Effects of microwave electric fields on the translational diffusion of dipolar molecules in surface potential: A simulation study

NASA Astrophysics Data System (ADS)

Kapranov, Sergey V.; Kouzaev, Guennadi A.

2018-01-01

Variations of effective diffusion coefficient of polar molecules exposed to microwave electric fields in a surface potential are studied by solving coupled stochastic differential equations of motion with a deterministic component of the surface force. Being an essential tool for the simulation interpretation, a theoretical approach to effective diffusion in surface potential is first developed. The effective diffusion coefficient is represented as the product of the normal diffusion coefficient and potential-dependent correction function, whose temperature dependence is close to the Arrhenius form. The analytically found zero-diffusion condition defines the state of thermal equilibrium at the surface. The diffusion of a water-like dipole molecule in the potential of graphite surface is simulated in the field-free conditions and in the presence of the alternating electric fields of various magnitude intensities and frequencies. Temperature dependence of the correction function exhibits field-induced variations of the effective Lennard-Jones energy parameter. It demonstrates maximum departure from the zero-field value at certain frequencies and intensities, which is associated with variations in the rotational dynamics. A concept of the amplitude-frequency resonance put forward to interpret the simulation results is explained using a heuristic reasoning and is corroborated by semi-quantitative considerations in terms of the Dissado-Hill cluster theory of dielectric relaxation.

Simulation of variation of apparent resistivity in resistivity surveys using finite difference modelling with Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Aguirre, E. E.; Karchewski, B.

2017-12-01

DC resistivity surveying is a geophysical method that quantifies the electrical properties of the subsurface of the earth by applying a source current between two electrodes and measuring potential differences between electrodes at known distances from the source. Analytical solutions for a homogeneous half-space and simple subsurface models are well known, as the former is used to define the concept of apparent resistivity. However, in situ properties are heterogeneous meaning that simple analytical models are only an approximation, and ignoring such heterogeneity can lead to misinterpretation of survey results costing time and money. The present study examines the extent to which random variations in electrical properties (i.e. electrical conductivity) affect potential difference readings and therefore apparent resistivities, relative to an assumed homogeneous subsurface model. We simulate the DC resistivity survey using a Finite Difference (FD) approximation of an appropriate simplification of Maxwell's equations implemented in Matlab. Electrical resistivity values at each node in the simulation were defined as random variables with a given mean and variance, and are assumed to follow a log-normal distribution. The Monte Carlo analysis for a given variance of electrical resistivity was performed until the mean and variance in potential difference measured at the surface converged. Finally, we used the simulation results to examine the relationship between variance in resistivity and variation in surface potential difference (or apparent resistivity) relative to a homogeneous half-space model. For relatively low values of standard deviation in the material properties (<10% of mean), we observed a linear correlation between variance of resistivity and variance in apparent resistivity.

Relationship between the global electric circuit and electrified cloud parameters at diurnal, seasonal, and interannual timescales

NASA Astrophysics Data System (ADS)

Lavigne, Thomas; Liu, Chuntao; Deierling, Wiebke; Mach, Douglas

2017-08-01

In the early 1900s, J. W. Whipple began to validate C. T. R. Wilson's global electric circuit (GEC) hypothesis by correlating the diurnal variation of global thunder days with the diurnal variation of the fair weather electric field measured by the Carnegie Cruise. This study applies 16+ years of precipitation feature (PF) data from the Tropical Rainfall Measuring Mission, including lightning data from the Lightning Imaging Sensor, alongside 12 years of electric field measurements from Vostok, Antarctica, to further examine this relationship. Joint diurnal-seasonal variations of the electric field are introduced and compared with a variety of PF parameters that are potentially related to the GEC. All tested PF parameters showed significant correlations to the electric field on the joint seasonal-diurnal timescale, with the flash rate and volume of 30 dBZ between the -5°C and -35°C isotherms showing the best linear correlations with R2 values of 0.67 and 0.62, respectively. Furthermore, these relationships are analyzed during the two different phases of the El Niño-Southern Oscillation. Results show different seasonal-diurnal variations of the electric field during El Niño and La Niña periods, with enhancements in the electric field between the months of January through April at 16-24 UTC in La Niña years. A similar trend is shown in global PF parameters, indicating relationships between the variations seen in the fair weather electric field and the variations of global PFs at diurnal, seasonal, and interannual timescales. This provides further evidence that PFs around the globe have a direct connection to the GEC.

Accounting for the Variation of Driver Aggression in the Simulation of Conventional and Advanced Vehicles

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

Neubauer, J.; Wood, E.

2013-01-01

Hybrid electric vehicles, plug-in hybrid electric vehicles, and battery electric vehicles offer the potential to reduce both oil imports and greenhouse gases, as well as to offer a financial benefit to the driver. However, assessing these potential benefits is complicated by several factors, including the driving habits of the operator. We focus on driver aggression, i.e., the level of acceleration and velocity characteristic of travel, to (1) assess its variation within large, real-world drive datasets, (2) quantify its effect on both vehicle efficiency and economics for multiple vehicle types, (3) compare these results to those of standard drive cycles commonlymore » used in the industry, and (4) create a representative drive cycle for future analyses where standard drive cycles are lacking.« less

Electrical Signals in Prayer Plants (Marantaceae)? Insights into the Trigger Mechanism of the Explosive Style Movement

PubMed Central

Jerominek, Markus; Claßen-Bockhoff, Regine

2015-01-01

The explosive pollination mechanism of the prayer plants (Marantaceae) is unique among plants. After a tactile stimulus by a pollinator, the style curls up rapidly and mediates pollen exchange. It is still under discussion whether this explosive movement is released electrophysiologically, i.e. by a change in the membrane potential (as in Venus flytrap), or purely mechanically. In the present study, electrophysiological experiments are conducted to clarify the mechanism. Artificial release experiments (chemical and electrical) and electrophysiological measurements were conducted with two phylogenetically distant species, Goeppertia bachemiana (E. Morren) Borchs. & S. Suárez and Donax canniformis (G. Forst.) K. Schum. Electric responses recorded after style release by extracellular measurements are characterised as variation potentials due to their long repolarization phase and lack of self-perpetuation. In both species, chemical and electric stimulations do not release the style movement. It is concluded that the style movement in Marantaceae is released mechanically by relieving the tissue pressure. Accordingly, the variation potential is an effect of the movement and not its cause. The study exemplarily shows that fast movements in plants are not necessarily initiated by electric changes of the membrane as known from the Venus flytrap. PMID:25997015

Electrical signals in prayer plants (marantaceae)? Insights into the trigger mechanism of the explosive style movement.

PubMed

Jerominek, Markus; Claßen-Bockhoff, Regine

2015-01-01

The explosive pollination mechanism of the prayer plants (Marantaceae) is unique among plants. After a tactile stimulus by a pollinator, the style curls up rapidly and mediates pollen exchange. It is still under discussion whether this explosive movement is released electrophysiologically, i.e. by a change in the membrane potential (as in Venus flytrap), or purely mechanically. In the present study, electrophysiological experiments are conducted to clarify the mechanism. Artificial release experiments (chemical and electrical) and electrophysiological measurements were conducted with two phylogenetically distant species, Goeppertia bachemiana (E. Morren) Borchs. & S. Suárez and Donax canniformis (G. Forst.) K. Schum. Electric responses recorded after style release by extracellular measurements are characterised as variation potentials due to their long repolarization phase and lack of self-perpetuation. In both species, chemical and electric stimulations do not release the style movement. It is concluded that the style movement in Marantaceae is released mechanically by relieving the tissue pressure. Accordingly, the variation potential is an effect of the movement and not its cause. The study exemplarily shows that fast movements in plants are not necessarily initiated by electric changes of the membrane as known from the Venus flytrap.

System and method for islanding detection and prevention in distributed generation

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

Bhowmik, Shibashis; Mazhari, Iman; Parkhideh, Babak

Various examples are directed to systems and methods for detecting an islanding condition at an inverter configured to couple a distributed generation system to an electrical grid network. A controller may determine a command frequency and a command frequency variation. The controller may determine that the command frequency variation indicates a potential islanding condition and send to the inverter an instruction to disconnect the distributed generation system from the electrical grid network. When the distributed generation system is disconnected from the electrical grid network, the controller may determine whether the grid network is valid.

Multi-agent electricity market modeling with EMCAS.

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

North, M.; Macal, C.; Conzelmann, G.

2002-09-05

Electricity systems are a central component of modern economies. Many electricity markets are transitioning from centrally regulated systems to decentralized markets. Furthermore, several electricity markets that have recently undergone this transition have exhibited extremely unsatisfactory results, most notably in California. These high stakes transformations require the introduction of largely untested regulatory structures. Suitable tools that can be used to test these regulatory structures before they are applied to real systems are required. Multi-agent models can provide such tools. To better understand the requirements such as tool, a live electricity market simulation was created. This experience helped to shape the developmentmore » of the multi-agent Electricity Market Complex Adaptive Systems (EMCAS) model. To explore EMCAS' potential, several variations of the live simulation were created. These variations probed the possible effects of changing power plant outages and price setting rules on electricity market prices.« less

Voltage contrast X-ray photoelectron spectroscopy reveals graphene-substrate interaction in graphene devices fabricated on the C- and Si- faces of SiC

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

Aydogan, Pinar; Suzer, Sefik, E-mail: suzer@fen.bilkent.edu.tr; Arslan, Engin

2015-09-21

We report on an X-ray photoelectron spectroscopy (XPS) study of two graphene based devices that were analyzed by imposing a significant current under +3 V bias. The devices were fabricated as graphene layers(s) on hexagonal SiC substrates, either on the C- or Si-terminated faces. Position dependent potential distributions (IR-drop), as measured by variations in the binding energy of a C1s peak are observed to be sporadic for the C-face graphene sample, but very smooth for the Si-face one, although the latter is less conductive. We attribute these sporadic variations in the C-face device to the incomplete electrical decoupling between the graphenemore » layer(s) with the underlying buffer and/or substrate layers. Variations in the Si2p and O1s peaks of the underlayer(s) shed further light into the electrical interaction between graphene and other layers. Since the potential variations are amplified only under applied bias (voltage-contrast), our methodology gives unique, chemically specific electrical information that is difficult to obtain by other techniques.« less

Analysis of the Diurnal Variation of the Global Electric Circuit Obtained From Different Numerical Models

NASA Astrophysics Data System (ADS)

Jánský, Jaroslav; Lucas, Greg M.; Kalb, Christina; Bayona, Victor; Peterson, Michael J.; Deierling, Wiebke; Flyer, Natasha; Pasko, Victor P.

2017-12-01

This work analyzes different current source and conductivity parameterizations and their influence on the diurnal variation of the global electric circuit (GEC). The diurnal variations of the current source parameterizations obtained using electric field and conductivity measurements from plane overflights combined with global Tropical Rainfall Measuring Mission satellite data give generally good agreement with measured diurnal variation of the electric field at Vostok, Antarctica, where reference experimental measurements are performed. An approach employing 85 GHz passive microwave observations to infer currents within the GEC is compared and shows the best agreement in amplitude and phase with experimental measurements. To study the conductivity influence, GEC models solving the continuity equation in 3-D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model Community Earth System Model (CESM). Then, using current source parameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnal variation of the ionospheric potential of the GEC decreases from 24% to 20%. The main reason for the change is the presence of clouds while effects of 222Rn ionization, aerosols, and topography are less pronounced. The simulated peak to peak diurnal variation of the electric field at Vostok is increased from 15% to 18% from the diurnal variation of the global current in the GEC if conductivity from CESM is used.

Accounting for the Variation of Driver Aggression in the Simulation of Conventional and Advanced Vehicles: Preprint

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

Neubauer, J.; Wood, E.

2013-03-01

Hybrid electric vehicles, plug-in hybrid electric vehicles, and battery electric vehicles offer the potential to reduce both oil imports and greenhouse gases, as well as to offer a financial benefit to the driver. However, assessing these potential benefits is complicated by several factors, including the driving habits of the operator. We focus on driver aggression, i.e., the level of acceleration and velocity characteristic of travel, to (1) assess its variation within large, real-world drive datasets, (2) quantify its effect on both vehicle efficiency and economics for multiple vehicle types, (3) compare these results to those of standard drive cycles commonlymore » used in the industry, and (4) create a representative drive cycle for future analyses where standard drive cycles are lacking.« less

Apparatus for sensing patterns of electrical field variations across a surface

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

Warren, William L.; Devine, Roderick A. B.

An array of nonvolatile field effect transistors used to sense electric potential variations. The transistors owe their nonvolatility to the movement of protons within the oxide layer that occurs only in response to an externally applied electric potential between the gate on one side of the oxide and the source/drain on the other side. The position of the protons within the oxide layer either creates or destroys a conducting channel in the adjacent source/channel/drain layer below it, the current in the channel being measured as the state of the nonvolatile memory. The protons can also be moved by potentials createdmore » by other instrumentalities, such as charges on fingerprints or styluses above the gates, pressure on a piezoelectric layer above the gates, light shining upon a photoconductive layer above the gates. The invention allows sensing of fingerprints, handwriting, and optical images, which are converted into digitized images thereof in a nonvolatile format.« less

Aircraft measurements of the atmospheric electrical global circuit during the period 1971-1984

NASA Technical Reports Server (NTRS)

Markson, R.

1985-01-01

This report will update an investigation of the global circuit conducted over the last 14 years through aircraft measurements of the variation of ionospheric potential and associated parameters. The data base included electric field, conductivity, and air-earth current density profiles from the tropics (25 deg N) to the Arctic (79 deg N). Almost all of the data have been obtained over the ocean to reduce noise associated with local generators, aerosols, and convection. Recently, two aircraft have been utilized to obtain, for the first time, quasi-periodic sets of simultaneous ionospheric potential (VI) soundings at remote locations and extending over time spans sufficiently long so that the universal time diurnal variation (Carnegie curve) could be observed. In additon, these measurements provided the first detection of the modulation of electric fields in the troposphere caused by the double vortex ionospheric convection pattern. Besides summarizing these measurements and comparing them to similar data obtained by other groups, this report discusses meteorological sources of error and criteria for determining if the global circuit is being measured rather than variations caused by local meteorological processes.

Self-potential characteristics of the dormant period of Izu-Oshima volcano

NASA Astrophysics Data System (ADS)

Matsushima, Nobuo; Nishi, Yuji; Onizawa, Shin'ya; Takakura, Shinichi; Hase, Hideaki; Ishido, Tsuneo

2017-12-01

Continuous self-potential (SP) monitoring has been conducted at Izu-Oshima volcano to detect signals resulting from volcanic activity since the installation of an SP monitoring network in March 2006. Since the installation, annual variations of up to 100 mV have been recorded. If we exclude these annual variations, temporal variations in SP do not show notable changes. This is consistent with the volcano being in a state of quiescence during the measurement period. The annual variations have the different amplitudes and mean levels between stations. To investigate the causes of these annual variations, we carried out numerical simulations of SP generation associated with downward meteoric water flow through electrokinetic coupling in a 550 m thick unsaturated layer. The results show that the vertical electric potential gradient varies with changes in liquid-phase saturation in the unsaturated layer. These changes are caused by variations in the rate of meteoric water percolation. This, in turn, correlates with fluctuations in daily precipitation, thus explaining the annual SP variation recorded at the ground surface. Differences in the amplitude and mean level of SP variation are shown to be associated with different rock properties, especially permeability, porosity, and electrical conductivity. Our results indicate that observable SP changes will appear at stations near the summit if the distributions of liquid-phase saturation and/or pertinent parameters controlling the electrokinetic coupling in the thick unsaturated layer are modified the upward flow of volcanic gas.

The variation of the ground electric field associated with the Mei-Nung earthquake on Feb. 6, 2016

NASA Astrophysics Data System (ADS)

Bing-Chih Chen, Alfred; Yeh, Er-Chun; Chuang, Chia-Wen

2017-04-01

Recent studies show that a strong coupling exists between lithosphere, atmosphere and extending up to the ionosphere. Natural phenomena on the ground surface such as oceans variation, volcanic and seismic activities such as earthquakes, and lightning possibly generate significant impacts at ionosphere immediately by electrodynamic processes. The electric field near the ground is one of the potential quantities to explore this coupling process, especially caused by earthquake. Unfortunately, thunderstorm, dust storm or human activities also affect the measured electric field at ground. To investigate the feasibility of a network to monitor the variation of the ground electric field driven by the lightning and earthquake, a filed mill has been deployed in the NCKU campus since Dec. 2015, and luckily experienced the earthquake with a moment magnitude of 6.4 struck 28 km on 6 Feb. 2016. The recorded ground electric field deceased steadily since 1.5 days before the earthquake, and returned to normal level gradually. Moreover, this special feature can not be identified in the other period of the field test. The detail analysis is reported in this presentation.

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.

Electrokinetically driven active micro-mixers utilizing zeta potential variation induced by field effect

NASA Astrophysics Data System (ADS)

Lee, Chia-Yen; Lee, Gwo-Bin; Fu, Lung-Ming; Lee, Kuo-Hoong; Yang, Ruey-Jen

2004-10-01

This paper presents a new electrokinetically driven active micro-mixer which uses localized capacitance effects to induce zeta potential variations along the surface of silica-based microchannels. The mixer is fabricated by etching bulk flow and shielding electrode channels into glass substrates and then depositing Au/Cr thin films within the latter to form capacitor electrodes, which establish localized zeta potential variations near the electrical double layer (EDL) region of the electroosmotic flow (EOF) within the microchannels. The potential variations induce flow velocity changes within a homogeneous fluid and a rapid mixing effect if an alternating electric field is provided. The current experimental data confirm that the fluid velocity can be actively controlled by using the capacitance effect of the buried shielding electrodes to vary the zeta potential along the channel walls. While compared with commonly used planar electrodes across the microchannels, the buried shielding electrodes prevent current leakage caused by bad bonding and allow direct optical observation during operation. It also shows that the buried shielding electrodes can significantly induce the field effect, resulting in higher variations of zeta potential. Computational fluid dynamic simulations are also used to study the fluid characteristics of the developed active mixers. The numerical and experimental results demonstrate that the developed microfluidic device permits a high degree of control over the fluid flow and an efficient mixing effect. Moreover, the developed device could be used as a pumping device as well. The development of the active electrokinetically driven micro-mixer could be crucial for micro-total-analysis-systems.

A Molecular Dynamics of Cold Neutral Atoms Captured by Carbon Nanotube Under Electric Field and Thermal Effect as a Selective Atoms Sensor.

PubMed

Santos, Elson C; Neto, Abel F G; Maneschy, Carlos E; Chen, James; Ramalho, Teodorico C; Neto, A M J C

2015-05-01

Here we analyzed several physical behaviors through computational simulation of systems consisting of a zig-zag type carbon nanotube and relaxed cold atoms (Rb, Au, Si and Ar). These atoms were chosen due to their different chemical properties. The atoms individually were relaxed on the outside of the nanotube during the simulations. Each system was found under the influence of a uniform electric field parallel to the carbon nanotube and under the thermal effect of the initial temperature at the simulations. Because of the electric field, the cold atoms orbited the carbon nanotube while increasing the initial temperature allowed the variation of the radius of the orbiting atoms. We calculated the following quantities: kinetic energy, potential energy and total energy and in situ temperature, molar entropy variation and average radius of the orbit of the atoms. Our data suggest that only the action of electric field is enough to generate the attractive potential and this system could be used as a selected atoms sensor.

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.

Calculations of neoclassical impurity transport in stellarators

NASA Astrophysics Data System (ADS)

Mollén, Albert; Smith, Håkan M.; Langenberg, Andreas; Turkin, Yuriy; Beidler, Craig D.; Helander, Per; Landreman, Matt; Newton, Sarah L.; García-Regaña, José M.; Nunami, Masanori

2017-10-01

The new stellarator Wendelstein 7-X has finished the first operational campaign and is restarting operation in the summer 2017. To demonstrate that the stellarator concept is a viable candidate for a fusion reactor and to allow for long pulse lengths of 30 min, i.e. ``quasi-stationary'' operation, it will be important to avoid central impurity accumulation typically governed by the radial neoclassical transport. The SFINCS code has been developed to calculate neoclassical quantities such as the radial collisional transport and the ambipolar radial electric field in 3D magnetic configurations. SFINCS is a cutting-edge numerical tool which combines several important features: the ability to model an arbitrary number of kinetic plasma species, the full linearized Fokker-Planck collision operator for all species, and the ability to calculate and account for the variation of the electrostatic potential on flux surfaces. In the present work we use SFINCS to study neoclassical impurity transport in stellarators. We explore how flux-surface potential variations affect the radial particle transport, and how the radial electric field is modified by non-trace impurities and flux-surface potential variations.

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.

Design, Analysis and Implementation of an Experimental System to Harvest Energy From Atmospheric Temperature Variations Using Ethyl Chloride Filled Bellows

NASA Astrophysics Data System (ADS)

Ali, Gibran

The increase in global warming and the dwindling supplies of fossil fuels have shifted the focus from traditional to alternate sources of energy. This has resulted in a concerted effort towards finding new energy sources as well as better understanding traditional renewable energy sources such as wind and solar power. In addition to the shift in focus towards alternate energy, the last two decades have offered a dramatic rise in the use of digital technologies such as wireless sensor networks that require small but isolated power supplies. Energy harvesting, a method to gather energy from ambient sources including sunlight, vibrations, heat, etc., has provided some success in powering these systems. One of the unexplored areas of energy harvesting is the use of atmospheric temperature variations to obtain usable energy. This thesis investigates an innovative mechanism to extract energy from atmospheric variations using ethyl chloride filled mechanical bellows. The energy harvesting process was divided into two parts. The first part consisted of extracting energy from the temperature variations and converting it into the potential energy stored in a linear coil spring. This was achieved by designing and fabricating an apparatus that consisted of an ethyl chloride filled bellows working against a mechanical spring in a closed and controlled environment. The bellows expanded/contracted depending upon the ambient temperature and the energy harvested was calculated as a function of the bellows' length. The experiments showed that 6 J of potential energy may be harvested for a 23°C change in temperature. The numerical results closely correlated to the experimental data with an error magnitude of 1%. In regions with high diurnal temperature variation, such an apparatus may yield approximately 250 microwatts depending on the diurnal temperature range. The second part of the energy harvesting process consisted of transforming linear expansion of the bellows into electric power. A system was designed and simulated using Mathworks Simulink and SimDriveline packages that converted the linear oscillations of the bellows into electric power. This was achieved in two steps; a gear train was designed that would convert the linear displacement of the bellows into potential energy stored in a spiral spring. The spiral spring would then periodically engage to a small generator producing electric power. The electrical power generated was found to depend solely on the potential energy stored in the spring. It was discovered that for a sinusoidal force with constant amplitude and frequency, the potential energy stored in the spring depended on the duration of force input and the parameters of the drivetrain such as the spring stiffness, the gear ratios, and the pinion radii. After simulating the system for different parameters, an optimal set of values was presented to maximize the electrical energy output for a given duration of time. For constant amplitude (120 N) sinusoidal force input with a time period of T seconds, the system stored 37 J, 65 J, and 90 J after a time of 3T, 5T, and 7T, respectively. The electric power output was 7.14 microwatts for a conversion efficiency of 5%. The next step is building a physical geartrain generator assembly based on the design presented in the thesis. The physical system will first be verified by simulating the force input using a pneumatic cylinder. The two parts of the research experiment can then be integrated into one system that would generate electric power directly from temporal temperature and pressure variations.

Spatio-temporal mapping of variation potentials in leaves of Helianthus annuus L. seedlings in situ using multi-electrode array

PubMed Central

Zhao, Dong-Jie; Wang, Zhong-Yi; Huang, Lan; Jia, Yong-Peng; Leng, John Q.

2014-01-01

Damaging thermal stimuli trigger long-lasting variation potentials (VPs) in higher plants. Owing to limitations in conventional plant electrophysiological recording techniques, recorded signals are composed of signals originating from all of the cells that are connected to an electrode. This limitation does not enable detailed spatio-temporal distributions of transmission and electrical activities in plants to be visualised. Multi-electrode array (MEA) enables the recording and imaging of dynamic spatio-temporal electrical activities in higher plants. Here, we used an 8 × 8 MEA with a polar distance of 450 μm to measure electrical activities from numerous cells simultaneously. The mapping of the data that were recorded from the MEA revealed the transfer mode of the thermally induced VPs in the leaves of Helianthus annuus L. seedlings in situ. These results suggest that MEA can enable recordings with high spatio-temporal resolution that facilitate the determination of the bioelectrical response mode of higher plants under stress. PMID:24961469

Spatio-temporal mapping of variation potentials in leaves of Helianthus annuus L. seedlings in situ using multi-electrode array.

PubMed

Zhao, Dong-Jie; Wang, Zhong-Yi; Huang, Lan; Jia, Yong-Peng; Leng, John Q

2014-06-25

Damaging thermal stimuli trigger long-lasting variation potentials (VPs) in higher plants. Owing to limitations in conventional plant electrophysiological recording techniques, recorded signals are composed of signals originating from all of the cells that are connected to an electrode. This limitation does not enable detailed spatio-temporal distributions of transmission and electrical activities in plants to be visualised. Multi-electrode array (MEA) enables the recording and imaging of dynamic spatio-temporal electrical activities in higher plants. Here, we used an 8 × 8 MEA with a polar distance of 450 μm to measure electrical activities from numerous cells simultaneously. The mapping of the data that were recorded from the MEA revealed the transfer mode of the thermally induced VPs in the leaves of Helianthus annuus L. seedlings in situ. These results suggest that MEA can enable recordings with high spatio-temporal resolution that facilitate the determination of the bioelectrical response mode of higher plants under stress.

A Variational Approach to the Analysis of Dissipative Electromechanical Systems

PubMed Central

Allison, Andrew; Pearce, Charles E. M.; Abbott, Derek

2014-01-01

We develop a method for systematically constructing Lagrangian functions for dissipative mechanical, electrical, and electromechanical systems. We derive the equations of motion for some typical electromechanical systems using deterministic principles that are strictly variational. We do not use any ad hoc features that are added on after the analysis has been completed, such as the Rayleigh dissipation function. We generalise the concept of potential, and define generalised potentials for dissipative lumped system elements. Our innovation offers a unified approach to the analysis of electromechanical systems where there are energy and power terms in both the mechanical and electrical parts of the system. Using our novel technique, we can take advantage of the analytic approach from mechanics, and we can apply these powerful analytical methods to electrical and to electromechanical systems. We can analyse systems that include non-conservative forces. Our methodology is deterministic, and does does require any special intuition, and is thus suitable for automation via a computer-based algebra package. PMID:24586221

Electric potential structures of auroral acceleration region border from multi-spacecraft Cluster data

NASA Astrophysics Data System (ADS)

Sadeghi, S.; Emami, M. R.

2018-04-01

This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region's poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80 s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.

Electrically Conductive Polyimide Films Containing Gold Surface

NASA Technical Reports Server (NTRS)

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

1994-01-01

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

Effect of electric field on RbCl quantum pseudodot qubit

NASA Astrophysics Data System (ADS)

Liang, Zhi-Hui; Xiao, Jing-Lin

2018-04-01

By employing the variational method of Pekar type, we study the effects of electric field on RbCl quantum pseudodot (QPD) qubits. Our results confirm that (1) the electron oscillates in the RbCl QPD with a certain period; (2) the electron's probability density is a raising function of electric field; (3) the oscillating frequency is an increasing one of the electric field and the two-dimensional electron gas chemical potential. Two ways are found for prolonging the lifetime of the qubit and suppressing the decoherence in the quantum information field.

On the relationship between the tree and its environment, based on electrical potential difference monitoring on trunk of trees

NASA Astrophysics Data System (ADS)

Koppan, A.; Fenyvesi, A.; Szarka, L.; Wesztergom, V.

2002-05-01

Electrical potential differences (EPD) in the trunk of a Turkey oak tree (measured by using non-polarising electrodes deepened in the sap wood) have been continuously recorded in the Geophysical Observatory "Istv n Széchenyi" of the Hungarian Academy of Sciences since 1997. Besides of various geophysical observations, meteorological and direct sap-flow measurements have also been carried out in the observatory. As it was found (Kopp n A., Szarka L., Wesztergom V., 2000: Annual fluctuation in amplitudes of daily variations of electrical signals measured in the trunk of a standing tree. C.R. Acad. Sci. Paris, Life Sciences 323, 559-563), the measured electric potential difference data have a characteristic sinusoidal daily fluctuation, and the intensity of the diurnal variations has a double-peak annual characteristics, which coincides with the life activity maximums of the tree. We have found a remarkable inter-correlation between trunk EPD, water potential of air (derived from meteorological data), and direct sap flow velocity data from a neighboring tree. All these results clearly demonstrate that the sap streaming due to the transpiration and root pressure generates the largest part of measured potential differences. The ratio of the flow velocity of a diluted solution forced through stems and the potential differences was found to be constant (Gindl, W., L”ppert, H.-G., Wimmer, R., 1999: Relationship between streaming potential and sap velocity in Salix alba L. Phyton, 39, 217-224.). On the contrary in our in-vivo experiments the relationship between the measured sap flow velocity and EPD is non-linear, which means that the conductivity (i.e. ion concentration) of the xylem sap itself also has a daily fluctuation.

Control of the Earth's electric field intensity through solar wind modulation of galactic cosmic radiation: Support for a proposed atmospheric electrical sun-weather mechanism

NASA Technical Reports Server (NTRS)

Markson, R.

1980-01-01

The ionospheric potential and galactic cosmic radiation, found to be inversely correlated with the solar wind velocity are examined as being germane to weather modification. Since the ionospheric potential is proportional to the fair weather electric field intensity and cosmic radiation is the dominant source of atmospheric ionization, it is concluded that the Earth's overall electric field varies in phase with atmospheric ionization and that the latter is modulated by the solar wind. A proposed mechanism, in which solar control of ionizing radiation influences atmospheric electrification and thus possibly cloud physical processes is discussed. An experimental approach to critically test the proposed mechanism through comparison of the temporal variation of the Earth's electric field with conditions in the interplanetary medium is outlined.

Consumers’ perceptions of energy use and energy savings: A literature review

NASA Astrophysics Data System (ADS)

Lesic, Vedran; Bruine de Bruin, Wändi; Davis, Matthew C.; Krishnamurti, Tamar; Azevedo, Inês M. L.

2018-03-01

Background. Policy makers and program managers need to better understand consumers’ perceptions of their energy use and savings to design effective strategies for promoting energy savings. Methods. We reviewed 14 studies from the emerging interdisciplinary literature examining consumers’ perceptions electricity use by specific appliances, and potential savings. Results. We find that: (1) electricity use is often overestimated for low-energy consuming appliances, and underestimated for high-energy consuming appliances; (2) curtailment strategies are typically preferred over energy efficiency strategies; (3) consumers lack information about how much electricity can be saved through specific strategies; (4) consumers use heuristics for assessing the electricity use of specific appliances, with some indication that more accurate judgments are made among consumers with higher numeracy and stronger pro-environmental attitudes. However, design differences between studies, such as variations in reference points, reporting units and assessed time periods, may affect consumers’ reported perceptions. Moreover, studies differ with regard to whether accuracy of perceptions was evaluated through comparisons with general estimates of actual use, self-reported use, household-level meter readings, or real-time smart meter readings. Conclusion. Although emerging findings are promising, systematic variations in the measurement of perceived and actual electricity use are potential cause for concern. We propose avenues for future research, so as to better understand, and possibly inform, consumers’ perceptions of their electricity use. Ultimately, this literature will have implications for the design of effective electricity feedback for consumers, and related policies.

Self-Potential Monitoring of Landslides on Field and Laboratory Scale

NASA Astrophysics Data System (ADS)

Heinze, T.; Limbrock, J. K.; Weigand, M.; Wagner, F. M.; Kemna, A.

2017-12-01

Among several other geophysical methods used to observe water movement in the ground, the electrical self-potential method has been applied to a broad range of monitoring studies, especially focusing on volcanism and dam leakage but also during hydraulic fracturing. Electrical self-potential signals may be caused by various mechanisms. Though, the most relevant source of the self-potential field in the given context of landslides is the streaming potential, caused by a flowing electrolyte through porous media with electrically charged internal surfaces. So far, existing models focus on monitoring water flow in non-deformable porous media. However, as the self-potential is sensitive to hydraulic parameters of the soil, any change in these parameters will cause an alteration of the electric signal. Mass movement will significantly influence the hydraulic parameters of the solid as well as the pressure field, assuming that fluid movement is faster than pressure diffusion. We present self-potential measurements from over a year of continuous monitoring at an old landslide site. Using a three-dimensional electric-resistivity underground model, the self-potential signal is analyzed with respect to precipitation and the resulting flow in the ground. Additional data from electrical measurements and conventional sensors are included to assess saturation. The field observations are supplemented by laboratory experiments in which we study the behavior of the self-potential during failure of a piled land slope. For the undrained scenarios, we observe a clear correlation between the mass movements and signals in the electric potential, which clearly differ from the underlying potential variations due to increased saturation and fluid flow. In the drained experiments, we do not observe any measurable change in the electric potential. We therefore assume that change in fluid properties and release of the load causes disturbances in flow and streaming potential. Our results indicate that electrical self-potential measurements are very well suitable for surveillance of landslide prone hills, as water flow can be observed and soil movement can be detected.

Electric field computation analysis for the Electric Field Detector (EFD) on board the China Seismic-Electromagnetic Satellite (CSES)

NASA Astrophysics Data System (ADS)

Diego, P.; Bertello, I.; Candidi, M.; Mura, A.; Coco, I.; Vannaroni, G.; Ubertini, P.; Badoni, D.

2017-11-01

The floating potential variability of the Electric Field Detector (EFD) probes, on board the Chinese Seismo-Electromagnetic Satellite (CSES), has been modeled, and the effects of several structural and environmental elements have been determined. The expected floating potentials of the probes are computed considering the ambient ionospheric plasma parameter variations. In addition, the ion collection variability, due to the different probe attitudes along the orbit, and its effect on each floating potential, are considered. Particular attention is given to the analysis of the shadow produced by the stubs, in order to determine the artificial electric field introduced by instrumental effects which has to be subtracted from the real measurements. The modulation of the altered electric field, due to the effect on shadowing of the ion drift, as measured by the ESA satellite Swarm A in a similar orbit, is also modeled. Such simulations are made in preparation of real EFD data analysis performed during the upcoming flight of CSES.

On hybridising lettuce seedlings with nanoparticles and the resultant effects on the organisms' electrical characteristics.

PubMed

Gizzie, Nina; Mayne, Richard; Patton, David; Kendrick, Paul; Adamatzky, Andrew

2016-09-01

Lettuce seedlings are attracting interest in the computing world due to their capacity to become hybrid circuit components, more specifically, in the creation of living 'wires'. Previous studies have shown that seedlings can be hybridised with gold nanoparticles and withstand mild electrical currents. In this study, lettuce seedlings were hybridised with a variety of metallic and non-metallic nanomaterials: carbon nanotubes, graphene oxide, aluminium oxide and calcium phosphate. Toxic effects and the following electrical properties were monitored: mean potential, resistance and capacitance. Macroscopic observations revealed only slight deleterious health effects after administration with one variety of particle, aluminium oxide. Mean potential in calcium phosphate-hybridised seedlings showed a considerable increase when compared with the control, whereas those administered with graphene oxide showed a small decrease; there were no notable variations across the remaining treatments. Electrical resistance decreased substantially in graphene oxide-treated seedlings whereas slight increases were shown following calcium phosphate and carbon nanotubes applications. Capacitance showed no considerable variation across treated seedlings. These results demonstrate that use of some nanomaterials, specifically graphene oxide and calcium phosphate, may be towards biohybridisation purposes including the generation of living 'wires'. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A numerical study on electrochemical transport of ions in calcium fluoride slag

NASA Astrophysics Data System (ADS)

Karimi-Sibaki, E.; Kharicha, A.; Wu, M.; Ludwig, A.

2016-07-01

Electrically resistive CaF 2-based slags are widely used in electroslag remelting (ESR) process to generate Joule heat for the melting of electrode. The electric current is conducted by ions (electrolyte) such as Ca +2 or F -, thus it is necessary to establish electrochemical models to study electrical behavior of slag. This paper presents a numerical model on electrochemical transport of ions in an arbitrary symmetrical (ZZ) and non-symmetrical (CaF2) stagnant electrolytes blocked by two parallel, planar electrodes. The dimensionless Poisson-Nernst-Planck (PNP) equations are solved to model electro-migration and diffusion of ions. The ions are considered to be inert that no Faradic reactions occur. Spatial variations of concentrations of ions, charge density and electric potential across the electrolyte are analyzed. It is shown that the applied potential has significant influence on the system response. At high applied voltage, the anodic potential drop near the electrode is significantly larger than cathodic potential drop in fully dissociated CaF2 electrolyte.

Electric field prediction for a human body-electric machine system.

PubMed

Ioannides, Maria G; Papadopoulos, Peter J; Dimitropoulou, Eugenia

2004-01-01

A system consisting of an electric machine and a human body is studied and the resulting electric field is predicted. A 3-phase induction machine operating at full load is modeled considering its geometry, windings, and materials. A human model is also constructed approximating its geometry and the electric properties of tissues. Using the finite element technique the electric field distribution in the human body is determined for a distance of 1 and 5 m from the machine and its effects are studied. Particularly, electric field potential variations are determined at specific points inside the human body and for these points the electric field intensity is computed and compared to the limit values for exposure according to international standards.

Missile launch detection electric field perturbation experiment. Final report

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

Kane, R.J.; Rynne, T.M.

1993-04-28

The Lawrence Livermore National Laboratory and SARA Inc. participated in the ATMD missile launch activities that occurred at WSMR during January 1993. LLNL and SARA deployed sensors for monitoring of basic phenomena. An attempt was made to measure perturbations of the earth geo-potential during the launch of a Lance missile. The occurrence of the perturbation is expected from the conducting body of the missile and the exhaust plume. A set of voltage-probe antennas were used to monitor the local electric field perturbation from the launch at ranges of approximately 1 km. Examination of the data acquired during the launch periodmore » failed to show identifiable correlation of the field variations with the launch event. Three reasons are ascribed to this lack of event data: (1) The electric field potential variations have a limited spatial correlation length - the fields measured in one region have little correlation to measurements made at distances of a kilometer away. The potential variations are related to localized atmospheric disturbances and are generally unpredictable. A value for the spatial correlation length is also not known. (2) The conductivity of the plume and missile body are not adequate to produce a field perturbation of adequate magnitude. Phenomena related to the exhaust plume and missile may exist and be outside of the collection range of the equipment employed for these measurements. (3) The presence of 60 Hz power line noise was of sufficient magnitude to irreversibly contaminate measurements.« less

Impact of underlap spacer region variation on electrostatic and analog performance of symmetrical high-k SOI FinFET at 20 nm channel length

NASA Astrophysics Data System (ADS)

Jain, Neeraj; Raj, Balwinder

2017-12-01

Continued scaling of CMOS technology to achieve high performance and low power consumption of semiconductor devices in the complex integrated circuits faces the degradation in terms of electrostatic integrity, short channel effects (SCEs), leakage currents, device variability and reliability etc. Nowadays, multigate structure has become the promising candidate to overcome these problems. SOI FinFET is one of the best multigate structures that has gained importance in all electronic design automation (EDA) industries due to its improved short channel effects (SCEs), because of its more effective gate-controlling capabilities. In this paper, our aim is to explore the sensitivity of underlap spacer region variation on the performance of SOI FinFET at 20 nm channel length. Electric field modulation is analyzed with spacer length variation and electrostatic performance is evaluated in terms of performance parameter like electron mobility, electric field, electric potential, sub-threshold slope (SS), ON current (I on), OFF current (I off) and I on/I off ratio. The potential benefits of SOI FinFET at drain-to-source voltage, V DS = 0.05 V and V DS = 0.7 V towards analog and RF design is also evaluated in terms of intrinsic gain (A V), output conductance (g d), trans-conductance (g m), gate capacitance (C gg), and cut-off frequency (f T = g m/2πC gg) with spacer region variations.

Low-altitude acceleration of auroral electrons during breakup observed by a mother-daughter rocket

NASA Technical Reports Server (NTRS)

Johnstone, A. D.; Davis, T. N.

1974-01-01

By the use of a mother-daughter rocket combination and ground-based observations with television, time and space variations are resolved in particle measurements in breakup aurora. The spectral variations measured during a temporal variation in the aurora can be explained by a nearly uniform acceleration of all the electrons such as would be caused by an electric potential drop along the magnetic field lines. Many other explanations can be eliminated.

Electrodynamics of frictional interaction in tribolink “metal-polymer”

NASA Astrophysics Data System (ADS)

Volchenko, N. A.; Krasin, P. S.; Volchenko, A. I.; Zhuravlev, D. Yu

2018-03-01

The materials of the article illustrate the estimation of the energy loading of a metal friction element in the metal-electrolyte-polymer friction pair while forming various types of double electrical layers with the release of its thermal stabilization state. The energy loading of the contact spots of the microprotrusions of the friction pairs of braking devices depends to a large extent on the electrical, thermal and chemical fields that are of a different nature to an allowable temperature and are above the surface layers of the polymer patch. The latter is significantly influenced by double electrical layers that are formed at the boundaries of the phases “metal-metal”, “metal-polymer”, “metal-semiconductor”, “semiconductor-semiconductor” and “metal-electrolyte”. When two electrically conducting phases come into contact with electrothermomechanical friction, a difference in electrical potentials arises, which is due to the formation of a double electric layer, that is an asymmetric distribution of charged particles near the phase boundary. The structure of the double electric layer does not matter for the magnitude of the reversible electrode potential, which is determined by the variation of the isobaric-isothermal potential of the corresponding electrochemical reaction.

Continuous and embedded solutions for SHM of concrete structures using changing electrical potential in self-sensing cement-based composites

NASA Astrophysics Data System (ADS)

Downey, Austin; Garcia-Macias, Enrique; D'Alessandro, Antonella; Laflamme, Simon; Castro-Triguero, Rafael; Ubertini, Filippo

2017-04-01

Interest in the concept of self-sensing structural materials has grown in recent years due to its potential to enable continuous low-cost monitoring of next-generation smart-structures. The development of cement-based smart sensors appears particularly well suited for monitoring applications due to their numerous possible field applications, their ease of use and long-term stability. Additionally, cement-based sensors offer a unique opportunity for structural health monitoring of civil structures because of their compatibility with new or existing infrastructure. Particularly, the addition of conductive carbon nanofillers into a cementitious matrix provides a self-sensing structural material with piezoresistive characteristics sensitive to deformations. The strain-sensing ability is achieved by correlating the external loads with the variation of specific electrical parameters, such as the electrical resistance or impedance. Selection of the correct electrical parameter for measurement to correlate with features of interest is required for the condition assessment task. In this paper, we investigate the potential of using altering electrical potential in cement-based materials doped with carbon nanotubes to measure strain and detect damage in concrete structures. Experimental validation is conducted on small-scale specimens including a steel-reinforced beam of conductive cement paste. Comparisons are made with constant electrical potential and current methods commonly found in the literature. Experimental results demonstrate the ability of the changing electrical potential at detecting features important for assessing the condition of a structure.

Detecting rapid mass movements using electrical self-potential measurements

NASA Astrophysics Data System (ADS)

Heinze, Thomas; Limbrock, Jonas; Pudasaini, Shiva P.; Kemna, Andreas

2017-04-01

Rapid mass movements are a latent danger for lives and infrastructure in almost any part of the world. Often such mass movements are caused by increasing pore pressure, for example, landslides after heavy rainfall or dam breaking after intrusion of water in the dam. Among several other geophysical methods used to observe water movement, the electrical self-potential method has been applied to a broad range of monitoring studies, especially focusing on volcanism and dam leakage but also during hydraulic fracturing and for earthquake prediction. Electrical self-potential signals may be caused by various mechanisms. Though, the most relevant source of the self-potential field in the given context is the streaming potential, caused by a flowing electrolyte through porous media with electrically charged internal surfaces. So far, existing models focus on monitoring water flow in non-deformable porous media. However, as the self-potential is sensitive to hydraulic parameters of the soil, any change in these parameters will cause an alteration of the electric signal. Mass movement will significantly influence the hydraulic parameters of the solid as well as the pressure field, assuming that fluid movement is faster than the pressure diffusion. We will present results of laboratory experiments under drained and undrained conditions with fluid triggered as well as manually triggered mass movements, monitored with self-potential measurements. For the undrained scenarios, we observe a clear correlation between the mass movements and signals in the electric potential, which clearly differ from the underlying potential variations due to increased saturation and fluid flow. In the drained experiments, we do not observe any measurable change in the electric potential. We therefore assume that change in fluid properties and release of the load causes disturbances in flow and streaming potential. We will discuss results of numerical simulations reproducing the observed effect. Our results indicate that electrical self-potential measurements can observe rapid mass movements when the movement is large and fast enough to disturb the fluid pressure field significantly.

Coupled structural, thermal, phase-change and electromagnetic analysis for superconductors, volume 2

NASA Technical Reports Server (NTRS)

Felippa, Carlos A.; Farhat, Charbel; Park, K. C.; Militello, Carmelo; Schuler, James J.

1993-01-01

Two families of parametrized mixed variational principles for linear electromagnetodynamics are constructed. The first family is applicable when the current density distribution is known a priori. Its six independent fields are magnetic intensity and flux density, magnetic potential, electric intensity and flux density and electric potential. Through appropriate specialization of parameters the first principle reduces to more conventional principles proposed in the literature. The second family is appropriate when the current density distribution and a conjugate Lagrange multiplier field are adjoined, giving a total of eight independently varied fields. In this case it is shown that a conventional variational principle exists only in the time-independent (static) case. Several static functionals with reduced number of varied fields are presented. The application of one of these principles to construct finite elements with current prediction capabilities is illustrated with a numerical example.

Global surface temperatures and the atmospheric electrical circuit

NASA Technical Reports Server (NTRS)

Price, Colin

1993-01-01

To monitor future global temperature trends, it would be extremely useful if parameters nonlinearly related to surface temperature could be found, thereby amplifying any warming signal that may exist. Evidence that global thunderstorm activity is nonlinearly related to diurnal, seasonal and interannual temperature variations is presented. Since global thunderstorm activity is also well correlated with the earth's ionospheric potential, it appears that variations of ionospheric potential, that can be measured at a single location, may be able to supply valuable information regarding global surface temperature fluctuations. The observations presented enable a prediction that a 1 percent increase in global surface temperatures may result in a 20 percent increase in ionospheric potential.

Optimal electric potential profile in a collisional magnetized thruster

NASA Astrophysics Data System (ADS)

Fruchtman, Amnon; Makrinich, Gennady

2016-10-01

A major figure of merit in propulsion in general and in electric propulsion in particular is the thrust per unit of deposited power, the ratio of thrust over power. We have recently demonstrated experimentally and theoretically that for a fixed deposited power in the ions, the momentum delivered by the electric force is larger if the accelerated ions collide with neutrals during the acceleration. As expected, the higher thrust for given power is achieved for a collisional plasma at the expense of a lower thrust per unit mass flow rate. Operation in the collisional regime can be advantageous for certain space missions. We analyze a Hall thruster configuration in which the flow is only weakly ionized but there are frequent ion-neutral collisions. With a variational method we seek an electric potential profile that maximizes thrust over power. We then examine what radial magnetic field profile should determine such a potential profile. Supported by the Israel Science Foundation Grant 765/11.

Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

NASA Technical Reports Server (NTRS)

Winckler, J. R.; Erickson, K. N.

1990-01-01

The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

A study on parameter variation effects on battery packs for electric vehicles

NASA Astrophysics Data System (ADS)

Zhou, Long; Zheng, Yuejiu; Ouyang, Minggao; Lu, Languang

2017-10-01

As one single cell cannot meet power and driving range requirement in an electric vehicle, the battery packs with hundreds of single cells connected in parallel and series should be constructed. The most significant difference between a single cell and a battery pack is cell variation. Not only does cell variation affect pack energy density and power density, but also it causes early degradation of battery and potential safety issues. The cell variation effects on battery packs are studied, which are of great significant to battery pack screening and management scheme. In this study, the description for the consistency characteristics of battery packs was first proposed and a pack model with 96 cells connected in series was established. A set of parameters are introduced to study the cell variation and their impacts on battery packs are analyzed through the battery pack capacity loss simulation and experiments. Meanwhile, the capacity loss composition of the battery pack is obtained and verified by the temperature variation experiment. The results from this research can demonstrate that the temperature, self-discharge rate and coulombic efficiency are the major affecting parameters of cell variation and indicate the dissipative cell equalization is sufficient for the battery pack.

Performance and operational economics estimates for a coal gasification combined-cycle cogeneration powerplant

NASA Technical Reports Server (NTRS)

Nainiger, J. J.; Burns, R. K.; Easley, A. J.

1982-01-01

A performance and operational economics analysis is presented for an integrated-gasifier, combined-cycle (IGCC) system to meet the steam and baseload electrical requirements. The effect of time variations in steam and electrial requirements is included. The amount and timing of electricity purchases from sales to the electric utility are determined. The resulting expenses for purchased electricity and revenues from electricity sales are estimated by using an assumed utility rate structure model. Cogeneration results for a range of potential IGCC cogeneration system sizes are compared with the fuel consumption and costs of natural gas and electricity to meet requirements without cogeneration. The results indicate that an IGCC cogeneration system could save about 10 percent of the total fuel energy presently required to supply steam and electrical requirements without cogeneration. Also for the assumed future fuel and electricity prices, an annual operating cost savings of 21 percent to 26 percent could be achieved with such a cogeneration system. An analysis of the effects of electricity price, fuel price, and system availability indicates that the IGCC cogeneration system has a good potential for economical operation over a wide range in these assumptions.

Simulation of the Universal-Time Diurnal Variation of the Global Electric Circuit Charging Rate

NASA Technical Reports Server (NTRS)

Mackerras, D.; Darvenzia, M.; Orville, R. E.; Williams, E. R.; Goodman, S. J.

1999-01-01

A global lightning model that includes diurnal and annual lightning variation, and total flash density versus latitude for each major land and ocean, has been used as the basis for simulating the global electric circuit charging rate. A particular objective has been to reconcile the difference in amplitude ratios [AR=(max-min)/mean] between global lightning diurnal variation (AR approx. = 0.8) and the diurnal variation of typical atmospheric potential gradient curves (AR approx. = 0.35). A constraint on the simulation is that the annual mean charging current should be about 1000 A. The global lightning model shows that negative ground flashes can contribute, at most, about 10-15% of the required current. For the purpose of the charging rate simulation, it was assumed that each ground flash contributes 5 C to the charging process. It was necessary to assume that all electrified clouds contribute to charging by means other than lightning, that the total flash rate can serve as an indirect indicator of the rate of charge transfer, and that oceanic electrified clouds contribute to charging even though they are relatively inefficient in producing lightning. It was also found necessary to add a diurnally invariant charging current component. By trial and error it was found that charging rate diurnal variation curves in Universal time (UT) could be produced with amplitude ratios and general shapes similar to those of the potential gradient diurnal variation curves measured over ocean and arctic regions during voyages of the Carnegie Institute research vessels.

Influence of the Ambient Electric Field on Measurements of the Actively Controlled Spacecraft Potential by MMS

NASA Astrophysics Data System (ADS)

Torkar, K.; Nakamura, R.; Andriopoulou, M.; Giles, B. L.; Jeszenszky, H.; Khotyaintsev, Y. V.; Lindqvist, P.-A.; Torbert, R. B.

2017-12-01

Space missions with sophisticated plasma instrumentation such as Magnetospheric Multiscale, which employs four satellites to explore near-Earth space benefit from a low electric potential of the spacecraft, to improve the plasma measurements and therefore carry instruments to actively control the potential by means of ion beams. Without control, the potential varies in anticorrelation with plasma density and temperature to maintain an equilibrium between the plasma current and the one of photoelectrons produced at the surface and overcoming the potential barrier. A drawback of the controlled, almost constant potential is the difficulty to use it as convenient estimator for plasma density. This paper identifies a correlation between the spacecraft potential and the ambient electric field, both measured by double probes mounted at the end of wire booms, as the main responsible for artifacts in the potential data besides the known effect of the variable photoelectron production due to changing illumination of the surface. It is shown that the effect of density variations is too weak to explain the observed correlation with the electric field and that a correction of the artifacts can be achieved to enable the reconstruction of the uncontrolled potential and plasma density in turn. Two possible mechanisms are discussed: the asymmetry of the current-voltage characteristic determining the probe to plasma potential and the fact that a large equipotential structure embedded in an electric field results in asymmetries of both the emission and spatial distribution of photoelectrons, which results in an increase of the spacecraft potential.

High-resolution non-contact measurement of the electrical activity of plants in situ using optical recording

PubMed Central

Zhao, Dong-Jie; Chen, Yang; Wang, Zi-Yang; Xue, Lin; Mao, Tong-Lin; Liu, Yi-Min; Wang, Zhong-Yi; Huang, Lan

2015-01-01

The limitations of conventional extracellular recording and intracellular recording make high-resolution multisite recording of plant bioelectrical activity in situ challenging. By combining a cooled charge-coupled device camera with a voltage-sensitive dye, we recorded the action potentials in the stem of Helianthus annuus and variation potentials at multiple sites simultaneously with high spatial resolution. The method of signal processing using coherence analysis was used to determine the synchronization of the selected signals. Our results provide direct visualization of the phloem, which is the distribution region of the electrical activities in the stem and leaf of H. annuus, and verify that the phloem is the main action potential transmission route in the stems of higher plants. Finally, the method of optical recording offers a unique opportunity to map the dynamic bioelectrical activity and provides an insight into the mechanisms of long-distance electrical signal transmission in higher plants. PMID:26333536

Behavioral and Single-Neuron Sensitivity to Millisecond Variations in Temporally Patterned Communication Signals

PubMed Central

Baker, Christa A.; Ma, Lisa; Casareale, Chelsea R.

2016-01-01

In many sensory pathways, central neurons serve as temporal filters for timing patterns in communication signals. However, how a population of neurons with diverse temporal filtering properties codes for natural variation in communication signals is unknown. Here we addressed this question in the weakly electric fish Brienomyrus brachyistius, which varies the time intervals between successive electric organ discharges to communicate. These fish produce an individually stereotyped signal called a scallop, which consists of a distinctive temporal pattern of ∼8–12 electric pulses. We manipulated the temporal structure of natural scallops during behavioral playback and in vivo electrophysiology experiments to probe the temporal sensitivity of scallop encoding and recognition. We found that presenting time-reversed, randomized, or jittered scallops increased behavioral response thresholds, demonstrating that fish's electric signaling behavior was sensitive to the precise temporal structure of scallops. Next, using in vivo intracellular recordings and discriminant function analysis, we found that the responses of interval-selective midbrain neurons were also sensitive to the precise temporal structure of scallops. Subthreshold changes in membrane potential recorded from single neurons discriminated natural scallops from time-reversed, randomized, and jittered sequences. Pooling the responses of multiple neurons improved the discriminability of natural sequences from temporally manipulated sequences. Finally, we found that single-neuron responses were sensitive to interindividual variation in scallop sequences, raising the question of whether fish may analyze scallop structure to gain information about the sender. Collectively, these results demonstrate that a population of interval-selective neurons can encode behaviorally relevant temporal patterns with millisecond precision. SIGNIFICANCE STATEMENT The timing patterns of action potentials, or spikes, play important roles in representing information in the nervous system. However, how these temporal patterns are recognized by downstream neurons is not well understood. Here we use the electrosensory system of mormyrid weakly electric fish to investigate how a population of neurons with diverse temporal filtering properties encodes behaviorally relevant input timing patterns, and how this relates to behavioral sensitivity. We show that fish are behaviorally sensitive to millisecond variations in natural, temporally patterned communication signals, and that the responses of individual midbrain neurons are also sensitive to variation in these patterns. In fact, the output of single neurons contains enough information to discriminate stereotyped communication signals produced by different individuals. PMID:27559179

Behavioral and Single-Neuron Sensitivity to Millisecond Variations in Temporally Patterned Communication Signals.

PubMed

Baker, Christa A; Ma, Lisa; Casareale, Chelsea R; Carlson, Bruce A

2016-08-24

In many sensory pathways, central neurons serve as temporal filters for timing patterns in communication signals. However, how a population of neurons with diverse temporal filtering properties codes for natural variation in communication signals is unknown. Here we addressed this question in the weakly electric fish Brienomyrus brachyistius, which varies the time intervals between successive electric organ discharges to communicate. These fish produce an individually stereotyped signal called a scallop, which consists of a distinctive temporal pattern of ∼8-12 electric pulses. We manipulated the temporal structure of natural scallops during behavioral playback and in vivo electrophysiology experiments to probe the temporal sensitivity of scallop encoding and recognition. We found that presenting time-reversed, randomized, or jittered scallops increased behavioral response thresholds, demonstrating that fish's electric signaling behavior was sensitive to the precise temporal structure of scallops. Next, using in vivo intracellular recordings and discriminant function analysis, we found that the responses of interval-selective midbrain neurons were also sensitive to the precise temporal structure of scallops. Subthreshold changes in membrane potential recorded from single neurons discriminated natural scallops from time-reversed, randomized, and jittered sequences. Pooling the responses of multiple neurons improved the discriminability of natural sequences from temporally manipulated sequences. Finally, we found that single-neuron responses were sensitive to interindividual variation in scallop sequences, raising the question of whether fish may analyze scallop structure to gain information about the sender. Collectively, these results demonstrate that a population of interval-selective neurons can encode behaviorally relevant temporal patterns with millisecond precision. The timing patterns of action potentials, or spikes, play important roles in representing information in the nervous system. However, how these temporal patterns are recognized by downstream neurons is not well understood. Here we use the electrosensory system of mormyrid weakly electric fish to investigate how a population of neurons with diverse temporal filtering properties encodes behaviorally relevant input timing patterns, and how this relates to behavioral sensitivity. We show that fish are behaviorally sensitive to millisecond variations in natural, temporally patterned communication signals, and that the responses of individual midbrain neurons are also sensitive to variation in these patterns. In fact, the output of single neurons contains enough information to discriminate stereotyped communication signals produced by different individuals. Copyright © 2016 the authors 0270-6474/16/368985-16$15.00/0.

Analog Computer Solution of the Electrodiffusion Equation for a Simple Membrane

ERIC Educational Resources Information Center

Onega, Ronald J.

1972-01-01

An analog solution was obtained for the Nenst-Planck and Poisson equations which describe the ion concentration across a simple membrane held at a potential difference. The electric field variation within the membrane was also determined. (Author/TS)

Nationwide Analysis of U.S. Commercial Building Solar Photovoltaic (PV) Breakeven Conditions

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

Davidson, Carolyn; Gagnon, Pieter; Denholm, Paul

2015-10-01

The commercial sector offers strong potential for solar photovoltaics (PV) owing to abundant available roof space suitable for PV and the opportunity to offset the sector's substantial retail electricity purchases. This report evaluated the breakeven price of PV for 15 different building types and various financing options by calculating electricity savings based on detailed rate structures for most U.S. utility territories (representing approximately two thirds of U.S. commercial customers). We find that at current capital costs, an estimated 1/3 of U.S. commercial customers break even in the cash scenario and approximately 2/3 break even in the loan scenario. Variation inmore » retail rates is a stronger driver of breakeven prices than is variation in building load or solar generation profiles. At the building level, variation in the average breakeven price is largely driven by the ability for a PV system to reduce demand charges.« less

Detection de fuite dans les barrages en remblai par la methode de polarisation spontanee et par tomographie electrique: Cas de la jonction de deux barrages en remblai

NASA Astrophysics Data System (ADS)

Nzumotcha Tchoumkam, Linda Armelle

The infiltration through the core of foundation of embankment dams is a problem which is worrying for safety and economical dams. The mechanism of infiltration can be progressive and can disturb the stability or the durability of the structures. Consequently, its evolution can undermine public security. Statistics made for 11192 embankment dams through the world showed that until 1986, 48% of damages have been caused by internal erosion. This internal erosion was generated by infiltration through the core or the foundation of embankment dam. Electrical, electromagnetic and thermometric methods are usually considered as investigation methods. The goal of this work is to study the sensibility of the self-potential method (S.P.) to detect seepage for the case of embankment dams. We used S.P jointly with electrical resistance tomography (ERT). To attain this objective, we acquired self-potential and resistivity data with periodic changes of the water level in the reservoir. These changes were made every spring (in November) and every summer (in April) at the emptying and impounding of the reservoir. For this project, measures have been conducted over a period of two years (2008-2010). Before that, thermometry, self-potential and magnetic methods were applied on the site to acquire information about seepage and its approximate position. Flow rate was also measured. In April 2010, injection of grout was used to clog seepage. The measurements allowed to represent the variation of potential with time and space. That permitted to make a distinction between different sources of self-potential signal. The mapping of the electric potential during the emptying and the impounding of the reservoir showed a negative anomaly which correlate to an outflow located in the upstream of the dam. The monitoring of the S.P. signal permitted to dissociate an anomaly zone which can be related to the site of injection of grout. The gradient of self-potential decreased with the increase of pressure gradient. We have computed the effective electro kinetic (EK) coupling coefficient of the dam from the variation of the potential with water level. Time-lapse ERT is used to control the variation of electrical conductivity of the material together with changes in water level. The anomaly in the time-lapse represented agrees with the outflow. We also propose a 3D numerical model to interpret the measurements in a semi-quantitative manner. Comparing between results of modeling and the survey data, differences are noted that can be explained in different ways. More work would be needed to elucidate those differences, in particular with the measurement strategy and the estimation of coupling coefficients. Nevertheless, the proposed approach allowed to underline different variations under the ground. These results have also been used to discuss the limitations of the self-potential method applied to detect seepage in the dam.

Electric shocks at work in Europe: development of a job exposure matrix.

PubMed

Huss, Anke; Vermeulen, Roel; Bowman, Joseph D; Kheifets, Leeka; Kromhout, Hans

2013-04-01

Electric shocks have been suggested as a potential risk factor for neurological disease, in particular for amyotrophic lateral sclerosis. While actual exposure to shocks is difficult to measure, occurrence and variation of electric injuries could serve as an exposure proxy. We assessed risk of electric injury, using occupational accident registries across Europe to develop an electric shock job-exposure-matrix (JEM). Injury data were obtained from five European countries, and the number of workers per occupation and country from EUROSTAT was compiled at a 3-digit International Standard Classification of Occupations 1988 level. We pooled accident rates across countries with a random effects model and categorised jobs into low, medium and high risk based on the 75th and 90th percentile. We next compared our JEM to a JEM that classified extremely low frequency magnetic field exposure of jobs into low, medium and high. Of 116 job codes, occupations with high potential for electric injury exposure were electrical and electronic equipment mechanics and fitters, building frame workers and finishers, machinery mechanics and fitters, metal moulders and welders, assemblers, mining and construction labourers, metal-products machine operators, ships' decks crews and power production and related plant operators. Agreement between the electrical injury and magnetic field JEM was 67.2%. Our JEM classifies occupational titles according to risk of electric injury as a proxy for occurrence of electric shocks. In addition to assessing risk potentially arising from electric shocks, this JEM might contribute to disentangling risks from electric injury from those of extremely low frequency magnetic field exposure.

Trade-off results and preliminary designs of Near-Term Hybrid Vehicles

NASA Technical Reports Server (NTRS)

Sandberg, J. J.

1980-01-01

Phase I of the Near-Term Hybrid Vehicle Program involved the development of preliminary designs of electric/heat engine hybrid passenger vehicles. The preliminary designs were developed on the basis of mission analysis, performance specification, and design trade-off studies conducted independently by four contractors. THe resulting designs involve parallel hybrid (heat engine/electric) propulsion systems with significant variation in component selection, power train layout, and control strategy. Each of the four designs is projected by its developer as having the potential to substitute electrical energy for 40% to 70% of the petroleum fuel consumed annually by its conventional counterpart.

Numerical and experimental study of the effect of the induced electric potential in Lorentz force velocimetry

NASA Astrophysics Data System (ADS)

Hernández, Daniel; Boeck, Thomas; Karcher, Christian; Wondrak, Thomas

2018-01-01

Lorentz force velocimetry (LFV) is a contactless velocity measurement technique for electrically conducting fluids. When a liquid metal or a molten glass flows through an externally applied magnetic field, eddy currents and a flow-braking force are generated inside the liquid. This force is proportional to the velocity or flow rate of the fluid and, due to Newton’s third law, a force of the same magnitude but in opposite direction acts on the source of the applied magnetic field which in our case are permanent magnets. According to Ohm’s law for moving conductors at low magnetic Reynolds numbers, an electric potential is induced which ensures charge conservation. In this paper, we analyze the contribution of the induced electric potential to the total Lorentz force by considering two different scenarios: conducting walls of finite thickness and aspect ratio variation of the cross-section of the flow. In both the cases, the force component generated by the electric potential is always in the opposite direction to the total Lorentz force. This force component is sensitive to the electric boundary conditions of the flow of which insulating and perfectly conducting walls are the two limiting cases. In the latter case, the overall electric resistance of the system is minimized, resulting in a considerable increase in the measured Lorentz force. Additionally, this force originating from the electric potential also decays when the aspect ratio of the cross-section of the flow is changed. Hence, the sensitivity of the measurement technique is enhanced by either increasing wall conductivity or optimizing the aspect ratio of the cross-section of the flow.

