, and (3) a low conductivity anomaly beneath and in the vicinity of northern Japan. (b) A three-year long deployment of ocean bottom electro-magnetometers (OBEM's) was conducted in the Philippine Sea and west Pacific Ocean from 2005 to 2008. As a preliminary investigation, MT response functions from 20 sites in the Philippine Sea and 4 sites in the west Pacific basin in the period range between 300 and 80000 sec were respectively inverted to one-dimensional (1-D) profile of electrical conductivity by quantitatively considering the effect of the heterogeneous conductivity distribution (ocean and lands) at the surface. The resultant 1-D models show three main features: (1) Strong contrast in the conductivity for the shallower 200 km of the upper mantle depths is recognized between the two regions, which is qualitatively consistent with the difference in lithospheric age. (2) The conductivity at 200-300 km depth is more or less similar to each other at about 0.3 S /m. (3) The conductivity around the MTZ depth is higher for the Philippine Sea mantle than for the Pacific mantle, which is consistent with the implication obtained from a semi-global approach (a). As already suggested in our previous work, the high conductivity in the MTZ below the Philippine Sea can be explained by the excess conduction due to the presence of hydrogen (water) in wadesleyite or in ringwoodite. Therefore, it implies a large scale circulation of water in the back arc mantle not only in the upper mantle but also down to the MTZ depth. However, our interpretation indicates that the high conductivity of the Philippine Sea uppermost upper mantle cannot be explained only by the effect of hydrogen conduction in olivine, but that additional conduction enhancement such as the presence of partial melt is required.

Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2015-03-01

Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

Semiautomatic and Automatic Cooperative Inversion of Seismic and Magnetotelluric Data

NASA Astrophysics Data System (ADS)

Le, Cuong V. A.; Harris, Brett D.; Pethick, Andrew M.; Takam Takougang, Eric M.; Howe, Brendan

2016-09-01

Natural source electromagnetic methods have the potential to recover rock property distributions from the surface to great depths. Unfortunately, results in complex 3D geo-electrical settings can be disappointing, especially where significant near-surface conductivity variations exist. In such settings, unconstrained inversion of magnetotelluric data is inexorably non-unique. We believe that: (1) correctly introduced information from seismic reflection can substantially improve MT inversion, (2) a cooperative inversion approach can be automated, and (3) massively parallel computing can make such a process viable. Nine inversion strategies including baseline unconstrained inversion and new automated/semiautomated cooperative inversion approaches are applied to industry-scale co-located 3D seismic and magnetotelluric data sets. These data sets were acquired in one of the Carlin gold deposit districts in north-central Nevada, USA. In our approach, seismic information feeds directly into the creation of sets of prior conductivity model and covariance coefficient distributions. We demonstrate how statistical analysis of the distribution of selected seismic attributes can be used to automatically extract subvolumes that form the framework for prior model 3D conductivity distribution. Our cooperative inversion strategies result in detailed subsurface conductivity distributions that are consistent with seismic, electrical logs and geochemical analysis of cores. Such 3D conductivity distributions would be expected to provide clues to 3D velocity structures that could feed back into full seismic inversion for an iterative practical and truly cooperative inversion process. We anticipate that, with the aid of parallel computing, cooperative inversion of seismic and magnetotelluric data can be fully automated, and we hold confidence that significant and practical advances in this direction have been accomplished.

Stability of spatial distributions of stink bugs, boll injury, and NDVI in cotton

USDA-ARS?s Scientific Manuscript database

A two-year study was conducted to determine the degree of aggregation of thrips, stink bugs, and aphids in cotton, Gossypium hirsutum L., and their spatial association with soil apparent electrical conductivity (ECa), a multispectral vegetation index (Normalized Difference Vegetation Index [NDVI]), ...

Investigation of influence of conductivity on the polyaniline fiber mats, produced via electrospinning

NASA Astrophysics Data System (ADS)

Varnaitė-Žuravliova, Sandra; Savest, Natalja; Abraitienė, Aušra; Baltušnikaitė-Guzaitienė, Julija; Krumme, Andres

2018-05-01

Intrinsically conductive polymers are one very attractive material, because of their good electrical, electrochemical and optical properties, and a wide range of applications. The spinnability of Polyaniline (PANI) solutions is generally insufficient for it to be electrospun directly into fibers, but addition of another polymer to the organic solutions or usage of dopant and solvent may improve it. The aim of the research was: to produce nanofibers of the smallest diameter as possible by using conventional electrospinning setup; to investigate the influence of viscosity and electrical conductivity to the spinnability of PANI solutions; to control the electrical conductivity of prepared solutions and electrospun nanofibers by changing concentrations of chemicals used. The results of investigations made with prepared solutions shave showed, that the viscosity increases and the electrical conductivity is tending to decrease with increase of Polyethylenoxide (PEO) concentration in the spinning solution. In order to achieve greater conductivity, the Dimethylformamide (DMF) was added as a dopant. Though the conductivity of solutions was reached high enough, but the loss in viscosity resulted in depriation of greater spinnability of PANI nanofibers. Also it was noticed, that despite the fact that the electrical conductivity of all solutions was different, the electrical conductivity of fiber mats can be divided in two groups: fiber mats without DMF and fiber mats with DMF. The morphological analysis of produced fiber mats have showed, that higher PEO concentration resulted in thicker PANI nanofibers—the diameter varied from 333 nm till 4434 nm. The usage of DMF gave an opportunity to receive almost twice thinner conductive PANI nanofibers with narrower distribution in diameter. Slower flow rate of the electrospinning process resulted in thinner nanofibers as well.

Preparation and Dielectric Properties of SiC/LSR Nanocomposites for Insulation of High Voltage Direct Current Cable Accessories

PubMed Central

Shang, Nanqiang; Chen, Qingguo; Wei, Xinzhe

2018-01-01

The conductivity mismatch in the composite insulation of high voltage direct current (HVDC) cable accessories causes electric field distribution distortion and even insulation breakdown. Therefore, a liquid silicone rubber (LSR) filled with SiC nanoparticles is prepared for the insulation of cable accessories. The micro-morphology of the SiC/LSR nanocomposites is observed by scanning electron microscopy, and their trap parameters are characterized using thermal stimulated current (TSC) tests. Moreover, the dielectric properties of SiC/LSR nanocomposites with different SiC concentrations are tested. The results show that the 3 wt % SiC/LSR sample has the best nonlinear conductivity, more than one order of magnitude higher than that of pure LSR with improved temperature and nonlinear conductivity coefficients. The relative permittivity increased 0.2 and dielectric loss factor increased 0.003, while its breakdown strength decreased 5 kV/mm compared to those of pure LSR. Moreover, the TSC results indicate the introduction of SiC nanoparticles reduced the trap level and trap density. Furthermore, the SiC nanoparticles filling significantly increased the sensitivity of LSR to electric field stress and temperature changes, enhancing the conductivity and electric field distribution within the HVDC cable accessories, thus improving the reliability of the HVDC cable accessories. PMID:29518054

Preparation and Dielectric Properties of SiC/LSR Nanocomposites for Insulation of High Voltage Direct Current Cable Accessories.

PubMed

Shang, Nanqiang; Chen, Qingguo; Wei, Xinzhe

2018-03-08

The conductivity mismatch in the composite insulation of high voltage direct current (HVDC) cable accessories causes electric field distribution distortion and even insulation breakdown. Therefore, a liquid silicone rubber (LSR) filled with SiC nanoparticles is prepared for the insulation of cable accessories. The micro-morphology of the SiC/LSR nanocomposites is observed by scanning electron microscopy, and their trap parameters are characterized using thermal stimulated current (TSC) tests. Moreover, the dielectric properties of SiC/LSR nanocomposites with different SiC concentrations are tested. The results show that the 3 wt % SiC/LSR sample has the best nonlinear conductivity, more than one order of magnitude higher than that of pure LSR with improved temperature and nonlinear conductivity coefficients. The relative permittivity increased 0.2 and dielectric loss factor increased 0.003, while its breakdown strength decreased 5 kV/mm compared to those of pure LSR. Moreover, the TSC results indicate the introduction of SiC nanoparticles reduced the trap level and trap density. Furthermore, the SiC nanoparticles filling significantly increased the sensitivity of LSR to electric field stress and temperature changes, enhancing the conductivity and electric field distribution within the HVDC cable accessories, thus improving the reliability of the HVDC cable accessories.

Magnetoacoustic tomography with magnetic induction for imaging electrical impedance of biological tissue

NASA Astrophysics Data System (ADS)

Li, Xu; Xu, Yuan; He, Bin

2006-03-01

An experimental feasibility study was conducted on magnetoacoustic tomography with magnetic induction (MAT-MI). It is demonstrated that the two-dimensional MAT-MI system can detect and image the boundaries between regions of different electrical conductivities with high spatial resolution. Utilizing a magnetic stimulation coil, MAT-MI evokes magnetically induced eddy current in an object which is placed in a static magnetic field. Because of the existence of Lorenz forces, the eddy current in turn causes acoustic vibrations, which are measured around the object in order to reconstruct the electrical impedance distribution of the object. The present experimental results from the saline and gel phantoms are promising and suggest the merits of MAT-MI in imaging electrical impedance of biological tissue with high spatial resolution.

Imagerie par modulation acoustique de conductivite electrique destinee au diagnostic du cancer du sein

NASA Astrophysics Data System (ADS)

Gendron, Mathieu

This thesis describes a new medical imaging technique for determining the electrical conductivity distribution of tissues in a body region with a resolution comparable to that of current ultrasound techniques. The new technique, henceforth referred to as "Acousto-Electric Conductivity Modulation" (AECM) imaging, is based on the interaction of a sound wave with an electrical field. In its simplest form, four electrodes located near the region to be imaged apply a low-amplitude electrical current and measure the potential difference arising from current flow in the tissues. A focused ultrasound transducer directs a pressure wave to a voxel of the region of interest, modifying its conductivity distribution and, as a result, the amplitude of the potential measured by the electrodes. An image of the conductivity distribution can thus be constructed point-by-point by moving the electrodes and transducer to scan the object. In this context, the acoustic wave acts as the localization agent while the electrical potential provides a measure of the local conductivity change that occurs in the voxel. The first model presented in the thesis is based on the use of bipolar acoustic waves for excitation. This waveform is generally used with narrow band transducers. Acoustic waves generated by an ultrasound transducer driven with a burst of sine waves consists of alternating compression and rarefaction phases which tend to cancel each other in terms of the conductivity changes they produce. However when the thickness of the target object is small compared to the wavelength of the acoustic wave, this cancelling effect will not occur and the AECM signals will have sufficiently high amplitude to achieve image reconstruction using successive transducer positions to scan the region of interest. By extracting from the spectra of the AECM signals the amplitude of the peak at the excitation frequency, a map of the acousto-electric sensitivity of the system can be obtained. This map is then used to reconstruct the electrical conductivity distribution. The second model presented in the thesis uses a unipolar acoustic wave to generate AECM signals of relatively large amplitude. There are two aspects related to this type of wave. The first aspect is that the acoustic modulation is unidirectional if the applied pressure is unidirectional. As a result, a positive pressure only produces an increase in electrical conductivity and this will result in a large AECM signal even when the thickness of the object is large. The second aspect concerns the shape of the acoustic field. Since the unipolar acoustic wave is not focused, it modulates the conductivity over a large area, and thus the associated AECM signals needs to be processed through a reconstruction algorithm so as to recover local conductivity. In this model, the data required for image reconstruction are acquired by rotating the transducer around the target object. An experimental setup has been developed during our project to get values of certain parameter that are required to define the numerical models. The setup comprises a large tank which is filled with water and in which are immersed the ultrasound transducer, a hydrophone and a measurement cell. The acousto-electric interaction takes place within this cell. A computer controlled positioning system allows precise displacements of the transducer relative to the hydrophone and the measurement cell. This cell comprises a cavity in which the object to be analyzed is placed and that is then filled with an electrolytic solution. The cavity is closed on two sides by an acoustic window to allow propagation of the ultrasound wave and on another side by six Ag/AgCl electrodes that are used to apply current and to measure the resulting electrical potential. Mammography is presently the most widely used medical imaging procedure for breast cancer screening. The average sensitivity of this technique is 80 % but it is less for younger women. According to recent studies, MRI offers a higher sensitivity and the possibility of detecting very small tumors, thus allowing earlier treatment. The operating costs of MRI systems are at the moment too high to consider using the modality for breast cancer screening on a large scale. AECM imaging could eventually provide an interesting compromise between operating costs and the sensitivity required for screening patients of all ages. (Abstract shortened by UMI.).

Electric field computation and measurements in the electroporation of inhomogeneous samples

NASA Astrophysics Data System (ADS)

Bernardis, Alessia; Bullo, Marco; Campana, Luca Giovanni; Di Barba, Paolo; Dughiero, Fabrizio; Forzan, Michele; Mognaschi, Maria Evelina; Sgarbossa, Paolo; Sieni, Elisabetta

2017-12-01

In clinical treatments of a class of tumors, e.g. skin tumors, the drug uptake of tumor tissue is helped by means of a pulsed electric field, which permeabilizes the cell membranes. This technique, which is called electroporation, exploits the conductivity of the tissues: however, the tumor tissue could be characterized by inhomogeneous areas, eventually causing a non-uniform distribution of current. In this paper, the authors propose a field model to predict the effect of tissue inhomogeneity, which can affect the current density distribution. In particular, finite-element simulations, considering non-linear conductivity against field relationship, are developed. Measurements on a set of samples subject to controlled inhomogeneity make it possible to assess the numerical model in view of identifying the equivalent resistance between pairs of electrodes.

Study of Dynamic Membrane Behavior in Applied DC Electric Field

NASA Astrophysics Data System (ADS)

Dutta, Prashanta; Morshed, Adnan; Hossan, Mohammad

2017-11-01

Electrodeformation of vesicles can be used as a useful tool to understand the characteristics of biological soft matter, where vesicles immersed in a fluid medium are subjected to an applied electric field. The complex response of the vesicle membrane strongly depends on the conductivity of surrounding fluid, vesicle size and shape, and applied electric field We studied the electrodeformation of vesicles immersed in a fluid media under a short DC electric pulse. An immersed interface method is used to solve the electric field over the domain with conductive or non-conductive vesicles while an immersed boundary scheme is employed to solve fluid flow, fluid-solid interaction, membrane mechanics and vesicle movement. Force analysis on the membrane surface reveals almost linear relation with vesicle size, but highly nonlinear influence of applied field as well as the conductivity ratios inside and outside of the vesicle. Results also point towards an early linear deformation regime followed by an equilibrium stage for the membranes. Moreover, significant influence of the initial aspect ratio of the vesicle on the force distribution is observed across a range of conductivity ratios. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM122081.

Relationship of the interplanetary electric field to the high-latitude ionospheric electric field and currents Observations and model simulation

NASA Technical Reports Server (NTRS)

Clauer, C. R.; Banks, P. M.

1986-01-01

The electrical coupling between the solar wind, magnetosphere, and ionosphere is studied. The coupling is analyzed using observations of high-latitude ion convection measured by the Sondre Stromfjord radar in Greenland and a computer simulation. The computer simulation calculates the ionospheric electric potential distribution for a given configuration of field-aligned currents and conductivity distribution. The technique for measuring F-region in velocities at high time resolution over a large range of latitudes is described. Variations in the currents on ionospheric plasma convection are examined using a model of field-aligned currents linking the solar wind with the dayside, high-latitude ionosphere. The data reveal that high-latitude ionospheric convection patterns, electric fields, and field-aligned currents are dependent on IMF orientation; it is observed that the electric field, which drives the F-region plasma curve, responds within about 14 minutes to IMF variations in the magnetopause. Comparisons of the simulated plasma convection with the ion velocity measurements reveal good correlation between the data.

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 1. Electromagnetic properties

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The marked decrease in bulk electrical conductivity of sediments in the presence of gas hydrates has been used to interpret borehole electrical resistivity logs and, to a lesser extent, the results of controlled source electromagnetic surveys to constrain the spatial distribution and predicted concentration of gas hydrate in natural settings. Until now, an exhaustive laboratory data set that could be used to assess the impact of gas hydrate on the electromagnetic properties of different soils (sand, silt, and clay) at different effective stress and with different saturations of hydrate has been lacking. The laboratory results reported here are obtained using a standard geotechnical cell and the hydrate-formed tetrahydrofuran (THF), a liquid that is fully miscible in water and able to produce closely controlled saturations of hydrate from dissolved phase. Both permittivity and electrical conductivity are good indicators of the volume fraction of free water in the sediment, which is in turn dependent on hydrate saturation. Permittivity in the microwave frequency range is particularly predictive of free water content since it is barely affected by ionic concentration, pore structure, and surface conduction. Electrical conductivity (or resistivity) is less reliable for constraining water content or hydrate saturation: In addition to fluid-filled porosity, other factors, such as the ionic concentration of the pore fluid and possibly other conduction effects (e.g., surface conduction in high specific surface soils having low conductivity pore fluid), also influence electrical conductivity.

Unavoidable electric current caused by inhomogeneities and its influence on measured material parameters of thermoelectric materials

NASA Astrophysics Data System (ADS)

Song, K.; Song, H. P.; Gao, C. F.

2018-03-01

It is well known that the key factor determining the performance of thermoelectric materials is the figure of merit, which depends on the thermal conductivity (TC), electrical conductivity, and Seebeck coefficient (SC). The electric current must be zero when measuring the TC and SC to avoid the occurrence of measurement errors. In this study, the complex-variable method is used to analyze the thermoelectric field near an elliptic inhomogeneity in an open circuit, and the field distributions are obtained in closed form. Our analysis shows that an electric current inevitably exists in both the matrix and the inhomogeneity even though the circuit is open. This unexpected electric current seriously affects the accuracy with which the TC and SC are measured. These measurement errors, both overall and local, are analyzed in detail. In addition, an error correction method is proposed based on the analytical results.

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.

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

Inhester, B.; Untiedt, J.; Segatz, M.

From two-dimensional ground magnetic and ionospheric electric field observations it should in principle be possible to estimate the two-dimensional distribution of the ionospheric conductance. The authors have developed a method to directly deduce the Hall conductance distribution {Sigma}{sub H} from ground magnetic and ionospheric electric field observations based upon some assumption for the ratio of the Hall to the Pedersen conductivity. In general, the solutions are shown not to be unique because for a specific solution the value of {Sigma}{sub H} on certain parts of the boundary of the two-dimensional domain has to be specified. However, in many situations, especiallymore » in the presence of strong and isolated field-aligned currents, these boundary values become less influential, and the solution can be shown to be practically unique over a large area of the domain. In some cases, a rather restrictive relation between the electric field and the equivalent height-integrated current density is shown to hold that could be used to cross-check the quality of the observations. As a specific example, they apply their formalism to the observation of a Harang discontinuity obtained in northern Scandinavia simultaneously by the STARE coherent radar system and the IMS Scandinavian Magnetometer Array.« less

Improving the Ionospheric Auroral Conductance in a Global Ring Current Model and the Effects on the Ionospheric Electrodynamics

NASA Astrophysics Data System (ADS)

Yu, Y.; Jordanova, V. K.; McGranaghan, R. M.; Solomon, S. C.

2017-12-01

The ionospheric conductance, height-integrated electric conductivity, can regulate both the ionospheric electrodynamics and the magnetospheric dynamics because of its key role in determining the electric field within the coupled magnetosphere-ionosphere system. State-of-the-art global magnetosphere models commonly adopt empirical conductance calculators to obtain the auroral conductance. Such specification can bypass the complexity of the ionosphere-thermosphere chemistry but on the other hand breaks the self-consistent link within the coupled system. In this study, we couple a kinetic ring current model RAM-SCB-E that solves for anisotropic particle distributions with a two-stream electron transport code (GLOW) to more self-consistently compute the height-dependent electric conductivity, provided the auroral electron precipitation from the ring current model. Comparisons with the traditional empirical formula are carried out. It is found that the newly coupled modeling framework reveals smaller Hall and Pedersen conductance, resulting in a larger electric field. As a consequence, the subauroral polarization streams demonstrate a better agreement with observations from DMSP satellites. It is further found that the commonly assumed Maxwellian spectrum of the particle precipitation is not globally appropriate. Instead, a full precipitation spectrum resulted from wave particle interactions in the ring current accounts for a more comprehensive precipitation spectrum.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

NASA Astrophysics Data System (ADS)

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J.; Miranda, Pedro C.

2015-09-01

Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm-1. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm-1, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study.

PubMed

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2015-09-21

Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm(-1). Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm(-1), independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

PubMed Central

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2015-01-01

Tumor Treating Fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1 - 3 V/cm. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V/cm, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields. PMID:26350296

Electrical and thermal behavior of unsaturated soils: experimental results

NASA Astrophysics Data System (ADS)

Nouveau, Marie; Grandjean, Gilles; Leroy, Philippe; Philippe, Mickael; Hedri, Estelle; Boukcim, Hassan

2016-05-01

When soil is affected by a heat source, some of its properties are modified, and in particular, the electrical resistivity due to changes in water content. As a result, these changes affect the thermal properties of soil, i.e., its thermal conductivity and diffusivity. We experimentally examine the changes in electrical resistivity and thermal conductivity for four soils with different grain size distributions and clay content over a wide range of temperatures, from 20 to 100 °C. This temperature range corresponds to the thermal conditions in the vicinity of a buried high voltage cable or a geothermal system. Experiments were conducted at the field scale, at a geothermal test facility, and in the laboratory using geophysical devices and probing systems. The results show that the electrical resistivity decreases and the thermal conductivity increases with temperature up to a critical temperature depending on soil types. At this critical temperature, the air volume in the pore space increases with temperature, and the resulting electrical resistivity also increases. For higher temperatures , the thermal conductivity increases sharply with temperature up to a second temperature limit. Beyond it, the thermal conductivity drops drastically. This limit corresponds to the temperature at which most of the water evaporates from the soil pore space. Once the evaporation is completed, the thermal conductivity stabilizes. To explain these experimental results, we modeled the electrical resistivity variations with temperature and water content in the temperature range 20 - 100°C, showing that two critical temperatures influence the main processes occurring during heating at temperatures below 100 °C.

Inspecting Friction Stir Welding using Electromagnetic Probes

NASA Technical Reports Server (NTRS)

Kinchen, David G.

2004-01-01

A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

Synthesis and electrical properties of (LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramics

NASA Astrophysics Data System (ADS)

Ram, Moti

2010-03-01

(LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramic was synthesized via solution-based chemical method. X-ray diffraction analysis was carried out on the synthesized powder sample at room temperature, which confirms the orthorhombic structure with the lattice parameters of a = 10.3646 (20) Å, b = 3.7926 (20) Å, c = 9.2131 (20) Å. Field emission scanning electron microscopic analysis was carried out on the sintered pellet sample that indicates grains of unequal sizes (˜0.1 to 2 μm) presents average grains size with polydisperse distribution on the surface of the ceramic. Complex impedance spectroscopy (CIS) technique is used for the study of electrical properties. CIS analysis identifies: (i) grain interior, grain boundary and electrode-material interface contributions to electrical response (ii) the presence of temperature dependent electrical relaxation phenomena in the ceramics. Detailed conductivity study indicates that electrical conduction in the material is a thermally activated process. The variation of A.C. conductivity with frequency at different temperatures obeys Jonscher's universal law.

Electrical conductivity of nanocomposites based on carbon nanotubes: a 3D multiscale modeling approach

NASA Astrophysics Data System (ADS)

Grabowski, Krzysztof; Zbyrad, Paulina; Staszewski, Wieslaw J.; Uhl, Tadeusz; Wiatr, Kazimierz; Packo, Pawel

2016-04-01

Remarkable electrical properties of carbon nanotubes (CNT) have lead to increased interest in studying CNT- based devices. Many of current researches are devoted to using all kinds of carbon nanomaterials in the con- struction of sensory elements. One of the most common applications is the development of high performance, large scale sensors. Due to the remarkable conductivity of CNT's such devices represent very high sensitivity. However, there are no sufficient tools for studying and designing such sensors. The main objective of this paper is to develop and validate a multiscale numerical model for a carbon nanotubes based sensor. The device utilises the change of electrical conductivity of a nanocomposite material under applied deformation. The nanocomposite consists of a number of CNTs dispersed in polymer matrix. The paper is devoted to the analysis of the impact of spatial distribution of carbon nanotubes in polymer matrix on electrical conductivity of the sensor. One of key elements is also to examine the impact of strain on electric charge ow in such anisotropic composite structures. In the following work a multiscale electro-mechanical model for CNT - based nanocomposites is proposed. The model comprises of two length scales, namely the meso- and the macro-scale for mechanical and electrical domains. The approach allows for evaluation of macro-scale mechanical response of a strain sensor. Electrical properties of polymeric material with certain CNT fractions were derived considering electrical properties of CNTs, their contact and the tunnelling effect.

4D ERT-based calibration and prediction of biostimulant induced changes in fluid conductivity

NASA Astrophysics Data System (ADS)

Johnson, T. C.; Versteeg, R. J.; Day-Lewis, F. D.; Major, W. R.; Wright, K. E.

2008-12-01

In-situ bioremediation is an emerging and cost-effective method of removing organic contaminants from groundwater. The performance of bioremedial systems depends on the adequate delivery and distribution of biostimulants to contaminated zones. Monitoring the distribution of biostimulants using monitoring wells is expensive, time consuming, and provides inadequate information between sampling wells. We discuss a Hydrogeophysical Performance Monitoring System (HPMS) deployed to monitor bioremediation efforts at a TCE-contaminated Superfund site in Brandywine MD. The HPMS enables autonomous electrical geophysical data acquisition, processing, quality-assurance/quality-control, and inversion. Our objective is to demonstrate the feasibility and cost effectiveness of the HPMS to provide near real-time information on the spatiotemporal behavior of injected biostimulants. As a first step, we use time-lapse electrical resistivity tomography (ERT) to estimate changes in bulk conductivity caused by the injectate. We demonstrate how ERT-based bulk conductivity estimates can be calibrated with a small number of fluid conductivity measurements to produce ERT-based estimates of fluid conductivity. The calibration procedure addresses the spatially variable resolution of the ERT tomograms. To test the validity of these estimates, we used the ERT results to predict the fluid conductivity at tens of points prior to field sampling of fluid conductivity at the same points. The comparison of ERT-predicted vs. observed fluid conductivity displays a high degree of correlation (correlation coefficient over 0.8), and demonstrates the ability of the HPMS to estimate the four-dimensional (4D) distribution of fluid conductivity caused by the biostimulant injection.

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation

PubMed Central

Janssen, A M; Rampersad, S M; Lucka, F; Lanfer, B; Lew, S; Aydin, Ü; Wolters, C H; Stegeman, D F; Oostendorp, T F

2013-01-01

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation (TMS). One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between the CSF and GM (Thielscher et al. 2011; Bijsterbosch et al. 2012), or by resizing the whole brain (Wagner et al. 2008). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images (MRI), was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location. PMID:23787706

Electrical and mechanical behavior of polymethyl methacrylate/cadmium sulphide composites

NASA Astrophysics Data System (ADS)

Kaur, Rajdeep; Samra, Kawaljeet Singh

2018-06-01

In the present investigation, electrical and mechanical behavior of cadmium sulphide (CdS) doped polymethyl methacrylate (PMMA) have been studied using different techniques. Dip casting technique was used for preparing free standing films of pristine and CdS doped PMMA at different compositions (i.e. 1 and 5 wt%). Optical absorbance as a function of wavelength was studied, by UV-visible spectroscopy, to find the impact of CdS doping on the optical band gap of synthesized PMMA/CdS composite. DC and AC conductivities were measured as a function of dopant concentration and temperature. Considerable increase in electrical conductivity was observed with the increase of CdS contents in polymer matrix. Overall electrical conduction mechanism in PMMA/CdS composites was attributed to movement of electrons through the uniformly distributed CdS aggregates within the matrix of PMMA. Mechanical properties, such as Young's modulus, tensile strength, elongation and ductility, of PMMA/CdS composites were determined and relevant responsible phenomena were discussed.

Structural and electrical properties of LiCo3/5Cu2/5VO4 ceramics

NASA Astrophysics Data System (ADS)

Ram, Moti

2010-05-01

The LiCo3/5Cu2/5VO4 compound is prepared by a solution-based chemical method and characterized by the techniques of X-ray diffraction, scanning electron microscopy and complex impedance spectroscopy. The X-ray diffraction study shows an orthorhombic unit cell structure of the material with lattice parameters a=13.8263 (30) Å, b=8.7051 (30) Å and c=3.1127 (30) Å. The nature of scanning electron micrographs of a sintered pellet of the material reveals that grains of unequal sizes (˜0.2-3 μm) present an average grain size with a polydisperse distribution on the surface of the sample. Complex plane diagrams indicate grain interior and grain boundary contributions to the electrical response in the material. The electrical conductivity study reveals that electrical conduction in the material is a thermally activated process. The frequency dependence of the a.c. conductivity obeys Jonscher’s universal law.

Characteristics of Sodium Polyacrylate/Nano-Sized Carbon Hydrogel for Biomedical Patch.

PubMed

Park, Jong-Kyu; Seo, Sun-Kyo; Cho, Seungkwan; Kim, Han-Sung; Lee, Chi-Hwan

2018-03-01

Conductive hydrogels were prepared for biomedical patch in order to improve the electrical conductivity. Sodium polyacrylate and nano-sized carbon were mixed and fabricated by aqueous solution gelation process in various contents of nano-sized carbon with 0.1, 0.5, 1.0 and 2.0 wt%. Sodium polyacrylate/nano-sized carbon conductive hydrogels were investigated by molecular structure, surface morphology and electrical conductivity. The conductivity of the hydrogel/nano-sized carbon conductive hydrogel proved to be 10% higher than conductive hydrogel without nano-sized carbon. However, it was founded that conductive hydrogels with nano-sized carbon content from 0.5 up to 2.0 wt% were remarkably decreased. This may be due to the non-uniform distribution of nano-sized carbon, resulting from agglomerates of nano-sized carbon. The developed hydrogel is intended for use in the medical and cosmetic fields that is applicable to supply micro-current from device to human body.

Evaluating the potential for quantitative monitoring of in situ chemical oxidation of aqueous-phase TCE using in-phase and quadrature electrical conductivity

NASA Astrophysics Data System (ADS)

Hort, R. D.; Revil, A.; Munakata-Marr, J.; Mao, D.

2015-07-01

Electrical resistivity measurements can potentially be used to remotely monitor fate and transport of ionic oxidants such as permanganate (MnO4-) during in situ chemical oxidation (ISCO) of contaminants like trichloroethene (TCE). Time-lapse two-dimensional bulk conductivity and induced polarization surveys conducted during a sand tank ISCO simulation demonstrated that MnO4- plume movement could be monitored in a qualitative manner using bulk conductivity tomograms, although chargeability was below sensitivity limits. We also examined changes to in-phase and quadrature electrical conductivity resulting from ion injection, MnO2 and Cl- production, and pH change during TCE and humate oxidation by MnO4- in homogeneous aqueous solutions and saturated porous media samples. Data from the homogeneous samples demonstrated that inversion of the sand tank resistivity data using a common Tikhonov regularization approach was insufficient to recover an accurate conductivity distribution within the tank. While changes to in-phase conductivity could be successfully modeled, quadrature conductivity values could not be directly related to TCE oxidation product or MnO4- concentrations at frequencies consistent with field induced polarization surveys, limiting the utility of quadrature conductivity for monitoring ISCO.

Exposure to electromagnetic fields aboard high-speed electric multiple unit trains.

PubMed

Niu, D; Zhu, F; Qiu, R; Niu, Q

2016-01-01

High-speed electric multiple unit (EMU) trains generate high-frequency electric fields, low-frequency magnetic fields, and high-frequency wideband electromagnetic emissions when running. Potential human health concerns arise because the electromagnetic disturbances are transmitted mainly into the car body from windows, and from there to passengers and train staff. The transmission amount and amplitude distribution characteristics that dominate electromagnetic field emission need to be studied, and the exposure level of electromagnetic field emission to humans should be measured. We conducted a series of tests of the on board electromagnetic field distribution on several high-speed railway lines. While results showed that exposure was within permitted levels, the possibility of long-term health effects should be investigated.

Dependence of B1+ and B1- Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency.

PubMed

Vaidya, Manushka V; Collins, Christopher M; Sodickson, Daniel K; Brown, Ryan; Wiggins, Graham C; Lattanzi, Riccardo

2016-02-01

In high field MRI, the spatial distribution of the radiofrequency magnetic ( B 1 ) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green's functions, or experimentally measured over a range of frequencies inside an object whose electrical properties were varied to illustrate a variety of transmit [Formula: see text] and receive [Formula: see text] field patterns. In this work, we examine how changes in polarization of the field and interference of propagating waves in an object can affect the B 1 spatial distribution. Results are explained conceptually using Maxwell's equations and intuitive illustrations. We demonstrate that the electrical conductivity alters the spatial distribution of distinct polarized components of the field, causing "twisted" transmit and receive field patterns, and asymmetries between [Formula: see text] and [Formula: see text]. Additionally, interference patterns due to wavelength effects are observed at high field in samples with high relative permittivity and near-zero conductivity, but are not present in lossy samples due to the attenuation of propagating EM fields. This work provides a conceptual framework for understanding B 1 spatial distributions for surface coils and can provide guidance for RF engineers.

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

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

Sajib, Saurav Z. K.; Jeong, Woo Chul; Oh, Tong In

Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At lowmore » frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.« less

Polarization induced conductive AFM on cobalt doped ZnO nanostructures

NASA Astrophysics Data System (ADS)

Sahoo, Pradosh Kumar; Mangamma, G.; Rajesh, A.; Kamruddin, M.; Dash, S.

2017-05-01

In the present work cobalt doped ZnO (CZO) nanostructures (NS) have been synthesized by of sol-gel and spin coating process. After the crystal phase confirmation by GIXRD and Raman spectroscopy, Conductive Atomic Force Microscopy (C-AFM) measurement was performed on CZO NS which shows the random distribution of electrically conducting zones on the surface of the material exhibiting current in the range 4-170 pA. We provide the possible mechanisms for variation in current distribution essential for quantitative understanding of transport properties of ZnO NS in doped and undoped forms.

Estimation of electric fields and current from ground-based magnetometer data

NASA Technical Reports Server (NTRS)

Kamide, Y.; Richmond, A. D.

1984-01-01

Recent advances in numerical algorithms for estimating ionospheric electric fields and currents from groundbased magnetometer data are reviewed and evaluated. Tests of the adequacy of one such algorithm in reproducing large-scale patterns of electrodynamic parameters in the high-latitude ionosphere have yielded generally positive results, at least for some simple cases. Some encouraging advances in producing realistic conductivity models, which are a critical input, are pointed out. When the algorithms are applied to extensive data sets, such as the ones from meridian chain magnetometer networks during the IMS, together with refined conductivity models, unique information on instantaneous electric field and current patterns can be obtained. Examples of electric potentials, ionospheric currents, field-aligned currents, and Joule heating distributions derived from ground magnetic data are presented. Possible directions for future improvements are also pointed out.

Impact of monovalent cations on soil structure. Part I. Results of an Iranian soil

NASA Astrophysics Data System (ADS)

Farahani, Elham; Emami, Hojat; Keller, Thomas; Fotovat, Amir; Khorassani, Reza

2018-01-01

This study investigated the impact of monovalent cations on clay dispersion, aggregate stability, soil pore size distribution, and saturated hydraulic conductivity on agricultural soil in Iran. The soil was incubated with treatment solutions containing different concentrations (0-54.4 mmol l-1) of potassium and sodium cations. The treatment solutions included two levels of electrical conductivity (EC=3 or 6 dS m-1) and six K:Na ratios per electrical conductivity level. At both electrical conductivity levels, spontaneously dispersible clay increased with increasing K concentration, and with increasing K:Na ratio. A negative linear relationship between percentage of water-stable aggregates and spontaneously dispersible clay was observed. Clay dispersion generally reduced the mean pore size, presumably due to clogging of pores, resulting in increased water retention. At both electrical conductivity levels, hydraulic conductivity increased with increasing exchangeable potassium percentage at low exchangeable potassium percentage values, but decreased with further increases in exchangeable potassium percentage at higher exchangeable potassium percentage. This is in agreement with earlier studies, but seems in conflict with our data showing increasing spontaneously dispersible clay with increasing exchangeable potassium percentage. Our findings show that clay dispersion increased with increasing K concentration and increasing K:Na ratio, demonstrating that K can have negative impacts on soil structure.

Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosification.

PubMed

Zhu, Tongtong; Liu, Yingjun; Ding, Tao; Fu, Wai Yuen; Jarman, John; Ren, Christopher Xiang; Kumar, R Vasant; Oliver, Rachel A

2017-03-27

Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices. For many device applications, it is highly desirable to achieve not only high reflectivity and low absorption, but also good conductivity to allow effective electrical injection of charges. Here, we demonstrate the wafer-scale fabrication of highly reflective and conductive non-polar gallium nitride (GaN) DBRs, consisting of perfectly lattice-matched non-polar (11-20) GaN and mesoporous GaN layers that are obtained by a facile one-step electrochemical etching method without any extra processing steps. The GaN/mesoporous GaN DBRs exhibit high peak reflectivities (>96%) across the entire visible spectrum and wide spectral stop-band widths (full-width at half-maximum >80 nm), while preserving the material quality and showing good electrical conductivity. Such mesoporous GaN DBRs thus provide a promising and scalable platform for high performance GaN-based optoelectronic, photonic, and quantum photonic devices.

X-ray studies of aluminum alloy of the Al-Mg-Si system subjected to SPD processing

NASA Astrophysics Data System (ADS)

Sitdikov, V. D.; Murashkin, M. Yu; Khasanov, M. R.; Kasatkin, I. A.; Chizhov, P. S.; Bobruk, E. V.

2014-08-01

Recently it has been established that during high pressure torsion dynamic aging takes place in aluminum Al-Mg-Si alloys resulting in formation of nanosized particles of strengthening phases in the aluminum matrix, which greatly improves the electrical conductivity and strength properties. In the present paper structural characterization of ultrafine-grained (UFG) samples of aluminum 6201 alloy produced by severe plastic deformation (SPD) was performed using X-ray diffraction analysis. As a result, structure features (lattice parameter, size of coherent scattering domains) after dynamic aging of UFG samples were determined. The size and distribution of second- phase particles in the Al matrix were assessed with regard to HPT regimes. Impact of the size and distribution of the formed secondary phases on the strength, ductility and electrical conductivity is discussed.

Thermal Conductivity in Soil: Theoretical Approach by 3D Infinite Resistance Grid Model

NASA Astrophysics Data System (ADS)

Changjan, A.; Intaravicha, N.

2018-05-01

Thermal conductivity in soil was elementary characteristic of soil that conduct heat, measured in terms of Fourier’s Law for heat conduction and useful application in many fields: such as Utilizing underground cable for transmission and distribution systems, the rate of cooling of the cable depends on the thermal properties of the soil surrounding the cable. In this paper, we investigated thermal conductivity in soil by infinite three dimensions (3D) electrical resistance circuit concept. Infinite resistance grid 3D was the grid of resistors that extends to infinity in all directions. Model of thermal conductivity in soil of this research was generated from this concept: comparison between electrical resistance and thermal resistance in soil. Finally, we investigated the analytical form of thermal conductivity in soil which helpful for engineering and science students that could exhibit education with a principle of physics that applied to real situations.

Distributed Processing System for Restoration of Electric Power Distribution Network Using Two-Layered Contract Net Protocol

NASA Astrophysics Data System (ADS)

Kodama, Yu; Hamagami, Tomoki

Distributed processing system for restoration of electric power distribution network using two-layered CNP is proposed. The goal of this study is to develop the restoration system which adjusts to the future power network with distributed generators. The state of the art of this study is that the two-layered CNP is applied for the distributed computing environment in practical use. The two-layered CNP has two classes of agents, named field agent and operating agent in the network. In order to avoid conflicts of tasks, operating agent controls privilege for managers to send the task announcement messages in CNP. This technique realizes the coordination between agents which work asynchronously in parallel with others. Moreover, this study implements the distributed processing system using a de-fact standard multi-agent framework, JADE(Java Agent DEvelopment framework). This study conducts the simulation experiments of power distribution network restoration and compares the proposed system with the previous system. We confirmed the results show effectiveness of the proposed system.

Development of a Bio-nanobattery for Distributed Power Storage Systems

NASA Technical Reports Server (NTRS)

King, Glen C.; Choi, Sang H.; Chu, Sang-Hyon; Kim, Jae-Woo; Park, Yeonjoon; Lillehei, Peter; Watt, Gerald D.; Davis, Robert; Harb, John N.

2004-01-01

Currently available power storage systems, such as those used to supply power to microelectronic devices, typically consist of a single centralized canister and a series of wires to supply electrical power to where it is needed in a circuit. As the size of electrical circuits and components become smaller, there exists a need for a distributed power system to reduce Joule heating, wiring, and to allow autonomous operation of the various functions performed by the circuit. Our research is being conducted to develop a bio-nanobattery using ferritins reconstituted with both an iron core (Fe-ferritin) and a cobalt core (Co-ferritin). Both Co-ferritin and Fe-ferritin were synthesized and characterized as candidates for the bio-nanobattery. The reducing capability was determined as well as the half-cell electrical potentials, indicating an electrical output of nearly 0.5 V for the battery cell. Ferritins having other metallic cores are also being investigated, in order to increase the overall electrical output. Two dimensional ferritin arrays were also produced on various substrates, demonstrating the necessary building blocks for the bio-nanobattery. The bio-nanobattery will play a key role in moving to a distributed power storage system for electronic applications.

Identification of subsurface structures using electromagnetic data and shape priors

NASA Astrophysics Data System (ADS)

Tveit, Svenn; Bakr, Shaaban A.; Lien, Martha; Mannseth, Trond

2015-03-01

We consider the inverse problem of identifying large-scale subsurface structures using the controlled source electromagnetic method. To identify structures in the subsurface where the contrast in electric conductivity can be small, regularization is needed to bias the solution towards preserving structural information. We propose to combine two approaches for regularization of the inverse problem. In the first approach we utilize a model-based, reduced, composite representation of the electric conductivity that is highly flexible, even for a moderate number of degrees of freedom. With a low number of parameters, the inverse problem is efficiently solved using a standard, second-order gradient-based optimization algorithm. Further regularization is obtained using structural prior information, available, e.g., from interpreted seismic data. The reduced conductivity representation is suitable for incorporation of structural prior information. Such prior information cannot, however, be accurately modeled with a gaussian distribution. To alleviate this, we incorporate the structural information using shape priors. The shape prior technique requires the choice of kernel function, which is application dependent. We argue for using the conditionally positive definite kernel which is shown to have computational advantages over the commonly applied gaussian kernel for our problem. Numerical experiments on various test cases show that the methodology is able to identify fairly complex subsurface electric conductivity distributions while preserving structural prior information during the inversion.

Magnetic resonance electrical impedance tomography (MREIT) based on the solution of the convection equation using FEM with stabilization.

PubMed

Oran, Omer Faruk; Ider, Yusuf Ziya

2012-08-21

Most algorithms for magnetic resonance electrical impedance tomography (MREIT) concentrate on reconstructing the internal conductivity distribution of a conductive object from the Laplacian of only one component of the magnetic flux density (∇²B(z)) generated by the internal current distribution. In this study, a new algorithm is proposed to solve this ∇²B(z)-based MREIT problem which is mathematically formulated as the steady-state scalar pure convection equation. Numerical methods developed for the solution of the more general convection-diffusion equation are utilized. It is known that the solution of the pure convection equation is numerically unstable if sharp variations of the field variable (in this case conductivity) exist or if there are inconsistent boundary conditions. Various stabilization techniques, based on introducing artificial diffusion, are developed to handle such cases and in this study the streamline upwind Petrov-Galerkin (SUPG) stabilization method is incorporated into the Galerkin weighted residual finite element method (FEM) to numerically solve the MREIT problem. The proposed algorithm is tested with simulated and also experimental data from phantoms. Successful conductivity reconstructions are obtained by solving the related convection equation using the Galerkin weighted residual FEM when there are no sharp variations in the actual conductivity distribution. However, when there is noise in the magnetic flux density data or when there are sharp variations in conductivity, it is found that SUPG stabilization is beneficial.

Sodium benzoate, potassium sorbate, and citric acid induce sublethal injury and enhance pulsed electric field inactivation of E. coli O157:H7 and nonpathogenic surrogate E. coli in strawberry juice

USDA-ARS?s Scientific Manuscript database

Current FDA regulations require that juice processors effect a 5 log CFU/ml reduction of a target pathogen prior to distributing products. Whereas thermal pasteurization reduces the sensory characteristics of juice by altering flavor components, pulsed electric field (PEF) treatment can be conducte...

Complex conductivity of organic-rich shales

NASA Astrophysics Data System (ADS)

Woodruff, W. F.; Revil, A.; Torres-Verdin, C.

