Nonlinear impedance of mineral‐electrolyte interfaces: Part II. Galena, Chalcopyrite, and Graphite

Geophysics ◽  
1978 ◽  
Vol 43 (6) ◽  
pp. 1235-1249 ◽  
Author(s):  
J. D. Klein ◽  
R. T. Shuey
Keyword(s):  
Low Frequency ◽  
Reference Electrode ◽  
Drill Hole ◽  
Hydrogen Gas ◽  
Mineral Dissolution ◽  
Nonlinear Phenomena ◽  
Reaction Products ◽  
Single Interface ◽  
Current Flows ◽  
Anodic Reactions

The impedance of the interface between an acidic electrolyte and monomineralic, polished electrodes of galena, graphite, and chalcopyrite has been investigated at current densities in the nonlinear range (up to [Formula: see text]). The potential across a single interface relative to a reference electrode was measured in response to a current sinusoid of low frequency, 0.002 Hz. Polarization curves, or linear plots of current density versus electrode potential, consisted of distorted Lissajous patterns. Onset of a new electrochemical reaction resulted in a decrease in impedance of the interface, and hence increase in slope of the polarization curve. For some reactions, the electrical characteristics were diagnostic of bulk mineral composition. Diagnostic reactions include (1) mineral dissolution and gas evolution reactions at extreme anodic and cathodic potentials, (2) reactions at intermediate potentials which involve reaction products from previous reactions. Response is thus dependent on previous reactions and therefore on sample history. Anodic reactions were generally independent of pH, and consisted primarily of mineral dissolution reactions. Potentials of cathodic reactions increased with increasing pH indicating the involvement of [Formula: see text] as demonstrated by the evolution of hydrogen gas and/or [Formula: see text] gas. The potentials of the main graphite reactions were larger in magnitude than any of the sulfide reaction potentials. Measurements with polymineralic electrodes indicate that current flows mainly through minerals with reactions at less extreme potentials and consequently reactions involving other minerals at higher potential do not occur. Due to its more extreme reaction potentials, graphite does not respond in the presence of sulfide minerals. It appears that nonlinear phenomena could be used for mineral discrimination in drill hole logging.

Nonlinear impedance of mineral‐electrolyte interfaces: Part I. Pyrite

Geophysics ◽  
1978 ◽  
Vol 43 (6) ◽  
pp. 1222-1234 ◽  
Author(s):  
J. D. Klein ◽  
R. T. Shuey
Keyword(s):  
Low Frequency ◽  
Reference Electrode ◽  
Nonlinear Behavior ◽  
Hydrogen Gas ◽  
Polarization Curves ◽  
Reaction Products ◽  
Single Interface ◽  
Secondary Reactions ◽  
Current Densities ◽  
A Current

The impedance of the interface between an acidic electrolyte and polished electrodes of pyrite has been investigated at current densities in the nonlinear range (up to [Formula: see text]). The potential across a single interface relative to a reference electrode was measured in response to a current sinusoid of low frequency (0.002 Hz). Polarization curves, or linear plots of current density versus electrode potential, consisted of distorted Lissajous patterns. At peak current densities the interface impedance is low and is dominated by activation controlled reactions involving pyrite dissolution and hydrogen gas evolution. The polarization curves have a series of step‐like features at intermediate potentials due to current‐limited reactions. These secondary reactions involve solid and/or aqueous reaction products from previous reactions. The high impedance portion of each reaction step corresponds to a limit current caused by either depletion of a particular solid reactant or employment of a current larger than can be carried by diffusion of aqueous reactants. Nonlinear behavior of pyrite was found to be independent of carrier type and conductivity. The potential of the anodic pyrite dissolution reaction was weakly dependent on pH. Potentials of cathodic reactions increased with increasing pH, indicating the involvement of [Formula: see text], as demonstrated by the evolution of hydrogen gas and [Formula: see text] gas.

scholarly journals A parameterization of Long-Continuing-Current (LCC) lightning in the lightning submodel LNOX (version 3.0) of the Modular Earth Submodel System (MESSy, version 2.54)