DC Electric Field Measurement by the Double Probe System Aboard Geotail and its Simulation

NASA Astrophysics Data System (ADS)

Kasaba, Y.; Hayakawa, H.; Ishisaka, K.; Okada, T.; Matsuoka, A.; Mukai, T.; Okada, M.

2005-12-01

We summarize the characteristics of the DC electric field measurement by the double probe system, PANT and EFD-P, aboard Geotail. The accuracy and correction factors for the gain (effective length) and off-set, which depends on ambient plasma conditions, are provided. Accurate measurements of electric fields are essential for space plasma studies, for example, plasma convection, wave-particle interactions, violation of MHD approximation, etc. One typical measurement techniques is the 'Double Probe method', identical to that of a voltmeter: the potential difference between two top-hat probes [cf. Pedersen et al., 1984]. This method can measure electric fields passively and continuously in all plasma conditions. However, the accuracy of the measured electric field values is limited. The probe measurement is also subjected to the variable gain (effective length) of the probe antenna and the artificial offset of the measured values. Those depend on a) the disturbance from ambient plasma and b) the disturbance from the spacecraft and the probe itself. In this paper, we show the results of the characteristics of DC electric field measurement by the PANT probe and the EFD-P (Electric Field Detector - Probe technique) receiver aboard Geotail [Tsuruda et al., 1994], in order to evaluate the accuracy, gain, and offset controlled by ambient plasmas. We conclude that the Geotail electric field measurement by the double probe system has the accuracy 0.4 mV/m for Ex and 0.3 mV/m for Ey, after the correction of the gain and offset. In better conditions, accuracy of Ey is 0.2 mV/m. The potential accuracy would be better because those values are limited by the accuracy of the particle measurement especially in low density conditions. In practical use, the corrections by long-term variation and spacecraft potential are effective to refine the electric field data. The characteristics of long-term variation and the dependences on ambient plasma are not fully understood well, yet. Further works will be needed based on the calibrated LEP data after 1998. It will also cover the conditions rejected in this paper, i.e., low density regions, potential controlled period, electric field quasi-parallel to magnetic field, etc. The comparison with EFD-B (EFD - Beam technique) data will also be included in order to reject the ambiguity in particle observations. In addition, we are trying to establish the numerical model of the double probe system for the full-quantitative understanding of the effect of potential structure and photoelectron distributions. Those will be the basis for planned experiments, BepiColombo to Mercury, ERG to the inner magnetosphere, and the multi-spacecraft magnetospheric mission SCOPE.

Laser-Induced Modification Of Energy Bands Of Transparent Solids

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly

2010-10-01

Laser-induced variations of electron energy bands of transparent solids significantly affect the initial stages of laser-induced ablation (LIA) influencing rates of ionization and light absorption by conduction-band electrons. We analyze fast variations with characteristic duration in femto-second time domain that include: 1) switching electron functions from bonding to anti-bonding configuration due to laser-induced ionization; 2) laser-driven oscillations of electrons in quasi-momentum space; and 3) direct distortion of the inter-atomic potential by electric field of laser radiation. Among those effects, the latter two have zero delay and reversibly modify band structure taking place from the beginning of laser action. They are of special interest due to their strong influence on the initial stage and threshold of laser ablation. The oscillations modify the electron-energy bands by adding pondermotive potential. The direct action of radiation's electric field leads to high-frequency Franz-Keldysh effect (FKE) spreading the allowed electron states into the forbidden-energy bands. FKE provides decrease of the effective band gap while the electron oscillations lead either to monotonous increase or oscillatory variations of the gap. We analyze the competition between those two opposite trends and their role in initiating LIA.

Measuring the vertical electrical field above an oceanic convection system using a meteorological sounding balloon

NASA Astrophysics Data System (ADS)

Chen, A. B.; Chiu, C.; Lai, S.; Chen, C.; Kuo, C.; Su, H.; Hsu, R.

2012-12-01

The vertical electric field above thundercloud plays an important role in the generation and modeling of transient luminous events. For example, Pasko [1995] proposed that the high quasi-static E-field following the positive cloud-to-ground lightning could accelerate and input energy to ambient electrons; as they collide and excite nitrogen and oxygen molecules in upper atmosphere, sprites may be induced. A series of balloon experiments led by Holzworth have investigated the temporal and spatial fluctuations of the electric field and conductivity in the upper atmosphere at different sites [Holzworth 2005, and references in]. But the strength and variation of the vertical electric field above thundercloud, especially oceanic ones, are not well documented so far. A lightweight, low-cost measurement system including an electric field meter and the associated aviation electronics are developed to carry out the in-situ measurement of the vertical electric field and the inter-cloud charge distribution. Our measuring system was first deployed using a meteorological sounding balloon from Taitung, Taiwan in May 2012. The measured electric field below 3km height shows an exponential decay and it is consistent with the expected potential gradient variation between ionosphere and the Earth surface. But the background strength of the measured E-field grows up exponentially and a violent fluctuations is also observed when the balloon flew over a developing oceanic convection cell. The preliminary results from this flight will be reported and discussed. This low-cost electric field meter is developed within one year. In the coming months, more flights will be performed with the aim to measure the rapid variation of the electric field above thundercloud as well as the E-field that may induce transient luminous events. Our ground campaigns show that the occurrence rates of blue and gigantic jet are relatively high in the vicinity of Taiwan. Our experiment can be used to diagnose the dynamics of the E-field associated with blue and gigantic jets.

Vector electric field measurement via position-modulated Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Dwyer, Ryan P.; Smieska, Louisa M.; Tirmzi, Ali Moeed; Marohn, John A.

2017-10-01

High-quality spatially resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy that enables spatially resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT) organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.

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

NASA Astrophysics Data System (ADS)

Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

2015-04-01

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

46 CFR 111.01-17 - Voltage and frequency variations.

Code of Federal Regulations, 2013 CFR

2013-10-01

....01-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless otherwise stated, electrical equipment must function at variations of at least ±5 percent of rated frequency...

46 CFR 111.01-17 - Voltage and frequency variations.

Code of Federal Regulations, 2010 CFR

2010-10-01

....01-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless otherwise stated, electrical equipment must function at variations of at least ±5 percent of rated frequency...

46 CFR 111.01-17 - Voltage and frequency variations.

Code of Federal Regulations, 2011 CFR

2011-10-01

....01-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless otherwise stated, electrical equipment must function at variations of at least ±5 percent of rated frequency...

46 CFR 111.01-17 - Voltage and frequency variations.

Code of Federal Regulations, 2012 CFR

2012-10-01

....01-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless otherwise stated, electrical equipment must function at variations of at least ±5 percent of rated frequency...

46 CFR 111.01-17 - Voltage and frequency variations.

Code of Federal Regulations, 2014 CFR

2014-10-01

....01-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-17 Voltage and frequency variations. Unless otherwise stated, electrical equipment must function at variations of at least ±5 percent of rated frequency...

Characterization of structural and electrostatic complexity in pentacene thin films by scanning probe microscopy

NASA Astrophysics Data System (ADS)

Puntambekar, Kanan Prakash

The advancement of organic electronics for applications in solar energy conversion, printed circuitry, displays, and solid-state lighting depends upon optimization of structure and properties for a variety of organic semiconductor interfaces. Organic semiconductor/insulator (O/I) and organic-metal (O/M) interfaces, in particular, are critical to the operation of organic thin film transistors (OTFTs) currently being developed for printed flexible electronics. Scanning probe microscopy (SPM) is a powerful tool to isolate and characterize the bottlenecks to charge transport at these interfaces. This thesis establishes a direct correlation between the structural disorder and electrical complexity at these interfaces, using various SPM based methods and discusses the implications of such complexity on device performance. To examine the O/M interfaces, surface potentials of operating pentacene TFTs with two different contact geometries (bottom or top) were mapped by Kelvin probe force microscopy (KFM). The surface potential distribution was used to isolate the potential drops at the source and drain contacts. Simultaneously obtained topography and surface potential maps elucidated the correlation between the morphology and contact resistance at the O/M interface; the bottom contact TFTs were observed to be contact limited at large gate voltages, while the top contact TFTs were not contact limited. A direct correlation between structural defects and electric potential variations at the pentacene and silicon dioxide, a common insulator, is demonstrated. Lateral force microscopy (LFM) generates striking images of the polycrystalline microstructure of a monolayer thick pentacene film, allowing clear visualization of the grain boundary network. Further more, surface potential wells localized at the grain boundaries were observed by KFM, suggesting that the grain boundaries may serve as charge carrier (hole) traps. Line dislocations were also revealed in the second monolayer by chemical etching and SPM and produce strong variations in the surface potential that must affect the interfacial charge conductance. Structural disorder at the O/I and O/M interfaces degrades both injection and transport of charge, and therefore needs to be minimized. Thus both visualization and correlation of structural and electrical complexity at these interfaces have important implications for understanding electrical transport in OTFTs and for defining strategies to improve device performance.

Transport of ions through a (6,6) carbon nanotube under electric fields

NASA Astrophysics Data System (ADS)

Shen, Li; Xu, Zhen; Zhou, Zhe-Wei; Hu, Guo-Hui

2014-11-01

The transport of water and ions through carbon nanotubes (CNTs) is crucial in nanotechnology and biotechnology. Previous investigation indicated that the ions can hardly pass through (6,6) CNTs due to their hydrated shells. In the present study, utilizing molecular dynamics simulation, it is shown that the energy barrier mainly originating from the hydrated water molecules could be overcome by applying an electric field large enough in the CNT axis direction. Potential of mean force is calculated to show the reduction of energy barrier when the electric field is present for (Na+, K+, Cl-) ions. Consequently, ionic flux through (6,6) CNTs can be found once the electric field becomes larger than a threshold value. The variation of the coordination numbers of ions at different locations from the bulk to the center of the CNT is also explored to elaborate this dynamic process. The thresholds of the electric field are different for Na+, K+, and Cl- due to their characteristics. This consequence might be potentially applied in ion selectivity in the future.

Signal variation and its morphological correlates in Paramormyrops kingsleyae provide insight into the evolution of electrogenic signal diversity in mormyrid electric fish.

PubMed

Gallant, Jason R; Arnegard, Matthew E; Sullivan, John P; Carlson, Bruce A; Hopkins, Carl D

2011-08-01

We describe patterns of geographic variation in electric signal waveforms among populations of the mormyrid electric fish species Paramormyrops kingsleyae. This analysis includes study of electric organs and electric organ discharge (EOD) signals from 553 specimens collected from 12 localities in Gabon, West-Central Africa from 1998 to 2009. We measured time, slope, and voltage values from nine defined EOD "landmarks" and determined peak spectral frequencies from each waveform; these data were subjected to principal components analysis. The majority of variation in EODs is explained by two factors: the first related to EOD duration, the second related to the magnitude of the weak head-negative pre-potential, P0. Both factors varied clinally across Gabon. EODs are shorter in eastern Gabon and longer in western Gabon. Peak P0 is slightly larger in northern Gabon and smaller in southern Gabon. P0 in the EOD is due to the presence of penetrating-stalked (Pa) electrocytes in the electric organ while absence is due to the presence of non-penetrating stalked electrocytes (NPp). Across Gabon, the majority of P. kingsleyae populations surveyed have only individuals with P0-present EODs and Pa electrocytes. We discovered two geographically distinct populations, isolated from others by barriers to migration, where all individuals have P0-absent EODs with NPp electrocytes. At two sites along a boundary between P0-absent and P0-present populations, P0-absent and P0-present individuals were found in sympatry; specimens collected there had electric organs of intermediate morphology. This pattern of geographic variation in EODs is considered in the context of current phylogenetic work. Multiple independent paedomorphic losses of penetrating stalked electrocytes have occurred within five Paramormyrops species and seven genera of mormyrids. We suggest that this key anatomical feature in EOD signal evolution may be under a simple mechanism of genetic control, and may be easily influenced by selection or drift throughout the evolutionary history of mormyrids.

Vibration and bending analyses of magneto-electro-thermo-elastic sandwich microplates resting on viscoelastic foundation

NASA Astrophysics Data System (ADS)

Arefi, Mohammad; Zenkour, Ashraf M.

2017-08-01

Magneto-electro-thermo-mechanical bending and free vibration analysis of a sandwich microplate using strain gradient theory is expressed in this paper. The sandwich plate is made of a core and two integrated piezo-magnetic face sheets. The structure is subjected to electric and magnetic potentials, thermal loadings, and resting on Pasternak's foundation. Electro-magnetic equations are developed by considering the variation form of Hamilton's principle. The effects of important parameters of this problem such as applied electric and magnetic potentials, direct and shear parameter of foundation, three microlength-scale parameters, and two parameters of temperature rising are investigated on the vibration and bending results of problem.

The effect of an external electric field on the growth of incongruent-melting material

NASA Astrophysics Data System (ADS)

Uda, Satoshi; Huang, Xinming; Wang, Shou-Qi

2005-02-01

The significance of an electric field on the crystallization process is differentiated into two consequences; (i) thermodynamic effect and (ii) growth-dynamic effect. The former modifies the chemical potential of the associated phases which changes the equilibrium phase relationship while the latter influences the solute transport, growth kinetics, surface creation and defect generation during growth. The intrinsic electric field generating during growth is attributed to the crystallization-related electromotive force and the thermoelectric power driven by the temperature gradient at the interface which influences the solute transport and solute partitioning. The external electric field was applied to the growth apparatus in the ternary system of La2O3- Ga2O3- SiO2 so that the chemical potential of both solid and liquid phases changed leading to the variation of the equilibrium phase relationship. Imposing a 500 V/cm electric field on the system moved the boundary of primary phase field of lanthanum gallate ( LaGaO3) and Ga-bearing lanthanum silicate ( La14GaxSi9-xO) toward the SiO2 apex by 5 mol% which clearly demonstrated the change of the phase relationship by the external electric field.

New Method for Solving Inductive Electric Fields in the Ionosphere

NASA Astrophysics Data System (ADS)

Vanhamäki, H.

2005-12-01

We present a new method for calculating inductive electric fields in the ionosphere. It is well established that on large scales the ionospheric electric field is a potential field. This is understandable, since the temporal variations of large scale current systems are generally quite slow, in the timescales of several minutes, so inductive effects should be small. However, studies of Alfven wave reflection have indicated that in some situations inductive phenomena could well play a significant role in the reflection process, and thus modify the nature of ionosphere-magnetosphere coupling. The input to our calculation method are the time series of the potential part of the ionospheric electric field together with the Hall and Pedersen conductances. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfven wave reflection from uniformly conducting ionosphere.

Simulation of the Universal-Time Diurnal Variation of the Global Electric Circuit Charging Rate

NASA Technical Reports Server (NTRS)

Mackerras, David; Darveniza, Mat; Orville, Richard E.; Williams, Earle R.; Goodman, Steven J.

1999-01-01

A global lightning model that includes diurnal and annual lightning variation, and total flash density versus latitude for each major land and ocean, has been used as the basis for simulating the global electric circuit charging rate. A particular objective has been to reconcile the difference in amplitude ratios [AR=(max-min)/mean] between global lightning diurnal variation (AR approximately equals 0.8) and the diurnal variation of typical atmospheric potential gradient curves (AR approximately equals 0.35). A constraint on the simulation is that the annual mean charging current should be about 1000 A. The global lightning model shows that negative ground flashes can contribute, at most, about 10-15% of the required current. For the purpose of the charging rate simulation, it was assumed that each ground flash contributes 5 C to the charging process. It was necessary to assume that all electrified clouds contribute to charging by means other than lightning, that the total flash rate can serve as an indirect indicator of the rate of charge transfer, and that oceanic electrified clouds contribute to charging even though they are relatively inefficient in producing lightning. It was also found necessary to add a diurnally invariant charging current component. By trial and error it was found that charging rate diurnal variation curves could be produced with amplitude ratios and general shapes similar to those of the potential gradient diurnal variation curves measured over ocean and arctic regions during voyages of the Carnegie Institute research vessels. The comparisons were made for the northern winter (Nov.-Feb.), the equinox (Mar., Apr., Sept., Oct.), the northern summer (May-Aug.), and the whole year.

Nano-scale mass sensor based on the vibration analysis of a magneto-electro-elastic nanoplate resting on a visco-Pasternak substrate

NASA Astrophysics Data System (ADS)

Khanmirza, E.; Jamalpoor, A.; Kiani, A.

2017-10-01

In this paper, a magneto-electro-elastic nanoplate resting on a visco-Pasternak medium with added concentrated nanoparticles is presented as a mass nanosensor according to the vibration analysis. The MEE nanoplate is supposed to be subject to external electric voltage and magnetic potential. In order to take into account the size effect on the sensitivity of the sensor, the nonlocal elasticity theory in conjunction with the Kirchhoff plate theory is applied. Partial differential equations are derived by implementing Hamilton's variational principle. Equilibrium equations were solved analytically to determine an explicit closed-form statement for both the damped frequency shift and the relative damped frequency shift using Navier's approach. A genetic algorithm (GA) is employed to achieve the optimal added nanoparticle location to gain the most sensitivity performance of the nanosensor. Numerical studies are performed to illustrate the variation of the sensitivity property corresponding to various values of the number of attached nanoparticles, the mass of each nanoparticle, the nonlocal parameter, external electric voltage and magnetic potential, the aspect ratio, and visco-Pasternak parameters. Some numerical outcomes of this paper show that the minimum value of the damped frequency shift occurs for a certain value of the length-to-thickness ratio. Also, it is shown that the external magnetic and external electric potentials have a different effect on the sensitivity property. It is anticipated that the results reported in this work can be considered as a benchmark in future micro-structures issues.

Monitoring the Dynamics of Water Flow at a High-Mountain Permafrost Site Using Electrical Self-Potential Measurements

NASA Astrophysics Data System (ADS)

Kemna, A.; Weigand, M.; Wagner, F.; Hilbich, C.; Hauck, C.

2016-12-01

Flow of (liquid) water plays a crucial role in the dynamics of coupled thermo-hydro-mechanical processes in terrestrial permafrost systems. To better understand these processes in the active layer of permafrost regions, with the ultimate goal of adequately incorporating them in numerical models for improved scenario prediction, monitoring approaches offering high spatial and temporal resolution, areal coverage, and especially sensitivity to subsurface water flow, are highly desired. This particularly holds for high-mountain slopes, where strong variability in topography, precipitation, and snow cover, along with significant subsurface soil/rock heterogeneity, gives rise to complex spatio-temporal patterns of water flow during seasonal thawing and freezing periods. The electrical self-potential (SP) method is well known to, in theory, meeting the above monitoring demands by measuring the electrical streaming potential which is generated at the microscopic scale when water flows along electrically non-neutral interfaces. Despite its inherent sensitivity to subsurface water flow, the SP method has not yet been used for the monitoring of high-mountain permafrost sites. We here present first results from an SP monitoring survey conducted at the Schilthorn (2970 m asl) in the Bernese Alps, Switzerland, where SP data have been collected since September 2013 at a sampling rate of 10 min on a permanently installed array of 12 non-polarizing electrodes covering an area of 35 m by 15 m. While the SP time series exhibit systematic daily variations, with part of the signal clearly correlated with temperature, in particular in the snow-free periods, the largest temporal changes in the SP signal occur in spring, when the snow cover melts and thawing sets on in the active layer. The period of higher temporal SP variations continues until autumn, when the signal gradually returns to relatively low variations, coinciding with the freezing of the ground. Our results suggest that the SP method is a suitable tool for the monitoring of seasonal water flow dynamics at high-mountain permafrost sites. Current work is directed towards an improved field setup, as well as the quantitative analysis of the SP data based on laboratory calibration measurements.

Self-potential response to periodic pumping test: a numerical study

NASA Astrophysics Data System (ADS)

Konosavsky, Pavel; Maineult, Alexis; Narbut, Mikhail; Titov, Konstantin

2017-09-01

We numerically model self-potential responses associated with periodic pumping test experiments by sequential calculation of the hydraulic response and the coupled electrical potential. We assume the pumping test experiments with a fully saturated confined aquifer. Application of different excitation functions leads to quasi-linear trends in electrical records whose direction and intensity depend on the form of the excitation function. The hydraulic response is phase shifted compared to the excitation function; the phase shift increases quasi-linearly with the distance from the pumping well. For the electrical signals, we investigated separately the cases of conducting and insulating casings of the pumping well. For the conducting casing the electrical signals are larger in magnitude than that for the insulating casing; they reproduce the drawdown signals in the pumping well at any distance from the well and exhibit any phase shift with the increased distance. For the insulating casing, the electrical signals are phase shifted and their shape depends on the distance from the pumping well. Three characteristic regimes were found for the phase shift, φ, with the increased distance and for various hydraulic diffusivity values. At small distances φ increases quasi-linearly; at intermediate distances φ attends the value of π/2 and stay about this value (for relatively small diffusivity values); and at large distances φ attends the value of π and, stay about this value at larger distances. This behaviour of the electrical signals can be explained by two electrical sources of reverse polarity. They are (i) linear, time independent, and located at the pumping interval of the well; and (ii) volumetric, time dependent, with maximum value located in the aquifer at the distance corresponding to maximum variation of the hydraulic head magnitude with time. We also model the variation of the amplitude and phase of the hydraulic and electrical signals with increased excitation function period, and we show the characteristic periods corresponding to transition of the periodic pumping test regime to the classical pumping test regime, when the excitation function is considered as the step-function. This transition depends on the distance from the pumping well and the hydraulic diffusivity value of aquifer. Finally, with this modelling of saturated flow we reproduced in sufficient details the field data previously obtained by Maineult et al.

Hysteresis in voltage-gated channels.

PubMed

Villalba-Galea, Carlos A

2017-03-04

Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels.

Manipulating the magnetism and resistance state of Mn:ZnO/Pb(Zr0.52Ti0.48)O3 heterostructured films through electric fields

NASA Astrophysics Data System (ADS)

Li, Yong-Chao; Wu, Jun; Pan, Hai-Yang; Wang, Jue; Wang, Guang-Hou; Liu, Jun-Ming; Wan, Jian-Guo

2018-05-01

Mn:ZnO/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructured films have been prepared on Pt/Ti/SiO2/Si wafers by a sol-gel process. Nonvolatile and reversible manipulation of the magnetism and resistance by electric fields has been realized. Compared with the saturation magnetic moment (Ms) in the +3.0 V case, the modulation gain of Ms can reach 270% in the -3.0 V case at room temperature. The resistance change is attributed to the interfacial potential barrier height variation and the formation of an accumulation (or depletion) layer at the Mn:ZnO/PZT interface, which can be regulated by the ferroelectric polarization direction. The magnetism of Mn:ZnO originates from bound magnetic polarons. The mobile carrier variation in Mn:ZnO, owing to interfacial polarization coupling and the ferroelectric field effect, enables the electric manipulation of the magnetism in the Mn:ZnO/PZT heterostructured films. This work presents an effective method for modulating the magnetism of magnetic semiconductors and provides a promising avenue for multifunctional devices with both electric and magnetic functionalities.

Ultrafast laser-induced modifications of energy bands of non-metal crystals

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly

2009-10-01

Ultrafast laser-induced variations of electron energy bands of transparent solids significantly influence ionization and conduction-band electron absorption driving the initial stage of laser-induced damage (LID). The mechanisms of the variations are attributed to changing electron functions from bonding to anti-bonding configuration via laser-induced ionization; laser-driven electron oscillations in quasi-momentum space; and direct distortion of the inter-atomic potential by electric field of laser radiation. The ionization results in the band-structure modification via accumulation of broken chemical bonds between atoms and provides significant contribution to the overall modification only when enough excited electrons are accumulated in the conduction band. The oscillations are associated with modification of electron energy by pondermotive potential of the oscillations. The direct action of radiation's electric field leads to specific high-frequency Franz-Keldysh effect (FKE) spreading the allowed electron states into the bands of forbidden energy. Those processes determine the effective band gap that is a laser-driven energy gap between the modified electron energy bands. Among those mechanisms, the latter two provide reversible band-structure modification that takes place from the beginning of the ionization and are, therefore, of special interest due to their strong influence on the initial stage of the ionization. The pondermotive potential results either in monotonous increase or oscillatory variations of the effective band gap that has been taken into account in some ionization models. The classical FKE provides decrease of the band gap. We analyzing the competition between those two opposite trends of the effective-band-gap variations and discuss applications of those effects for considerations of the laser-induced damage and its threshold in transparent solids.

Effectiveness of a worker-worn electric-field sensor to detect power-line proximity and electrical-contact.

PubMed

Zeng, Shengke; Powers, John R; Newbraugh, Bradley H

2010-06-01

Construction workers suffer the most electrocutions among all industries. Currently, there are no electrical contact warning devices on the market to protect workers. This paper proposes a worker-worn electric-field sensor. As the worker is in proximity to, or in contact with, a live power-circuit, the sensor sets off an audible/visual warning alarm. The sensor also has the potential to wirelessly trip a wireless-capable circuit breaker, and to trigger a wireless transmitter to notify emergency response of an electrical contact. An experiment was conducted to measure electric-field variation on simulated human-wrists (10 defrosted hog-legs) in various proximities and in electrical-contact to a simulated power-circuit. The purpose of these tests was to determine the feasibility of developing a worker-worn electric-field detection sensor for use in protecting workers from contact with energized electrical conductors. This study observed a significant electric-field-magnitude increase as a hog-leg approaches the live-circuit, and the distinct electric-field-magnitude jump as the leg contacts with the live-circuit. The observation indicates that this sensor can be an effective device to warn the workers of electrical hazards. Additionally, the sensor has the potential to wirelessly trip a wireless-capable circuit-breaker and trigger a wireless transmitter (such as a cell phone) to notify an emergency response. The prompt notification prevents the worker from further injury caused by postponed medical-care. Widespread use of this sensor could lower electrocution and electrically related injury rates in the construction industry. (c) 2010 Elsevier Ltd. All rights reserved.

Numerical investigation of the effect of net charge injection on the electric field deviation in a TE CO2 laser

NASA Astrophysics Data System (ADS)

Jahanianl, Nahid; Aram, Majid; Morshedian, Nader; Mehramiz, Ahmad

2018-03-01

In this report, the distribution of and deviation in the electric field were investigated in the active medium of a TE CO2 laser. The variation in the electric field is due to injection of net electron and proton charges as a plasma generator. The charged-particles beam density is assumed to be Gaussian. The electric potential and electric field distribution were simulated by solving Poisson’s equation using the SOR numerical method. The minimum deviation of the electric field obtained was about 2.2% and 6% for the electrons and protons beams, respectively, for a charged-particles beam-density of 106 cm-3. This result was obtained for a system geometry ensuring a mean-free-path of the particles beam of 15 mm. It was also found that the field deviation increases for a the mean-free-path smaller than that or larger than 25 mm. Moreover, the electric field deviation decreases when the electrons beam density exceeds 106 cm-3.

Dielectric screening of early differentiation patterns in mesenchymal stem cells induced by steroid hormones.

PubMed

Ron, Amit; Shur, Irena; Daniel, Ramiz; Singh, Ragini Raj; Fishelson, Nick; Croitoru, Nathan; Benayahu, Dafna; Shacham-Diamand, Yosi

2010-06-01

In the framework of this study, target identification and localization of differentiation patterns by means of dielectric spectroscopy is presented. Here, a primary pre-osteoblastic bone marrow-derived MBA-15 cellular system was used to study the variations in the dielectric properties of mesenchymal stem cells while exposed to differentiation regulators. Using the fundamentals of mixed dielectric theories combined with finite numerical tools, the permittivity spectra of MBA-15 cell suspensions have been uniquely analyzed after being activated by steroid hormones to express osteogenic phenotypes. Following the spectral analysis, significant variations were revealed in the dielectric properties of the activated cells in comparison to the untreated populations. Based on the differentiation patterns of MBA-15, the electrical modifications were found to be highly correlated with the activation of specific cellular mechanisms which directly react to the hormonal inductions. In addition, by describing the dielectric dispersion in terms of transfer functions, it is shown that the spectral perturbations are well adapted to variations in the electrical characteristics of the cells. The reported findings vastly emphasize the tight correlation between the cellular and electrical state of the differentiated cells. It therefore emphasizes the vast abilities of impedance-based techniques as potential screening tools for stem cell analysis. Copyright 2009 Elsevier B.V. All rights reserved.

Spectral analysis of pipe-to-soil potentials with variations of the Earth's magnetic field in the Australian region

NASA Astrophysics Data System (ADS)

Marshall, R. A.; Waters, C. L.; Sciffer, M. D.

2010-05-01

Long, steel pipelines used to transport essential resources such as gas and oil are potentially vulnerable to space weather. In order to inhibit corrosion, the pipelines are usually coated in an insulating material and maintained at a negative electric potential with respect to Earth using cathodic protection units. During periods of enhanced geomagnetic activity, potential differences between the pipeline and surrounding soil (referred to as pipe-to-soil potentials (PSPs)) may exhibit large voltage swings which place the pipeline outside the recommended "safe range" and at an increased risk of corrosion. The PSP variations result from the "geoelectric" field at the Earth's surface and associated geomagnetic field variations. Previous research investigating the relationship between the surface geoelectric field and geomagnetic source fields has focused on the high-latitude regions where line currents in the ionosphere E region are often the assumed source of the geomagnetic field variations. For the Australian region Sq currents also contribute to the geomagnetic field variations and provide the major contribution during geomagnetic quiet times. This paper presents the results of a spectral analysis of PSP measurements from four pipeline networks from the Australian region with geomagnetic field variations from nearby magnetometers. The pipeline networks extend from Queensland in the north of Australia to Tasmania in the south and provide PSP variations during both active and quiet geomagnetic conditions. The spectral analyses show both consistent phase and amplitude relationships across all pipelines, even for large separations between magnetometer and PSP sites and for small-amplitude signals. Comparison between the observational relationships and model predictions suggests a method for deriving a geoelectric field proxy suitable for indicating PSP-related space weather conditions.

Analytical study of spheroidal dust grains in plasma

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

Zahed, H.; Mahmoodi, J.; Sobhanian, S.

2006-05-15

Using the modified spheroidal equations, the potential of a spheroidal conducting grain, floated in a plasma, is calculated. The electric field and capacitance for both prolate and oblate spheroidal grains are investigated. The solutions, obtained up to the second-order approximation, show that the plasma screening causes the equipotential surfaces around the grain to be more elongated or flattened than the potential spheroids of the Laplace equation. This leads to the variation of the plasma concentration around the grain.

Proton cellular influx as a probable mechanism of variation potential influence on photosynthesis in pea.

PubMed

Sukhov, Vladimir; Sherstneva, Oksana; Surova, Lyubov; Katicheva, Lyubov; Vodeneev, Vladimir

2014-11-01

Electrical signals (action potential and variation potential, VP) caused by environmental stimuli are known to induce various physiological responses in plants, including changes in photosynthesis; however, their functional mechanisms remain unclear. In this study, the influence of VP on photosynthesis in pea (Pisum sativum L.) was investigated and the proton participation in this process analysed. VP, induced by local heating, inactivated photosynthesis and activated respiration, with the initiation of the photosynthetic response connected with inactivation of the photosynthetic dark stage; however, direct VP influence on the light stage was also probable. VP generation was accompanied with pH increases in apoplasts (0.17-0.30 pH unit) and decreases in cytoplasm (0.18-0.60 pH unit), which probably reflected H(+) -ATPase inactivation and H(+) influx during this electrical event. Imitation of H(+) influx using the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) induced a photosynthetic response that was similar with a VP-induced response. Experiments on chloroplast suspensions showed that decreased external pH also induced an analogous response and that its magnitude depended on the magnitude of pH change. Thus, the present results showed that proton cellular influx was the probable mechanism of VP's influence on photosynthesis in pea. Potential means of action for this influence are discussed. © 2014 John Wiley & Sons Ltd.

Hysteresis in voltage-gated channels

PubMed Central

2017-01-01

ABSTRACT Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels. PMID:27689426

A comprehensive analysis of surface acoustic wave reflections

NASA Astrophysics Data System (ADS)

Robinson, H.; Hahn, Y.; Gau, J. N.

1989-06-01

A thorough study of the perturbative and variational approaches is carried out for the surface acoustic wave reflection problem. We have shown that the perturbation treatment by Datta and Hunsinger and potentially powerful variational formulation by Chen and Haus [IEEE Trans. Sonics Ultrason. SU-32, 395 (1985)] are mutually consistent. In their common region of validity, these two approaches yield nearly identical results for the reflection coefficients and velocity shifts due to metal finger and groove overlays. Term-by-term comparison of the mass- and stress-loading effects, and also the electric shorting effect, is carried out to provide a coherent picture of the reflection phenomena. The on- and off-resonance behavior of the reflection coefficient can be described correctly using either one of these theories, with proper inclusion of the overlay shape dependence. A new term for electric shorting is derived for groove overlays.

The investigation of tethered satellite system dynamics

NASA Technical Reports Server (NTRS)

Lorenzini, E.

1985-01-01

A progress report is presented that deals with three major topics related to Tethered Satellite System Dynamics. The SAO rotational dynamics computer code was updated. The program is now suitable to deal with inclined orbits. The output has been also modified in order to show the satellite Euler angles referred to the rotating orbital frame. The three-dimensional high resolution computer program SLACK3 was developed. The code simulates the three-dimensional dynamics of a tether going slack taking into account the effect produced by boom rotations. Preliminary simulations on the three-dimensional dynamics of a recoiling slack tether are shown in this report. A program to evaluate the electric potential around a severed tether is immersed in a plasma. The potential is computed on a three-dimensional grid axially symmetric with respect to the tether longitudinal axis. The electric potential variations due to the plasma are presently under investigation.

An electrical analogy to Mie scattering

PubMed Central

Caridad, José M.; Connaughton, Stephen; Ott, Christian; Weber, Heiko B.; Krstić, Vojislav

2016-01-01

Mie scattering is an optical phenomenon that appears when electromagnetic waves, in particular light, are elastically scattered at a spherical or cylindrical object. A transfer of this phenomenon onto electron states in ballistic graphene has been proposed theoretically, assuming a well-defined incident wave scattered by a perfectly cylindrical nanometer scaled potential, but experimental fingerprints are lacking. We present an experimental demonstration of an electrical analogue to Mie scattering by using graphene as a conductor, and circular potentials arranged in a square two-dimensional array. The tabletop experiment is carried out under seemingly unfavourable conditions of diffusive transport at room-temperature. Nonetheless, when a canted arrangement of the array with respect to the incident current is chosen, cascaded Mie scattering results robustly in a transverse voltage. Its response on electrostatic gating and variation of potentials convincingly underscores Mie scattering as underlying mechanism. The findings presented here encourage the design of functional electronic metamaterials. PMID:27671003

Band-Like Behavior of Localized States of Metal Silicide Precipitate in Silicon

NASA Astrophysics Data System (ADS)

Bondarenko, Anton; Vyvenko, Oleg

2018-03-01

Deep-level transient spectroscopy (DLTS) investigations of energy levels of charge-carrier traps associated with precipitates of metal silicide often show that they behave not like localized monoenergetic traps but as a continuous density of allowed states in the bandgap with fast carrier exchange between these states, so-called band-like behavior. This kind of behavior was ascribed to the dislocation loop bounding the platelet, which in addition exhibits an attractive potential caused by long-range elastic strain. In previous works, the presence of the dislocation-related deformation potential in combination with the external electric field of the Schottky diode was included to obtain a reasonable fit of the proposed model to experimental data. Another well-known particular property of extended defects—the presence of their own strong electric field in their vicinity that is manifested in the logarithmic kinetics of electron capture—was not taken into account. We derive herein a theoretical model that takes into account both the external electric field and the intrinsic electric field of dislocation self-charge as well as its deformation potential, which leads to strong temporal variation of the activation energy during charge-carrier emission. We performed numerical simulations of the DLTS spectra based on such a model for a monoenergetic trap, finding excellent agreement with available experimental data.

Mild degradation processes in ZnO-based varistors: the role of Zn vacancies

NASA Astrophysics Data System (ADS)

Ponce, M. A.; Macchi, C.; Schipani, F.; Aldao, C. M.; Somoza, A.

2015-03-01

The effects of a degradation process on the structural and electrical properties of ZnO-based varistors induced by the application of dc bias voltage were analysed. Capacitance and resistance measurements were carried out to electrically characterize the polycrystalline semiconductor before and after different degrees of mild degradation. Vacancies' changes in the varistors were studied with positron annihilation lifetime spectroscopy. Variations on the potential barrier height and effective doping concentration were determined by fitting the experimental data from impedance spectroscopy measurements. These results indicate two different stages in the degradation process consistent with vacancy-like concentration changes.

An efficient finite element with layerwise mechanics for smart piezoelectric composite and sandwich shallow shells

NASA Astrophysics Data System (ADS)

Yasin, M. Yaqoob; Kapuria, S.

2014-01-01

In this work, we present a new efficient four-node finite element for shallow multilayered piezoelectric shells, considering layerwise mechanics and electromechanical coupling. The laminate mechanics is based on the zigzag theory that has only seven kinematic degrees of freedom per node. The normal deformation of the piezoelectric layers under the electric field is accounted for without introducing any additional deflection variables. A consistent quadratic variation of the electric potential across the piezoelectric layers with the provision of satisfying the equipotential condition of electroded surfaces is adopted. The performance of the new element is demonstrated for the static response under mechanical and electric potential loads, and for free vibration response of smart shells under different boundary conditions. The predictions are found to be very close to the three dimensional piezoelasticity solutions for hybrid shells made of not only single-material composite substrates, but also sandwich substrates with a soft core for which the equivalent single layer (ESL) theories perform very badly.

Controlled generation of different orbital angular momentum states in a hybrid optical fiber

NASA Astrophysics Data System (ADS)

Heng, Xiaobo; Gan, Jiulin; Zhang, Zhishen; Qian, Qi; Xu, Shanhui; Yang, Zhongmin

2017-11-01

A new kind of hybrid optical fiber for different orbital angular momentum (OAM) states generation is proposed and investigated by simulation. The hybrid fiber is composed of three main regions: the core, the cladding and the bow-tie-shaped stress-applying zones (SAZs). The SAZs are symmetrically distributed on both sides of the core and filled with piezoelectric material PZT-5H which would generate radial mechanical movement when subjected to an electric field. The strain applied by the SAZs introduces anisotropic variation of the material permittivity which affect the propagation of the guided modes along the fiber core. The OAM modes of | l | = 1 , 2 , 3 can be generated by setting the appropriate electric potential applied in the SAZs. This fiber-based structure and electric control design enable the generation and adjustment of OAM states with the merits of accuracy, compactness and practicality, which would have potential application in OAM optical fiber communication systems and other systems utilizing OAM light.

Copy number variations in patients with electrical status epilepticus in sleep.

PubMed

Kevelam, Sietske H G; Jansen, Floor E; Binsbergen, Ellen van; Braun, Kees P J; Verbeek, Nienke E; Lindhout, Dick; Poot, Martin; Brilstra, Eva H

2012-02-01

Electrical status epilepticus in sleep syndrome is the association of the electroencephalographic pattern and deficits in language or global cognitive function and behavioral problems. The etiology is often unknown, but genetic risk factors have been implicated. Array-based comparative genomic hybridization was used to identify copy number variations in 13 children with electrical status epilepticus in sleep syndrome to identify possible underlying risk factors. Seven copy number variations were detected in 4 of the 13 patients, which consisted of 6 novel gains and 1 loss, the recurrent 15q13.3 microdeletion. Two patients carried a probable pathogenic copy number variation containing a gene involved in the cholinergic pathway. Genetic aberrations in patients with electrical status epilepticus in sleep syndrome can provide an entry in the investigation of the etiology of electrical status epilepticus in sleep. However, further studies are needed to confirm our findings.

Electrokinetic coupling in unsaturated porous media.

PubMed

Revil, A; Linde, N; Cerepi, A; Jougnot, D; Matthäi, S; Finsterle, S

2007-09-01

We consider a charged porous material that is saturated by two fluid phases that are immiscible and continuous on the scale of a representative elementary volume. The wetting phase for the grains is water and the nonwetting phase is assumed to be an electrically insulating viscous fluid. We use a volume-averaging approach to derive the linear constitutive equations for the electrical current density as well as the seepage velocities of the wetting and nonwetting phases on the scale of a representative elementary volume. These macroscopic constitutive equations are obtained by volume-averaging Ampère's law together with the Nernst-Planck equation and the Stokes equations. The material properties entering the macroscopic constitutive equations are explicitly described as functions of the saturation of the water phase, the electrical formation factor, and parameters that describe the capillary pressure function, the relative permeability functions, and the variation of electrical conductivity with saturation. New equations are derived for the streaming potential and electro-osmosis coupling coefficients. A primary drainage and imbibition experiment is simulated numerically to demonstrate that the relative streaming potential coupling coefficient depends not only on the water saturation, but also on the material properties of the sample, as well as the saturation history. We also compare the predicted streaming potential coupling coefficients with experimental data from four dolomite core samples. Measurements on these samples include electrical conductivity, capillary pressure, the streaming potential coupling coefficient at various levels of saturation, and the permeability at saturation of the rock samples. We found very good agreement between these experimental data and the model predictions.

A modified Stillinger-Weber potential for TlBr and its polymorphic extension

DOE PAGES

Zhou, Xiaowang; Foster, Michael E.; Jones, Reese E.; ...

2015-04-30

TlBr is promising for g- and x- radiation detection, but suffers from rapid performance degradation under the operating external electric fields. To enable molecular dynamics (MD) studies of this degradation, we have developed a Stillinger-Weber type of TlBr interatomic potential. During this process, we have also addressed two problems of wider interests. First, the conventional Stillinger-Weber potential format is only applicable for tetrahedral structures (e.g., diamond-cubic, zinc-blende, or wurtzite). Here we have modified the analytical functions of the Stillinger-Weber potential so that it can now be used for other crystal structures. Second, past modifications of interatomic potentials cannot always bemore » applied by a broad community because any new analytical functions of the potential would require corresponding changes in the molecular dynamics codes. Here we have developed a polymorphic potential model that simultaneously incorporates Stillinger-Weber, Tersoff, embedded-atom method, and any variations (i.e., modified functions) of these potentials. As a result, we have implemented this polymorphic model in MD code LAMMPS, and demonstrated that our TlBr potential enables stable MD simulations under external electric fields.« less

The value of residential photovoltaic systems: A comprehensive assessment

NASA Technical Reports Server (NTRS)

Borden, C. S.

1983-01-01

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

The value of residential photovoltaic systems: A comprehensive assessment

NASA Astrophysics Data System (ADS)

Borden, C. S.

1983-09-01

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

An electron of helium atom under a high-intensity laser field

NASA Astrophysics Data System (ADS)

Falaye, Babatunde James; Sun, Guo-Hua; Adepoju, Adenike Grace; Liman, Muhammed S.; Oyewumi, K. J.; Dong, Shi-Hai

2017-02-01

We scrutinize the behavior of eigenvalues of an electron in a helium (He) atom as it interacts with electric field directed along the z-axis and is exposed to linearly polarized intense laser field radiation. To achieve this, we freeze one electron of the He atom at its ionic ground state and the motion of the second electron in the ion core is treated via a more general case of screened Coulomb potential model. Using the Kramers-Henneberger (KH) unitary transformation, which is the semiclassical counterpart of the Block-Nordsieck transformation in the quantized field formalism, the squared vector potential that appears in the equation of motion is eliminated and the resultant equation is expressed in the KH frame. Within this frame, the resulting potential and the corresponding wave function are expanded in Fourier series and using Ehlotzky’s approximation, we obtain a laser-dressed potential to simulate intense laser field. By fitting the more general case of screened Coulomb potential model into the laser-dressed potential, and then expanding it in Taylor series up to O≤ft({{r}4},α 09\\right) , we obtain the solution (eigenvalues and wave function) of an electron in a He atom under the influence of external electric field and high-intensity laser field, within the framework of perturbation theory formalism. We found that the variation in frequency of laser radiation has no effect on the eigenvalues of a He electron for a particular electric field intensity directed along z-axis. Also, for a very strong external electric field and an infinitesimal screening parameter, the system is strongly bound. This work has potential application in the areas of atomic and molecular processes in external fields including interactions with strong fields and short pulses.

Microscopic studies of the fate of charges in organic semiconductors: Scanning Kelvin probe measurements of charge trapping, transport, and electric fields in p- and n-type devices

NASA Astrophysics Data System (ADS)

Smieska, Louisa Marion

Organic semiconductors could have wide-ranging applications in lightweight, efficient electronic circuits. However, several fundamental questions regarding organic electronic device behavior have not yet been fully addressed, including the nature of chemical charge traps, and robust models for injection and transport. Many studies focus on engineering devices through bulk transport measurements, but it is not always possible to infer the microscopic behavior leading to the observed measurements. In this thesis, we present scanning-probe microscope studies of organic semiconductor devices in an effort to connect local properties with local device behavior. First, we study the chemistry of charge trapping in pentacene transistors. Working devices are doped with known pentacene impurities and the extent of charge trap formation is mapped across the transistor channel. Trap-clearing spectroscopy is employed to measure an excitation of the pentacene charge trap species, enabling identification of the degradationrelated chemical trap in pentacene. Second, we examine transport and trapping in peryelene diimide (PDI) transistors. Local mobilities are extracted from surface potential profiles across a transistor channel, and charge injection kinetics are found to be highly sensitive to electrode cleanliness. Trap-clearing spectra generally resemble PDI absorption spectra, but one derivative yields evidence indicating variation in trap-clearing mechanisms for different surface chemistries. Trap formation rates are measured and found to be independent of surface chemistry, contradicting a proposed silanol trapping mechanism. Finally, we develop a variation of scanning Kelvin probe microscopy that enables measurement of electric fields through a position modulation. This method avoids taking a numeric derivative of potential, which can introduce high-frequency noise into the electric field signal. Preliminary data is presented, and the theoretical basis for electric field noise in both methods is examined.

Binding energy of donor impurity states and optical absorption in the Tietz-Hua quantum well under an applied electric field

NASA Astrophysics Data System (ADS)

Al, E. B.; Kasapoglu, E.; Sakiroglu, S.; Duque, C. A.; Sökmen, I.

2018-04-01

For a quantum well which has the Tietz-Hua potential, the ground and some excited donor impurity binding energies and the total absorption coefficients, including linear and third order nonlinear terms for the transitions between the related impurity states with respect to the structure parameters and the impurity position as well as the electric field strength are investigated. The binding energies were obtained using the effective-mass approximation within a variational scheme and the optical transitions between any two impurity states were calculated by using the density matrix formalism and the perturbation expansion method. Our results show that the effects of the electric field and the structure parameters on the optical transitions are more pronounced. So we can adjust the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric field as well as the structure parameters.

Surface electrical properties of stainless steel fibres: An AFM-based study

NASA Astrophysics Data System (ADS)

Yin, Jun; D'Haese, Cécile; Nysten, Bernard

2015-03-01

Atomic force microscopy (AFM) electrical modes were used to study the surface electrical properties of stainless steel fibres. The surface electrical conductivity was studied by current sensing AFM and I-V spectroscopy. Kelvin probe force microscopy was used to measure the surface contact potential. The oxide film, known as passivation layer, covering the fibre surface gives rise to the observation of an apparently semiconducting behaviour. The passivation layer generally exhibits a p-type semiconducting behaviour, which is attributed to the predominant formation of chromium oxide on the surface of the stainless steel fibres. At the nanoscale, different behaviours are observed from points to points, which may be attributed to local variations of the chemical composition and/or thickness of the passivation layer. I-V curves are well fitted with an electron tunnelling model, indicating that electron tunnelling may be the predominant mechanism for electron transport.

Oahu wind power survey, first report

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

Ramage, C.S.; Daniels, P.A.; Schroeder, T.A.

1977-05-01

A wind power survey has been conducted on Oahu since summer 1975. At seventeen potentially windy sites, calibrated anemometers and wind vanes were installed and recordings made on computer-processable magnetic tape cassettes. From monthly mean wind speeds--normalized by comparing with Honolulu Airport means winds--it was concluded that about 23 mi/hr represented the highest average annual wind speed likely to be attained on Oahu and that the Koko Head and Kahuku areas gave the most promise for wind energy generation. Diurnal variation of the wind in these areas roughly parallels diurnal variation of electric power demand.

Detection of temperature distribution via recovering electrical conductivity in MREIT.

PubMed

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

2013-04-21

In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 °C.

Imaging of the interaction of low frequency electric fields with biological tissues by optical coherence tomography

NASA Astrophysics Data System (ADS)

Peña, Adrian F.; Devine, Jack; Doronin, Alexander; Meglinski, Igor

2014-03-01

We report the use of conventional Optical Coherence Tomography (OCT) for visualization of propagation of low frequency electric field in soft biological tissues ex vivo. To increase the overall quality of the experimental images an adaptive Wiener filtering technique has been employed. Fourier domain correlation has been subsequently applied to enhance spatial resolution of images of biological tissues influenced by low frequency electric field. Image processing has been performed on Graphics Processing Units (GPUs) utilizing Compute Unified Device Architecture (CUDA) framework in the frequencydomain. The results show that variation in voltage and frequency of the applied electric field relates exponentially to the magnitude of its influence on biological tissue. The magnitude of influence is about twice more for fresh tissue samples in comparison to non-fresh ones. The obtained results suggest that OCT can be used for observation and quantitative evaluation of the electro-kinetic changes in biological tissues under different physiological conditions, functional electrical stimulation, and potentially can be used non-invasively for food quality control.

Interface Magnetoelectric Coupling in Co/Pb(Zr,Ti)O3.

PubMed

Vlašín, Ondřej; Jarrier, Romain; Arras, Rémi; Calmels, Lionel; Warot-Fonrose, Bénédicte; Marcelot, Cécile; Jamet, Matthieu; Ohresser, Philippe; Scheurer, Fabrice; Hertel, Riccardo; Herranz, Gervasi; Cherifi-Hertel, Salia

2016-03-23

Magnetoelectric coupling at multiferroic interfaces is a promising route toward the nonvolatile electric-field control of magnetization. Here, we use optical measurements to study the static and dynamic variations of the interface magnetization induced by an electric field in Co/PbZr0.2Ti0.8O3 (Co/PZT) bilayers at room temperature. The measurements allow us to identify different coupling mechanisms. We further investigate the local electronic and magnetic structure of the interface by means of transmission electron microscopy, soft X-ray magnetic circular dichroism, and density functional theory to corroborate the coupling mechanism. The measurements demonstrate a mixed linear and quadratic optical response to the electric field, which results from a magneto-electro-optical effect. We propose a decomposition method of the optical signal to discriminate between different components involved in the electric field-induced polarization rotation of the reflected light. This allows us to extract a signal that we can ascribe to interface magnetoelectric coupling. The associated surface magnetization exhibits a clear hysteretic variation of odd symmetry with respect to the electric field and nonzero remanence. The interface coupling is remarkably stable over a wide frequency range (1-50 kHz), and the application of a bias magnetic field is not necessary for the coupling to occur. These results show the potential of exploiting interface coupling with the prospect of optimizing the performance of magnetoelectric memory devices in terms of stability, as well as fast and dissipationless operation.

Feasibility of Autonomous Monitoring of CO2 Leakage in Aquifers: Results From Controlled Laboratory Experiments

NASA Astrophysics Data System (ADS)

Versteeg, R.; Leger, E.; Dafflon, B.

2016-12-01

Geologic sequestration of CO2 is one of the primary proposed approaches for reducing total atmospheric CO2 concentrations. MVAA (Monitoring, Verification, Accounting and Assessment) of CO2 sequestration is an essential part of the geologic CO2 sequestration cycle. MVAA activities need to meet multiple operational, regulatory and environmental objectives, including ensuring the protection of underground sources of drinking water. Anticipated negative consequences of CO2 leakage into groundwater, besides possible brine contamination and release of gaseous CO2, include a significant increase of dissolved CO2 into shallow groundwater systems, which will decrease groundwater pH and can potentially mobilize naturally occurring trace metals and ions that are commonly absorbed to or contained in sediments. Autonomous electrical geophysical monitoring in aquifers has the potential of allowing for rapid and automated detection of CO2 leakage. However, while the feasibility of such monitoring has been demonstrated by a number of different field experiments, automated interpretation of complex electrical resistivity data requires the development of quantitative relationships between complex electrical resistivity signatures and dissolved CO2 in the aquifer resulting from leakage Under a DOE SBIR funded effort we performed multiple tank scale experiments in which we investigated complex electrical resistivity signatures associated with dissolved CO2 plumes in saturated sediments. We also investigated the feasibility of distinguishing CO2 leakage signatures from signatures associated with other processes such as salt water movement, temperature variations and other variations in chemical or physical conditions. In addition to these experiments we also numerically modeled the tank experiments. These experiments showed that (a) we can distinguish CO2 leakage signatures from other signatures, (b) CO2 leakage signatures have a consistent characteristic, (c) laboratory experiments are in agreement with field results, and (d) we can numerically simulate the main characteristics of CO2 leakage and associated electrical geophysical signatures.

Integration of SPS with utility system networks

NASA Technical Reports Server (NTRS)

Kaupang, B. M.

1980-01-01

The integration of Satellite Power System (SPS) power in electric utility power systems is discussed. Specifically, the nature of the power output variations from the spacecraft to the rectenna, the operational characteristics of the rectenna power, and the impacts on the electric utility system from utilizing SPS power to serve part of the system load are treated. It is concluded that if RF beam control is an acceptable method for power control, and that the site distribution of SPS rectennas do not cause a very high local penetration (40 to 50%), SPS may be integrated into electric utility system with a few negative impacts. Increased regulating duty on the conventional generation, and a potential impact on system reliability for SPS penetration in excess of about 25% appear to be two areas of concern.

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.

Hydrodynamic dispersion in a combined magnetohydrodynamic- electroosmotic-driven flow through a microchannel with slowly varying wall zeta potentials

NASA Astrophysics Data System (ADS)

Vargas, C.; Arcos, J.; Bautista, O.; Méndez, F.

2017-09-01

The effective dispersion coefficient of a neutral solute in the combined electroosmotic (EO) and magnetohydrodynamic (MHD)-driven flow of a Newtonian fluid through a parallel flat plate microchannel is studied. The walls of the microchannel are assumed to have modulated and low zeta potentials that vary slowly in the axial direction in a sinusoidal manner. The flow field required to obtain the dispersion coefficient is solved using the lubrication approximation theory. The solution of the electrical potential is based on the Debye-Hückel approximation for a symmetric (Z :Z ) electrolyte solution. The EO and MHD effects, together with the variations in the zeta potentials of the walls, are observed to notably modify the axial distribution of the effective dispersion coefficient. The problem is formulated for two cases of the zeta potential function. Note that the dispersion coefficient primarily depends on the Hartmann number, on the ratio of the half height of the microchannel to the Debye length, and on the assumed variation in the zeta potentials of the walls.

Quantum confined Stark effects of single dopant in polarized hemispherical quantum dot: Two-dimensional finite difference approach and Ritz-Hassé variation method

NASA Astrophysics Data System (ADS)

El Harouny, El Hassan; Nakra Mohajer, Soukaina; Ibral, Asmaa; El Khamkhami, Jamal; Assaid, El Mahdi

2018-05-01

Eigenvalues equation of hydrogen-like off-center single donor impurity confined in polarized homogeneous hemispherical quantum dot deposited on a wetting layer, capped by insulated matrix and submitted to external uniform electric field is solved in the framework of the effective mass approximation. An infinitely deep potential is used to describe effects of quantum confinement due to conduction band offsets at surfaces where quantum dot and surrounding materials meet. Single donor ground state total and binding energies in presence of electric field are determined via two-dimensional finite difference approach and Ritz-Hassé variation principle. For the latter method, attractive coulomb correlation between electron and ionized single donor is taken into account in the expression of trial wave function. It appears that off-center single dopant binding energy, spatial extension and radial probability density are strongly dependent on hemisphere radius and single dopant position inside quantum dot. Influence of a uniform electric field is also investigated. It shows that Stark effect appears even for very small size dots and that single dopant energy shift is more significant when the single donor is near hemispherical surface.

The Progress of Physics

NASA Astrophysics Data System (ADS)

Schuster, Arthur

2015-10-01

Introduction; 1. Scope of lectures. State of physics in 1875. Science of energy. Theory of gases. Elastic solid theory of light. Maxwell's theory of electricity. Training of students. Maxwell's view. Accurate measurement and discovery of Argon. German methods. Kirchhoff's laboratory. Wilhelm Weber's laboratory. The two laboratories of Berlin. Laboratory instruction at Manchester. Position of physics in mathematical tripos at Cambridge. Todhunter's views. The Cavendish laboratory. Spectrum analysis. The radiometer. Theory of vortex atom; 2. Action at a distance. Elastic solid of theory of light. Maxwell's theory of electrical action. Electro-magnetic theory. Verification of electromagnetic theory by Hertz. Electro-magnetic waves. Wireless telegraphy. First suggestion of molecular structure of electricity. Early experiments in the electric discharge through gases. Kathode rays. Works of Goldstein and Crookes. Hittorf's investigations. Own work on the discharge through gases. Ionization of gases. Magnetic deflexion of kathode rays. J. J. Thomson's experiments. Measurement of atomic charge; 3. Roentgen's discovery. Theories of Roentgen rays. Ionizing power of Roentgen rays. Conduction of electricity through ionized gases. Discovery of radio-activity. Discovery of radium. Magnetic deflexion of rays emitted by radio-active bodies. Discovery of emanations. Theory of radio-active change. Decay of the atom. Connexion between helium and the a ray. Helium produced by radium. Strutt's researches on helium accumulated in rocks. Electric inertia. Constitution of atom. J. J. Thomson's theory of Roentgen radiation. The Michelson-Morley experiment. Principle of relativity. The Zeeman effect. Other consequences of electron theory. Contrast between old and modern school of physics; 4. Observational sciences. Judgment affected by scale. Terrestrial magnetism. Existence of potential. Separation of internal and external causes. Diurnal variation. Magnetic storms. Their causes. Solar influence. Theories of secular variation. Atmospheric electricity. Negative charge of Earth. Ionization of air. Origin of atmospheric electricity. Electric charge of rain. Ebert's theory. Cause of thunderstorms. The age of the Earth. Rigidity of Earth. Displacement of axis. Gravitation. Identity of molecules of the same kind; Index.

Equilibrium shapes of a heterogeneous bubble in an electric field: a variational formulation and numerical verifications

NASA Astrophysics Data System (ADS)

Wang, Hanxiong; Liu, Liping; Liu, Dong

2017-03-01

The equilibrium shape of a bubble/droplet in an electric field is important for electrowetting over dielectrics (EWOD), electrohydrodynamic (EHD) enhancement for heat transfer and electro-deformation of a single biological cell among others. In this work, we develop a general variational formulation in account of electro-mechanical couplings. In the context of EHD, we identify the free energy functional and the associated energy minimization problem that determines the equilibrium shape of a bubble in an electric field. Based on this variational formulation, we implement a fixed mesh level-set gradient method for computing the equilibrium shapes. This numerical scheme is efficient and validated by comparing with analytical solutions at the absence of electric field and experimental results at the presence of electric field. We also present simulation results for zero gravity which will be useful for space applications. The variational formulation and numerical scheme are anticipated to have broad applications in areas of EWOD, EHD and electro-deformation in biomechanics.

Buffer thermal energy storage for a solar thermal powered 1-MW sub e electrical plant

NASA Astrophysics Data System (ADS)

Polzien, R. E.

The application of a latent heat thermal energy buffer storage (TEBS) subsystem to the small community solar thermal power experiment (SCSE) is discussed. The SCSE is a 1-MW sub e solar thermal electric plant consisting of multiple paraboloidal concentrators with an organic Rankine cycle power conversion unit mounted at the focus of each concentrator. Objective of the TEBS is to minimize plant shutdowns during intermittent cloud coverage thereby improving life expectancy of major subsystems. An SCSE plant performance model is used with time varying insolation to show that 70 to 80 percent of the potential engine shutdowns may be averted with the TEBS system. Parametric variation of engine life dependency on start/stop cycles shows the potential for a 4 percent reduction in levelized bus bar energy cost using TEBS.

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.

Diversification of intrinsic motoneuron electrical properties during normal development and botulinum toxin-induced muscle paralysis in early postnatal mice.

PubMed

Nakanishi, S T; Whelan, P J

2010-05-01

During early postnatal development, between birth and postnatal days 8-11, mice start to achieve weight-bearing locomotion. In association with the progression of weight-bearing locomotion there are presumed developmental changes in the intrinsic electrical properties of spinal -motoneurons. However, these developmental changes in the properties of -motoneuron properties have not been systematically explored in mice. Here, data are presented documenting the developmental changes of selected intrinsic motoneuron electrical properties, including statistically significant changes in action potential half-width, intrinsic excitability and diversity (quantified as coefficient of variation) of rheobase current, afterhyperpolarization half-decay time, and input resistance. In various adult mammalian preparations, the maintenance of intrinsic motoneuron electrical properties is dependent on activity and/or transmission-sensitive motoneuron-muscle interactions. In this study, we show that botulinum toxin-induced muscle paralysis led to statistically significant changes in the normal development of intrinsic motoneuron electrical properties in the postnatal mouse. This suggests that muscle activity during early neonatal life contributes to the development of normal motoneuron electrical properties.

Accelerating acquisition strategies for low-frequency conductivity imaging using MREIT

NASA Astrophysics Data System (ADS)

Song, Yizhuang; Seo, Jin Keun; Chauhan, Munish; Indahlastari, Aprinda; Ashok Kumar, Neeta; Sadleir, Rosalind

2018-02-01

We sought to improve efficiency of magnetic resonance electrical impedance tomography data acquisition so that fast conductivity changes or electric field variations could be monitored. Undersampling of k-space was used to decrease acquisition times in spin-echo-based sequences by a factor of two. Full MREIT data were reconstructed using continuity assumptions and preliminary scans gathered without current. We found that phase data were reconstructed faithfully from undersampled data. Conductivity reconstructions of phantom data were also possible. Therefore, undersampled k-space methods can potentially be used to accelerate MREIT acquisition. This method could be an advantage in imaging real-time conductivity changes with MREIT.

Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

PubMed

Gokhale, Tanmay A; Kim, Jong M; Kirkton, Robert D; Bursac, Nenad; Henriquez, Craig S

2017-01-01

To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell.

Electric Field Sensor for Lightning Early Warning System

NASA Astrophysics Data System (ADS)

Premlet, B.; Mohammed, R.; Sabu, S.; Joby, N. E.

2017-12-01

Electric field mills are used popularly for atmospheric electric field measurements. Atmospheric Electric Field variation is the primary signature for Lightning Early Warning systems. There is a characteristic change in the atmospheric electric field before lightning during a thundercloud formation.A voltage controlled variable capacitance is being proposed as a method for non-contacting measurement of electric fields. A varactor based mini electric field measurement system is developed, to detect any change in the atmospheric electric field and to issue lightning early warning system. Since this is a low-cost device, this can be used for developing countries which are facing adversities. A network of these devices can help in forming a spatial map of electric field variations over a region, and this can be used for more improved atmospheric electricity studies in developing countries.

A statistical study of the inner edge of the electron plasma sheet and the net convection potential as a function of geomagnetic activity

NASA Astrophysics Data System (ADS)

Jiang, F.; Kivelson, M. G.; Walker, R. J.; Khurana, K. K.; Angelopoulos, V.; Hsu, T.

2011-06-01

A widely accepted explanation of the location of the inner edge of the electron plasma sheet and its dependence on electron energy is based on drift motions of individual particles. The boundary is identified as the separatrix between drift trajectories linking the tail to the dayside magnetopause (open paths) and trajectories closed around the Earth. A statistical study of the inner edge of the electron plasma sheet using THEMIS Electrostatic Analyzer plasma data from November 2007 to April 2009 enabled us to examine this model. Using a dipole magnetic field and a Volland-Stern electric field with shielding, we find that a steady state drift boundary model represents the average location of the electron plasma sheet boundary and reflects its variation with the solar wind electric field in the local time region between 21:00 and 06:00, except at high activity levels. However, the model does not reproduce the observed energy dispersion of the boundaries. We have also used the location of the inner edge of the electron plasma sheet to parameterize the potential drop of the tail convection electric field as a function of solar wind electric field (Esw) and geomagnetic activity. The range of Esw examined is small because the data were acquired near solar minimum. For the range of values tested (meaningful statistics only for Esw < 2 mV/m), reasonably good agreement is found between the potential drop of the tail convection electric field inferred from the location of the inner edge and the polar cap potential drop calculated from the model of Boyle et al. (1997).

