Lightning Magnetic Field Measurements around Langmuir Laboratory

NASA Astrophysics Data System (ADS)

Stock, M.; Krehbiel, P. R.; Rison, W.; Aulich, G. D.; Edens, H. E.; Sonnenfeld, R. G.

2010-12-01

In the absence of artificial conductors, underground lightning transients are produced by diffusion of the horizontal surface magnetic field of a return stroke vertically downward into the conducting earth. The changing magnetic flux produces an orthogonal horizontal electric field, generating a dispersive, lossy transverse electromagnetic wave that penetrates a hundred meters or more into the ground according to the skin depth of the medium. In turn, the electric field produces currents that flow toward or away from the channel to ground depending on the stroke polarity. The underground transients can produce large radial horizontal potential gradients depending on the distance from the discharge and depth below the surface. In this study we focus on the surface excitation field. The goal of the work is to compare measurements of surface magnetic field waveforms B(t) at different distances from natural lightning discharges with simple and detailed models of the return stroke fields. In addition to providing input to the diffusion mechanism, the results should aid in further understanding return stroke field generation processes. The observational data are to be obtained using orthogonal sets of straightened Rogowski coils to measure magnetic field waveforms in N-S and E-W directions. The waveforms are sampled at 500 kS/s over 1.024 second time intervals and recorded directly onto secure digital cards. The instrument operates off of battery power for several days or weeks at a time in remote, unattended locations and measures magnetic field strengths of up to several tens of amperes/meter. The observations are being made in conjunction with collocated slow electric field change measurements and under good 3-D lightning mapping array (LMA) and fast electric field change coverage.

Waveform control of orientation-dependent ionization of DCl in few-cycle laser fields.

PubMed

Znakovskaya, I; von den Hoff, P; Schirmel, N; Urbasch, G; Zherebtsov, S; Bergues, B; de Vivie-Riedle, R; Weitzel, K-M; Kling, M F

2011-05-21

Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D(+) and Cl(+) fragments were recorded via velocity-map imaging. A waveform-dependent anti-correlated directional emission of D(+) and Cl(+) fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl(+) and in turn the directional emission of charged fragments upon the breakup of the molecular ion. © The Owner Societies 2011

Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: excitation dynamics and ion flux asymmetry

DOE PAGES

Bruneau, B.; Diomede, P.; Economou, D. J.; ...

2016-06-08

Parallel plate capacitively coupled plasmas in hydrogen at relatively high pressure (~1 Torr) are excited with tailored voltage waveforms containing up to five frequencies. Predictions of a hybrid model combining a particle-in-cell simulation with Monte Carlo collisions and a fluid model are compared to phase resolved optical emission spectroscopy measurements, yielding information on the dynamics of the excitation rate in these discharges. When the discharge is excited with amplitude asymmetric waveforms, the discharge becomes electrically asymmetric, with different ion energies at each of the two electrodes. Unexpectedly, large differences in themore » $$\\text{H}_{2}^{+}$$ fluxes to each of the two electrodes are caused by the different $$\\text{H}_{3}^{+}$$ energies. When the discharge is excited with slope asymmetric waveforms, only weak electrical asymmetry of the discharge is observed. In this case, electron power absorption due to fast sheath expansion at one electrode is balanced by electron power absorption at the opposite electrode due to a strong electric field reversal.« less

A study on the influence of corona on currents and electromagnetic fields predicted by a nonlinear lightning return-stroke model

NASA Astrophysics Data System (ADS)

De Conti, Alberto; Silveira, Fernando H.; Visacro, Silvério

2014-05-01

This paper investigates the influence of corona on currents and electromagnetic fields predicted by a return-stroke model that represents the lightning channel as a nonuniform transmission line with time-varying (nonlinear) resistance. The corona model used in this paper allows the calculation of corona currents as a function of the radial electric field in the vicinity of the channel. A parametric study is presented to investigate the influence of corona parameters, such as the breakdown electric field and the critical electric field for the stable propagation of streamers, on predicted currents and electromagnetic fields. The results show that, regardless of the assumed corona parameters, the incorporation of corona into the nonuniform and nonlinear transmission line model under investigation modifies the model predictions so that they consistently reproduce most of the typical features of experimentally observed lightning electromagnetic fields and return-stroke speed profiles. In particular, it is shown that the proposed model leads to close vertical electric fields presenting waveforms, amplitudes, and decay with distance in good agreement with dart leader electric field changes measured in triggered lightning experiments. A comparison with popular engineering return-stroke models further confirms the model's ability to predict consistent electric field waveforms in the close vicinity of the channel. Some differences observed in the field amplitudes calculated with the different models can be related to the fact that current distortion, while present in the proposed model, is ultimately neglected in the considered engineering return-stroke models.

Lightning Return-Stroke Current Waveforms Aloft, From Measured Field Change, Current, and Channel Geometry

NASA Technical Reports Server (NTRS)

Willett, J. C.; LeVine, D. M.

2002-01-01

Direct current measurements are available near the attachment point from both natural cloud-to-ground lightning and rocket-triggered lightning, but little is known about the rise time and peak amplitude of return-stroke currents aloft. We present, as functions of height, current amplitudes, rise times, and effective propagation velocities that have been estimated with a novel remote-sensing technique from data on 24 subsequent return strokes in six different lightning flashes that were triggering at the NASA Kennedy Space Center, FL, during 1987. The unique feature of this data set is the stereo pairs of still photographs, from which three-dimensional channel geometries were determined previously. This has permitted us to calculate the fine structure of the electric-field-change (E) waveforms produced by these strokes, using the current waveforms measured at the channel base together with physically reasonable assumptions about the current distributions aloft. The computed waveforms have been compared with observed E waveforms from the same strokes, and our assumptions have been adjusted to maximize agreement. In spite of the non-uniqueness of solutions derived by this technique, several conclusions seem inescapable: 1) The effective propagation speed of the current up the channel is usually significantly (but not unreasonably) faster than the two-dimensional velocity measured by a streak camera for 14 of these strokes. 2) Given the deduced propagation speed, the peak amplitude of the current waveform often must decrease dramatically with height to prevent the electric field from being over-predicted. 3) The rise time of the current wave front must always increase rapidly with height in order to keep the fine structure of the calculated field consistent with the observations.

Department of Defense Interface Standard Electromagnetic Environmental Effects Requirements for Systems

DTIC Science & Technology

2002-12-19

effective tool in evaluating IMI. A5.2.2 Shipboard internal electromagnetic environment (EME). For ship applications, electric fields (peak V/m-rms...effects waveform parameters ........................................ 9 MIL-STD-464A v CONTENTS Page TABLES 2B Electromagnetic fields from near...blasting of hardware. 3.8 Lightning indirect effects. Electrical transients induced by lightning due to coupling of electromagnetic fields . 3.9

Recommended E3 HEMP Heave Electric Field Waveform for the Critical Infrastructures. Volume 2

DTIC Science & Technology

2017-07-31

OF THE COMMISSION TO ASSESS THE THREAT TO THE UNITED STATES FROM ELECTROMAGNETIC PULSE (EMP) ATTACK The cover photo depicts Fishbowl Starfish...Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack. The Commission was established by Congress in the FY2001 National...Department of Defense E electric field EMP electromagnetic pulse EPRI Electric Power Research Institute FERC Federal Energy Regulatory Commission GMD

Comparison of fast electric field changes from subsequent return strokes of natural and triggered lightning

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Willett, J. C.; Bailey, J. C.

1989-01-01

Fast electric field changes from subsequent return strokes of natural and triggered lightning with propagation paths almost entirely over water are compared. Data were collected at the Kennedy Space Center, Florida, during the summer of 1987. Comparisons have been made of the average shape, the risetime, and the spectrum of the electric field changes. To a first approximation, the waveforms are very similar; however, the electric field changes from the triggered flashes tend to rise to peak faster and decay faster than do their counterparts in natural cloud-to-ground flashes.

Electroporation of Mammalian Cells by Nanosecond Electric Field Oscillations and its Inhibition by the Electric Field Reversal

DTIC Science & Technology

2015-09-08

Report 3. DATES COVERED (From – To) March 2013 to July 2015 4 . TITLE AND SUBTITLE Electroporation of mammalian cells by nanosecond electric field...NEFO was a damped sine wave with 140 ns first phase duration at 50% height; the peak amplitude of phases 2- 4 decreased to 35%, 12%, and 7% of the...first phase. This waveform was rectified to produce unipolar NEFO by cutting off phases 2 and 4 . Membrane permeabilization was quantified in CHO and

Onboard Processing on PWE OFA/WFC (Onboard Frequency Analyzer/Waveform Capture) aboard the ERG (ARASE) Satellite

NASA Astrophysics Data System (ADS)

Matsuda, S.; Kasahara, Y.; Kojima, H.; Kasaba, Y.; Yagitani, S.; Ozaki, M.; Imachi, T.; Ishisaka, K.; Kurita, S.; Ota, M.; Kumamoto, A.; Tsuchiya, F.; Yoshizumi, M.; Matsuoka, A.; Teramoto, M.; Shinohara, I.

2017-12-01

Exploration of energization and Radiation in Geospace (ERG) is a mission for understanding particle acceleration, loss mechanisms, and the dynamic evolution of space storms in the context of cross-energy and cross-regional coupling [Miyoshi et al., 2012]. The ERG (ARASE) satellite was launched on December 20, 2016, and successfully inserted into an orbit. The Plasma Wave Experiment (PWE) is one of the science instruments on board the ERG satellite to measure electric field and magnetic field in the inner magnetosphere. PWE consists of three sub-components, EFD (Electric Field Detector), OFA/WFC (Onboard Frequency Analyzer and Waveform Capture), and HFA (High Frequency Analyzer). Especially, OFA/WFC measures electric and magnetic field spectrum and waveform from a few Hz to 20 kHz. OFA/WFC processes signals detected by a couple of dipole wire-probe antenna (WPT) and tri-axis magnetic search coils (MSC) installed onboard the satellite. The PWE-OFA subsystem calculates and produces three kind of data; OFA-SPEC (power spectrum), OFA-MATRIX (spectrum matrix), and OFA-COMPLEX (complex spectrum). They are continuously processed 24 hours per day and all data are sent to the ground. OFA-MATRIX and OFA-COMPLEX are used for polarization analyses and direction finding of the plasma waves. The PWE-WFC subsystem measures raw (64 kHz sampled) and down-sampled (1 kHz sampled) burst waveform detected by the WPT and the MSC sensors. It activates by a command, automatic triggering, and scheduling. The initial check-out process of the PWE successfully completed, and initial data has been obtained. In this presentation, we introduce onboard processing technique on PWE OFA/WFC and its initial results.

FDTD Modeling of LEMP Propagation in the Earth-Ionosphere Waveguide With Emphasis on Realistic Representation of Lightning Source

NASA Astrophysics Data System (ADS)

Tran, Thang H.; Baba, Yoshihiro; Somu, Vijaya B.; Rakov, Vladimir A.

2017-12-01

The finite difference time domain (FDTD) method in the 2-D cylindrical coordinate system was used to compute the nearly full-frequency-bandwidth vertical electric field and azimuthal magnetic field waveforms produced on the ground surface by lightning return strokes. The lightning source was represented by the modified transmission-line model with linear current decay with height, which was implemented in the FDTD computations as an appropriate vertical phased-current-source array. The conductivity of atmosphere was assumed to increase exponentially with height, with different conductivity profiles being used for daytime and nighttime conditions. The fields were computed at distances ranging from 50 to 500 km. Sky waves (reflections from the ionosphere) were identified in computed waveforms and used for estimation of apparent ionospheric reflection heights. It was found that our model reproduces reasonably well the daytime electric field waveforms measured at different distances and simulated (using a more sophisticated propagation model) by Qin et al. (2017). Sensitivity of model predictions to changes in the parameters of atmospheric conductivity profile, as well as influences of the lightning source characteristics (current waveshape parameters, return-stroke speed, and channel length) and ground conductivity were examined.

A sensor for vector electric field measurements through a nonlinear anisotropic optical crystal

NASA Astrophysics Data System (ADS)

Barbieri, Luca; Gondola, Marco; Potenza, Marco; Villa, Andrea; Malgesini, Roberto

2017-11-01

Electrical applications require the development of electric field sensors that can reproduce vector electric field waveforms with a very large spectral width ranging from 50 Hz to at least 70 MHz. This makes it possible to measure both the normal operation modes of electrical components and abnormal behaviors such as the corona emission and partial discharges. In this work, we aim to develop a fully dielectric sensor capable of measuring two components of the electric field using a wide class of optical crystals including anisotropic ones, whereas most of the efforts in this field have been devoted to isotropic crystals. We report the results of the measurements performed at 50 Hz and with a lightning impulse, to validate the sensor.

PAVE PAWS Early Warning Radar Operation Cape Cod Air Force Station, MA. Record of Decision

DTIC Science & Technology

2009-06-01

Electrical and Electronics Engineers (IEEE) C95.1-1999. Accordingly, the highest measurement was obtained directly in front of the feedhorn (i.e...waveform characterization of the Cape Cod AFS Pave PAWS radar. The data acquired during the Phase IV survey indicated that the electric fields produced...level observed among the ambient sites. During this survey, peak/average power density measurements and peak/average electric field measurements

Field-Oriented Control Of Induction Motors

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Roth, Mary Ellen; Zinger, Don S.

1993-01-01

Field-oriented control system provides for feedback control of torque or speed or both. Developed for use with commercial three-phase, 400-Hz, 208-V, 5-hp motor. Systems include resonant power supply operating at 20 kHz. Pulse-population-modulation subsystem selects individual pulses of 20-kHz single-phase waveform as needed to synthesize three waveforms of appropriate lower frequency applied to three phase windings of motor. Electric actuation systems using technology currently being built to peak powers of 70 kW. Amplitude of voltage of effective machine-frequency waveform determined by momentary frequency of pulses, while machine frequency determined by rate of repetition of overall temporal pattern of pulses. System enables independent control of both voltage and frequency.

Frequency domain and full waveform time domain inversion of ground based magnetometer, electrometer and incoherent scattering radar arrays to image strongly heterogenous 3-D Earth structure, ionospheric structure, and to predict the intensity of GICs in the power grid

NASA Astrophysics Data System (ADS)

Schultz, A.; Imamura, N.; Bonner, L. R., IV; Cosgrove, R. B.

2016-12-01

Ground-based magnetometer and electrometer arrays provide the means to probe the structure of the Earth's interior, the interactions of space weather with the ionosphere, and to anticipate the intensity of geomagnetically induced currents (GICs) in power grids. We present a local-to-continental scale view of a heterogeneous 3-D crust and mantle as determined from magnetotelluric (MT) observations across arrays of ground-based electric and magnetic field sensors. MT impedance tensors describe the relationship between electric and magnetic fields at a given site, thus implicitly they contain all known information on the 3-D electrical resistivity structure beneath and surrounding that site. By using multivariate transfer functions to project real-time magnetic observatory network data to areas surrounding electric power grids, and by projecting those magnetic fields through MT impedance tensors, the projected magnetic field can be transformed into predictions of electric fields along the path of the transmission lines, an essential element of predicting the intensity of GICs in the grid. Finally, we explore GICs, i.e. Earth-ionosphere coupling directly in the time-domain. We consider the fully coupled EM system, where we allow for a non-stationary ionospheric source field of arbitrary complexity above a 3-D Earth. We solve the simultaneous inverse problem for 3-D Earth conductivity and source field structure directly in the time domain. In the present work, we apply this method to magnetotelluric data obtained from a synchronously operating array of 25 MT stations that collected continuous MT waveform data in the interior of Alaska during the autumn and winter of 2015 under the footprint of the Poker Flat (Alaska) Incoherent Scattering Radar (PFISR). PFISR data yield functionals of the ionospheric electric field and ionospheric conductivity that constrain the MT source field. We show that in this region conventional robust MT processing methods struggle to produce reliable MT response functions at periods much greater than about 2,000 s, a consequence, we believe, of the complexity of the ionospheric source fields in this high latitude setting. This provides impetus for direct waveform inversion methods that dispense with typical parametric assumptions made about the MT source fields.

Application of the Lienard-Wiechert solution to a lightning return stroke model

NASA Technical Reports Server (NTRS)

Meneghini, R.

1983-01-01

The electric and magnetic fields associated with the lightning return stroke are expressed as a convolution of the current waveform shape and the fields generated by a moving charge of amplitude one (i.e., the Lienard-Wiechert solution for a unit charge). The representation can be used to compute the fields produced by a current waveform of non-uniform velocity that propagates along a filament of arbitrary, but finite, curvature. To study numerically the effects of linear charge acceleration and channel curvature two simple channel models are used: the linear and the hyperbolic.

Application of the Lienard-Wiechert solution to a lightning return stroke model

NASA Technical Reports Server (NTRS)

Meneghini, R.

1984-01-01

The electric and magnetic fields associated with the lightning return stroke are expressed as a convolution of the current waveform shape and the fields generated by a moving charge of amplitude one (i.e., the Lienard-Wiechert solution for a unit charge). The representation can be used to compute the fields produced by a current waveform of non-uniform velocity that propagates along a filament of arbitrary, but finite, curvature. To study numerically the effects of linear charge acceleration and channel curvature two simple channel models are used: the linear and the hyperbolic.

Optimization of an electrokinetic mixer for microfluidic applications.

PubMed

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P J

2012-06-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly.

Optimization of an electrokinetic mixer for microfluidic applications

PubMed Central

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P. J.

2012-01-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly. PMID:22712034

Study of electric field distorted by space charges under positive lightning impulse voltage

NASA Astrophysics Data System (ADS)

Wang, Zezhong; Geng, Yinan

2018-03-01

Actually, many insulation problems are related to electric fields. And measuring electric fields is an important research topic of high-voltage engineering. In particular, the electric field distortion caused by space charge is the basis of streamer theory, and thus quantitatively measuring the Poisson electric field caused by space charge is significant to researching the mechanism of air gap discharge. In this paper, we used our photoelectric integrated sensor to measure the electric field distribution in a 1-m rod-plane gap under positive lightning impulse voltage. To verify the reliability of this quantitative measurement, we compared the measured results with calculated results from a numerical simulation. The electric-field time domain waveforms on the axis of the 1-m rod-plane out of the space charge zone were measured with various electrodes. The Poisson electric fields generated by space charge were separated from the Laplace electric field generated by applied voltages, and the amplitudes and variations were measured for various applied voltages and at various locations. This work also supplies the feasible basis for directly measuring strong electric field under high voltage.

The Polar Plasma Wave Instrument

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Persoon, A. M.; Randall, R. F.; Odem, D. L.; Remington, S. L.; Averkamp, T. F.; Debower, M. M.; Hospodarsky, G. B.; Huff, R. L.; Kirchner, D. L.

1995-01-01

The Plasma Wave Instrument on the Polar spacecraft is designed to provide measurements of plasma waves in the Earth's polar regions over the frequency range from 0.1 Hz to 800 kHz. Three orthogonal electric dipole antennas are used to detect electric fields, two in the spin plane and one aligned along the spacecraft spin axis. A magnetic loop antenna and a triaxial magnetic search coil antenna are used to detect magnetic fields. Signals from these antennas are processed by five receiver systems: a wideband receiver, a high-frequency waveform receiver, a low-frequency waveform receiver, two multichannel analyzers; and a pair of sweep frequency receivers. Compared to previous plasma wave instruments, the Polar plasma wave instrument has several new capabilities. These include (1) an expanded frequency range to improve coverage of both low- and high-frequency wave phenomena, (2) the ability to simultaneously capture signals from six orthogonal electric and magnetic field sensors, and (3) a digital wideband receiver with up to 8-bit resolution and sample rates as high as 249k samples s(exp -1).

Pulse shaping system

DOEpatents

Skeldon, Mark D.; Letzring, Samuel A.

1999-03-23

Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses.

Pulse shaping system

DOEpatents

Skeldon, M.D.; Letzring, S.A.

1999-03-23

Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses. 8 figs.

A High Voltage Asymmetric Waveform Generator for FAIMS

PubMed Central

Canterbury, Jesse D.; Gladden, James; Buck, Lon; Olund, Roy; MacCoss, Michael J.

2010-01-01

High field asymmetric waveform ion mobility spectrometry (FAIMS) has been used increasingly in recent years as an additional method of ion separation and selection prior to mass spectrometry. The FAIMS electrodes are relatively simple to design and fabricate for laboratories wishing to implement their own FAIMS designs. However, construction of the electronics apparatus needed to produce the required high magnitude asymmetric electric field oscillating at a frequency of several hundred kilohertz is not trivial. Here we present an entirely custom-built electronics setup capable of supplying the required waveforms and voltages. The apparatus is relatively simple and inexpensive to implement. We also present data acquired on this system demonstrating the use of FAIMS as a gas phase ion filter interface to an ion trap mass spectrometer. PMID:20332067

Research on the discharge characteristics for water tree in crosslinked polyethylene cable based on plasma-chemical model

NASA Astrophysics Data System (ADS)

Fan, Yang; Qi, Yang; Bing, Gao; Rong, Xia; Yanjie, Le; Iroegbu, Paul Ikechukwu

2018-03-01

Water tree is the predominant defect in high-voltage crosslinked polyethylene cables. The microscopic mechanism in the discharge process is not fully understood; hence, a drawback is created towards an effective method to evaluate the insulation status. In order to investigate the growth of water tree, a plasma-chemical model is developed. The dynamic characteristics of the discharge process including voltage waveform, current waveform, electron density, electric potential, and electric field intensity are analyzed. Our results show that the distorted electric field is the predominant contributing factor of electron avalanche formation, which inevitably leads to the formation of pulse current. In addition, it is found that characteristic parameters such as the pulse width and pulse number have a great relevance to the length of water tree. Accordingly, the growth of water tree can be divided into the initial stage, development stage, and pre-breakdown stage, which provides a reference for evaluating the deteriorated stages of crosslinked polyethylene cables.

Geometrical Effects on the Electromagnetic Radiation from Lightning Return Strokes

NASA Technical Reports Server (NTRS)

Willett, John C.; Smith, David A.; LeVine, David M.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The Los Alamos National Laboratory (LANL) Sferic Array has recorded electric-field-change waveforms simultaneously at several stations surrounding the ground-strike points of numerous return strokes in cloud-to-ground lightning flashes. Such data are available from the five-station sub-networks in both Florida and New Mexico. With these data it has been possible for the first time to compare the waveforms radiated in different directions by a given stroke. Such comparisons are of interest to assess both the effects of channel geometry on the fine structure of subsequent-stroke radiation fields and the role of branches in the more jagged appearance of first-stroke waveforms. This paper presents multiple-station, time-domain waveforms with a 200 Hz to 500 kHz pass-band from both first and subsequent return strokes at ranges generally between 100 and 200 km. The differences among waveforms of the same stroke received at stations in different directions from the lightning channel are often obvious. These differences are illustrated and interpreted in the context of channel tortuosity and branches.

Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

NASA Technical Reports Server (NTRS)

Malaspina, David; Horanyi, M.; Zaslavsky, A.; Goetz, K.; Wilson, L. B., III; Kersten, K.

2014-01-01

Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

The fine structure of Langmuir waves observed upstream of the bow shock at Venus

NASA Technical Reports Server (NTRS)

Hospodarsky, G. B.; Gurnett, D. A.; Kurth, W. S.; Kivelson, M. G.; Strangeway, R. J.; Bolton, S. J.

1994-01-01

Highly structured Langmuir waves, also known as electron plasma oscillations, have been observed in the foreshock of Venus using the plasma wave experiment on the Galileo spacecraft during the gravity assist flyby on February 10, 1990. The Galileo wideband sampling system provides digital electric field waveform measurements at sampling rates up to 201,600 samples per second, much higher than any previous instrument of this type. The main Langmuir wave emission band occurs near the local electron plasma frequency, which was approximately 43 kHz. The Langmuir waves are observed to shift above and below the plasma frequency, sometimes by as much as 20 kHz. The shifts in frequency are closely correlated with the downstream distance from the tangent field line, implying that the shifts are controlled by the electron beam velocity. Considerable fine structure is also evident, with time scales as short as 0.15 milliseconds, corresponding to spatial scales of a few tens of Debye lengths. The frequency spectrum often consists of beat-type waveforms, with beat frequencies ranging from 0.2 to 7 kHz, and in a few cases, isolated wavepackets. The peak electric field strengths are approximately 1 mV/m. These field strengths are too small for strongly nonlinear processes to be important. The beat-type waveforms are suggestive of a parametric decay process.

Calculations of lightning return stroke electric and magnetic fields above ground

NASA Technical Reports Server (NTRS)

Master, M. J.; Uman, M. A.; Ling, Y. T.; Standler, R. B.

1981-01-01

Lin et al., (1980) presented a lightning return stroke model with which return stroke electric and magnetic fields measured at ground level could be reproduced. This model and a modified version of it, in which the initial current peak decays with height above ground, are used to compute waveforms for altitudes from 0-10 km and at ranges of 20 m to 10 km. Both the original and modified models gave accurate predictions of measured ground-based fields. The use of the calculated fields in calibrating airborne field measurements from simultaneous ground and airborne data is discussed.

Effect of Frequency and Waveform on Inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in Salsa by Ohmic Heating

PubMed Central

Lee, Su-Yeon; Ryu, Sangryeol

2013-01-01

The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform. PMID:23023752

Effect of frequency and waveform on inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in salsa by ohmic heating.

PubMed

Lee, Su-Yeon; Ryu, Sangryeol; Kang, Dong-Hyun

2013-01-01

The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform.

Evaluation and characterization of fetal exposures to low frequency magnetic fields generated by laptop computers.

PubMed

Zoppetti, Nicola; Andreuccetti, Daniele; Bellieni, Carlo; Bogi, Andrea; Pinto, Iole

2011-12-01

Portable - or "laptop" - computers (LCs) are widely and increasingly used all over the world. Since LCs are often used in tight contact with the body even by pregnant women, fetal exposures to low frequency magnetic fields generated by these units can occur. LC emissions are usually characterized by complex waveforms and are often generated by the main AC power supply (when connected) and by the display power supply sub-system. In the present study, low frequency magnetic field emissions were measured for a set of five models of portable computers. For each of them, the magnetic flux density was characterized in terms not just of field amplitude, but also of the so called "weighted peak" (WP) index, introduced in the 2003 ICNIRP Statement on complex waveforms and confirmed in the 2010 ICNIRP Guidelines for low frequency fields. For the model of LC presenting the higher emission, a deeper analysis was also carried out, using numerical dosimetry techniques to calculate internal quantities (current density and in-situ electric field) with reference to a digital body model of a pregnant woman. Since internal quantities have complex waveforms too, the concept of WP index was extended to them, considering the ICNIRP basic restrictions defined in the 1998 Guidelines for the current density and in the 2010 Guidelines for the in-situ electric field. Induced quantities and WP indexes were computed using an appropriate original formulation of the well known Scalar Potential Finite Difference (SPFD) numerical method for electromagnetic dosimetry in quasi-static conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Methods and devices for high-throughput dielectrophoretic concentration

DOEpatents

Simmons, Blake A.; Cummings, Eric B.; Fiechtner, Gregory J.; Fintschenko, Yolanda; McGraw, Gregory J.; Salmi, Allen

2010-02-23

Disclosed herein are methods and devices for assaying and concentrating analytes in a fluid sample using dielectrophoresis. As disclosed, the methods and devices utilize substrates having a plurality of pores through which analytes can be selectively prevented from passing, or inhibited, on application of an appropriate electric field waveform. The pores of the substrate produce nonuniform electric field having local extrema located near the pores. These nonuniform fields drive dielectrophoresis, which produces the inhibition. Arrangements of electrodes and porous substrates support continuous, bulk, multi-dimensional, and staged selective concentration.

Dynamic of microwave breakdown in the localized places of transmitting line driving by Cherenkov-type oscillator

NASA Astrophysics Data System (ADS)

Xie, Jialing; Chen, Changhua; Chang, Chao; Wu, Cheng; Shi, Yanchao; Cao, Yibing; Song, Zhimin; Zhang, Yuchuan

2018-02-01

A breakdown cavity is designed to study the breakdown phenomena of high-power microwaves in transmission waveguides. The maximum electric field within the cavity varies in amplitude from 400 kV/cm to 1.8 MV/cm and may surpass breakdown thresholds. The breakdown cavities were studied in particle-in-cell simulations and experiments, the results of which yielded waveforms that were consistent. The experimental results indicate that the microwave pulse does not shorten, and the amplitude of the electric field does not fall below 800 kV/cm. Moreover, large numbers of electrons are not emitted in microwaves below 670 kV/cm at 9.75 GHz frequency and 25-ns pulse width transmitted in stainless steel waveguides. The radiation waveforms of breakdown cavity with different materials are compared in experiments, with titanium material performing better.

Application of Wave Distribution Function Method to the ERG/PWE Data

NASA Astrophysics Data System (ADS)

Ota, M.; Kasahara, Y.; Matsuda, S.; Kojima, H.; Matsuoka, A.; Hikishima, M.; Kasaba, Y.; Ozaki, M.; Yagitani, S.; Tsuchiya, F.; Kumamoto, A.

2017-12-01

The ERG (Arase) satellite was launched on 20 December 2016 to study acceleration and loss mechanisms of relativistic electrons in the Earth's magnetosphere. The Plasma Wave Experiment (PWE), which is one of the science instruments on board the ERG satellite, measures electric field and magnetic field. The PWE consists of three sub-systems; EFD (Electric Field Detector), OFA/WFC (Onboard Frequency Analyzer and Waveform Capture), and HFA (High Frequency Analyzer).The OFA/WFC measures electromagnetic field spectra and raw waveforms in the frequency range from few Hz to 20 kHz. The OFA produces three kind of data; OFA-SPEC (power spectrum), OFA-MATRIX (spectral matrix), and OFA-COMPLEX (complex spectrum). The OFA-MATRIX measures ensemble averaged complex cross-spectra of two electric field components, and of three magnetic field components. The OFA-COMPLEX measures instantaneous complex spectra of electric and magnetic fields. These data are produced every 8 seconds in the nominal mode, and it can be used for polarization analysis and wave propagation direction finding.In general, spectral matrix composed by cross-spectra of observed signals is used for direction finding, and many algorithms have been proposed. For example, Means method and SVD method can be applied on the assumption that the spectral matrix is consists of a single plane wave, while wave distribution function (WDF) method is applicable even to the data in which multiple numbers of plane waves are simultaneously included. In this presentation, we introduce the results when the WDF method is applied to the ERG/PWE data.

PLASMA DEVICE

DOEpatents

Baker, W.R.

1961-08-22

A device is described for establishing and maintaining a high-energy, rotational plasma for use as a fast discharge capacitor. A disc-shaped, current- conducting plasma is formed in an axinl magnetic field and a crossed electric field, thereby creating rotational kinetic enengy in the plasma. Such energy stored in the rotation of the plasma disc is substantial and is convertible tc electrical energy by generator action in an output line electrically coupled to the plasma volume. Means are then provided for discharging the electrical energy into an external circuit coupled to the output line to produce a very large pulse having an extremely rapid rise time in the waveform thereof. (AE C)

Theoretical simulation of the multipole seismoelectric logging while drilling

NASA Astrophysics Data System (ADS)

Guan, Wei; Hu, Hengshan; Zheng, Xiaobo

2013-11-01

Acoustic logging-while-drilling (LWD) technology has been commercially used in the petroleum industry. However it remains a rather difficult task to invert formation compressional and shear velocities from acoustic LWD signals due to the unwanted strong collar wave, which covers or interferes with signals from the formation. In this paper, seismoelectric LWD is investigated for solving that problem. The seismoelectric field is calculated by solving a modified Poisson's equation, whose source term is the electric disturbance induced electrokinetically by the travelling seismic wave. The seismic wavefield itself is obtained by solving Biot's equations for poroelastic waves. From the simulated waveforms and the semblance plots for monopole, dipole and quadrupole sources, it is found that the electric field accompanies the collar wave as well as other wave groups of the acoustic pressure, despite the fact that seismoelectric conversion occurs only in porous formations. The collar wave in the electric field, however, is significantly weakened compared with that in the acoustic pressure, in terms of its amplitude relative to the other wave groups in the full waveforms. Thus less and shallower grooves are required to damp the collar wave if the seismoelectric LWD signals are recorded for extracting formation compressional and shear velocities.

Subfemtosecond directional control of chemical processes in molecules

NASA Astrophysics Data System (ADS)

Alnaser, Ali S.; Litvinyuk, Igor V.

2017-02-01

Laser pulses with a waveform-controlled electric field and broken inversion symmetry establish the opportunity to achieve directional control of molecular processes on a subfemtosecond timescale. Several techniques could be used to break the inversion symmetry of an electric field. The most common ones include combining a fundamental laser frequency with its second harmonic or with higher -frequency pulses (or pulse trains) as well as using few-cycle pulses with known carrier-envelope phase (CEP). In the case of CEP, control over chemical transformations, typically occurring on a timescale of many femtoseconds, is driven by much faster sub-cycle processes of subfemtosecond to few-femtosecond duration. This is possible because electrons are much lighter than nuclei and fast electron motion is coupled to the much slower nuclear motion. The control originates from populating coherent superpositions of different electronic or vibrational states with relative phases that are dependent on the CEP or phase offset between components of a two-color pulse. In this paper, we review the recent progress made in the directional control over chemical processes, driven by intense few-cycle laser pulses a of waveform-tailored electric field, in different molecules.

High-frequency thermal-electrical cycles for pyroelectric energy conversion

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

Bhatia, Bikram; Damodaran, Anoop R.; Cho, Hanna

2014-11-21

We report thermal to electrical energy conversion from a 150 nm thick BaTiO{sub 3} film using pyroelectric cycles at 1 kHz. A microfabricated platform enables temperature and electric field control with temporal resolution near 1 μs. The rapid electric field changes as high as 11 × 10{sup 5 }kV/cm-s, and temperature change rates as high as 6 × 10{sup 5 }K/s allow exploration of pyroelectric cycles in a previously unexplored operating regime. We investigated the effect of phase difference between electric field and temperature cycles, and electric field and temperature change rates on the electrical energy generated from thermal-electrical cycles based on the pyroelectric Ericsson cycle. Complete thermodynamic cyclesmore » are possible up to the highest cycle rates tested here, and the energy density varies significantly with phase shifts between temperature and electric field waveforms. This work could facilitate the design and operation of pyroelectric cycles at high cycle rates, and aid in the design of new pyroelectric systems.« less

High-Speed Terahertz Waveform Measurement for Intense Terahertz Light Using 100-kHz Yb-Doped Fiber Laser.

PubMed

Tsubouchi, Masaaki; Nagashima, Keisuke

2018-06-14

We demonstrate a high-speed terahertz (THz) waveform measurement system for intense THz light with a scan rate of 100 Hz. To realize the high scan rate, a loudspeaker vibrating at 50 Hz is employed to scan the delay time between THz light and electro-optic sampling light. Because the fast scan system requires a high data sampling rate, we develop an Yb-doped fiber laser with a repetition rate of 100 kHz optimized for effective THz light generation with the output electric field of 1 kV/cm. The present system drastically reduces the measurement time of the THz waveform from several minutes to 10 ms.

Digital coherent receiver based transmitter penalty characterization.

PubMed

Geisler, David J; Kaufmann, John E

2016-12-26

For optical communications links where receivers are signal-power-starved, such as through free-space, it is important to design transmitters and receivers that can operate as close as practically possible to theoretical limits. A total system penalty is typically assessed in terms of how far the end-to-end bit-error rate (BER) is from these limits. It is desirable, but usually difficult, to determine the division of this penalty between the transmitter and receiver. This paper describes a new rigorous and computationally based method that isolates which portion of the penalty can be assessed against the transmitter. There are two basic parts to this approach: (1) use of a coherent optical receiver to perform frequency down-conversion of a transmitter's optical signal waveform to the electrical domain, preserving both optical field amplitude and phase information, and (2): software-based analysis of the digitized electrical waveform. The result is a single numerical metric that quantifies how close a transmitter's signal waveform is to the ideal, based on its BER performance with a perfect software-defined matched-filter receiver demodulator. A detailed description of applying the proposed methodology to the waveform characterization of an optical burst-mode differential phase-shifted keying (DPSK) transmitter is experimentally demonstrated.

Co-adaptation of Electric Organ Discharges and Chirps in South American Ghost Knifefishes (Apteronotidae)

PubMed Central

Petzold, Jacquelyn M.; Marsat, Gary; Smith, G. Troy

2016-01-01

Animal communication signals that simultaneously share the same sensory channel are likely to coevolve to maximize the transmission of each signal component. Weakly electric fish continuously produce a weakly electric field that functions in communication. Fish modulate the electric organ discharge (EOD) on short timescales to produce context-specific signals called chirps. EODs and chirps are simultaneously detected by electroreceptors and processed in the electrosensory system. We analyzed these signals, first to explore whether EOD waveform is encoded in the signal received by electroreceptors and then to examine how EODs and chirps interact to influence conspicuousness. Our findings show that gross discrimination of sinusoidal from complex EOD waveforms is feasible for all species, but fine discrimination of waveform may be possible only for species with waveforms of intermediate complexity. The degree of chirp frequency modulation and chirp relative decay strongly influenced chirp conspicuousness, but other chirp parameters were less influential. The frequency difference between the interacting EODs also strongly impacted chirp conspicuousness. Finally, we developed a method for creating hybrid chirp/EOD combinations to independently analyze the impact of chirp species, EOD species, and EOD difference frequency on chirp conspicuousness. All three components and their interactions strongly influenced chirp conspicuousness, which suggests that evolutionary changes in parameters of either chirps or EODs are likely to influence chirp detection. Examining other environmental factors such as noise created by fish movement and species-typical patterns of sociality may enrich our understanding of how interacting EODs affect the detection and discrimination of chirps across species. PMID:27989653

The development of the miniaturized waveform receiver with the function measuring Antenna Impedance in space plasmas

NASA Astrophysics Data System (ADS)

Ishii, H.; Kojima, H.; Fukuhara, H.; Okada, S.; Yamakawa, H.

2012-04-01

Plasma wave is one of the most essential physical quantities in the solar terrestrial physics. The role of plasma wave receiver onboard satellites is to detect plasma waves in space with a good signal to noise ratio. There are two types of plasma wave receivers, the sweep frequency analyzer and the waveform capture. While the sweep frequency analyzer provides plasma wave spectra, the waveform capture obtains waveforms with phase information that is significant in studying nonlinear phenomena. Antenna sensors to observe electric fields of the plasma waves show different features in plasmas from in vacuum. The antenna impedances have specific characteristics in the frequency domain because of the dispersion of plasmas. These antenna impedances are expressed with complex number. We need to know not only the antenna impedances but also the transfer functions of plasma wave receiver's circuits in order to calibrate observed waveforms precisely. The impedances of the electric field antennas are affected by a state of surrounding plasmas. Since satellites run through various regions with different plasma parameters, we precisely should measure the antenna impedances onboard spacecraft. On the contrary, we can obtain the plasma density and by measuring the antenna impedances. Several formulas of the antenna impedance measurement system were proposed. A synchronous detection method is used on the BepiColombo Mercury Magnetospheric Orbiter (MMO), which will be launched in 2014. The digital data are stored in the onboard memory. They are read out and converted to the analog waveforms by D/A converter. They are fed into the input of the preamplifiers of antenna sensors through a resistor. We can calculate a transfer function of the circuit by applying the synchronous detection method to the output waveform from waveform receivers and digital data as a signal source. The size of this system is same as an A5 board. In recent years, Application Specific Integrated Circuit (ASIC) is in attention which is a technique to integrate large scale and complicated circuits. Lots of ASICs have been applied to high energy astrophysics. In this paper, we show our attempt to miniaturize the antennas impedances measurement system and Waveform Capture using the analogue ASIC. We design 8bits segment D/A converter that is implemented inside the waveform receiver ASIC chip. We improve input logic of the D/A converter to generate very weak signals accurately. The designed chip realizes the measurement of the antenna impedance as well as the waveform observation in the board size of business cards.

Quantum control via a genetic algorithm of the field ionization pathway of a Rydberg electron

NASA Astrophysics Data System (ADS)

Gregoric, Vincent C.; Kang, Xinyue; Liu, Zhimin Cheryl; Rowley, Zoe A.; Carroll, Thomas J.; Noel, Michael W.

2017-08-01

Quantum control of the pathway along which a Rydberg electron field ionizes is experimentally and computationally demonstrated. Selective field ionization is typically done with a slowly rising electric field pulse. The (1/n*)4 scaling of the classical ionization threshold leads to a rough mapping between arrival time of the electron signal and principal quantum number of the Rydberg electron. This is complicated by the many avoided level crossings that the electron must traverse on the way to ionization, which in general leads to broadening of the time-resolved field ionization signal. In order to control the ionization pathway, thus directing the signal to the desired arrival time, a perturbing electric field produced by an arbitrary wave-form generator is added to a slowly rising electric field. A genetic algorithm evolves the perturbing field in an effort to achieve the target time-resolved field ionization signal.

Sonic spectrometer and treatment system

DOEpatents

Slomka, B.J.

1997-06-03

A novel system and method is developed for treating an object with sonic waveforms. A traveling broad-band sonic waveform containing a broad-band of sonic frequencies is radiated at the object. A traveling reflected sonic waveform containing sonic frequencies reflected by the object is received in response to the traveling broad-band sonic waveform. A traveling transmitted sonic waveform containing sonic frequencies transmitted through the object is also received in response to the traveling broad-band sonic waveform. In a resonance mode, the frequency spectra of the broad-band and reflected sonic waveforms is analyzed so as to select one or more sonic frequencies that cause the object to resonate. An electrical resonance treatment sonic waveform containing the sonic frequencies that cause the object to resonate is then radiated at the object so as to treat the object. In an absorption mode, the frequency spectra of the electrical broad-band, reflected, and transmitted sonic waveforms is compared so as to select one or more sonic frequencies that are absorbed by the object. An electrical absorption treatment sonic waveform containing the sonic frequencies that are absorbed by the object is then radiated at the object so as to treat the object. 1 fig.

Sonic spectrometer and treatment system

DOEpatents

Slomka, Bogdan J.

1997-06-03

A novel system and method for treating an object with sonic waveforms. A traveling broad-band sonic waveform containing a broad-band of sonic frequencies is radiated at the object. A traveling reflected sonic waveform containing sonic frequencies reflected by the object is received in response to the traveling broad-band sonic waveform. A traveling transmitted sonic waveform containing sonic frequencies transmitted through the object is also received in response to the traveling broad-band sonic waveform. In a resonance mode, the frequency spectra of the broad-band and reflected sonic waveforms is analyzed so as to select one or more sonic frequencies that cause the object to resonate. An electrical resonance treatment sonic waveform containing the sonic frequencies that cause the object to resonate is then radiated at the object so as to treat the object. In an absorption mode, the frequency spectra of the electrical broad-band, reflected, and transmitted sonic waveforms is compared so as to select one or more sonic frequencies that are absorbed by the object. An electrical absorption treatment sonic waveform containing the sonic frequencies that are absorbed by the object is then radiated at the object so as to treat the object.

Measured close lightning leader-step electric-field-derivative waveforms.

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

Jordan, Doug M.; Hill, Dustin; Biagi, Christopher J.

2010-12-01

We characterize the measured electric field-derivative (dE/dt) waveforms of lightning stepped-leader steps from three negative lightning flashes at distances of tens to hundreds of meters. Electromagnetic signatures of leader steps at such close distances have rarely been documented in previous literature. Individual leader-step three-dimensional locations are determined by a dE/dt TOA system. The leader-step field derivative is typically a bipolar pulse with a sharp initial half-cycle of the same polarity as that of the return stroke, followed by an opposite polarity overshoot that decays relatively slowly to background level. This overshoot increases in amplitude relative to the initial peak andmore » becomes dominant as range decreases. The initial peak is often preceded by a 'slow front,' similar to the slow front that precedes the fast transition to peak in first return stroke dE/dt and E waveforms. The overall step-field waveform duration is typically less than 1 {micro}s. The mean initial peak of dE/dt, range-normalized to 100 km, is 7.4 V m{sup -1} {micro}s{sup -1} (standard deviation (S.D.), 3.7 V m{sup -1} {micro}s{sup -1}, N = 103), the mean half-peak width is 33.5 ns (S.D., 11.9 ns, N = 69), and the mean 10-to-90% risetime is 43.6 ns (S.D., 24.2 ns, N = 69). From modeling, we determine the properties of the leader step currents which produced two typical measured field derivatives, and we use one of these currents to calculate predicted leader step E and dE/dt as a function of source range and height, the results being in good agreement with our observations. The two modeled current waveforms had maximum rates of current rise-to-peak near 100 kA {micro}s{sup -1}, peak currents in the 5-7 kA range, current half-peak widths of about 300 ns, and charge transfers of {approx}3 mC. As part of the modeling, those currents were propagated upward at 1.5 x 10{sup 8} m s{sup -1}, with their amplitudes decaying exponentially with a decay height constant of 25 m.« less

Converter topologies for common mode voltage reduction

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

Rodriguez, Fernando

An inverter includes a three-winding transformer, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, and an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adaptedmore » to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid. At least two of the DC-AC inverter, the cycloconverter, or the active filter are electrically coupled via a common reference electrical interconnect.« less

The Galileo plasma wave investigation

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Kurth, W. S.; Shaw, R. R.; Roux, A.; Gendrin, R.; Kennel, C. F.; Scarf, F. L.; Shawhan, S. D.

1992-01-01

The purpose of the Galileo plasma wave investigation is to study plasma waves and radio emissions in the magnetosphere of Jupiter. The plasma wave instrument uses an electric dipole antenna to detect electric fields, and two search coil magnetic antennas to detect magnetic fields. The frequency range covered is 5 Hz to 5.6 MHz for electric fields and 5 Hz to 160 kHz for magnetic fields. Low time-resolution survey spectrums are provided by three on-board spectrum analyzers. In the normal mode of operation the frequency resolution is about 10 percent, and the time resolution for a complete set of electric and magnetic field measurements is 37.33 s. High time-resolution spectrums are provided by a wideband receiver. The wideband receiver provides waveform measurements over bandwidths of 1, 10, and 80 kHz. Compared to previous measurements at Jupiter this instrument has several new capabilities. These new capabilities include (1) both electric and magnetic field measurements to distinguish electrostatic and electromagnetic waves, (2) direction finding measurements to determine source locations, and (3) increased bandwidth for the wideband measurements.

High-field asymmetric waveform ion mobility spectrometry for mass spectrometry-based proteomics.

PubMed

Swearingen, Kristian E; Moritz, Robert L

2012-10-01

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an atmospheric pressure ion mobility technique that separates gas-phase ions by their behavior in strong and weak electric fields. FAIMS is easily interfaced with electrospray ionization and has been implemented as an additional separation mode between liquid chromatography (LC) and mass spectrometry (MS) in proteomic studies. FAIMS separation is orthogonal to both LC and MS and is used as a means of on-line fractionation to improve the detection of peptides in complex samples. FAIMS improves dynamic range and concomitantly the detection limits of ions by filtering out chemical noise. FAIMS can also be used to remove interfering ion species and to select peptide charge states optimal for identification by tandem MS. Here, the authors review recent developments in LC-FAIMS-MS and its application to MS-based proteomics.

Efficient Charge Collection in Coplanar-Grid Radiation Detectors

NASA Astrophysics Data System (ADS)

Kunc, J.; Praus, P.; Belas, E.; Dědič, V.; Pekárek, J.; Grill, R.

2018-05-01

We model laser-induced transient-current waveforms in radiation coplanar-grid detectors. Poisson's equation is solved by the finite-element method and currents induced by a photogenerated charge are obtained using the Shockley-Ramo theorem. The spectral response on a radiation flux is modeled by Monte Carlo simulations. We show a 10 × improved spectral resolution of the coplanar-grid detector using differential signal sensing. We model the current waveform dependence on the doping, depletion width, diffusion, and detector shielding, and their mutual dependence is discussed in terms of detector optimization. The numerical simulations are successfully compared to experimental data, and further model simplifications are proposed. The space charge below electrodes and a nonhomogeneous electric field on a coplanar-grid anode are found to be the dominant contributions to laser-induced transient-current waveforms.

Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields.

PubMed

Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

2016-06-21

An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform's size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke's brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

Dynamic properties of micro-magnetic noise in soft ferromagnetic materials

NASA Astrophysics Data System (ADS)

Stupakov, A.; Perevertov, A.

2018-06-01

Dynamic response of magnetic hysteresis, magnetic Barkhausen noise and magneto-acoustic emission in a soft ribbon and electrical steels was studied comprehensively. The measurements were performed under controllable magnetization conditions: sinusoidal/triangular waveforms of the magnetic induction and a triangular waveform of the magnetic field. Magnetizing frequency was varied in a wide range: fmag = 0.5 - 500 and 0.5-100 Hz for the ribbon and the electrical steels, respectively. Magnetization amplitude was fixed on a near-saturation level Hmax ≃ 100 A/m. Barkhausen noise signal was detected by a sample-wrapping/surface-mounted coil and differently filtered. It was found that intensity of the Barkhausen noise rises approximately as a square root function of the magnetizing frequency. Whereas, level of the magneto-acoustic emission follows the hysteresis loss trend with an additional linear term (classical loss component).

Optimum Waveforms for Differential Ion Mobility Spectrometry (FAIMS)

PubMed Central

Shvartsburg, Alexandre A.; Smith, Richard D.

2009-01-01

Differential mobility spectrometry or field asymmetric waveform ion mobility spectrometry (FAIMS) is a new tool for separation and identification of gas-phase ions, particularly in conjunction with mass-spectrometry. In FAIMS, ions are filtered by the difference between mobilities in gases (K) at high and low electric field intensity (E) using asymmetric waveforms. An infinite number of possible waveform profiles make maximizing the performance within engineering constraints a major issue for FAIMS technology refinement. Earlier optimizations assumed the non-constant component of mobility to scale as E2, producing the same result for all ions. Here we show that the optimum profiles are defined by the full series expansion of K(E) that includes terms beyond the 1st that is proportional to E2. For many ion/gas pairs, the first two terms have different signs, and the optimum profiles at sufficiently high E in FAIMS may differ substantially from those previously reported, improving the resolving power by up to 2.2 times. This situation arises for some ions in all FAIMS systems, but becomes more common in recent miniaturized devices that employ higher E. With realistic K(E) dependences, the maximum waveform amplitude is not necessarily optimum and reducing it by up to ∼20 – 30% is beneficial in some cases. The present findings are particularly relevant to targeted analyses where separation depends on the difference between K(E) functions for specific ions. PMID:18585054

Feasibility of Higher-Order Differential Ion Mobility Separations Using New Asymmetric Waveforms

PubMed Central

Shvartsburg, Alexandre A.; Mashkevich, Stefan V.; Smith, Richard D.

2011-01-01

Technologies for separating and characterizing ions based on their transport properties in gases have been around for three decades. The early method of ion mobility spectrometry (IMS) distinguished ions by absolute mobility that depends on the collision cross section with buffer gas atoms. The more recent technique of field asymmetric waveform IMS (FAIMS) measures the difference between mobilities at high and low electric fields. Coupling IMS and FAIMS to soft ionization sources and mass spectrometry (MS) has greatly expanded their utility, enabling new applications in biomedical and nanomaterials research. Here, we show that time-dependent electric fields comprising more than two intensity levels could, in principle, effect an infinite number of distinct differential separations based on the higher-order terms of expression for ion mobility. These analyses could employ the hardware and operational procedures similar to those utilized in FAIMS. Methods up to the 4th or 5th order (where conventional IMS is 1st order and FAIMS is 2nd order) should be practical at field intensities accessible in ambient air, with still higher orders potentially achievable in insulating gases. Available experimental data suggest that higher-order separations should be largely orthogonal to each other and to FAIMS, IMS, and MS. PMID:16494377

The plasma wave experiment (PWE) on board the Arase (ERG) Satellite Initial results and collaboration with the ground network stations and Van Allen Probes

NASA Astrophysics Data System (ADS)

Kasahara, Y.; Matsuda, S.; Kasaba, Y.; Kojima, H.; Tsuchiya, F.; Kumamoto, A.; Ozaki, M.; Yagitani, S.; Ishisaka, K.; Miyoshi, Y.; Hikishima, M.; Kitahara, M.; Katoh, Y.; Ota, M.; Kurita, S.; Shoji, M.; Imachi, T.; Teramoto, M.; Matsuoka, A.; Shinohara, I.; Hosokawa, K.; Ogawa, Y.; Shiokawa, K.; Kadokura, A.; Wygant, J. R.; Kletzing, C.

2017-12-01

The ERG (Exploration of energization and Radiation in Geospace) project is a mission to study acceleration and loss mechanisms of relativistic electrons around the Earth. To achieve comprehensive observations of plasma/particles, fields, and waves, the Arase satellite was launched on December 20, 2016. The Plasma Wave Experiment (PWE) is one of scientific instruments on board Arase. It measures electric field from DC to 10 MHz by the wire-probe antennas (WPT), and magnetic field from a few Hz to 100 kHz by the magnetic search coils (MSC). Three kinds of receivers are implemented in the PWE; EFD (Electric Field Detector), OFA/WFC (Onboard Frequency Analyzer and Waveform Capture), and HFA (High Frequency Analyzer). Several kinds of operational modes are implemented in the PWE, and the telemetry data consists of several kinds of data such as power spectrum, waveform, spectral matrix and DC E-field. The Arase has started nominal scientific operation in March 2017. Varieties of wave phenomena such as chorus, EMIC, and lightning whistlers have been successfully observed by the PWE. The wave activities are sometimes correlated with drastic variation of electron density derived from UHR frequency along the trajectory. We have also conducted cooperative observations with the ground-based stations, Van Allen Probes and the other satellites in the magnetosphere. During these conjunction periods, we intensively conducted the PWE burst mode operations, by which waveforms were continuously captured and once stored in the mission data recorder (MDR). The data stored in the MDP were selected and downloaded to the tracking stations according to the decision of the stakeholders of the campaign observation. In the presentation, we introduce the initial observation results of the PWE as well as quick report on the conjunction studies with the ground network stations and Van Allen Probes. Acknowledgements: We are greatly indebted to Mitsubishi Heavy Industries Ltd. for their fabrication and total arrangement of the PWE, to Meisei Electric Co. Ltd. for their fabrication of the HFA, and to NIPPI Co. Ltd. for their fabrication of the WPT, MSC and mast.

Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry

NASA Technical Reports Server (NTRS)

Willett, J. C.; LeVine, D. M.; Idone, V. P.

2006-01-01

Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and electric-field-change waveforms measured at a range of 5.2 kilometers for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the rise times, propagation speeds, and amplitudes of relative light intensity for comparison with the electrical inferences. Results include the following: 1) The fine structure of the field-change waveforms that were radiated by these subsequent return strokes can be explained, in large part, by channel geometry. 2) The average 10 - 90% rise time of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 plus or minus 0.17 microseconds at the surface to an inferred 2.2 plus or minus 0.5 microcseconds at 1 kilometer path length above the surface. 3) The three-dimensional propagation speed of the current front averaged 1.80 plus or minus 0.24 X 10(exp 8) meters per second over channel lengths typically greater than 1 kilometer. 4) Assuming that the measured current was entirely due to the return stroke forced an unreasonably large and abrupt reduction in inferred current amplitude over the first few tens of meters above the surface, especially in cases when the leader was bright relative to its stroke. Therefore, a significant fraction of the current at the surface was probably due to the leader, at least in such cases. 5) Peak return-stroke currents decreased by approximately 37 plus or minus 12% from 100 meters to 1 kilometer of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, we are unable to infer the variation of current amplitude near the ground.

High Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) for Mass Spectrometry-Based Proteomics

PubMed Central

Swearingen, Kristian E.; Moritz, Robert L.

2013-01-01

SUMMARY High field asymmetric waveform ion mobility spectrometry (FAIMS) is an atmospheric pressure ion mobility technique that separates gas-phase ions by their behavior in strong and weak electric fields. FAIMS is easily interfaced with electrospray ionization and has been implemented as an additional separation mode between liquid chromatography (LC) and mass spectrometry (MS) in proteomic studies. FAIMS separation is orthogonal to both LC and MS and is used as a means of on-line fractionation to improve detection of peptides in complex samples. FAIMS improves dynamic range and concomitantly the detection limits of ions by filtering out chemical noise. FAIMS can also be used to remove interfering ion species and to select peptide charge states optimal for identification by tandem MS. Here, we review recent developments in LC-FAIMS-MS and its application to MS-based proteomics. PMID:23194268

Experimental and analytic studies of the triggered lightning environment of the F106B

NASA Technical Reports Server (NTRS)

Rudolph, Terence; Easterbrook, Calvin C.; Ng, Poh H.; Haupt, Robert W.; Perala, Rodney A.

1987-01-01

The triggered lightning environment of the F106B aircraft is investigated. Scale modeling of the F106B with a metallized model was done to measure electric field enhancement factors on the aircraft and on canonically shaped conducting objects. These are then compared to numerically determined quantities. Detailed numerical modeling is done of the development of the triggered lightning channel. This is done using nonlinear air chemistry models to model a variety of physical phenomena which occur in a triggered lightning event. The effect of a triggered lightning strike on internal wires in the F106B is investigated using finite difference models and transmission line models to calculate the electromagnetic coupling of lightning currents through seams and joints of the aircraft to internal cables. Time domain waveforms are computed and compared to measured waveforms. The effect of thunderstorm particles on the initial triggering of a lightning strike is investigated. The electric field levels needed to cause air breakdown in the presence and absence of thunderstorm particles are calculated. This is done as a function of the size, shape, and density of the particles.

Energy-optimal electrical excitation of nerve fibers.

PubMed

Jezernik, Saso; Morari, Manfred

2005-04-01

We derive, based on an analytical nerve membrane model and optimal control theory of dynamical systems, an energy-optimal stimulation current waveform for electrical excitation of nerve fibers. Optimal stimulation waveforms for nonleaky and leaky membranes are calculated. The case with a leaky membrane is a realistic case. Finally, we compare the waveforms and energies necessary for excitation of a leaky membrane in the case where the stimulation waveform is a square-wave current pulse, and in the case of energy-optimal stimulation. The optimal stimulation waveform is an exponentially rising waveform and necessitates considerably less energy to excite the nerve than a square-wave pulse (especially true for larger pulse durations). The described theoretical results can lead to drastically increased battery lifetime and/or decreased energy transmission requirements for implanted biomedical systems.

Voltages induced on a power distribution line by overhead cloud lightning

NASA Technical Reports Server (NTRS)

Yacoub, Ziad; Rubinstein, Marcos; Uman, Martin A.; Thomson, Ewen M.; Medelius, Pedro J.

1991-01-01

Voltages induced by overhead cloud lightning on a 448 m open circuited power distribution line and the corresponding north-south component of the lightning magnetic field were simultaneously measured at the NASA Kennedy Space Center during the summer of 1986. The incident electric field was calculated from the measured magnetic field. The electric field was then used as an input to the computer program, EMPLIN, that calculated the voltages at the two ends of the power line. EMPLIN models the frequency domain field/power coupling theory found, for example, in Ianoz et al. The direction of the source, which is also one of the inputs to EMPLIN, was crudely determined from a three station time delay technique. The authors found reasonably good agreement between calculated and measured waveforms.

Improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Jiang, Xiongwei; Peng, Qingjun; Sun, Potao

2018-05-01

Electrical breakdown is an important physical phenomenon in electrical equipment and electronic devices. Many related models and theories of electrical breakdown have been proposed. However, a widely recognized understanding on the following phenomenon is still lacking: impulse breakdown strength which varies with waveform parameters, decrease in the breakdown strength of AC voltage with increasing frequency, and higher impulse breakdown strength than that of AC. In this work, an improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers is proposed based on the Harmonic oscillator model. Simulation and experimental results show that, the energy of trapped charges obtained from AC stress is higher than that of impulse voltage, and the absorbed activation energy increases with the increase in the electric field frequency. Meanwhile, the frequency-dependent relative dielectric constant ε r and dielectric loss tanδ also affect the absorption of activation energy. The absorbed activation energy and modified trap level synergistically determine the breakdown strength. The mechanism analysis of breakdown strength under various voltage waveforms is consistent with the experimental results. Therefore, the proposed model of activation energy absorption in the present work may provide a new possible method for analyzing and explaining the breakdown phenomenon in semi-crystalline insulating polymers.

Interaction of Low Frequency External Electric Fields and Pancreatic β-Cell: A Mathematical Modeling Approach to Identify the Influence of Excitation Parameters.

PubMed

Farashi, Sajjad; Sasanpour, Pezhman; Rafii-Tabar, Hashem

2018-05-24

Purpose-Although the effect of electromagnetic fields on biological systems has attracted attraction in recent years, there has not been any conclusive result concerning the effects of interaction and the underlying mechanisms involved. Besides the complexity of biological systems, the parameters of the applied electromagnetic field have not been estimated in most of the experiments. Material and Method-In this study, we have used computational approach in order to find the excitation parameters of an external electric field which produces sensible effects in the function of insulin secretory machinery, whose failure triggers the diabetes disease. A mathematical model of the human β-cell has been used and the effects of external electric fields with different amplitudes, frequencies and wave shapes have been studied. Results-The results from our simulations show that the external electric field can influence the membrane electrical activity and perhaps the insulin secretion when its amplitude exceeds a threshold value. Furthermore, our simulations reveal that different waveforms have distinct effects on the β-cell membrane electrical activity and the characteristic features of the excitation like frequency would change the interaction mechanism. Conclusion-The results could help the researchers to investigate the possible role of the environmental electromagnetic fields on the promotion of diabetes disease.

XM-1 Tank EMP Susceptibility and Survivability Test Program and Plan

DTIC Science & Technology

1980-11-01

electric field vector. The Vertical EMP Electromagnetic interference (EMI) shielding Simulator ( VEMPS ) produces a non-threat- is used on cable...polarized fields in the VEMPS to determine 2.3 Oveiall Program Activity Flow 5 , bulk current waveforms on interior cabling Figure 1 (p. 8) expresses...measured. The vertically polarized VEMPS the ground, it is not readily obvious how the will be used to measure harness sheath cur- currents on the

Converter topologies and control

DOEpatents

Rodriguez, Fernando; Qin, Hengsi; Chapman, Patrick

2018-05-01

An inverter includes a transformer that includes a first winding, a second winding, and a third winding, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adapted to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid.

Aligned Carbon Nanotube Tape for Sensor Applications

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.

2013-01-01

For this effort, will concentrate on three applications: Vibration Gyroscope utilizes piezoelectric properties of the tape and Coriolis effect Accelerometer utilizes the piezoresistive property Strain Gauge utilizes piezoresistive property Accelerometer and Strain Gauge can also utilize piezoelectric effect Test piezoelectric properties using facilities at the Microfabrication Laboratory (AMRDEC) . Enhance piezoelectric effect using polyvinylidine fluoride and P(VDF ]TrFE) which is readily polarizable .Spray matrix solution while winding fiber; Sandwich of CNT tape and PVDF film (DOE .Two Level) . Construct and test prototype vibration gyroscope . Construct and test prototype accelerometer using cantilever design . Test strain sensitivity of CNT tape against industrial strain gauge . Embed CNT tape in composite samples as well as on surface and test to failure (4 ]point bend) A piezoelectric device exhibits an electrical response from a mechanical applied stress. . A piezoelectric device has both capacitance and resistance properties in which by applying an electric field from a waveform will exert a mechanical stress that can be monitored for a response. . The typical waveform applied is a sinusoidal waveform of a defined voltage for a defined period. The defined voltage is driven from 0 volts to the positive defined volts then back to 0 and driven to negative defined volts then back to 0. . Example. Vmax set to 10V and period set to 10 ms. . Voltage will start at zero, go to 10 volts, return to zero, go to ]10 volts and return to zero during 10 ms. . Applying this electrical field to a DUT, the capacitance response and resistance response can be observed. CNT tape is easier to manufacture and cheaper than micromachining silicon or other ceramic piezoelectric used in gyroscopes and accelerometers CNT tape properties can be modified during manufacture for specific application CNT tape has enhanced mechanical and thermal properties in addition to unique electrical properties CNT tape as a strain gauge in Structural Health Monitoring will provide an excellent material to embed within composite structures

Waveform generation in the weakly electric fish Gymnotus coropinae (Hoedeman): the electric organ and the electric organ discharge.

PubMed

Castelló, María E; Rodríguez-Cattáneo, Alejo; Aguilera, Pedro A; Iribarne, Leticia; Pereira, Ana Carolina; Caputi, Angel A

2009-05-01

This article deals with the electric organ and its discharge in Gymnotus coropinae, a representative species of one of the three main clades of the genus. Three regions with bilateral symmetry are described: (1) subopercular (medial and lateral columns of complex shaped electrocytes); (2) abdominal (medial and lateral columns of cuboidal and fusiform electrocytes); and (3) main [four columns, one dorso-lateral (containing fusiform electrocytes) and three medial (containing cuboidal electrocytes)]. Subopercular electrocytes are all caudally innervated whereas two of the medial subopercular ones are also rostrally innervated. Fusiform electrocytes are medially innervated at the abdominal portion, and at their rostral and caudal poles at the main portion. Cuboidal electrocytes are always caudally innervated. The subopercular portion generates a slow head-negative wave (V(1r)) followed by a head-positive spike (V(3r)). The abdominal and main portions generate a fast tetra-phasic complex (V(2345ct)). Since subopercular components prevail in the near field and the rest in the far field, time coincidence of V(3r) with V(2) leads to different waveforms depending on the position of the receiver. This confirms the splitting hypothesis of communication and exploration channels based on the different timing, frequency band and reach of the regional waveforms. The following hypothesis is compatible with the observed anatomo-functional organization: V(1r) corresponds to the rostral activation of medial subopercular electrocytes and V(3r) to the caudal activation of all subopercular electrocytes; V(2), and part of V(3ct), corresponds to the successive activation of the rostral and caudal poles of dorso-lateral fusiform electrocytes; and V(345ct) is initiated in the caudal face of cuboidal electrocytes by synaptic activation (V(3ct)) and it is completed (V(45ct)) by the successive activation of rostral and caudal faces by the action currents evoked in the opposite face.

100 GHz pulse waveform measurement based on electro-optic sampling

NASA Astrophysics Data System (ADS)

Feng, Zhigang; Zhao, Kejia; Yang, Zhijun; Miao, Jingyuan; Chen, He

2018-05-01

We present an ultrafast pulse waveform measurement system based on an electro-optic sampling technique at 1560 nm and prepare LiTaO3-based electro-optic modulators with a coplanar waveguide structure. The transmission and reflection characteristics of electrical pulses on a coplanar waveguide terminated with an open circuit and a resistor are investigated by analyzing the corresponding time-domain pulse waveforms. We measure the output electrical pulse waveform of a 100 GHz photodiode and the obtained rise times of the impulse and step responses are 2.5 and 3.4 ps, respectively.

Characteristics of M-component in rocket-triggered lightning and a discussion on its mechanism

NASA Astrophysics Data System (ADS)

Jiang, Rubin; Qie, Xiushu; Yang, Jing; Wang, Caixia; Zhao, Yang

2013-09-01

The current and electric field pulses associated with M-component following dart leader-return stroke sequences in negative rocket-triggered lightning flashes were analyzed in detail by using the data from Shandong Artificially Triggering Lightning Experiment, conducted from 2005 to 2010. For 63 M-components with current waveforms superimposed on the relatively steady continuing current, the geometric mean values of the peak current, duration, and charge transfer were 276 A, 1.21 ms, and 101 mC, respectively. The behaviors of the channel base current versus close electric field changes and the observation facts by different authors were carefully examined for investigation on mechanism of the M-component. A modified model based on Rakov's "two-wave" theory is proposed and confirms that the evolution of M-component through the lightning channel involves a downward wave transferring negative charge from the upper to the lower channel and an upward wave draining the charge transported by the downward wave. The upward wave serves to deplete the negative charge by the downward wave at its interface and makes the charge density of the channel beneath the interface layer to be roughly zero. Such modified concept is recognized to be reasonable by the simulated results showing a good agreement between the calculated and the measured E-field waveforms.

Electrical neurostimulation with imbalanced waveform mitigates dissolution of platinum electrodes

PubMed Central

Kumsa, Doe; Hudak, Eric M; Montague, Fred W; Kelley, Shawn C; Untereker, Darrel F; Hahn, Benjamin P; Condit, Chris; Cholette, Martin; Lee, Hyowon; Bardot, Dawn; Takmakov, Pavel

2017-01-01

Objective Electrical neurostimulation has traditionally been limited to the use of charge-balanced waveforms. Charge-imbalanced and monophasic waveforms are not used to deliver clinical therapy, because it is believed that these stimulation paradigms may generate noxious electrochemical species that cause tissue damage. Approach In this study, we investigated the dissolution of platinum as one of such irreversible reactions over a range of charge densities up to 160 µC cm−2 with current-controlled first phase, capacitive discharge second phase waveforms of both cathodic-first and anodic-first polarity. We monitored the concentration of platinum in solution under different stimulation delivery conditions including charge-balanced, charge-imbalanced, and monophasic pulses. Main results We observed that platinum dissolution decreased during charge-imbalanced and monophasic stimulation when compared to charge-balanced waveforms. Significance This observation provides an opportunity to re-evaluate the charge-balanced waveform as the primary option for sustainable neural stimulation. PMID:27650936

Non-invasive electrocardiogram detection of in vivo zebrafish embryos using electric potential sensors

NASA Astrophysics Data System (ADS)

Rendon-Morales, E.; Prance, R. J.; Prance, H.; Aviles-Espinosa, R.

2015-11-01

In this letter, we report the continuous detection of the cardiac electrical activity in embryonic zebrafish using a non-invasive approach. We present a portable and cost-effective platform based on the electric potential sensing technology, to monitor in vivo electrocardiogram activity from the zebrafish heart. This proof of principle demonstration shows how electrocardiogram measurements from the embryonic zebrafish may become accessible by using electric field detection. We present preliminary results using the prototype, which enables the acquisition of electrophysiological signals from in vivo 3 and 5 days-post-fertilization zebrafish embryos. The recorded waveforms show electrocardiogram traces including detailed features such as QRS complex, P and T waves.

Modeling Long-Distance ELF Radio Atmospherics Generated by Rocket-Triggered Lightning

NASA Astrophysics Data System (ADS)

Moore, R. C.; Kunduri, B.; Anand, S.; Dupree, N.; Mitchell, M.; Agrawal, D.

2010-12-01

This paper addresses the generation and propagation of radio atmospherics (sferics) radiated by lightning in order to assess the ability to infer the electrical properties of lightning from great distances. This ability may prove to greatly enhance the understanding of lightning processes that are associated with the production of transient luminous events (TLEs) as well as other ionospheric effects associated with lightning. The modeling of the sferic waveform is carried out using a modified version of the Long Wavelength Propagation Capability (LWPC) code developed by the Naval Ocean Systems Center over a period of many years. LWPC is an inherently narrowband propagation code that has been modified to predict the broadband response of the Earth-ionosphere waveguide to an impulsive lightning flash. Unlike other similar efforts, the modified code presented preserves the ability of LWPC to account for waveguide mode-coupling and to account for changes to the electrical properties of the ground and ionosphere along the propagation path. The effort described is conducted in advance of the deployment of a global extremely low frequency (ELF) magnetic field array, which is presently under construction. The global ELF array is centered on the International Center for Lightning Research and Testing (ICLRT) located at Camp Blanding, Florida. The ICLRT is well-known for conducting rocket-triggered lightning experiments over the last 15-20 years. This paper uses lightning current waveforms directly measured at the base of the lightning channel (observations performed at the ICLRT) as an input to the model to predict the sferic waveform to be observed by the array under various ionospheric conditions. An analysis of the predicted sferic waveforms is presented, and the components of the lightning current waveform that most effectively excite the Earth-ionosphere waveguide are identified.

The dE/dt and E Waveforms Radiated by Leader Steps Just Before the First Return Stroke in Cloud-to-Ocean Lightning

NASA Astrophysics Data System (ADS)

Krider, E. P.; Baffou, G.; Murray, N. D.; Willett, J. C.

2004-12-01

We have analyzed the shapes and other characteristics of the electric field, E, and dE/dt waveforms that were radiated by leader steps just before the first return stroke in cloud-to-ocean lightning. dE/dt waveforms were recorded using an 8-bit digitizer sampling at 100 MHz, and an integrated waveform, Eint, was computed by numerically integrating dE/dt and comparing the result with an analog E waveform digitized at 10 MHz. All signals were recorded under conditions where the lightning locations were known and there was minimal distortion in the fields due to the effects of ground-wave propagation. The dE/dt waveforms radiated by leader steps tend to fall into three categories: (1) "simple" - an isolated negative peak that is immediately followed by a positive overshoot (where negative polarity follows the normal physics convention), (2) "double" - two simple waveforms that occur at almost the same time, and (3) "burst" - a complex cluster of pulses with a total duration of about one microsecond. In this paper, we will give examples of each of these waveform types, and we will summarize their characteristics on a submicrosecond time-scale. For example, in an interval starting 9 μ s before to 4 μ s before the largest, negative (dominant) peak in dE/dt peak in the return stroke, 131 first strokes produced a total of 296 impulses with a peak amplitude greater than 10% of the dominant peak, and the average amplitude of these pulses was 0.21 of the dominant peak. The last leader step in a 12 μ s interval before the dominant peak was a simple waveform in 51 first strokes, and in these cases, the average time-interval between the peak dE/dt of the step and the dominant peak of the stroke was 5.8 ± 1.7 μ s, a value that is in good agreement with prior measurements. The median full-width-at-half-maximum (FWHM) of 274 simple Eint signatures was 141 ns, and the associated mean and standard deviation were 187 ± 131 ns.

Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

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

Bruneau, B., E-mail: bastien.bruneau@polytechnique.edu; Johnson, E.; Korolov, I.

2016-04-28

We report investigations of capacitively coupled carbon tetrafluoride (CF{sub 4}) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries stronglymore » influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.« less

Frequency Response Calculations of Input Characteristics of Cavity-Backed Aperture Antennas Using AWE with Hybrid FEM/MoM Technique

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.

1997-01-01

Application of Asymptotic Waveform Evaluation (AWE) is presented in conjunction with a hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique to calculate the input characteristics of cavity-backed aperture antennas over a frequency range. The hybrid FEM/MoM technique is used to form an integro-partial-differential equation to compute the electric field distribution of the cavity-backed aperture antenna. The electric field, thus obtained, is expanded in a Taylor series around the frequency of interest. The coefficients of 'Taylor series (called 'moments') are obtained using the frequency derivatives of the integro-partial-differential Equation formed by the hybrid FEM/MoM technique. Using the moments, the electric field in the cavity is obtained over a frequency range. Using the electric field at different frequencies, the input characteristics of the antenna are obtained over a wide frequency band. Numerical results for an open coaxial line, probe fed cavity, and cavity-backed microstrip patch antennas are presented. Good agreement between AWE and the exact solution over the frequency range is observed.

Electromagnetic phenomena analysis in brushless DC motor with speed control using PWM method

NASA Astrophysics Data System (ADS)

Ciurys, Marek Pawel

2017-12-01

Field-circuit model of a brushless DC motor with speed control using PWM method was developed. Waveforms of electrical and mechanical quantities of the designed motor with a high pressure vane pump built in a rotor of the motor were computed. Analysis of electromagnetic phenomena in the system: single phase AC network - converter - BLDC motor was carried out.

Two Step Acceleration Process of Electrons in the Outer Van Allen Radiation Belt by Time Domain Electric Field Bursts and Large Amplitude Chorus Waves

NASA Astrophysics Data System (ADS)

Agapitov, O. V.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.; Lejosne, S.

2014-12-01

A huge number of different non-linear structures (double layers, electron holes, non-linear whistlers, etc) have been observed by the electric field experiment on the Van Allen Probes in conjunction with relativistic electron acceleration in the Earth's outer radiation belt. These structures, found as short duration (~0.1 msec) quasi-periodic bursts of electric field in the high time resolution electric field waveform, have been called Time Domain Structures (TDS). They can quite effectively interact with radiation belt electrons. Due to the trapping of electrons into these non-linear structures, they are accelerated up to ~10 keV and their pitch angles are changed, especially for low energies (˜1 keV). Large amplitude electric field perturbations cause non-linear resonant trapping of electrons into the effective potential of the TDS and these electrons are then accelerated in the non-homogeneous magnetic field. These locally accelerated electrons create the "seed population" of several keV electrons that can be accelerated by coherent, large amplitude, upper band whistler waves to MeV energies in this two step acceleration process. All the elements of this chain acceleration mechanism have been observed by the Van Allen Probes.

Investigation on magnetoacoustic signal generation with magnetic induction and its application to electrical conductivity reconstruction.

PubMed

Ma, Qingyu; He, Bin

2007-08-21

A theoretical study on the magnetoacoustic signal generation with magnetic induction and its applications to electrical conductivity reconstruction is conducted. An object with a concentric cylindrical geometry is located in a static magnetic field and a pulsed magnetic field. Driven by Lorentz force generated by the static magnetic field, the magnetically induced eddy current produces acoustic vibration and the propagated sound wave is received by a transducer around the object to reconstruct the corresponding electrical conductivity distribution of the object. A theory on the magnetoacoustic waveform generation for a circular symmetric model is provided as a forward problem. The explicit formulae and quantitative algorithm for the electrical conductivity reconstruction are then presented as an inverse problem. Computer simulations were conducted to test the proposed theory and assess the performance of the inverse algorithms for a multi-layer cylindrical model. The present simulation results confirm the validity of the proposed theory and suggest the feasibility of reconstructing electrical conductivity distribution based on the proposed theory on the magnetoacoustic signal generation with magnetic induction.

Effect of gas properties on the dynamics of the electrical slope asymmetry effect in capacitive plasmas: comparison of Ar, H 2 and CF 4

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

Bruneau, Bastien; Lafleur, T.; Gans, T.

2015-12-01

Tailored voltage excitation waveforms provide an efficient control of the ion energy (through the electrical asymmetry effect) in capacitive plasmas by varying the 'amplitude' asymmetry of the waveform. In this work, the effect of a 'slope' asymmetry of the waveform is investigated by using sawtooth-like waveforms, through which the sheath dynamic can be manipulated. A remarkably different discharge dynamic is found for Ar, H 2, and CF 4 gases, which is explained by the different dominant electron heating mechanisms and plasma chemistries. In comparison to Argon we find that the electrical asymmetry can even be reversed by using an electronegativemore » gas such as CF 4. Phase resolved optical emission spectroscopy measurements, probing the spatiotemporal distribution of the excitation rate show excellent agreement with the results of particle-in-cell simulations, confirming the high degree of correlation between the excitation rates with the dominant heating mechanisms in the various gases. It is shown that, depending on the gas used, sawtooth-like voltage waveforms may cause a strong asymmetry.« less

Impact of Steep-Front Short-Duration Impulse on Electric Power System Insulation. Phase 2. Laboratory Evaluation of Selected Power System Components

DTIC Science & Technology

1991-04-01

SEALS - _------ OIL LEVEL STAINLESS STEEL INDICATOR EXPANSION CHAMBER MULTIPLE COMPRESSION GASKET SPRINGS CONDUCTOR RO) UPPER PORCELAIN_ OIL...GENERATED WAVEFORM) FIELD Electric (E) 40 kV/m 50 kV/m 10 kV/m STRENGTH ( FREE SPACE) Magnetic(M) 300 A/m 1000 A/m 300 A/m Rise time 20-500 ns 10 ns 10 ns...Laboratory Interaction Note IN435, 1983. 4. P. R_ Barnes, "The Axial Current Induced on an Infinitely Long, Perfectly Conducting, Circular Cylinder in Free

Amplitude spectral area: predicting the success of electric shock delivered by defibrillators with different waveforms.

PubMed

Nakagawa, Yoshihide; Sato, Yoji; Kojima, Takeshi; Wakabayashi, Tsutomu; Morita, Seiji; Amino, Mari; Inokuchi, Sadaki

2013-07-20

Prolonged ventricular fibrillation (VF) is associated with a low rate of return of spontaneous circulation (ROSC) following electric shock. Moreover, electric shock that does not reestablish spontaneous circulation causes myocardial dysfunction even if ROSC is subsequently achieved. Amplitude spectral area (AMSA), calculated by analysis of VF waveforms immediately before electric shock, is considered to predict the outcome of electric shock. This study aimed to evaluate the prognostic value of AMSA in relation to waveforms of defibrillators in prehospital settings. The AMSA values of 81 patients with VF confirmed by ambulance crews were compared according to the type of defibrillators with different waveforms and between those with and without ROSC. With a biphasic defibrillator, the mean AMSA was significantly different between the 14 patients who achieved ROSC (25.3 ± 9.5 mV-Hz) and the 43 subjects who did not achieve ROSC (15.4 ± 8.1 mV-Hz; p = 0.0006). No significant difference was seen in the corresponding values when a monophasic defibrillator was used, at 19.1 ± 2.4 mV-Hz for 3 ROSC patients and 16.1 ± 7.5mV-Hz for 21 non-ROSC patients. AMSA may serve as a predictive measure for ROSC following electric shock delivered by a biphasic defibrillator.

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms.

PubMed

Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

2015-05-01

We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

Method and apparatus for resonant frequency waveform modulation

DOEpatents

Taubman, Matthew S [Richland, WA

2011-06-07

A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

PubMed

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

Characterization of Direct Current-Electrical Penetration Graph Waveforms and Correlation With the Probing Behavior of Matsumuratettix hiroglyphicus (Hemiptera: Cicadellidae), the Insect Vector of Sugarcane White Leaf Phytoplasma.

PubMed

Roddee, J; Kobori, Y; Yorozuya, H; Hanboonsong, Y

2017-06-01

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is an important vector of phytoplasma causing white leaf disease in sugarcane. Thus, the aim of our study was to understand and describe the stylet-probing activities of this vector while feeding on sugarcane plants, by using direct current (DC) electrical penetration graph (EPG) monitoring. The EPG signals were classified into six distinct waveforms, according to amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into the host plant tissues (probing). These six EPG waveforms of probing behavior comprise no stylet penetration (NP); stylet pathway through epidermis, mesophyll, and parenchymal cells (waveform A); contact at the bundle sheath layer (waveform B); salivation into phloem sieve elements (waveform C); phloem sap ingestion (waveform D); and short ingestion time of xylem sap (waveform E). The above waveform patterns were correlated with histological data of salivary sheath termini in plant tissue generated from insect stylet tips. The key findings of this study were that M. hiroglyphicus ingests the phloem sap at a relatively higher rate and for longer duration from any other cell type, suggesting that M. hiroglyphicus is mainly a phloem-feeder. Quantitative comparison of probing behavior revealed that females typically probe more frequently and longer in the phloem than males. Thus, females may acquire and inoculate greater amounts of phytoplasma than males, enhancing the efficiency of phytoplasma transmission and potentially exacerbating disease spreading. Overall, our study provides basic information on the probing behavior and transmission mechanism of M. hiroglyphicus. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Characteristics of negative lightning leaders to ground observed by TVLS

NASA Astrophysics Data System (ADS)

Qiu, Shi; Jiang, Zhidong; Shi, Lihua; Niu, Zhencong; Zhang, Peng

2015-12-01

The Thunder and VHF lightning Locating System (termed TVLS) is established and utilized to observe leader behaviors of negative cloud to ground (CG) flashes. This system takes advantages of VHF broadband interferometer and thunder imaging technique, which could provide the temporal and quasi-3D spatial evolution of lightning discharges. In conjunction with synchronized electric field changes (E-changes) and electric field derivatives (dE/dt) records, 10 leaders from two CG flashes are presented and analyzed. Based on the characteristic evolution of leader velocities, E-changes, dE/dt waveforms and VHF intervals, three stepped leaders, five dart leaders and two dart-stepped leaders are identified. The stepped leaders behave impulsive while approaching ground, with average speed (1.3∼3.9)×105 m/s. All normal dart leaders presented here exhibit irregular (or termed "chaotic") fluctuations in E-change and dE/dt waveforms, with the similar speeds ((1.0∼2.9)×107 m/s) and durations ((300∼700) μs) of the "chaotic" leaders observed by other investigators. The irregular fluctuations would be weak if the channels keep conductive until the leader enters the less conductive branches, coinciding with VHF radiations in time sequence. The dart-stepped leader could be divided into the dart stage and the stepped stage by a transition region, which usually lies around the branch junctions of previous active channel. The dart stage resembles the normal dart leader, and the stepped stage usually associates with regular pulse trains in E-change and dE/dt waveforms.

Circuit for detecting initial systole and dicrotic notch. [for monitoring arterial pressure

NASA Technical Reports Server (NTRS)

Gebben, V. D.; Webb, J. A., Jr. (Inventor)

1974-01-01

Circuitry is disclosed for processing an arterial pressure waveform to produce during any one cycle a pulse corresponding to the initial systole and a pulse corresponding to the dicrotic notch. In a first channel, an electrical analog of the arterial pressure waveform is filtered and then compared to the original waveform to produce an initial systole signal. In a second channel, the analog is differentiated, filtered, and fed through a gate controlled by pulses from the first channel to produce an electrical pulse corresponding to the dicrotic notch.

Coincident Observation of Lightning using Spaceborne Spectrophotometer and Ground-Level Electromagnetic Sensors

NASA Technical Reports Server (NTRS)

Adachi, Toru; Cohen, Morris; Li, Jingbo; Cummer, Steve; Blakeslee, Richard; Marshall, THomas; Stolzenberg, Maribeth; Karunarathne, Sumedhe; Hsu, Rue-Ron; Su, Han-Tzong;

Radiation from lightning return strokes over a finitely conducting earth

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Gesell, L.; Kao, Michael

1986-01-01

The effects of the conductivity of the earth on radiation from lightning return strokes are examined theoretically using a piecewise linear transmission line model for the return stroke. First, calculations are made of the electric field radiated during the return stroke, and then this electric field is used to compute the response of conventional AM radio receivers and electric field change systems during the return stroke. The calculations apply to the entire transient waveform (they are not restricted to the initial portions of the return stroke) and yield fast field changes and RF radiation in agreement with measurements made during real lightning. This research was motivated by measurements indicating that a time delay exists between the time of arrival of the fast electric field change and the RF radiation from first return strokes. The time delay is on the order of 20 microsec for frequencies in the HF-UHF range for lightning in Florida. The time delay is obtained theoretically in this paper. It occurs when both the effects of attenuation due to conductivity of the earth, and the finite velocity of propagation of the current pulse up the return stroke channel, are taken into account in the model.

Sub-nanosecond resolution electric field measurements during ns pulse breakdown in ambient air

NASA Astrophysics Data System (ADS)

Simeni Simeni, Marien; Goldberg, Ben; Gulko, Ilya; Frederickson, Kraig; Adamovich, Igor V.

2018-01-01

Electric field during ns pulse discharge breakdown in ambient air has been measured by ps four-wave mixing, with temporal resolution of 0.2 ns. The measurements have been performed in a diffuse plasma generated in a dielectric barrier discharge, in plane-to-plane geometry. Absolute calibration of the electric field in the plasma is provided by the Laplacian field measured before breakdown. Sub-nanosecond time resolution is obtained by using a 150 ps duration laser pulse, as well as by monitoring the timing of individual laser shots relative to the voltage pulse, and post-processing four-wave mixing signal waveforms saved for each laser shot, placing them in the appropriate ‘time bins’. The experimental data are compared with the analytic solution for time-resolved electric field in the plasma during pulse breakdown, showing good agreement on ns time scale. Qualitative interpretation of the data illustrates the effects of charge separation, charge accumulation/neutralization on the dielectric surfaces, electron attachment, and secondary breakdown. Comparison of the present data with more advanced kinetic modeling is expected to provide additional quantitative insight into air plasma kinetics on ~ 0.1-100 ns scales.

The efficacy of electrical stimulation in lower extremity cutaneous wound healing: A systematic review.

PubMed

Ashrafi, Mohammed; Alonso-Rasgado, Teresa; Baguneid, Mohamed; Bayat, Ardeshir

2017-02-01

Current gold standard lower extremity cutaneous wound management is not always effective. Cutaneous wounds generate a "current of injury" which is directly involved in wound healing processes. Application of exogenous electrical stimulation has been hypothesised to imitate the natural electric current that occurs in cutaneous wounds. The aim of this extensive review was to provide a detailed update on the variety of electrical stimulation modalities used in the management of lower extremity wounds. Several different waveforms and delivery methods of electrical stimulation have been used. Pulsed current appears superior to other electrical modalities available. The majority of studies support the beneficial effects of pulsed current over conservative management of lower extremity cutaneous wounds. Although it appears to have no benefit over causal surgical intervention, it is a treatment option which could be utilised in those patients unsuitable for surgery. Other waveforms and modalities appear promising; however, they still lack large trial data to recommend a firm conclusion with regards to their use. Current studies also vary in quantity, quality and protocol across the different modalities. The ideal electrical stimulation device needs to be non-invasive, portable and cost-effective and provides minimal interference with patients' daily life. Further studies are necessary to establish the ideal electrical stimulation modality, parameters, method of delivery and duration of treatment. The development and implementation of newer devices in the management of acute and chronic wounds provides an exciting direction in the field of electrotherapy. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Electro-optic sampling of near-infrared waveforms

NASA Astrophysics Data System (ADS)

Keiber, Sabine; Sederberg, Shawn; Schwarz, Alexander; Trubetskov, Michael; Pervak, Volodymyr; Krausz, Ferenc; Karpowicz, Nicholas

2016-03-01

Access to the complete electric field evolution of a laser pulse is essential for attosecond science in general, and for the scrutiny and control of electron phenomena in solid-state physics specifically. Time-resolved field measurements are routine in the terahertz spectral range, using electro-optic sampling (EOS), photoconductive switches and field-induced second harmonic generation. EOS in particular features outstanding sensitivity and ease of use, making it the basis of time-resolved spectroscopic measurements for studying charge carrier dynamics and active optical devices. In this Letter, we show that careful optical filtering allows the bandwidth of this technique to be extended to wavelengths as short as 1.2 μm (230 THz) with half-cycle durations 2.3 times shorter than the sampling pulse. In a proof-of-principle application, we measure the influence of optical parametric amplification (OPA) on the electric field dynamics of a few-cycle near-infrared (NIR) pulse.

High pressure effects in high-field asymmetric waveform ion mobility spectrometry.

PubMed

Wang, Yonghuan; Wang, Xiaozhi; Li, Lingfen; Chen, Chilai; Xu, Tianbai; Wang, Tao; Luo, Jikui

2016-08-30

High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) is an analytical technique based on the principle of non-linear electric field dependence of coefficient of mobility of ions for separation that was originally conceived in the Soviet Union in the early 1980s. Being well developed over the past decades, FAIMS has become an efficient method for the separation and characterization of gas-phase ions at ambient pressure, often in air, to detect trace amounts of chemical species including explosives, toxic chemicals, chemical warfare agents and other compounds. However the resolution of FAIMS and ion separation capability need to be improved for more applications of the technique. The effects of above-ambient pressure varying from 1 to 3 atm on peak position, resolving power, peak width, and peak intensity are investigated theoretically and experimentally using micro-fabricated planar FAIMS in purified air. Peak positions, varying with pressure in a way as a function of dispersion voltage, could be simplified by expressing both compensation and dispersion fields in Townsend units for E/N, the ratio of electric field intensity (E) to the gas number density (N). It is demonstrated that ion Townsend-scale peak positions remain unchanged for a range of pressures investigated, implying that the higher the pressure is, stronger compensation and separation fields are needed within limits of air breakdown field. Increase in pressure is found to separate ions that could not be distinguished in ambient pressure, which could be interpreted as the differentials of ions' peak compensation voltage expanded wider than the dilation of peak widths leading to resolving power enhancement with pressure. Increase in pressure can also result in an increase in peak intensity. Copyright © 2016 John Wiley & Sons, Ltd.

Ion pump as Brownian motor: theory of electroconformational coupling and proof of ratchet mechanism for Na,K-ATPase action

NASA Astrophysics Data System (ADS)

Tsong, Tian Yow; Chang, Cheng-Hung

2003-04-01

This article reviews some concepts of the Brownian Ratchet which are relevant to our discussion of mechanisms of action of Na,K-ATPase, a universal ion pump and an elemental motor protein of the biological cell. Under wide ranges of ionic compositions it can hydrolyze an ATP and use the γ-phosphorous bond energy of ATP to pump 3 Na + out of, and 2 K + into the cell, both being uphill transport. During the ATP-dependent pump cycle, the enzyme oscillates between E1 and E2 states. Our experiment replaces ATP with externally applied electric field of various waveforms, amplitudes, and frequencies. The field enforced-oscillation, or fluctuation of E1 and E2 states enables the enzyme to harvest energy from the applied field and convert it to the chemical gradient energy of cations. A theory of electroconformational coupling (TEC), which embodies all the essential features of the Brownian Ratchet, successfully simulates these experimental results. Our analysis based on a four-state TEC model indicates that the equilibrium and the rate constants of the transport system define the frequency and the amplitude of the field for the optimal activation. Waveform, frequency, and amplitude are three elements of signal. Thus, electric signal of the ion pump is found by TEC analysis of the experimental data. Electric noise (white) superimposed on an electric signal changes the pump efficiency and produces effects similar to the stochastic resonance reported in other biological systems. The TEC concept is compared with the most commonly used Michaelis-Menten enzyme mechanism (MME) for similarities and differences. Both MME and TEC are catalytic wheels, which recycle the catalyst in each turnover. However, a MME can only catalyze reaction of descending free energy while a TEC enzyme can catalyze reaction of ascending free energy by harvesting needed energy from an off-equilibrium electric noise. The TEC mechanism is shown to be applicable to other biological motors and engines, as well. Deterministic and non-deterministic noise is examined in reference to future extension of the TEC model for biological transduction of free energy.

Development of a full-waveform voltage and current recording device for multichannel transient electromagnetic transmitters

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Zhang, Qisheng; Wang, Meng; Kong, Qiang; Zhang, Shengquan; He, Ruihao; Liu, Shenghui; Li, Shuhan; Yuan, Zhenzhong

2017-11-01

Due to the pressing demand for metallic ore exploration technology in China, several new technologies are being employed in the relevant exploration instruments. In addition to possessing the high resolution of the traditional transient electromagnetic method, high-efficiency measurements, and a short measurement time, the multichannel transient electromagnetic method (MTEM) technology can also sensitively determine the characteristics of a low-resistivity geologic body, without being affected by the terrain. Besides, the MTEM technology also solves the critical, existing interference problem in electrical exploration technology. This study develops a full-waveform voltage and current recording device for MTEM transmitters. After continuous acquisition and storage of the large, pseudo-random current signals emitted by the MTEM transmitter, these signals are then convoluted with the signals collected by the receiver to obtain the earth's impulse response. In this paper, the overall design of the full-waveform recording apparatus, including the hardware and upper-computer software designs, the software interface display, and the results of field test, is discussed in detail.

Maximizing fluid delivered by bubble-free electroosmotic pump with optimum pulse voltage waveform.

PubMed

Tawfik, Mena E; Diez, Francisco J

2017-03-01

In generating high electroosmotic (EO) flows for use in microfluidic pumps, a limiting factor is faradaic reactions that are more pronounced at high electric fields. These reactions lead to bubble generation at the electrodes and pump efficiency reduction. The onset of gas generation for high current density EO pumping depends on many parameters including applied voltage, working fluid, and pulse duration. The onset of gas generation can be delayed and optimized for maximum volume pumped in the minimum time possible. This has been achieved through the use of a novel numerical model that predicts the onset of gas generation during EO pumping using an optimized pulse voltage waveform. This method allows applying current densities higher than previously reported. Optimal pulse voltage waveforms are calculated based on the previous theories for different current densities and electrolyte molarity. The electroosmotic pump performance is investigated by experimentally measuring the fluid volume displaced and flow rate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of Waveform Structure Features on Time Domain Target Recognition under Cross Polarization

NASA Astrophysics Data System (ADS)

Selver, M. A.; Seçmen, M.; Zoral, E. Y.

2016-08-01

Classification of aircraft targets from scattered electromagnetic waves is a challenging application, which suffers from aspect angle dependency. In order to eliminate the adverse effects of aspect angle, various strategies were developed including the techniques that rely on extraction of several features and design of suitable classification systems to process them. Recently, a hierarchical method, which uses features that take advantage of waveform structure of the scattered signals, is introduced and shown to have effective results. However, this approach has been applied to the special cases that consider only a single planar component of electric field that cause no-cross polarization at the observation point. In this study, two small scale aircraft models, Boeing-747 and DC-10, are selected as the targets and various polarizations are used to analyse the cross-polarization effects on system performance of the aforementioned method. The results reveal the advantages and the shortcomings of using waveform structures in time-domain target identification.

Unintended effects of electrofishing on nongame fishes

USGS Publications Warehouse

Miranda, Leandro E.; Kidwell, R. H.

2010-01-01

Most studies of injury associated with electrofishing have focused on game fishes, but few have given attention to cohabiting small nongame species. Under controlled laboratory conditions, we subjected small nongame cyprinids, ictalurids, and percids to a wide range of voltages and waveforms to examine potential harmful effects. Fish were treated with power levels distributed uniformly between the thresholds required to immobilize game fish and also were subjected multiple times to those thresholds to simulate the range of conditions that might exist in a heterogeneous electrical field formed during electrofishing in field situations. Across waveforms and species, the incidence of hemorrhages averaged 2% (range = 0–20%), the incidence of spinal injuries averaged 6% (range = 0–30%), and mortality averaged 16% (range = 0–90%). Continuous DC was generally less harmful than pulsed-DC waveforms; hemorrhages and spinal injuries tended to increase with high pulse frequencies, and mortalities tended to increase with low pulse frequencies. Ambiguities in the results were apparent, suggesting that some species may experience extensive harm, whereas others may not. Given the potential to harm numerically small populations and populations of imperiled species, we suggest (1) expanded efforts to overcome the power limitations that prevent effective use of continuous-DC electrofishing in many field situations and (2) pilot studies at geographic locations where numerically small populations of nongame species may be a concern.

Accurate calibration of waveform data measured by the Plasma Wave Experiment on board the ARASE satellite

NASA Astrophysics Data System (ADS)

Kitahara, M.; Katoh, Y.; Hikishima, M.; Kasahara, Y.; Matsuda, S.; Kojima, H.; Ozaki, M.; Yagitani, S.

2017-12-01

The Plasma Wave Experiment (PWE) is installed on board the ARASE satellite to measure the electric field in the frequency range from DC to 10 MHz, and the magnetic field in the frequency range from a few Hz to 100 kHz using two dipole wire-probe antennas (WPT) and three magnetic search coils (MSC), respectively. In particular, the Waveform Capture (WFC), one of the receivers of the PWE, can detect electromagnetic field waveform in the frequency range from a few Hz to 20 kHz. The Software-type Wave Particle Interaction Analyzer (S-WPIA) is installed on the ARASE satellite to measure the energy exchange between plasma waves and particles. Since S-WPIA uses the waveform data measured by WFC to calculate the relative phase angle between the wave magnetic field and velocity of energetic electrons, the high-accuracy is required to calibration of both amplitude and phase of the waveform data. Generally, the calibration procedure of the signal passed through a receiver consists of three steps; the transformation into spectra, the calibration by the transfer function of a receiver, and the inverse transformation of the calibrated spectra into the time domain. Practically, in order to reduce the side robe effect, a raw data is filtered by a window function in the time domain before applying Fourier transform. However, for the case that a first order differential coefficient of the phase transfer function of the system is not negligible, the phase of the window function convoluted into the calibrated spectra is shifted differently at each frequency, resulting in a discontinuity in the time domain of the calibrated waveform data. To eliminate the effect of the phase shift of a window function, we suggest several methods to calibrate a waveform data accurately and carry out simulations assuming simple sinusoidal waves as an input signal and using transfer functions of WPT, MSC, and WFC obtained in pre-flight tests. In consequence, we conclude that the following two methods can reduce an error contaminated through the calibration to less than 0.1 % of amplitude of input waves; (1) a Turkey-type window function with a flat top region of one-third of the window length and (2) modification of the window function for each frequency by referring the estimation of the phase shift due to the first order differential coefficient from the transfer functions.

Optically activated switches for the generation of complex electrical waveforms with multigigahertz bandwidth

NASA Astrophysics Data System (ADS)

Skeldon, Mark D.; Okishev, Andrey V.; Letzring, Samuel A.; Donaldson, William R.; Green, Kenton; Seka, Wolf D.; Fuller, Lynn F.

1995-01-01

An electrical pulse-generation system using two optically activated Si photoconductive switches can generate shaped electrical pulses with multigigahertz bandwidth. The Si switches are activated by an optical pulse whose leading edge is steepened by stimulated Brillouin scattering (SBS) in CCl4. With the bandwidth generated by the SBS process, a laser having a 1- to 3-ns pulse width is used to generate electrical pulses with approximately 80-ps rise times (approximately 4-GHz bandwidth). Variable impedance microstrip lines are used to generate complex electrical waveforms that can be transferred to a matched load with minimal loss of bandwidth.

Nonlinear effective permittivity of field grading composite dielectrics

NASA Astrophysics Data System (ADS)

Yang, Xiao; Zhao, Xiaolei; Li, Qi; Hu, Jun; He, Jinliang

2018-02-01

Field grading composite dielectrics with good nonlinear electrical properties can function as smart materials for electrical field control in a high-voltage apparatus. Besides the well-documented nonlinear conducting behavior, the field-dependent effective permittivity of field grading composites were also reported; however, in-depth research on the mechanism and influencing factors of this nonlinear permittivity are absent. This paper theoretically discusses the origin of the nonlinear effective permittivity, and the mechanism is illustrated through the waveform analysis of the nonlinear response of ZnO microvaristor/silicone rubber composites under a pure AC field. The field-dependent effective permittivity and loss property of the ZnO composites are measured by a dielectric spectrometer in both DC and AC fields under different frequencies. Through comparison of measurement results and theoretical models, the influence of the filler concentration, frequency, and time domain characteristics of the applied field on the nonlinear permittivity of the field grading composites are well explained. This paper provides insight into the nonlinear permittivity of field grading composites, and will be helpful for further tuning the performance of field grading composites.

Application of AWE Along with a Combined FEM/MoM Technique to Compute RCS of a Cavity-Backed Aperture in an Infinite Ground Plane Over a Frequency Range

NASA Technical Reports Server (NTRS)

Reddy, C.J.; Deshpande, M.D.

1997-01-01

A hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique in conjunction with the Asymptotic Waveform Evaluation (AWE) technique is applied to obtain radar cross section (RCS) of a cavity-backed aperture in an infinite ground plane over a frequency range. The hybrid FEM/MoM technique when applied to the cavity-backed aperture results in an integro-differential equation with electric field as the unknown variable, the electric field obtained from the solution of the integro-differential equation is expanded in Taylor series. The coefficients of the Taylor series are obtained using the frequency derivatives of the integro-differential equation formed by the hybrid FEM/MoM technique. The series is then matched via the Pade approximation to a rational polynomial, which can be used to extrapolate the electric field over a frequency range. The RCS of the cavity-backed aperture is calculated using the electric field at different frequencies. Numerical results for a rectangular cavity, a circular cavity, and a material filled cavity are presented over a frequency range. Good agreement between AWE and the exact solution over the frequency range is obtained.

High-resolution moisture profiles from full-waveform probabilistic inversion of TDR signals

NASA Astrophysics Data System (ADS)

Laloy, Eric; Huisman, Johan Alexander; Jacques, Diederik

2014-11-01

This study presents an novel Bayesian inversion scheme for high-dimensional undetermined TDR waveform inversion. The methodology quantifies uncertainty in the moisture content distribution, using a Gaussian Markov random field (GMRF) prior as regularization operator. A spatial resolution of 1 cm along a 70-cm long TDR probe is considered for the inferred moisture content. Numerical testing shows that the proposed inversion approach works very well in case of a perfect model and Gaussian measurement errors. Real-world application results are generally satisfying. For a series of TDR measurements made during imbibition and evaporation from a laboratory soil column, the average root-mean-square error (RMSE) between maximum a posteriori (MAP) moisture distribution and reference TDR measurements is 0.04 cm3 cm-3. This RMSE value reduces to less than 0.02 cm3 cm-3 for a field application in a podzol soil. The observed model-data discrepancies are primarily due to model inadequacy, such as our simplified modeling of the bulk soil electrical conductivity profile. Among the important issues that should be addressed in future work are the explicit inference of the soil electrical conductivity profile along with the other sampled variables, the modeling of the temperature-dependence of the coaxial cable properties and the definition of an appropriate statistical model of the residual errors.

Electroosmotic flow in microchannels with arbitrary geometry and arbitrary distribution of wall charge.

PubMed

Xuan, Xiangchun; Li, Dongqing

2005-09-01

General solutions are developed for direct current (DC) and alternating current (AC) electroosmotic flows in microfluidic channels with arbitrary cross-sectional geometry and arbitrary distribution of wall charge (zeta potential). The applied AC electric field can also be of arbitrary waveform. By proposing a nondimensional time scale varpi defined as the ratio of the diffusion time of momentum across the electric double-layer thickness to the period of the applied electric field, we demonstrate analytically that the Helmholtz-Smoluchowski electroosmotic velocity is an appropriate slip condition for AC electroosmotic flows in typical microfluidic applications. With this slip condition approach, electroosmotic flows in rectangular and asymmetric trapezoidal microchannels with nonuniform wall charge, as examples, are investigated. The unknown constants in the proposed general solutions are numerically determined with a least-squares method through matching the boundary conditions. We find that the wall charge affects significantly the electroosmotic flow while the channel geometry does not. Moreover, the flow feature is characterized by another nondimensional time scale Omega defined as the ratio of the diffusion time of momentum across the channel hydraulic radius to the period of the applied electric field. The onset of phase shift between AC electroosmotic velocity and applied electric field is also examined analytically.

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.

Toward a terahertz-driven electron gun

PubMed Central

Huang, W. Ronny; Nanni, Emilio A.; Ravi, Koustuban; Hong, Kyung-Han; Fallahi, Arya; Wong, Liang Jie; Keathley, Phillip D.; Zapata, Luis E.; Kärtner, Franz X.

2015-01-01

Femtosecond electron bunches with keV energies and eV energy spread are needed by condensed matter physicists to resolve state transitions in carbon nanotubes, molecular structures, organic salts, and charge density wave materials. These semirelativistic electron sources are not only of interest for ultrafast electron diffraction, but also for electron energy-loss spectroscopy and as a seed for x-ray FELs. Thus far, the output energy spread (hence pulse duration) of ultrafast electron guns has been limited by the achievable electric field at the surface of the emitter, which is 10 MV/m for DC guns and 200 MV/m for RF guns. A single-cycle THz electron gun provides a unique opportunity to not only achieve GV/m surface electric fields but also with relatively low THz pulse energies, since a single-cycle transform-limited waveform is the most efficient way to achieve intense electric fields. Here, electron bunches of 50 fC from a flat copper photocathode are accelerated from rest to tens of eV by a microjoule THz pulse with peak electric field of 72 MV/m at 1 kHz repetition rate. We show that scaling to the readily-available GV/m THz field regime would translate to monoenergetic electron beams of ~100 keV. PMID:26486697

Electric field studies: TLE-induced waveforms and ground conductivity impact on electric field propagation

NASA Astrophysics Data System (ADS)

Farges, Thomas; Garcia, Geraldine; Blanc, Elisabeth

2010-05-01

We review in this paper main results obtained from electric field (from VLF to HF) measurement campaigns realized by CEA in the framework of the Eurosprite program [Neubert et al., 2005, 2008] from 2003 to 2009 in France in different configurations. Two main topics have been studied: sprite or elve induced phenomena (radiation or perturbation) and wave propagation. Using a network of 4 stations, VLF radiations from sprite have been successfully located at 10 km from the sprite parent lightning, in agreement with possible sprite location, generally displaced from the parent lightning. The MF (300 kHz - 3 MHz) source bursts were identified simultaneously with the occurrence of sprites observed with cameras [Farges et al., 2004; Neubert et al., 2008]. These observations are compared to recent broadband measurements, assumed to be due to relativistic electron beam radiation related to sprites [Fullekrug et al., 2009]. Recently, in 2009, with a new instrumentation, an ELF tail has been clearly measured after the lightning waveform, while sprites were observed at about 500 km from our station. This ELF tail is usually observed at distances higher than thousand km and is associated to sprite generation. This opens the capacity to measure the charge moment of the parent-lightning, using such measurement close to the source. Farges et al. [2007] showed that just after a lightning return stroke, a strong transient attenuation is very frequently observed in the MF waves of radio transmissions. They showed that this perturbation is due to heating of the lower ionosphere by the lightning-induced EMP during few milliseconds. These perturbations are then the MF radio signature of the lightning EMP effects on the lower ionosphere, in the same way as elves correspond to their optical signature. The experiment also provided the electric field waveforms directly associated to elves, while lightning were not detected by Météorage. Many of them present a double peak feature. The propagation of the electromagnetic waves generated by lightning has also been studied in the frequency range 1 kHz-1MHz at distances lower than 1000 km from the lightning source. A propagation model has been developed to determine the ground waves which propagate in a homogenous medium using the analytical expression given by Maclean and Wu [1993]. This approach takes into account the electric finite conductivity and the fact that the Earth is spherical, which allow us to deal with over-the-horizon propagation. We installed in 2008 four stations which were more or less aligned - the maximum distance between two stations was about 870 km. Two stations were located close to the Mediterranean Sea and the two others inside the continent, at the centre of France. This station distribution and the observation period (from August to December) allowed statistical and physical studies, such as the influence of the electric conductivity on wave propagation. Comparison of electric field spectra, measured after propagation only over sea and only over ground, showed clearly the effects of ground conductivity on propagation. Comparison between observations and modelling has been used to evaluate the ground conductivity. In the future we will implement the sky-wave inside our model and validate it with the database.

The electric field changes and UHF radiations caused by the triggered lightning in Japan

NASA Technical Reports Server (NTRS)

Kawasaki, Zen-Ichiro; Kanao, Tadashi; Matsuura, Kenji; Nakano, Minoru; Horii, Kenji; Nakamura, Koichi

1991-01-01

In the rocket triggered lightning experiment of fiscal 1989, researchers observed electromagnetic field changes and UHF electromagnetic radiation accompanying rocket triggered lightning. It was found that no rapid changes corresponding to the return stroke of natural lightning were observed in the electric field changes accompanying rocket triggered lightning. However, continuous currents were present. In the case of rocket triggered lightning to the tower, electromagnetic field changes corresponding to the initiation of triggered lightning showed a bipolar pulse of a relatively large amplitude. In contrast, the rocket triggered lightning to the ground did not have such a bipolar pulse. The UHF radiation accompanying the rocket triggered lightning preceded the waveform portions corresponding to the first changes in electromagnetic fields. The number of isolated pulses in the UHF radiation showed a correlation with the time duration from rocket launching up to triggered lightning. The time interval between consecutive isolated pulses tended to get shorter with the passage of time, just like the stepped leaders of natural lightning.