2021 ◽  
Author(s):  
Francisco Javier Pérez-Invernón ◽  
Heidi Huntrieser ◽  
Patrick Jöckel ◽  
Francisco J. Gordillo-Vázquez
Keyword(s):  
Meteorological Data ◽  
Space Station ◽  
Low Frequency ◽  
Electrical Current ◽  
Pressure Level ◽  
Convective Precipitation ◽  
Atmospheric Models ◽  
Optical Instruments ◽  
Current Flows ◽  
Imaging Sensor

Abstract. Lightning flashes can produce a discharge in which a continuing electrical current flows for more than 40 ms. This type of flashes are proposed to be the main precursors of lightning-ignited wildfires and also to trigger sprite discharges in the mesosphere. However, lightning parameterizations implemented in global atmospheric models do not include information about the continuing electrical current of flashes. The continuing current of lightning flashes cannot be detected by conventional lightning location systems. Instead, these so-called Long-Continuing-Current (LCC) flashes are commonly observed by Extreme Low Frequency (ELF) sensors and by optical instruments located in space. Previous reports of LCC lightning flashes tend to occur in winter and oceanic thunderstorms, which suggests a connection between weak convection and the occurrence of this type of discharge. In this study, we develop a parameterization of LCC lightning flashes based on a climatology derived from optical lightning measurements reported by the Lightning Imaging Sensor (LIS) on-board the International Space Station (ISS) between March 2017 and March 2020. We use meteorological data from reanalyses to find a global parameterization that uses the vertical velocity at 450 hPa pressure level as a proxy for the ratio of LCC to typical lightning in thunderstorms. We implement this parameterization into the LNOX submodel of the Modular Earth Submodel System (MESSy) for usage within the EMAC model, and compare the observed and the simulated climatologies of LCC lightning flashes using six different lightning parameterizations. We find that the best agreement between the simulated and the observed spatial distribution is obtained when using a novel combined lightning parameterization based on the cloud top height over land and on the convective precipitation over ocean.

Observations of low-frequency oscillations during relativistic-electron-beam-plasma interactions

1991 ◽  
Vol 46 (2) ◽  
pp. 237-246
Author(s):  
A. S. Paithankar ◽  
G. P. Gupta
Keyword(s):  
Electron Beam ◽  
Relativistic Electron ◽  
Relativistic Electron Beam ◽  
Low Frequency ◽  
Hydrogen Gas ◽  
The Novel ◽  
Low Frequency Oscillations ◽  
Wave Forms ◽  
Beam Parameters ◽  
Pressure Regime

During propagation of a relativistic electron beam in hydrogen gas at sub-torr pressures using a foil-less diode, low-frequency oscillations in the megahertz range are observed in the net current wave forms, and continue even after passage of the beam. The novel feature of the experiment is that both beam generation and propagation take place in the same low-pressure regime, and hence the beam parameters are functions of gas pressures. Analysis of the experimental results shows that the low-frequency oscillations result from the resistive-hose instability.

scholarly journals Investigating Data Cleaning Methods to Improve Performance of Brain–Computer Interfaces Based on Stereo-Electroencephalography

2021 ◽  
Vol 15 ◽  
Author(s):  
Shengjie Liu ◽  
Guangye Li ◽  
Shize Jiang ◽  
Xiaolong Wu ◽  
Jie Hu ◽  
...  
Keyword(s):  
Data Cleaning ◽  
Brain Activity ◽  
Low Frequency ◽  
Reference Electrode ◽  
Brain Regions ◽  
Subcortical Structures ◽  
Implanted Electrodes ◽  
Average Reference ◽  
Depth Electrodes ◽  
Cleaning Methods