Managing Wind-based Electricity Generation and Storage

NASA Astrophysics Data System (ADS)

Zhou, Yangfang

Among the many issues that profoundly affect the world economy every day, energy is one of the most prominent. Countries such as the U.S. strive to reduce reliance on the import of fossil fuels, and to meet increasing electricity demand without harming the environment. Two of the most promising solutions for the energy issue are to rely on renewable energy, and to develop efficient electricity storage. Renewable energy---such as wind energy and solar energy---is free, abundant, and most importantly, does not exacerbate the global warming problem. However, most renewable energy is inherently intermittent and variable, and thus can benefit greatly from coupling with electricity storage, such as grid-level industrial batteries. Grid storage can also help match the supply and demand of an entire electricity market. In addition, electricity storage such as car batteries can help reduce dependence on oil, as it can enable the development of Plug-in Hybrid Electric Vehicles, and Battery Electric Vehicles. This thesis focuses on understanding how to manage renewable energy and electricity storage properly together, and electricity storage alone. In Chapter 2, I study how to manage renewable energy, specifically wind energy. Managing wind energy is conceptually straightforward: generate and sell as much electricity as possible when prices are positive, and do nothing otherwise. However, this leads to curtailment when wind energy exceeds the transmission capacity, and possible revenue dilution when current prices are low but are expected to increase in the future. Electricity storage is being considered as a means to alleviate these problems, and also enables buying electricity from the market for later resale. But the presence of storage complicates the management of electricity generation from wind, and the value of storage for a wind-based generator is not entirely understood. I demonstrate that for such a combined generation and storage system the optimal policy does not have any apparent structure, and that using overly simple policies can be considerably suboptimal. I thus develop and analyze a triple-threshold policy that I show to be near-optimal. Using a financial engineering price model and calibrating it to data from the New York Independent System Operator, I show that storage can substantially increase the monetary value of a wind farm: If transmission capacity is tight, the majority of this value arises from reducing curtailment and time-shifting generation; if transmission capacity is abundant this value stems primarily from time-shifting generation and arbitrage. In addition, I find that while more storage capacity always increases the average energy sold to the market, it may actually decrease the average wind energy sold when transmission capacity is abundant. In Chapter 3, I examine how electricity storage can be used to help match electricity supply and demand. Conventional wisdom suggests that when supply exceeds demand, any electricity surpluses should be stored for future resale. However, because electricity prices can be negative, another potential strategy of dealing with surpluses is to destroy them. Using real data, I find that for a merchant who trades electricity in a market, the strategy of destroying surpluses is potentially more valuable than the conventional strategy of storing surpluses. In Chapter 4, I study how the operation and valuation of electricity storage facilities can be affected by their physical characteristics and operating dynamics. Examples are the degradation of energy capacity over time and the variation of round-trip efficiency at different charging/discharging rates. These dynamics are often ignored in the literature, thus it has not been established whether it is important to model these characteristics. Specifically, it remains an open question whether modeling these dynamics might materially change the prescribed operating policy and the resulting valuation of a storage facility. I answer this question using a representative setting, in which a battery is utilized to trade electricity in an energy arbitrage market. Using engineering models, I capture energy capacity degradation and efficiency variation explicitly, evaluating three types of batteries: lead acid, lithium-ion, and Aqueous Hybrid Ion---a new commercial battery technology. I calibrate the model for each battery to manufacturers' data and value these batteries using the same calibrated financial engineering price model as in Chapter 2. My analysis shows that: (a) it is quite suboptimal to operate each battery as if it did not degrade, particularly for lead acid and lithium-ion; (b) reducing degradation and efficiency variation have a complimentary effect: the value of reducing both together is greater than the sum of the value of reducing one individually; and (c) decreasing degradation may have a bigger effect than decreasing efficiency variation.

Effect of electrical stimulation and cooking temperature on the within-sample variation of cooking loss and shear force of lamb.

PubMed

Lewis, P K; Babiker, S A

1983-01-01

Electrical stimulation decreased the shear force and increased the cooking loss in seven paired lamb Longissimus dorsi (LD) muscles. This treatment did not have any effect on the within-sample variation. Cooking in 55°, 65° and 75°C water baths for 90 min caused a linear increase in the cooking loss and shear force. There was no stimulation-cooking temperature interaction observed. Cooking temperature also had no effect on the within-sample variation. A possible explanation as to why electrical stimulation did not affect the within-sample variation is given. Copyright © 1983. Published by Elsevier Ltd.

Application of Artificial Neuro-Fuzzy Logic Inference System for Predicting the Microbiological Pollution in Fresh Water

NASA Astrophysics Data System (ADS)

Bouharati, S.; Benmahammed, K.; Harzallah, D.; El-Assaf, Y. M.

The classical methods for detecting the micro biological pollution in water are based on the detection of the coliform bacteria which indicators of contamination. But to check each water supply for these contaminants would be a time-consuming job and a qualify operators. In this study, we propose a novel intelligent system which provides a detection of microbiological pollution in fresh water. The proposed system is a hierarchical integration of an Artificial Neuro-Fuzzy Inference System (ANFIS). This method is based on the variations of the physical and chemical parameters occurred during bacteria growth. The instantaneous result obtained by the measurements of the variations of the physical and chemical parameters occurred during bacteria growth-temperature, pH, electrical potential and electrical conductivity of many varieties of water (surface water, well water, drinking water and used water) on the number Escherichia coli in water. The instantaneous result obtained by measurements of the inputs parameters of water from sensors.

Microscopic resolution broadband dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Mukherjee, S.; Watson, P.; Prance, R. J.

2011-08-01

Results are presented for a non-contact measurement system capable of micron level spatial resolution. It utilises the novel electric potential sensor (EPS) technology, invented at Sussex, to image the electric field above a simple composite dielectric material. EP sensors may be regarded as analogous to a magnetometer and require no adjustments or offsets during either setup or use. The sample consists of a standard glass/epoxy FR4 circuit board, with linear defects machined into the surface by a PCB milling machine. The sample is excited with an a.c. signal over a range of frequencies from 10 kHz to 10 MHz, from the reverse side, by placing it on a conducting sheet connected to the source. The single sensor is raster scanned over the surface at a constant working distance, consistent with the spatial resolution, in order to build up an image of the electric field, with respect to the reference potential. The results demonstrate that both the surface defects and the internal dielectric variations within the composite may be imaged in this way, with good contrast being observed between the glass mat and the epoxy resin.

Modulation of band gap by an applied electric field in BN-based heterostructures

NASA Astrophysics Data System (ADS)

Luo, M.; Xu, Y. E.; Zhang, Q. X.

2018-05-01

First-principles density functional theory (DFT) calculations are performed on the structural and electronic properties of the SiC/BN van der Waals (vdW) heterostructures under an external electric field (E-field). Our results reveal that the SiC/BN vdW heterostructure has a direct band gap of 2.41 eV in the raw. The results also imply that electrons are likely to transfer from BN to SiC monolayer due to the deeper potential of BN monolayer. It is also observed that, by applying an E-field, ranging from -0.50 to +0.65 V/Å, the band gap decreases from 2.41 eV to zero, which presents a parabola-like relationship around 0.0 V/Å. Through partial density of states (PDOS) plots, it is revealed that, p orbital of Si, C, B, and N atoms are responsible for the significant variations of band gap. These obtained results predict that, the electric field tunable band gap of the SiC/BN vdW heterostructures carries potential applications for nanoelectronics and spintronic device applications.

Constructiveness and destructiveness of temperature in asymmetric quantum pseudo dot qubit system

NASA Astrophysics Data System (ADS)

Chen, Ying-Jie; Song, Hai-Tao; Xiao, Jing-Lin

2018-06-01

By using the variational method of the Pekar type, we theoretically study the temperature effects on the asymmetric quantum pseudo dot qubit with a pseudoharmonic potential under an electromagnetic field. The numerical results are analyzed and discussed in detail and show that the relationships of the ground and first excited state energies, the electron oscillation period and the electron probability density in the superposition state of the ground state and the first-excited state with the temperature, the chemical potential, the pseudoharmonic potential, the electric field strength, the cyclotron frequency, the electron phonon coupling constant, the transverse and longitudinal effective confinement length, respectively.

Variation of the electric properties along the diaphysis of bovine femoral bone.

PubMed

De Mercato, G; García Sánchez, F J

1991-07-01

A preliminary study is presented of the variability of the electric properties, in the axial, tangential and radial directions, as a function of position in the diaphysis of a femoral bovine bone. The measurements were carried out at three frequencies: 100 Hz, 10 kHz and 1 MHz. It is shown that both the conductivity and the permittivity exhibit significant variations along the diaphysis, and increase in magnitude towards the epiphyses. From this study, the variation of the electric properties cannot be clearly and directly ascribed to the longitudinal variability of the total volumetric fluid content of the bone. The results reflect the orthotropic nature of the electric properties, at any given location, and indicate a position-dependent tendency towards axis symmetry.

Uncooled Split-off Quantum Infrared Sensors for 3-5 Micron Imaging Applications

DTIC Science & Technology

2012-12-20

nonuniformity and needs to be optimized. Figure 5 (a) shows plots of Figure 3: (a) The responsivity and (b) detectivity variation with emitter...devices with larger mesa sizes than that with smaller sizes. The current nonuniformity originally results from the electric potential gradient in the...respectively. x = 0 represents the device center. The nonuniformity becomes remarkable when the temperature is increased. 5 2.3 Design of resonant

Significant manipulation of output performance of a bridge-structured spin valve magnetoresistance sensor via an electric field

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

Zhang, Yue; Yan, Baiqian; Ou-Yang, Jun

2016-01-28

Through principles of spin-valve giant magnetoresistance (SV-GMR) effect and its application in magnetic sensors, we have investigated electric-field control of the output performance of a bridge-structured Co/Cu/NiFe/IrMn SV-GMR sensor on a PZN-PT piezoelectric substrate using the micro-magnetic simulation. We centered on the influence of the variation of uniaxial magnetic anisotropy constant (K) of Co on the output of the bridge, and K was manipulated via the stress of Co, which is generated from the strain of a piezoelectric substrate under an electric field. The results indicate that when K varies between 2 × 10{sup 4 }J/m{sup 3} and 10 × 10{sup 4 }J/m{sup 3}, the outputmore » performance can be significantly manipulated: The linear range alters from between −330 Oe and 330 Oe to between −650 Oe and 650 Oe, and the sensitivity is tuned by almost 7 times, making it possible to measure magnetic fields with very different ranges. According to the converse piezoelectric effect, we have found that this variation of K can be realized by applying an electric field with the magnitude of about 2–20 kV/cm on a PZN-PT piezoelectric substrate, which is realistic in application. This result means that electric-control of SV-GMR effect has potential application in developing SV-GMR sensors with improved performance.« less

Pilot evaluation of electricity-reliability and power-quality monitoring in California's Silicon Valley with the I-Grid(R) system

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

Eto, Joseph; Divan, Deepak; Brumsickle, William

2004-02-01

Power-quality events are of increasing concern for the economy because today's equipment, particularly computers and automated manufacturing devices, is susceptible to these imperceptible voltage changes. A small variation in voltage can cause this equipment to shut down for long periods, resulting in significant business losses. Tiny variations in power quality are difficult to detect except with expensive monitoring equipment used by trained technicians, so many electricity customers are unaware of the role of power-quality events in equipment malfunctioning. This report describes the findings from a pilot study coordinated through the Silicon Valley Manufacturers Group in California to explore the capabilitiesmore » of I-Grid(R), a new power-quality monitoring system. This system is designed to improve the accessibility of power-quality in formation and to increase understanding of the growing importance of electricity reliability and power quality to the economy. The study used data collected by I-Grid sensors at seven Silicon Valley firms to investigate the impacts of power quality on individual study participants as well as to explore the capabilities of the I-Grid system to detect events on the larger electricity grid by means of correlation of data from the sensors at the different sites. In addition, study participants were interviewed about the value they place on power quality, and their efforts to address electricity-reliability and power-quality problems. Issues were identified that should be taken into consideration in developing a larger, potentially nationwide, network of power-quality sensors.« less

Synthesis, crystal structure and electrical properties of the tetrahedral quaternary chalcogenides CuM{sub 2}InTe{sub 4} (M=Zn, Cd)

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

Nolas, George S., E-mail: gnolas@usf.edu; Hassan, M. Shafiq; Dong, Yongkwan

Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn{sub 2}InSe{sub 4}. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficientmore » and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications. - Graphical abstract: The structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. The unique crystal structure allows for relatively good electrical transports and therefore potential for thermoelectric applications. - Highlights: • The physical properties of CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. • These materials have potential for thermoelectric applications. • Their direct band gaps also suggest potential for photovoltaics applications.« less

Wall charging of a helicon antenna wrapped plasma filled dielectric tube

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

Barada, Kshitish K., E-mail: kbarada@physics.ucla.edu; Chattopadhyay, P. K., E-mail: pkchatto@ipr.res.in; Ghosh, J.

2015-01-15

Dielectric wall charging of a cylindrical glass wall surrounded by a helicon antenna of 18 cm length is measured in a linear helicon plasma device with a diverging magnetic field. The ions because of their lesser mobility do not respond to the high frequency electric field and the electrons charge the wall to a negative DC potential also known as the DC self-bias. The wall potential in this device is characterized for different neutral pressure, magnetic field, and radio frequency (RF) power. Axial variation of wall potential shows higher self-bias potentials near the antenna rings. Ion magnetization in the source chambermore » increases both wall charging and plasma potential of the source due to confinement.« less

Global Electric Circuit Diurnal Variation Derived from Storm Overflight and Satellite Optical Lightning Datasets

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Blakeslee, R. J.; Bateman, M. J.; Bailey, J. C.

2011-01-01

We have combined analyses of over 1000 high altitude aircraft observations of electrified clouds with diurnal lightning statistics from the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) to produce an estimate of the diurnal variation in the global electric circuit. Using basic assumptions about the mean storm currents as a function of flash rate and location, and the global electric circuit, our estimate of the current in the global electric circuit matches the Carnegie curve diurnal variation to within 4% for all but two short periods of time. The agreement with the Carnegie curve was obtained without any tuning or adjustment of the satellite or aircraft data. Mean contributions to the global electric circuit from land and ocean thunderstorms are 1.1 kA (land) and 0.7 kA (ocean). Contributions to the global electric circuit from ESCs are 0.22 kA for ocean storms and 0.04 kA for land storms. Using our analysis, the mean total conduction current for the global electric circuit is 2.0 kA.

Global Electric Circuit Implications of Total Current Measurements over Electrified Clouds

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Blakeslee, Richard J.; Bateman, Monte G.

2009-01-01

We determined total conduction (Wilson) currents and flash rates for 850 overflights of electrified clouds spanning regions including the Southeastern United States, the Western Atlantic Ocean, the Gulf of Mexico, Central America and adjacent oceans, Central Brazil, and the South Pacific. The overflights include storms over land and ocean, with and without lightning, and with positive and negative Wilson currents. We combined these individual storm overflight statistics with global diurnal lightning variation data from the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) to estimate the thunderstorm and electrified shower cloud contributions to the diurnal variation in the global electric circuit. The contributions to the global electric circuit from lightning producing clouds are estimated by taking the mean current per flash derived from the overflight data for land and ocean overflights and combining it with the global lightning rates (for land and ocean) and their diurnal variation derived from the LIS/OTD data. We estimate the contribution of non-lightning producing electrified clouds by assuming several different diurnal variations and total non-electrified storm counts to produce estimates of the total storm currents (lightning and non-lightning producing storms). The storm counts and diurnal variations are constrained so that the resultant total current diurnal variation equals the diurnal variation in the fair weather electric field (+/-15%). These assumptions, combined with the airborne and satellite data, suggest that the total mean current in the global electric circuit ranges from 2.0 to 2.7 kA, which is greater than estimates made by others using other methods.

Electric Field Feature of Moving Magnetic Field

NASA Astrophysics Data System (ADS)

Chen, You Jun

2001-05-01

A new fundamental relationship of electric field with magnetic field has been inferred from the fundamental experimental laws and theories of classical electromagnetics. It can be described as moving magnetic field has or gives electric feature. When a field with magnetic induction of B moves in the velocity of V, it will show electric field character, the electric field intensity E is E = B x V and the direction of E is in the direction of the vector B x V. It is improper to use the time-varying electromagnetics theories as the fundamental theory of the electromagnetics and group the electromagnetic field into static kind and time-varying kind for the static is relative to motional not only time-varying. The relationship of time variation of magnetic field induction or magnetic flux with electric field caused by magnetic field is fellowship not causality. Thus time-varying magnetic field can cause electric field is not a nature principle. Sometime the time variation of magnetic flux is equal to the negative electromotive force or the time variation of magnetic field induction is equal to the negative curl of electric field caused by magnetic field motion, but not always. And not all motion of magnetic field can cause time variation of magnetic field. Therefore Faraday-Lenz`s law can only be used as mathematics tool to calculate the quantity relation of the electricity with the magnetism in some case like the magnetic field moving in uniform medium. Faraday-Lenz`s law is unsuitable to be used in moving uniform magnetic field or there is magnetic shield. Key word: Motional magnetic field, Magnetic induction, Electric field intensity, Velocity, Faraday-Lenz’s law

Nanoscale lubrication of ionic surfaces controlled via a strong electric field

DOE PAGES

Strelcov, Evgheni; Bocharova, Vera; Sumpter, Bobby G.; ...

2015-01-27

Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip andmore » salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. Lastly, the demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.« less

Studies on surface morphology and electrical conductivity of PEDOT:PSS thin films in presence of gold nanoparticles

NASA Astrophysics Data System (ADS)

Bhowal, Ashim Chandra; Kundu, Sarathi

2018-04-01

PEDOT:PSS is a water soluble conducting polymer consists of positively charged PEDOT and negatively charged PSS. However, this polymer suffers low conductivity problem which restrict its use. In this paper, electrical conductivity of PEDOT:PSS thin films is improved by using charged gold nanoparticles. The nanoparticles used are synthesized using lysozyme protein. The nanoparticles coated with lysozyme protein possess positive zeta potential. In the presence of gold nanoparticles due to electrostatic interaction between positively charged nanoparticles and negatively charged PSS chains, modification takes place in the surface morphology and electrical behaviors of PEDOT:PSS thin films. The changes in the polymer matrix conformations in the presence of nanoparticles are studied by Fourier transformed Infra-red (FTIR) spectroscopy, whereas the surface morphology of prepared thin films before and after interaction with nanoparticles is investigated through atomic force microscopy (AFM). Four probe method is used to measure the variation of electrical conductivity from I-V characteristics curves.

Linear excitation and detection in Fourier transform ion cyclotron resonance mass spectrometry

NASA Astrophysics Data System (ADS)

Grosshans, Peter B.; Chen, Ruidan; Limbach, Patrick A.; Marshall, Alan G.

1994-11-01

We present the first Fourier transform ion cyclotron resonance (FT-ICR) ion trap designed to produce both a linear spatial variation of the excitation electric potential field and a linear response of the detection circuit to the motion of the confined ions. With this trap, the magnitude of the detected signal at a given ion cyclotron frequency varies linearly with both the number of ions of given mass-to-charge ratio and also with the magnitude-mode excitation signal at the ion cyclotron orbital frequency; the proportionality constant is mass independent. Interestingly, this linearization may be achieved with any ion trap geometry. The excitation/detection design consists of an array of capacitively coupled electrodes which provide a voltage-divider network that produces a nearly spatially homogeneous excitation electric field throughout the linearized trap; resistive coupling to the electrodes isolates the a.c. excitation (or detection) circuit from the d.c. (trapping) potential. The design is based on analytical expressions for the potential associated with each electrode, from which we are able to compute the deviation from linearity for a trap with a finite number of elements. Based on direct experimental comparisons to an unmodified cubic trap, the linearized trap demonstrates the following performance advantages at the cost of some additional mechanical complexity: (a) signal response linearly proportional to excitation electric field amplitude; (b) vastly reduced axial excitation/ejection for significantly improved ion relative abundance accuracy; (c) elimination of harmonics and sidebands of the fundamental frequencies of ion motion. As a result, FT-ICR mass spectra are now more reproducible. Moreover, the linearized trap should facilitate the characterization of other fundamental aspects of ion behavior in an ICR ion trap, e.g. effects of space charge, non-quadrupolar electrostatic trapping field, etc. Furthermore, this novel design should improve significantly the precision of ion relative abundance and mass accuracy measurements, while removing spectral artifacts of the detection process. We discuss future modifications that linearize the spatial variation of the electrostatic trapping electric field as well, thereby completing the linearization of the entire FT-ICR mass spectrometric techniques. Suggested FT-ICR mass spectrometric applications for the linearized trap are discussed.

Local electric and electro-chemical investigations of cyanobacteria films

NASA Astrophysics Data System (ADS)

Marlière, C.; Ramonda, M.; de Wit, R.

2009-12-01

Carbonate reservoirs are submitted to microbial metabolic processes promoting either the precipitation or the dissolution of calcium carbonate, especially in network of fractures and fault zones. Such phenomena may act as a seal during fault zone evolution and, later, reservoir production, modifying greatly the connectivity of fractures, permeability structure and drainage in the vicinity of otherwise major fluid conduits. Several laboratory studies have demonstrated the utility of geophysical methods such as complex electrical conductivity ones for the investigation of microbial-induced changes in porous geologic media. The primary suggestion of these studies was that temporal variations in the geophysical signatures corresponded with microbial-induced changes in the geologic media. However these variations of electric signal could be due to the combined effects of surface and volume contributions in the studied geologic medium. Surface effects such as attachment of the bacteria on substrate surface or reactions of carbonate precipitation/dissolution are crucial for concerns about local seal or opening or, more generally, modification in connectivity of fracture or porosity network in reservoirs. That is why we have launched a new study in order to clearly distinguish surface effects from volume one in electrical responses mediated by biogenic material. The surface processes of cell growth, attachment onto substrate surfaces and the reactions of carbonate precipitation/dissolution are studied by local (at sub-micrometric scales) methods such as atomic force microscopy (AFM) and scanning electrochemical potential microscopy (SECM) probing. These methods are carried out with living biological specimen under in situ conditions. Our first studies have been done by AFM in tunnelling mode on cyanobacteria (from CaCO3 rich sediments from a hyper saline lake). The immobilized bacteria have been scanned in ambient gaseous atmosphere by the nanometric AFM tip. In these conditions the cyanobacteria are recovered by a micrometric film of water. Both the roughness signal and electric current flowing from the tip to the substrate through the sample have simultaneously been measured for different values of electrical voltage. The measured electrical signals are weak but well above the noise level. Our observations of the local variations of the electro-chemical signal at a high spatial resolution (at sub-micrometer level) and at short acquisition times will be presented and discussed in detail.

Mirror symmetry of ions and electron temperature variations within the dusty dynamo layer of the auroral ionosphere

NASA Astrophysics Data System (ADS)

Timofeev, Evgeny; Kangas, Jorma; Vallinkoski, Matti

Quasi-periodic (consisting of a dozen electro-thermal structures, ETS) variations of ionospheric parameters during April, 10 and March, 23 1988 substorms were investigated using the data of EISCAT radars in Tromso. These variations were measured at the lower edge of dynamo-layer 106 km and include the ion and electron temperature, electron density and ionospheric electric field; all data were smoothed out using moving average with optimal lag window. It was shown that: 1) ETS clusters are observed when value of the electric field is < 10 mV/m and average electron density is about (5-10)*10 (4) /sm (3) , 2) For each ETS the envelop demonstrate the so called mirror symmetry, that is antiphased variations of the ion and electron temperature (when Ti increases and Te decreases), 3) The symmetry breaks when the electric field is larger than FB instability threshold (15-20 mVm), 4) The periods of these variations is in the range of 3-10 min, 5) The self-similarity of the scales is observed: smaller scales are included into the larger scales, 6) Temperature variations were accompanied by the electric field variations with amplitude of 4-7 mV/m, 7) Large scale structures (and sometimes dyads formed by two subsequent structures) were accompanied by the electric field rotation up to the whole circle. Specific ETS and plasma parameters variations can be interpreted as a result of Ekman-type instability in the dusty plasma of the dynamo layer. The mirror symmetry of plasma temperature variations is an evidence of a partial blocking of energy transfer between the ions and electrons at low values of the external electric field (below FB instability threshold) because the main energy in such a kind of plasma is attributed to dusty macro-particles (Fortov et al., 2010). Under these conditions the time scale of the dust particle energy variations are considerably larger than the corresponding scales of the temperature variations. According to our previous results (Timofeev et al, 2009-2013) the coherent increase of correlation coefficient (CC) of plasma temperature time variations and smoothed value of the electric field means that the CC can be used as an indicator of the ETS "rigidity" (hence the energy and charge of macro-particles). We used this coherence to estimate the time scale of the macro-particles energy growth (during preliminary phase of March 23, 1988 substorm) and get values of 12-19 min. In the present study we used the same event to estimate the time scale of the plasma temperatures mirror variations and obtained that they are at least 2-3 times shorter. Such a difference in the time scale determines the ETS formation. Finally, after FB instability excitation the electrons can quickly exchange their energy with plasmons, so that the mirror symmetry in temperature variations breaks down.

Low-Energy Electron Effects on the Polar Wind Observed by the POLAR Spacecraft

NASA Technical Reports Server (NTRS)

Horwitz, J. L.; Su, Y.-J.; Dors, E. E.; Moore, Thomas E.; Giles, Barbara L.; Chandler, Michael O.; Craven, Paul D.; Chang, S.-W.; Scudder, J.

1998-01-01

Large ion outflow velocity variation at POLAR apogee have been observed. The observed H+ flow velocities were in the range of 23-110 km/s and 0+ flow velocities were in the range of 5-25 km/s. These velocity ranges lie between those predicted by simulations of the photoelectron-driven polar wind and "baseline" polar wind. The electric current contributions of the photoelectrons and polar rain are expected to control the size and altitude of an electric potential drop which accelerates the polar wind at relatively high altitudes. In this presentation, we compare polar wind characteristics observed near 5000 km and 8 RE altitudes by the Thermal Ion Dynamics Experiment (TIDE) with measurements of low-energy electrons sampled by HYDRA, both from the POLAR spacecraft, to examine possible effects of the polar rain and photoelectrons on the polar wind. Both correlations and anti-correlations are found between the polar wind velocities and the polar rain fluxes at POLAR apogee during different polar cap crossings. Also, the low-altitude upward/downward photoelectron spectra are used to estimates the potential drops above the spacecraft. We interpret these observations in terms of the effects that both photoelectrons and polar rain may have on the electric potential and polar wind acceleration along polar cap magnetic field lines.

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.

Use of Electrical Impedance Tomography to Monitor Regional Cerebral Edema during Clinical Dehydration Treatment

PubMed Central

Hu, Shi-Jie; Li, Xia; Xu, Can-Hua; Wang, Bing; Yang, Bin; Tang, Meng-Xing; Dong, Xiu-Zhen; Fei, Zhou; Shi, Xue-Tao

2014-01-01

Objective Variations of conductive fluid content in brain tissue (e.g. cerebral edema) change tissue impedance and can potentially be measured by Electrical Impedance Tomography (EIT), an emerging medical imaging technique. The objective of this work is to establish the feasibility of using EIT as an imaging tool for monitoring brain fluid content. Design a prospective study. Setting In this study EIT was used, for the first time, to monitor variations in cerebral fluid content in a clinical model with patients undergoing clinical dehydration treatment. The EIT system was developed in house and its imaging sensitivity and spatial resolution were evaluated on a saline-filled tank. Patients 23 patients with brain edema. Interventions The patients were continuously imaged by EIT for two hours after initiation of dehydration treatment using 0.5 g/kg intravenous infusion of mannitol for 20 minutes. Measurement and Main Results Overall impedance across the brain increased significantly before and after mannitol dehydration treatment (p = 0.0027). Of the all 23 patients, 14 showed high-level impedance increase and maintained this around 4 hours after the dehydration treatment whereas the other 9 also showed great impedance gain during the treatment but it gradually decreased after the treatment. Further analysis of the regions of interest in the EIT images revealed that diseased regions, identified on corresponding CT images, showed significantly less impedance changes than normal regions during the monitoring period, indicating variations in different patients' responses to such treatment. Conclusions EIT shows potential promise as an imaging tool for real-time and non-invasive monitoring of brain edema patients. PMID:25474474

Long-term electrical resistivity monitoring of recharge-induced contaminant plume behavior.

PubMed

Gasperikova, Erika; Hubbard, Susan S; Watson, David B; Baker, Gregory S; Peterson, John E; Kowalsky, Michael B; Smith, Meagan; Brooks, Scott

2012-11-01

Geophysical measurements, and electrical resistivity tomography (ERT) data in particular, are sensitive to properties that are related (directly or indirectly) to hydrological processes. The challenge is in extracting information from geophysical data at a relevant scale that can be used to gain insight about subsurface behavior and to parameterize or validate flow and transport models. Here, we consider the use of ERT data for examining the impact of recharge on subsurface contamination at the S-3 ponds of the Oak Ridge Integrated Field Research Challenge (IFRC) site in Tennessee. A large dataset of time-lapse cross-well and surface ERT data, collected at the site over a period of 12 months, is used to study time variations in resistivity due to changes in total dissolved solids (primarily nitrate). The electrical resistivity distributions recovered from cross-well and surface ERT data agrees well, and both of these datasets can be used to interpret spatiotemporal variations in subsurface nitrate concentrations due to rainfall, although the sensitivity of the electrical resistivity response to dilution varies with nitrate concentration. Using the time-lapse surface ERT data interpreted in terms of nitrate concentrations, we find that the subsurface nitrate concentration at this site varies as a function of spatial position, episodic heavy rainstorms (versus seasonal and annual fluctuations), and antecedent rainfall history. These results suggest that the surface ERT monitoring approach is potentially useful for examining subsurface plume responses to recharge over field-relevant scales. Published by Elsevier B.V.

Electromagnetic interaction of spacecraft with ambient environment

NASA Astrophysics Data System (ADS)

Ku, Hwar-Ching; Silver, David M.

1993-01-01

A model of the midcourse space experiment (MSX) spacecraft and its electromagnetic environment has been developed using the potential of large spacecraft in the Auroral region (POLAR) code. The geometric model has a resolution of 0.341 meters and uses six materials to simulate the electrical surface properties of MSX. The vehicle model includes features such as the major instruments, electronic boxes, radiators, a dewar and open bay, a booster attachment ring, and three different orientations of the solar panels. The electron and ion composition and temperature environment are modeled as a function of the solar activity. Additional parameters include the ram-wake orientation, the hot electron spectrum, day-night-twilight variations, latitudinal variations, and solar panel voltage biasing. Nominal low spacecraft charging cases are described. Calculation with a high peak energetic electron flux produces a ground potential of -180 volts and differential charging as high as 66 volts.

Cognitive and Neural Bases of Skilled Performance

DTIC Science & Technology

1990-08-09

torso. The only significant source of noise was a slow variation of the ambient field, which produces a drift of the baseline. The first depended upon...brief survey. Scand. J. of Psychology, Suppl. 1:170-174, 1982. [25] S. A. Hillyard, R. F. Hink , V. L. Schwent, and T. W. Picton. Electrical signs of...Okada, L. Kaufman, and S. J. Williamson. The hippocampal formation as a source of the slow endogenous potentials. Electroencepk. Clin. Neurophysiol

Study on electrical current variations in electromembrane extraction process: Relation between extraction recovery and magnitude of electrical current.

PubMed

Rahmani, Turaj; Rahimi, Atyeh; Nojavan, Saeed

2016-01-15

This contribution presents an experimental approach to improve analytical performance of electromembrane extraction (EME) procedure, which is based on the scrutiny of current pattern under different extraction conditions such as using different organic solvents as supported liquid membrane, electrical potentials, pH values of donor and acceptor phases, variable extraction times, temperatures, stirring rates, different hollow fiber lengths and the addition of salts or organic solvents to the sample matrix. In this study, four basic drugs with different polarities were extracted under different conditions with the corresponding electrical current patterns compared against extraction recoveries. The extraction process was demonstrated in terms of EME-HPLC analyses of selected basic drugs. Comparing the obtained extraction recoveries with the electrical current patterns, most cases exhibited minimum recovery and repeatability at the highest investigated magnitude of electrical current. . It was further found that identical current patterns are associated with repeated extraction efficiencies. In other words, the pattern should be repeated for a successful extraction. The results showed completely different electrical currents under different extraction conditions, so that all variable parameters have contributions into the electrical current pattern. Finally, the current patterns of extractions from wastewater, plasma and urine samples were demonstrated. The results indicated an increase in the electrical current when extracting from complex matrices; this was seen to decrease the extraction efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Electroosmotic flow in a rectangular channel with variable wall zeta-potential: comparison of numerical simulation with asymptotic theory.

PubMed

Datta, Subhra; Ghosal, Sandip; Patankar, Neelesh A

2006-02-01

Electroosmotic flow in a straight micro-channel of rectangular cross-section is computed numerically for several situations where the wall zeta-potential is not constant but has a specified spatial variation. The results of the computation are compared with an earlier published asymptotic theory based on the lubrication approximation: the assumption that any axial variations take place on a long length scale compared to a characteristic channel width. The computational results are found to be in excellent agreement with the theory even when the scale of axial variations is comparable to the channel width. In the opposite limit when the wavelength of fluctuations is much shorter than the channel width, the lubrication theory fails to describe the solution either qualitatively or quantitatively. In this short wave limit the solution is well described by Ajdari's theory for electroosmotic flow between infinite parallel plates (Ajdari, A., Phys. Rev. E 1996, 53, 4996-5005.) The infinitely thin electric double layer limit is assumed in the theory as well as in the simulation.

An interpretation of induced electric currents in long pipelines caused by natural geomagnetic sources of the upper atmosphere

USGS Publications Warehouse

Campbell, W.H.

1986-01-01

Electric currents in long pipelines can contribute to corrosion effects that limit the pipe's lifetime. One cause of such electric currents is the geomagnetic field variations that have sources in the Earth's upper atmosphere. Knowledge of the general behavior of the sources allows a prediction of the occurrence times, favorable locations for the pipeline effects, and long-term projections of corrosion contributions. The source spectral characteristics, the Earth's conductivity profile, and a corrosion-frequency dependence limit the period range of the natural field changes that affect the pipe. The corrosion contribution by induced currents from geomagnetic sources should be evaluated for pipelines that are located at high and at equatorial latitudes. At midlatitude locations, the times of these natural current maxima should be avoided for the necessary accurate monitoring of the pipe-to-soil potential. ?? 1986 D. Reidel Publishing Company.

Performance of Electricity Generation from Bryophyllum Leaf for Practical Utilisation

NASA Astrophysics Data System (ADS)

Khan, Md. Kamrul Alam

2017-01-01

Constructing an affordable cost, environment friendly simplified electrical energy source with Pathor Kuchi Leaf (PKL) for power electrifications which will significantly upgrade the life style of 1.6 billion people especially, who live in rural areas of Bangladesh. However, one fifth of the world's population still lack access to electricity-well, mainly in Sub-Saharan Africa and South Asia (Bangladesh, India, Sri Lanka, Pakistan, Nepal and Bhutan). This innovative technology will meet essential requirements as lighting, telecommunication as well as information access. Electrodes are put into the Bryophyllum Pinnatum Leaf (BPL) or Pathor Kuchi Leaf (PKL) sap and they produce substantially sufficient amount of electricity to power energy consumed electronics and electrical appliances. CuSO4.5H2O solution is used as a secondary salt. The role of CuSO4.5H2O solution has been studied. The electrical and chemical properties, a very important factor for PKL electricity generation device have been studied in this research work. The electrical properties are: internal resistance, voltage regulation, energy efficiency, pulse performance, self discharge characteristics, discharge characteristics with load, capacity of the PKL cell, temperature characteristics and life cycle of the PKL cell. The chemical properties are: variation of voltage, current with the variation of [Zn2+], [Cu2+] and time. The performance of the production of the two bi-products (fertilizer and hydrogen gas production) has been studied. Variation of concentration of Zn2+ and Cu2+ with the variation of percentage of the I am grateful to the authority of the Science and technology ministry,Bangladesh for financial support during the research work.

Modeling of the coupled magnetospheric and neutral wind dynamos

NASA Technical Reports Server (NTRS)

Thayer, Jeff P.

1993-01-01

The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet to be quantitatively evaluated. In this program, we are evaluating the coupled magnetospheric and neutral wind dynamos at high latitudes under various conditions. In addition to examining the impact of seasonal variations, we are investigating the consequences of the separate dynamos having pure current-source or voltage-source behaviors.

Effects of strong earthquakes in variations of electrical and meteorological parameters of the near-surface atmosphere in Kamchatka region

NASA Astrophysics Data System (ADS)

Smirnov, S. E.; Mikhailova, G. A.; Mikhailov, Yu. M.; Kapustina, O. V.

2017-09-01

The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, M = 8.3; January 13, 2007, M = 8.1; January 30, 2016, M = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six-seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

Electrically Guided Assembly of Colloidal Particles

NASA Astrophysics Data System (ADS)

Ristenpart, W. D.; Aksay, I. A.; Saville, D. A.

2002-11-01

In earlier work it was shown that the strength and frequency of an applied electric field alters the dynamic arrangement of particles on an electrode. Two-dimensional 'gas,' 'liquid' and 'solid' arrangements were formed, depending on the field strength and frequency. Since the particles are similarly charged, yet migrate over large distances under the influence of steady or oscillatory fields, it is clear that both hydrodynamic and electrical processes are involved. Here we report on an extensive study of electrically induced ordering in a parallel electrode cell. First, we discuss the kinetics of aggregation in a DC field as measured using video microscopy and digital image analysis. Rate constants were determined as a function of applied electric field strength and particle zeta potential. The kinetic parameters are compared to models based on electrohydrodynamic and electroosmotic fluid flow mechanisms Second, using monodisperse micron-sized particles, we examined the average interparticle spacing over a wide range of applied frequencies and field strengths. Variation of these parameters allows formation of closely-spaced arrangements and ordered arrays of widely separated particles. We find that there is a strong dependence on frequency, but there is surprisingly little influence of the electric field strength past a small threshold. Last, we present experiments with binary suspensions of similarly sized particles with negative but unequal surface potentials. A long-range lateral attraction is observed in an AC field. Depending on the frequency, this attractive interaction results in a diverse set of aggregate morphologies, including superstructured hexagonal lattices. These results are discussed in terms of induced dipole-dipole interactions and electrohydrodynamic flow. Finally, we explore the implications for practical applications.

Estimating Renewable Energy Economic Potential in the United States. Methodology and Initial Results

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

Brown, Austin; Beiter, Philipp; Heimiller, Donna

This report describes a geospatial analysis method to estimate the economic potential of several renewable resources available for electricity generation in the United States. Economic potential, one measure of renewable generation potential, may be defined in several ways. For example, one definition might be expected revenues (based on local market prices) minus generation costs, considered over the expected lifetime of the generation asset. Another definition might be generation costs relative to a benchmark (e.g., a natural gas combined cycle plant) using assumptions of fuel prices, capital cost, and plant efficiency. Economic potential in this report is defined as the subsetmore » of the available resource technical potential where the cost required to generate the electricity (which determines the minimum revenue requirements for development of the resource) is below the revenue available in terms of displaced energy and displaced capacity. The assessment is conducted at a high geospatial resolution (more than 150,000 technology-specific sites in the continental United States) to capture the significant variation in local resource, costs, and revenue potential. This metric can be a useful screening factor for understanding the economic viability of renewable generation technologies at a specific location. In contrast to many common estimates of renewable energy potential, economic potential does not consider market dynamics, customer demand, or most policy drivers that may incent renewable energy generation.« less

Reconstruction of the water table from self-potential data: a bayesian approach.

PubMed

Jardani, A; Revil, A; Barrash, W; Crespy, A; Rizzo, E; Straface, S; Cardiff, M; Malama, B; Miller, C; Johnson, T

2009-01-01

Ground water flow associated with pumping and injection tests generates self-potential signals that can be measured at the ground surface and used to estimate the pattern of ground water flow at depth. We propose an inversion of the self-potential signals that accounts for the heterogeneous nature of the aquifer and a relationship between the electrical resistivity and the streaming current coupling coefficient. We recast the inversion of the self-potential data into a Bayesian framework. Synthetic tests are performed showing the advantage in using self-potential signals in addition to in situ measurements of the potentiometric levels to reconstruct the shape of the water table. This methodology is applied to a new data set from a series of coordinated hydraulic tomography, self-potential, and electrical resistivity tomography experiments performed at the Boise Hydrogeophysical Research Site, Idaho. In particular, we examine one of the dipole hydraulic tests and its reciprocal to show the sensitivity of the self-potential signals to variations of the potentiometric levels under steady-state conditions. However, because of the high pumping rate, the response was also influenced by the Reynolds number, especially near the pumping well for a given test. Ground water flow in the inertial laminar flow regime is responsible for nonlinearity that is not yet accounted for in self-potential tomography. Numerical modeling addresses the sensitivity of the self-potential response to this problem.

Measuring of the pitch variation of cholesteric liquid crystals under electric field using wavelength-swept laser

NASA Astrophysics Data System (ADS)

Ko, Myeong Ock; Kim, Sung-Jo; Kim, Jong-Hyun; Jeon, Min Yong

2017-04-01

We measure the pitch variation of cholesteric liquid crystals (CLCs) according to the applied electric field using a wavelength-swept laser. While the electric field is applied to the CLC, the pitch of the CLC is elongated normal to the direction of electric field. Therefore, the reflection band is shifted to the longer wavelength. When the applied electric field to the CLC cell was over 1.52 V/μm, the reflection band was changed to the longer wavelength of about 75.1 nm. We believe that the dynamic behavior of the CLC can be analyzed if a high-speed wavelength-swept laser is used as an optical source.

The harmonic impact of electric vehicle battery charging

NASA Astrophysics Data System (ADS)

Staats, Preston Trent

The potential widespread introduction of the electric vehicle (EV) presents both opportunities and challenges to the power systems engineers who will be required to supply power to EV batteries. One of the challenges associated with EV battery charging comes from the potentially high harmonic currents associated with the conversion of ac power system voltages to dc EV battery voltages. Harmonic currents lead to increased losses in distribution circuits and reduced life expectancy of such power distribution components as capacitors and transformers. Harmonic current injections also cause harmonic voltages on power distribution networks. These distorted voltages can affect power system loads and specific standards exist regulating acceptable voltage distortion. This dissertation develops and presents the theory required to evaluate the electric vehicle battery charger as a harmonic distorting load and its possible harmonic impact on various aspects of power distribution systems. The work begins by developing a method for evaluating the net harmonic current injection of a large collection of EV battery chargers which accounts for variation in the start-time and initial battery state-of-charge between individual chargers. Next, this method is analyzed to evaluate the effect of input parameter variation on the net harmonic currents predicted by the model. We then turn to an evaluation of the impact of EV charger harmonic currents on power distribution systems, first evaluating the impact of these currents on a substation transformer and then on power distribution system harmonic voltages. The method presented accounts for the uncertainty in EV harmonic current injections by modeling the start-time and initial battery state-of-charge (SOC) of an individual EV battery charger as random variables. Thus, the net harmonic current, and distribution system harmonic voltages are formulated in a stochastic framework. Results indicate that considering variation in start-time and SOC leads to reduced estimates of harmonic current injection when compared to more traditional methods that do not account for variation. Evaluation of power distribution system harmonic voltages suggests that for any power distribution network there is a definite threshold penetration of EVs, below which the total harmonic distortion of voltage exceeds 5% at an insignificant number of buses. Thus, most existing distribution systems will probably be able to accommodate the early introduction of EV battery charging without widespread harmonic voltage problems.

Short term variations in Jupiter's synchrotron radiation derived from VLA data analysis

NASA Astrophysics Data System (ADS)

Kita, H.; Misawa, H.; Tsuchiya, F.; Morioka, A.

2011-12-01

Jupiter's synchrotron radiation (JSR) is the emission from relativistic electrons in the strong magnetic field of the inner magnetosphere, and it is the most effective prove for remote sensing of Jupiter's radiation belt from the Earth. Although JSR has been thought to be stable for a long time, intensive observations for JSR have made after the collisions of comet P/SL9 to Jupiter in 1994, and these observations revealed short term variations of JSR on time scale of days to weeks. However, the mechanisms which cause the short term variations of total flux density and brightness distribution have not been revealed well. In order to reveal the mechanism of short term variations of JSR more precisely, we have made radio image analysis using the NRAO (National Radio Astronomy Observatory) archived data of the VLA [*]. Brice and McDonough [1973, Icarus] proposed a scenario for the short term variations: i.e, the solar UV/EUV heating for Jupiter's upper atmosphere drives neutral wind perturbations and then the induced dynamo electric field leads to enhancement of radial diffusion. It is also suggested that induced dynamo electric field produce dawn-dusk electric potential difference, which cause dawn-dusk asymmetry in electron spatial distribution and emission distribution. So far the following results have been indicated for the short term variations. Miyoshi et al. [1999, GRL] showed that a short term variation event at 2.3GHz is well correlate to solar UV/EUV flux variations. Tsuchiya et al. [2010, Adv. Geosci.] showed that JSR at 325MHz and 785MHz have short term variations. These JSR observations confirmed the existence of the short term variation which is caused by solar UV/EUV. However, the effect of solar UV/EUV heating on the spatial distribution of JSR has never been confirmed, so this study is the first attempt to confirm the solar UV/EUV effect on spatial distribution of JSR. We have selected the data observed from 28th Jan. to 5th Feb. 2000 at 327MHz. During the period, solar UV/EUV flux expected on Jupiter showed almost monotonic increase. It is expected from the analysis for the period that the enhancement of radial diffusion caused by solar UV/EUV heating produces total flux enhancement and dawn-dusk asymmetry of the emission distribution of the JSR. We can therefore examine the scenario by measuring total flux density and dawn-dusk peak emission ratio of JSR, and their relationships to the variation of solar UV/EUV activity. A preliminary result shows that total flux density variations occurred corresponding to the solar UV/EUV variations, but we couldn't find variations in the dawn-dusk asymmetry above the one rms level calculated from the background image. *The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Solid State Lighting: A Nanoenabled Case Study in Sustainability

NASA Astrophysics Data System (ADS)

Hicks, Andrea L.

This work uses three household lighting technology options (incandescent, compact fluorescent (CFL), and light emitting diode (LED)) in a nanoenabled case study of artificial lighting. Life cycle assessment (LCA) is used to analyze the environmental impact of three lighting types across all four lifecycle phases: raw materials acquisition, manufacturing, use, and end of life. Using the average United States electricity profile, the use phase is found to have the greatest impact in all nine impact categories defined by TRACI (Tool for the Reduction and Assessment of Chemical and other environmental Impacts). Agent based modeling (ABM) is used to further investigate the use phase with respect to the adoption of energy efficient lighting and the rebound effect. Survey data on the consumer adoption and use of energy efficient lighting technology yields insight into consumer actions and the potential for rebound to occur, and is used to inform the ABM. Based on the results of the ABM analysis it is suggested that regardless of the type of energy efficient lighting, as long as the consumption of light continues to increase, efficiency alone will not reduce energy consumption. Over extended periods of time (~70 years), energy consumption rebounds to levels of pre-efficiency periods. There is a need for policy measures that are coupled with efficiency increases in such a way that energy savings are sustainable. Geographical and temporal variations in electricity profiles and their associated impacts are explored using LCA. It is found that there is the potential for significant variation in the lifetime environmental impact of lighting options based on shifts in the electricity profile. These results suggest the need for effective local policy in coordination with flexible national policy.

Lethal effect of electric fields on isolated ventricular myocytes.

PubMed

de Oliveira, Pedro Xavier; Bassani, Rosana Almada; Bassani, José Wilson Magalhães

2008-11-01

Defibrillator-type shocks may cause electric and contractile dysfunction. In this study, we determined the relationship between probability of lethal injury and electric field intensity (E in isolated rat ventricular myocytes, with emphasis on field orientation and stimulus waveform. This relationship was sigmoidal with irreversible injury for E > 50 V/cm . During both threshold and lethal stimulation, cells were twofold more sensitive to the field when it was applied longitudinally (versus transversally) to the cell major axis. For a given E, the estimated maximum variation of transmembrane potential (Delta V(max)) was greater for longitudinal stimuli, which might account for the greater sensitivity to the field. Cell death, however, occurred at lower maximum Delta V(max) values for transversal shocks. This might be explained by a less steep spatial decay of transmembrane potential predicted for transversal stimulation, which would possibly result in occurrence of electroporation in a larger membrane area. For the same stimulus duration, cells were less sensitive to field-induced injury when shocks were biphasic (versus monophasic). Ours results indicate that, although significant myocyte death may occur in the E range expected during clinical defibrillation, biphasic shocks are less likely to produce irreversible cell injury.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Barium strontium titanate thin film growth with variation of lanthanum dopant compatibility as sensor prototype in the satellite technology

NASA Astrophysics Data System (ADS)

Mulyadi; Wahyuni, Rika; Hardhienata, Hendradi; Irzaman

2018-05-01

Electrical properties of barium strontium titanate thin films were investigated. Three layers of barium strontium titanate thin films have been prepared by chemical solution deposition method and spin coating technique at 8000 rpm rotational speed for 30 seconds and temperature of annealing at 850°C for eight hours with temperature increment of 1.67°C/minute. Materials produced by the process of lanthanum dopant with doping variations of 2%, 4% and 6% above type-p silicon (100) substrates. Film obtained was then carried out the characterization using USB 2000 VIS-NIR and tauc plot method. As a result, the barium strontium titanate thin film has the value of band gap energy of 1.58 eV, 1.92 eV and 2.24 eV respectively. The characterization of electrical properties shows that the band gap value of barium strontium titanate thin film with lanthanum dopant was in the range of semiconductor value. Barium strontium titanate thin films with lanthanum dopant are sensitive to temperature changes, so it potentially to be applied to temperature monitoring on satellite technology.

Why the short face? Developmental disintegration of the neurocranium drives convergent evolution in neotropical electric fishes.

PubMed

Evans, Kory M; Waltz, Brandon; Tagliacollo, Victor; Chakrabarty, Prosanta; Albert, James S

2017-03-01

Convergent evolution is widely viewed as strong evidence for the influence of natural selection on the origin of phenotypic design. However, the emerging evo-devo synthesis has highlighted other processes that may bias and direct phenotypic evolution in the presence of environmental and genetic variation. Developmental biases on the production of phenotypic variation may channel the evolution of convergent forms by limiting the range of phenotypes produced during ontogeny. Here, we study the evolution and convergence of brachycephalic and dolichocephalic skull shapes among 133 species of Neotropical electric fishes (Gymnotiformes: Teleostei) and identify potential developmental biases on phenotypic evolution. We plot the ontogenetic trajectories of neurocranial phenotypes in 17 species and document developmental modularity between the face and braincase regions of the skull. We recover a significant relationship between developmental covariation and relative skull length and a significant relationship between developmental covariation and ontogenetic disparity. We demonstrate that modularity and integration bias the production of phenotypes along the brachycephalic and dolichocephalic skull axis and contribute to multiple, independent evolutionary transformations to highly brachycephalic and dolichocephalic skull morphologies.

Polar cap potential saturation during the Bastille Day storm event using global MHD simulation

NASA Astrophysics Data System (ADS)

Kubota, Y.; Nagatsuma, T.; Den, M.; Tanaka, T.; Fujita, S.

2017-04-01

We investigated the temporal variations and saturation of the cross polar cap potential (CPCP) in the Bastille Day storm event (15 July 2000) by global magnetohydrodynamics (MHD) simulation. The CPCP is considered to depend on the electric field and dynamic pressure of the solar wind as well as on the ionospheric conductivity. Previous studies considered only the ionospheric conductivity due to solar extreme ultraviolet (EUV) variations. In this paper, we dealt with the changes in the CPCP attributable to auroral conductivity variations caused by pressure enhancement in the inner magnetosphere owing to energy injection from the magnetosphere because the energy injection is considerably enhanced in a severe magnetic storm event. Our simulation reveals that the auroral conductivity enhancement is significant for the CPCP variation in a severe magnetic storm event. The numerical results concerning the Bastille Day event show that the ionospheric conductivity averaged over the auroral oval is enhanced up to 18 mho in the case of Bz of less than -59 nT. On the other hand, the average conductivity without the auroral effect is almost 6 mho throughout the entire period. Resultantly, the saturated CPCP is about 240 kV in the former and 704 kV in the latter when Bz is -59 nT. This result indicates that the CPCP variations could be correctly reproduced when the time variation of auroral conductivity caused by pressure enhancement due to the energy injection from the magnetosphere is correctly considered in a severe magnetic storm event.

Electric fields preceding cloud-to-ground lightning flashes

NASA Astrophysics Data System (ADS)

Beasley, W.; Uman, M. A.; Rustan, P. L., Jr.

1982-06-01

A detailed analysis is presented of the electric-field variations preceding the first return strokes of 80 cloud-to-ground lightning flashes in nine different storms observed at the NASA Kennedy Space Center during the summers of 1976 and 1977. It is suggested that the electric-field variations can best be characterized as having two sections: preliminary variations and stepped leader. The stepped-leader change begins during a transition period of a few milliseconds marked by characteristic bipolar pulses; the duration of stepped leaders lies most frequently in the 6-20 millisecond range. It is also suggested that there is only one type of stepped leader, not two types (alpha and beta) often referred to in the literature.

Remote sensing of freeze-thaw transitions in Arctic soils using the complex resistivity method

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

Wu, Yuxin; Hubbard, Susan S; Ulrich, Craig

2013-01-01

Our ability to monitor freeze - thaw transitions is critical to developing a predictive understanding of biogeochemical transitions and carbon dynamics in high latitude environments. In this study, we conducted laboratory column experiments to explore the potential of the complex resistivity method for monitoring the freeze - thaw transitions of the arctic permafrost soils. Samples for the experiment were collected from the upper active layer of Gelisol soils at the Barrow Environmental Observatory, Barrow Alaska. Freeze - thaw transitions were induced through exposing the soil column to controlled temperature environments at 4 C and -20 C. Complex resistivity and temperaturemore » measurements were collected regularly during the freeze - thaw transitions using electrodes and temperature sensors installed along the column. During the experiments, over two orders of magnitude of resistivity variations were observed when the temperature was increased or decreased between -20 C and 0 C. Smaller resistivity variations were also observed during the isothermal thawing or freezing processes that occurred near 0 C. Single frequency electrical phase response and imaginary conductivity at 1 Hz were found to be exclusively related to the unfrozen water in the soil matrix, suggesting that these geophysical 24 attributes can be used as a proxy for the monitoring of the onset and progression of the freeze - thaw transitions. Spectral electrical responses and fitted Cole Cole parameters contained additional information about the freeze - thaw transition affected by the soil grain size distribution. Specifically, a shift of the observed spectral response to lower frequency was observed during isothermal thawing process, which we interpret to be due to sequential thawing, first from fine then to coarse particles within the soil matrix. Our study demonstrates the potential of the complex resistivity method for remote monitoring of freeze - thaw transitions in arctic soils. Although conducted at the laboratory scale, this study provides the foundation for exploring the potential of the complex resistivity signals for monitoring spatiotemporal variations of freeze - thaw transitions over field-relevant scales.« less

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

Skordas, E. S., E-mail: eskordas@phys.uoa.gr

By applying Detrended Fluctuation Analysis (DFA) to the time series of the geomagnetic data recorded at three measuring stations in Japan, Rong et al. in 2012 recently reported that anomalous magnetic field variations were identified well before the occurrence of the disastrous Tohoku M{sub w}9.0 earthquake that occurred on 11 March 2011 in Japan exhibiting increased “non-uniform” scaling behavior. Here, we provide an explanation for the appearance of this increase of “non-uniform” scaling on the following grounds: These magnetic field variations are the ones that accompany the electric field variations termed Seismic Electric Signals (SES) activity which have been repeatedlymore » reported that precede major earthquakes. DFA as well as multifractal DFA reveal that the latter electric field variations exhibit scaling behavior as shown by analyzing SES activities observed before major earthquakes in Greece. Hence, when these variations are superimposed on a background of pseudosinusoidal trend, their long range correlation properties—quantified by DFA—are affected resulting in an increase of the “non-uniform” scaling behavior. The same is expected to hold for the former magnetic field variations. This explanation is strengthened by recent findings showing that the fluctuations of the order parameter of seismicity exhibited an unprecedented minimum almost two months before the Tohoku earthquake occurrence which is characteristic for an almost simultaneous emission of Seismic Electric Signals activity.« less

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Electrical characteristics of silicon nanowire CMOS inverters under illumination.

PubMed

Yoo, Jeuk; Kim, Yoonjoong; Lim, Doohyeok; Kim, Sangsig

2018-02-05

In this study, we examine the electrical characteristics of complementary metal-oxide-semiconductor (CMOS) inverters with silicon nanowire (SiNW) channels on transparent substrates under illumination. The electrical characteristics vary with the wavelength and power of light due to the variation in the generation rates of the electric-hole pairs. Compared to conventional optoelectronic devices that sense the on/off states by the variation in the current, our device achieves the sensing of the on/off states with more precision by using the voltage variation induced by the wavelength or intensity of light. The device was fabricated on transparent substrates to maximize the light absorption using conventional CMOS technologies. The key difference between our SiNW CMOS inverters and conventional optoelectronic devices is the ability to control the flow of charge carriers more effectively. The improved sensitivity accomplished with the use of SiNW CMOS inverters allows better control of the on/off states.

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

NASA Astrophysics Data System (ADS)

Wan, Li; Xu, Shixin; Liao, Maijia; Liu, Chun; Sheng, Ping

2014-01-01

In this work, we treat the Poisson-Nernst-Planck (PNP) equations as the basis for a consistent framework of the electrokinetic effects. The static limit of the PNP equations is shown to be the charge-conserving Poisson-Boltzmann (CCPB) equation, with guaranteed charge neutrality within the computational domain. We propose a surface potential trap model that attributes an energy cost to the interfacial charge dissociation. In conjunction with the CCPB, the surface potential trap can cause a surface-specific adsorbed charge layer σ. By defining a chemical potential μ that arises from the charge neutrality constraint, a reformulated CCPB can be reduced to the form of the Poisson-Boltzmann equation, whose prediction of the Debye screening layer profile is in excellent agreement with that of the Poisson-Boltzmann equation when the channel width is much larger than the Debye length. However, important differences emerge when the channel width is small, so the Debye screening layers from the opposite sides of the channel overlap with each other. In particular, the theory automatically yields a variation of σ that is generally known as the "charge regulation" behavior, attendant with predictions of force variation as a function of nanoscale separation between two charged surfaces that are in good agreement with the experiments, with no adjustable or additional parameters. We give a generalized definition of the ζ potential that reflects the strength of the electrokinetic effect; its variations with the concentration of surface-specific and surface-nonspecific salt ions are shown to be in good agreement with the experiments. To delineate the behavior of the electro-osmotic (EO) effect, the coupled PNP and Navier-Stokes equations are solved numerically under an applied electric field tangential to the fluid-solid interface. The EO effect is shown to exhibit an intrinsic time dependence that is noninertial in its origin. Under a step-function applied electric field, a pulse of fluid flow is followed by relaxation to a new ion distribution, owing to the diffusive counter current. We have numerically evaluated the Onsager coefficients associated with the EO effect, L21, and its reverse streaming potential effect, L12, and show that L12=L21 in accordance with the Onsager relation. We conclude by noting some of the challenges ahead.

Numerical study of active control of mixing in electro-osmotic flows by temperature difference using lattice Boltzmann methods.

PubMed

Alizadeh, A; Wang, J K; Pooyan, S; Mirbozorgi, S A; Wang, M

2013-10-01

In this paper, the effect of temperature difference between inlet flow and walls on the electro-osmotic flow through a two-dimensional microchannel is investigated. The main objective is to study the effect of temperature variations on the distribution of ions and consequently internal electric potential field, electric body force, and velocity fields in an electro-osmotic flow. We assume constant temperature and zeta potential on walls and use the mean temperature of each cross section to characterize the Boltzmann ion distribution across the channel. Based on these assumptions, the multiphysical transports are still able to be described by the classical Poisson-Boltzmann model. In this work, the Navier-Stokes equation for fluid flow, the Poisson-Boltzmann equation for ion distribution, and the energy equation for heat transfer are solved by a couple lattice Boltzmann method. The modeling results indicate that the temperature difference between walls and the inlet solution may lead to two symmetrical vortices at the entrance region of the microchannel which is appropriate for mixing enhancements. The advantage of this phenomenon for active control of mixing in electro-osmotic flow is the manageability of the vortex scale without extra efforts. For instance, the effective domain of this pattern could broaden by the following modulations: decreasing the external electric potential field, decreasing the electric double layer thickness, or increasing the temperature difference between inlet flow and walls. This work may provide a novel strategy for design or optimization of microsystems. Copyright © 2013 Elsevier Inc. All rights reserved.

Performance of Savonius Blade Waterwheel with Variation of Blade Number

NASA Astrophysics Data System (ADS)

Sule, L.; Rompas, P. T. D.

2018-02-01

The utilization of water energy source is mainly used as a provider of electrical energy through hydroelectric power. The potential utilization of water flow energy is relatively small. The objective of this study is to know the best blade of Savonius waterwheel with various variables such as water discharge, blade number, and loading. The data used the efficiency of waterwheel, variation of blade number, variable water discharge, and loading in the shaft. The test results have shown that the performances of a top-water mill with the semicircular curve where the variation in the number of blades are 4, 6, and 8 at discharge and loading of 0.01587 m3/s and 1000 grams respectively were 9.945%, 13.929%, and 17.056% respectively. The blades number of 8 obtained the greatest performance. The more number of blades the greater the efficiency of the waterwheel Savonius.

The Effect of Variation in Permittivity of Different Tissues on Induced Electric Field in the Brain during Transcranial Magnetic Stimulation

NASA Astrophysics Data System (ADS)

Hadimani, Ravi; Porzig, Konstantin; Crowther, Lawrence; Brauer, Hartmut; Toepfer, Hannes; Jiles, David; Department of Electrical and Computer Engineering, Iowa State University Team; Department of Advanced Electromagnetics, Ilmenau University of Technology Team

2013-03-01

Estimation of electric field in the brain during Transcranial Magnetic Stimulation (TMS) requires knowledge of the electric property of brain tissue. Grey and white matters have unusually high relative permittivities of ~ 106 at low frequencies. However, relative permittivity of cerebrospinal fluid is ~ 102. With such a variation it is necessary to consider the effect of boundaries. A model consisting of 2 hemispheres was used in the model with the properties of one hemisphere kept constant at σ1 = 0.1Sm-1 and ɛr 1 = 10 while the properties of the second hemisphere were changed kept at σ2 = 0.1Sm-1 to 2Sm-1 and ɛr 2 = 102 to 105. A 70 mm diameter double coil was used as the source of the magnetic field. The amplitude of the current in the coil was 5488 A at a frequency of 2.9 kHz. The results show that the electric field, E induced during magnetic stimulation is independent of the relative permittivity, ɛr and varies with the conductivity. Thus the variation in E, calculated with homogeneous and heterogeneous head models was due to variation in conductivity of the tissues and not due to variation in permittivities.

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.

The temperature signature of an IMF-driven change to the global atmospheric electric circuit (GEC) in the Antarctic troposphere

NASA Astrophysics Data System (ADS)

Freeman, Mervyn; Lam, Mai Mai; Chisham, Gareth

2017-04-01

We use National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data to show that Antarctic surface air temperature anomalies result from differences in the daily-mean duskward component,By, of the interplanetary magnetic field (IMF). We find the anomalies have strong geographical and seasonal variations. Regional anomalies are evident poleward of 60˚ S and are of diminishing representative peak amplitude from autumn (3.2˚ C) to winter (2.4˚ C) to spring (1.6˚ C) to summer (0.9˚ C). We demonstrate that anomalies of statistically-significant amplitude are due to geostrophic wind anomalies, resulting from the same By changes, moving air across large meridional gradients in zonal mean air temperature between 60 and 80˚ S. Additionally, we find that the mean tropospheric temperature anomaly for geographical latitudes ≤ -70˚ peaks at about 0.7 K and is statistically significant at the 1 - 5% level between air pressures of 1000 and 500 hPa (i.e., ˜0.1 to 5.6 km altitude above sea level) and for time lags with respect to the IMF of up to 7 days. The signature propagates vertically between air pressure p ≥ 850 hPa (≤ 1.5 km) and p = 500 hPa (˜5.6 km). The characteristics of prompt response and vertical propagation within the troposphere have previously been seen in the correlation between the IMF and high-latitude air pressure anomalies, known as the Mansurov effect, at higher statistical significances (1%). We conclude that we have identified the temperature signature of the Mansurov effect in the Antarctic troposphere. Since these tropospheric anomalies have been associated with By-driven anomalies in the electric potential of the ionosphere, we further conclude that they are caused by IMF-induced changes to the global atmospheric electric circuit (GEC). Our results support the view that variations in the ionospheric potential act on the troposphere via the action of resulting variations in the downwards current of the GEC on tropospheric clouds.