Optimum Operating Conditions for PZT Actuators for Vibrotactile Wearables

NASA Astrophysics Data System (ADS)

Logothetis, Irini; Matsouka, Dimitra; Vassiliadis, Savvas; Vossou, Clio; Siores, Elias

2018-04-01

Recently, vibrotactile wearables have received much attention in fields such as medicine, psychology, athletics and video gaming. The electrical components presently used to generate vibration are rigid; hence, the design and creation of ergonomical wearables are limited. Significant advances in piezoelectric components have led to the production of flexible actuators such as piezoceramic lead zirconate titanate (PZT) film. To verify the functionality of PZT actuators for use in vibrotactile wearables, the factors influencing the electromechanical conversion were analysed and tested. This was achieved through theoretical and experimental analyses of a monomorph clamped-free structure for the PZT actuator. The research performed for this article is a three-step process. First, a theoretical analysis presents the equations governing the actuator. In addition, the eigenfrequency of the film was analysed preceding the experimental section. For this stage, by applying an electric voltage and varying the stimulating electrical characteristics (i.e., voltage, electrical waveform and frequency), the optimum operating conditions for a PZT film were determined. The tip displacement was measured referring to the mechanical energy converted from electrical energy. From the results obtained, an equation for the mechanical behaviour of PZT films as actuators was deduced. It was observed that the square waveform generated larger tip displacements. In conjunction with large voltage inputs at the predetermined eigenfrequency, the optimum operating conditions for the actuator were achieved. To conclude, PZT films can be adapted to assist designers in creating comfortable vibrotactile wearables.

Optimum Operating Conditions for PZT Actuators for Vibrotactile Wearables

NASA Astrophysics Data System (ADS)

Logothetis, Irini; Matsouka, Dimitra; Vassiliadis, Savvas; Vossou, Clio; Siores, Elias

2018-07-01

Recently, vibrotactile wearables have received much attention in fields such as medicine, psychology, athletics and video gaming. The electrical components presently used to generate vibration are rigid; hence, the design and creation of ergonomical wearables are limited. Significant advances in piezoelectric components have led to the production of flexible actuators such as piezoceramic lead zirconate titanate (PZT) film. To verify the functionality of PZT actuators for use in vibrotactile wearables, the factors influencing the electromechanical conversion were analysed and tested. This was achieved through theoretical and experimental analyses of a monomorph clamped-free structure for the PZT actuator. The research performed for this article is a three-step process. First, a theoretical analysis presents the equations governing the actuator. In addition, the eigenfrequency of the film was analysed preceding the experimental section. For this stage, by applying an electric voltage and varying the stimulating electrical characteristics (i.e., voltage, electrical waveform and frequency), the optimum operating conditions for a PZT film were determined. The tip displacement was measured referring to the mechanical energy converted from electrical energy. From the results obtained, an equation for the mechanical behaviour of PZT films as actuators was deduced. It was observed that the square waveform generated larger tip displacements. In conjunction with large voltage inputs at the predetermined eigenfrequency, the optimum operating conditions for the actuator were achieved. To conclude, PZT films can be adapted to assist designers in creating comfortable vibrotactile wearables.

Linear bunchers and half-frequency bunching method

NASA Astrophysics Data System (ADS)

Tang, J. Y.; Jiang, J. Z.; Shi, A. M.; Yin, Z. K.; Wang, Y. F.

2000-12-01

A new buncher system consisting of two bunchers has been designed and constructed for HIRFL injector cyclotron, working at the SFC acceleration modes of H=1 and H=3, respectively. The bunchers use saw-tooth RF waveform, but with double-gap drift tube electrodes and single-gap grid electrodes, respectively. The special merit of the design is introduction of the half-frequency bunching mode, utilizing half of the cyclotron RF frequency. With this method, a perfect longitudinal match between the injector SFC and the main cyclotron SSC has been reached theoretically, compared to the original efficiency of 50% for most cases. Detailed studies have been made concerning space charge effects, longitudinal dispersions through the yoke hole and the spiral inflector, and non-linearity in both the RF waveform and the stray electric field of electrodes.

System Design of One-chip Wave Particle Interaction Analyzer for SCOPE mission.

NASA Astrophysics Data System (ADS)

Fukuhara, Hajime; Ueda, Yoshikatsu; Kojima, Hiro; Yamakawa, Hiroshi

In past science spacecrafts such like GEOTAIL, we usually capture electric and magnetic field waveforms and observe energetic eletron and ion particles as velocity distributions by each sensor. We analyze plasma wave-particle interactions by these respective data and the discussions are sometimes restricted by the difference of time resolution and by the data loss in desired regions. One-chip Wave Particle Interaction Analyzer (OWPIA) conducts direct quantitative observations of wave-particle interaction by direct 'E dot v' calculation on-board. This new instruments have a capability to use all plasma waveform data and electron particle informations. In the OWPIA system, we have to calibrate the digital observation data and transform the same coordinate system. All necessary calculations are processed in Field Programmable Gate Array(FPGA). In our study, we introduce a basic concept of the OWPIA system and a optimization method for each calculation functions installed in FPGA. And we also discuss the process speed, the FPGA utilization efficiency, the total power consumption.

Definition of Shifts of Optical Transitions Frequencies due to Pulse Perturbation Action by the Photon Echo Signal Form

NASA Astrophysics Data System (ADS)

Lisin, V. N.; Shegeda, A. M.; Samartsev, V. V.

2015-09-01

A relative phase shift between the different groups of excited dipoles, which appears as result of its frequency splitting due to action of a pulse of electric or magnetic fields, depends on a time, if the pulse overlaps in time with echo-pulse. As а consequence, the echo waveform is changed. The echo time form is modulated. The inverse modulation period well enough approximates Zeeman and pseudo-Stark splitting in the cases of magnetic and, therefore, electrical fields. Thus the g-factors of ground 4I15/2 and excited 4F9/2 optical states of Er3+ ion in LuLiF4 and YLiF4 have been measured and pseudo-Stark shift of R1 line in ruby has been determined.

Influence of strike object grounding on close lightning electric fields

NASA Astrophysics Data System (ADS)

Baba, Yoshihiro; Rakov, Vladimir A.

2008-06-01

Using the finite difference time domain (FDTD) method, we have calculated vertical electric field Ez, horizontal (radial) electric field Eh, and azimuthal magnetic field Hϕ produced on the ground surface by lightning strikes to 160-m- and a 553-m-high conical strike objects representing the Peissenberg tower (Germany) and the CN Tower (Canada), respectively. The fields were computed for a typical subsequent stroke at distances d' from the bottom of the object ranging from 5 to 100 m for the 160-m tower and from 10 to 300 m for the 553-m tower. Grounding of the 160-m object was assumed to be accomplished by its underground basement represented by a 10-m-radius and 8-m-long perfectly conducting cylinder with or without a reference ground plane located 2 m below. The reference ground plane simulates, to some extent, a higher-conducting ground layer that is expected to exist below the water table. The configuration without reference ground plane actually means that this plane is present, but is located at an infinitely large depth. Grounding of the 553-m object was modeled in a similar manner but in the absence of reference ground plane only. In all cases considered, waveforms of Eh and Hϕ are not much influenced by the presence of strike object, while waveforms of Ez are. Waveforms of Ez are essentially unipolar (as they are in the absence of strike object) when the ground conductivity σ is 10 mS/m (the equivalent transient grounding impedance is several ohms) or greater. Thus, for the CN Tower, for which σ ≥ 10 mS/m, the occurrence of Ez polarity change is highly unlikely. For the 160-m tower and for σ = 1 and 0.1 mS/m, waveforms of Ez become bipolar (exhibit polarity change) at d' ≤ 10 m and d' ≤ 50 m, respectively, regardless of the presence of the reference ground plane. The corresponding equivalent transient grounding impedances are about 30 and 50 Ω in the absence of the reference ground plane and smaller than 10 Ω in the presence of the reference ground plane. The source of opposite polarity Ez is the potential rise at the object base (at the air/ground interface) relative to the reference ground plane. For a given grounding electrode geometry, the strength of this source increases with decreasing σ, provided that the grounding impedance is linear. Potential rises at the strike object base for σ = 1 and 0.1 mS/m are some hundreds of kilovolts, which is sufficient to produce electrical breakdown from relatively sharp edges of the basement over a distance of several meters (or more) along the ground surface. The resultant ground surface arcs will serve to reduce the equivalent grounding impedance and, hence, potential rise. Therefore, the polarity change of Ez near the Peissenberg tower, for which σ is probably about 1 mS/m, should be a rare phenomenon, if it occurs at all. The equivalent transient grounding impedance of the cylindrical basement is similar to that of a hemispherical grounding electrode of the same radius. For the 160-m tower and for hemispherical grounding electrode, the transient grounding impedance is higher than its dc grounding resistance for σ = 10 and 1 mS/m, but lower for σ = 0.1 mS/m. For the 553-m tower, the transient grounding impedance of hemispherical electrode is equal to or larger than its dc resistance for all values of σ considered.

Charge and energy minimization in electrical/magnetic stimulation of nervous tissue

NASA Astrophysics Data System (ADS)

Jezernik, Sašo; Sinkjaer, Thomas; Morari, Manfred

2010-08-01

In this work we address the problem of stimulating nervous tissue with the minimal necessary energy at reduced/minimal charge. Charge minimization is related to a valid safety concern (avoidance and reduction of stimulation-induced tissue and electrode damage). Energy minimization plays a role in battery-driven electrical or magnetic stimulation systems (increased lifetime, repetition rates, reduction of power requirements, thermal management). Extensive new theoretical results are derived by employing an optimal control theory framework. These results include derivation of the optimal electrical stimulation waveform for a mixed energy/charge minimization problem, derivation of the charge-balanced energy-minimal electrical stimulation waveform, solutions of a pure charge minimization problem with and without a constraint on the stimulation amplitude, and derivation of the energy-minimal magnetic stimulation waveform. Depending on the set stimulus pulse duration, energy and charge reductions of up to 80% are deemed possible. Results are verified in simulations with an active, mammalian-like nerve fiber model.

Charge and energy minimization in electrical/magnetic stimulation of nervous tissue.

PubMed

Jezernik, Saso; Sinkjaer, Thomas; Morari, Manfred

2010-08-01

In this work we address the problem of stimulating nervous tissue with the minimal necessary energy at reduced/minimal charge. Charge minimization is related to a valid safety concern (avoidance and reduction of stimulation-induced tissue and electrode damage). Energy minimization plays a role in battery-driven electrical or magnetic stimulation systems (increased lifetime, repetition rates, reduction of power requirements, thermal management). Extensive new theoretical results are derived by employing an optimal control theory framework. These results include derivation of the optimal electrical stimulation waveform for a mixed energy/charge minimization problem, derivation of the charge-balanced energy-minimal electrical stimulation waveform, solutions of a pure charge minimization problem with and without a constraint on the stimulation amplitude, and derivation of the energy-minimal magnetic stimulation waveform. Depending on the set stimulus pulse duration, energy and charge reductions of up to 80% are deemed possible. Results are verified in simulations with an active, mammalian-like nerve fiber model.

A unified engineering model of the first stroke in downward negative lightning

NASA Astrophysics Data System (ADS)

Nag, Amitabh; Rakov, Vladimir A.

2016-03-01

Each stroke in a negative cloud-to-ground lightning flash is composed of downward leader and upward return stroke processes, which are usually modeled individually. The first stroke leader is stepped and starts with preliminary breakdown (PB) which is often viewed as a separate process. We present the first unified engineering model for computing the electric field produced by a sequence of PB, stepped leader, and return stroke processes, serving to transport negative charge to ground. We assume that a negatively charged channel extends downward in a stepped fashion during both the PB and leader stages. Each step involves a current wave that propagates upward along the newly formed channel section. Once the leader attaches to ground, an upward propagating return stroke neutralizes the charge deposited along the channel. Model-predicted electric fields are in reasonably good agreement with simultaneous measurements at both near (hundreds of meters, electrostatic field component is dominant) and far (tens of kilometers, radiation field component is dominant) distances from the lightning channel. Relations between the features of computed electric field waveforms and model input parameters are examined. It appears that peak currents associated with PB pulses are similar to return stroke peak currents, and the observed variation of electric radiation field peaks produced by leader steps at different heights above ground is influenced by the ground corona space charge.

Application of AWE for RCS Frequency Response Calculations Using Method of Moments

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.

1996-01-01

An implementation of the Asymptotic Waveform Evaluation (AWE) technique is presented for obtaining the frequency response of the Radar Cross Section (RCS) of arbitrarily shaped, three-dimensional perfect electric conductor (PEC) bodies. An Electric Field Integral Equation (EFIE) is solved using the Method of Moments (MoM) to compute the RCS. The electric current, thus obtained, is expanded in a Taylor series around the frequency of interest. The coefficients of the Taylor series (called 'moments') are obtained using the frequency derivatives of the EFIE. Using the moments, the electric current on the PEC body is obtained over a frequency band. Using the electric current at different frequencies, RCS of the PEC body is obtained over a wide frequency band. Numerical results for a square plate, a cube, and a sphere are presented over a bandwidth. A good agreement between AWE and the exact solution over the bandwidth is observed.

Food restriction promotes signaling effort in response to social challenge in a short-lived electric fish.

PubMed

Gavassa, Sat; Stoddard, Philip K

2012-09-01

Vertebrates exposed to stressful conditions release glucocorticoids to sustain energy expenditure. In most species elevated glucocorticoids inhibit reproduction. However individuals with limited remaining reproductive opportunities cannot afford to forgo reproduction and should resist glucocorticoid-mediated inhibition of reproductive behavior. The electric fish Brachyhypopomus gauderio has a single breeding season in its lifetime, thus we expect males to resist glucocorticoid-mediated inhibition of their sexual advertisement signals. We studied stress resistance in male B. gauderio (i) by examining the effect of exogenous cortisol administration on the signal waveform and (ii) by investigating the effect of food limitation on androgen and cortisol levels, the amplitude of the electric signal waveform, the responsiveness of the electric signal waveform to social challenge, and the amount of feeding activity. Exogenous cortisol administration did reduce signal amplitude and pulse duration, but endogenous cortisol levels did not rise with food limitation or social challenge. Despite food limitation, males responded to social challenges by further increasing androgen levels and enhancing the amplitude and duration of their electric signal waveforms. Food-restricted males increased androgen levels and signal pulse duration more than males fed ad libitum. Socially challenged fish increased food consumption, probably to compensate for their elevated energy expenditure. Previous studies showed that socially challenged males of this species simultaneously elevate testosterone and cortisol in proportion to signal amplitude. Thus, B. gauderio appears to protect its cortisol-sensitive electric advertisement signal by increasing food intake, limiting cortisol release, and offsetting signal reduction from cortisol with signal-enhancing androgens. Copyright © 2012 Elsevier Inc. All rights reserved.

Evaluation of Motor Neuron Excitability by CMAP Scanning with Electric Modulated Current

PubMed Central

Araújo, Tiago; Candeias, Rui; Nunes, Neuza; Gamboa, Hugo

2015-01-01

Introduction. Compound Muscle Action Potential (CMAP) scan is a noninvasive promissory technique for neurodegenerative pathologies diagnosis. In this work new CMAP scan protocols were implemented to study the influence of electrical pulse waveform on peripheral nerve excitability. Methods. A total of 13 healthy subjects were tested. Stimulation was performed with an increasing intensities range from 4 to 30 mA. The procedure was repeated 4 times per subject, using a different single pulse stimulation waveform: monophasic square and triangular and quadratic and biphasic square. Results. Different waveforms elicit different intensity-response amplitude curves. The square pulse needs less current to generate the same response amplitude regarding the other waves and this effect is gradually decreasing for the triangular, quadratic, and biphasic pulse, respectively. Conclusion. The stimulation waveform has a direct influence on the stimulus-response slope and consequently on the motoneurons excitability. This can be a new prognostic parameter for neurodegenerative disorders. PMID:26413499

Streamer development in barrier discharge in air: spectral signatures and electric field

NASA Astrophysics Data System (ADS)

Hoder, Tomas; Simek, Milan; Bonaventura, Zdenek; Prukner, Vaclav

2015-09-01

Electrical breakdown in the upper atmosphere takes form of so called Transient Luminous Events (TLE). Down to the certain pressure limit, the first phases of the TLE-phenomena are controlled by the streamer mechanism. In order to understand the development of these events, streamers in 10 torr air were generated in volume barrier discharge. Stability and reproducibility of generated streamers were secured by proper electrode geometry and specific applied voltage waveform. In this work, spectrally resolved measurements of the streamer head emission with high spatial and temporal resolution are presented. Precise recordings of the emission of the second positive and first negative systems of molecular nitrogen allowed the determination of the spatio-temporal development of the reduced electric field in the streamer head. This unique experimental result reveals in more details the early stages of the streamer development and gives, besides values for streamer velocity and its diameter, quantitative information on the magnitude of the electric field. T.H. was financed through the ESF Programme TEA-IS (Grant No. 4219), M.S. and V.P. by the AVCR under collaborative project M100431201 and Z.B. acknowledges the support of grant of Czech Science Foundation GA15-04023S.

Electric organ discharge diversity in the genus Gymnotus: anatomo-functional groups and electrogenic mechanisms.

PubMed

Rodríguez-Cattáneo, A; Aguilera, P; Cilleruelo, E; Crampton, W G R; Caputi, A A

2013-04-15

Previous studies describe six factors accounting for interspecific diversity of electric organ discharge (EOD) waveforms in Gymnotus. At the cellular level, three factors determine the locally generated waveforms: (1) electrocyte geometry and channel repertoire; (2) the localization of synaptic contacts on electrocyte surfaces; and (3) electric activity of electromotor axons preceding the discharge of electrocytes. At the organismic level, three factors determine the integration of the EOD as a behavioral unit: (4) the distribution of different types of electrocytes and specialized passive tissue forming the electric organ (EO); (5) the neural mechanisms of electrocyte discharge coordination; and (6) post-effector mechanisms. Here, we reconfirm the importance of the first five of these factors based on comparative studies of a wider diversity of Gymnotus than previously investigated. Additionally, we report a hitherto unseen aspect of EOD diversity in Gymnotus. The central region of the EO (which has the largest weight on the conspecific-received field) usually exhibits a negative-positive-negative pattern where the delay between the early negative and positive peaks (determined by neural coordination mechanisms) matches the delay between the positive and late negative peaks (determined by electrocyte responsiveness). Because delays between peaks typically determine the peak power frequency, this matching implies a co-evolution of neural and myogenic coordination mechanisms in determining the spectral specificity of the intraspecific communication channel. Finally, we define four functional species groups based on EO/EOD structure. The first three exhibit a heterogeneous EO in which doubly innervated electrocytes are responsible for a main triphasic complex. Group I species exhibit a characteristic cephalic extension of the EO. Group II species exhibit an early positive component of putative neural origin, and strong EO auto-excitability. Group III species exhibit an early, slow, negative wave of abdominal origin, and variation in EO auto-excitability. Representatives of Group IV generate a unique waveform comprising a main positive peak followed by a small, load-dependent negative component.

Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields

NASA Astrophysics Data System (ADS)

Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

2016-06-01

An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform’s size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke’s brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

A review of natural lightning - Experimental data and modeling

NASA Technical Reports Server (NTRS)

Uman, M. A.; Krider, E. P.

1982-01-01

A critical review is presented of the currents and the electric and magnetic fields characteristic of each of the salient discharge processes which make up cloud-to-ground and intracloud lightning. Emphasis is placed on the more recent work in which measured waveform variation is in the microsecond and submicrosecond range, since it is this time-scale that is of primary importance in lightning/aircraft interactions. The state-of-the-art of the modeling of lightning currents and fields is discussed in detail. A comprehensive bibliography is given of all literature relating to both lightning measurements and models.

Neuronal responses to an asymmetrical alternating current field can mimic those produced by an imposed direct current field in vitro.

PubMed

Pan, Linjie; Cirillo, John; Borgens, Richard Ben

2012-08-01

The remarkable polarity-dependent growth and anatomical organization of neurons in vitro produced by imposed direct current (DC) voltage gradients (electrical fields; Ef) can be mimicked by another type of electrical cue. This is a properly structured asymmetrical alternating current (AC) electrical field (A-ACEf). Here we provide details on the construction of an AC signal generator in which all components of an AC waveform can be individually controlled. We show that 1) conventional symmetrical AC voltage gradients will not induce growth, guidance, or architectural changes in sympathetic neurons. We also provide the first qualitative and quantitative data showing that an asymmetric AC application can indeed mimic the DC response in chick sympathetic neurons and their growing neurites. This shift in orientation and neuronal anatomy requires dieback of some neurites and the extension of others to produce a preferred orientation perpendicular to the gradient of voltage. Our new results may lead to a noninvasive means to modify nerve growth and organization by magnetic inductive coupling at distance. These data also indicate the possibility of a means to mimic DC-dependent release of drugs or other biologically active molecules from electrically sensitive that can be loaded with these chemical cargos. Copyright © 2012 Wiley Periodicals, Inc.

Conformable actively multiplexed high-density surface electrode array for brain interfacing

DOEpatents

Rogers, John; Kim, Dae-Hyeong; Litt, Brian; Viventi, Jonathan

2015-01-13

Provided are methods and devices for interfacing with brain tissue, specifically for monitoring and/or actuation of spatio-temporal electrical waveforms. The device is conformable having a high electrode density and high spatial and temporal resolution. A conformable substrate supports a conformable electronic circuit and a barrier layer. Electrodes are positioned to provide electrical contact with a brain tissue. A controller monitors or actuates the electrodes, thereby interfacing with the brain tissue. In an aspect, methods are provided to monitor or actuate spatio-temporal electrical waveform over large brain surface areas by any of the devices disclosed herein.

Large-Amplitude Transmitter-Associated and Lightning-Associated Whistler Waves in the Earth's Inner Plasmasphere at L less than 2

NASA Technical Reports Server (NTRS)

Breneman, A.; Cattell, C.; Wygant, J.; Kersten, K.; Wilson, L. B., III; Schreiner, S.; Kellogg, P. J.; Goetz, K.

2011-01-01

We report observations of very large amplitude whistler mode waves in the Earth fs nightside inner radiation belt enabled by the STEREO Time Domain Sampler. Amplitudes range from 30.110 mV/m (zero ]peak), 2 to 3 orders of magnitude larger than previously observed in this region. Measurements from the peak electric field detector (TDSMax) indicate that these large ]amplitude waves are prevalent throughout the plasmasphere. A detailed examination of high time resolution electric field waveforms is undertaken on a subset of these whistlers at L < 2, associated with pump waves from lightning flashes and the naval transmitter NPM in Hawaii, that become unstable after propagation through the ionosphere and grow to large amplitudes. Many of the waveforms undergo periodic polarization reversals near the lower hybrid and NPM naval transmitter frequencies. The reversals may be related to finite plasma temperature and gradients in density induced by ion cyclotron heating of the plasma at 200 Hz, the modulation frequency of the continuous ]mode NPM naval transmitter signal. Test particle simulations using the amplitudes and durations of the waves observed herein suggest that they can interact strongly with high ]energy (>100 keV) electrons on a time scale of <1 s and thus may be an important previously unaccounted for source of energization or pitch ]angle scattering in the inner radiation belt.

Quincke random walkers

NASA Astrophysics Data System (ADS)

Pradillo, Gerardo; Heintz, Aneesh; Vlahovska, Petia

2017-11-01

The spontaneous rotation of a sphere in an applied uniform DC electric field (Quincke effect) has been utilized to engineer self-propelled particles: if the sphere is initially resting on a surface, it rolls. The Quincke rollers have been widely used as a model system to study collective behavior in ``active'' suspensions. If the applied field is DC, an isolated Quincke roller follows a straight line trajectory. In this talk, we discuss the design of a Quincke roller that executes a random-walk-like behavior. We utilize AC field - upon reversal of the field direction a fluctuation in the axis of rotation (which is degenerate in the plane perpendicular to the field and parallel to the surface) introduces randomness in the direction of motion. The MSD of an isolated Quincke walker depends on frequency, amplitude, and waveform of the electric field. Experiment and theory are compared. We also investigate the collective behavior of Quincke walkers,the transport of inert particles in a bath of Quincke walkers, and the spontaneous motion of a drop containing Quincke active particle. supported by NSF Grant CBET 1437545.

Standardizing electrofishing power for boat electrofishing: chapter 14

USGS Publications Warehouse

Miranda, L.E. (Steve); Bonar, Scott A.; Hubert, Wayne A.; Willis, David W.

2009-01-01

Standardizing boat electrofishing entails achieving an accepted level of collection consistency by managing various brand factors, including (1) the temporal and spatial distribution of sampling effort, (2) boat operation, (3) equipment configuration, (4) characteristics of the waveform and energized field, and (5) power transferred to fish. This chapter focuses exclusively on factor 5:L factors 1-4 have been addressed in earlier chapters. Additionally, while the concepts covered in this chapter address boat electrofishing in general, the power settings discussed were developed from tests with primarily warmwater fish communities. Others (see Chapter 9) recommend lower power settings for communities consisting of primarily coldwater fishes. For reviews of basic concepts of electricity, electrofishing theory and systems, fish behavior relative to diverse waveforms, and injury matter, the reader is referred to Novotny (1990), Reynold (1996), and Snyder (2003).

Properties of the unusually short pulse sequences occurring prior to the first strokes of negative cloud-to-ground lightning flashes

NASA Astrophysics Data System (ADS)

Kolmasova, Ivana; Santolik, Ondrej; Farges, Thomas; Rison, William; Lan, Radek; Uhlir, Ludek

2014-05-01

We analyze pulse sequences occurring prior to first return strokes of negative cloud-to-ground lightning flashes. The magnetic-field waveforms are measured close to the thunderstorm using a broad-band analyzer with a sampling interval of 12.5 ns. The electric-field waveforms are measured at the distance of ~ 400 km using an analyzer with a sampling interval of 80 ns. The sequence is usually composed of three parts. It begins with a larger pulse train which is believed to be connected with initial breakdown processes. The train of preliminary breakdown pulses ("B" part) is followed by a relatively low and irregular pulse activity ("I" part), which is sometimes missing. The sequence ends with a pulse train attributed to the stepped leader ("L" part). We recognize two different patterns ("B-I-L" and "B-L" types) in recorded waveforms. For the first time, we analyze the time evolution of the pulse amplitudes in the "B" part of "B-I-L" type sequences. The pulse amplitude is decreasing on average by 34% of the maximum value within a given train. We observe an unusually short duration of sequences. This is probably linked to a low height of the thundercloud. Another possible explanation may be based on an untypical precipitation mix resulting in faster steeped leaders.

Electrical Stimulation Technologies for Wound Healing

PubMed Central

Kloth, Luther C.

2014-01-01

Objective: To discuss the physiological bases for using exogenously applied electric field (EF) energy to enhance wound healing with conductive electrical stimulation (ES) devices. Approach: To describe the types of electrical currents that have been reported to enhance chronic wound-healing rate and closure. Results: Commercial ES devices that generate direct current (DC), and mono and biphasic pulsed current waveforms represent the principal ES technologies which are reported to enhance wound healing. Innovation: Wafer-thin, disposable ES technologies (wound dressings) that utilize mini or micro-batteries to deliver low-level DC for wound healing and antibacterial wound-treatment purposes are commercially available. Microfluidic wound-healing chips are currently being used with greater accuracy to investigate the EF effects on cellular electrotaxis. Conclusion: Numerous clinical trials described in subsequent sections of this issue have demonstrated that ES used adjunctively with standard wound care (SWC), enhances wound healing rate faster than SWC alone. PMID:24761348

Characteristics of corona impulses from insulated wires subjected to high ac voltages

NASA Technical Reports Server (NTRS)

Doreswamy, C. V.; Crowell, C. S.

1976-01-01

Corona discharges arise due to ionization of air or gas subject to high electric fields. The free electrons and ions contained in these discharges interact with molecules of insulating materials, resulting in chemical changes and destroying the electrical insulating properties. The paper describes some results of measurements aimed at determining corona pulse waveforms, their repetition rate, and amplitude distribution during various randomly-sampled identical time periods of a 60-Hz high-voltage wave. Described are properties of positive and negative corona impulses generated from typical conductors at various test high voltages. A possible method for calculating the energies, densities, and electromagnetic interferences by making use of these results is suggested.

Lightning Detection and Ranging system LDAR system description and performance objectives

NASA Technical Reports Server (NTRS)

Poehler, H. A.; Lennon, C. L.

1979-01-01

The instruments used at the six remote stations to measure both the time-of-arrival of the envelope of the pulsed 60 MHz to 80 MHz portion of the RF signal emitted by lightning, and the electric field waveforms are described as well as the two methods of transmitting the signal to the central station. Other topics discussed include data processing, recording, and reduction techniques and the software used for the 2100S, 2114, and 2116 computers.

A Laboratory Study of Aircraft Precipitation Static Charging

DTIC Science & Technology

1984-05-01

Hallett, Laboratory measurements of electric phenomena occurring during the freezing of S" charge transfer during multiple ice-ice coll - dilute aqueous...direction of field and the radius to the point are polarisation charges which flow along the sur - of contact. Gravitational separation of the two face of...mechanism is being obeyed. This is consistent 10 C 50/5 ,’ ;with the unity value of f derived previously. . lOup . 0um 40 " Several waveform of the same shape

Ion Mobility Spectrometry (IMS) and Mass Spectrometry

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

Shvartsburg, Alexandre A.

2010-04-20

In a media of finite viscosity, the Coulomb force of external electric field moves ions with some terminal speed. This dynamics is controlled by “mobility” - a property of the interaction potential between ions and media molecules. This fact has been used to separate and characterize gas-phase ions in various modes of ion mobility spectrometry (IMS) developed since 1970. Commercial IMS devices were introduced in 1980-s for field detection of volatile traces such as explosives and chemical warfare agents. Coupling to soft-ionization sources, mass spectrometry (MS), and chromatographic methods in 1990-s had allowed IMS to handle complex samples, enabling newmore » applications in biological and environmental analyses, nanoscience, and other areas. Since 2003, the introduction of commercial systems by major instrument vendors started bringing the IMS/MS capability to broad user community. The other major development of last decade has been the differential IMS or “field asymmetric waveform IMS” (FAIMS) that employs asymmetric time-dependent electric field to sort ions not by mobility itself, but by the difference between its values in strong and weak electric fields. Coupling of FAIMS to conventional IMS and stacking of conventional IMS stages have enabled two-dimensional separations that dramatically expand the power of ion mobility methods.« less

Tsunami Source Estimate for the 1960 Chilean Earthquake from Near- and Far-Field Observations

NASA Astrophysics Data System (ADS)

Ho, T.; Satake, K.; Watada, S.; Fujii, Y.

2017-12-01

The tsunami source of the 1960 Chilean earthquake was estimated from the near- and far-field tsunami data. The 1960 Chilean earthquake is known as the greatest earthquake instrumentally ever recorded. This earthquake caused a large tsunami which was recorded by 13 near-field tidal gauges in South America, and 84 far-field stations around the Pacific Ocean at the coasts of North America, Asia, and Oceania. The near-field stations had been used for estimating the tsunami source [Fujii and Satake, Pageoph, 2013]. However, far-field tsunami waveforms have not been utilized because of the discrepancy between observed and simulated waveforms. The observed waveforms at the far-field stations are found systematically arrived later than the simulated waveforms. This phenomenon has been also observed in the tsunami of the 2004 Sumatra earthquake, the 2010 Chilean earthquake, and the 2011 Tohoku earthquake. Recently, the factors for the travel time delay have been explained [Watada et al., JGR, 2014; Allgeyer and Cummins, GRL, 2014], so the far-field data are usable for tsunami source estimation. The phase correction method [Watada et al., JGR, 2014] converts the tsunami waveforms computed by the linear long wave into the dispersive waveform which accounts for the effects of elasticity of the Earth and ocean, ocean density stratification, and gravitational potential change associated with tsunami propagation. We apply the method to correct the computed waveforms. For the preliminary initial sea surface height inversion, we use 12 near-field stations and 63 far-field stations, located in the South and North America, islands in the Pacific Ocean, and the Oceania. The estimated tsunami source from near-field stations is compared with the result from both near- and far-field stations. Two estimated sources show a similar pattern: a large sea surface displacement concentrated at the south of the epicenter close to the coast and extended to south. However, the source estimated from near-field stations shows larger displacement than one from both dataset.

Discharge dynamics of self-oriented microplasma coupling between cross adjacent cavities in micro-structure device driven by a bipolar pulse waveform

NASA Astrophysics Data System (ADS)

Wang, Yaogong; Zhang, Xiaoning; Liu, Lingguang; Zhou, Xuan; Liu, Chunliang; Zhang, Qiaogen

2018-04-01

The excitation dynamics and self-oriented plasma coupling of a micro-structure plasma device with a rectangular cross-section are investigated. The device consists of 7 × 7 microcavity arrays, which are blended into a unity by a 50 μm-thick bulk area above them. The device is operated in argon with a pressure of 200 Torr, driven by a bipolar pulse waveform of 20 kHz. The discharge evolution is characterized by means of electrical measurements and optical emission profiles. It has been found that different emission patterns are observed within microcavities. The formation of these patterns induced by the combined action between the applied electric field and surface deactivation is discussed. The microplasma distribution in some specific regions along the diagonal direction of cavities in the bulk area is observed, and self-oriented microplasma coupling is explored, while the plasma interaction occurred between cross adjacent cavities, contributed by the ionization wave propagation. The velocity of ionization wave propagation is measured to be 1.2 km/s to 3.5 km/s. The exploration of this plasma interaction in the bulk area is of value to applications in electromagnetics and signal processing.

Severe storm electricity

NASA Technical Reports Server (NTRS)

Rust, W. D.; Macgorman, D. R.; Taylor, W.; Arnold, R. T.

1984-01-01

Severe storms and lightning were measured with a NASA U2 and ground based facilities, both fixed base and mobile. Aspects of this program are reported. The following results are presented: (1) ground truth measurements of lightning for comparison with those obtained by the U2. These measurements include flash type identification, electric field changes, optical waveforms, and ground strike location; (2) simultaneous extremely low frequency (ELF) waveforms for cloud to ground (CG) flashes; (3) the CG strike location system (LLP) using a combination of mobile laboratory and television video data are assessed; (4) continued development of analog-to-digital conversion techniques for processing lightning data from the U2, mobile laboratory, and NSSL sensors; (5) completion of an all azimuth TV system for CG ground truth; (6) a preliminary analysis of both IC and CG lightning in a mesocyclone; and (7) the finding of a bimodal peak in altitude lightning activity in some storms in the Great Plains and on the east coast. In the forms on the Great Plains, there was a distinct class of flash what forms the upper mode of the distribution. These flashes are smaller horizontal extent, but occur more frequently than flashes in the lower mode of the distribution.

The optical and radiation field signatures produced by lightning return strokes

NASA Technical Reports Server (NTRS)

Guo, C.; Krider, E. P.

1982-01-01

Typical examples of the signals that are produced by first and subsequent return strokes in cloud-to-ground lightning on a microsecond time scale are presented. Statistics on the structure of the waveforms and the radiance of the channels are given. The relationship between the light signals and the associated electric field signatures is discussed. It is shown that the initial light signal from a return stroke tends to be linear for about 15 microsec and then rises more slowly to a peak that is delayed by approximately 60 microsec from the electric field peak. It is thought that the transition between the fast linear portion and the slower rise may be due to the return stroke entering the cloud base. A small percentage of the records suggest that two different branches of the same stepped leader can initiate separate return strokes. The light pulses from cloud discharges tend to be smaller and to vary more slowly than those from return strokes.

The Properties of Large Amplitude Whistler Mode Waves in the Magnetosphere: Propagation and Relationship with Geomagnetic Activity

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Wygant, J. R.; Goetz, K.; Breneman, A.; Kersten, K.

2011-01-01

Wepresent resultsof a studyof the characteristicsof very large amplitude whistler mode waves inside the terrestrial magnetosphere at radial distances of less than 15 RE using waveform capture data from the Wind spacecraft. We observed 247 whistler mode waves with at least one electric field component (105/247 had !80 mV/m peak!to!peak amplitudes) and 66 whistler mode waves with at least one search coil magnetic field component (38/66 had !0.8 nT peak!to!peak amplitudes). Wave vectors determined from events with three magnetic field components indicate that 30/46 propagate within 20 of the ambient magnetic field, though some are more oblique (up to "50 ). No relationship was observed between wave normal angle and GSM latitude. 162/247 of the large amplitude whistler mode waves were observed during magnetically active periods (AE > 200 nT). 217 out of 247 total whistler mode waves examined were observed inside the radiation belts. We present a waveform capture with the largest whistler wave magnetic field amplitude (^8 nT peak!to!peak) ever reported in the radiation belts. The estimated Poynting flux magnitude associated with this wave is ^300 mW/m2, roughly four orders of magnitude above estimates from previous satellite measurements. Such large Poynting flux values are consistent with rapid energization of electrons.

Electrical features of eighteen automated external defibrillators: a systematic evaluation.

PubMed

Kette, Fulvio; Locatelli, Aldo; Bozzola, Marcella; Zoli, Alberto; Li, Yongqin; Salmoiraghi, Marco; Ristagno, Giuseppe; Andreassi, Aida

2013-11-01

Assessment and comparison of the electrical parameters (energy, current, first and second phase waveform duration) among eighteen AEDs. Engineering bench tests for a descriptive systematic evaluation in commercially available AEDs. AEDs were tested through an ECG simulator, an impedance simulator, an oscilloscope and a measuring device detecting energy delivered, peak and average current, and duration of first and second phase of the biphasic waveforms. All tests were performed at the engineering facility of the Lombardia Regional Emergency Service (AREU). Large variations in the energy delivered at the first shock were observed. The trend of current highlighted a progressive decline concurrent with the increases of impedance. First and second phase duration varied substantially among the AEDs using the exponential biphasic waveform, unlike rectilinear waveform AEDs in which phase duration remained relatively constant. There is a large variability in the electrical features of the AEDs tested. Energy is likely not to be the best indicator for strength dose selection. Current and shock duration should be both considered when approaching the technical features of AEDs. These findings may prompt further investigations to define the optimal current and duration of the shock waves to increase the success rate in the clinical setting. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Electromechanical systems with transient high power response operating from a resonant ac link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant ac link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control all four operating quadrants. Incorporating the ac link allows the converter in these systems to switch at the zero crossing of every half cycle of the ac waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed under contract to NASA.

Mathematical Constraints on the Use of Transmission Line Models for Simulating Initial Breakdown Pulses in Lightning Discharges

NASA Astrophysics Data System (ADS)

da Silva, C. L.; Merrill, R. A.; Pasko, V. P.

2015-12-01

A significant portion of the in-cloud lightning development is observed as a series of initial breakdown pulses (IBPs) that are characterized by an abrupt change in the electric field at a remote sensor. Recent experimental and theoretical studies have attributed this process to the stepwise elongation of an initial lightning leader inside the thunderstorm [da Silva and Pasko, JGR, 120, 4989-5009, 2015, and references therein]. Attempts to visually observe these events are hampered due to the fact that clouds are opaque to optical radiation. Due to this reason, throughout the last decade, a number of researchers have used the so-called transmission line models (also commonly referred to as engineering models), widely employed for return stroke simulations, to simulate the waveshapes of IBPs, and also of narrow bipolar events. The transmission line (TL) model approach is to prescribe the source current dynamics in a certain manner to match the measured E-field change waveform, with the purpose of retrieving key information about the source, such as its height, peak current, size, speed of charge motion, etc. Although the TL matching method is not necessarily physics-driven, the estimated source characteristics can give insights on the dominant length- and time-scales, as well as, on the energetics of the source. This contributes to better understanding of the environment where the onset and early stages of lightning development takes place.In the present work, we use numerical modeling to constrain the number of source parameters that can be confidently inferred from the observed far-field IBP waveforms. We compare different modified TL models (i.e., with different attenuation behaviors) to show that they tend to produce similar waveforms in conditions where the channel is short. We also demonstrate that it is impossible to simultaneously retrieve the speed of source current propagation and channel length from an observed IBP waveform, in contrast to what has been previously done in the literature. Finally, we demonstrate that the simulated field-to-current conversion factor in IBP sources can vary by more than one order of magnitude, making peak current estimates for intracloud lightning processes a challenging task.

Effect of moisture on the field dependence of mobility for gas-phase ions of organophosphorus compounds at atmospheric pressure with field asymmetric ion mobility spectrometry.

PubMed

Krylova, N; Krylov, E; Eiceman, G A; Stone, J A

2003-05-15

The electric field dependence of the mobilities of gas-phase protonated monomers [(MH+(H2O)n] and proton-bound dimers [M2H+(H2O)n] of organophosphorus compounds was determined at E/N values between 0 and 140 Td at ambient pressure in air with moisture between 0.1 and 15 000 ppm. Field dependence was described as alpha (E/N) and was obtained from the measurements of compensation voltage versus field amplitude in a planar high-field asymmetric waveform ion mobility spectrometer. The alpha function for protonated monomers to 140 Td was constant from 0.1 to 10 ppm moisture in air with onset of effect at approximately 50 ppm. The value of alpha increased 2-fold from 100 to 1000 ppm at all E/N values. At moisture values between 1000 and 10 000 ppm, a 2-fold or more increase in alpha (E/N) was observed. In a model proposed here, field dependence for mobility through changes in collision cross sections is governed by the degree of solvation of the protonated molecule by neutral molecules. The process of ion declustering at high E/N values was consistent with the kinetics of ion-neutral collisional periods, and the duty cycle of the waveform applied to the drift tube. Water was the principal neutral above 50 ppm moisture in air, and nitrogen was proposed as the principal neutral below 50 ppm.

Signal Analysis and Waveform Reconstruction of Shock Waves Generated by Underwater Electrical Wire Explosions with Piezoelectric Pressure Probes.

PubMed

Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici

2016-04-22

Underwater shock waves (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak pressure, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric pressure probes, and reconstruct the correct pressure waveform from the distorted one measured by the pressure probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW pressure value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential pressure waveform model, which has considered the faster pressure decay at the early stage and the slower pressure decay in longer times. Based on this model and the energy conservation law, the pressure waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak pressures are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable.

Signal Analysis and Waveform Reconstruction of Shock Waves Generated by Underwater Electrical Wire Explosions with Piezoelectric Pressure Probes

PubMed Central

Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici

2016-01-01

Underwater shock waves (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak pressure, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric pressure probes, and reconstruct the correct pressure waveform from the distorted one measured by the pressure probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW pressure value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential pressure waveform model, which has considered the faster pressure decay at the early stage and the slower pressure decay in longer times. Based on this model and the energy conservation law, the pressure waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak pressures are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable. PMID:27110789

An EPG waveform library for sharpshooters and preliminary effects of applied voltage on behaviors controlling Xylella fastidiosa inoculation

USDA-ARS?s Scientific Manuscript database

Electropenetrography (EPG) waveforms represent electrical conductivity of fluids flowing through an insect’s mouthparts. Over the 50 years since its invention, EPG has undergone three major electronic transformations. The newest, third generation of electropenetrograph, the AC-DC EPG monitor, offers...

Physical mechanism of initial breakdown pulses and narrow bipolar events in lightning discharges

NASA Astrophysics Data System (ADS)

da Silva, Caitano L.; Pasko, Victor P.

2015-05-01

To date the true nature of initial breakdown pulses (IBPs) and narrow bipolar events (NBEs) in lightning discharges remains a mystery. Recent experimental evidence has correlated IBPs to the initial development of lightning leaders inside the thundercloud. NBE wideband waveforms resemble classic IBPs in both amplitude and duration. Most NBEs are quite peculiar in the sense that very frequently they occur in isolation from other lightning processes. The remaining fraction, 16% of positive polarity NBEs, according to Wu et al. (2014), happens as the first event in an otherwise regular intracloud lightning discharge. These authors point out that the initiator type of NBEs has no difference with other NBEs that did not start lightning, except for the fact that they occur deeper inside the thunderstorm (i.e., at lower altitudes). In this paper, we propose a new physical mechanism to explain the source of both IBPs and NBEs. We propose that IBPs and NBEs are the electromagnetic transients associated with the sudden (i.e., stepwise) elongation of the initial negative leader extremity in the thunderstorm electric field. To demonstrate our hypothesis a novel computational/numerical model of the bidirectional lightning leader tree is developed, consisting of a generalization of electrostatic and transmission line approximations found in the literature. Finally, we show how the IBP and NBE waveform characteristics directly reflect the properties of the bidirectional lightning leader (such as step length, for example) and amplitude of the thunderstorm electric field.

Electrical Switching of Perovskite Thin-Film Resistors

NASA Technical Reports Server (NTRS)

Liu, Shangqing; Wu, Juan; Ignatiev, Alex

2010-01-01

Electronic devices that exploit electrical switching of physical properties of thin films of perovskite materials (especially colossal magnetoresistive materials) have been invented. Unlike some related prior devices, these devices function at room temperature and do not depend on externally applied magnetic fields. Devices of this type can be designed to function as sensors (exhibiting varying electrical resistance in response to varying temperature, magnetic field, electric field, and/or mechanical pressure) and as elements of electronic memories. The underlying principle is that the application of one or more short electrical pulse(s) can induce a reversible, irreversible, or partly reversible change in the electrical, thermal, mechanical, and magnetic properties of a thin perovskite film. The energy in the pulse must be large enough to induce the desired change but not so large as to destroy the film. Depending on the requirements of a specific application, the pulse(s) can have any of a large variety of waveforms (e.g., square, triangular, or sine) and be of positive, negative, or alternating polarity. In some applications, it could be necessary to use multiple pulses to induce successive incremental physical changes. In one class of applications, electrical pulses of suitable shapes, sizes, and polarities are applied to vary the detection sensitivities of sensors. Another class of applications arises in electronic circuits in which certain resistance values are required to be variable: Incorporating the affected resistors into devices of the present type makes it possible to control their resistances electrically over wide ranges, and the lifetimes of electrically variable resistors exceed those of conventional mechanically variable resistors. Another and potentially the most important class of applications is that of resistance-based nonvolatile-memory devices, such as a resistance random access memory (RRAM) described in the immediately following article, Electrically Variable Resistive Memory Devices (MFS-32511-1).

Immobilization thresholds of electrofishing relative to fish size

USGS Publications Warehouse

Dolan, C.R.; Miranda, L.E.

2003-01-01

Fish size and electrical waveforms have frequently been associated with variation in electrofishing effectiveness. Under controlled laboratory conditions, we measured the electrical power required by five electrical waveforms to immobilize eight fish species of diverse sizes and shapes. Fish size was indexed by total body length, surface area, volume, and weight; shape was indexed by the ratio of body length to body depth. Our objectives were to identify immobilization thresholds, elucidate the descriptors of fish size that were best associated with those immobilization thresholds, and determine whether the vulnerability of a species relative to other species remained constant across electrical treatments. The results confirmed that fish size is a key variable controlling the immobilization threshold and further suggested that the size descriptor best related to immobilization is fish volume. The peak power needed to immobilize fish decreased rapidly with increasing fish volume in small fish but decreased slowly for fish larger than 75-100 cm 3. Furthermore, when we controlled for size and shape, different waveforms did not favor particular species, possibly because of the overwhelming effect of body size. Many of the immobilization inconsistencies previously attributed to species might simply represent the effect of disparities in body size.

Ultimate waveform reproducibility of extreme-ultraviolet pulses by high-harmonic generation in quartz

NASA Astrophysics Data System (ADS)

Garg, M.; Kim, H. Y.; Goulielmakis, E.

2018-05-01

Optical waveforms of light reproducible with subcycle precision underlie applications of lasers in ultrafast spectroscopies, quantum control of matter and light-based signal processing. Nonlinear upconversion of optical pulses via high-harmonic generation in gas media extends these capabilities to the extreme ultraviolet (EUV). However, the waveform reproducibility of the generated EUV pulses in gases is inherently sensitive to intensity and phase fluctuations of the driving field. We used photoelectron interferometry to study the effects of intensity and carrier-envelope phase of an intense single-cycle optical pulse on the field waveform of EUV pulses generated in quartz nanofilms, and contrasted the results with those obtained in gas argon. The EUV waveforms generated in quartz were found to be virtually immune to the intensity and phase of the driving field, implying a non-recollisional character of the underlying emission mechanism. Waveform-sensitive photonic applications and precision measurements of fundamental processes in optics will benefit from these findings.

The Influence of Measurement Methodology on the Accuracy of Electrical Waveform Distortion Analysis

NASA Astrophysics Data System (ADS)

Bartman, Jacek; Kwiatkowski, Bogdan

2018-04-01

The present paper covers a review of documents that specify measurement methods of voltage waveform distortion. It also presents measurement stages of waveform components that are uncommon in the classic fundamentals of electrotechnics and signal theory, including the creation process of groups and subgroups of harmonics and interharmonics. Moreover, the paper discusses selected distortion factors of periodic waveforms and presents analyses that compare the values of these distortion indices. The measurements were carried out in the cycle per cycle mode and the measurement methodology that was used complies with the IEC 61000-4-7 norm. The studies showed significant discrepancies between the values of analyzed parameters.

Dual-frequency glow discharges in atmospheric helium

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

Huang, Xiaojiang; Guo, Ying; Magnetic Confinement Fusion Research Center, Ministry of Education of the People's Republic of China, Shanghai 201620

2015-10-15

In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

An infrared-driven flexible pyroelectric generator for non-contact energy harvester

NASA Astrophysics Data System (ADS)

Zhao, Tingting; Jiang, Weitao; Liu, Hongzhong; Niu, Dong; Li, Xin; Liu, Weihua; Li, Xuan; Chen, Bangdao; Shi, Yongsheng; Yin, Lei; Lu, Bingheng

2016-04-01

In recent years, energy harvesting technologies, which can scavenge many kinds of energies from our living environment to power micro/nanodevices, have attracted increasing attention. However, remote energy transmission, flexibility and electric waveform controllability remain the key challenges for wireless power supply by an energy harvester. In this paper, we design a new infrared-driven non-contact pyroelectric generator for harvesting heat energy, which avoids direct contact between the pyroelectric generator and heat source and realizes remote energy transfer exploiting the photothermal and penetrability of infrared light. The output voltage (under the input impedance of 100 MOhm) and short-circuit current of the pyroelectric generator consisting of a CNT/PVDF/CNT layer (20 mm × 5 mm × 100 μm) can be as large as 1.2 V and 9 nA, respectively, under a 1.45 W cm-2 near-infrared laser (808 nm). We also demonstrate the means by which the pyroelectric generator can modulate square waveforms with controllable periods through irradiation frequency, which is essential for signal sources and medical stimulators. The overshoot of square waveforms are in a range of 9.0%-13.1% with a rise time of 120 ms. The prepared pyroelectric generator can light a liquid crystal display (LCD) in a vacuum chamber from outside. This work paves the way for non-contact energy harvesting for some particular occasions where near-field energy control is not available.In recent years, energy harvesting technologies, which can scavenge many kinds of energies from our living environment to power micro/nanodevices, have attracted increasing attention. However, remote energy transmission, flexibility and electric waveform controllability remain the key challenges for wireless power supply by an energy harvester. In this paper, we design a new infrared-driven non-contact pyroelectric generator for harvesting heat energy, which avoids direct contact between the pyroelectric generator and heat source and realizes remote energy transfer exploiting the photothermal and penetrability of infrared light. The output voltage (under the input impedance of 100 MOhm) and short-circuit current of the pyroelectric generator consisting of a CNT/PVDF/CNT layer (20 mm × 5 mm × 100 μm) can be as large as 1.2 V and 9 nA, respectively, under a 1.45 W cm-2 near-infrared laser (808 nm). We also demonstrate the means by which the pyroelectric generator can modulate square waveforms with controllable periods through irradiation frequency, which is essential for signal sources and medical stimulators. The overshoot of square waveforms are in a range of 9.0%-13.1% with a rise time of 120 ms. The prepared pyroelectric generator can light a liquid crystal display (LCD) in a vacuum chamber from outside. This work paves the way for non-contact energy harvesting for some particular occasions where near-field energy control is not available. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09290f

Observations of Seismoeletric Signals Induced by a Hydro-fracturing Experiment in a Deep Geothermal Reservoir

NASA Astrophysics Data System (ADS)

Marquis, G.; Darnet, M.; Michelet, S.; Baria, R.

2003-12-01

During a hydro-fracturing experiment at the Soultz-sous-Forêts Hot Dry Rock site, more than 100,000 microseismic events of magnitude greater than -2.0 were induced by the continuous injection of 30,000 m3 of fresh water at 5 km depth. At the same time, we carried out monitoring of surface electric fields at a sampling rate of 2 kHz with two pairs of unpolarizable electrodes. After removal of the man-made noise, we observed strong electric field perturbations associated to the 48 microseismic events of magnitude greater than 1.8. Their maximum amplitude is 20 mV for the largest event (M = 2.7) while the background electrical noise is roughly 70 mV. The start of these electric perturbations coincides with the P-arrival time of the seismic waves at a depth of 1.5 km i.e. roughly half a second before the surface arrival time and their duration is about one second. As the sediments - granite interface is located at the same depth, the source of these electromagnetic signals could be an electroseismic conversion at this high acoustic impedance contrast. Moreover, a detailed analysis of the electric waveform reveals that several electric phases are arriving on the surface after the first pulse which may be caused by electroseismic conversions within the sediment layers. We did not however observe any electric field perturbations prior to rupture and the alleged first pulse associated with piezoelectric effect. It seems therefore that the prevailing effect when monitoring high-frequency (>= 1 Hz) synearthquake EM phenomena is seismoelectric.

Species-Specific Diversity of a Fixed Motor Pattern: The Electric Organ Discharge of Gymnotus

PubMed Central

Rodríguez-Cattaneo, Alejo; Pereira, Ana Carolina; Aguilera, Pedro A.; Crampton, William G. R.; Caputi, Angel A.