2013-12-01

We can accurately determine the intrinsic anisotropy and material properties in the laboratory, providing empirical evidence of transverse isotropy and the polarization of the organic and metallic fractions in saturated and unsaturated shales. We develop two distinct approaches to obtain the complex conductivity tensor from spectral induced polarization (SIP) measurements. Experimental results indicate clear anisotropy, and characterize the effects of thermal maturation, TOC, and pyrite, aiding in the calibration and interpretation of geophysical data. SIP is a non-intrusive measurement, sensitive to the surface conductance of mineral grains, frequency-dependent polarization of the electrical double layer, and bulk conductivity of the pore water. The in-phase and quadrature components depend upon parameters of principal importance in unconventional shale formation evaluation (e.g., the distribution of pore throat sizes, formation factor, permeability, salinity and cation exchange capacity (CEC), fluid saturation and wettability). In addition to the contribution of the electrical double layer of non-conducting minerals to surface conductivity, we have observed a clear relaxation associated with kerogen pyrolysis, pyrite distribution, and evidence that the CEC of the kerogen fraction may also contribute, depending on thermal maturation history. We utilize a recent model for anisotropic complex conductivity, and rigorous experimental protocols to quantify the role of kerogen and pyrolysis on surface and quadrature conductivity in mudrocks. The complex conductivity tensor σ* describes the directional dependence of electrical conduction in a porous medium, and accounts for both conduction and polarization. The complex-valued tensor components are given as σ*ij , where σ'ij represents in-phase and σ"ij denotes quadrature conductivities. The directional dependence of the complex conductivity tensor is relegated to the textural properties of the material. The components of the formation factor and connectivity (tortuosity) tensors Fij and Tij (affecting the bulk and surface conductivity, respectively) are correlated as Fij=TijΦ. Both conductivity and connectivity tensors share the same eigenvectors; the anisotropy ratio is equivalent in TI media. At high pore water salinity, surface and quadrature conductivity share the same bulk tortuosity; when surface conductivity dominates (low salinity), conductivity is controlled by the surface conductance, and the tortuosity of electrical current along mineral surfaces usually higher than that of the pore water. We developed two distinct SIP measurement protocols to obtain the tensor: (1) azimuthal sampling and inversion of phasor potentials through the full-field solution of the Laplace equation; (2) direct measurement of complex conductivity eigenvalues by polarized, single-component stimulus current. Experiments also include unsaturated and saturated measurements with three brines of known salinity and pH, at log-distributed frequencies ranging 1 mHz to 45 kHz. Both azimuthal spectra and eigenvalue spectra validate the theoretical model and illustrate the effectiveness of the protocols themselves. We obtain the textural tensors and invert key parameters including Archie exponents and CEC, and characterize the relaxation phenomena associated with kerogen content and maturity for multiphase fluid systems.

Mitigating Space Weather Impacts on the Power Grid in Real-Time: Applying 3-D EarthScope Magnetotelluric Data to Forecasting Reactive Power Loss in Power Transformers

NASA Astrophysics Data System (ADS)

Schultz, A.; Bonner, L. R., IV

2017-12-01

Current efforts to assess risk to the power grid from geomagnetic disturbances (GMDs) that result in geomagnetically induced currents (GICs) seek to identify potential "hotspots," based on statistical models of GMD storm scenarios and power distribution grounding models that assume that the electrical conductivity of the Earth's crust and mantle varies only with depth. The NSF-supported EarthScope Magnetotelluric (MT) Program operated by Oregon State University has mapped 3-D ground electrical conductivity structure across more than half of the continental US. MT data, the naturally occurring time variations in the Earth's vector electric and magnetic fields at ground level, are used to determine the MT impedance tensor for each site (the ratio of horizontal vector electric and magnetic fields at ground level expressed as a complex-valued frequency domain quantity). The impedance provides information on the 3-D electrical conductivity structure of the Earth's crust and mantle. We demonstrate that use of 3-D ground conductivity information significantly improves the fidelity of GIC predictions over existing 1-D approaches. We project real-time magnetic field data streams from US Geological Survey magnetic observatories into a set of linear filters that employ the impedance data and that generate estimates of ground level electric fields at the locations of MT stations. The resulting ground electric fields are projected to and integrated along the path of power transmission lines. This serves as inputs to power flow models that represent the power transmission grid, yielding a time-varying set of quasi-real-time estimates of reactive power loss at the power transformers that are critical infrastructure for power distribution. We demonstrate that peak reactive power loss and hence peak risk for transformer damage from GICs does not necessarily occur during peak GMD storm times, but rather depends on the time-evolution of the polarization of the GMD's inducing fields and the complex ground (3-D) electric field response, and the resulting alignment of the ground electric fields with the power transmission line paths. This is informing our efforts to provide a set of real-time tools for power grid operators to use in mitigating damage from space weather events.

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.

Electrically conductive poly-ɛ-caprolactone/polyethylene glycol/multi-wall carbon nanotube nanocomposite scaffolds coated with fibrin glue for myocardial tissue engineering

NASA Astrophysics Data System (ADS)

Mehdikhani, Mehdi; Ghaziof, Sharareh

2018-01-01

In this research, poly-ɛ-caprolactone (PCL), polyethylene glycol (PEG), multi-wall carbon nanotubes (MWCNTs), and nanocomposite scaffolds containing 0.5 and 1% (w/w) MWCNTs coated with fibrin glue (FG) were prepared via solvent casting and freeze-drying technique for cardiac tissue engineering. Scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, and X-ray diffraction were used to characterize the samples. Furthermore, mechanical properties, electrical conductivity, degradation, contact angle, and cytotoxicity of the samples were evaluated. Results showed the uniform distribution of the MWCNTs with some aggregates in the prepared nanocomposite scaffolds. The scaffolds containing 1% (w/w) MWCNTs with and without FG coating illustrated optimum modulus of elasticity, high electrical conductivity, and wettability compared with PCL/PEG and PCL/PEG/0.5%(w/w) MWCNTs' scaffolds. FG coating enhanced electrical conductivity and cell response, and increased wettability of the constructs. The prepared scaffolds were degraded significantly after 60 days of immersion in PBS. Meanwhile, the nanocomposite containing 1% (w/w) MWCNTs with FG coating (S3) showed proper spreading and viability of the myoblasts seeded on it after 1, 4, and 7 days of culture. The scaffold containing 1% (w/w) MWCNTs with FG coating demonstrated optimal properties including acceptable mechanical properties, proper wettability, high electrical conductivity, satisfactory degradation, and excellent myoblasts response to it.

Effect of Precipitating Electrons on Stormtime Inner Magnetospheric Electric Fields during the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C. L.; Sazykin, S. Y.; Wolf, R.; Hecht, J. H.; Walterscheid, R. L.; Boyd, A. J.; Turner, D. L.

2015-12-01

We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions and how the precipitating electrons modify the ionospheric conductivity and electric potentials during the large 17 March 2013 magnetic storm. Of particular interest is how electron precipitation in the evening sector affects the development of the Sub-auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating electron distributions and the electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. We compare simulated trapped and precipitating electron flux distributions with measurements from Van Allen Probes/MagEIS, POES/TED and MEPED, respectively, to validate the electron loss model. Ground-based (SuperDARN) and in-situ (Van Allen Probes/EFW) observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons on the SAPS and inner magnetospheric electric field through the data-model comparisons.

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.

Influence of surface error on electromagnetic performance of reflectors based on Zernike polynomials

NASA Astrophysics Data System (ADS)

Li, Tuanjie; Shi, Jiachen; Tang, Yaqiong

2018-04-01

This paper investigates the influence of surface error distribution on the electromagnetic performance of antennas. The normalized Zernike polynomials are used to describe a smooth and continuous deformation surface. Based on the geometrical optics and piecewise linear fitting method, the electrical performance of reflector described by the Zernike polynomials is derived to reveal the relationship between surface error distribution and electromagnetic performance. Then the relation database between surface figure and electric performance is built for ideal and deformed surfaces to realize rapidly calculation of far-field electric performances. The simulation analysis of the influence of Zernike polynomials on the electrical properties for the axis-symmetrical reflector with the axial mode helical antenna as feed is further conducted to verify the correctness of the proposed method. Finally, the influence rules of surface error distribution on electromagnetic performance are summarized. The simulation results show that some terms of Zernike polynomials may decrease the amplitude of main lobe of antenna pattern, and some may reduce the pointing accuracy. This work extracts a new concept for reflector's shape adjustment in manufacturing process.

Deposition of Electrically Conductive Coatings on Castable Polyurethane Elastomers by the Flame Spraying Process

NASA Astrophysics Data System (ADS)

Ashrafizadeh, H.; McDonald, A.; Mertiny, P.

2016-02-01

Deposition of metallic coatings on elastomeric polymers is a challenging task due to the heat sensitivity and soft nature of these materials and the high temperatures in thermal spraying processes. In this study, a flame spraying process was employed to deposit conductive coatings of aluminum-12silicon on polyurethane elastomers. The effect of process parameters, i.e., stand-off distance and air added to the flame spray torch, on temperature distribution and corresponding effects on coating characteristics, including electrical resistivity, were investigated. An analytical model based on a Green's function approach was employed to determine the temperature distribution within the substrate. It was found that the coating porosity and electrical resistance decreased by increasing the pressure of the air injected into the flame spray torch during deposition. The latter also allowed for a reduction of the stand-off distance of the flame spray torch. Dynamic mechanical analysis was performed to investigate the effect of the increase in temperature within the substrate on its dynamic mechanical properties. It was found that the spraying process did not significantly change the storage modulus of the polyurethane substrate material.

Numerical simulations of electric potential field for alternating current potential drop associated with surface cracks in low-alloy steel nuclear material

NASA Astrophysics Data System (ADS)

Yeh, Chun-Ping; Huang, Jiunn-Yuan

2018-04-01

Low-alloy steels used as structural materials in nuclear power plants are subjected to cyclic stresses during power plant operations. As a result, cracks may develop and propagate through the material. The alternating current potential drop technique is used to measure the lengths of cracks in metallic components. The depth of the penetration of the alternating current is assumed to be small compared to the crack length. This assumption allows the adoption of the unfolding technique to simplify the problem to a surface Laplacian field. The numerical modelling of the electric potential and current density distribution prediction model for a compact tension specimen and the unfolded crack model are presented in this paper. The goal of this work is to conduct numerical simulations to reduce deviations occurring in the crack length measurements. Numerical simulations were conducted on AISI 4340 low-alloy steel with different crack lengths to evaluate the electric potential distribution. From the simulated results, an optimised position for voltage measurements in the crack region was proposed.

EIT Imaging Regularization Based on Spectral Graph Wavelets.

PubMed

Gong, Bo; Schullcke, Benjamin; Krueger-Ziolek, Sabine; Vauhkonen, Marko; Wolf, Gerhard; Mueller-Lisse, Ullrich; Moeller, Knut

2017-09-01

The objective of electrical impedance tomographic reconstruction is to identify the distribution of tissue conductivity from electrical boundary conditions. This is an ill-posed inverse problem usually solved under the finite-element method framework. In previous studies, standard sparse regularization was used for difference electrical impedance tomography to achieve a sparse solution. However, regarding elementwise sparsity, standard sparse regularization interferes with the smoothness of conductivity distribution between neighboring elements and is sensitive to noise. As an effect, the reconstructed images are spiky and depict a lack of smoothness. Such unexpected artifacts are not realistic and may lead to misinterpretation in clinical applications. To eliminate such artifacts, we present a novel sparse regularization method that uses spectral graph wavelet transforms. Single-scale or multiscale graph wavelet transforms are employed to introduce local smoothness on different scales into the reconstructed images. The proposed approach relies on viewing finite-element meshes as undirected graphs and applying wavelet transforms derived from spectral graph theory. Reconstruction results from simulations, a phantom experiment, and patient data suggest that our algorithm is more robust to noise and produces more reliable images.

NREL Paves the Way to Commercialization of Silicon Ink (Fact Sheet)

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

Not Available

In 2008, Innovalight, a start-up company in Sunnyvale, California, invented a liquid form of silicon, called Silicon Ink. It contains silicon nanoparticles that are suspended evenly within the solution. Those nanoparticles contain dopant atoms that can be driven into silicon solar cells, which changes the conductivity of the silicon and creates the internal electric fields that are needed to turn photons into electrons -- and thus into electricity. The ink is applied with a standard screen printer, already commonly used in the solar industry. The distinguishing feature of Silicon Ink is that it can be distributed in exact concentrations inmore » precisely the correct locations on the surface of the solar cell. This allows most of the surface to be lightly doped, enhancing its response to blue light, while heavily doping the area around the electrical contacts, raising the conductivity in that area to allow the contact to work more efficiently. The accuracy and uniformity of the ink distribution allows the production of solar cells that achieve higher power production at a minimal additional cost.« less

Distributed Energy Resources and Dynamic Microgrid: An Integrated Assessment

NASA Astrophysics Data System (ADS)

Shang, Duo Rick

The overall goal of this thesis is to improve understanding in terms of the benefit of DERs to both utility and to electricity end-users when integrated in power distribution system. To achieve this goal, a series of two studies was conducted to assess the value of DERs when integrated with new power paradigms. First, the arbitrage value of DERs was examined in markets with time-variant electricity pricing rates (e.g., time of use, real time pricing) under a smart grid distribution paradigm. This study uses a stochastic optimization model to estimate the potential profit from electricity price arbitrage over a five-year period. The optimization process involves two types of PHEVs (PHEV-10, and PHEV-40) under three scenarios with different assumptions on technology performance, electricity market and PHEV owner types. The simulation results indicate that expected arbitrage profit is not a viable option to engage PHEVs in dispatching and in providing ancillary services without more favorable policy and PHEV battery technologies. Subsidy or change in electricity tariff or both are needed. Second, it examined the concept of dynamic microgrid as a measure to improve distribution resilience, and estimates the prices of this emerging service. An economic load dispatch (ELD) model is developed to estimate the market-clearing price in a hypothetical community with single bid auction electricity market. The results show that the electricity market clearing price on the dynamic microgrid is predominantly decided by power output and cost of electricity of each type of DGs. At circumstances where CHP is the only source, the electricity market clearing price in the island is even cheaper than the on-grid electricity price at normal times. Integration of PHEVs in the dynamic microgrid will increase electricity market clearing prices. It demonstrates that dynamic microgrid is an economically viable alternative to enhance grid resilience.

Redox potential distribution of an organic-rich contaminated site obtained by the inversion of self-potential data

NASA Astrophysics Data System (ADS)

Abbas, M.; Jardani, A.; Soueid Ahmed, A.; Revil, A.; Brigaud, L.; Bégassat, Ph.; Dupont, J. P.

2017-11-01

Mapping the redox potential of shallow aquifers impacted by hydrocarbon contaminant plumes is important for the characterization and remediation of such contaminated sites. The redox potential of groundwater is indicative of the biodegradation of hydrocarbons and is important in delineating the shapes of contaminant plumes. The self-potential method was used to reconstruct the redox potential of groundwater associated with an organic-rich contaminant plume in northern France. The self-potential technique is a passive technique consisting in recording the electrical potential distribution at the surface of the Earth. A self-potential map is essentially the sum of two contributions, one associated with groundwater flow referred to as the electrokinetic component, and one associated with redox potential anomalies referred to as the electroredox component (thermoelectric and diffusion potentials are generally negligible). A groundwater flow model was first used to remove the electrokinetic component from the observed self-potential data. Then, a residual self-potential map was obtained. The source current density generating the residual self-potential signals is assumed to be associated with the position of the water table, an interface characterized by a change in both the electrical conductivity and the redox potential. The source current density was obtained through an inverse problem by minimizing a cost function including a data misfit contribution and a regularizer. This inversion algorithm allows the determination of the vertical and horizontal components of the source current density taking into account the electrical conductivity distribution of the saturated and non-saturated zones obtained independently by electrical resistivity tomography. The redox potential distribution was finally determined from the inverted residual source current density. A redox map was successfully built and the estimated redox potential values correlated well with in-situ measurements.

Predicting the Electric Field Distribution in the Brain for the Treatment of Glioblastoma

PubMed Central

Miranda, Pedro C.; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J.

2014-01-01

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a “virtual lesion” in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V/cm and exceeded 1.0 V/cm in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor’s necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning. PMID:25003941

Predicting the electric field distribution in the brain for the treatment of glioblastoma

NASA Astrophysics Data System (ADS)

Miranda, Pedro C.; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J.

2014-08-01

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a ‘virtual lesion’ in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V cm - 1 and exceeded 1.0 V cm - 1 in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor’s necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning.

Predicting the electric field distribution in the brain for the treatment of glioblastoma.

PubMed

Miranda, Pedro C; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J

2014-08-07

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a 'virtual lesion' in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V cm( - 1) and exceeded 1.0 V cm( - 1) in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor's necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning.

Large transient fault current test of an electrical roll ring

NASA Technical Reports Server (NTRS)

Yenni, Edward J.; Birchenough, Arthur G.

1992-01-01

The space station uses precision rotary gimbals to provide for sun tracking of its photoelectric arrays. Electrical power, command signals and data are transferred across the gimbals by roll rings. Roll rings have been shown to be capable of highly efficient electrical transmission and long life, through tests conducted at the NASA Lewis Research Center and Honeywell's Satellite and Space Systems Division in Phoenix, AZ. Large potential fault currents inherent to the power system's DC distribution architecture, have brought about the need to evaluate the effects of large transient fault currents on roll rings. A test recently conducted at Lewis subjected a roll ring to a simulated worst case space station electrical fault. The system model used to obtain the fault profile is described, along with details of the reduced order circuit that was used to simulate the fault. Test results comparing roll ring performance before and after the fault are also presented.

Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring

PubMed Central

Soto, Matias; Esteva, Milton; Martínez-Romero, Oscar; Baez, Jesús; Elías-Zúñiga, Alex

2015-01-01

A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss–Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature. PMID:28793594

Evaluation of critical nuclear power plant electrical cable response to severe thermal fire conditions

NASA Astrophysics Data System (ADS)

Taylor, Gabriel James

The failure of electrical cables exposed to severe thermal fire conditions are a safety concern for operating commercial nuclear power plants (NPPs). The Nuclear Regulatory Commission (NRC) has promoted the use of risk-informed and performance-based methods for fire protection which resulted in a need to develop realistic methods to quantify the risk of fire to NPP safety. Recent electrical cable testing has been conducted to provide empirical data on the failure modes and likelihood of fire-induced damage. This thesis evaluated numerous aspects of the data. Circuit characteristics affecting fire-induced electrical cable failure modes have been evaluated. In addition, thermal failure temperatures corresponding to cable functional failures have been evaluated to develop realistic single point thermal failure thresholds and probability distributions for specific cable insulation types. Finally, the data was used to evaluate the prediction capabilities of a one-dimension conductive heat transfer model used to predict cable failure.

Numerical modeling of friction welding of bi-metal joints for electrical applications

NASA Astrophysics Data System (ADS)

Velu, P. Shenbaga; Hynes, N. Rajesh Jesudoss

2018-05-01

In the manufacturing industries, and more especially in electrical engineering applications, the usage of non-ferrous materials plays a vital role. Today's engineering applications relies upon some of the significant properties such as a good corrosion resistance, mechanical properties, good heat conductivity and higher electrical conductivity. Copper-aluminum bi-metal joint is one such combination that meets the demands requirements for electrical applications. In this work, the numerical simulation of AA 6061 T6 alloy/Copper was carried out under joining conditions. By using this developed model, the temperature distribution along the length of the dissimilar joint is predicted and the time-temperature profile has also been generated. Besides, a Finite Element Model has been developed by using the numerical simulation Tool "ABAQUS". This developed FEM is helpful in predicting various output parameters during friction welding of this dissimilar joint combination.

Nonideal ultrathin mantle cloak for electrically large conducting cylinders.

PubMed

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

2014-09-01

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

Current distribution in tissues with conducted electrical weapons operated in drive-stun mode.

PubMed

Panescu, Dorin; Kroll, Mark W; Brave, Michael

2016-08-01

The TASER® conducted electrical weapon (CEW) is best known for delivering electrical pulses that can temporarily incapacitate subjects by overriding normal motor control. The alternative drive-stun mode is less understood and the goal of this paper is to analyze the distribution of currents in tissues when the CEW is operated in this mode. Finite element modeling (FEM) was used to approximate current density in tissues with boundary electrical sources placed 40 mm apart. This separation was equivalent to the distance between drive-stun mode TASER X26™, X26P, X2 CEW electrodes located on the device itself and between those located on the expended CEW cartridge. The FEMs estimated the amount of current flowing through various body tissues located underneath the electrodes. The FEM simulated the attenuating effects of both a thin and of a normal layer of fat. The resulting current density distributions were used to compute the residual amount of current flowing through deeper layers of tissue. Numerical modeling estimated that the skin, fat and skeletal muscle layers passed at least 86% or 91% of total CEW current, assuming a thin or normal fat layer thickness, respectively. The current density and electric field strength only exceeded thresholds which have increased probability for ventricular fibrillation (VFTJ), or for cardiac capture (CCTE), in the skin and the subdermal fat layers. The fat layer provided significant attenuation of drive-stun CEW currents. Beyond the skeletal muscle layer, only fractional amounts of the total CEW current were estimated to flow. The regions presenting risk for VF induction or for cardiac capture were well away from the typical heart depth.

Cylindrical Electrolyser Enhanced Electrokinetic Remediation of Municipal Solid Waste Incineration Fly Ashes

NASA Astrophysics Data System (ADS)

Huang, Tao; Zhou, Lulu; Tao, Junjun; Liu, Longfei

2018-01-01

The paper discusses enhancement and efficiency of removing spiked heavy metal (HM) contaminants from the municipal solid waste incineration (MSWI) fly ashes in the cylindrical electrolyser device. The characterization parameters of the electrolyte solution pH, electric current, electrical conductivity, voltage gradient were discussed after the experiment. The chemical speciation of HMs was analysed between the original samples and remediated ones by BCR sequential extraction. The detoxification efficiencies of Zn, Pb, Cu and Cd in the column-uniform device were compared with that in the traditional rectangular apparatus. The pH value changed smoothly with small amplitude of oscillation in general in cathode and anode compartments except the initial break. The electrical current rapidly increased on the first day of the experiment and steadily declined after that and the electrical conductivity presented a clear rising trend. The residual partition of detoxified samples were obviously lifted which was much higher than the analysis data of the raw materials. The pH and the electrical conductivity in sample region were distributed more uniformly and the blind area was effectively eliminated in the electrolytic cells which was indirectly validated by the contrastive detoxification result of the spiked HMs between the rectangular and cylindrical devices.

Photovoltaic technology for sustainability: An investigation of the distributed utility concept as a policy framework

NASA Astrophysics Data System (ADS)

Letendre, Steven Emery

The U.S. electric utility sector in its current configuration is unsustainable. The majority of electricity in the United States is produced using finite fossil fuels. In addition, significant potential exists to improve the nation's efficient use of energy. A sustainable electric utility sector will be characterized by increased use of renewable energy sources and high levels of end-use efficiency. This dissertation analyzes two alternative policy approaches designed to move the U.S. electric utility sector toward sustainability. One approach is labeled incremental which involves maintaining the centralized structure of the electric utility sector but facilitating the introduction of renewable energy and efficiency into the electrical system through the pricing mechanism. A second policy approach was described in which structural changes are encouraged based on the emerging distributed utility (DU) concept. A structural policy orientation attempts to capture the unique localized benefits that distributed renewable resources and energy efficiency offer to electric utility companies and their customers. A market penetration analysis of PV in centralized energy supply and distributed peak-shaving applications is conducted for a case-study electric utility company. Sensitivity analysis was performed based on incremental and structural policy orientations. The analysis provides compelling evidence which suggests that policies designed to bring about structural change in the electric utility sector are needed to move the industry toward sustainability. Specifically, the analysis demonstrates that PV technology, a key renewable energy option likely to play an important role in a renewable energy future, will begin to penetrate the electrical system in distributed peak-shaving applications long before the technology is introduced as a centralized energy supply option. Most policies to date, which I term incremental, attempt to encourage energy efficiency and renewables through the pricing system. Based on past policy experience, it is unlikely that such an approach would allow PV to compete in Delaware as an energy supply option in the next ten to twenty years. Alternatively, a market-based, or green pricing, approach will not create significant market opportunities for PV as a centralized energy supply option. However, structural policies designed to encourage the explicit recognition of the localized benefits of distributed resources could result in PV being introduced into the electrical system early in the next century.

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Janssen, A. M.; Rampersad, S. M.; Lucka, F.; Lanfer, B.; Lew, S.; Aydin, Ü.; Wolters, C. H.; Stegeman, D. F.; Oostendorp, T. F.

2013-07-01

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation. One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between cerebrospinal fluid (CSF) and grey matter (Thielscher et al 2011 NeuroImage 54 234-43, Bijsterbosch et al 2012 Med. Biol. Eng. Comput. 50 671-81), or by resizing the whole brain (Wagner et al 2008 Exp. Brain Res. 186 539-50). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images, was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location.

Electrically conductive concrete : a laboratory study.

DOT National Transportation Integrated Search

1987-01-01

In the cathodic protection of existing reinforced concrete bridge decks, there is a need for a simple secondary-anode system to facilitate the distribution of direct current over the structure being protected. It is believed that a durable, electrica...

Controle de l'alignement des nanotubes de carbone multiparois a l'interieur d'un polymere et d''un materiau composite multi-echelles a l'aide d'un champ electrique

NASA Astrophysics Data System (ADS)

Arguin, Maxime

Composite materials are lightweight and have very good mechanical properties which make them a good alternative to metallic structures traditionally used in aircraft. However, these materials have a very low electrical conductivity compared to metal which limits their use for electrical application such as current return network. For example, carbon fiber composites have relatively good in-plane conductivity but a resistance between each ply, generated by the epoxy, reduced the conductivity through the thickness of the material by a thousand. The anisotropy results in a poor current diffusion through each layer of the composite and heat generation at surface when an electric current is applied on a composite panel. For this reason, the electrical conductivity of carbon fibers composite must be improved to be used for electrical applications. This thesis shows a new procedure to enhance the electrical conductivity of composite material in a preferential way (i.e., through the thickness). Multi-walled carbon nanotubes (MWCNTs) were added to the epoxy matrix of a composite to create multiscale composite. An electric field was also used to control the global distribution of the NTCs. Alignment results made on a UV epoxy reinforced with 0.01wt.% of MWCNTs showed a decrease of the resistivity by four orders of magnitude. This decrease of resistivity was also associated with formation of a filamentary microstructure that goes from one electrode to the others creating preferential conduction pathways. Afterwards, a hand lay-up process was modified to incorporate electric field alignment during the manufacturing of the composite. An improvement of the conductivity of 36% and 99% were obtained when an electric of 60V/mm were used to align the nanoparticles in multiscale composites containing 0.01wt.% and 0.1wt.% of MWCNTs, respectively. However, these modest improvements were still not enough to reach a complete current diffusion through the thickness but this technique is still a potential way to achieve it. Finally, the project shows the potential of using electric field induced alignment of the MWCNTs to improve the conductivity of multiscale composite. Furthermore, this technique has the advantage to be suitable to other common manufacturing processes using in the industry.

Efficient Third-Order Distributed Feedback Laser with Enhanced Beam Pattern

NASA Technical Reports Server (NTRS)

Hu, Qing (Inventor); Lee, Alan Wei Min (Inventor); Kao, Tsung-Yu (Inventor)

2015-01-01

A third-order distributed feedback laser has an active medium disposed on a substrate as a linear array of segments having a series of periodically spaced interstices therebetween and a first conductive layer disposed on a surface of the active medium on each of the segments and along a strip from each of the segments to a conductive electrical contact pad for application of current along a path including the active medium. Upon application of a current through the active medium, the active medium functions as an optical waveguide, and there is established an alternating electric field, at a THz frequency, both in the active medium and emerging from the interstices. Spacing of adjacent segments is approximately half of a wavelength of the THz frequency in free space or an odd integral multiple thereof, so that the linear array has a coherence length greater than the length of the linear array.

Controlling charge transport mechanisms in molecular junctions: Distilling thermally induced hopping from coherent-resonant conduction.

PubMed

Kim, Hyehwang; Segal, Dvira

2017-04-28

The electrical conductance of molecular junctions may depend strongly on the temperature and weakly on molecular length, under two distinct mechanisms: phase-coherent resonant conduction, with charges proceeding via delocalized molecular orbitals, and incoherent thermally assisted multi-step hopping. While in the case of coherent conduction, the temperature dependence arises from the broadening of the Fermi distribution in the metal electrodes, in the latter case it corresponds to electron-vibration interaction effects on the junction. With the objective to distill the thermally activated hopping component, thus exposing intrinsic electron-vibration interaction phenomena on the junction, we suggest the design of molecular junctions with "spacers," extended anchoring groups that act to filter out phase-coherent resonant electrons. Specifically, we study the electrical conductance of fixed-gap and variable-gap junctions that include a tunneling block, with spacers at the boundaries. Using numerical simulations and analytical considerations, we demonstrate that in our design, resonant conduction is suppressed. As a result, the electrical conductance is dominated by two (rather than three) mechanisms: superexchange (deep tunneling) and multi-step thermally induced hopping. We further exemplify our analysis on DNA junctions with an A:T block serving as a tunneling barrier. Here, we show that the electrical conductance is insensitive to the number of G:C base-pairs at the boundaries. This indicates that the tunneling-to-hopping crossover revealed in such sequences truly corresponds to the properties of the A:T barrier.

Student difficulties in translating between mathematical and graphical representations in introductory physics

NASA Astrophysics Data System (ADS)

Lin, Shih-Yin; Maries, Alexandru; Singh, Chandralekha

2013-01-01

We investigate introductory physics students' difficulties in translating between mathematical and graphical representations and the effect of scaffolding on students' performance. We gave a typical problem that can be solved using Gauss's law involving a spherically symmetric charge distribution (a conducting sphere concentric with a conducting spherical shell) to 95 calculus-based introductory physics students. We asked students to write a mathematical expression for the electric field in various regions and asked them to graph the electric field. We knew from previous experience that students have great difficulty in graphing the electric field. Therefore, we implemented two scaffolding interventions to help them. Students who received the scaffolding support were either (1) asked to plot the electric field in each region first (before having to plot it as a function of distance from the center of the sphere) or (2) asked to plot the electric field in each region after explicitly evaluating the electric field at the beginning, mid and end points of each region. The comparison group was only asked to plot the electric field at the end of the problem. We found that students benefited the most from intervention (1) and that intervention (2), although intended to aid students, had an adverse effect. Also, recorded interviews were conducted with a few students in order to understand how students were impacted by the aforementioned interventions.

The application of the electrodynamic separator in minerals beneficiation

NASA Astrophysics Data System (ADS)

Skowron, M.; Syrek, P.; Surowiak, A.

2017-05-01

The aim of presented paper is elaboration of methodology of upgrading natural minerals in example of chalcocite and bornite sample. The results were obtained by means of laboratory drum separator. This device operates in accordance to properties of materials, which in this case was electrical conductivity. The study contains the analysis of the forces occurring inside of electrodynamic separator chamber, that act on the particles of various electrical properties. Both, the potential and electric field strength distributions were calculated, with set of separators setpoints. Theoretical analysis influenced on separator parameters, and hence impacted the empirical results too. Next, the authors conducted empirical research on chalcocite and bornite beneficiation by means of electrodynamic separation. The results of this process were shown graphically in form of upgrading curves of chalcocite considering elementary copper and lead.

On the influence of Aerosols in measurement of electric field from Earth surface using a Field-Mill

NASA Astrophysics Data System (ADS)

Ghosh, Abhijit; Sundar De, Syam; Paul, Suman; Hazra, Pranab; Guha, Gautam

2016-07-01

Aerosol particles influence the electrical conductivity of air. The value is reduced through the removal of small ions responsible for the conductivity. The metropolitan city, Kolkata (latitude 22.56° N, longitude 88.5° E) is densely populated surrounded by various types of Industries. Air is highly invaded by pollutant particles here for which the city falls under small-scale fair-weather condition where electric field and air-earth current get perturbed by ionization and different aerosols produced locally. Fine particles having diameter < 0.1 μm (Aitken nuclei) are distributed in air which decreases the electrical conductivity and increases the columnar resistance. Aerosol particles steadily change the status at different times of the day through coagulation, sedimentation, charge-transfer initiated by precipitation. The diurnal variation of potential gradient is caused mainly due to urbanization, emission from industry and traffic. The rate of production of haze (atmospheric suspension) and their vertical transportation control the daily variation of atmospheric potential. The nuclei of pollutant particles combine with ions and decrease the concentration of small ions thereby reducing the conductivity. The pollutants, influenced by CO _{2} and other green house gas emission from fossil fuels are also responsible for the variation of electric field. Variation in consumption of Oil and Gasoline due to traffic in the city contributes a high Aitken count and there are changes in atmospheric dispersion following reduction of conductivity of the medium. Outcome of some important measurement of potential gradient and air-earth current will be presented. Different parameters like air-conductivity, relative abundance of smoke, visibility would offer new signatures of aerosol-influence on electric potential gradient. Some of those will be reported here.

Theoretical models for electron conduction in polymer systems—I. Macroscopic calculations of d.c. transient conductivity after pulse irradiation

NASA Astrophysics Data System (ADS)

Bartczak, Witold M.; Kroh, Jerzy

The simulation of the transient d.c. conductivity in a quasi one-dimensional system of charges produced by a pulse of ionizing radiation in a solid sample has been performed. The simulation is based on the macroscopic conductivity equations and can provide physical insight into d.c. conductivity measurements, particularly for the case of transient currents in samples with internal space charge. We consider the system of mobile (negative) and immobile (positive) charges produced by a pulse of ionizing radiation in the sample under a fixed external voltage V0. The presence of space charge results in an electric field which is a function of both the spatial and the time variable: E( z, t). Given the space charge density, the electric field can be calculated from the Poisson equation. However, for an arbitrary space charge distribution, the corresponding equations can only be solved numerically. The two non-trivial cases for which approximate analytical solutions can be provided are: (i) The density of the current carriers n( z, t) is negligible in comparison with the density of immobile space charge N( z). A general analytical solution has been found for this case using Green's functions. The solutions for two cases, viz. the homogeneous distribution of space charge N( z) = N, and the non-homogeneous exponential distribution N( z) = A exp(- Bz), have been separately discussed. (ii) The space charge created in the pulse without any space charge present prior to the irradiation.

Magnetic resonance electrical impedance tomography (MREIT): simulation study of J-substitution algorithm.

PubMed

Kwon, Ohin; Woo, Eung Je; Yoon, Jeong-Rock; Seo, Jin Keun

2002-02-01

We developed a new image reconstruction algorithm for magnetic resonance electrical impedance tomography (MREIT). MREIT is a new EIT imaging technique integrated into magnetic resonance imaging (MRI) system. Based on the assumption that internal current density distribution is obtained using magnetic resonance imaging (MRI) technique, the new image reconstruction algorithm called J-substitution algorithm produces cross-sectional static images of resistivity (or conductivity) distributions. Computer simulations show that the spatial resolution of resistivity image is comparable to that of MRI. MREIT provides accurate high-resolution cross-sectional resistivity images making resistivity values of various human tissues available for many biomedical applications.

The direct-current response of electrically conducting fractures excited by a grounded current source

DOE PAGES

Weiss, Chester J.; Aldridge, David F.; Knox, Hunter A.; ...

2016-05-01

Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross–cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long–term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures — knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electricalmore » conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. As a result, this approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity — the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.« less

The direct-current response of electrically conducting fractures excited by a grounded current source

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

Weiss, Chester J.; Aldridge, David F.; Knox, Hunter A.

Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross–cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long–term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures — knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electricalmore » conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. As a result, this approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity — the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.« less

Method for uniformly distributing carbon flakes in a positive electrode, the electrode made thereby and compositions

DOEpatents

Mrazek, Franklin C.; Smaga, John A.; Battles, James E.

1983-01-01

A positive electrode for a secondary electrochemical cell wherein an electrically conductive current collector is in electrical contact with a particulate mixture of gray cast iron and an alkali metal sulfide and an electrolyte including alkali metal halides or alkaline earth metal halides. Also present may be a transition metal sulfide and graphite flakes from the conversion of gray cast iron to iron sulfide. Also disclosed is a method of distributing carbon flakes in a cell wherein there is formed an electrochemical cell of a positive electrode structure of the type described and a suitable electrolyte and a second electrode containing a material capable of alloying with alkali metal ions. The cell is connected to a source of electrical potential to electrochemically convert gray cast iron to an iron sulfide and uniformly to distribute carbon flakes formerly in the gray cast iron throughout the positive electrode while forming an alkali metal alloy in the negative electrode. Also disclosed are compositions useful in preparing positive electrodes.

Percolation dans des reseaux realistes de nanostructures de carbone

NASA Astrophysics Data System (ADS)

Simoneau, Louis-Philippe

Carbon nanotubes have very interesting mechanical and electrical properties for various applications in electronics. They are highly resistant to deformation and can be excellent conductors or semiconductors. However, manipulating individual nanotubes to build structured devices remains very difficult. There is no method for controlling all of the electrical properties, the orientation and the spatial positioning of a large number of nanotubes. The fabrication of disordered networks of nanotubes is much easier, and these systems have a good electrical conductivity which makes them very interesting, especially as materials of transparent and flexible electrodes. There are three main methods of production used to make networks of nanotubes: the solution deposition, the direct growth on substrate and the embedding in a polymer matrix. The solution deposition method can form networks of various densities on a variety of substrates, the direct growth of nanotubes allows the creation of very clean networks on substrates such as SiO2, and the embedding in a polymer matrix can give composite volumes containing varying amounts of nanotubes. Many parameters such as the length of the tubes, their orientation or their tortuosity influence the properties of these networks and the presence of structural disorder complicates the understanding of their interactions. Predicting the properties of a network, such as conductivity, from a few characteristics such as size and density of the tubes can be difficult. This task becomes even more complex if one wants to identify the parameters that will optimize the performance of a device containing the material. We chose to address the carbon nanotube networks problem by developing a series of computer simulation tools that are mainly based on the Monte Carlo method. We take into account a large number of parameters to describe the characteristics of the networks, which allows for a more reliable representation of real networks as well as versatility in the choice of network components that can be simulated. The tools we have developed, grouped together in the RPH-HPN software Reseaux percolatifs hybrides - Hybrid Percolation Networks, construct random networks, detect contact between the tubes, translate the systems to equivalent electrical circuits and calculate global properties. An infinity of networks can have the same basic characteristics (size, diameter, etc.) and therefore the properties of a particular random network are not necessarily representative of the average properties of all networks. To obtain those general properties, we simulate a large number of random networks with the same basic characteristics and the average of the quantities is determined. The network constituent elements can be spheres, rods or snakes. The use of such geometries for network elements makes contact detection simple and quick, and more faithfully reproduce the form of carbon nanotubes. We closely monitor the geometrical and electrical properties of these elements through stochastic distributions of our choice. We can choose the length, diameter, orientation, chirality, tortuosity and impenetrable nature of the elements in order to properly reproduce real networks characteristics. We have considered statistical distribution functions that are rectangular, Gaussian, and Lorentzian, but all other distributions that can be expressed mathematically can also be envisioned. During the creation of a particular network, we generate the elements one by one. Each of their properties is sampled from a preselected distribution. Efficient algorithms used in various fields were adapted to our needs to manage the detection of contacts, clusters and percolation. In addition, we model more realistic contact between rigid nanotubes using an original method used to create the network that does not require a relaxation phase. Finally, we use Kirchhoff's laws to solve the equivalent electrical circuit conventionally. First, we evaluated the impact of a simplification widely used in other nanotube networks simulations studies. Values of the contact resistance at the junction between two nanotubes that are reported in the literature vary over a wide range, while almost all the simulations use a unique value for this parameter. Therefore, we assessed the effect of the presence of various stochastic distributions of contact resistances on the electrical properties of the networks. To do this, we used the experimental results of our collaborators in order to reproduce them by simulation. Our results show that, despite the existence of a wide range of contact resistance values, the nature of the statistical distribution has little impact on the conductivity obtained by simulation. Use of a single value for all connections of a network gives a total conductivity comparable to the experimental conductivity, and similar to that obtained using Gaussian, Lorentzian and uniform rectangular distributions. In fact, the dominant factor is not the type of distribution used to represent the resistance, but the central value of the distribution. Furthermore, we showed by studying bimodal distributions that the presence of lower resistance paths, even in small proportion, can rapidly increase the conductivity of the network. However, the type of stochastic distribution used to sample the spatial orientation of the nanotubes has a significant impact. We observed different behaviors for each of the three forms of distribution of orientation angles that we studied. In each case, a different distribution width maximize the conductivity of the networks. To optimize the conductivity, this distribution width, which is actually the deviation from the main direction, should in general be narrow. The formation of conductive paths is greatly enhanced in the presence of a majority of tubes closely aligned with the conduction direction and a small portion of tubes randomly aligned. The portion of misaligned tubes strongly contributes to the connectivity of nanotubes network by linking several clusters of aligned tubes. In order to increase the realism of our simulations, we also studied the influence of the interpenetrability of nanotubes on the electrical properties of networks. To do this, we describe the nanotubes with mutually impenetrable rigid cores that are surrounded by permeable shells. Thus, by varying the radius of the rigid cores, we have shown that a decrease in the interpenetrability of the nanotubes can increase the conductivity of the networks up to five orders of magnitude. We attribute this increase in conductivity to a greater connectivity of the nanotubes in the network. The more tubes are impenetrable, the more they push back against each other, and the better is the spreading of connected clusters in space. The second parameter on which we focused to improve the realism is the tortuosity of the nanotubes. We investigated the electrical properties of networks where the nanotubes are segmented into ten sections joined end to end. The angle between two consecutive segments is sampled from a uniform rectangular distribution and the variation of the bounds of this distribution allows us to vary the general tortuosity of the network. We observe that the more the tubes are tortuous, the higher the percolation threshold is, and the lower is the total conductivity. This can be nearly two orders of magnitude lower for networks with twisted tubes. We further note that the increase of the percolation threshold is attenuated when the wavy nanotubes have rigid cores. As part of our project, we have developed tools that, to the best of our knowledge, offer the best physical representation of nanotubes in a network of carbon nanotubes to date. This allowed us to study networks of complex geometries and measure the importance of the statistical distributions of parameters in optimizing the conductivity of networks. We have also established that the rigid tube-tube contacts and the nanotube tortuosity have strong impacts on the percolation threshold and conductivity. This work has demonstrated the importance of modeling for the understanding and the adequate description of complex processes, and the development needed to accurately reproduce the behavior of real systems. These tools can now be used to guide the creation of nanotube networks with targeted properties, and also to explore even more complex systems containing for example mixtures of nanotubes and quantum dots.

Reaction formulation for radiation and scattering from plates, corner reflectors and dielectric-coated cylinders

NASA Technical Reports Server (NTRS)

Wang, N. N.

1974-01-01

The reaction concept is employed to formulate an integral equation for radiation and scattering from plates, corner reflectors, and dielectric-coated conducting cylinders. The surface-current density on the conducting surface is expanded with subsectional bases. The dielectric layer is modeled with polarization currents radiating in free space. Maxwell's equation and the boundary conditions are employed to express the polarization-current distribution in terms of the surface-current density on the conducting surface. By enforcing reaction tests with an array of electric test sources, the moment method is employed to reduce the integral equation to a matrix equation. Inversion of the matrix equation yields the current distribution, and the scattered field is then obtained by integrating the current distribution. The theory, computer program and numerical results are presented for radiation and scattering from plates, corner reflectors, and dielectric-coated conducting cylinders.

Electrical properties of methane hydrate + sediment mixtures

USGS Publications Warehouse

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M; Roberts, Jeffery J.

2015-01-01

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

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

Robinson, Judith; Johnson, Timothy C.; Slater, Lee D.