Electric-field-induced modification in Dzyaloshinskii-Moriya interaction of Co monolayer on Pt(111)

NASA Astrophysics Data System (ADS)

Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori; Ono, Teruo; Weinert, Michael

Magnetism induced by an external electric field (E-field) has received much attention as a potential approach for controlling magnetism at the nano-scale with the promise of ultra-low energy power consumption. Here, the E-field-induced modification of the Dzyaloshinskii-Moriya interaction (DMI) for a prototypical transition-metal thin layer of a Co monolayer on Pt(111) is investigated by first-principles calculations by using the full-potential linearized augmented plane wave method that treats spin-spiral structures in an E-field. With inclusion of the spin-orbit coupling (SOC) by the second variational method for commensurate spin-spiral structures, the DMI constants were estimated from an asymmetric contribution in the total energy with respect to the spin-spiral wavevector. The results predicted that the DMI is modified by the E-field, but the change is found to be small compared to that in the exchange interaction (a symmetric contribution in the total energy) by a factor of ten.

Electric-field-induced modification in Curie temperature of Co monolayer on Pt(111)

NASA Astrophysics Data System (ADS)

Nakamura, Kohji; Oba, Mikito; Akiyama, Toru; Ito, Tomonori; Weinert, Michael

2015-03-01

Magnetism induced by an external electric field (E-field) has received much attention as a potential approach for controlling magnetism at the nano-scale with the promise of ultra-low energy power consumption. Here, the E-field-induced modification of the Curie temperature for a prototypical transition-metal thin layer of a Co monolayer on Pt(111) is investigated by first-principles calculations by using the full-potential linearized augmented plane wave method that treats spin-spiral structures in an E-field. An applied E-field modifies the magnon (spin-spiral formation) energies by a few meV, which leads to a modification of the exchange pair interaction parameters within the classical Heisenberg model. With inclusion of the spin-orbit coupling (SOC), the magnetocrystalline anisotropy and the Dzyaloshinskii-Morita interaction are obtained by the second variation SOC method. An E-field-induced modification of the Curie temperature is demonstrated by Monte Carlo simulations, in which a change in the exchange interaction is found to play a key role.

Mathematical modelling of the uptake and transport of salt in plant roots.

PubMed

Foster, Kylie J; Miklavcic, Stanley J

2013-11-07

In this paper, we present and discuss a mathematical model of ion uptake and transport in roots of plants. The underlying physical model of transport is based on the mechanisms of forced diffusion and convection. The model can take account of local variations in effective ion and water permeabilities across the major tissue regions of plant roots, represented through a discretized coupled system of governing equations including mass balance, forced diffusion, convection and electric potential. We present simulation results of an exploration of the consequent enormous parameter space. Among our findings we identify the electric potential as a major factor affecting ion transport across, and accumulation in, root tissues. We also find that under conditions of a constant but realistic level of bulk soil salt concentration and plant-soil hydraulic pressure, diffusion plays a significant role even when convection by the water transpiration stream is operating. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Electric-field induced surface instabilities of soft dielectrics and their effects on optical transmittance and scattering

NASA Astrophysics Data System (ADS)

Shian, Samuel; Kjeer, Peter; Clarke, David R.

2018-03-01

When a voltage is applied to a percolative, mechanically compliant mat of carbon nanotubes (CNTs) on a smooth elastomer bilayer attached to an ITO coated glass substrate, the in-line optical transmittance decreases with increasing voltage. Two regimes of behavior have been identified based on optical scattering, bright field optical microscopy, and confocal optical microscopy. In the low field regime, the electric field produces a spatially inhomogeneous surface deformation of the elastomer that causes local variations in optical refraction and modulates the light transmittance. The spatial variation is associated with the distribution of the CNTs over the surface. At higher fields, above a threshold voltage, an array of pits in the surface form by a nucleation and growth mechanism and these also scatter light. The formation of pits, and creases, in the thickness of the elastomer, is due to a previously identified electro-mechanical surface instability. When the applied voltage is decreased from its maximum, the transmittance returns to its original value although there is a transmittance hysteresis and a complicated time response. When the applied voltage exceeds the threshold voltage, there can be remnant optical contrast associated with creasing of the elastomer and the recovery time appears to be dependent on local jamming of CNTs in areas where the pits formed. A potential application of this work as an electrically tunable privacy window or camouflaging devices is demonstrated.

Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

NASA Technical Reports Server (NTRS)

Fejer, B. G.; Kelley, M. C.; Senior, C.; De La Beaujardiere, O.; Lepping, R.

1990-01-01

The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

Power quality analysis based on spatial correlation

NASA Astrophysics Data System (ADS)

Li, Jiangtao; Zhao, Gang; Liu, Haibo; Li, Fenghou; Liu, Xiaoli

2018-03-01

With the industrialization and urbanization, the status of electricity in the production and life is getting higher and higher. So the prediction of power quality is the more potential significance. Traditional power quality analysis methods include: power quality data compression, disturbance event pattern classification, disturbance parameter calculation. Under certain conditions, these methods can predict power quality. This paper analyses the temporal variation of power quality of one provincial power grid in China from time angle. The distribution of power quality was analyzed based on spatial autocorrelation. This paper tries to prove that the research idea of geography is effective for mining the potential information of power quality.

Mechanisms of the global electric circuit and lightning variability on the ENSO time scale

NASA Astrophysics Data System (ADS)

Mareev, Evgeny; Volodin, Evgeny; Slyunyaev, Nikolay

2017-04-01

Many studies of lightning activity on the El Niño-Southern Oscillation (ENSO) time scale show increased activity over tropical land areas during the warm El Niño phase (e.g., Satori et al., 2009; Price, 2009). The mechanisms of this variability—particularly in terms of its role in the global electric circuit (GEC)—are still under debate (e.g., Williams and Mareev, 2014). In this study a general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modelling the GEC variability on the ENSO time scale. The ionospheric potential (IP) and the lightning flash rate are calculated to study regional peculiarities and possible mechanisms of lightning variation. The IP parameterisation is used (Mareev and Volodin, 2014) which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The account of conductivity variation in the IP parameterisation is suggested based on the approach realised in (Slyunyaev et al., 2014). Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. Numerical simulations suggest that the inter-annual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature (SST) in the Pacific Ocean (180W-100W, 5S-5N—El Niño area). The IP maximum corresponds to the SST minimum. This result can be explained taking into account that during El Niño (positive temperature anomaly) precipitations in the equatorial part of the Pacific increase while in other tropic zones including the land areas they decrease. Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. During the El Niño period in the model, the mean aerosol content in the atmosphere decrease, which is caused by the weakening of the winds over Sahara and South-West Asia lifting dust into the atmosphere. Taking into consideration the decrease in the number of thunderstorms, this does not explain the observed global lightning variation. As another possible explanation for the enhanced El Niño lightning activity, the variation of the atmospheric aerosols and cloud condensation nuclei due to fires is discussed. The work was supported by a grant from the Government of the Russian Federation (contract no. 14.B25.31.0023) and by RFBR grant no. 16-05-01086. References Mareev E.A., Volodin E.M. (2014), Variation of the global electric circuit and ionospheric potential in a general circulation model, Geophys. Res. Lett., V. 41, P. 9009-9016. Sátori G., Williams E., Lemperger I. (2009), Variability of global lightning activity on the ENSO time scale, Atmos. Res., V. 91, P. 500-507. Price C. (2009), Will a drier climate result in a more lightning?, Atmos. Res., V. 91, P. 479-484. Williams E.R., Mareev E.A. (2014), Recent progress on the global electrical circuit, Atmos. Res., V. 135-136, P. 208-227. Slyunyaev N.N., Mareev E.A., Kalinin A.V., Zhidkov A.A. (2014), Influence of large-scale conductivity inhomogeneities in the atmosphere on the global electric circuit, J. Atmos. Sci., V. 71, P. 4382-4396.

The effect of photoelectrons on boom-satellite potential differences during electron beam ejection

NASA Technical Reports Server (NTRS)

Lai, Shu T.; Cohen, Herbert A.; Aggson, Thomas L.; Mcneil, William J.

1987-01-01

Data taken on the SCATHA satellite at geosynchronous altitudes during periods of electron beam ejection in sunlight showed that the potential difference between an electrically isolated boom and the satellite main body was a function of beam current, energy, and boom-sun angle. The potential difference decreased as the boom area illuminated by the sun increased; the maximum and minimum potential differences were measured when minimum and maximum boom areas, respectively, were exposed to the sun. It is shown that photoelectrons, created on the boom, could be engulfed in the electrostatic field of the highly charged satellite main body. Theoretical calculations made using a simple current balance model showed that these electrons could provide a substantial discharging current to the main body and cause the observed variations in the potential difference between the main body and the booms.

Dynamic Variation in Pleasure in Children Predicts Nonlinear Change in Lateral Frontal Brain Electrical Activity

ERIC Educational Resources Information Center

Light, Sharee N.; Coan, James A.; Frye, Corrina; Goldsmith, H. Hill; Davidson, Richard J.

2009-01-01

Individual variation in the experience and expression of pleasure may relate to differential patterns of lateral frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral frontal cortex in positive emotion, but the excellent time resolution of these measures has not been used to capture…

Large tangential electric fields in plasmas close to temperature screening

NASA Astrophysics Data System (ADS)

Velasco, J. L.; Calvo, I.; García-Regaña, J. M.; Parra, F. I.; Satake, S.; Alonso, J. A.; the LHD team

2018-07-01

Low collisionality stellarator plasmas usually display a large negative radial electric field that has been expected to cause accumulation of impurities due to their high charge number. In this paper, two combined effects that can potentially modify this scenario are discussed. First, it is shown that, in low collisionality plasmas, the kinetic contribution of the electrons to the radial electric field can make it negative but small, bringing the plasma close to impurity temperature screening (i.e., to a situation in which the ion temperature gradient is the main drive of impurity transport and causes outward flux); in plasmas of very low collisionality, such as those of the large helical device displaying impurity hole (Ida et al (The LHD Experimental Group) 2009 Phys. Plasmas 16 056111; Yoshinuma et al (The LHD Experimental Group) 2009 Nucl. Fusion 49 062002), screening may actually occur. Second, the component of the electric field that is tangent to the flux surface (in other words, the variation of the electrostatic potential on the flux surface), although smaller than the radial component, has recently been suggested to be an additional relevant drive for radial impurity transport. Here, it is explained that, especially when the radial electric field is small, the tangential magnetic drift has to be kept in order to correctly compute the tangential electric field, that can be larger than previously expected. This can have a strong impact on impurity transport, as we illustrate by means of simulations using the newly developed code kinetic orbit-averaging-solver for stellarators, although it is not enough to explain by itself the behavior of the fluxes in situations like the impurity hole.

New Content Addressable Memory (CAM) Technologies for Big Data and Intelligent Electronics Enabled by Magneto-Electric Ternary CAM

DTIC Science & Technology

2017-12-11

provides ultra-low energy search operations. To improve throughput, the in-array pipeline scheme has been developed, allowing the MeTCAM to operate at a...controlled magnetic tunnel junction (VC-MTJ), which not only reduces cell area (thus achieving higher density) but also eliminates standby energy . This...Variations of the cell design are presented and evaluated. The results indicated a potential 90x improvement in the energy efficiency and a 50x

Considerations on sample holder design and custom-made non-polarizable electrodes for Spectral Induced Polarization measurements on unsaturated soils

NASA Astrophysics Data System (ADS)

Kaouane, C.; Chouteau, M. C.; Fauchard, C.; Cote, P.

2014-12-01

Spectral Induced Polarization (SIP) is a geophysical method sensitive to water content, saturation and grain size distribution. It could be used as an alternative to nuclear probes to assess the compaction of soils in road works. To evaluate the potential of SIP as a practical tool, we designed an experiment for complex conductivity measurements on unsaturated soil samples.Literature presents a large variety of sample holders and designs, each depending on the context. Although we might find some precise description about the sample holder, exact replication is not always possible. Furthermore, the potential measurements are often done using custom-made Ag/AgCl electrodes and very few indications are given on their reliability with time and temperature. Our objective is to perform complex conductivity measurements on soil samples compacted in a PVC cylindrical mould (10 cm-long, 5 cm-diameter) according to geotechnical standards. To expect homogeneous current density, electrical current is transmitted through the sample via chambers filled with agar gel. Agar gel is a good non-polarizable conductor within the frequency range (1 mHz -20kHz). Its electrical properties are slightly known. We measured increasing of agar-agar electrical conductivity in time. We modelled the influence of this variation on the measurement. If the electrodes are located on the sample, it is minimized. Because of the dimensions at stake and the need for simple design, potential electrodes are located outside the sample, hence the gel contributes to the measurements. Since the gel is fairly conductive, we expect to overestimate the sample conductivity. Potential electrodes are non-polarizable Ag/AgCl electrodes. To avoid any leakage, the KCl solution in the electrodes is replaced by saturated KCl-agar gel. These electrodes are low cost and show a low, stable, self-potential (<1mV). In addition, the technique of making electrode can be easily reproduced and storage and maintenance are simple. We measured a variation of less than 1 mS/m of the electrolyte conductivity during the time of measurement (~1h40) for a conductivity range 25-100 mS/m, showing no ionic contamination of the solution by the electrodes. An improvement to the cell design would be to control the internal temperature of the sample.

A phenomenological force model of Li-ion battery packs for enhanced performance and health management

NASA Astrophysics Data System (ADS)

Oh, Ki-Yong; Epureanu, Bogdan I.

2017-10-01

A 1-D phenomenological force model of a Li-ion battery pack is proposed to enhance the control performance of Li-ion battery cells in pack conditions for efficient performance and health management. The force model accounts for multiple swelling sources under the operational environment of electric vehicles to predict swelling-induced forces in pack conditions, i.e. mechanically constrained. The proposed force model not only incorporates structural nonlinearities due to Li-ion intercalation swelling, but also separates the overall range of states of charge into three ranges to account for phase transitions. Moreover, an approach to study cell-to-cell variations in pack conditions is proposed with serial and parallel combinations of linear and nonlinear stiffness, which account for battery cells and other components in the battery pack. The model is shown not only to accurately estimate the reaction force caused by swelling as a function of the state of charge, battery temperature and environmental temperature, but also to account for cell-to-cell variations due to temperature variations, SOC differences, and local degradation in a wide range of operational conditions of electric vehicles. Considering that the force model of Li-ion battery packs can account for many possible situations in actual operation, the proposed approach and model offer potential utility for the enhancement of current battery management systems and power management strategies.

Theory, modeling, and integrated studies in the Arase (ERG) project

NASA Astrophysics Data System (ADS)

Seki, Kanako; Miyoshi, Yoshizumi; Ebihara, Yusuke; Katoh, Yuto; Amano, Takanobu; Saito, Shinji; Shoji, Masafumi; Nakamizo, Aoi; Keika, Kunihiro; Hori, Tomoaki; Nakano, Shin'ya; Watanabe, Shigeto; Kamiya, Kei; Takahashi, Naoko; Omura, Yoshiharu; Nose, Masahito; Fok, Mei-Ching; Tanaka, Takashi; Ieda, Akimasa; Yoshikawa, Akimasa

2018-02-01

Understanding of underlying mechanisms of drastic variations of the near-Earth space (geospace) is one of the current focuses of the magnetospheric physics. The science target of the geospace research project Exploration of energization and Radiation in Geospace (ERG) is to understand the geospace variations with a focus on the relativistic electron acceleration and loss processes. In order to achieve the goal, the ERG project consists of the three parts: the Arase (ERG) satellite, ground-based observations, and theory/modeling/integrated studies. The role of theory/modeling/integrated studies part is to promote relevant theoretical and simulation studies as well as integrated data analysis to combine different kinds of observations and modeling. Here we provide technical reports on simulation and empirical models related to the ERG project together with their roles in the integrated studies of dynamic geospace variations. The simulation and empirical models covered include the radial diffusion model of the radiation belt electrons, GEMSIS-RB and RBW models, CIMI model with global MHD simulation REPPU, GEMSIS-RC model, plasmasphere thermosphere model, self-consistent wave-particle interaction simulations (electron hybrid code and ion hybrid code), the ionospheric electric potential (GEMSIS-POT) model, and SuperDARN electric field models with data assimilation. ERG (Arase) science center tools to support integrated studies with various kinds of data are also briefly introduced.[Figure not available: see fulltext.

Ephemeral Electric Potential and Electric Field Sensor

NASA Technical Reports Server (NTRS)

Generazio, Edward R. (Inventor)

2017-01-01

Systems, methods, and devices of the various embodiments provide for the minimization of the effects of intrinsic and extrinsic leakage electrical currents enabling true measurements of electric potentials and electric fields. In an embodiment, an ephemeral electric potential and electric field sensor system may have at least one electric field sensor and a rotator coupled to the electric field sensor and be configured to rotate the electric field sensor at a quasi-static frequency. In an embodiment, ephemeral electric potential and electric field measurements may be taken by rotating at least one electric field sensor at a quasi-static frequency, receiving electrical potential measurements from the electric field sensor when the electric field sensor is rotating at the quasi-static frequency, and generating and outputting images based at least in part on the received electrical potential measurements.

Variational calculations of subbands in a quantum well with uniform electric field - Gram-Schmidt orthogonalization approach

NASA Technical Reports Server (NTRS)

Ahn, Doyeol; Chuang, S. L.

1986-01-01

Variational calculations of subband eigenstates in an infinite quantum well with an applied electric field using Gram-Schmidt orthogonalized trial wave functions are presented. The results agree very well with the exact numerical solutions even up to 1200 kV/cm. It is also shown that, for increasing electric fields, the energy of the ground state decreases, while that of higher subband states increases slightly up to 1000 kV/cm and then decreases for a well size of 100 A.

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.

Dynamic linear modeling of monthly electricity demand in Japan: Time variation of electricity conservation effect

PubMed Central

Shiraki, Hiroto; Ashina, Shuichi

2018-01-01

After the severe nuclear disaster in Fukushima, which was triggered by the Great East Japan earthquake in March 2011, nuclear power plants in Japan were temporarily shut down for mandatory inspections. To prevent large-scale blackouts, the Japanese government requested companies and households to reduce electricity consumption in summer and winter. It is reported that the domestic electricity demand had a structural decrease because of the electricity conservation effect (ECE). However, quantitative analysis of the ECE is not sufficient, and especially time variation of the ECE remains unclear. Understanding the ECE is important because Japan’s NDC (nationally determined contribution) assumes the reduction of CO2 emissions through aggressive energy conservation. In this study, we develop a time series model of monthly electricity demand in Japan and estimate time variation of the ECE. Moreover, we evaluate the impact of electricity conservation on CO2 emissions from power plants. The dynamic linear model is used to separate the ECE from the effects of other irrelevant factors (e.g. air temperature, economic production, and electricity price). Our result clearly shows that consumers’ electricity conservation behavior after the earthquake was not temporary but became established as a habit. Between March 2011 and March 2016, the ECE on industrial electricity demand ranged from 3.9% to 5.4%, and the ECE on residential electricity demand ranged from 1.6% to 7.6%. The ECE on the total electricity demand was estimated at 3.2%–6.0%. We found a seasonal pattern that the residential ECE in summer is higher than that in winter. The emissions increase from the shutdown of nuclear power plants was mitigated by electricity conservation. The emissions reduction effect was estimated at 0.82 MtCO2–2.26 MtCO2 (−4.5% on average compared to the zero-ECE case). The time-varying ECE is necessary for predicting Japan’s electricity demand and CO2 emissions after the earthquake. PMID:29708988

Dynamic linear modeling of monthly electricity demand in Japan: Time variation of electricity conservation effect.

PubMed

Honjo, Keita; Shiraki, Hiroto; Ashina, Shuichi

2018-01-01

After the severe nuclear disaster in Fukushima, which was triggered by the Great East Japan earthquake in March 2011, nuclear power plants in Japan were temporarily shut down for mandatory inspections. To prevent large-scale blackouts, the Japanese government requested companies and households to reduce electricity consumption in summer and winter. It is reported that the domestic electricity demand had a structural decrease because of the electricity conservation effect (ECE). However, quantitative analysis of the ECE is not sufficient, and especially time variation of the ECE remains unclear. Understanding the ECE is important because Japan's NDC (nationally determined contribution) assumes the reduction of CO2 emissions through aggressive energy conservation. In this study, we develop a time series model of monthly electricity demand in Japan and estimate time variation of the ECE. Moreover, we evaluate the impact of electricity conservation on CO2 emissions from power plants. The dynamic linear model is used to separate the ECE from the effects of other irrelevant factors (e.g. air temperature, economic production, and electricity price). Our result clearly shows that consumers' electricity conservation behavior after the earthquake was not temporary but became established as a habit. Between March 2011 and March 2016, the ECE on industrial electricity demand ranged from 3.9% to 5.4%, and the ECE on residential electricity demand ranged from 1.6% to 7.6%. The ECE on the total electricity demand was estimated at 3.2%-6.0%. We found a seasonal pattern that the residential ECE in summer is higher than that in winter. The emissions increase from the shutdown of nuclear power plants was mitigated by electricity conservation. The emissions reduction effect was estimated at 0.82 MtCO2-2.26 MtCO2 (-4.5% on average compared to the zero-ECE case). The time-varying ECE is necessary for predicting Japan's electricity demand and CO2 emissions after the earthquake.

Global Potential for Hydro-generated Electricity and Climate Change Impact

NASA Astrophysics Data System (ADS)

Zhou, Y.; Hejazi, M. I.; Leon, C.; Calvin, K. V.; Thomson, A. M.; Li, H. Y.

2014-12-01

Hydropower is a dominant renewable energy source at the global level, accounting for more than 15% of the world's total power supply. It is also very vulnerable to climate change. Improved understanding of climate change impact on hydropower can help develop adaptation measures to increase the resilience of energy system. In this study, we developed a comprehensive estimate of global hydropower potential using runoff and stream flow data derived from a global hydrologic model with a river routing sub-model, along with turbine technology performance, cost assumptions, and environmental consideration (Figure 1). We find that hydropower has the potential to supply a significant portion of the world energy needs, although this potential varies substantially by regions. Resources in a number of countries exceed by multiple folds the total current demand for electricity, e.g., Russia and Indonesia. A sensitivity analysis indicates that hydropower potential can be highly sensitive to a number of parameters including designed flow for capacity, cost and financing, turbine efficiency, and stream flow. The climate change impact on hydropower potential was evaluated by using runoff outputs from 4 climate models (HadCM3, PCM, CGCM2, and CSIRO2). It was found that the climate change on hydropower shows large variation not only by regions, but also climate models, and this demonstrates the importance of incorporating climate change into infrastructure-planning at the regional level though the existing uncertainties.

Regulation of Cell Cytoskeleton and Membrane Mechanics by Electric Field: Role of Linker Proteins

PubMed Central

Titushkin, Igor; Cho, Michael

2009-01-01

Abstract Cellular mechanics is known to play an important role in the cell homeostasis including proliferation, motility, and differentiation. Significant variation in the mechanical properties between different cell types suggests that control of the cell metabolism is feasible through manipulation of the cell mechanical parameters using external physical stimuli. We investigated the electrocoupling mechanisms of cellular biomechanics modulation by an electrical stimulation in two mechanically distinct cell types—human mesenchymal stem cells and osteoblasts. Application of a 2 V/cm direct current electric field resulted in approximately a twofold decrease in the cell elasticity and depleted intracellular ATP. Reduction in the ATP level led to inhibition of the linker proteins that are known to physically couple the cell membrane and cytoskeleton. The membrane separation from the cytoskeleton was confirmed by up to a twofold increase in the membrane tether length that was extracted from the cell membrane after an electrical stimulation. In comparison to human mesenchymal stem cells, the membrane-cytoskeleton attachment in osteoblasts was much stronger but, in response to the same electrical stimulation, the membrane detachment from the cytoskeleton was found to be more pronounced. The observed effects mediated by an electric field are cell type- and serum-dependent and can potentially be used for electrically assisted cell manipulation. An in-depth understanding and control of the mechanisms to regulate cell mechanics by external physical stimulus (e.g., electric field) may have great implications for stem cell-based tissue engineering and regenerative medicine. PMID:19167316

Overview Of Impedance Sensors

NASA Astrophysics Data System (ADS)

Abele, John E.

1989-08-01

Electrical impedance has been one of the many "tools of great promise" that physicians have employed in their quest to measure and/or monitor body function or physiologic events. So far, the expectations for its success have always exceeded its performance. In simplistic terms, physiologic impedance is a measure of the resistance in the volume between electrodes which changes as a function of changes in that volume, the relative impedance of that volume, or a combination of these two. The history and principles of electrical impedance are very nicely reviewed by Geddes and Baker in their textbook "Principles of Applied Biomedical Instrumentation". It is humbling, however, to note that Cremer recorded variations in electrical impedance in frog hearts as early as 1907. The list of potential applications includes the measurement of thyroid function, estrogen activity, galvanic skin reflex, respiration, blood flow by conductivity dilution, nervous activity and eye movement. Commercial devices employing impedance have been and are being used to measure respiration (pneumographs and apneamonitors), pulse volume (impedance phlebographs) and even noninvasive cardiac output.

Shielded capacitive electrode

DOEpatents

Kireeff Covo, Michel

2013-07-09

A device is described, which is sensitive to electric fields, but is insensitive to stray electrons/ions and unlike a bare, exposed conductor, it measures capacitively coupled current while rejecting currents due to charged particle collected or emitted. A charged particle beam establishes an electric field inside the beam pipe. A grounded metallic box with an aperture is placed in a drift region near the beam tube radius. The produced electric field that crosses the aperture generates a fringe field that terminates in the back surface of the front of the box and induces an image charge. An electrode is placed inside the grounded box and near the aperture, where the fringe fields terminate, in order to couple with the beam. The electrode is negatively biased to suppress collection of electrons and is protected behind the front of the box, so the beam halo cannot directly hit the electrode and produce electrons. The measured signal shows the net potential (positive ion beam plus negative electrons) variation with time, as it shall be observed from the beam pipe wall.

Determination of efficiencies, loss mechanisms, and performance degradation factors in chopper controlled dc vehical motors. Section 2: The time dependent finite element modeling of the electromagnetic field in electrical machines: Methods and applications. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hamilton, H. B.; Strangas, E.

1980-01-01

The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.

Electrical detection of single viruses

NASA Astrophysics Data System (ADS)

Patolsky, Fernando; Zheng, Gengfeng; Hayden, Oliver; Lakadamyali, Melike; Zhuang, Xiaowei; Lieber, Charles M.

2004-09-01

We report direct, real-time electrical detection of single virus particles with high selectivity by using nanowire field effect transistors. Measurements made with nanowire arrays modified with antibodies for influenza A showed discrete conductance changes characteristic of binding and unbinding in the presence of influenza A but not paramyxovirus or adenovirus. Simultaneous electrical and optical measurements using fluorescently labeled influenza A were used to demonstrate conclusively that the conductance changes correspond to binding/unbinding of single viruses at the surface of nanowire devices. pH-dependent studies further show that the detection mechanism is caused by a field effect, and that the nanowire devices can be used to determine rapidly isoelectric points and variations in receptor-virus binding kinetics for different conditions. Lastly, studies of nanowire devices modified with antibodies specific for either influenza or adenovirus show that multiple viruses can be selectively detected in parallel. The possibility of large-scale integration of these nanowire devices suggests potential for simultaneous detection of a large number of distinct viral threats at the single virus level.

Designing lead-free antiferroelectrics for energy storage

PubMed Central

Xu, Bin; Íñiguez, Jorge; Bellaiche, L.

2017-01-01

Dielectric capacitors, although presenting faster charging/discharging rates and better stability compared with supercapacitors or batteries, are limited in applications due to their low energy density. Antiferroelectric (AFE) compounds, however, show great promise due to their atypical polarization-versus-electric field curves. Here we report our first-principles-based theoretical predictions that Bi1−xRxFeO3 systems (R being a lanthanide, Nd in this work) can potentially allow high energy densities (100–150 J cm−3) and efficiencies (80–88%) for electric fields that may be within the range of feasibility upon experimental advances (2–3 MV cm−1). In addition, a simple model is derived to describe the energy density and efficiency of a general AFE material, providing a framework to assess the effect on the storage properties of variations in doping, electric field magnitude and direction, epitaxial strain, temperature and so on, which can facilitate future search of AFE materials for energy storage. PMID:28555655

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

NASA Astrophysics Data System (ADS)

Jin, Jing; Tian, Hai-Ting; Pan, Xiong; Song, Ning-Fang

2010-03-01

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.

Simple Pixel Structure Using Video Data Correction Method for Nonuniform Electrical Characteristics of Polycrystalline Silicon Thin-Film Transistors and Differential Aging Phenomenon of Organic Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Hai-Jung In,; Oh-Kyong Kwon,

2010-03-01

A simple pixel structure using a video data correction method is proposed to compensate for electrical characteristic variations of driving thin-film transistors (TFTs) and the degradation of organic light-emitting diodes (OLEDs) in active-matrix OLED (AMOLED) displays. The proposed method senses the electrical characteristic variations of TFTs and OLEDs and stores them in external memory. The nonuniform emission current of TFTs and the aging of OLEDs are corrected by modulating video data using the stored data. Experimental results show that the emission current error due to electrical characteristic variation of driving TFTs is in the range from -63.1 to 61.4% without compensation, but is decreased to the range from -1.9 to 1.9% with the proposed correction method. The luminance error due to the degradation of an OLED is less than 1.8% when the proposed correction method is used for a 50% degraded OLED.

Wavelet analysis of corneal endothelial electrical potential difference reveals cyclic operation of the secretory mechanism.

PubMed

Cacace, V I; Montalbetti, N; Kusnier, C; Gomez, M P; Fischbarg, J

2011-09-01

The corneal endothelium is a fluid-transporting epithelium. As other similar tissues, it displays an electrical potential of ~1 mV (aqueous side negative) across the entire layer [transendothelial potential difference (TEPD)]. It appears that this electrical potential is mainly the result of the transport of anions across the cell layer (from stroma to aqueous). There is substantial evidence that the TEPD is related linearly to fluid transport; hence, under proper conditions, its measure could serve as a measure of fluid transport. Furthermore, the TEPD is not steady; instead, it displays a spectrum of frequency components (0-15 Hz) recognized recently using Fourier transforms. Such frequency components appear due to charge-separating (electrogenic) processes mediated by epithelial plasma membrane proteins (both ionic channels and ionic cotransporters). In particular, the endothelial TEPD oscillations of the highest amplitude (1-2 Hz) were linked to the operation of so-called sodium bicarbonate cotransporters. However, no time localization of that activity could be obtained with the Fourier methodology utilized. For that reason we now characterize the TEPD using wavelet analysis with the aim to localize in time the variations in TEPD. We find that the mentioned high-amplitude oscillatory components of the TEPD appear cyclically during the several hours that an endothelial preparation survives in vitro. They have a period of 4.6 ± 0.4 s on average (n=4). The wavelet power value at the peak of such oscillations is 1.5 ± 0.1 mV(2) Hz on average (n = 4), and is remarkably narrow in its distribution.

A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

PubMed Central

Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

2016-01-01

Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced. PMID:27527179

Three-dimensional current flow in a large-scale model of the cochlea and the mechanism of amplification of sound.

PubMed

Mistrík, Pavel; Mullaley, Chris; Mammano, Fabio; Ashmore, Jonathan

2009-03-06

The mammalian inner ear uses its sensory hair cells to detect and amplify incoming sound. It is unclear whether cochlear amplification arises uniquely from a voltage-dependent mechanism (electromotility) associated with outer hair cells (OHCs) or whether other mechanisms are necessary, for the voltage response of OHCs is apparently attenuated excessively by the membrane electrical filter. The cochlea contains many thousands of hair cells organized in extensive arrays, embedded in an electrically coupled system of supporting cells. We have therefore constructed a multi-element, large-scale computational model of cochlear sound transduction to study the underlying potassium (K+) recirculation. We have included experimentally determined parameters of cochlear macromechanics, which govern sound transduction, and data on hair cells' electrical parameters including tonotopical variation in the membrane conductance of OHCs. In agreement with the experiment, the model predicts an exponential decay of extracellular longitudinal K+ current spread. In contrast to the predictions from isolated cells, it also predicts low attenuation of the OHC transmembrane receptor potential (-5 dB per decade) in the 0.2-30 kHz range. This suggests that OHC electromotility could be driven by the transmembrane potential. Furthermore, the OHC electromotility could serve as a single amplification mechanism over the entire hearing range.

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

PubMed

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

2017-06-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-06-01

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

On-Chip Electrophoresis in Supported Lipid Bilayer Membranes Achieved Using Low Potentials

PubMed Central

2013-01-01

A micro supported lipid bilayer (SLB) electrophoresis method was developed, which functions at low potentials and appreciable operating times. To this end, (hydroxymethyl)-ferrocene (FcCH2OH) was employed to provide an electrochemical reaction at the anode and cathode at low applied potential to avoid electrolysis of water. The addition of FcCH2OH did not alter the SLB characteristics or affect biomolecule function, and pH and temperature variations and bubble formation were eliminated. Applying potentials of 0.25–1.2 V during flow gave homogeneous electrical fields and a fast, reversible, and strong build-up of a charged dye-modified lipid in the direction of the oppositely charged electrode. Moreover, streptavidin mobility could be modulated. This method paves the way for further development of analytical devices. PMID:24345193

Thermal modeling of the lithium/polymer battery

NASA Astrophysics Data System (ADS)

Pals, C. R.

1994-10-01

Research in the area of advanced batteries for electric-vehicle applications has increased steadily since the 1990 zero-emission-vehicle mandate of the California Air Resources Board. Due to their design flexibility and potentially high energy and power densities, lithium/polymer batteries are an emerging technology for electric-vehicle applications. Thermal modeling of lithium/polymer batteries is particularly important because the transport properties of the system depend exponentially on temperature. Two models have been presented for assessment of the thermal behavior of lithium/polymer batteries. The one-cell model predicts the cell potential, the concentration profiles, and the heat-generation rate during discharge. The cell-stack model predicts temperature profiles and heat transfer limitations of the battery. Due to the variation of ionic conductivity and salt diffusion coefficient with temperature, the performance of the lithium/polymer battery is greatly affected by temperature. Because of this variation, it is important to optimize the cell operating temperature and design a thermal management system for the battery. Since the thermal conductivity of the polymer electrolyte is very low, heat is not easily conducted in the direction perpendicular to cell layers. Temperature profiles in the cells are not as significant as expected because heat-generation rates in warmer areas of the cell stack are lower than heat-generation rates in cooler areas of the stack. This nonuniform heat-generation rate flattens the temperature profile. Temperature profiles as calculated by this model are not as steep as those calculated by previous models that assume a uniform heat-generation rate.

Hy-wire measurements of atmospheric potential

NASA Astrophysics Data System (ADS)

Holzworth, Robert H.

1984-02-01

A method of directly measuring the electric potential drop across the lowest portion of the atmosphere by using an apparatus called Hy-wire is described. This tethered balloon-borne system has been operated extensively at altitudes near 0.62 km at which voltages over 150 k V were measured with a high impedance device. Also described are measurements of system parameters such as system capacitance (5.6 pf/m), impedance (1010Ω), and response time (tens of seconds). Hy-wire measurements from an around the-clock experiment at Wallops Island, Va., having a characteristic repetitive diurnal pattern of variability exceeding 40% of the mean, are presented. This diurnal pattern is discussed in terms of both local and global current sources. A demonstration using Hy-wire as a lightning channel model is also presented. These experiments have so far been conducted at mid-latitudes but can also be flown from other locations in an effort to determine whether the lowest atmospheric electric circuit is affected by high altitude and possibly global current systems, and if so how much. The data presented in this paper are not definitive about the source of potential variations. The data are, however, representative of the new Hy-wire technique and demonstrative of the potential usefulness of this technique.

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

PubMed

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

2010-09-01

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

Ionospheric response to 17 March 2013 geomagnetic storm identified by data assimilation result

NASA Astrophysics Data System (ADS)

Yue, Xinan; Zhao, Biqiang; Hu, Lianhuan; She, Chengli

2017-04-01

Based on slant total electron content (TEC) observations made by 10 satellites and 450 ground IGS GNSS stations, we constructed a 4-D ionospheric electron density reanalysis during the March 17, 2013 geomagnetic storm. Four main large-scale ionospheric disturbances are identified from reanalysis: (1) The positive storm during the initial phase; (2) The SED (storm enhanced density) structure in both northern and southern hemisphere; (3) The large positive storm in main phase; (4) The significant negative storm in middle and low latitude during recovery phase. We then run the NCAR-TIEGCM model with Heelis electric potential empirical model as polar input. The TIEGCM can reproduce 3 of 4 large-scale structures (except SED) very well. We then further analyzed the altitudinal variations of these large-scale disturbances and found several interesting things, such as the altitude variation of SED, the rotation of positive/negative storm phase with local time. Those structures could not be identified clearly by traditional used data sources, which either has no global coverage or no vertical resolution. The drivers such as neutral wind/density and electric field from TIEGCM simulations are also analyzed to self-consistently explain the identified disturbance features.

Large Scale Ionospheric Response During March 17, 2013 Geomagnetic Storm: Reanalysis Based on Multiple Satellites Observations and TIEGCM Simulations

NASA Astrophysics Data System (ADS)

Yue, X.; Wang, W.; Schreiner, W. S.; Kuo, Y. H.; Lei, J.; Liu, J.; Burns, A. G.; Zhang, Y.; Zhang, S.

2015-12-01

Based on slant total electron content (TEC) observations made by ~10 satellites and ~450 ground IGS GNSS stations, we constructed a 4-D ionospheric electron density reanalysis during the March 17, 2013 geomagnetic storm. Four main large-scale ionospheric disturbances are identified from reanalysis: (1) The positive storm during the initial phase; (2) The SED (storm enhanced density) structure in both northern and southern hemisphere; (3) The large positive storm in main phase; (4) The significant negative storm in middle and low latitude during recovery phase. We then run the NCAR-TIEGCM model with Heelis electric potential empirical model as polar input. The TIEGCM can reproduce 3 of 4 large-scale structures (except SED) very well. We then further analyzed the altitudinal variations of these large-scale disturbances and found several interesting things, such as the altitude variation of SED, the rotation of positive/negative storm phase with local time. Those structures could not be identified clearly by traditional used data sources, which either has no gloval coverage or no vertical resolution. The drivers such as neutral wind/density and electric field from TIEGCM simulations are also analyzed to self-consistantly explain the identified disturbance features.

Correlation of ISS Electric Potential Variations with Mission Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda Neergaard

2014-01-01

Orbiting approximately 400 km above the Earth, the International Space Station (ISS) is a unique research laboratory used to conduct ground-breaking science experiments in space. The ISS has eight Solar Array Wings (SAW), and each wing is 11.7 meters wide and 35.1 meters long. The SAWs are controlled individually to maximize power output, minimize stress to the ISS structure, and minimize interference with other ISS operations such as vehicle dockings and Extra-Vehicular Activities (EVA). The Solar Arrays are designed to operate at 160 Volts. These large, high power solar arrays are negatively grounded to the ISS and collect charged particles (predominately electrons) as they travel through the space plasma in the Earth's ionosphere. If not controlled, this collected charge causes floating potential variations which can result in arcing, causing injury to the crew during an EVA or damage to hardware [1]. The environmental catalysts for ISS floating potential variations include plasma density and temperature fluctuations and magnetic induction from the Earth's magnetic field. These alone are not enough to cause concern for ISS, but when they are coupled with the large positive potential on the solar arrays, floating potentials up to negative 95 Volts have been observed. Our goal is to differentiate the operationally induced fluctuations in floating potentials from the environmental causes. Differentiating will help to determine what charging can be controlled, and we can then design the proper operations controls for charge collection mitigation. Additionally, the knowledge of how high power solar arrays interact with the environment and what regulations or design techniques can be employed to minimize charging impacts can be applied to future programs.

An Integration of Geophysical Methods to Explore Buried Structures on the Bench and in the Field

NASA Astrophysics Data System (ADS)

Booterbaugh, A. P.; Lachhab, A.

2011-12-01

In the following study, an integration of geophysical methods and devices were implemented on the bench and in the field to accurately identify buried structures. Electrical resistivity and ground penetrating radar methods, including both a fabricated electrical resistivity apparatus and an electrical resistivity device were all used in this study. The primary goal of the study was to test the accuracy and reliability of the apparatus which costs a fraction of the price of a commercially sold resistivity instrument. The apparatus consists of four electrodes, two multimeters, a 12-volt battery, a DC to AC inverter and wires. Using this apparatus, an electrical current, is injected into earth material through the outer electrodes and the potential voltage is measured across the inner electrodes using a multimeter. The recorded potential and the intensity of the current can then be used to calculate the apparent resistivity of a given material. In this study the Wenner array, which consists of four equally spaced electrodes, was used due to its higher accuracy and greater resolution when investigating lateral variations of resistivity in shallow depths. In addition, the apparatus was used with an electrical resistivity device and a ground penetrating radar unit to explore the buried building foundation of Gustavus Adolphus Hall located on Susquehanna University Campus, Selinsgrove, PA. The apparatus successfully produced consistent results on the bench level revealing the location of small bricks buried under a soil material. In the summer of 2010, seventeen electrical resistivity transects were conducted on the Gustavus Adolphus site where and revealed remnants of the foundation. In the summer of 2011, a ground penetrating radar survey and an electrical resistivity tomography survey were conducted to further explore the site. Together these methods identified the location of the foundation and proved that the apparatus was a reliable tool for regular use on the bench and in the field.

Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency

PubMed Central

An, Ran; Massa, Katherine

2014-01-01

AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H+] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H+] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial position. PMID:25553200

Rapid systemic up-regulation of genes after heat-wounding and electrical stimulation

NASA Technical Reports Server (NTRS)

Davies, E.; Vian, A.; Vian, C.; Stankovic, B.

1997-01-01

When one leaf of a tomato plant is electrically-stimulated or heat-wounded, proteinase inhibitor genes are rapidly up-regulated in distant leaves. The identity of the systemic wound signal(s) is not yet known, but major candidates include hormones transmitted via the phloem or the xylem, the electrically-stimulated self-propagating electrical signal in the phloem (the action potential, AP), or the heat-wound-induced surge in hydraulic pressure in the xylem evoking a local change in membrane potential in adjacent living cells (the variation potential, VP). In order to discriminate between these signals we have adopted two approaches. The first approach involves applying stimuli that evoke known signals and determining whether these signals have similar effects on the "model" transcripts for proteinase inhibitors (pin) and calmodulin (cal). Here we show that a heat wound almost invariably evokes a VP, while an electrical stimulation occasionally evokes an AP, and both of these signals induce accumulation of transcripts encoding proteinase inhibitors. The second approach involves identifying the array of genes turned on by heat-wounding. To this end, we have constructed a subtractive library for heat-wounded tissue, isolated over 800 putatively up-regulated clones, and shown that all but two of the fifty that we have analyzed by Northern hybridization are, indeed, up-regulated. Here we show the early kinetics of up-regulation of three of these transcripts in the terminal (4th) leaf in response to heat-wounding the 3rd leaf, about 5 cm away. Even though these transcripts show somewhat different time courses of induction, with one peaking at 30 min, another at 15 min, and another at 5 min after flaming of a distant leaf, they all exhibit a similar pattern, i.e., a transient period of transcript accumulation preceding a period of transcript decrease, followed by a second period of transcript accumulation.

Waste Heat Recovery from High Temperature Off-Gases from Electric Arc Furnace

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

Nimbalkar, Sachin U; Thekdi, Arvind; Keiser, James R

2014-01-01

This article presents a study and review of available waste heat in high temperature Electric Arc Furnace (EAF) off gases and heat recovery techniques/methods from these gases. It gives details of the quality and quantity of the sensible and chemical waste heat in typical EAF off gases, energy savings potential by recovering part of this heat, a comprehensive review of currently used waste heat recovery methods and potential for use of advanced designs to achieve a much higher level of heat recovery including scrap preheating, steam production and electric power generation. Based on our preliminary analysis, currently, for all electricmore » arc furnaces used in the US steel industry, the energy savings potential is equivalent to approximately 31 trillion Btu per year or 32.7 peta Joules per year (approximately $182 million US dollars/year). This article describes the EAF off-gas enthalpy model developed at Oak Ridge National Laboratory (ORNL) to calculate available and recoverable heat energy for a given stream of exhaust gases coming out of one or multiple EAF furnaces. This Excel based model calculates sensible and chemical enthalpy of the EAF off-gases during tap to tap time accounting for variation in quantity and quality of off gases. The model can be used to estimate energy saved through scrap preheating and other possible uses such as steam generation and electric power generation using off gas waste heat. This article includes a review of the historical development of existing waste heat recovery methods, their operations, and advantages/limitations of these methods. This paper also describes a program to develop and test advanced concepts for scrap preheating, steam production and electricity generation through use of waste heat recovery from the chemical and sensible heat contained in the EAF off gases with addition of minimum amount of dilution or cooling air upstream of pollution control equipment such as bag houses.« less

20∶60∶20 - Differences in Energy Behaviour and Conservation between and within Households with Electricity Monitors

PubMed Central

Murtagh, Niamh; Gatersleben, Birgitta; Uzzell, David

2014-01-01

The introduction of electricity monitors (in-home displays; IHDs), which show accurate and up-to-the-minute energy usage, is expected to lead to reduction in consumption. Studies of feedback on domestic electricity use have generally supported this view. However, such studies also demonstrate wide variation between households. Examining the heterogeneity of responses is essential for understanding the actual and potential effectiveness of IHDs and in order to target interventions effectively. To explore differences between households' responses to IHDs, we conducted a qualitative study with 21 households who had an IHD for more than six months. Of the 21, only four households continued to refer to the IHD and the findings suggest that attempts to reduce energy consumption were situated in wider social and physical contexts. Further, the participants demonstrated energy saving behaviour before and outside of IHD usage. The patterns of energy behaviours and attempts at electricity conservation could best be understood by categorising the households into three types: the Monitor Enthusiasts (20%), the Aspiring Energy Savers (60%) and the Energy Non-Engaged (20%). The factors of importance in energy behaviour differed between the categories. Financial savings contributed to efforts to reduce energy use but only up to boundaries which varied considerably between households. Social practices and social relationships appeared to constrain what actions households were prepared to undertake, illuminating aspects of inter-household variation. Within the household, all energy users were not equal and we found that women were particularly influential on energy use through their primary responsibility for domestic labour on behalf of the household. The implications of the findings for environmental campaigning are discussed. PMID:24642946

20:60:20--differences in energy behaviour and conservation between and within households with electricity monitors.

PubMed

Murtagh, Niamh; Gatersleben, Birgitta; Uzzell, David

2014-01-01

The introduction of electricity monitors (in-home displays; IHDs), which show accurate and up-to-the-minute energy usage, is expected to lead to reduction in consumption. Studies of feedback on domestic electricity use have generally supported this view. However, such studies also demonstrate wide variation between households. Examining the heterogeneity of responses is essential for understanding the actual and potential effectiveness of IHDs and in order to target interventions effectively. To explore differences between households' responses to IHDs, we conducted a qualitative study with 21 households who had an IHD for more than six months. Of the 21, only four households continued to refer to the IHD and the findings suggest that attempts to reduce energy consumption were situated in wider social and physical contexts. Further, the participants demonstrated energy saving behaviour before and outside of IHD usage. The patterns of energy behaviours and attempts at electricity conservation could best be understood by categorising the households into three types: the Monitor Enthusiasts (20%), the Aspiring Energy Savers (60%) and the Energy Non-Engaged (20%). The factors of importance in energy behaviour differed between the categories. Financial savings contributed to efforts to reduce energy use but only up to boundaries which varied considerably between households. Social practices and social relationships appeared to constrain what actions households were prepared to undertake, illuminating aspects of inter-household variation. Within the household, all energy users were not equal and we found that women were particularly influential on energy use through their primary responsibility for domestic labour on behalf of the household. The implications of the findings for environmental campaigning are discussed.

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

NASA Astrophysics Data System (ADS)

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

2018-06-01

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

Electrostatic and magnetic fields in bilayer graphene

NASA Astrophysics Data System (ADS)

Jellal, Ahmed; Redouani, Ilham; Bahlouli, Hocine

2015-08-01

We compute the transmission probability through rectangular potential barriers and p-n junctions in the presence of a magnetic and electric fields in bilayer graphene taking into account contributions from the full four bands of the energy spectrum. For energy E higher than the interlayer coupling γ1 (E >γ1) two propagation modes are available for transport giving rise to four possible ways for transmission and reflection coefficients. However, when the energy is less than the height of the barrier the Dirac fermions exhibit transmission resonances and only one mode of propagation is available for transport. We study the effect of the interlayer electrostatic potential denoted by δ and variations of different barrier geometry parameters on the transmission probability.

Tests of Convection Electric Field Models For The January 10, 1997, Geomagnetic Storm

NASA Astrophysics Data System (ADS)

Jordanova, V.; Boonsiriseth, A.; Thorne, R.; Dotan, Y.

The January 10-11, 1997, geomagnetic storm was caused by the passage at Earth of a magnetic cloud with a negative to positive Bz variation extending for 1 day. The ge- omagnetic indices had values of minimum Dst=-83 nT and maximum Kp=6 during the period of southward IMF within the cloud. We simulate ring current development during this storm using our kinetic drift-loss model and compare the results inferred from Volland-Stern type, Weimer, and AMIE convection electric field models. A pen- etration electric field is added to the AMIE model [Boonsiriseth et al., 2001] in order to improve the agreement with measurements from the electric field instrument on Po- lar spacecraft. The ionospheric electric potentials are mapped to the equatorial plane using the Tsyganenko 1996 magnetic field model and the resulting equatorial poten- tial models are coupled with our ring current model. While the temporal evolution of the large-scale features is similar in all three convection models, detailed comparison indicates that AMIE model shows highly variable small-scale features not present in the Volland-Stern or Weimer convection models. Results from our kinetic ring current model are compared with energetic particle data from the HYDRA, TIMAS, IPS, and CAMMICE instruments on Polar to test the applicability of the convection electric field models for this storm period.

30 CFR 57.12011 - High-potential electrical conductors.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false High-potential electrical conductors. 57.12011... Electricity Surface and Underground § 57.12011 High-potential electrical conductors. High-potential electrical conductors shall be covered, insulated, or placed to prevent contact with low potential conductors. ...

30 CFR 57.12011 - High-potential electrical conductors.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false High-potential electrical conductors. 57.12011... Electricity Surface and Underground § 57.12011 High-potential electrical conductors. High-potential electrical conductors shall be covered, insulated, or placed to prevent contact with low potential conductors. ...

The propagation of ion-acoustic waves carrying orbital angular momentum in the electron-positron-ion plasmas

NASA Astrophysics Data System (ADS)

Mehdian, H.; Nobahar, D.; Hajisharifi, K.

2018-02-01

Ion-acoustic (IA) waves carrying orbital angular momentum (OAM) are investigated in an unmagnetized, uniform, and collisionless electron-positron-ion (e-p-i) plasma system. Employing the hydrodynamic theory, the paraxial equation in term of ion perturbed number density is derived and discussed about its Laguerre-Gaussian (LG) beam solutions. Obtaining an approximate solution for the electrostatic potential, the IA wave characteristics including helical electric field structure, energy density, and OAM density are theoretically studied. Based on the numerical analysis, the effects of positron concentration, radial and angular mode number as well as beam waist on the obtained potential profile are investigated. It is shown that the depth (height) and width of the LG potential profile wells (barriers) are considerably modify by the variation of positron concentration.

RichMol: A general variational approach for rovibrational molecular dynamics in external electric fields

NASA Astrophysics Data System (ADS)

Owens, Alec; Yachmenev, Andrey

2018-03-01

In this paper, a general variational approach for computing the rovibrational dynamics of polyatomic molecules in the presence of external electric fields is presented. Highly accurate, full-dimensional variational calculations provide a basis of field-free rovibrational states for evaluating the rovibrational matrix elements of high-rank Cartesian tensor operators and for solving the time-dependent Schrödinger equation. The effect of the external electric field is treated as a multipole moment expansion truncated at the second hyperpolarizability interaction term. Our fully numerical and computationally efficient method has been implemented in a new program, RichMol, which can simulate the effects of multiple external fields of arbitrary strength, polarization, pulse shape, and duration. Illustrative calculations of two-color orientation and rotational excitation with an optical centrifuge of NH3 are discussed.

Potential Arbitrage Revenue of Energy Storage Systems in PJM

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

Salles, Mauricio; Huang, Junling; Aziz, Michael

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), the largest U.S. regional transmission organization, using hourly locational marginal prices over the seven-year period 2008–2014. Assuming a price-taking ESS with perfect foresight in the real-time market, we optimized the charge-discharge profile to determine the maximum potential revenue for a 1 MW system as a function of energy/power ratio, or rated discharge duration, from 1 to 14more » h, including a limited analysis of sensitivity to round-trip efficiency. We determined minimum potential revenue with a similar analysis of the day-ahead market. We presented the distribution over the set of nodes and years of price, price volatility, and maximum potential arbitrage revenue. From these results, we determined the break even overnight installed cost of an ESS below which arbitrage would be profitable, its dependence on rated discharge duration, its distribution over grid nodes, and its variation over the years. We showed that dispatch into real-time markets based on day-ahead market settlement prices is a simple, feasible method that raises the lower bound on the achievable arbitrage revenue.« less

Potential Arbitrage Revenue of Energy Storage Systems in PJM

DOE PAGES

Salles, Mauricio; Huang, Junling; Aziz, Michael; ...

2017-07-27

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), the largest U.S. regional transmission organization, using hourly locational marginal prices over the seven-year period 2008–2014. Assuming a price-taking ESS with perfect foresight in the real-time market, we optimized the charge-discharge profile to determine the maximum potential revenue for a 1 MW system as a function of energy/power ratio, or rated discharge duration, from 1 to 14more » h, including a limited analysis of sensitivity to round-trip efficiency. We determined minimum potential revenue with a similar analysis of the day-ahead market. We presented the distribution over the set of nodes and years of price, price volatility, and maximum potential arbitrage revenue. From these results, we determined the break even overnight installed cost of an ESS below which arbitrage would be profitable, its dependence on rated discharge duration, its distribution over grid nodes, and its variation over the years. We showed that dispatch into real-time markets based on day-ahead market settlement prices is a simple, feasible method that raises the lower bound on the achievable arbitrage revenue.« less

Variation in electrical properties of gamma irradiated cadmium selenate nanowires

NASA Astrophysics Data System (ADS)

Chauhan, R. P.; Rana, Pallavi; Narula, Chetna; Panchal, Suresh; Choudhary, Ritika

2016-07-01

Preparation of low-dimensional materials attracts more and more interest in the last few years, mainly due to the wide field of potential commercial applications ranging from life sciences, medicine and biotechnology to communication and electronics. One-dimensional systems are the smallest dimension structures that can be used for efficient transport of electrons and thus expected to be critical to the function and integration of nanoscale devices. Nanowires with well controlled morphology and extremely high aspect ratio can be obtained by replicating a nanoporous polymer ion-track membrane with cylindrical pores of controlled dimensions. With this technique, materials can be deposited within the pores of the membrane by electrochemical reduction of the desired ion. In the present study, cadmium selenate nanowires were synthesized potentiostatically via template method. These synthesized nanowires were then exposed to gamma rays by using a 60Co source at the Inter University Accelerator Centre, New Delhi, India. Structural, morphological, electrical and elemental characterizations were made in order to analyze the effect of gamma irradiation on the synthesized nanowires. I-V measurements of cadmium selenate nanowires, before and after irradiation were made with the help of Keithley 2400 source meter and Ecopia probe station. A significant change in the electrical conductivity of cadmium selenate nanowires was found after gamma irradiation. The crystallography of the synthesized nanowires was also studied using a Rigaku X-ray diffractrometer equipped with Cu-Kα radiation. XRD patterns of irradiated samples showed no variation in the peak positions or phase change.

Influence of temperature on the electrical conductivity of leachate from municipal solid waste.

PubMed

Grellier, Solenne; Robain, Henri; Bellier, Gérard; Skhiri, Nathalie

2006-09-01

A bioreactor landfill is designed to manage municipal solid waste, through accelerated waste biodegradation, and stabilisation of the process by means of the controlled addition of liquid, i.e. leachate recirculation. The measurement of electrical resistivity by Electrical Resistivity Tomography (ERT) allows to monitor water content present in the bioreactors. Variations in electrical resistivity are linked to variations in moisture content and temperature. In order to overcome this ambiguity, two laboratory experiments were carried out to establish a relationship between temperature and electrical conductivity: the first set of measurements was made for leachate alone, whereas the second set was made with two different granular media saturated with leachate. Both experiments confirm a well known increase in conductivity of about 2% degrees C(-1). However, higher suspended matter concentrations lead to a lower dependence of electrical conductivity on temperature. Furthermore, for various porous media saturated with an identical leachate, the higher the specific surface of the granular matrix, the lower the effective bulk electrical conductivity. These observations show that a correct understanding of the electrical properties of liquids requires the nature and (in particular) the size of the electrical charge carriers to be taken into account.

COMSOL based Simulation on the Effect of Electric Field changes due to Lightning on Ground

NASA Astrophysics Data System (ADS)

Premlet, B.; Joby, N. E.; Sabu, S.

2017-12-01

The phenomenon of lightning is accompanied by localised changes in atmospheric electric fields. In cloud-to-ground strike locations, changes in atmospheric electric fields can even be observed at the ground a few minutes prior to a strike. A lot of research has been done already on the electrostatic changes prior to lightning in the region above ground. Through this work, we investigate into the effects of lightning electric fields on/under ground with the aid of simulations done in COMSOL Multiphysics. Horizontal and vertical profiles of voltage gradient, electric field, polarisation etc. are investigated. Simulation experiments were conducted using a general model of lightning electric fields formed using data recorded by the Electric Field Mills(EFMs) from three diverse parts of the world- Kennedy Space Centre (KSC),Florida (Using GHRC datasets),Sonnblick Observatory, Austria and National Centre for Earth Science Studies Trivandrum (NCESS),India. COMSOL models of the global electric circuit were developed using Sandstone as the base model for ground. Similar works in literature have only dealt with lightning electric fields above the ground. This work is the first step towards a high-level simulation on the effects of atmospheric electric field on/below ground. The results of this simulation work can aid lightning forecasting and preparedness by opening new doors for voltage based prediction methods at ground. It is also a tool to understand phenomena such as fulgurites, corona effect etc. It also helps in the design of buried cables and improved grounding systems. This work can also be a first step towards understanding localised potential variations at the ground during lightning.

Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations

PubMed Central

Velikonja, Aljaž; Perutkova, Šarka; Gongadze, Ekaterina; Kramar, Peter; Polak, Andraž; Maček-Lebar, Alenka; Iglič, Aleš

2013-01-01

The lipid bilayer is a basic building block of biological membranes and can be pictured as a barrier separating two compartments filled with electrolyte solution. Artificial planar lipid bilayers are therefore commonly used as model systems to study the physical and electrical properties of the cell membranes in contact with electrolyte solution. Among them the glycerol-based polar phospholipids which have dipolar, but electrically neutral head groups, are most frequently used in formation of artificial lipid bilayers. In this work the electrical properties of the lipid layer composed of zwitterionic lipids with non-zero dipole moments are studied theoretically. In the model, the zwitterionic lipid bilayer is assumed to be in contact with aqueous solution of monovalent salt ions. The orientational ordering of water, resulting in spatial variation of permittivity, is explicitly taken into account. It is shown that due to saturation effect in orientational ordering of water dipoles the relative permittivity in the zwitterionic headgroup region is decreased, while the corresponding electric potential becomes strongly negative. Some of the predictions of the presented mean-field theoretical consideration are critically evaluated using the results of molecular dynamics (MD) simulation. PMID:23434651

Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

NASA Astrophysics Data System (ADS)

Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

2016-02-01

Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Ab initio design of laser pulses to control molecular motion

NASA Astrophysics Data System (ADS)

Balint-Kurti, Gabriel; Ren, Qinghua; Manby, Frederick; Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel; Zou, Shiyang; Singh, Harjinder

2007-03-01

Our recent attempts to design laser pulses entirely theoretically, in a quantitative and accurate manner, so as to fully understand the underlying mechanisms active in the control process will be outlined. We have developed a new Born-Oppenheimer like separation called the electric-nuclear Born-Oppenheimer (ENBO) approximation. In this approximation variations of both the nuclear geometry and of the external electric field are assumed to be slow compared with the speed at which the electronic degrees of freedom respond to these changes. This assumption permits the generation of a potential energy surface that depends not only on the relative geometry of the nuclei, but also on the electric field strength and on the orientation of the molecule with respect to the electric field. The range of validity of the ENBO approximation is discussed. Optimal control theory is used along with the ENBO approximation to design laser pulses for exciting vibrational and rotational motion in H2 and CO molecules. Progress on other applications, including controlling photodissociation processes, isotope separation, stabilization of molecular Bose-Einstein condensates as well as applications to biological molecules also be presented. *Support acknowledged from EPSRC.

Physicochemical Properties of Cartilage in the Light of Ion Exchange Theory

PubMed Central

Maroudas, Alice

1968-01-01

Ion exchange theory has been applied to articular cartilage. Relationships were derived between permeability, diffusivity, electrical conductivity, and streaming potential. Systematic measurements were undertaken on these properties. Experimental techniques are described and data tabulated. Theoretical correlations were found to hold within the experimental error. The concentration of fixed negatively-charged groups in cartilage was shown to be the most important parameter. Fixed charge density was found to increase with distance from the articular surface and this variation was reflected in the other properties. PMID:5699797

Thermodynamic potentials in anisotropic and nonlinear dielectrics

NASA Astrophysics Data System (ADS)

Parravicini, Jacopo

2018-07-01

The variation of total energy, entropy, Helmoltz free energy due to the application of a static electric field is calculated and discussed, under suitable conditions, in the case of a dielectric with either anisotropic or nonlinear response. The proposed approach starts from Fröhlich's theory of dielectric thermodynamics and, by analyzing its assumptions, provides a method to generalize it. The obtained relationships can be employed for describing the thermodynamics of different classes of dielectric materials, also in experimental investigations. Specifically, the anisotropy and nonlinearity conditions are considered and relative examples are indicated and discussed.

The Auroral Particles experiment

NASA Technical Reports Server (NTRS)

1981-01-01

An instrument for the detection of particles in the energy range of 0.1 ev to 80 Kev was designed, built, tested, calibrated, and flown onboard the spacecraft ATS-6. Data from this instrument generated the following research: intensive studies of the plasma in the vicinity of the spacecraft; global variations of plasmas; correlative studies using either other spacecraft or ground based measurements; and studies of spacecraft interactions with ambient plasmas including charging, local electric fields due to differential charging, and active control of spacecraft potential. Results from this research are presented.

Photo-ionization cross-section of donor-related in (In,Ga)N/GaN core/shell under hydrostatic pressure and electric field effects

NASA Astrophysics Data System (ADS)

El Ghazi, Haddou; John Peter, A.

2017-04-01

Hydrogenic-like donor-impurity related self and induced polarizations, bending energy and photo-ionization cross section in spherical core/shell zinc blende (In,Ga)N/GaN are computed. Based on the variational approach and within effective-mass and one parabolic approximations, the calculations are made under finite potential barrier taking into account of the discontinuity of the effective-mass and the constant dielectric. The photo-ionization cross section is studied according to the photon incident energy considering the effects of hydrostatic pressure, applied electric field, structure's radius, impurity's position and indium composition in the core. It is obtained that the influences mentioned above lead to either blue shifts or redshifts of the resonant peak of the photo-ionization cross section spectrum. The unusual behavior related to the structure radius is discussed which is as a consequence of the finite potential confinement. We have shown that the photo-ionization cross section can be controlled with adjusting the internal and external factors. These properties can be useful for producing some device applications such as quantum dot infrared photodetectors.

Ion-mediated enhancement of xylem hydraulic conductivity in four Acer species: relationships with ecological and anatomical features.

PubMed

Nardini, Andrea; Dimasi, Federica; Klepsch, Matthias; Jansen, Steven

2012-12-01

The 'ionic effect', i.e., changes in xylem hydraulic conductivity (k(xyl)) due to variation of the ionic sap composition in vessels, was studied in four Acer species growing in contrasting environments differing in water availability. Hydraulic measurements of the ionic effect were performed together with measurements on the sap electrical conductivity, leaf water potential and vessel anatomy. The low ionic effect recorded in Acer pseudoplatanus L. and Acer campestre L. (15.8 and 14.7%, respectively), which represented two species from shady and humid habitats, was associated with a low vessel grouping index, high sap electrical conductivity and least negative leaf water potential. Opposite traits were found for Acer monspessulanum L. and Acer platanoides L., which showed an ionic effect of 23.6 and 23.1%, respectively, and represent species adapted to higher irradiance and/or lower water availability. These findings from closely related species provide additional support that the ionic effect could function as a compensation mechanism for embolism-induced loss of k(xyl), either as a result of high evaporative demand or increased risk of hydraulic failure.

The Thomas-Fermi model in the theory of systems of charged particles above the surface of liquid dielectrics

NASA Astrophysics Data System (ADS)

Lytvtnenko, D. M.; Slyusarenko, Yu. V.; Kirdin, A. I.