2008-01-01

Understanding fixed motor pattern diversity across related species provides a window for exploring the evolution of their underlying neural mechanisms. The electric organ discharges of weakly electric fishes offer several advantages as paradigmatic models for investigating how a neural decision is transformed into a spatiotemporal pattern of action. Here, we compared the far fields, the near fields and the electromotive force patterns generated by three species of the pulse generating New World gymnotiform genus Gymnotus. We found a common pattern in electromotive force, with the far field and near field diversity determined by variations in amplitude, duration, and the degree of synchronization of the different components of the electric organ discharges. While the rostral regions of the three species generate similar profiles of electromotive force and local fields, most of the species-specific differences are generated in the main body and tail regions of the fish. This causes that the waveform of the field is highly site dependant in all the studied species. These findings support a hypothesis of the relative separation of the electrolocation and communication carriers. The presence of early head negative waves in the rostral region, a species-dependent early positive wave at the caudal region, and the different relationship between the late negative peak and the main positive peak suggest three points of lability in the evolution of the electrogenic system: a) the variously timed neuronal inputs to different groups of electrocytes; b) the appearance of both rostrally and caudally innervated electrocytes, and c) changes in the responsiveness of the electrocyte membrane. PMID:18461122

Method and system employing finite state machine modeling to identify one of a plurality of different electric load types

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

Du, Liang; Yang, Yi; Harley, Ronald Gordon

A system is for a plurality of different electric load types. The system includes a plurality of sensors structured to sense a voltage signal and a current signal for each of the different electric loads; and a processor. The processor acquires a voltage and current waveform from the sensors for a corresponding one of the different electric load types; calculates a power or current RMS profile of the waveform; quantizes the power or current RMS profile into a set of quantized state-values; evaluates a state-duration for each of the quantized state-values; evaluates a plurality of state-types based on the powermore » or current RMS profile and the quantized state-values; generates a state-sequence that describes a corresponding finite state machine model of a generalized load start-up or transient profile for the corresponding electric load type; and identifies the corresponding electric load type.« less

A multi-functional high voltage experiment apparatus for vacuum surface flashover switch research.

PubMed

Zeng, Bo; Su, Jian-cang; Cheng, Jie; Wu, Xiao-long; Li, Rui; Zhao, Liang; Fang, Jin-peng; Wang, Li-min

2015-04-01

A multifunctional high voltage apparatus for experimental researches on surface flashover switch and high voltage insulation in vacuum has been developed. The apparatus is composed of five parts: pulse generating unit, axial field unit, radial field unit, and two switch units. Microsecond damped ringing pulse with peak-to-peak voltage 800 kV or unipolar pulse with maximum voltage 830 kV is generated, forming transient axial or radial electrical field. Different pulse waveforms and field distributions make up six experimental configurations in all. Based on this apparatus, preliminary experiments on vacuum surface flashover switch with different flashover dielectric materials have been conducted in the axial field unit, and nanosecond pulse is generated in the radial field unit which makes a pulse transmission line in the experiment. Basic work parameters of this kind of switch such as lifetime, breakdown voltage are obtained.

Nonlinear electrostatic solitary waves in electron-positron plasmas

NASA Astrophysics Data System (ADS)

Lazarus, I. J.; Bharuthram, R.; Moolla, S.; Singh, S. V.; Lakhina, G. S.

2016-02-01

The generation of nonlinear electrostatic solitary waves (ESWs) is explored in a magnetized four component two-temperature electron-positron plasma. Fluid theory is used to derive a set of nonlinear equations for the ESWs, which propagate obliquely to an external magnetic field. The electric field structures are examined for various plasma parameters and are shown to yield sinusoidal, sawtooth and bipolar waveforms. It is found that an increase in the densities of the electrons and positrons strengthen the nonlinearity while the periodicity and nonlinearity of the wave increases as the cool-to-hot temperature ratio increases. Our results could be useful in understanding nonlinear propagation of waves in astrophysical environments and related laboratory experiments.

New conducted electrical weapons: Electrical safety relative to relevant standards.

PubMed

Panescu, Dorin; Nerheim, Max; Kroll, Mark W; Brave, Michael A

2017-07-01

We have previously published about TASER ® conducted electrical weapons (CEW) compliance with international standards. CEWs deliver electrical pulses that can inhibit a person's neuromuscular control or temporarily incapacitate. An eXperimental Rotating-Field (XRF) waveform CEW and the X2 CEW are new 2-shot electrical weapon models designed to target a precise amount of delivered charge per pulse. They both can deploy 1 or 2 dart pairs, delivered by 2 separate cartridges. Additionally, the XRF controls delivery of incapacitating pulses over 4 field vectors, in a rotating sequence. As in our previous study, we were motivated by the need to understand the cardiac safety profile of these new CEWs. The goal of this paper is to analyze the nominal electrical outputs of TASER XRF and X2 CEWs in reference to provisions of all relevant international standards that specify safety requirements for electrical medical devices and electrical fences. Although these standards do not specifically mention CEWs, they are the closest electrical safety standards and hence give very relevant guidance. The outputs of several TASER XRF and X2 CEWs were measured under normal operating conditions. The measurements were compared against manufacturer specifications. CEWs electrical output parameters were reviewed against relevant safety requirements of UL 69, IEC 60335-2-76 Ed 2.1, IEC 60479-1, IEC 60479-2, AS/NZS 60479.1, AS/NZS 60479.2, IEC 60601-1 and BS EN 60601-1. Our study confirmed that the nominal electrical outputs of TASER XRF and X2 CEWs lie within safety bounds specified by relevant standards.

Recognition and processing of randomly fluctuating electric signals by Na,K-ATPase.

PubMed Central

Xie, T. D.; Marszalek, P.; Chen, Y. D.; Tsong, T. Y.

1994-01-01

Previous work has shown that Na,K-ATPase of human erythrocytes can extract free energy from sinusoidal electric fields to pump cations up their respective concentration gradients. Because regularly oscillating waveform is not a feature of the transmembrane electric potential of cells, questions have been raised whether these observed effects are biologically relevant. Here we show that a random-telegraph fluctuating electric field (RTF) consisting of alternating square electric pulses with random lifetimes can also stimulate the Rb(+)-pumping mode of the Na,K-ATPase. The net RTF-stimulated, ouabain-sensitive Rb+ pumping was monitored with 86Rb+. The tracer-measured, Rb+ influx exhibited frequency and amplitude dependencies that peaked at the mean frequency of 1.0 kHz and amplitude of 20 V/cm. At 4 degrees C, the maximal pumping activity under these optimal conditions was 28 Rb+/RBC-hr, which is approximately 50% higher than that obtained with the sinusoidal electric field. These findings indicate that Na,K-ATPase can recognize an electric signal, either regularly oscillatory or randomly fluctuating, for energy coupling, with high fidelity. The use of RTF for activation also allowed a quantitative theoretical analysis of kinetics of a membrane transport model of any complexity according to the theory of electroconformational coupling (ECC) by the diagram methods. A four-state ECC model was shown to produce the amplitude and the frequency windows of the Rb(+)-pumping if the free energy of interaction of the transporter with the membrane potential was to include a nonlinear quadratic term. Kinetic constants for the ECC model have been derived. These results indicate that the ECC is a plausible mechanism for the recognition and processing of electric signals by proteins of the cell membrane. PMID:7811939

Aircraft Lightning Electromagnetic Environment Measurement

NASA Technical Reports Server (NTRS)

Ely, Jay J.; Nguyen, Truong X.; Szatkowski, George N.

2011-01-01

This paper outlines a NASA project plan for demonstrating a prototype lightning strike measurement system that is suitable for installation onto research aircraft that already operate in thunderstorms. This work builds upon past data from the NASA F106, FAA CV-580, and Transall C-180 flight projects, SAE ARP5412, and the European ILDAS Program. The primary focus is to capture airframe current waveforms during attachment, but may also consider pre and post-attachment current, electric field, and radiated field phenomena. New sensor technologies are being developed for this system, including a fiber-optic Faraday polarization sensor that measures lightning current waveforms from DC to over several Megahertz, and has dynamic range covering hundreds-of-volts to tens-of-thousands-of-volts. A study of the electromagnetic emission spectrum of lightning (including radio wave, microwave, optical, X-Rays and Gamma-Rays), and a compilation of aircraft transfer-function data (including composite aircraft) are included, to aid in the development of other new lightning environment sensors, their placement on-board research aircraft, and triggering of the onboard instrumentation system. The instrumentation system will leverage recent advances in high-speed, high dynamic range, deep memory data acquisition equipment, and fiber-optic interconnect.

Fundamentals of Transcranial Electric and Magnetic Stimulation Dose: Definition, Selection, and Reporting Practices

PubMed Central

Peterchev, Angel V.; Wagner, Timothy A.; Miranda, Pedro C.; Nitsche, Michael A.; Paulus, Walter; Lisanby, Sarah H.; Pascual-Leone, Alvaro; Bikson, Marom

2011-01-01

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. The biological effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biological effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated. This paper provides fundamental definition and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. PMID:22305345

Fundamentals of transcranial electric and magnetic stimulation dose: definition, selection, and reporting practices.

PubMed

Peterchev, Angel V; Wagner, Timothy A; Miranda, Pedro C; Nitsche, Michael A; Paulus, Walter; Lisanby, Sarah H; Pascual-Leone, Alvaro; Bikson, Marom

2012-10-01

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. This paper provides fundamental definitions and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. The biologic effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biologic effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated. Copyright © 2012 Elsevier Inc. All rights reserved.

An Arbitrary Waveform Wearable Neuro-stimulator System for Neurophysiology Research on Freely Behaving Animals.

PubMed

Samani, Mohsen Mosayebi; Mahnam, Amin; Hosseini, Nasrin

2014-04-01

Portable wireless neuro-stimulators have been developed to facilitate long-term cognitive and behavioral studies on the central nervous system in freely moving animals. These stimulators can provide precisely controllable input(s) to the nervous system, without distracting the animal attention with cables connected to its body. In this study, a low power backpack neuro-stimulator was developed for animal brain researches that can provides arbitrary stimulus waveforms for the stimulation, while it is small and light weight to be used for small animals including rats. The system consists of a controller that uses an RF link to program and activate a small and light microprocessor-based stimulator. A Howland current source was implemented to produce precise current controlled arbitrary waveform stimulations. The system was optimized for ultra-low power consumption and small size. The stimulator was first tested for its electrical specifications. Then its performance was evaluated in a rat experiment when electrical stimulation of medial longitudinal fasciculus induced circling behavior. The stimulator is capable of delivering programmed stimulations up to ± 2 mA with adjusting steps of 1 μA, accuracy of 0.7% and compliance of 6 V. The stimulator is 15 mm × 20 mm × 40 mm in size, weights 13.5 g without battery and consumes a total power of only 5.l mW. In the experiment, the rat could easily carry the stimulator and demonstrated the circling behavior for 0.1 ms current pulses of above 400 μA. The developed system has a competitive size and weight, whereas providing a wide range of operation and the flexibility of generating arbitrary stimulation patterns ideal for long-term experiments in the field of cognitive and neuroscience research.

Feasibility study on measurement of magnetocardiography (MCG) using fluxgate magnetometer

NASA Astrophysics Data System (ADS)

Sengottuvel, S.; Sharma, Akash; Biswal, Deepak; Khan, Pathan Fayaz; Swain, Pragyna Parimita; Patel, Rajesh; Gireesan, K.

2018-04-01

This paper reports the feasibility of measuring weak magnetic fields generated by the electrical activity of the heart using a portable tri-axial fluxgate magnetometer inside a magnetically shielded room. Measurement of Magnetocardiogram (MCG) signals could be successfully demonstrated from a healthy subject using a novel set-up involving a reference fluxgate sensor which simultaneously measures the magnetic fields associated with the ECG waveform measured on the same subject. The timing information provided by R wave peaks of ECG recorded by the reference sensor is utilized to generate trigger locked average of the sensor output of the measurement fluxgate, and extract MCG signals in all the three orthogonal directions (X, Y and Z) on the anterior thorax. It is expected that such portable room temperature measurements using fluxgate sensor could assist in validating the direction of the equivalent current dipole associated with the electrical activity of the human heart. This is somewhat difficult in conventional MCG measurements using SQUID sensors, which usually furnish only the z component of the magnetic field and its spatial derivatives.

THOR Fields and Wave Processor - FWP

NASA Astrophysics Data System (ADS)

Soucek, Jan; Rothkaehl, Hanna; Ahlen, Lennart; Balikhin, Michael; Carr, Christopher; Dekkali, Moustapha; Khotyaintsev, Yuri; Lan, Radek; Magnes, Werner; Morawski, Marek; Nakamura, Rumi; Uhlir, Ludek; Yearby, Keith; Winkler, Marek; Zaslavsky, Arnaud

2017-04-01

If selected, Turbulence Heating ObserveR (THOR) will become the first spacecraft mission dedicated to the study of plasma turbulence. The Fields and Waves Processor (FWP) is an integrated electronics unit for all electromagnetic field measurements performed by THOR. FWP will interface with all THOR fields sensors: electric field antennas of the EFI instrument, the MAG fluxgate magnetometer, and search-coil magnetometer (SCM), and perform signal digitization and on-board data processing. FWP box will house multiple data acquisition sub-units and signal analyzers all sharing a common power supply and data processing unit and thus a single data and power interface to the spacecraft. Integrating all the electromagnetic field measurements in a single unit will improve the consistency of field measurement and accuracy of time synchronization. The scientific value of highly sensitive electric and magnetic field measurements in space has been demonstrated by Cluster (among other spacecraft) and THOR instrumentation will further improve on this heritage. Large dynamic range of the instruments will be complemented by a thorough electromagnetic cleanliness program, which will prevent perturbation of field measurements by interference from payload and platform subsystems. Taking advantage of the capabilities of modern electronics and the large telemetry bandwidth of THOR, FWP will provide multi-component electromagnetic field waveforms and spectral data products at a high time resolution. Fully synchronized sampling of many signals will allow to resolve wave phase information and estimate wavelength via interferometric correlations between EFI probes. FWP will also implement a plasma resonance sounder and a digital plasma quasi-thermal noise analyzer designed to provide high cadence measurements of plasma density and temperature complementary to data from particle instruments. FWP will rapidly transmit information about magnetic field vector and spacecraft potential to the particle instrument data processing unit (PPU) via a dedicated digital link. This information will help particle instruments to optimize energy and angular sweeps and calculate on-board moments. FWP will also coordinate the acquisition of high resolution waveform snapshots with very high time resolution electron data from the TEA instrument. This combined wave/particle measurement will provide the ultimate dataset for investigation of wave-particle interactions on electron scales. The FWP instrument shall be designed and built by an international consortium of scientific institutes from Czech Republic, Poland, France, UK, Sweden and Austria.

Bandwidth scalable, coherent transmitter based on the parallel synthesis of multiple spectral slices using optical arbitrary waveform generation.

PubMed

Geisler, David J; Fontaine, Nicolas K; Scott, Ryan P; He, Tingting; Paraschis, Loukas; Gerstel, Ori; Heritage, Jonathan P; Yoo, S J B

2011-04-25

We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.

Comparison of five different defibrillators using recommended energy protocols.

PubMed

Zelinka, M; Buić, D; Zelinka, I

2007-09-01

Biphasic defibrillators represent a great step ahead in defibrillation. The manufacturers claim that biphasic defibrillators are able to compensate for differences in transthoracic impedance. That should mean that all patients should be defibrillated with approximately the same amount of current, regardless of their transthoracic impedance. We assessed one monophasic and four biphasic defibrillators. The defibrillators were discharged into resistive loads of 50, 90 and 130 Omega, simulating transthoracic impedance. For each waveform we used energy protocols recommended by the manufacturers and guidelines 2005. Waveforms were observed with on a digitising oscilloscope on a current sensing resistor. We compared the electrical properties of different waveforms and two defibrillators with the same type of waveform. The influence of different impedance on shape, duration and amplitude of current flow were also observed for each waveform. Measurements showed a significant difference in current flow at different impedance loads. At low impedance the mean current is well above expectations for all the defibrillators studied and at high impedance load we observed a big reduction of current amplitude. We can conclude that the compensating mechanisms of biphasic defibrillators are, from electrical point of view, negligible. From the laws of physics it is practically impossible to keep same level of current at given time with same energy at higher impedance. That is why we should reconsider the use of different energy equivalents between patients with different transthoracic impedance and not between different defibrillation impulses.

Preliminary Design of a Lightning Optical Camera and ThundEr (LOCATE) Sensor

NASA Technical Reports Server (NTRS)

Phanord, Dieudonne D.; Koshak, William J.; Rybski, Paul M.; Arnold, James E. (Technical Monitor)

2001-01-01

The preliminary design of an optical/acoustical instrument is described for making highly accurate real-time determinations of the location of cloud-to-ground (CG) lightning. The instrument, named the Lightning Optical Camera And ThundEr (LOCATE) sensor, will also image the clear and cloud-obscured lightning channel produced from CGs and cloud flashes, and will record the transient optical waveforms produced from these discharges. The LOCATE sensor will consist of a full (360 degrees) field-of-view optical camera for obtaining CG channel image and azimuth, a sensitive thunder microphone for obtaining CG range, and a fast photodiode system for time-resolving the lightning optical waveform. The optical waveform data will be used to discriminate CGs from cloud flashes. Together, the optical azimuth and thunder range is used to locate CGs and it is anticipated that a network of LOCATE sensors would determine CG source location to well within 100 meters. All of this would be accomplished for a relatively inexpensive cost compared to present RF lightning location technologies, but of course the range detection is limited and will be quantified in the future. The LOCATE sensor technology would have practical applications for electric power utility companies, government (e.g. NASA Kennedy Space Center lightning safety and warning), golf resort lightning safety, telecommunications, and other industries.

Detection of sinkholes or anomalies using full seismic wave fields.

DOT National Transportation Integrated Search

2013-04-01

This research presents an application of two-dimensional (2-D) time-domain waveform tomography for detection of embedded sinkholes and anomalies. The measured seismic surface wave fields were inverted using a full waveform inversion (FWI) technique, ...

Tracking Characteristics of a Triangular-Aperture Mounted Optical Head Slider to Which a Polarized Violet Laser Source Is Applied

NASA Astrophysics Data System (ADS)

Ohkubo, Toshifumi; Park, Majung; Hirata, Masakazu; Oumi, Manabu; Nakajima, Kunio

In near-field optical recording, the combination of a triangular aperture and a polarized illuminating light is thought to be one of the most promising breakthroughs for improving both spatial resolution and signal-to-noise ratio. In light of this, we have already fabricated a triangular-aperture mounted optical head slider and demonstrated its superior performance while clarifying the influence of the polarization direction on the spatial resolution in the circumferential direction. When the polarization direction was perpendicular to the bottom side (which is parallel to the slider trailing edge) of the aperture, the highest spatial resolution and signal contrast were obtained, in spite of the usage of a fairly large aperture, indicating the presence of clear readout signal waveforms corresponding down to 100 nm line-and-space (L/S) patterns. In this study, we tried to experimentally clarify the influence of the polarization direction of the illuminating light on an aperture's field spread in the radial direction. In order to concretely evaluate the field spread, we prepared 1-mm-long linearly arranged (in the circumferential direction) L/S patterns on a metal-layered medium, and a piezo-electric actuator combined positioner. Intersecting the aperture at two portions of the tracks, directly acquired signal waveforms could be successfully transformed into the waveforms that would be obtained if the aperture had crossed the track at right angles. The field spreads in the radial direction were estimated to be approximately 250 nm when the polarization direction was perpendicular to the bottom side. In contrast, when the polarization direction was 45 degrees, the stationary field spread in the radial direction was estimated to be approximately 350 - 370 nm. It could be confirmed experimentally that both the highest spatial resolution in the circumferential direction and the smallest field spread in the radial direction were realized with the combination of the triangular aperture and the illuminating polarized light whose direction was perpendicular to the bottom side. Based on these results, the signal-to-noise ratio will be evaluated and discussed in the future with respect to the above-mentioned optimum aperture structure and conditions.

Experimental and theoretical analysis of neuron-transistor hybrid electrical coupling: the relationships between the electro-anatomy of cultured Aplysia neurons and the recorded field potentials.

PubMed

Cohen, Ariel; Shappir, Joseph; Yitzchaik, Shlomo; Spira, Micha E

2006-12-15

Understanding the mechanisms that generate field potentials (FPs) by neurons grown on semiconductor chips is essential for implementing neuro-electronic devices. Earlier studies emphasized that FPs are generated by current flow between differentially expressed ion channels on the membranes facing the chip surface, and those facing the culture medium in electrically compact cells. Less is known, however, about the mechanisms that generate FPs by action potentials (APs) that propagate along typical non-isopotential neurons. Using Aplysia neurons cultured on floating gate-transistors, we found that the FPs generated by APs in cultured neurons are produced by current flow along neuronal compartments comprising the axon, cell body, and neurites, rather than by flow between the membrane facing the chip substrate and that facing the culture medium. We demonstrate that the FPs waveform generated by non-isopotential neurons largely depends on the morphology of the neuron.

Implementation of a portable electronic system for providing pain relief to patellofemoral pain syndrome patients

NASA Astrophysics Data System (ADS)

Chang Chien, Jia-Ren; Lin, Guo-Hong; Hsu, Ar-Tyan

2011-10-01

In this study, a portable electromyogram (EMG) system and a stimulator are developed for patellofemoral pain syndrome patients, with the objective of reducing the pain experienced by these patients; the patellar pain is caused by an imbalance between the vastus medialis obliquus (VMO) and the vastus lateralis (VL). The EMG measurement circuit and the electrical stimulation device proposed in this study are specifically designed for the VMO and the VL; they are capable of real-time waveform recording, possess analyzing functions, and can upload their measurement data to a computer for storage and analysis. The system can calculate and record the time difference between the EMGs of the VMO and the VL, as well as the signal strengths of both the EMGs. As soon as the system detects the generation of the EMG of the VL, it quickly calculates and processes the event and stimulates the VMO as feedback through electrical stimulation units, in order to induce its contraction. The system can adjust the signal strength, time length, and the sequence of the electrical stimulation, both manually and automatically. The output waveform of the electrical stimulation circuit is a dual-phase asymmetrical pulse waveform. The primary function of the electrical simulation circuit is to ensure that the muscles contract effectively. The performance of the device can be seen that the width of each pulse is 20-1000 μs, the frequency of each pulse is 10-100 Hz, and current strength is 10-60 mA.

Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

PubMed

Lee, Chung Jun; Kim, Jip; Kim, Taegyu

2016-02-01

Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

Comparative In Situ Measurements of Plasma Instabilities in the Equatorial and Auroral Electrojets

NASA Technical Reports Server (NTRS)

Pfaff, Robert F.

2008-01-01

This presentation provides a comparison of in situ measurements of plasma instabilities gathered by rocket-borne probes in the equatorial and auroral electrojets. Specifically, using detailed measurements of the DC electric fields, current density, and plasma number density within the unstable daytime equatorial electrojet from Brazil (Guara Campaign) and in the auroral electrojet from Sweden (ERRIS Campaign), we present comparative observations and general conclusions regarding the observed physical properties of Farley-Buneman two-stream waves and large scale, gradient drift waves. The two stream observations reveal coherent-like waves propagating near the E x B direction but at reduced speeds (nearer to the presumed acoustic velocity) with wavelengths of approximately 5-10m in both the equatorial and auroral electrojet, as measured using the spaced-receiver technique. The auroral electrojet data generally shows extensions to shorter wavelengths, in concert with the fact that these waves are driven harder. With respect to gradient-drift driven waves, observations of this instability are much more pronounced in the equatorial electrojet, given the more favorable geometry for growth provided by the vertical gradient and horizontal magnetic field lines. We present new analysis of Guara rocket observations of electric field and plasma density data that reveal considerable structuring in the middle and lower portion of the electrojet (90-105 km) where the ambient plasma density gradient is unstable. Although the electric field amplitudes are largest (approximately 10-15 mV/m) in the zonal direction, considerable structure (approximately 5-10 mV/m) is also observed in the vertical electric field component as well, implying that the dominant large scale waves involve significant vertical interaction and coupling within the narrow altitude range where they are observed. Furthermore, a detailed examination of the phase of the waveforms show that on some, but not all occasions, locally enhanced eastward fields are associated with locally enhanced upwards (polarization) electric fields. The measurements are discussed in terms of theories involving the non-linear evolution and structuring of plasma waves.

Seizure entrainment with polarizing low-frequency electric fields in a chronic animal epilepsy model

NASA Astrophysics Data System (ADS)

Sunderam, Sridhar; Chernyy, Nick; Peixoto, Nathalia; Mason, Jonathan P.; Weinstein, Steven L.; Schiff, Steven J.; Gluckman, Bruce J.

2009-08-01

Neural activity can be modulated by applying a polarizing low-frequency (Lt100 Hz) electric field (PLEF). Unlike conventional pulsed stimulation, PLEF stimulation has a graded, modulatory effect on neuronal excitability, and permits the simultaneous recording of neuronal activity during stimulation suitable for continuous feedback control. We tested a prototype system that allows for simultaneous PLEF stimulation with minimal recording artifact in a chronic tetanus toxin animal model (rat) of hippocampal epilepsy with spontaneous seizures. Depth electrode local field potentials recorded during seizures revealed a characteristic pattern of field postsynaptic potentials (fPSPs). Sinusoidal voltage-controlled PLEF stimulation (0.5-25 Hz) was applied in open-loop cycles radially across the CA3 of ventral hippocampus. For stimulated seizures, fPSPs were transiently entrained with the PLEF waveform. Statistical significance of entrainment was assessed with Thomson's harmonic F-test, with 45/132 stimulated seizures in four animals individually demonstrating significant entrainment (p < 0.04). Significant entrainment for multiple presentations at the same frequency (p < 0.01) was observed in three of four animals in 42/64 stimulated seizures. This is the first demonstration in chronically implanted freely behaving animals of PLEF modulation of neural activity with simultaneous recording.

Simulation of Transient Response of Ir-TES for Position-Sensitive TES with Waveform Domain Multiplexing

NASA Astrophysics Data System (ADS)

Minamikawa, Y.; Sato, H.; Mori, F.; Damayanthi, R. M. T.; Takahashi, H.; Ohno, M.

2008-04-01

We are developing a new x-ray microcalorimeter based on a superconducting transition edge sensor (TES) as an imaging sensor. Our measurement shows unique waveforms which we consider as an expression of thermal nonuniformity of TES films. This arises from the different thermal responses, so that response signal shapes would vary according to the position of the incident x-ray. This position dependency deteriorate the measured energy resolution, but with appropriate waveform analysis, this would be useful for imaging device. For more inspection, we have developed a simulation code which enables a dynamic simulation to obtain a transient response of the TES by finite differential method. Temperature and electric current distributions are calculated. As a result, we successfully obtained waveform signals. The calculated signal waveforms have similar characteristics to the measured signals. This simulation visualized the transition state of the device and will help to design better detector.

Arbitrary magnetic field gradient waveform correction using an impulse response based pre-equalization technique.

PubMed

Goora, Frédéric G; Colpitts, Bruce G; Balcom, Bruce J

2014-01-01

The time-varying magnetic fields used in magnetic resonance applications result in the induction of eddy currents on conductive structures in the vicinity of both the sample under investigation and the gradient coils. These eddy currents typically result in undesired degradations of image quality for MRI applications. Their ubiquitous nature has resulted in the development of various approaches to characterize and minimize their impact on image quality. This paper outlines a method that utilizes the magnetic field gradient waveform monitor method to directly measure the temporal evolution of the magnetic field gradient from a step-like input function and extracts the system impulse response. With the basic assumption that the gradient system is sufficiently linear and time invariant to permit system theory analysis, the impulse response is used to determine a pre-equalized (optimized) input waveform that provides a desired gradient response at the output of the system. An algorithm has been developed that calculates a pre-equalized waveform that may be accurately reproduced by the amplifier (is physically realizable) and accounts for system limitations including system bandwidth, amplifier slew rate capabilities, and noise inherent in the initial measurement. Significant improvements in magnetic field gradient waveform fidelity after pre-equalization have been realized and are summarized. Copyright © 2013 Elsevier Inc. All rights reserved.

JTRS/SCA and Custom/SDR Waveform Comparison

NASA Technical Reports Server (NTRS)

Oldham, Daniel R.; Scardelletti, Maximilian C.

2007-01-01

This paper compares two waveform implementations generating the same RF signal using the same SDR development system. Both waveforms implement a satellite modem using QPSK modulation at 1M BPS data rates with one half rate convolutional encoding. Both waveforms are partitioned the same across the general purpose processor (GPP) and the field programmable gate array (FPGA). Both waveforms implement the same equivalent set of radio functions on the GPP and FPGA. The GPP implements the majority of the radio functions and the FPGA implements the final digital RF modulator stage. One waveform is implemented directly on the SDR development system and the second waveform is implemented using the JTRS/SCA model. This paper contrasts the amount of resources to implement both waveforms and demonstrates the importance of waveform partitioning across the SDR development system.

Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge

PubMed Central

Sullivan, John P.; Zuanon, Jansen; Cox Fernandes, Cristina

2013-01-01

Abstract We describe two new, closely related species of toothed Brachyhypopomus (Hypopomidae: Gymnotiformes: Teleostei) from the central Amazon basin and create a new subgenus for them. Odontohypopomus, new subgenus of Brachyhypopomus, is diagnosed by (1) small teeth present on premaxillae; (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life (and to lesser extent in preservation) distinctly yellowish with head and sides peppered with small, widely spaced, very dark brown stellate chromatophores that greatly contrast with light background coloration; (4) a dark blotch or bar of subcutaneous pigment below the eye; (5) electric organ discharge waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent) and slow pulse repetition rate (3–16 Hz). The type species of the new subgenus, Brachyhypopomus (Odontohypopomus) walteri sp. n., is diagnosed by the following additional character states: (1) subcutaneous dark pigment at base of orbit particularly prominent, (2) body semi-translucent and nearly bright yellow background coloration in life, (3) a biphasic electric organ discharge (EOD) waveform of very long duration (between 3.5 and 4 milliseconds at 25° C) with head-positive first phase significantly longer than second head-negative phase in both sexes. Brachyhypopomus (Odontohypopomus) bennetti sp. n. is diagnosed by two character states in addition to those used to diagnose the subgenus Odontohypopomus: (1) a deep electric organ, visible as large semi-transparent area, occupying approximately 14–17% body depth directly posterior to the abdominal cavity in combination with a short, but deep, caudal filament, and (2) a monophasic, head-positive EOD waveform, approximately 2.1 milliseconds in duration in both sexes. These are the only described rhamphichthyoid gymnotiforms with oral teeth, and Brachyhypopomus bennetti is the first Brachyhypopomus reported to have a monophasic (head-positive) EOD waveform. Unlike biphasic species, the waveform of its EOD is largely unaffected by tail damage from predators. Such injuries are common among specimens in our collections. This species’ preference for floating meadow habitat along the major channels of the Amazon River basin may put it at particularly high risk of predation and “tail grazing.” PMID:24167419

Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge.

PubMed

Sullivan, John P; Zuanon, Jansen; Cox Fernandes, Cristina

2013-01-01

We describe two new, closely related species of toothed Brachyhypopomus (Hypopomidae: Gymnotiformes: Teleostei) from the central Amazon basin and create a new subgenus for them. Odontohypopomus, new subgenus of Brachyhypopomus, is diagnosed by (1) small teeth present on premaxillae; (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life (and to lesser extent in preservation) distinctly yellowish with head and sides peppered with small, widely spaced, very dark brown stellate chromatophores that greatly contrast with light background coloration; (4) a dark blotch or bar of subcutaneous pigment below the eye; (5) electric organ discharge waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent) and slow pulse repetition rate (3-16 Hz). The type species of the new subgenus, Brachyhypopomus (Odontohypopomus) walteri sp. n., is diagnosed by the following additional character states: (1) subcutaneous dark pigment at base of orbit particularly prominent, (2) body semi-translucent and nearly bright yellow background coloration in life, (3) a biphasic electric organ discharge (EOD) waveform of very long duration (between 3.5 and 4 milliseconds at 25° C) with head-positive first phase significantly longer than second head-negative phase in both sexes. Brachyhypopomus (Odontohypopomus) bennetti sp. n. is diagnosed by two character states in addition to those used to diagnose the subgenus Odontohypopomus: (1) a deep electric organ, visible as large semi-transparent area, occupying approximately 14-17% body depth directly posterior to the abdominal cavity in combination with a short, but deep, caudal filament, and (2) a monophasic, head-positive EOD waveform, approximately 2.1 milliseconds in duration in both sexes. These are the only described rhamphichthyoid gymnotiforms with oral teeth, and Brachyhypopomus bennetti is the first Brachyhypopomus reported to have a monophasic (head-positive) EOD waveform. Unlike biphasic species, the waveform of its EOD is largely unaffected by tail damage from predators. Such injuries are common among specimens in our collections. This species' preference for floating meadow habitat along the major channels of the Amazon River basin may put it at particularly high risk of predation and "tail grazing."

Using 3D Simulation of Elastic Wave Propagation in Laplace Domain for Electromagnetic-Seismic Inverse Modeling

NASA Astrophysics Data System (ADS)

Petrov, P.; Newman, G. A.

2010-12-01

Quantitative imaging of the subsurface objects is essential part of modern geophysical technology important in oil and gas exploration and wide-range engineering applications. A significant advancement in developing a robust, high resolution imaging technology is concerned with using the different geophysical measurements (gravity, EM and seismic) sense the subsurface structure. A joint image of the subsurface geophysical attributes (velocity, electrical conductivity and density) requires the consistent treatment of the different geophysical data (electromagnetic and seismic) due to their differing physical nature - diffusive and attenuated propagation of electromagnetic energy and nonlinear, multiple scattering wave propagation of seismic energy. Recent progress has been reported in the solution of this problem by reducing the complexity of seismic wave field. Works formed by Shin and Cha (2009 and 2008) suggests that low-pass filtering the seismic trace via Laplace-Fourier transformation can be an effective approach for obtaining seismic data that has similar spatial resolution to EM data. The effect of Laplace- Fourier transformation on the low-pass filtered trace changes the modeling of the seismic wave field from multi-wave propagation to diffusion. The key benefit of transformation is that diffusive wave-field inversion works well for both data sets seismic (Shin and Cha, 2008) and electromagnetic (Commer and Newman 2008, Newman et al., 2010). Moreover the different data sets can also be matched for similar and consistent resolution. Finally, the low pass seismic image is also an excellent choice for a starting model when analyzing the entire seismic waveform to recover the high spatial frequency components of the seismic image; its reflectivity (Shin and Cha, 2009). Without a good starting model full waveform seismic imaging and migration can encounter serious difficulties. To produce seismic wave fields consistent for joint imaging in the Laplace-Fourier domain we had developed 3D code for full-wave field simulation in the elastic media which take into account nonlinearity introduced by free-surface effects. Our approach is based on the velocity-stress formulation. In the contrast to conventional formulation we defined the material properties such as density and Lame constants not at nodal points but within cells. This second order finite differences method formulated in the cell-based grid, generate numerical solutions compatible with analytical ones within the range errors determinate by dispersion analysis. Our simulator will be embedded in an inversion scheme for joint seismic- electromagnetic imaging. It also offers possibilities for preconditioning the seismic wave propagation problems in the frequency domain. References. Shin, C. & Cha, Y. (2009), Waveform inversion in the Laplace-Fourier domain, Geophys. J. Int. 177(3), 1067- 1079. Shin, C. & Cha, Y. H. (2008), Waveform inversion in the Laplace domain, Geophys. J. Int. 173(3), 922-931. Commer, M. & Newman, G. (2008), New advances in three-dimensional controlled-source electromagnetic inversion, Geophys. J. Int. 172(2), 513-535. Newman, G. A., Commer, M. & Carazzone, J. J. (2010), Imaging CSEM data in the presence of electrical anisotropy, Geophysics, in press.

Analysis of electromagnetic fields on an F-106B aircraft during lightning strikes

NASA Technical Reports Server (NTRS)

Trost, T. F.; Pitts, F. L.

1982-01-01

Information on the exterior electromagnetic environment of an aircraft when it is struck by lightning has been obtained during thunderstorm penetrations with an F-106B aircraft. Electric and magnetic fields were observed, using mainly time-derivative type sensors, with bandwidths to 50 MHz. Lightning pulse lengths ranging from 25 ns to 7 microsec have been recorded. Sufficient high-frequency content was present to excite electromagnetic resonances of the aircraft, and peaks in the frequency spectra of the waveforms in the range 7 to 23 MHz are in agreement with the resonant frequencies determined in laboratory scale-model tests. Both positively and negatively charged strikes were experienced, and most of the data suggest low values of peak current.

An experimental test of the 'transmission-line model' of electromagnetic radiation from triggered lightning return strokes

NASA Technical Reports Server (NTRS)

Willett, J. C.; Idone, V. P.; Orville, R. E.; Leteinturier, C.; Eybert-Berard, A.

1988-01-01

Peak currents, two-dimensional average propagation speeds, and electric field waveforms for a number of subsequent return strikes in rocket-triggered lightning flashes were measured in order to test the 'transmission-line model' of return-stroke radiation of Uman and McLain (1970). Reasonable agreement is found between the propagation speeds measured with the streak camera and those deduced from the transmission-line model. A modification of the model is proposed in which two wave fronts travel upward and downward away from a junction point a short distance above the ground.

Simulations of electron avalanches in an ultra-low-background proportional counter

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

Robinson, John W.; Aalseth, Craig; Dion, Michael P.

2016-02-01

New classes have been added to the simulation package Garfield++ to import the potential and electric field solutions generated by ANSYS R MaxwellTM v.16. Using these tools we report results on the simulation of electron avalanches and induced signal waveforms in comparison to experimental data of the ultra-lowbackground gas proportional counters being developed at Pacific Northwest National Laboratory. Furthermore, an improved mesh search algorithm based on Delaunay triangulation was implemented and provided at least a three order of magnitude time savings when compared to the built-in point-location search class of Garfield++.

Dust impact effects recorded by the APV-N experiment during Comet Halley encounters

NASA Astrophysics Data System (ADS)

Oberc, P.; Orlowski, D.; Klimov, S.

1986-12-01

During the Vega 1 and 2 comet Halley encounters plasma wave instrument APV-N entered a region of impulsive noise 220,000 km from nucleus. The noise is attributed to dust grain impacts onto spacecraft body. Regression analysis of impact induced effects recorded during flyby shows that from 100,000 km from closest approach most plasma wave spectra measured by APV-N onboard Vega 1 and 2 are significantly influenced by dust impact effects. Signals associated with large dust impacts are directly recorded on the E2 0.1 to 25 Hz electric field waveform channel.

The ISPM unified radio and plasma wave experiment

NASA Technical Reports Server (NTRS)

Stone, R. G.; Caldwell, J.; Deconchy, Y.; Deschanciaux, C.; Ebbett, R.; Epstein, G.; Groetz, K.; Harvey, C. C.; Hoang, S.; Howard, R.

1983-01-01

Hardware for the International Solar Polar Mission (ISPM) Unified Radio and Plasma (URAP) wave experiment is presented. The URAP determines direction and polarization of distant radio sources for remote sensing of the heliosphere, and studies local wave phenomena which determine the transport coefficients of the ambient plasma. Electric and magnetic field antennas and preamplifiers; the electromagnetic compatibility plan and grounding; radio astronomy and plasma frequency receivers; a fast Fourier transformation data processing unit waveform analyzer; dc voltage measurements; a fast envelope sampler for the solar wind, and plasmas near Jupiter; a sounder; and a power converter are described.

An experimental test of the 'transmission-line model' of electromagnetic radiation from triggered lightning return strokes

NASA Astrophysics Data System (ADS)

Willett, J. C.; Idone, V. P.; Orville, R. E.; Leteinturier, C.; Eybert-Berard, A.

1988-04-01

Peak currents, two-dimensional average propagation speeds, and electric field waveforms for a number of subsequent return strikes in rocket-triggered lightning flashes were measured in order to test the 'transmission-line model' of return-stroke radiation of Uman and McLain (1970). Reasonable agreement is found between the propagation speeds measured with the streak camera and those deduced from the transmission-line model. A modification of the model is proposed in which two wave fronts travel upward and downward away from a junction point a short distance above the ground.

Monolithic carrier-envelope phase-stabilization scheme.

PubMed

Fuji, Takao; Rauschenberger, Jens; Apolonski, Alexander; Yakovlev, Vladislav S; Tempea, Gabriel; Udem, Thomas; Gohle, Christoph; Hänsch, Theodor W; Lehnert, Walter; Scherer, Michael; Krausz, Ferenc

2005-02-01

A new scheme for stabilizing the carrier-envelope (CE) phase of a few-cycle laser pulse train is demonstrated. Self-phase modulation and difference-frequency generation in a single periodically poled lithium niobate crystal that transmits the main laser beam allows CE phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE phase control, coupling into microstructured fiber, and separation and recombination of spectral components. As a consequence, the output yields 6-fs, 800-nm pulses with an unprecedented degree of short- and long-term reproducibility of the electric field waveform.

A photoelectric technique for measuring lightning-channel propagation velocities from a mobile laboratory

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Rust, W. David

1989-01-01

The present device for lightning channel propagation-velocity determination employs eight photodetectors mounted behind precision horizontal slits in the focal plane of a photographic camera lens. The eight photodetector pulses, IRIG-B time, and slow and fast electric field-change waveforms are recorded on a 14-track analog tape recorder. A comparison of the present results with those obtained by a streaking camera shows no significant differences between the velocities obtained from the same strokes with the two systems; neither is there any difference in pulse characteristics or in the velocities calculated from them.

Dust Impacts In the Outer Solar System Detected by Voyagers 1 and 2

NASA Astrophysics Data System (ADS)

Gurnett, D. A.; Persoon, A. M.; Granroth, L. J.; Kurth, W. S.

2011-12-01

The plasma wave instruments (PWS) on the Voyager 1 and 2 spacecraft, which are currently at about 119 and 97 AU, have been consistently detecting a low rate of dust impacts as the spacecraft proceed outward from the Sun into interstellar space. Because of the high radial velocity of the spacecraft, ~ 17 and 15 km/sec, when a dust particle strikes the spacecraft it is almost instantly vaporized and ionized, thereby producing a rapidly expanding cloud of plasma that causes a voltage pulse in the PWS electric antenna. The voltage pulse has a very rapid rise time of about 10 μs and is an easily identifiable waveform in the wideband electric field data. Due to a failure in the Voyager 2 waveform receiver no impact data are available from Voyager 2 beyond about 60 AU. However, the Voyager 1 waveform receiver is still working. Because of the very high data rates involved, 115.2 kb/s, antenna voltage waveforms can only be recorded for less than a minute per week, so the effective observing time is very small. Nonetheless, once the regions around the outer planets are excluded, a consistent background impact rate of a few impacts per hour is observed by both spacecraft. The impact rate appears to be increasing slightly with increasing radial distance, from about 3 ± 1 impacts per hour at 30 AU, to 6 ± 4 impacts per hour at 110 AU. If the impact cross-section of the spacecraft is assumed to be determined by the spacecraft high gain antenna, which has an area of 10.75 square meters, the corresponding particle flux varies from about 0.75 x 10-14 m-2 s-1 at 30 AU, to about 1.5 x 10-14 m-2 s-1 at 110 AU. Although we have no reliable method of estimating the size or origin of the particles, we note that this flux is consistent with the flux of submicron particles (10-15 to 10-9 g) arriving from interstellar space as detected by the Ulysses spacecraft at radial distances inside of 5 AU. Therefore, we believe that the particles are probably of interstellar origin.

A coaxial-output capacitor-loaded annular pulse forming line.

PubMed

Li, Rui; Li, Yongdong; Su, Jiancang; Yu, Binxiong; Xu, Xiudong; Zhao, Liang; Cheng, Jie; Zeng, Bo

2018-04-01

A coaxial-output capacitor-loaded annular pulse forming line (PFL) is developed in order to reduce the flat top fluctuation amplitude of the forming quasi-square pulse and improve the quality of the pulse waveform produced by a Tesla-pulse forming network (PFN) type pulse generator. A single module composed of three involute dual-plate PFNs is designed, with a characteristic impedance of 2.44 Ω, an electrical length of 15 ns, and a sustaining voltage of 60 kV. The three involute dual-plate PFNs connected in parallel have the same impedance and electrical length. Due to the existed small inductance and capacitance per unit length in each involute dual-plate PFN, the upper cut-off frequency of the PFN is increased. As a result, the entire annular PFL has better high-frequency response capability. Meanwhile, the three dual-plate PFNs discharge in parallel, which is much closer to the coaxial output. The series connecting inductance between adjacent two modules is significantly reduced when the annular PFL modules are connected in series. The pulse waveform distortion is reduced when the pulse transfers along the modules. Finally, the shielding electrode structure is applied on both sides of the module. The electromagnetic field is restricted in the module when a single module discharges, and the electromagnetic coupling between the multi-stage annular PFLs is eliminated. Based on the principle of impedance matching between the multi-stage annular PFL and the coaxial PFL, the structural optimization design of a mixed PFL in a Tesla type pulse generator is completed with the transient field-circuit co-simulation method. The multi-stage annular PFL consists of 18 stage annular PFL modules in series, with the characteristic impedance of 44 Ω, the electrical length of 15 ns, and the sustaining voltage of 1 MV. The mixed PFL can generate quasi-square electrical pulses with a pulse width of 43 ns, and the fluctuation ratio of the pulse flat top is less than 8% when the pulse rise time is about 5 ns.

A coaxial-output capacitor-loaded annular pulse forming line

NASA Astrophysics Data System (ADS)

Li, Rui; Li, Yongdong; Su, Jiancang; Yu, Binxiong; Xu, Xiudong; Zhao, Liang; Cheng, Jie; Zeng, Bo

2018-04-01

A coaxial-output capacitor-loaded annular pulse forming line (PFL) is developed in order to reduce the flat top fluctuation amplitude of the forming quasi-square pulse and improve the quality of the pulse waveform produced by a Tesla-pulse forming network (PFN) type pulse generator. A single module composed of three involute dual-plate PFNs is designed, with a characteristic impedance of 2.44 Ω, an electrical length of 15 ns, and a sustaining voltage of 60 kV. The three involute dual-plate PFNs connected in parallel have the same impedance and electrical length. Due to the existed small inductance and capacitance per unit length in each involute dual-plate PFN, the upper cut-off frequency of the PFN is increased. As a result, the entire annular PFL has better high-frequency response capability. Meanwhile, the three dual-plate PFNs discharge in parallel, which is much closer to the coaxial output. The series connecting inductance between adjacent two modules is significantly reduced when the annular PFL modules are connected in series. The pulse waveform distortion is reduced when the pulse transfers along the modules. Finally, the shielding electrode structure is applied on both sides of the module. The electromagnetic field is restricted in the module when a single module discharges, and the electromagnetic coupling between the multi-stage annular PFLs is eliminated. Based on the principle of impedance matching between the multi-stage annular PFL and the coaxial PFL, the structural optimization design of a mixed PFL in a Tesla type pulse generator is completed with the transient field-circuit co-simulation method. The multi-stage annular PFL consists of 18 stage annular PFL modules in series, with the characteristic impedance of 44 Ω, the electrical length of 15 ns, and the sustaining voltage of 1 MV. The mixed PFL can generate quasi-square electrical pulses with a pulse width of 43 ns, and the fluctuation ratio of the pulse flat top is less than 8% when the pulse rise time is about 5 ns.

Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Peterson, Peter; Hofer, Richard; Mikellides, Ioannis

2016-01-01

NASAs Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front pole cover thruster configuration with the thruster body electrically tied to cathode and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68 and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability was mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 110-5 Torr-Xe (for thruster flow rate above 8 mgs). Power spectral density analysis of the discharge current waveform showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant frequency. Finally the IVB maps of the TDU-1 thruster taken at elevated magnetic fields indicated that the discharge current became more oscillatory with increased facility background pressure at lower thruster mass flow rates, where thruster operation at higher flow rates resulted in less change to the thrusters IVB characteristics.

Computer Analysis of 400 HZ Aircraft Electrical Generator Test Data.

DTIC Science & Technology

1980-06-01

Data Acquisition System. ............ 6 3 Voltage Waveform with Data Points. ....... 19 14 Zero Crossover Interpolation. ........ 20 5 Numerical...difference between successive positive-sloped zero crossovers of the waveform. However, the exact time of zero crossover is not known. This is because...data sampling and the generator output are not synchronized. This unsynchronization means that data points which correspond with an exact zero crossover

Partial discharge detection and analysis in low pressure environments

NASA Astrophysics Data System (ADS)

Liu, Xin

Typical aerospace vehicles (aircraft and spacecraft) experience a wide range of operating pressures during ascending and returning to earth. Compared to the sea-level atmospheric pressure (760 Torr), the pressure at about 60 km altitude is 2 Torr. The performance of the electric power system components of the aerospace vehicles must remain reliable even under such sub-atmospheric operating conditions. It is well known that the dielectric strength of gaseous insulators, while the electrode arrangement remains unchanged, is pressure dependent. Therefore, characterization of the performance and behavior of the electrical insulation in flight vehicles in low-pressure environments is extremely important. Partial discharge testing is one of the practical methods for evaluating the integrity of electrical insulation in aerospace vehicles. This dissertation describes partial discharge (PD) measurements performed mainly with 60 Hz ac energization in air, argon and helium, for pressures between 2 and 760 Torr. Two main electrode arrangements were used. One was a needle-plane electrode arrangement with a Teflon insulating barrier. The other one was a twisted pair of insulated conductors taken from a standard aircraft wiring harness. The measurement results are presented in terms of typical PD current pulse waveforms and waveform analysis for both main electrode arrangements. The evaluation criteria are the waveform polarity, magnitude, shape, rise time, and phase angle (temporal location) relative to the source voltage. Two-variable histograms and statistical averages of the PD parameters are presented. The PD physical mechanisms are analyzed. For PD pattern recognition, both statistical methods (such as discharge parameter dot pattern representation, discharge parameter phase distribution, statistical operator calculations, and PD fingerprint development) and wavelet transform applications are investigated. The main conclusions of the dissertation include: (1) The PD current pulse waveforms are dependent on the pressure. (2) The rise time of the waveform is another effective PD current pulse characteristic indicator. (3) PD fingerprint patterns that are already available for atmospheric pressure (760 Torr) conditions are inadequate for the evaluation of PD pulses at low pressures. (4) Various wavelet transform techniques can be used effectively for PD pulse signal denoising purposes, and for PD pulse waveform transient feature recognition.

Electron series resonance in a magnetized 13.56 MHz symmetric capacitive coupled discharge

NASA Astrophysics Data System (ADS)

Joshi, J. K.; Binwal, S.; Karkari, S. K.; Kumar, Sunil

2018-03-01

A 13.56 MHz capacitive coupled radio-frequency (RF) argon discharge under transverse magnetic field has been investigated. The discharge is operated in a push-pull mode using a 1:1 isolation transformer with its centre tap grounded to a RF generator. The power delivered to the plasma has been calculated from phase-calibrated RF current/voltage waveforms measured on the secondary side of the isolation transformer. An equivalent electrical circuit of the discharge has been described to determine the net plasma impedance. It is found that in the presence of magnetic field, the discharge impedance exhibits a series resonance as the RF power level is increased gradually. However, in the un-magnetized case, the discharge remains entirely capacitive. A qualitative discussion has been given to explain the role of external magnetic field in achieving the series resonance.

Source analysis of MEG activities during sleep (abstract)

NASA Astrophysics Data System (ADS)

Ueno, S.; Iramina, K.

1991-04-01

The present study focuses on magnetic fields of the brain activities during sleep, in particular on K-complexes, vertex waves, and sleep spindles in human subjects. We analyzed these waveforms based on both topographic EEG (electroencephalographic) maps and magnetic fields measurements, called MEGs (magnetoencephalograms). The components of magnetic fields perpendicular to the surface of the head were measured using a dc SQUID magnetometer with a second derivative gradiometer. In our computer simulation, the head is assumed to be a homogeneous spherical volume conductor, with electric sources of brain activity modeled as current dipoles. Comparison of computer simulations with the measured data, particularly the MEG, suggests that the source of K-complexes can be modeled by two current dipoles. A source for the vertex wave is modeled by a single current dipole which orients along the body axis out of the head. By again measuring the simultaneous MEG and EEG signals, it is possible to uniquely determine the orientation of this dipole, particularly when it is tilted slightly off-axis. In sleep stage 2, fast waves of magnetic fields consistently appeared, but EEG spindles appeared intermittently. The results suggest that there exist sources which are undetectable by electrical measurement but are detectable by magnetic-field measurement. Such source can be described by a pair of opposing dipoles of which directions are oppositely oriented.

Waveform generation in the EETS

NASA Astrophysics Data System (ADS)

Wilshire, J. P.

1985-05-01

Design decisions and analysis for the waveform generation portion of an electrical equipment test set are discussed. This test set is unlike conventional ATE in that it is portable and designed to operate in forward area sites for the USMC. It is also unique in that it provides for functional testing for 32 electronic units from the AV-88 Harrier II aircraft. Specific requirements for the waveform generator are discussed, including a wide frequency range, high resolution and accuracy, and low total harmonic distortion. Several approaches to meet these requirements are considered and a specific concept is presented in detail, which consists of a digitally produced waveform that feeds a deglitched analog conversion circuit. Rigorous mathematical analysis is presented to prove that this concept meets the requirements. Finally, design alternatives and enhancements are considered.

Ventilator waveforms on anesthesia machine: a simple tool for intraoperative mapping of phrenic nerve and mid-cervical roots.

PubMed

Georgoulis, George; Papagrigoriou, Eirini; Sindou, Marc

2015-12-01

A crucial aspect of surgery on the supraclavicular region, lateral neck, and mid-cervical vertebral region is the identification and sparing of the phrenic nerve and cervical (C4) root that are responsible for diaphragmatic innervation. Therefore intraoperative mapping of these nerve structures can be useful for difficult cases. Electrical stimulation with simultaneous observation of the ventilator waveforms of the anesthesia machine provides an effective method for the precise intraoperative mapping of these structures. In the literature, there is only one publication reporting the use of one of the waveforms (capnography) for this purpose. Capnography and pressure-time waveforms, two mandatory curves in anesthesiological monitoring, were studied under electrical stimulation of the phrenic nerve (one patient) and the C4 root (eight patients). The aim was to detect changes that would verify diaphragmatic contraction. No modifications in anesthesia or surgery and no additional maneuvers were required. In all patients, stimulation was followed by identifiable changes in the two waveforms, compatible with diaphragmatic contraction: acute reduction in amplitude on capnography and repetitive saw-like elevations on pressure-time curve. Frequency of patterns on pressure-time curve coincided with the frequency of stimulation; therefore the two recordings were complementary. This simple method proved effective in identifying the neural structures responsible for diaphragmatic function. We therefore suggest that it should be employed in the various types of surgery where these structures are at risk.

Multifunction waveform generator for EM receiver testing

NASA Astrophysics Data System (ADS)

Chen, Kai; Jin, Sheng; Deng, Ming

2018-01-01

In many electromagnetic (EM) methods - such as magnetotelluric, spectral-induced polarization (SIP), time-domain-induced polarization (TDIP), and controlled-source audio magnetotelluric (CSAMT) methods - it is important to evaluate and test the EM receivers during their development stage. To assess the performance of the developed EM receivers, controlled synthetic data that simulate the observed signals in different modes are required. In CSAMT and SIP mode testing, the waveform generator should use the GPS time as the reference for repeating schedule. Based on our testing, the frequency range, frequency precision, and time synchronization of the currently available function waveform generators on the market are deficient. This paper presents a multifunction waveform generator with three waveforms: (1) a wideband, low-noise electromagnetic field signal to be used for magnetotelluric, audio-magnetotelluric, and long-period magnetotelluric studies; (2) a repeating frequency sweep square waveform for CSAMT and SIP studies; and (3) a positive-zero-negative-zero signal that contains primary and secondary fields for TDIP studies. In this paper, we provide the principles of the above three waveforms along with a hardware design for the generator. Furthermore, testing of the EM receiver was conducted with the waveform generator, and the results of the experiment were compared with those calculated from the simulation and theory in the frequency band of interest.

Waveform LiDAR across forest biomass gradients

NASA Astrophysics Data System (ADS)

Montesano, P. M.; Nelson, R. F.; Dubayah, R.; Sun, G.; Ranson, J.