There is an increasing need to characterize discrete fractures away from boreholes to better define fracture distributions and monitor solute transport. We performed a 3D evaluation of static and time-lapse cross-borehole electrical resistivity tomography (ERT) data sets from a limestone quarry in which flow and transport are controlled by a bedding-plane feature. Ten boreholes were discretized using an unstructured tetrahedral mesh, and 2D panel measurements were inverted for a 3D distribution of conductivity. We evaluated the benefits of 3D versus 2.5D inversion of ERT data in fractured rock while including the use of borehole regularization disconnects (BRDs) and borehole conductivitymore » constraints. High-conductivity halos (inversion artifacts) surrounding boreholes were removed in static images when BRDs and borehole conductivity constraints were implemented. Furthermore, applying these constraints focused transient changes in conductivity resulting from solute transport on the bedding plane, providing a more physically reasonable model for conductivity changes associated with solute transport at this fractured rock site. Assuming bedding-plane continuity between fractures identified in borehole televiewer data, we discretized a planar region between six boreholes and applied a fracture regularization disconnect (FRD). Although the FRD appropriately focused conductivity changes on the bedding plane, the conductivity distribution within the discretized fracture was nonunique and dependent on the starting homogeneous model conductivity. Synthetic studies performed to better explain field observations showed that inaccurate electrode locations in boreholes resulted in low-conductivity halos surrounding borehole locations. These synthetic studies also showed that the recovery of the true conductivity within an FRD depended on the conductivity contrast between the host rock and fractures. Our findings revealed that the potential exists to improve imaging of fractured rock through 3D inversion and accurate modeling of boreholes. However, deregularization of localized features can result in significant electrical conductivity artifacts, especially when representing features with a high degree of spatial uncertainty.« less

Monte Carlo simulations of electrical percolation in multicomponent thin films with nanofillers

NASA Astrophysics Data System (ADS)

Ni, Xiaojuan; Hui, Chao; Su, Ninghai; Jiang, Wei; Liu, Feng

2018-02-01

We developed a 2D disk-stick percolation model to investigate the electrical percolation behavior of an insulating thin film reinforced with 1D and 2D conductive nanofillers via Monte Carlo simulation. Numerical predictions of the percolation threshold in single component thin films showed good agreement with the previous published work, validating our model for investigating the characteristics of the percolation phenomena. Parametric studies of size effect, i.e., length of 1D nanofiller and diameter of 2D nanofiller, were carried out to predict the electrical percolation threshold for hybrid systems. The relationships between the nanofillers in two hybrid systems was established, which showed differences from previous linear assumption. The effective electrical conductance was evaluated through Kirchhoff’s current law by transforming it into a resistor network. The equivalent resistance was obtained from the distribution of nodal voltages by solving a system of linear equations with a Gaussian elimination method. We examined the effects of stick length, relative concentration, and contact patterns of 1D/2D inclusions on electrical performance. One novel aspect of our study is its ability to investigate the effective conductance of nanocomposites as a function of relative concentrations, which shows there is a synergistic effect when nanofillers with different dimensionalities combine properly. Our work provides an important theoretical basis for designing the conductive networks and predicting the percolation properties of multicomponent nanocomposites.

Analytical study of the performance of a geomembrane leak detection system.

PubMed

Lugli, Francesco; Mahler, Claudio Fernando

2016-05-01

The electrical detection of leaks in geomembranes is a method that allows identifying leakage of contaminants in lined facilities (e.g. sanitary landfills, pollutant ponds, etc.). The procedure in the field involves placing electrodes above and below the geomembrane, to generate an electrical current, which in turn engenders an electric potential distribution in the protective layer (generally a clayey soil). The electric potential will be greater in areas with higher current density, i.e. near leaks. In this study, we combined models from the literature to carry out a parametric analysis to identify the variables that most influence the amplitude of the electrical signals produced by leaks. The basic hypothesis is that the electrical conduction phenomena in a liner system could be depicted by a direct current circuit. After determining the value of the current at the leak, we calculated the electric potential distribution according to the model of Darilek and Laine. This enabled analysing the sensitivity of the parameters, which can be useful in the design of landfills and facilitate the location of leaks. This study showed that geomembranes with low electrical resistance (owing to low thickness, low resistivity, or extensive area) can hinder the leak detection process. In contrast, low thickness and high resistivity of the protection layer magnify the leak signal. © The Author(s) 2016.

Study of polarization properties of fiber-optics probes with use of a binary phase plate.

PubMed

Alferov, S V; Khonina, S N; Karpeev, S V

2014-04-01

We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

Generation of dynamo magnetic fields in the primordial solar nebula

NASA Technical Reports Server (NTRS)

Stepinski, Tomasz F.

1992-01-01

The present treatment of dynamo-generated magnetic fields in the primordial solar nebula proceeds in view of the ability of the combined action of Keplerian rotation and helical convention to generate, via alpha-omega dynamo, large-scale magnetic fields in those parts of the nebula with sufficiently high, gas-and magnetic field coupling electrical conductivity. Nebular gas electrical conductivity and the radial distribution of the local dynamo number are calculated for both a viscous-accretion disk model and the quiescent-minimum mass nebula. It is found that magnetic fields can be easily generated and maintained by alpha-omega dynamos occupying the inner and outer parts of the nebula.

Electrical pulse generator

DOEpatents

Norris, Neil J.

1979-01-01

A technique for generating high-voltage, wide dynamic range, shaped electrical pulses in the nanosecond range. Two transmission lines are coupled together by resistive elements distributed along the length of the lines. The conductance of each coupling resistive element as a function of its position along the line is selected to produce the desired pulse shape in the output line when an easily produced pulse, such as a step function pulse, is applied to the input line.

Solar thermal power systems point-focusing thermal and electric applications projects. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Marriott, A.

1980-01-01

The activities of the Point-Focusing Thermal and Electric Applications (PETEA) project for the fiscal year 1979 are summarized. The main thrust of the PFTEA Project, the small community solar thermal power experiment, was completed. Concept definition studies included a small central receiver approach, a point-focusing distributed receiver system with central power generation, and a point-focusing distributed receiver concept with distributed power generation. The first experiment in the Isolated Application Series was initiated. Planning for the third engineering experiment series, which addresses the industrial market sector, was also initiated. In addition to the experiment-related activities, several contracts to industry were let and studies were conducted to explore the market potential for point-focusing distributed receiver (PFDR) systems. System analysis studies were completed that looked at PFDR technology relative to other small power system technology candidates for the utility market sector.

Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

NASA Technical Reports Server (NTRS)

Schnepf, N. R.; Kuvshinov, A.; Sabaka, T.

2015-01-01

A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

Magnetoacoustic tomography with magnetic induction for high-resolution bioimepedance imaging through vector source reconstruction under the static field of MRI magnet.

PubMed

Mariappan, Leo; Hu, Gang; He, Bin

2014-02-01

Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ∼ 1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction.

Current density in a model of a human body with a conductive implant exposed to ELF electric and magnetic fields.

PubMed

Valic, Blaz; Gajsek, Peter; Miklavcic, Damijan

2009-10-01

A numerical model of a human body with an intramedullary nail in the femur was built to evaluate the effects of the implant on the current density distribution in extremely low frequency electric and magnetic fields. The intramedullary nail was chosen because it is one of the longest high conductive implants used in the human body. As such it is expected to alter the electric and magnetic fields significantly. The exposure was a simultaneous combination of inferior to superior electric field and posterior to anterior magnetic field both alternating at 50 Hz with the values corresponding to the ICNIRP reference levels: 5000 V m(-1) for electric field and 100 microT for magnetic flux density. The calculated current density distribution inside the model was compared to the ICNIRP basic restrictions for general public (2 mA m(-2)). The results show that the implant significantly increases the current density up to 9.5 mA m(-2) in the region where it is in contact with soft tissue in the model with the implant in comparison to 0.9 mA m(-2) in the model without the implant. As demonstrated the ICNIRP basic restrictions are exceeded in a limited volume of the tissue in spite of the compliance with the ICNIRP reference levels for general public, meaning that the existing safety limits do not necessarily protect implanted persons to the same extent as they protect people without implants.

Electrophoretic sample insertion. [device for uniformly distributing samples in flow path

NASA Technical Reports Server (NTRS)

Mccreight, L. R. (Inventor)

1974-01-01

Two conductive screens located in the flow path of an electrophoresis sample separation apparatus are charged electrically. The sample is introduced between the screens, and the charge is sufficient to disperse and hold the samples across the screens. When the charge is terminated, the samples are uniformly distributed in the flow path. Additionally, a first separation by charged properties has been accomplished.

Massively parallel electrical conductivity imaging of the subsurface: Applications to hydrocarbon exploration

NASA Astrophysics Data System (ADS)

Newman, Gregory A.; Commer, Michael

2009-07-01

Three-dimensional (3D) geophysical imaging is now receiving considerable attention for electrical conductivity mapping of potential offshore oil and gas reservoirs. The imaging technology employs controlled source electromagnetic (CSEM) and magnetotelluric (MT) fields and treats geological media exhibiting transverse anisotropy. Moreover when combined with established seismic methods, direct imaging of reservoir fluids is possible. Because of the size of the 3D conductivity imaging problem, strategies are required exploiting computational parallelism and optimal meshing. The algorithm thus developed has been shown to scale to tens of thousands of processors. In one imaging experiment, 32,768 tasks/processors on the IBM Watson Research Blue Gene/L supercomputer were successfully utilized. Over a 24 hour period we were able to image a large scale field data set that previously required over four months of processing time on distributed clusters based on Intel or AMD processors utilizing 1024 tasks on an InfiniBand fabric. Electrical conductivity imaging using massively parallel computational resources produces results that cannot be obtained otherwise and are consistent with timeframes required for practical exploration problems.

Mechanism of the free charge carrier generation in the dielectric breakdown

NASA Astrophysics Data System (ADS)

Rahim, N. A. A.; Ranom, R.; Zainuddin, H.

2017-12-01

Many studies have been conducted to investigate the effect of environmental, mechanical and electrical stresses on insulator. However, studies on physical process of discharge phenomenon, leading to the breakdown of the insulator surface are lacking and difficult to comprehend. Therefore, this paper analysed charge carrier generation mechanism that can cause free charge carrier generation, leading toward surface discharge development. Besides, this paper developed a model of surface discharge based on the charge generation mechanism on the outdoor insulator. Nernst’s Planck theory was used in order to model the behaviour of the charge carriers while Poisson’s equation was used to determine the distribution of electric field on insulator surface. In the modelling of surface discharge on the outdoor insulator, electric field dependent molecular ionization was used as the charge generation mechanism. A mathematical model of the surface discharge was solved using method of line technique (MOL). The result from the mathematical model showed that the behaviour of net space charge density was correlated with the electric field distribution.

Smart grid integration of small-scale trigeneration systems

NASA Astrophysics Data System (ADS)

Vacheva, Gergana; Kanchev, Hristiyan; Hinov, Nikolay

2017-12-01

This paper presents a study on the possibilities for implementation of local heating, air-conditioning and electricity generation (trigeneration) as distributed energy resource in the Smart Grid. By the means of microturbine-based generators and absorption chillers buildings are able to meet partially or entirely their electrical load curve or even supply power to the grid by following their heating and air-conditioning daily schedule. The principles of small-scale cooling, heating and power generation systems are presented at first, then the thermal calculations of an example building are performed: the heat losses due to thermal conductivity and the estimated daily heating and air-conditioning load curves. By considering daily power consumption curves and weather data for several winter and summer days, the heating/air-conditioning schedule is estimated and the available electrical energy from a microturbine-based cogeneration system is estimated. Simulation results confirm the potential of using cogeneration and trigeneration systems for local distributed electricity generation and grid support in the daily peaks of power consumption.

Preliminary Study of 2-D Time Domain Electromagnetic (TDEM) Modeling to Analyze Subsurface Resistivity Distribution and its Application to the Geothermal Systems

NASA Astrophysics Data System (ADS)

Aji Hapsoro, Cahyo; Purqon, Acep; Srigutomo, Wahyu

2017-07-01

2-D Time Domain Electromagnetic (TDEM) has been successfully conducted to illustrate the value of Electric field distribution under the Earth surface. Electric field compared by magnetic field is used to analyze resistivity and resistivity is one of physical properties which very important to determine the reservoir potential area of geothermal systems as one of renewable energy. In this modeling we used Time Domain Electromagnetic method because it can solve EM field interaction problem with complex geometry and to analyze transient problems. TDEM methods used to model the value of electric and magnetic fields as a function of the time combined with the function of distance and depth. The result of this modeling is Electric field intensity value which is capable to describe the structure of the Earth’s subsurface. The result of this modeling can be applied to describe the Earths subsurface resistivity values to determine the reservoir potential of geothermal systems.

3-D time-domain induced polarization tomography: a new approach based on a source current density formulation

NASA Astrophysics Data System (ADS)

Soueid Ahmed, A.; Revil, A.

2018-04-01

Induced polarization (IP) of porous rocks can be associated with a secondary source current density, which is proportional to both the intrinsic chargeability and the primary (applied) current density. This gives the possibility of reformulating the time domain induced polarization (TDIP) problem as a time-dependent self-potential-type problem. This new approach implies a change of strategy regarding data acquisition and inversion, allowing major time savings for both. For inverting TDIP data, we first retrieve the electrical resistivity distribution. Then, we use this electrical resistivity distribution to reconstruct the primary current density during the injection/retrieval of the (primary) current between the current electrodes A and B. The time-lapse secondary source current density distribution is determined given the primary source current density and a distribution of chargeability (forward modelling step). The inverse problem is linear between the secondary voltages (measured at all the electrodes) and the computed secondary source current density. A kernel matrix relating the secondary observed voltages data to the source current density model is computed once (using the electrical conductivity distribution), and then used throughout the inversion process. This recovered source current density model is in turn used to estimate the time-dependent chargeability (normalized voltages) in each cell of the domain of interest. Assuming a Cole-Cole model for simplicity, we can reconstruct the 3-D distributions of the relaxation time τ and the Cole-Cole exponent c by fitting the intrinsic chargeability decay curve to a Cole-Cole relaxation model for each cell. Two simple cases are studied in details to explain this new approach. In the first case, we estimate the Cole-Cole parameters as well as the source current density field from a synthetic TDIP data set. Our approach is successfully able to reveal the presence of the anomaly and to invert its Cole-Cole parameters. In the second case, we perform a laboratory sandbox experiment in which we mix a volume of burning coal and sand. The algorithm is able to localize the burning coal both in terms of electrical conductivity and chargeability.

Synthesis of Stretchable Gold Films with Nanocracks: Stretched up to 120% Strain while Maintaining Conductivity

NASA Astrophysics Data System (ADS)

Yu, Mei; Wang, Chong; Yang, Cancan; Yu, Zhe

2017-11-01

With the great deformability of stretch, compression, bend and twisting, while preserving electrical property, metal films on elastomeric substrates have many applications for serving as bioelectrical interfaces. However, at present, most polymer-supported thin metal films reported rupture at small elongations (<10%). In this work, highly stretchable thin gold films were fabricated on PDMS substrates by a novel micro-processing technology. The as deposited films can be stretched by a maximum 120% strain while maintaining their electrical conductivity. Electrical characteristics of the gold films under single-cycle and multi-cycle stretch deformations are investigated in this work. SEM images imply that the gold films are under the structure of nanocracks. The mechanisms of the stretchability of the gold films can be explained by the nanocraks, which uniformly distribute with random orientation in the films.

Volt-VAR Optimization on American Electric Power Feeders in Northeast Columbus

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

Schneider, Kevin P.; Weaver, T. F.

2012-05-10

In 2007 American Electric Power launched the gridSMART® initiative with the goals of increasing efficiency of the electricity delivery system and improving service to the end-use customers. As part of the initiative, a coordinated Volt-VAR system was deployed on eleven distribution feeders at five substations in the Northeast Columbus Ohio Area. The goal of the coordinated Volt-VAR system was to decrease the amount of energy necessary to provide end-use customers with the same quality of service. The evaluation of the Volt-VAR system performance was conducted in two stages. The first stage was composed of simulation, analysis, and estimation, while themore » second stage was composed of analyzing collected field data. This panel paper will examine the analysis conducted in both stages and present the estimated improvements in system efficiency.« less

Radial density distribution of a warm dense plasma formed by underwater electrical explosion of a copper wire

NASA Astrophysics Data System (ADS)

Nitishinskiy, M.; Yanuka, D.; Virozub, A.; Krasik, Ya. E.

2017-12-01

Time- and space-resolved evolution of the density (down to 0.07 of solid state density) of a copper wire during its microsecond timescale electrical explosion in water was obtained by X-ray backlighting. In the present research, a flash X-ray source of 20 ns pulse-width and >60 keV photon energy was used. The conductivity of copper was evaluated for a temperature of 10 kK and found to be in good agreement with the data obtained in earlier experiments [DeSilva and Katsouros, Phys. Rev. E 57, 5945 (1998) and Sheftman and Krasik, Phys. Plasmas 18, 092704 (2011)] where only electrical and optical diagnostics were applied. Magneto-hydrodynamic simulation shows a good agreement between the simulated and experimental waveforms of the current and voltage and measured the radial expansion of the exploding wire. Also, the radial density distribution obtained by an inverse Abel transform analysis agrees with the results of these simulations. Thus, the validity of the equations of state for copper and the conductivity model used in the simulations was confirmed for the parameters of the exploding wire realized in the present research.

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

Wang, Lingyan, E-mail: l.y.wang@mail.xjtu.edu.cn, E-mail: wren@mail.xjtu.edu.cn; Ren, Wei, E-mail: l.y.wang@mail.xjtu.edu.cn, E-mail: wren@mail.xjtu.edu.cn; Shi, Peng

Lead-free ferroelectric un-doped and doped K{sub 0.5}Na{sub 0.5}NbO{sub 3} (KNN) films with different amounts of manganese (Mn) were prepared by a chemical solution deposition method. The thicknesses of all films are about 1.6 μm. Their phase, microstructure, leakage current behavior, and electrical properties were investigated. With increasing the amounts of Mn, the crystallinity became worse. Fortunately, the electrical properties were improved due to the decreased leakage current density after Mn-doping. The study on leakage behaviors shows that the dominant conduction mechanism at low electric field in the un-doped KNN film is ohmic mode and that at high electric field is space-charge-limitedmore » and Pool-Frenkel emission. After Mn doping, the dominant conduction mechanism at high electric field of KNN films changed single space-charge-limited. However, the introduction of higher amount of Mn into the KNN film would lead to a changed conduction mechanism from space-charge-limited to ohmic mode. Consequently, there exists an optimal amount of Mn doping of 2.0 mol. %. The 2.0 mol. % Mn doped KNN film shows the lowest leakage current density and the best electrical properties. With the secondary ion mass spectroscopies and x-ray photoelectron spectroscopy analyses, the homogeneous distribution in the KNN films and entrance of Mn element in the lattice of KNN perovskite structure were also confirmed.« less

Electron Beam Irradiated Intercalated CNT Yarns For Aerospace Applications

NASA Technical Reports Server (NTRS)

Waters, Deborah L.; Gaier, James R.; Williams, Tiffany S.; Lopez Calero, Johnny E.; Ramirez, Christopher; Meador, Michael A.

2015-01-01

Multi-walled CNT yarns have been experimentally and commercially created to yield lightweight, high conductivity fibers with good tensile properties for application as electrical wiring and multifunctional tendons. Multifunctional tendons are needed as the cable structures in tensegrity robots for use in planetary exploration. These lightweight robust tendons can provide mechanical strength for movement of the robot in addition to power distribution and data transmission. In aerospace vehicles, such as Orion, electrical wiring and harnessing mass can approach half of the avionics mass. Use of CNT yarns as electrical power and data cables could reduce mass of the wiring by thirty to seventy percent. These fibers have been intercalated with mixed halogens to increase their specific electrical conductivity to that near copper. This conductivity, combined with the superior strength and fatigue resistance makes it an attractive alternative to copper for wiring and multifunctional tendon applications. Electron beam irradiation has been shown to increase mechanical strength in pristine CNT fibers through increased cross-linking. Both pristine and intercalated CNT yarns have been irradiated using a 5-megavolt electron beam for various durations and the conductivities and tensile properties will be discussed. Structural information obtained using a field emission scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy will correlate microstructural details with bulk properties.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

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

PubMed Central

Hu, Gang; He, Bin

2011-01-01

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

Electrostatic force microscopy on oriented graphite surfaces: coexistence of insulating and conducting behaviors.

PubMed

Lu, Yonghua; Muñoz, M; Steplecaru, C S; Hao, Cheng; Bai, Ming; Garcia, N; Schindler, K; Esquinazi, P

2006-08-18

We present measurements of the electric potential fluctuations on the surface of highly oriented pyrolytic graphite using electrostatic force and atomic force microscopy. Micrometric domainlike potential distributions are observed even when the sample is grounded. Such potential distributions are unexpected given the good metallic conductivity of graphite because the surface should be an equipotential. Our results indicate the coexistence of regions with "metalliclike" and "insulatinglike" behaviors showing large potential fluctuations of the order of 0.25 V. In lower quality graphite, this effect is not observed. Experiments are performed in Ar and air atmospheres.

Matrix of moments of the Legendre polynomials and its application to problems of electrostatics

NASA Astrophysics Data System (ADS)

Savchenko, A. O.

2017-01-01

In this work, properties of the matrix of moments of the Legendre polynomials are presented and proven. In particular, the explicit form of the elements of the matrix inverse to the matrix of moments is found and theorems of the linear combination and orthogonality are proven. On the basis of these properties, the total charge and the dipole moment of a conducting ball in a nonuniform electric field, the charge distribution over the surface of the conducting ball, its multipole moments, and the force acting on a conducting ball situated on the axis of a nonuniform axisymmetric electric field are determined. All assertions are formulated in theorems, the proofs of which are based on the properties of the matrix of moments of the Legendre polynomials.

Nonlinear Hall effect and multichannel conduction in LaTiO3/SrTiO3 superlattices

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

Kim, Jun Sung; Seo, Sung Seok A; Chisholm, Matthew F

2010-01-01

We report magnetotransport properties of heterointerfaces between the Mott insulator LaTiO{sub 3} and the band insulator SrTiO{sub 3} in a delta-doping geometry. At low temperatures, we have found a strong nonlinearity in the magnetic field dependence of the Hall resistivity, which can be effectively controlled by varying the temperature and the electric field. We attribute this effect to multichannel conduction of interfacial charges generated by an electronic reconstruction. In particular, the formation of a highly mobile conduction channel revealed by our data is explained by the greatly increased dielectric permeability of SrTiO{sub 3} at low temperatures and its electric fieldmore » dependence reflects the spatial distribution of the quasi-two-dimensional electron gas.« less

Crystal Structure, Electric Polarization and Heat Capacity Measurements on Small R-Ion Multiferroic Hexagonal RMnO3

NASA Astrophysics Data System (ADS)

Yu, Tian; Gao, Peng; Wu, Tao; Tyson, Trevor; Lalancette, Roger

2013-03-01

Crystal structure, electric polarization and heat capacity measurements on the hexagonal multiferroic RMnO3 reveal that small R ion (Lu and lower cation size) systems are ferroelectric and possess the same space-group as YMnO3. Combined local and long range structural measurements were conducted by XAFS, PDF and single crystal and powder XRD methods. The influence of the Mn-O and R-O distribution on the electric polarization is discussed. Point charge estimates of the electrical polarization are given for comparison with the YMnO3 system. This work is supported by DOE Grant DE-FG02-07ER46402.

Peridynamic thermal diffusion

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

Oterkus, Selda; Madenci, Erdogan, E-mail: madenci@email.arizona.edu; Agwai, Abigail

This study presents the derivation of ordinary state-based peridynamic heat conduction equation based on the Lagrangian formalism. The peridynamic heat conduction parameters are related to those of the classical theory. An explicit time stepping scheme is adopted for numerical solution of various benchmark problems with known solutions. It paves the way for applying the peridynamic theory to other physical fields such as neutronic diffusion and electrical potential distribution.

Magnetic Field of Conductive Objects as Superposition of Elementary Eddy Currents and Eddy Current Tomography

NASA Astrophysics Data System (ADS)

Sukhanov, D. Ya.; Zav'yalova, K. V.

2018-03-01

The paper represents induced currents in an electrically conductive object as a totality of elementary eddy currents. The proposed scanning method includes measurements of only one component of the secondary magnetic field. Reconstruction of the current distribution is performed by deconvolution with regularization. Numerical modeling supported by the field experiments show that this approach is of direct practical relevance.

Polyaniline particles: Material properties when synthesized with aqueous nonionic micelles and environmental stability

NASA Astrophysics Data System (ADS)

Hobaica, Stephen Charles

Polyaniline is a member of the class of electrically conducting polymers, which have possible commercial applications as anticorrosive or static charge removal coatings. Aqueous-based polyaniline coatings are preferred over organic solvent or strong acid based coatings because the water used in these coatings does not pollute the environment. The overall goal of this dissertation was to further the development of useful water-based polyaniline coatings by studying new methods of synthesizing polyaniline particles for water-based coatings, to investigate the material properties of these particles such as molecular weight, electrical conductivity, particle size distribution, and stability of polyaniline in air and water. One method of polymerizing polyaniline for aqueous-based coatings uses micelles, which are composed of a cluster of amphiphile surfactants. Micelles can change the local environment by aligning and absorbing the monomer, and may yield polymers with improved material properties and reaction rates. Nonionic micelles have not been extensively investigated. Therefore the first specific goal of this work was to use an aqueous nonionic micelle solution of nonylphenoxypoly(ethyleneoxy) ethanol surfactant (NP-30 surfactant) to comprehensively investigate a one step chemical polymerization of polyaniline conducted at -3°C, in 1.25 M HCl, with ammonium peroxydisulfate oxidizer. The results show that increasing surfactant concentrations caused a decrease in molecular weight, electrical conductivity and sharper particle size distribution of the polymer. The second specific objective of this dissertation was to determine the effect of water and air on polyaniline. The results showed no degradation of molecular weight, a decrease in chloride and hydrogen composition, and decrease in electrical conductivity for polyaniline immersed in water for extended periods. A chloride ion diffusion coefficient of 2.5 to 74 x 10-9 cm2/hour was measured. The aging of polyaniline powders in a desiccator for 5 years showed no effect on the molecular structure as indicated by the FTIR spectrum. The third specific goal of the research was to measure the real and imaginary refractive index of polyaniline saturated with 1.25 M HCl, which was found to be 1.345 to 1.355 and 0.025 to 0.027, respectively. This information is crucial to measuring the distribution of polyaniline colloids by light scattering.

Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements

NASA Astrophysics Data System (ADS)

Dragonetti, Giovanna; Comegna, Alessandro; Ajeel, Ali; Piero Deidda, Gian; Lamaddalena, Nicola; Rodriguez, Giuseppe; Vignoli, Giulio; Coppola, Antonio

2018-02-01

This paper deals with the issue of monitoring the spatial distribution of bulk electrical conductivity, σb, in the soil root zone by using electromagnetic induction (EMI) sensors under different water and salinity conditions. To deduce the actual distribution of depth-specific σb from EMI apparent electrical conductivity (ECa) measurements, we inverted the data by using a regularized 1-D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss-Newton method with truncated generalized singular value decomposition (TGSVD). The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI results in the presence of sharp boundaries (otherwise smeared out after the application of more standard Occam-like regularization strategies searching for smooth solutions). Time-domain reflectometry (TDR) data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean, and irrigated with water at two different salinity levels and using two different irrigation volumes. Clearly, this induces different salinity and water contents within the soil profiles. For each transect, 26 regularly spaced monitoring soundings (1 m apart) were selected for the collection of (i) Geonics EM-38 and (ii) Tektronix reflectometer data. Despite the original discrepancies in the EMI and TDR data, we found a significant correlation of the means and standard deviations of the two data series; in particular, after a low-pass spatial filtering of the TDR data. Based on these findings, this paper introduces a novel methodology to calibrate EMI-based electrical conductivities via TDR direct measurements. This calibration strategy consists of a linear mapping of the original inversion results into a new conductivity spatial distribution with the coefficients of the transformation uniquely based on the statistics of the two original measurement datasets (EMI and TDR conductivities).

Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

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

Afaah, A. N., E-mail: afaahabdullah@yahoo.com; Asib, N. A. M., E-mail: amierahasib@yahoo.com; Aadila, A., E-mail: aadilaazizali@gmail.com

2016-07-06

p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO{sub 3} as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films weremore » characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.« less

Study of Damage and Recovery of Electron Irradiated Polyimide using EPR and NMR Spectroscopy

NASA Astrophysics Data System (ADS)

Humagain, Sunita; Jhonson, Jessica; Stallworth, Phillip; Engelhart, Daniel; Plis, Elena; Ferguson, Dale; Cooper, Russell; Hoffmann, Ryan; Greenbaum, Steve

The main objective of this research is to probe radical concentrations in electron irradiated polyimide (PI, Kapton®) and to examine the impact on the electrical properties using EPR and NMR spectroscopy. PI is an electrical insulator used in space missions as a thermal management blanketing material, it is therefore critical for spacecraft designers to understand the nature of electron transport (electrical conductivity) within the bulk of the material. The recovery mechanism (radical evolution) of PI in vacuum, argon and air after having been subjected to 90 KeV electron irradiation, was studied. The formation and subsequent exponential decay of the radical concentrations was recorded using EPR. This signal decay agrees well with the recovery mechanism being probed by electrical conductivity measurements and implies a strong relation between the two. To investigate the distribution of radicals in the polymer, 1H NMR relaxation time (T1) were measured at 300MHz. Additional NMR experiments, in particular 13C, were performed to search for direct evidence of structural defects.

Evolution of volume fractions and droplet sizes by analysis of electrical conductance curves during destabilization of oil-in-water emulsions.

PubMed

Kostoglou, M; Varka, E-M; Kalogianni, E P; Karapantsios, T D

2010-09-01

Destabilization of hexane-in-water emulsions is studied by a continuous, non-intrusive, multi-probe, electrical conductance technique. Emulsions made of different oil fractions and surfactant (C(10)E(5)) concentrations are prepared in a stirred vessel using a Rushton turbine to break and agitate droplets. During the separation of phases, electrical signals from pairs of ring electrodes mounted at different heights onto the vessel wall, are recorded. The evolution of the local water volume fractions at the locations of the electrodes is estimated from these signals. It is found that in the absence of coalescence, the water fraction evolution curve from the bottom pair of electrodes is compatible with a bidisperse oil droplet size distribution. The sizes and volume fractions of the two droplet modes are estimated using theoretical arguments. The electrically determined droplet sizes are compared to data from microscopy image analysis. Results are discussed in detail. Copyright 2010 Elsevier Inc. All rights reserved.

A Molecular Dynamics Study on Selective Cation Depletion from an Ionic Liquid Droplet under an Electric Field

NASA Astrophysics Data System (ADS)

Yang, Yudong; Ahn, Myungmo; Im, Dojin; Oh, Jungmin; Kang, Inseok

2017-11-01

General electrohydrodynamic behavior of ionic liquid droplets under an electric field is investigated using MD simulations. Especially, a unique behavior of ion depletion of an ionic liquid droplet under a uniform electric field is studied. Shape deformation due to electric stress and ion distributions inside the droplet are calculated to understand the ionic motion of imidazolium-based ionic liquid droplets with 200 ion pairs of 2 kinds of ionic liquids: EMIM-NTf2 and EMIM-ES. The intermolecular force between cations and anions can be significantly different due to the nature of the structure and charge distribution of the ions. Together with an analytical interpretation of the conducting droplet in an electric field, the MD simulation successfully explains the mechanism of selective ion depletion of an ionic liquid droplet in an electric field. The selective ion depletion phenomenon has been adopted to explain the experimentally observed retreating motion of a droplet in a uniform electric field. The effect of anions on the cation depletion phenomenon can be accounted for from a direct approach to the intermolecular interaction. This research was supproted by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (No. 2017R1D1A1B05035211).

Dynamic generation of supercritical water fluid in a strong electrical discharge in a liquid

NASA Astrophysics Data System (ADS)

Antonov, V.; Kalinin, N.; Kovalenko, A.

2016-11-01

A new impetus for the development of electro physics is associated with using different types of electrical discharges in biology and medicine. These applications are based on their energetic and non-toxic factors affecting the medium on a cellular level. For the study of such processes, a mathematical model of a high-current low-temperature Z-discharge in a liquid, forming by the electrical explosion of a thin-walled metal shell, connected to a pulsed high-voltage generator, has been developed. High efficiency energy conversion, introduced into the plasma discharge to the energy of fluid motion, provides various bio chemical applications of such physical processes. The investigation is conducted through numerical solution of one-dimensional single-temperature non-stationary equations of radiation magneto hydrodynamics, one way describing the evolution of hydrodynamic, thermal and electrical characteristics of the medium throughout the area under consideration. The electrical approximation based on the assumption that the electric field in the discharge has a uniform distribution. The results are presented as a function of the electric current and the plasma channel length of time, as well as the temperature and pressure distributions at different time points along the radius of the cylindrical region in which the explosion occurs.

The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

NASA Astrophysics Data System (ADS)

Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

Electrically conductive ZnO/GaN distributed Bragg reflectors grown by hybrid plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Hjort, Filip; Hashemi, Ehsan; Adolph, David; Ive, Tommy; Haglund, Àsa

2017-02-01

III-nitride-based vertical-cavity surface-emitting lasers have so far used intracavity contacting schemes since electrically conductive distributed Bragg reflectors (DBRs) have been difficult to achieve. A promising material combination for conductive DBRs is ZnO/GaN due to the small conduction band offset and ease of n-type doping. In addition, this combination offers a small lattice mismatch and high refractive index contrast, which could yield a mirror with a broad stopband and a high peak reflectivity using less than 20 DBR-pairs. A crack-free ZnO/GaN DBR was grown by hybrid plasma-assisted molecular beam epitaxy. The ZnO layers were approximately 20 nm thick and had an electron concentration of 1×1019 cm-3, while the GaN layers were 80-110 nm thick with an electron concentration of 1.8×1018 cm-3. In order to measure the resistance, mesa structures were formed by dry etching through the top 3 DBR-pairs and depositing non-annealed Al contacts on the GaN-layers at the top and next to the mesas. The measured specific series resistance was dominated by the lateral and contact contributions and gave an upper limit of 10-3Ωcm2 for the vertical resistance. Simulations show that the ZnO electron concentration and the cancellation of piezoelectric and spontaneous polarization in strained ZnO have a large impact on the vertical resistance and that it could be orders of magnitudes lower than what was measured. This is the first report on electrically conductive ZnO/GaN DBRs and the upper limit of the resistance reported here is close to the lowest values reported for III-nitride-based DBRs.

Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

PubMed Central

Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

2016-01-01

The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

Carbon Nanotube Based Light Sensor

NASA Technical Reports Server (NTRS)

Wincheski, russell A. (Inventor); Smits, Jan M. (Inventor); Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Ingram, JoAnne L. (Inventor)

2006-01-01

A light sensor substrate comprises a base made from a semi-conductive material and topped with a layer of an electrically non-conductive material. A first electrode and a plurality of carbon nanotube (CNT)-based conductors are positioned on the layer of electrically non-conductive material with the CNT-based conductors being distributed in a spaced apart fashion about a periphery of the first electrode. Each CNT-based conductor is coupled on one end thereof to the first electrode and extends away from the first electrode to terminate at a second free end. A second or gate electrode is positioned on the non-conductive material layer and is spaced apart from the second free end of each CNT-based conductor. Coupled to the first and second electrode is a device for detecting electron transfer along the CNT-based conductors resulting from light impinging on the CNT-based conductors.

A single molecule rectifier with strong push-pull coupling

NASA Astrophysics Data System (ADS)

Saraiva-Souza, Aldilene; Macedo de Souza, Fabricio; Aleixo, Vicente F. P.; Girão, Eduardo Costa; Filho, Josué Mendes; Meunier, Vincent; Sumpter, Bobby G.; Souza Filho, Antônio Gomes; Del Nero, Jordan

2008-11-01

We theoretically investigate the electronic charge transport in a molecular system composed of a donor group (dinitrobenzene) coupled to an acceptor group (dihydrophenazine) via a polyenic chain (unsaturated carbon bridge). Ab initio calculations based on the Hartree-Fock approximations are performed to investigate the distribution of electron states over the molecule in the presence of an external electric field. For small bridge lengths (n =0-3) we find a homogeneous distribution of the frontier molecular orbitals, while for n >3 a strong localization of the lowest unoccupied molecular orbital is found. The localized orbitals in between the donor and acceptor groups act as conduction channels when an external electric field is applied. We also calculate the rectification behavior of this system by evaluating the charge accumulated in the donor and acceptor groups as a function of the external electric field. Finally, we propose a phenomenological model based on nonequilibrium Green's function to rationalize the ab initio findings.

Analysis of Electric Vehicle Charging Impact on the Electric Power Grid

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

Jiang, Zeming; Tian, Hao; Beshir, Mohammed J.

2016-09-24

In order to evaluate the impact of electric vehicles (EVs) on the distribution grid and assess their potential benefits to the future smart grid, it is crucial to study the EV charging patterns and the usage charging station. Though EVs are not yet widely adopted nationwide, a valuable methodology to conduct such studies is the statistical analysis of real-world charging data. This paper presents actual EV charging behavior of 64 EVs (5 brands, 8 models) from EV users and charging stations at Los Angeles Department of Water and Power for more than one year. Twenty-four-hour EV charging load curves havemore » been generated and studied for various load periods: daily, monthly, seasonally and yearly. Finally, the effect and impact of EV load on the California distribution network are evaluated at different EV penetration rates.« less

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

DOE PAGES

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; ...

2015-07-30

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

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

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Descriptive Study of Occupational Accidents and their Causes among Electricity Distribution Company Workers at an Eight-year Period in Iran

PubMed Central

Rahmani, Abdolrasoul; Khadem, Monireh; Madreseh, Elham; Aghaei, Habib-Allah; Raei, Mehdi; Karchani, Mohsen

2013-01-01

Background Occupational accidents are unplanned events that cause damage. The socio-economic impacts and human costs of accidents are tremendous around the world. Many fatalities happen every year in workplaces such as electricity distribution companies. Some electrical injuries are electrocution, electric shock, and burns. This study was conducted in an electricity distribution company (with rotational 12-hour shift work) in Iran during an 8-year period to survey descriptive factors of injuries. Methods Variables collected included accident time, age of injured worker, employment type, work experience, injury cause, educational background, and other information about accidents. Results Results indicated that most of the accidents occurred in summer, and 51.3% were during shift work. Worker negligence (malpractice) was the cause of 75% of deaths. Type of employment had a significant relationship with type of injuries (p < 0.05). Most injuries were electrical burns. Conclusion High rate of accidents in summer may be due to the warm weather or insufficient professional skills in seasonal workers. Shift workers are at risk of sleep complaints leading to a high rate of work injuries. Acquiring knowledge about safety was related to job experiences. Temporary workers have no chance to work all year like permanent workers, therefore impressive experiences may be less in them. Because the lack of protective equipment and negligence are main causes of accidents, periodical inspections in workshops are necessary. PMID:24106647

Advancing Underwater Acoustic Communication for Autonomous Distributed Networks via Sparse Channel Sensing, Coding, and Navigation Support

DTIC Science & Technology

2013-09-30

underwater acoustic communication technologies for autonomous distributed underwater networks, through innovative signal processing, coding, and navigation...in real enviroments , an offshore testbed has been developed to conduct field experimetns. The testbed consists of four nodes and has been deployed...Leadership by the Connecticut Technology Council. Dr. Zhaohui Wang joined the faculty of the Department of Electrical and Computer Engineering at

Influence of the microstructure on the physicomechanical properties of the aluminum alloy Al-Mg-Si nanostructured under severe plastic deformation

NASA Astrophysics Data System (ADS)

Mavlyutov, A. M.; Kasatkin, I. A.; Murashkin, M. Yu.; Valiev, R. Z.; Orlova, T. S.

2015-10-01

The microstructural features, strength, and electrical conductivity of the electrotechnical aluminum alloy 6201 of the Al-Mg-Si system was investigated. The alloy was nanostructured using severe plastic deformation by high pressure torsion at different temperatures and in different deformation regimes. As a result, the samples had an ultrafine-grain structure with nanoinclusions of secondary phases, which provided an excellent combination of high strength (conventional yield strength σ0.2 = 325-410 MPa) and electrical conductivity (55-52% IACS). The contributions from different mechanisms to the strengthening were analyzed. It was experimentally found that the introduction of an additional dislocation density (an increase from 2 × 1013 to 5 × 1013 m-2) with the same basic parameters of the ultrafine-grain structure (grain size, size and distribution of particles of secondary strengthening phases) leads to an increase in the strength of the alloy by ~15%, while the electrical conductivity of the material changes insignificantly. The contribution from grain boundaries to the electrical resistivity of the alloy with an ultrafine-grain structure upon the change in their state, most likely, due to a change in the degree of nonequilibrium was estimated.

Network Capacity Assessment of CHP-based Distributed Generation on Urban Energy Distribution Networks

NASA Astrophysics Data System (ADS)

Zhang, Xianjun

The combined heat and power (CHP)-based distributed generation (DG) or dis-tributed energy resources (DERs) are mature options available in the present energy market, considered to be an effective solution to promote energy efficiency. In the urban environment, the electricity, water and natural gas distribution networks are becoming increasingly interconnected with the growing penetration of the CHP-based DG. Subsequently, this emerging interdependence leads to new topics meriting serious consideration: how much of the CHP-based DG can be accommodated and where to locate these DERs, and given preexisting constraints, how to quantify the mutual impacts on operation performances between these urban energy distribution networks and the CHP-based DG. The early research work was conducted to investigate the feasibility and design methods for one residential microgrid system based on existing electricity, water and gas infrastructures of a residential community, mainly focusing on the economic planning. However, this proposed design method cannot determine the optimal DG sizing and siting for a larger test bed with the given information of energy infrastructures. In this context, a more systematic as well as generalized approach should be developed to solve these problems. In the later study, the model architecture that integrates urban electricity, water and gas distribution networks, and the CHP-based DG system was developed. The proposed approach addressed the challenge of identifying the optimal sizing and siting of the CHP-based DG on these urban energy networks and the mutual impacts on operation performances were also quantified. For this study, the overall objective is to maximize the electrical output and recovered thermal output of the CHP-based DG units. The electricity, gas, and water system models were developed individually and coupled by the developed CHP-based DG system model. The resultant integrated system model is used to constrain the DG's electrical output and recovered thermal output, which are affected by multiple factors and thus analyzed in different case studies. The results indicate that the designed typical gas system is capable of supplying sufficient natural gas for the DG normal operation, while the present water system cannot support the complete recovery of the exhaust heat from the DG units.

Sensor devices comprising field-structured composites

DOEpatents

Martin, James E.; Hughes, Robert C.; Anderson, Robert A.

2001-02-27

A new class of sensor devices comprising field-structured conducting composites comprising a textured distribution of conducting magnetic particles is disclosed. The conducting properties of such field-structured materials can be precisely controlled during fabrication so as to exhibit a large change in electrical conductivity when subject to any environmental influence which changes the relative volume fraction. Influences which can be so detected include stress, strain, shear, temperature change, humidity, magnetic field, electromagnetic radiation, and the presence or absence of certain chemicals. This behavior can be made the basis for a wide variety of sensor devices.

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.

Architecture, Voltage, and Components for a Turboelectric Distributed Propulsion Electric Grid

NASA Technical Reports Server (NTRS)

Armstrong, Michael J.; Blackwelder, Mark; Bollman, Andrew; Ross, Christine; Campbell, Angela; Jones, Catherine; Norman, Patrick

2015-01-01

The development of a wholly superconducting turboelectric distributed propulsion system presents unique opportunities for the aerospace industry. However, this transition from normally conducting systems to superconducting systems significantly increases the equipment complexity necessary to manage the electrical power systems. Due to the low technology readiness level (TRL) nature of all components and systems, current Turboelectric Distributed Propulsion (TeDP) technology developments are driven by an ambiguous set of system-level electrical integration standards for an airborne microgrid system (Figure 1). While multiple decades' worth of advancements are still required for concept realization, current system-level studies are necessary to focus the technology development, target specific technological shortcomings, and enable accurate prediction of concept feasibility and viability. An understanding of the performance sensitivity to operating voltages and an early definition of advantageous voltage regulation standards for unconventional airborne microgrids will allow for more accurate targeting of technology development. Propulsive power-rated microgrid systems necessitate the introduction of new aircraft distribution system voltage standards. All protection, distribution, control, power conversion, generation, and cryocooling equipment are affected by voltage regulation standards. Information on the desired operating voltage and voltage regulation is required to determine nominal and maximum currents for sizing distribution and fault isolation equipment, developing machine topologies and machine controls, and the physical attributes of all component shielding and insulation. Voltage impacts many components and system performance.

Two-Dimensional Lorentz Force Image Reconstruction for Magnetoacoustic Tomography with Magnetic Induction

NASA Astrophysics Data System (ADS)

Li, Yi-Ling; Liu, Zhen-Bo; Ma, Qing-Yu; Guo, Xia-Sheng; Zhang, Dong

2010-08-01

Magnetoacoustic tomography with magnetic induction has shown potential applications in imaging the electrical impedance for biological tissues. We present a novel methodology for the inverse problem solution of the 2-D Lorentz force distribution reconstruction based on the acoustic straight line propagation theory. The magnetic induction and acoustic generation as well as acoustic detection are theoretically provided as explicit formulae and also validated by the numerical simulations for a multilayered cylindrical phantom model. The reconstructed 2-D Lorentz force distribution reveals not only the conductivity configuration in terms of shape and size but also the amplitude value of the Lorentz force in the examined layer. This study provides a basis for further study of conductivity distribution reconstruction of MAT-MI in medical imaging.

Method for uniformly distributing carbon flakes in a positive electrode, the electrode made thereby and compositions. [Patent application

DOEpatents

Mrazek, F.C.; Smaga, J.A.; Battles, J.E.