2012-10-01

A consistent theory of equilibrium states of same sign charges above the surface of liquid dielectric film located on solid substrate in the presence of external attracting constant electric field is proposed. The approach to the development of the theory is based on the Thomas-Fermi model generalized to the systems under consideration and on the variational principle. The using of self-consistent field model allows formulating a theory containing no adjustable constants. In the framework of the variational principle we obtain the self-consistency equations for the parameters describing the system: the distribution function of charges above the liquid dielectric surface, the electrostatic field potentials in all regions of the system and the surface profile of the liquid dielectric. The self-consistency equations are used to describe the phase transition associated with the formation of spatially periodic structures in the system of charges on liquid dielectric surface. Assuming the non-degeneracy of the gas of charges above the surface of liquid dielectric film the solutions of the self-consistency equations near the critical point are obtained. In the case of the symmetric phase we obtain the expressions for the potentials and electric fields in all regions of the studied system. The distribution of the charges above the surface of liquid dielectric film for the symmetric phase is derived. The system parameters of the phase transition to nonsymmetric phase - the states with a spatially periodic ordering are obtained. We derive the expression determining the period of two-dimensional lattice as a function of physical parameters of the problem - the temperature, the external attractive electric field, the number of electrons per unit of the flat surface area of the liquid dielectric, the density of the dielectric, its surface tension and permittivity, and the permittivity of the solid substrate. The possibility of generalizing the developed theory in the case of degenerate gas of like-charged particles above the liquid dielectric surface is discussed.

Electrical conductivity structure of the mantle derived from inversion of geomagnetic observatory data: implications for lateral variations in temperature, composition and water content.

NASA Astrophysics Data System (ADS)

Munch, Federico; Grayver, Alexander; Khan, Amir; Kuvshinov, Alexey

2017-04-01

As most of Earth's interior remains geochemically unsampled, geophysical techniques based on seismology, geodesy, gravimetry, and electromagnetic studies play prominent roles because of their ability to sense structure at depth. Although seismic tomography maps show a variety of structures, separating thermal and compositional contributions from seismic velocities alone still remains a challenging task. Alternatively, as electrical conductivity is sensitive to temperature, chemical composition, oxygen fugacity, water content, and the presence of melt, it can serve for determining chemistry, mineralogy, and physical structure of the deep mantle. In this work we estimate and invert local C-responses (period range 3-100 days) for a number of worldwide geomagnetic observatories to map lateral variations of electrical conductivity in Earth's mantle (400-1600 km depth). The obtained conductivity profiles are interpreted in terms of basalt fraction in a basalt-harzburgite mixture, temperature structure, and water content variations. Interpretation is based on a self-consistent thermodynamic calculation of mineral phase equilibria, electrical conductivity databases, and probabilistic inverse methods.

Deep Zonal Flow and Time Variation of Jupiter’s Magnetic Field

NASA Astrophysics Data System (ADS)

Cao, Hao; Stevenson, David J.

2017-10-01

All four giant planets in the Solar System feature zonal flows on the order of 100 m/s in the cloud deck, and large-scale intrinsic magnetic fields on the order of 1 Gauss near the surface. The vertical structure of the zonal flows remains obscure. The end-member scenarios are shallow flows confined in the radiative atmosphere and deep flows throughout the entire planet. The electrical conductivity increases rapidly yet smoothly as a function of depth inside Jupiter and Saturn. Deep zonal flows will advect the non-axisymmetric component of the magnetic field, at depth with even modest electrical conductivity, and create time variations in the magnetic field.The observed time variations of the geomagnetic field has been used to derive surface flows of the Earth’s outer core. The same principle applies to Jupiter, however, the connection between the time variation of the magnetic field (dB/dt) and deep zonal flow (Uphi) at Jupiter is not well understood due to strong radial variation of electrical conductivity. Here we perform a quantitative analysis of the connection between dB/dt and Uphi for Jupiter adopting realistic interior electrical conductivity profile, taking the likely presence of alkali metals into account. This provides a tool to translate expected measurement of the time variation of Jupiter’s magnetic field to deep zonal flows. We show that the current upper limit on the dipole drift rate of Jupiter (3 degrees per 20 years) is compatible with 10 m/s zonal flows with < 500 km vertical scale height below 0.972 Rj. We further demonstrate that fast drift of resolved magnetic features (e.g. magnetic spots) at Jupiter is a possibility.

In situ visualization and detection of surface potential variation of mono and multilayer MoS2 under different humidities using Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Feng, Yulin; Zhang, Kailiang; Li, Hui; Wang, Fang; Zhou, Baozeng; Fang, Mingxu; Wang, Weichao; Wei, Jun; Wong, H. S. Philip

2017-07-01

The surface potential (SP) variations in mono and multilayer molybdenum disulfide (MoS2) are visualized in situ and detected using Kelvin probe force microscopy (KPFM) in different humidity conditions for the first time. N-type doping, which originates from the SiO2 substrate, is discovered in the exfoliated MoS2 and is accompanied by a screening length of five layers. The influence of water, which serves as an environmental gating for MoS2, is investigated by controlling the relative humidities (RHs) in the environmental chamber. A monotonic decrease in the SP is observed when the threshold concentration is achieved. This corresponds to the Fermi level variation, which is dominated by different processes. The results also indicate that water adsorption could result in MoS2 p-type doping and provide compensation that partially counteracts the substrate effect. Under this condition, the interlayer screening effect is influenced because of the water dipole-induced electric field. Density functional theory calculations are performed to determine the band structure variations and the interactions between water molecules and between water molecules and the MoS2 surface in mono and trilayer MoS2 under different RHs. The calculations are in excellent agreement with the experimental results. We propose that in situ measurements of the SP using KPFM under different environmental regimes is a noninvasive and effective method to provide real-time visualization and detection of electronic property variations in two-dimensional materials.

Zonal variations in K+ currents in vestibular crista calyx terminals

PubMed Central

Meredith, Frances L.

2014-01-01

We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na+ but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K+ currents were observed at potentials above −60 mV. K+ currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K+ channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K+ channel blocker 4-aminopyridine (10–50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K+ conductances may contribute to different firing responses in calyx afferents. PMID:25343781

Zonal variations in K+ currents in vestibular crista calyx terminals.

PubMed

Meredith, Frances L; Rennie, Katherine J

2015-01-01

We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na(+) but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K(+) currents were observed at potentials above -60 mV. K(+) currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K(+) channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K(+) channel blocker 4-aminopyridine (10-50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K(+) conductances may contribute to different firing responses in calyx afferents. Copyright © 2015 the American Physiological Society.

Parametric distribution approach for flow availability in small hydro potential analysis

NASA Astrophysics Data System (ADS)

Abdullah, Samizee; Basri, Mohd Juhari Mat; Jamaluddin, Zahrul Zamri; Azrulhisham, Engku Ahmad; Othman, Jamel

2016-10-01

Small hydro system is one of the important sources of renewable energy and it has been recognized worldwide as clean energy sources. Small hydropower generation system uses the potential energy in flowing water to produce electricity is often questionable due to inconsistent and intermittent of power generated. Potential analysis of small hydro system which is mainly dependent on the availability of water requires the knowledge of water flow or stream flow distribution. This paper presented the possibility of applying Pearson system for stream flow availability distribution approximation in the small hydro system. By considering the stochastic nature of stream flow, the Pearson parametric distribution approximation was computed based on the significant characteristic of Pearson system applying direct correlation between the first four statistical moments of the distribution. The advantage of applying various statistical moments in small hydro potential analysis will have the ability to analyze the variation shapes of stream flow distribution.

Quantum Transmission Conditions for Diffusive Transport in Graphene with Steep Potentials

NASA Astrophysics Data System (ADS)

Barletti, Luigi; Negulescu, Claudia

2018-05-01

We present a formal derivation of a drift-diffusion model for stationary electron transport in graphene, in presence of sharp potential profiles, such as barriers and steps. Assuming the electric potential to have steep variations within a strip of vanishing width on a macroscopic scale, such strip is viewed as a quantum interface that couples the classical regions at its left and right sides. In the two classical regions, where the potential is assumed to be smooth, electron and hole transport is described in terms of semiclassical kinetic equations. The diffusive limit of the kinetic model is derived by means of a Hilbert expansion and a boundary layer analysis, and consists of drift-diffusion equations in the classical regions, coupled by quantum diffusive transmission conditions through the interface. The boundary layer analysis leads to the discussion of a four-fold Milne (half-space, half-range) transport problem.

30 CFR 57.12011 - High-potential electrical conductors.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false High-potential electrical conductors. 57.12011 Section 57.12011 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Electricity Surface and Underground § 57.12011 High-potential electrical conductors. High-potential electrical...

30 CFR 57.12011 - High-potential electrical conductors.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false High-potential electrical conductors. 57.12011 Section 57.12011 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Electricity Surface and Underground § 57.12011 High-potential electrical conductors. High-potential electrical...

30 CFR 57.12011 - High-potential electrical conductors.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false High-potential electrical conductors. 57.12011 Section 57.12011 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Electricity Surface and Underground § 57.12011 High-potential electrical conductors. High-potential electrical...

Method of boundary testing of the electric circuits and its application for calculating electric tolerances. [electric equipment tests

NASA Technical Reports Server (NTRS)

Redkina, N. P.

1974-01-01

Boundary testing of electric circuits includes preliminary and limiting tests. Preliminary tests permit determination of the critical parameters causing the greatest deviation of the output parameter of the system. The boundary tests offer the possibility of determining the limits of the fitness of the system with simultaneous variation of its critical parameters.

Small temperature coefficient of resistivity of graphene/graphene oxide hybrid membranes.

PubMed

Sun, Pengzhan; Zhu, Miao; Wang, Kunlin; Zhong, Minlin; Wei, Jinquan; Wu, Dehai; Zhu, Hongwei

2013-10-09

Materials with low temperature coefficient of resistivity (TCR) are of great importance in some areas, for example, highly accurate electronic measurement instruments and microelectronic integrated circuits. In this work, we demonstrated the ultrathin graphene-graphene oxide (GO) hybrid films prepared by layer-by-layer assembly with very small TCR (30-100 °C) in the air. Electrical response of the hybrid films to temperature variation was investigated along with the progressive reduction of GO sheets. The mechanism of electrical response to temperature variation of the hybrid film was discussed, which revealed that the interaction between graphene and GO and the chemical doping effect were responsible for the tunable control of its electrical response to temperature variation. The unique properties of graphene-GO hybrid film made it a promising candidate in many areas, such as high-end film electronic device and sensor applications.

Can we quantify the variability of soil moisture across scales using Electromagnetic Induction ?

NASA Astrophysics Data System (ADS)

Robinet, Jérémy; von Hebel, Christian; van der Kruk, Jan; Govers, Gerard; Vanderborght, Jan

2017-04-01

Soil moisture is a key variable in many natural processes. Therefore, technological and methodological advancements are of primary importance to provide accurate measurements of spatial and temporal variability of soil moisture. In that context, ElectroMagnetic Induction (EMI) instruments are often cited as a hydrogeophysical method with a large potential, through the measurement of the soil apparent electrical conductivity (ECa). To our knowledge, no studies have evaluated the potential of EMI to characterize variability of soil moisture on both agricultural and forested land covers in a (sub-) tropical environment. These differences in land use could be critical as differences in temperature, transpiration and root water uptake can have significant effect, notably on the electrical conductivity of the pore water. In this study, we used an EMI instrument to carry out a first assessment of the impact of deforestation and agriculture on soil moisture in a subtropical region in the south of Brazil. We selected slopes of different topographies (gentle vs. steep) and contrasting land uses (natural forest vs. agriculture) within two nearby catchments. At selected locations on the slopes, we measured simultaneously ECa using EMI and a depth-weighted average of the soil moisture using TDR probes installed within soil pits. We found that the temporal variability of the soil moisture could not be measured accurately with EMI, probably because of important temporal variations of the pore water electrical conductivity and the relatively small temporal variations in soil moisture content. However, we found that its spatial variability could be effectively quantified using a non-linear relationship, for both intra- and inter-slopes variations. Within slopes, the ECa could explained between 67 and 90% of the variability of the soil moisture, while a single non-linear model for all the slopes could explain 55% of the soil moisture variability. We eventually showed that combining a specific relationship for the most degraded slope (steep slope under agriculture) and a single relationship for all the other slopes, both non-linear relations, yielded the best results with an overall explained variance of 90%. We applied the latter model to measurements of the ECa along transects at the different slopes, which allowed us to highlight the strong control of topography on the soil moisture content. We also observed a significant impact of the land use with higher moisture content on the agricultural slopes, probably due to a reduced evapotranspiration.

Spatially resolved imaging of opto-electrical property variations

DOEpatents

Nikiforov, Maxim; Darling, Seth B; Suzer, Ozgun; Guest, Jeffrey; Roelofs, Andreas

2014-09-16

Systems and methods for opto electric properties are provided. A light source illuminates a sample. A reference detector senses light from the light source. A sample detector receives light from the sample. A positioning fixture allows for relative positioning of the sample or the light source with respect to each other. An electrical signal device measures the electrical properties of the sample. The reference detector, sample detector and electrical signal device provide information that may be processed to determine opto-electric properties of the same.

Drift-driven evolution of electric signals in a Neotropical knifefish.

PubMed

Picq, Sophie; Alda, Fernando; Bermingham, Eldredge; Krahe, Rüdiger

2016-09-01

Communication signals are highly diverse traits. This diversity is usually assumed to be shaped by selective forces, whereas the null hypothesis of divergence through drift is often not considered. In Panama, the weakly electric fish Brachyhypopomus occidentalis is widely distributed in multiple independent drainage systems, which provide a natural evolutionary laboratory for the study of genetic and signal divergence in separate populations. We quantified geographic variation in the electric signals of 109 fish from five populations, and compared it to the neutral genetic variation estimated from cytochrome oxidase I (COI) sequences of the same individuals, to test whether drift may be driving divergence of their signals. Signal distances were highly correlated with genetic distances, even after controlling for geographic distances, suggesting that drift alone is sufficient to explain geographic variation in electric signals. Significant differences at smaller geographic scales (within drainages) showed, however, that electric signals may evolve at a faster rate than expected under drift, raising the possibility that additional adaptive forces may be contributing to their evolution. Overall, our data point to stochastic forces as main drivers of signal evolution in this species and extend the role of drift in the evolution of communication systems to fish and electrocommunication. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Computer Power. Part 2: Electrical Power Problems and Their Amelioration.

ERIC Educational Resources Information Center

Price, Bennett J.

1989-01-01

Describes electrical power problems that affect computer users, including spikes, sags, outages, noise, frequency variations, and static electricity. Ways in which these problems may be diagnosed and cured are discussed. Sidebars consider transformers; power distribution units; surge currents/linear and non-linear loads; and sizing the power…

Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved

PubMed Central

Chang, Cheng-Hsun-Tony; Kuo, Wei-Hsu; Chang, Yu-Chieh; Tsay, Jyh-Shen; Yau, Shueh-Lin

2017-01-01

A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability. PMID:28255160

Electric field measurements from Halley, Antarctica

NASA Astrophysics Data System (ADS)

Nicoll, Keri; Harrison, R. Giles

2016-04-01

Antarctica is a unique location for the study of atmospheric electricity. Not only is it one of the most pollutant free places on Earth, but its proximity to the south magnetic pole means that it is an ideal location to study the effects of solar variability on the atmospheric electric field. This is due to the reduced shielding effect of the geomagnetic field at the poles which leads to a greater flux of incoming Galactic Cosmic Rays (GCRs) as well as an increased probability of energetic particle precipitation from SEPs and relativistic electrons. To investigate such effects, two electric field mills of different design were installed at the British Antarctic Survey Halley base in February 2015 (75. 58 degrees south, 26.66 degrees west). Halley is situated on the Brunt Ice Shelf in the south east of the Weddell Sea and has snow cover all year round. Preliminary analysis has focused on selection of fair weather criteria using wind speed and visibility measurements which are vital to assess the effects of falling snow, blowing snow and freezing fog on the electric field measurements. When the effects of such adverse weather conditions are removed clear evidence of the characteristic Carnegie Curve diurnal cycle exists in the Halley electric field measurements (with a mean value of 50V/m and showing a 40% peak to peak variation in comparison to the 34% variation in the Carnegie data). Since the Carnegie Curve represents the variation in thunderstorm activity across the Earth, its presence in the Halley data confirms the presence of the global atmospheric electric circuit signal at Halley. The work presented here will discuss the details of the Halley electric field dataset, including the variability in the fair weather measurements, with a particular focus on magnetic field fluctuations.

Bioelectric potentials in the soil-plant system

NASA Astrophysics Data System (ADS)

Pozdnyakov, A. I.

2013-07-01

A detailed study of the electric potentials in the soil-plant system was performed. It was found that the electric potential depends on the plant species and the soil properties. A theoretical interpretation of the obtained data was given. All the plants, independently from their species and their state, always had a negative electric potential relative to the soil. The electric potential of the herbaceous plants largely depended on the leaf area. In some plants, such as burdock ( Arctium lappa) and hogweed ( Heracleum sosnowskyi), the absolute values of the negative electric potential exceeded 100 mV. The electric potential was clearly differentiated by the plant organs: in the flowers, it was lower than in the leaves; in the leaves, it was usually lower than in the leaf rosettes and stems. The electric potentials displayed seasonal dynamics. As a rule, the higher the soil water content, the lower the electric potential of the plants. However, an inverse relationship was observed for dandelions ( Taraxacum officinale). It can be supposed that the electric potential between the soil and the plant characterizes the vital energy of the plant.

Precise measurement of the performance of thermoelectric modules

NASA Astrophysics Data System (ADS)

Díaz-Chao, Pablo; Muñiz-Piniella, Andrés; Selezneva, Ekaterina; Cuenat, Alexandre

2016-08-01

The potential exploitation of thermoelectric modules into mass market applications such as exhaust gas heat recovery in combustion engines requires an accurate knowledge of their performance. Further expansion of the market will also require confidence on the results provided by suppliers to end-users. However, large variation in performance and maximum operating point is observed for identical modules when tested by different laboratories. Here, we present the first metrological study of the impact of mounting and testing procedures on the precision of thermoelectric modules measurement. Variability in the electrical output due to mechanical pressure or type of thermal interface materials is quantified for the first time. The respective contribution of the temperature difference and the mean temperature to the variation in the output performance is quantified. The contribution of these factors to the total uncertainties in module characterisation is detailed.

Studies on the seasonal variation of atmospheric electricity parameters at a tropical station in Kolkata, India

NASA Astrophysics Data System (ADS)

De, S. S.; Paul, Suman; Barui, S.; Pal, Pinaki; Bandyopadhyay, B.; Kala, D.; Ghosh, A.

2013-12-01

The paper deals with the analyses of the atmospheric vertical potential gradient (PG) from the ground for 90 fair weather days during 2006-2009 measured at Kolkata (Lat: 22.56°N). The variations of PG have been studied extensively to investigate their values during monsoon and winter seasons. Higher values of PG at Kolkata are observed due to higher abundance of pollutant particles. The observed PG are compared with the results of Potsdam station (Lat: 52°N) and Johannesburg station (Lat: 26°S), with 9 years data and 2 years data respectively. The correlations studies are carried out among PG, PDC (Point Discharge Current) as well as negative and positive carrier conductivities. The corresponding correlation coefficients are obtained as 0.93, -0.842 and -0.844.

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

NASA Astrophysics Data System (ADS)

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

2012-09-01

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

Investigating the Conceptual Variation of Major Physics Textbooks

NASA Astrophysics Data System (ADS)

Stewart, John; Campbell, Richard; Clanton, Jessica

2008-04-01

The conceptual problem content of the electricity and magnetism chapters of seven major physics textbooks was investigated. The textbooks presented a total of 1600 conceptual electricity and magnetism problems. The solution to each problem was decomposed into its fundamental reasoning steps. These fundamental steps are, then, used to quantify the distribution of conceptual content among the set of topics common to the texts. The variation of the distribution of conceptual coverage within each text is studied. The variation between the major groupings of the textbooks (conceptual, algebra-based, and calculus-based) is also studied. A measure of the conceptual complexity of the problems in each text is presented.

Variations of magnetic and electrostatic atmospheric parameters and dynamics of the heart rate in mHz range

NASA Astrophysics Data System (ADS)

Nagorskiy, Petr; Zenchenko, Tatiana; Breus, Tamara; Smirnov, Sergey

The objective of this work was to study the degree of synchronization of heart rate (HR) of healthy volunteers with magnetic variations and various weather conditions in mHz - frequency range. Experimental results for synchronic registration of physiological variations, atmospheric electrical and meteorological parameters with a time resolution of 0.5-1 min are presented. The experiment was conducted in a building of IMCES SB RAS (Tomsk). 15 experiments of 60 minutes each were conducted, and four volunteers of all ages in a state of rest were examined. Meteorological parameters (atmospheric pressure, relative air humidity and temperatureas well as a wind speed) were measured using standard meteorological devices located on the roof of the same building and also on the open area. Data on geomagnetic activity on the nearest magnetic station Klyichi were obtained from the site http://ottawa.intermagnet.org/apps/download/index-eng.php # view. The electric field intensity was recorded the following way: in the room (5-storey panel ferroconcrete building) by the autonomous fluxmeter CS110 at a distance of 1.5 meters from the investigated volunteers, and on the open test - area by the stationary electric fluxmeter "Field 2". Data analysis techniques were: cross-correlation analysis, spectral analysis (Fourier transform and the calculation of the coherence function) and wavelet analysis. It was found that the dependence of the heart rate variation dynamics from the X-component of the Earth magnetic field magnitude was observed in 53% of cases, from the relative humidity - in 33%, from the atmospheric pressure, the wind speed and intensity of the electric field in an open area - in 20%, from the intensity the electric field in the room of the experiment - in 7% of cases. It was found not only coincidence of observed values of oscillation periods in physiological and geophysical series lasting 5-30 minutes, but also moments of approximate synchronicity in their appearance and disappearance. The highest degree of synchronization of HR with the variations of the geomagnetic field (in all four conducted experiments in this day) was observed in the most geomagnetically quiet day - 04.10.12 (Ap = 1), while the lowest one - in the day of the geomagnetic disturbances - 01.10.12 (Ap = 32). The characteristics of the electric field variations in the time-frequency domain in the experiments conducted indoors and outdoors differ fundamentally.

Investigation of tenuous plasma environment using Active Spacecraft Potential Control (ASPOC) on Magnetospheric Multiscale (MMS) Mission

NASA Astrophysics Data System (ADS)

Nakamura, Rumi; Jeszenszky, Harald; Torkar, Klaus; Andriopoulou, Maria; Fremuth, Gerhard; Taijmar, Martin; Scharlemann, Carsten; Svenes, Knut; Escoubet, Philippe; Prattes, Gustav; Laky, Gunter; Giner, Franz; Hoelzl, Bernhard

2015-04-01

The NASA's Magnetospheric Multiscale (MMS) Mission is planned to be launched on March 12, 2015. The scientific objectives of the MMS mission are to explore and understand the fundamental plasma physics processes of magnetic reconnection, particle acceleration and turbulence in the Earth's magnetosphere. The region of scientific interest of MMS is in a tenuous plasma environment where the positive spacecraft potential reaches an equilibrium at several tens of Volts. An Active Spacecraft Potential Control (ASPOC) instrument neutralizes the spacecraft potential by releasing positive charge produced by indium ion emitters. ASPOC thereby reduces the potential in order to improve the electric field and low-energy particle measurement. The method has been successfully applied on other spacecraft such as Cluster and Double Star. Two ASPOC units are present on each of the MMS spacecraft. Each unit contains four ion emitters, whereby one emitter per instrument is operated at a time. ASPOC for MMS includes new developments in the design of the emitters and the electronics enabling lower spacecraft potentials, higher reliability, and a more uniform potential structure in the spacecraft's sheath compared to previous missions. Model calculations confirm the findings from previous applications that the plasma measurements will not be affected by the beam's space charge. A perfectly stable spacecraft potential precludes the utilization of the spacecraft as a plasma probe, which is a conventional technique used to estimate ambient plasma density from the spacecraft potential. The small residual variations of the potential controlled by ASPOC, however, still allow to determine ambient plasma density by comparing two closely separated spacecraft and thereby reconstructing the uncontrolled potential variation from the controlled potential. Regular intercalibration of controlled and uncontrolled potentials is expected to increase the reliability of this new method.

Magnetic field line reconnection experiments. V - Current disruptions and double layers

NASA Technical Reports Server (NTRS)

Stenzel, R. L.; Gekelman, W.; Wild, N.

1983-01-01

An investigation is conducted of the stability of a large laboratory plasma current sheet, which has been generated in the process of magnetic field line reconnection, with respect to local current increases. Magnetic flux variations in regions remote from the current sheet generate an inductive voltage in the current loop that drops off inside the plasma in the form of a potential double layer, leading to particle acceleration with velocities much larger than those expected from the steady state electric fields in the plasma. A model for the mechanism of the current disruptions is formulated in which the potential structure leads to ion expulsion, creating a localized density drop. The associated current drop in an inductive circuit drives the potential structure, providing feedback for the disruptive instability. Similarities to, and differences from, magnetospheric substorm phenomena are noted.

Self-consistent many-electron theory of electron work functions and surface potential characteristics for selected metals

NASA Technical Reports Server (NTRS)

Smith, J. R.

1969-01-01

Electron work functions, surface potentials, and electron number density distributions and electric fields in the surface region of 26 metals were calculated from first principles within the free electron model. Calculation proceeded from an expression of the total energy as a functional of the electron number density, including exchange and correlation energies, as well as a first inhomogeneity term. The self-consistent solution was obtained via a variational procedure. Surface barriers were due principally to many-body effects; dipole barriers were small only for some alkali metals, becoming quite large for the transition metals. Surface energies were inadequately described by this model, which neglects atomistic effects. Reasonable results were obtained for electron work functions and surface potential characteristics, maximum electron densities varying by a factor of over 60.

Soft exfoliation of 2D SnO with size-dependent optical properties

NASA Astrophysics Data System (ADS)

Singh, Mandeep; Della Gaspera, Enrico; Ahmed, Taimur; Walia, Sumeet; Ramanathan, Rajesh; van Embden, Joel; Mayes, Edwin; Bansal, Vipul

2017-06-01

Two-dimensional (2D) materials have recently gained unprecedented attention as potential candidates for next-generation (opto)electronic devices due to their fascinating optical and electrical properties. Tin monoxide, SnO, is an important p-type semiconductor with applications across photocatalysis (water splitting) and electronics (transistors). However, despite its potential in several important technological applications, SnO remains underexplored in its 2D form. Here we present a soft exfoliation strategy to produce 2D SnO nanosheets with tunable optical and electrical properties. Our approach involves the initial synthesis of layered SnO microspheres, which are readily exfoliated through a low-power sonication step to form high quality SnO nanosheets. We demonstrate that the properties of 2D SnO are strongly dependent on its dimensions. As verified through optical absorption and photoluminescence studies, a strong size-dependent quantum confinement effect in 2D SnO leads to substantial variation in its optical and electrical properties. This results in a remarkable (>1 eV) band gap widening in atomically thin SnO. Through photoconductivity measurements, we further validate a strong correlation between the quantum-confined properties of 2D SnO and the selective photoresponse of atomically thin sheets in the high energy UV light. Such tunable semiconducting properties of 2D SnO could be exploited for a variety of applications including photocatalysis, photovoltaics and optoelectronics in general.

The implementation of anaerobic digestion of food waste in a highly populated urban area: an LCA evaluation.

PubMed

Grosso, Mario; Nava, Chiara; Testori, Roberta; Rigamonti, Lucia; Viganò, Federico

2012-09-01

While source separation of waste packaging materials for recycling is well established in several metropolitan areas, the collection of food waste from the households is less widespread because of its more difficult implementation. Source segregation of food waste in densely populated areas is raising new interest, as the availability of biogas following its anaerobic digestion (AD) paves the road to a number of possibilities, from electric energy production to its upgrading to biomethane and subsequent feeding in to the natural gas network or in vehicles as a fuel. The study addresses this waste management option by analysing a real metropolitan situation where food waste currently ends up mixed with the residual waste in a waste-to-energy plant (WTE). We assume to establish a new collection scheme for household food waste, followed by its treatment in a new AD and post-composting facility. A comparative life cycle assessment was carried out, where possible synergies between the existing WTE plant and the new one were evaluated. All new scenarios based on AD attained similar or better results compared with the reference scenario for almost all of the impact indicators. The most robust indication is related to global warming potential, with a potential improvement of up to 37%. Finally, a sensitivity analysis was carried out to assess the effect of the variation of the most relevant parameters. Results have proven to be very sensible to the hypothesis on the type of substituted electric energy. All the other examined sensitivities resulted in variations well below 10%.

Electrical resistivity tomography to delineate greenhouse soil variability

NASA Astrophysics Data System (ADS)

Rossi, R.; Amato, M.; Bitella, G.; Bochicchio, R.

2013-03-01

Appropriate management of soil spatial variability is an important tool for optimizing farming inputs, with the result of yield increase and reduction of the environmental impact in field crops. Under greenhouses, several factors such as non-uniform irrigation and localized soil compaction can severely affect yield and quality. Additionally, if soil spatial variability is not taken into account, yield deficiencies are often compensated by extra-volumes of crop inputs; as a result, over-irrigation and overfertilization in some parts of the field may occur. Technology for spatially sound management of greenhouse crops is therefore needed to increase yield and quality and to address sustainability. In this experiment, 2D-electrical resistivity tomography was used as an exploratory tool to characterize greenhouse soil variability and its relations to wild rocket yield. Soil resistivity well matched biomass variation (R2=0.70), and was linked to differences in soil bulk density (R2=0.90), and clay content (R2=0.77). Electrical resistivity tomography shows a great potential in horticulture where there is a growing demand of sustainability coupled with the necessity of stabilizing yield and product quality.

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.

INSTRUMENTATION AND CONTROLS DIVISION, ELECTRICAL DESIGN STANDARDS AND GRAPHICAL SYMBOLS

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

Bates, A.E.G.; Bowelle, M.M.; Horton, J.L.

1960-10-01

Recommendations of the Instrumentation and Controls Division Committee on Electrical and Electronic Symbols and Drawings are presented. The American Standards Associrtion Graphical Symbols for Electrical Diagrams are given, with certain variations or additions recommended by the Committee to clarify or more positively identify the device or element symbolized. Recommendations regarding electrical elementary diagram 1ayout, device coding, etc., are included. (W.D.M.)

Breakup of Solid Ice Covers Due to Rapid Water Level Variations,

DTIC Science & Technology

1982-02-01

Larsen, and Dr. Devinder S. Sodhi for their valuable comments and reviews of the report. He also thanks Dr. Ashton and Guenther E. Frankenstein for the...for wave periods larger than about 10 seconds. What are the minimum wave lengths that might be generated by discharge variations at a hydro- electric ...Canadian Electrical Association, Research and Development, Suite 580, One Westmount Square, Montreal, Canada. 2. Ashton, G.D. (1974a) Entrainment of ice

On neoclassical impurity transport in stellarator geometry

NASA Astrophysics Data System (ADS)

García-Regaña, J. M.; Kleiber, R.; Beidler, C. D.; Turkin, Y.; Maaßberg, H.; Helander, P.

2013-07-01

The impurity dynamics in stellarators has become an issue of moderate concern due to the inherent tendency of the impurities to accumulate in the core when the neoclassical ambipolar radial electric field points radially inwards (ion root regime). This accumulation can lead to collapse of the plasma due to radiative losses, and thus limit high performance plasma discharges in non-axisymmetric devices. A quantitative description of the neoclassical impurity transport is complicated by the breakdown of the assumption of small E × B drift and trapping due to the electrostatic potential variation on a flux surface \\tilde{\\Phi} compared with those due to the magnetic field gradient. This work examines the impact of this potential variation on neoclassical impurity transport in the Large Helical Device heliotron. It shows that the neoclassical impurity transport can be strongly affected by \\tilde{\\Phi} . The central numerical tool used is the δf particle in cell Monte Carlo code EUTERPE. The \\tilde{\\Phi} used in the calculations is provided by the neoclassical code GSRAKE. The possibility of obtaining a more general \\tilde{\\Phi} self-consistently with EUTERPE is also addressed and a preliminary calculation is presented.

Improved Ionospheric Electrodynamic Models and Application to Calculating Joule Heating Rates

NASA Technical Reports Server (NTRS)

Weimer, D. R.

2004-01-01

Improved techniques have been developed for empirical modeling of the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters. The FAC model is constructed using scalar magnetic Euler potentials, and functions as a twin to the electric potential model. The improved models have more accurate field values as well as more accurate boundary locations. Non-linear saturation effects in the solar wind-magnetosphere coupling are also better reproduced. The models are constructed using a hybrid technique, which has spherical harmonic functions only within a small area at the pole. At lower latitudes the potentials are constructed from multiple Fourier series functions of longitude, at discrete latitudinal steps. It is shown that the two models can be used together in order to calculate the total Poynting flux and Joule heating in the ionosphere. An additional model of the ionospheric conductivity is not required in order to obtain the ionospheric currents and Joule heating, as the conductivity variations as a function of the solar inclination are implicitly contained within the FAC model's data. The models outputs are shown for various input conditions, as well as compared with satellite measurements. The calculations of the total Joule heating are compared with results obtained by the inversion of ground-based magnetometer measurements. Like their predecessors, these empirical models should continue to be a useful research and forecast tools.

Non-invasive monitoring of the degradation of organic contaminants: A laboratory investigation

NASA Astrophysics Data System (ADS)

Fernandez, Perrine M.; Bloem, Esther; Philippe, Romain; Binley, Andrew; French, Helen K.

2016-04-01

Degradation of organic chemicals under various fluid saturation conditions is a process highly relevant to the protection of groundwater quality. Redox potential drives the degradation of organic compounds; its variation affects the water chemistry, gas release and also the geo-electrical signature. This study explores how non-invasive measurements sensitive to geo-electrical properties provides quantitative information about the in-situ redox conditions. Our laboratory experiment focuses on the degradation of de-icing chemicals commonly used, for example, in Norwegian airports. The experiment was conducted in a number of (1.0x0.5x0.4 m) sand boxes. Two ends of each box was contaminated with propylene glycol, an aircraft deicing fluid. Each source was placed near the water table under static hydraulic conditions. At one side of the tank, a conductor linking the contamination zone, near the water table and the unsaturated zone with a low water content, was placed to improve the degradation by facilitating the electron exchange. At the other side, degradation occurred under natural conditions. Each box was equipped with 288 electrodes, distributed on six faces to perform 3D resistivity measurements. In addition, self-potential measurements were taken from electrodes on the sand surface. Four observation wells were installed above and below the water table to provide more information on the degradation processes. Moreover, measurements of carbon dioxide on the surface were performed as higher concentrations were expected where the pollutant degraded. We would like to present and discuss a selection of the preliminary results of 3D electrical resistivity and self-potential techniques from our laboratory setup.

Electromagnetic Field Modeling of Transcranial Electric and Magnetic Stimulation: Targeting, Individualization, and Safety of Convulsive and Subconvulsive Applications

NASA Astrophysics Data System (ADS)

Deng, Zhi-De

The proliferation of noninvasive transcranial electric and magnetic brain stimulation techniques and applications in recent years has led to important insights into brain function and pathophysiology of brain-based disorders. Transcranial electric and magnetic stimulation encompasses a wide spectrum of methods that have developed into therapeutic interventions for a variety of neurological and psychiatric disorders. Although these methods are at different stages of development, the physical principle underlying these techniques is the similar. Namely, an electromagnetic field is induced in the brain either via current injection through scalp electrodes or via electromagnetic induction. The induced electric field modulates the neuronal transmembrane potentials and, thereby, neuronal excitability or activity. Therefore, knowledge of the induced electric field distribution is key in the design and interpretation of basic research and clinical studies. This work aims to delineate the fundamental physical limitations, tradeoffs, and technological feasibility constraints associated with transcranial electric and magnetic stimulation, in order to inform the development of technologies that deliver safer, and more spatially, temporally, and patient specific stimulation. Part I of this dissertation expounds on the issue of spatial targeting of the electric field. Contrasting electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) configurations that differ markedly in efficacy, side effects, and seizure induction efficiency could advance our understanding of the principles linking treatment parameters and therapeutic outcome and could provide a means of testing hypotheses of the mechanisms of therapeutic action. Using the finite element method, we systematically compare the electric field characteristics of existing forms of ECT and MST. We introduce a method of incorporating a modality-specific neural activation threshold in the electric field models that can inform dosage requirements in convulsive therapies. Our results indicate that the MST electric field is more focal and more confined to the superficial cortex compared to ECT. Further, the conventional ECT current amplitude is much higher than necessary for seizure induction. One of the factors important to clinical outcome is seizure expression. However, it is unknown how the induced electric field is related to seizure onset and propagation. In this work, we explore the effect of the electric field distribution on the quantitative ictal electroencephalography and current source density in ECT and MST. We further demonstrate how the ECT electrode shape, size, spacing, and current can be manipulated to yield more precise control of the induced electric field. If desirable, ECT can be made as focal as MST while using simpler stimulation equipment. Next, we demonstrate how the electric field induced by transcranial magnetic stimulation (TMS) can be controlled. We present the most comprehensive comparison of TMS coil electric field penetration and focality to date. The electric field distributions of more than 50 TMS coils were simulated. We show that TMS coils differ markedly in their electric field characteristics, but they all are subject to a consistent depth-focality tradeoff. Specifically, the ability to directly stimulate deeper brain structures is obtained at the expense of inducing wider electric field spread. Figure-8 type coils are fundamentally more focal compared to circular type coils. Understanding the depth-focality tradeoff can help researchers and clinicians to appropriately select coils and interpret TMS studies. This work also enables the development of novel TMS coils with electronically switchable active and sham modes as well as for deep TMS. Design considerations of these coils are extensively discussed. Part II of the dissertation aims to quantify the effect of individual, sex, and age differences in head geometry and conductivity on the induced neural stimulation strength and focality of ECT and MST. Across and within ECT studies, there is marked unexplained variability in seizure threshold and clinical outcomes. It is not known to what extent the age and sex effects on seizure threshold are mediated by interindividual variation in neural excitability and/or anatomy of the head. Addressing this question, we examine the effect on ECT and MST induced field characteristics of the variability in head diameter, scalp and skull thicknesses and conductivities, as well as brain volume, in a range of values that are representative of the patient population. Variations in the local tissue properties such as scalp and skull thickness and conductivity affect the existing ECT configurations more than MST. On the other hand, the existing MST coil configurations show greater sensitivity to head diameter variation compared to ECT. Due to the high focality of MST compared to ECT, the stimulated brain volume in MST is more sensitive to variation in tissue layer thicknesses. We further demonstrate how individualization of the stimulus pulse current amplitude, which is not presently done in ECT or MST, can be used as a means of compensating for interindividual anatomical variability, which could lead to better and more consistent clinical outcomes. Part III of the dissertation aims to systemically investigate, both computationally and experimentally, the safety of TMS and ECT in patients with a deep-brain stimulation system, and propose safety guidelines for the dual-device therapy. We showed that the induction of significant voltages in the subcutaneous leads in the scalp during TMS could result in unintended and potentially dangerous levels of electrical currents in the DBS electrode contacts. When applying ECT in patients with intracranial implants, we showed that there is an increase in the electric field strength in the brain due to conduction through the burr holes, especially when the burr holes are not fitted with nonconductive caps. Safety concerns presently limit the access of patients with intracranial electronic devices to therapies involving transcranial stimulation technology, which may preclude them from obtaining appropriate medical treatments. Gaining better understanding of the interactions between transcranial and implanted stimulation devices will demarcate significant safety risks from benign interactions, and will provide recommendations for reducing risk, thus enhancing the patient's therapeutic options.

Ionosonde observations of the effects of the major magnetic storm of September 22-26, 1999 at equatorial station in west Africa

NASA Astrophysics Data System (ADS)

Coulibaly, I. S.; Adohi, B. J.-P.; Tanoh, K. S.

2018-05-01

A new approach to study the mechanisms of storm-time variations in the F-layer height and critical frequency at dip-equator is proposed. The latitudinal variations in the magnetic disturbance index DP were combined with h'F and foF2 data from an IPS 42-type ionosonde at Korkogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, to investigate the nighttime ionospheric effects of the geomagnetic storm of September 22-26, 1999 in the West-African sector. A clear equatorward penetration of magnetic disturbances from high latitudes regions was observed. At dip-equator, the DP magnetic disturbance pattern showed up to four distinct regimes of disturbance electric fields, each associated with a specific phase of the storm. A regime of westward transient electric fields followed by a regime of eastward transient electric fields occurred during the main phase of the storm. This was preceded by a period of quasi-absence of disturbance during the compression phase, the whole followed by a regime of westward persistent disturbance electric fields during the recovery phase. From the latitudinal variations and the shapes of these perturbations, we could associate the regime of westward (resp. eastward) disturbance electric fields with prompt penetration (resp. overshielding) occasioned by magnetospheric convections and the persistent one with a cumulative effect of storm-time winds and magnetospheric convections from high latitudes regions. The h'F variations were found to be strongly correlated with the DP ones, clearly providing evidence for the prevalence of these electric fields on the observed F-layer motions. Additionally, the foF2 variations showed two periods of depleted electron density, one in the evening during the compression phase of the storm and the other near midnight. We discussed the mechanisms of these ionospheric negative storms in the light of earlier investigations of storm-time ionospheric disturbances and validated our method by comparison of the above results with those based on criteria by other authors.

The effect of adding selective mixed culture of alternative electricity production based on tempe wastewater on tubular microbial fuel cell

NASA Astrophysics Data System (ADS)

Mariana, Elisabeth, Utami, Tania Surya; Arbianti, Rita; Hermansyah, Heri

2017-05-01

Bacteria has long been known could produce electricity. MFC (Microbial Fuel Cell) is a technology that uses bacteria. MFC is potential as producer of alternative renewable energy through the conversion of waste by bacteria into electrical energy. However, this technology cannot reach the target value of the minimum voltage. This research is focused on reviewing the effect of the addition of gram positive and negative bacteria (selective mixed culture) contained in tempe wastewater as well as the optimal volume additions gram using a tubular single chamber membranless reactor. The result shows that the addition of selective mixed culture can increase voltage of MFC. Gram negative bacteria dominate tempe wastewater and has better ability to transfer electrons than gram-positive. The voltage increases with increasing amount of bacteria up to a certain maximum point. Addition of 1 mL gram-negative bacteria improve electrical output and provide the most optimal results of 0.0697 mW/m2 mV or 92.14% excalation against the initial control experiment with the average power density of 0.0702 mW1m2. Additions of most optimum variation also give good results on the use of industrial waste, with electrical voltage and power density high of 8.90 mV and 0.02 mW/m2.

Development of a Waterproof Crack-Based Stretchable Strain Sensor Based on PDMS Shielding.

PubMed

Hong, Seong Kyung; Yang, Seongjin; Cho, Seong J; Jeon, Hyungkook; Lim, Geunbae

2018-04-12

This paper details the design of a poly(dimethylsiloxane) (PDMS)-shielded waterproof crack-based stretchable strain sensor, in which the electrical characteristics and sensing performance are not influenced by changes in humidity. This results in a higher number of potential applications for the sensor. A previously developed omni-purpose stretchable strain (OPSS) sensor was used as the basis for this work, which utilizes a metal cracking structure and provides a wide sensing range and high sensitivity. Changes in the conductivity of the OPSS sensor, based on humidity conditions, were investigated along with the potential possibility of using the design as a humidity sensor. However, to prevent conductivity variation, which can decrease the reliability and sensing ability of the OPSS sensor, PDMS was utilized as a shielding layer over the OPSS sensor. The PDMS-shielded OPSS sensor showed approximately the same electrical characteristics as previous designs, including in a high humidity environment, while maintaining its strain sensing capabilities. The developed sensor shows promise for use under high humidity conditions and in underwater applications. Therefore, considering its unique features and reliable sensing performance, the developed PDMS-shielded waterproof OPSS sensor has potential utility in a wide range of applications, such as motion monitoring, medical robotics and wearable healthcare devices.

Rheodynamic model of cardiac pressure pulsations.

PubMed

Petrov, V G; Nikolov, S G

1999-03-15

To analyse parametrically (in terms of the qualitative theory of dynamical systems) the mechanical influence of inertia, resistance (positive and negative), elasticity and other global properties of the heart-muscle on the left ventricular pressure, an active rheodynamic model based on the Newtons's principles is proposed. The equation of motion of the heart mass centre is derived from an energy conservation law balancing the rate of mechanical (kinetic and potential) energy variation and the power of chemical energy influx and dissipative energy outflux. A corresponding dynamical system of two ordinary differential equations is obtained and parametrically analysed in physiological conditions. As a result, the following main conclusion is made: in physiological norm, because of the heart electrical activity, its equilibrium state is unstable and around it, mechanical self-oscillations emerge. In case the electrical activity ceases, an inverse phase reconstruction occurs during which the unstable equilibrium state of the system becomes stable and the self-oscillations disappear.

Wearable Health Monitoring Systems

NASA Technical Reports Server (NTRS)

Bell, John

2015-01-01

The shrinking size and weight of electronic circuitry has given rise to a new generation of smart clothing that enables biological data to be measured and transmitted. As the variation in the number and type of deployable devices and sensors increases, technology must allow their seamless integration so they can be electrically powered, operated, and recharged over a digital pathway. Nyx Illuminated Clothing Company has developed a lightweight health monitoring system that integrates medical sensors, electrodes, electrical connections, circuits, and a power supply into a single wearable assembly. The system is comfortable, bendable in three dimensions, durable, waterproof, and washable. The innovation will allow astronaut health monitoring in a variety of real-time scenarios, with data stored in digital memory for later use in a medical database. Potential commercial uses are numerous, as the technology enables medical personnel to noninvasively monitor patient vital signs in a multitude of health care settings and applications.

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

8 MeV electron beam induced modifications in the thermal, structural and electrical properties of nanophase CeO2 for potential electronics applications

NASA Astrophysics Data System (ADS)

Babitha, K. K.; Sreedevi, A.; Priyanka, K. P.; Ganesh, S.; Varghese, Thomas

2018-06-01

The effect of 8 MeV electron beam irradiation on the thermal, structural and electrical properties of CeO2 nanoparticles synthesized by chemical precipitation route was investigated. The dose dependent effect of electron irradiation was studied using various characterization techniques such as, thermogravimetric and differential thermal analyses, X-ray diffraction, Fourier transformed infrared spectroscopy and impedance spectroscopy. Systematic investigation based on the results of structural studies confirm that electron beam irradiation induces defects and particle size variation on CeO2 nanoparticles, which in turn results improvements in AC conductivity, dielectric constant and loss tangent. Structural modifications and high value of dielectric constant for CeO2 nanoparticles due to electron beam irradiation make it as a promising material for the fabrication of gate dielectric in metal oxide semiconductor devices.

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

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

USGS Publications Warehouse

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

2014-01-01

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

Laboratory investigation of dust impacts induced signals on antennas in space

NASA Astrophysics Data System (ADS)

Rocha, J. R.; Collette, A.; Malaspina, D.; Gruen, E.; Sternovsky, Z.

2014-12-01

Recent observations of sharp voltage spikes by the WAVES electric field experiments onboard the twin STEREO spacecraft have been attributed to plasma clouds generated by the impact ionization of high velocity dust particles. The reported dust fluxes are much higher than those measured by dedicated dust detectors at 1 AU, which leads to the interpretation that the STEREO observations are due to nanometer-sized dust particles originating from the inner solar system and accelerated to high velocities by the solar wind magnetic field. However, this interpretation is based on a simplified model of coupling between the expanding plasma cloud from the dust impact and the WAVES electric field instrument. A series of laboratory measurements are performed to validate this model and to calibrate/investigate the effect of various impact parameters on the signals measured by the electric field instrument. The dust accelerator facility operating at the University of Colorado is used for the measurement with micron and submicron sized particles accelerated to 50 km/s. The first set of measurements was aimed at the understanding of the charge yield of impact-generated plasmas from common materials used on spacecraft, i.e. BeCu, germanium coated black Kapton, MLI, and solar cells. The measurements show that at 10 km/s these materials yield similar charge signals. At higher speeds (~50 km/s) the variation is with material increases. The impact charge is also found to depend on angle of incidence; the data suggest a maximum at 45 degrees. The second set of measurements investigates the variation of the induced dust signal with bias potential applied on the simulated spacecraft.

The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission

NASA Astrophysics Data System (ADS)

Wygant, J. R.; Bonnell, J. W.; Goetz, K.; Ergun, R. E.; Mozer, F. S.; Bale, S. D.; Ludlam, M.; Turin, P.; Harvey, P. R.; Hochmann, R.; Harps, K.; Dalton, G.; McCauley, J.; Rachelson, W.; Gordon, D.; Donakowski, B.; Shultz, C.; Smith, C.; Diaz-Aguado, M.; Fischer, J.; Heavner, S.; Berg, P.; Malsapina, D. M.; Bolton, M. K.; Hudson, M.; Strangeway, R. J.; Baker, D. N.; Li, X.; Albert, J.; Foster, J. C.; Chaston, C. C.; Mann, I.; Donovan, E.; Cully, C. M.; Cattell, C. A.; Krasnoselskikh, V.; Kersten, K.; Brenneman, A.; Tao, J. B.

2013-11-01

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ˜15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).

Analysis of the variation of atmospheric electric field during solar events

NASA Astrophysics Data System (ADS)

Tacza, J.; Raulin, J. P.

2016-12-01

We present the capability of a new network of electric field mill sensors to monitor the atmospheric electric field at various locations in South America. The first task is to obtain a diurnal curve of atmospheric electric field variations under fair weather conditions, which we will consider as a reference curve. To accomplish this, we made daily, monthly, seasonal and annual averages. For all sensor location, the results show significant similarities with the Carnegie curve. The Carnegie curve is the characteristic curve in universal time of atmospheric electric field in fair weather and one thinks it is related to the currents flowing in the global atmospheric electric circuit. Ultimately, we pretend to study departures of the daily observations from the standard curve. This difference can be caused by solar, geophysical and atmospheric phenomena such as the solar activity cycle, solar flares and energetic charged particles, galactic cosmic rays, seismic activity and/or specific meteorological events. As an illustration we investigate solar effects on the atmospheric electric field observed at CASLEO (Lat. 31.798°S, Long. 69.295°W, Altitude: 2552 masl) by the method of superposed epoch analysis, between January 2010 and December 2015.

Utility Sector Impacts of Reduced Electricity Demand

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

Coughlin, Katie

2014-12-01

This report presents a new approach to estimating the marginal utility sector impacts associated with electricity demand reductions. The method uses publicly available data and provides results in the form of time series of impact factors. The input data are taken from the Energy Information Agency's Annual Energy Outlook (AEO) projections of how the electric system might evolve in the reference case, and in a number of side cases that incorporate different effciency and other policy assumptions. The data published with the AEO are used to define quantitative relationships between demand-side electricity reductions by end use and supply-side changes tomore » capacity by plant type, generation by fuel type and emissions of CO2, Hg, NOx and SO2. The impact factors define the change in each of these quantities per unit reduction in site electricity demand. We find that the relative variation in these impacts by end use is small, but the time variation can be significant.« less

Effects of electric and magnetic fields on the electronic properties of zigzag carbon and boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh; Ahmadi, Eghbal

2012-04-01

We have investigated the electronic properties of zigzag CNTs and BNNTs under the external transverse electric field and axial magnetic field, using tight binding approximation. It was found that after switching on the electric and magnetic fields, the band modification such as distortion of the degeneracy, change in energy dispersion, subband spacing and band gap size reduction occurs. The band gap of zigzag BNNTs decreases linearly with increasing the electric field strength but the band gap variation for CNTs increases first and later decreases (Metallic) or first hold constant and then decreases (semiconductor). For type (II) CNTs, at a weak magnetic field, by increasing the electric field strength, the band gap remains constant first and then decreases and in a stronger magnetic field the band gap reduction becomes parabolic. For type (III) CNTs, in any magnetic field, the band gap increases slowly until reaches a maximum value and then decreases linearly. Unlike to CNTs, the magnetic field has less effects on the BNNTs band gap variation.

Prediction of ppm level electrical failure by using physical variation analysis

NASA Astrophysics Data System (ADS)

Hou, Hsin-Ming; Kung, Ji-Fu; Hsu, Y.-B.; Yamazaki, Y.; Maruyama, Kotaro; Toyoshima, Yuya; Chen, Chu-en

2016-03-01

The quality of patterns printed on wafer may be attributed to factors such as process window control, pattern fidelity, overlay performance, and metrology. Each of these factors play an important role in making the process more effective by ensuring that certain design- and process-specific parameters are kept within acceptable variation. Since chip size and pattern density are increasing accordingly, in-line real time catching the in-chip weak patterns/defects per million opportunities (WP-DPMO) plays more and more significant role for product yield with high density memory. However, the current in-line inspection tools focus on single layer defect inspection, not effectively and efficiently to catch multi-layer weak patterns/defects even through voltage contrast and/or special test structure design [1]-[2]. In general, the multi-layer weak patterns/defects are escaped easily by using in-line inspection and cause ignorance of product dysfunction until off-line time-consuming final PFA/EFA will be used. To effectively and efficiently in-line real time monitor the potential multi-layer weak patterns, we quantify the bridge electrical metric between contact and gate electrodes into CD physical metric via big data from the larger field of view (FOV: 8k x 16k with 3 nm pixel equalizes to image main field size 34 um x 34 um @ 3 nm pixel) e-beam quality image contour compared to layout GDS database (D2DB) as shown in Fig. 1. Hadoop-based distributed parallel computing is implemented to improve the performance of big data architectures, Fig. 2. Therefore, the state of art in-line real time catching in-chip potential multi-layer weak patterns can be proven and achieved by following some studying cases [3]. Therefore, manufacturing sources of variations can be partitioned to systematic and random variations by applying statistical techniques based on the big data fundamental infrastructures. After big data handling, the in-chip CD and AA variations are distinguished by their spatial correlation distance. For local variations (LV) there is no correlation, whereas for global variations (GV) the correlation distance is very large [7]-[9]. This is the first time to certificate the validation of spatial distribution from the affordable bias contour big data fundamental infrastructures. And then apply statistical techniques to dig out the variation sources. The GV come from systematic issue, which could be compensated by adaptive LT condition or OPC correction. But LV comes from random issue, which being considered as intrinsic problem such as structure, material, tool capability… etc. In this paper studying, we can find out the advanced technology node SRAM contact CD local variation (LV) dominates in total variation, about 70%. It often plays significant in-line real time catching WP-DPMO role of the product yield loss, especially for wafer edge is the worst loss within wafer distribution and causes serious reliability concern. The major root cause of variations comes from the PR material induced burr defect (LV), the second one comes from GV enhanced wafer edge short opportunity, which being attributed to three factors, first one factor is wafer edge CD deliberated enlargement for yield improvement as shown in Fig. 10. Second factor is overlaps/AA shifts due to tool capability dealing with incoming wafer's war page issue and optical periphery layout dependent working pitch issue as shown in Fig. 9 (1)., the last factor comes from wafer edge burr enhanced by wafer edge larger Photo Resistance (PR) spin centrifugal force. After implementing KPIs such as GV related AA/CD indexes as shown in Fig. 9 (1) and 10, respectively, and LV related burr index as shown in Fig. 11., we can construct the parts per million (PPM) level short probability model via multi-variables regression, canonical correlation analysis and logistic transformation. The model provides prediction of PPM level electrical failure by using in-line real time physical variation analysis. However in order to achieve Total Quality Management (TQM), the adaptive Statistical Process Control (SPC) charts can be implemented to in-line real time catch PPM level product malfunction at manufacturing stage. Applying for early stage monitor likes incoming raw material, Photo Resistance (PR) … etc., the LV related burr KPI SPC charts could be a powerful quality inspection vehicle. To sum up the paper's contributions, the state of art in-line real time catching in-chip potential multi-layer physical weak patterns can be proven and achieved effectively and efficiently to associate with PPM level product dysfunction.

Intelligent electrical outlet for collective load control

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

Lentine, Anthony L.; Ford, Justin R.; Spires, Shannon V.

Various technologies described herein pertain to an electrical outlet that autonomously manages loads in a microgrid. The electrical outlet can provide autonomous load control in response to variations in electrical power generation supply in the microgrid. The electrical outlet includes a receptacle, a sensor operably coupled to the receptacle, and an actuator configured to selectively actuate the receptacle. The sensor measures electrical parameters at the receptacle. Further, a processor autonomously controls the actuator based at least in part on the electrical parameters measured at the receptacle, electrical parameters from one or more disparate electrical outlets in the microgrid, and amore » supply of generated electric power in the microgrid at a given time.« less

Flexible connector

DOEpatents

Savage, Mark E.; Simpson, Walter W.

1999-01-01

An electrical connector accommodates high current, is not labor intensive to assemble and disassemble, and allows a wide range of motion to accommodate mechanical variations and movement of connected components. The connector comprises several parts with joints therebetween, wherein each joint provides electrical connection between and allows relative motion of the joined parts. The combination of parts and joints maintains electrical connection between two electrical components even if the components are misaligned or move after connection.

Example Solar Electric Propulsion System asteroid tours using variational calculus

NASA Technical Reports Server (NTRS)

Burrows, R. R.

1985-01-01

Exploration of the asteroid belt with a vehicle utilizing a Solar Electric Propulsion System has been proposed in past studies. Some of those studies illustrated multiple asteroid rendezvous with trajectories obtained using approximate methods. Most of the inadequacies of those approximations are overcome in this paper, which uses the calculus of variations to calculate the trajectories and associated payloads of four asteroid tours. The modeling, equations, and solution techniques are discussed, followed by a presentation of the results.

Example Solar Electric Propulsion System asteroid tours using variational calculus

NASA Astrophysics Data System (ADS)

Burrows, R. R.

1985-06-01

Exploration of the asteroid belt with a vehicle utilizing a Solar Electric Propulsion System has been proposed in past studies. Some of those studies illustrated multiple asteroid rendezvous with trajectories obtained using approximate methods. Most of the inadequacies of those approximations are overcome in this paper, which uses the calculus of variations to calculate the trajectories and associated payloads of four asteroid tours. The modeling, equations, and solution techniques are discussed, followed by a presentation of the results.

Floating potential of emitting surfaces in plasmas with respect to the space potential

DOE PAGES

Kraus, B. F.; Raitses, Y.

2018-03-19

The potential difference between a floating emitting surface and the plasma surrounding it has been described by several sheath models, including the space-charge-limited sheath, the electron sheath with high emission current, and the inverse sheath produced by charge-exchange ion trapping. Our measurements reveal that each of these models has its own regime of validity. We determine the potential of an emissive filament relative to the plasma potential, emphasizing variations in emitted current density and neutral particle density. The potential of a filament in a diffuse plasma is first shown to vanish, consistent with the electron sheath model and increasing electronmore » emission. In a denser plasma with ample neutral pressure, the floating filament potential is positive, as predicted by a derived ion trapping condition. In conclusion, the filament floated negatively in a third plasma, where flowing ions and electrons and nonnegligible electric fields may have disrupted ion trapping. Depending on the regime chosen, emitting surfaces can float positively or negatively with respect to the plasma potential.« less

Floating potential of emitting surfaces in plasmas with respect to the space potential

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

Kraus, B. F.; Raitses, Y.

The potential difference between a floating emitting surface and the plasma surrounding it has been described by several sheath models, including the space-charge-limited sheath, the electron sheath with high emission current, and the inverse sheath produced by charge-exchange ion trapping. Our measurements reveal that each of these models has its own regime of validity. We determine the potential of an emissive filament relative to the plasma potential, emphasizing variations in emitted current density and neutral particle density. The potential of a filament in a diffuse plasma is first shown to vanish, consistent with the electron sheath model and increasing electronmore » emission. In a denser plasma with ample neutral pressure, the floating filament potential is positive, as predicted by a derived ion trapping condition. In conclusion, the filament floated negatively in a third plasma, where flowing ions and electrons and nonnegligible electric fields may have disrupted ion trapping. Depending on the regime chosen, emitting surfaces can float positively or negatively with respect to the plasma potential.« less

Potentiality Prediction of Electric Power Replacement Based on Power Market Development Strategy

NASA Astrophysics Data System (ADS)

Miao, Bo; Yang, Shuo; Liu, Qiang; Lin, Jingyi; Zhao, Le; Liu, Chang; Li, Bin

2017-05-01

The application of electric power replacement plays an important role in promoting the development of energy conservation and emission reduction in our country. To exploit the potentiality of regional electric power replacement, the regional GDP (gross domestic product) and energy consumption are taken as potentiality evaluation indicators. The principal component factors are extracted with PCA (principal component analysis), and the integral potentiality analysis is made to the potentiality of electric power replacement in the national various regions; a region is taken as a research object, and the potentiality of electric power replacement is defined and quantified. The analytical model for the potentiality of multi-scenario electric power replacement is developed, and prediction is made to the energy consumption with the grey prediction model. The relevant theoretical research is utilized to realize prediction analysis on the potentiality amount of multi-scenario electric power replacement.

Uniform electric field generation in circular multi-well culture plates using polymeric inserts

NASA Astrophysics Data System (ADS)

Tsai, Hsieh-Fu; Cheng, Ji-Yen; Chang, Hui-Fang; Yamamoto, Tadashi; Shen, Amy Q.

2016-05-01

Applying uniform electric field (EF) in vitro in the physiological range has been achieved in rectangular shaped microchannels. However, in a circular-shaped device, it is difficult to create uniform EF from two electric potentials due to different electrical resistances originated from the length difference between the diameter of the circle and the length of any parallel chord of the bottom circular chamber where cells are cultured. To address this challenge, we develop a three-dimensional (3D) computer-aided designed (CAD) polymeric insert to create uniform EF in circular shaped multi-well culture plates. A uniform EF with a coefficient of variation (CV) of 1.2% in the 6-well plate can be generated with an effective stimulation area percentage of 69.5%. In particular, NIH/3T3 mouse embryonic fibroblast cells are used to validate the performance of the 3D designed Poly(methyl methacrylate) (PMMA) inserts in a circular-shaped 6-well plate. The CAD based inserts can be easily scaled up (i.e., 100 mm dishes) to further increase effective stimulation area percentages, and also be implemented in commercially available cultureware for a wide variety of EF-related research such as EF-cell interaction and tissue regeneration studies.

Surface structuring of boron doped CVD diamond by micro electrical discharge machining

NASA Astrophysics Data System (ADS)

Schubert, A.; Berger, T.; Martin, A.; Hackert-Oschätzchen, M.; Treffkorn, N.; Kühn, R.

2018-05-01

Boron doped diamond materials, which are generated by Chemical Vapor Deposition (CVD), offer a great potential for the application on highly stressed tools, e. g. in cutting or forming processes. As a result of the CVD process rough surfaces arise, which require a finishing treatment in particular for the application in forming tools. Cutting techniques such as milling and grinding are hardly applicable for the finish machining because of the high strength of diamond. Due to its process principle of ablating material by melting and evaporating, Electrical Discharge Machining (EDM) is independent of hardness, brittleness or toughness of the workpiece material. EDM is a suitable technology for machining and structuring CVD diamond, since boron doped CVD diamond is electrically conductive. In this study the ablation characteristics of boron doped CVD diamond by micro electrical discharge machining are investigated. Experiments were carried out to investigate the influence of different process parameters on the machining result. The impact of tool-polarity, voltage and discharge energy on the resulting erosion geometry and the tool wear was analyzed. A variation in path overlapping during the erosion of planar areas leads to different microstructures. The results show that micro EDM is a suitable technology for finishing of boron doped CVD diamond.

A Particle-in-Cell Simulation for the Traveling Wave Direct Energy Converter (TWDEC) for Fusion Propulsion

NASA Technical Reports Server (NTRS)

Chap, Andrew; Tarditi, Alfonso G.; Scott, John H.

2013-01-01

A Particle-in-cell simulation model has been developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC) applied to the conversion of charged fusion products into electricity. In this model the availability of a beam of collimated fusion products is assumed; the simulation is focused on the conversion of the beam kinetic energy into alternating current (AC) electric power. The model is electrostatic, as the electro-dynamics of the relatively slow ions can be treated in the quasistatic approximation. A two-dimensional, axisymmetric (radial-axial coordinates) geometry is considered. Ion beam particles are injected on one end and travel along the axis through ring-shaped electrodes with externally applied time-varying voltages, thus modulating the beam by forming a sinusoidal pattern in the beam density. Further downstream, the modulated beam passes through another set of ring electrodes, now electrically oating. The modulated beam induces a time alternating potential di erence between adjacent electrodes. Power can be drawn from the electrodes by connecting a resistive load. As energy is dissipated in the load, a corresponding drop in beam energy is measured. The simulation encapsulates the TWDEC process by reproducing the time-dependent transfer of energy and the particle deceleration due to the electric eld phase time variations.

Nonlinear pyroelectric energy harvesting from relaxor single crystals.