2011-12-01

Detailed information on the quantity and distribution of aboveground biomass (AGB) is needed to understand how it varies across space and changes over time. Waveform LiDAR data is routinely used to derive the heights of scattering elements in each illuminated footprint, and the vertical structure of vegetation is related to AGB. Changes in LiDAR waveforms across vegetation structure gradients can demonstrate instrument sensitivity to land cover transitions. A close examination of LiDAR waveforms in footprints across a forest gradient can provide new insight into the relationship of vegetation structure and forest AGB. In this study we use field measurements of individual trees within Laser Vegetation Imaging Sensor (LVIS) footprints along transects crossing forest to non-forest gradients to examine changes in LVIS waveform characteristics at sites with low (< 50Mg/ha) AGB. We relate field AGB measurements to original and adjusted LVIS waveforms to detect the forest AGB interval along a forest - non-forest transition in which the LVIS waveform lose the ability to discern differences in AGB. Our results help identify the lower end the forest biomass range that a ~20m footprint waveform LiDAR can detect, which can help infer accumulation of biomass after disturbances and during forest expansion, and which can guide the use of LiDAR within a multi-sensor fusion biomass mapping approach.

Utilization of multiple spinal cord stimulation (SCS) waveforms in chronic pain patients.

PubMed

Berg, Anthony P; Mekel-Bobrov, Nitzan; Goldberg, Edward; Huynh, Dat; Jain, Roshini

2017-08-01

Advances in spinal cord stimulation (SCS) have improved patient outcomes, leading to its increased utilization for chronic pain. Chronic pain is dynamic showing exacerbations, variable severity, and evolving pain patterns. Given this complexity, SCS systems that provide a broad range of stimulation waveforms may be valuable. The aim of this research was to characterize the usage pattern of stimulation waveforms and field shapes in chronic pain patients implanted with the Spectra System. A review of daily device usage in a cohort of 250 patients implanted for a minimum duration of one month was conducted. With follow-ups ranging between 1 month and 1 year post-implant, 72.8% of patients used Standard Rate, 34.8% Anode Intensification, 23.2% Higher Rate, and 8.4% Burst stimulation waveforms. Collectively, 60% used 1 or more advanced waveforms, either exclusively or along with Standard Rate. A trend showed patients continuing to use up to 3 programs one year post-implant. When given a choice, SCS patients often utilize a variety of waveforms, suggesting that patients may benefit from a single system that provides multiple waveforms and field shapes to customize therapy and improve efficacy.

CAP waveform estimation from the measured electrical bioimpedance values: Patient's heart rate variability analysis.

PubMed

Krivoshei, A; Uuetoa, H; Min, M; Annus, P; Uuetoa, T; Lamp, J

2015-08-01

The paper presents analysis of the generic transfer function (TF) between Electrical Bioimpedance (EBI) measured non-invasively on the wrist and Central Aortic Pressure (CAP) invasively measured at the aortic root. Influence of the Heart Rate (HR) variations on the generic TF and on reconstructed CAP waveforms is investigated. The HR variation analysis is provided on a single patient data to exclude inter-patient influences at the current research stage. A new approach for the generic TF estimating from a data ensemble is presented as well. Moreover, an influence of the cardiac period beginning point selection is analyzed and empirically optimal solution for its selection is proposed.

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).

Occupational exposure to intermediate frequency and extremely low frequency magnetic fields among personnel working near electronic article surveillance systems.

PubMed

Roivainen, Päivi; Eskelinen, Tuomo; Jokela, Kari; Juutilainen, Jukka

2014-05-01

Cashiers are potentially exposed to intermediate frequency (IF) magnetic fields at their workplaces because of the electronic article surveillance (EAS) systems used in stores to protect merchandise against theft. This study aimed at investigating occupational exposure of cashiers to IF magnetic fields in Finnish stores. Exposure to extremely low frequency (ELF) magnetic fields was also evaluated because cashiers work near various devices operating with 50 Hz electric power. The peak magnetic flux density was measured for IF magnetic fields, and was found to vary from 0.2 to 4 µT at the cashier's seat. ELF magnetic fields from 0.03 to 4.5 µT were found at the cashier's seat. These values are much lower than exposure limits. However, according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) occupational reference levels for IF magnetic fields (141 µT for the peak field) were exceeded in some cases (maximum 189 µT) for short periods of time when cashiers walked through the EAS gates. As the ICNIRP reference levels do not define any minimum time for exposure, additional investigations are recommended to determine compliance with basic restrictions. Even if the basic restrictions are not exceeded, persons working near EAS devices represent an exceptional group of workers with respect to exposure to electromagnetic fields. This group could serve as a basis for epidemiological studies addressing possible health effects of IF magnetic fields. Compliance with the reference levels for IF fields was evaluated using both broadband measurement of peak fields and the ICNIRP summation rule for multiple frequencies. The latter was generally more conservative, and the difference between the two methods was large (>10-fold) for EAS systems using a 58 kHz signal with complex waveform. This indicates that the ICNIRP multiple frequency rule can be unnecessarily conservative when measuring complex waveforms. © 2014 Wiley Periodicals, Inc.

Electromagnetic field radiation model for lightning strokes to tall structures

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

Motoyama, H.; Janischewskyj, W.; Hussein, A.M.

1996-07-01

This paper describes observation and analysis of electromagnetic field radiation from lightning strokes to tall structures. Electromagnetic field waveforms and current waveforms of lightning strokes to the CN Tower have been simultaneously measured since 1991. A new calculation model of electromagnetic field radiation is proposed. The proposed model consists of the lightning current propagation and distribution model and the electromagnetic field radiation model. Electromagnetic fields calculated by the proposed model, based on the observed lightning current at the CN Tower, agree well with the observed fields at 2km north of the tower.

Acoustic emission signatures of damage modes in concrete

NASA Astrophysics Data System (ADS)

Aggelis, D. G.; Mpalaskas, A. C.; Matikas, T. E.; Van Hemelrijck, D.

2014-03-01

The characterization of the dominant fracture mode may assist in the prediction of the remaining life of a concrete structure due to the sequence between successive tensile and shear mechanisms. Acoustic emission sensors record the elastic responses after any fracture event converting them into electric waveforms. The characteristics of the waveforms vary according to the movement of the crack tips, enabling characterization of the original mode. In this study fracture experiments on concrete beams are conducted. The aim is to examine the typical acoustic signals emitted by different fracture modes (namely tension due to bending and shear) in a concrete matrix. This is an advancement of a recent study focusing on smaller scale mortar and marble specimens. The dominant stress field and ultimate fracture mode is controlled by modification of the four-point bending setup while acoustic emission is monitored by six sensors at fixed locations. Conclusions about how to distinguish the sources based on waveform parameters of time domain (duration, rise time) and frequency are drawn. Specifically, emissions during the shear loading exhibit lower frequencies and longer duration than tensile. Results show that, combination of AE features may help to characterize the shift between dominant fracture modes and contribute to the structural health monitoring of concrete. This offers the basis for in-situ application provided that the distortion of the signal due to heterogeneous wave path is accounted for.

Real-time digital signal recovery for a multi-pole low-pass transfer function system.

PubMed

Lee, Jhinhwan

2017-08-01

In order to solve the problems of waveform distortion and signal delay by many physical and electrical systems with multi-pole linear low-pass transfer characteristics, a simple digital-signal-processing (DSP)-based method of real-time recovery of the original source waveform from the distorted output waveform is proposed. A mathematical analysis on the convolution kernel representation of the single-pole low-pass transfer function shows that the original source waveform can be accurately recovered in real time using a particular moving average algorithm applied on the input stream of the distorted waveform, which can also significantly reduce the overall delay time constant. This method is generalized for multi-pole low-pass systems and has noise characteristics of the inverse of the low-pass filter characteristics. This method can be applied to most sensors and amplifiers operating close to their frequency response limits to improve the overall performance of data acquisition systems and digital feedback control systems.

A multichannel and wide suitablity digital control device for liquid-crystal microlens controlled electrically

NASA Astrophysics Data System (ADS)

Zhang, Bo; Xin, Zhaowei; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2017-11-01

In order to overcome the difficulty in imaging detection of high-speed moving targets under complex environments, and to get more comprehensive image information of the target, there is a urgent need to develop new high-performance optical imaging components. Compared to traditional lenses which have fixed shapes and immutable focal length, liquid-crystal microlens (LCMs) can not only adjust the focal length without changing the external shape, but also realize many practical functions such as swinging focus, spectral selection, depth of field adjustment, etc. The physical properties of spatial electric fields constructed between electrode plates of the LCMs are directly related to the light-field adjusting performances of LCMs, such as the polarity of electric field, the frequency and amplitude of applied voltage signal. In other words, the optical behaviors of LCMs will be affected remarkably by the parameters of driving voltage signal mentioned above. To implement these important functions flexibly and effectively, the driving voltage signal must be powerful and flexible. It had better to have multiple channels to control the direction of swinging focus, with relatively wide variance range to spread spectrum selection range, and with high precision to ensure accurately controlling LCMs. In addition, special waveforms may be required to support special functions of LCMs. Therefore a digital control device, which meet the requirements mentioned above, is designed, and then LCMs with it can realize imaging detection of targets in complex environment.

Physiological and Molecular Genetic Effects of Time-Varying Electromagnetic Fields on Human Neuronal Cells

NASA Technical Reports Server (NTRS)

Goodwin, Thomas J.

2003-01-01

The present investigation details the development of model systems for growing two- and three-dimensional human neural progenitor cells within a culture medium facilitated by a time-varying electromagnetic field (TVEMF). The cells and culture medium are contained within a two- or three-dimensional culture vessel, and the electromagnetic field is emitted from an electrode or coil. These studies further provide methods to promote neural tissue regeneration by means of culturing the neural cells in either configuration. Grown in two dimensions, neuronal cells extended longitudinally, forming tissue strands extending axially along and within electrodes comprising electrically conductive channels or guides through which a time-varying electrical current was conducted. In the three-dimensional aspect, exposure to TVEMF resulted in the development of three-dimensional aggregates, which emulated organized neural tissues. In both experimental configurations, the proliferation rate of the TVEMF cells was 2.5 to 4.0 times the rate of the non-waveform cells. Each of the experimental embodiments resulted in similar molecular genetic changes regarding the growth potential of the tissues as measured by gene chip analyses, which measured more than 10,000 human genes simultaneously.

Physiological and modeling evidence for focal transcranial electrical brain stimulation in humans: A basis for high-definition tDCS

PubMed Central

Edwards, Dylan; Cortes, Mar; Datta, Abhishek; Minhas, Preet; Wassermann, Eric M.; Bikson, Marom

2015-01-01

Transcranial Direct Current Stimulation (tDCS) is a non-invasive, low-cost, well-tolerated technique producing lasting modulation of cortical excitability. Behavioral and therapeutic outcomes of tDCS are linked to the targeted brain regions, but there is little evidence that current reaches the brain as intended. We aimed to: (1) validate a computational model for estimating cortical electric fields in human transcranial stimulation, and (2) assess the magnitude and spread of cortical electric field with a novel High-Definition tDCS (HD-tDCS) scalp montage using a 4×1-Ring electrode configuration. In three healthy adults, Transcranial Electrical Stimulation (TES) over primary motor cortex (M1) was delivered using the 4×1 montage (4× cathode, surrounding a single central anode; montage radius ~3 cm) with sufficient intensity to elicit a discrete muscle twitch in the hand. The estimated current distribution in M1 was calculated using the individualized MRI-based model, and compared with the observed motor response across subjects. The response magnitude was quantified with stimulation over motor cortex as well as anterior and posterior to motor cortex. In each case the model data were consistent with the motor response across subjects. The estimated cortical electric fields with the 4×1 montage were compared (area, magnitude, direction) for TES and tDCS in each subject. We provide direct evidence in humans that TES with a 4×1-Ring configuration can activate motor cortex and that current does not substantially spread outside the stimulation area. Computational models predict that both TES and tDCS waveforms using the 4×1-Ring configuration generate electric fields in cortex with comparable gross current distribution, and preferentially directed normal (inward) currents. The agreement of modeling and experimental data for both current delivery and focality support the use of the HD-tDCS 4×1-Ring montage for cortically targeted neuromodulation. PMID:23370061

A theoretical and experimental investigation of the linear and nonlinear impulse responses from a magnetoplasma column

NASA Technical Reports Server (NTRS)

Grody, N. C.

1973-01-01

Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.

EXPERIMENTAL DETERMINATION OF WHISTLER WAVE DISPERSION RELATION IN THE SOLAR WIND

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

Stansby, D.; Horbury, T. S.; Chen, C. H. K.

2016-09-20

The origins and properties of large-amplitude whistler wavepackets in the solar wind are still unclear. In this Letter, we utilize single spacecraft electric and magnetic field waveform measurements from the ARTEMIS mission to calculate the plasma frame frequency and wavevector of individual wavepackets over multiple intervals. This allows direct comparison of experimental measurements with theoretical dispersion relations to identify the observed waves as whistler waves. The whistlers are right-hand circularly polarized, travel anti-sunward, and are aligned with the background magnetic field. Their dispersion is strongly affected by the local electron parallel beta in agreement with linear theory. The properties measuredmore » are consistent with the electron heat flux instability acting in the solar wind to generate these waves.« less

Algorithm theoretical basis for GEDI level-4A footprint above ground biomass density.

NASA Astrophysics Data System (ADS)

Kellner, J. R.; Armston, J.; Blair, J. B.; Duncanson, L.; Hancock, S.; Hofton, M. A.; Luthcke, S. B.; Marselis, S.; Tang, H.; Dubayah, R.

2017-12-01

The Global Ecosystem Dynamics Investigation is a NASA Earth-Venture-2 mission that will place a multi-beam waveform lidar instrument on the International Space Station. GEDI data will provide globally representative measurements of vertical height profiles (waveforms) and estimates of above ground carbon stocks throughout the planet's temperate and tropical regions. Here we describe the current algorithm theoretical basis for the L4A footprint above ground biomass data product. The L4A data product is above ground biomass density (AGBD, Mg · ha-1) at the scale of individual GEDI footprints (25 m diameter). Footprint AGBD is derived from statistical models that relate waveform height metrics to field-estimated above ground biomass. The field estimates are from long-term permanent plot inventories in which all free-standing woody plants greater than a diameter size threshold have been identified and mapped. We simulated GEDI waveforms from discrete-return airborne lidar data using the GEDI waveform simulator. We associated height metrics from simulated waveforms with field-estimated AGBD at 61 sites in temperate and tropical regions of North and South America, Europe, Africa, Asia and Australia. We evaluated the ability of empirical and physically-based regression and machine learning models to predict AGBD at the footprint level. Our analysis benchmarks the performance of these models in terms of site and region-specific accuracy and transferability using a globally comprehensive calibration and validation dataset.

A high voltage pulse generator based on silicon-controlled rectifier for field-reversed configuration experiment.

PubMed

Lin, Munan; Liu, Ming; Zhu, Guanghui; Wang, Yanpeng; Shi, Peiyun; Sun, Xuan

2017-08-01

A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 μs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment.

A high voltage pulse generator based on silicon-controlled rectifier for field-reversed configuration experiment

NASA Astrophysics Data System (ADS)

Lin, Munan; Liu, Ming; Zhu, Guanghui; Wang, Yanpeng; Shi, Peiyun; Sun, Xuan

2017-08-01

A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 μs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment.

Gas breakdown driven by L band short-pulse high-power microwave

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

Yang Yiming; Yuan Chengwei; Qian Baoliang

2012-12-15

High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF{sub 6} breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdownmore » waveforms of air and SF{sub 6} are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF{sub 6} breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF{sub 6} breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF{sub 6} is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.« less

Seizure entrainment with polarizing low frequency electric fields in a chronic animal epilepsy model

PubMed Central

Sunderam, Sridhar; Chernyy, Nick; Peixoto, Nathalia; Mason, Jonathan P.; Weinstein, Steven L.; Schiff, Steven J.; Gluckman, Bruce J.

2009-01-01

Neural activity can be modulated by applying a polarizing low frequency (≪ 100 Hz) electric field (PLEF). Unlike conventional pulsed stimulation, PLEF stimulation has a graded, modulatory effect on neuronal excitability, and permits the simultaneous recording of neuronal activity during stimulation suitable for continuous feedback control. We tested a prototype system that allows for simultaneous PLEF stimulation with minimal recording artifact in a chronic tetanus toxin animal model (rat) of hippocampal epilepsy with spontaneous seizures. Depth electrode local field potentials recorded during seizures revealed a characteristic pattern of field postsynaptic potentials (fPSPs). Sinusoidal voltage-controlled PLEF stimulation (0.5–25 Hz) was applied in open-loop cycles radially across the CA3 of ventral hippocampus. For stimulated seizures, fPSPs were transiently entrained with the PLEF waveform. Statistical significance of entrainment was assessed with Thomson’s harmonic F-test, with 45/132 stimulated seizures in 4 animals individually demonstrating significant entrainment (p < 0.04). Significant entrainment for multiple presentations at the same frequency (p < 0.01) was observed in 3 of 4 animals in 42/64 stimulated seizures. This is the first demonstration in chronically implanted freely behaving animals of PLEF modulation of neural activity with simultaneous recording. PMID:19602730

Electromechanical systems with transient high power response operating from a resonant AC link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant AC link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control in all four operating quadrants. Incorporating the AC link allows the converter in these systems to switch at the zero crossing of every half cycle of the AC waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed by LeRC and General Dynamics Space Systems Division under contract to NASA. A description of a single motor, electromechanical actuation system is presented. Then, focus is on a conceptual design for an AC electric vehicle. This design incorporates an induction motor/generator together with a flywheel for peak energy storage. System operation and implications along with the associated circuitry are addressed. Such a system would greatly improve all-electric vehicle ranges over the Federal Urban Driving Cycle (FUD).

Nanosecond electric pulses modulate skeletal muscle calcium dynamics and contraction

NASA Astrophysics Data System (ADS)

Valdez, Chris; Jirjis, Michael B.; Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.

2017-02-01

Irreversible electroporation therapy is utilized to remove cancerous tissues thru the delivery of rapid (250Hz) and high voltage (V) (1,500V/cm) electric pulses across microsecond durations. Clinical research demonstrated that bipolar (BP) high voltage microsecond pulses opposed to monophasic waveforms relieve muscle contraction during electroporation treatment. Our group along with others discovered that nanosecond electric pulses (nsEP) can activate second messenger cascades, induce cytoskeletal rearrangement, and depending on the nsEP duration and frequency, initiate apoptotic pathways. Of high interest across in vivo and in vitro applications, is how nsEP affects muscle physiology, and if nuances exist in comparison to longer duration electroporation applications. To this end, we exposed mature skeletal muscle cells to monopolar (MP) and BP nsEP stimulation across a wide range of electric field amplitudes (1-20 kV/cm). From live confocal microscopy, we simultaneously monitored intracellular calcium dynamics along with nsEP-induced muscle movement on a single cell level. In addition, we also evaluated membrane permeability with Yo-PRO-1 and Propidium Iodide (PI) across various nsEP parameters. The results from our findings suggest that skeletal muscle calcium dynamics, and nsEP-induced contraction exhibit exclusive responses to both MP and BP nsEP exposure. Overall the results suggest in vivo nsEP application may elicit unique physiology and field applications compared to longer pulse duration electroporation.

Efficiency Analysis of Waveform Shape for Electrical Excitation of Nerve Fibers

PubMed Central

Wongsarnpigoon, Amorn; Woock, John P.; Grill, Warren M.

2011-01-01

Stimulation efficiency is an important consideration in the stimulation parameters of implantable neural stimulators. The objective of this study was to analyze the effects of waveform shape and duration on the charge, power, and energy efficiency of neural stimulation. Using a population model of mammalian axons and in vivo experiments on cat sciatic nerve, we analyzed the stimulation efficiency of four waveform shapes: square, rising exponential, decaying exponential, and rising ramp. No waveform was simultaneously energy-, charge-, and power-optimal, and differences in efficiency among waveform shapes varied with pulse width (PW) For short PWs (≤ 0.1 ms), square waveforms were no less energy-efficient than exponential waveforms, and the most charge-efficient shape was the ramp. For long PWs (≥0.5 ms), the square was the least energy-efficient and charge-efficient shape, but across most PWs, the square was the most power-efficient shape. Rising exponentials provided no practical gains in efficiency over the other shapes, and our results refute previous claims that the rising exponential is the energy-optimal shape. An improved understanding of how stimulation parameters affect stimulation efficiency will help improve the design and programming of implantable stimulators to minimize tissue damage and extend battery life. PMID:20388602

Mechanism of Small Current Generation under Impulse Voltage Applications in Vacuum

NASA Astrophysics Data System (ADS)

Aoki, Keita; Yasukawa, Hideaki; Kojima, Hiroki; Homma, Mitsutaka; Shioiri, Tetsu; Okubo, Hitoshi

Small discharge not to accompany breakdown can occur under high electric field in vacuum, however the mechanism is not well clarified. We have found that the current of small discharge decreases with repeated voltage applications, and leads to electrode conditioning effect of raising withstand voltage. The inception of the current is delayed with the decrease of current, and the inception time and waveform change by gap length. On the other hand, under low vacuum condition, the current increases and reaches saturation with repeated voltage applications. From these discussions, we concluded that the generating process of small current depended on the adsorption and absorption gas of electrodes.

Observation of Oscillatory Radial Electric Field Relaxation in a Helical Plasma.

PubMed

Alonso, J A; Sánchez, E; Calvo, I; Velasco, J L; McCarthy, K J; Chmyga, A; Eliseev, L G; Estrada, T; Kleiber, R; Krupnik, L I; Melnikov, A V; Monreal, P; Parra, F I; Perfilov, S; Zhezhera, A I

2017-05-05

Measurements of the relaxation of a zonal electrostatic potential perturbation in a nonaxisymmetric magnetically confined plasma are presented. A sudden perturbation of the plasma equilibrium is induced by the injection of a cryogenic hydrogen pellet in the TJ-II stellarator, which is observed to be followed by a damped oscillation in the electrostatic potential. The waveform of the relaxation is consistent with theoretical calculations of zonal potential relaxation in a nonaxisymmetric magnetic geometry. The turbulent transport properties of a magnetic confinement configuration are expected to depend on the features of the collisionless damping of zonal flows, of which the present Letter is the first direct observation.

Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

NASA Technical Reports Server (NTRS)

Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

2012-01-01

One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

Stray electrical currents in laparoscopic instruments used in da Vinci® robot-assisted surgery: an in vitro study.

PubMed

Mendez-Probst, Carlos E; Vilos, George; Fuller, Andrew; Fernandez, Alfonso; Borg, Paul; Galloway, David; Pautler, Stephen E

2011-09-01

The da Vinci(®) surgical system requires the use of electrosurgical instruments. The re-use of such instruments creates the potential for stray electrical currents from capacitive coupling and/or insulation failure. We used objective measures to report the prevalence and magnitude of such stray currents. Thirty-seven robotic instruments were tested using an electrosurgical unit (ESU) at pure coagulation and cut waveforms at four different settings. Conductive gel-coated instruments were tested at 40W, 80W, and maximum ESU output (coagulation 120W, cut 300W). The magnitude of stray currents was measured by an electrosurgical analyzer. At coagulation waveform in open air, 86% of instruments leaked a mean of 0.4W. In the presence of gel-coated instruments, stray currents were detected in all instruments with means (and standard deviation) of 3.4W (± 2), 4.1W (± 2.3), and 4.1W (± 2.3) at 40W, 80W, and 120W, respectively. At cut waveform in open air, none of the instruments leaked current, while gel-coated instruments leaked a mean of 2.2W (± 1.3), 2.2W (± 1.9) and 3.2W (± 1.9) at 40W, 80W, and 300W, respectively. All tested instruments in our study demonstrated energy leakage. Stray currents were higher during coagulation (high voltage) waveforms, and the magnitude was not always proportionate to the ESU settings. Stray currents have the potential to cause electrical burns. We support the programmed end of life of da Vinci instruments on the basis of safety. Consideration should be given to alternate energy sources or the adoption of active electrode monitoring technology to all monopolar instruments.

Project FOOTPRINT: Substation modeling and simulations for E1 pulses

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

Nelson, Scott D.; Larson, D. J.; Kirkendall, B. A.

This report includes a presentation with an: Introduction to CW coupling; Introduction to single-pulse coupling; Description of E1 waveforms; Structures in a substation yard --articulated (as part of the substation's defined electrical functionality)--unarticulated (not as part of the substation's defined electrical functionality); Coupling --electrical coupling (capacitive coupling) --magnetic coupling (inductive coupling); Connectivity to long-line transmission lines; Control infrastructure; Summary; and References.

Evaluating coastal sea surface heights based on a novel sub-waveform approach using sparse representation and conditional random fields

NASA Astrophysics Data System (ADS)

Uebbing, Bernd; Roscher, Ribana; Kusche, Jürgen

2016-04-01

Satellite radar altimeters allow global monitoring of mean sea level changes over the last two decades. However, coastal regions are less well observed due to influences on the returned signal energy by land located inside the altimeter footprint. The altimeter emits a radar pulse, which is reflected at the nadir-surface and measures the two-way travel time, as well as the returned energy as a function of time, resulting in a return waveform. Over the open ocean the waveform shape corresponds to a theoretical model which can be used to infer information on range corrections, significant wave height or wind speed. However, in coastal areas the shape of the waveform is significantly influenced by return signals from land, located in the altimeter footprint, leading to peaks which tend to bias the estimated parameters. Recently, several approaches dealing with this problem have been published, including utilizing only parts of the waveform (sub-waveforms), estimating the parameters in two steps or estimating additional peak parameters. We present a new approach in estimating sub-waveforms using conditional random fields (CRF) based on spatio-temporal waveform information. The CRF piece-wise approximates the measured waveforms based on a pre-derived dictionary of theoretical waveforms for various combinations of the geophysical parameters; neighboring range gates are likely to be assigned to the same underlying sub-waveform model. Depending on the choice of hyperparameters in the CRF estimation, the classification into sub-waveforms can either be more fine or coarse resulting in multiple sub-waveform hypotheses. After the sub-waveforms have been detected, existing retracking algorithms can be applied to derive water heights or other desired geophysical parameters from particular sub-waveforms. To identify the optimal heights from the multiple hypotheses, instead of utilizing a known reference height, we apply a Dijkstra-algorithm to find the "shortest path" of all possible heights. We apply our approach to Jason-2 data in different coastal areas, such as the Bangladesh coast or in the North Sea and compare our sea surface heights to various existing retrackers. Using the sub-waveform approach, we are able to derive meaningful water heights up to a few kilometers off the coast, where conventional retrackers, such as the standard ocean retracker, no longer provide useful data.

A model for the harmonic of compressional Pc 5 waves

NASA Technical Reports Server (NTRS)

Takahashi, K.; Zanetti, L. J.; Potemra, T. A.; Acuna, M. H.

1987-01-01

Compressional Pc 5 magnetic waves in the magnetosphere are a unique phenomenon showing a nonsinusoidal waveform in spite of a well-defined period. Although the waveform can be Fourier-decomposed into the fundamental and the second harmonics, the phase between the two is kept constant from event to event, implying that the waveform is not the result of a chance superposition of two magnetospheric eigenmodes. A phenomenological explanation to this waveform is offered using a field-line configuration model that is a modified version of a previously proposed antisymmetric standing wave. In this model, the location of the equatorial node of field-line displacement is assumed to oscillate with the wave, with a peak-to-peak amplitude greater than 10 percent of the wavelength of the standing wave. The predicted waveform at various magnetic latitudes is found to be in excellent agreement with an observation taken near the magnetic equator by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer spacecraft.

A model for the harmonic of compressional Pc 5 waves

NASA Astrophysics Data System (ADS)

Takahashi, K.; Zanetti, L. J.; Potemra, T. A.; Acuna, M. H.

1987-04-01

Compressional Pc 5 magnetic waves in the magnetosphere are a unique phenomenon showing a nonsinusoidal waveform in spite of a well-defined period. Although the waveform can be Fourier-decomposed into the fundamental and the second harmonics, the phase between the two is kept constant from event to event, implying that the waveform is not the result of a chance superposition of two magnetospheric eigenmodes. A phenomenological explanation to this waveform is offered using a field-line configuration model that is a modified version of a previously proposed antisymmetric standing wave. In this model, the location of the equatorial node of field-line displacement is assumed to oscillate with the wave, with a peak-to-peak amplitude greater than 10 percent of the wavelength of the standing wave. The predicted waveform at various magnetic latitudes is found to be in excellent agreement with an observation taken near the magnetic equator by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer spacecraft.

Magnetic Field Effect on Ultrashort Two-dimensional Optical Pulse Propagation in Silicon Nanotubes

NASA Astrophysics Data System (ADS)

Konobeeva, N. N.; Evdokimov, R. A.; Belonenko, M. B.

2018-05-01

The paper deals with the magnetic field effect which provides a stable propagation of ultrashort pulses in silicon nanotubes from the viewpoint of their waveform. The equation is derived for the electromagnetic field observed in silicon nanotubes with a glance to the magnetic field for two-dimensional optical pulses. The analysis is given to the dependence between the waveform of ultrashort optical pulses and the magnetic flux passing through the cross-sectional area of the nanotube.

Transcranial electric and magnetic stimulation: technique and paradigms.

PubMed

Paulus, Walter; Peterchev, Angel V; Ridding, Michael

2013-01-01

Transcranial electrical and magnetic stimulation techniques encompass a broad physical variety of stimuli, ranging from static magnetic fields or direct current stimulation to pulsed magnetic or alternating current stimulation with an almost infinite number of possible stimulus parameters. These techniques are continuously refined by new device developments, including coil or electrode design and flexible control of the stimulus waveforms. They allow us to influence brain function acutely and/or by inducing transient plastic after-effects in a range from minutes to days. Manipulation of stimulus parameters such as pulse shape, intensity, duration, and frequency, and location, size, and orientation of the electrodes or coils enables control of the immediate effects and after-effects. Physiological aspects such as stimulation at rest or during attention or activation may alter effects dramatically, as does neuropharmacological drug co-application. Non-linear relationships between stimulus parameters and physiological effects have to be taken into account. © 2013 Elsevier B.V. All rights reserved.

Power spectra at radio frequency of lightning return stroke waveforms

NASA Technical Reports Server (NTRS)

Lanzerotti, L. J.; Thomson, D. J.; Maclennan, C. G.; Rinnert, K.; Krider, E. P.

1989-01-01

The power spectra of the wideband (10 Hz to 100 kHz) magnetic field signals in a number of lightning return strokes (primarily first return strokes) measured during a lightning storm which occurred in Lindau, West Germany in August, 1984 have been calculated. The RF magnetic field data were obtained with the engineering unit of the Galileo Jupiter Probe lightning experiment. The spectra of the magnetic field data definitely show fine structure, with two or three distinct peaks appearing in the spectra of many of the waveforms. An enhancement of power at frequencies of about 60-70 kHz is often seen in the spectra of the waveform time segments preceding and following the rise-to-peak amplitude of the return stroke.

Mechanical Damage of Tympanic Membrane in Relation to Impulse Pressure Waveform – A Study in Chinchillas

PubMed Central

Gan, Rong Z.; Nakmali, Don; Ji, Xiao D.; Leckness, Kegan; Yokell, Zachary

2016-01-01

Mechanical damage to middle ear components in blast exposure directly causes hearing loss, and the rupture of the tympanic membrane (TM) is the most frequent injury of the ear. However, it is unclear how the severity of injury graded by different patterns of TM rupture is related to the overpressure waveforms induced by blast waves. In the present study, the relationship between the TM rupture threshold and the impulse or overpressure waveform has been investigated in chinchillas. Two groups of animals were exposed to blast overpressure simulated in our lab under two conditions: open field and shielded with a stainless steel cup covering the animal head. Auditory brainstem response (ABR) and wideband tympanometry were measured before and after exposure to check the hearing threshold and middle ear function. Results show that waveforms recorded in the shielded case were different from those in the open field and the TM rupture threshold in the shielded case was lower than that in the open field (3.4±0.7 vs. 9.1±1.7 psi or 181±1.6 vs. 190±1.9 dB SPL). The impulse pressure energy spectra analysis of waveforms demonstrates that the shielded waveforms include greater energy at high frequencies than that of the open field waves. Finally, a 3D finite element (FE) model of the chinchilla ear was used to compute the distributions of stress in the TM and the TM displacement with impulse pressure waves. The FE model-derived change of stress in response to pressure loading in the shielded case was substantially faster than that in the open case. This finding provides the biomechanical mechanisms for blast induced TM damage in relation to overpressure waveforms. The TM rupture threshold difference between the open and shielded cases suggests that an acoustic role of helmets may exist, intensifying ear injury during blast exposure. PMID:26807796

Average current is better than peak current as therapeutic dosage for biphasic waveforms in a ventricular fibrillation pig model of cardiac arrest.

PubMed

Chen, Bihua; Yu, Tao; Ristagno, Giuseppe; Quan, Weilun; Li, Yongqin

2014-10-01

Defibrillation current has been shown to be a clinically more relevant dosing unit than energy. However, the effects of average and peak current in determining shock outcome are still undetermined. The aim of this study was to investigate the relationship between average current, peak current and defibrillation success when different biphasic waveforms were employed. Ventricular fibrillation (VF) was electrically induced in 22 domestic male pigs. Animals were then randomized to receive defibrillation using one of two different biphasic waveforms. A grouped up-and-down defibrillation threshold-testing protocol was used to maintain the average success rate of 50% in the neighborhood. In 14 animals (Study A), defibrillations were accomplished with either biphasic truncated exponential (BTE) or rectilinear biphasic waveforms. In eight animals (Study B), shocks were delivered using two BTE waveforms that had identical peak current but different waveform durations. Both average and peak currents were associated with defibrillation success when BTE and rectilinear waveforms were investigated. However, when pathway impedance was less than 90Ω for the BTE waveform, bivariate correlation coefficient was 0.36 (p=0.001) for the average current, but only 0.21 (p=0.06) for the peak current in Study A. In Study B, a high defibrillation success (67.9% vs. 38.8%, p<0.001) was observed when the waveform delivered more average current (14.9±2.1A vs. 13.5±1.7A, p<0.001) while keeping the peak current unchanged. In this porcine model of VF, average current was better than peak current to be an adequate parameter to describe the therapeutic dosage when biphasic defibrillation waveforms were used. The institutional protocol number: P0805. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Feeding behavior of the stink bug Bagrada hilaris is changed by the electrical signals applied during EPG recordings

USDA-ARS?s Scientific Manuscript database

Feeding behavior of piercing-sucking insects is most rigorously studied using eletropenetrography (EPG). This technique utilizes an electrical circuit to record waveforms caused by voltage fluctuations when a wired insect inserts its stylet into an electrified plant. Past researchers have asserted t...

Enhancing high-order harmonic generation by sculpting waveforms with chirp

NASA Astrophysics Data System (ADS)

Peng, Dian; Frolov, M. V.; Pi, Liang-Wen; Starace, Anthony F.

2018-05-01

We present a theoretical analysis showing how chirp can be used to sculpt two-color driving laser field waveforms in order to enhance high-order harmonic generation (HHG) and/or extend HHG cutoff energies. Specifically, we consider driving laser field waveforms composed of two ultrashort pulses having different carrier frequencies in each of which a linear chirp is introduced. Two pairs of carrier frequencies of the component pulses are considered: (ω , 2 ω ) and (ω , 3 ω ). Our results show how changing the signs of the chirps in each of the two component pulses leads to drastic changes in the HHG spectra. Our theoretical analysis is based on numerical solutions of the time-dependent Schrödinger equation and on a semiclassical analytical approach that affords a clear physical interpretation of how our optimized waveforms lead to enhanced HHG spectra.

Analysis and Optimization of Pulse Dynamics for Magnetic Stimulation

PubMed Central

Goetz, Stefan M.; Truong, Cong Nam; Gerhofer, Manuel G.; Peterchev, Angel V.; Herzog, Hans-Georg; Weyh, Thomas

2013-01-01

Magnetic stimulation is a standard tool in brain research and has found important clinical applications in neurology, psychiatry, and rehabilitation. Whereas coil designs and the spatial field properties have been intensively studied in the literature, the temporal dynamics of the field has received less attention. Typically, the magnetic field waveform is determined by available device circuit topologies rather than by consideration of what is optimal for neural stimulation. This paper analyzes and optimizes the waveform dynamics using a nonlinear model of a mammalian axon. The optimization objective was to minimize the pulse energy loss. The energy loss drives power consumption and heating, which are the dominating limitations of magnetic stimulation. The optimization approach is based on a hybrid global-local method. Different coordinate systems for describing the continuous waveforms in a limited parameter space are defined for numerical stability. The optimization results suggest that there are waveforms with substantially higher efficiency than that of traditional pulse shapes. One class of optimal pulses is analyzed further. Although the coil voltage profile of these waveforms is almost rectangular, the corresponding current shape presents distinctive characteristics, such as a slow low-amplitude first phase which precedes the main pulse and reduces the losses. Representatives of this class of waveforms corresponding to different maximum voltages are linked by a nonlinear transformation. The main phase, however, scales with time only. As with conventional magnetic stimulation pulses, briefer pulses result in lower energy loss but require higher coil voltage than longer pulses. PMID:23469168

Digital model of a vacuum circuit breaker for the analysis of switching waveforms in electrical circuits

NASA Astrophysics Data System (ADS)

Budzisz, Joanna; Wróblewski, Zbigniew

2016-03-01

The article presents a method of modelling a vaccum circuit breaker in the ATP/EMTP package, the results of the verification of the correctness of the developed digital circuit breaker model operation and its practical usefulness for analysis of overvoltages and overcurrents occurring in commutated capacitive electrical circuits and also examples of digital simulations of overvoltages and overcurrents in selected electrical circuits.

Nonlinear waveform distortion and shock formation in the near field of a continuous wave piston source

NASA Astrophysics Data System (ADS)

Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Cathignol, Dominique

2004-05-01

A classical effect of nonlinear acoustics is that a plane sinusoidal acoustic wave propagating in a nonlinear medium transforms to a sawtooth wave with one shock per cycle. However, the waveform evolution can be quite different in the near field of a plane source due to diffraction. Previous numerical simulations of nonlinear acoustic waves in the near field of a circular piston source predict the development of two shocks per wave cycle [Khokhlova et al., J. Acoust. Soc. Am. 110, 95-108 (2001)]. Moreover, at some locations the peak pressure may be up to 4 times the source amplitude. The motivation of this work was to experimentally verify and further explain the phenomena of the nonlinear waveform distortion. Measurements were conducted in water with a 47-mm-diameter unfocused transducer, working at 1-MHz frequency. For pressure amplitudes higher than 0.5 MPa, two shocks per cycle were observed in the waveform beyond the last minimum of the fundamental harmonic amplitude. With the increase of the observation distance, these two shocks collided and formed one shock (per cycle), i.e., the waveform developed into the classical sawtooth wave. The experimental results were in a very good agreement with the modeling based on the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation.

Waveform-preserved unidirectional acoustic transmission based on impedance-matched acoustic metasurface and phononic crystal

NASA Astrophysics Data System (ADS)

Song, Ai-Ling; Chen, Tian-Ning; Wang, Xiao-Peng; Wan, Le-Le

2016-08-01

The waveform distortion happens in most of the unidirectional acoustic transmission (UAT) devices proposed before. In this paper, a novel type of waveform-preserved UAT device composed of an impedance-matched acoustic metasurface (AMS) and a phononic crystal (PC) structure is proposed and numerically investigated. The acoustic pressure field distributions and transmittance are calculated by using the finite element method. The subwavelength AMS that can modulate the wavefront of the transmitted wave at will is designed and the band structure of the PC structure is calculated and analyzed. The sound pressure field distributions demonstrate that the unidirectional acoustic transmission can be realized by the proposed UAT device without changing the waveforms of the output waves, which is the distinctive feature compared with the previous UAT devices. The physical mechanism of the unidirectional acoustic transmission is discussed by analyzing the refraction angle changes and partial band gap map. The calculated transmission spectra show that the UAT device is valid within a relatively broad frequency range. The simulation results agree well with the theoretical predictions. The proposed UAT device provides a good reference for designing waveform-preserved UAT devices and has potential applications in many fields, such as medical ultrasound, acoustic rectifiers, and noise insulation.

Pure phase encode magnetic field gradient monitor.

PubMed

Han, Hui; MacGregor, Rodney P; Balcom, Bruce J

2009-12-01

Numerous methods have been developed to measure MRI gradient waveforms and k-space trajectories. The most promising new strategy appears to be magnetic field monitoring with RF microprobes. Multiple RF microprobes may record the magnetic field evolution associated with a wide variety of imaging pulse sequences. The method involves exciting one or more test samples and measuring the time evolution of magnetization through the FIDs. Two critical problems remain. The gradient waveform duration is limited by the sample T(2)*, while the k-space maxima are limited by gradient dephasing. The method presented is based on pure phase encode FIDs and solves the above two problems in addition to permitting high strength gradient measurement. A small doped water phantom (1-3 mm droplet, T(1), T(2), T(2)* < 100 micros) within a microprobe is excited by a series of closely spaced broadband RF pulses each followed by FID single point acquisition. Two trial gradient waveforms have been chosen to illustrate the technique, neither of which could be measured by the conventional RF microprobe measurement. The first is an extended duration gradient waveform while the other illustrates the new method's ability to measure gradient waveforms with large net area and/or high amplitude. The new method is a point monitor with simple implementation and low cost hardware requirements.

Low-Complexity Adaptive Multisine Waveform Design for Wireless Power Transfer

NASA Astrophysics Data System (ADS)

Clerckx, Bruno; Bayguzina, Ekaterina

Far-field Wireless Power Transfer (WPT) has attracted significant attention in the last decade. Recently, channel-adaptive waveforms have been shown to significantly increase the DC power level at the output of the rectifier. However the design of those waveforms is generally computationally complex and does not lend itself easily to practical implementation. We here propose a low-complexity channel-adaptive multisine waveform design whose performance is very close to that of the optimal design. Performance evaluations confirm the benefits of the new design in various rectifier topologies.

A Fiber Bragg Grating Sensor for Radial Artery Pulse Waveform Measurement.

PubMed

Jia, Dagong; Chao, Jing; Li, Shuai; Zhang, Hongxia; Yan, Yingzhan; Liu, Tiegen; Sun, Ye

2018-04-01

In this paper, we report the design and experimental validation of a novel optical sensor for radial artery pulse measurement based on fiber Bragg grating (FBG) and lever amplification mechanism. Pulse waveform analysis is a diagnostic tool for clinical examination and disease diagnosis. High fidelity radial artery pulse waveform has been investigated in clinical studies for estimating central aortic pressure, which is proved to be predictors of cardiovascular diseases. As a three-dimensional cylinder, the radial artery needs to be examined from different locations to achieve optimal pulse waveform for estimation and diagnosis. The proposed optical sensing system is featured as high sensitivity and immunity to electromagnetic interference for multilocation radial artery pulse waveform measurement. The FBG sensor can achieve the sensitivity of 8.236 nm/N, which is comparable to a commonly used electrical sensor. This FBG-based system can provide high accurate measurement, and the key characteristic parameters can be then extracted from the raw signals for clinical applications. The detecting performance is validated through experiments guided by physicians. In the experimental validation, we applied this sensor to measure the pulse waveforms at various positions and depths of the radial artery in the wrist according to the diagnostic requirements. The results demonstrate the high feasibility of using optical systems for physiological measurement and using this FBG sensor for radial artery pulse waveform in clinical applications.

Combining GOES-16 Geostationary Lightning Mapper with the ground based Earth Networks Total Lightning Network

NASA Astrophysics Data System (ADS)

Stock, M.; Lapierre, J. L.; Zhu, Y.

2017-12-01

Recently, the Geostationary Lightning Mapper (GLM) began collecting optical data to locate lightning events and flashes over the North and South American continents. This new instrument promises uniformly high detection efficiency (DE) over its entire field of view, with location accuracy on the order of 10 km. In comparison, Earth Networks Total Lightning Networks (ENTLN) has a less uniform coverage, with higher DE in regions with dense sensor coverage, and lower DE with sparse sensor coverage. ENTLN also offers better location accuracy, lightning classification, and peak current estimation for their lightning locations. It is desirable to produce an integrated dataset, combining the strong points of GLM and ENTLN. The easiest way to achieve this is to simply match located lightning processes from each system using time and distance criteria. This simple method will be limited in scope by the uneven coverage of the ground based network. Instead, we will use GLM group locations to look up the electric field change data recorded by ground sensors near each GLM group, vastly increasing the coverage of the ground network. The ground waveforms can then be used for: improvements to differentiation between glint and lightning for GLM, higher precision lighting location, current estimation, and lightning process classification. Presented is an initial implementation of this type of integration using preliminary GLM data, and waveforms from ENTLN.

Evaluation of human exposure to complex waveform magnetic fields generated by arc-welding equipment according to European safety standards.

PubMed

Zoppetti, Nicola; Bogi, Andrea; Pinto, Iole; Andreuccetti, Daniele

2015-02-01

In this paper, a procedure is described for the assessment of human exposure to magnetic fields with complex waveforms generated by arc-welding equipment. The work moves from the analysis of relevant guidelines and technical standards, underlining their strengths and their limits. Then, the procedure is described with particular attention to the techniques used to treat complex waveform fields. Finally, the procedure is applied to concrete cases encountered in the workplace. The discussion of the results highlights the critical points in the procedure, as well as those related to the evolution of the technical and exposure standards. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

STRS Compliant FPGA Waveform Development

NASA Technical Reports Server (NTRS)

Nappier, Jennifer; Downey, Joseph; Mortensen, Dale

2008-01-01

The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. The extension of STRS to the SSP hardware will promote easier waveform reconfiguration and reuse. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. A FPGA-based transmit waveform implementation of the proposed standard interfaces on a laboratory breadboard SDR will be discussed.

Transport of particles and microorganisms in microfluidic channels using rectified ac electro-osmotic flow

PubMed Central

Wu, Wen-I; Selvaganapathy, P. Ravi; Ching, Chan Y.

2011-01-01

A new method is demonstrated to transport particles, cells, and other microorganisms using rectified ac electro-osmotic flows in open microchannels. The rectified flow is obtained by synchronous zeta potential modulation with the driving potential in the microchannel. Experiments were conducted to transport both neutral, charged particles, and microorganisms of various sizes. A maximum speed of 50 μm∕s was obtained for 8 μm polystyrene beads, without any electrolysis, using a symmetrical square waveform driving electric field of 5 V∕mm at 10 Hz and a 360 V gate potential with its polarity synchronized with the driving potential (phase lag=0°). PMID:21522497

Simultaneous inversion of seismic velocity and moment tensor using elastic-waveform inversion of microseismic data: Application to the Aneth CO2-EOR field

NASA Astrophysics Data System (ADS)

Chen, Y.; Huang, L.

2017-12-01

Moment tensors are key parameters for characterizing CO2-injection-induced microseismic events. Elastic-waveform inversion has the potential to providing accurate results of moment tensors. Microseismic waveforms contains information of source moment tensors and the wave propagation velocity along the wavepaths. We develop an elastic-waveform inversion method to jointly invert the seismic velocity model and moment tensor. We first use our adaptive moment-tensor joint inversion method to estimate moment tensors of microseismic events. Our adaptive moment-tensor inversion method jointly inverts multiple microseismic events with similar waveforms within a cluster to reduce inversion uncertainty for microseismic data recorded using a single borehole geophone array. We use this inversion result as the initial model for our elastic-waveform inversion to minimize the cross-correlated-based data misfit between observed data and synthetic data. We verify our method using synthetic microseismic data and obtain improved results of both moment tensors and seismic velocity model. We apply our new inversion method to microseismic data acquired at a CO2-enhanced oil recovery field in Aneth, Utah, using a single borehole geophone array. The results demonstrate that our new inversion method significantly reduces the data misfit compared to the conventional ray-theory-based moment-tensor inversion.

Electrodiffusion Models of Neurons and Extracellular Space Using the Poisson-Nernst-Planck Equations—Numerical Simulation of the Intra- and Extracellular Potential for an Axon Model

PubMed Central

Pods, Jurgis; Schönke, Johannes; Bastian, Peter

2013-01-01

In neurophysiology, extracellular signals—as measured by local field potentials (LFP) or electroencephalography—are of great significance. Their exact biophysical basis is, however, still not fully understood. We present a three-dimensional model exploiting the cylinder symmetry of a single axon in extracellular fluid based on the Poisson-Nernst-Planck equations of electrodiffusion. The propagation of an action potential along the axonal membrane is investigated by means of numerical simulations. Special attention is paid to the Debye layer, the region with strong concentration gradients close to the membrane, which is explicitly resolved by the computational mesh. We focus on the evolution of the extracellular electric potential. A characteristic up-down-up LFP waveform in the far-field is found. Close to the membrane, the potential shows a more intricate shape. A comparison with the widely used line source approximation reveals similarities and demonstrates the strong influence of membrane currents. However, the electrodiffusion model shows another signal component stemming directly from the intracellular electric field, called the action potential echo. Depending on the neuronal configuration, this might have a significant effect on the LFP. In these situations, electrodiffusion models should be used for quantitative comparisons with experimental data. PMID:23823244

Vlasov Simulation Study of Landau Damping Near the Persisting to Arrested Transition

NASA Astrophysics Data System (ADS)

Vinas, A. F.; Klimas, A. J.; Araneda, J. A.

2017-12-01

A 1-D electrostatic filtered Vlasov-Poisson simulation study is discussed. The transition from persisting to arrested Landau damping that is produced by increasing the strength of a sinusoidal perturbation on a background Vlasov-Poisson equilibrium is explored. Emphasis is placed on observed features of the electron phase-space distribution when the perturbation strength is near the transition value. A single ubiquitous waveform is found perturbing the space-averaged phase space distribution at almost any time in all of the simulations; the sole exception is the saturation stage that can occur at the end of the arrested damping scenario. This waveform contains relatively strong, very narrow structures in velocity bracketing ±vres - the velocities at which electrons must move to traverse the dominant field mode wavelength in one of its oscillation periods - and propagating with ±vres respectively. Local streams of electrons are found in these structures crossing the resonant velocities from low speed to high speed during Landau damping and from high speed to low speed during Landau growth. At the arrest time, when the field strength is briefly constant, these streams vanish. It is conjectured that the expected transfer of energy between electrons and field during Landau growth or damping has been visualized for the first time. No evidence is found in the phase-space distribution to support recent well established discoveries of a second order phase transition in the electric field evolution. While trapping is known to play a role for larger perturbation strengths, it is shown that trapping plays no role at any time in any of the simulations near the transition perturbation strength.

Controlled Waveform Magnets

NASA Astrophysics Data System (ADS)

Campbell, L. J.; Schlllig, J. B.

Issues for the design and operation of high field controlled waveform magnets and their power supplies are discussed. The basic technical elements are reviewed and applied to problems specific to this class of magnets. Examples are given along with a guide to the literature.

Passive Wearable Skin Patch Sensor Measures Limb Hemodynamics Based on Electromagnetic Resonance.

PubMed

Cluff, Kim; Becker, Ryan; Jayakumar, Balakumar; Han, Kiyun; Condon, Ernie; Dudley, Kenneth; Szatkowski, George; Pipinos, Iraklis I; Amick, Ryan Z; Patterson, Jeremy

2018-04-01

The objectives of this study were to design and develop an open-circuit electromagnetic resonant skin patch sensor, characterize the fluid volume and resonant frequency relationship, and investigate the sensor's ability to measure limb hemodynamics and pulse volume waveform features. The skin patch was designed from an open-circuit electromagnetic resonant sensor comprised of a single baseline trace of copper configured into a square planar spiral which had a self-resonating response when excited by an external radio frequency sweep. Using a human arm phantom with a realistic vascular network, the sensor's performance to measure limb hemodynamics was evaluated. The sensor was able to measure pulsatile blood flow which registered as shifts in the sensor's resonant frequencies. The time-varying waveform pattern of the resonant frequency displayed a systolic upstroke, a systolic peak, a dicrotic notch, and a diastolic down stroke. The resonant frequency waveform features and peak systolic time were validated against ultrasound pulse wave Doppler. A statistical correlation analysis revealed a strong correlation () between the resonant sensor peak systolic time and the pulse wave Doppler peak systolic time. The sensor was able to detect pulsatile flow, identify hemodynamic waveform features, and measure heart rate with 98% accuracy. The open-circuit resonant sensor design leverages the architecture of a thin planar spiral which is passive (does not require batteries), robust and lightweight (does not have electrical components or electrical connections), and may be able to wirelessly monitor cardiovascular health and limb hemodynamics.

Full-waveform inversion of GPR data for civil engineering applications

NASA Astrophysics Data System (ADS)

van der Kruk, Jan; Kalogeropoulos, Alexis; Hugenschmidt, Johannes; Klotzsche, Anja; Busch, Sebastian; Vereecken, Harry

2014-05-01

Conventional GPR ray-based techniques are often limited in their capability to image complex structures due to the pertaining approximations. Due to the increased computational power, it is becoming more easy to use modeling and inversion tools that explicitly take into account the detailed electromagnetic wave propagation characteristics. In this way, new civil engineering application avenues are opening up that enable an improved high resolution imaging of quantitative medium properties. In this contribution, we show recent developments that enable the full-waveform inversion of off-ground, on-ground and crosshole GPR data. For a successful inversion, a proper start model must be used that generates synthetic data that overlaps the measured data with at least half a wavelength. In addition, the GPR system must be calibrated such that an effective wavelet is obtained that encompasses the complexity of the GPR source and receiver antennas. Simple geometries such as horizontal layers can be described with a limited number of model parameters, which enable the use of a combined global and local search using the Simplex search algorithm. This approach has been implemented for the full-waveform inversion of off-ground and on-ground GPR data measured over horizontally layered media. In this way, an accurate 3D frequency domain forward model of Maxwell's equation can be used where the integral representation of the electric field is numerically evaluated. The full-waveform inversion (FWI) for a large number of unknowns uses gradient-based optimization methods where a 3D to 2D conversion is used to apply this method to experimental data. Off-ground GPR data, measured over homogeneous concrete specimens, were inverted using the full-waveform inversion. In contrast to traditional ray-based techniques we were able to obtain quantitative values for the permittivity and conductivity and in this way distinguish between moisture and chloride effects. For increasing chloride content increasing frequency-dependent conductivity values were obtained. The off-ground full-waveform inversion was extended to invert for positive and negative gradients in conductivity and the conductivity gradient direction could be correctly identified. Experimental specimen containing gradients were generated by exposing a concrete slab to controlled wetting-drying cycles using a saline solution. Full-waveform inversion of the measured data correctly identified the conductivity gradient direction which was confirmed by destructive analysis. On-ground CMP GPR data measured over a concrete layer overlying a metal plate show interfering multiple reflections, which indicates that the structure acts as a waveguide. Calculation of the phase-velocity spectrum shows the presence of several higher order modes. Whereas the dispersion inversion returns the thickness and layer height, the full-waveform inversion was also able to estimate quantitative conductivity values. This abstract is a contribution to COST Action TU1208

Note: Unshielded bilateral magnetoencephalography system using two-dimensional gradiometers

NASA Astrophysics Data System (ADS)

Seki, Yusuke; Kandori, Akihiko; Ogata, Kuniomi; Miyashita, Tsuyoshi; Kumagai, Yukio; Ohnuma, Mitsuru; Konaka, Kuni; Naritomi, Hiroaki

2010-09-01

Magnetoencephalography (MEG) noninvasively measures neuronal activity with high temporal resolution. The aim of this study was to develop a new type of MEG system that can measure bilateral MEG waveforms without a magnetically shielded room, which is an obstacle to reducing both the cost and size of an MEG system. An unshielded bilateral MEG system was developed using four two-dimensional (2D) gradiometers and two symmetric cryostats. The 2D gradiometer, which is based on a low-Tc superconducting quantum interference device and wire-wound pickup coil detects a magnetic-field gradient in two orthogonal directions, or ∂/∂x(∂2Bz/∂z2), and reduces environmental magnetic-field noise by more than 50 dB. The cryostats can be symmetrically positioned in three directions: vertical, horizontal, and rotational. This makes it possible to detect bilateral neuronal activity in the cerebral cortex simultaneously. Bilateral auditory-evoked fields (AEF) of 18 elderly subjects were measured in an unshielded hospital environment using the MEG system. As a result, both the ipsilateral and the contralateral AEF component N100m, which is the magnetic counterpart of electric N100 in electroencephalography and appears about 100 ms after the onset of an auditory stimulus, were successfully detected for all the subjects. Moreover, the ipsilateral P50m and the contralateral P50m were also detected for 12 (67%) and 16 (89%) subjects, respectively. Experimental results demonstrate that the unshielded bilateral MEG system can detect MEG waveforms, which are associated with brain dysfunction such as epilepsy, Alzheimer's disease, and Down syndrome.