1981-01-19

A positive electrode for a secondary electrochemical cell is described wherein an electrically conductive current collector is in electrical contact with a particulate mixture of gray cast iron and an alkali metal sulfide and an electrolyte including alkali metal halides or alkaline earth metal halides. Also present may be a transition metal sulfide and graphite flakes from the conversion of gray cast iron to iron sulfide. Also disclosed is a method of distributing carbon flakes in a cell wherein there is formed an electrochemical cell of a positive electrode structure of the type described and a suitable electrolyte and a second electrode containing a material capable of alloying with alkali metal ions. The cell is connected to a source of electrical potential to electrochemically convert gray cast iron to an iron sulfide and uniformly to distribute carbon flakes formerly in the gray cast iron throughout the positive electrode while forming an alkali metal alloy in the negative electrode. Also disclosed are compositions useful in preparing positive electrodes.

Origin of conductivity anomalies in the asthenosphere

NASA Astrophysics Data System (ADS)

Yoshino, T.; Zhang, B.

2013-12-01

Electrical conductivity anomalies with anisotropy parallel to the plate motion have been observed beneath the oceanic lithosphere by electromagnetic studies (e.g., Evans et al., 2005; Baba et al., 2010; Naif et al., 2013). Electrical conductivity of the oceanic asthenosphere at ~100 km depth is very high, about 10-2 to 10-1 S/m. This zone is also known in seismology as the low velocity zone. Since Karato (1990) first suggested that electrical conductivity is sensitive to water content in NAMs, softening of asthenosphere has been regarded as a good indicator for constraining the distribution of water. There are two difficulties to explain the observed conductivity features in the asthenosphere. Recent publications on electrical conductivity of hydrous olivine suggested that olivine with the maximum soluble H2O content at the top of the asthenosphere has much lower conductivity less than 0.1 S/m (e.g., Yoshino et al., 2006; 2009a; Poe et al., 2010; Du Frane and Tyburczy, 2012; Yang, 2012), which is a typical value of conductivity anomaly observed in the oceanic mantle. Partial melting has been considered as an attractive agent for substantially raising the conductivity in this region (Shankland and Waff, 1977), because basaltic melt has greater electrical conductivity (> 100.5 S/m) and high wetting properties. However, dry mantle peridotite cannot reach the solidus temperature at depth 100 km. Volatile components can dramatically reduce melting temperature, even if its amount is very small. Recent studies on conductivity measurement of volatile-bearing melt suggest that conductivity of melt dramatically increases with increasing volatile components (H2O: Ni et al., 2010a, b; CO2: Gaillard et al., 2008; Yoshino et al., 2010; 2012a). Because incipient melt includes higher amount of volatile components, conductivity enhancement by the partial melt is very effective at temperatures just above that of the volatile-bearing peridotite solidus. In this study, the electrical conductivity of peridotite with trace amount of volatile phases was measured in single crystal olivine capsule to protect escape of water from the sample at 3 GPa. The conductivity values were significantly higher than those of dry peridotite, suggesting that the observed conductivity anomalies at the asthenosphere are caused by a presence of trace amount of volatile component in fluid or melt. On the other hand, conductivity of partial molten peridotite measured under shear showed that the conductivity parallel to the shear direction becomes one order of magnitude higher than that normal direction. These observations suggest that partial melting can explain softening and the observed geophysical anomalies of asthenosphere.

Required Accuracy of Structural Constraints in the Inversion of Electrical Resistivity Data for Improved Water Content Estimation

NASA Astrophysics Data System (ADS)

Heinze, T.; Budler, J.; Weigand, M.; Kemna, A.

2017-12-01

Water content distribution in the ground is essential for hazard analysis during monitoring of landslide prone hills. Geophysical methods like electrical resistivity tomography (ERT) can be utilized to determine the spatial distribution of water content using established soil physical relationships between bulk electrical resistivity and water content. However, often more dominant electrical contrasts due to lithological structures outplay these hydraulic signatures and blur the results in the inversion process. Additionally, the inversion of ERT data requires further constraints. In the standard Occam inversion method, a smoothness constraint is used, assuming that soil properties change softly in space. While this applies in many scenarios, sharp lithological layers with strongly divergent hydrological parameters, as often found in landslide prone hillslopes, are typically badly resolved by standard ERT. We use a structurally constrained ERT inversion approach for improving water content estimation in landslide prone hills by including a-priori information about lithological layers. The smoothness constraint is reduced along layer boundaries identified using seismic data. This approach significantly improves water content estimations, because in landslide prone hills often a layer of rather high hydraulic conductivity is followed by a hydraulic barrier like clay-rich soil, causing higher pore pressures. One saturated layer and one almost drained layer typically result also in a sharp contrast in electrical resistivity, assuming that surface conductivity of the soil does not change in similar order. Using synthetic data, we study the influence of uncertainties in the a-priori information on the inverted resistivity and estimated water content distribution. We find a similar behavior over a broad range of models and depths. Based on our simulation results, we provide best-practice recommendations for field applications and suggest important tests to obtain reliable, reproducible and trustworthy results. We finally apply our findings to field data, compare conventional and improved analysis results, and discuss limitations of the structurally-constrained inversion approach.

A Numerical Investigation of the Electric and Thermal Cell Kill Distributions in Electroporation-Based Therapies in Tissue

PubMed Central

Garcia, Paulo A.; Davalos, Rafael V.; Miklavcic, Damijan

2014-01-01

Electroporation-based therapies are powerful biotechnological tools for enhancing the delivery of exogeneous agents or killing tissue with pulsed electric fields (PEFs). Electrochemotherapy (ECT) and gene therapy based on gene electrotransfer (EGT) both use reversible electroporation to deliver chemotherapeutics or plasmid DNA into cells, respectively. In both ECT and EGT, the goal is to permeabilize the cell membrane while maintaining high cell viability in order to facilitate drug or gene transport into the cell cytoplasm and induce a therapeutic response. Irreversible electroporation (IRE) results in cell kill due to exposure to PEFs without drugs and is under clinical evaluation for treating otherwise unresectable tumors. These PEF therapies rely mainly on the electric field distributions and do not require changes in tissue temperature for their effectiveness. However, in immediate vicinity of the electrodes the treatment may results in cell kill due to thermal damage because of the inhomogeneous electric field distribution and high current density during the electroporation-based therapies. Therefore, the main objective of this numerical study is to evaluate the influence of pulse number and electrical conductivity in the predicted cell kill zone due to irreversible electroporation and thermal damage. Specifically, we simulated a typical IRE protocol that employs ninety 100-µs PEFs. Our results confirm that it is possible to achieve predominant cell kill due to electroporation if the PEF parameters are chosen carefully. However, if either the pulse number and/or the tissue conductivity are too high, there is also potential to achieve cell kill due to thermal damage in the immediate vicinity of the electrodes. Therefore, it is critical for physicians to be mindful of placement of electrodes with respect to critical tissue structures and treatment parameters in order to maintain the non-thermal benefits of electroporation and prevent unnecessary damage to surrounding healthy tissue, critical vascular structures, and/or adjacent organs. PMID:25115970

Influence of material uncertainties on the RLC parameters of wound inductors modeled using the finite element method

NASA Astrophysics Data System (ADS)

Lossa, Geoffrey; Deblecker, Olivier; Grève, Zacharie De

2018-05-01

In this work, we highlight the influence of the material uncertainties (magnetic permeability, electric conductivity of a Mn-Zn ferrite core, and electric permittivity of wire insulation) on the RLC parameters of a wound inductor extracted from the finite element method. To that end, the finite element method is embedded in a Monte Carlo simulation. We show that considering mentioned different material properties as real random variables, leads to significant variations in the distributions of the RLC parameters.

Optimization of metals and plastics recovery from electric cable wastes using a plate-type electrostatic separator.

PubMed

Richard, Gontran; Touhami, Seddik; Zeghloul, Thami; Dascalescu, Lucien

2017-02-01

Plate-type electrostatic separators are commonly employed for the selective sorting of conductive and non-conductive granular materials. The aim of this work is to identify the optimal operating conditions of such equipment, when employed for separating copper and plastics from either flexible or rigid electric wire wastes. The experiments are performed according to the response surface methodology, on samples composed of either "calibrated" particles, obtained by manually cutting of electric wires at a predefined length (4mm), or actual machine-grinded scraps, characterized by a relatively-wide size distribution (1-4mm). The results point out the effect of particle size and shape on the effectiveness of the electrostatic separation. Different optimal operating conditions are found for flexible and rigid wires. A separate processing of the two classes of wire wastes is recommended. Copyright © 2016 Elsevier Ltd. All rights reserved.

Higher order total variation regularization for EIT reconstruction.

PubMed

Gong, Bo; Schullcke, Benjamin; Krueger-Ziolek, Sabine; Zhang, Fan; Mueller-Lisse, Ullrich; Moeller, Knut

2018-01-08

Electrical impedance tomography (EIT) attempts to reveal the conductivity distribution of a domain based on the electrical boundary condition. This is an ill-posed inverse problem; its solution is very unstable. Total variation (TV) regularization is one of the techniques commonly employed to stabilize reconstructions. However, it is well known that TV regularization induces staircase effects, which are not realistic in clinical applications. To reduce such artifacts, modified TV regularization terms considering a higher order differential operator were developed in several previous studies. One of them is called total generalized variation (TGV) regularization. TGV regularization has been successively applied in image processing in a regular grid context. In this study, we adapted TGV regularization to the finite element model (FEM) framework for EIT reconstruction. Reconstructions using simulation and clinical data were performed. First results indicate that, in comparison to TV regularization, TGV regularization promotes more realistic images. Graphical abstract Reconstructed conductivity changes located on selected vertical lines. For each of the reconstructed images as well as the ground truth image, conductivity changes located along the selected left and right vertical lines are plotted. In these plots, the notation GT in the legend stands for ground truth, TV stands for total variation method, and TGV stands for total generalized variation method. Reconstructed conductivity distributions from the GREIT algorithm are also demonstrated.

High Resolution Global Electrical Conductivity Variations in the Earth's Mantle

NASA Astrophysics Data System (ADS)

Kelbert, A.; Sun, J.; Egbert, G. D.

2013-12-01

Electrical conductivity of the Earth's mantle is a valuable constraint on the water content and melting processes. In Kelbert et al. (2009), we obtained the first global inverse model of electrical conductivity in the mantle capable of providing constraints on the lateral variations in mantle water content. However, in doing so we had to compromise on the problem complexity by using the historically very primitive ionospheric and magnetospheric source assumptions. In particular, possible model contamination by the auroral current systems had greatly restricted our use of available data. We have now addressed this problem by inverting for the external sources along with the electrical conductivity variations. In this study, we still focus primarily on long period data that are dominated by quasi-zonal source fields. The improved understanding of the ionospheric sources allows us to invert the magnetic fields directly, without a correction for the source and/or the use of transfer functions. It allows us to extend the period range of available data to 1.2 days - 102 days, achieving better sensitivity to the upper mantle and transition zone structures. Finally, once the source effects in the data are accounted for, a much larger subset of observatories may be used in the electrical conductivity inversion. Here, we use full magnetic fields at 207 geomagnetic observatories, which include mid-latitude, equatorial and high latitude data. Observatory hourly means from the years 1958-2010 are employed. The improved quality and spatial distribution of the data set, as well as the high resolution modeling and inversion using degree and order 40 spherical harmonics mapped to a 2x2 degree lateral grid, all contribute to the much improved resolution of our models, representing a conceptual step forward in global electromagnetic sounding. We present a fully three-dimensional, global electrical conductivity model of the Earth's mantle as inferred from ground geomagnetic observatory data, and use additional constraints to interpret these results in terms of mantle processes and compositional variations.

Partial independence of bioelectric and biomagnetic fields and its implications for encephalography and cardiography

NASA Astrophysics Data System (ADS)

Irimia, Andrei; Swinney, Kenneth R.; Wikswo, John P.

2009-05-01

In this paper, we clearly demonstrate that the electric potential and the magnetic field can contain different information about current sources in three-dimensional conducting media. Expressions for the magnetic fields of electric dipole and quadrupole current sources immersed in an infinite conducting medium are derived, and it is shown that two different point dipole distributions that are electrically equivalent have different magnetic fields. Although measurements of the electric potential are not sufficient to determine uniquely the characteristics of a quadrupolar source, the radial component of the magnetic field can supply the additional information needed to resolve these ambiguities and to determine uniquely the configuration of dipoles required to specify the electric quadrupoles. We demonstrate how the process can be extended to even higher-order terms in an electrically silent series of magnetic multipoles. In the context of a spherical brain source model, it has been mathematically demonstrated that the part of the neuronal current generating the electric potential lives in the orthogonal complement of the part of the current generating the magnetic potential. This implies a mathematical relationship of complementarity between electroencephalography and magnetoencephalography, although the theoretical result in question does not apply to the nonspherical case [G. Dassios, Math. Med. Biol. 25, 133 (2008)]. Our results have important practical applications in cases where electrically silent sources that generate measurable magnetic fields are of interest. Moreover, electrically silent, magnetically active moments of higher order can be useful when cancellation due to superposition of fields can occur, since this situation leads to a substantial reduction in the measurable amplitude of the signal. In this context, information derived from magnetic recordings of electrically silent, magnetically active multipoles can supplement electrical recordings for the purpose of studying the physiology of the brain. Magnetic fields of the electric multipole sources in a conducting medium surrounded by an insulating spherical shell are also presented and the relevance of this calculation to cardiographic and encephalographic experimentation is discussed.

Study of GO-Cu2O and RGO-Cu nanocomposite monolayer sheets prepared by modified Langmuir Blodgett route

NASA Astrophysics Data System (ADS)

Botcha, V. Divakar; Sutar, D. S.; Major, S. S.

2018-07-01

The modified Langmuir-Blodgett (MLB) technique has been improvised and extended to transfer GO-Cu2O nanocomposite monolayer sheets, by introducing Cu2+ ions into the subphase at room temperature. Morphological studies of as-transferred sheets revealed the presence of closely spaced GO monolayer sheets, with slightly enhanced roughness. XPS studies of as-transferred sheets confirmed the presence of copper, either as metallic Cu or Cu2O, along with significant Cu(OH)2 component, but TEM results confirmed the formation of Cu2O nanocrystallites of size (7 ± 2) nm, distributed uniformly over GO sheets. After heat treatment in vacuum at 400 °C, the nanocomposite sheets were covered with a uniform distribution of larger size nanoparticles. Based on Raman, XPS and TEM studies it has been confirmed that heat treatment at 400 °C in vacuum results in the formation of agglomerated Cu nanoparticles of size (23 ± 9) nm distributed uniformly over reduced graphene oxide (RGO) sheets. The electrical characterization of nanocomposite sheets on SiO2/Si in back-gated FET geometry revealed that the electrical conductivity of as-transferred GO-Cu2O sheets was similar to that usually observed for GO monolayer sheets. The RGO-Cu sheets also displayed electrical conductivity and field effect mobility values comparable to those reported for RGO sheets obtained by chemical/thermal reduction, and was unaffected by the presence of Cu nanoparticles.

Use of 3-D magnetic resonance electrical impedance tomography in detecting human cerebral stroke: a simulation study*

PubMed Central

Gao, Nuo; Zhu, Shan-an; He, Bin

2005-01-01

We have developed a new three dimensional (3-D) conductivity imaging approach and have used it to detect human brain conductivity changes corresponding to acute cerebral stroke. The proposed Magnetic Resonance Electrical Impedance Tomography (MREIT) approach is based on the J-Substitution algorithm and is expanded to imaging 3-D subject conductivity distribution changes. Computer simulation studies have been conducted to evaluate the present MREIT imaging approach. Simulations of both types of cerebral stroke, hemorrhagic stroke and ischemic stroke, were performed on a four-sphere head model. Simulation results showed that the correlation coefficient (CC) and relative error (RE) between target and estimated conductivity distributions were 0.9245±0.0068 and 8.9997%±0.0084%, for hemorrhagic stroke, and 0.6748±0.0197 and 8.8986%±0.0089%, for ischemic stroke, when the SNR (signal-to-noise radio) of added GWN (Gaussian White Noise) was 40. The convergence characteristic was also evaluated according to the changes of CC and RE with different iteration numbers. The CC increases and RE decreases monotonously with the increasing number of iterations. The present simulation results show the feasibility of the proposed 3-D MREIT approach in hemorrhagic and ischemic stroke detection and suggest that the method may become a useful alternative in clinical diagnosis of acute cerebral stroke in humans. PMID:15822161

Effect of surfactants and manufacturing methods on the electrical and thermal conductivity of carbon nanotube/silicone composites.

PubMed

Vilčáková, Jarmila; Moučka, Robert; Svoboda, Petr; Ilčíková, Markéta; Kazantseva, Natalia; Hřibová, Martina; Mičušík, Matej; Omastová, Mária

2012-11-05

The effect of ionic surfactants and manufacturing methods on the separation and distribution of multi-wall carbon nanotubes (CNTs) in a silicone matrix are investigated. The CNTs are dispersed in an aqueous solution of the anionic surfactant dodecylbenzene sulfonic acid (DBSA), the cationic surfactant cetyltrimethylammonium bromide (CTAB), and in a DBSA/CTAB surfactant mixture. Four types of CNT-based composites of various concentrations from 0 to 6 vol.% are prepared by simple mechanical mixing and sonication. The morphology, electrical and thermal conductivity of the CNT-based composites are analyzed. The incorporation of both neat and modified CNTs leads to an increase in electrical and thermal conductivity. The dependence of DC conductivity versus CNT concentration shows percolation behaviour with a percolation threshold of about 2 vol.% in composites with neat CNT. The modification of CNTs by DBSA increases the percolation threshold to 4 vol.% due to the isolation/separation of individual CNTs. This, in turn, results in a significant decrease in the complex permittivity of CNT–DBSA-based composites. In contrast to the percolation behaviour of DC conductivity, the concentration dependence of thermal conductivity exhibits a linear dependence, the thermal conductivity of composites with modified CNTs being lower than that of composites with neat CNTs. All these results provide evidence that the modification of CNTs by DBSA followed by sonication allows one to produce composites with high homogeneity.

A Modeling Study of the Spatial Structure of Electric Fields Generated by Electrified Clouds with Screening Layers

NASA Astrophysics Data System (ADS)

Biagi, C. J.; Cummins, K. L.

2015-12-01

The growing possibility of inexpensive airborne observations of electric fields using one or more small UAVs increases the importance of understanding what can be determined about cloud electrification and associated electric fields outside cloud boundaries. If important information can be inferred from carefully selected flight paths outside of a cloud, then the aircraft and its instrumentation will be much cheaper to develop and much safer to operate. These facts have led us to revisit this long-standing topic using quasi-static, finite-element modeling inside and outside arbitrarily shaped clouds with a variety of internal charge distributions. In particular, we examine the effect of screening layers on electric fields outside of electrified clouds by comparing modeling results for charged clouds having electrical conductivities that are both equal to and lower than the surrounding clear air. The comparisons indicate that the spatial structure of the electric field is approximately the same regardless of the difference in the conductivities between the cloud and clear air and the formation of a screening layer, even for altitude-dependent electrical conductivities. This result is consistent with the numerical modeling results reported by Driscoll et al [1992]. The similarity of the spatial structure of the electric field outside of clouds with and without a screening layer suggests that "bulk" properties related to cloud electrification might be determined using measurements of the electric field at multiple locations in space outside the cloud, particularly at altitude. Finally, for this somewhat simplified model, the reduction in electric field magnitude outside the cloud due to the presence of a screening layer exhibits a simple dependence on the difference in conductivity between the cloud and clear air. These results are particularly relevant for studying clouds that are not producing lightning, such as developing thunderstorms and decaying anvils associated with mature storm systems.Driscoll K.T., R.J. Blakeslee, M.E. Baginski, 1992, A modeling study of the time-averaged electric currents in the vicinity of isolated thunderstorms, J. Geophys. Res., 97, D11, pp 11535-11551.

Investigating the Defect Structures in Transparent Conducting Oxides Using X-ray and Neutron Scattering Techniques

PubMed Central

González, Gabriela B.

2012-01-01

Transparent conducting oxide (TCO) materials are implemented into a wide variety of commercial devices because they possess a unique combination of high optical transparency and high electrical conductivity. Created during the processing of the TCOs, defects within the atomic-scale structure are responsible for their desirable optical and electrical properties. Therefore, studying the defect structure is essential to a better understanding of the behavior of transparent conductors. X-ray and neutron scattering techniques are powerful tools to investigate the atomic lattice structural defects in these materials. This review paper presents some of the current developments in the study of structural defects in n-type TCOs using x-ray diffraction (XRD), neutron diffraction, extended x-ray absorption fine structure (EXAFS), pair distribution functions (PDFs), and x-ray fluorescence (XRF). PMID:28817010

30 CFR 77.501 - Electric distribution circuits and equipment; repair.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Electric distribution circuits and equipment... OF UNDERGROUND COAL MINES Electrical Equipment-General § 77.501 Electric distribution circuits and equipment; repair. No electrical work shall be performed on electric distribution circuits or equipment...

Size-ordered 63Ni nanocluster film as a betavoltaic battery unit

NASA Astrophysics Data System (ADS)

Borisyuk, P. V.; Yakovlev, V. P.; Vasiliev, O. S.; Lebedinskii, Yu. Yu.; Fetisov, V. V.; Kozlova, T. I.; Kozodaev, M. G.

2018-04-01

We create thin metallic films formed as a size-ordered deposition of Ni nanoclusters whose sizes are distributed over the range of 2-7 nm. The morphology, chemical composition, and electrical characteristics of the films are measured. The conductivity of the films under investigation changes approximately as the inverse square root of the average nanocluster size. We observe experimentally that, under irradiation by electrons with energies of 10-25 keV, the films show signs of being subjected to the electromotive force. We discuss how this effect is connected with the size-ordered spatial distribution of metallic nanoclusters. We analyze the possibility of using 63Ni nanocluster films in betavoltaic battery units and estimate the expected efficiency of converting β-decay energy into electricity.

Three-dimensional thermal finite element modeling of lithium-ion battery in thermal abuse application

NASA Astrophysics Data System (ADS)

Guo, Guifang; Long, Bo; Cheng, Bo; Zhou, Shiqiong; Xu, Peng; Cao, Binggang

In order to better understand the thermal abuse behavior of high capacities and large power lithium-ion batteries for electric vehicle application, a three-dimensional thermal model has been developed for analyzing the temperature distribution under abuse conditions. The model takes into account the effects of heat generation, internal conduction and convection, and external heat dissipation to predict the temperature distribution in a battery. Three-dimensional model also considers the geometrical features to simulate oven test, which are significant in larger cells for electric vehicle application. The model predictions are compared to oven test results for VLP 50/62/100S-Fe (3.2 V/55 Ah) LiFePO 4/graphite cells and shown to be in great agreement.

The Implementation Internet of Things(IoT) Technology in Real Time Monitoring of Electrical Quantities

NASA Astrophysics Data System (ADS)

Despa, D.; Nama, G. F.; Muhammad, M. A.; Anwar, K.

2018-04-01

Electrical quantities such as Voltage, Current, Power, Power Factor, Energy, and Frequency in electrical power system tends to fluctuate, as a result of load changes, disturbances, or other abnormal states. The change-state in electrical quantities should be identify immediately, otherwise it can lead to serious problem for whole system. Therefore a necessity is required to determine the condition of electricity change-state quickly and appropriately in order to make effective decisions. Online monitoring of power distribution system based on Internet of Things (IoT) technology was deploy and implemented on Department of Mechanical Engineering University of Lampung (Unila), especially at three-phase main distribution panel H-building. The measurement system involve multiple sensors such current sensors and voltage sensors, while data processing conducted by Arduino, the measurement data stored in to the database server and shown in a real-time through a web-based application. This measurement system has several important features especially for realtime monitoring, robust data acquisition and logging, system reporting, so it will produce an important information that can be used for various purposes of future power analysis such estimation and planning. The result of this research shown that the condition of electrical power system at H-building performed unbalanced load, which often leads to drop-voltage condition

Theory of electrical conductivity and dielectric permittivity of highly aligned graphene-based nanocomposites.

PubMed

Xia, Xiaodong; Hao, Jia; Wang, Yang; Zhong, Zheng; Weng, George J

2017-05-24

Highly aligned graphene-based nanocomposites are of great interest due to their excellent electrical properties along the aligned direction. Graphene fillers in these composites are not necessarily perfectly aligned, but their orientations are highly confined to a certain angle, [Formula: see text] with 90° giving rise to the randomly oriented state and 0° to the perfectly aligned one. Recent experiments have shown that electrical conductivity and dielectric permittivity of highly aligned graphene-polymer nanocomposites are strongly dependent on this distribution angle, but at present no theory seems to exist to address this issue. In this work we present a new effective-medium theory that is derived from the underlying physical process including the effects of graphene orientation, filler loading, aspect ratio, percolation threshold, interfacial tunneling, and Maxwell-Wagner-Sillars polarization, to determine these two properties. The theory is formulated in the context of preferred orientational average. We highlight this new theory with an application to rGO/epoxy nanocomposites, and demonstrate that the calculated in-plane and out-of-plane conductivity and permittivity are in agreement with the experimental data as the range of graphene orientations changes from the randomly oriented to the highly aligned state. We also show that the percolation thresholds of highly aligned graphene nanocomposites are in general different along the planar and the normal directions, but they converge into a single one when the statistical distribution of graphene fillers is spherically symmetric.

Spatial resolution of gas hydrate and permeability changes from ERT data in LARS simulating the Mallik gas hydrate production test

NASA Astrophysics Data System (ADS)

Priegnitz, Mike; Thaler, Jan; Spangenberg, Erik; Schicks, Judith M.; Abendroth, Sven

2014-05-01

The German gas hydrate project SUGAR studies innovative methods and approaches to be applied in the production of methane from hydrate-bearing reservoirs. To enable laboratory studies in pilot scale, a large reservoir simulator (LARS) was realized allowing for the formation and dissociation of gas hydrates under simulated in-situ conditions. LARS is equipped with a series of sensors. This includes a cylindrical electrical resistance tomography (ERT) array composed of 25 electrode rings featuring 15 electrodes each. The high-resolution ERT array is used to monitor the spatial distribution of the electrical resistivity during hydrate formation and dissociation experiments over time. As the present phases of poorly conducting sediment, well conducting pore fluid, non-conducting hydrates, and isolating free gas cover a wide range of electrical properties, ERT measurements enable us to monitor the spatial distribution of these phases during the experiments. In order to investigate the hydrate dissociation and the resulting fluid flow, we simulated a hydrate production test in LARS that was based on the Mallik gas hydrate production test (see abstract Heeschen et al., this volume). At first, a hydrate phase was produced from methane saturated saline water. During the two months of gas hydrate production we measured the electrical properties within the sediment sample every four hours. These data were used to establish a routine estimating both the local degrees of hydrate saturation and the resulting local permeabilities in the sediment's pore space from the measured resistivity data. The final gas hydrate saturation filled 89.5% of the total pore space. During hydrate dissociation, ERT data do not allow for a quantitative determination of free gas and remaining gas hydrates since both phases are electrically isolating. However, changes are resolved in the spatial distribution of the conducting liquid and the isolating phase with gas being the only mobile isolating phase. Hence, it is possible to detect areas in the sediment sample where free gas is released due to hydrate dissociation and displaces the liquid phase. Combined with measurements and numerical simulation of the total two-phase fluxes from the sediment sample (see abstract Abendroth et al., this volume), the LARS experiments allow for detailed information on the dissociation process during hydrate production. Here we present the workflow and first results estimating local hydrate saturations and permeabilities during hydrate formation and the movement of liquid and gas phases during hydrate dissociation, respectively.

Research Electrical Distribution Bus | Energy Systems Integration Facility

Science.gov Websites

| NREL Research Electrical Distribution Bus Research Electrical Distribution Bus The research electrical distribution bus (REDB) is the heart of the Energy Systems Integration Facility electrical system throughout the laboratories. Photo of a technician performing maintenance on the Research Electrical

Magnetotelluric Forward Modeling and Inversion In 3 -d Conductivity Model of The Vesuvio Volcano

NASA Astrophysics Data System (ADS)

Spichak, V.; Patella, D.

Three-dimensional forward modeling of MT fields in the simplified conductivity model of the Vesuvio volcano (T=0.1, 1, 10, 100 and 1000s) indicates that the best image of the magma chamber could be obtained basing on the pseudo-section of the determinant apparent resitivity phase as well as on the real and imaginary components of the electric field. Another important result of the studies conducted is that it was demonstrated the principal opportunity of detection and contouring the magma chamber by 2-D pseudo-sections constructed basing on the data transforms mentioned above. Bayesian three-dimensional inversion of synthetic MT data in the volcano model indicates that it is possible to determine the depth and vertical size of the magma chamber, however, simultaneous detection of the conductivity distribution inside the domain of search is of pure quality. However, if the geometrical parameters of the magma chamber are determined in advance, it becomes quite realistic to find out the conductivity distribution inside. The accuracy of such estimation strongly depends on the uncertainty in its prior value: the more narrow is the prior conductivity palette the closer could be the posterior conductivity distribution to the true one.

Electrospray methodologies for characterization and deposition of nanoparticles

NASA Astrophysics Data System (ADS)

Modesto Lopez, Luis Balam

Electrospray is an aerosolization method that generates highly charged droplets from solutions or suspensions and, after a series of solvent evaporation -- droplet fission cycles, it results in particles carrying multiple charges. Highly charged particles are used in a variety of applications, including particle characterization, thin film deposition, nanopatterning, and inhalation studies among several others. In this work, a soft X-ray photoionization was coupled with an electrospray to obtain monodisperse, singly charged nanoparticles for applications in online size characterization with electrical mobility analysis. Photoionization with the soft X-ray charger enhanced the diffusion neutralization rate of the highly charged bacteriophages, proteins, and solid particles. The effect of nanoparticle surface charge and nanoparticle agglomeration in liquids on the electrospray process was studied experimentally and a modified expression to calculate the effective electrical conductivity of nanosuspensions was proposed. The effective electrical conductivity of TiO2 nanoparticle suspensions is strongly dependent on the electrical double layer and the agglomeration dynamics of the particles; and such dependence is more remarkable in liquids with low ionic strength. TiO2 nanoparticle agglomerates with nearly monodisperse sizes in the nanometer and submicrometer ranges were generated, by electrospraying suspensions with tuned effective electrical conductivity, and used to deposit photocatalytic films for water-splitting. Nanostructured films of iron oxide with uniform distribution of particles over the entire deposition area were formed with an electrospray system. The micro-Raman spectra of the iron oxide films showed that transverse and longitudinal optical modes are highly sensitive to the crystallize size of the electrospray-deposited films. The fabrication of films of natural light-harvesting complexes, with the aim of designing biohybrid photovoltaic devices, was explored with an electrospray. The ability to charge chlorosomes with large number of charges allowed their ballistic deposition onto TiO2 nanostructured columnar films simultaneously maintaining their light-harvesting properties. Single units of natural light-harvesting complexes were isolated in charged electrospray droplets for subsequent size characterization. The charge distribution of natural light-harvesting complexes, aerosolized with a collision nebulizer, was determined with tandem differential mobility analysis. It was found that nebulized light-harvesting complexes were multiply charged; hence they have potential applications in the deposition of functional films using electric fields. The studies conducted as part of this dissertation addressed fundamental issues in the characterization and deposition of nanoparticle suspensions and elucidated applications of the electrospray technique, particularly for solar energy utilization.

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.

New equivalent-electrical circuit model and a practical measurement method for human body impedance.

PubMed

Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

2015-01-01

Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

An addressable conducting network for autonomic structural health management of composite structures

NASA Astrophysics Data System (ADS)

Takahashi, Kosuke; Park, Jong Se; Hahn, H. Thomas

2010-10-01

The electrical resistance change method (ERCM) has long been an area of interest as an in-service health monitoring system. To apply the ERCM to existing structures, a new concept, the addressable conducting network (ACN), is proposed for autonomic structural health management of graphite/polymer composites. The ACN consists of two sets of conducting lines normal to each other, where one set resides on the top surface of the laminate and the other on the bottom surface. Damage can be detected by monitoring the resistance change 'through the laminate thickness' between two lines. By using a thermally mendable polymer as the matrix, the same conducting lines can be used to supply the electric current needed for resistive heating, thereby allowing the detected damage to be healed. As shown experimentally, the electrical resistance change method using an ACN distinguishes between laminates made of properly and improperly cured prepreg as well as revealing damage generated during three-point bending tests. Finite element analysis was performed to examine the feasibility of the ACN and indicated that the damage can be easily located from the spatial distribution of resistance changes and that the damaged area can be locally heated by supplying a large amount of current to selected conducting lines.

Direct Observation of Surface Potential Distribution in Insulation Resistance Degraded Acceptor-Doped BaTiO3 Multilayered Ceramic Capacitors

NASA Astrophysics Data System (ADS)

Hong, Kootak; Lee, Tae Hyung; Suh, Jun Min; Park, Jae-Sung; Kwon, Hyung-Soon; Choi, Jaeho; Jang, Ho Won

2018-05-01

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

An in-depth description of bipolar resistive switching in Cu/HfOx/Pt devices, a 3D kinetic Monte Carlo simulation approach

NASA Astrophysics Data System (ADS)

Aldana, S.; Roldán, J. B.; García-Fernández, P.; Suñe, J.; Romero-Zaliz, R.; Jiménez-Molinos, F.; Long, S.; Gómez-Campos, F.; Liu, M.

2018-04-01

A simulation tool based on a 3D kinetic Monte Carlo algorithm has been employed to analyse bipolar conductive bridge RAMs fabricated with Cu/HfOx/Pt stacks. Resistive switching mechanisms are described accounting for the electric field and temperature distributions within the dielectric. The formation and destruction of conductive filaments (CFs) are analysed taking into consideration redox reactions and the joint action of metal ion thermal diffusion and electric field induced drift. Filamentary conduction is considered when different percolation paths are formed in addition to other conventional transport mechanisms in dielectrics. The simulator was tuned by using the experimental data for Cu/HfOx/Pt bipolar devices that were fabricated. Our simulation tool allows for the study of different experimental results, in particular, the current variations due to the electric field changes between the filament tip and the electrode in the High Resistance State. In addition, the density of metallic atoms within the CF can also be characterized along with the corresponding CF resistance description.

Negative differential photoconductance in gold nanoparticle arrays in the Coulomb blockade regime.

PubMed

Mangold, Markus A; Calame, Michel; Mayor, Marcel; Holleitner, Alexander W

2012-05-22

We investigate the photoconductance of gold nanoparticle arrays in the Coulomb blockade regime. Two-dimensional, hexagonal crystals of nanoparticles are produced by self-assembly. The nanoparticles are weakly coupled to their neighbors by a tunneling conductance. At low temperatures, the single electron charging energy of the nanoparticles dominates the conductance properties of the array. The Coulomb blockade of the nanoparticles can be lifted by optical excitation with a laser beam. The optical excitation leads to a localized heating of the arrays, which in turn gives rise to a local change in conductance and a redistribution of the overall electrical potential in the arrays. We introduce a dual-beam optical excitation technique to probe the distribution of the electrical potential in the nanoparticle array. A negative differential photoconductance is the direct consequence of the redistribution of the electrical potential upon lifting of the Coulomb blockade. On the basis of our model, we calculate the optically induced current from the dark current-voltage characteristics of the nanoparticle array. The calculations closely reproduce the experimental observations.

Automatic Realistic Real Time Stimulation/Recording in Weakly Electric Fish: Long Time Behavior Characterization in Freely Swimming Fish and Stimuli Discrimination

PubMed Central

Forlim, Caroline G.; Pinto, Reynaldo D.

2014-01-01

Weakly electric fish are unique model systems in neuroethology, that allow experimentalists to non-invasively, access, central nervous system generated spatio-temporal electric patterns of pulses with roles in at least 2 complex and incompletely understood abilities: electrocommunication and electrolocation. Pulse-type electric fish alter their inter pulse intervals (IPIs) according to different behavioral contexts as aggression, hiding and mating. Nevertheless, only a few behavioral studies comparing the influence of different stimuli IPIs in the fish electric response have been conducted. We developed an apparatus that allows real time automatic realistic stimulation and simultaneous recording of electric pulses in freely moving Gymnotus carapo for several days. We detected and recorded pulse timestamps independently of the fish’s position for days. A stimulus fish was mimicked by a dipole electrode that reproduced the voltage time series of real conspecific according to previously recorded timestamp sequences. We characterized fish behavior and the eletrocommunication in 2 conditions: stimulated by IPIs pre-recorded from other fish and random IPI ones. All stimuli pulses had the exact Gymontus carapo waveform. All fish presented a surprisingly long transient exploratory behavior (more than 8 h) when exposed to a new environment in the absence of electrical stimuli. Further, we also show that fish are able to discriminate between real and random stimuli distributions by changing several characteristics of their IPI distribution. PMID:24400122

Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

NASA Astrophysics Data System (ADS)

Higuchi, A.; Watanabe, T.

2013-12-01

Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure. Elastic wave velocities and electrical conductivity showed reproducibly contrasting changes for a small increase in the confining pressure. The elastic wave velocities increased only by 5% as the confining pressure increased from 0.1 MPa to 25 MPa, while the electrical conductivity decreased by an order of magnitude. Based on the SEM examinations, open grain boundaries work as cracks. The changes in elastic wave velocities and electrical conductivity must be caused by the closure of open grain boundaries. Most (˜80%) of the decrease in electrical conductivity occurred below the confining pressure of 5 MPa. As the confining pressure increased from 0.1 MPa to 5 MPa, cracks with the aspect ratio smaller than 7.5×10-5 were closed. The decrease in porosity was only 0.0005%. Such a small change in porosity caused a large change in electrical conductivity. The connectivity of fluid was maintained at the confining pressure of 25 MPa by cracks with the aspect ratio larger than 3.7×10-4. Simultaneous measurements have provided us a lot of information on the microstructure of fluid-bearing rocks.

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.

Simplified realistic human head model for simulating Tumor Treating Fields (TTFields).

PubMed

Wenger, Cornelia; Bomzon, Ze'ev; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2016-08-01

Tumor Treating Fields (TTFields) are alternating electric fields in the intermediate frequency range (100-300 kHz) of low-intensity (1-3 V/cm). TTFields are an anti-mitotic treatment against solid tumors, which are approved for Glioblastoma Multiforme (GBM) patients. These electric fields are induced non-invasively by transducer arrays placed directly on the patient's scalp. Cell culture experiments showed that treatment efficacy is dependent on the induced field intensity. In clinical practice, a software called NovoTalTM uses head measurements to estimate the optimal array placement to maximize the electric field delivery to the tumor. Computational studies predict an increase in the tumor's electric field strength when adapting transducer arrays to its location. Ideally, a personalized head model could be created for each patient, to calculate the electric field distribution for the specific situation. Thus, the optimal transducer layout could be inferred from field calculation rather than distance measurements. Nonetheless, creating realistic head models of patients is time-consuming and often needs user interaction, because automated image segmentation is prone to failure. This study presents a first approach to creating simplified head models consisting of convex hulls of the tissue layers. The model is able to account for anisotropic conductivity in the cortical tissues by using a tensor representation estimated from Diffusion Tensor Imaging. The induced electric field distribution is compared in the simplified and realistic head models. The average field intensities in the brain and tumor are generally slightly higher in the realistic head model, with a maximal ratio of 114% for a simplified model with reasonable layer thicknesses. Thus, the present pipeline is a fast and efficient means towards personalized head models with less complexity involved in characterizing tissue interfaces, while enabling accurate predictions of electric field distribution.

Patterns of zone management uncertainty in cotton using tarnished plant bug distributions, NDVI, soil EC, yield and thermal imagery

USDA-ARS?s Scientific Manuscript database

Management zones for various crops have been delineated using NDVI (Normalized Difference Vegetation Index), apparent bulk soil electrical conductivity (ECa - Veris), and yield data; however, estimations of uncertainty for these data layers are equally important considerations. The objective of this...

Solid state thermal rectifier

DOEpatents

None

2016-07-05

Thermal rectifiers using linear nanostructures as core thermal conductors have been fabricated. A high mass density material is added preferentially to one end of the nanostructures to produce an axially non-uniform mass distribution. The resulting nanoscale system conducts heat asymmetrically with greatest heat flow in the direction of decreasing mass density. Thermal rectification has been demonstrated for linear nanostructures that are electrical insulators, such as boron nitride nanotubes, and for nanostructures that are conductive, such as carbon nanotubes.

Enhanced electrical conductivity and piezoresistive sensing in multi-wall carbon nanotubes/polydimethylsiloxane nanocomposites via the construction of a self-segregated structure.

PubMed

Wang, Ming; Zhang, Kai; Dai, Xin-Xin; Li, Yin; Guo, Jiang; Liu, Hu; Li, Gen-Hui; Tan, Yan-Jun; Zeng, Jian-Bing; Guo, Zhanhu

2017-08-10

Formation of highly conductive networks is essential for achieving flexible conductive polymer composites (CPCs) with high force sensitivity and high electrical conductivity. In this study, self-segregated structures were constructed in polydimethylsiloxane/multi-wall carbon nanotube (PDMS/MWCNT) nanocomposites, which then exhibited high piezoresistive sensitivity and low percolation threshold without sacrificing their mechanical properties. First, PDMS was cured and pulverized into 40-60 mesh-sized particles (with the size range of 250-425 μm) as an optimum self-segregated phase to improve the subsequent electrical conductivity. Then, the uncured PDMS/MWCNT base together with the curing agent was mixed with the abovementioned PDMS particles, serving as the segregated phase. Finally, the mixture was cured again to form the PDMS/MWCNT nanocomposites with self-segregated structures. The morphological evaluation indicated that MWCNTs were located in the second cured three-dimensional (3D) continuous PDMS phase, resulting in an ultralow percolation threshold of 0.003 vol% MWCNTs. The nanocomposites with self-segregated structures with 0.2 vol% MWCNTs achieved a high electrical conductivity of 0.003 S m -1 , whereas only 4.87 × 10 -10 S m -1 was achieved for the conventional samples with 0.2 vol% MWCNTs. The gauge factor GF of the self-segregated samples was 7.4-fold that of the conventional samples at 30% compression strain. Furthermore, the self-segregated samples also showed higher compression modulus and strength as compared to the conventional samples. These enhanced properties were attributed to the construction of 3D self-segregated structures, concentrated distribution of MWCNTs, and strong interfacial interaction between the segregated phase and the continuous phase with chemical bonds formed during the second curing process. These self-segregated structures provide a new insight into the fabrication of elastomers with high electrical conductivity and piezoresistive sensitivity for flexible force-sensitive materials.

Conducted electrical weapons or stun guns: a review of 46 cases examined in casualty.

PubMed

Becour, Bertrand

2013-06-01

Low-lethality weapons are intended to neutralize a person with maximum security and with minimal risk of injury or death to the user of the weapon, the person arrested, and the witnesses. Under the same circumstances, the use of a firearm is causing mortality of 50%. Marketed since 1974, the Taser X26 is currently staffing services in the French police and gendarmerie. The Taser device has 3 damaging mechanisms: the direct effect of electric current on the tissues, the conversion of electrical energy into thermal energy, and the injuries caused by the general muscle contraction and resulting fall. The study aimed to analyze the specificities of the conducted electrical weapon-related injuries treated in a emergency department on a series of 46 cases. The study population was predominantly middle-aged men. The circumstances of use of the Taser X26 were most often related to an arrest. The frequency of consultation after a shot by Taser X26 was stable. The management is essentially an outpatient because of frequent and benign lesions. The impacts of electrical impulse mainly affect the chest and abdomen. This distribution of impact zones is inhomogeneous, depending on the circumstances of use.

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

Thomas, H. P.; Basso, T. S.; Kroposki, B.

The Department of Energy (DOE) Distributed Power Program (DPP) is conducting work to complete, validate in the field, and support the development of a national interconnection standard for distributed energy resources (DER), and to address the institutional and regulatory barriers slowing the commercial adoption of DER systems. This work includes support for the IEEE standards, including P1547 Standard for Interconnecting Distributed Resources with Electric Power Systems, P1589 Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, and the P1608 Application Guide. Work is also in progress on system integration research and development (R&D) on themore » interface and control of DER with local energy systems. Additional efforts are supporting high-reliability power for industry, evaluating innovative concepts for DER applications, and exploring plug-and-play interface and control technologies for intelligent autonomous interconnection systems. This paper summarizes (1) the current status of the IEEE interconnection standards and application guides in support of DER, and (2) the R&D in progress at the National Renewable Energy Laboratory (NREL) for interconnection and system integration and application of distributed energy resources.« less

Preparation of monodisperse microbubbles using an integrated embedded capillary T-junction with electrohydrodynamic focusing.