PubMed

Khodayari, Akram; Pruvost, Sebastien; Sebald, Gael; Guyomar, Daniel; Mohammadi, Saber

2009-04-01

Energy harvesting from temperature variations in a Pb(Zn(1/3)Nb(2/3))(0.955)Ti(0.045)O(3) single crystal was studied and evaluated using the Ericsson thermodynamic cycle. The efficiency of this cycle related to Carnot cycle is 100 times higher than direct pyroelectric energy harvesting, and it can be as high as 5.5% for a 10 degrees C temperature variation and 2 kV/mm electric field. The amount of harvested energy for a 60 degrees C temperature variation and 2 kV/mm electric field is 242.7 mJ x cm(-3). The influence of ferroelectric phase transitions on the energy harvesting performance is discussed and illustrated with experimental results.

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.

Optical Interconnection Via Computer-Generated Holograms

NASA Technical Reports Server (NTRS)

Liu, Hua-Kuang; Zhou, Shaomin

1995-01-01

Method of free-space optical interconnection developed for data-processing applications like parallel optical computing, neural-network computing, and switching in optical communication networks. In method, multiple optical connections between multiple sources of light in one array and multiple photodetectors in another array made via computer-generated holograms in electrically addressed spatial light modulators (ESLMs). Offers potential advantages of massive parallelism, high space-bandwidth product, high time-bandwidth product, low power consumption, low cross talk, and low time skew. Also offers advantage of programmability with flexibility of reconfiguration, including variation of strengths of optical connections in real time.

A theoretical study of hot plasma spheroids in the presence of low-frequency electromagnetic waves

NASA Astrophysics Data System (ADS)

Ahmadizadeh, Y.; Jazi, B.; Barjesteh, S.

2016-07-01

While taking into account thermal motion of electrons, scattering of electromagnetic waves with low frequency from hot plasma spheroids is investigated. In this theoretical research, ions are heavy to respond to electromagnetic fluctuations. The solution of scalar wave equation in spheroidal coordinates for electric potential inside the plasma spheroids are obtained. The variations of resonance frequencies vs. Debye length are studied and consistency between the obtained results in this paper and the results for the well-known plasma objects such as plasma column and spherical plasma have been proved.

Probabilistic Physics-Based Risk Tools Used to Analyze the International Space Station Electrical Power System Output

NASA Technical Reports Server (NTRS)

Patel, Bhogila M.; Hoge, Peter A.; Nagpal, Vinod K.; Hojnicki, Jeffrey S.; Rusick, Jeffrey J.

2004-01-01

This paper describes the methods employed to apply probabilistic modeling techniques to the International Space Station (ISS) power system. These techniques were used to quantify the probabilistic variation in the power output, also called the response variable, due to variations (uncertainties) associated with knowledge of the influencing factors called the random variables. These uncertainties can be due to unknown environmental conditions, variation in the performance of electrical power system components or sensor tolerances. Uncertainties in these variables, cause corresponding variations in the power output, but the magnitude of that effect varies with the ISS operating conditions, e.g. whether or not the solar panels are actively tracking the sun. Therefore, it is important to quantify the influence of these uncertainties on the power output for optimizing the power available for experiments.

Influence of Ni-Cr substitution on the magnetic and electric properties of magnesium ferrite nanomaterials

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

Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Ahmad, Zahoor; Meydan, Turgut

2012-02-15

Graphical abstract: Variation of saturation magnetization (M{sub S}) and magnetocrystalline anisotropy coefficient (K{sub 1}) with Ni-Cr content for Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5). Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} are synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer High field regime of M-H loops are modeled using Law of Approach to saturation. Black-Right-Pointing-Pointer A considerable increase in the value of M{sub S} from 148 kA/m to 206 kA/m is achieved Black-Right-Pointing-Pointer {rho}{sup RT} enhanced to the order of 10{sup 9} {Omega}cm at potential operational range around 300 K. -- Abstract: The effect of variationmore » of composition on the structural, morphological, magnetic and electric properties of Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5) nanocrystallites is presented. The samples were prepared by novel polyethylene glycol (PEG) assisted microemulsion method with average crystallite size of 15-47 nm. The microstructure, chemical, and phase analyses of the samples were studied by the scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray fluorescence (ED-XRF), and X-ray diffraction (XRD). Compositional variation greatly affected the magnetic and structural properties. The high-field regimes of the magnetic loops are modelled using the Law of Approach (LOA) to saturation in order to extract information about their anisotropy and the saturation magnetization. Thermal demagnetization measurements are carried out using VSM and significant enhancement of the Curie temperature from 681 K to 832 K has been achieved by substitution of different contents of Ni-Cr. The dc-electrical resistivity ({rho}{sup RT}) at potential operational range around 300 K is increased from 7.5 Multiplication-Sign 10{sup 8} to 4.85 Multiplication-Sign 10{sup 9} {Omega}cm with the increase in Ni-Cr contents. Moreover, the results of the present study provide sufficient evidence to show that the electric and magnetic properties of Mg-ferrite have been improved significantly by substituting low contents of Ni-Cr.« less

Effects of Temporal Wind Patterns on the Value of Wind-GeneratedElectricity at Different Sites in California and the Northwest

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

Fripp, Matthias; Wiser, Ryan

2006-08-04

Wind power production varies on a diurnal and seasonal basis. In this paper, we use wind speed data from three different sources to assess the effects of wind timing on the value of electric power from potential wind farm locations in California and the Northwestern United States. By ''value'', we refer to either the contribution of wind power to meeting the electric system's peak loads, or the financial value of wind power in electricity markets. Sites for wind power projects are often screened or compared based on the annual average power production that would be expected from wind turbines atmore » each site (Baban and Parry 2001; Brower et al. 2004; Jangamshetti and Rau 2001; Nielsen et al. 2002; Roy 2002; Schwartz 1999). However, at many locations, variations in wind speeds during the day and year are correlated with variations in the electric power system's load and wholesale market prices (Burton et al. 2001; Carlin 1983; Kennedy and Rogers 2003; Man Bae and Devine 1978; Sezgen et al. 1998); this correlation may raise or lower the value of wind power generated at each location. A number of previous reports address this issue somewhat indirectly by studying the contribution of individual wind power sites to the reliability or economic operation of the electric grid, using hourly wind speed data (Fleten et al.; Kahn 1991; Kirby et al. 2003; Milligan 2002; van Wijk et al. 1992). However, we have not identified any previous study that examines the effect of variations in wind timing across a broad geographical area on wholesale market value or capacity contribution of those different wind power sites. We have done so, to determine whether it is important to consider wind-timing when planning wind power development, and to try to identify locations where timing would have a more positive or negative effect. The research reported in this paper seeks to answer three specific questions: (1) How large of an effect can the temporal variation of wind power have on the value of wind in different wind resource areas? (2) Which locations are affected most positively or negatively by the seasonal and diurnal timing of wind speeds? (3) How compatible are wind resources in California and the Northwest (Washington, Oregon, Idaho, Montana and Wyoming) with wholesale power prices and loads in either region? The latter question is motivated by the fact that wind power projects in the Northwest could sell their output into California (and vice versa), and that California has an aggressive renewable energy policy that may ultimately yield such imports. We also assess whether modeled wind data from TrueWind Solutions, LLC, can help answer such questions, by comparing results found using the TrueWind data to those found using anemometers or wind farm power production data. This paper summarizes results that are presented in more detail in a recent report from Lawrence Berkeley National Laboratory (Fripp and Wiser 2006). The full report is available at http://eetd.lbl.gov/EA/EMP/re-pubs.html.« less

Phase modulation of mid-infrared radiation in double-quantum-well structures under a lateral electric field

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

Balagula, R. M.; Vinnichenko, M. Ya.; Makhov, I. S.

2017-03-15

The modulation of polarized radiation by GaAs/AlGaAs structures with tunnel-coupled double quantum wells in a strong lateral electric field is studied. The spectra of the variation in the refractive index under a lateral electric field in the vicinity of the intersubband resonance are experimentally investigated.

Organic Light-Emitting Diode-on-Silicon Pixel Circuit Using the Source Follower Structure with Active Load for Microdisplays

NASA Astrophysics Data System (ADS)

Kwak, Bong-Choon; Lim, Han-Sin; Kwon, Oh-Kyong

2011-03-01

In this paper, we propose a pixel circuit immune to the electrical characteristic variation of organic light-emitting diodes (OLEDs) for organic light-emitting diode-on-silicon (OLEDoS) microdisplays with a 0.4 inch video graphics array (VGA) resolution and a 6-bit gray scale. The proposed pixel circuit is implemented using five p-channel metal oxide semiconductor field-effect transistors (MOSFETs) and one storage capacitor. The proposed pixel circuit has a source follower with a diode-connected transistor as an active load for improving the immunity against the electrical characteristic variation of OLEDs. The deviation in the measured emission current ranges from -0.165 to 0.212 least significant bit (LSB) among 11 samples while the anode voltage of OLED is 0 V. Also, the deviation in the measured emission current ranges from -0.262 to 0.272 LSB in pixel samples, while the anode voltage of OLED varies from 0 to 2.5 V owing to the electrical characteristic variation of OLEDs.

Medium and large-scale variations of dynamo-induced electric fields from AE ion drift measurements

NASA Technical Reports Server (NTRS)

Coley, W. R.; Mcclure, J. P.

1986-01-01

Current models of the low latitude electric field are largely based on data from incoherent scatter radars. These observations are extended through the addition of the rather extensive high quality electric field measurements from the Ion Drift Meter (IDM) aboard the Atmosphere Explorer (AE) spacecraft. Some preliminary results obtained from the Unified Abstract files of satellite AE-E are presented. This satellite was active from the end of 1975 through June 1981 in various elliptical and circular orbits having an inclination near 20 deg. The resulting data can be examined for the variation of ion drift with latitude, longitude, season, solar cycle, altitude, and magnetic activity. The results presented deal primarily with latitudinal variations of the drift features. Diagrams of data are given and briefly interpreted. The preliminary results presented here indicate that IDM data from the AE and the more recent Dynamics Explorer B spacecraft should continue to disclose some interesting and previously unobserved dynamical features of the low latitude F region.

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

Consonni, Stefano; LEAP - Laboratorio Energia Ambiente Piacenza, Via Bixio 27, 29100 Piacenza; Vigano, Federico, E-mail: federico.vigano@polimi.it

Highlights: > The amount of waste available for energy recovery is significantly higher than the Unsorted Residual Waste (URW). > Its energy potential is always higher than the complement to 100% of the Source Separation Level (SSL). > Increasing SSL has marginal effects on the potential for energy recovery. > Variations in the composition of the waste fed to WtE plants affect only marginally their performances. > A large WtE plant with a treatment capacity some times higher than a small plant achieves electric efficiency appreciably higher. - Abstract: This article is part of a set of six coordinated papersmore » reporting the main findings of a research project carried out by five Italian universities on 'Material and energy recovery in Integrated Waste Management Systems (IWMS)'. An overview of the project and a summary of the most relevant results can be found in the introductory article of the series. This paper describes the work related to the evaluation of mass and energy balances, which has consisted of three major efforts (i) development of a model for quantifying the energy content and the elemental compositions of the waste streams appearing in a IWMS; (ii) upgrade of an earlier model to predict the performances of Waste-to-Energy (WtE) plants; (iii) evaluation of mass and energy balances of all the scenarios and the recovery paths considered in the project. Results show that not only the amount of material available for energy recovery is significantly higher than the Unsorted Residual Waste (URW) left after Separate Collection (SC), because selection and recycling generate significant amounts of residues, but its heating value is higher than that of the original, gross waste. Therefore, the energy potential of what is left after recycling is always higher than the complement to 100% of the Source Separation Level (SSL). Also, increasing SSL has marginal effects on the potential for energy recovery: nearly doubling SSL (from 35% to 65%) reduces the energy potential only by one fourth. Consequently, even at high SSL energy recovery is a fundamental step of a sustainable waste management system. Variations of SSL do bring about variations of the composition, heating value and moisture content of the material fed to WtE plants, but these variations (i) are smaller than one can expect; (ii) have marginal effects on the performances of the WtE plant. These considerations suggest that the mere value of SSL is not a good indicator of the quality of the waste management system, nor of its energy and environmental outcome. Given the well-known dependence of the efficiency of steam power plants with their power output, the efficiency of energy recovery crucially depends on the size of the IWMS served by the WtE plant. A fivefold increase of the amount of gross waste handled in the IWMS (from 150,000 to 750,000 tons per year of gross waste) allows increasing the electric efficiencies of the WtE plant by about 6-7 percentage points (from 21-23% to 28.5% circa).« less

Flexible connector

DOEpatents

Savage, M.E.; Simpson, W.W.

1999-07-27

An electrical connector accommodates high current, is not labor intensive to assemble and disassemble, and allows a wide range of motion to accommodate mechanical variations and movement of connected components. The connector comprises several parts with joints therebetween, wherein each joint provides electrical connection between and allows relative motion of the joined parts. The combination of parts and joints maintains electrical connection between two electrical components even if the components are misaligned or move after connection. 6 figs.

Electric dipole moment of the diatomic tif in its higher vibrational states

NASA Astrophysics Data System (ADS)

Nair, K. P. R.; Hoeft, J.

1983-04-01

The electric dipole moment of 205Tl 19F has been measured in its higher vibrational states up to ν = 7 by studying the Statk effect in the J = O → 1 rotational transitions. The variation of the electric dipole moment with vibrational states is discussed. The electric dipole moment can be written as lμ νl = 4.1941 (15) + 0.0681(12) (ν + 1/2) D.

Work function variation of MoS{sub 2} atomic layers grown with chemical vapor deposition: The effects of thickness and the adsorption of water/oxygen molecules

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

Kim, Jong Hun; Kim, Jae Hyeon; Park, Jeong Young, E-mail: peterlee@skku.edu, E-mail: jeongypark@kaist.ac.kr

2015-06-22

The electrical properties of two-dimensional atomic sheets exhibit remarkable dependences on layer thickness and surface chemistry. Here, we investigated the variation of the work function properties of MoS{sub 2} films prepared with chemical vapor deposition (CVD) on SiO{sub 2} substrates with the number of film layers. Wafer-scale CVD MoS{sub 2} films with 2, 4, and 12 layers were fabricated on SiO{sub 2}, and their properties were evaluated by using Raman and photoluminescence spectroscopies. In accordance with our X-ray photoelectron spectroscopy results, our Kelvin probe force microscopy investigation found that the surface potential of the MoS{sub 2} films increases by ∼0.15 eVmore » when the number of layers is increased from 2 to 12. Photoemission spectroscopy (PES) with in-situ annealing under ultra high vacuum conditions was used to directly demonstrate that this work function shift is associated with the screening effects of oxygen or water molecules adsorbed on the film surface. After annealing, it was found with PES that the surface potential decreases by ∼0.2 eV upon the removal of the adsorbed layers, which confirms that adsorbed species have a role in the variation in the work function.« less

Quantifying the roles of random motility and directed motility using advection-diffusion theory for a 3T3 fibroblast cell migration assay stimulated with an electric field.

PubMed

Simpson, Matthew J; Lo, Kai-Yin; Sun, Yung-Shin

2017-03-17

Directed cell migration can be driven by a range of external stimuli, such as spatial gradients of: chemical signals (chemotaxis); adhesion sites (haptotaxis); or temperature (thermotaxis). Continuum models of cell migration typically include a diffusion term to capture the undirected component of cell motility and an advection term to capture the directed component of cell motility. However, there is no consensus in the literature about the form that the advection term takes. Some theoretical studies suggest that the advection term ought to include receptor saturation effects. However, others adopt a much simpler constant coefficient. One of the limitations of including receptor saturation effects is that it introduces several additional unknown parameters into the model. Therefore, a relevant research question is to investigate whether directed cell migration is best described by a simple constant tactic coefficient or a more complicated model incorporating saturation effects. We study directed cell migration using an experimental device in which the directed component of the cell motility is driven by a spatial gradient of electric potential, which is known as electrotaxis. The electric field (EF) is proportional to the spatial gradient of the electric potential. The spatial variation of electric potential across the experimental device varies in such a way that there are several subregions on the device in which the EF takes on different values that are approximately constant within those subregions. We use cell trajectory data to quantify the motion of 3T3 fibroblast cells at different locations on the device to examine how different values of the EF influences cell motility. The undirected (random) motility of the cells is quantified in terms of the cell diffusivity, D, and the directed motility is quantified in terms of a cell drift velocity, v. Estimates D and v are obtained under a range of four different EF conditions, which correspond to normal physiological conditions. Our results suggest that there is no anisotropy in D, and that D appears to be approximately independent of the EF and the electric potential. The drift velocity increases approximately linearly with the EF, suggesting that the simplest linear advection term, with no additional saturation parameters, provides a good explanation of these physiologically relevant data. We find that the simplest linear advection term in a continuum model of directed cell motility is sufficient to describe a range of different electrotaxis experiments for 3T3 fibroblast cells subject to normal physiological values of the electric field. This is useful information because alternative models that include saturation effects involve additional parameters that need to be estimated before a partial differential equation model can be applied to interpret or predict a cell migration experiment.

The impacts of wind power integration on sub-daily variation in river flows downstream of hydroelectric dams.

PubMed

Kern, Jordan D; Patino-Echeverri, Dalia; Characklis, Gregory W

2014-08-19

Due to their operational flexibility, hydroelectric dams are ideal candidates to compensate for the intermittency and unpredictability of wind energy production. However, more coordinated use of wind and hydropower resources may exacerbate the impacts dams have on downstream environmental flows, that is, the timing and magnitude of water flows needed to sustain river ecosystems. In this paper, we examine the effects of increased (i.e., 5%, 15%, and 25%) wind market penetration on prices for electricity and reserves, and assess the potential for altered price dynamics to disrupt reservoir release schedules at a hydroelectric dam and cause more variable and unpredictable hourly flow patterns (measured in terms of the Richards-Baker Flashiness (RBF) index). Results show that the greatest potential for wind energy to impact downstream flows occurs at high (∼25%) wind market penetration, when the dam sells more reserves in order to exploit spikes in real-time electricity prices caused by negative wind forecast errors. Nonetheless, compared to the initial impacts of dam construction (and the dam's subsequent operation as a peaking resource under baseline conditions) the marginal effects of any increased wind market penetration on downstream flows are found to be relatively minor.

Application of Multivariable Analysis and FTIR-ATR Spectroscopy to the Prediction of Properties in Campeche Honey

PubMed Central

Pat, Lucio; Ali, Bassam; Guerrero, Armando; Córdova, Atl V.; Garduza, José P.

2016-01-01

Attenuated total reflectance-Fourier transform infrared spectrometry and chemometrics model was used for determination of physicochemical properties (pH, redox potential, free acidity, electrical conductivity, moisture, total soluble solids (TSS), ash, and HMF) in honey samples. The reference values of 189 honey samples of different botanical origin were determined using Association Official Analytical Chemists, (AOAC), 1990; Codex Alimentarius, 2001, International Honey Commission, 2002, methods. Multivariate calibration models were built using partial least squares (PLS) for the measurands studied. The developed models were validated using cross-validation and external validation; several statistical parameters were obtained to determine the robustness of the calibration models: (PCs) optimum number of components principal, (SECV) standard error of cross-validation, (R 2 cal) coefficient of determination of cross-validation, (SEP) standard error of validation, and (R 2 val) coefficient of determination for external validation and coefficient of variation (CV). The prediction accuracy for pH, redox potential, electrical conductivity, moisture, TSS, and ash was good, while for free acidity and HMF it was poor. The results demonstrate that attenuated total reflectance-Fourier transform infrared spectrometry is a valuable, rapid, and nondestructive tool for the quantification of physicochemical properties of honey. PMID:28070445

Effects of Lipid Composition on Bilayer Membranes Quantified by All-Atom Molecular Dynamics.

PubMed

Ding, Wei; Palaiokostas, Michail; Wang, Wen; Orsi, Mario

2015-12-10

Biological bilayer membranes typically contain varying amounts of lamellar and nonlamellar lipids. Lamellar lipids, such as dioleoylphosphatidylcholine (DOPC), are defined by their tendency to form the lamellar phase, ubiquitous in biology. Nonlamellar lipids, such as dioleoylphosphatidylethanolamine (DOPE), prefer instead to form nonlamellar phases, which are mostly nonbiological. However, nonlamellar lipids mix with lamellar lipids in biomembrane structures that remain overall lamellar. Importantly, changes in the lamellar vs nonlamellar lipid composition are believed to affect membrane function and modulate membrane proteins. In this work, we employ atomistic molecular dynamics simulations to quantify how a range of bilayer properties are altered by variations in the lamellar vs nonlamellar lipid composition. Specifically, we simulate five DOPC/DOPE bilayers at mixing ratios of 1/0, 3/1, 1/1, 1/3, and 0/1. We examine properties including lipid area and bilayer thickness, as well as the transmembrane profiles of electron density, lateral pressure, electric field, and dipole potential. While the bilayer structure is only marginally altered by lipid composition changes, dramatic effects are observed for the lateral pressure, electric field, and dipole potential profiles. Possible implications for membrane function are discussed.

Dosage Considerations for Transcranial Direct Current Stimulation in Children: A Computational Modeling Study

PubMed Central

Kessler, Sudha Kilaru; Minhas, Preet; Woods, Adam J.; Rosen, Alyssa; Gorman, Casey; Bikson, Marom

2013-01-01

Transcranial direct current stimulation (tDCS) is being widely investigated in adults as a therapeutic modality for brain disorders involving abnormal cortical excitability or disordered network activity. Interest is also growing in studying tDCS in children. Limited empirical studies in children suggest that tDCS is well tolerated and may have a similar safety profile as in adults. However, in electrotherapy as in pharmacotherapy, dose selection in children requires special attention, and simple extrapolation from adult studies may be inadequate. Critical aspects of dose adjustment include 1) differences in neurophysiology and disease, and 2) variation in brain electric fields for a specified dose due to gross anatomical differences between children and adults. In this study, we used high-resolution MRI derived finite element modeling simulations of two healthy children, ages 8 years and 12 years, and three healthy adults with varying head size to compare differences in electric field intensity and distribution. Multiple conventional and high-definition tDCS montages were tested. Our results suggest that on average, children will be exposed to higher peak electrical fields for a given applied current intensity than adults, but there is likely to be overlap between adults with smaller head size and children. In addition, exposure is montage specific. Variations in peak electrical fields were seen between the two pediatric models, despite comparable head size, suggesting that the relationship between neuroanatomic factors and bioavailable current dose is not trivial. In conclusion, caution is advised in using higher tDCS doses in children until 1) further modeling studies in a larger group shed light on the range of exposure possible by applied dose and age and 2) further studies correlate bioavailable dose estimates from modeling studies with empirically tested physiologic effects, such as modulation of motor evoked potentials after stimulation. PMID:24086698

Energy Levels in Quantum Wells.

NASA Astrophysics Data System (ADS)

Zang, Jan Xin

Normalized analytical equations for eigenstates of an arbitrary one-dimensional configuration of square potentials in a well have been derived. The general formulation is used to evaluate the energy levels of a particle in a very deep potential well containing seven internal barriers. The configuration can be considered as a finite superlattice sample or as a simplified model for a sample with only several atom layers. The results are shown in graphical forms as functions of the height and width of the potential barriers and as functions of the ratio of the effective mass in barrier to the mass in well. The formation of energy bands and surface eigenstates from eigenstates of a deep single well, the coming close of two energy bands and a surface state which are separate ordinarily, and mixing of the wave function of a surface state with the bulk energy bands are seen. Then the normalized derivation is extended to study the effect of a uniform electric field applied across a one-dimensional well containing an internal configuration of square potentials The general formulation is used to calculate the electric field dependence of the energy levels of a deep well with five internal barriers. Typical results are shown in graphical forms as functions of the barrier height, barrier width, barrier effective mass and the field strength. The formation of Stark ladders and surface states from the eigenstates of a single deep well in an electric field, the localization process of wave functions with changing barrier height, width, and field strength and their anticrossing behaviors are seen. The energy levels of a hydrogenic impurity in a uniform medium and in a uniform magnetic field are calculated with variational methods. The energy eigenvalues for the eigenstates with major quantum number less than or equal to 3 are obtained. The results are consistent with previous results. Furthermore, the energy levels of a hydrogenic impurity at the bottom of a one-dimensional parabolic quantum well with a magnetic field normal to the plane of the well are calculated with the finite-basis-set variational method. The limit of small radial distance and the limit of great radial distance are considered to choose a set of proper basis functions. It is found that the energy levels increase with increasing parabolic parameter alpha and increase with increasing normalized magnetic field strength gamma except those levels with magnetic quantum number m < 0 at small gamma.

Cholinergic interneurons in the feeding system of the pond snail Lymnaea stagnalis. II. N1 interneurons make cholinergic synapses with feeding motoneurons.

PubMed

Elliott, C J; Kemenes, G

1992-05-29

The N1 neurons are a population of interneurons active during the protraction phase of the feeding rhythm. All the N1 neurons are coupled by electrical synapses which persist in a high Mg/low Ca saline which blocks chemical synapses. Individual N1 spikes produce discrete electrotonic postsynaptic potentials (PSPS) in other N1 cells, but the coupling is not strong enough to ensure 1:1 firing. Bursts of N1 spikes generate compound PSPS in the feeding motoneurons. The sign (excitation or inhibition) of the N1 input corresponds with the synaptic barrage recorded during the protraction phase. Discrete PSPS are only resolved in a Hi-Di saline. Their variation in latency and number can be explained by variation in electrotonic propagation within the electrically coupled network of N1 cells. The excitatory postsynaptic potentials (ESPS) in the 1 cell are reduced by 0.5 mM antagonists hexamethonium (HMT), atropine (ATR), curare (d-TC) and by methylxylocholine (MeXCh), all of which block the excitatory cholinergic receptor (Elliott et al. (Phil. Trans. R. Soc. Lond. 336, 157-166 (Preceding paper.) (1992)). The 1 cell EPSPS were transiently blocked by phenyltrimethylammonium (PTMA), which is both an agonist and antagonist at the 1 cell excitatory acetylcholine (ACh) receptor (Elliott et al. 1992). The inhibitory postsynaptic potential (IPSP) in the 3 cell is blocked by bath applications of MeXCh and PTMA, which both abolish the response of the 3 cell to ACh (Elliott et. al. 1992). The effects of the cholinergic antagonists on the response of 4 cluster and 5 cells to N1 stimulation matches their response to ACh (Elliott et al. 1992). It is concluded that the population of N1 cells are multiaction, premotor cholinergic interneurons.

Numerical modelling of electrochemical polarization around charged metallic particles

NASA Astrophysics Data System (ADS)

Bücker, Matthias; Undorf, Sabine; Flores Orozco, Adrián; Kemna, Andreas

2017-04-01

We extend an existing analytical model and carry out numerical simulations to study the polarization process around charged metallic particles immersed in an electrolyte solution. Electro-migration and diffusion processes in the electrolyte are described by the Poisson-Nernst-Planck system of partial differential equations. To model the surface charge density, we consider a time- and frequency-invariant electric potential at the particle surface, which leads to the build-up of a static electrical double layer (EDL). Upon excitation by an external electric field at low frequencies, we observe the superposition of two polarization processes. On the one hand, the induced dipole moment on the metallic particle leads to the accumulation of opposite charges in the electrolyte. This charge polarization corresponds to the long-known response of uncharged metallic particles. On the other hand, the unequal cation and anion concentrations in the EDL give rise to a salinity gradient between the two opposite sides of the metallic particle. The resulting concentration polarization enhances the magnitude of the overall polarization response. Furthermore, we use our numerical model to study the effect of relevant model parameters such as surface charge density and ionic strength of the electrolyte on the resulting spectra of the effective conductivity of the composite model system. Our results do not only give interesting new insight into the time-harmonic variation of electric potential and ion concentrations around charged metallic particle. They are also able to reduce incongruities between earlier model predictions and geophysical field and laboratory measurements. Our model thereby improves the general understanding of IP signatures of metallic particles and represents the next step towards a quantitative interpretation of IP imaging results. Part of this research is funded by the Austrian Federal Ministry of Science, Research and Economy under the Raw Materials Initiative.

Laboratory Simulation of Electrical Discharge in Surface Lunar Regolith

NASA Astrophysics Data System (ADS)

Shusterman, M.; Izenberg, N.; Wing, B. R.; Liang, S.

2016-12-01

Physical, chemical, and optical characteristics of space-weathered surface materials on airless bodies are produced primarily from bombardment by solar energetic particles and micrometeoroid impacts. On bodies such as the Moon and Mercury, soils in permanently shadowed regions (PSRs) are very cold, have low electrical conductivities, and are subjected to a high flux of incoming energetic particles accelerated by solar events. Theoretical models predict that up to 25% of gardened soils in the lunar polar regions are altered by dielectric breakdown; a potentially significant weathering process that is currently unconfirmed. Although electrical properties of lunar soils have been studied in relation to flight electronics and spacecraft safety, no studies have characterized potential alterations to soils resulting from electrical discharge. To replicate the surface charge field in PSRs, lunar regolith simulant JSC-1A was placed between two parallel plane electrodes under both low and high vacuum environments, 10e-3 torr and 2.5e-6 torr, respectively. Voltage was increased until discharge occurred within the sample. Grains were analyzed using an SVC fiber-fed point spectrometer, Olympus BX51 upright metallurgical microscope, and a Hitachi TM3000 scanning electron microscope with Bruker Quantax-70 X-ray spectrometer. Discharges occurring in samples under low vacuum resulted in surficial melting, silicate vapor deposition, coalescence of metallic iron, and micro-scale changes to surface topography. Samples treated under a high vacuum environment showed similar types of effects, but fewer in number compared to low vacuum samples. The variation in alteration abundances between the two environments implies that discharges may be occurring across surface contaminants, even at high vacuum conditions, inhibiting dielectric breakdown in our laboratory simulations.

Measurement and modeling of electric field and space-charge distributions in obstructed helium discharge

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

Fendel, Peter; Ganguly, Biswa N.; Bletzinger, Peter

Axial and radial variations of electric field have been measured in dielectric shielded 0.025 m diameter parallel plate electrode with 0.0065 m gap for 1.6 mA, 2260 V helium dc discharge at 1.75 Torr. The axial and radial electric field profiles have been measured from the Stark splitting of 2{sup 1}S→11 {sup 1}P transition through collision induced fluorescence from 4{sup 3}D→2{sup 3}P. The electric field values showed a strong radial variation peaking to 500 kV/m near the cathode radial boundary, and decreasing to about 100 kV/m near the anode edge, suggesting the formation of an obstructed discharge for this low nd condition, where n is the gasmore » density and d is the gap distance. The off-axis Stark spectra showed that the electric field vector deviates from normal to the cathode surface which permits longer path electron trajectories in the inter-electrode gap. Also, the on-axis electric field gradient was very small and off-axis electric field gradient was large indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with the COMSOL finite element modeling program. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) = ρ{sub 0}(r/r{sub 0}){sup 3}, where ρ(r) is the local space charge density, ρ{sub 0} = 6 × 10{sup −3} Coulomb/m{sup 3}, r is the local radial value, and r{sub 0} is the radius of the electrode.« less

Dimensional Analysis and Electric Potential Due to a Uniformly Charged Sheet

ERIC Educational Resources Information Center

Aghamohammadi, Amir

2011-01-01

Dimensional analysis, superposition principle, and continuity of electric potential are used to study the electric potential of a uniformly charged square sheet on its plane. It is shown that knowing the electric potential on the diagonal and inside the square sheet is equivalent to knowing it everywhere on the plane of the square sheet. The…

Distributed electrical time domain reflectometry (ETDR) structural sensors: design models and proof-of-concept experiments

NASA Astrophysics Data System (ADS)

Stastny, Jeffrey A.; Rogers, Craig A.; Liang, Chen

1993-07-01

A parametric design model has been created to optimize the sensitivity of the sensing cable in a distributed sensing system. The system consists of electrical time domain reflectometry (ETDR) signal processing equipment and specially designed sensing cables. The ETDR equipment sends a high-frequency electric pulse (in the giga hertz range) along the sensing cable. Some portion of the electric pulse will be reflected back to the ETDR equipment as a result of the variation of the cable impedance. The electric impedance variation in the sensing cable can be related to its mechanical deformation, such as cable elongation (change in the resistance), shear deformation (change in the capacitance), corrosion of the cable or the materials around the cable (change in inductance and capacitance), etc. The time delay, amplitude, and shape of the reflected pulse provides the means to locate, determine the magnitude, and indicate the nature of the change in the electrical impedance, which is then related to the distributed structural deformation. The sensing cables are an essential part of the health-monitoring system. By using the parametric design model, the optimum cable parameters can be determined for specific deformation. Proof-of-concept experiments also are presented in the paper to demonstrate the utility of an electrical TDR system in distributed sensing applications.

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

NASA Astrophysics Data System (ADS)

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

2011-08-01

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

Revealing dynamically-organized receptor ion channel clusters in live cells by a correlated electric recording and super-resolution single-molecule imaging approach.

PubMed

Yadav, Rajeev; Lu, H Peter

2018-03-28

The N-methyl-d-aspartate (NMDA) receptor ion-channel is activated by the binding of ligands, along with the application of action potential, important for synaptic transmission and memory functions. Despite substantial knowledge of the structure and function, the gating mechanism of the NMDA receptor ion channel for electric on-off signals is still a topic of debate. We investigate the NMDA receptor partition distribution and the associated channel's open-close electric signal trajectories using a combined approach of correlating single-molecule fluorescence photo-bleaching, single-molecule super-resolution imaging, and single-channel electric patch-clamp recording. Identifying the compositions of NMDA receptors, their spatial organization and distributions over live cell membranes, we observe that NMDA receptors are organized inhomogeneously: nearly half of the receptor proteins are individually dispersed; whereas others exist in heterogeneous clusters of around 50 nm in size as well as co-localized within the diffraction limited imaging area. We demonstrate that inhomogeneous interactions and partitions of the NMDA receptors can be a cause of the heterogeneous gating mechanism of NMDA receptors in living cells. Furthermore, comparing the imaging results with the ion-channel electric current recording, we propose that the clustered NMDA receptors may be responsible for the variation in the current amplitude observed in the on-off two-state ion-channel electric signal trajectories. Our findings shed new light on the fundamental structure-function mechanism of NMDA receptors and present a conceptual advancement of the ion-channel mechanism in living cells.

Streaming potential in nature

NASA Astrophysics Data System (ADS)

Schuch, M.

For the first time, QUINCKE found in 1859 the phenomenon of electric streaming potential. Twenty years later HELMHOLTZ published a mathematical expression for the streaming potential. In the following years a number of scientists studied the phenomenon. BIKERMAN (1932) showed that each electric streaming potential causes an electric current in the contrary direction. SWARTZENDRUBER postulated in 1967 that this electric field tries to stop the streaming potential as a result of the energy balance.

Small scale characterization of vine plant root zone via 3D electrical resistivity tomography and Mise-à-la-Masse method: a case study in a Bordeaux Vineyard

NASA Astrophysics Data System (ADS)

Mary, Benjamin; Peruzzo, Luca; Boaga, Jacopo; Schmutz, Myriam; Wu, Yuxin; Hubbard, Susan S.; Cassiani, Giorgio

2017-04-01

Nowadays, best viticulture practices require the joint interpretation of climate and soils data. However, information about the soil structure and subsoil processes is often lacking, as point measurements, albeit precise, cannot ensure sufficient spatial coverage and resolution. Non-invasive methods can provide spatially extensive, high resolution information that, supported by traditional point-like data, help complete the complex picture of subsoil static and dynamic reality. So far very little emphasis has been given to investigating the role of soil properties and even less of roots activity on winegrapes. Vine plant's root systems play an important role in providing the minerals to the plants, but also control the water uptake and thus the water state of the vines, which is a key factor determining the grape quality potential. In this contribution we report about the measurements conducted since June 2016 in a vineyard near Bordeaux (France, Pessac Leognan Chateau). Two neighbor plants of different sizes have been selected. In order to spot small scale soil variations and root zone physical structure at the vicinity of the vine plants, we applied a methodology using longitudinal 2D tomography, 3D borehole-based electrical resistivity tomography and a variation of the mise-à-la-masse method (MALM) to assess the effect of plant roots on the current injection in the ground. Time-lapse measurements are particularly informative about the plant dynamics, and the focus is particularly applied on this approach. The time-lapse 3D ERT and MALM results are presented, and the potential to assimilate these data into a hydrological model that can account for the root water uptake as a function of atmospheric conditions is discussed.

Altered profile of mRNA expression in atrioventricular node of streptozotocin-induced diabetic rats

PubMed Central

Howarth, Frank Christopher; Parekh, Khatija; Jayaprakash, Petrilla; Inbaraj, Edward Samuel; Oz, Murat; Dobrzynski, Halina; Adrian, Thomas Edward

2017-01-01

Prolonged action potential duration, reduced action potential firing rate, upstroke velocity and rate of diastolic depolarization have been demonstrated in atrioventricular node (AVN) cells from streptozotocin (STZ)-induced diabetic rats. To further clarify the molecular basis of these electrical disturbances, the mRNA profiles encoding a variety of proteins associated with the generation and conduction of electrical activity in the AVN, were evaluated in the STZ-induced diabetic rat heart. Expression of mRNA was measured in AVN biopsies using reverse transcription-quantitative polymerase chain reaction techniques. Notable differences in mRNA expression included upregulation of genes encoding membrane and intracellular Ca2+ transport, including solute carrier family 8 member A1, transient receptor potential channel 1, ryanodine receptor 2/3, hyperpolarization-activated cyclic-nucleotide 2 and 3, calcium channel voltage-dependent, β2 subunit and sodium channels 3a, 4a, 7a and 3b. In addition to this, potassium channels potassium voltage-gated channel subfamily A member 4, potassium channel calcium activated intermediate/small conductance subfamily N α member 2, potassium voltage-gated channel subfamily J members 3, 5, and 11, potassium channel subfamily K members 1, 2, 3 and natriuretic peptide B (BNP) were upregulated in AVN of STZ heart, compared with controls. Alterations in gene expression were associated with upregulation of various proteins including the inwardly rectifying, potassium channel Kir3.4, NCX1 and BNP. The present study demonstrated notable differences in the profile of mRNA encoding proteins associated with the generation, conduction and regulation of electrical signals in the AVN of the STZ-induced diabetic rat heart. These data will provide a basis for a substantial range of future studies to investigate whether variations in mRNA translate into alterations in electrophysiological function. PMID:28731153

The plasma-wall transition layers in the presence of collisions with a magnetic field parallel to the wall

NASA Astrophysics Data System (ADS)

Moritz, J.; Faudot, E.; Devaux, S.; Heuraux, S.

2018-01-01

The plasma-wall transition is studied by means of a particle-in-cell (PIC) simulation in the configuration of a parallel to the wall magnetic field (B), with collisions between charged particles vs. neutral atoms taken into account. The investigated system consists of a plasma bounded by two absorbing walls separated by 200 electron Debye lengths (λd). The strength of the magnetic field is chosen such as the ratio λ d / r l , with rl being the electron Larmor radius, is smaller or larger than unity. Collisions are modelled with a simple operator that reorients randomly ion or electron velocity, keeping constant the total kinetic energy of both the neutral atom (target) and the incident charged particle. The PIC simulations show that the plasma-wall transition consists in a quasi-neutral region (pre-sheath), from the center of the plasma towards the walls, where the electric potential or electric field profiles are well described by an ambipolar diffusion model, and in a second region at the vicinity of the walls, called the sheath, where the quasi-neutrality breaks down. In this peculiar geometry of B and for a certain range of the mean-free-path, the sheath is found to be composed of two charged layers: the positive one, close to the walls, and the negative one, towards the plasma and before the neutral pre-sheath. Depending on the amplitude of B, the spatial variation of the electric potential can be non-monotonic and presents a maximum within the sheath region. More generally, the sheath extent as well as the potential drop within the sheath and the pre-sheath is studied with respect to B, the mean-free-path, and the ion and electron temperatures.

The ionic DTI model (iDTI) of dynamic diffusion tensor imaging (dDTI)

PubMed Central

Makris, Nikos; Gasic, Gregory P.; Garrido, Leoncio

2014-01-01

Measurements of water molecule diffusion along fiber tracts in CNS by diffusion tensor imaging (DTI) provides a static map of neural connections between brain centers, but does not capture the electrical activity along axons for these fiber tracts. Here, a modification of the DTI method is presented to enable the mapping of active fibers. It is termed dynamic diffusion tensor imaging (dDTI) and is based on a hypothesized “anisotropy reduction due to axonal excitation” (“AREX”). The potential changes in water mobility accompanying the movement of ions during the propagation of action potentials along axonal tracts are taken into account. Specifically, the proposed model, termed “ionic DTI model”, was formulated as follows.•First, based on theoretical calculations, we calculated the molecular water flow accompanying the ionic flow perpendicular to the principal axis of fiber tracts produced by electrical conduction along excited myelinated and non-myelinated axons.•Based on the changes in molecular water flow we estimated the signal changes as well as the changes in fractional anisotropy of axonal tracts while performing a functional task.•The variation of fractional anisotropy in axonal tracts could allow mapping the active fiber tracts during a functional task. Although technological advances are necessary to enable the robust and routine measurement of this electrical activity-dependent movement of water molecules perpendicular to axons, the proposed model of dDTI defines the vectorial parameters that will need to be measured to bring this much needed technique to fruition. PMID:25431757

Heavy metals in soil at a waste electrical and electronic equipment processing area in China.

PubMed

Gu, Weihua; Bai, Jianfeng; Yao, Haiyan; Zhao, Jing; Zhuang, Xuning; Huang, Qing; Zhang, Chenglong; Wang, JingWei

2017-11-01

For the objective of evaluating the contamination degree of heavy metals and analysing its variation trend in soil at a waste electrical and electronic equipment processing area in Shanghai, China, evaluation methods, which include single factor index method, geo-accumulation index method, comprehensive pollution index method, and potential ecological risk index method, were adopted in this study. The results revealed that the soil at a waste electrical and electronic equipment processing area was polluted by arsenic, cadmium, copper, lead, zinc, and chromium. It also demonstrated that the concentrations of heavy metals were increased over time. Exceptionally, the average value of the metalloid (arsenic) was 73.31 mg kg -1 in 2014, while it was 58.31 mg kg -1 in the first half of 2015, and it was 2.93 times and 2.33 times higher than that of the Chinese Environmental Quality Standard for Soil in 2014 and the first half of 2015, respectively. The sequences of the contamination degree of heavy metals in 2014 and the first half of 2015 were cadmium > lead > copper > chromium > zinc and cadmium > lead > chromium > zinc > copper. From the analysis of the potential ecological risk index method, arsenic and cadmium had higher ecological risk than other heavy metals. The integrated ecological risk index of heavy metals (cadmium, copper, lead, zinc, and chromium) and metalloid (arsenic) was 394.10 in 2014, while it was 656.16 in the first half of 2015, thus documenting a strong ecological risk.

Analysis of the costs of fuel supply for wood-fired electric power plants in rural Liberia

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

Perlack, R.D.; Barron, W.F.; Samuels, G.

1985-06-01

In recent years the quality of rural electric services in Liberia has been declining and the future economic viability of these power stations is a growing concern. Each of the ten operating and each of the planned rural public power stations is designed to operate exclusively on gas oil (diesel fuel). Fuel expenditures by the Liberian Electricity Corporation (LEC) for the rural public stations represent a major and growing burden on the financially hardpressed utility. Liberia has two potentially significant alternatives to oil-fired electric power for its up-country towns: small (1 to 5 MW) hydroelectric facilities, and wood-fired steam ormore » gasifier plants (0.2 to 2 MW). Although small hydroelectric facilities appear viable for several locations, they cannot serve all locations and will require thermal back-up. The economics of supplying wood to a rural electric power plant or rural grid were evaluated under several scenarios involving: (1) different sources of the feedstock, and (2) differences in wood supply requirements for plants based on the use of steam or gasifier technology, and variation in the utilization level for such plants. With a few minor exceptions, wood energy supplies are plentiful throughout Liberia. Liberia has four different potential sources of wood fuel supply: the commercial cutting of retired rubber trees; the harvesting of secondary growth forest just prior to the land returning to temporary cultivation as part of a system of shifting agriculture; adding to the system of shifting agriculture the planting of fast-growing wood species and harvesting these trees when the land again is brought back under cultivation (generally after about five to seven years); and the establishment of commercial short-rotation wood energy plantations. Results indicate that the use of wood to fuel rural power stations is a viable economic option.« less

Development of a new medium frequency EM device: Mapping soil water content variations using electrical conductivity and dielectric permittivity

NASA Astrophysics Data System (ADS)

Kessouri, P.; Buvat, S.; Tabbagh, A.

2012-12-01

Both electrical conductivity and dielectric permittivity of soil are influenced by its water content. Dielectric permittivity is usually measured in the high frequency range, using GPR or TDR, where the sensitivity to water content is high. However, its evaluation is limited by a low investigation depth, especially for clay rich soils. Electrical conductivity is closely related not only to soil water content, but also to clay content and soil structure. A simultaneous estimation of these electrical parameters can allow the mapping of soil water content variations for an investigation depth close to 1m. In order to estimate simultaneously both soil electrical conductivity and dielectric permittivity, an electromagnetic device working in the medium frequency range (between 100 kHz and 10 MHz) has been designed. We adopted Slingram geometry for the EM prototype: its PERP configuration (vertical transmission loop Tx and horizontal measuring loop Rx) was defined using 1D ground models. As the required investigation depth is around 1m, the coil spacing was fixed to 1.2m. This prototype works in a frequency range between 1 and 5 MHz. After calibration, we tested the response of prototype to objects with known properties. The first in situ measurements were led on experimental sites with different types of soils and different water content variations (artificially created or natural): sandy alluvium on a plot of INRA (French National Institute for Agricultural Research) in Orléans (Centre, France), a clay-loam soil on an experimental site in Estrée-Mons (Picardie, France) and fractured limestone at the vicinity of Grand (Vosges, France). In the case of the sandy alluvium, the values of dielectric permittivity measured are close to those of HF permittivity and allow the use of existing theoretical models to determine the soil water content. For soils containing higher amount of clay, the coupled information brought by the electrical conductivity and the dielectric permittivity is used. Variations of water content detected by the EM prototype are confirmed by additional DC electrical profiling and direct mass water content measurements along depth. For the clay-loam soil, containing more than 20% of clay, the relative dielectric permittivity values, ranging from 63 to 138, are much higher than those expected in the high frequency range (above 20 MHz, the highest measured permittivity is equal to 81 for water). In the medium frequency range, those values are very likely due to interfacial polarization. This effect, also known as Maxwell-Wagner polarization, should increase with the soil clay content. The first measuring trial is coherent with the gravimetric water content as well as DC electrical profiling measurements. For a clay rich soil, the EM prototype is able to detect water content variations for an investigation depth close to 1m with both electrical conductivity and dielectric permittivity in the medium frequency range. Other field experiments are scheduled to confirm these results on other types of soils.

Electric thruster research

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1981-01-01

The multipole discharge chamber of an electrostatic ion thruster is discussed. No reductions in discharge losses were obtained, despite repeated demonstration of anode potentials more positive than the bulk of the discharge plasma. The penalty associated with biased anode operation was reduced as the magnetic integral above the biased anodes was increased. The hollow cathode is discussed. The experimental configuration of the Hall current thruster had a uniform field throughout the ion generation and acceleration regions. To obtain reliable ion generation, it was necessary to reduce the magnetic field strength, to the point where excessive electron backflow was required to establish ion acceleration. The theoretical study of ion acceleration with closed electron drift paths resulted in two classes of solutions. One class has the continuous potential variation in the acceleration region that is normally associated with a Hall current accelerator. The other class has an almost discontinuous potential step near the anode end of the acceleration region. This step includes a significant fraction of the total acceleration potential difference.

Assessing the Quality and Potential Efficacy of Commercial Extracts of Rhodiola rosea L. by Analyzing the Salidroside and Rosavin Content and the Electrophysiological Activity in Hippocampal Long-Term Potentiation, a Synaptic Model of Memory.

PubMed

Dimpfel, Wilfried; Schombert, Leonie; Panossian, Alexander G

2018-01-01

Rhodiola rosea L. roots and rhizome extracts are active ingredients in adaptogenic herbal medicinal products (HMP) and dietary supplements for temporary relief of symptoms of stress, such as fatigue and weakness. R. rosea extract has a stimulating effect on the CNS, suggesting potential benefits on cognitive functions, memory, learning, and attention. The reproducible efficacy and quality of preparations of the underground parts of R. rosea depend on the highly variable content of the active markers, salidroside and rosavin, which affect the quality of HMP and dietary supplements. However, it is not clear which analytical markers are important for assessing the efficacy of R. rosea preparations intended for use in aging-induced mild cognitive disorders, such as attenuated memory, attention, and learning. Furthermore, the activity of various commercial R. rosea extracts has not been correlated with their content. Here, the biological activities of salidroside, rosavin, and seven commercial extracts of underground parts of R. rosea were assessed using a synaptic model of memory: long-term potentiation (LTP) of synaptic transmission in hippocampus slices. A high degree of variation in the content of all active markers was observed. One extract from China lacked rosavin, and there was even variation in the extracts from the Altai geographic region. In vitro , rosavin, salidroside and all tested R. rosea extracts potentiated electric stimulation of an intra-hippocampal electric circuit, which resulted in higher responses of the pyramidal cells in isolated hippocampus slices. Rosavin was more active at higher concentrations than salidroside; while, salidroside was more effective at lower concentrations. The highest content of both active markers was found in the extracts that were active at the lowest concentrations tested; while, some extracts contained some other compounds that presumably reduced the efficacy due to antagonistic interactions. Standardized content of active markers is necessary for the quality control of herbal preparations containing R. rosea extracts, but insufficient for assessment of their potential efficacy. Additional bioassays are needed to assure the reproducible pharmacological activity of R. rosea extracts; therefore, the LTP of synaptic transmission in hippocampus slices may serve as a validation tool for the quality control of R. rosea extracts.

Energy use and recovery in waste management and implications for accounting of greenhouse gases and global warming contributions.

PubMed

Fruergaard, Thilde; Astrup, Tomas; Ekvall, Thomas

2009-11-01

The energy system plays an essential role in accounting of greenhouse gas (GHG) emissions from waste management systems and waste technologies. This paper focuses on energy use and energy recovery in waste management and outlines how these aspects should be addressed consistently in a GHG perspective. Essential GHG emission data for the most common fuels, electricity and heat are provided. Average data on electricity provision show large variations from country to country due to different fuels being used and different efficiencies for electricity production in the individual countries (0.007-1.13 kg CO(2)-eq. kWh(-1)). Marginal data on electricity provision show even larger variations (0.004-3 kg CO(2)-eq. kWh( -1)). Somewhat less variation in GHG emissions is being found for heat production (0.01-0.69 kg CO(2)-eq. kWh( -1)). The paper further addresses allocation principles and the importance of applying either average or marginal energy data, and it discusses the consequences of introducing reduction targets on CO( 2) emissions. All discussed aspects were found to significantly affect the outcome of GHG accounts suggesting transparent reporting to be critical. Recommendations for use of average/marginal energy data are provided.

TEC Variations Over Korean Peninsula During Magnetic Storm

NASA Astrophysics Data System (ADS)

Ji, E.-Y.; Choi, B.-K.; Kim, K.-H.; Lee, D.-H.; Cho, J.-H.; Chung, J.-K.; Park, J.-U.

2008-03-01

By analyzing the observations from a number of ground- and space-based instruments, including ionosonde, magnetometers, and ACE interplanetary data, we examine the response of the ionospheric TEC over Korea during 2003 magnetic storms. We found that the variation of vertical TEC is correlated with the southward turning of the interplanetary magnetic field B_z. It is suggested that the electric fields produced by the dynamo process in the high-latitude region and the prompt penetration in the low-latitude region are responsible for TEC increases. During the June 16 event, dayside TEC values increase more than 15%. And the ionospheric F2-layer peak height (hmF2) was ˜300km higher and the vertical E×B drift (estimated from ground-based magnetometer equatorial electrojet delta H) showed downward drift, which may be due to the ionospheric disturbance dynamo electric field produced by the large amount of energy dissipation into high-latitude regions. In contr! ast, during November 20 event, the nightside TEC increases may be due to the prompt penetration westward electric field. The ionospheric F2-layer peak height was below 200km and the vertical E×B drift showed downward drift. Also, a strong correlation is observed between enhanced vertical TEC and enhanced interplanetary electric field. It is shown that, even though TEC increases are caused by the different processes, the electric field disturbances in the ionosphere play an important role in the variation of TEC over Korea.

Complex resistivity signatures of ethanol in sand-clay mixtures

USGS Publications Warehouse

Personna, Yves Robert; Slater, Lee; Ntarlagiannis, Dimitrios; Werkema, Dale D.; Szabo, Zoltan

2013-01-01

We performed complex resistivity (CR) measurements on laboratory columns to investigate changes in electrical properties as a result of varying ethanol (EtOH) concentration (0% to 30% v/v) in a sand–clay (bentonite) matrix. We applied Debye decomposition, a phenomenological model commonly used to fit CR data, to determine model parameters (time constant: τ, chargeability: m, and normalized chargeability: mn). The CR data showed a significant (P ≤ 0.001) time-dependent variation in the clay driven polarization response (~ 12 mrad) for 0% EtOH concentration. This temporal variation probably results from the clay–water reaction kinetics trending towards equilibrium in the sand–clay–water system. The clay polarization is significantly suppressed (P ≤ 0.001) for both measured phase (ϕ) and imaginary conductivity (σ″) with increasing EtOH concentration. Normalized chargeability consistently decreases (by up to a factor of ~ 2) as EtOH concentration increases from 0% to 10% and 10 to 20%, respectively. We propose that such suppression effects are associated with alterations in the electrical double layer (EDL) at the clay–fluid interface due to (a) strong EtOH adsorption on clay, and (b) complex intermolecular EtOH–water interactions and subsequent changes in ionic mobility on the surface in the EDL. Changes in the CR data following a change of the saturating fluid from EtOH 20% to plain water indicate strong hysteresis effects in the electrical response, which we attribute to persistent EtOH adsorption on clay. Our results demonstrate high sensitivity of CR measurements to clay–EtOH interactions in porous media, indicating the potential application of this technique for characterization and monitoring of ethanol contamination in sediments containing clays.

CRSP, numerical results for an electrical resistivity array to detect underground cavities

NASA Astrophysics Data System (ADS)

Amini, Amin; Ramazi, Hamidreza

2017-03-01

This paper is devoted to the application of the Combined Resistivity Sounding and Profiling electrode configuration (CRSP) to detect underground cavities. Electrical resistivity surveying is among the most favorite geophysical methods due to its nondestructive and economical properties in a wide range of geosciences. Several types of the electrode arrays are applied to detect different certain objectives. In one hand, the electrode array plays an important role in determination of output resolution and depth of investigations in all resistivity surveys. On the other hand, they have their own merits and demerits in terms of depth of investigations, signal strength, and sensitivity to resistivity variations. In this article several synthetic models, simulating different conditions of cavity occurrence, were used to examine the responses of some conventional electrode arrays and also CRSP array. The results showed that CRSP electrode configuration can detect the desired objectives with a higher resolution rather than some other types of arrays. Also a field case study was discussed in which electrical resistivity approach was conducted in Abshenasan expressway (Tehran, Iran) U-turn bridge site for detecting potential cavities and/or filling loose materials. The results led to detect an aqueduct tunnel passing beneath the study area.

Investigation of Characteristics of Large dB/dt for Geomagnetically Induced Currents

NASA Astrophysics Data System (ADS)

Munoz, D.; Ngwira, C.; Damas, M. C.

2016-12-01

When geomagnetically induced currents (GICs) flow through electrical networks, they become a potential threat for electrical power systems. Changes in the geomagnetic field (dB/dt) during severe geomagnetic disturbances are the main sources of GICs. These dB/dt phenomena were studied by selecting 24 strong geomagnetic storms with Dst ≤ - 150 nT. ACE spacecraft solar wind data: flow speed, proton density, By and Bz IMF components of the solar wind were correlated with measurements of the magnetic field detected on ground stations at different latitudes. This article reports characteristics of the solar wind during time intervals of large changes in the horizontal geomagnetic field with a threshold of dB/dt ≥ ± 20 nT/min for the 24 geomagnetic storms. The results of this investigation can help scientists to understand the mechanisms responsible for causing large magnetic field variations in order to predict and mitigate possible large events in the future, which is critical for our society that relies constantly on electricity for livelihood and security. In addition, this ongoing project will continue to investigate electron flux response before, during, and after large changes in geomagnetic field.

Electrically tunable transport and high-frequency dynamics in antiferromagnetic S r3I r2O7

NASA Astrophysics Data System (ADS)

Seinige, Heidi; Williamson, Morgan; Shen, Shida; Wang, Cheng; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

2016-12-01

We report dc and high-frequency transport properties of antiferromagnetic S r3I r2O7 . Temperature-dependent resistivity measurements show that the activation energy of this material can be tuned by an applied dc electrical bias. The latter allows for continuous variations in the sample resistivity of as much as 50% followed by a reversible resistive switching at higher biases. Such a switching is of high interest for antiferromagnetic applications in high-speed memory devices. Interestingly, we found the switching behavior to be strongly affected by a high-frequency (microwave) current applied to the sample. The microwaves at 3-7 GHz suppress the dc switching and produce resonancelike features that we tentatively associated with the dissipationless magnonics recently predicted to occur in antiferromagnetic insulators subject to ac electric fields. We have characterized the effects of microwave irradiation on electronic transport in S r3I r2O7 as a function of microwave frequency and power, strength and direction of external magnetic field, strength and polarity of applied dc bias, and temperature. Our observations support the potential of antiferromagnetic materials for high-speed/high-frequency spintronic applications.

Acceleration of barium ions near 8000 km above an aurora

NASA Technical Reports Server (NTRS)

Stenbaek-Nielsen, H. C.; Hallinan, T. J.; Wescott, E. M.; Foeppl, H.

1984-01-01

A barium shaped charge, named Limerick, was released from a rocket launched from Poker Flat Research Range, Alaska, on March 30, 1982, at 1033 UT. The release took place in a small auroral breakup. The jet of ionized barium reached an altitude of 8100 km 14.5 min after release, indicating that there were no parallel electric fields below this altitude. At 8100 km the jet appeared to stop. Analysis shows that the barium at this altitude was effectively removed from the tip. It is concluded that the barium was actually accelerated upward, resulting in a large decrease in the line-of-sight density and hence the optical intensity. The parallel electric potential in the acceleration region must have been greater than 1 kV over an altitude interval of less than 200 km. The acceleration region, although presumably auroral in origin, did not seem to be related to individual auroral structures, but appeared to be a large-scale horizontal structure. The perpendicular electric field below, as deduced from the drift of the barium, was temporally and spatially very uniform and showed no variation related to individual auroral structures passing through.

Approach to Modeling Boundary Layer Ingestion Using a Fully Coupled Propulsion-RANS Model

NASA Technical Reports Server (NTRS)

Gray, Justin S.; Mader, Charles A.; Kenway, Gaetan K. W.; Martins, Joaquim R. R. A.

2017-01-01

Airframe-propulsion integration concepts that use boundary layer ingestion have the potential to reduce aircraft fuel burn. One concept that has been recently explored is NASA's Starc-ABL aircraft configuration, which offers the potential for 12% mission fuel burn reduction by using a turbo-electric propulsion system with an aft-mounted electrically driven boundary layer ingestion propulsor. This large potential for improved performance motivates a more detailed study of the boundary layer ingestion propulsor design, but to date, analyses of boundary layer ingestion have used uncoupled methods. These methods account for only aerodynamic effects on the propulsion system or propulsion system effects on the aerodynamics, but not both simultaneously. This work presents a new approach for building fully coupled propulsive-aerodynamic models of boundary layer ingestion propulsion systems. A 1D thermodynamic cycle analysis is coupled to a RANS simulation to model the Starc-ABL aft propulsor at a cruise condition and the effects variation in propulsor design on performance are examined. The results indicates that both propulsion and aerodynamic effects contribute equally toward the overall performance and that the fully coupled model yields substantially different results compared to uncoupled. The most significant finding is that boundary layer ingestion, while offering substantial fuel burn savings, introduces throttle dependent aerodynamics effects that need to be accounted for. This work represents a first step toward the multidisciplinary design optimization of boundary layer ingestion propulsion systems.

Understanding the electrical behavior of the action potential in terms of elementary electrical sources.

PubMed

Rodriguez-Falces, Javier

2015-03-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However, this model is unsuitably complex for teaching purposes. In addition, the Hodgkin and Huxley approach describes the shape of the action potential only in terms of ionic currents, i.e., it is unable to explain the electrical significance of the action potential or describe the electrical field arising from this source using basic concepts of electromagnetic theory. The goal of the present report was to propose a new model to describe the electrical behaviour of the action potential in terms of elementary electrical sources (in particular, dipoles). The efficacy of this model was tested through a closed-book written exam. The proposed model increased the ability of students to appreciate the distributed character of the action potential and also to recognize that this source spreads out along the fiber as function of space. In addition, the new approach allowed students to realize that the amplitude and sign of the extracellular electrical potential arising from the action potential are determined by the spatial derivative of this intracellular source. The proposed model, which incorporates intuitive graphical representations, has improved students' understanding of the electrical potentials generated by bioelectrical sources and has heightened their interest in bioelectricity. Copyright © 2015 The American Physiological Society.

Atmospheric electrical detection of organized convection.

PubMed

Markson, R

1975-06-20

Relatively simple atmospheric electrical instrumentation carried on a small aircraft constitutes a flexible and sensitive system for detecting organized convection. Data can be obtained close to the sea surface, and low-velocity flight enhances the spatial resolution. With a slow-flying airplane or powered glider, it may be possible to trace the circulation of individual convection cells and to investigate the trajectory of air which forms cumulus clouds, one of the major unsolved problems in tropical meteorology. Since space charge near the ocean surface was found on some days to be organized on a horizontal scale equivalent to the cumulus cloud scale, this suggests that some of the air which forms maritime cumulus clouds may come from within a few meters of the ocean and that atmospheric electrical instrumentation may have the potential for tracing air from the sea surface to the clouds. Although the atmospheric electrical instrumentation technique described here cannot be used for direct measurement of air velocity, it may be possible to develop model that can be used to calculate air velocities from electric field data. Even though with the technique described here it is not possible to make direct measurements of wind velocity, airborne electric field records can provide useful information about convection by delineating patterns in the wind field and structural features of thermals (rising bodies of relatively warm air) and by making possible the remote detection of thermals (29). Future plans include attempting to trace interfaces between adjacent roll vortices from the sea surface through the depth of the mixed layer (i) by flying the aircraft parallel to the wind so as to nullify the horizontal electric field (measured between wing-tip probes) while ascending and descending along the interface between adjacent roll vortices and (ii) by measuring vertical and horizontal potential gradient variations at different flight levels (30). The sensitivity of atmospheric electrical instrumentation to the top of the mixed layer and structure within it can be used to explore another important problem in boundary layer convection-why convective cloud cover and oceanic rainfall are greater at night than during the day(31). Workers in atmospheric electricity have long recognized that their domain is strongly controlled by turbulence in the lower atmosphere, and many have believed that the most effective use of atmospheric electrical techniques to assist meteorological research would be in studying exchange processes. Reiter [see (8)] effectively extended atmospheric electrical studies of boundary layer phenomena through a height range by mounting instruments on cable cars traveling between the valley floor and mountain tops in the Alps. The airborne measurements described here extend this approach. Relating the electrical structure of the atmosphere to its dynamic structure poses an interesting problem which may contribute to our understanding of the atmosphere.

Anisotropy in electromagnetic field variations and its implication for lateral inhomogeneity of the electrical conductivity structure

NASA Astrophysics Data System (ADS)

Honkura, Y.; Watanabe, N.; Kaneko, Y.; Oshima, S.

1989-03-01

Two-dimensional analyses of magnetotelluric data provide information on anisotropic response for two different polarization cases; the so-called B-polarization and E-polarization cases. Similar anisotropy should also be observed in the horizontal components of magnetic field variations. On the assumption that a reference station provides the normal magnetic field, transfer functions for the horizontal magnetic fields can be derived in a fashion similar to the impedance analysis for magnetotelluric data. We applied this method to magnetic data obtained at some observation sites in a geothermal area in Japan. Transfer functions for the horizontal magnetic fields exhibit a strong anisotropy with the preferred direction nearly perpendicular to that for the electric field. This result implies the existence of strong electric currents flowing in the direction perpendicular to the above preferred direction for the magnetic field. The present method was also applied to the horizontal components of magnetic field variations observed at the seafloor. In this case, a magnetic observatory on land was taken as the reference station, and attenuation of the amplitude of horizontal magnetic field variation was examined. Anisotropy in attenuation was then found with the preferred direction perpendicular to the axis of the Okinawa trough where the seafloor measurement was undertaken.

Electrical Power Distribution and Control Modeling and Analysis

NASA Technical Reports Server (NTRS)

Fu, Johnny S.; Liffring, Mark; Mehdi, Ishaque S.