Mechanical damage of tympanic membrane in relation to impulse pressure waveform - A study in chinchillas.

PubMed

Gan, Rong Z; Nakmali, Don; Ji, Xiao D; Leckness, Kegan; Yokell, Zachary

2016-10-01

Mechanical damage to middle ear components in blast exposure directly causes hearing loss, and the rupture of the tympanic membrane (TM) is the most frequent injury of the ear. However, it is unclear how the severity of injury graded by different patterns of TM rupture is related to the overpressure waveforms induced by blast waves. In the present study, the relationship between the TM rupture threshold and the impulse or overpressure waveform has been investigated in chinchillas. Two groups of animals were exposed to blast overpressure simulated in our lab under two conditions: open field and shielded with a stainless steel cup covering the animal head. Auditory brainstem response (ABR) and wideband tympanometry were measured before and after exposure to check the hearing threshold and middle ear function. Results show that waveforms recorded in the shielded case were different from those in the open field and the TM rupture threshold in the shielded case was lower than that in the open field (3.4 ± 0.7 vs. 9.1 ± 1.7 psi or 181 ± 1.6 vs. 190 ± 1.9 dB SPL). The impulse pressure energy spectra analysis of waveforms demonstrates that the shielded waveforms include greater energy at high frequencies than that of the open field waves. Finally, a 3D finite element (FE) model of the chinchilla ear was used to compute the distributions of stress in the TM and the TM displacement with impulse pressure waves. The FE model-derived change of stress in response to pressure loading in the shielded case was substantially faster than that in the open case. This finding provides the biomechanical mechanisms for blast induced TM damage in relation to overpressure waveforms. The TM rupture threshold difference between the open and shielded cases suggests that an acoustic role of helmets may exist, intensifying ear injury during blast exposure. Copyright © 2016 Elsevier B.V. All rights reserved.

Controlling the dynamics of electrons and ions in large area capacitive radio frequency plasmas via the Electrical Asymmetry Effect

NASA Astrophysics Data System (ADS)

Schuengel, Edmund

2014-10-01

The processing of large area surfaces in capacitive radio-frequency plasmas is a crucial step in the manufacturing of various high-technological products. To optimize these discharges for applications, understanding and controlling the dynamics of electrons and ions is vitally important. A recently proposed method of controlling these dynamics is based on the Electrical Asymmetry Effect (EAE): By driving the capacitive discharge with a dual-frequency voltage waveform composed of two consecutive harmonics, the symmetry of the discharge can be varied by tuning the relative phase. In this experimental study, the EAE is tested in hydrogen diluted silane discharges. The electron dynamics visualized by Phase Resolved Optical Emission Spectroscopy depends on the electrical asymmetry, the heating mode, and the presence of dust particles agglomerating in the plasma volume. In particular, a transition from the α-mode (heating by sheath expansion and field reversal) to the Ω-mode (heating by drift field in the bulk) is observed. The ion dynamics are strongly affected by the sheaths electric fields, which can be controlled via the EAE: Separate control of the flux and mean energy of ions onto the electrodes is possible via the EAE. Furthermore, investigations of the spatially resolved ion flux in the electromagnetic regime, i.e. using higher driving frequencies, reveal that the ion flux profile is controllable via the phase, as well, allowing for a significant improvement of the uniformity. Thus, it is demonstrated that the EAE is a powerful tool to control the properties of large area capacitive discharges in the volume and at the surfaces in various ways. Funded by the German Federal Ministry for the Environment, Nature conservation, and Nuclear Safety (0325210B).

Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip.

PubMed

Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T; Xuan, Yi; Leaird, Daniel E; Wang, Xi; Gan, Fuwan; Weiner, Andrew M; Qi, Minghao

2015-01-12

Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4 ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics.

Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip

PubMed Central

Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T.; Xuan, Yi; Leaird, Daniel E.; Wang, Xi; Gan, Fuwan; Weiner, Andrew M.; Qi, Minghao

2015-01-01

Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4 ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics. PMID:25581847

Acoustic characterization of high intensity focused ultrasound fields: A combined measurement and modeling approach

PubMed Central

Canney, Michael S.; Bailey, Michael R.; Crum, Lawrence A.; Khokhlova, Vera A.; Sapozhnikov, Oleg A.

2008-01-01

Acoustic characterization of high intensity focused ultrasound (HIFU) fields is important both for the accurate prediction of ultrasound induced bioeffects in tissues and for the development of regulatory standards for clinical HIFU devices. In this paper, a method to determine HIFU field parameters at and around the focus is proposed. Nonlinear pressure waveforms were measured and modeled in water and in a tissue-mimicking gel phantom for a 2 MHz transducer with an aperture and focal length of 4.4 cm. Measurements were performed with a fiber optic probe hydrophone at intensity levels up to 24 000 W∕cm2. The inputs to a Khokhlov–Zabolotskaya–Kuznetsov-type numerical model were determined based on experimental low amplitude beam plots. Strongly asymmetric waveforms with peak positive pressures up to 80 MPa and peak negative pressures up to 15 MPa were obtained both numerically and experimentally. Numerical simulations and experimental measurements agreed well; however, when steep shocks were present in the waveform at focal intensity levels higher than 6000 W∕cm2, lower values of the peak positive pressure were observed in the measured waveforms. This underrepresentation was attributed mainly to the limited hydrophone bandwidth of 100 MHz. It is shown that a combination of measurements and modeling is necessary to enable accurate characterization of HIFU fields. PMID:19062878

STRS Compliant FPGA Waveform Development

NASA Technical Reports Server (NTRS)

Nappier, Jennifer; Downey, Joseph

2008-01-01

The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. Current standards were researched and new standard interfaces were proposed. The implementation of the proposed standard interfaces on a laboratory breadboard SDR will be presented.

Optimisation of a Generic Ionic Model of Cardiac Myocyte Electrical Activity

PubMed Central

Guo, Tianruo; Al Abed, Amr; Lovell, Nigel H.; Dokos, Socrates

2013-01-01

A generic cardiomyocyte ionic model, whose complexity lies between a simple phenomenological formulation and a biophysically detailed ionic membrane current description, is presented. The model provides a user-defined number of ionic currents, employing two-gate Hodgkin-Huxley type kinetics. Its generic nature allows accurate reconstruction of action potential waveforms recorded experimentally from a range of cardiac myocytes. Using a multiobjective optimisation approach, the generic ionic model was optimised to accurately reproduce multiple action potential waveforms recorded from central and peripheral sinoatrial nodes and right atrial and left atrial myocytes from rabbit cardiac tissue preparations, under different electrical stimulus protocols and pharmacological conditions. When fitted simultaneously to multiple datasets, the time course of several physiologically realistic ionic currents could be reconstructed. Model behaviours tend to be well identified when extra experimental information is incorporated into the optimisation. PMID:23710254

Characteristics of Currents and Electric Fields Associated with the Initial Stage of Upward Lightning

NASA Astrophysics Data System (ADS)

Watanabe, N.; Nag, A.; Diendorfer, G.; Pichler, H.; Schulz, W.

2017-12-01

There is increasing interest in understanding processes associated with the initiation of upward lightning from tall structures. Characterization of such processes is essential for the development of appropriate models. We examine current and electric field waveforms for 15 negative upward flashes occurring in 2007-2009 initiated from the Gaisberg Tower located in Salzburg, Austria. Current was measured at the top of the tower using a 0.25 mΩ shunt. Electric field was measured simultaneously at close (170 m from the tower) and far (79 km from the tower in 2007 and 109 km in 2008-2009) distances. The initial stage (IS) of these flashes comprised of relatively slowly varying "background" current (having durations ranging from 132 to 692 ms), with faster, more impulsive current variations (pulses having durations ranging from 4.7 µs to 22.9 ms) overlaid on this background current. In five of the 15 (33%) flashes, this IS background current was negative while in the other ten (67%) flashes, the current was bipolar (changing between negative and positive values). 150 current pulses occurred during the IS of these 15 flashes, of which 28 (19%) were positive bipolar (positive initial polarity with a negative opposite polarity overshoot), 5 (3.3%) were positive unipolar (positive initial polarity with no opposite polarity overshoot), and 117 (78%) were negative unipolar. No negative bipolar pulses were found. The median peak current and risetime for the 28 bipolar pulses were 0.74 kA and 2.8 µs, respectively, and those for the 122 unipolar pulses were 0.87 kA and 70 µs, respectively. Generally speaking, majority of the pulses occurring at the beginning of the initial stage were lower-amplitude positive bipolar, while higher-amplitude unipolar pulses were more likely to occur at later times. These 150 IS current pulses produced 133 detectable electric field change signatures at the near station and 59 at the far station (all recorded at 79 km in 12 flashes occurring in 2007). We will examine in detail the characteristics of these electric field pulses in order to gain insights into the mechanisms of the underlying processes.

Fiber-Optic Sensor for Aircraft Lightning Current Measurement

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George G.; Mata, Carlos T.; Mata,Angel G.; Snyder, Gary P.

2012-01-01

An electric current sensor based on Faraday rotation effect in optical fiber was developed for measuring aircraft lightning current. Compared to traditional sensors, the design has many advantages including the ability to measure total current and to conform to structure geometries. The sensor is also small, light weight, non-conducting, safe from interference, and free of hysteresis and saturation. Potential applications include characterization of lightning current waveforms, parameters and paths, and providing environmental data for aircraft certifications. In an optical fiber as the sensing medium, light polarization rotates when exposed to a magnetic field in the direction of light propagation. By forming closed fiber loops around a conductor and applying Ampere s law, measuring the total light rotation yields the enclosed current. A reflective polarimetric scheme is used, where polarization change is measured after the polarized light travels round-trip through the sensing fiber. The sensor system was evaluated measuring rocket-triggered lightning over the 2011 summer. Early results compared very well against a reference current shunt resistor, demonstrating the sensor's accuracy and feasibility in a lightning environment. While later comparisons show gradually increasing amplitude deviations for an undetermined cause, the overall waveforms still compared very well.

Fiber-Optic Sensor for Aircraft Lightning Current Measurement

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George G.; Mata, Carlos T.; Mata, Angel G.; Snyder, Gary P.

2012-01-01

An electric current sensor based on Faraday rotation effect in optical fiber was developed for measuring aircraft lightning current. Compared to traditional sensors, the design has many advantages including the ability to measure total current and to conform to structure geometries. The sensor is also small, light weight, non-conducting, safe from interference, and free of hysteresis and saturation. Potential applications include characterization of lightning current waveforms, parameters and paths, and providing environmental data for aircraft certifications. In an optical fiber as the sensing medium, light polarization rotates when exposed to a magnetic field in the direction of light propagation. By forming closed fiber loops around a conductor and applying Ampere s law, measuring the total light rotation yields the enclosed current. A reflective polarimetric scheme is used, where polarization change is measured after the polarized light travels round-trip through the sensing fiber. The sensor system was evaluated measuring rocket-triggered lightning over the 2011 summer. Early results compared very well against a reference current shunt resistor, demonstrating the sensor s accuracy and feasibility in a lightning environment. While later comparisons show gradually increasing amplitude deviations for an undetermined cause, the overall waveforms still compared very well.

Electrochemical measurements on a droplet using gold microelectrodes

NASA Astrophysics Data System (ADS)

Jenabi, Amin; Souri, Asma; Rastkhadiv, Ali

2016-03-01

Facile methods of ion recognition are important for the fabrication of electronic tongue systems. In this work, we demonstrate performing pulsed conductometry on microliter electrolyte droplets dropped on gold microelectrodes vapor deposited on soda lime glass slides. A droplet is dropped between two microelectrodes when a voltage waveform from a preprogramed power supply is applied on them. The temporal variation of the electric current passing through the droplet is recorded, digitized and stored. The obtained data are compared with the database formed out of the previous experiences for the classification of the sample electrolytes. It is shown that the shape of the voltage waveform is the important parameter of the process. We devised a method for the optimization of the voltage waveform profile for obtaining the maximum of discriminating information from the recorded current variations.

The development and modeling of devices and paradigms for transcranial magnetic stimulation

PubMed Central

Goetz, Stefan M.; Deng, Zhi-De

2017-01-01

Magnetic stimulation is a noninvasive neurostimulation technique that can evoke action potentials and modulate neural circuits through induced electric fields. Biophysical models of magnetic stimulation have become a major driver for technological developments and the understanding of the mechanisms of magnetic neurostimulation and neuromodulation. Major technological developments involve stimulation coils with different spatial characteristics and pulse sources to control the pulse waveform. While early technological developments were the result of manual design and invention processes, there is a trend in both stimulation coil and pulse source design to mathematically optimize parameters with the help of computational models. To date, macroscopically highly realistic spatial models of the brain as well as peripheral targets, and user-friendly software packages enable researchers and practitioners to simulate the treatment-specific and induced electric field distribution in the brains of individual subjects and patients. Neuron models further introduce the microscopic level of neural activation to understand the influence of activation dynamics in response to different pulse shapes. A number of models that were designed for online calibration to extract otherwise covert information and biomarkers from the neural system recently form a third branch of modeling. PMID:28443696

The development and modelling of devices and paradigms for transcranial magnetic stimulation.

PubMed

Goetz, Stefan M; Deng, Zhi-De

2017-04-01

Magnetic stimulation is a non-invasive neurostimulation technique that can evoke action potentials and modulate neural circuits through induced electric fields. Biophysical models of magnetic stimulation have become a major driver for technological developments and the understanding of the mechanisms of magnetic neurostimulation and neuromodulation. Major technological developments involve stimulation coils with different spatial characteristics and pulse sources to control the pulse waveform. While early technological developments were the result of manual design and invention processes, there is a trend in both stimulation coil and pulse source design to mathematically optimize parameters with the help of computational models. To date, macroscopically highly realistic spatial models of the brain, as well as peripheral targets, and user-friendly software packages enable researchers and practitioners to simulate the treatment-specific and induced electric field distribution in the brains of individual subjects and patients. Neuron models further introduce the microscopic level of neural activation to understand the influence of activation dynamics in response to different pulse shapes. A number of models that were designed for online calibration to extract otherwise covert information and biomarkers from the neural system recently form a third branch of modelling.

Finite-difference modeling of the electroseismic logging in a fluid-saturated porous formation

NASA Astrophysics Data System (ADS)

Guan, Wei; Hu, Hengshan

2008-05-01

In a fluid-saturated porous medium, an electromagnetic (EM) wavefield induces an acoustic wavefield due to the electrokinetic effect. A potential geophysical application of this effect is electroseismic (ES) logging, in which the converted acoustic wavefield is received in a fluid-filled borehole to evaluate the parameters of the porous formation around the borehole. In this paper, a finite-difference scheme is proposed to model the ES logging responses to a vertical low frequency electric dipole along the borehole axis. The EM field excited by the electric dipole is calculated separately by finite-difference first, and is considered as a distributed exciting source term in a set of extended Biot's equations for the converted acoustic wavefield in the formation. This set of equations is solved by a modified finite-difference time-domain (FDTD) algorithm that allows for the calculation of dynamic permeability so that it is not restricted to low-frequency poroelastic wave problems. The perfectly matched layer (PML) technique without splitting the fields is applied to truncate the computational region. The simulated ES logging waveforms approximately agree with those obtained by the analytical method. The FDTD algorithm applies also to acoustic logging simulation in porous formations.

Broad Separation of Isomeric Lipids by High-Resolution Differential Ion Mobility Spectrometry with Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Bowman, Andrew P.; Abzalimov, Rinat R.; Shvartsburg, Alexandre A.

2017-08-01

Maturation of metabolomics has brought a deeper appreciation for the importance of isomeric identity of lipids to their biological role, mirroring that for proteoforms in proteomics. However, full characterization of the lipid isomerism has been thwarted by paucity of rapid and effective analytical tools. A novel approach is ion mobility spectrometry (IMS) and particularly differential or field asymmetric waveform IMS (FAIMS) at high electric fields, which is more orthogonal to mass spectrometry. Here we broadly explore the power of FAIMS to separate lipid isomers, and find a 75% success rate across the four major types of glycero- and phospho- lipids ( sn, chain length, double bond position, and cis/ trans). The resolved isomers were identified using standards, and (for the first two types) tandem mass spectrometry. These results demonstrate the general merit of incorporating high-resolution FAIMS into lipidomic analyses.

First Ground-Based Observation of Sprites Over Southern Africa and Estimation of Their Physical and Optical Characteristics

NASA Astrophysics Data System (ADS)

Nnadih, O.; Martinez, P.; Kosch, M.; Lotz, S.; Fullekrug, M.

2016-12-01

We present the first ground-based observations of sprites over convective thunderstorms in southern Africa. The observations, acquired during the austral summer of 2015/16. show sprites with dendritic, carrot, angel and jellyfish-like shapes. The sprite locations are compared with lightning locations and peak amplitudes determined from the lightning detection network operated by the South African Weather Service, and also with the lightning locations reported by the World Wide Lightning Location Network (WLLN) and Low Frequency radio waveforms of the electric field strength recorded in the conjugate hemisphere in South-West England. The charge moment of the lightning discharges causing sprites is inferred from Extremely Low Frequency magnetic field measurements recorded at remote distances. These measurements reveal that a number of the sprites that we observed were triggered below and above the charge moment threshold for sprite production.

Experimental and theoretical characterization of the voltage distribution generated by deep brain stimulation.

PubMed

Miocinovic, Svjetlana; Lempka, Scott F; Russo, Gary S; Maks, Christopher B; Butson, Christopher R; Sakaie, Ken E; Vitek, Jerrold L; McIntyre, Cameron C

2009-03-01

Deep brain stimulation (DBS) is an established therapy for the treatment of Parkinson's disease and shows great promise for numerous other disorders. While the fundamental purpose of DBS is to modulate neural activity with electric fields, little is known about the actual voltage distribution generated in the brain by DBS electrodes and as a result it is difficult to accurately predict which brain areas are directly affected by the stimulation. The goal of this study was to characterize the spatial and temporal characteristics of the voltage distribution generated by DBS electrodes. We experimentally recorded voltages around active DBS electrodes in either a saline bath or implanted in the brain of a non-human primate. Recordings were made during voltage-controlled and current-controlled stimulation. The experimental findings were compared to volume conductor electric field models of DBS parameterized to match the different experiments. Three factors directly affected the experimental and theoretical voltage measurements: 1) DBS electrode impedance, primarily dictated by a voltage drop at the electrode-electrolyte interface and the conductivity of the tissue medium, 2) capacitive modulation of the stimulus waveform, and 3) inhomogeneity and anisotropy of the tissue medium. While the voltage distribution does not directly predict the neural response to DBS, the results of this study do provide foundational building blocks for understanding the electrical parameters of DBS and characterizing its effects on the nervous system.

Optimal design of neural stimulation current waveforms.

PubMed

Halpern, Mark

2009-01-01

This paper contains results on the design of electrical signals for delivering charge through electrodes to achieve neural stimulation. A generalization of the usual constant current stimulation phase to a stepped current waveform is presented. The electrode current design is then formulated as the calculation of the current step sizes to minimize the peak electrode voltage while delivering a specified charge in a given number of time steps. This design problem can be formulated as a finite linear program, or alternatively by using techniques for discrete-time linear system design.

Optically-synchronized encoder and multiplexer scheme for interleaved photonics analog-to-digital conversion

NASA Astrophysics Data System (ADS)

Villa, Carlos; Kumavor, Patrick; Donkor, Eric

2008-04-01

Photonics Analog-to-Digital Converters (ADCs) utilize a train of optical pulses to sample an electrical input waveform applied to an electrooptic modulator or a reverse biased photodiode. In the former, the resulting train of amplitude-modulated optical pulses is detected (converter to electrical) and quantized using a conversional electronics ADC- as at present there are no practical, cost-effective optical quantizers available with performance that rival electronic quantizers. In the latter, the electrical samples are directly quantized by the electronics ADC. In both cases however, the sampling rate is limited by the speed with which the electronics ADC can quantize the electrical samples. One way to increase the sampling rate by a factor N is by using the time-interleaved technique which consists of a parallel array of N electrical ADC converters, which have the same sampling rate but different sampling phase. Each operating at a quantization rate of fs/N where fs is the aggregated sampling rate. In a system with no real-time operation, the N channels digital outputs are stored in memory, and then aggregated (multiplexed) to obtain the digital representation of the analog input waveform. Alternatively, for real-time operation systems the reduction of storing time in the multiplexing process is desired to improve the time response of the ADC. The complete elimination of memories come expenses of concurrent timing and synchronization in the aggregation of the digital signal that became critical for a good digital representation of the analog signal waveform. In this paper we propose and demonstrate a novel optically synchronized encoder and multiplexer scheme for interleaved photonics ADCs that utilize the N optical signals used to sample different phases of an analog input signal to synchronize the multiplexing of the resulting N digital output channels in a single digital output port. As a proof of concept, four 320 Megasamples/sec 12-bit of resolution digital signals were multiplexed to form an aggregated 1.28 Gigasamples/sec single digital output signal.

Electrical energy consumption control apparatuses and electrical energy consumption control methods

DOEpatents

Hammerstrom, Donald J.

2012-09-04

Electrical energy consumption control apparatuses and electrical energy consumption control methods are described. According to one aspect, an electrical energy consumption control apparatus includes processing circuitry configured to receive a signal which is indicative of current of electrical energy which is consumed by a plurality of loads at a site, to compare the signal which is indicative of current of electrical energy which is consumed by the plurality of loads at the site with a desired substantially sinusoidal waveform of current of electrical energy which is received at the site from an electrical power system, and to use the comparison to control an amount of the electrical energy which is consumed by at least one of the loads of the site.

Radiation from a current filament driven by a traveling wave

NASA Technical Reports Server (NTRS)

Levine, D. M.; Meneghini, R.

1976-01-01

Solutions are presented for the electromagnetic fields radiated by an arbitrarily oriented current filament located above a perfectly conducting ground plane and excited by a traveling current wave. Both an approximate solution, valid in the fraunhofer region of the filament and predicting the radiation terms in the fields, and an exact solution, which predicts both near and far field components of the electromagnetic fields, are presented. Both solutions apply to current waveforms which propagate along the channel but are valid regardless of the actual waveshape. The exact solution is valid only for waves which propagate at the speed of light, and the approximate solution is formulated for arbitrary velocity of propagation. The spectrum-magnitude of the fourier transform-of the radiated fields is computed by assuming a compound exponential model for the current waveform. The effects of channel orientation and length, as well as velocity of propagation of the current waveform and location of the observer, are discussed. It is shown that both velocity of propagation and an effective channel length are important in determining the shape of the spectrum.

Broadband optical frequency comb generator based on driving N-cascaded modulators by Gaussian-shaped waveform

NASA Astrophysics Data System (ADS)

Hmood, Jassim K.; Harun, Sulaiman W.

2018-05-01

A new approach for realizing a wideband optical frequency comb (OFC) generator based on driving cascaded modulators by a Gaussian-shaped waveform, is proposed and numerically demonstrated. The setup includes N-cascaded MZMs, a single Gaussian-shaped waveform generator, and N-1 electrical time delayer. The first MZM is driven directly by a Gaussian-shaped waveform, while delayed replicas of the Gaussian-shaped waveform drive the other MZMs. An analytical model that describes the proposed OFC generator is provided to study the effect of number and chirp factor of cascaded MZM as well as pulse width on output spectrum. Optical frequency combs at frequency spacing of 1 GHz are generated by applying Gaussian-shaped waveform at pulse widths ranging from 200 to 400 ps. Our results reveal that, the number of comb lines is inversely proportional to the pulse width and directly proportional to both number and chirp factor of cascaded MZMs. At pulse width of 200 ps and chirp factor of 4, 67 frequency lines can be measured at output spectrum of two-cascaded MZMs setup. Whereas, increasing the number of cascaded stages to 3, 4, and 5, the optical spectra counts 89, 109 and 123 frequency lines; respectively. When the delay time is optimized, 61 comb lines can be achieved with power fluctuations of less than 1 dB for five-cascaded MZMs setup.

Response of nickel to zinc cells to electric vehicle chopper discharge waveforms

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1981-01-01

The preliminary results of simulated electric vehicle chopper controlled discharge of a Nickel/Zinc battery shows delivered energy increases of 5 to 25 percent compared to constant current discharges of the same average current. The percentage increase was a function of chopper frequency, the ratio of peak to average current, and the magnitude of the discharge current. Because the chopper effects are of a complex nature, electric vehicle battery/speed controller interaction must be carefully considered in vehicle design to optimize battery performance.

Analysis of impulse signals with Hylaty ELF station

NASA Astrophysics Data System (ADS)

Kulak, A.; Mlynarczyk, J.; Ostrowski, M.; Kubisz, J.; Michalec, A.

2012-04-01

Lighting discharges generate electromagnetic field pulses that propagate in the Earth-ionosphere waveguide. The attenuation in the ELF range is so small that the pulses originating from strong atmospheric discharges can be observed even several thousand kilometers away from the individual discharge. The recorded waveform depends on the discharge process, the Earth-ionosphere waveguide properties on the source-receiver path, and the transfer function of the receiver. If the distance from the source is known, an inverse method can be used for reconstructing the current moment waveform and the charge moment of the discharge. In order to reconstruct the source parameters from the recorded signal a reliable model of the radio wave propagation in the Earth-ionosphere waveguide as well as practical signal processing techniques are necessary. We present two methods, both based on analytical formulas. The first method allows for fast calculation of the charge moment of relatively short atmospheric discharges. It is based on peak amplitude measurement of the recorded magnetic component of the ELF EM field and it takes into account the receiver characteristics. The second method, called "inverse channel method" allows reconstructing the complete current moment waveform of strong atmospheric discharges that exhibit the continuing current phase, such as Gigantic Jets and Sprites. The method makes it possible to fully remove from the observed waveform the distortions related to the receiver's impulse response as well as the influence of the Earth-ionosphere propagation channel. Our ELF station is equipped with two magnetic antennas for Bx and By components measurement in the 0.03 to 55 Hz frequency range. ELF Data recording is carried out since 1993, with continuous data acquisition since 2005. The station features low noise level and precise timing. It is battery powered and located in the sparsely populated area, far from major electric power lines, which results in high quality signal recordings and allows for precise calculations of the charge moments of upward discharges and strong cloud-to-ground discharges originating from distant sources. The same data is used for Schumann resonance observation. We demonstrate the use of our methods based on recent recordings from the Hylaty ELF station. We include examples of GJ (Gigantic Jet) and TGF (Terrestrial Gamma-ray Flash) related discharges.

Detection of chlorinated and brominated byproducts of drinking water disinfection using electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

PubMed

Ells, B; Barnett, D A; Froese, K; Purves, R W; Hrudey, S; Guevremont, R

1999-10-15

The lower limit of detection for low molecular weight polar and ionic analytes using electrospray ionization-mass spectrometry (ESI-MS) is often severely compromised by an intense background that obscures ions of trace components in solution. Recently, a new technique, referred to as high-field asymmetric waveform ion mobility spectrometry (FAIMS), has been shown to separate gas-phase ions at atmospheric pressure and room temperature. A FAIMS instrument is an ion filter that may be tuned, by control of electrical voltages, to continuously transmit selected ions from a complex mixture. This capability offers significant advantages when FAIMS is coupled with ESI, a source that generates a wide variety of ions, including solvent clusters and salt adducts. In this report, the tandem arrangement of ESI-FAIMS-MS is used for the analysis of haloacetic acids, a class of disinfection byproducts regulated by the US EPA. FAIMS is shown to effectively discriminate against background ions resulting from the electrospray of tap water solutions containing the haloacetic acids. Consequently, mass spectra are simplified, the selectivity of the method is improved, and the limits of detection are lowered compared with conventional ESI-MS. The detection limits of ESI-FAIMS-MS for six haloacetic acids ranged between 0.5 and 4 ng/mL in 9:1 methanol/tap water (5 and 40 ng/mL in the original tap water samples) with no preconcentration, derivatization, or chromatographic separation prior to analysis.

A ceramic radial insulation structure for a relativistic electron beam vacuum diode.

PubMed

Xun, Tao; Yang, Hanwu; Zhang, Jiande; Liu, Zhenxiang; Wang, Yong; Zhao, Yansong

2008-06-01

For one kind of a high current diode composed of a small disk-type alumina ceramic insulator water/vacuum interface, the insulation structure was designed and experimentally investigated. According to the theories of vacuum flashover and the rules for radial insulators, a "cone-column" anode outline and the cathode shielding rings were adopted. The electrostatic field along the insulator surface was obtained by finite element analysis simulating. By adjusting the outline of the anode and reshaping the shielding rings, the electric fields were well distributed and the field around the cathode triple junction was effectively controlled. Area weighted statistical method was applied to estimate the surface breakdown field. In addition, the operating process of an accelerator based on a spiral pulse forming line (PFL) was simulated through the PSPICE software to get the waveform of charging and diode voltage. The high voltage test was carried out on a water dielectric spiral PFL accelerator with long pulse duration, and results show that the diode can work stably in 420 kV, 200 ns conditions. The experimental results agree with the theoretical and simulated results.

Data processing in Software-type Wave-Particle Interaction Analyzer onboard the Arase satellite

NASA Astrophysics Data System (ADS)

Hikishima, Mitsuru; Kojima, Hirotsugu; Katoh, Yuto; Kasahara, Yoshiya; Kasahara, Satoshi; Mitani, Takefumi; Higashio, Nana; Matsuoka, Ayako; Miyoshi, Yoshizumi; Asamura, Kazushi; Takashima, Takeshi; Yokota, Shoichiro; Kitahara, Masahiro; Matsuda, Shoya

2018-05-01

The software-type wave-particle interaction analyzer (S-WPIA) is an instrument package onboard the Arase satellite, which studies the magnetosphere. The S-WPIA represents a new method for directly observing wave-particle interactions onboard a spacecraft in a space plasma environment. The main objective of the S-WPIA is to quantitatively detect wave-particle interactions associated with whistler-mode chorus emissions and electrons over a wide energy range (from several keV to several MeV). The quantity of energy exchanges between waves and particles can be represented as the inner product of the wave electric-field vector and the particle velocity vector. The S-WPIA requires accurate measurement of the phase difference between wave and particle gyration. The leading edge of the S-WPIA system allows us to collect comprehensive information, including the detection time, energy, and incoming direction of individual particles and instantaneous-wave electric and magnetic fields, at a high sampling rate. All the collected particle and waveform data are stored in the onboard large-volume data storage. The S-WPIA executes calculations asynchronously using the collected electric and magnetic wave data, data acquired from multiple particle instruments, and ambient magnetic-field data. The S-WPIA has the role of handling large amounts of raw data that are dedicated to calculations of the S-WPIA. Then, the results are transferred to the ground station. This paper describes the design of the S-WPIA and its calculations in detail, as implemented onboard Arase.[Figure not available: see fulltext.

PWM Inverter control and the application thereof within electric vehicles

DOEpatents

Geppert, Steven

1982-01-01

An inverter (34) which provides power to an A.C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A.C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A.C. machine is optimized. The control circuit includes a micro-computer and memory element which receive various parametric inputs and calculate optimized machine control data signals therefrom. The control data is asynchronously loaded into the inverter through an intermediate buffer (38). In its preferred embodiment, the present invention is incorporated within an electric vehicle (10) employing a 144 VDC battery pack (32) and a three-phase induction motor (18).

Device for two-dimensional gas-phase separation and characterization of ion mixtures

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2006-12-12

The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.

A comparison of the optical pulse characteristics of intracloud and cloud-to-ground lightning as observed above clouds

NASA Technical Reports Server (NTRS)

Goodman, Steven J.; Christian, Hugh J.; Rust, W. David

1988-01-01

The optical-pulse characteristics of intracloud (IC) and cloud-to-ground (CG) lightning flashes were investigated. The time-resolved optical waveforms at 777.4 nm and electric-field changes produced by lightning flashes were measured aboard a U2 aircraft flying above clouds at the same time that ground-based lightning measurements were carried out. The pulse shapes and intensities of IC and CG flashes, as viewed from above cloud, were found to exhibit remarkably similar waveshapes, radiances, and radiant energy densities. The median radiance at cloud top was found to be about 0.007 W/sq m per sr, and the median energy density about 0.000003 J/sq m per sr.

Design and Testing of Space Telemetry SCA Waveform

NASA Technical Reports Server (NTRS)

Mortensen, Dale J.; Handler, Louis M.; Quinn, Todd M.

2006-01-01

A Software Communications Architecture (SCA) Waveform for space telemetry is being developed at the NASA Glenn Research Center (GRC). The space telemetry waveform is implemented in a laboratory testbed consisting of general purpose processors, field programmable gate arrays (FPGAs), analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). The radio hardware is integrated with an SCA Core Framework and other software development tools. The waveform design is described from both the bottom-up signal processing and top-down software component perspectives. Simulations and model-based design techniques used for signal processing subsystems are presented. Testing with legacy hardware-based modems verifies proper design implementation and dynamic waveform operations. The waveform development is part of an effort by NASA to define an open architecture for space based reconfigurable transceivers. Use of the SCA as a reference has increased understanding of software defined radio architectures. However, since space requirements put a premium on size, mass, and power, the SCA may be impractical for today s space ready technology. Specific requirements for an SCA waveform and other lessons learned from this development are discussed.

Design and performance of heart assist or artificial heart control systems

NASA Technical Reports Server (NTRS)

Webb, J. A., Jr.; Gebben, V. D.

1978-01-01

The factors leading to the design of a controlled driving system for either a heart assist pump or artificial heart are discussed. The system provides square pressure waveform to drive a pneumatic-type blood pump. For assist usage the system uses an R-wave detector circuit that can detect the R-wave of the electrocardiogram in the presence of electrical disturbances. This circuit provides a signal useful for synchronizing an assist pump with the natural heart. It synchronizes a square wave circuit, the output of which is converted into square waveforms of pneumatic pressure suitable for driving both assist device and artificial heart. The pressure levels of the driving waveforms are controlled by means of feedback channels to maintain physiological regulation of the artificial heart's output flow. A more compact system that could achieve similar regulatory characteristics is also discussed.

THOR Field and Wave Processor - FWP

NASA Astrophysics Data System (ADS)

Soucek, Jan; Rothkaehl, Hanna; Balikhin, Michael; Zaslavsky, Arnaud; Nakamura, Rumi; Khotyaintsev, Yuri; Uhlir, Ludek; Lan, Radek; Yearby, Keith; Morawski, Marek; Winkler, Marek

2016-04-01

If selected, Turbulence Heating ObserveR (THOR) will become the first mission ever flown in space dedicated to plasma turbulence. The Fields and Waves Processor (FWP) is an integrated electronics unit for all electromagnetic field measurements performed by THOR. FWP will interface with all fields sensors: electric field antennas of the EFI instrument, the MAG fluxgate magnetometer and search-coil magnetometer (SCM) and perform data digitization and on-board processing. FWP box will house multiple data acquisition sub-units and signal analyzers all sharing a common power supply and data processing unit and thus a single data and power interface to the spacecraft. Integrating all the electromagnetic field measurements in a single unit will improve the consistency of field measurement and accuracy of time synchronization. The feasibility of making highly sensitive electric and magnetic field measurements in space has been demonstrated by Cluster (among other spacecraft) and THOR instrumentation complemented by a thorough electromagnetic cleanliness program will further improve on this heritage. Taking advantage of the capabilities of modern electronics, FWP will provide simultaneous synchronized waveform and spectral data products at high time resolution from the numerous THOR sensors, taking advantage of the large telemetry bandwidth of THOR. FWP will also implement a plasma a resonance sounder and a digital plasma quasi-thermal noise analyzer designed to provide high cadence measurements of plasma density and temperature complementary to data from particle instruments. FWP will be interfaced with the particle instrument data processing unit (PPU) via a dedicated digital link which will enable performing on board correlation between waves and particles, quantifying the transfer of energy between waves and particles. The FWP instrument shall be designed and built by an international consortium of scientific institutes from Czech Republic, Poland, France, UK, Sweden and Austria.

Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Peterson, Peter Y.; Williams, George J.; Gilland, James; Hofer, Richard; Mikellides, Ioannis

2016-01-01

NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front magnetic pole cover thruster configuration with the thruster body electrically tied to cathode, and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68% and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the discharge current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability were mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 1×10-5 Torr-Xe (for thruster flow rates of 20.5 mg/s). Power spectral density analysis of the discharge current waveforms showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant breathing mode frequency. Finally, IVB maps of the TDU-1 thruster indicated that the discharge current became more oscillatory with higher discharge current peak-to-peak and RMS values with increased facility background pressure at lower thruster mass flow rates; thruster operation at higher flow rates resulted in less change to the thruster's IVB characteristics with elevated background pressure.

Nitrate removal from pharmaceutical wastewater using microbial electrochemical system supplied through low frequency-low voltage alternating electric current.

PubMed

Hoseinzadeh, Edris; Rezaee, Abbas; Farzadkia, Mahdi

2018-04-01

In this study, a microbial electrochemical system (MES) was designed to evaluate the effects of a low frequency-low voltage alternating electrical current on denitrification efficacy in the presence of ibuprofen as a low biodegradable organic carbon source. Cylindrical carbon cloth and stainless steel mesh electrodes containing a consortium of heterotrophic and autotrophic bacteria were mounted in the wall of the designed laboratory-scale bioreactor. The effects of inlet nitrate concentration (50-800mgL -1 ), retention time (2.5-24h), waveform magnitude (0.1-9.6V p-p ), adjustable direct current voltage added to offset voltage (0.1-4.9V), alternating current frequency (10-60Hz), and waveforms (sinusoidal, square, and ramp) were studied in this work. The results showed that the proposed system removes 800mgL -1 nitrate up to 95% during 6.5h. Optimum conditions were obtained in the 8V p-p using a frequency of 10Hz of a sinusoidal waveform. The morphology studies confirmed bacterial morphology change when applying the alternating current. Dehydrogenase activity of biofilms formed on surface of stainless steel electrodes increased to 15.24μgTFmg biomass cm -2 d. The maximum bacterial activity was obtained at a voltage of 8V p-p . The experimental results revealed that the MES using a low frequency-low voltage alternating electrical current is a promising technique for nitrate removal from pharmaceutical wastewaters in the presence of low biodegradability of carbon sources such as ibuprofen. Copyright © 2017 Elsevier B.V. All rights reserved.

Muscle contraction during electro-muscular incapacitation: A comparison between square-wave pulses and the TASER(®) X26 Electronic control device.

PubMed

Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

2011-01-01

Electronic control devices (including the Advanced TASER(®) X26 model produced by TASER International) incapacitate individuals by causing muscle contractions. To provide information relevant to development of future potential devices, effects of monophasic square waves with different parameters were compared with those of the X26 electronic control device, using two animal models (frogs and swine). Pulse power, electrical pulse charge, pulse duration, and pulse repetition frequency affected muscle contraction. There was no difference in the charge required, between the square waveform and the X26 waveform, to cause approximately the same muscle-contraction response (in terms of the strength-duration curve). Thus, on the basis of these initial studies, the detailed shape of a waveform may not be important in terms of generating electro-muscular incapacitation. More detailed studies, however, may be required to thoroughly test all potential waveforms to be considered for future use in ECDs. 2010 American Academy of Forensic Sciences. Published 2010. This article is a U.S. Government work and is in the public domain in the U.S.A.

Mach-Zehnder interferometry method for acoustic shock wave measurements in air and broadband calibration of microphones.

PubMed

Yuldashev, Petr; Karzova, Maria; Khokhlova, Vera; Ollivier, Sébastien; Blanc-Benon, Philippe

2015-06-01

A Mach-Zehnder interferometer is used to measure spherically diverging N-waves in homogeneous air. An electrical spark source is used to generate high-amplitude (1800 Pa at 15 cm from the source) and short duration (50 μs) N-waves. Pressure waveforms are reconstructed from optical phase signals using an Abel-type inversion. It is shown that the interferometric method allows one to reach 0.4 μs of time resolution, which is 6 times better than the time resolution of a 1/8-in. condenser microphone (2.5 μs). Numerical modeling is used to validate the waveform reconstruction method. The waveform reconstruction method provides an error of less than 2% with respect to amplitude in the given experimental conditions. Optical measurement is used as a reference to calibrate a 1/8-in. condenser microphone. The frequency response function of the microphone is obtained by comparing the spectra of the waveforms resulting from optical and acoustical measurements. The optically measured pressure waveforms filtered with the microphone frequency response are in good agreement with the microphone output voltage. Therefore, an optical measurement method based on the Mach-Zehnder interferometer is a reliable tool to accurately characterize evolution of weak shock waves in air and to calibrate broadband acoustical microphones.

Measuring Power Flow in Electric Vehicles

NASA Technical Reports Server (NTRS)

Griffin, Daniel C., Jr; Wiker, G. A.

1983-01-01

Instrument accommodates fast rise and fall times of waveforms characteristic of modern, efficient power controllers. Power meter multiplies analog signals proportional to voltage and current, and converts resulting signal to frequency. Two mechanical counters provided: one for charging, one for discharging.

Digital electronic bone growth stimulator

DOEpatents

Kronberg, James W.

1995-01-01

A device for stimulating bone tissue by applying a low level alternating current signal directly to the patient's skin. A crystal oscillator, a binary divider chain and digital logic gates are used to generate the desired waveforms that reproduce the natural electrical characteristics found in bone tissue needed for stimulating bone growth and treating osteoporosis. The device, powered by a battery, contains a switch allowing selection of the correct waveform for bone growth stimulation or osteoporosis treatment so that, when attached to the skin of the patient using standard skin contact electrodes, the correct signal is communicated to the underlying bone structures.

Laboratory studies of near-grazing impulsive sound propagating over rough water.

PubMed

Qin, Qin; Lukaschuk, Sergei; Attenborough, Keith

2008-08-01

Acoustic impulses due to an electrical spark source (main acoustic energy near 15 kHz) have been measured after propagating near to the water surface in a shallow container resting on a vibrating platform. Control of the platform vibration enabled control of water wave amplitudes. Analysis of the results reveals systematic variations in the received acoustic waveforms as the mean trough-to-crest water wave amplitude is increased up to 7 mm. The amplitudes of the peaks corresponding to specular reflections are reduced and the variability in the tails of the waveforms is increased.

Airfoil gust response and the sound produced by airifoil-vortex interaction

NASA Technical Reports Server (NTRS)

Amiet, R. K.

1986-01-01

This paper contributes to the understanding of the noise generation process of an airfoil encountering an unsteady upwash. By using a fast Fourier transform together with accurate airfoil response functions, the lift-time waveform for an airfoil encountering a delta function gust (the indicial function) is calculated for a flat plate airfoil in a compressible flow. This shows the interesting property that the lift is constant until the generated acoustic wave reaches the trailing edge. Expressions are given for the magnitude of this constant and for the pressure distribution on the airfoil during this time interval. The case of an airfoil cutting through a line vortex is also analyzed. The pressure-time waveform in the far field is closely related to the left-time waveform for the above problem of an airfoil entering a delta function gust. The effects of varying the relevant parameters in the problem are studied, including the observed position, the core diameter of the vortex, the vortex orientation and the airfoil span. The far field sound varies significantly with observer position, illustrating the importance of non-compactness effects. Increasing the viscous core diameter tends to smooth the pressure-time waveform. For small viscous core radius and infinite span, changing the vortex orientation changes only the amplitude of the pressure-time waveform, and not the shape.

Development of water level estimation algorithms using SARAL/Altika dataset and validation over the Ukai reservoir, India

NASA Astrophysics Data System (ADS)

Chander, Shard; Ganguly, Debojyoti

2017-01-01

Water level was estimated, using AltiKa radar altimeter onboard the SARAL satellite, over the Ukai reservoir using modified algorithms specifically for inland water bodies. The methodology was based on waveform classification, waveform retracking, and dedicated inland range corrections algorithms. The 40-Hz waveforms were classified based on linear discriminant analysis and Bayesian classifier. Waveforms were retracked using Brown, Ice-2, threshold, and offset center of gravity methods. Retracking algorithms were implemented on full waveform and subwaveforms (only one leading edge) for estimating the improvement in the retrieved range. European Centre for Medium-Range Weather Forecasts (ECMWF) operational, ECMWF re-analysis pressure fields, and global ionosphere maps were used to exactly estimate the range corrections. The microwave and optical images were used for estimating the extent of the water body and altimeter track location. Four global positioning system (GPS) field trips were conducted on same day as the SARAL pass using two dual frequency GPS. One GPS was mounted close to the dam in static mode and the other was used on a moving vehicle within the reservoir in Kinematic mode. In situ gauge dataset was provided by the Ukai dam authority for the time period January 1972 to March 2015. The altimeter retrieved water level results were then validated with the GPS survey and in situ gauge dataset. With good selection of virtual station (waveform classification, back scattering coefficient), Ice-2 retracker and subwaveform retracker both work better with an overall root-mean-square error <15 cm. The results support that the AltiKa dataset, due to a smaller foot-print and sharp trailing edge of the Ka-band waveform, can be utilized for more accurate water level information over inland water bodies.

Dynamic Range Enhancement of High-Speed Electrical Signal Data via Non-Linear Compression

NASA Technical Reports Server (NTRS)

Laun, Matthew C. (Inventor)

2016-01-01

Systems and methods for high-speed compression of dynamic electrical signal waveforms to extend the measuring capabilities of conventional measuring devices such as oscilloscopes and high-speed data acquisition systems are discussed. Transfer function components and algorithmic transfer functions can be used to accurately measure signals that are within the frequency bandwidth but beyond the voltage range and voltage resolution capabilities of the measuring device.

Focal mechanisms and moment magnitudes of micro-earthquakes in central Brazil by waveform inversion with quality assessment and inference of the local stress field

NASA Astrophysics Data System (ADS)

Carvalho, Juraci; Barros, Lucas Vieira; Zahradník, Jiří

2016-11-01

This paper documents an investigation on the use of full waveform inversion to retrieve focal mechanisms of 11 micro-earthquakes (Mw 0.8 to 1.4). The events represent aftershocks of a 5.0 mb earthquake that occurred on October 8, 2010 close to the city of Mara Rosa in the state of Goiás, Brazil. The main contribution of the work lies in demonstrating the feasibility of waveform inversion of such weak events. The inversion was made possible thanks to recordings available at 8 temporary seismic stations in epicentral distances of less than 8 km, at which waveforms can be successfully modeled at relatively high frequencies (1.5-2.0 Hz). On average, the fault-plane solutions obtained are in agreement with a composite focal mechanism previously calculated from first-motion polarities. They also agree with the fault geometry inferred from precise relocation of the Mara Rosa aftershock sequence. The focal mechanisms provide an estimate of the local stress field. This paper serves as a pilot study for similar investigations in intraplate regions where the stress-field investigations are difficult due to rare earthquake occurrences, and where weak events must be studied with a detailed quality assessment.

Synthesis and measurement of ultrafast waveforms from five discrete optical harmonics.

PubMed

Chan, Han-Sung; Hsieh, Zhi-Ming; Liang, Wei-Hong; Kung, A H; Lee, Chao-Kuei; Lai, Chien-Jen; Pan, Ru-Pin; Peng, Lung-Han

2011-03-04

Achieving the control of light fields in a manner similar in sophistication to the control of electromagnetic fields in the microwave and radiofrequency regimes has been a major challenge in optical physics research. We manipulated the phase and amplitude of five discrete harmonics spanning the blue to mid-infrared frequencies to produce instantaneous optical fields in the shape of square, sawtooth, and subcycle sine and cosine pulses at a repetition rate of 125 terahertz. Furthermore, we developed an all-optical shaper-assisted linear cross-correlation technique to retrieve these fields and thereby verified their shapes and confirmed the critical role of carrier-envelope phase in Fourier synthesis of optical waveforms.

Numerical results for near surface time domain electromagnetic exploration: a full waveform approach

NASA Astrophysics Data System (ADS)

Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.

2015-12-01

Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two layered models with half sine current waveform as examples. We find the on time responses are quite sensitive to resistivity or depth changes. The results show the potential use of full waveform responses in time domain electromagnetic surveys.

Sub-cycle control of terahertz high-harmonic generation by dynamical Bloch oscillations

NASA Astrophysics Data System (ADS)

Schubert, O.; Hohenleutner, M.; Langer, F.; Urbanek, B.; Lange, C.; Huttner, U.; Golde, D.; Meier, T.; Kira, M.; Koch, S. W.; Huber, R.

2014-02-01

Ultrafast charge transport in strongly biased semiconductors is at the heart of high-speed electronics, electro-optics and fundamental solid-state physics. Intense light pulses in the terahertz spectral range have opened fascinating vistas. Because terahertz photon energies are far below typical electronic interband resonances, a stable electromagnetic waveform may serve as a precisely adjustable bias. Novel quantum phenomena have been anticipated for terahertz amplitudes, reaching atomic field strengths. We exploit controlled (multi-)terahertz waveforms with peak fields of 72 MV cm-1 to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide. These dynamics entail the emission of phase-stable high-harmonic transients, covering the entire terahertz-to-visible spectral domain between 0.1 and 675 THz. Quantum interference of different ionization paths of accelerated charge carriers is controlled via the waveform of the driving field and explained by a quantum theory of inter- and intraband dynamics. Our results pave the way towards all-coherent terahertz-rate electronics.

Detection of hidden mineral deposits by airborne spectral analysis of forest canopies. [Spirit Lake, Washington; Catheart Mountain, Maine; Blacktail Mountain, Montana; and Cotter Basin, Montana

NASA Technical Reports Server (NTRS)

Collins, W.; Chang, S. H.; Kuo, J. T.

1984-01-01

Data from field surveys and biogeochemical tests conducted in Maine, Montana, and Washington strongly correlate with results obtained using high resolution airborne spectroradiometer which detects an anomalous spectral waveform that appears definitely associated with sulfide mineralization. The spectral region most affected by mineral stress is between 550 nm and 750 nm. Spectral variations observed in the field occur on the wings of the red chlorophyll band centered at about 690 nm. The metal-stress-induced variations on the absorption band wing are most successfully resolved in the high spectral resolution field data using a waveform analysis technique. The development of chlorophyll pigments was retarded in greenhouse plants doped with copper and zinc in the laboratory. The lowered chlorophyll production resulted in changes on the wings of the chlorophyll bands of reflectance spectra of the plants. The airborne spectroradiometer system and waveform analysis remains the most sensitive technique for biogeochemical surveys.

Recent Advances in the Development of Ferroelectric Generators

DTIC Science & Technology

2013-06-01

multi FEG- VIG oscillator operating at only 20% maximum voltage (Fig. 4) can generate 10s of kV/m fields at 3 m. The waveform in Fig. 5 was produced...Figure 5. Waveforms produced by a Radiance multi-FEG array driving a VIG (Courtesy of Zachary Roberts, Radiance). This requires large antennas to

FAST TRACK COMMUNICATION: Nanocrystalline silicon film growth morphology control through RF waveform tailoring

NASA Astrophysics Data System (ADS)

Johnson, Erik V.; Verbeke, Thomas; Vanel, Jean-Charles; Booth, Jean-Paul

2010-10-01

We demonstrate the application of RF waveform tailoring to generate an electrical asymmetry in a capacitively coupled plasma-enhanced chemical vapour deposition system, and its use to control the growth mode of hydrogenated amorphous and nanocrystalline silicon thin films deposited at low temperature (150 °C). A dramatic shift in the dc bias potential at the powered electrode is observed when simply inverting the voltage waveform from 'peaks' to 'troughs', indicating an asymmetric distribution of the sheath voltage. By enhancing or suppressing the ion bombardment energy at the substrate (situated on the grounded electrode), the growth of thin silicon films can be switched between amorphous and nanocrystalline modes, as observed using in situ spectroscopic ellipsometry. The effect is observed at pressures sufficiently low that the collisional reduction in average ion bombardment energy is not sufficient to allow nanocrystalline growth (<100 mTorr).

Optimal generation of spatially coherent soft X-ray isolated attosecond pulses in a gas-filled waveguide using two-color synthesized laser pulses

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

Jin, Cheng; Hong, Kyung -Han; Lin, C. D.

2016-12-08

Here, we numerically demonstrate the generation of intense, low-divergence soft X-ray isolated attosecond pulses in a gas-filled hollow waveguide using synthesized few-cycle two-color laser waveforms. The waveform is a superposition of a fundamental and its second harmonic optimized such that highest harmonic yields are emitted from each atom. We then optimize the gas pressure and the length and radius of the waveguide such that bright coherent high-order harmonics with angular divergence smaller than 1 mrad are generated, for photon energy from the extreme ultraviolet to soft X-rays. By selecting a proper spectral range enhanced isolated attosecond pulses are generated. Wemore » study how dynamic phase matching caused by the interplay among waveguide mode, neutral atomic dispersion, and plasma effect is achieved at the optimal macroscopic conditions, by performing time-frequency analysis and by analyzing the evolution of the driving laser’s electric field during the propagation. Our results, when combined with the on-going push of high-repetition-rate lasers (sub- to few MHz’s) may eventually lead to the generation of high-flux, low-divergence soft X-ray tabletop isolated attosecond pulses for applications.« less

AC Electroosmotic Pumping in Nanofluidic Funnels.

PubMed

Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

2016-06-21

We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip.

Measurement and analysis of time-domain characteristics of corona-generated radio interference from a single positive corona source

NASA Astrophysics Data System (ADS)

Li, Xuebao; Li, Dayong; Chen, Bo; Cui, Xiang; Lu, Tiebing; Li, Yinfei

2018-04-01

The corona-generated electromagnetic interference commonly known as radio interference (RI) has become a limiting factor for the design of high voltage direct current transmission lines. In this paper, a time-domain measurement system is developed to measure the time-domain characteristics of corona-generated RI from a single corona source under a positive corona source. In the experiments, the corona current pulses are synchronously measured through coupling capacitors. The one-to-one relationship between the corona current pulse and measured RI voltage pulse is observed. The statistical characteristics of pulse parameters are analyzed, and the correlations between the corona current pulse and RI voltage pulse in the time-domain and frequency-domain are analyzed. Depending on the measured corona current pulses, the time-domain waveform of corona-generated RI is calculated on the basis of the propagation model of corona current on the conductor, the dipolar model for electric field calculation, and the antenna model for inducing voltage calculation. The well matched results between measured and simulated waveforms of RI voltage can show the validity of the measurement and calculation method presented in this paper, which also further show the close correlation between corona current and corona-generated RI.