PubMed

Parhizkar, Maryam; Stride, Eleanor; Edirisinghe, Mohan

2014-07-21

This work investigates the generation of monodisperse microbubbles using a microfluidic setup combined with electrohydrodynamic processing. A basic T-junction microfluidic device was modified by applying an electrical potential difference across the outlet channel. A model glycerol air system was selected for the experiments. In order to investigate the influence of the electric field strength on bubble formation, the applied voltage was increased systematically up to 21 kV. The effect of solution viscosity and electrical conductivity was also investigated. It was found that with increasing electrical potential difference, the size of the microbubbles reduced to ~25% of the capillary diameter whilst their size distribution remained narrow (polydispersity index ~1%). A critical value of 12 kV was found above which no further significant reduction in the size of the microbubbles was observed. The findings suggest that the size of the bubbles formed in the T-junction (i.e. in the absence of the electric field) is strongly influenced by the viscosity of the solution. The eventual size of bubbles produced by the composite device, however, was only weakly dependent upon viscosity. Further experiments, in which the solution electrical conductivity was varied by the addition of a salt indicated that this had a much stronger influence upon bubble size.

Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices

DOEpatents

Chassin, David P [Pasco, WA; Donnelly, Matthew K [Kennewick, WA; Dagle, Jeffery E [Richland, WA

2011-12-06

Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices are described. In one aspect, an electrical power distribution control method includes providing electrical energy from an electrical power distribution system, applying the electrical energy to a load, providing a plurality of different values for a threshold at a plurality of moments in time and corresponding to an electrical characteristic of the electrical energy, and adjusting an amount of the electrical energy applied to the load responsive to an electrical characteristic of the electrical energy triggering one of the values of the threshold at the respective moment in time.

Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices

DOEpatents

Chassin, David P.; Donnelly, Matthew K.; Dagle, Jeffery E.

2006-12-12

Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices are described. In one aspect, an electrical power distribution control method includes providing electrical energy from an electrical power distribution system, applying the electrical energy to a load, providing a plurality of different values for a threshold at a plurality of moments in time and corresponding to an electrical characteristic of the electrical energy, and adjusting an amount of the electrical energy applied to the load responsive to an electrical characteristic of the electrical energy triggering one of the values of the threshold at the respective moment in time.

The influence of the breakdown electric field in the configuration of lightning corona sheath on charge distribution in the channel

NASA Astrophysics Data System (ADS)

Ignjatovic, Milan; Cvetic, Jovan; Heidler, Fridolin; Markovic, Slavoljub; Djuric, Radivoje

2014-11-01

A model of corona sheath that surrounds the thin core of the lightning channel has been investigated by using a generalized traveling current source return stroke model. The lightning channel is modeled by a charged corona sheath that stretches around a highly conductive central core through which the main current flows. The channel core with the negatively charged outer channel sheath forms a strong electric field, with an overall radial orientation. The return stroke process is modeled as the negative leader charge in the corona sheath being discharged by the positive charge coming from the channel core. Expressions that describe how the corona sheath radius evolves during the return stroke are obtained from the corona sheath model, which predicts charge motion within the sheath. The corona sheath model, set forth by Maslowski and Rakov (2006), Tausanovic et al. (2010), Marjanovic and Cvetic (2009), Cvetic et al. (2011) and Cvetic et al. (2012), divides the sheath onto three zones: zone 1 (surrounding the channel core with net positive charge), zone 2 (surrounding zone 1 with negative charge) and zone 3 (the outer zone, representing uncharged virgin air). In the present study, we have assumed a constant electric field inside zone 1, as suggested by experimental research of corona discharges in coaxial geometry conducted by Cooray (2000). The present investigation builds upon previous studies by Tausanovic et al. (2010) and Cvetic et al. (2012) in several ways. The value of the breakdown electric field has been varied for probing its effect on channel charge distribution prior and during the return stroke. With the aim of investigating initial space charge distribution along the channel, total electric field at the outer surface of the channel corona sheath, just before the return stroke, is calculated and compared for various return stroke models. A self-consistent algorithm is applied to the generalized traveling current source return stroke model, so that the boundary condition for total electric field is fulfilled. The new density of space charge and the new radius of channel corona envelope, immediately before the return stroke stage, are calculated. The obtained results indicate a strong dependence of channel charge distribution on the breakdown electric field value. Among the compared return stroke models, transmission-line-type models have exhibited a good agreement with the predictions of the Gauss' law regarding total breakdown electric field on the corona sheath's outer surface. The generalized lightning traveling current source return stroke model gives similar results if the adjustment of the space charge density inside the corona sheath is performed.

Magnetoacoustic tomography with magnetic induction for high-resolution bioimepedance imaging through vector source reconstruction under the static field of MRI magnet

PubMed Central

Mariappan, Leo; Hu, Gang; He, Bin

2014-01-01

Purpose: Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. Methods: In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. Results: The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ∼1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. Conclusions: The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction. PMID:24506649

Influence of Carbon Nanotube Clustering on Mechanical and Electrical Properties of Cement Pastes

PubMed Central

Jang, Sung-Hwan; Kawashima, Shiho; Yin, Huiming

2016-01-01

Given the continued challenge of dispersion, for practical purposes, it is of interest to evaluate the impact of multi-walled carbon nanotubes (MWCNTs) at different states of clustering on the eventual performance properties of cement paste. This study evaluated the clustering of MWCNTs and the resultant effect on the mechanical and electrical properties when incorporated into cement paste. Cement pastes containing different concentrations of MWCNTs (up to 0.5% by mass of cement) with/without surfactant were characterized. MWCNT clustering was assessed qualitatively in an aqueous solution through visual observation, and quantitatively in cement matrices using a scanning electron microscopy technique. Additionally, the corresponding 28-day compressive strength, tensile strength, and electrical conductivity were measured. Results showed that the use of surfactant led to a downward shift in the MWCNT clustering size distribution in the matrices of MWCNT/cement paste, indicating improved dispersion of MWCNTs. The compressive strength, tensile strength, and electrical conductivity of the composites with surfactant increased with MWCNT concentration and were higher than those without surfactant at all concentrations. PMID:28773348

Trap Modulated Charge Carrier Transport in Polyethylene/Graphene Nanocomposites.

PubMed

Li, Zhonglei; Du, Boxue; Han, Chenlei; Xu, Hang

2017-06-21

The role of trap characteristics in modulating charge transport properties is attracting much attentions in electrical and electronic engineering, which has an important effect on the electrical properties of dielectrics. This paper focuses on the electrical properties of Low-density Polyethylene (LDPE)/graphene nanocomposites (NCs), as well as the corresponding trap level characteristics. The dc conductivity, breakdown strength and space charge behaviors of NCs with the filler content of 0 wt%, 0.005 wt%, 0.01 wt%, 0.1 wt% and 0.5 wt% are studied, and their trap level distributions are characterized by isothermal discharge current (IDC) tests. The experimental results show that the 0.005 wt% LDPE/graphene NCs have a lower dc conductivity, a higher breakdown strength and a much smaller amount of space charge accumulation than the neat LDPE. It is indicated that the graphene addition with a filler content of 0.005 wt% introduces large quantities of deep carrier traps that reduce charge carrier mobility and result in the homocharge accumulation near the electrodes. The deep trap modulated charge carrier transport attributes to reduce the dc conductivity, suppress the injection of space charges into polymer bulks and enhance the breakdown strength, which is of great significance in improving electrical properties of polymer dielectrics.

Photoelectric charging of partially sunlit dielectric surfaces in space

NASA Technical Reports Server (NTRS)

De, B. R.; Criswell, D. R.

1977-01-01

Sunlight-shadow effects may substantially alter the charging situation for a dielectric surface. The sunlight-shadow boundary tends to be the site of intense multipole electric fields. Charges on a sunlit dielectric surface have a finite effective mobility. The charge distribution tends to resemble that on a conducting surface. A boundary between a conducting and a dielectric surface may not represent a conductivity discontinuity when this boundary is sunlit; charges may migrate at a nontrivial rate across the boundary. A contracting or expanding sunlit area may experience a supercharging.

On the Induced Flow of an Electrically Conducting Liquid in a Rectangular Duct by Electric and Magnetic Fields of Finite Extent

NASA Technical Reports Server (NTRS)

Rossow, Vernon J.; Jones, William Prichard; Huerta, Robert H.

1961-01-01

Reported here are the results of a systematic study of a model of the direct-current electromagnetic pump. Of particular interest is the motion imparted to the electrically conducting fluid in the rectangular duct by the body forces that result from applied electric and magnetic fields. The purpose of the investigation is to associate the observed fluid motion with the characteristics of the electric and magnetic fields which cause them. The experiments were carried out with electromagnetic fields that moved a stream of copper sulphate solution through a clear plastic channel. Ink filaments injected into the stream ahead of the region where the fields were applied identify the motion of the fluid elements as they passed through the test channel. Several magnetic field configurations were employed with a two-dimensional electric current distribution in order to study and identify the magnitude of some of the effects on the fluid motion brought about by nonuniformities in the electromagnetic fields. A theoretical analysis was used to guide and evaluate the identification of the several fluid motions observed. The agreement of the experimental data with the theoretical predictions is satisfactory. It is found that sizable variations in the velocity profile and pressure head of the output stream are produced by the shape of the electric and magnetic fields.

Potential release of fibers from burning carbon composites. [aircraft fires

NASA Technical Reports Server (NTRS)

Bell, V. L.

1980-01-01

A comprehensive experimental carbon fiber source program was conducted to determine the potential for the release of conductive carbon fibers from burning composites. Laboratory testing determined the relative importance of several parameters influencing the amounts of single fibers released, while large-scale aviation jet fuel pool fires provided realistic confirmation of the laboratory data. The dimensions and size distributions of fire-released carbon fibers were determined, not only for those of concern in an electrical sense, but also for those of potential interest from a health and environmental standpoint. Fire plume and chemistry studies were performed with large pool fires to provide an experimental input into an analytical modelling of simulated aircraft crash fires. A study of a high voltage spark system resulted in a promising device for the detection, counting, and sizing of electrically conductive fibers, for both active and passive modes of operation.

Solar modulation of atmospheric electrification through variation of the conductivity over thunderstorms

NASA Technical Reports Server (NTRS)

Markson, R.

1975-01-01

It is suggested that variations of the current in the global atmospheric electrical circuit can be produced through regulation of the resistance between the tops of thunderclouds and the ionosphere. Long- and short-term changes in the conductivity of this region occur due to changes in the ionization rate resulting from solar activity. Previous suggestions that the phenomena might be due to conductivity variations in the fair weather part of the world or an influx of space charge to the upper atmosphere are discussed and considered unlikely. It might be possible to test the proposed mechanism by measuring the temporal variation of the ionospheric potential during distributed solar periods. Another approach would be to measure simultaneously the variation in ionization rate and electric current over thunderstorms. Several ways in which changes in atmospheric electrification might influence other meteorological phenomena are mentioned.

Non-scaling behavior of electroosmotic flow in voltage-gated nanopores

DOE PAGES

Lian, Cheng; Gallegos, Alejandro; Liu, Honglai; ...

2016-11-17

Ionic transport through nanopores is of fundamental importance for the design and development of nanofiltration membranes and novel electrochemical devices including supercapacitors, fuel cells and batteries. Recent experiments have shown an unusual variation of electrical conductance with the pore size and the electrolyte parameters that defies conventional scaling relations. Here ionic transport through voltage-gated nanopores was studied by using the classical density functional theory for ion distributions in combination with the Navier–Stokes equation for the electroosmotic flow. We also identified a significant influence of the gating potential on the scaling behavior of the conductance with changes in the pore sizemore » and the salt concentration. Finally, for ion transport in narrow pores with a high gating voltage, the conductivity shows an oscillatory dependence on the pore size owing to the strong overlap of electric double layers.« less

Immobilization of silver nanoparticles on exfoliated mica nanosheets to form highly conductive nanohybrid films

NASA Astrophysics Data System (ADS)

Chiu, Chih-Wei; Ou, Gang-Bo; Tsai, Yu-Hsuan; Lin, Jiang-Jen

2015-11-01

Highly electrically conductive films were prepared by coating organic/inorganic nanohybrid solutions with a polymeric dispersant and exfoliated mica nanosheets (Mica) on which silver nanoparticles (AgNPs) had been dispersed in various components. Transmission electronic microscopy showed that the synthesized AgNPs had a narrow size distribution and a diameter of approximately 20 nm. Furthermore, a 60 μm thick film with a sheet resistance as low as 4.5 × 10-2 Ω/sq could be prepared by controlling the heating temperature and by using AgNPs/POE-imide/Mica in a weight ratio of 20:20:1. During the heating process, the surface color of the hybrid film changed from dark golden to white, suggesting the accumulation of the AgNPs through surface migration and their melting to form an interconnected network. These nanohybrid films have potential for use in various electrically conductive devices.

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.

The Analysis of a Vortex Type Magnetohydrodynamic Induction Generator

NASA Technical Reports Server (NTRS)

Lengyel, L. L.

1962-01-01

Consideration it is given to the performance to the characteristics of an AC magnetohydrodynamic power generator, A rotating magnetic field is imposed on the vortex flow of an electrically conducting fluid, which is injected tangentially into an annulus formed by two nonconducting concentric cylinders and two nonconducting end plates. A perturbation technique is used to determine the two dimensional velocity and three dimensional electromagnetic field and current distributions. Finally, the generated power, the ohmic losses, the effective power and the electrical efficiency of the converter system are calculated.

Energy-efficient electric motors study

NASA Astrophysics Data System (ADS)

1981-03-01

A survey conducted of purchasers of integral horsepower polyphase motors measured current knowledge of and awareness of energy efficient motors, decision making criteria, information sources, purchase and usage patterns, and related factors. The data obtained were used for the electric motor market penetration analysis. Additionally, a telephone survey was made. The study also provides analyses of distribution channels, commercialization constraints, and the impacts of government programs and rising energy prices. Study findings, conclusions, and recommendations are presented. Sample questionnaires and copies of letters to respondents are presented in appendices as well as descriptions of the methods used.

An electrical conductivity inspection methodology of polycrystalline diamond cutters

NASA Astrophysics Data System (ADS)

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

2012-05-01

The polycrystalline diamond cutter (PDC) is widely used in oil and gas drilling operations. It is manufactured by sintering diamond powder onto a tungsten carbide substrate at 6 GPa and 1500 C. During sintering, molten cobalt from the substrate infiltrates the diamond table. The residual metal content correlates with cutter performance. We present an instrument that employs electrical impedance tomography capable of imaging the 3D metal content distribution in the diamond table. These images can be used to predict cutter performance as well as detect flaws.

Hyperthermia with implanted electrodes.

PubMed

Brezovich, I A; Young, J H

1981-01-01

A general solution is given for the steady state form of the heat conduction equation applied to a simple tumor model which is imagined as being heated by means of electrical currents flowing between metallic electrodes. The model assumes a homogeneous tumor with no bloodflow. The solution for the special case of constant temperature and potential at the surface of the heated volume is examined in detail. The solution shows that there exists, independent of the particular tumor and electrode geometry, a close relationship between the steady state temperature distribution and the electrical potential. Among the more important implications of this relationship are that equipotential surfaces within the heated volume are also isothermal surfaces and that no areas of excessive heat at or near any sharp edges or corners of the electrodes should develop, despite the high electric field intensity. Based on the theory, a procedure is outlined which might greatly facilitate the determination of temperature distributions in phantoms. Finally, the usefulness and the limitations of the theoretical models in clinical hyperthermia are discussed.

Infrared identification of internal overheating components inside an electric control cabinet by inverse heat transfer problem

NASA Astrophysics Data System (ADS)

Yang, Li; Wang, Ye; Liu, Huikai; Yan, Guanghui; Kou, Wei

2014-11-01

The components overheating inside an object, such as inside an electric control cabinet, a moving object, and a running machine, can easily lead to equipment failure or fire accident. The infrared remote sensing method is used to inspect the surface temperature of object to identify the overheating components inside the object in recent years. It has important practical application of using infrared thermal imaging surface temperature measurement to identify the internal overheating elements inside an electric control cabinet. In this paper, through the establishment of test bench of electric control cabinet, the experimental study was conducted on the inverse identification technology of internal overheating components inside an electric control cabinet using infrared thermal imaging. The heat transfer model of electric control cabinet was built, and the temperature distribution of electric control cabinet with internal overheating element is simulated using the finite volume method (FVM). The outer surface temperature of electric control cabinet was measured using the infrared thermal imager. Combining the computer image processing technology and infrared temperature measurement, the surface temperature distribution of electric control cabinet was extracted, and using the identification algorithm of inverse heat transfer problem (IHTP) the position and temperature of internal overheating element were identified. The results obtained show that for single element overheating inside the electric control cabinet the identifying errors of the temperature and position were 2.11% and 5.32%. For multiple elements overheating inside the electric control cabinet the identifying errors of the temperature and positions were 3.28% and 15.63%. The feasibility and effectiveness of the method of IHTP and the correctness of identification algorithm of FVM were validated.

Initiation of non-tropical thunderstorms by solar activity

NASA Technical Reports Server (NTRS)

Herman, J. R.; Goldberg, R. A.

1976-01-01

Correlative evidence accumulating since 1926 suggests that there must be some physical coupling mechanism between solar activity and thunderstorm occurrence in middle to high latitudes. Such a link may be provided by alteration of atmospheric electric parameters through the combined influence of high-energy solar protons and decreased cosmic ray intensities, both of which are associated with active solar events. The protons produce excess ionization near and above 20km, while the Forbush decreases a lowered conductivity and enhanced fair-weather atmospheric electric field below that altitude. Consequent effects ultimately lead to a charge distribution similar to that found in thunderclouds, and then other cloud physics processes take over to generate the intense electric fields required for lightning discharge.

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

PubMed Central

Huang, Yu; Liu, Anli A; Lafon, Belen; Friedman, Daniel; Dayan, Michael; Wang, Xiuyuan; Bikson, Marom; Doyle, Werner K; Devinsky, Orrin; Parra, Lucas C

2017-01-01

Transcranial electric stimulation aims to stimulate the brain by applying weak electrical currents at the scalp. However, the magnitude and spatial distribution of electric fields in the human brain are unknown. We measured electric potentials intracranially in ten epilepsy patients and estimated electric fields across the entire brain by leveraging calibrated current-flow models. When stimulating at 2 mA, cortical electric fields reach 0.8 V/m, the lower limit of effectiveness in animal studies. When individual whole-head anatomy is considered, the predicted electric field magnitudes correlate with the recorded values in cortical (r = 0.86) and depth (r = 0.88) electrodes. Accurate models require adjustment of tissue conductivity values reported in the literature, but accuracy is not improved when incorporating white matter anisotropy or different skull compartments. This is the first study to validate and calibrate current-flow models with in vivo intracranial recordings in humans, providing a solid foundation to target stimulation and interpret clinical trials. DOI: http://dx.doi.org/10.7554/eLife.18834.001 PMID:28169833

Study on nondestructive inspection using HTS-SQUID for friction stir welding between dissimilar metals

NASA Astrophysics Data System (ADS)

Hatsukade, Y.; Takahashi, T.; Yasui, T.; Tsubaki, M.; Fukumono, M.; Tanaka, S.

2007-10-01

We have developed an SQUID-NDI technique for evaluation of friction stir welding (FSW) between aluminum alloy A6063 and stainless steel SUS304 from the electric conductivities in board specimens bonded by FSW. A SQUID-NDI system employing an HTS-SQUID gradiometer was constructed to measure current distribution in the FSW specimens by applying voltage to the specimen. By measuring field gradients dBz/dy and dBz/dx above the FSW specimens made with various FSW conditions and then converting them to current vector Jx and Jy, conductivities of FSW areas were estimated. Due to the difference in the FSW conditions, the conductivity distributions varied dramatically. From these results, it was suggested that the conductivities in FSW areas should be varied due to the temperature heated by the friction between the milling tool and the materials.

Catalyst containing oxygen transport membrane

DOEpatents

Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

2017-02-07

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Satellite control of electric power distribution

NASA Technical Reports Server (NTRS)

Bergen, L.

1981-01-01

An L-band frequencies satellite link providing the medium for direct control of electrical loads at individual customer sites from remote central locations is described. All loads supplied under interruptible-service contracts are likely condidates for such control, and they can be cycled or switched off to reduce system loads. For every kW of load eliminated or deferred to off-peak hours, the power company reduces its need for additional generating capacity. In addition, the satellite could switch meter registers so that their readings automatically reflected the time of consumption. The system would perform load-shedding operations during emergencies, disconnecting large blocks of load according to predetermined priorities. Among the distribution operations conducted by the satellite in real time would be: load reconfiguration, voltage regulation, fault isolation, and capacitor and feeder load control.

Reconstruction of a piecewise constant conductivity on a polygonal partition via shape optimization in EIT

NASA Astrophysics Data System (ADS)

Beretta, Elena; Micheletti, Stefano; Perotto, Simona; Santacesaria, Matteo

2018-01-01

In this paper, we develop a shape optimization-based algorithm for the electrical impedance tomography (EIT) problem of determining a piecewise constant conductivity on a polygonal partition from boundary measurements. The key tool is to use a distributed shape derivative of a suitable cost functional with respect to movements of the partition. Numerical simulations showing the robustness and accuracy of the method are presented for simulated test cases in two dimensions.

Measurement of effective bulk and contact resistance of gas diffusion layer under inhomogeneous compression - Part I: Electrical conductivity

NASA Astrophysics Data System (ADS)

Vikram, Ajit; Chowdhury, Prabudhya Roy; Phillips, Ryan K.; Hoorfar, Mina

2016-07-01

This paper describes a measurement technique developed for the determination of the effective electrical bulk resistance of the gas diffusion layer (GDL) and the contact resistance distribution at the interface of the GDL and the bipolar plate (BPP). The novelty of this study is the measurement and separation of the bulk and contact resistance under inhomogeneous compression, occurring in an actual fuel cell assembly due to the presence of the channels and ribs on the bipolar plates. The measurement of the electrical contact resistance, contributing to nearly two-third of the ohmic losses in the fuel cell assembly, shows a non-linear distribution along the GDL/BPP interface. The effective bulk resistance of the GDL under inhomogeneous compression showed a decrease of nearly 40% compared to that estimated for homogeneous compression at different compression pressures. Such a decrease in the effective bulk resistance under inhomogeneous compression could be due to the non-uniform distribution of pressure under the ribs and the channels. This measurement technique can be used to identify optimum GDL, BPP and channel-rib structures based on minimum bulk and contact resistances measured under inhomogeneous compression.

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).

Substorm Birkeland currents and Cowling channels in the ionosphere

NASA Astrophysics Data System (ADS)

Fujii, R.

2016-12-01

Field-aligned current (FAC) connects electromagnetically the ionosphere with the magnetosphere and plays important roles on dynamics and energetics in the magnetosphere and the ionosphere. In particular, connections between FACs in the ionosphere give important information on various current sources in the magnetosphere and the linkage between them, although the connection between FACs in the ionosphere does not straightforwardly give that in the magnetosphere. FACs in the ionosphere are closed to each other through ionospheric currents determined with the electric field and the Hall and Pedersen conductivities. The electric field and the conductivities are not independently distributed, but rather they are harmonized with each other spatially and temporarily in a physically consistent manner to give a certain FAC. In particular, the divergence of the Hall current due to the inhomogeneity of the Hall conductivity either flows in/out to the magnetosphere as a secondary FAC or accumulates excess charges that produce a secondary electric field. This electric field drives a current circuit connecting the Hall current with the Pedersen current; a Cowling channel current circuit. The FAC (the electric field) we observe is the sum of the primary and secondary FACs (electric fields). The talk will present characteristics of FACs and associated electric field and auroras during substorms, and the ionospheric current closures between the FACs. A statistical study has shown that the majority of region 1 currents are connected to their adjacent region 2 or region 0 currents, indicating the Pedersen current closure rather than the Hall current closure is dominant. On the other hand, the Pedersen currents associated with surge and substorm-related auroras often are connected to the Hall currents, forming a Cowling channel current circuit within the ionosphere.

Sintering temperature effect on electrical and thermal properties of Zn1-xAlxO as thermoelectric material candidate

NASA Astrophysics Data System (ADS)

Fajarin, Rindang; Rahel, Amelthia; Widyastuti

2018-04-01

Thermoelectric is a device to convert residual heat energy into electricity. Electrical and thermal properties of constituent material determine thermoelectric efficiency. One of metal oxides, namely zinc oxide (ZnO), is highly stable in a large temperature range, non-toxic, low cost and eco-friendly, has potential application as thermoelectric at high temperature. The aims of this study are to synthesize Zn0.98Al0.02O by coprecipitation method using ZnO and Al2O3 powders as raw materials, and to investigate the effect of sintering temperatures (at 700, 800, 900, and 950°C) on the electrical and thermal properties of the material. The sample products were analyzed by x-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive x-ray (EDX) measurements to identify phase content, to observe particle morphology and to analyze distribution of elements in the sample, respectively. LCR meter was conducted to study electrical measurements of the samples. Further, thermal properties of the samples were analyzed by TGA measurements. The data show that Al3+ ions have been successfully doped into ZnO crystal lattice and they tend to increase the electrical conductivity of the samples. The sintered Zn0.98Al0.02O sample at 900°C has the highest conductivity value (4.53 × 10-4 S/m) compared to the others. It is relatively stable at high temperature, and thus, it can be used as one promising candidate for thermoelectric material at high temperature.

Time-Lapse Electrical Geophysical Monitoring of Amendment-Based Biostimulation

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

Johnson, Timothy C.; Versteeg, Roelof; Day-Lewis, Frederick D.

Biostimulation is increasingly used to accelerate microbial remediation of recalcitrant groundwater contaminants. Effective application of biostimulation requires successful emplacement of amendment in the contaminant target zone. Verification of remediation performance requires postemplacement assessment and contaminant monitoring. Sampling based approaches are expensive and provide low-density spatial and temporal information. Time-lapse electrical resistivity tomography (ERT) is an effective geophysical method for determining temporal changes in subsurface electrical conductivity. Because remedial amendments and biostimulation-related biogeochemical processes often change subsurface electrical conductivity, ERT can complement and enhance sampling-based approaches for assessing emplacement and monitoring biostimulation-based remediation. Field studies demonstrating the ability of time-lapse ERTmore » to monitor amendment emplacement and behavior were performed during a biostimulation remediation effort conducted at the Department of Defense Reutilization and Marketing Office (DRMO) Yard, in Brandywine, Maryland, United States. Geochemical fluid sampling was used to calibrate a petrophysical relation in order to predict groundwater indicators of amendment distribution. The petrophysical relations were field validated by comparing predictions to sequestered fluid sample results, thus demonstrating the potential of electrical geophysics for quantitative assessment of amendment-related geochemical properties. Crosshole radar zero-offset profile and borehole geophysical logging were also performed to augment the data set and validate interpretation. In addition to delineating amendment transport in the first 10 months after emplacement, the time-lapse ERT results show later changes in bulk electrical properties interpreted as mineral precipitation. Results support the use of more cost-effective surfacebased ERT in conjunction with limited field sampling to improve spatial and temporal monitoring of amendment emplacement and remediation performance.« less

Time-lapse electrical geophysical monitoring of amendment-based biostimulation

USGS Publications Warehouse

Johnson, Timothy C.; Versteeg, Roelof J.; Day-Lewis, Frederick D.; Major, William; Lane, John W.

2015-01-01

Biostimulation is increasingly used to accelerate microbial remediation of recalcitrant groundwater contaminants. Effective application of biostimulation requires successful emplacement of amendment in the contaminant target zone. Verification of remediation performance requires postemplacement assessment and contaminant monitoring. Sampling-based approaches are expensive and provide low-density spatial and temporal information. Time-lapse electrical resistivity tomography (ERT) is an effective geophysical method for determining temporal changes in subsurface electrical conductivity. Because remedial amendments and biostimulation-related biogeochemical processes often change subsurface electrical conductivity, ERT can complement and enhance sampling-based approaches for assessing emplacement and monitoring biostimulation-based remediation.Field studies demonstrating the ability of time-lapse ERT to monitor amendment emplacement and behavior were performed during a biostimulation remediation effort conducted at the Department of Defense Reutilization and Marketing Office (DRMO) Yard, in Brandywine, Maryland, United States. Geochemical fluid sampling was used to calibrate a petrophysical relation in order to predict groundwater indicators of amendment distribution. The petrophysical relations were field validated by comparing predictions to sequestered fluid sample results, thus demonstrating the potential of electrical geophysics for quantitative assessment of amendment-related geochemical properties. Crosshole radar zero-offset profile and borehole geophysical logging were also performed to augment the data set and validate interpretation.In addition to delineating amendment transport in the first 10 months after emplacement, the time-lapse ERT results show later changes in bulk electrical properties interpreted as mineral precipitation. Results support the use of more cost-effective surface-based ERT in conjunction with limited field sampling to improve spatial and temporal monitoring of amendment emplacement and remediation performance.

Searching for the best thermoelectrics through the optimization of transport distribution function

NASA Astrophysics Data System (ADS)

Fan, Zheyong; Wang, Hui-Qiong; Zheng, Jin-Cheng

2011-04-01

The thermoelectric performance of materials is dependent on the interplay or competition among three key components, the electrical conductivity, thermopower, and thermal conductivity, which can be written as integrals of a single function, the transport distribution function (TDF). Mahan and Sofo [Proc. Natl. Acad. Sci. USA 93, 7436 (1996)] found that, mathematically, the thermoelectric properties could be maximized by a delta-shaped transport distribution, which was associated with a narrow distribution of the energy of the electrons participating in the transport process. In this work, we revisited the shape effect of TDF on thermoelectric figure of merit. It is confirmed both heuristically and numerically that among all the normalized TDF the Dirac delta function leads to the largest thermoelectric figure of merit. Whereas, for the case of TDF being bounded, a rectangular-shape distribution is instead found to be the most favorable one, which could be achieved through nanoroute. Our results also indicate that high thermoelectric figure of merit is associated with appropriate violations of the Wiedemann-Franz law.

Current-induced alternating reversed dual-echo-steady-state for joint estimation of tissue relaxation and electrical properties.

PubMed

Lee, Hyunyeol; Sohn, Chul-Ho; Park, Jaeseok

2017-07-01

To develop a current-induced, alternating reversed dual-echo-steady-state-based magnetic resonance electrical impedance tomography for joint estimation of tissue relaxation and electrical properties. The proposed method reverses the readout gradient configuration of conventional, in which steady-state-free-precession (SSFP)-ECHO is produced earlier than SSFP-free-induction-decay (FID) while alternating current pulses are applied in between the two SSFPs to secure high sensitivity of SSFP-FID to injection current. Additionally, alternating reversed dual-echo-steady-state signals are modulated by employing variable flip angles over two orthogonal injections of current pulses. Ratiometric signal models are analytically constructed, from which T 1 , T 2 , and current-induced B z are jointly estimated by solving a nonlinear inverse problem for conductivity reconstruction. Numerical simulations and experimental studies are performed to investigate the feasibility of the proposed method in estimating relaxation parameters and conductivity. The proposed method, if compared with conventional magnetic resonance electrical impedance tomography, enables rapid data acquisition and simultaneous estimation of T 1 , T 2 , and current-induced B z , yielding a comparable level of signal-to-noise ratio in the parameter estimates while retaining a relative conductivity contrast. We successfully demonstrated the feasibility of the proposed method in jointly estimating tissue relaxation parameters as well as conductivity distributions. It can be a promising, rapid imaging strategy for quantitative conductivity estimation. Magn Reson Med 78:107-120, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

The Charging of Composites in the Space Environment

NASA Technical Reports Server (NTRS)

Czepiela, Steven A.

1997-01-01

Deep dielectric charging and subsequent electrostatic discharge in composite materials used on spacecraft have become greater concerns since composite materials are being used more extensively as main structural components. Deep dielectric charging occurs when high energy particles penetrate and deposit themselves in the insulating material of spacecraft components. These deposited particles induce an electric field in the material, which causes the particles to move and thus changes the electric field. The electric field continues to change until a steady state is reached between the incoming particles from the space environment and the particles moving away due to the electric field. An electrostatic discharge occurs when the electric field is greater than the dielectric strength of the composite material. The goal of the current investigation is to investigate deep dielectric charging in composite materials and ascertain what modifications have to be made to the composite properties to alleviate any breakdown issues. A 1-D model was created. The space environment, which is calculated using the Environmental Workbench software, the composite material properties, and the electric field and voltage boundary conditions are input into the model. The output from the model is the charge density, electric field, and voltage distributions as functions of the depth into the material and time. Analysis using the model show that there should be no deep dielectric charging problem with conductive composites such as carbon fiber/epoxy. With insulating materials such as glass fiber/epoxy, Kevlar, and polymers, there is also no concern of deep dielectric charging problems with average day-to-day particle fluxes. However, problems can arise during geomagnetic substorms and solar particle events where particle flux levels increase by several orders of magnitude, and thus increase the electric field in the material by several orders of magnitude. Therefore, the second part of this investigation was an experimental attempt to measure the continuum electrical properties of a carbon fiber/epoxy composite, and to create a composite with tailorable conductivity without affecting its mechanical properties. The measurement of the conductivity and dielectric strength of carbon fiber/epoxy composites showed that these properties are surface layer dominated and difficult to measure. In the second experimental task, the conductivity of a glass fiber/epoxy composite was increased by 3 orders of magnitude, dielectric constant was increased approximately by a factor of 16, with minimal change to the mechanical properties, by adding conductive carbon black to the epoxy.

Passive safety device and internal short tested method for energy storage cells and systems

DOEpatents

Keyser, Matthew; Darcy, Eric; Long, Dirk; Pesaran, Ahmad

2015-09-22

A passive safety device for an energy storage cell for positioning between two electrically conductive layers of the energy storage cell. The safety device also comprising a separator and a non-conductive layer. A first electrically conductive material is provided on the non-conductive layer. A first opening is formed through the separator between the first electrically conductive material and one of the electrically conductive layers of the energy storage device. A second electrically conductive material is provided adjacent the first electrically conductive material on the non-conductive layer, wherein a space is formed on the non-conductive layer between the first and second electrically conductive materials. A second opening is formed through the non-conductive layer between the second electrically conductive material and another of the electrically conductive layers of the energy storage device. The first and second electrically conductive materials combine and exit at least partially through the first and second openings to connect the two electrically conductive layers of the energy storage device at a predetermined temperature.

DC breakdown characteristics of silicone polymer composites for HVDC insulator applications

NASA Astrophysics Data System (ADS)

Han, Byung-Jo; Seo, In-Jin; Seong, Jae-Kyu; Hwang, Young-Ho; Yang, Hai-Won

2015-11-01

Critical components for HVDC transmission systems are polymer insulators, which have stricter requirements that are more difficult to achieve compared to those of HVAC insulators. In this study, we investigated the optimal design of HVDC polymer insulators by using a DC electric field analysis and experiments. The physical properties of the polymer specimens were analyzed to develop an optimal HVDC polymer material, and four polymer specimens were prepared for DC breakdown experiments. Single and reverse polarity breakdown tests were conducted to analyze the effect of temperature on the breakdown strength of the polymer. In addition, electric fields were analyzed via simulations, in which a small-scale polymer insulator model was applied to prevent dielectric breakdown due to electric field concentration, with four DC operating conditions taken into consideration. The experimental results show that the electrical breakdown strength and the electric field distribution exhibit significant differences in relation to different DC polarity transition procedures.

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.

Influence of propellant choice on MPD arcjet cathode surface current density distribution

NASA Astrophysics Data System (ADS)

Sheshadri, T. S.

1989-10-01

The radial current density on an MPD arcjet cathode surface is theoretically investigated for five propellants. It is found that excessive current concentration at the upstream end of the cathode occurs in the case of hydrogen. This undesirable effect is traced to the higher electrical conductivity of hydrogen plasma.

The electric field distributions in anatomical head models during transcranial direct current stimulation for post-stroke rehabilitation.

PubMed

Manoli, Zoi; Parazzini, Marta; Ravazzani, Paolo; Samaras, Theodoros

2017-01-01

The lack of knowledge of the electric field distribution inside the brain of stroke patients receiving transcranial direct current stimulation (tDCS) calls for estimating it computationally. Moreover, the impact on this distribution of a novel clinical management approach which involves secondary motor areas (SMA) in stroke rehabilitation needs to be evaluated. Finally, the differences in the electric field distributions due to gender and age need to be investigated. This work presents the development of two different anatomical models (young adult female and elderly male) with an ischemic stroke region of spherical volume 10 cm 3 or 50 cm 3 , using numerical models of the Virtual Population (ViP). The stroke phase was considered as acute or chronic, resulting in different electrical properties of the area. Two different electrode montages were used - One over the lesion area and the contralateral supra-orbital region and the other over the SMA and the contralateral supra-orbital region. A quasi-electrostatic solver was used to numerically solve the Laplace equation with the finite-difference technique. Both the 99th percentile of the electric field intensity distribution ("E peak value") and the percentage of the tissue volumes with electric field intensity over 50% and 70% of the E peak value were assessed inside the target areas of the primary motor cortex (M1) and the SMA, as well as in other brain tissues (hypothalamus and cerebellum). In the acute phase of an ischemic stroke, the normalized electric field intensity distributions do not differ noticeably compared to those in the brain of a healthy person (mean square difference < 2%). The difference becomes larger (up to 4.5%) for the chronic phase of a large ischemic lesion. Moreover, the maximum values of the induced electric field in the tissues in the SMA are almost equal for both electrode montages. The peak values of the electric field distribution ("E peak values") in cerebellum and hypothalamus for both electrode montages are rather small but different from those of healthy patients. The largest difference of 21% decrease with respect to a healthy subject was noticed in the elder adult model with a large chronic lesion. The comparison of the different electrode montages shows that the use of a stimulating electrode over the affected area creates larger values of the electric field in M1, by up to 26% for a small chronic lesion in the young female model. On the contrary, the montage does not affect considerably (change less than 8%) the E peak values in the SMA. This implies that for exciting M1, the M1-Fp2 montage should be favored. The presence and the phase of an ischemic stroke lesion, as well as the configuration of electrode montages affect the distribution and the maximum value of the electric field induced in tissues. Moreover, patients whom seem to benefit most from tDCS are those in the chronic phase of an ischemic stroke, since contrasts in the tissue conductivity result in a higher electric field induced around the lesion volume, which could stimulate the remaining healthy tissue in the area. © 2016 American Association of Physicists in Medicine.

Runoff generation in karst catchments: multifractal analysis

NASA Astrophysics Data System (ADS)

Majone, Bruno; Bellin, Alberto; Borsato, Andrea

2004-07-01

Time series of hydrological and geochemical signals at two karst springs, located in the Dolomiti del Brenta region, near Trento, Italy, are used to infer how karst catchments work internally to generate runoff. The data analyzed include precipitation, spring flow and electric conductivity of the spring water. All the signals show the signature of multifractality but with different intermittency and non-stationarity. In particular, precipitation and spring flow are shown to have nearly the same degree of non-stationarity and intermittency, while electric conductivity, which mimics the travel time distribution of water in the karst system, is less intermittent and smoother than both spring flow and precipitations. We found that spring flow can be obtained from precipitation through fractional convolution with a power law transfer function. An important result of our study is that the probability distribution of travel times is inconsistent with the advection dispersion equation, while it supports the anomalous transport model. This result is in line with what was observed by Painter et al. [Geophys. Res. Lett. 29 (2002) 21.1] for transport in fractured rocks.

Temperature and composition dependent density of states extracted using overlapping large polaron tunnelling model in MnxCo1-xFe2O4 (x=0.25, 0.5, 0.75) nanoparticles

NASA Astrophysics Data System (ADS)

Jamil, Arifa; Afsar, M. F.; Sher, F.; Rafiq, M. A.

2017-03-01

We report detailed ac electrical and structural characterization of manganese cobalt ferrite nanoparticles, prepared by coprecipitation technique. X-ray diffraction (XRD) confirmed single-phase cubic spinel structure of the nanoparticles. Tetrahedral (A) and octahedral (B) group complexes were present in the spinel lattice as determined by Fourier Transform Infrared Spectroscopy (FTIR). Scanning Electron Microscope (SEM) images revealed presence of spherical shape nanoparticles having an average diameter 50-80 nm. Composition, temperature and frequency dependent ac electrical study of prepared nanoparticles interpreted the role of cationic distribution between A and B sites. Overlapping large polaron tunnelling (OLPT) conduction mechanism was observed from 290 to 200 K. Frequency exponent s was fitted theoretically using OLPT model. High values of Density of States (DOS) of the order of 1022-1024 eV-1 cm-3 were extracted from ac conductivity for different compositions. We found that DOS was dependent on distribution of cations in the tunnel-type cavities along the a and b axis.

CSI-EPT in Presence of RF-Shield for MR-Coils.

PubMed

Arduino, Alessandro; Zilberti, Luca; Chiampi, Mario; Bottauscio, Oriano

2017-07-01

Contrast source inversion electric properties tomography (CSI-EPT) is a recently developed technique for the electric properties tomography that recovers the electric properties distribution starting from measurements performed by magnetic resonance imaging scanners. This method is an optimal control approach based on the contrast source inversion technique, which distinguishes itself from other electric properties tomography techniques for its capability to recover also the local specific absorption rate distribution, essential for online dosimetry. Up to now, CSI-EPT has only been described in terms of integral equations, limiting its applicability to homogeneous unbounded background. In order to extend the method to the presence of a shield in the domain-as in the recurring case of shielded radio frequency coils-a more general formulation of CSI-EPT, based on a functional viewpoint, is introduced here. Two different implementations of CSI-EPT are proposed for a 2-D transverse magnetic model problem, one dealing with an unbounded domain and one considering the presence of a perfectly conductive shield. The two implementations are applied on the same virtual measurements obtained by numerically simulating a shielded radio frequency coil. The results are compared in terms of both electric properties recovery and local specific absorption rate estimate, in order to investigate the requirement of an accurate modeling of the underlying physical problem.

Investigations of microwave plasmas - Applications in electrothermal thruster systems

NASA Technical Reports Server (NTRS)

Haraburda, Scott S.; Hawley, Martin C.

1989-01-01

Experimental studies which have been conducted to develop understanding of plasma processes used for spacecraft propulsion are reviewed. The techniques discussed are calorimetry and volume measurements using the TM 011 and TM 012 modes in the microwave cavity system. The use of plasmas in electrical propulsion and microwave induction is reviewed. Plasma containment, microwave power production, energy distribution, and the pressure and flow dependence of the energy distribution are addressed. The plasma dimensions and their dependence on pressure, flow, and power are considered.

Investigations of microwave plasmas - Applications in electrothermal thruster systems

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

Haraburda, S.S.; Hawley, M.C.

1989-01-01

Experimental studies which have been conducted to develop understanding of plasma processes used for spacecraft propulsion are reviewed. The techniques discussed are calorimetry and volume measurements using the TM 011 and TM 012 modes in the microwave cavity system. The use of plasmas in electrical propulsion and microwave induction is reviewed. Plasma containment, microwave power production, energy distribution, and the pressure and flow dependence of the energy distribution are addressed. The plasma dimensions and their dependence on pressure, flow, and power are considered. 10 refs.

Electromagnetic Fields of a Uniform Sphere in a Uniform Conducting Medium with Application to Dipole Sources

DTIC Science & Technology

1991-09-01

12b. DISTRIBUTION CODE Approved for public release; distribution is unlimited. 13. ABSTRACT (Maximum 200 words) Vector spherical harmonic expansions are...electric and magnetic field vectors from E rand B - r alone. Genural expressions are given relating the scattered field expansion coefficients to the source...Prescnbed by ANSI Std. Z39-18 29W-102 NCSC TR 426-90 CONTENTS Pag o INTRODUCTION 1 BACKGROUND 1 ANGULAR MOMENTUM OPERATOR AND VECTOR SPHERICAL

Characterizing root system characteristics with Electrical resistivity Tomography: a virtual rhizotron simulation

NASA Astrophysics Data System (ADS)

Rao, Sathyanarayan; Ehosioke, Solomon; Lesparre, Nolwenn; Nguyen, Frédéric; Javaux, Mathieu

2017-04-01

Electrical Resistivity Tomography (ERT) is more and more used for monitoring soil water content in a cropped soil. Yet, the impact of roots on the signal is often neglected and a topic of controversy. In several studies related to soil-root system, it has been showed that the measured root mass density statistically correlates with the electrical conductivity (EC) data obtained from ERT. In addition, some studies suggest that some roots are more electrically conductive than soil for most water content. Thus, higher EC of roots suggest that it might have a measurable impact on ERT signals. In this work, virtual rhizotrons are simulated using the software package called R-SWMS that solves water and solute transport in plant root-soil system, including root growth. The distribution of water content obtained from R-SWMS simulation is converted into EC data using pedo-physical models. The electrical properties of roots and rhizosphere are explicitly included in the EC data to form a conductivity map (CM) with a very detailed spatial resolution. Forward ERT simulations is then carried out for CM generated for various root architectures and soil conditions to study the impact of roots on ERT forward (current and voltage patterns) and inverse solutions. It is demonstrated that under typical injection schemes with lateral electrodes, root system is hardly measurable. However, it is showed that adding electrodes and constraints on the ERT inversion based on root architecture help quantifying root system mass and extent.

Fluid Distribution in Synthetic Wet Halite Rocks : Inference from Measured Elastic Wave Velocity and Electrical Conductivity

NASA Astrophysics Data System (ADS)

Watanabe, T.; Kitano, M.