2001-01-01

This slide presentation reviews the use of Electrical Power Distribution and Control (EPD&C) Modeling and how modeling can support analysis. The presentation discusses using the EASY5 model to simulate and analyze the Space Shuttle Electric Auxiliary Power Unit. Diagrams of the model schematics are included, as well as graphs of the battery cell impedance, hydraulic load dynamics, and EPD&C response to hydraulic load variations.

Analysis on Potential of Electric Energy Market based on Large Industrial Consumer

NASA Astrophysics Data System (ADS)

Lin, Jingyi; Zhu, Xinzhi; Yang, Shuo; Xia, Huaijian; Yang, Di; Li, Hao; Lin, Haiying

2018-01-01

The implementation of electric energy substitution by enterprises plays an important role in promoting the development of energy conservation and emission reduction in china. In order to explore alternative energy potential of industrial enterprises, to simulate and analyze the process of industrial enterprises, identify high energy consumption process and equipment, give priority to alternative energy technologies, and determine the enterprise electric energy substitution potential predictive value, this paper constructs the evaluation model of the influence factors of the electric energy substitution potential of industrial enterprises, and uses the combined weight method to determine the weight value of the evaluation factors to calculate the target value of the electric energy substitution potential. Taking the iron and steel industry as an example, this method is used to excavate the potential. The results show that the method can effectively tap the potential of the electric power industry

Performance characteristics of an electric vehicle lead-acid battery pack at elevated temperatures

NASA Technical Reports Server (NTRS)

Chapman, P.

1982-01-01

Discharge testing data electric car battery pack over initial electrolyte temperature variations between 27 and 55 C are presented. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Battery discharge capacity increased with temperature for constant current discharges, and battery energy capacity increased with temperature for constant power discharges. Dynamometer tests of the electric test vehicle showed an increase in range of 25% for the higher electrolyte temperature.

Impact of anion replacement on the optoelectronic and thermoelectric properties of CaMg2X2, X= (N, P, As, Sb, Bi) compounds

NASA Astrophysics Data System (ADS)

Khan, Abdul Ahad; Yaseen, M.; Laref, A.; Murtaza, G.

2018-07-01

The structural, electronic, optical and thermoelectric properties of ternary CaMg2X2 (X = N, P, As, Sb and Bi) compounds are investigated using all electrons full potential linearized augment plane wave method. By using generalized gradient approximation (GGA), unit cell volumes of the compounds are optimized. For calculations of optical and electronic properties the modified Becke Johnson exchange potential is used along with the GGA. The direct energy band gap decreases by replacing the pnictogen elements, while indirect bandgap also decreases except for CaMg2As2. The optical properties show a prominent variation over the change of anion from N to Bi. There is inverse variation between refractive index and the band gap. The refractive indices of these compounds are high in the visible region and sharply decreased in the ultraviolet region. The thermoelectric properties are also studied using Boltzmann statistics through BoltzTrap code. A positive non-zero value of Seebeck coefficient shows a P-type semiconducting behavior of these compounds. High figure of merits (ZT) and optical conductivity peaks for all compounds reveal that they are good candidates for the thermo-electric and optoelectronics devices.

Thickness dependence of optical properties of amorphous indium oxide thin films deposited by reactive evaporation

NASA Astrophysics Data System (ADS)

Uluta, K.; Deer, D.; Skarlatos, Y.

2006-08-01

The electrical conductivity and absorption coefficient of amorphous indium oxide thin films, thermally evaporated on glass substrates at room temperature, were evaluated. For direct transitions the variation of the optical band gap with thickness was determined and this variation was supposed to appear due to the variation of localized gap states, whereas the variation of conductivity with thickness was supposed to be due to the variation of carrier concentration. We attribute the variation of absorption coefficient with thickness to the variation of optical band gap energy rather than optical interference.

An experimental approach of decoupling Seebeck coefficient and electrical resistivity

NASA Astrophysics Data System (ADS)

Muhammed Sabeer N., A.; Paulson, Anju; Pradyumnan, P. P.

2018-04-01

The Thermoelectrics (TE) has drawn increased attention among renewable energy technologies. The performance of a thermoelectric material is quantified by a dimensionless thermoelectric figure of merit, ZT=S2σT/κ, where S and σ vary inversely each other. Thus, improvement in ZT is not an easy task. So, researchers have been trying different parameter variations during thin film processing to improve TE properties. In this work, tin nitride (Sn3N4) thin films were deposited on glass substrates by reactive RF magnetron sputtering and investigated its thermoelectric response. To decouple the covariance nature of Seebeck coefficient and electrical resistivity for the enhancement of power factor (S2σ), the nitrogen gas pressure during sputtering was reduced. Reduction in nitrogen gas pressure reduced both sputtering pressure and amount of nitrogen available for reaction during sputtering. This experimental approach of combined effect introduced preferred orientation and stoichiometric variations simultaneously in the sputtered Sn3N4 thin films. The scattering mechanism associated with these variations enhanced TE properties by independently drive the Seebeck coefficient and electrical resistivity parameters.

Zonal Drift Variations and Suppression of Ionospheric Scintillation During St. Patrick's Day Storm Observed by Pingtung SCINDA Station in Taiwan

NASA Astrophysics Data System (ADS)

Su, S. Y.; Nayak, C.; Tsai, L. C.; Caton, R. G.; Groves, K. M.

2016-12-01

Variations of zonal drift and ionospheric VHF scintillations observed by a SCINDA station in Southern Taiwan during the St. Patrick's day geomagnetic storm are studied. Although scintillations were observed for 6 consecutive days before the storm, they were absence during the storm period. Data from VHF receivers, ionosonde and in situ plasma density observations from ESA's SWARM constellation are used to study the ionospheric irregularity/scintillation events in the Taiwanese sector to compare with what happened in the Indian sectors. The absence of scintillation in the Taiwanese sector during the storm period seems to be caused by a reduced pre-reversal enhancement (PRE) electric field from a westward prompt-penetration electric field (PPEF) during the storm. A low post-sunset ionosphere thus becomes unfavorable for the Rayleigh-Taylor instability to occur. On the contrary, the PPEFs were found to strongly enhance the PRE electric field in the Indian sector to cause the ionospheric irregularities/scintillations in the post-sunset sector. Zonal drift variations during the storm time are also discussed in conjunction with the irregularity/scintillation occurrences.

Electrotonic and action potentials in the Venus flytrap.

PubMed

Volkov, Alexander G; Vilfranc, Chrystelle L; Murphy, Veronica A; Mitchell, Colee M; Volkova, Maia I; O'Neal, Lawrence; Markin, Vladislav S

2013-06-15

The electrical phenomena and morphing structures in the Venus flytrap have attracted researchers since the nineteenth century. We have observed that mechanical stimulation of trigger hairs on the lobes of the Venus flytrap induces electrotonic potentials in the lower leaf. Electrostimulation of electrical circuits in the Venus flytrap can induce electrotonic potentials propagating along the upper and lower leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear electrical response in plant tissues. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small electrotonic potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of the applied voltage. Electrical stimulation of the lower leaf induces electrical signals, which resemble action potentials, in the trap between the lobes and the midrib. The trap closes if the stimulating voltage is above the threshold level of 4.4V. Electrical responses in the Venus flytrap were analyzed and reproduced in the discrete electrical circuit. The information gained from this study can be used to elucidate the coupling of intracellular and intercellular communications in the form of electrical signals within plants. Copyright © 2013 Elsevier GmbH. All rights reserved.

Multimodal electromechanical model of piezoelectric transformers by Hamilton's principle.

PubMed

Nadal, Clement; Pigache, Francois

2009-11-01

This work deals with a general energetic approach to establish an accurate electromechanical model of a piezoelectric transformer (PT). Hamilton's principle is used to obtain the equations of motion for free vibrations. The modal characteristics (mass, stiffness, primary and secondary electromechanical conversion factors) are also deduced. Then, to illustrate this general electromechanical method, the variational principle is applied to both homogeneous and nonhomogeneous Rosen-type PT models. A comparison of modal parameters, mechanical displacements, and electrical potentials are presented for both models. Finally, the validity of the electrodynamical model of nonhomogeneous Rosen-type PT is confirmed by a numerical comparison based on a finite elements method and an experimental identification.

Simultaneous detection of refractive index and surface charges in nanolaser biosensors

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

Watanabe, Keisuke; Kishi, Yoji; Hachuda, Shoji

2015-01-12

The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

Fuel Consumption Sensitivity of Conventional and Hybrid Electric Light-Duty Gasoline Vehicles to Driving Style

DOE PAGES

Thomas, John; Huff, Shean; West, Brian; ...

2017-08-11

Aggressive driving is a very important topic for many reasons, one of which is higher energy used per unit distance traveled, potentially accompanied by an elevated production of greenhouse gases and other pollutants. Examining a large data set of self-reported fuel economy (FE) values revealed that the dispersion of FE values is quite large and is larger for hybrid electric vehicles (HEVs) than for conventional gasoline vehicles. This occurred despite the fact that the city and highway FE ratings for HEVs are generally much closer in value than for conventional gasoline vehicles. A study was undertaken to better understand thismore » and better quantify the effects of aggressive driving, including reviewing past aggressive driving studies, developing and exercising a new vehicle energy model, and conducting a related experimental investigation. The vehicle energy model focused on the limitations of regenerative braking in combination with varying levels of driving-style aggressiveness to show that this could account for greater FE variation in an HEV compared to a similar conventional vehicle. A closely matched pair of gasoline-fueled sedans, one an HEV and the other having a conventional powertrain, was chosen for both modeling and chassis dynamometer experimental comparisons. Results indicate that the regenerative braking limitations could be a main contributor to the greater HEV FE variation under the range of drive cycles considered. Finally, the complete body of results gives insight into the range of fuel use penalties that results from aggressive driving and why the variation can be larger on a percent basis for an HEV compared to a similar conventional vehicle, while the absolute fuel use penalty for aggressive driving is generally larger for conventional vehicles than HEVs.« less

Energy harvesting from arterial blood pressure for powering embedded micro sensors in human brain

NASA Astrophysics Data System (ADS)

Nanda, Aditya; Karami, M. Amin

2017-03-01

This manuscript investigates energy harvesting from arterial blood pressure via the piezoelectric effect for the purpose of powering embedded micro-sensors in the human brain. One of the major hurdles in recording and measuring electrical data in the human nervous system is the lack of implantable and long term interfaces that record neural activity for extended periods of time. Recently, some authors have proposed micro sensors implanted deep in the brain that measure local electrical and physiological data which are then communicated to an external interrogator. This paper proposes a way of powering such interfaces. The geometry of the proposed harvester consists of a piezoelectric, circular, curved bimorph that fits into the blood vessel (specifically, the Carotid artery) and undergoes bending motion because of blood pressure variation. In addition, the harvester thickness is constrained such that it does not modify arterial wall dynamics. This transforms the problem into a known strain problem and the integral form of Gauss's law is used to obtain an equation relating arterial wall motion to the induced voltage. The theoretical model is validated by means of a Multiphysics 3D-FEA simulation comparing the harvested power at different load resistances. The peak harvested power achieved for the Carotid artery (proximal to Brain), with PZT-5H, was 11.7 μW. The peak power for the Aorta was 203.4 μW. Further, the variation of harvested power with variation in the harvester width and thickness, arterial contractility, and pulse rate is investigated. Moreover, potential application of the harvester as a chronic, implantable and real-time Blood pressure sensor is considered. Energy harvested via this mechanism will also have applications in long-term, implantable Brain Micro-stimulation.

Fuel Consumption Sensitivity of Conventional and Hybrid Electric Light-Duty Gasoline Vehicles to Driving Style

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

Thomas, John; Huff, Shean; West, Brian

Aggressive driving is a very important topic for many reasons, one of which is higher energy used per unit distance traveled, potentially accompanied by an elevated production of greenhouse gases and other pollutants. Examining a large data set of self-reported fuel economy (FE) values revealed that the dispersion of FE values is quite large and is larger for hybrid electric vehicles (HEVs) than for conventional gasoline vehicles. This occurred despite the fact that the city and highway FE ratings for HEVs are generally much closer in value than for conventional gasoline vehicles. A study was undertaken to better understand thismore » and better quantify the effects of aggressive driving, including reviewing past aggressive driving studies, developing and exercising a new vehicle energy model, and conducting a related experimental investigation. The vehicle energy model focused on the limitations of regenerative braking in combination with varying levels of driving-style aggressiveness to show that this could account for greater FE variation in an HEV compared to a similar conventional vehicle. A closely matched pair of gasoline-fueled sedans, one an HEV and the other having a conventional powertrain, was chosen for both modeling and chassis dynamometer experimental comparisons. Results indicate that the regenerative braking limitations could be a main contributor to the greater HEV FE variation under the range of drive cycles considered. Finally, the complete body of results gives insight into the range of fuel use penalties that results from aggressive driving and why the variation can be larger on a percent basis for an HEV compared to a similar conventional vehicle, while the absolute fuel use penalty for aggressive driving is generally larger for conventional vehicles than HEVs.« less

Vertical electron transport in van der Waals heterostructures with graphene layers

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

Ryzhii, V., E-mail: v-ryzhii@riec.tohoku.ac.jp; Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University and Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 111005; Otsuji, T.

We propose and analyze an analytical model for the self-consistent description of the vertical electron transport in van der Waals graphene-layer (GL) heterostructures with the GLs separated by the barriers layers. The top and bottom GLs serve as the structure emitter and collector. The vertical electron transport in such structures is associated with the propagation of the electrons thermionically emitted from GLs above the inter-GL barriers. The model under consideration describes the processes of the electron thermionic emission from and the electron capture to GLs. It accounts for the nonuniformity of the self-consistent electric field governed by the Poisson equationmore » which accounts for the variation of the electron population in GLs. The model takes also under consideration the cooling of electrons in the emitter layer due to the Peltier effect. We find the spatial distributions of the electric field and potential with the high-electric-field domain near the emitter GL in the GL heterostructures with different numbers of GLs. Using the obtained spatial distributions of the electric field, we calculate the current-voltage characteristics. We demonstrate that the Peltier cooling of the two-dimensional electron gas in the emitter GL can strongly affect the current-voltage characteristics resulting in their saturation. The obtained results can be important for the optimization of the hot-electron bolometric terahertz detectors and different devices based on GL heterostructures.« less

Donor impurity binding energies of coaxial GaAs / Alx Ga1 - x As cylindrical quantum wires in a parallel applied magnetic field

NASA Astrophysics Data System (ADS)

Tshipa, M.; Winkoun, D. P.; Nijegorodov, N.; Masale, M.

2018-04-01

Theoretical investigations are carried out of binding energies of a donor charge assumed to be located exactly at the center of symmetry of two concentric cylindrical quantum wires. The intrinsic confinement potential in the region of the inner cylinder is modeled in any one of the three profiles: simple parabolic, shifted parabolic or the polynomial potential. The potential inside the shell is taken to be a potential step or potential barrier of a finite height. Additional confinement of the charge carriers is due to the vector potential of the axial applied magnetic field. It is found that the binding energies attain maxima in their variations with the radius of the inner cylinder irrespective of the particular intrinsic confinement of the inner cylinder. As the radius of the inner cylinder is increased further, the binding energies corresponding to either the parabolic or the polynomial potentials attain minima at some critical core-radius. Finally, as anticipated, the binding energies increase with the increase of the parallel applied magnetic field. This behaviour of the binding energies is irrespective of the particular electric potential of the nanostructure or its specific dimensions.

Interfacial ionic 'liquids': connecting static and dynamic structures

DOE PAGES

Uysal, Ahmet; Zhou, Hua; Feng, Guang; ...

2014-12-05

It is well known that room temperature ionic liquids (RTILs) often adopt a charge-separated layered structure, i.e. with alternating cation- and anion-rich layers, at electrified interfaces. However, the dynamic response of the layered structure to temporal variations in applied potential is not well understood. For this research, we used in situ, real-time x-ray reflectivity to study the potential-dependent electric double layer (EDL) structure of an imidazolium-based RTIL on charged epitaxial graphene during potential cycling as a function of temperature. The results suggest that the graphene–RTIL interfacial structure is bistable in which the EDL structure at any intermediate potential can bemore » described by the combination of two extreme-potential structures whose proportions vary depending on the polarity and magnitude of the applied potential. This picture is supported by the EDL structures obtained by fully atomistic molecular dynamics simulations at various static potentials. Lastly, the potential-driven transition between the two structures is characterized by an increasing width but with an approximately fixed hysteresis magnitude as a function of temperature. The results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (~0.15 eV).« less

Interfacial ionic 'liquids': connecting static and dynamic structures.

PubMed

Uysal, Ahmet; Zhou, Hua; Feng, Guang; Lee, Sang Soo; Li, Song; Cummings, Peter T; Fulvio, Pasquale F; Dai, Sheng; McDonough, John K; Gogotsi, Yury; Fenter, Paul

2015-01-28

It is well known that room temperature ionic liquids (RTILs) often adopt a charge-separated layered structure, i.e. with alternating cation- and anion-rich layers, at electrified interfaces. However, the dynamic response of the layered structure to temporal variations in applied potential is not well understood. We used in situ, real-time x-ray reflectivity to study the potential-dependent electric double layer (EDL) structure of an imidazolium-based RTIL on charged epitaxial graphene during potential cycling as a function of temperature. The results suggest that the graphene-RTIL interfacial structure is bistable in which the EDL structure at any intermediate potential can be described by the combination of two extreme-potential structures whose proportions vary depending on the polarity and magnitude of the applied potential. This picture is supported by the EDL structures obtained by fully atomistic molecular dynamics simulations at various static potentials. The potential-driven transition between the two structures is characterized by an increasing width but with an approximately fixed hysteresis magnitude as a function of temperature. The results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (∼0.15 eV).

An in vivo study of electrical charge distribution on the bacterial cell wall by atomic force microscopy in vibrating force mode

NASA Astrophysics Data System (ADS)

Marlière, Christian; Dhahri, Samia

2015-05-01

We report an in vivo electromechanical atomic force microscopy (AFM) study of charge distribution on the cell wall of Gram+ Rhodococcus wratislaviensis bacteria, naturally adherent to a glass substrate, under physiological conditions. The method presented in this paper relies on a detailed study of AFM approach/retract curves giving the variation of the interaction force versus distance between the tip and the sample. In addition to classical height and mechanical (as stiffness) data, mapping of local electrical properties, such as bacterial surface charge, was proved to be feasible at a spatial resolution better than a few tens of nanometers. This innovative method relies on the measurement of the cantilever's surface stress through its deflection far from (>10 nm) the repulsive contact zone: the variations of surface stress come from the modification of electrical surface charge of the cantilever (as in classical electrocapillary measurements) likely stemming from its charging during contact of both the tip and the sample electrical double layers. This method offers an important improvement in local electrical and electrochemical measurements at the solid/liquid interface, particularly in high-molarity electrolytes when compared to techniques focused on the direct use of electrostatic force. It thus opens a new way to directly investigate in situ biological electrical surface processes involved in numerous practical applications and fundamental problems such as bacterial adhesion, biofilm formation, microbial fuel cells, etc.We report an in vivo electromechanical atomic force microscopy (AFM) study of charge distribution on the cell wall of Gram+ Rhodococcus wratislaviensis bacteria, naturally adherent to a glass substrate, under physiological conditions. The method presented in this paper relies on a detailed study of AFM approach/retract curves giving the variation of the interaction force versus distance between the tip and the sample. In addition to classical height and mechanical (as stiffness) data, mapping of local electrical properties, such as bacterial surface charge, was proved to be feasible at a spatial resolution better than a few tens of nanometers. This innovative method relies on the measurement of the cantilever's surface stress through its deflection far from (>10 nm) the repulsive contact zone: the variations of surface stress come from the modification of electrical surface charge of the cantilever (as in classical electrocapillary measurements) likely stemming from its charging during contact of both the tip and the sample electrical double layers. This method offers an important improvement in local electrical and electrochemical measurements at the solid/liquid interface, particularly in high-molarity electrolytes when compared to techniques focused on the direct use of electrostatic force. It thus opens a new way to directly investigate in situ biological electrical surface processes involved in numerous practical applications and fundamental problems such as bacterial adhesion, biofilm formation, microbial fuel cells, etc. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00968e

Predictions of the Contribution of HCN Half-Maximal Activation Potential Heterogeneity to Variability in Intrinsic Adaptation of Spiral Ganglion Neurons.

PubMed

Boulet, Jason; Bruce, Ian C

2017-04-01

Spiral ganglion neurons (SGNs) exhibit a wide range in their strength of intrinsic adaptation on a timescale of 10s to 100s of milliseconds in response to electrical stimulation from a cochlear implant (CI). The purpose of this study was to determine how much of that variability could be caused by the heterogeneity in half-maximal activation potentials of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels, which are known to produce intrinsic adaptation. In this study, a computational membrane model of cat type I SGN was developed based on the Hodgkin-Huxley model plus HCN and low-threshold potassium (KLT) conductances in which the half-maximal activation potential of the HCN channel was varied and the response of the SGN to pulse train and paired-pulse stimulation was simulated. Physiologically plausible variation of HCN half-maximal activation potentials could indeed determine the range of adaptation on the timescale of 10s to 100s of milliseconds and recovery from adaptation seen in the physiological data while maintaining refractoriness within physiological bounds. This computational model demonstrates that HCN channels may play an important role in regulating the degree of adaptation in response to pulse train stimulation and therefore contribute to variable constraints on acoustic information coding by CIs. This finding has broad implications for CI stimulation paradigms in that cell-to-cell variation of HCN channel properties are likely to significantly alter SGN excitability and therefore auditory perception.

Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings.

PubMed

Sherstneva, O N; Vodeneev, V A; Katicheva, L A; Surova, L M; Sukhov, V S

2015-06-01

Electrical signals presented in plants by action potential and by variation potential (VP) can induce a reversible inactivation of photosynthesis. Changes in the intracellular and extracellular pH during VP generation are a potential mechanism of photosynthetic response induction; however, this hypothesis requires additional experimental investigation. The purpose of the present work was to analyze the influence of pH changes on induction of the photosynthetic response in pumpkin. It was shown that a burning of the cotyledon induced VP propagation into true leaves of pumpkin seedlings inducing a decrease in the photosynthetic CO2 assimilation and an increase in non-photochemical quenching of fluorescence, whereas respiration was activated insignificantly. The photosynthetic response magnitude depended linearly on the VP amplitude. The intracellular and extracellular concentrations of protons were analyzed using pH-sensitive fluorescent probes, and the VP generation was shown to be accompanied by apoplast alkalization (0.4 pH unit) and cytoplasm acidification (0.3 pH unit). The influence of changes in the incubation medium pH on the non-photochemical quenching of fluorescence of isolated chloroplasts was also investigated. It was found that acidification of the medium stimulated the non-photochemical quenching, and the magnitude of this increase depended on the decrease in pH. Our results confirm the contribution of changes in intracellular and extracellular pH to induction of the photosynthetic response caused by VP. Possible mechanisms of the influence of pH changes on photosynthesis are discussed.

High-resolution photoluminescence electro-modulation microscopy by scanning lock-in

NASA Astrophysics Data System (ADS)

Koopman, W.; Muccini, M.; Toffanin, S.

2018-04-01

Morphological inhomogeneities and structural defects in organic semiconductors crucially determine the charge accumulation and lateral transport in organic thin-film transistors. Photoluminescence Electro-Modulation (PLEM) microscopy is a laser-scanning microscopy technique that relies on the modulation of the thin-film fluorescence in the presence of charge-carriers to image the spatial distribution of charges within the active organic semiconductor. Here, we present a lock-in scheme based on a scanning beam approach for increasing the PLEM microscopy resolution and contrast. The charge density in the device is modulated by a sinusoidal electrical signal, phase-locked to the scanning beam of the excitation laser. The lock-in detection scheme is achieved by acquiring a series of images with different phases between the beam scan and the electrical modulation. Application of high resolution PLEM to an organic transistor in accumulation mode demonstrates its potential to image local variations in the charge accumulation. A diffraction-limited precision of sub-300 nm and a signal to noise ratio of 21.4 dB could be achieved.

Initial effect of the Fukushima accident on atmospheric electricity

NASA Astrophysics Data System (ADS)

Takeda, M.; Yamauchi, M.; Makino, M.; Owada, T.

2011-08-01

Vertical atmospheric DC electric field at ground level, or potential gradient (PG), suddenly dropped by one order of magnitude at Kakioka, 150 km southwest from the Fukushima Dai-ichi nuclear power plant (FNPP) right after the plant released a massive amount of radioactive material southward on 14 March, 2011. The PG stayed at this level for days with very small daily variations. Such a long-lasting near-steady low PG has never been observed at Kakioka. The sudden drop of PG with one-hour time scale is similar to those associated with rain-induced radioactive fallout after nuclear tests and the Chernobyl disaster. A comparison with the PG data with the radiation dose rate data at different places revealed that arrival of the radioactive dust by low-altitude wind caused the PG drop without rain. Furthermore, the PG might have reflected a minor release several hours before this release at the distance of 150 km. It is recommended that all nuclear power plant to have a network of PG observation surrounding the plant.

Comparison of Integrated Gasifier-Combined Cycle and AFB-steam turbine systems for industrial cogeneration

NASA Technical Reports Server (NTRS)

Nainiger, J. J.; Abbott, J. M.; Burns, R. K.

1981-01-01

In the cogeneration technology alternatives study (CTAS) a number of advanced coal fired systems were examined and systems using a integrated coal gasifier IGCC or a fluid bed combustor AFB were found to yield attractive cogeneration results in industrial cogeneration applications. A range of site requirements and cogeneration sizing strategies using ground rules based on CTAS were used in comparing an IGCC and an AFB. The effect of time variations in site requirements and the sensitivity to fuel and electricity price assumptions are examined. The economic alternatives of industrial or utility ownership are also considered. The results indicate that the IGCC system has potentially higher fuel and emission savings and could be an attractive option for utility ownership. The AFB steam turbine system has a potentially higher return on investment and could be attractive assuming industrial ownership.

Electrostatic and hydrodynamics effects in a sedimented magnetorheological suspension.

PubMed

Domínguez-García, P; Pastor, J M; Melle, Sonia; Rubio, Miguel A

2009-08-01

We present experimental results on the equilibrium microstructure of a sedimented magnetorheological suspension, namely, an aqueous suspension of micron-sized superparamagnetic particles. We develop a study of the electrical interactions on the suspension by processing video-microscopy images of the sedimented particles. We calculate the pair distribution function, g(r), which yields the electrostatic pair potential u(r), showing an anomalous attractive interaction for distances on the order of twice the particle diameter, with characteristic parameters whose values show a dependence with the two-dimensional concentration of particles. The repulsive body of the potential is adjusted to a DLVO expression in order to calculate the Debye screening length and the effective surface charge density. Influence of confinement and variations on the Boltzmann sedimentation profile because of the electrostatic interactions appear to be essential for the interpretation of experimental results.

Electrical Characterization of 4H-SiC JFET Wafer: DC Parameter Variations for Extreme Temperature IC Design

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Chen, Liangyu; Spry, David J.; Beheim, Glenn M.; Chang, Carl W.

2014-01-01

This work reports DC electrical characterization of a 76 mm diameter 4H-SiC JFET test wafer fabricated as part of NASA's on-going efforts to realize medium-scale ICs with prolonged and stable circuit operation at temperatures as high as 500 degC. In particular, these measurements provide quantitative parameter ranges for use in JFET IC design and simulation. Larger than expected parameter variations were observed both as a function of position across the wafer as well as a function of ambient testing temperature from 23 degC to 500 degC.

Temperature-Dependent Electrical Conductivity of GeTe-Based RF Switches

DTIC Science & Technology

2015-03-31

Short, high temperature pulses result in a melt -quench cycle, amorphizing the GeTe and leaving the switch in the electrically insulating OFF state...Longer, lower temperature pulses result in the recrystallization of the GeTe, leaving the switch in the electrically conductive ON state. The...shown to vary only weakly with temperature. OFF-state S-parameters also exhibit slight temperature variation, with an inflection point of ~175

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

NASA Astrophysics Data System (ADS)

Wiendartun, Syarif, Dani Gustaman

2010-10-01

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

Changes in H(+)-ATP Synthase Activity, Proton Electrochemical Gradient, and pH in Pea Chloroplast Can Be Connected with Variation Potential.

PubMed

Sukhov, Vladimir; Surova, Lyubov; Morozova, Ekaterina; Sherstneva, Oksana; Vodeneev, Vladimir

2016-01-01

Local stimulation induces generation and propagation of electrical signals, including the variation potential (VP) and action potential, in plants. Burning-induced VP changes the physiological state of plants; specifically, it inactivates photosynthesis. However, the mechanisms that decrease photosynthesis are poorly understood. We investigated these mechanisms by measuring VP-connected systemic changes in CO2 assimilation, parameters of light reactions of photosynthesis, electrochromic pigment absorbance shifts, and light scattering. We reveal that inactivation of photosynthesis in the pea, including inactivation of dark and light reactions, was connected with the VP. Inactivation of dark reactions decreased the rate constant of the fast relaxation of the electrochromic pigment absorbance shift, which reflected a decrease in the H(+)-ATP synthase activity. This decrease likely contributed to the acidification of the chloroplast lumen, which developed after VP induction. However, VP-connected decrease of the proton motive force across the thylakoid membrane, possibly, reflected a decreased pH in the stroma. This decrease may be another mechanism of chloroplast lumen acidification. Overall, stroma acidification can decrease electron flow through photosystem I, and lumen acidification induces growth of fluorescence non-photochemical quenching and decreases electron flow through photosystem II, i.e., pH decreases in the stroma and lumen, possibly, contribute to the VP-induced inactivation of light reactions of photosynthesis.

Sensitivity of Rabbit Ventricular Action Potential and Ca2+ Dynamics to Small Variations in Membrane Currents and Ion Diffusion Coefficients

PubMed Central

Lo, Yuan Hung; Peachey, Tom; Abramson, David; McCulloch, Andrew

2013-01-01

Little is known about how small variations in ionic currents and Ca2+ and Na+ diffusion coefficients impact action potential and Ca2+ dynamics in rabbit ventricular myocytes. We applied sensitivity analysis to quantify the sensitivity of Shannon et al. model (Biophys. J., 2004) to 5%–10% changes in currents conductance, channels distribution, and ion diffusion in rabbit ventricular cells. We found that action potential duration and Ca2+ peaks are highly sensitive to 10% increase in L-type Ca2+ current; moderately influenced by 10% increase in Na+-Ca2+ exchanger, Na+-K+ pump, rapid delayed and slow transient outward K+ currents, and Cl− background current; insensitive to 10% increases in all other ionic currents and sarcoplasmic reticulum Ca2+ fluxes. Cell electrical activity is strongly affected by 5% shift of L-type Ca2+ channels and Na+-Ca2+ exchanger in between junctional and submembrane spaces while Ca2+-activated Cl−-channel redistribution has the modest effect. Small changes in submembrane and cytosolic diffusion coefficients for Ca2+, but not in Na+ transfer, may alter notably myocyte contraction. Our studies highlight the need for more precise measurements and further extending and testing of the Shannon et al. model. Our results demonstrate usefulness of sensitivity analysis to identify specific knowledge gaps and controversies related to ventricular cell electrophysiology and Ca2+ signaling. PMID:24222910

Electric potential calculation in molecular simulation of electric double layer capacitors

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Olmsted, David L.; Asta, Mark; Laird, Brian B.

2016-11-01

For the molecular simulation of electric double layer capacitors (EDLCs), a number of methods have been proposed and implemented to determine the one-dimensional electric potential profile between the two electrodes at a fixed potential difference. In this work, we compare several of these methods for a model LiClO4-acetonitrile/graphite EDLC simulated using both the traditional fixed-charged method (FCM), in which a fixed charge is assigned a priori to the electrode atoms, or the recently developed constant potential method (CPM) (2007 J. Chem. Phys. 126 084704), where the electrode charges are allowed to fluctuate to keep the potential fixed. Based on an analysis of the full three-dimensional electric potential field, we suggest a method for determining the averaged one-dimensional electric potential profile that can be applied to both the FCM and CPM simulations. Compared to traditional methods based on numerically solving the one-dimensional Poisson’s equation, this method yields better accuracy and no supplemental assumptions.

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

The Role of Electrical Anisotropy in Modeling and Interpreting Controlled-Source Electromagnetic Responses for Hydraulic Fracture Monitoring

NASA Astrophysics Data System (ADS)

Trevino, S., III; Hickey, M. S.; Everett, M. E.

2017-12-01

Controlled-Source Electromagnetics (CSEM) can be used to monitor the movement and extent of injection fluid during a hydraulic fracture. The response of the fluid to energization by a CSEM source is dependent upon the electrical conductivity difference between the fluid and background geological formation. An important property that must be taken into account when modeling and interpreting CSEM responses is that electrical conductivity may be anisotropic. We study the effect of electrical anisotropy in both the background formation and the fluid-injection zone. First, various properties of the background formation can affect anisotropy including variations in grain size, composition and bedding-plane orientation. In certain formations, such as shale, the horizontal component of the conductivity can be more than an order of magnitude larger than the vertical component. We study this effect by computing differences in surface CSEM responses using the analytic 1-D anisotropic primary solution of a horizontal electric dipole positioned at the surface. Second, during hydraulic fracturing, the injected fluid can create new fractures and infill existing natural fractures. To include the explicit fracture geometry in modeling, a large increase in the number of nodes and computational time is required which may not be feasible. An alternative is to instead model the large-scale fracture geometry as a uniform slab with an appropriate bulk conductivity. Micro-scale fracture geometry may cause preferential fluid propagation in a single direction or plane which can be represented by electrical anisotropy of the slab. To study such effects of bulk anisotropy on CSEM responses we present results from multiple scenarios of surface to surface hydraulic fracture monitoring using 3-D finite element modeling. The model uses Coulomb-gauged potentials to solve Maxwell's equations in the frequency domain and we have updated the code to allow a triaxial electrical conductivity tensor to be specified. By allowing for formation and target electrical anisotropy these modeling results contribute to a better understanding and faster interpretation of field data.

DC Electric Field measurement in the Mid-latitude Ionosphere during MSTID by S-520-27 Sounding Rocket Experiments

NASA Astrophysics Data System (ADS)

Ishisaka, K.; Yamamoto, M.; Yokoyama, T.; Tanaka, M.; Abe, T.; Kumamoto, A.

2015-12-01

In the middle latitude ionospheric F region, mainly in summer, wave structures of electron density that have wave length of 100-200 km and period of one hour are observed. This phenomena is called Medium Scale Traveling Ionosphiric Disturbance; MSTID. MSTID has been observed by GPS receiving network, and its characteristic were studied. In the past, MSTID was thought to be generated by the Perkins instability, but its growth ratio was too small to be effective so far smaller than the real. Recently coupling process between ionospheric E and F regions are studied by using two radars and by computer simulations. Through these studies, we now have hypothesis that MSTID is generated by the combination of E-F region coupling and Perkins instability. The S-520-27 sounding rocket experiment on E-layer and F-layer was planned in order to verify this hypothesis. S-520-27 sounding rocket was launched at 23:57 JST on 20th July, 2013 from JAXA Uchinoura Space Center. S-520-27 sounding rocket reached 316km height. The S-520-27 payload was equipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure DC electric field in the spin plane of the payload. The electrodes of two double probe antennas were used to gather the potentials which were detected with high impedance pre-amplifier using the floating (unbiased) double probe technique. As a results of measurements of DC electric fields by the EFD, the natural electric field was about +/-5mV/m, and varied the direction from southeast to east. Then the electric field was mapped to the horizontal plane at 280km height along the geomagnetic field line. In this presentation, we show the detail result of DC electric field measurement by S-520-27 sounding rocket and then we discuss about the correlation between the natural electric field and TEC variation by using the GPS-TEC.

Dependence of Ru2O3 Activity on Composition of Silicate Melts: Using Statistical Correlations to Infer Thermodynamic Behavior in the Melt

NASA Technical Reports Server (NTRS)

Colson, R. O.; Malum, K. M.

2005-01-01

Understanding variations in activity with composition is an essential step in improving prediction of partition coefficients during magma evolution. Variations in activity with composition are complex and do not generally exhibit ideal behavior relative to a traditional melt-component set. Although deviations from component ideality can be modeled numerically by simply fitting to compositional variables (such as in a regular or subregular solution model), such models have not been particularly successful for describing variations in trace component activities. A better approach might be to try to identify components that do a better job of describing the behavior of the species in the melt. Electrochemical Measurement of Ru2O3 activities: Electrodes were inserted into silicate melt beads of various compositions (Table 1) suspended on Ptwire loops in a 1-atm gas mixing furnace. An electrical potential was imposed between the electrodes, the imposed potential increasing along a step ramp with a pulse imposed on each step (Fig. 1). Current flows between electrodes when electroactive species in the melt are oxidized or reduced at the electrodes. The resulting current was measured at the top and bottom of the voltage pulse, and the difference (the differential current) was plotted against potential. The peak of the resulting curve is related to the activity coefficient for the particular electroactive species (Ru2O3) in the melt [1, 2, 3]. A significant part of the nonideal contribution to activity is due not to intrinsic properties of the component in the melt, but to our ignorance about the state and mixing properties of the component in the melt.

Sensitivity of cell-based biosensors to environmental variables.

PubMed

Gilchrist, Kristin H; Giovangrandi, Laurent; Whittington, R Hollis; Kovacs, Gregory T A

2005-01-15

Electrically active living cells cultured on extracellular electrode arrays are utilized to detect biologically active agents. Because cells are highly sensitive to environmental conditions, environmental fluctuations can elicit cellular responses that contribute to the noise in a cell-based biosensor system. Therefore, the characterization and control of environmental factors such as temperature, pH, and osmolarity is critical in such a system. The cell-based biosensor platform described here utilizes the measurement of action potentials from cardiac cells cultured on electrode arrays. A recirculating fluid flow system is presented for use in dose-response experiments that regulates temperature within +/-0.2 degrees C, pH to within +/-0.05 units, and allows no significant change in osmolarity. Using this system, the relationship between the sensor output parameters and environmental variation was quantified. Under typical experimental conditions, beat rate varied approximately 10% per degree change in temperature or per 0.1 unit change in pH. Similar relationships were measured for action potential amplitude, duration, and conduction velocity. For the specific flow system used in this work, the measured environmental sensitivity resulted in an overall beat rate variation of +/-4.7% and an overall amplitude variation of +/-3.3%. The magnitude of the noise due to environmental sensitivity has a large impact on the detection capability of the cell-based system. The significant responses to temperature, pH, and osmolarity have important implications for the use of living cells in detection systems and should be considered in the design and evaluation of such systems.

Modeling of the Through-the-Thickness Electric Potentials of a Piezoelectric Bimorph Using the Spectral Element Method

PubMed Central

Dong, Xingjian; Peng, Zhike; Hua, Hongxing; Meng, Guang

2014-01-01

An efficient spectral element (SE) with electric potential degrees of freedom (DOF) is proposed to investigate the static electromechanical responses of a piezoelectric bimorph for its actuator and sensor functions. A sublayer model based on the piecewise linear approximation for the electric potential is used to describe the nonlinear distribution of electric potential through the thickness of the piezoelectric layers. An equivalent single layer (ESL) model based on first-order shear deformation theory (FSDT) is used to describe the displacement field. The Legendre orthogonal polynomials of order 5 are used in the element interpolation functions. The validity and the capability of the present SE model for investigation of global and local responses of the piezoelectric bimorph are confirmed by comparing the present solutions with those obtained from coupled 3-D finite element (FE) analysis. It is shown that, without introducing any higher-order electric potential assumptions, the current method can accurately describe the distribution of the electric potential across the thickness even for a rather thick bimorph. It is revealed that the effect of electric potential is significant when the bimorph is used as sensor while the effect is insignificant when the bimorph is used as actuator, and therefore, the present study may provide a better understanding of the nonlinear induced electric potential for bimorph sensor and actuator. PMID:24561399

An incremental double-layer capacitance of a planar nano gap and its application in cardiac-troponin T detection.

PubMed

Hsueh, Hsiao-Ting; Lin, Chih-Ting

2016-05-15

Surface potential is one of the most important properties at solid-liquid interfaces. It can be modulated by the voltage applied on the electrode or by the surface properties. Hence, surface potential is a good indicator for surface modifications, such as biomolecular bindings. In this work, we proposed a planar nano-gap structure for surface-potential difference monitoring. Based on the proposed architecture, the variance of surface-potential difference can be determined by electrical double layer capacitance (EDLC) between the nano-gap electrodes. Using cyclic voltammetry method, in this work, we demonstrated a relationship between surface potential and EDLC by chemically modifying surface properties. Finally, we also showed the proposed planar nano-gap device provides the capability for cardiac-troponin T (cTnT) measurements with co-existed 10 µg/ml BSA interference. The detection dynamic range is from 100 pg/ml to 1 µg/ml. Based on experimental results and extrapolation, the detection limit is less than 100 pg/ml in diluted PBS buffer (0.01X PBS). These results demonstrated the planar nano-gap architecture having potentials on biomolecular detection through monitoring of surface-potential variation. Copyright © 2015 Elsevier B.V. All rights reserved.

Time-lapse electrical resistivity tomography: a powerful tool for landslide monitoring?

NASA Astrophysics Data System (ADS)

Perrone, A.

2011-12-01

The extreme rainfall events and the quick snowmelt occurrences play an important role in the triggering of the landslides. The occurrence of one of these factors can determine the variation of water content in the first layers of the subsoil and as a consequence a quick soil saturation inducing both an increase in pore-water pressures and the overloaded of the slopes progressively collapsing. The electrical resistivity, self-potential, electromagnetic induction and GPR methods can be considered as the most appropriate for assessing the presence of water in the underground. Such methods allow us to study the behavior of water content over much wider and deeper areas than those offered by traditional methods (thermo-gravimetric, tensiometric, TDR, etc) based on spot measures and concerning small volumes. In particular, the Electrical Resistivity Tomography (ERT), which has already proved to be a powerful tool both for the geometrical reconstruction of a landslide body (location of sliding surface, estimation of the thickness of the slide material) and the individuation of high water content areas, can be considered as an alternative tool to be employed for a qualitative and quantitative water content monitoring in the first layers of the subsoil. Indeed, time-lapse 2D ERT can be tested in order to gather information on the temporal and spatial patterns of water infiltration processes and water content variation. This work reports the preliminary results from a new prototype system planned to obtain time-lapse 2D ERTs, TDR and precipitation measurements in two landslide areas located in the Southern Apennine chain (Italy). The system was planned with the aim to estimate the variation of the resistivity parameter on a long period considering the water content variation, the rain water infiltration and the seasonal changes. The prototype system, linked to a pc used for storing data and managing the time interval acquisition, consists of: a resistivimeter connected to a multichannel cable, 48 steel electrodes buried in the soil at a depth of about 0.5 m at a distance of 1 or 5 m; a TDR system linked to 4 probes 20 cm length, buried at different depths along the same profile of the geoelectrical one; while a weather station consists of a rain gauge to quantify the amount of rain falling on that area, one sensor to measure the temperature and another to determine the speed and direction of the wind. At the beginning the time-lapse ERT were analysed to verify the functionality and stability of the system and to decide the measurement time intervals. After that, the statistical analysis of the results obtained was performed with the aim to define the water content variation in the first layers of the subsoil, in particular in the vadose zone. The results were compared with the TDR ones and the piezometric measurements were performed in the area thanks to the presence of equipped boreholes. The correlation between the variation of the parameters measured (electrical resistivity, water content and piezometric level) and the rain-gauge measurements was also considered. The preliminary results seem to be encouraged also if the analysis of the data acquired on a longer period could better highlight the capability of the system.

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

PubMed

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

2004-01-01

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

Estimating spatial variations in water content of clay soils from time-lapse electrical conductivity surveys

USDA-ARS?s Scientific Manuscript database

Soil water content (theta) is one of the most important drivers for many biogeochemical fluxes at different temporal and spatial scales. Hydrogeophysical non-invasive sensors that measure the soil apparent electrical conductivity (ECa) have been widely used to infer spatial and temporal patterns of...

Sensor system for web inspection

DOEpatents

Sleefe, Gerard E.; Rudnick, Thomas J.; Novak, James L.

2002-01-01

A system for electrically measuring variations over a flexible web has a capacitive sensor including spaced electrically conductive, transmit and receive electrodes mounted on a flexible substrate. The sensor is held against a flexible web with sufficient force to deflect the path of the web, which moves relative to the sensor.

Effect of presynaptic membrane potential on electrical vs. chemical synaptic transmission

PubMed Central

Evans, Colin G.; Ludwar, Bjoern Ch.; Kang, Timothy

2011-01-01

The growing realization that electrical coupling is present in the mammalian brain has sparked renewed interest in determining its functional significance and contrasting it with chemical transmission. One question of interest is whether the two types of transmission can be selectively regulated, e.g., if a cell makes both types of connections can electrical transmission occur in the absence of chemical transmission? We explore this issue in an experimentally advantageous preparation. B21, the neuron we study, is an Aplysia sensory neuron involved in feeding that makes electrical and chemical connections with other identified cells. Previously we demonstrated that chemical synaptic transmission is membrane potential dependent. It occurs when B21 is centrally depolarized prior to and during peripheral activation, but does not occur if B21 is peripherally activated at its resting membrane potential. In this article we study effects of membrane potential on electrical transmission. We demonstrate that maximal potentiation occurs in different voltage ranges for the two types of transmission, with potentiation of electrical transmission occurring at more hyperpolarized potentials (i.e., requiring less central depolarization). Furthermore, we describe a physiologically relevant type of stimulus that induces both spiking and an envelope of depolarization in the somatic region of B21. This depolarization does not induce functional chemical synaptic transmission but is comparable to the depolarization needed to maximally potentiate electrical transmission. In this study we therefore characterize a situation in which electrical and chemical transmission can be selectively controlled by membrane potential. PMID:21593394

Development and application of measurement techniques for evaluating localised magnetic properties in electrical steel

NASA Astrophysics Data System (ADS)

Lewis, N. J.; Anderson, P. I.; Gao, Y.; Robinson, F.

2018-04-01

This paper reports the development of a measurement probe which couples local flux density measurements obtained using the needle probe method with the local magnetising field attained via a Hall effect sensor. This determines the variation in magnetic properties including power loss and permeability at increasing distances from the punched edge of 2.4% and 3.2% Si non-oriented electrical steel sample. Improvements in the characterisation of the magnetic properties of electrical steels would aid in optimising the efficiency in the design of electric machines.

Thermal-electrical properties and resistance stability of silver coated yarns

NASA Astrophysics Data System (ADS)

Li, Yafang; Liu, Hao; Li, Xiaojiu

2017-03-01

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

Protective carrier for microcircuit devices

DOEpatents

Robinson, Lyle A.

1976-10-26

An improved protective carrier for microcircuit devices having beam leads wherein a compressible member is disposed on the carrier base beneath and overlapping the periphery of an aperture in a flexible circuit element, the element being adapted to receive and make electrical contact with microcircuit device beam leads, the compressible member disposed or arranged to achieve flexing of the circuit element against the microcircuit device beam leads to conform to variations in thicknesses of the device beam leads or circuit element electrical paths and thereby insure electrical connection between the beam leads and the electrical paths.

Improved outcomes in auditory brainstem implantation with the use of near-field electrical compound action potentials.

PubMed

Mandalà, Marco; Colletti, Liliana; Colletti, Giacomo; Colletti, Vittorio

2014-12-01

To compare the outcomes (auditory threshold and open-set speech perception at 48-month follow-up) of a new near-field monitoring procedure, electrical compound action potential, on positioning the auditory brainstem implant electrode array on the surface of the cochlear nuclei versus the traditional far-field electrical auditory brainstem response. Retrospective study. Tertiary referral center. Among the 202 patients with auditory brainstem implants fitted and monitored with electrical auditory brainstem response during implant fitting, 9 also underwent electrical compound action potential recording. These subjects were matched retrospectively with a control group of 9 patients in whom only the electrical auditory brainstem response was recorded. Electrical compound action potentials were obtained using a cotton-wick recording electrode located near the surface of the cochlear nuclei and on several cranial nerves. Significantly lower potential thresholds were observed with the recording electrode located on the cochlear nuclei surface compared with the electrical auditory brainstem response (104.4 ± 32.5 vs 158.9 ± 24.2, P = .0030). Electrical brainstem response and compound action potentials identified effects on the neighboring cranial nerves on 3.2 ± 2.4 and 7.8 ± 3.2 electrodes, respectively (P = .0034). Open-set speech perception outcomes at 48-month follow-up had improved significantly in the near- versus far-field recording groups (78.9% versus 56.7%; P = .0051). Electrical compound action potentials during auditory brainstem implantation significantly improved the definition of the potential threshold and the number of auditory and extra-auditory waves generated. It led to the best coupling between the electrode array and cochlear nuclei, significantly improving the overall open-set speech perception. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

Method of imaging the electrical conductivity distribution of a subsurface

DOEpatents

Johnson, Timothy C.

2017-09-26

A method of imaging electrical conductivity distribution of a subsurface containing metallic structures with known locations and dimensions is disclosed. Current is injected into the subsurface to measure electrical potentials using multiple sets of electrodes, thus generating electrical resistivity tomography measurements. A numeric code is applied to simulate the measured potentials in the presence of the metallic structures. An inversion code is applied that utilizes the electrical resistivity tomography measurements and the simulated measured potentials to image the subsurface electrical conductivity distribution and remove effects of the subsurface metallic structures with known locations and dimensions.

Developing an Ear Prosthesis Fabricated in Polyvinylidene Fluoride by a 3D Printer with Sensory Intrinsic Properties of Pressure and Temperature

PubMed Central

Suaste-Gómez, Ernesto; Rodríguez-Roldán, Grissel; Reyes-Cruz, Héctor; Terán-Jiménez, Omar

2016-01-01

An ear prosthesis was designed in 3D computer graphics software and fabricated using a 3D printing process of polyvinylidene fluoride (PVDF) for use as a hearing aid. In addition, the prosthesis response to pressure and temperature was observed. Pyroelectric and piezoelectric properties of this ear prosthesis were investigated using an astable multivibrator circuit, as changes in PVDF permittivity were observed according to variations of pressure and temperature. The results show that this prosthesis is reliable for use under different conditions of pressure (0 Pa to 16,350 Pa) and temperature (2 °C to 90 °C). The experimental results show an almost linear and inversely proportional behavior between the stimuli of pressure and temperature with the frequency response. This 3D-printed ear prosthesis is a promising tool and has a great potentiality in the biomedical engineering field because of its ability to generate an electrical potential proportional to pressure and temperature, and it is the first time that such a device has been processed by the additive manufacturing process (3D printing). More work needs to be carried out to improve the performance, such as electrical stimulation of the nervous system, thereby extending the purpose of a prosthesis to the area of sensory perception. PMID:26959026

Developing an Ear Prosthesis Fabricated in Polyvinylidene Fluoride by a 3D Printer with Sensory Intrinsic Properties of Pressure and Temperature.

PubMed

Suaste-Gómez, Ernesto; Rodríguez-Roldán, Grissel; Reyes-Cruz, Héctor; Terán-Jiménez, Omar

2016-03-04

An ear prosthesis was designed in 3D computer graphics software and fabricated using a 3D printing process of polyvinylidene fluoride (PVDF) for use as a hearing aid. In addition, the prosthesis response to pressure and temperature was observed. Pyroelectric and piezoelectric properties of this ear prosthesis were investigated using an astable multivibrator circuit, as changes in PVDF permittivity were observed according to variations of pressure and temperature. The results show that this prosthesis is reliable for use under different conditions of pressure (0 Pa to 16,350 Pa) and temperature (2 °C to 90 °C). The experimental results show an almost linear and inversely proportional behavior between the stimuli of pressure and temperature with the frequency response. This 3D-printed ear prosthesis is a promising tool and has a great potentiality in the biomedical engineering field because of its ability to generate an electrical potential proportional to pressure and temperature, and it is the first time that such a device has been processed by the additive manufacturing process (3D printing). More work needs to be carried out to improve the performance, such as electrical stimulation of the nervous system, thereby extending the purpose of a prosthesis to the area of sensory perception.

Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS2 Transistors.

PubMed

Matsunaga, Masahiro; Higuchi, Ayaka; He, Guanchen; Yamada, Tetsushi; Krüger, Peter; Ochiai, Yuichi; Gong, Yongji; Vajtai, Robert; Ajayan, Pulickel M; Bird, Jonathan P; Aoki, Nobuyuki

2016-10-05

Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS 2 ), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS 2 . Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS 2 bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.

Development and validation of a new kind of coupling element for wheel-hub motors

NASA Astrophysics Data System (ADS)

Perekopskiy, Sergey; Kasper, Roland

2018-05-01

For the automotive industry, electric powered vehicles are becoming an increasingly relevant factor in the competition against climate change. Application of one special example - a wheel-hub motor, for electric powered vehicle can support this challenge. Patented slotless air gap winding invented at the chair of mechatronics of the Otto von Guericke University Magdeburg has great application potential in constantly growing e-mobility field, especially for wheel-hub motors based on this technology due to its advantages, such as a high gravimetric power density and high efficiency. However, advantages of this technology are decreased by its sensibility to the loads out of driving maneuvers by dimensional variations of air gap consistency. This article describes the development and validation of a coupling element for the designed wheel-hub motor. To find a suitable coupling concept first the assembly structure of the motor was analyzed and developed design of the coupling element was checked. Based on the geometry of the motor and wheel a detailed design of the coupling element was generated. The analytical approach for coupling element describes a potential of the possible loads on the coupling element. The FEM simulation of critical load cases for the coupling element validated results of the analytical approach.

Investigation of dielectric pocket induced variations in tunnel field effect transistor

NASA Astrophysics Data System (ADS)

Upasana; Narang, Rakhi; Saxena, Manoj; Gupta, Mridula

2016-04-01

The performance of conventional Tunnel FETs struggling from ambipolar issues, insufficient on-current, lower transconductance value, higher delay and lower cut off frequency has been improved by introducing several material and device engineering concepts in past few years. Keeping this in view, another interesting and reliable option i.e. Dielectric Pocket TFET (featuring a dielectric pocket placement near tunneling junction) has been comprehensively and qualitatively demonstrated using ATLAS device simulator. The architecture has been explored in terms of various device electrostatic parameters such as potential, energy band profile, electron and hole concentration, electric field variation and band to band generation rate (GBTB) near the tunneling junction where the Dielectric Pocket (DP) has been introduced. Subsequently, a detailed investigation by changing the position and dielectric constant of pocket at respective junctions has been made where DP induced variations in drain current, transconductance and parasitic capacitance have been examined. The work highlights major improvements over conventional TFET in terms of lower subthreshold swing and threshold voltage, higher drain current and transconductance, improved on-to-off current ratio, suppressed ambipolar conduction and improved dynamic power dissipation issues for low voltage analog and digital applications.

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

Bonneville, Alain H.; Kouzes, Richard T.

Imaging subsurface geological formations, oil and gas reservoirs, mineral deposits, cavities or magma chambers under active volcanoes has been for many years a major quest of geophysicists and geologists. Since these objects cannot be observed directly, different indirect geophysical methods have been developed. They are all based on variations of certain physical properties of the subsurface that can be detected from the ground surface or from boreholes. Electrical resistivity, seismic wave’s velocities and density are certainly the most used properties. If we look at density, indirect estimates of density distributions are performed currently by seismic reflection methods - since themore » velocity of seismic waves depend also on density - but they are expensive and discontinuous in time. Direct estimates of density are performed using gravimetric data looking at variations of the gravity field induced by the density variations at depth but this is not sufficiently accurate. A new imaging technique using cosmic-ray muon detectors has emerged during the last decade and muon tomography - or muography - promises to provide, for the first time, a complete and precise image of the density distribution in the subsurface. Further, this novel approach has the potential to become a direct, real-time, and low-cost method for monitoring fluid displacement in subsurface reservoirs.« less

Development of theoretical approach for describing electronic properties of hetero-interface systems under applied bias voltage.

PubMed

Iida, Kenji; Noda, Masashi; Nobusada, Katsuyuki

2017-02-28

We have developed a theoretical approach for describing the electronic properties of hetero-interface systems under an applied electrode bias. The finite-temperature density functional theory is employed for controlling the chemical potential in their interfacial region, and thereby the electronic charge of the system is obtained. The electric field generated by the electronic charging is described as a saw-tooth-like electrostatic potential. Because of the continuum approximation of dielectrics sandwiched between electrodes, we treat dielectrics with thicknesses in a wide range from a few nanometers to more than several meters. Furthermore, the approach is implemented in our original computational program named grid-based coupled electron and electromagnetic field dynamics (GCEED), facilitating its application to nanostructures. Thus, the approach is capable of comprehensively revealing electronic structure changes in hetero-interface systems with an applied bias that are practically useful for experimental studies. We calculate the electronic structure of a SiO 2 -graphene-boron nitride (BN) system in which an electrode bias is applied between the graphene layer and an electrode attached on the SiO 2 film. The electronic energy barrier between graphene and BN is varied with an applied bias, and the energy variation depends on the thickness of the BN film. This is because the density of states of graphene is so low that the graphene layer cannot fully screen the electric field generated by the electrodes. We have demonstrated that the electronic properties of hetero-interface systems are well controlled by the combination of the electronic charging and the generated electric field.

Postfatigue potentiation of the paralyzed soleus muscle: evidence for adaptation with long-term electrical stimulation training

PubMed Central

Shields, Richard K.; Dudley-Javoroski, Shauna; Littmann, Andrew E.

2012-01-01

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI. PMID:16575026

Postfatigue potentiation of the paralyzed soleus muscle: evidence for adaptation with long-term electrical stimulation training.

PubMed

Shields, Richard K; Dudley-Javoroski, Shauna; Littmann, Andrew E

2006-08-01

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI.

Electromagnetic wave energy converter

NASA Technical Reports Server (NTRS)

Bailey, R. L. (Inventor)

1973-01-01

Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.

Ultrasonic Characterization of Superhard Material: Osmium Diboride

NASA Astrophysics Data System (ADS)

Yadawa, P. K.

2012-12-01

Higher order elastic constants have been calculated in hexagonal structured superhard material OsB2 at room temperature following the interaction potential model. The temperature variation of the ultrasonic velocities is evaluated along different angles with unique axis of the crystal using the second order elastic constants. The ultrasonic velocity decreases with the temperature along particular orientation with the unique axis. Temperature variation of the thermal relaxation time and Debye average velocities are also calculated along the same orientation. The temperature dependency of the ultrasonic properties is discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behaviour of ultrasonic attenuation as a function of temperature and the responsible cause of attenuation is phonon-phonon interaction. The mechanical properties of OsB2 at low temperature are better than at high temperature, because at low temperature it has low ultrasonic velocity and ultrasonic attenuation. Superhard material OsB2 has many industrial applications, such as abrasives, cutting tools and hard coatings.

Microbial, physical and chemical properties of irrigation water in rice fields of Southern Brazil.

PubMed

Reche, Maria Helena L R; Machado, Vilmar; Saul, Danilo A; Macedo, Vera R M; Marcolin, Elio; Knaak, Neiva; Fiuza, Lidia M

2016-03-01

This paper presents the results of the statistical analysis of microbiological, physical and chemical parameters related to the quality of the water used in rice fields in Southern Brazil. Data were collected during three consecutive crop years, within structure of a comprehensive monitoring program. The indicators used were: potential hydrogen, electrical conductivity, turbidity, nitrogen, phosphorus, potassium, calcium, total and fecal coliforms. Principal Component and Discriminant Analysis showed consistent differences between the water irrigation and drainage, as the temporal variation demonstrated a clear reduction in the concentration of most of the variables analyzed. The pattern of this reduction is not the same in the two regions - that is, the importance of each of the different variables in the observed differentiation is modified in two locations. These results suggested that the variations in the water quality utilized for rice irrigation was influenced by certain specific aspects of each rice region in South Brazilian - such as anthropic action or soil/climate conditions in each hydrographic basin.

Wind power in Jamaica

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

Chen, A.A.; Daniel, A.R.; Daniel, S.T.

1990-01-01

Parameters to evaluate the potential for using wind energy to generate electricity in Jamaica were obtained. These include the average wind power scaled to a height of 20 m at existing weather stations and temporary anemometer sites, the variation in annual and monthly wind power, and the frequency distribution of wind speed and wind energy available. Four small commercial turbines were assumed to be operating at some of the sites, and the estimated energy captured by them, the time they operated above their cut-in speed and their capacity factors were also determined. Diurnal variations of wind speed and prevailing windmore » directions are discussed and a map showing wind power at various sites was produced. Two stations with long-term averages, Manley and Morant Point, gave results which warranted further investigation. Results from some temporary stations are also encouraging. Mean wind speeds at two other sites in the Caribbean are given for comparison. A method for estimating the power exponent for scaling the wind speed from climatic data is described in Appendix 2.« less

Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity

NASA Astrophysics Data System (ADS)

Uyeda, S.; Nagao, T.; Hattori, K.; Hayakawa, M.; Miyaki, K.; Molchanov, O.; Gladychev, V.; Baransky, L.; Chtchekotov, A.; Fedorov, E.; Pokhotelov, O.; Andreevsky, S.; Rozhnoi, A.; Khabazin, Y.; Gorbatikov, A.; Gordeev, E.; Chebrov, V.; Sinitzin, V.; Lutikov, A.; Yunga, S.; Kosarev, G.; Surkov, V.; Belyaev, G.

Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity). The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 - 40 Hz) and meteorological recordings, together with seismo-acoustic (∆F = 30 - 1000 Hz) and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 - 30 Hz), three-component electric potential variations ( ∆F < 1.0 Hz), and VLF transmitter's signal perturbations ( ∆F ~ 10 - 40 kHz).

Investigations on an electroactive polymer based tunable Helmholtz resonator

NASA Astrophysics Data System (ADS)

Abbad, A.; Rabenorosoa, K.; Ouisse, M.; Atalla, N.

2017-04-01

A Helmholtz resonator is a passive acoustic resonator classically used to control a single frequency resulting from the cavity volume and the resonator neck size. The aim of the proposed study is to present a new concept and strategy allowing real-time tunability of the Helmholtz resonator in order to enhance acoustic absorption performances at low frequencies (< 500 Hz). The proposed concept consists in replacing the resonator rigid front plate by an electroactive polymer (EAP) membrane. The first proposed strategy consists on a change in the mechanical properties of the membrane resulting from the applied electric field. This induces a resonance frequency shift. A second strategy is based on a well-located spring, which could direct the membrane deformation following the axis of the resonator to obtain a cavity volume variation. Both strategies allow variation of the resonance frequency of the device. Experimental measurements are performed to determine the potential of this concept for improvement of low-frequency performances of the acoustic devices.

Self-adaptive strain-relaxation optimization for high-energy lithium storage material through crumpling of graphene.

PubMed

Zhao, Yunlong; Feng, Jiangang; Liu, Xue; Wang, Fengchao; Wang, Lifen; Shi, Changwei; Huang, Lei; Feng, Xi; Chen, Xiyuan; Xu, Lin; Yan, Mengyu; Zhang, Qingjie; Bai, Xuedong; Wu, Hengan; Mai, Liqiang

2014-08-01

High-energy lithium battery materials based on conversion/alloying reactions have tremendous potential applications in new generation energy storage devices. However, these applications are limited by inherent large volume variations and sluggish kinetics. Here we report a self-adaptive strain-relaxed electrode through crumpling of graphene to serve as high-stretchy protective shells on metal framework, to overcome these limitations. The graphene sheets are self-assembled and deeply crumpled into pinecone-like structure through a contraction-strain-driven crumpling method. The as-prepared electrode exhibits high specific capacity (2,165 mAh g(-1)), fast charge-discharge rate (20 A g(-1)) with no capacity fading in 1,000 cycles. This kind of crumpled graphene has self-adaptive behaviour of spontaneous unfolding-folding synchronized with cyclic expansion-contraction volumetric variation of core materials, which can release strain and maintain good electric contact simultaneously. It is expected that such findings will facilitate the applications of crumpled graphene and the self-adaptive materials.

Physical and technological principles of designing layer-gradient multicomponent surfaces by combining the methods of ion-diffusion saturation and magnetron- and vacuum-arc deposition

NASA Astrophysics Data System (ADS)

Savostikov, V. M.; Potekaev, A. I.; Tabachenko, A. N.

2011-12-01

Using a technological system proposed by the authors, a combined process is developed for formation of stratified-gradient surface layers and multicomponent coatings. It is implemented under the conditions of a combined serial-parallel operation of a hot-cathode gas plasma generator and a duomagnetron with two targets and two electric-arc evaporators. The extended functional potential is ensured by using advanced multi-element and multi-phase cathode targets made of borides, carbides, silicides, and sulfides of metals produced by the SHS-process followed by their immediate compaction. The variations in composition, structure, and physicomechanical properties in the cross-section of the stratified-gradient surface layers and coating is provided by a predetermined alternating replacement of the sputtered cathode targets of the plasma sources, the plasma flow intensity ratios, and variation in the particle energy incident on the substrate, which is determined by the accelerating voltage on the substrate.