Stereo-electroencephalography (SEEG) utilizes localized and penetrating depth electrodes to directly measure electrophysiological brain activity. The implanted electrodes generally provide a sparse sampling of multiple brain regions, including both cortical and subcortical structures, making the SEEG neural recordings a potential source for the brain–computer interface (BCI) purpose in recent years. For SEEG signals, data cleaning is an essential preprocessing step in removing excessive noises for further analysis. However, little is known about what kinds of effect that different data cleaning methods may exert on BCI decoding performance and, moreover, what are the reasons causing the differentiated effects. To address these questions, we adopted five different data cleaning methods, including common average reference, gray–white matter reference, electrode shaft reference, bipolar reference, and Laplacian reference, to process the SEEG data and evaluated the effect of these methods on improving BCI decoding performance. Additionally, we also comparatively investigated the changes of SEEG signals induced by these different methods from multiple-domain (e.g., spatial, spectral, and temporal domain). The results showed that data cleaning methods could improve the accuracy of gesture decoding, where the Laplacian reference produced the best performance. Further analysis revealed that the superiority of the data cleaning method with excellent performance might be attributed to the increased distinguishability in the low-frequency band. The findings of this work highlighted the importance of applying proper data clean methods for SEEG signals and proposed the application of Laplacian reference for SEEG-based BCI.

Low Frequency Oscillatory Ventilation through the Suction Channel of a Pediatric Bronchoscope

1989 ◽  
Vol 98 (4) ◽  
pp. 251-255 ◽  
Author(s):  
Jacob Nutman ◽  
Waldemar A. Carlo ◽  
Robert L. Chatburn
Keyword(s):  
Premature Infants ◽  
Low Frequency ◽  
Lung Model ◽  
Jet Ventilation ◽  
Air Trapping ◽  
Similar System ◽  
Single Interface ◽  
Oscillatory Ventilation ◽  
Residual Capacity

To determine whether low frequency oscillatory ventilation (LFOV) may be safely applied through the suction channel of a pediatric fiberoptic bronchoscope, we devised a system using a combination of jet ventilation and constant air suction, both delivered with a single interface valve. The system was tested on an in vitro lung model and on rabbits. With tidal volumes of 12 mL, inadvertent increase in functional residual capacity (FRC) measured in the lung model was minimal. All rabbits experienced marked hypoventilation (PaCO2 62 ± 2 torr) on introduction of the bronchoscope, which promptly improved with administration of LFOV (PaCO2 41 ± 4 torr). That baseline FRC remained stable indicated that air trapping did not occur. We conclude that LFOV improves ventilation in rabbits during bronchoscopy without causing air trapping. A similar system might be applied during bronchoscopy in full-term and premature infants, thus facilitating safer and more complete visualization of their airways and preserving the possibility of obtaining samples by suction.

Measurement of Electrical Conductivity Degree of some Metallic Conductors by Using the LC Circuit

2020 ◽  
Vol 1002 ◽  
pp. 239-247
Author(s):  
Shahir Fleyeh Nawaf ◽  
Sabah Saddem Salih ◽  
Mohammad Omar Salih
Keyword(s):  
Electrical Conductivity ◽  
Low Frequency ◽  
Test Results ◽  
Induced Voltage ◽  
Sample Tube ◽  
Metallic Conductor ◽  
Lc Circuit ◽  
Metallic Sample ◽  
Pass Through ◽  
Current Flows

Metallic conductors have different degrees of their electrical conductivity. The aim of this research is to measure the electrical conductivity degree for some metallic conductors by measuring the induced voltage in a coil probe, which moves inside the metallic conductor sample tube. When a low frequency of alternating current flows through the LC circuit, it will pass through the solenoid and will generate a magnetic field, which will be reduced due to the presence of the metallic sample tube. The magnetic flux strength generated inside the solenoid determine the electrical conductivity (σ ) of this metallic tube by measuring the EM force induced on the solenoid in the presence the sample tube and without it. Measurements are conducted on two sample models (zinc and aluminum). Test results shows deviation of 10 % compared with the reference values ​​.