2011-12-01

Intercrystalline fluid can significantly affect rheological and transport properties of rocks. Its influences are strongly dependent on its distribution. The dihedral angle between solid and liquid phases has been widely accepted as a key parameter that controls solid-liquid textures. The liquid phase is not expected to be interconnected if the dihedral angle is larger than 60 degree. However, observations contradictory to dihedral angle values have been reported. Watanabe (2010) suggested the coexistence of grain boundary fluid with a positive dihedral angle. For good understanding of fluid distribution, it is thus critical to study the nature of grain boundary fluid. We have developed a high pressure and temperature apparatus for study of intercrystalline fluid distribution. It was specially designed for measurements of elastic wave velocities and electrical conductivity. The apparatus mainly consists of a conventional cold-seal vessel with an external heater. The pressure medium is silicon oil of the viscosity of 0.1 Pa s. The pressure and temperature can be controlled from 0 to 200 MPa and from 20 to 200 C, respectively. Dimensions of a sample are 9 mm in diameter, and 15 mm in length. Halite-water system is used as an analog for crustal rocks. The dihedral angle has been studied systematically at various pressure and temperature conditions [Lewis and Holness, 1996]. The dihedral angle is larger than 60 degree at lower pressure and temperature. It decreases to be smaller than 60 degree with increasing pressure and temperature. A sample is prepared by cold-pressing and annealing of wet NaCl powder. Optical examination has shown that synthesized samples are microstructurally homogeneous. Grains are polygonal and equidimensional with a mean diameter of 100 micrometer. Grain boundaries vary from straight to bowed and 120 degree triple junctions are common. Gas and fluid bearing inclusions are visible on the grain boundaries. There are spherical inclusions or isolated worm-like channels. In this presentation, we will report preliminary results of compressional wave velocity and electrical conductivity measurements.

Nano silver diffusion behaviour on conductive polymer during doping process for high voltage application

NASA Astrophysics Data System (ADS)

Mohammad, A.; Mahmood, A.; Chin, K. T.; Danquah, M. K.; van Stratan, S.

2017-06-01

Conductive polymer had opened a new era of engineering for microelectronics and semiconductor applications. However, it is still a challenge for high voltage applications due to lower electrical conductivity compare to metals. This results tremendous energy losses during transmission and restricts its usage. In order to address such problem a novel method was investigated using nano silver particle doped iodothiophene since silver is the highest electrical conductive material. The experiments were carried out to study the organometallic diffusion behaviour of nanosilver doped iodothiophene with different concentration of iodothiophene. Five different mixing ratio between nanosilver and the solution of iodothiophene dissolved in diethyl ether were used which are 1:1.25, 1:1.5, 1:2.5, 1:3 and l:5. It was revealed that there is an effective threshold concentration of which the nano silver evenly distributed and there was no coagulation observed. These parameters laid the foundation of better doping process between the nano silver and the polymer significantly which would contribute developing conductive polymer towards high voltage application for industries that are vulnerable to corrosive environment.

Economic analysis of biomass power generation schemes under renewable energy initiative with Renewable Portfolio Standards (RPS) in Korea.

PubMed

Moon, Ji-Hong; Lee, Jeung-Woo; Lee, Uen-Do

2011-10-01

An economic analysis of biomass power generation was conducted. Two key technologies--direct combustion with a steam turbine and gasification with a syngas engine--were mainly examined. In view of the present domestic biomass infrastructure of Korea, a small and distributed power generation system ranging from 0.5 to 5 MW(e) was considered. It was found that gasification with a syngas engine becomes more economically feasible as the plant size decreases. Changes in the economic feasibilities with and without RPS or heat sales were also investigated. A sensitivity analysis of each system was conducted for representative parameters. Regarding the cost of electricity generation, electrical efficiency and fuel cost significantly affect both direct combustion and gasification systems. Regarding the internal rate of return (IRR), the heat sales price becomes important for obtaining a higher IRR, followed by power generation capacity and electrical efficiency. Copyright © 2011 Elsevier Ltd. All rights reserved.

Polypyrrole-MWCNT-Ag composites for electromagnetic shielding: Comparison between chemical deposition and UV-reduction approaches

NASA Astrophysics Data System (ADS)

Ebrahimi, Izadyar; Gashti, Mazeyar Parvinzadeh

2018-07-01

In this study, we focused on the synthesis of polypyrrole-MWCNT-Ag composites and we evaluated their electrical properties to determine the electromagnetic interference shielding performance. We reduced silver nanoparticles in composites using two different in situ methods: UV-reduction and chemical deposition. Composites were characterized using spectroscopic and microscopic tools for evaluation of the chemical, morphological, electrical conductivity and electromagnetic shielding effectiveness. Results from Fourier transform infrared spectroscopy and dispersive Raman microscope showed chemical interactions between silver and the polypyrrole-MWCNT composite due to the charge-transfer within the structure. X-ray diffraction confirmed appearance of two new peaks for silver nanoparticles embedded in polypyrrole-MWCNT independent to reduction method. According to microscopy images, silver nanoparticles were homogenously distributed at the PPy-MWCNTs interfaces by UV reduction, while, chemical reduction resulted to deposition of silver within the PPy matrix. Finally, our results revealed that the polypyrrole-MWCNT-Ag composite produced via UV-reduction has higher electrical conductivity and shielding effectiveness in comparison to chemically reduced one.

Investigation of dust transport on the lunar surface in laboratory plasmas

NASA Astrophysics Data System (ADS)

Wang, X.; Horanyi, M.; Robertson, S. H.

2009-12-01

There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. To learn about the basic physical process, we investigated the dynamics of dust grains on a conducting surface in laboratory plasmas. The first experiment was conducted with a dust pile (JSC-Mars-1) sitting on a negatively biased surface in plasma. The dust pile spread and formed a diffusing dust ring. Dust hopping was confirmed by noticing grains on protruding surfaces. The electrostatic potential distributions measured above the dust pile show an outward pointing electrostatic force and a non-monotonic sheath above the dust pile, indicating a localized upward electrostatic force responsible for lifting dust off the surface. The second experiment was conducted with a dust pile sitting on an electrically floating conducting surface in plasma with an electron beam. Potential measurements show a horizontal electric field at the dust/surface boundary and an enhanced vertical electric field in the sheath above the dust pile when the electron beam current is set to be comparable to the Bohm ion current. Secondary electrons emitted from the surfaces play an important role in this case.

Simulation Study to Improve Focalization of a Figure Eight Coil by Using a Conductive Shield Plate and a Ferromagnetic Block.

PubMed

Zhao, Chen; Zhang, Shunqi; Liu, Zhipeng; Yin, Tao

2015-07-01

A new method to improve the focalization and efficiency of the Figure of Eight (FOE) coil in rTMS is discussed in this paper. In order to decrease the half width of the distribution curve (HWDC), as well to increase the ratio of positive peak value to negative peak value (RPN) of the induced electric field, a shield plate with a window and a ferromagnetic block are assumed to enhance the positive peak value of the induced electrical field. The shield is made of highly conductive copper, and the block is made of highly permeable soft magnetic ferrite. A computer simulation is conducted on ANSYS® software to conduct the finite element analysis (FEA). Two comparing coefficients were set up to optimize the sizes of the shield window and the block. Simulation results show that a shield with a 60 mm × 30 mm sized window, together with a block 40 mm thick, can decrease the focal area of a FOE coil by 46.7%, while increasing the RPN by 135.9%. The block enhances the peak value of the electrical field induced by a shield-FOE by 8.4%. A real human head model was occupied in this paper to further verify our method.

Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Sadeghi, Arman

2017-06-01

Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well as to validate the analytical solutions. We show that, with the exception of the migratory ionic conductivity, all the physicochemical parameters are strong functions of the channel aspect ratio. Accordingly, a slit geometry is not a good representative of a rectangular channel when the width is comparable to the height. It is also observed that the distribution of the electrical potential is not uniform over the surface of a charge-regulated channel. In addition, unlike ordinary channels for which an increase in the background salt concentration is always accompanied by higher flow rates, quite the opposite may be true for a pH-regulated duct at higher salt concentrations.

Downhole transmission system

DOEpatents

Hall, David R [Provo, UT; Fox, Joe [Spanish Fork, UT

2008-01-15

A transmission system in a downhole component comprises a data transmission element in both ends of the downhole component. Each data transmission element houses an electrically conducting coil in a MCEI circular trough. An electrical conductor connects both the transmission elements. The electrical conductor comprises at least three electrically conductive elements insulated from each other. In the preferred embodiment the electrical conductor comprises an electrically conducting outer shield, an electrically conducting inner shield and an electrical conducting core. In some embodiments of the present invention, the electrical conductor comprises an electrically insulating jacket. In other embodiments, the electrical conductor comprises a pair of twisted wires. In some embodiments, the electrical conductor comprises semi-conductive material.

The influence of reduced graphene oxide on electrical conductivity of LiFePO{sub 4}-based composite as cathode material

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

Arifin, Muhammad; Aimon, Akfiny Hasdi; Winata, Toto

2016-02-08

LiFePO{sub 4} is fascinating cathode active materials for Li-ion batteries application because of their high electrochemical performance such as a stable voltage at 3.45 V and high specific capacity at 170 mAh.g{sup −1}. However, their low intrinsic electronic conductivity and low ionic diffusion are still the hindrance for their further application on Li-ion batteries. Therefore, the efforts to improve their conductivity are very important to elevate their prospecting application as cathode materials. Herein, we reported preparation of additional of reduced Graphene Oxide (rGO) into LiFePO{sub 4}-based composite via hydrothermal method and the influence of rGO on electrical conductivity of LiFePO{sub 4}−basedmore » composite by varying mass of rGO in composition. Vibration of LiFePO{sub 4}-based composite was detected on Fourier Transform Infrared Spectroscopy (FTIR) spectra, while single phase of LiFePO{sub 4} nanocrystal was observed on X-Ray Diffraction (XRD) pattern, it furthermore, Scanning Electron Microscopy (SEM) images showed that rGO was distributed around LiFePO4-based composite. Finally, the 4-point probe measurement result confirmed that the optimum electrical conductivity is in additional 2 wt% rGO for range 1 to 2 wt% rGO.« less

Motion of Doped-Polymer-Cholesteric Liquid Crystal Flakes in a Direct-Current Electric Field

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

Trajkovska Petkoska, A.; Kosc, T.Z.; Marshall, K.L.

The behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in silicone oil host fluids has been explored in the presence of a direct-current electric field. In addition to “neat” (undoped) flakes, the PCLC material was doped with either conductive, carbon-based particles or highly dielectric inorganic particles to modify the dielectric properties of the resulting PCLC flakes. Doping with conductive particles produced flakes with a net charge, and they exhibited either translational or rotational motion depending on both the distribution of dopant within the flake and the dielectric characteristics of the host fluid. Flakes doped with titania (TiO2) particles reorientedmore » 90º when suspended in a host fluid with a differing dielectric permittivity« less

Electrocution

USGS Publications Warehouse

Thomas, N.J.

1999-01-01

Power lines and power poles present a potential electrocution hazard to wild birds. Many birds, especially raptors, select power poles for perching, and, sometimes, for nesting (Figs. 50.1–3). If a bird’s appendages bridge the gap between two energized parts or between an energized and a grounded metal part, electricity flows through the “bridge” that is filling the gap and the bird is electrocuted. Most commonly, birds are electrocuted where conducting wires (conductors) are placed closer together than the wingspan of birds that frequent the poles (Fig. 50.2). Feathers are poor electrical conductors, but if contact is made between points on the skin, talons, or beak, or if the feathers are wet, conduction can occur. Common anatomical sites of contact include conduction between the wrists of each wing or between the skin of one wing and a foot or leg. The resulting shock causes severe, usually fatal, cardiovascular injury. Because conductors on distribution lines are placed closer together than high voltage transmission lines, birds are more frequently electrocuted on distribution lines despite their lower voltage. In addition to one to three conductors, power poles may also carry ground wires, transformers, or grounded metal crossarm braces. Complicated wiring configurations that put multiple energized and grounded metal parts near attractive perching or nesting sites are the most hazardous configurations (Fig. 50.3).

Visualizing Simulated Electrical Fields from Electroencephalography and Transcranial Electric Brain Stimulation: A Comparative Evaluation

PubMed Central

Eichelbaum, Sebastian; Dannhauer, Moritz; Hlawitschka, Mario; Brooks, Dana; Knösche, Thomas R.; Scheuermann, Gerik

2014-01-01

Electrical activity of neuronal populations is a crucial aspect of brain activity. This activity is not measured directly but recorded as electrical potential changes using head surface electrodes (electroencephalogram - EEG). Head surface electrodes can also be deployed to inject electrical currents in order to modulate brain activity (transcranial electric stimulation techniques) for therapeutic and neuroscientific purposes. In electroencephalography and noninvasive electric brain stimulation, electrical fields mediate between electrical signal sources and regions of interest (ROI). These fields can be very complicated in structure, and are influenced in a complex way by the conductivity profile of the human head. Visualization techniques play a central role to grasp the nature of those fields because such techniques allow for an effective conveyance of complex data and enable quick qualitative and quantitative assessments. The examination of volume conduction effects of particular head model parameterizations (e.g., skull thickness and layering), of brain anomalies (e.g., holes in the skull, tumors), location and extent of active brain areas (e.g., high concentrations of current densities) and around current injecting electrodes can be investigated using visualization. Here, we evaluate a number of widely used visualization techniques, based on either the potential distribution or on the current-flow. In particular, we focus on the extractability of quantitative and qualitative information from the obtained images, their effective integration of anatomical context information, and their interaction. We present illustrative examples from clinically and neuroscientifically relevant cases and discuss the pros and cons of the various visualization techniques. PMID:24821532

The electrical structure of lithosphere beneath Northeast China —Preliminary results from SinoProbe-01-04

NASA Astrophysics Data System (ADS)

Hui, F.; Qing, Z.; Gengen, Q.; Fagen, P.; Dawei, B.; Baotun, G.; Jingqi, L.; Changwang, L.; Xiaochang, L.; Meixing, H.; Bingrui, D.

2012-12-01

Being constituted by the Seberia, Northern China fossil plate and Pacific Plate, the tectonics of Northeast China are very complicated. In order to study the electrical structure in these areas, the project SinoProbe-01-04 'Experimental study of 'standard monitoring network' of continental EM parameters in Northeast China' have established a 4°×4°regional MT array covering the whole Northeast China(Fig. 1). To make sure that MT data observed on each standard point representatively, a cross profile with the standard point being center and eight auxiliary measuring points around has been designed in practical work, and the same direction of the physical measuring point should have 20 km space, the observation time should be more than 120 hours in standard point and more than 24 hours in each auxiliary station. Both broadband MT equipment (V5-2000) and long-period MT equipment (LEMI-417M) have been used together in standard point, then the ultra-wideband electromagnetic signals at 320HZ-1/10000Hz can be acquired by combining the field data observed by each equipment. Eleven MT standard network control point with total 99 physical measuring points have been finished in 2010, then those works were repeated again in 2011 to make sure observed result reliable. Based on the observed result, this article preliminary analysis the electrical structure of each major tectonic element in Northeast China, which including the regularity of distribution of regional electrical spindle, the distribution characteristics of vertical conductivity, development status of the low resistivity layer in the crust, and the depth of the high conductivity layer in upper mantle. It has been founded that the electrical features of the major tectonic element in Northeast China are different and appear electrical-heterogeneous in cross direction. Fig.1 MT array observed site

Mapping soil salinity and a fresh-water intrusion in three-dimensions using a quasi-3d joint-inversion of DUALEM-421S and EM34 data

NASA Astrophysics Data System (ADS)

Zare, Ehsan; Huang, Jingyi; Koganti, Triven; Triantafilis, John

2017-04-01

In order to understand the drivers of topsoil salinization, the distribution and movement of salt in accordance with groundwater need mapping. In this study, we described a method to map the distribution of soil salinity, as measured by the electrical conductivity of a saturated soil-paste extract (ECe), and in 3-dimensions around a water storage reservoir in an irrigated field near Bourke, New South Wales, Australia. A quasi-3d electromagnetic conductivity image (EMCI) or model of the true electrical conductivity (sigma) was developed using 133 apparent electrical conductivity (ECa) measurements collected on a 50 m grid and using various coil arrays of DUALEM-421S and EM34 instruments. For the DUALEM-421S we considered ECa in horizontal coplanar (i.e., 1 mPcon, 2 mPcon and 4 mPcon) and vertical coplanar (i.e., 1 mHcon, 2 mHcon and 4 mHcon) arrays. For the EM34, three measurements in the horizontal mode (i.e., EM34-10H, EM34-20H and EM34-40H) were considered. We estimated σ using a quasi-3d joint-inversion algorithm (EM4Soil). The best correlation (R2 = 0.92) between σ and measured soil ECe was identified when a forward modelling (FS), inversion algorithm (S2) and damping factor (lambda = 0.2) were used and using both DUALEM-421 and EM34 data; but not including the 4 m coil arrays of the DUALEM-421S. A linear regression calibration model was used to predict ECe in 3-dimensions beneath the study field. The predicted ECe was consistent with previous studies and revealed the distribution of ECe and helped to infer a freshwater intrusion from a water storage reservoir at depth and as a function of its proximity to near-surface prior stream channels and buried paleochannels. It was concluded that this method can be applied elsewhere to map the soil salinity and water movement and provide guidance for improved land management.|

Mapping soil salinity and a fresh-water intrusion in three-dimensions using a quasi-3d joint-inversion of DUALEM-421S and EM34 data.

PubMed

Huang, J; Koganti, T; Santos, F A Monteiro; Triantafilis, J

2017-01-15

In order to understand the drivers of topsoil salinization, the distribution and movement of salt in accordance with groundwater need mapping. In this study, we described a method to map the distribution of soil salinity, as measured by the electrical conductivity of a saturated soil-paste extract (EC e ), and in 3-dimensions around a water storage reservoir in an irrigated field near Bourke, New South Wales, Australia. A quasi-3d electromagnetic conductivity image (EMCI) or model of the true electrical conductivity (σ) was developed using 133 apparent electrical conductivity (EC a ) measurements collected on a 50m grid and using various coil arrays of DUALEM-421S and EM34 instruments. For the DUALEM-421S we considered EC a in horizontal coplanar (i.e., 1mPcon, 2mPcon and 4mPcon) and vertical coplanar (i.e., 1mHcon, 2mHcon and 4mHcon) arrays. For the EM34, three measurements in the horizontal mode (i.e., EM34-10H, EM34-20H and EM34-40H) were considered. We estimated σ using a quasi-3d joint-inversion algorithm (EM4Soil). The best correlation (R 2 =0.92) between σ and measured soil EC e was identified when a forward modelling (FS), inversion algorithm (S2) and damping factor (λ=0.2) were used and using both DUALEM-421 and EM34 data; but not including the 4m coil arrays of the DUALEM-421S. A linear regression calibration model was used to predict EC e in 3-dimensions beneath the study field. The predicted EC e was consistent with previous studies and revealed the distribution of EC e and helped to infer a freshwater intrusion from a water storage reservoir at depth and as a function of its proximity to near-surface prior stream channels and buried paleochannels. It was concluded that this method can be applied elsewhere to map the soil salinity and water movement and provide guidance for improved land management. Copyright © 2016 Elsevier B.V. All rights reserved.

Super-sensing technology: industrial applications and future challenges of electrical tomography.

PubMed

Wei, Kent Hsin-Yu; Qiu, Chang-Hua; Primrose, Ken

2016-06-28

Electrical tomography is a relatively new imaging technique that can image the distribution of the passive electrical properties of an object. Since electrical tomography technology was proposed in the 1980s, the technique has evolved rapidly because of its low cost, easy scale-up and non-invasive features. The technique itself can be sensitive to all passive electrical properties, such as conductivity, permittivity and permeability. Hence, it has a huge potential to be applied in many applications. Owing to its ill-posed nature and low image resolution, electrical tomography attracts more attention in industrial fields than biomedical fields. In the past decades, there have been many research developments and industrial implementations of electrical tomography; nevertheless, the awareness of this technology in industrial sectors is still one of the biggest limitations for technology implementation. In this paper, the authors have summarized several representative applications that use electrical tomography. Some of the current tomography research activities will also be discussed. This article is part of the themed issue 'Supersensing through industrial process tomography'. © 2016 The Author(s).

Solar-terrestrial coupling through atmospheric electricity

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

Interaction of excitable waves emitted from two defects by pulsed electric fields

NASA Astrophysics Data System (ADS)

Chen, Jiang-Xing; Zhang, Han; Qiao, Li-Yan; Liang, Hong; Sun, Wei-Gang

2018-01-01

In response to a pulsed electric field, spatial distributed heterogeneities in excitable media can serve as nucleation sites for the generation of intramural electrical waves, a phenomenon called as ;wave emission from heterogeneities; (WEH effect). Heterogeneities in cardiac tissue strongly influence each other in the WEH effect. We study the WEH effect in a medium possessing two defects. The role of two defects and their interaction by pulsed DC electric fields (DEF) and rotating electric fields (REF) are investigated. The direction of the applied electric field plays a major role not only in the minimum electrical field necessary to originate wave propagation, but also in the degree of influences of nearby defects. The distance between two defects, i.e. the density of defects, also play an important role in the WEH effect. Generally, the REF is better than the DEF when pulsed electric fields are applied. These results may contribute to the improved application of WEH, especially in older patients with fibrosis and scarring, which are accompanied by a higher incidence of conductivity discontinuities.

In-Situ Wire Damage Detection System

NASA Technical Reports Server (NTRS)

Jolley, Scott T. (Inventor); Gibson, Tracy L. (Inventor); Medelius, Pedro J. (Inventor); Roberson, Luke B. (Inventor); Tate, Lanetra C. (Inventor); Smith, Trent M. (Inventor); Williams, Martha K. (Inventor)

2014-01-01

An in-situ system for detecting damage in an electrically conductive wire. The system includes a substrate at least partially covered by a layer of electrically conductive material forming a continuous or non-continuous electrically conductive layer connected to an electrical signal generator adapted to delivering electrical signals to the electrically conductive layer. Data is received and processed to identify damage to the substrate or electrically conductive layer. The electrically conductive material may include metalized carbon fibers, a thin metal coating, a conductive polymer, carbon nanotubes, metal nanoparticles or a combination thereof.

The behavior of plasma with an arbitrary degree of degeneracy of electron gas in the conductive layer

NASA Astrophysics Data System (ADS)

Latyshev, A. V.; Gordeeva, N. M.

2017-09-01

We obtain an analytic solution of the boundary problem for the behavior (fluctuations) of an electron plasma with an arbitrary degree of degeneracy of the electron gas in the conductive layer in an external electric field. We use the kinetic Vlasov-Boltzmann equation with the Bhatnagar-Gross-Krook collision integral and the Maxwell equation for the electric field. We use the mirror boundary conditions for the reflections of electrons from the layer boundary. The boundary problem reduces to a one-dimensional problem with a single velocity. For this, we use the method of consecutive approximations, linearization of the equations with respect to the absolute distribution of the Fermi-Dirac electrons, and the conservation law for the number of particles. Separation of variables then helps reduce the problem equations to a characteristic system of equations. In the space of generalized functions, we find the eigensolutions of the initial system, which correspond to the continuous spectrum (Van Kampen mode). Solving the dispersion equation, we then find the eigensolutions corresponding to the adjoint and discrete spectra (Drude and Debye modes). We then construct the general solution of the boundary problem by decomposing it into the eigensolutions. The coefficients of the decomposition are given by the boundary conditions. This allows obtaining the decompositions of the distribution function and the electric field in explicit form.

Improving water content estimation on landslide-prone hillslopes using structurally-constrained inversion of electrical resistivity data

NASA Astrophysics Data System (ADS)

Heinze, Thomas; Möhring, Simon; Budler, Jasmin; Weigand, Maximilian; Kemna, Andreas

2017-04-01

Rainfall-triggered landslides are a latent danger in almost any place of the world. Due to climate change heavy rainfalls might occur more often, increasing the risk of landslides. With pore pressure as mechanical trigger, knowledge of water content distribution in the ground is essential for hazard analysis during monitoring of potentially dangerous rainfall events. Geophysical methods like electrical resistivity tomography (ERT) can be utilized to determine the spatial distribution of water content using established soil physical relationships between bulk electrical resistivity and water content. However, often more dominant electrical contrasts due to lithological structures outplay these hydraulic signatures and blur the results in the inversion process. Additionally, the inversion of ERT data requires further constraints. In the standard Occam inversion method, a smoothness constraint is used, assuming that soil properties change softly in space. This applies in many scenarios, as for example during infiltration of water without a clear saturation front. Sharp lithological layers with strongly divergent hydrological parameters, as often found in landslide prone hillslopes, on the other hand, are typically badly resolved by standard ERT. We use a structurally constrained ERT inversion approach for improving water content estimation in landslide prone hills by including a-priori information about lithological layers. Here the standard smoothness constraint is reduced along layer boundaries identified using seismic data or other additional sources. This approach significantly improves water content estimations, because in landslide prone hills often a layer of rather high hydraulic conductivity is followed by a hydraulic barrier like clay-rich soil, causing higher pore pressures. One saturated layer and one almost drained layer typically result also in a sharp contrast in electrical resistivity, assuming that surface conductivity of the soil does not change in similar order. Using synthetic data, we study the influence of uncertainties in the a-priori information on the inverted resistivity and estimated water content distribution. Based on our simulation results, we provide best-practice recommendations for field applications and suggest important tests to obtain reliable, reproducible and trustworthy results. We finally apply our findings to field data, compare conventional and improved analysis results, and discuss limitations of the structurally-constrained inversion approach.

Acoustic dipole radiation based conductivity image reconstruction for magnetoacoustic tomography with magnetic induction

NASA Astrophysics Data System (ADS)

Sun, Xiaodong; Zhang, Feng; Ma, Qingyu; Tu, Juan; Zhang, Dong

2012-01-01

Based on the acoustic dipole radiation theory, a tomograhic conductivity image reconstruction algorithm is developed for the magnetoacoustic tomography with magnetic induction (MAT-MI) in a cylindrical measurement configuration. It has been experimentally proved for a tissue-like phantom that not only the configuration but also the inner conductivity distribution can be reconstructed without any borderline stripe. Furthermore, the spatial resolution also can be improved without the limitation of acoustic vibration. The favorable results have provided solid verification for the feasibility of conductivity image reconstruction and suggested the potential applications of MAT-MI in the area of medical electrical impedance imaging.

Laser-Based Production of Metallic Conducting Paths

NASA Astrophysics Data System (ADS)

Vedder, Christian; Stollenwerk, Jochen; Wissenbach, Konrad; Pirch, Norbert

For numerous devices such as OLEDs, solar cells or heated windows conducting paths are needed for collecting or distributing electricity on poorly or non-conducting surfaces. With established techniques the metallic paths can only be produced with a great deal of effort, incurring high costs for plant, equipment and energy. A new laser based process to manufacture conducting paths allows for writing narrow paths (down to 35 μm width) of Al, Cu, Ag or similar materials onto flat surfaces of glass (plain or coated with ITO) and silicon wafers by melting and vaporizing a metal foil through optical energy at high speeds of up to 2.5 m/s.

The effects of metallic implants on electroporation therapies: feasibility of irreversible electroporation for brachytherapy salvage.

PubMed

Neal, Robert E; Smith, Ryan L; Kavnoudias, Helen; Rosenfeldt, Franklin; Ou, Ruchong; Mclean, Catriona A; Davalos, Rafael V; Thomson, Kenneth R

2013-12-01

Electroporation-based therapies deliver brief electric pulses into a targeted volume to destabilize cellular membranes. Nonthermal irreversible electroporation (IRE) provides focal ablation with effects dependent on the electric field distribution, which changes in heterogeneous environments. It should be determined if highly conductive metallic implants in targeted regions, such as radiotherapy brachytherapy seeds in prostate tissue, will alter treatment outcomes. Theoretical and experimental models determine the impact of prostate brachytherapy seeds on IRE treatments. This study delivered IRE pulses in nonanimal, as well as in ex vivo and in vivo tissue, with and in the absence of expired radiotherapy seeds. Electrical current was measured and lesion dimensions were examined macroscopically and with magnetic resonance imaging. Finite-element treatment simulations predicted the effects of brachytherapy seeds in the targeted region on electrical current, electric field, and temperature distributions. There was no significant difference in electrical behavior in tissue containing a grid of expired radiotherapy seeds relative to those without seeds for nonanimal, ex vivo, and in vivo experiments (all p > 0.1). Numerical simulations predict no significant alteration of electric field or thermal effects (all p > 0.1). Histology showed cellular necrosis in the region near the electrodes and seeds within the ablation region; however, there were no seeds beyond the ablation margins. This study suggests that electroporation therapies can be implemented in regions containing small metallic implants without significant changes to electrical and thermal effects relative to use in tissue without the implants. This supports the ability to use IRE as a salvage therapy option for brachytherapy.

Local time distribution of the SSC-associated HF-Doppler frequency shifts

NASA Technical Reports Server (NTRS)

Kikuchi, T.; Sugiuchi, H.; Ishimine, T.

1985-01-01

The HF-Doppler frequency shift observed at the storm's sudden commencement is composed of a frequency increase (+) and decrease (-), and classified into four types, SCF(+ -), SCF(- +), SCF(+) and SCF(-). Since the latter two types are special cases of the former two types, two different kinds of electrical field exist in the F region and cause the ExB drift motion of plasma. HUANG (1976) interpreted the frequency increase of SCF(+ -) as due to the westward induction electric field proportional to delta H/ delta t and the succeeding frequency decrease due to the eastward conduction electric field which produces ionospheric currents responsible for the magnetic increase on the ground. In spite of his success in interpreting the SCF(+ -), some other interpretations are needed for the explanation of the whole set of SCF's, particularly SCF(- +). Local time distributions of the SCF's are derived from 41 SCF's which are observed on the HF standard signal (JJY) as received in Okinawa (path length =1600 km) and Kokubunji (60 km). It is shown that the SCF(+ -) appears mainly during the day, whereas the SCF(- +) is observed during the night. The results indicate that the preliminary frequency shift (+) of SCF(+ -) and (-) of SCF(- +) is caused by a westward electric field in the dayside hemisphere, while by an eastward electric field in the nightside hemisphere. The main frequency shift (-) of SCF(+ -) and (+) of SCF(- +) is caused by the reversed electric field. Consequently, the preliminary frequency shift is caused by the dusk-to-dawn electric field, while the main frequency shift by the dawn-to-dusk electric field.

46 CFR 28.855 - Electrical distribution systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Electrical distribution systems. 28.855 Section 28.855... FISHING INDUSTRY VESSELS Aleutian Trade Act Vessels § 28.855 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.360 - Electrical distribution systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Electrical distribution systems. 28.360 Section 28.360... Operate With More Than 16 Individuals on Board § 28.360 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.360 - Electrical distribution systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Electrical distribution systems. 28.360 Section 28.360... Operate With More Than 16 Individuals on Board § 28.360 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.360 - Electrical distribution systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Electrical distribution systems. 28.360 Section 28.360... Operate With More Than 16 Individuals on Board § 28.360 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.855 - Electrical distribution systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Electrical distribution systems. 28.855 Section 28.855... FISHING INDUSTRY VESSELS Aleutian Trade Act Vessels § 28.855 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.360 - Electrical distribution systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Electrical distribution systems. 28.360 Section 28.360... Operate With More Than 16 Individuals on Board § 28.360 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.855 - Electrical distribution systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Electrical distribution systems. 28.855 Section 28.855... FISHING INDUSTRY VESSELS Aleutian Trade Act Vessels § 28.855 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

46 CFR 28.855 - Electrical distribution systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Electrical distribution systems. 28.855 Section 28.855... FISHING INDUSTRY VESSELS Aleutian Trade Act Vessels § 28.855 Electrical distribution systems. (a) Each electrical distribution system which has a neutral bus or conductor must have the neutral bus or conductor...

Fracture Flow Characterization from Seismic and Electric Properties: Insight from Experimental and Numerical Approaches

NASA Astrophysics Data System (ADS)

Sawayama, K.; Kitamura, K.; Tsuji, T.; Fujimitsu, Y.

2017-12-01

The estimation of fluid flow and its distribution in the fracture is essential to evaluate subsurface fluid (e.g., geothermal water, ground water, oil and gas). Recently, fluid flow in the geothermal reservoir has been attracting attention to develop EGS (enhanced geothermal system) technique. To detect the fluid distribution under the ground, geophysical exploration such as seismic and electromagnetic methods have been broadly applied. For better interpretation of these exploration data, more detailed investigation about the effect of fluid on seismic and electric properties of fracture is required. In this study, we measured and calculated seismic and electric properties of a cracked rock to discuss the effect of water distribution and saturation on them as well as fluid flow. For the experimental observation, we developed the technique to measure electrical impedance, P-wave velocity and water saturation simultaneously during the fluid-flow test. The test has been conducted as follows; a cracked andesite core sample was filled with nitrogen gas (Pp = 10 MPa) under 20 MPa of confining pressure and then, brine (1wt.%-KCl, 1.75 S/m) was injected into the sample to replace the gas. During the test, water saturation, permeability, electrical impedance and P-wave velocity were measured. As a result of this experimental study, electrical impedance dramatically decreased from 105 to 103 Ω and P-wave velocity increased by 2% due to the brine injection. This remarkable change of the electrical impedance could be due to the replacement of pre-filled nitrogen gas to the brine in the broad fracture. After the brine injection, electrical impedance decreased with injection pressure by up to 40% while P-wave velocity was almost constant. This decrease of electrical impedance could be related to the flow to the narrow path (microcrack) which cannot be detected by P-wave velocity. These two types of fluid flow mechanism were also suggested from other parameters such as permeability, water saturation and saturation exponent of Archie's law. To quantify the fluid flow and its distribution in the fracture, we applied fluid flow simulation by LBM (Lattice Boltzmann Method). From this result, we calculate physical parameters by FEM and FDM and then discuss effect of fluid on them as well as their comparison with experimental results.

Tissue heterogeneity in structure and conductivity contribute to cell survival during irreversible electroporation ablation by “electric field sinks”

PubMed Central

Golberg, Alexander; Bruinsma, Bote G.; Uygun, Basak E.; Yarmush, Martin L.

2015-01-01

Irreversible electroporation (IRE) is an emerging, minimally invasive technique for solid tumors ablation, under clinical investigation for cancer therapy. IRE affects only the cell membrane, killing cells while preserving the extracellular matrix structure. Current reports indicate tumors recurrence rate after IRE averaging 31% of the cases, of which 10% are local recurrences. The mechanisms for these recurrences are not known and new explanations for incomplete cell death are needed. Using finite elements method for electric field distribution, we show that presence of vascular structures with blood leads to the redistribution of electric fields leading to the areas with more than 60% reduced electric field strength in proximity to large blood vessels and clustered vessel structures. In an in vivo rat model of liver IRE ablation, we show that cells located in the proximity of larger vessel structures and in proximity of clustered vessel structures appear less affected by IRE ablation than cells in the tissue parenchyma or in the proximity of small, more isolated vessels. These findings suggest a role for “electric field sinks” in local tumors recurrences after IRE and emphasize the importance of the precise mapping of the targeted organ structure and conductivity for planning of electroporation procedures. PMID:25684630

A cardiac electrical activity model based on a cellular automata system in comparison with neural network model.

PubMed

Khan, Muhammad Sadiq Ali; Yousuf, Sidrah

2016-03-01

Cardiac Electrical Activity is commonly distributed into three dimensions of Cardiac Tissue (Myocardium) and evolves with duration of time. The indicator of heart diseases can occur randomly at any time of a day. Heart rate, conduction and each electrical activity during cardiac cycle should be monitor non-invasively for the assessment of "Action Potential" (regular) and "Arrhythmia" (irregular) rhythms. Many heart diseases can easily be examined through Automata model like Cellular Automata concepts. This paper deals with the different states of cardiac rhythms using cellular automata with the comparison of neural network also provides fast and highly effective stimulation for the contraction of cardiac muscles on the Atria in the result of genesis of electrical spark or wave. The specific formulated model named as "States of automaton Proposed Model for CEA (Cardiac Electrical Activity)" by using Cellular Automata Methodology is commonly shows the three states of cardiac tissues conduction phenomena (i) Resting (Relax and Excitable state), (ii) ARP (Excited but Absolutely refractory Phase i.e. Excited but not able to excite neighboring cells) (iii) RRP (Excited but Relatively Refractory Phase i.e. Excited and able to excite neighboring cells). The result indicates most efficient modeling with few burden of computation and it is Action Potential during the pumping of blood in cardiac cycle.

Tissue heterogeneity in structure and conductivity contribute to cell survival during irreversible electroporation ablation by "electric field sinks".

PubMed

Golberg, Alexander; Bruinsma, Bote G; Uygun, Basak E; Yarmush, Martin L

2015-02-16

Irreversible electroporation (IRE) is an emerging, minimally invasive technique for solid tumors ablation, under clinical investigation for cancer therapy. IRE affects only the cell membrane, killing cells while preserving the extracellular matrix structure. Current reports indicate tumors recurrence rate after IRE averaging 31% of the cases, of which 10% are local recurrences. The mechanisms for these recurrences are not known and new explanations for incomplete cell death are needed. Using finite elements method for electric field distribution, we show that presence of vascular structures with blood leads to the redistribution of electric fields leading to the areas with more than 60% reduced electric field strength in proximity to large blood vessels and clustered vessel structures. In an in vivo rat model of liver IRE ablation, we show that cells located in the proximity of larger vessel structures and in proximity of clustered vessel structures appear less affected by IRE ablation than cells in the tissue parenchyma or in the proximity of small, more isolated vessels. These findings suggest a role for "electric field sinks" in local tumors recurrences after IRE and emphasize the importance of the precise mapping of the targeted organ structure and conductivity for planning of electroporation procedures.

[INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

NASA Astrophysics Data System (ADS)

Gamaly, Eugene G.; Rode, Andrei V.

2016-08-01

Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval's axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

A two-stage stochastic optimization model for scheduling electric vehicle charging loads to relieve distribution-system constraints

DOE PAGES

Wu, Fei; Sioshansi, Ramteen

2017-05-25

Electric vehicles (EVs) hold promise to improve the energy efficiency and environmental impacts of transportation. However, widespread EV use can impose significant stress on electricity-distribution systems due to their added charging loads. This paper proposes a centralized EV charging-control model, which schedules the charging of EVs that have flexibility. This flexibility stems from EVs that are parked at the charging station for a longer duration of time than is needed to fully recharge the battery. The model is formulated as a two-stage stochastic optimization problem. The model captures the use of distributed energy resources and uncertainties around EV arrival timesmore » and charging demands upon arrival, non-EV loads on the distribution system, energy prices, and availability of energy from the distributed energy resources. We use a Monte Carlo-based sample-average approximation technique and an L-shaped method to solve the resulting optimization problem efficiently. We also apply a sequential sampling technique to dynamically determine the optimal size of the randomly sampled scenario tree to give a solution with a desired quality at minimal computational cost. Here, we demonstrate the use of our model on a Central-Ohio-based case study. We show the benefits of the model in reducing charging costs, negative impacts on the distribution system, and unserved EV-charging demand compared to simpler heuristics. Lastly, we also conduct sensitivity analyses, to show how the model performs and the resulting costs and load profiles when the design of the station or EV-usage parameters are changed.« less

Experimental and theoretical characterization of the voltage distribution generated by deep brain stimulation.

PubMed

Miocinovic, Svjetlana; Lempka, Scott F; Russo, Gary S; Maks, Christopher B; Butson, Christopher R; Sakaie, Ken E; Vitek, Jerrold L; McIntyre, Cameron C

2009-03-01

Deep brain stimulation (DBS) is an established therapy for the treatment of Parkinson's disease and shows great promise for numerous other disorders. While the fundamental purpose of DBS is to modulate neural activity with electric fields, little is known about the actual voltage distribution generated in the brain by DBS electrodes and as a result it is difficult to accurately predict which brain areas are directly affected by the stimulation. The goal of this study was to characterize the spatial and temporal characteristics of the voltage distribution generated by DBS electrodes. We experimentally recorded voltages around active DBS electrodes in either a saline bath or implanted in the brain of a non-human primate. Recordings were made during voltage-controlled and current-controlled stimulation. The experimental findings were compared to volume conductor electric field models of DBS parameterized to match the different experiments. Three factors directly affected the experimental and theoretical voltage measurements: 1) DBS electrode impedance, primarily dictated by a voltage drop at the electrode-electrolyte interface and the conductivity of the tissue medium, 2) capacitive modulation of the stimulus waveform, and 3) inhomogeneity and anisotropy of the tissue medium. While the voltage distribution does not directly predict the neural response to DBS, the results of this study do provide foundational building blocks for understanding the electrical parameters of DBS and characterizing its effects on the nervous system.

Applications for Electrical Impedance Tomography (EIT) and Electrical Properties of the Human Body.

PubMed

Lymperopoulos, Georgios; Lymperopoulos, Panagiotis; Alikari, Victoria; Dafogianni, Chrisoula; Zyga, Sofia; Margari, Nikoletta

2017-01-01

Electrical Impedance Tomography (EIT) is a promising application that displays changes in conductivity within a body. The basic principle of the method is the repeated measurement of surface voltages of a body, which are a result of rolling injection of known and small-volume sinusoidal AC current to the body through the electrodes attached to its surface. This method finds application in biomedicine, biology and geology. The objective of this paper is to present the applications of Electrical Impedance Tomography, along with the method's capabilities and limitations due to the electrical properties of the human body. For this purpose, investigation of existing literature has been conducted, using electronic databases, PubMed, Google Scholar and IEEE Xplore. In addition, there was a secondary research phase, using paper citations found during the first research phase. It should be noted that Electrical Impedance Tomography finds use in a plethora of medical applications, as the different tissues of the body have different conductivities and dielectric constants. Main applications of EIT include imaging of lung function, diagnosis of pulmonary embolism, detection of tumors in the chest area and diagnosis and distinction of ischemic and hemorrhagic stroke. EIT advantages include portability, low cost and safety, which the method provide, since it is a noninvasive imaging method that does not cause damage to the body. The main disadvantage of the method, which blocks its wider spread, appears in the image composition from the voltage measurements, which are conducted by electrodes placed on the periphery of the body, because the injected currents are affected nonlinearly by the general distribution of the electrical properties of the body. Furthermore, the complex impedance of the skin-electrode interface can be modelled by using a capacitor and two resistor, as a result of skin properties. In conclusion, Electrical Impedance Tomography is a promising method for the development of noninvasive diagnostic medicine, since it is able to provide imaging of the interior of the human body in real time without causing harm or putting the human body in risk.

Chemically modified graphene/polyimide composite films based on utilization of covalent bonding and oriented distribution.

PubMed

Huang, Ting; Lu, Renguo; Su, Chao; Wang, Hongna; Guo, Zheng; Liu, Pei; Huang, Zhongyuan; Chen, Haiming; Li, Tongsheng

2012-05-01

Herein, we have developed a rather simple composite fabrication approach to achieving molecular-level dispersion and planar orientation of chemically modified graphene (CMG) in the thermosetting polyimide (PI) matrix as well as realizing strong adhesion at the interfacial regions between reinforcing filler and matrix. The covalent adhesion of CMG to PI matrix and oriented distribution of CMG were carefully confirmed and analyzed by detailed investigations. Combination of covalent bonding and oriented distribution could enlarge the effectiveness of CMG in the matrix. Efficient stress transfer was found at the CMG/PI interfaces. Significant improvements in the mechanical performances, thermal stability, electrical conductivity, and hydrophobic behavior were achieved by addition of only a small amount of CMG. Furthermore, it is noteworthy that the hydrophilic-to-hydrophobic transition and the electrical percolation were observed at only 0.2 wt % CMG in this composite system. This facile methodology is believed to afford broad application potential in graphene-based polymer nanocomposites, especially other types of high-performance thermosetting systems.

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

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

Detecting Kondo Entanglement by Electron Conductance

NASA Astrophysics Data System (ADS)

Yoo, Gwangsu; Lee, S.-S. B.; Sim, H.-S.

2018-04-01

Quantum entanglement between an impurity spin and electrons nearby is a key property of the single-channel Kondo effects. We show that the entanglement can be detected by measuring electron conductance through a double quantum dot in an orbital Kondo regime. We derive a relation between the entanglement and the conductance, when the SU(2) spin symmetry of the regime is weakly broken. The relation reflects the universal form of many-body states near the Kondo fixed point. Using it, the spatial distribution of the entanglement—hence, the Kondo cloud—can be detected, with breaking of the symmetry spatially nonuniformly by electrical means.