One-dimensional kinetic description of nonlinear traveling-pulse and traveling-wave disturbances in long coasting charged particle beams

DOE PAGES

Davidson, Ronald C.; Qin, Hong

2015-09-21

This study makes use of a one-dimensional kinetic model to investigate the nonlinear longitudinal dynamics of a long coasting beam propagating through a perfectly conducting circular pipe with radius r w. The average axial electric field is expressed as < E z >=-(∂/∂z)=-e bg 0∂λ b/∂z-e bg 2r 2 w∂ 3λ b/∂z 3, where g 0 and g 2 are constant geometric factors, λ b(z,t)=∫dp zF b(z,p z,t) is the line density of beam particles, and F b(z,p z,t) satisfies the 1D Vlasov equation. Detailed nonlinear properties of traveling-wave and traveling-pulse (soliton) solutions with time-stationary waveform are examined for amore » wide range of system parameters extending from moderate-amplitudes to large-amplitude modulations of the beam charge density. Two classes of solutions for the beam distribution function are considered, corresponding to: (i) the nonlinear waterbag distribution, where F b=const in a bounded region of p z-space; and (ii) nonlinear Bernstein-Green-Kruskal (BGK)-like solutions, allowing for both trapped and untrapped particle distributions to interact with the self-generated electric field < E z >.« less

One-dimensional kinetic description of nonlinear traveling-pulse and traveling-wave disturbances in long coasting charged particle beams

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

Davidson, Ronald C.; Qin, Hong

This study makes use of a one-dimensional kinetic model to investigate the nonlinear longitudinal dynamics of a long coasting beam propagating through a perfectly conducting circular pipe with radius r w. The average axial electric field is expressed as < E z >=-(∂/∂z)=-e bg 0∂λ b/∂z-e bg 2r 2 w∂ 3λ b/∂z 3, where g 0 and g 2 are constant geometric factors, λ b(z,t)=∫dp zF b(z,p z,t) is the line density of beam particles, and F b(z,p z,t) satisfies the 1D Vlasov equation. Detailed nonlinear properties of traveling-wave and traveling-pulse (soliton) solutions with time-stationary waveform are examined for amore » wide range of system parameters extending from moderate-amplitudes to large-amplitude modulations of the beam charge density. Two classes of solutions for the beam distribution function are considered, corresponding to: (i) the nonlinear waterbag distribution, where F b=const in a bounded region of p z-space; and (ii) nonlinear Bernstein-Green-Kruskal (BGK)-like solutions, allowing for both trapped and untrapped particle distributions to interact with the self-generated electric field < E z >.« less

EPG waveform library for Graphocephala atropunctata (Hemiptera: Cicadellidae): Effect of adhesive, input resistor, and voltage levels on waveform appearance and stylet probing behaviors.

PubMed

Cervantes, Felix A; Backus, Elaine A

2018-05-31

Blue-green sharpshooter, Graphocephala atropunctata, is a native California vector of Xylella fastidiosa (Xf), a foregut-borne bacterium that is the causal agent of Pierce's disease in grapevines. A 3rd-generation, AC-DC electropenetrograph (EPG monitor) was used to record stylet probing and ingestion behaviors of adult G. atropunctata on healthy grapevines. This study presents for the first time a complete, updated waveform library for this species, as well as effects of different electropenetrograph settings and adhesives on waveform appearances. Both AC and DC applied signals were used with input resistor (Ri) levels (amplifier sensitivities) of 10 6 , 10 7 , 10 8 and 10 9  Ohms, as well as two type of adhesives, conducting silver paint and handmade silver glue. Waveform description, characterization of electrical origins (R versus emf components), and proposed biological meanings of waveforms are reported, as well as qualitative differences in waveform appearances observed with different electropenetrograph settings and adhesives. In addition, a quantitative study with AC signal, using two applied voltage levels (50 and 200 mV) and two Ri levels (10 7 and 10 9  Ohms) was performed. Intermediate Ri levels 10 7 and 10 8  Ohms provided EPG waveforms with the greatest amount of information, because both levels captured similar proportions of R and emf components, as supported by appearance, clarity, and definition of waveforms. Similarly, use of a gold wire loop plus handmade silver glue provided more definition of waveforms than a gold wire loop plus commercial conducting silver paint. Qualitative/observational evidence suggested that AC applied signal caused fewer aberrant behaviors/waveforms than DC applied signal. In the quantitative study, behavioral components of the sharpshooter X wave were the most affected by changes in Ri and voltage level. Because the X wave probably represents X. fastidiosa inoculation behavior, future studies of X. fastidiosa inoculation via EPG will require carefully determined instrument settings. An intermediate Ri level such as 10 8  Ohms with low voltage, AC applied signal, and gold wire loop plus silver glue is recommended as the best electropenetrograph methods to conduct future EPG studies of sharpshooter inoculation behaviors on Xf-resistant and -susceptible grapevine. Copyright © 2018. Published by Elsevier Ltd.

Specifying and calibrating instrumentations for wideband electronic power measurements. [in switching circuits

NASA Technical Reports Server (NTRS)

Lesco, D. J.; Weikle, D. H.

1980-01-01

The wideband electric power measurement related topics of electronic wattmeter calibration and specification are discussed. Tested calibration techniques are described in detail. Analytical methods used to determine the bandwidth requirements of instrumentation for switching circuit waveforms are presented and illustrated with examples from electric vehicle type applications. Analog multiplier wattmeters, digital wattmeters and calculating digital oscilloscopes are compared. The instrumentation characteristics which are critical to accurate wideband power measurement are described.

Measurement of optical to electrical and electrical to optical delays with ps-level uncertainty.

PubMed

Peek, H Z; Pinkert, T J; Jansweijer, P P M; Koelemeij, J C J

2018-05-28

We present a new measurement principle to determine the absolute time delay of a waveform from an optical reference plane to an electrical reference plane and vice versa. We demonstrate a method based on this principle with 2 ps uncertainty. This method can be used to perform accurate time delay determinations of optical transceivers used in fiber-optic time-dissemination equipment. As a result the time scales in optical and electrical domain can be related to each other with the same uncertainty. We expect this method will be a new breakthrough in high-accuracy time transfer and absolute calibration of time-transfer equipment.

Electron heating and the Electrical Asymmetry Effect in capacitively coupled RF discharges

NASA Astrophysics Data System (ADS)

Schulze, Julian

2011-10-01

For applications of capacitive radio frequency discharges, the control of particle distribution functions at the substrate surface is essential. Their spatio-temporal shape is the result of complex heating mechanisms of the respective species. Enhanced process control, therefore, requires a detailed understanding of the heating dynamics. There are two known modes of discharge operation: α- and γ-mode. In α-mode, most ionization is caused by electron beams generated by the expanding sheaths and field reversals during sheath collapse, while in γ-mode secondary electrons dominate the ionisation. In strongly electronegative discharges, a third heating mode is observed. Due to the low electron density in the discharge center the bulk conductivity is reduced and a high electric field is generated to drive the RF current through the discharge center. In this field, electrons are accelerated and cause significant ionisation in the bulk. This bulk heating mode is observed experimentally and by PIC simulations in CF4 discharges. The electron dynamics and mode transitions as a function of driving voltage and pressure are discussed. Based on a detailed understanding of the heating dynamics, the concept of separate control of the ion mean energy and flux in classical dual-frequency discharges is demonstrated to fail under process relevant conditions. To overcome these limitations of process control, the Electrical Asymmetry Effect (EAE) is proposed in discharges driven at multiple consecutive harmonics with adjustable phase shifts between the driving frequencies. Its concept and a recipe to optimize the driving voltage waveform are introduced. The functionality of the EAE in different gases and first applications to large area solar cell manufacturing are discussed. Finally, limitations caused by the bulk heating in strongly electronegative discharges are outlined.

A dual-channel flux-switching permanent magnet motor for hybrid electric vehicles

NASA Astrophysics Data System (ADS)

Hua, Wei; Wu, Zhongze; Cheng, Ming; Wang, Baoan; Zhang, Jianzhong; Zhou, Shigui

2012-04-01

The flux-switching permanent magnet (FSPM) motor is a relatively novel brushless machine having both magnets and concentrated windings in the stator, which exhibits inherently sinusoidal PM flux-linkage, back-EMF waveforms, and high torque capability. However, in the application of hybrid electric vehicles, it is essential to prevent magnets and armature windings moving in radial direction due to the possible vibration during operation, and to ensure fault-tolerant capability. Hence, in this paper based on an original FSPM motor, a dual-channel FSPM (DC-FSPM) motor with modified structure to fix both armature windings and magnets and improved reliability is proposed for a practical 10 kW integral starter/generator (ISG) in hybrid electric vehicles. The influences of different solutions and the end-effect on the static characteristics, are evaluated based on the 2D and 3D finite element analysis, respectively. Finally, both the predicted and experimental results, compared with a prototype DC-FSPM motor and an interior PM motor used in Honda Civic, confirm that the more sinusoidal back-EMF waveform and lower torque ripple can be achieved in the DC-FSPM motor, whereas the torque is smaller under the same coil current.

Analysis of Even Harmonics Generation in an Isolated Electric Power System

NASA Astrophysics Data System (ADS)

Kanao, Norikazu; Hayashi, Yasuhiro; Matsuki, Junya

Harmonics bred from loads are mainly odd order because the current waveform has half-wave symmetry. Since the even harmonics are negligibly small, those are not generally measured in electric power systems. However, even harmonics were measured at a 500/275/154kV substation in Hokuriku Electric Power Company after removal of a transmission line fault. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as automatic supervisory signal. This paper describes the mechanism of generation of the even harmonics by comparing measured waveforms with ATP-EMTP simulation results. As a result of analysis, it is cleared that even harmonics are generated by three causes. The first cause is a magnetizing current of transformers due to flux deviation by DC component of a fault current. The second one is due to harmonic conversion of a synchronous machine which generates even harmonics when direct current component or even harmonic current flow into the machine. The third one is that increase of harmonic impedance due to an isolated power system produces harmonic voltages. The design of the input filter of protective digital relays should consider even harmonics generation in an isolated power system.

An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance. Ph.D. Thesis Final Technical Report, 1 Feb. 1985 - 1 Sep. 1989

NASA Technical Reports Server (NTRS)

Kearns, James A.

1989-01-01

Phenomena associated with long range propagation of sound over irregular topography motivated this work, which was to analyze the diffraction effects which would occur near the tops of hills and ridges. The diffraction of a high frequency plane wave due to its grazing of a two-dimensional curved surface of finite impedance was also studied. Laboratory scale models were constructed and measurements were made of the field on, above, and behind either of two curved surfaces possessing distinctly different impedances; that is, one was soft while the other was hard. The experimental technique consisted of simultaneously measuring the pressure at a reference point and at a field point due to a transient pulse generated by an electric spark. The pressure waveforms were digitized and processed. The ratio of the discrete Fourier transforms of the two waveforms provided an estimate of the insertion loss between them. The results of the measurements were compared with the predictions of a theory which was derived by Pierce using the method of Matched Asymptotic Expansions (MAE). The predictions relied upon the experimental evaluation of the impedance of each surface at grazing angles of incidence. This evaluation was achieved by a fairly standard technique involving empirical models of various generic types of surfaces. An example was shown of the important role that the structural intricacies of a surface play in the determination of an appropriate model. The comparison between the measurements and predictions indicated that the theory gives an excellent description of the field anywhere near a curved surface. Further, with a simple modification, the theory was also shown to give nearly as good of a description of the field surrounding a curved surface even at distances far behind the surface yet near the line of sight.

Understanding the molecular mechanism of pulse current charging for stable lithium-metal batteries

PubMed Central

Li, Qi; Tan, Shen; Li, Linlin; Lu, Yingying; He, Yi

2017-01-01

High energy and safe electrochemical storage are critical components in multiple emerging fields of technologies. Rechargeable lithium-metal batteries are considered to be promising alternatives for current lithium-ion batteries, leading to as much as a 10-fold improvement in anode storage capacity (from 372 to 3860 mAh g−1). One of the major challenges for commercializing lithium-metal batteries is the reliability and safety issue, which is often associated with uneven lithium electrodeposition (lithium dendrites) during the charging stage of the battery cycling process. We report that stable lithium-metal batteries can be achieved by simply charging cells with square-wave pulse current. We investigated the effects of charging period and frequency as well as the mechanisms that govern this process at the molecular level. Molecular simulations were performed to study the diffusion and the solvation structure of lithium cations (Li+) in bulk electrolyte. The model predicts that loose association between cations and anions can enhance the transport of Li+ and eventually stabilize the lithium electrodeposition. We also performed galvanostatic measurements to evaluate the cycling behavior and cell lifetime under pulsed electric field and found that the cell lifetime can be more than doubled using certain pulse current waveforms. Both experimental and simulation results demonstrate that the effectiveness of pulse current charging on dendrite suppression can be optimized by choosing proper time- and frequency-dependent pulses. This work provides a molecular basis for understanding the mechanisms of pulse current charging to mitigating lithium dendrites and designing pulse current waveforms for stable lithium-metal batteries. PMID:28776039

Design and analysis of a high power moderate band radiator using a switched oscillator

NASA Astrophysics Data System (ADS)

Armanious, Miena Magdi Hakeem

Quarter-wave switched oscillators (SWOs) are an important technology for the generation of high-power, moderate bandwidth (mesoband) wave forms. The use of SWOs in high power microwave sources has been discussed for the past 10 years [1--6], but a detailed discussion of the design of this type of oscillators for particular waveforms has been lacking. In this dissertation I develop a design methodology for a realization of SWOs, also known as MATRIX oscillators in the scientific community. A key element in the design of SWOs is the self-breakdown switch, which is created by a large electric field. In order for the switch to close as expected from the design, it is essential to manage the electrostatic field distribution inside the oscillator during the charging time. This enforces geometric constraints on the shape of the conductors inside MATRIX. At the same time, the electrodynamic operation of MATRIX is dependent on the geometry of the structure. In order to generate a geometry that satisfies both the electrostatic and electrodynamic constraints, a new approach is developed to generate this geometry using the 2-D static solution of the Laplace equation, subject to a particular set of boundary conditions. These boundary conditions are manipulated to generate equipotential lines with specific dimensions that satisfy the electrodynamic constraints. Meanwhile, these equipotential lines naturally support an electrostatic field distribution that meets the requirements for the switch operation. To study the electrodynamic aspects of MATRIX, three different (but interrelated) numerical models are built. Depending on the assumptions made in each model, different information about the electrodynamic properties of the designed SWO are obtained. In addition, the agreement and consistency between the different models, validate and give confidence in the calculated results. Another important aspect of the design process is understanding the relationship between the geometric parameters of MATRIX and the output waveforms. Using the numerical models, the relationship between the dimensions of MATRIX and its calculated resonant parameters are studied. For a given set of geometric constraints, this provides more flexibility to the output specifications. Finally, I present a comprehensive design methodology that generates the geometry of a MATRIX system from the desired specification then calculates the radiated waveform.

Use of electricity to sedate Lake Trout for intracoelomic implantation of electronic transmitters

USGS Publications Warehouse

Faust, Matthew D.; Vandergoot, Christopher; Hostnik, Eric T.; Binder, Thomas R.; Mida Hinderer, Julia L.; Ives, Jessica T.; Krueger, Charles C.

2017-01-01

Use of telemetry data to inform fisheries conservation and management is becoming increasingly common; as such, fish typically must be sedated before surgical implantation of transmitters into the coelom. Given that no widely available, immediate-release chemical sedative currently exists in North America, we investigated the feasibility of using electricity to sedate Lake Trout Salvelinus namaycush long enough for an experienced surgeon to implant an electronic transmitter (i.e., 180 s). Specifically, our study objectives were to determine (1) whether some combination of electrical waveform characteristics (i.e., duty cycle, frequency, voltage, and pulse type) could sedate Lake Trout for at least 180 s; and (2) whether Lake Trout that were sequentially exposed to continuous DC and pulsed DC had greater rates of spinal injury and short-term mortality than control fish. A Portable Electrosedation System unit was used to sedate hatchery and wild Lake Trout. Dual-frequency pulsed-DC and two-stage approaches successfully sedated Lake Trout and had similar induction and recovery times. Lake Trout sedated using the two-stage approach did not have survival rates or spinal abnormalities that were significantly different from those of control fish. We concluded that electricity was a viable alternative to chemical sedatives for sedating Lake Trout before surgical implantation of an electronic transmitter, but we suggest that Lake Trout and other closely related species (e.g., Arctic Char Salvelinus alpinus) may require morphotype-specific electrical waveforms due to their morphological diversity.

Calcium channel dynamics limit synaptic release in response to prosthetic stimulation with sinusoidal waveforms

PubMed Central

Freeman, Daniel K.; Jeng, Jed S.; Kelly, Shawn K.; Hartveit, Espen; Fried, Shelley I.

2011-01-01

Extracellular electric stimulation with sinusoidal waveforms has been shown to allow preferential activation of individual types of retinal neurons by varying stimulus frequency. It is important to understand the mechanisms underlying this frequency dependence as a step towards improving methods of preferential activation. In order to elucidate these mechanisms, we implemented a morphologically realistic model of a retinal bipolar cell and measured the response to extracellular stimulation with sinusoidal waveforms. We compared the frequency response of a passive membrane model to the kinetics of voltage-gated calcium channels that mediate synaptic release. The passive electrical properties of the membrane exhibited lowpass filtering with a relatively high cutoff frequency (nominal value = 717 Hz). This cutoff frequency was dependent on intra-axonal resistance, with shorter and wider axons yielding higher cutoff frequencies. However, we found that the cutoff frequency of bipolar cell synaptic release was primarily limited by the relatively slow opening kinetics of Land T-type calcium channels. The cutoff frequency of calcium currents depended nonlinearly on stimulus amplitude, but remained lower than the cutoff frequency of the passive membrane model for a large range of membrane potential fluctuations. These results suggest that while it may be possible to modulate the membrane potential of bipolar cells over a wide range of stimulus frequencies, synaptic release will only be initiated at the lower end of this range. PMID:21628768

Digital electronic bone growth stimulator

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

Kronberg, J.W.

1995-05-09

A device is described for stimulating bone tissue by applying a low level alternating current signal directly to the patient`s skin. A crystal oscillator, a binary divider chain and digital logic gates are used to generate the desired waveforms that reproduce the natural electrical characteristics found in bone tissue needed for stimulating bone growth and treating osteoporosis. The device, powered by a battery, contains a switch allowing selection of the correct waveform for bone growth stimulation or osteoporosis treatment so that, when attached to the skin of the patient using standard skin contact electrodes, the correct signal is communicated tomore » the underlying bone structures. 5 figs.« less

Digital electronic bone growth stimulator

DOEpatents

Kronberg, J.W.

1995-05-09

A device is described for stimulating bone tissue by applying a low level alternating current signal directly to the patient`s skin. A crystal oscillator, a binary divider chain and digital logic gates are used to generate the desired waveforms that reproduce the natural electrical characteristics found in bone tissue needed for stimulating bone growth and treating osteoporosis. The device, powered by a battery, contains a switch allowing selection of the correct waveform for bone growth stimulation or osteoporosis treatment so that, when attached to the skin of the patient using standard skin contact electrodes, the correct signal is communicated to the underlying bone structures. 5 figs.

Optimization of multi-color laser waveform for high-order harmonic generation

NASA Astrophysics Data System (ADS)

Jin, Cheng; Lin, C. D.

2016-09-01

With the development of laser technologies, multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms. A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes. We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm. By choosing different fitness criteria, we demonstrate that: (i) harmonic yields can be enhanced by 10 to 100 times, (ii) harmonic cutoff energy can be substantially extended, (iii) specific harmonic orders can be selectively enhanced, and (iv) single attosecond pulses can be efficiently generated. The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed. The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years. Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 30916011207), Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy (Grant No. DE-FG02-86ER13491), and Air Force Office of Scientific Research, USA (Grant No. FA9550-14-1-0255).

Scientific Lightning Detection Network for Kazakhstan

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Lozbin, A.; Inchin, A.; Shpadi, Y.; Inchin, P.; Shpadi, M.; Ayazbayev, G.; Bykayev, R.; Mailibayeva, L.

2015-12-01

In the frame of grant financing of the scientific research in 2015-2017 the project "To Develop Electromagnetic System for lightning location and atmosphere-lithosphere coupling research" was found. The project was start in January, 2015 and should be done during 3 years. The purpose is to create a system of electromagnetic measurements for lightning location and atmosphere-lithosphere coupling research consisting of a network of electric and magnetic sensors and the dedicated complex for data processing and transfer to the end user. The main tasks are to set several points for electromagnetic measurements with 100-200 km distance between them, to develop equipment for these points, to develop the techniques and software for lightning location (Time-of-arrival and Direction Finding (TOA+DF)) and provide a lightning activity research in North Tien-Shan region with respect to seismicity and other natural and manmade activities. Also, it is planned to use lightning data for Global Electric Circuit (GEC) investigation. Currently, there are lightning detection networks in many countries. In Kazakhstan we have only separate units in airports. So, we don't have full lightning information for our region. It is planned, to setup 8-10 measurement points with magnetic and electric filed antennas for VLF range. The final data set should be including each stroke location, time, type (CG+, CG-, CC+ or CC-) and waveform from each station. As the magnetic field lightning antenna the ferrite rod VLF antenna will be used. As the electric field antenna the wide range antenna with specific frequencies filters will be used. For true event detection TOA and DF methods needs detected stroke from minimum 4 stations. In this case we can get location accuracy about 2-3 km and better.

Measurements of induced voltages and currents in a distribution power line and associated atmospheric parameters

NASA Technical Reports Server (NTRS)

Santiago-Perez, Julio

1988-01-01

The frequency and intensity of thunderstorms around the Kennedy Space Center (KSC) has affected scheduled launch, landing, and other ground operations for many years. In order to protect against and provide safe working facilities, KSC has performed and hosted several studies on lightning phenomena. For the reasons mentioned above, KSC has established the Atmospheric Science Field Laboratory (ASFL). At these facilities KSC launches wire-towing rockets into thunderstorms to trigger natural lightning to the launch site. A program named Rocket Triggered Lightning Program (RTLP) is being conducted at the ASFL. This report calls for two of the experiments conducted in the summer 1988 Rocket Triggered Lightning Program. One experiment suspended an electric field mill over the launching areas from a balloon about 500 meters high to measure the space charges over the launching area. The other was to connect a waveform recorder to a nearby distribution power line to record currents and voltages wave forms induced by natural and triggered lightning.

Measurements of induced voltages and currents in a distribution power line and associated atmospheric parameters

NASA Astrophysics Data System (ADS)

Santiago-Perez, Julio

1988-10-01

The frequency and intensity of thunderstorms around the Kennedy Space Center (KSC) has affected scheduled launch, landing, and other ground operations for many years. In order to protect against and provide safe working facilities, KSC has performed and hosted several studies on lightning phenomena. For the reasons mentioned above, KSC has established the Atmospheric Science Field Laboratory (ASFL). At these facilities KSC launches wire-towing rockets into thunderstorms to trigger natural lightning to the launch site. A program named Rocket Triggered Lightning Program (RTLP) is being conducted at the ASFL. This report calls for two of the experiments conducted in the summer 1988 Rocket Triggered Lightning Program. One experiment suspended an electric field mill over the launching areas from a balloon about 500 meters high to measure the space charges over the launching area. The other was to connect a waveform recorder to a nearby distribution power line to record currents and voltages wave forms induced by natural and triggered lightning.

Hooked differential mobility spectrometry apparatus and method therefore

DOEpatents

Shvartsburg, Alexandre A [Richland, WA; Tang, Keqi [Richland, WA; Ibrahim, Yehia M [Richland, WA; Smith, Richard D [Richland, WA

2009-02-17

Disclosed are a device and method for improved interfacing of differential mobility spectrometry (DMS) or field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of substantially planar geometry to subsequent or preceding instrument stages. Interfacing is achieved using curved DMS elements, where a thick ion beam emitted by planar DMS analyzers or injected into them for ion filtering is compressed to the gap median by DMS ion focusing effect in a spatially inhomogeneous electric field. Resulting thinner beams are more effectively transmitted through necessarily constrained conductance limit apertures to subsequent instrument stages operated at a pressure lower than DMS, and/or more effectively injected into planar DMS analyzers. The technology is synergetic with slit apertures, slit aperture/ion funnels, and high-pressure ion funnel interfaces known in the art which allow for increasing cross-sectional area of MS inlets. The invention may be used in integrated analytical platforms, including, e.g., DMS/MS, LC/DMS/MS, and DMS/IMS/MS that could replace and/or enhance current LC/MS methods, e.g., for proteomics research.

Large Capacity SMES for Voltage Dip Compensation

NASA Astrophysics Data System (ADS)

Iwatani, Yu; Saito, Fusao; Ito, Toshinobu; Shimada, Mamoru; Ishida, Satoshi; Shimanuki, Yoshio

Voltage dips of power grids due to thunderbolts, snow damage, and so on, cause serious damage to production lines of precision instruments, for example, semiconductors. In recent years, in order to solve this problem, uninterruptible power supply systems (UPS) are used. UPS, however, has small capacity, so a great number of UPS are needed in large factories. Therefore, we have manufactured the superconducting magnetic energy storage (SMES) system for voltage dip compensation able to protect loads with large capacity collectively. SMES has advantages such as space conservation, long lifetime and others. In field tests, cooperating with CHUBU Electric Power Co., Inc. we proved that SMES is valuable for compensating voltage dips. Since 2007, 10MVA SMES improved from field test machines has been running in a domestic liquid crystal display plant, and in 2008, it protected plant loads from a number of voltage dips. In this paper, we report the action principle and components of the improved SMES for voltage dip compensation, and examples of waveforms when 10MVA SMES compensated voltage dips.

Usage monitoring of electrical devices in a smart home.

PubMed

Rahimi, Saba; Chan, Adrian D C; Goubran, Rafik A

2011-01-01

Profiling the usage of electrical devices within a smart home can be used as a method for determining an occupant's activities of daily living. A nonintrusive load monitoring system monitors the electrical consumption at a single electrical source (e.g., main electric utility service entry) and the operating schedules of individual devices are determined by disaggregating the composite electrical consumption waveforms. An electrical device's load signature plays a key role in nonintrusive load monitoring systems. A load signature is the unique electrical behaviour of an individual device when it is in operation. This paper proposes a feature-based model, using the real power and reactive power as features for describing the load signatures of individual devices. Experimental results for single device recognition for 7 devices show that the proposed approach can achieve 100% classification accuracy with discriminant analysis using Mahalanobis distances.

Geometrical Effects on the Electromagnetic Radiation from Lightning Return Strokes

NASA Technical Reports Server (NTRS)

Willett, J. C.; Smith, D. A.; LeVine, D. M.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

The morphological difference between the electromagnetic radiation-field waveforms of "first" and "subsequent" return strokes in cloud-to-ground lightning flashes is well known and can be used to identify the formation of new channels to ground. This difference is generally believed due to the existence of branches on first-stroke channels, whereas subsequent strokes re-illuminate only the main channel of a previous stroke; but experimental evidence for this hypothesis is relatively weak. It has been argued for the influence of channel geometry on the fine structure of radiation from subsequent return strokes by comparing the field-change waveforms recorded at the same station from strokes within the same flash and between different flashes of both natural and triggered lightning. The present paper introduces new evidence for both of these hypotheses from a comparison of waveforms between sensors in different directions from the same stroke.

Measuring Geophysical Parameters of the Greenland Ice Sheet using Airborne Radar Altimetry

NASA Technical Reports Server (NTRS)

Ferraro, Ellen J.; Swift. Calvin T.

1995-01-01

This paper presents radar-altimeter scattering models for each of the diagenetic zones of the Greenland ice sheet. AAFE radar- altimeter waveforms obtained during the 1991 and 1993 NASA multi-sensor airborne altimetry experiments over Greenland reveal that the Ku-band return pulse changes significantly with the different diagenetic zones. These changes are due to varying amounts of surface and volume scattering in the return waveform. In the ablation and soaked zones, where surface scattering dominates the AAFE return, geophysical parameters such as rms surface height and rms surface slope are obtained by fitting the waveforms to a surface-scattering model. Waveforms from the percolation zone show that the sub-surface ice features have a much more significant effect on the return pulse than the surrounding snowpack. Model percolation waveforms, created using a combined surface- and volume-scattering model and an ice-feature distribution obtained during the 1993 field season, agree well with actual AAFE waveforms taken in the same time period. Using a combined surface- and volume-scattering model for the dry-snow-zone return waveforms, the rms surface height and slope and the attenuation coefficient of the snowpack are obtained. These scattering models not only allow geophysical parameters of the ice sheet to be measured but also help in the understanding of satellite radar-altimeter data.

On the field-to-current conversion factors for large bipolar lightning discharge events in winter thunderstorms in Japan

NASA Astrophysics Data System (ADS)

Chen, Long; Zhang, Qilin; Hou, Wenhao; Tao, Yulang

2015-07-01

In this paper we have simulated the far-field waveform characteristic of large bipolar events (LBEs) occurred in winter thunderstorms in Japan and compared the field-to-current conversion factors (FCCFs) of LBEs with that of the lightning cloud-to-ground (CG) return stroke (RS) in summer thunderstorm. As for the physical process of LBEs, Wu et al. (2014) considered that LBEs may be very similar to the typical lightning RS (RS-like process) or caused by an initial continuous current pulse (ICC-like process) in upward lightning flashes. We assume that the lightning channel length of LBEs ranges from 500 m to 1000 m, and the height of tall object struck by LBEs is from 100 m to 300 m. By using the bouncing wave model, we found that only when the injected current waveform of LBEs is characterized with a symmetric Gaussian pulse, the simulated far-field waveform of LBEs both for RS-like process and ICC-like process is similar to that observed by Wu et al. (2014). For striking tall objects with heights from 100 m and 300 m, the FCCFs of LBEs are positively correlated with its channel length and derivatives of injected current waveform, and the FCCF for RS-like process is about similar to that for ICC-like process. However, the FCCFs of LBEs are very different from lightning RS in summer thunderstorm; that is to say, the FCCFs developed for the well-known lightning RS in summer thunderstorm are not suitable for LBEs.

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

PubMed Central

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

2016-01-01

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

Extremely low frequency (ELF) stray magnetic fields of laboratory equipment: a possible co-exposure conducting experiments on cell cultures.

PubMed

Gresits, Iván; Necz, Péter Pál; Jánossy, Gábor; Thuróczy, György

2015-09-01

Measurements of extremely low frequency (ELF) magnetic fields were conducted in the environment of commercial laboratory equipment in order to evaluate the possible co-exposure during the experimental processes on cell cultures. Three types of device were evaluated: a cell culture CO2 incubator, a thermostatic water bath and a laboratory shaker table. These devices usually have electric motors, heating wires and electronic control systems, therefore may expose the cell cultures to undesirable ELF stray magnetic fields. Spatial distributions of magnetic field time domain signal waveform and frequency spectral analysis (FFT) were processed. Long- and short-term variation of stray magnetic field was also evaluated under normal use of investigated laboratory devices. The results show that the equipment under test may add a considerable ELF magnetic field to the ambient environmental magnetic field or to the intentional exposure to ELF, RF or other physical/chemical agents. The maximum stray magnetic fields were higher than 3 µT, 20 µT and 75 µT in the CO2 incubator, in water bath and on the laboratory shaker table, respectively, with high variation of spatial distribution and time domain. Our investigation emphasizes possible confounding factors conducting cell culture studies related to low-level ELF-EMF exposure due to the existing stray magnetic fields in the ambient environment of laboratory equipment.

Categorisation of full waveform data provided by laser scanning devices

NASA Astrophysics Data System (ADS)

Ullrich, Andreas; Pfennigbauer, Martin

2011-11-01

In 2004, a laser scanner device for commercial airborne laser scanning applications, the RIEGL LMS-Q560, was introduced to the market, making use of a radical alternative approach to the traditional analogue signal detection and processing schemes found in LIDAR instruments so far: digitizing the echo signals received by the instrument for every laser pulse and analysing these echo signals off-line in a so-called full waveform analysis in order to retrieve almost all information contained in the echo signal using transparent algorithms adaptable to specific applications. In the field of laser scanning the somewhat unspecific term "full waveform data" has since been established. We attempt a categorisation of the different types of the full waveform data found in the market. We discuss the challenges in echo digitization and waveform analysis from an instrument designer's point of view and we will address the benefits to be gained by using this technique, especially with respect to the so-called multi-target capability of pulsed time-of-flight LIDAR instruments.

Improved linearity using harmonic error rejection in a full-field range imaging system

NASA Astrophysics Data System (ADS)

Payne, Andrew D.; Dorrington, Adrian A.; Cree, Michael J.; Carnegie, Dale A.

2008-02-01

Full field range imaging cameras are used to simultaneously measure the distance for every pixel in a given scene using an intensity modulated illumination source and a gain modulated receiver array. The light is reflected from an object in the scene, and the modulation envelope experiences a phase shift proportional to the target distance. Ideally the waveforms are sinusoidal, allowing the phase, and hence object range, to be determined from four measurements using an arctangent function. In practice these waveforms are often not perfectly sinusoidal, and in some cases square waveforms are instead used to simplify the electronic drive requirements. The waveforms therefore commonly contain odd harmonics which contribute a nonlinear error to the phase determination, and therefore an error in the range measurement. We have developed a unique sampling method to cancel the effect of these harmonics, with the results showing an order of magnitude improvement in the measurement linearity without the need for calibration or lookup tables, while the acquisition time remains unchanged. The technique can be applied to existing range imaging systems without having to change or modify the complex illumination or sensor systems, instead only requiring a change to the signal generation and timing electronics.

A New SAS program for behavioral analysis of electrical penetration graph data

USDA-ARS?s Scientific Manuscript database

Monitoring feeding behaviors of insects whose piercing-sucking mouthparts are inserted into plant tissue is done by making the insect part of an electronic circuit, using electropenetrography (EPG). Fluctuating voltage signals in the circuit are graphed, and resulting waveforms are interpreted as sp...

10 CFR 431.282 - Test Procedures [Reserved

Code of Federal Regulations, 2010 CFR

2010-01-01

..., metal halide, and high-pressure sodium lamps. Mercury vapor lamp means a high intensity discharge lamp..., current, and waveform) for starting and operating. High intensity discharge lamp means an electric... light is produced by radiation from mercury typically operating at a partial vapor pressure in excess of...

KTX circuit model and discharge waveform prediction

NASA Astrophysics Data System (ADS)

Bai, Wei; Lan, T.; Mao, W. Z.; You, W.; Li, H.; Liu, A. D.; Xie, J. L.; Wan, S. D.; Liu, W. D.; Yang, L.; Fu, P.; Xiao, C. J.; Ding, W. X.

2013-10-01

The Keda Torus eXperiment (KTX) is a constructing reversed field pinch (RFP) device in University of Science and Technology of China. The KTX power supply system includes the Ohmic heating, field shaping and toroidal power supply systems, which produce the Ohmic field, equilibrium field and toroidal field, respectively. The detailed circuit model will be introduced in this poster. Another purpose is to predict its discharge waveforms using the modified Bessel function mode (MBFM), which describes the evolution of plasma current and magnetic flux in RFP base on Taylor theory. Furthermore, the power supply requirements of external field shaping winding are also predicted in the model, which will be very helpful for the design of plasma equilibrium controlling system. Supported by ITER-China program (No. 2011GB106000), NNSFC (Nos. 10990210, 10990211, 10335060 and 10905057), CPSF (No. 20080440104), YIF (No. WK2030040019) and KIPCAS (No. kjcx-yw-n28).

Towards seismic waveform inversion of long-offset Ocean-Bottom Seismic data for deep crustal imaging offshore Western Australia

NASA Astrophysics Data System (ADS)

Monnier, S.; Lumley, D. E.; Kamei, R.; Goncharov, A.; Shragge, J. C.

2016-12-01

Ocean Bottom Seismic datasets have become increasingly used in recent years to develop high-resolution, wavelength-scale P-wave velocity models of the lithosphere from waveform inversion, due to their recording of long-offset transmitted phases. New OBS surveys evolve towards novel acquisition geometries involving longer offsets (several hundreds of km), broader frequency content (1-100 Hz), while receiver sampling often remains sparse (several km). Therefore, it is critical to assess the effects of such geometries on the eventual success and resolution of waveform inversion velocity models. In this study, we investigate the feasibility of waveform inversion on the Bart 2D OBS profile acquired offshore Western Australia, to investigate regional crustal and Moho structures. The dataset features 14 broadband seismometers (0.01-100 Hz) from AuScope's national OBS fleet, offsets in excess of 280 km, and a sparse receiver sampling (18 km). We perform our analysis in four stages: (1) field data analysis, (2) 2D P-wave velocity model building, synthetic data (3) modelling, and (4) waveform inversion. Data exploration shows high-quality active-source signal down to 2Hz, and usable first arrivals to offsets greater than 100 km. The background velocity model is constructed by combining crustal and Moho information in continental reference models (e.g., AuSREM, AusMoho). These low-resolution studies suggest a crustal thickness of 20-25 km along our seismic line and constitute a starting point for synthetic modelling and inversion. We perform synthetic 2D time-domain modelling to: (1) evaluate the misfit between synthetic and field data within the usable frequency band (2-10 Hz); (2) validate our velocity model; and (3) observe the effects of sparse OBS interval on data quality. Finally, we apply 2D acoustic frequency-domain waveform inversion to the synthetic data to generate velocity model updates. The inverted model is compared to the reference model to investigate the improved crustal resolution and Moho boundary delineation that could be realized using waveform inversion, and to evaluate the effects of the acquisition parameters. The inversion strategies developed through the synthetic tests will help the subsequent inversion of sparse, long-offset OBS field data.

Electron microscopy of electromagnetic waveforms.

PubMed

Ryabov, A; Baum, P

2016-07-22

Rapidly changing electromagnetic fields are the basis of almost any photonic or electronic device operation. We report how electron microscopy can measure collective carrier motion and fields with subcycle and subwavelength resolution. A collimated beam of femtosecond electron pulses passes through a metamaterial resonator that is previously excited with a single-cycle electromagnetic pulse. If the probing electrons are shorter in duration than half a field cycle, then time-frozen Lorentz forces distort the images quasi-classically and with subcycle time resolution. A pump-probe sequence reveals in a movie the sample's oscillating electromagnetic field vectors with time, phase, amplitude, and polarization information. This waveform electron microscopy can be used to visualize electrodynamic phenomena in devices as small and fast as available. Copyright © 2016, American Association for the Advancement of Science.

Pseudo 2D elastic waveform inversion for attenuation in the near surface

NASA Astrophysics Data System (ADS)

Wang, Yue; Zhang, Jie

2017-08-01

Seismic waveform propagation could be significantly affected by heterogeneities in the near surface zone (0 m-500 m depth). As a result, it is important to obtain as much near surface information as possible. Seismic attenuation, characterized by QP and QS factors, may affect seismic waveform in both phase and amplitude; however, it is rarely estimated and applied to the near surface zone for seismic data processing. Applying a 1D elastic full waveform modelling program, we demonstrate that such effects cannot be overlooked in the waveform computation if the value of the Q factor is lower than approximately 100. Further, we develop a pseudo 2D elastic waveform inversion method in the common midpoint (CMP) domain that jointly inverts early arrivals for QP and surface waves for QS. In this method, although the forward problem is in 1D, by applying 2D model regularization, we obtain 2D QP and QS models through simultaneous inversion. A cross-gradient constraint between the QP and Qs models is applied to ensure structural consistency of the 2D inversion results. We present synthetic examples and a real case study from an oil field in China.

Estimating Extracellular Spike Waveforms from CA1 Pyramidal Cells with Multichannel Electrodes

PubMed Central

Molden, Sturla; Moldestad, Olve; Storm, Johan F.

2013-01-01

Extracellular (EC) recordings of action potentials from the intact brain are embedded in background voltage fluctuations known as the “local field potential” (LFP). In order to use EC spike recordings for studying biophysical properties of neurons, the spike waveforms must be separated from the LFP. Linear low-pass and high-pass filters are usually insufficient to separate spike waveforms from LFP, because they have overlapping frequency bands. Broad-band recordings of LFP and spikes were obtained with a 16-channel laminar electrode array (silicone probe). We developed an algorithm whereby local LFP signals from spike-containing channel were modeled using locally weighted polynomial regression analysis of adjoining channels without spikes. The modeled LFP signal was subtracted from the recording to estimate the embedded spike waveforms. We tested the method both on defined spike waveforms added to LFP recordings, and on in vivo-recorded extracellular spikes from hippocampal CA1 pyramidal cells in anaesthetized mice. We show that the algorithm can correctly extract the spike waveforms embedded in the LFP. In contrast, traditional high-pass filters failed to recover correct spike shapes, albeit produceing smaller standard errors. We found that high-pass RC or 2-pole Butterworth filters with cut-off frequencies below 12.5 Hz, are required to retrieve waveforms comparable to our method. The method was also compared to spike-triggered averages of the broad-band signal, and yielded waveforms with smaller standard errors and less distortion before and after the spike. PMID:24391714

Assessing the Threat from Electromagnetic Pulse (EMP). Volume 1: Executive Report

DTIC Science & Technology

2017-07-31

high -altitude electromagnetic pulse threat waveform and its ground pattern. This need arises because of the effect of very low frequency electric...system Equipment to Failure ..................................... 15 Intelligence Community Assessment of the EMP Threat...17 APPENDIX A Legislation Re-establishing the Commission ..................................................... 19 APPENDIX B High

16 CFR 1505.6 - Performance.

Code of Federal Regulations, 2012 CFR

2012-01-01

... waveform of the test voltage shall approximate a sine wave as closely as possible. (iii) The applied test... stalled-rotor current of the toy at maximum rated voltage. There shall be no electrical or mechanical... voltage with the rotor of the motor locked into position. During the test, exposed dead metal parts of the...

16 CFR 1505.6 - Performance.

Code of Federal Regulations, 2011 CFR

2011-01-01

... waveform of the test voltage shall approximate a sine wave as closely as possible. (iii) The applied test... stalled-rotor current of the toy at maximum rated voltage. There shall be no electrical or mechanical... voltage with the rotor of the motor locked into position. During the test, exposed dead metal parts of the...

16 CFR 1505.6 - Performance.

Code of Federal Regulations, 2014 CFR

2014-01-01

... waveform of the test voltage shall approximate a sine wave as closely as possible. (iii) The applied test... stalled-rotor current of the toy at maximum rated voltage. There shall be no electrical or mechanical... voltage with the rotor of the motor locked into position. During the test, exposed dead metal parts of the...

Linear beam raster magnet driver based on H-bridge technique

DOEpatents

Sinkine, Nikolai I.; Yan, Chen; Apeldoorn, Cornelis; Dail, Jeffrey Glenn; Wojcik, Randolph Frank; Gunning, William

2006-06-06

An improved raster magnet driver for a linear particle beam is based on an H-bridge technique. Four branches of power HEXFETs form a two-by-two switch. Switching the HEXFETs in a predetermined order and at the right frequency produces a triangular current waveform. An H-bridge controller controls switching sequence and timing. The magnetic field of the coil follows the shape of the waveform and thus steers the beam using a triangular rather than a sinusoidal waveform. The system produces a raster pattern having a highly uniform raster density distribution, eliminates target heating from non-uniform raster density distributions, and produces higher levels of beam current.

Multimode seismoelectric phenomena generated using explosive and vibroseis sources

NASA Astrophysics Data System (ADS)

Butler, Karl E.; Kulessa, Bernd; Pugin, André J.-M.

2018-05-01

A field trial of seismoelectric surveying was carried out at a site underlain by 20 m of water-saturated clayey Champlain Sea sediments, renowned for their amenability to high resolution imaging by seismic reflection surveys. Seismically induced electrokinetic effects were recorded using an array of 26 grounded dipole electric field antennas, and two different seismic sources including an eight-gauge shotgun, and a moderate power (10 000 lb Minivib) vibrator. Despite the high electrical conductivity of the sediments, shot records show evidence of possible interfacial seismoelectric conversions caused by the arrival of P-waves at the base of the clay/top of bedrock and at the top of a layer of elevated porosity and conductivity within the clay at 7 m depth. However, the data are more remarkable for the fact that P-wave, S-wave, and PS/SP converted wave reflections evident in the seismic records all give rise to electrical arrivals exhibiting very similar moveout patterns in the seismoelectric records. Superficially, these electrical responses could be misinterpreted as simple coseismic seismoelectric effects associated with the arrival of reflected seismic waves at each dipole antenna on surface. However, their broader bandwidth, superior coherency and earlier arrival times compared to their corresponding seismic arrivals indicate that the electrical effects are generated by the arrival of seismic reflections below each dipole at the shallow intraclay interface 7 m below surface. Such quasi-coseismic arrivals have recently been predicted by full-waveform seismoelectric modelling and characterized as evanescent electromagnetic (EM) waves. In retrospect, they were also observed in earlier seismoelectric field trials, but not measured as clearly nor recognized as a distinct seismoelectric mode intermediate between interfacial and coseismic effects. We propose that the observed quasi-coseismic effect can be understood physically as a fringing field emanating from the travelling charge separation associated with a P-wave (direct or mode-converted) crossing a subsurface interface at an oblique angle. Such effects may be nearly indistinguishable from coseismic effects if the interface depth is small compared to the seismic wavelength, but recognition of the phenomenon contributes to an improved understanding of the seismoelectric wavefield, and will lead to improved interpretations. From a practical standpoint, the results of this field trial suggest that using electric field receivers to supplement geophones on surface could yield significantly higher resolution seismic reflection images in those areas where suitable near-surface layers exist for the generation of quasi-coseismic effects. The results also reinforce the importance of using multichannel recording to allow interfacial seismoelectric conversions originating at depth to be distinguished from stronger coseismic and quasi-coseismic arrivals originating in the near-surface by measurement of their arrival time versus offset (moveout) and amplitude versus offset behaviours.

Pulse charging of lead-acid traction cells

NASA Technical Reports Server (NTRS)

Smithrick, J. J.

1980-01-01

Pulse charging, as a method of rapidly and efficiently charging 300 amp-hour lead-acid traction cells for an electric vehicle application was investigated. A wide range of charge pulse current square waveforms were investigated and the results were compared to constant current charging at the time averaged pulse current values. Representative pulse current waveforms were: (1) positive waveform-peak charge pulse current of 300 amperes (amps), discharge pulse-current of zero amps, and a duty cycle of about 50%; (2) Romanov waveform-peak charge pulse current of 300 amps, peak discharge pulse current of 15 amps, and a duty of 50%; and (3) McCulloch waveform peak charge pulse current of 193 amps, peak discharge pulse current of about 575 amps, and a duty cycle of 94%. Experimental results indicate that on the basis of amp-hour efficiency, pulse charging offered no significant advantage as a method of rapidly charging 300 amp-hour lead-acid traction cells when compared to constant current charging at the time average pulse current value. There were, however, some disadvantages of pulse charging in particular a decrease in charge amp-hour and energy efficiencies and an increase in cell electrolyte temperature. The constant current charge method resulted in the best energy efficiency with no significant sacrifice of charge time or amp-hour output. Whether or not pulse charging offers an advantage over constant current charging with regard to the cell charge/discharge cycle life is unknown at this time.

Detecting the propagation effect of terahertz wave inside the two-color femtosecond laser filament in the air

NASA Astrophysics Data System (ADS)

Zhao, J.; Zhang, X.; Li, S.; Liu, C.; Chen, Y.; Peng, Y.; Zhu, Y.

2018-03-01

In this work, to decide the existence of terahertz (THz) wave propagation effect, THz pulses emitted from a blocked two-color femtosecond laser filament with variable length were recorded by a standard electric-optic sampling setup. The phenomenon of temporal advance of the THz waveform's peak with the increasing filament length has been observed. Together with another method of knife-edge measurement which aims at directly retrieving the THz beam diameter, both the experimental approaches have efficiently indicated the same filament range within which THz wave propagated inside the plasma column. At last, a preliminary two-dimensional near-field scanning imaging of the THz spot inside the cross section of the filament has been suggested as the third way to determine the issue of THz wave propagation effect.

Nano- and micro-electromechanical switch dynamics

NASA Astrophysics Data System (ADS)

Pulskamp, Jeffrey S.; Proie, Robert M.; Polcawich, Ronald G.

2013-01-01

This paper reports theoretical analysis and experimental results on the dynamics of piezoelectric MEMS mechanical logic relays. The multiple degree of freedom analytical model, based on modal decomposition, utilizes modal parameters obtained from finite element analysis and an analytical model of piezoelectric actuation. The model accounts for exact device geometry, damping, drive waveform variables, and high electric field piezoelectric nonlinearity. The piezoelectrically excited modal force is calculated directly and provides insight into design optimization for switching speed. The model accurately predicts the propagation delay dependence on actuation voltage of mechanically distinct relay designs. The model explains the observed discrepancies in switching speed of these devices relative to single degree of freedom switching speed models and suggests the strong potential for improved switching speed performance in relays designed for mechanical logic and RF circuits through the exploitation of higher order vibrational modes.

Ionospheric effects of thunderstorms and lightning

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

Lay, Erin H.

2014-02-03

Tropospheric thunderstorms have been reported to disturb the lower ionosphere (~65-90 km) by convective atmospheric gravity waves and by electromagnetic field changes produced by lightning discharges. However, due to the low electron density in the lower ionosphere, active probing of its electron distribution is difficult, and the various perturbative effects are poorly understood. Recently, we have demonstrated that by using remotely-detected ?me waveforms of lightning radio signals it is possible to probe the lower ionosphere and its fluctuations in a spatially and temporally-resolved manner. Here we report evidence of gravity wave effects on the lower ionosphere originating from the thunderstorm.more » We also report variations in the nighttime ionosphere atop a small thunderstorm and associate the variations with the storm’s electrical activity. Finally, we present a data analysis technique to map ionospheric acoustic waves near thunderstorms.« less

An electric stimulation system for electrokinetic particle manipulation in microfluidic devices.

PubMed

Lopez-de la Fuente, M S; Moncada-Hernandez, H; Perez-Gonzalez, V H; Lapizco-Encinas, B H; Martinez-Chapa, S O

2013-03-01

Microfluidic devices have grown significantly in the number of applications. Microfabrication techniques have evolved considerably; however, electric stimulation systems for microdevices have not advanced at the same pace. Electric stimulation of micro-fluidic devices is an important element in particle manipulation research. A flexible stimulation instrument is desired to perform configurable, repeatable, automated, and reliable experiments by allowing users to select the stimulation parameters. The instrument presented here is a configurable and programmable stimulation system for electrokinetic-driven microfluidic devices; it consists of a processor, a memory system, and a user interface to deliver several types of waveforms and stimulation patterns. It has been designed to be a flexible, highly configurable, low power instrument capable of delivering sine, triangle, and sawtooth waveforms with one single frequency or two superimposed frequencies ranging from 0.01 Hz to 40 kHz, and an output voltage of up to 30 Vpp. A specific stimulation pattern can be delivered over a single time period or as a sequence of different signals for different time periods. This stimulation system can be applied as a research tool where manipulation of particles suspended in liquid media is involved, such as biology, medicine, environment, embryology, and genetics. This system has the potential to lead to new schemes for laboratory procedures by allowing application specific and user defined electric stimulation. The development of this device is a step towards portable and programmable instrumentation for electric stimulation on electrokinetic-based microfluidic devices, which are meant to be integrated with lab-on-a-chip devices.

An electric stimulation system for electrokinetic particle manipulation in microfluidic devices

NASA Astrophysics Data System (ADS)

Lopez-de la Fuente, M. S.; Moncada-Hernandez, H.; Perez-Gonzalez, V. H.; Lapizco-Encinas, B. H.; Martinez-Chapa, S. O.

2013-03-01

Microfluidic devices have grown significantly in the number of applications. Microfabrication techniques have evolved considerably; however, electric stimulation systems for microdevices have not advanced at the same pace. Electric stimulation of micro-fluidic devices is an important element in particle manipulation research. A flexible stimulation instrument is desired to perform configurable, repeatable, automated, and reliable experiments by allowing users to select the stimulation parameters. The instrument presented here is a configurable and programmable stimulation system for electrokinetic-driven microfluidic devices; it consists of a processor, a memory system, and a user interface to deliver several types of waveforms and stimulation patterns. It has been designed to be a flexible, highly configurable, low power instrument capable of delivering sine, triangle, and sawtooth waveforms with one single frequency or two superimposed frequencies ranging from 0.01 Hz to 40 kHz, and an output voltage of up to 30 Vpp. A specific stimulation pattern can be delivered over a single time period or as a sequence of different signals for different time periods. This stimulation system can be applied as a research tool where manipulation of particles suspended in liquid media is involved, such as biology, medicine, environment, embryology, and genetics. This system has the potential to lead to new schemes for laboratory procedures by allowing application specific and user defined electric stimulation. The development of this device is a step towards portable and programmable instrumentation for electric stimulation on electrokinetic-based microfluidic devices, which are meant to be integrated with lab-on-a-chip devices.

Multichannel electrical stimulation of the auditory nerve in man. I. Basic psychophysics.

PubMed

Shannon, R V

1983-08-01

Basic psychophysical measurements were obtained from three patients implanted with multichannel cochlear implants. This paper presents measurements from stimulation of a single channel at a time (either monopolar or bipolar). The shape of the threshold vs. frequency curve can be partially related to the membrane biophysics of the remaining spiral ganglion and/or dendrites. Nerve survival in the region of the electrode may produce some increase in the dynamic range on that electrode. Loudness was related to the stimulus amplitude by a power law with exponents between 1.6 and 3.4, depending on frequency. Intensity discrimination was better than for normal auditory stimulation, but not enough to offset the small dynamic range for electrical stimulation. Measures of temporal integration were comparable to normals, indicating a central mechanism that is still intact in implant patients. No frequency analysis of the electrical signal was observed. Each electrode produced a unique pitch sensation, but they were not simply related to the tonotopic position of the stimulated electrode. Pitch increased over more than 4 octaves (for one patient) as the frequency was increased from 100 to 300 Hz, but above 300 Hz no pitch change was observed. Possibly the major limitation of single channel cochlear implants is the 1-2 ms integration time (probably due to the capacitative properties of the nerve membrane which acts as a low-pass filter at 100 Hz). Another limitation of electrical stimulation is that there is no spectral analysis of the electrical waveform so that temporal waveform alone determines the effective stimulus.

Phase-space topography characterization of nonlinear ultrasound waveforms.