Tridimensional reconstruction of the Co-Seismic Ionospheric Disturbance around the time of 2015 Nepal earthquake

NASA Astrophysics Data System (ADS)

Kong, Jian; Yao, Yibin; Zhou, Chen; Liu, Yi; Zhai, Changzhi; Wang, Zemin; Liu, Lei

2018-01-01

The Co-Seismic Ionospheric Disturbance of the 2015 Nepal earthquake is analyzed in this paper. GNSS data are used to obtain the Satellite-Station TEC sequences. After removing the de-trended TEC variation, a clear ionospheric disturbance was observed 10 min after the earthquake, while the geomagnetic conditions, solar activity, and weather condition remained calm according to the Kp, Dst, F10.7 indices and meteorological records during the period of interest. Computerized ionosphere tomography (CIT) is then used to present the tridimensional ionosphere variation with a 10-min time resolution. The CIT results indicate that (1) the disturbance of the ionospheric electron density above the epicenter during the 2015 Nepal earthquake is confined at a relatively low altitude (approximately 150-300 km); (2) the ionospheric disturbances on the west side and east sides of the epicenter are precisely opposite. A newly established electric field penetration model of the lithosphere-atmosphere-ionosphere coupling is used to investigate the potential physical mechanism.

The Potential Wind Power Resource in Australia: A New Perspective

PubMed Central

Hallgren, Willow; Gunturu, Udaya Bhaskar; Schlosser, Adam

2014-01-01

Australia’s wind resource is considered to be very good, and the utilization of this renewable energy resource is increasing rapidly: wind power installed capacity increased by 35% from 2006 to 2011 and is predicted to account for over 12% of Australia’s electricity generation in 2030. Due to this growth in the utilization of the wind resource and the increasing importance of wind power in Australia’s energy mix, this study sets out to analyze and interpret the nature of Australia’s wind resources using robust metrics of the abundance, variability and intermittency of wind power density, and analyzes the variation of these characteristics with current and potential wind turbine hub heights. We also assess the extent to which wind intermittency, on hourly or greater timescales, can potentially be mitigated by the aggregation of geographically dispersed wind farms, and in so doing, lessen the severe impact on wind power economic viability of long lulls in wind and power generated. Our results suggest that over much of Australia, areas that have high wind intermittency coincide with large expanses in which the aggregation of turbine output does not mitigate variability. These areas are also geographically remote, some are disconnected from the east coast’s electricity grid and large population centers, which are factors that could decrease the potential economic viability of wind farms in these locations. However, on the eastern seaboard, even though the wind resource is weaker, it is less variable, much closer to large population centers, and there exists more potential to mitigate it’s intermittency through aggregation. This study forms a necessary precursor to the analysis of the impact of large-scale circulations and oscillations on the wind resource at the mesoscale. PMID:24988222

The potential wind power resource in Australia: a new perspective.

PubMed

Hallgren, Willow; Gunturu, Udaya Bhaskar; Schlosser, Adam

2014-01-01

Australia's wind resource is considered to be very good, and the utilization of this renewable energy resource is increasing rapidly: wind power installed capacity increased by 35% from 2006 to 2011 and is predicted to account for over 12% of Australia's electricity generation in 2030. Due to this growth in the utilization of the wind resource and the increasing importance of wind power in Australia's energy mix, this study sets out to analyze and interpret the nature of Australia's wind resources using robust metrics of the abundance, variability and intermittency of wind power density, and analyzes the variation of these characteristics with current and potential wind turbine hub heights. We also assess the extent to which wind intermittency, on hourly or greater timescales, can potentially be mitigated by the aggregation of geographically dispersed wind farms, and in so doing, lessen the severe impact on wind power economic viability of long lulls in wind and power generated. Our results suggest that over much of Australia, areas that have high wind intermittency coincide with large expanses in which the aggregation of turbine output does not mitigate variability. These areas are also geographically remote, some are disconnected from the east coast's electricity grid and large population centers, which are factors that could decrease the potential economic viability of wind farms in these locations. However, on the eastern seaboard, even though the wind resource is weaker, it is less variable, much closer to large population centers, and there exists more potential to mitigate it's intermittency through aggregation. This study forms a necessary precursor to the analysis of the impact of large-scale circulations and oscillations on the wind resource at the mesoscale.

Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device

NASA Astrophysics Data System (ADS)

Martin, M. J.; Gekelman, W.; Van Compernolle, B.; Pribyl, P.; Carter, T.

2017-11-01

An experiment in a linear device, the Large Plasma Device, is used to study sheaths caused by an actively powered radio frequency (rf) antenna. The rf antenna used in the experiment consists of a single current strap recessed inside a copper box enclosure without a Faraday screen. A large increase in the plasma potential was observed along magnetic field lines that connect to the antenna limiter. The electric field from the spatial variation of the rectified plasma potential generated E →×B→0 flows, often referred to as convective cells. The presence of the flows generated by these potentials is confirmed by Mach probes. The observed convective cell flows are seen to cause the plasma in front of the antenna to flow away and cause a density modification near the antenna edge. These can cause hot spots and damage to the antenna and can result in a decrease in the ion cyclotron range of frequencies antenna coupling.

Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device.

PubMed

Martin, M J; Gekelman, W; Van Compernolle, B; Pribyl, P; Carter, T

2017-11-17

An experiment in a linear device, the Large Plasma Device, is used to study sheaths caused by an actively powered radio frequency (rf) antenna. The rf antenna used in the experiment consists of a single current strap recessed inside a copper box enclosure without a Faraday screen. A large increase in the plasma potential was observed along magnetic field lines that connect to the antenna limiter. The electric field from the spatial variation of the rectified plasma potential generated E[over →]×B[over →]_{0} flows, often referred to as convective cells. The presence of the flows generated by these potentials is confirmed by Mach probes. The observed convective cell flows are seen to cause the plasma in front of the antenna to flow away and cause a density modification near the antenna edge. These can cause hot spots and damage to the antenna and can result in a decrease in the ion cyclotron range of frequencies antenna coupling.

Probing interval timing with scalp-recorded electroencephalography (EEG).

PubMed

Ng, Kwun Kei; Penney, Trevor B

2014-01-01

Humans, and other animals, are able to easily learn the durations of events and the temporal relationships among them in spite of the absence of a dedicated sensory organ for time. This chapter summarizes the investigation of timing and time perception using scalp-recorded electroencephalography (EEG), a non-invasive technique that measures brain electrical potentials on a millisecond time scale. Over the past several decades, much has been learned about interval timing through the examination of the characteristic features of averaged EEG signals (i.e., event-related potentials, ERPs) elicited in timing paradigms. For example, the mismatch negativity (MMN) and omission potential (OP) have been used to study implicit and explicit timing, respectively, the P300 has been used to investigate temporal memory updating, and the contingent negative variation (CNV) has been used as an index of temporal decision making. In sum, EEG measures provide biomarkers of temporal processing that allow researchers to probe the cognitive and neural substrates underlying time perception.

Silicon Nanowire Field Effect Transistor Sensors with Minimal Sensor to Sensor Variations and Enhanced Sensing Characteristics.

PubMed

Zafar, Sufi; D'Emic, Christopher; Jagtiani, Ashish; Kratschmer, Ernst; Miao, Xin; Zhu, Yu; Mo, Renee; Sosa, Norma; Hamann, Hendrik F; Shahidi, Ghavam; Riel, Heike

2018-06-22

Silicon nanowire field effect transistor (FET) sensors have demonstrated their ability for rapid and label free detection of proteins, nucleotide sequences, and viruses at ultralow concentrations with the potential to be a transformative diagnostic technology. Their nanoscale size gives them their unique ultralow detection ability but also makes their fabrication challenging with large sensor to sensor variations, thus limiting their commercial applications. In this work, a combined approach of nanofabrication, device simulation, materials and electrical characterization is applied towards identifying and improving fabrication steps that induce sensor to sensor variations. An enhanced complementary metal-oxide-semiconductor (CMOS) compatible process for fabricating silicon nanowire FET sensors is demonstrated. Nanowire (30 nm width) FETs with aqueous solution as gates are shown to have the Nernst limit sub-threshold swing SS = 60 mV/decade with ~1.7% variations, whereas literature values for SS are ≥ 80 mV/decade with larger (>10 times) variations. Also, their threshold voltage variations are significantly (~3 times) reduced, compared to literature values. Furthermore, these improved FETs have significantly reduced drain current hysteresis (~0.6 mV) and enhanced on-current to off-current ratios (~10 6 ). These improvements resulted in nanowire FET sensors with lowest (~3%) reported sensor to sensor variations, compared to literature studies. Also, these improved nanowire sensors have the highest reported sensitivity and enhanced signal to noise ratio with the lowest reported defect density of 1x10 18 eV -1 cm -3 in comparison to literature data. In summary, this work brings the nanowire sensor technology a step closer to commercial products for early diagnosis and monitoring of diseases.

Variations in the electrical short-circuit current decay for recombination lifetime and velocity measurements

NASA Technical Reports Server (NTRS)

Jung, Tae-Won; Lindholm, Fredrik A.; Neugroschel, Arnost

1987-01-01

An improved measurement system for electrical short-circuit current decay is presented that extends applicability of the method to silicon solar cells having an effective lifetime as low as 1 microsec. The system uses metal/oxide/semiconductor transistors as voltage-controlled switches. Advances in theory developed here increase precision and sensitivity in the determination of the minority-carrier recombination lifetime and recombination velocity. A variation of the method, which exploits measurements made on related back-surface field and back-ohmic contact devices, further improves precision and sensitivity. The improvements are illustrated by application to 15 different silicon solar cells.

Electrodynamics of the middle atmosphere: Superpressure balloon program

NASA Technical Reports Server (NTRS)

Holzworth, Robert H.

1987-01-01

In this experiment a comprehensive set of electrical parameters were measured during eight long duration flights in the southern hemisphere stratosphere. These flight resulted in the largest data set ever collected from the stratosphere. The stratosphere has never been electrodynamically sampled in the systematic manner before. New discoveries include short term variability in the planetary scale electric current system, the unexpected observation of stratospheric conductivity variations over thunderstorms and the observation of direct stratospheric conductivity variations following a relatively small solar flare. Major statistical studies were conducted of the large scale current systems, the stratospheric conductivity and the neutral gravity waves (from pressure and temperature data) using the entire data set.

Real-Time Electrical Impedimetric Monitoring of Blood Coagulation Process under Temperature and Hematocrit Variations Conducted in a Microfluidic Chip

PubMed Central

Lei, Kin Fong; Chen, Kuan-Hao; Tsui, Po-Hsiang; Tsang, Ngan-Ming

2013-01-01

Blood coagulation is an extremely complicated and dynamic physiological process. Monitoring of blood coagulation is essential to predict the risk of hemorrhage and thrombosis during cardiac surgical procedures. In this study, a high throughput microfluidic chip has been developed for the investigation of the blood coagulation process under temperature and hematocrit variations. Electrical impedance of the whole blood was continuously recorded by on-chip electrodes in contact with the blood sample during coagulation. Analysis of the impedance change of the blood was conducted to investigate the characteristics of blood coagulation process and the starting time of blood coagulation was defined. The study of blood coagulation time under temperature and hematocrit variations was shown a good agreement with results in the previous clinical reports. The electrical impedance measurement for the definition of blood coagulation process provides a fast and easy measurement technique. The microfluidic chip was shown to be a sensitive and promising device for monitoring blood coagulation process even in a variety of conditions. It is found valuable for the development of point-of-care coagulation testing devices that utilizes whole blood sample in microliter quantity. PMID:24116099

A Strip Cell in Pyroelectric Devices

PubMed Central

Siao, An-Shen; Chao, Ching-Kong; Hsiao, Chun-Ching

2016-01-01

The pyroelectric effect affords the opportunity to convert temporal temperature fluctuations into usable electrical energy in order to develop abundantly available waste heat. A strip pyroelectric cell, used to enhance temperature variation rates by lateral temperature gradients and to reduce cell capacitance to further promote the induced voltage, is described as a means of improving pyroelectric energy transformation. A precision dicing saw was successfully applied in fabricating the pyroelectric cell with a strip form. The strip pyroelectric cell with a high-narrow cross section is able to greatly absorb thermal energy via the side walls of the strips, thereby inducing lateral temperature gradients and increasing temperature variation rates in a thicker pyroelectric cell. Both simulation and experimentation show that the strip pyroelectric cell improves the electrical outputs of pyroelectric cells and enhances the efficiency of pyroelectric harvesters. The strip-type pyroelectric cell has a larger temperature variation when compared to the trenched electrode and the original type, by about 1.9 and 2.4 times, respectively. The measured electrical output of the strip type demonstrates a conspicuous increase in stored energy as compared to the trenched electrode and the original type, by of about 15.6 and 19.8 times, respectively. PMID:26999134

Simulation Tools and Techniques for Analyzing the Impacts of Photovoltaic System Integration

NASA Astrophysics Data System (ADS)

Hariri, Ali

Solar photovoltaic (PV) energy integration in distribution networks is one of the fastest growing sectors of distributed energy integration. The growth in solar PV integration is incentivized by various clean power policies, global interest in solar energy, and reduction in manufacturing and installation costs of solar energy systems. The increase in solar PV integration has raised a number of concerns regarding the potential impacts that might arise as a result of high PV penetration. Some impacts have already been recorded in networks with high PV penetration such as in China, Germany, and USA (Hawaii and California). Therefore, network planning is becoming more intricate as new technologies are integrated into the existing electric grid. The integrated new technologies pose certain compatibility concerns regarding the existing electric grid infrastructure. Therefore, PV integration impact studies are becoming more essential in order to have a better understanding of how to advance the solar PV integration efforts without introducing adverse impacts into the network. PV impact studies are important for understanding the nature of the new introduced phenomena. Understanding the nature of the potential impacts is a key factor for mitigating and accommodating for said impacts. Traditionally, electric power utilities relied on phasor-based power flow simulations for planning their electric networks. However, the conventional, commercially available, phasor-based simulation tools do not provide proper visibility across a wide spectrum of electric phenomena. Moreover, different types of simulation approaches are suitable for specific types of studies. For instance, power flow software cannot be used for studying time varying phenomena. At the same time, it is not practical to use electromagnetic transient (EMT) tools to perform power flow solutions. Therefore, some electric phenomena caused by the variability of PV generation are not visible using the conventional utility simulation software. On the other hand, EMT simulation tools provide high accuracy and visibility over a wide bandwidth of frequencies at the expense of larger processing and memory requirements, limited network size, and long simulation time. Therefore, there is a gap in simulation tools and techniques that can efficiently and effectively identify potential PV impact. New planning simulation tools are needed in order to accommodate for the simulation requirements of new integrated technologies in the electric grid. The dissertation at hand starts by identifying some of the potential impacts that are caused by high PV penetration. A phasor-based quasi-static time series (QSTS) analysis tool is developed in order to study the slow dynamics that are caused by the variations in the PV generation that lead to voltage fluctuations. Moreover, some EMT simulations are performed in order to study the impacts of PV systems on the electric network harmonic levels. These studies provide insights into the type and duration of certain impacts, as well as the conditions that may lead to adverse phenomena. In addition these studies present an idea about the type of simulation tools that are sufficient for each type of study. After identifying some of the potential impacts, certain planning tools and techniques are proposed. The potential PV impacts may cause certain utilities to refrain from integrating PV systems into their networks. However, each electric network has a certain limit beyond which the impacts become substantial and may adversely interfere with the system operation and the equipment along the feeder; this limit is referred to as the hosting limit (or hosting capacity). Therefore, it is important for utilities to identify the PV hosting limit on a specific electric network in order to safely and confidently integrate the maximum possible PV systems. In the following dissertation, two approaches have been proposed for identifying the hosing limit: 1. Analytical approach: this is a theoretical mathematical approach that demonstrated the understanding of the fundamentals of electric power system operation. It provides an easy way to estimate the maximum amount of PV power that can be injected at each node in the network. This approach has been tested and validated. 2. Stochastic simulation software approach: this approach provides a comprehensive simulation software that can be used in order to identify the PV hosting limit. The software performs a large number of stochastic simulation while varying the PV system size and location. The collected data is then analyzed for violations in the voltage levels, voltage fluctuations and reverse power flow. (Abstract shortened by ProQuest.).

Characterization of Stress in Thallium Bromide Devices

NASA Astrophysics Data System (ADS)

Datta, Amlan; Motakef, Shariar

2015-04-01

Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. Several surface modification techniques have been demonstrated to increase the lifetime of TlBr devices at room temperature. However, absence of reproducibility in the performance of TlBr detectors (even with low ionic conduction at -20°C) suggests presence of unexplored bulk phenomena. Stress in the TlBr crystal due to various intrinsic (e.g. grain boundaries and dislocations networks) in conjunction with external factors such as thermal, mechanical, and electrical loadings explains detector-to-detector variations. Photoelasticity and opto-electrical techniques were applied to visualize and qualitatively correlate the device performance with stress. Changes in stress patterns with variations in ambient temperature were clearly demonstrated. Electric field fluctuations in TlBr detectors with time were for the first time observed using the Pockels effect.

Neutral winds and electric fields from model studies using reduced ionograms

NASA Technical Reports Server (NTRS)

Baran, D. E.

1974-01-01

A relationship between the vertical component of the ion velocity and electron density profiles derived from reduced ionograms is developed. Methods for determining the horizontal components of the neutral winds and electric fields by using this relationship and making use of the variations of the inclinations and declinations of the earth's magnetic field are presented. The effects that electric fields have on the neutral wind calculations are estimated to be small but not second order. Seasonal and latitudinal variations of the calculated neutral winds are presented. From the calculated neutral winds a new set of neutral pressure gradients is determined. The new pressure gradients are compared with those generated from several static neutral atmospheric models. Sensitivity factors relating the pressure gradients and neutral winds are calculated and these indicate that mode coupling and harmonic generation are important to studies which assume linearized theories.

Advanced Cogeneration Technology Economic Optimization Study (ACTEOS)

NASA Technical Reports Server (NTRS)

Nanda, P.; Ansu, Y.; Manuel, E. H., Jr.; Price, W. G., Jr.

1980-01-01

The advanced cogeneration technology economic optimization study (ACTEOS) was undertaken to extend the results of the cogeneration technology alternatives study (CTAS). Cost comparisons were made between designs involving advanced cogeneration technologies and designs involving either conventional cogeneration technologies or not involving cogeneration. For the specific equipment cost and fuel price assumptions made, it was found that: (1) coal based cogeneration systems offered appreciable cost savings over the no cogeneration case, while systems using coal derived liquids offered no costs savings; and (2) the advanced cogeneration systems provided somewhat larger cost savings than the conventional systems. Among the issues considered in the study included: (1) temporal variations in steam and electric demands; (2) requirements for reliability/standby capacity; (3) availability of discrete equipment sizes; (4) regional variations in fuel and electricity prices; (5) off design system performance; and (6) separate demand and energy charges for purchased electricity.

Electrical properties of binary mixtures of amino silicone oil and methyl iso butyl ketone

NASA Astrophysics Data System (ADS)

Shah, K. N.; Rana, V. A.; Vankar, H. P.

2018-05-01

The real and imaginary parts of the dielectric function of the binary mixtures of the methyl iso butyl ketone and amino silicone oil in the frequency range 100 Hz to 2 MHz were measured using precision LCR meter at 305.15 K. The electrical properties such as electrical modulus M*(ω), electrical conductivity σ*(ω) and complex impedance Z*(ω) were calculated using the dielectric function ɛ*(ω). The ionic polarization relaxation time (Τσ) and D.C. conductivity (σdc) were also calculated using electrical properties. The ionic behavior of methyl iso butyl ketone and non-ionic behavior of amino silicone oil are also explained. The electrical parameters are used to gain information about the effect of concentration variation of components of the mixtures on the electrical properties.

Effects of hydrogen-like impurity and electromagnetic field on quantum transition of an electron in a Gaussian potential with QD thickness

NASA Astrophysics Data System (ADS)

Xin, Wei; Zhao, Yu-Wei; Sudu; Eerdunchaolu

2018-05-01

Considering Hydrogen-like impurity and the thickness effect, the eigenvalues and eigenfunctions of the electronic ground and first exited states in a quantum dot (QD) are derived by using the Lee-Low-Pins-Pekar variational method with the harmonic and Gaussian potentials as the transverse and longitudinal confinement potentials, respectively. A two-level system is constructed on the basis of those two states, and the electronic quantum transition affected by an electromagnetic field is discussed in terms of the two-level system theory. The results indicate the Gaussian potential reflects the real confinement potential more accurately than the parabolic one; the influence of the thickness of the QD on the electronic transition probability is interesting and significant, and cannot be ignored; the electronic transition probability Γ is influenced significantly by some physical quantities, such as the strength of the electron-phonon coupling α, the electric-field strength F, the magnetic-field cyclotron frequency ωc , the barrier height V0 and confinement range L of the asymmetric Gaussian potential, suggesting the transport and optical properties of the QD can be manipulated further though those physical quantities.

Estimating the Economic Potential of Offshore Wind in the United States

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

Beiter, P.; Musial, W.; Smith, A.

The potential for cost reduction and market deployment for offshore wind varies considerably within the United States. This analysis estimates the future economic viability of offshore wind at more than 7,000 sites under a variety of electric sector and cost reduction scenarios. Identifying the economic potential of offshore wind at a high geospatial resolution can capture the significant variation in local offshore resource quality, costs, and revenue potential. In estimating economic potential, this article applies a method initially developed in Brown et al. (2015) to offshore wind and estimates the sensitivity of results under a variety of most likely electricmore » sector scenarios. For the purposes of this analysis, a theoretical framework is developed introducing a novel offshore resource classification system that is analogous to established resource classifications from the oil and gas sector. Analyzing economic potential within this framework can help establish a refined understanding across industries of the technology and site-specific risks and opportunities associated with future offshore wind development. The results of this analysis are intended to inform the development of the U.S. Department of Energy's offshore wind strategy.« less

Radiation dose response of N channel MOSFET submitted to filtered X-ray photon beam

NASA Astrophysics Data System (ADS)

Gonçalves Filho, Luiz C.; Monte, David S.; Barros, Fabio R.; Santos, Luiz A. P.

2018-01-01

MOSFET can operate as a radiation detector mainly in high-energy photon beams, which are normally used in cancer treatments. In general, such an electronic device can work as a dosimeter from threshold voltage shift measurements. The purpose of this article is to show a new way for measuring the dose-response of MOSFETs when they are under X-ray beams generated from 100kV potential range, which is normally used in diagnostic radiology. Basically, the method consists of measuring the MOSFET drain current as a function of the radiation dose. For this the type of device, it has to be biased with a high value resistor aiming to see a substantial change in the drain current after it has been irradiated with an amount of radiation dose. Two types of N channel device were used in the experiment: a signal transistor and a power transistor. The delivered dose to the device was varied and the electrical curves were plotted. Also, a sensitivity analysis of the power MOSFET response was made, by varying the tube potential of about 20%. The results show that both types of devices have responses very similar, the shift in the electrical curve is proportional to the radiation dose. Unlike the power MOSFET, the signal transistor does not provide a linear function between the dose rate and its drain current. We also have observed that the variation in the tube potential of the X-ray equipment produces a very similar dose-response.

Effects of source and seasonal variations of natural organic matters on the fate and transport of CeO2 nanoparticles in the environment

EPA Science Inventory

Natural organic matter (NOM) affects the stability and transport of nanoparticles (NPs) in natural waters by modifying their physiochemical properties. Source location, and seasonal variations, influence their molecular, physical and electrical charge properties. To understand th...

Electrical impedance spectroscopy for quality assessment of meat and fish: A review on basic principles, measurement methods, and recent advances

USDA-ARS?s Scientific Manuscript database

Electrical impedance spectroscopy (EIS), as an effective analytical technique for electrochemical system, has shown a wide application for food quality and safety assessment recently. Individual differences of livestock cause high variation in quality of raw meat and fish and their commercialized pr...

Resistivity in Play-Doh: Time and Color Variations

ERIC Educational Resources Information Center

Fuse, Christopher; August, Brandon; Cannaday, Ashley; Barker, Casey

2013-01-01

The study of electricity and magnetism is fundamental to all first-year physics courses. Developing simple electricity laboratory experiences that are open ended and inquiry based can be difficult. We wished to create a lab experiment where the students have some control over the experimental design, data analysis is required, and students…

Variation in the electrical properties of ion beam irradiated cadmium selenate nanowires

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

Chauhan, R. P., E-mail: chauhanrpc@gmail.com; Narula, Chetna; Panchal, Suresh

The key feature of nanowires consists in the pronounced change in properties induced by the low dimensionality and high surface to volume ratio. The study of electrical transport properties of nanowires is important for electronic device applications. Energetic ions create changes, which may be structural or chemical, in a material along their track and these changes might alter the material’s properties. The demand of the modern technology is to understand the effect of radiation on the different properties of the material for its further applications. The present study is on the high-energy Nickel ion beam (160 MeV Ni{sup +12}) induced modificationsmore » in the electrical and structural properties of the cadmium selenate nanowires. An enhancement in the electrical conductivity of irradiated wires was observed as the ion fluence was increased especially in the forward I–V characteristics. The creation of defects by ion irradiation and the synergy of the ions during their passage in the sample with the intrinsic charge carriers may be responsible for the variation in the transport properties of the irradiated nanowires.« less

Relation Between Lightning Activity of Summer and Winter Thunderclouds and Surface Electric Field Variation, Japan

NASA Technical Reports Server (NTRS)

Michimoto, K.; Shimura, T.; Suzuki, T.

1999-01-01

In winter, active convective clouds frequently form along the coastline of the Hokuriku district, in association with strong advection of Siberian air masses over the Sea of Japan. On the other hand, in summer, many thunderclouds form in the Kanto region in the afternoon every day. Summer and winter thunderclouds were investigated by field works, operation of the C- and X-band weather radars and a car-borne fieldmill. The investigation found a very close relation between the temporal variation of 3-dimensional radar echo and surface electric field magnitude detected by a car-borne fieldmill in the case of summer thunderclouds and winter convective clouds or thunderclouds. The study probed the close relation among radar echoes, quantity of thunderclouds and surface electric field magnitude in the summer and winter seasons. We think that summer thundercloud activity can basically be equated with winter thundercloud lightning activity, except that the magnitude of surface electric field under summer thunderclouds in the case of the Kanto region cannot be equated with that under winter thunderclouds in the case of the Hokuriku district in winter.

Degradation of the electrical characteristics of MOS structures with erbium, gadolinium, and dysprosium oxides under the effect of an electric field

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

Shalimova, M. B., E-mail: shamb@samsu.ru; Sachuk, N. V.

2015-08-15

The degradation of the characteristics of silicon metal-oxide-semiconductor (MOS) structures with oxides of rare-earth elements under the effect of electric fields with intensities of 0.1–4 MV/cm during the course of electroforming is studied. A specific feature of electroforming consists in the possibility of multiple switching of the structures from the insulating state to the low-resistivity one and back. The temporal characteristics of the degradation of MOS structures during the course of electroforming are exponential. The current-voltage characteristics follow the power law in the range of 0.2–3 V; the effect of an electric field brings about a variation in the distributionmore » of the energy density of traps responsible for currents limited by space charge. It is established that multiple cycles of electroforming lead to an increase in the density of surface states at the Si-oxide interface and to a variation in the energy position of the trap levels, which affects the charge state of the traps.« less

Fuel cell system including a unit for electrical isolation of a fuel cell stack from a manifold assembly and method therefor

DOEpatents

Kelley; Dana A. , Farooque; Mohammad , Davis; Keith

2007-10-02

A fuel cell system with improved electrical isolation having a fuel cell stack with a positive potential end and a negative potential, a manifold for use in coupling gases to and from a face of the fuel cell stack, an electrical isolating assembly for electrically isolating the manifold from the stack, and a unit for adjusting an electrical potential of the manifold such as to impede the flow of electrolyte from the stack across the isolating assembly.

Spatial Mapping of the Mobility-Lifetime (microtau) Production in Cadmium Zinc Telluride Nuclear Radiation Detectors Using Transport Imaging

DTIC Science & Technology

2013-06-01

Under the influence of an electrical field, these electrons and holes migrate to their respective electrodes, where they are collected and...an electrical response which translates to an intensity reading on the detector’s readout meter. Since high-resolution detector materials are the...magnitude of three factors: inherent statistical variation of the electric signal measured at the detector’s contacts (Fano noise ∆EF), random electron

Understanding the Electrical Behavior of the Action Potential in Terms of Elementary Electrical Sources

ERIC Educational Resources Information Center

Rodriguez-Falces, Javier

2015-01-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However,…

Steps Towards Industrialization of Cu–III–VI2Thin‐Film Solar Cells:Linking Materials/Device Designs to Process Design For Non‐stoichiometric Photovoltaic Materials

PubMed Central

Chang, Hsueh‐Hsin; Sharma, Poonam; Letha, Arya Jagadhamma; Shao, Lexi; Zhang, Yafei; Tseng, Bae‐Heng

2016-01-01

The concept of in‐line sputtering and selenization become industrial standard for Cu–III–VI2 solar cell fabrication, but still it's very difficult to control and predict the optical and electrical parameters, which are closely related to the chemical composition distribution of the thin film. The present review article addresses onto the material design, device design and process design using parameters closely related to the chemical compositions. Its variation leads to change in the Poisson equation, current equation, and continuity equation governing the device design. To make the device design much realistic and meaningful, we need to build a model that relates the opto‐electrical properties to the chemical composition. The material parameters as well as device structural parameters are loaded into the process simulation to give a complete set of process control parameters. The neutral defect concentrations of non‐stoichiometric CuMSe2 (M = In and Ga) have been calculated under the specific atomic chemical potential conditions using this methodology. The optical and electrical properties have also been investigated for the development of a full‐function analytical solar cell simulator. The future prospects regarding the development of copper–indium–gallium–selenide thin film solar cells have also been discussed. PMID:27840790

Ground-based measurements of the vertical E-field in mountainous regions and the "Austausch" effect

NASA Astrophysics Data System (ADS)

Yaniv, Roy; Yair, Yoav; Price, Colin; Mkrtchyan, Hripsime; Lynn, Barry; Reymers, Artur

2017-06-01

Past measurements of the atmospheric vertical electric field (Ez or potential gradient) at numerous land stations showed a strong response of the daily electric field to a morning local effect known as ;Austausch; - the transport of electrical charges due to increased turbulence. In mountainous regions, nocturnal charge accumulation, followed by an attachment process to aerosols near the surface in valleys, known as the electrode effect, is lifted as a charged aerosol layer by anabatic (upslope) winds during the morning hours due to solar heating. Ground-based measurements during fair weather days were conducted at three mountain stations in Israel and Armenia. We present results of the mean diurnal variation of Ez and make comparisons with the well-known Carnegie curve and with past measurements of Ez on mountains. We report a good agreement between the mean diurnal curves of Ez at various mountain stations and the time of local sunrise when the Ez is found to increase. We attribute this morning maximum to the Austausch (or exchange) layer effect. We support our findings with conduction and turbulent current measurements showing high values of ions and charged aerosols being transported by winds from morning to noon local time, and by model simulations showing the convergence of winds in the early morning hours toward the mountain peak.

Langmuir probe diagnostic suite in the C-2 field-reversed configuration

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

Roche, T., E-mail: troche@trialphaenergy.com; Armstrong, S.; Knapp, K.

2014-11-15

Several in situ probes have been designed and implemented into the diagnostic array of the C-2 field-reversed configuration (FRC) at Tri Alpha Energy [M. Tuszewski et al. (the TAE Team), Phys. Rev. Lett. 108, 255008 (2012)]. The probes are all variations on the traditional Langmuir probe. They include linear arrays of triple probes, linear arrays of single-tipped swept probes, a multi-faced Gundestrup probe, and an ion-sensitive probe. The probes vary from 5 to 7 mm diameter in size to minimize plasma perturbations. They also have boron nitride outer casings that prevent unwanted electrical breakdown and reduce the introduction of impurities.more » The probes are mounted on motorized linear-actuators allowing for programmatic scans of the various plasma parameters over the course of several shots. Each probe has a custom set of electronics that allows for measurement of the desired signals. High frequency ( > 5MHz) analog optical-isolators ensure that plasma parameters can be measured at sub-microsecond time scales while providing electrical isolation between machine and data acquisition systems. With these probes time-resolved plasma parameters (temperature, density, spatial potential, flow, and electric field) can be directly/locally measured in the FRC jet and edge/scrape-off layer.« less

Steps Towards Industrialization of Cu-III-VI2Thin-Film Solar Cells:Linking Materials/Device Designs to Process Design For Non-stoichiometric Photovoltaic Materials.

PubMed

Hwang, Huey-Liang; Chang, Hsueh-Hsin; Sharma, Poonam; Letha, Arya Jagadhamma; Shao, Lexi; Zhang, Yafei; Tseng, Bae-Heng

2016-10-01

The concept of in-line sputtering and selenization become industrial standard for Cu-III-VI 2 solar cell fabrication, but still it's very difficult to control and predict the optical and electrical parameters, which are closely related to the chemical composition distribution of the thin film. The present review article addresses onto the material design, device design and process design using parameters closely related to the chemical compositions. Its variation leads to change in the Poisson equation, current equation, and continuity equation governing the device design. To make the device design much realistic and meaningful, we need to build a model that relates the opto-electrical properties to the chemical composition. The material parameters as well as device structural parameters are loaded into the process simulation to give a complete set of process control parameters. The neutral defect concentrations of non-stoichiometric CuMSe 2 (M = In and Ga) have been calculated under the specific atomic chemical potential conditions using this methodology. The optical and electrical properties have also been investigated for the development of a full-function analytical solar cell simulator. The future prospects regarding the development of copper-indium-gallium-selenide thin film solar cells have also been discussed.

Numerical dosimetry of transcranial magnetic stimulation coils

NASA Astrophysics Data System (ADS)

Crowther, Lawrence; Hadimani, Ravi; Jiles, David

2014-03-01

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique capable of stimulating neurons by means of electromagnetic induction. TMS can be used to map brain function and shows promise for the diagnosis and treatment of neurological and psychiatric disorders. Calculation of fields induced in the brain are necessary to accurately identify stimulated neural tissue during TMS. This allows the development of novel TMS coil designs capable of stimulating deeper brain regions and increasing the localization of stimulation that can be achieved. We have performed numerical calculations of magnetic and electric field with high-resolution anatomically realistic human head models to find these stimulated brain regions for a variety of proposed TMS coil designs. The realistic head models contain heterogeneous tissue structures and electrical conductivities, yielding superior results to those obtained from the simplified homogeneous head models that are commonly employed. The attenuation of electric field as a function of depth in the brain and the localization of stimulating field have been methodically investigated. In addition to providing a quantitative comparison of different TMS coil designs the variation of induced field between subjects has been investigated. We also show the differences in induced fields between adult, adolescent and child head models to preemptively identify potential safety issues in the application of pediatric TMS.

Global Electromagnetic Imaging of Lithosphere and Upper Mantle from Space and Ground. Recent Results and Challenges

NASA Astrophysics Data System (ADS)

Kuvshinov, A. V.

2016-12-01

Electrical conductivity is one of the characteristic physical parameters of materials making up Earth's interior which is sensitive to variations of temperature, chemical composition, water content, and partial melt. As a consequence, estimating lithosphere and upper mantle (LUM) electrical conductivity structure is a potentially strong tool for mapping their chemistry, mineralogy and physical structure thus presenting a complementary method to seismic studies that focus on LUM elastic properties. Global electromagnetic (EM) studies, which provide information on LUM electrical conductivity, have attracted increasing interest during the last decade, mainly for three reasons. A primary reason is the recent growth in the amount of EM data available, especially from low-Earth orbiting magnetic satellite missions (Oersted, CHAMP, SAC-C, and Swarm). A second reason is the great interest in the characterization of the three-dimensional properties of Earth's interior on a global scale. Finally, the interest has also resulted from the significant methodological progress made during the last years in EM data analysis, forward modelling and inversion. In this talk I will summarize advances and challenges in EM data interpretation, and present recent global and regional models of LUM conductivity derived from satellite and ground-based data. I will also discuss possible topics for future research.

Al-implanted on-axis 4H-SiC MOSFETs

NASA Astrophysics Data System (ADS)

Florentin, M.; Cabello, M.; Rebollo, J.; Montserrat, J.; Brosselard, P.; Henry, A.; Godignon, P.

2017-03-01

In this paper, the impact of temperature and time stress on gate oxide stability of several multi-implanted and epitaxied 4H-SiC nMOSFET is presented. The oxide layer was processed under a rapid thermal process (RTP) furnace. The variation of the main electrical parameters is shown. We report the high quality and stability of such implanted MOSFETs, and point out the very low roughness effect of the on-axis-cut sample. Particularly, in the best case, effective channel mobility (μ fe) overcomes 20 cm2.V-1.s-1 at 300 °C for a channel length of 12 μm, which is very encouraging for implantation technology. Starting from 200 °C, the apparent increase of the μ fe peak of the MOSFET ceases and tends to saturate with further temperature increase. This is an indication of the potential of MOSFETs built on on-axis substrates. Thus, starting from the real case of an implanted MOSFET, the global purpose is to show that the electrical performance of such an on-axis-built device can tend to reach that of the ideal case, i.e. epitaxied MOSFET, and even overcome its electrical limitation, e.g. in terms of threshold voltage stability at high temperature.

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.

On the possibility of collective attraction in complex plasmas

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

Chaudhuri, M.; Morfill, G. E.; Kompaneets, R.

2010-06-15

An investigation on the possible collective electric attraction between like-charged dust particles has been performed in an isotropic homogeneous complex (dusty) plasma in which a balance between plasma creation due to ionization and plasma loss due to the absorption on dust particles has been reached. The analysis is made on the basis of a self-consistent fluid model, which includes plasma ionization, plasma loss on dust particles, dust charge variations, and ion-neutral friction. It is shown that the interaction potential can have an attractive part in the stability regime of the ionization-absorption balance with respect to ion perturbations only under verymore » limited circumstances.« less

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

Farrell, John T; Kelly, Kenneth J; Duran, Adam W

Range-extended electric vehicle (EV) technology can be a viable option for reducing fuel consumption from medium-duty (MD) and heavy-duty (HD) engines by approximately 50 percent or more. Such engines have wide variations in use and duty cycles, however, and identifying the vocations/duty cycles most suitable for range-extended applications is vital for maximizing the potential benefits. This presentation provides information about NREL's research on range-extended EV technologies, with a focus on NREL's real-world data collection and analysis approach to identifying the vocations/duty cycles best suited for range-extender applications and to help guide related powertrain optimization and design requirements. The presentation alsomore » details NREL's drive cycle development process as it pertains to package delivery applications.« less

Detection of a diabetic sural nerve from the magnetic field after electric stimulation

NASA Astrophysics Data System (ADS)

Hayami, Takehito; Iramina, Keiji; Hyodo, Akira; Chen, Xian; Sunagawa, Kenji

2009-04-01

In this study, we proposed a new diagnostic technique for diabetic neuropathy using biomagnetic measurement. Peripheral neuropathy is one of the most common complications of diabetes. To examine the injury, the skin potential around the nerve is often measured after electric stimulation. However, measuring the magnetic field may reveal precise condition of the injury. To evaluate the effect of measuring the magnetic field, a simulation study was performed. A diabetic sural nerve was simulated as a bundle of myelinated nerve fibers. Each fiber was modeled as an electric cable of Ranvier's nodes. Anatomical data were used to determine the number of nerve fibers and distribution of nerve fiber diameters. The electric potential and the magnetic field on the skin after electric stimulation were computed to the boundary element method. Biphasic time courses were obtained as the electric potential and the magnetic flux density at measurement points. In diabetic nerves, the longer interpeak latency of the electric potential wave and the shorter interpeak latency of the magnetic flux wave were obtained. Measuring both the electric potential and the magnetic flux density seemed to provide a noninvasive and objective marker for diabetic neuropathy.

Electrical transport and capacitance characteristics of metal-insulator-metal structures using hexagonal and cubic boron nitride films as dielectrics

NASA Astrophysics Data System (ADS)

Teii, Kungen; Kawamoto, Shinsuke; Fukui, Shingo; Matsumoto, Seiichiro

2018-04-01

Metal-insulator-metal capacitor structures using thick hexagonal and cubic boron nitride (hBN and cBN) films as dielectrics are produced by plasma jet-enhanced chemical vapor deposition, and their electrical transport and capacitance characteristics are studied in a temperature range of 298 to 473 K. The resistivity of the cBN film is of the order of 107 Ω cm at 298 K, which is lower than that of the hBN film by two orders of magnitude, while it becomes the same order as the hBN film above ˜423 K. The dominant current transport mechanism at high fields (≥1 × 104 V cm-1) is described by the Frenkel-Poole emission and thermionic emission models for the hBN and cBN films, respectively. The capacitance of the hBN film remains stable for a change in alternating-current frequency and temperature, while that of the cBN film has variations of at most 18%. The dissipation factor as a measure of energy loss is satisfactorily low (≤5%) for both films. The origin of leakage current and capacitance variation is attributed to a high defect density in the film and a transition interlayer between the substrate and the film, respectively. This suggests that cBN films with higher crystallinity, stoichiometry, and phase purity are potentially applicable for dielectrics like hBN films.

On electromagnetic forming processes in finitely strained solids: Theory and examples

NASA Astrophysics Data System (ADS)

Thomas, J. D.; Triantafyllidis, N.

2009-08-01

The process of electromagnetic forming (EMF) is a high velocity manufacturing technique that uses electromagnetic (Lorentz) body forces to shape sheet metal parts. EMF holds several advantages over conventional forming techniques: speed, repeatability, one-sided tooling, and most importantly considerable ductility increase in several metals. Current modeling techniques for EMF processes are not based on coupled variational principles to simultaneously account for electromagnetic and mechanical effects. Typically, separate solutions to the electromagnetic (Maxwell) and motion (Newton) equations are combined in staggered or lock-step methods, sequentially solving the mechanical and electromagnetic problems. The present work addresses these issues by introducing a fully coupled Lagrangian (reference configuration) least-action variational principle, involving magnetic flux and electric potentials and the displacement field as independent variables. The corresponding Euler-Lagrange equations are Maxwell's and Newton's equations in the reference configuration, which are shown to coincide with their current configuration counterparts obtained independently by a direct approach. The general theory is subsequently simplified for EMF processes by considering the eddy current approximation. Next, an application is presented for axisymmetric EMF problems. It is shown that the proposed variational principle forms the basis of a variational integration numerical scheme that provides an efficient staggered solution algorithm. As an illustration a number of such processes are simulated, inspired by recent experiments of freely expanding uncoated and polyurea-coated aluminum tubes.

The analysis of Taiwan's residential electricity demand under the electricity tariff policy

NASA Astrophysics Data System (ADS)

Chen, Po-Jui

In October 2013, the Taiwan Power Company (Taipower), the monopolized state utility service in Taiwan, implemented an electricity tariff adjustment policy to reduce residential electricity demand. Using bi-monthly billing data from 6,932 electricity consumers, this study examine how consumers respond to an increase in electricity prices. This study employs an empirical approach that takes advantage of quasi-random variation over a period of time when household bills were affected by a change in electricity price. The study found that this price increase caused a 1.78% decline in residential electricity consumption, implying a price elasticity of -0.19 for summer-season months and -0.15 for non-summer-season months. The demand for electricity is therefore relatively inelastic, likely because it is hard for people to change their electricity consumption behavior in the short-term. The results of this study highlight that demand-side management cannot be the only lever used to address Taiwan's forecasted decrease in electricity supply.

Electrostatic potential in a bent piezoelectric nanowire with consideration of size-dependent piezoelectricity and semiconducting characterization.

PubMed

Wang, K F; Wang, B L

2018-06-22

Determining the electric potential in a bent piezoelectric nanowire (NW) is a fundamental issue of nanogenerators and nanopiezotronics. The combined influence of the flexoelectric effect, the semiconducting performance and the angle of atomic force microscope (AFM) tip has never been studied previously and will be investigated in this paper. The exact solution for the electric potential of a bent piezoelectric semiconductor NW is derived. The electric potential of the present model with consideration of flexoelectric effect varies along the length of the NW and is different from that of the classical piezoelectric model. Flexoelectric effect enhances but the semiconducting performance reduces the electric potential of the NW. In addition, it is found that if the angle of the AFM tip reaches 30°, the error of the electric potential obtained from the model ignored the effect of the angle of the AFM tip is almost 16%, which is unacceptable.

Electrostatic potential in a bent piezoelectric nanowire with consideration of size-dependent piezoelectricity and semiconducting characterization

NASA Astrophysics Data System (ADS)

Wang, K. F.; Wang, B. L.

2018-06-01

Determining the electric potential in a bent piezoelectric nanowire (NW) is a fundamental issue of nanogenerators and nanopiezotronics. The combined influence of the flexoelectric effect, the semiconducting performance and the angle of atomic force microscope (AFM) tip has never been studied previously and will be investigated in this paper. The exact solution for the electric potential of a bent piezoelectric semiconductor NW is derived. The electric potential of the present model with consideration of flexoelectric effect varies along the length of the NW and is different from that of the classical piezoelectric model. Flexoelectric effect enhances but the semiconducting performance reduces the electric potential of the NW. In addition, it is found that if the angle of the AFM tip reaches 30°, the error of the electric potential obtained from the model ignored the effect of the angle of the AFM tip is almost 16%, which is unacceptable.

Energy variational analysis of ions in water and channels: Field theory for primitive models of complex ionic fluids

PubMed Central

Eisenberg, Bob; Hyon, YunKyong; Liu, Chun

2010-01-01

Ionic solutions are mixtures of interacting anions and cations. They hardly resemble dilute gases of uncharged noninteracting point particles described in elementary textbooks. Biological and electrochemical solutions have many components that interact strongly as they flow in concentrated environments near electrodes, ion channels, or active sites of enzymes. Interactions in concentrated environments help determine the characteristic properties of electrodes, enzymes, and ion channels. Flows are driven by a combination of electrical and chemical potentials that depend on the charges, concentrations, and sizes of all ions, not just the same type of ion. We use a variational method EnVarA (energy variational analysis) that combines Hamilton’s least action and Rayleigh’s dissipation principles to create a variational field theory that includes flow, friction, and complex structure with physical boundary conditions. EnVarA optimizes both the action integral functional of classical mechanics and the dissipation functional. These functionals can include entropy and dissipation as well as potential energy. The stationary point of the action is determined with respect to the trajectory of particles. The stationary point of the dissipation is determined with respect to rate functions (such as velocity). Both variations are written in one Eulerian (laboratory) framework. In variational analysis, an “extra layer” of mathematics is used to derive partial differential equations. Energies and dissipations of different components are combined in EnVarA and Euler–Lagrange equations are then derived. These partial differential equations are the unique consequence of the contributions of individual components. The form and parameters of the partial differential equations are determined by algebra without additional physical content or assumptions. The partial differential equations of mixtures automatically combine physical properties of individual (unmixed) components. If a new component is added to the energy or dissipation, the Euler–Lagrange equations change form and interaction terms appear without additional adjustable parameters. EnVarA has previously been used to compute properties of liquid crystals, polymer fluids, and electrorheological fluids containing solid balls and charged oil droplets that fission and fuse. Here we apply EnVarA to the primitive model of electrolytes in which ions are spheres in a frictional dielectric. The resulting Euler–Lagrange equations include electrostatics and diffusion and friction. They are a time dependent generalization of the Poisson–Nernst–Planck equations of semiconductors, electrochemistry, and molecular biophysics. They include the finite diameter of ions. The EnVarA treatment is applied to ions next to a charged wall, where layering is observed. Applied to an ion channel, EnVarA calculates a quick transient pile-up of electric charge, transient and steady flow through the channel, stationary “binding” in the channel, and the eventual accumulation of salts in “unstirred layers” near channels. EnVarA treats electrolytes in a unified way as complex rather than simple fluids. Ad hoc descriptions of interactions and flow have been used in many areas of science to deal with the nonideal properties of electrolytes. It seems likely that the variational treatment can simplify, unify, and perhaps derive and improve those descriptions. PMID:20849161

Nanoprobe studies: Electrical transport in carbon nanotubes and crystal structure of aluminum nitride surfaces

NASA Astrophysics Data System (ADS)

Biswas, Sujit Kumar

Nanoprobes are an extraordinary set of experimental tools that allow fabrication, manipulation, and measurement in nano-scale systems. The primary use of a nanoprobe for imaging tiny objects is supplemented by powerful electrical techniques, namely scanning surface potential microscopy and current sensing atomic force microscopy. They allow us to measure potential, and current in carbon nanotube circuits. Nanoprobes are superior to conventional two- or four-probe measurements because they can provide spatial information of local electronic properties. This makes them highly attractive in studying junctions and contacts with carbon nanotubes. We have studied single-walled carbon nanotube circuits, forming junctions to other nanotubes. The experimental results indicate that these junctions act like potential barriers of about 50 meV that can confine electrons with an effective mass of 0.003 me , within nanotube channels of length 0.5 mum lying in-between two such potential barriers. This leads to quantization of the channel, forming a resonant tunneling structure. We have also found that single-walled nanotubes have phase coherence lengths of the order of 1 mum. This leads to situations where the electron interference effects at scattering centers need to be considered. We have seen direct evidence of this, in the non-linear resistance increase within nanotubes with few defects. Ambipolar transistor behavior was measured in a p-type single-walled nanotube circuit that showed electron injection across the Schottky junction at high positive bias. We have also studied multi-walled carbon nanotube circuits using scanning potential microscopy, and found that a back gate potential can vary the resistance of the channel. Vertical nanotube arrays, suitable for interconnects, were also measured. These hollow multi-walled nanotube channels were about 45 nm in diameter, and 50 mum in length, fabricated in an anodized alumina template. We found that these structures could sustain current densities greater than 105 A/cm2. Conventional use of nanoprobes in imaging aluminum nitride surfaces displayed curious step bunching structures. We have used an innovative analysis technique with which the bulk lattice constant of the crystal was measured to an accuracy of about 4% of X-ray crystallography value of 0.497 nm. In addition, this technique showed that there were regions on the surface that had a larger lattice parameter of 0.64 nm, which we interpreted to be due to a variation in the chemical composition of the surface such as oxide formation. We believe that this technique may prove useful as a study of chemical-composition variations on a surface as well as relaxation of the surface layer.

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.

Active and passive electromagnetic sounding on comets and moons

NASA Astrophysics Data System (ADS)

Przyklenk, Anita; Auster, Hans-Ulrich

We want to present the method of electromagnetic sounding on small extraterrestrial bodies to determine interior structures of those. Our sensors are perfectly suited for rover or lander missions, because they do not weight much (sum of all devices is approximately 600g) and can be easily installed at the bottom of a rover or at lander feet. The aim is to measure the material-specific complex resistivity, which depends on the electrical resistivity and electrical permittivity, for various sounding depth. This penetration depth depends on the 2 different operating modes. In the active mode, that is the so called Capacitive Resistivity (CR) method, the sounding depth is around a few meters. The CR is a purely electrical field measurement and works with a 4 electrode array. 2 of them are transmitter electrodes. They inject AC signals with frequencies between 100 Hz and 100 kHz into the subsurface. Then 2 receiver electrodes pick up the generated potentials. And a 4-point impedance can be calculated that depends on the electrical parameters among others [Grard, 1990a and b] [Kuras, 2002]. The second operating mode is the passive one. In the so called magneto telluric method the penetration depth depends on electrical parameters and can be in range of several 100m to km. Here, for excitation natural magnetic field variations are used. The magnetic field components are measured with our Fluxgate Magnetometer (FGM) (flight heritage: Rosetta, Venus Express, Themis,…). Induced electrical field components are measured again with the CR electrode array. Then the electromagnetic impedance can be derived, which depends on electrical resistivity among others. In the end, we want to discuss advantages and disadvantages of investigations during space missions compared to surveys on earth. As examples we have a closer look at the jovian moon Ganymede, the earth moon and the comet 67P/Churyumov-Gerasimenko and consider the applicability of electromagnetic sounding on this objects from a theoretical point of view.

Separation of Electric Fields Into Potential and Inductive Parts, and Implications for Radial Diffusion

NASA Astrophysics Data System (ADS)

Chan, A. A.; Ilie, R.; Elkington, S. R.; Albert, J.; Huie, W.

2017-12-01

It has been traditional to separate radiation belt radial-diffusion coefficients into two contributions: an "electrostatic" diffusion coefficient, which is assumed to be due to a potential (non-inductive) electric field, and an "electromagnetic" diffusion coefficient , which is assumed to be due to the combined effect of an inductive electric field and the corresponding time-dependent magnetic field. One difficulty in implementing this separation when using magnetospheric fields obtained from measurements, or from MHD simulations, is that only the total electric field is given; the separation of the electric field into potential and inductive parts is not readily available. In this work we separate the electric field using a numerical method based on the Helmholtz decomposition of the total motional electric field calculated by the BATS-R-US MHD code. The inner boundary for the electric potential is based on the Ridley Ionospheric Model solution and we assume floating boundary conditions in the solar wind. Using different idealized solar wind drivers, including a solar wind density that is oscillating at a single frequency or with a broad spectrum of frequencies, we calculate potential and inductive electric fields, electric and magnetic power spectral densities, and corresponding radial diffusion coefficients. Simulations driven by idealized solar wind conditions show a clear separation of the potential and inductive contributions to the power spectral densities and diffusion coefficients. Simulations with more realistic solar wind drivers are underway to better assess the use of electrostatic and electromagnetic diffusion coefficients in understanding ULF wave-particle interactions in Earth's radiation belts.

Flexible gas insulated transmission line having regions of reduced electric field

DOEpatents

Cookson, Alan H.; Fischer, William H.; Yoon, Kue H.; Meyer, Jeffry R.

1983-01-01

A gas insulated transmission line having radially flexible field control means for reducing the electric field along the periphery of the inner conductor at predetermined locations wherein the support insulators are located. The radially flexible field control means of the invention includes several structural variations of the inner conductor, wherein careful controlling of the length to depth of surface depressions produces regions of reduced electric field. Several embodiments of the invention dispose a flexible connector at the predetermined location along the inner conductor where the surface depressions that control the reduced electric field are located.

Evolution of Edge Pedestal Profiles Over the L-H Transition

NASA Astrophysics Data System (ADS)

Sayer, M. S.; Stacey, W. M.; Floyd, J. P.; Groebner, R. J.

2012-10-01

The detailed time evolution of thermal diffusivities, electromagnetic forces, pressure gradients, particle pinch and momentum transport frequencies (which determine the diffusion coefficient) have been analyzed during the L-H transition in a DIII-D discharge. Density, temperature, rotation velocity and electric field profiles at times just before and after the L-H transition are analyzed in terms of these quantities. The analysis is based on the fluid particle balance, energy balance, force balance and heat conduction equations, as in Ref. [1], but with much greater time resolution and with account for thermal ion orbit loss. The variation of diffusive and non-diffusive transport over the L-H transition is determined from the variation in the radial force balance (radial electric field, VxB force, and pressure gradient) and the variation in the interpreted diffusive transport coefficients. 6pt [1] W.M. Stacey and R.J. Groebner, Phys. Plasmas 17, 112512 (2010).

A Survey on Gas Sensing Technology

PubMed Central

Liu, Xiao; Cheng, Sitian; Liu, Hong; Hu, Sha; Zhang, Daqiang; Ning, Huansheng

2012-01-01

Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches. PMID:23012563

Electric fields and current densities under small Florida thunderstorms

NASA Technical Reports Server (NTRS)

Deaver, Lance E.; Krider, E. P.

1991-01-01

Results are presented of measurements of the electric field E and Maxwell current density that were performed simultaneously under and near small Florida thunderstorms. It is shown that the amplitude of JM is of the order of 1 nA/sq cm or less in the absence of precipitation and that there are regular time variations in JM during the intervals between lightning discharges that tend to have the same shapes after different discharges in different storms. It is argued that the major causes of time variations in JM between lightning discharges are currents that flow in the finitely conducting atmosphere in response to the field changes rather than rapid time variations in the strength of cloud current sources. The displacement current densities that are computed from the E records dominate JM except when there is precipitation, when E is large and steady, or when E is unusually noisy.

Modelisation temporelle de la consommation electrique en analyse du cycle de vie appliquee au contexte des TIC

NASA Astrophysics Data System (ADS)

Maurice, Elsa

Fossil fuels are a scarce energy resource. Since the industrial revolution, mankind uses and abuses of non-renewable energies. They are responsible for many environmental damages. The production of energy is one of the main challenges for a global sustainable development. In our society, we can witness an exponential increase of the usage of the systems of Information and Communication Technologies (ICT) such as Internet, phone calls, etc. The ICT development allows the creation and optimization of many smart systems, the pooling of services, and it also helps damping the climate change. However, because of their electric consumption, the ICT are also responsible for some green house gases (GHG) emissions: 3% in total. This fact gives them the willingness to change in order to limit their GHG emissions. In order to properly evaluate and optimize the ICT services, it is necessary to use some methods of evaluation that comply with the specificity of these systems. Currently, the methods used to evaluate the GHG emissions are not adapted to dynamic systems, which include the ICT systems. The variations of the production of electricity in a day or even a month are not yet taken into account. This problem is far from being restricted to the modelling of GHG emissions, it widens to the global variation in production and consumption of electricity. The Life Cycle Assessment (LCA) method grants useful and complete tools to analyse their environmental impacts, but, as with the GHG computation methods, it should be dynamically adapted. In the ICT framework, the first step to solve this LCA problem is to be able to model the variations in time of the electricity production. This master thesis introduces a new way to include the variation in time of the consumption and production of electricity in LCA methods. First, it generates an historical hourly database of the electricity production and import-export of three Canadian states: Alberta, Ontario and Quebec. Then it develops a model in function of time to predict their electricity consumption. This study is done for a project implementing a " cloud computing " service in between these states. The consumption model then provides information to optimize the best place and time to make use of ICT services such as Internet messaging or server maintenance. This first-ever implementation of time parameter allows more precision and vision in LCA data. The disintegration of electrical inventory flows in LCA refines the effects of the electricity production both historically and in real time. Some short-term predictions for the state of Quebec electrical exportations and importations were also computed in this thesis. The goal is to foresee and optimize in real time the ICT services use. The origin of a kilowatt-hour consumed in Quebec depends on the import-export variable with its surrounding states. This parameter relies mainly on the price of the electricity, the weather and the need for the state of Quebec in energy. This allows to plot a time-varying estimate of the environmental consequences for the consumption of a kilowatt-hour in Quebec. This can then be used to limit the GHG emission of ICT services like " cloud-computing " or " smart-grids ". A smart trade-off between electricity consumption and environmental issues will lead to a more efficient sustainable development.

A clustering approach applied to time-lapse ERT interpretation - Case study of Lascaux cave

NASA Astrophysics Data System (ADS)

Xu, Shan; Sirieix, Colette; Riss, Joëlle; Malaurent, Philippe

2017-09-01

The Lascaux cave, located in southwest France, is one of the most important prehistoric cave in the world that shows Paleolithic paintings. This study aims to characterize the structure of the weathered epikarst setting located above the cave using Time-Lapse Electrical Resistivity Tomography (ERT) combined with local hydrogeological and climatic environmental data. Twenty ERT profiles were carried out for two years and helped us to record the seasonal and spatial variations of the electrical resistivity of the hydraulic upstream area of the Lascaux cave. The 20 interpreted resistivity models were merged into a single synthetic model using a multidimensional statistical method (Hierarchical Agglomerative Clustering). The individual blocks from the synthetic model associated with a similar resistivity variability were gathered into 7 clusters. We combined the resistivity temporal variations with climatic and hydrogeological data to propose a geo-electrical model that relates to a conceptual geological model. We provide a geological interpretation for each cluster regarding epikarst features. The superficial clusters (no 1 & 2) are linked to effective rainfall and trees, probably a fractured limestone. Another two clusters (no 6 & 7) are linked to detrital formations (sand and clay respectively). The cluster 3 may correspond to a marly limestone that forms a non-permeable horizon. Finally, the electrical behavior of the last two clusters (no 4 & 5) is correlated with the variation of flow rate; they may be a privileged feed zone of the flow in the cave.

Quantization of charged fields in the presence of critical potential steps

NASA Astrophysics Data System (ADS)

Gavrilov, S. P.; Gitman, D. M.

2016-02-01

QED with strong external backgrounds that can create particles from the vacuum is well developed for the so-called t -electric potential steps, which are time-dependent external electric fields that are switched on and off at some time instants. However, there exist many physically interesting situations where external backgrounds do not switch off at the time infinity. E.g., these are time-independent nonuniform electric fields that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x -electric potential steps for charged particles. They can also create particles from the vacuum, the Klein paradox being closely related to this process. Approaches elaborated for treating quantum effects in the t -electric potential steps are not directly applicable to the x -electric potential steps and their generalization for x -electric potential steps was not sufficiently developed. We believe that the present work represents a consistent solution of the latter problem. We have considered a canonical quantization of the Dirac and scalar fields with x -electric potential step and have found in- and out-creation and annihilation operators that allow one to have particle interpretation of the physical system under consideration. To identify in- and out-operators we have performed a detailed mathematical and physical analysis of solutions of the relativistic wave equations with an x -electric potential step with subsequent QFT analysis of correctness of such an identification. We elaborated a nonperturbative (in the external field) technique that allows one to calculate all characteristics of zero-order processes, such, for example, scattering, reflection, and electron-positron pair creation, without radiation corrections, and also to calculate Feynman diagrams that describe all characteristics of processes with interaction between the in-, out-particles and photons. These diagrams have formally the usual form, but contain special propagators. Expressions for these propagators in terms of in- and out-solutions are presented. We apply the elaborated approach to two popular exactly solvable cases of x -electric potential steps, namely, to the Sauter potential and to the Klein step.

Impact of local environmental conditions on atmospheric electrical potential gradient measurements

NASA Astrophysics Data System (ADS)

Buzás, Attila; Barta, Veronika; Steinbach, Péter; Bór, József

2017-04-01

The atmospheric electrical potential gradient (PG) is a fundamental parameter of the global electric circuit (GEC) which comprises all large scale quasi-static electrical processes occurring in between the surface of the Earth and the lower ionosphere. The observation of PG near the Earth's surface plays a pivotal role in surveying our atmospheric electrical environment. The PG shows high variability in different temporal and spatial scales and it is especially sensitive to local effects. Therefore, obtaining a PG value which represents the general state of the GEC over a larger area rather than various effects due to measuring site-specific local factors is a challenging task. PG measurements are going on in the Széchenyi István Geophysical Observatory (NCK, 47°38' N, 16°43' E) of the Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences near Nagycenk, Hungary since 1961. PG sensors are set up in NCK in an open area surrounded by buildings and trees within 20 m distance. The effect of the changing vegetation on the long-term trend observed in the PG variation at NCK has been subject of debates [1,2,3]. In order to examine the possible bias in the measured PG values due to the relatively close buildings and trees at NCK, two sets of simultaneous PG measurements from two EFM-100 field mills were compared. One field mill was kept at a fixed location while the other was moved to grid points covering the open area around the fixed field mill. The measurement was done in fair weather conditions in summer and was repeated during the winter. The poster demonstrates the performance of this method in surveying the effect of various objects and the state of vegetation on the measured PG values by comparing the measured PG differences to those obtained from electrostatic models calculated by the finite element method using the FEMM 4.2 software package. [1] F. Märcz and R. G. Harrison, 2003, Annales Gephysicae, 21: 2193-2200 [2] F. Märcz and R. G. Harrison, 2005, Annales Gephysicae, 23: 1987-1995 [3] E. Williams, R. Markson and S. Heckman, 2005, Geophysical Research Letters, vol. 32

Electric-field assisted switching of magnetization in perpendicularly magnetized (Ga,Mn)As films at high temperatures

NASA Astrophysics Data System (ADS)

Wang, Hailong; Ma, Jialin; Yu, Xueze; Yu, Zhifeng; Zhao, Jianhua

2017-01-01

The electric-field effects on the magnetism in perpendicularly magnetized (Ga,Mn)As films at high temperatures have been investigated. An electric-field as high as 0.6 V nm-1 is applied by utilizing a solid-state dielectric Al2O3 film as a gate insulator. The coercive field, saturation magnetization and magnetic anisotropy have been clearly changed by the gate electric-field, which are detected via the anomalous Hall effect. In terms of the Curie temperature, a variation of about 3 K is observed as determined by the temperature derivative of the sheet resistance. In addition, electrical switching of the magnetization assisted by a fixed external magnetic field at 120 K is demonstrated, employing the gate-controlled coercive field. The above experimental results have been attributed to the gate voltage modulation of the hole density in (Ga,Mn)As films, since the ferromagnetism in (Ga,Mn)As is carrier-mediated. The limited modulation magnitude of magnetism is found to result from the strong charge screening effect introduced by the high hole concentration up to 1.10  ×  1021 cm-3, while the variation of the hole density is only about 1.16  ×  1020 cm-3.