Phononic crystal devices

DOEpatents

El-Kady, Ihab F [Albuquerque, NM; Olsson, Roy H [Albuquerque, NM

2012-01-10

Phononic crystals that have the ability to modify and control the thermal black body phonon distribution and the phonon component of heat transport in a solid. In particular, the thermal conductivity and heat capacity can be modified by altering the phonon density of states in a phononic crystal. The present invention is directed to phononic crystal devices and materials such as radio frequency (RF) tags powered from ambient heat, dielectrics with extremely low thermal conductivity, thermoelectric materials with a higher ratio of electrical-to-thermal conductivity, materials with phononically engineered heat capacity, phononic crystal waveguides that enable accelerated cooling, and a variety of low temperature application devices.

29 CFR 1915.181 - Electrical circuits and distribution boards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 7 2010-07-01 2010-07-01 false Electrical circuits and distribution boards. 1915.181... Electrical Machinery § 1915.181 Electrical circuits and distribution boards. (a) The provisions of this... employee is permitted to work on an electrical circuit, except when the circuit must remain energized for...

Against the grain: The physical properties of anisotropic partially molten rocks

NASA Astrophysics Data System (ADS)

Ghanbarzadeh, S.; Hesse, M. A.; Prodanovic, M.

2014-12-01

Partially molten rocks commonly develop textures that appear close to textural equilibrium, where the melt network evolves to minimize the energy of the melt-solid interfaces, while maintaining the dihedral angle θ at solid-solid-melt contact lines. Textural equilibrium provides a powerful model for the melt distribution that controls the petro-physical properties of partially molten rocks, e.g., permeability, elastic moduli, and electrical resistivity. We present the first level-set computations of three-dimensional texturally equilibrated melt networks in rocks with an anisotropic fabric. Our results show that anisotropy induces wetting of smaller grain boundary faces for θ > 0 at realistic porosities ϕ < 3%. This was previously not thought to be possible at textural equilibrium and reconciles the theory with experimental observations. Wetting of the grain boundary faces leads to a dramatic redistribution of the melt from the edges to the faces that introduces strong anisotropy in the petro-physical properties such as permeability, effective electrical conductivity and mechanical properties. Figure, on left, shows that smaller grain boundaries become wetted at relatively low melt fractions of 3% in stretched polyhedral grains with elongation factor 1.5. Right plot represents the ratio of melt electrical conductivity to effective conductivity of medium (known as formation factor) as an example of anisotropy in physical properties. The plot shows that even slight anisotropy in grains induces considerable anisotropy in electrical properties.

Resistivity changes in conductive silicone sheets under stretching.

PubMed

González-Correa, C A; Screaton, G; Hose, D R; Brown, B H; Avis, N J; Kleinermann, F

2002-02-01

This paper reports a preliminary finding associated with an investigation of how tissues respond to mechanical stress. The stress distribution within the tissue may be the result of normal function, for example, joint forces, or it may result from interventions such as tissue suturing during or after surgery. We sought to combine electrical and mechanical computational models in order to better understand the interaction between the two. For example, if mechanical stress is applied to tissue this may change the cell arrangements within the tissue matrix and hence change the electrical properties. If this interaction could be determined, then it should be possible to use electrical impedance tomography measurements to identify stress patterns in tissues. Measurements of resistivity changes have been made in conductive silicone rubber sheets when subject to a uniaxial stress of up to 10%. Relatively large changes in resistivity are produced (up to 200%). These changes are far larger than those predicted arising from topological changes alone. It is suggested that under stress the conductive islands of carbon within the silicone rubber sheet undergo a reversible disassociation from their neighbours and that the material's electrical properties change under load. If similar stress-resistivity relationships occur within biological materials it may be possible to recover the stress fields within tissues from transfer impedance measurements and thereby predict if actions such as inappropriate suture tension will compromise tissue viability.

Comparing bulk electrical conductivities spatial series obtained by Time Domain Reflectometry and Electromagnetic Induction sensors

NASA Astrophysics Data System (ADS)

Saeed, Ali; Ajeel, Ali; dragonetti, giovanna; Comegna, Alessandro; Lamaddalena, Nicola; Coppola, Antonio

2016-04-01

The ability to determine and monitor the effects of salts on soils and plants, are of great importance to agriculture. To control its harmful effects, soil salinity needs to be monitored in space and time. This requires knowledge of its magnitude, temporal dynamics, and spatial variability. Conventional ground survey procedures by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity (σb) directly in the field. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on Electromagnetic Induction (EMI) techniques are non-invasive methods and represent a viable alternative to traditional techniques for soil characterization. The problem is that all these techniques give depth-weighted apparent electrical conductivity (σa) measurements, depending on the specific depth distribution of the σb, as well as on the depth response function of the sensor used. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from EMI. Because of their relatively lower observation window, TDR sensors provide quasi-point values and do not adequately integrate the spatial variability of the chemical concentration distribution in the soil solution (and of the water content) induced by natural soil heterogeneity. Thus, the variability of TDR readings is expected to come from a combination of smaller and larger-scale variations. By contrast, an EMI sensor reading partly smoothes the small-scale variability seen by a TDR probe. As a consequence, the variability revealed by profile-integrated EMI and local (within a given depth interval) TDR readings may have completely different characteristics. In this study, a comparison between the variability patterns of σb revealed by TDR and EMI sensors was carried out. The database came from a field experiment conducted in the Mediterranean Agronomic Institute (MAI) of Valenzano (Bari). The soil was pedologically classified as Colluvic Regosol, consisting of a silty loam with an average depth of 60 cm on a shallow fractured calcareous rock. The experimental field (30m x 15.6 m; for a total area of 468 m2) consisted of three transects of 30 m length and 4.2 width, cultivated with green bean and irrigated with three different salinity levels (1 dS/m, 3dS/m, 6dS/m). Each transect consisted of seven crop rows irrigated by a drip irrigation system (dripper discharge q=2 l/h.). Water salinity was induced by adding CaCl2 to the tap water. All crop-soil measurements were conducted along the middle row at 24 monitoring sites, 1m apart. The spatial and temporal evolution of bulk electrical conductivity (σb) of soil was monitored by i) an Electromagnetic Induction method (EM38-DD) and ii) Time Domain Reflectometry (TDR). Herein we will focus on the methodology we used to elaborate the database of this experiment. Mostly, the data elaboration was devoted to make TDR and EMI data actually comparable. Specifically, we analysed the effect of the different observation windows of TDR and EMI sensors on the different spatial and temporal variability observed in the data series coming from the two sensors. After exploring the different patterns and structures of variability of the original EMI and TDR data series the study assessed the potential of applying a Fourier's analysis to filter the original data series to extract the predominant, high-variance signal after removing the small- scale (high frequency) variance observed in the TDR data series.

Hydrogen Analysis with the Sandia ParaChoice Model.

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

Levinson, Rebecca Sobel; West, Todd H.

2017-07-01

In the coming decades, light-duty vehicle options and their supporting infrastructure must undergo significant transformations to achieve aggressive national targets for reducing petroleum consumption and lowering greenhouse gas emissions. FCEVs, battery and hybrid electric vehicles, and biofuels are among the promising advanced technology options. This project examines the market penetration of FCEVs in a range of market segments, and in different energy, technology, and policy futures. Analyses are conducted in the context of varying hydrogen production and distribution pathways, as well as public infrastructure availability, fuel (gasoline, ethanol, hydrogen) and electricity costs, vehicle costs and fuel economies to better understandmore » under what conditions, and for which market segments, FCEVs can best compete with battery electric and other alternative fuel vehicles.« less

Apparatus for detecting alpha radiation in difficult access areas

DOEpatents

Steadman, Peter; MacArthur, Duncan W.

1997-09-02

An electrostatic alpha radiation detector for measuring alpha radiation emitted from inside an enclosure comprising an electrically conductive expandable electrode for insertion into the enclosure. After insertion, the electrically conductive expandable electrode is insulated from the enclosure and defines a decay cavity between the electrically conductive expandable electrode and the enclosure so that air ions generated in the decay cavity are electrostatically captured by the electrically conductive expandable electrode and the enclosure when an electric potential is applied between the electrically conductive expandable electrode and the enclosure. Indicator means are attached to the electrically conductive expandable electrode for indicating an electrical current produced by generation of the air ions generated in the decay cavity by collisions between air molecules and the alpha particles emitted from the enclosure. A voltage source is connected between the indicator means and the electrically conductive enclosure for creating an electric field between the electrically conductive expandable electrode and the enclosure.

Study on probability distribution of prices in electricity market: A case study of zhejiang province, china

NASA Astrophysics Data System (ADS)

Zhou, H.; Chen, B.; Han, Z. X.; Zhang, F. Q.

2009-05-01

The study on probability density function and distribution function of electricity prices contributes to the power suppliers and purchasers to estimate their own management accurately, and helps the regulator monitor the periods deviating from normal distribution. Based on the assumption of normal distribution load and non-linear characteristic of the aggregate supply curve, this paper has derived the distribution of electricity prices as the function of random variable of load. The conclusion has been validated with the electricity price data of Zhejiang market. The results show that electricity prices obey normal distribution approximately only when supply-demand relationship is loose, whereas the prices deviate from normal distribution and present strong right-skewness characteristic. Finally, the real electricity markets also display the narrow-peak characteristic when undersupply occurs.

Effective conductivity and permittivity of unsaturated porous materials in the frequency range 1 mHz–1GHz

PubMed Central

Revil, A

2013-01-01

A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823

Heat and electricity from the sun using parabolic dish collector systems

NASA Technical Reports Server (NTRS)

Truscello, V. C.; Williams, A. N.

1979-01-01

The paper investigates point focus distributed receiver (PFDR) solar thermal technology for the production of electric power and of industrial process heat. Attention is given to a thermal systems project conducted by JPL under DOE sponsorship. It is reported that project emphasis is on the development of cost-effective systems which will accelerate the commercialization and industrialization of plants up to 10 MWe, using parabolic dish collectors. Also discussed are the characteristics of PFDR systems, the cost targets for major systems hardware, and markets for this technology. Finally, the present system status of the technology development effort is discussed.

Design analysis and computer-aided performance evaluation of shuttle orbiter electrical power system. Volume 1: Summary

NASA Technical Reports Server (NTRS)

1974-01-01

Studies were conducted to develop appropriate space shuttle electrical power distribution and control (EPDC) subsystem simulation models and to apply the computer simulations to systems analysis of the EPDC. A previously developed software program (SYSTID) was adapted for this purpose. The following objectives were attained: (1) significant enhancement of the SYSTID time domain simulation software, (2) generation of functionally useful shuttle EPDC element models, and (3) illustrative simulation results in the analysis of EPDC performance, under the conditions of fault, current pulse injection due to lightning, and circuit protection sizing and reaction times.

Time-Lapse Electrical Geophysical Monitoring of Amendment-Based Biostimulation.

PubMed

Johnson, Timothy C; Versteeg, Roelof J; Day-Lewis, Frederick D; Major, William; Lane, John W

2015-01-01

Biostimulation is increasingly used to accelerate microbial remediation of recalcitrant groundwater contaminants. Effective application of biostimulation requires successful emplacement of amendment in the contaminant target zone. Verification of remediation performance requires postemplacement assessment and contaminant monitoring. Sampling-based approaches are expensive and provide low-density spatial and temporal information. Time-lapse electrical resistivity tomography (ERT) is an effective geophysical method for determining temporal changes in subsurface electrical conductivity. Because remedial amendments and biostimulation-related biogeochemical processes often change subsurface electrical conductivity, ERT can complement and enhance sampling-based approaches for assessing emplacement and monitoring biostimulation-based remediation. Field studies demonstrating the ability of time-lapse ERT to monitor amendment emplacement and behavior were performed during a biostimulation remediation effort conducted at the Department of Defense Reutilization and Marketing Office (DRMO) Yard, in Brandywine, Maryland, United States. Geochemical fluid sampling was used to calibrate a petrophysical relation in order to predict groundwater indicators of amendment distribution. The petrophysical relations were field validated by comparing predictions to sequestered fluid sample results, thus demonstrating the potential of electrical geophysics for quantitative assessment of amendment-related geochemical properties. Crosshole radar zero-offset profile and borehole geophysical logging were also performed to augment the data set and validate interpretation. In addition to delineating amendment transport in the first 10 months after emplacement, the time-lapse ERT results show later changes in bulk electrical properties interpreted as mineral precipitation. Results support the use of more cost-effective surface-based ERT in conjunction with limited field sampling to improve spatial and temporal monitoring of amendment emplacement and remediation performance. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Low resistance thin film organic solar cell electrodes

DOEpatents

Forrest, Stephen [Princeton, NJ; Xue, Jiangeng [Piscataway, NJ

2008-01-01

A method which lower the series resistance of photosensitive devices includes providing a transparent film of a first electrically conductive material arranged on a transparent substrate; depositing and patterning a mask over the first electrically conductive material, such that openings in the mask have sloping sides which narrow approaching the substrate; depositing a second electrically conductive material directly onto the first electrically conductive material exposed in the openings of the mask, at least partially filling the openings; stripping the mask, leaving behind reentrant structures of the second electrically conductive material which were formed by the deposits in the openings of the mask; after stripping the mask, depositing a first organic material onto the first electrically conductive material in between the reentrant structures; and directionally depositing a third electrically conductive material over the first organic material deposited in between the reentrant structures, edges of the reentrant structures aligning deposition so that the third electrically conductive material does not directly contact the first electrically conductive material, and does not directly contact the second electrically conductive material.

Design and Development of a 200-kW Turbo-Electric Distributed Propulsion Testbed

NASA Technical Reports Server (NTRS)

Papathakis, Kurt V.; Kloesel, Kurt J.; Lin, Yohan; Clarke, Sean; Ediger, Jacob J.; Ginn, Starr

2016-01-01

The National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC) (Edwards, California) is developing a Hybrid-Electric Integrated Systems Testbed (HEIST) Testbed as part of the HEIST Project, to study power management and transition complexities, modular architectures, and flight control laws for turbo-electric distributed propulsion technologies using representative hardware and piloted simulations. Capabilities are being developed to assess the flight readiness of hybrid electric and distributed electric vehicle architectures. Additionally, NASA will leverage experience gained and assets developed from HEIST to assist in flight-test proposal development, flight-test vehicle design, and evaluation of hybrid electric and distributed electric concept vehicles for flight safety. The HEIST test equipment will include three trailers supporting a distributed electric propulsion wing, a battery system and turbogenerator, dynamometers, and supporting power and communication infrastructure, all connected to the AFRC Core simulation. Plans call for 18 high performance electric motors that will be powered by batteries and the turbogenerator, and commanded by a piloted simulation. Flight control algorithms will be developed on the turbo-electric distributed propulsion system.

Flexible neural interfaces with integrated stiffening shank

DOEpatents

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.; Shah, Kedar G.; Sheth, Heeral; Tolosa, Vanessa

2016-07-26

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

Optimal distance of multi-plane sensor in three-dimensional electrical impedance tomography.

PubMed

Hao, Zhenhua; Yue, Shihong; Sun, Benyuan; Wang, Huaxiang

2017-12-01

Electrical impedance tomography (EIT) is a visual imaging technique for obtaining the conductivity and permittivity distributions in the domain of interest. As an advanced technique, EIT has the potential to be a valuable tool for continuously bedside monitoring of pulmonary function. The EIT applications in any three-dimensional (3 D) field are very limited to the 3 D effects, i.e. the distribution of electric field spreads far beyond the electrode plane. The 3 D effects can result in measurement errors and image distortion. An important way to overcome the 3 D effect is to use the multiple groups of sensors. The aim of this paper is to find the best space resolution of EIT image over various electrode planes and select an optimal plane spacing in a 3 D EIT sensor, and provide guidance for 3 D EIT electrodes placement in monitoring lung function. In simulation and experiment, several typical conductivity distribution models, such as one rod (central, midway and edge), two rods and three rods, are set at different plane spacings between the two electrode planes. A Tikhonov regularization algorithm is utilized for reconstructing the images; the relative error and the correlation coefficient are utilized for evaluating the image quality. Based on numerical simulation and experimental results, the image performance at different spacing conditions is evaluated. The results demonstrate that there exists an optimal plane spacing between the two electrode planes for 3 D EIT sensor. And then the selection of the optimal plane spacing between the electrode planes is suggested for the electrodes placement of multi-plane EIT sensor.

Three-dimensional sensitivity distribution and sample volume of low-induction-number electromagnetic-induction instruments

USGS Publications Warehouse

Callegary, J.B.; Ferré, T.P.A.; Groom, R.W.

2012-01-01

There is an ongoing effort to improve the understanding of the correlation of soil properties with apparent soil electrical conductivity as measured by low-induction-number electromagnetic-induction (LIN FEM) instruments. At a minimum, the dimensions of LIN FEM instruments' sample volume, the spatial distribution of sensitivity within that volume, and implications for surveying and analyses must be clearly defined and discussed. Therefore, a series of numerical simulations was done in which a conductive perturbation was moved systematically through homogeneous soil to elucidate the three-dimensional sample volume of LIN FEM instruments. For a small perturbation with electrical conductivity similar to that of the soil, instrument response is a measure of local sensitivity (LS). Our results indicate that LS depends strongly on the orientation of the instrument's transmitter and receiver coils and includes regions of both positive and negative LS. Integration of the absolute value of LS from highest to lowest was used to contour cumulative sensitivity (CS). The 90% CS contour was used to define the sample volume. For both horizontal and vertical coplanar coil orientations, the longest dimension of the sample volume was at the surface along the main instrument axis with a length of about four times the intercoil spacing (s) with maximum thicknesses of about 1 and 0.3 s, respectively. The imaged distribution of spatial sensitivity within the sample volume is highly complex and should be considered in conjunction with the expected scale of heterogeneity before the use and interpretation of LIN FEM for mapping and profiling. ?? Soil Science Society of America.

Energy Management of Smart Distribution Systems

NASA Astrophysics Data System (ADS)

Ansari, Bananeh

Electric power distribution systems interface the end-users of electricity with the power grid. Traditional distribution systems are operated in a centralized fashion with the distribution system owner or operator being the only decision maker. The management and control architecture of distribution systems needs to gradually transform to accommodate the emerging smart grid technologies, distributed energy resources, and active electricity end-users or prosumers. The content of this document concerns with developing multi-task multi-objective energy management schemes for: 1) commercial/large residential prosumers, and 2) distribution system operator of a smart distribution system. The first part of this document describes a method of distributed energy management of multiple commercial/ large residential prosumers. These prosumers not only consume electricity, but also generate electricity using their roof-top solar photovoltaics systems. When photovoltaics generation is larger than local consumption, excess electricity will be fed into the distribution system, creating a voltage rise along the feeder. Distribution system operator cannot tolerate a significant voltage rise. ES can help the prosumers manage their electricity exchanges with the distribution system such that minimal voltage fluctuation occurs. The proposed distributed energy management scheme sizes and schedules each prosumer's ES to reduce the electricity bill and mitigate voltage rise along the feeder. The second part of this document focuses on emergency energy management and resilience assessment of a distribution system. The developed emergency energy management system uses available resources and redundancy to restore the distribution system's functionality fully or partially. The success of the restoration maneuver depends on how resilient the distribution system is. Engineering resilience terminology is used to evaluate the resilience of distribution system. The proposed emergency energy management scheme together with resilience assessment increases the distribution system operator's preparedness for emergency events.

The Flexible Solar Utility. Preparing for Solar's Impacts to Utility Planning and Operations

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

Sterling, John; Davidovich, Ted; Cory, Karlynn

2015-09-01

This paper seeks to provide a flexible utility roadmap for identifying the steps that need to be taken to place the utility in the best position for addressing solar in the future. Solar growth and the emergence of new technologies will change the electric utility of tomorrow. Although not every utility, region, or market will change in the same way or magnitude, developing a path forward will be needed to reach the Electric System of the Future in the coming decades. In this report, a series of potential future states are identified that could result in drastically different energy mixesmore » and profiles: 1) Business as Usual, 2) Low Carbon, Centralized Generation, 3) Rapid Distributed Energy Resource Growth, 4) Interactivity of Both the Grid and Demand, and 5) Grid or Load Defection. Complicating this process are a series of emerging disruptions; decisions or events that will cause the electric sector to change. Understanding and preparing for these items is critical for the transformation to any of the future states to be successful. Predicting which future state will predominate 15 years from now is not possible; however, utilities still will need to look ahead and try to anticipate how factors will impact their planning, operations, and business models. In order to dig into the potential transformations facing the utility industry, the authors conducted a series of utility interviews, held a working session at a major industry solar conference, and conducted a quantitative survey. To focus conversations, the authors leveraged the Rapid Distributed Energy Resource (DER) Growth future to draw out how utilities would have to adapt from current processes and procedures in order to manage and thrive in that new environment. Distributed solar was investigated specifically, and could serve as a proxy resource for all distributed generation (DG). It can also provide the foundation for all DERs.« less

Determination of grain-size characteristics from electromagnetic seabed mapping data: A NW Iberian shelf study

NASA Astrophysics Data System (ADS)

Baasch, Benjamin; Müller, Hendrik; von Dobeneck, Tilo; Oberle, Ferdinand K. J.

2017-05-01

The electric conductivity and magnetic susceptibility of sediments are fundamental parameters in environmental geophysics. Both can be derived from marine electromagnetic profiling, a novel, fast and non-invasive seafloor mapping technique. Here we present statistical evidence that electric conductivity and magnetic susceptibility can help to determine physical grain-size characteristics (size, sorting and mud content) of marine surficial sediments. Electromagnetic data acquired with the bottom-towed electromagnetic profiler MARUM NERIDIS III were analysed and compared with grain size data from 33 samples across the NW Iberian continental shelf. A negative correlation between mean grain size and conductivity (R=-0.79) as well as mean grain size and susceptibility (R=-0.78) was found. Simple and multiple linear regression analyses were carried out to predict mean grain size, mud content and the standard deviation of the grain-size distribution from conductivity and susceptibility. The comparison of both methods showed that multiple linear regression models predict the grain-size distribution characteristics better than the simple models. This exemplary study demonstrates that electromagnetic benthic profiling is capable to estimate mean grain size, sorting and mud content of marine surficial sediments at a very high significance level. Transfer functions can be calibrated using grains-size data from a few reference samples and extrapolated along shelf-wide survey lines. This study suggests that electromagnetic benthic profiling should play a larger role for coastal zone management, seafloor contamination and sediment provenance studies in worldwide continental shelf systems.

Effect of crystal size distribution on thermoelectric performance for Lanthanum-doped strontium titanate bulk material

NASA Astrophysics Data System (ADS)

Zhang, Boyu; Wang, Jun; Yaer, Xinba; Huo, Zhenzhen; Wu, Yin; Li, Yan; Miao, Lei; Liu, Chengyan; Zou, Tao; Ma, Wen

2015-07-01

Effect of crystal size distribution on thermoelectric performance of Lanthanum-doped strontium titanate (La-SrTiO3) ceramics are investigated in this study. Thermoelectric performance measurement, coupled with microstructure studies, shows that the electrical conductivity strongly depends on the crystal size, potential barrier on the grain boundary and porosity. Meantime, because the average potential barriers height are increased along with the reduction of crystal size, the Seebeck coefficients are increased by energy filtering effect at the large number of grain boundaries. As a result, by controlling of crystal size distribution, ZT value of La-SrTiO3 is improved.

Crustal-scale electrical conductivity anomaly beneath inflating Lazufre volcanic complex, Central Andes

NASA Astrophysics Data System (ADS)

Budach, Ingmar; Brasse, Heinrich; Díaz, Daniel

2013-03-01

Large-scale surface deformation was observed at Lazufre volcanic center in the Central Andes of Northern Chile/Northwestern Argentina by means of Interferometric Synthetic Aperture Radar (InSAR). Uplift started there after 1998 and increased dramatically in the following years up to a rate of 3 cm/a. Lazufre is now one of the largest deforming volcano systems on Earth, but the cause for uplift - likely influx of magmatic material into the crust - is still poorly understood. In the beginning of 2010 a magnetotelluric survey was conducted to delineate the electrical conductivity distribution in the area. Several long-period magnetotelluric (LMT) sites and two broadband magnetotelluric (BBMT) sites were set up on an EW trending profile crossing the volcanic center; furthermore some LMT sites were arranged circularly around Lazufre complex and adjacent Lastarria volcano. Data were processed using an algorithm for robust and remote reference transfer function estimation. Electrical strike directions were estimated and induction arrows were derived. Although electrical strike is rather ambiguous, in a first step a 2-D resistivity model was calculated. The most prominent feature of this model is a well conducting structure rising from the upper mantle to the shallow crust beneath the center of elevation. This can be interpreted as partial melts ascending from the asthenospheric wedge and feeding a potential magma reservoir beneath Lazufre volcanic center. An improved model is finally achieved by 3-D inversion, supporting this feature. We assume that these rising melts are the source of the observed uplift at Lazufre complex.

Modeling 3-D permeability distribution in alluvial fans using facies architecture and geophysical acquisitions

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

Zhu, Lin; Gong, Huili; Dai, Zhenxue

Alluvial fans are highly heterogeneous in hydraulic properties due to complex depositional processes, which make it difficult to characterize the spatial distribution of the hydraulic conductivity ( K). An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional (3-D) setting by using geological and geophysical data. More specifically, a large number of inexpensive vertical electric soundings are integrated with a facies model developed from borehole lithologic data to simulate the log 10( K) continuous distributions in multiple-zone heterogeneous alluvial megafans. The Chaobai River alluvial fan in the Beijing Plain,more » China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multiple-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (zone 1) to the lower (zone 3) portion along the flow direction. In zone 1, sediments were moved by higher-energy flooding, which induces poor sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from zone 1 to zone 3. Lastly, the results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of  K in alluvial fans.« less

Modeling 3-D permeability distribution in alluvial fans using facies architecture and geophysical acquisitions

DOE PAGES

Zhu, Lin; Gong, Huili; Dai, Zhenxue; ...

2017-02-03

Alluvial fans are highly heterogeneous in hydraulic properties due to complex depositional processes, which make it difficult to characterize the spatial distribution of the hydraulic conductivity ( K). An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional (3-D) setting by using geological and geophysical data. More specifically, a large number of inexpensive vertical electric soundings are integrated with a facies model developed from borehole lithologic data to simulate the log 10( K) continuous distributions in multiple-zone heterogeneous alluvial megafans. The Chaobai River alluvial fan in the Beijing Plain,more » China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multiple-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (zone 1) to the lower (zone 3) portion along the flow direction. In zone 1, sediments were moved by higher-energy flooding, which induces poor sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from zone 1 to zone 3. Lastly, the results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of  K in alluvial fans.« less

Mathematical Modeling of Electrodynamics Near the Surface of Earth and Planetary Water Worlds

NASA Technical Reports Server (NTRS)

Tyler, Robert H.

2017-01-01

An interesting feature of planetary bodies with hydrospheres is the presence of an electrically conducting shell near the global surface. This conducting shell may typically lie between relatively insulating rock, ice, or atmosphere, creating a strong constraint on the flow of large-scale electric currents. All or parts of the shell may be in fluid motion relative to main components of the rotating planetary magnetic field (as well as the magnetic fields due to external bodies), creating motionally-induced electric currents that would not otherwise be present. As such, one may expect distinguishing features in the types of electrodynamic processes that occur, as well as an opportunity for imposing specialized mathematical methods that efficiently address this class of application. The purpose of this paper is to present and discuss such specialized methods. Specifically, thin-shell approximations for both the electrodynamics and fluid dynamics are combined to derive simplified mathematical formulations describing the behavior of these electric currents as well as their associated electric and magnetic fields. These simplified formulae allow analytical solutions featuring distinct aspects of the thin-shell electrodynamics in idealized cases. A highly efficient numerical method is also presented that is useful for calculations under inhomogeneous parameter distributions. Finally, the advantages as well as limitations in using this mathematical approach are evaluated. This evaluation is presented primarily for the generic case of bodies with water worlds or other thin spherical conducting shells. More specific discussion is given for the case of Earth, but also Europa and other satellites with suspected oceans.

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida

NASA Astrophysics Data System (ADS)

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-08-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

Field observations of extended seawater intrusion through subsurface karst conduit networks at Wakulla Spring in the Woodville Karst Plain, Florida

NASA Astrophysics Data System (ADS)

Xu, Z.; Bassett, S.; Hu, B. X.; Dyer, S.

2016-12-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electric conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 14 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This abstract documented the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida.

PubMed

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-08-25

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida

PubMed Central

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-01-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer. PMID:27557803

Apparatus for detecting alpha radiation in difficult access areas

DOEpatents

Steadman, P.; MacArthur, D.W.

1997-09-02

An electrostatic alpha radiation detector for measuring alpha radiation emitted from inside an enclosure comprising an electrically conductive expandable electrode for insertion into the enclosure is disclosed. After insertion, the electrically conductive expandable electrode is insulated from the enclosure and defines a decay cavity between the electrically conductive expandable electrode and the enclosure so that air ions generated in the decay cavity are electrostatically captured by the electrically conductive expandable electrode and the enclosure when an electric potential is applied between the electrically conductive expandable electrode and the enclosure. Indicator means are attached to the electrically conductive expandable electrode for indicating an electrical current produced by generation of the air ions generated in the decay cavity by collisions between air molecules and the alpha particles emitted from the enclosure. A voltage source is connected between the indicator means and the electrically conductive enclosure for creating an electric field between the electrically conductive expandable electrode and the enclosure. 4 figs.

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

Newman, G.A.; Commer, M.

Three-dimensional (3D) geophysical imaging is now receiving considerable attention for electrical conductivity mapping of potential offshore oil and gas reservoirs. The imaging technology employs controlled source electromagnetic (CSEM) and magnetotelluric (MT) fields and treats geological media exhibiting transverse anisotropy. Moreover when combined with established seismic methods, direct imaging of reservoir fluids is possible. Because of the size of the 3D conductivity imaging problem, strategies are required exploiting computational parallelism and optimal meshing. The algorithm thus developed has been shown to scale to tens of thousands of processors. In one imaging experiment, 32,768 tasks/processors on the IBM Watson Research Blue Gene/Lmore » supercomputer were successfully utilized. Over a 24 hour period we were able to image a large scale field data set that previously required over four months of processing time on distributed clusters based on Intel or AMD processors utilizing 1024 tasks on an InfiniBand fabric. Electrical conductivity imaging using massively parallel computational resources produces results that cannot be obtained otherwise and are consistent with timeframes required for practical exploration problems.« less

BORE II

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

Bore II, co-developed by Berkeley Lab researchers Frank Hale, Chin-Fu Tsang, and Christine Doughty, provides vital information for solving water quality and supply problems and for improving remediation of contaminated sites. Termed "hydrophysical logging," this technology is based on the concept of measuring repeated depth profiles of fluid electric conductivity in a borehole that is pumping. As fluid enters the wellbore, its distinct electric conductivity causes peaks in the conductivity log that grow and migrate upward with time. Analysis of the evolution of the peaks enables characterization of groundwater flow distribution more quickly, more cost effectively, and with higher resolutionmore » than ever before. Combining the unique interpretation software Bore II with advanced downhole instrumentation (the hydrophysical logging tool), the method quantifies inflow and outflow locations, their associated flow rates, and the basic water quality parameters of the associated formation waters (e.g., pH, oxidation-reduction potential, temperature). In addition, when applied in conjunction with downhole fluid sampling, Bore II makes possible a complete assessment of contaminant concentration within groundwater.« less

Modulation of the electrical properties in amorphous indium-gallium zinc-oxide semiconductor films using hydrogen incorporation

NASA Astrophysics Data System (ADS)

Song, Aeran; Park, Hyun-Woo; Chung, Kwun-Bum; Rim, You Seung; Son, Kyoung Seok; Lim, Jun Hyung; Chu, Hye Yong

2017-12-01

The electrical properties of amorphous-indium-gallium-zinc-oxide (a-IGZO) thin films were investigated after thermal annealing and plasma treatment under different gas conditions. The electrical resistivity of a-IGZO thin films post-treated in a hydrogen ambient were lower than those without treatment and those annealed in air, regardless of the methods used for both thermal annealing and plasma treatment. The electrical properties can be explained by the quantity of hydrogen incorporated into the samples and the changes in the electronic structure in terms of the chemical bonding states, the distribution of the near-conduction-band unoccupied states, and the band alignment. As a result, the carrier concentrations of the hydrogen treated a-IGZO thin films increased, while the mobility decreased, due to the increase in the oxygen vacancies from the occurrence of unoccupied states in both shallow and deep levels.

Energy efficiency system development

NASA Astrophysics Data System (ADS)

Leman, A. M.; Rahman, K. A.; Chong, Haw Jie; Salleh, Mohd Najib Mohd; Yusof, M. Z. M.

2017-09-01

By subjecting to the massive usage of electrical energy in Malaysia, energy efficiency is now one of the key areas of focus in climate change mitigation. This paper focuses on the development of an energy efficiency system of household electrical appliances for residential areas. Distribution of Questionnaires and pay a visit to few selected residential areas are conducted during the fulfilment of the project as well as some advice on how to save energy are shared with the participants. Based on the collected data, the system developed by the UTHM Energy Team is then evaluated from the aspect of the consumers' behaviour in using electrical appliances and the potential reduction targeted by the team. By the end of the project, 60% of the participants had successfully reduced the electrical power consumption set by the UTHM Energy Team. The reasons for whether the success and the failure is further analysed in this project.

On optimal current patterns for electrical impedance tomography.

PubMed

Demidenko, Eugene; Hartov, Alex; Soni, Nirmal; Paulsen, Keith D

2005-02-01

We develop a statistical criterion for optimal patterns in planar circular electrical impedance tomography. These patterns minimize the total variance of the estimation for the resistance or conductance matrix. It is shown that trigonometric patterns (Isaacson, 1986), originally derived from the concept of distinguishability, are a special case of our optimal statistical patterns. New optimal random patterns are introduced. Recovering the electrical properties of the measured body is greatly simplified when optimal patterns are used. The Neumann-to-Dirichlet map and the optimal patterns are derived for a homogeneous medium with an arbitrary distribution of the electrodes on the periphery. As a special case, optimal patterns are developed for a practical EIT system with a finite number of electrodes. For a general nonhomogeneous medium, with no a priori restriction, the optimal patterns for the resistance and conductance matrix are the same. However, for a homogeneous medium, the best current pattern is the worst voltage pattern and vice versa. We study the effect of the number and the width of the electrodes on the estimate of resistivity and conductivity in a homogeneous medium. We confirm experimentally that the optimal patterns produce minimum conductivity variance in a homogeneous medium. Our statistical model is able to discriminate between a homogenous agar phantom and one with a 2 mm air hole with error probability (p-value) 1/1000.

Electromagnetic Measurements in an Active Oilfield Environment

NASA Astrophysics Data System (ADS)

Weiss, C. J.; Aur, K. A.; Schramm, K. A.; Aldridge, D. F.; O'rourke, W. T.

2016-12-01

An important issue in oilfield development is mapping fracture distributions (either natural or man-made) controlling subsurface fluid flow. Although microseismic monitoring has been successful in constraining fracture system geometry and dynamics, accurate interpretation of microseismic data can be confounded by factors such as complex or poorly-understood velocity distributions, reactivation of previously unknown faults and fractures, and the problem of relating flow patterns to the cloud of hypocenter locations. For the particular problem of hydrocarbon production, the question of which fractures remain sufficiently "open" to allow economical fluid extraction is critical. As a supplement to microseismic analysis, we are investigating a novel electromagnetic (EM) technique for detecting and mapping hydraulic fractures in a hydrocarbon or geothermal reservoir by introducing an electrically conductive contrast agent into the fracturing fluid. In the field experiment presented here, a proppant-filled fracture zone is illuminated by a large engineered antenna consisting of an insulated current-carrying cable, grounded to `Earth' near the wellhead, and grounded at the other end to the steel-cased borehole near the target. Time-lapse measurements of horizontal electric field are subsequently made on Earth's surface to map the change in subsurface conductivity due to proppant emplacement. As predicted by 3D numerical modelling, observed differences in electric field values are very small. While these numbers are above the noise floor of electric field sensors, pervasive anthropogenic EM noise and regional-scale magnetotelluric signals make extraction of the differences from the observed time series especially difficult. We present field-acquired data on ambient EM noise in an active oilfield environment and demonstrate techniques for extracting the difference signal due to proppant emplacement. These techniques include classical spectral methods along with estimation of time-domain Green's function by regularized, linear least squares methods.

Solution-processed assembly of ultrathin transparent conductive cellulose nanopaper embedding AgNWs

NASA Astrophysics Data System (ADS)

Song, Yuanyuan; Jiang, Yaoquan; Shi, Liyi; Cao, Shaomei; Feng, Xin; Miao, Miao; Fang, Jianhui

2015-08-01

Natural biomass based cellulose nanopaper is becoming a promising transparent substrate to supersede traditional petroleum based polymer films in realizing future flexible paper-electronics. Here, ultrathin, highly transparent, outstanding conductive hybrid nanopaper with excellent mechanical flexibility was synthesized by the assembly of nanofibrillated cellulose (NFC) and silver nanowires (AgNWs) using a pressured extrusion paper-making technique. The hybrid nanopaper with a thickness of 4.5 μm has a good combination of transparent conductive performance and mechanical stability using bamboo/hemp NFC and AgNWs cross-linked by hydroxypropylmethyl cellulose (HPMC). The heterogeneous fibrous structure of BNFC/HNFC/AgNWs endows a uniform distribution and an enhanced forward light scattering, resulting in high electrical conductivity and optical transmittance. The hybrid nanopaper with an optimal weight ratio of BNFC/HNFC to AgNWs shows outstanding synergistic properties with a transmittance of 86.41% at 550 nm and a sheet resistance of 1.90 ohm sq-1, equal to the electronic conductivity, which is about 500 S cm-1. The BNFC/HNFC/AgNW hybrid nanopaper maintains a stable electrical conductivity after the peeling test and bending at 135° for 1000 cycles, indicating remarkably strong adhesion and mechanical flexibility. Of importance here is that the high-performance and low-cost hybrid nanopaper shows promising potential for electronics application in solar cells, flexible displays and other high-technology products.Natural biomass based cellulose nanopaper is becoming a promising transparent substrate to supersede traditional petroleum based polymer films in realizing future flexible paper-electronics. Here, ultrathin, highly transparent, outstanding conductive hybrid nanopaper with excellent mechanical flexibility was synthesized by the assembly of nanofibrillated cellulose (NFC) and silver nanowires (AgNWs) using a pressured extrusion paper-making technique. The hybrid nanopaper with a thickness of 4.5 μm has a good combination of transparent conductive performance and mechanical stability using bamboo/hemp NFC and AgNWs cross-linked by hydroxypropylmethyl cellulose (HPMC). The heterogeneous fibrous structure of BNFC/HNFC/AgNWs endows a uniform distribution and an enhanced forward light scattering, resulting in high electrical conductivity and optical transmittance. The hybrid nanopaper with an optimal weight ratio of BNFC/HNFC to AgNWs shows outstanding synergistic properties with a transmittance of 86.41% at 550 nm and a sheet resistance of 1.90 ohm sq-1, equal to the electronic conductivity, which is about 500 S cm-1. The BNFC/HNFC/AgNW hybrid nanopaper maintains a stable electrical conductivity after the peeling test and bending at 135° for 1000 cycles, indicating remarkably strong adhesion and mechanical flexibility. Of importance here is that the high-performance and low-cost hybrid nanopaper shows promising potential for electronics application in solar cells, flexible displays and other high-technology products. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03218k

The Effects of Metallic Implants on Electroporation Therapies: Feasibility of Irreversible Electroporation for Brachytherapy Salvage

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

Neal, Robert E., E-mail: robert.neal@alfred.org.au; Smith, Ryan L., E-mail: ryan.smith@wbrc.org.au; Kavnoudias, Helen, E-mail: H.Kavnoudias@alfred.org.au

2013-12-15

Purpose: Electroporation-based therapies deliver brief electric pulses into a targeted volume to destabilize cellular membranes. Nonthermal irreversible electroporation (IRE) provides focal ablation with effects dependent on the electric field distribution, which changes in heterogeneous environments. It should be determined if highly conductive metallic implants in targeted regions, such as radiotherapy brachytherapy seeds in prostate tissue, will alter treatment outcomes. Theoretical and experimental models determine the impact of prostate brachytherapy seeds on IRE treatments. Materials and Methods: This study delivered IRE pulses in nonanimal, as well as in ex vivo and in vivo tissue, with and in the absence of expiredmore » radiotherapy seeds. Electrical current was measured and lesion dimensions were examined macroscopically and with magnetic resonance imaging. Finite-element treatment simulations predicted the effects of brachytherapy seeds in the targeted region on electrical current, electric field, and temperature distributions. Results: There was no significant difference in electrical behavior in tissue containing a grid of expired radiotherapy seeds relative to those without seeds for nonanimal, ex vivo, and in vivo experiments (all p > 0.1). Numerical simulations predict no significant alteration of electric field or thermal effects (all p > 0.1). Histology showed cellular necrosis in the region near the electrodes and seeds within the ablation region; however, there were no seeds beyond the ablation margins. Conclusion: This study suggests that electroporation therapies can be implemented in regions containing small metallic implants without significant changes to electrical and thermal effects relative to use in tissue without the implants. This supports the ability to use IRE as a salvage therapy option for brachytherapy.« less

Electrical appliance energy consumption control methods and electrical energy consumption systems

DOEpatents

Donnelly, Matthew K [Kennewick, WA; Chassin, David P [Pasco, WA; Dagle, Jeffery E [Richland, WA; Kintner-Meyer, Michael [Richland, WA; Winiarski, David W [Kennewick, WA; Pratt, Robert G [Kennewick, WA; Boberly-Bartis, Anne Marie [Alexandria, VA

2006-03-07

Electrical appliance energy consumption control methods and electrical energy consumption systems are described. In one aspect, an electrical appliance energy consumption control method includes providing an electrical appliance coupled with a power distribution system, receiving electrical energy within the appliance from the power distribution system, consuming the received electrical energy using a plurality of loads of the appliance, monitoring electrical energy of the power distribution system, and adjusting an amount of consumption of the received electrical energy via one of the loads of the appliance from an initial level of consumption to an other level of consumption different than the initial level of consumption responsive to the monitoring.

Electrical appliance energy consumption control methods and electrical energy consumption systems

DOEpatents

Donnelly, Matthew K [Kennewick, WA; Chassin, David P [Pasco, WA; Dagle, Jeffery E [Richland, WA; Kintner-Meyer, Michael [Richland, WA; Winiarski, David W [Kennewick, WA; Pratt, Robert G [Kennewick, WA; Boberly-Bartis, Anne Marie [Alexandria, VA

2008-09-02

Electrical appliance energy consumption control methods and electrical energy consumption systems are described. In one aspect, an electrical appliance energy consumption control method includes providing an electrical appliance coupled with a power distribution system, receiving electrical energy within the appliance from the power distribution system, consuming the received electrical energy using a plurality of loads of the appliance, monitoring electrical energy of the power distribution system, and adjusting an amount of consumption of the received electrical energy via one of the loads of the appliance from an initial level of consumption to an other level of consumption different than the initial level of consumption responsive to the monitoring.

Air-Stable n-type Conductors and Semiconductors

DTIC Science & Technology

2015-07-14

Distribution approved for public release.   10   4. Stretchable and self - healing materials and device development. Future electronic devices...that can self - heal at room temperature repeatedly and have electrical conductivity. Such materials, mimicking human skin functions, may have...particle polymer composites we then developed an elastic nanocomposite material with the ability to rapidly self - heal at room temperature by combining

Exploring Novel Spintronic Responses from Advanced Functional Organic Materials

DTIC Science & Technology

2015-11-12

March 20-22, 2014 (8) Interface enhanced photovoltaic and Seebeck effects in organic solar cells and thermoelectric devices DISTRIBUTION A...on thermoelectric effects by using polymer/metal interface-controllable thermal and electric conductions. The project explored a new strategy by using...following major breakthroughs on molecular metamaterials by using spin radicals and on thermoelectric effects by using polymer/metal interface

Electric Commerce

DTIC Science & Technology

1989-10-01

risk management, such as the coordination of letters of credit, shipping, payments, delivery, and insurance. All of these necessary steps require...vendor to conduct business with a human customer 6, at a dumb terminal7. In contrast, we want to computerize both. ATMs (Automatic Teller Machines) and...entered the store. Distributers with physical showrooms will always cater to the impulse buyer. Many supermarket items could be automatically procured 20

Lithographically defined microporous carbon structures

DOEpatents

Burckel, David Bruce; Washburn, Cody M.; Polsky, Ronen; Brozik, Susan M.; Wheeler, David R.

2013-01-08

A lithographic method is used to fabricate porous carbon structures that can provide electrochemical electrodes having high surface area with uniform and controllable dimensions, providing enormous flexibility to tailor the electrodes toward specific applications. Metal nanoparticles deposited on the surface of the porous carbon electrodes exhibit ultra small dimensions with uniform size distribution. The resulting electrodes are rugged, electrically conductive and show excellent electrochemical behavior.

A gridded global description of the ionosphere and thermosphere for 1996 - 2000

NASA Astrophysics Data System (ADS)

Ridley, A.; Kihn, E.; Kroehl, H.