LONG-RANGE FLUCTUATIONS OF RANDOM POTENTIAL LANDSCAPE AS A MECHANISM OF 1/f NOISE IN HYDROGENATED AMORPHOUS SILICON

2005 ◽  
Vol 05 (03) ◽  
pp. L443-L456
Author(s):  
BORIS V. FINE ◽  
JEROEN P. R. BAKKER ◽  
JAAP I. DIJKHUIS
Keyword(s):  
Amorphous Silicon ◽  
Long Range ◽  
Noise Intensity ◽  
Broad Class ◽  
Hydrogenated Amorphous Silicon ◽  
Low Frequency ◽  
Noise Spectrum ◽  
Current Flows ◽  
Charged Defects ◽  
Hydrogenated Amorphous

We describe a mechanism that links the long-range potential fluctuations induced by charged defects to the low-frequency resistance noise widely known as 1/fnoise. This mechanism is amenable to the first principles microscopic calculation of the noise spectrum, which includes the absolute noise intensity. We have performed such a calculation for the thin films of hydrogenated amorphous silicon ( a-Si:H ) under the condition that current flows perpendicular to the plane of the films, and have found a very good agreement between the theoretical noise intensity and the measured one. The mechanism described is quite general. It should be present in a broad class of systems containing poorly screened charged defects.

Hydrogen-Sensor Prepared Using Proton-Conducting Glass Films

2007 ◽  
Vol 124-126 ◽  
pp. 627-630 ◽  
Author(s):  
Midori Matsumura ◽  
Yusuke Daiko ◽  
Masayuki Nogami
Keyword(s):  
Thin Film ◽  
Indium Tin Oxide ◽  
High Speed ◽  
Sol Gel ◽  
Reference Electrode ◽  
Hydrogen Sensor ◽  
Hydrogen Gas ◽  
Oxide Thin Film ◽  
Proton Conducting ◽  
Glass Films

Solid-state potentiometric thin film hydrogen gas sensors were successfully fabricated using a sol-gel-derived high proton-conducting P2O5-SiO2 glass films. Manganese oxide thin film coated on an indium tin oxide (ITO)-coated glass substrate was used for reference electrode. The sensor exhibited high speed responsibility within 10 s and 120 s at 30 oC and -30oC, respectively, for 1 vol.% hydrogen gas. A linear relationship between the electromotive force (EMF) and the logarithmic hydrogen concentration of 0.1~1 vol.% was obtained in the temperature ranging from -30 to 30 oC. The sensing mechanism was also discussed to improve the sensitivity and sensing speed against low H2 concentration at low temperatures.

STUDIES ON HYDROGEN–OXYGEN SYSTEMS IN THE ELECTRIC DISCHARGE: I. THE REACTIONS OF HYDROGEN ATOMS WITH HYDROGEN PEROXIDE

1966 ◽  
Vol 44 (8) ◽  
pp. 869-876 ◽  
Author(s):  
Norisuke H Ata ◽  
Paul A. Glguère
Keyword(s):  
Hydrogen Peroxide ◽  
Water Vapor ◽  
Electric Discharge ◽  
Hydrogen Gas ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Eutectic Melting ◽  
Electrodeless Discharge ◽  
Liquid Nitrogen Trap ◽  
Unidentified Species

Hydrogen gas partly dissociated in an electrodeless discharge was mixed downstream with hydrogen peroxide vapor at low pressure (0.1 mm Hg) in a liquid nitrogen trap. The reaction products condensed readily on the wall as a clear, yellowish glass resembling that from dissociated water vapor and other related systems. A manometric study of the warming-up process has revealed four distinct steps. The first two, in which only traces of gas are given off, look like the recombination of trapped free radicals. The major evolution of oxygen upon crystallization of the glassy deposit at 160 °K is ascribed to the decomposition of hydrogen peroxide under the influence of some unidentified species generated in the electric discharge through hydrogen. Experimental evidence for this is presented. In any case the stoichiometry cannot be reconciled with the formation of a metastable intermediate, such as the hypothetical polyoxide H2O4.In the last step beginning around 215 °K more peroxide is decomposed during the eutectic melting of the solid. Qualitatively these phenomena are similar to those shown by the condensate from dissociated water vapor.

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