The modeling and simulation community has asked for a realistic representation of the near-Earth space environment covering a significant number of years to be used in scientific and engineering applications. The data, data management systems, assimilation techniques, physical models, and computer resources are now available to construct a realistic description of the ionosphere and thermosphere over a 5 year period. DMSP and NOAA POES satellite data and solar emissions were used to compute Hall and Pederson conductances in the ionosphere. Interplanetary magnetic field measurements on the ACE satellite define average electrostatic potential patterns over the northern and southern Polar Regions. These conductances, electric field patterns, and ground-based magnetometer data were input to the Assimilative Mapping of Ionospheric Electrodynamics model to compute the distribution of electric fields and currents in the ionosphere. The Global Thermosphere Ionosphere Model (GITM) used the ionospheric electrodynamic parameters to compute the distribution of particles and fields in the ionosphere and thermosphere. GITM uses a general circulation approach to solve the fundamental equations. Model results offer a unique opportunity to assess the relative importance of different forcing terms under a variety of conditions as well as the accuracies of different estimates of ionospheric electrodynamic parameters.

A study using a Monte Carlo method of the optimal configuration of a distribution network in terms of power loss sensing.

PubMed

Moon, Hyun Ho; Lee, Jong Joo; Choi, Sang Yule; Cha, Jae Sang; Kang, Jang Mook; Kim, Jong Tae; Shin, Myong Chul

2011-01-01

Recently there have been many studies of power systems with a focus on "New and Renewable Energy" as part of "New Growth Engine Industry" promoted by the Korean government. "New And Renewable Energy"-especially focused on wind energy, solar energy and fuel cells that will replace conventional fossil fuels-is a part of the Power-IT Sector which is the basis of the SmartGrid. A SmartGrid is a form of highly-efficient intelligent electricity network that allows interactivity (two-way communications) between suppliers and consumers by utilizing information technology in electricity production, transmission, distribution and consumption. The New and Renewable Energy Program has been driven with a goal to develop and spread through intensive studies, by public or private institutions, new and renewable energy which, unlike conventional systems, have been operated through connections with various kinds of distributed power generation systems. Considerable research on smart grids has been pursued in the United States and Europe. In the United States, a variety of research activities on the smart power grid have been conducted within EPRI's IntelliGrid research program. The European Union (EU), which represents Europe's Smart Grid policy, has focused on an expansion of distributed generation (decentralized generation) and power trade between countries with improved environmental protection. Thus, there is current emphasis on a need for studies that assesses the economic efficiency of such distributed generation systems. In this paper, based on the cost of distributed power generation capacity, calculations of the best profits obtainable were made by a Monte Carlo simulation. Monte Carlo simulations that rely on repeated random sampling to compute their results take into account the cost of electricity production, daily loads and the cost of sales and generate a result faster than mathematical computations. In addition, we have suggested the optimal design, which considers the distribution loss associated with power distribution systems focus on sensing aspect and distributed power generation.

On electrical and interfacial properties of iron and platinum Schottky barrier diodes on (111) n-type Si0.65Ge0.35

NASA Astrophysics Data System (ADS)

Hamri, D.; Teffahi, A.; Djeghlouf, A.; Chalabi, D.; Saidane, A.

2018-04-01

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) characteristics of Molecular Beam Epitaxy (MBE)-deposited Fe/n-Si0.65Ge0.35 (FM1) and Pt/n-Si0.65Ge0.35(PM2) (111) orientated Schottky barrier diodes (SBDs) have been investigated at room-temperature. Barrier height (ΦB0), ideality factor (n) and series resistance (RS) were extracted. Dominant current conduction mechanisms were determined. They revealed that Poole-Frenkel-type conduction mechanism dominated reverse current. Differences in shunt resistance confirmed the difference found in leakage current. Under forward bias, quasi-ohmic conduction is found at low voltage regions and space charge-limited conduction (SCLC) at higher voltage regions for both SBDs. Density of interface states (NSS) indicated a difference in interface reactivity. Distribution profiles of series resistance (RS) with bias gives a peak in depletion region at low-frequencies that disappears with increasing frequencies. These results show that interface states density and series resistance of Schottky diodes are important parameters that strongly influence electrical properties of FM1 and PM2 structures.

High conductance surge cable

DOEpatents

Murray, M.M.; Wilfong, D.H.; Lomax, R.E.

1998-12-08

An electrical cable for connecting transient voltage surge suppressors to electrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation. 6 figs.

Distributed charging of electrical assets

DOEpatents

Ghosh, Soumyadip; Phan, Dung; Sharma, Mayank; Wu, Chai Wah; Xiong, Jinjun

2016-02-16

The present disclosure relates generally to the field of distributed charging of electrical assets. In various examples, distributed charging of electrical assets may be implemented in the form of systems, methods and/or algorithms.

Model improvements to simulate charging in SEM

NASA Astrophysics Data System (ADS)

Arat, K. T.; Klimpel, T.; Hagen, C. W.

2018-03-01

Charging of insulators is a complex phenomenon to simulate since the accuracy of the simulations is very sensitive to the interaction of electrons with matter and electric fields. In this study, we report model improvements for a previously developed Monte-Carlo simulator to more accurately simulate samples that charge. The improvements include both modelling of low energy electron scattering and charging of insulators. The new first-principle scattering models provide a more realistic charge distribution cloud in the material, and a better match between non-charging simulations and experimental results. Improvements on charging models mainly focus on redistribution of the charge carriers in the material with an induced conductivity (EBIC) and a breakdown model, leading to a smoother distribution of the charges. Combined with a more accurate tracing of low energy electrons in the electric field, we managed to reproduce the dynamically changing charging contrast due to an induced positive surface potential.

Analysis of the Flicker Level Produced by a Fixed-Speed Wind Turbine

NASA Astrophysics Data System (ADS)

Suppioni, Vinicius; P. Grilo, Ahda

2013-10-01

In this article, the analysis of the flicker emission during continuous operation of a mid-scale fixed-speed wind turbine connected to a distribution system is presented. Flicker emission is investigated based on simulation results, and the dependence of flicker emission on short-circuit capacity, grid impedance angle, mean wind speed, and wind turbulence is analyzed. The simulations were conducted in different programs in order to provide a more realistic wind emulation and detailed model of mechanical and electrical components of the wind turbine. Such aim is accomplished by using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to simulate the mechanical parts of the wind turbine, Simulink/MatLab to simulate the electrical system, and TurbSim to obtain the wind model. The results show that, even for a small wind generator, the flicker level can limit the wind power capacity installed in a distribution system.

Method of Fault Detection and Rerouting

NASA Technical Reports Server (NTRS)

Gibson, Tracy L. (Inventor); Medelius, Pedro J. (Inventor); Lewis, Mark E. (Inventor)

2013-01-01

A system and method for detecting damage in an electrical wire, including delivering at least one test electrical signal to an outer electrically conductive material in a continuous or non-continuous layer covering an electrically insulative material layer that covers an electrically conductive wire core. Detecting the test electrical signals in the outer conductive material layer to obtain data that is processed to identify damage in the outer electrically conductive material layer.

Bounds on the conductivity of a suspension of random impenetrable spheres

NASA Astrophysics Data System (ADS)

Beasley, J. D.; Torquato, S.

1986-11-01

We compare the general Beran bounds on the effective electrical conductivity of a two-phase composite to the bounds derived by Torquato for the specific model of spheres distributed throughout a matrix phase. For the case of impenetrable spheres, these bounds are shown to be identical and to depend on the microstructure through the sphere volume fraction φ2 and a three-point parameter ζ2, which is an integral over a three-point correlation function. We evaluate ζ2 exactly through third order in φ2 for distributions of impenetrable spheres. This expansion is compared to the analogous results of Felderhof and of Torquato and Lado, all of whom employed the superposition approximation for the three-particle distribution function involved in ζ2. The results indicate that the exact ζ2 will be greater than the value calculated under the superposition approximation. For reasons of mathematical analogy, the results obtained here apply as well to the determination of the thermal conductivity, dielectric constant, and magnetic permeability of composite media and the diffusion coefficient of porous media.

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics.

PubMed

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-02-04

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level.

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics

PubMed Central

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-01-01

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level. PMID:26841954

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics

NASA Astrophysics Data System (ADS)

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-02-01

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level.

Characterizing fiber-reinforced composite structures using AC-impedance spectroscopy (AC-IS)

NASA Astrophysics Data System (ADS)

Woo, Leta Y.

Property enhancement in composites depends largely on the reinforcement. For fiber-reinforced composites, the distribution of fibers is crucial in determining the electrical and mechanical performance. Image analysis methods for characterization can be time-consuming and/or destructive. This work explores the capability of AC-impedance spectroscopy (AC-IS), an electrical measurement technique, to serve as a rapid, non-destructive tool for characterizing composite microstructure. The composite requirements include a filler that is electrically conducting or semi-conducting with higher conductivity than the matrix, and a high-impedance interface or coating between the filler and the matrix. To establish an AC-IS characterization method, cement-matrix composites with steel reinforcement were employed as both a technologically important and a model system to investigate how fibers affect the electrical response. Beginning with spherical particulates and then fibers, composites were examined using composite theory and an "intrinsic conductivity" approach. The intrinsic conductivity approach applies to composites with low volume fractions of fibers (i.e., in the dilute regime) and relates how the composite conductivity varies relative to the matrix as a function of volume fraction. A universal equivalent circuit model was created to understand the AC-IS response of composites based on the geometry and volume fraction of the filler. Deviation from predicted behavior was assessed using a developed f-function, which quantifies how fibers contribute to the overall electrical response of the composite. Using the f-function, an AC-IS method for investigating fiber dispersion was established to characterize alignment, settling/segregation, and aggregation. Alignment was investigated using measurements made in three directions. A point-probe technique characterized settling and/or large-scale inhomogeneous mixing in samples. Aggregation was quantified using a "dispersion factor" that compared theoretical with measured values and served as an upper limit for how well the fibers were dispersed. The AC-IS method was then extended to two different cement-matrix composite systems, low resistivity fresh-paste cement composites (confirmed by time domain reflectometry) and high resistivity cement composites, both of which required additional analysis to apply the AC-IS characterization method.

Electric shielding films for biased TEM samples and their application to in situ electron holography.

PubMed

Nomura, Yuki; Yamamoto, Kazuo; Hirayama, Tsukasa; Saitoh, Koh

2018-06-01

We developed a novel sample preparation method for transmission electron microscopy (TEM) to suppress superfluous electric fields leaked from biased TEM samples. In this method, a thin TEM sample is first coated with an insulating amorphous aluminum oxide (AlOx) film with a thickness of about 20 nm. Then, the sample is coated with a conductive amorphous carbon film with a thickness of about 10 nm, and the film is grounded. This technique was applied to a model sample of a metal electrode/Li-ion-conductive-solid-electrolyte/metal electrode for biasing electron holography. We found that AlOx film with a thickness of 10 nm has a large withstand voltage of about 8 V and that double layers of AlOx and carbon act as a 'nano-shield' to suppress 99% of the electric fields outside of the sample. We also found an asymmetry potential distribution between high and low potential electrodes in biased solid-electrolyte, indicating different accumulation behaviors of lithium-ions (Li+) and lithium-ion vacancies (VLi-) in the biased solid-electrolyte.

Two dimensional simulation of patternable conducting polymer electrode based organic thin film transistor

NASA Astrophysics Data System (ADS)

Nair, Shiny; Kathiresan, M.; Mukundan, T.

2018-02-01

Device characteristics of organic thin film transistor (OTFT) fabricated with conducting polyaniline:polystyrene sulphonic acid (PANi-PSS) electrodes, patterned by the Parylene lift-off method are systematically analyzed by way of two dimensional numerical simulation. The device simulation was performed taking into account field-dependent mobility, low mobility layer at the electrode-semiconductor interface, trap distribution in pentacene film and trapped charge at the organic/insulator interface. The electrical characteristics of bottom contact thin film transistor with PANi-PSS electrodes and pentacene active material is superior to those with palladium electrodes due to a lower charge injection barrier. Contact resistance was extracted in both cases by the transfer line method (TLM). The extracted charge concentration and potential profile from the two dimensional numerical simulation was used to explain the observed electrical characteristics. The simulated device characteristics not only matched the experimental electrical characteristics, but also gave an insight on the charge injection, transport and trap properties of the OTFTs as a function of different electrode materials from the perspectives of transistor operation.

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

DOEpatents

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

2015-01-13

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

Electric-field control of conductance in metal quantum point contacts by electric-double-layer gating

NASA Astrophysics Data System (ADS)

Shibata, K.; Yoshida, K.; Daiguji, K.; Sato, H.; , T., Ii; Hirakawa, K.

2017-10-01

An electric-field control of quantized conductance in metal (gold) quantum point contacts (QPCs) is demonstrated by adopting a liquid-gated electric-double-layer (EDL) transistor geometry. Atomic-scale gold QPCs were fabricated by applying the feedback-controlled electrical break junction method to the gold nanojunction. The electric conductance in gold QPCs shows quantized conductance plateaus and step-wise increase/decrease by the conductance quantum, G0 = 2e2/h, as EDL-gate voltage is swept, demonstrating a modulation of the conductance of gold QPCs by EDL gating. The electric-field control of conductance in metal QPCs may open a way for their application to local charge sensing at room temperature.

Electrical conductivity modeling in fractal non-saturated porous media

NASA Astrophysics Data System (ADS)

Wei, W.; Cai, J.; Hu, X.; Han, Q.

2016-12-01

The variety of electrical conductivity in non-saturated conditions is important to study electric conduction in natural sedimentary rocks. The electrical conductivity in completely saturated porous media is a porosity-function representing the complex connected behavior of single conducting phases (pore fluid). For partially saturated conditions, the electrical conductivity becomes even more complicated since the connectedness of pore. Archie's second law is an empirical electrical conductivity-porosity and -saturation model that has been used to predict the formation factor of non-saturated porous rock. However, the physical interpretation of its parameters, e.g., the cementation exponent m and the saturation exponent n, remains questionable. On basis of our previous work, we combine the pore-solid fractal (PSF) model to build an electrical conductivity model in non-saturated porous media. Our theoretical porosity- and saturation-dependent models contain endmember properties, such as fluid electrical conductivities, pore fractal dimension and tortuosity fractal dimension (representing the complex degree of electrical flowing path). We find the presented model with non-saturation-dependent electrical conductivity datasets indicate excellent match between theory and experiments. This means the value of pore fractal dimension and tortuosity fractal dimension change from medium to medium and depends not only on geometrical properties of pore structure but also characteristics of electrical current flowing in the non-saturated porous media.

Thermal history effects on electrical relaxation and conductivity for potassium silicate glass with low alkali concentrations

NASA Technical Reports Server (NTRS)

Angel, Paul W.; Hann, Raiford E.; Cooper, Alfred R.

1993-01-01

Electrical response measurements from 10 Hz to 100 kHz between 120 and 540 C were made on potassium-silicate glasses with alkali oxide contents of 2, 3, 5 and 10 mol percent. Low alkali content glasses were chosen in order to try to reduce the Coulombic interactions between alkali ions to the point that frozen structural effects from the glass could be observed. Conductivity and electrical relaxation responses for both annealed and quenched glasses of the same composition were compared. Lower DC conductivity (sigma(sub DC)) activation energies were measured for the quenched compared to the annealed glasses. The two glasses with the lowest alkali contents exhibited a non-Arrhenius concave up curvature in the log(sigma(sub DC)) against 1/T plots, which decreased upon quenching. A sharp decrease in sigma(sub DC) was observed for glasses containing K2O concentrations of 5 mol percent or less. The log modulus loss peak (M'') maximum frequency plots against 1/T all showed Arrhenius behavior for both annealed and quenched samples. The activation energies for these plots closely agreed with the sigma(sub DC) activation energies. A sharp increase in activation energy was observed for both series as the potassium oxide concentration decreased. Changes in the electrical response are attributed to structural effects due to different alkali concentrations. Differences between the annealed and quenched response are linked to a change in the distribution of activation energies (DAE).

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.

Space station electrical power system availability study

NASA Technical Reports Server (NTRS)

Turnquist, Scott R.; Twombly, Mark A.

1988-01-01

ARINC Research Corporation performed a preliminary reliability, and maintainability (RAM) anlaysis of the NASA space station Electric Power Station (EPS). The analysis was performed using the ARINC Research developed UNIRAM RAM assessment methodology and software program. The analysis was performed in two phases: EPS modeling and EPS RAM assessment. The EPS was modeled in four parts: the insolar power generation system, the eclipse power generation system, the power management and distribution system (both ring and radial power distribution control unit (PDCU) architectures), and the power distribution to the inner keel PDCUs. The EPS RAM assessment was conducted in five steps: the use of UNIRAM to perform baseline EPS model analyses and to determine the orbital replacement unit (ORU) criticalities; the determination of EPS sensitivity to on-orbit spared of ORUs and the provision of an indication of which ORUs may need to be spared on-orbit; the determination of EPS sensitivity to changes in ORU reliability; the determination of the expected annual number of ORU failures; and the integration of the power generator system model results with the distribution system model results to assess the full EPS. Conclusions were drawn and recommendations were made.

Electrically activated artificial muscles made with liquid crystal elastomers

NASA Astrophysics Data System (ADS)

Shahinpoor, Mohsen

2000-06-01

Composites of monodomain nematic liquid crystal elastomers and a conducting material distributed within their network are shown to exhibit large deformations, i.e. contraction, expansion, bending with strains of over 200% and appreciable force, by Joule heating through electrical activation. The electrical activation of the conducting material induces a rapid Joule heating in the sample leading to a nematic to isotropic phase transition where the elastomer of dimensions 32 mm x 7 mm x 0.4 mm contracted in less than a second. The cooling process, isotropic to nematic transition where the elastomer expands back to its original length, was slow and took 8 seconds. The material studied here is a highly novel liquid crystalline co-elastomer, invented and developed by Heino Finkelmann and co-workers at Albert-Ludwigs-Universitaet in Freiburg, Germany. The material is such that in which the mesogenic units are in both the side chains and the main chains of the elastomer. This co-elastomer was then mechanically loaded to induce a uniaxial network anisotropy before the cross-linking reaction was completed. These samples were then made into a composite with a conducting material such as dispersed silver particles or graphite fibers. The final samples was capable of undergoing more than 200% reversible strain in a few seconds.

Pressure-induced amorphization in single-crystal Ta2O5 nanowires: a kinetic mechanism and improved electrical conductivity.

PubMed

Lü, Xujie; Hu, Qingyang; Yang, Wenge; Bai, Ligang; Sheng, Howard; Wang, Lin; Huang, Fuqiang; Wen, Jianguo; Miller, Dean J; Zhao, Yusheng

2013-09-18

Pressure-induced amorphization (PIA) in single-crystal Ta2O5 nanowires is observed at 19 GPa, and the obtained amorphous Ta2O5 nanowires show significant improvement in electrical conductivity. The phase transition process is unveiled by monitoring structural evolution with in situ synchrotron X-ray diffraction, pair distribution function, Raman spectroscopy, and transmission electron microscopy. The first principles calculations reveal the phonon modes softening during compression at particular bonds, and the analysis on the electron localization function also shows bond strength weakening at the same positions. On the basis of the experimental and theoretical results, a kinetic PIA mechanism is proposed and demonstrated systematically that amorphization is initiated by the disruption of connectivity between polyhedra (TaO6 octahedra or TaO7 bipyramids) at the particular weak-bonding positions along the a axis in the unit cell. The one-dimensional morphology is well-preserved for the pressure-induced amorphous Ta2O5, and the electrical conductivity is improved by an order of magnitude compared to traditional amorphous forms. Such pressure-induced amorphous nanomaterials with unique properties surpassing those in either crystalline or conventional amorphous phases hold great promise for numerous applications in the future.

Analytical solution of electromagnetic radiation by a vertical electric dipole inside the earth and the effect of atmospheric electrical conductivity inhomogeneity

NASA Astrophysics Data System (ADS)

Mosayebidorcheh, Taha; Hosseinibalam, Fahimeh; Hassanzadeh, Smaeyl

2017-11-01

In this paper, the effect of atmospheric electrical conductivity on the electromagnetic waves radiated by a vertical electric dipole located in the earth, near the surface of the earth, is investigated. As far as electrical conductivity is concerned, the atmosphere is divided into three areas, in which the electrical conductivity changes with altitude. The Maxwell equations in these areas are investigated as well. Using the differential transform method, the differential equation is solved in a way that atmospheric electrical conductivity is variable. Solving the problem in these areas indicates that electrical conductivity in the middle and lower areas of atmosphere may be ignored. However, in the upper areas of atmosphere, the magnitude of the magnetic field in the ionosphere at a frequency of 10 kHz at night is five times smaller when electrical conductivity is considered compared to when it is neglected.

Role of dielectric constant in electrohydrodynamics of conducting fluids

NASA Technical Reports Server (NTRS)

Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

1992-01-01

Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

Simulation of Electromigration Based on Resistor Networks

NASA Astrophysics Data System (ADS)

Patrinos, Anthony John

A two dimensional computer simulation of electromigration based on resistor networks was designed and implemented. The model utilizes a realistic grain structure generated by the Monte Carlo method and takes specific account of the local effects through which electromigration damage progresses. The dynamic evolution of the simulated thin film is governed by the local current and temperature distributions. The current distribution is calculated by superimposing a two dimensional electrical network on the lattice whose nodes correspond to the particles in the lattice and the branches to interparticle bonds. Current is assumed to flow from site to site via nearest neighbor bonds. The current distribution problem is solved by applying Kirchhoff's rules on the resulting electrical network. The calculation of the temperature distribution in the lattice proceeds by discretizing the partial differential equation for heat conduction, with appropriate material parameters chosen for the lattice and its defects. SEReNe (for Simulation of Electromigration using Resistor Networks) was tested by applying it to common situations arising in experiments with real films with satisfactory results. Specifically, the model successfully reproduces the expected grain size, line width and bamboo effects, the lognormal failure time distribution and the relationship between current density exponent and current density. It has also been modified to simulate temperature ramp experiments but with mixed, in this case, results.

Heating the sun's lower transition region with fine-scale electric currents

NASA Technical Reports Server (NTRS)

Rabin, D.; Moore, R.

1984-01-01

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

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.

Changes in geophysical properties caused by fluid injection into porous rocks: analytical models: Geophysical changes in porous rocks

DOE PAGES

Pride, Steven R.; Berryman, James G.; Commer, Michael; ...

2016-08-30

Analytical models are provided that describe how the elastic compliance, electrical conductivity, and fluid-flow permeability of rocks depend on stress and fluid pressure. In order to explain published laboratory data on how seismic velocities and electrical conductivity vary in sandstones and granites, the models require a population of cracks to be present in a possibly porous host phase. The central objective is to obtain a consistent mean-field analytical model that shows how each modeled rock property depends on the nature of the crack population. We describe the crack populations by a crack density, a probability distribution for the crack aperturesmore » and radii, and the averaged orientation of the cracks. The possibly anisotropic nature of the elasticity, conductivity, and permeability tensors is allowed for; however, only the isotropic limit is used when comparing to laboratory data. For the transport properties of conductivity and permeability, the percolation effect of the crack population linking up to form a connected path across a sample is modeled. But, this effect is important only in crystalline rock where the host phase has very small conductivity and permeability. In general, the importance of the crack population to the transport properties increases as the host phase becomes less conductive and less permeable.« less

Changes in geophysical properties caused by fluid injection into porous rocks: analytical models: Geophysical changes in porous rocks

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

Pride, Steven R.; Berryman, James G.; Commer, Michael

Analytical models are provided that describe how the elastic compliance, electrical conductivity, and fluid-flow permeability of rocks depend on stress and fluid pressure. In order to explain published laboratory data on how seismic velocities and electrical conductivity vary in sandstones and granites, the models require a population of cracks to be present in a possibly porous host phase. The central objective is to obtain a consistent mean-field analytical model that shows how each modeled rock property depends on the nature of the crack population. We describe the crack populations by a crack density, a probability distribution for the crack aperturesmore » and radii, and the averaged orientation of the cracks. The possibly anisotropic nature of the elasticity, conductivity, and permeability tensors is allowed for; however, only the isotropic limit is used when comparing to laboratory data. For the transport properties of conductivity and permeability, the percolation effect of the crack population linking up to form a connected path across a sample is modeled. But, this effect is important only in crystalline rock where the host phase has very small conductivity and permeability. In general, the importance of the crack population to the transport properties increases as the host phase becomes less conductive and less permeable.« less

Electrical transport properties of thermally evaporated phthalocyanine (H 2Pc) thin films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Farid, A. M.; Attia, A. A.; Ali, H. A. M.

2006-08-01

Thin films of H 2Pc of various thicknesses have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity measurements were carried out at different temperatures in the range 298-473 K. An estimation of mean free path ( lo) of charge carriers in H 2Pc thin films was attempted. Measurements of thermoelectric power confirm that H 2Pc thin films behave as a p-type semiconductor. The current density-voltage characteristics of Au/H 2Pc/Au at room temperature showed ohmic conduction mechanism at low voltages. At higher voltages the space-charge-limited conduction (SCLC) accompanied by an exponential trap distribution was dominant. The temperature dependence of current density allows the determination of some essential parameters such as the hole mobility ( μh), the total trap concentration ( Nt), the characteristic temperature ( Tt) and the trap density P( E).

Antimony-Doped Tin Oxide Thin Films Grown by Home Made Spray Pyrolysis Technique

NASA Astrophysics Data System (ADS)

Yusuf, Gbadebo; Babatola, Babatunde Keji; Ishola, Abdulahi Dimeji; Awodugba, Ayodeji O.; Solar cell Collaboration

2016-03-01

Transparent conducting antimony-doped tin oxide (ATO) films have been deposited on glass substrates by home made spray pyrolysis technique. The structural, electrical and optical properties of the ATO films have been investigated as a function of Sb-doping level and annealing temperature. The optimum target composition for high conductivity and low resistivity was found to be 20 wt. % SnSb2 + 90 wt. ATO. Under optimized deposition conditions of 450oC annealing temperature, electrical resistivity of 5.2×10-4 Ω -cm, sheet resistance of 16.4 Ω/sq, average optical transmittance of 86% in the visible range, and average optical band-gap of 3.34eV were obtained. The film deposited at lower annealing temperature shows a relatively rough, loosely bound slightly porous surface morphology while the film deposited at higher annealing temperature shows uniformly distributed grains of greater size. Keywords: Annealing, Doping, Homemade spray pyrolysis, Tin oxide, Resistivity

Nanotube Tunneling as a Consequence of Probable Discrete Trajectories

NASA Technical Reports Server (NTRS)

Robinson, Daryl C.

2001-01-01

It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but is divided into charge "islands." A clear understanding of tunneling phenomena can be useful to elucidate the mechanism for electrical conduction in nanotubes. This paper represents the first attempt to shed light on the aforementioned phenomenon through viewing tunneling as a natural consequence of "discrete trajectories." The relevance of this analysis is that it may provide further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. In a situation involving particles impinging on a classically impenetrable barrier, the result of quantum mechanics that the probability of detecting transmitted particles falls off exponentially is derived without wave theory. This paper should provide a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

Bio-heat transfer model of deep brain stimulation-induced temperature changes

NASA Astrophysics Data System (ADS)

Elwassif, Maged M.; Kong, Qingjun; Vazquez, Maribel; Bikson, Marom

2006-12-01

There is a growing interest in the use of chronic deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. Fundamental questions remain about the physiologic effects of DBS. Previous basic research studies have focused on the direct polarization of neuronal membranes by electrical stimulation. The goal of this paper is to provide information on the thermal effects of DBS using finite element models to investigate the magnitude and spatial distribution of DBS-induced temperature changes. The parameters investigated include stimulation waveform, lead selection, brain tissue electrical and thermal conductivities, blood perfusion, metabolic heat generation during the stimulation and lead thermal conductivity/heat dissipation through the electrode. Our results show that clinical DBS protocols will increase the temperature of surrounding tissue by up to 0.8 °C depending on stimulation/tissue parameters.

Theoretical study on the electronic, structural, properties and reactivity of a series of mono-, di-, tri- and tetrachlorothiophenes as well as corresponding radical cation forms as monomers for conducting polymers.

PubMed

Shirani Il Beigi, Hossein; Jameh-Bozorghi, Saeed

2011-03-14

In this paper, electrical and structural properties of mono-, di-, tri- and tetrachlorothiophenes and their radical cations have been studied using the density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of chlorine atoms on the properties of the thiophene ring for all chlorothiophenes and their radical cations have been studied. Vibrational frequencies, nuclear chemical shielding constants, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizabilities and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-chlorothiophene are more delocalized and it is the best possible candidate monomer among all chlorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics.

Lockheed Martin T-Rex: Preliminary report

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

NONE

1997-07-31

T-Rex is a robot which may be used in toxic or flammable environments. The assessment of the T-Rex conducted at the Lockheed Martin facility was limited in its scope. The scope of the assessment was directed by the type of equipment being used and the amount of accessibility to the equipment. Due to severe time constraints--the assessment was conducted in one day--human factors interface activities were limited. This should be considered a preliminary assessment. This report covers aspects of the technology that were available to the assessment team. Recommendations for future evaluation of this technology are also included. The contentsmore » are as follows: Electrical Considerations; General Electrical Consideration; Trailing Cables; Grounding; Surface High Voltage Distribution; Low and Medium Voltage Alternating Current Circuits; Potential for Harmful Human Factor Incidents and Enterprise Disablement; Exclusion Zone Emergency Maintenance; and Recommendations.« less

High conductance surge cable

DOEpatents

Murray, Matthew M.; Wilfong, Dennis H.; Lomax, Ralph E.

1998-01-01

An electrical cable for connecting transient voltage surge suppressers to ectrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation.

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M; Hammerstrom, Donald J; Kintner-Meyer, Michael C.W.; Tuffner, Francis K

2013-07-02

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M.; Hammerstrom, Donald J.; Kintner-Meyer, Michael C. W.; Tuffner, Francis K.

2017-09-05

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Grid regulation services for energy storage devices based on grid frequency

DOEpatents

Pratt, Richard M; Hammerstrom, Donald J; Kintner-Meyer, Michael C.W.; Tuffner, Francis K

2014-04-15

Disclosed herein are representative embodiments of methods, apparatus, and systems for charging and discharging an energy storage device connected to an electrical power distribution system. In one exemplary embodiment, a controller monitors electrical characteristics of an electrical power distribution system and provides an output to a bi-directional charger causing the charger to charge or discharge an energy storage device (e.g., a battery in a plug-in hybrid electric vehicle (PHEV)). The controller can help stabilize the electrical power distribution system by increasing the charging rate when there is excess power in the electrical power distribution system (e.g., when the frequency of an AC power grid exceeds an average value), or by discharging power from the energy storage device to stabilize the grid when there is a shortage of power in the electrical power distribution system (e.g., when the frequency of an AC power grid is below an average value).

Electrical impedance tomography in anisotropic media with known eigenvectors

NASA Astrophysics Data System (ADS)

Abascal, Juan-Felipe P. J.; Lionheart, William R. B.; Arridge, Simon R.; Schweiger, Martin; Atkinson, David; Holder, David S.

2011-06-01

Electrical impedance tomography is an imaging method, with which volumetric images of conductivity are produced by injecting electrical current and measuring boundary voltages. It has the potential to become a portable non-invasive medical imaging technique. Until now, most implementations have neglected anisotropy even though human tissues like bone, muscle and brain white matter are markedly anisotropic. The recovery of an anisotropic conductivity tensor is uniquely determined by boundary measurements only up to a diffeomorphism that fixes the boundary. Nevertheless, uniqueness can be restored by providing information about the diffeomorphism. There are uniqueness results for two constraints: one eigenvalue and a multiple scalar of a general tensor. A useable constraint for medical applications is when the eigenvectors of the underlying tissue are known, which can be approximated from MRI or estimated from DT-MRI, although the eigenvalues are unknown. However there is no known theoretical result guaranteeing uniqueness for this constraint. In fact, only a few previous inversion studies have attempted to recover one or more eigenvalues assuming certain symmetries while ignoring nonuniqueness. In this work, the aim was to undertake a numerical study of the feasibility of the recovery of a piecewise linear finite element conductivity tensor in anisotropic media with known eigenvectors from the complete boundary data. The work suggests that uniqueness holds for this constraint, in addition to proposing a methodology for the incorporation of this prior for general conductivity tensors. This was carried out by performing an analysis of the Jacobian rank and by reconstructing four conductivity distributions: two diagonal tensors whose eigenvalues were linear and sinusoidal functions, and two general tensors whose eigenvectors resembled physiological tissue, one with eigenvectors spherically orientated like a spherical layered structure, and a sample of DT-MRI data of brain white matter. The Jacobian with respect to three eigenvalues was full-rank and it was possible to recover three eigenvalues for the four simulated distributions. This encourages further theoretical study of the uniqueness for this constraint and supports the use of this as a relevant usable method for medical applications.

The WAIS Melt Monitor: An automated ice core melting system for meltwater sample handling and the collection of high resolution microparticle size distribution data

NASA Astrophysics Data System (ADS)

Breton, D. J.; Koffman, B. G.; Kreutz, K. J.; Hamilton, G. S.

2010-12-01

Paleoclimate data are often extracted from ice cores by careful geochemical analysis of meltwater samples. The analysis of the microparticles found in ice cores can also yield unique clues about atmospheric dust loading and transport, dust provenance and past environmental conditions. Determination of microparticle concentration, size distribution and chemical makeup as a function of depth is especially difficult because the particle size measurement either consumes or contaminates the meltwater, preventing further geochemical analysis. Here we describe a microcontroller-based ice core melting system which allows the collection of separate microparticle and chemistry samples from the same depth intervals in the ice core, while logging and accurately depth-tagging real-time electrical conductivity and particle size distribution data. This system was designed specifically to support microparticle analysis of the WAIS Divide WDC06A deep ice core, but many of the subsystems are applicable to more general ice core melting operations. Major system components include: a rotary encoder to measure ice core melt displacement with 0.1 millimeter accuracy, a meltwater tracking system to assign core depths to conductivity, particle and sample vial data, an optical debubbler level control system to protect the Abakus laser particle counter from damage due to air bubbles, a Rabbit 3700 microcontroller which communicates with a host PC, collects encoder and optical sensor data and autonomously operates Gilson peristaltic pumps and fraction collectors to provide automatic sample handling, melt monitor control software operating on a standard PC allowing the user to control and view the status of the system, data logging software operating on the same PC to collect data from the melting, electrical conductivity and microparticle measurement systems. Because microparticle samples can easily be contaminated, we use optical air bubble sensors and high resolution ice core density profiles to guide the melting process. The combination of these data allow us to analyze melt head performance, minimize outer-to-inner fraction contamination and avoid melt head flooding. The WAIS Melt Monitor system allows the collection of real-time, sub-annual microparticle and electrical conductivity data while producing and storing enough sample for traditional Coulter-Counter particle measurements as well long term acid leaching of bioactive metals (e.g., Fe, Co, Cd, Cu, Zn) prior to chemical analysis.

Breakdown of water super-permeation in electrically insulating graphene oxide films: role of dual interlayer spacing.

PubMed

Kavitha, Maheshwari Kavirajan; Sakorikar, Tushar; Vayalamkuzhi, Pramitha; Jaiswal, Manu

2018-08-10

Conventional graphene oxide (GO) is characterized by low sp 2 content in a sp 3 rich matrix, which is responsible both for electrical insulation and water super-permeation. Upon reduction, electrical conduction is achieved at the expense of water permeation ability. Here, we demonstrate that charge conduction and water permeation can be simultaneously restricted in a functionalized form of GO. Gravimetric studies reveal that diffusion of water vapor through a glassy polymer membrane is arrested by loading a hydrophobic form of GO (H-GO) in the polymer matrix, even as such, water inhibition cannot be realized by substantially increasing the thickness of the bare polymer. As an application, the ability of the coating to impede the degradation of methyl ammonium lead iodide films under high humidity conditions is demonstrated. At the same time the H-GO film has a resistance over 10 7 times higher when compared to thermally reduced GO of similar sp 2 fraction. We attribute this unique behavior to the presence of a sub-micron matrix of GO with simultaneous presence of large (∼9.5 Å) and small (∼4.7 Å) interlayer spacing. This leads to disruption of the spatially distributed percolation pathways for electrical charge, and it also serves to block the nanocapillary networks for water molecules.

Electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine]beryllium investigated by impedance spectroscopy

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

Wang, Yanping; Chen, Jiangshan; Huang, Jinying

2014-06-14

The electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp{sub 2}) are investigated by impedance spectroscopy over a frequency range of 10 Hz to 13 MHz. The Cole-Cole plots demonstrate that the Bepp{sub 2}-based device can be represented by a single parallel resistance R{sub p} and capacitance C{sub p} network with a series resistance R{sub s}. The current-voltage characteristics and the variation of R{sub p} with applied bias voltage indicate the electron conduction of space-charge-limited current with exponential trap distributions in Bepp{sub 2}. It can be seen that the electron mobility exhibits strong field-dependence in low electric field region and almost saturate in highmore » electric field region. It is experimentally found that Bepp{sub 2} shows dispersion transport and becomes weak as the electric field increases. The activation energy is determined to be 0.043 eV by temperature-dependent conductivity, which is consistent with the result obtained from the temperature-dependent current density characteristics. The electron mobility reaches the orders of 10{sup −6}–10{sup −5} cm{sup 2} V{sup −1} s{sup −1}, depending on the electric field.« less

Installation restoration research program: Assessment of geophysical methods for subsurface geologic mapping, cluster 13, Edgewood Area, Aberdeen Proving Ground, Maryland. Final report

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

Butler, D.K.; Sharp, M.K.; Sjostrom, K.J.

1996-10-01

Seismic refraction, electrical resistivity, and transient electromagnetic surveys were conducted at a portion of Cluster 13, Edgewood Area of Aberdeen Proving Ground, Maryland. Seismic refraction cross sections map the topsoil layer and the water table (saturated zone). The water table elevations from the seismic surveys correlate closely with water table elevations in nearby monitoring wells. Electrical resistivity cross sections reveal a very complicated distribution of sandy and clayey facies in the upper 10 - 15 m of the subsurface. A continuous surficial (topsoil) layer correlates with the surficial layer of the seismic section and nearby boring logs. The complexity andmore » details of the electrical resistivity cross section correlate well with boring and geophysical logs from nearby wells. The transient electromagnetic surveys map the Pleistocene-Cretaceous boundary, the saprolite, and the top of the Precambrian crystalline rocks. Conducting the transient electromagnetic surveys on a grid pattern allows the construction of a three-dimensional representation of subsurface geology (as represented by variations of electrical resistivity). Thickness and depth of the saprolitic layer and depth to top of the Precambrian rocks are consistent with generalized geologic cross sections for the Edgewood Area and depths projected from reported depths at the Aberdeen Proving Ground NW boundary using regional dips.« less

Interaction of atmospheric pressure plasmas with dry and wet wounded skin

NASA Astrophysics Data System (ADS)

Babaeva, Natalia; Kushner, Mark

2010-11-01

Non-equilibrium plasmas in direct contact with living tissue can produce therapeutic effects. Dielectric barrier discharge (DBD) devices used for this purpose contain the powered electrode while the tissue being treated is usually the floating electrode. The plasma produces beneficial effects through: (i) electric fields, (ii) production of radicals and charged species, (iii) photons and (iv) energetic ions impinging onto wounds and tissue surfaces. Using a 2-d plasma hydrodynamics model, we discuss the interaction of DBD filaments with human skin. We model the propagation of the streamer across the gap, its intersection with skin, the charging of cell surfaces and the generation of conduction and displacement currents, and electric fields in the cells. The cellular structure in the first few mm of human skin is incorporated into the computational mesh with permittivity and conductivity to represent the electrical properties of the intra- and inter-cell structures. In this talk, we concentrate on the effects of plasmas on open wounds which are either dry or filled with blood serum. We will discuss the penetration of electric fields through the blood serum and into the underlying cells, including the possible interactions with blood platelets, and the distribution of ion energies onto the liquid and cellular surfaces.

Electrowetting on dielectric: experimental and model study of oil conductivity on rupture voltage

NASA Astrophysics Data System (ADS)

Zhao, Qing; Tang, Biao; Dong, Baoqin; Li, Hui; Zhou, Rui; Guo, Yuanyuan; Dou, Yingying; Deng, Yong; Groenewold, Jan; Henzen, Alexander Victor; Zhou, Guofu

2018-05-01

Electrowetting on dielectric devices uses a conducting (water) and insulating (oil) liquid phase in conjunction on a dielectric layer. In these devices, the wetting properties of the liquid phases can be manipulated by applying an electric field. The electric field can rupture the initially flat oil film and promotes further dewetting of the oil. Here, we investigate a problem in the operation of electrowetting on dielectric caused by a finite conductivity of the oil. In particular, we find that the voltage at which the oil film ruptures is sensitive to the application of relatively low DC voltages prior to switching. Here, we systematically investigate this dependence using controlled driving schemes. The mechanism behind these history effects point to charge transport processes in the dielectric and the oil, which can be modeled and characterized by a decay time. To quantify the effects the typical response timescales have been measured with a high-speed video camera. The results have been reproduced in simulations. In addition, a simplified yet accurate equivalent circuit model is developed to analyze larger data sets more conveniently. The experimental data support the hypothesis that each pixel can be characterized by a single decay time. We studied an ensemble of pixels and found that they showed a rather broad distribution of decay times with an average value of about 440 ms. This decay time can be interpreted as a discharge timescale of the oil, not to be confused with discharge of the entire system which is generally much faster (<1 ms). Through the equivalent circuit model, we also found that variations in the fluoropolymer (FP) conductivity cannot explain the distribution of decay times, while variations in oil conductivity can.

Apparatus for Use in Determining Surface Conductivity at Microwave Frequencies

NASA Technical Reports Server (NTRS)

Hearn, Chase P. (Inventor)

1995-01-01

An apparatus is provided for use in determining surface conductivity of a flat or shaped conductive material at microwave frequencies. A plate has an electrically conductive surface with first and second holes passing through the plate. An electrically conductive material under test (MUT) is maintained in a spaced apart relationship with the electrically conductive surface of the plate by one or more nonconductive spacers. A first coupling loop is electrically shielded within the first hole while a second coupling loop is electrically shielded within the second hole. A dielectric resonator element is positioned between the first and second coupling loops, while also being positioned closer to the MUT than the electrically conductive surface of the plate. Microwave energy at an operating frequency f is supplied from a signal source to the first coupling loop while microwave energy received at the second coupling loop is measured. The apparatus is capable of measuring the Q-factor of the dielectric resonator situated in the 'cavity' existing between the electrically conductive surface of the plate and the MUT. Surface conductivity of the electrically conductive surface can be determined via interpolation using: 1 ) the measured Q-factor with the electrically conductive surface in place, and 2) the measured Q-factor when the MUT is replaced with reference standards having known surface conductivities.

Price Based Local Power Distribution Management System (Local Power Distribution Manager) v1.0

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

BROWN, RICHARD E.; CZARNECKI, STEPHEN; SPEARS, MICHAEL

2016-11-28

A trans-active energy micro-grid controller is implemented in the VOLTTRON distributed control platform. The system uses the price of electricity as the mechanism for conducting transactions that are used to manage energy use and to balance supply and demand. In order to allow testing and analysis of the control system, the implementation is designed to run completely as a software simulation, while allowing the inclusion of selected hardware that physically manages power. Equipment to be integrated with the micro-grid controller must have an IP (Internet Protocol)-based network connection and a software "driver" must exist to translate data communications between themore » device and the controller.« less

60-Hz electric and magnetic fields generated by a distribution network.

PubMed

Héroux, P

1987-01-01

From a mobile unit, 60-Hz electric and magnetic fields generated by Hydro-Québec's distribution network were measured. Nine runs, representative of various human environments, were investigated. Typical values were 32 V/m and 0.16 microT. The electrical distribution networks investigated were major contributors to the electric and magnetic environments.

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.

Analysis of electrophoresis performance

NASA Technical Reports Server (NTRS)

Roberts, Glyn O.

1988-01-01

A flexible efficient computer code is being developed to simulate electrophoretic separation phenomena, in either a cylindrical or a rectangular geometry. The code will computer the evolution in time of the concentrations of an arbitrary number of chemical species, and of the temperature, pH distribution, conductivity, electric field, and fluid motion. Use of nonuniform meshes and fast accurate implicit time-stepping will yield accurate answers at economical cost.

Distributed automatic control of technological processes in conditions of weightlessness

NASA Technical Reports Server (NTRS)

Kukhtenko, A. I.; Merkulov, V. I.; Samoylenko, Y. I.; Ladikov-Royev, Y. P.

1986-01-01

Some problems associated with the automatic control of liquid metal and plasma systems under conditions of weightlessness are examined, with particular reference to the problem of stability of liquid equilibrium configurations. The theoretical fundamentals of automatic control of processes in electrically conducting continuous media are outlined, and means of using electromagnetic fields for simulating technological processes in a space environment are discussed.