PubMed

Dehghan-Niri, Ehsan; Al-Beer, Helem

2018-03-01

Fundamental understanding of ultrasound interaction with material discontinuities having closed interfaces has many engineering applications such as nondestructive evaluation of defects like kissing bonds and cracks in critical structural and mechanical components. In this paper, to analyze the acoustic field nonlinearities due to defects with closed interfaces, the use of a common technique in nonlinear physics, based on a phase-space topography construction of ultrasound waveform, is proposed. The central idea is to complement the "time" and "frequency" domain analyses with the "phase-space" domain analysis of nonlinear ultrasound waveforms. A nonlinear time series method known as pseudo phase-space topography construction is used to construct equivalent phase-space portrait of measured ultrasound waveforms. Several nonlinear models are considered to numerically simulate nonlinear ultrasound waveforms. The phase-space response of the simulated waveforms is shown to provide different topographic information, while the frequency domain shows similar spectral behavior. Thus, model classification can be substantially enhanced in the phase-space domain. Experimental results on high strength aluminum samples show that the phase-space transformation provides a unique detection and classification capabilities. The Poincaré map of the phase-space domain is also used to better understand the nonlinear behavior of ultrasound waveforms. It is shown that the analysis of ultrasound nonlinearities is more convenient and informative in the phase-space domain than in the frequency domain. Copyright © 2017 Elsevier B.V. All rights reserved.

An intelligent detection method for high-field asymmetric waveform ion mobility spectrometry.

PubMed

Li, Yue; Yu, Jianwen; Ruan, Zhiming; Chen, Chilai; Chen, Ran; Wang, Han; Liu, Youjiang; Wang, Xiaozhi; Li, Shan

2018-04-01

In conventional high-field asymmetric waveform ion mobility spectrometry signal acquisition, multi-cycle detection is time consuming and limits somewhat the technique's scope for rapid field detection. In this study, a novel intelligent detection approach has been developed in which a threshold was set on the relative error of α parameters, which can eliminate unnecessary time spent on detection. In this method, two full-spectrum scans were made in advance to obtain the estimated compensation voltage at different dispersion voltages, resulting in a narrowing down of the whole scan area to just the peak area(s) of interest. This intelligent detection method can reduce the detection time to 5-10% of that of the original full-spectrum scan in a single cycle.

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

NASA Astrophysics Data System (ADS)

Reisgen, Uwe; Schleser, Markus; Mokrov, Oleg; Zabirov, Alexander

2011-06-01

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.

Applications of electromagnetic principles in the design and development of proximity wireless sensors

NASA Astrophysics Data System (ADS)

Alam, Md Nazmul

Sensors and sensing system are playing dominant roles in monitoring the health of infrastructure, such as bridges, power lines, gas pipelines, rail roads etc. Sensing modalities employing Surface Acoustic Waves (SAW), Electromagnetic (EM) and optical have been investigated and reported. Sensors that utilize the perturbation of EM fields as function of the change in the physical structural or material phenomenon are of particular interest because of their inherent synergy with electronic system and diagnostic techniques, e.g. Time Domain Reflectometry (TDR), Joint-Time-Frequency-Domain-Reflectometry (JTFDR). The focus of this work is to study and develop new sensing and monitoring concepts that are based on EM principles. First, the analyses, design and development of a static electric field type sensor are presented for application in embedded concrete moisture content measurement. The analytical formulation and results based on conformal mapping method for an interdigitated sensor clearly show the dependency of the field penetration depth and the inter-electrode capacitance on the electrode sizes and their spacings. It is observed that larger electrode size and small separation are needed in order to achieve substantially higher capacitance or large field penetration depth. A meander and a circular sensor are fabricated and tested to demonstrate concrete moisture content measurements that show that moisture content is a linear function of sensor interelectrode capacitance. Second, sub-wavelength dimension non-intrusive wave launchers are designed and tested that can launch TDR or JTFDR type broadband surface wave waveforms in the VHF-UHF bands in order to detect cable faults. Greater than 3:1 transmission bandwidth (100-300 MHz) is obtained with a cylindrical launcher on square orthogonal ground plane while with a CSW launcher more than an octave (100-240 MHz) bandwidth is achieved. Open circuit faults are detected using surface waves and TDR on two XLPE cables. Third, a new mathematical method is developed that can be used to determine the changes in the dielectric constant of a cable insulating material. By comparing the experimental JTFDR waveform signatures from a new and an aged cable, it is demonstrated that the change in the average dielectric constant of the insulation material can be estimated from the phase transfer functions obtained from the FFT of measured magnitude and phase responses. The experimental data obtained for two types of cables, XLPE and EPR show that the dielectric constant decreases with accelerated aging. Finally, JTFDR surface wave sensing method is developed and applied to determine the locations of aging related insulation damage in power cables. The comparative power spectral responses of conducted and non-intrusive surface wave JTFDR waveforms clearly show the resulting bandwidth reduction in the latter primarily because of the reflective nature of the coupling. It is demonstrated that with the help of a non-intrusive wave launcher and a 120 MHz Gaussian chirp waveform the location of aging related insulation damages can be detected. Experiments conducted show the cross-correlation peaks at subsequent aging intervals as the cable is aged inside a heat chamber.

Induction of cell death by magnetic particles in response to a gradient magnetic field inside a uniform magnetic field

NASA Astrophysics Data System (ADS)

Amaya-Jaramillo, Carlos David; Pérez-Portilla, Adriana Patricia; Serrano-Olmedo, José Javier; Ramos-Gómez, Milagros

2017-10-01

A new instrument based on a magnetic force produced by an alternating magnetic field gradient, which is obtained through Maxwell coils, inside a constant field magnet has been designed and used to produce cell death. We have determined the interaction of microparticles and cells under different conditions such as incubation time with microparticles, particle size, magnetic field exposition time, and different current waveforms at different frequencies to produce a magnetic field gradient. We determined that the highest rate of cell death occurs at a frequency of 1 Hz with a square waveform and 1 h of irradiation. This method could be of great interest to remove cancer cells due mainly to the alterations in stiffness observed in the membranes of the tumor cells. Cancer cells can be eliminated in response to the forces caused by the movement of magnetic nanoparticles of the appropriate size under the application of a specific magnetic field. [Figure not available: see fulltext.

Toward establishing model organisms for marine protists: Successful transfection protocols for Parabodo caudatus (Kinetoplastida: Excavata).

PubMed

Gomaa, Fatma; Garcia, Paulo A; Delaney, Jennifer; Girguis, Peter R; Buie, Cullen R; Edgcomb, Virginia P

2017-09-01

We developed protocols for, and demonstrated successful transfection of, the free-living kinetoplastid flagellate Parabodo caudatus with three plasmids carrying a fluorescence reporter gene (pEF-GFP with the EF1 alpha promoter, pUB-GFP with Ubiquitin C promoter, and pEYFP-Mitotrap with CMV promoter). We evaluated three electroporation approaches: (1) a square-wave electroporator designed for eukaryotes, (2) a novel microfluidic transfection system employing hydrodynamically-controlled electric field waveforms, and (3) a traditional exponential decay electroporator. We found the microfluidic device provides a simple and efficient platform to quickly test a wide range of electric field parameters to find the optimal set of conditions for electroporation of target species. It also allows for processing large sample volumes (>10 ml) within minutes, increasing throughput 100 times over cuvettes. Fluorescence signal from the reporter gene was detected a few hours after transfection and persisted for 3 days in cells transfected by pEF-GFP and pUB-GFP plasmids and for at least 5 days post-transfection for cells transfected with pEYFP-Mitotrap. Expression of the reporter genes (GFP and YFP) was also confirmed using reverse transcription-PCR (RT-PCR). This work opens the door for further efforts with this taxon and close relatives toward establishing model systems for genome editing. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Participation in the scientific activities of the Waves in Space Plasma (WISP) project

NASA Technical Reports Server (NTRS)

Alpert, Yakov L.; Grossi, Mario D.

1994-01-01

This is the Final Report for Contract NAG5-1925, that consisted of experiment design, for possible use by the space science mission called WISP (Waves in Space Plasma). This mission is under study by the Canadian Space Agency and by NASA. Two WISP configurations are contemplated, under the name of BICEPS: one is called BOLAS, and the other WISPRS. Both these configurations are meant to perform bistatic sounding of the ionosphere, at a height close to F(sub 2) H(sub max) (about 350 Km), with a pair of satellites, either tethered or in free flight. Investigation A (with Y.L. Alpert as P.I.) addresses the subject of parametric decay effects, expected to arise in a magnetoplasma under the influence of high-intensity HF fields. Criteria were formulated that could be used in searching for parametric instabilities and of electric fields in the ionosphere and magnetosphere, by in-situ satellites, such as the BICEPS Pair. Investigation B (with M.D.Grossi as P.I.) addressed the bistatic measurement, by the BICEPS pair,of ionospheric features, such as large-scale and small-scale disturbances, travelling ionospheric disturbances, electron density irregularities, spread-F phenomena, etc. These measurements by BICEPS could be correlated with the waveform distortion and degradation experienced by microwave links from geosynchronous height to ground, such as the ACTS satellite, expected to radiate pulses as short as 1 nanosecond in the band 20 to 30 GHz. These links are transionospheric and propagate e.m. waves in the volume of the ionosphere where BICEPS operates. It will be possible, therefore, to correlate the two classes of measurements, and learn the causative mechanisms that are responsible for the time-spread and frequency-spread nature of communications waveforms at microwave, in geosynchronous height to ground paths.

Study on a Biometric Authentication Model based on ECG using a Fuzzy Neural Network

NASA Astrophysics Data System (ADS)

Kim, Ho J.; Lim, Joon S.

2018-03-01

Traditional authentication methods use numbers or graphic passwords and thus involve the risk of loss or theft. Various studies are underway regarding biometric authentication because it uses the unique biometric data of a human being. Biometric authentication technology using ECG from biometric data involves signals that record electrical stimuli from the heart. It is difficult to manipulate and is advantageous in that it enables unrestrained measurements from sensors that are attached to the skin. This study is on biometric authentication methods using the neural network with weighted fuzzy membership functions (NEWFM). In the biometric authentication process, normalization and the ensemble average is applied during preprocessing, characteristics are extracted using Haar-wavelets, and a registration process called “training” is performed in the fuzzy neural network. In the experiment, biometric authentication was performed on 73 subjects in the Physionet Database. 10-40 ECG waveforms were tested for use in the registration process, and 15 ECG waveforms were deemed the appropriate number for registering ECG waveforms. 1 ECG waveforms were used during the authentication stage to conduct the biometric authentication test. Upon testing the proposed biometric authentication method based on 73 subjects from the Physionet Database, the TAR was 98.32% and FAR was 5.84%.

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

USGS Publications Warehouse

Scott, James Henry; Farstad, Arnold J.

1977-01-01

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

Arctic lead detection using a waveform mixture algorithm from CryoSat-2 data

NASA Astrophysics Data System (ADS)

Lee, Sanggyun; Kim, Hyun-cheol; Im, Jungho

2018-05-01

We propose a waveform mixture algorithm to detect leads from CryoSat-2 data, which is novel and different from the existing threshold-based lead detection methods. The waveform mixture algorithm adopts the concept of spectral mixture analysis, which is widely used in the field of hyperspectral image analysis. This lead detection method was evaluated with high-resolution (250 m) MODIS images and showed comparable and promising performance in detecting leads when compared to the previous methods. The robustness of the proposed approach also lies in the fact that it does not require the rescaling of parameters (i.e., stack standard deviation, stack skewness, stack kurtosis, pulse peakiness, and backscatter σ0), as it directly uses L1B waveform data, unlike the existing threshold-based methods. Monthly lead fraction maps were produced by the waveform mixture algorithm, which shows interannual variability of recent sea ice cover during 2011-2016, excluding the summer season (i.e., June to September). We also compared the lead fraction maps to other lead fraction maps generated from previously published data sets, resulting in similar spatiotemporal patterns.

Centroid-moment tensor inversions using high-rate GPS waveforms

NASA Astrophysics Data System (ADS)

O'Toole, Thomas B.; Valentine, Andrew P.; Woodhouse, John H.

2012-10-01

Displacement time-series recorded by Global Positioning System (GPS) receivers are a new type of near-field waveform observation of the seismic source. We have developed an inversion method which enables the recovery of an earthquake's mechanism and centroid coordinates from such data. Our approach is identical to that of the 'classical' Centroid-Moment Tensor (CMT) algorithm, except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic GPS seismograms and their partial derivatives. We demonstrate the validity of our approach by calculating CMT solutions using 1 Hz GPS data for two recent earthquakes in Japan. These results are in good agreement with independently determined source models of these events. With wider availability of data, we envisage the CMT algorithm providing a tool for the systematic inversion of GPS waveforms, as is already the case for teleseismic data. Furthermore, this general inversion method could equally be applied to other near-field earthquake observations such as those made using accelerometers.

Near-field shock formation in noise propagation from a high-power jet aircraft.

PubMed

Gee, Kent L; Neilsen, Tracianne B; Downing, J Micah; James, Michael M; McKinley, Richard L; McKinley, Robert C; Wall, Alan T

2013-02-01

Noise measurements near the F-35A Joint Strike Fighter at military power are analyzed via spatial maps of overall and band pressure levels and skewness. Relative constancy of the pressure waveform skewness reveals that waveform asymmetry, characteristic of supersonic jets, is a source phenomenon originating farther upstream than the maximum overall level. Conversely, growth of the skewness of the time derivative with distance indicates that acoustic shocks largely form through the course of near-field propagation and are not generated explicitly by a source mechanism. These results potentially counter previous arguments that jet "crackle" is a source phenomenon.

Full waveform time domain solutions for source and induced magnetotelluric and controlled-source electromagnetic fields using quasi-equivalent time domain decomposition and GPU parallelization

NASA Astrophysics Data System (ADS)

Imamura, N.; Schultz, A.

2015-12-01

Recently, a full waveform time domain solution has been developed for the magnetotelluric (MT) and controlled-source electromagnetic (CSEM) methods. The ultimate goal of this approach is to obtain a computationally tractable direct waveform joint inversion for source fields and earth conductivity structure in three and four dimensions. This is desirable on several grounds, including the improved spatial resolving power expected from use of a multitude of source illuminations of non-zero wavenumber, the ability to operate in areas of high levels of source signal spatial complexity and non-stationarity, etc. This goal would not be obtainable if one were to adopt the finite difference time-domain (FDTD) approach for the forward problem. This is particularly true for the case of MT surveys, since an enormous number of degrees of freedom are required to represent the observed MT waveforms across the large frequency bandwidth. It means that for FDTD simulation, the smallest time steps should be finer than that required to represent the highest frequency, while the number of time steps should also cover the lowest frequency. This leads to a linear system that is computationally burdensome to solve. We have implemented our code that addresses this situation through the use of a fictitious wave domain method and GPUs to speed up the computation time. We also substantially reduce the size of the linear systems by applying concepts from successive cascade decimation, through quasi-equivalent time domain decomposition. By combining these refinements, we have made good progress toward implementing the core of a full waveform joint source field/earth conductivity inverse modeling method. From results, we found the use of previous generation of CPU/GPU speeds computations by an order of magnitude over a parallel CPU only approach. In part, this arises from the use of the quasi-equivalent time domain decomposition, which shrinks the size of the linear system dramatically.

16 CFR § 1505.6 - Performance.

Code of Federal Regulations, 2013 CFR

2013-01-01

... waveform of the test voltage shall approximate a sine wave as closely as possible. (iii) The applied test... stalled-rotor current of the toy at maximum rated voltage. There shall be no electrical or mechanical... voltage with the rotor of the motor locked into position. During the test, exposed dead metal parts of the...

Waveform synthesizer

DOEpatents

Franks, Larry A.; Nelson, Melvin A.

1981-01-01

A method of producing optical and electrical pulses of desired shape. An optical pulse of arbitrary but defined shape illuminates one end of an array of optical fiber waveguides of differing lengths to time differentiate the input pulse. The optical outputs at the other end of the array are combined to form a synthesized pulse of desired shape.

What is waveform library? Advances in EPG science made possible by the 3rd generation AC-DC universal monitor

USDA-ARS?s Scientific Manuscript database

Until recently, most Electrical Penetration Graph (EPG) studies have emphasized small-bodied sternorrhynchans, auchenorrhynchans, and thrips. EPG holds the potential to significantly improve research on a wider array of species, such as large heteropterans and blood-sucking vectors of medical/veteri...

Identification and definitions of Electrical Penetration Graph (EPG) waveforms for the potato psyllid, Bactericera cockerelli, on susceptible potato.

USDA-ARS?s Scientific Manuscript database

The potato psyllid, Bactericera cockerelli, is the vector of Ca. Liberibacter psyllaurous/solanacearum, a bacterium associated with a lethal potato disease with tuber-striping symptoms, termed Zebra Chip (ZC). Presently, there are no effective management tactics for ZC, although research to aid de...

A new SAS program for behavioral analysis of Electrical Penetration Graph (EPG) data

USDA-ARS?s Scientific Manuscript database

A new program is introduced that uses SAS software to duplicate output of descriptive statistics from the Sarria Excel workbook for EPG waveform analysis. Not only are publishable means and standard errors or deviations output, the user also is guided through four relatively simple sub-programs for ...

A Wavelet-based Fast Discrimination of Transformer Magnetizing Inrush Current

NASA Astrophysics Data System (ADS)

Kitayama, Masashi

Recently customers who need electricity of higher quality have been installing co-generation facilities. They can avoid voltage sags and other distribution system related disturbances by supplying electricity to important load from their generators. For another example, FRIENDS, highly reliable distribution system using semiconductor switches or storage devices based on power electronics technology, is proposed. These examples illustrates that the request for high reliability in distribution system is increasing. In order to realize these systems, fast relaying algorithms are indispensable. The author proposes a new method of detecting magnetizing inrush current using discrete wavelet transform (DWT). DWT provides the function of detecting discontinuity of current waveform. Inrush current occurs when transformer core becomes saturated. The proposed method detects spikes of DWT components derived from the discontinuity of the current waveform at both the beginning and the end of inrush current. Wavelet thresholding, one of the wavelet-based statistical modeling, was applied to detect the DWT component spikes. The proposed method is verified using experimental data using single-phase transformer and the proposed method is proved to be effective.

Experimental investigation on the energy deposition and morphology of the electrical explosion of copper wire in vacuum

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

Shi, Zongqian; Shi, Yuanjie; Wang, Kun

2016-03-15

This paper presents the experimental results of the electrical explosion of copper wires in vacuum using negative nanosecond-pulsed current with magnitude of 1–2 kA. The 20 μm-diameter copper wires with different lengths are exploded with three different current rates. A laser probe is applied to construct the shadowgraphy and interferometry diagnostics to investigate the distribution and morphology of the exploding product. The interference phase shift is reconstructed from the interferogram, by which the atomic density distribution is calculated. Experimental results show that there exist two voltage breakdown modes depending on the amount of the specific energy deposition. For the strong-shunting mode, shuntingmore » breakdown occurs, leading to the short-circuit-like current waveform. For the weak-shunting mode with less specific energy deposition, the plasma generated during the voltage breakdown is not enough to form a conductive plasma channel, resulting in overdamped declining current waveform. The influence of the wire length and current rate on the characteristics of the exploding wires is also analyzed.« less

FAIMS Operation for Realistic Gas Flow Profile and Asymmetric Waveforms Including Electronic Noise and Ripple

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

Shvartsburg, Alexandre A.; Tang, Keqi; Smith, Richard D.

The use of Field Asymmetric waveform Ion Mobility Spectrometry (FAIMS) has rapidly grown with the advent of commercial FAIMS systems coupled to mass spectrometry. However, many fundamental aspects of FAIMS remain obscure, hindering its technological improvement and expansion of analytical utility. Recently, we developed a comprehensive numerical simulation approach to FAIMS that can handle any device geometry and operational conditions. The formalism was originally set up in one dimension for a uniform gas flow and limited to ideal asymmetric voltage waveforms. Here we extend the model to account for a realistic gas flow velocity distribution in the analytical gap, axialmore » ion diffusion, and waveform imperfections (e.g. noise and ripple). The non-uniformity of gas flow velocity profile has only a minor effect, slightly improving resolution. However, waveform perturbations are significant even at very low levels, in some cases {approx} 0.01% of nominal voltage. These perturbations always improve resolution and decrease sensitivity. Variation of noise or ripple amplitude produces a trade-off between resolution and sensitivity. This trade-off is physically equivalent to that obtained via adjustment of the gap width and/or asymmetric waveform frequency, but the scaling of low-frequency ripple appears to be a more practical way to control FAIMS resolution.« less

Sub-Nyquist Sampling and Moire-Like Waveform Distortions

NASA Technical Reports Server (NTRS)

Williams, Glenn L.

2000-01-01

Investigations of aliasing effects in digital waveform sampling have revealed the existence of a mathematical field and a pseudo-alias domain lying to the left of a "Nyquist line" in a plane defining the boundary between two domains of sampling. To the right of the line lies the classic alias domain. For signals band-limited below the Nyquist limit, displayed output may show a false modulation envelope. The effect occurs whenever the sample rate and the signal frequency are related by ratios of mutually prime integers. Belying the principal of a 10:1 sampling ratio being "good enough", this distortion easily occurs in graphed one-dimensional waveforms and two-dimensional images and occurs daily on television.

Differences in electrosensory anatomy and social behavior in an area of sympatry between two species of mormyrid electric fishes.

PubMed

Carlson, Bruce A

2016-01-01

Sensory systems play a key role in social behavior by mediating the detection and analysis of communication signals. In mormyrid fishes, electric signals are processed within a dedicated sensory pathway, providing a unique opportunity to relate sensory biology to social behavior. Evolutionary changes within this pathway led to new perceptual abilities that have been linked to increased rates of signal evolution and species diversification in a lineage called 'clade A'. Previous field observations suggest that clade-A species tend to be solitary and territorial, whereas non-clade-A species tend to be clustered in high densities suggestive of schooling or shoaling. To explore behavioral differences between species in these lineages in greater detail, I studied population densities, social interactions, and electric signaling in two mormyrid species, Gnathonemus victoriae (clade A) and Petrocephalus degeni (non-clade A), from Lwamunda Swamp, Uganda. Petrocephalus degeni was found at higher population densities, but intraspecific diversity in electric signal waveform was greater in G. victoriae. In the laboratory, G. victoriae exhibited strong shelter-seeking behavior and competition for shelter, whereas P. degeni were more likely to abandon shelter in the presence of conspecifics as well as electric mimics of signaling conspecifics. In other words, P. degeni exhibited social affiliation whereas G. victoriae exhibited social competition. Further, P. degeni showed correlated electric signaling behavior whereas G. victoriae showed anti-correlated signaling behavior. These findings extend previous reports of social spacing, territoriality, and habitat preference among mormyrid species, suggesting that evolutionary divergence in electrosensory processing relates to differences in social behavior. © 2016. Published by The Company of Biologists Ltd.

Method and system employing graphical electric load categorization to identify one of a plurality of different electric load types

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

Yang, Yi; Du, Liang

A system for different electric loads includes sensors structured to sense voltage and current signals for each of the different electric loads; a hierarchical load feature database having a plurality of layers, with one of the layers including a plurality of different load categories; and a processor. The processor acquires voltage and current waveforms from the sensors for a corresponding one of the different electric loads; maps a voltage-current trajectory to a grid including a plurality of cells, each of which is assigned a binary value of zero or one; extracts a plurality of different features from the mapped gridmore » of cells as a graphical signature of the corresponding one of the different electric loads; derives a category of the corresponding one of the different electric loads from the database; and identifies one of a plurality of different electric load types for the corresponding one of the different electric loads.« less

Fine structure in RF spectra of lightning return stroke wave forms

NASA Technical Reports Server (NTRS)

Lanzerotti, L. J.; Thomson, D. J.; Maclennan, C. G.; Rinnert, K.; Krider, E. P.

1988-01-01

The power spectra of the wide-band (10 Hz to 100 kHz) magnetic-field signals for a number of lightning return strokes measured during a thunderstorm which occurred in Lindau in August, 1984 have been calculated. The RF magnetic field data are obtained with the engineering unit of the Galileo Jupiter Probe lightning experiment. Each return stroke data stream is passed through an adaptive filter designed to whiten its spectrum. The spectra of the magnetic field data definitely show fine structure, with two or three distinct peaks in the spectra of many of the waveforms. A peak at f of about 60-70 kHz is often seen in the power spectra of the waveform time segments preceding and following the rise-to-peak amplitude of the return stroke.

Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields.

PubMed

Noe, G Timothy; Katayama, Ikufumi; Katsutani, Fumiya; Allred, James J; Horowitz, Jeffrey A; Sullivan, David M; Zhang, Qi; Sekiguchi, Fumiya; Woods, Gary L; Hoffmann, Matthias C; Nojiri, Hiroyuki; Takeda, Jun; Kono, Junichiro

2016-12-26

We have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers in the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.

Sodium Channel β2 Subunits Prevent Action Potential Propagation Failures at Axonal Branch Points.

PubMed

Cho, In Ha; Panzera, Lauren C; Chin, Morven; Hoppa, Michael B

2017-09-27

Neurotransmitter release depends on voltage-gated Na + channels (Na v s) to propagate an action potential (AP) successfully from the axon hillock to a synaptic terminal. Unmyelinated sections of axon are very diverse structures encompassing branch points and numerous presynaptic terminals with undefined molecular partners of Na + channels. Using optical recordings of Ca 2+ and membrane voltage, we demonstrate here that Na + channel β2 subunits (Na v β2s) are required to prevent AP propagation failures across the axonal arborization of cultured rat hippocampal neurons (mixed male and female). When Na v β2 expression was reduced, we identified two specific phenotypes: (1) membrane excitability and AP-evoked Ca 2+ entry were impaired at synapses and (2) AP propagation was severely compromised with >40% of axonal branches no longer responding to AP-stimulation. We went on to show that a great deal of electrical signaling heterogeneity exists in AP waveforms across the axonal arborization independent of axon morphology. Therefore, Na v β2 is a critical regulator of axonal excitability and synaptic function in unmyelinated axons. SIGNIFICANCE STATEMENT Voltage-gated Ca 2+ channels are fulcrums of neurotransmission that convert electrical inputs into chemical outputs in the form of vesicle fusion at synaptic terminals. However, the role of the electrical signal, the presynaptic action potential (AP), in modulating synaptic transmission is less clear. What is the fidelity of a propagating AP waveform in the axon and what molecules shape it throughout the axonal arborization? Our work identifies several new features of AP propagation in unmyelinated axons: (1) branches of a single axonal arborization have variable AP waveforms independent of morphology, (2) Na + channel β2 subunits modulate AP-evoked Ca 2+ -influx, and (3) β2 subunits maintain successful AP propagation across the axonal arbor. These findings are relevant to understanding the flow of excitation in the brain. Copyright © 2017 the authors 0270-6474/17/379519-15$15.00/0.

Free microparticles—An inducing mechanism of pre-firing in high pressure gas switches for fast linear transformer drivers

NASA Astrophysics Data System (ADS)

Li, Xiaoang; Pei, Zhehao; Wu, Zhicheng; Zhang, Yuzhao; Liu, Xuandong; Li, Yongdong; Zhang, Qiaogen

2018-03-01

Microparticle initiated pre-firing of high pressure gas switches for fast linear transformer drivers (FLTDs) is experimentally and theoretically verified. First, a dual-electrode gas switch equipped with poly-methyl methacrylate baffles is used to capture and collect the microparticles. By analyzing the electrode surfaces and the collecting baffles by a laser scanning confocal microscope, microparticles ranging in size from tens of micrometers to over 100 μm are observed under the typical working conditions of FLTDs. The charging and movement of free microparticles in switch cavity are studied, and the strong DC electric field drives the microparticles to bounce off the electrode. Three different modes of free microparticle motion appear to be responsible for switch pre-firing. (i) Microparticles adhere to the electrode surface and act as a fixed protrusion which distorts the local electric field and initiates the breakdown in the gap. (ii) One particle escapes toward the opposite electrode and causes a near-electrode microdischarge, inducing the breakdown of the residual gap. (iii) Multiple moving microparticles are occasionally in cascade, leading to pre-firing. Finally, as experimental verification, repetitive discharges at ±90 kV are conducted in a three-electrode field-distortion gas switch, with two 8 mm gaps and pressurized with nitrogen. An ultrasonic probe is employed to monitor the bounce signals. In pre-firing incidents, the bounce is detected shortly before the collapse of the voltage waveform, which demonstrates that free microparticles contribute significantly to the mechanism that induces pre-firing in FLTD gas switches.

Free microparticles-An inducing mechanism of pre-firing in high pressure gas switches for fast linear transformer drivers.

PubMed

Li, Xiaoang; Pei, Zhehao; Wu, Zhicheng; Zhang, Yuzhao; Liu, Xuandong; Li, Yongdong; Zhang, Qiaogen

2018-03-01

Microparticle initiated pre-firing of high pressure gas switches for fast linear transformer drivers (FLTDs) is experimentally and theoretically verified. First, a dual-electrode gas switch equipped with poly-methyl methacrylate baffles is used to capture and collect the microparticles. By analyzing the electrode surfaces and the collecting baffles by a laser scanning confocal microscope, microparticles ranging in size from tens of micrometers to over 100 μm are observed under the typical working conditions of FLTDs. The charging and movement of free microparticles in switch cavity are studied, and the strong DC electric field drives the microparticles to bounce off the electrode. Three different modes of free microparticle motion appear to be responsible for switch pre-firing. (i) Microparticles adhere to the electrode surface and act as a fixed protrusion which distorts the local electric field and initiates the breakdown in the gap. (ii) One particle escapes toward the opposite electrode and causes a near-electrode microdischarge, inducing the breakdown of the residual gap. (iii) Multiple moving microparticles are occasionally in cascade, leading to pre-firing. Finally, as experimental verification, repetitive discharges at ±90 kV are conducted in a three-electrode field-distortion gas switch, with two 8 mm gaps and pressurized with nitrogen. An ultrasonic probe is employed to monitor the bounce signals. In pre-firing incidents, the bounce is detected shortly before the collapse of the voltage waveform, which demonstrates that free microparticles contribute significantly to the mechanism that induces pre-firing in FLTD gas switches.

Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems

NASA Astrophysics Data System (ADS)

Agapitov, O.; Drake, J. F.; Vasko, I.; Mozer, F. S.; Artemyev, A.; Krasnoselskikh, V.; Angelopoulos, V.; Wygant, J.; Reeves, G. D.

2018-03-01

Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave-particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high-amplitude whistlers suggest the importance of nonlinear wave-particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, presumably due to the feedback from hot resonant electrons. We have considered the nature and properties of such nonlinear whistler waves observed by the Van Allen Probes and Time History of Events and Macroscale Interactions define during Substorms in the inner magnetosphere, and we show that the significant enhancement of the wave electrostatic component can result from whistler wave coupling with the beam-driven electrostatic mode through the resonant interaction with hot electron beams. Being modulated by a whistler wave, the electron beam generates a driven electrostatic mode significantly enhancing the parallel electric field of the initial whistler wave. We confirm this mechanism using a self-consistent particle-in-cell simulation. The nonlinear electrostatic component manifests properties of the beam-driven electron acoustic mode and can be responsible for effective electron acceleration in the inhomogeneous magnetic field.

Compact biomedical pulsed signal generator for bone tissue stimulation

DOEpatents

Kronberg, J.W.

1993-06-08

An apparatus for stimulating bone tissue for stimulating bone growth or treating osteoporosis by applying directly to the skin of the patient an alternating current electrical signal comprising wave forms known to simulate the piezoelectric constituents in bone. The apparatus may, by moving a switch, stimulate bone growth or treat osteoporosis, as desired. Based on low-power CMOS technology and enclosed in a moisture-resistant case shaped to fit comfortably, two astable multivibrators produce the desired waveforms. The amplitude, pulse width and pulse frequency, and the subpulse width and subpulse frequency of the waveforms are adjustable. The apparatus, preferably powered by a standard 9-volt battery, includes signal amplitude sensors and warning signals indicate an output is being produced and the battery needs to be replaced.

Dynamic electrical characteristics of low-power ring oscillators constructed with inorganic nanoparticles on flexible plastics.

PubMed

Yun, Junggwon; Cho, Kyoungah; Kim, Sangsig

2012-11-01

In this study, we demonstrate for the first time the low-power and stable performance of a ring oscillator constructed on a flexible plastic with solution-processable inorganic nanoparticles (NPs). Our flexible ring oscillator is composed of three inverters based on n- and p-type inorganic NP thin-film transistors. Each of the component inverters exhibits a gain of ∼80 at a voltage of 5 V. For the ring oscillator, the sine waves are generated with a frequency of up to 12 kHz. The waveforms are undistorted under strained conditions and maintained even after 5000 bending cycles. The frequency and waveform of the output waves obtained from our flexible ring oscillator are analyzed and discussed in detail.

Compact biomedical pulsed signal generator for bone tissue stimulation

DOEpatents

Kronberg, James W.

1993-01-01

An apparatus for stimulating bone tissue for stimulating bone growth or treating osteoporosis by applying directly to the skin of the patient an alternating current electrical signal comprising wave forms known to simulate the piezoelectric constituents in bone. The apparatus may, by moving a switch, stimulate bone growth or treat osteoporosis, as desired. Based on low-power CMOS technology and enclosed in a moisture-resistant case shaped to fit comfortably, two astable multivibrators produce the desired waveforms. The amplitude, pulse width and pulse frequency, and the subpulse width and subpulse frequency of the waveforms are adjustable. The apparatus, preferably powered by a standard 9-volt battery, includes signal amplitude sensors and warning signals indicate an output is being produced and the battery needs to be replaced.

Reply to Comment by Nishimura Et Al.

NASA Astrophysics Data System (ADS)

Mozer, F. S.; Hull, A.; Lejosne, S.; Vasko, I. Y.

2018-03-01

Nishimura et al. (2010, https://doi.org/10.1126/science.1193186, 2011, https://doi.org/10.1029/2011JA016876, 2013, https://doi.org/10.1029/2012JA018242, and in their comment, hereafter called N18) have suggested that chorus waves interact with equatorial electrons to produce pulsating auroras. We agree that chorus can scatter electrons >10 keV, as do Time Domain Structures (TDSs). Lower-energy electrons occurring in pulsating auroras cannot be produced by chorus, but such electrons are scattered and accelerated by TDS. TDSs often occur with chorus and have power in their spectra at chorus frequencies. Thus, the absence of power at low frequencies is not evidence that TDSs are absent, as an example shows. Through examination of equatorial electric field waveforms and electron pitch angle distributions measured on the Time History of Events and Macroscale Interactions during Substorms satellites (in place of examining field and particle spectra, as done by Nishimura et al.), we show that chorus cannot produce the field-aligned electrons associated with pulsating auroras in the Nishimura et al. (2010, https://doi.org/10.1126/science.1193186) events, but TDSs can. Equatorial field-aligned electron distributions associated with pulsating auroras and created by TDS in the absence of chorus or any other wave at the equator are also shown.

Attosecond control of electronic processes by intense light fields.

PubMed

Baltuska, A; Udem, Th; Uiberacker, M; Hentschel, M; Goulielmakis, E; Gohle, Ch; Holzwarth, R; Yakovlev, V S; Scrinzi, A; Hänsch, T W; Krausz, F

2003-02-06

The amplitude and frequency of laser light can be routinely measured and controlled on a femtosecond (10(-15) s) timescale. However, in pulses comprising just a few wave cycles, the amplitude envelope and carrier frequency are not sufficient to characterize and control laser radiation, because evolution of the light field is also influenced by a shift of the carrier wave with respect to the pulse peak. This so-called carrier-envelope phase has been predicted and observed to affect strong-field phenomena, but random shot-to-shot shifts have prevented the reproducible guiding of atomic processes using the electric field of light. Here we report the generation of intense, few-cycle laser pulses with a stable carrier envelope phase that permit the triggering and steering of microscopic motion with an ultimate precision limited only by quantum mechanical uncertainty. Using these reproducible light waveforms, we create light-induced atomic currents in ionized matter; the motion of the electronic wave packets can be controlled on timescales shorter than 250 attoseconds (250 x 10(-18) s). This enables us to control the attosecond temporal structure of coherent soft X-ray emission produced by the atomic currents--these X-ray photons provide a sensitive and intuitive tool for determining the carrier-envelope phase.

Effect of solenoidal magnetic field on drifting laser plasma

NASA Astrophysics Data System (ADS)

Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

2013-04-01

An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

Modeling digital pulse waveforms by solving one-dimensional Navier-stokes equations.

PubMed

Fedotov, Aleksandr A; Akulova, Anna S; Akulov, Sergey A

2016-08-01

Mathematical modeling for composition distal arterial pulse wave in the blood vessels of the upper limbs was considered. Formation of distal arterial pulse wave is represented as a composition of forward and reflected pulse waves propagating along the arterial vessels. The formal analogy between pulse waves propagation along the human arterial system and the propagation of electrical oscillations in electrical transmission lines with distributed parameters was proposed. Dependencies of pulse wave propagation along the human arterial system were obtained by solving the one-dimensional Navier-Stokes equations for a few special cases.

Effects of combined electrical stimulation of the dorsal column and dorsal roots on wide-dynamic range neuronal activity in nerve-injured rats

PubMed Central

Yang, Fei; Zhang, Tong; Tiwari, Vinod; Shu, Bin; Zhang, Chen; Wang, Yun; Vera-Portocarrero, Louis P.; Raja, Srinivasa N.; Guan, Yun

2015-01-01

Objectives Electrical stimulation at the dorsal column (DC) and dorsal root (DR) may inhibit spinal wide-dynamic-range (WDR) neuronal activity in nerve-injured rats. The objective of this study was to determine if applying electrical conditioning stimulation (CS) at both sites provides additive or synergistic benefits. Materials and Methods By conducting in vivo extracellular recordings of WDR neurons in rats that had undergone L5 spinal nerve ligation, we tested whether combining 50 Hz CS at the two sites in either a concurrent (2.5 minutes) or alternate (5 minutes) pattern inhibits WDR neuronal activity better than CS at DC alone (5 minutes). The intensities of CS were determined by recording antidromic compound action potentials to graded stimulation at the DC and DR. We measured the current thresholds that resulted in the first detectable Aα/β waveform (Ab0) and the peak Aα/β waveform (Ab1) to select CS intensity at each site. The same number of electrical pulses and amount of current were delivered in different patterns to allow comparison. Results At a moderate intensity of 50%(Ab0+Ab1), different patterns of CS all attenuated the C-component of WDR neurons in response to graded intracutaneous electrical stimuli (0.1-10 mA, 2 ms), and inhibited windup in response to repetitive noxious stimuli (0.5 Hz). However, the inhibitory effects did not differ significantly between different patterns. At the lower intensity (Ab0), no CS inhibited WDR neurons. Conclusions These findings suggest that combined stimulation of DC and DR may not be superior to DC stimulation alone for inhibition of WDR neurons. PMID:26307526

Cardiac cycle-synchronized electrical muscle stimulator for lower limb training with the potential to reduce the heart's pumping workload

PubMed Central

Matsuse, Hiroo; Akimoto, Ryuji; Kamiya, Shiro; Moritani, Toshio; Sasaki, Motoki; Ishizaki, Yuta; Ohtsuka, Masanori; Nakayoshi, Takaharu; Ueno, Takafumi; Shiba, Naoto; Fukumoto, Yoshihiro

2017-01-01

Background The lower limb muscle may play an important role in decreasing the heart’s pumping workload. Aging and inactivity cause atrophy and weakness of the muscle, leading to a loss of the heart-assisting role. An electrical lower limb muscle stimulator can prevent atrophy and weakness more effectively than conventional resistance training; however, it has been reported to increase the heart’s pumping workload in some situations. Therefore, more effective tools should be developed. Methods We newly developed a cardiac cycle-synchronized electrical lower limb muscle stimulator by combining a commercially available electrocardiogram monitor and belt electrode skeletal muscle electrical stimulator, making it possible to achieve strong and wide but not painful muscle contractions. Then, we tested the stimulator in 11 healthy volunteers to determine whether the special equipment enabled lower limb muscle training without harming the hemodynamics using plethysmography and a percutaneous cardiac output analyzer. Results In 9 of 11 subjects, the stimulator generated diastolic augmentation waves on the dicrotic notches and end-diastolic pressure reduction waves on the plethysmogram waveforms of the brachial artery, showing analogous waveforms in the intra-aortic balloon pumping heart-assisting therapy. The heart rate, stroke volume, and cardiac output significantly increased during the stimulation. There was no change in the systolic or diastolic blood pressure during the stimulation. Conclusion Cardiac cycle-synchronized electrical muscle stimulation for the lower limbs may enable muscle training without harmfully influencing the hemodynamics and with a potential to reduce the heart’s pumping workload, suggesting a promising tool for effectively treating both locomotor and cardiovascular disorders. PMID:29117189

Evaluation of electrical conductivity of Cu and Al through sub microsecond underwater electrical wire explosion

NASA Astrophysics Data System (ADS)

Sheftman, D.; Shafer, D.; Efimov, S.; Krasik, Ya. E.

2012-03-01

Sub-microsecond timescale underwater electrical wire explosions using Cu and Al materials have been conducted. Current and voltage waveforms and time-resolved streak images of the discharge channel, coupled to 1D magneto-hydrodynamic simulations, have been used to determine the electrical conductivity of the metals for the range of conditions between hot liquid metal and strongly coupled non-ideal plasma, in the temperature range of 10-60 KK. The results of these studies showed that the conductivity values obtained are typically lower than those corresponding to modern theoretical electrical conductivity models and provide a transition between the conductivity values obtained in microsecond time scale explosions and those obtained in nanosecond time scale wire explosions. In addition, the measured wire expansion shows good agreement with equation of state tables.

Ring Current He Ion Control by Bounce Resonant ULF Waves

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Gerrard, Andrew J.; Lanzerotti, Louis J.; Soto-Chavez, Rualdo; Cohen, Ross J.; Manweiler, Jerry W.

2017-12-01

Ring current energy He ion (˜65 keV to ˜520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (˜9 h) of the spacecraft and is observed to be ˜50-100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of tens of seconds. These periods correspond to the bounce resonant timescales of the ring current He ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately 2 years) shows that the wave and He ion flux variations are generally anticorrelated, suggesting the bounce resonant pitch angle scattering process as a major component in the scattering of He ions.

Linear diffusion into a Faraday cage.

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

Warne, Larry Kevin; Lin, Yau Tang; Merewether, Kimball O.

2011-11-01

Linear lightning diffusion into a Faraday cage is studied. An early-time integral valid for large ratios of enclosure size to enclosure thickness and small relative permeability ({mu}/{mu}{sub 0} {le} 10) is used for this study. Existing solutions for nearby lightning impulse responses of electrically thick-wall enclosures are refined and extended to calculate the nearby lightning magnetic field (H) and time-derivative magnetic field (HDOT) inside enclosures of varying thickness caused by a decaying exponential excitation. For a direct strike scenario, the early-time integral for a worst-case line source outside the enclosure caused by an impulse is simplified and numerically integrated tomore » give the interior H and HDOT at the location closest to the source as well as a function of distance from the source. H and HDOT enclosure response functions for decaying exponentials are considered for an enclosure wall of any thickness. Simple formulas are derived to provide a description of enclosure interior H and HDOT as well. Direct strike voltage and current bounds for a single-turn optimally-coupled loop for all three waveforms are also given.« less

High-frequency and time resolution rocket observations of structured low- and medium-frequency whistler mode emissions in the auroral ionosphere

NASA Astrophysics Data System (ADS)

LaBelle, J.; McAdams, K. L.; Trimpi, M. L.

High bandwidth electric field waveform measurements on a recent auroral sounding rocket reveal structured whistler mode signals at 400-800 kHz. These are observed intermittently between 300 and 500 km with spectral densities 0-10 dB above the detection threshold of 1.5×10-11V2/m2Hz. The lack of correlation with local particle measurements suggests a remote source. The signals are composed of discrete structures, in one case having bandwidths of about 10 kHz and exhibiting rapid frequency variations of the order of 200 kHz per 100 ms. In one case, emissions near the harmonic of the whistler mode signals are detected simultaneously. Current theories of auroral zone whistler mode emissions have not been applied to explain quantitatively the fine structure of these signals, which resemble auroral kilometric radiation (AKR) rather than auroral hiss.

Nonlinear FDTD Analysis of Lightning-Generated Sferics

NASA Astrophysics Data System (ADS)

Erdman, A.; Moore, R. C.

2017-12-01

Lightning strikes are extremely powerful natural events producing wideband electromagnetic waves. The EMP radiation and quasi-electrostatic field changes from powerful lightning discharges are capable of directly heating and ionizing the lower ionosphere. These changes to the electrical parameters of the lower ionosphere in turn modify the way different components of the wideband sferic propagate through and reflect from the lower ionosphere. Here we present the results of a new FDTD model that utilizes a 2D cylindrically symmetric grid with second-order accurate centered-difference differentials to evaluate a large number of chemical reactions pertinent to the D-region in order to update the electron density and conductivity every iteration. Using this model, we are able to evaluate the impact of lightning strikes of varying magnitude and analyze the role of ionospheric self-action in changing in the sferic waveform observed on the ground.

Finite difference methods for transient signal propagation in stratified dispersive media

NASA Technical Reports Server (NTRS)

Lam, D. H.

1975-01-01

Explicit difference equations are presented for the solution of a signal of arbitrary waveform propagating in an ohmic dielectric, a cold plasma, a Debye model dielectric, and a Lorentz model dielectric. These difference equations are derived from the governing time-dependent integro-differential equations for the electric fields by a finite difference method. A special difference equation is derived for the grid point at the boundary of two different media. Employing this difference equation, transient signal propagation in an inhomogeneous media can be solved provided that the medium is approximated in a step-wise fashion. The solutions are generated simply by marching on in time. It is concluded that while the classical transform methods will remain useful in certain cases, with the development of the finite difference methods described, an extensive class of problems of transient signal propagating in stratified dispersive media can be effectively solved by numerical methods.

Simulation of Ion Motion in FAIMS through Combined Use of SIMION and Modified SDS

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

Prasad, Satendra; Tang, Keqi; Manura, David

2009-11-01

Over the years, the use of Field Asymmetric Ion Mobility Spectrometry (FAIMS) has grown with applications spanning from explosives detection to separation of complex biological mixtures. Although, the principles of ion separation in FAIMS is understood and comprehensively characterized, little effort has been made in developing commercially available computational tools that can simulate ion motion in FAIMS. Such a tool could be of great value for refining theory, optimizing the performance of the instrument for specific applications, and in modeling the fringe-fields caused by rf decay at the entrance and exit of FAIMS which can significantly affect ion transmission. Anmore » algorithm using SIMIONTM as its core structure was developed in this study to realistically compute ion trajectory at different ratios of electric field to buffer gas number density (E/N). The E/N can vary from a few Td to ~80 Td in FAIMS as created by an asymmetric square waveform. The Statistical Diffusion Simulation (SDS) model was further incorporated in the algorithm to simulate the ion diffusion in the FAIMS gap. The algorithm was validated using a FAIMS analyzer model similar to the Sionex Corporation model SVAC in terms of its dimensions and geometry. Hydroxyproline and Leucine ions with similar reduced mobility Ko (2.17 and 2.18 cm2.V-1.s-1, respectively) were used as model ions to test the new algorithm and demonstrate the effects of gas flow and waveform (voltage pulse amplitude and frequency) on peak shape and ion current transmission. Simulation results from three ion types: O2-(H2O)3, (A type), (C3H6O)2H+ (B type), and (C12H24O)2H+ (C type) were then compared with the experimental data (available in the literature). The SIMION-SDS-Field Dependent Mobility Calculation (FDMC) algorithm provided good agreement with experimental measurements of the ion peak position in FAIMS compensation voltage (CV) spectrum, peak width, and the ion transmission over a broad range of E/N.« less

VHF Lightning Spectra Determined from Satellite-based RF Sensors

NASA Astrophysics Data System (ADS)

Behnke, S. A.; Light, T. E.

2017-12-01

Electric field waveforms of narrow bipolar events (NBE) and positive return strokes (RS) collected by the FORTE satellite have been analyzed using Fourier methods to determine the frequency dependence of each event's amplitude spectrum. The FORTE satellite was launched in 1997 and had an RF payload consisting of a two-polarization log periodic antenna and two tunable RF receivers. Receiver 1 had dual 22 MHz passbands and Receiver 2 had an 85 MHz passband. Data collection was triggered by looking for coincidence in several 1 MHz-wide trigger sub-bands, which enabled triggering on relatively weak lightning events compared to previous satellite sensors. Receiver 1 was used for the first two years of FORTE's operation and Receiver 2 was used for the following two years; during this tenure over 2 million events were detected. A tightly constrained event classification algorithm identified NBE and RS waveforms using data in three sub-bands: 28-48 MHz and 120-140 MHz from Receiver 1, and 30-80 MHz from Receiver 2. The higher bands of Receiver 2 (100-300 MHz) were not explicitly excluded; the algorithm simply did not find events in the higher bands that met its criteria. The amplitude spectra for both NBE and RS waveforms was found to fall off as approximately f-1 in the 28-48 and 30-80 MHz sub-bands and as f-5 in the 120-140 MHz band. In the 28-48 MHz sub-band a distinct subset of events were identified in the return stroke data set that were relatively narrow (< 20 us) with a positive spectral slope ( +1). This study expands the frequency range over which previous spectral analysis has been done, well into the VHF. Prior studies were ground-based and thus had an upper frequency limit of 20 MHz due to signal attenuation at higher frequencies.

Imaging electrical conductivity, permeability, and/or permittivity contrasts using the Born Scattering Inversion (BSI)

NASA Astrophysics Data System (ADS)

Darrh, A.; Downs, C. M.; Poppeliers, C.

2017-12-01

Born Scattering Inversion (BSI) of electromagnetic (EM) data is a geophysical imaging methodology for mapping weak conductivity, permeability, and/or permittivity contrasts in the subsurface. The high computational cost of full waveform inversion is reduced by adopting the First Born Approximation for scattered EM fields. This linearizes the inverse problem in terms of Born scattering amplitudes for a set of effective EM body sources within a 3D imaging volume. Estimation of scatterer amplitudes is subsequently achieved by solving the normal equations. Our present BSI numerical experiments entail Fourier transforming real-valued synthetic EM data to the frequency-domain, and minimizing the L2 residual between complex-valued observed and predicted data. We are testing the ability of BSI to resolve simple scattering models. For our initial experiments, synthetic data are acquired by three-component (3C) electric field receivers distributed on a plane above a single point electric dipole within a homogeneous and isotropic wholespace. To suppress artifacts, candidate Born scatterer locations are confined to a volume beneath the receiver array. Also, we explore two different numerical linear algebra algorithms for solving the normal equations: Damped Least Squares (DLS), and Non-Negative Least Squares (NNLS). Results from NNLS accurately recover the source location only for a large dense 3C receiver array, but fail when the array is decimated, or is restricted to horizontal component data. Using all receiver stations and all components per station, NNLS results are relatively insensitive to a sub-sampled frequency spectrum, suggesting that coarse frequency-domain sampling may be adequate for good target resolution. Results from DLS are insensitive to diminishing array density, but contain spatially oscillatory structure. DLS-generated images are consistently centered at the known point source location, despite an abundance of surrounding structure.

Successful application of frequency-domain airborne electromagnetic system with a grounded electric source

NASA Astrophysics Data System (ADS)

Kang, L.; Lin, J.; Liu, C.; Zhou, H.; Ren, T.; Yao, Y.

2017-12-01

A new frequency-domain AEM system with a grounded electric source, which was called ground-airborne frequency-domain electromagnetic (GAFEM) system, was proposed to extend penetration depth without compromising the resolution and detection efficiency. In GAFEM system, an electric source was placed on the ground to enlarge the strength of response signals. UVA was chosen as aircraft to reduce interaction noise and improve its ability to adapt to complex terrain. Multi-source and multi-frequency emission method has been researched and applied to improve the efficiency of GAFEM system. 2n pseudorandom sequence was introduced as transmitting waveform, to ensure resolution and detection efficiency. Inversion-procedure based on full-space apparent resistivity formula was built to realize GAFEM method and extend the survey area to non-far field. Based on GAFEM system, two application was conducted in Changchun, China, to map the deep conductive structure. As shown in the results of this exploration, GAFEM system shows its effectiveness to conductive structure, obtaining a depth of about 1km with a source-receiver distance of over 6km. And it shows the same level of resolution with CSAMT method with an over 10 times of efficiency. This extended a range of important applications where the terrain is too complex to be accessed or large penetration depth is required in a large survey area.

Digital slip frequency generator and method for determining the desired slip frequency

DOEpatents

Klein, Frederick F.

1989-01-01

The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

Real-Time Control of the Embedded Waveform for External Defibrillation

DTIC Science & Technology

2001-10-25

independently from transthoracic electrical impedance changes during shock time. Keywords - External defibrillation, real-time control I. INTRODUCTION ...Additional such possibilities may be useful for development a new electrotherapy methods, as electrochemotherapy for cancer treatment [6]. II...Department, Moscow State Institute of Electronic Technology , Moscow, Russia Fig.1. High voltage delivery unit. Report Documentation Page Report Date 25

Visualizing the deep end of sound: plotting multi-parameter results from infrasound data analysis

NASA Astrophysics Data System (ADS)

Perttu, A. B.; Taisne, B.

2016-12-01

Infrasound is sound below the threshold of human hearing: approximately 20 Hz. The field of infrasound research, like other waveform based fields relies on several standard processing methods and data visualizations, including waveform plots and spectrograms. The installation of the International Monitoring System (IMS) global network of infrasound arrays, contributed to the resurgence of infrasound research. Array processing is an important method used in infrasound research, however, this method produces data sets with a large number of parameters, and requires innovative plotting techniques. The goal in designing new figures is to be able to present easily comprehendible, and information-rich plots by careful selection of data density and plotting methods.

Discharge processes and an electrical model of atmospheric pressure plasma jets in argon

NASA Astrophysics Data System (ADS)

Fang, Zhi; Shao, Tao; Yang, Jing; Zhang, Cheng

2016-01-01

In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage. The electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images. The change in discharge mode with applied voltage amplitude was studied and characterised, and three modes of corona discharge, dielectric barrier discharge (DBD) and jet discharge were identified, which appeared in turn with increasing applied voltage and can be distinguished clearly from the measured voltage-current waveforms, light-emission images and the changing gradient of discharge power with applied voltage. Based on the experimental results and discharge mechanism analysis, an equivalent electrical model and the corresponding equivalent circuit for characterising the whole discharge processes accurately was proposed, and the three discharge stages were characterised separately. A voltage-controlled current source (VCCS) associated with a resistance and a capacitance were used to represent the DBD stage, and the plasma plume and corona discharge were modelled by a variable capacitor in series with a variable resistor. Other factors that can influence the discharge, such as lead and stray capacitance values of the circuit, were also considered in the proposed model. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

Wire bonding quality monitoring via refining process of electrical signal from ultrasonic generator

NASA Astrophysics Data System (ADS)

Feng, Wuwei; Meng, Qingfeng; Xie, Youbo; Fan, Hong

2011-04-01

In this paper, a technique for on-line quality detection of ultrasonic wire bonding is developed. The electrical signals from the ultrasonic generator supply, namely, voltage and current, are picked up by a measuring circuit and transformed into digital signals by a data acquisition system. A new feature extraction method is presented to characterize the transient property of the electrical signals and further evaluate the bond quality. The method includes three steps. First, the captured voltage and current are filtered by digital bandpass filter banks to obtain the corresponding subband signals such as fundamental signal, second harmonic, and third harmonic. Second, each subband envelope is obtained using the Hilbert transform for further feature extraction. Third, the subband envelopes are, respectively, separated into three phases, namely, envelope rising, stable, and damping phases, to extract the tiny waveform changes. The different waveform features are extracted from each phase of these subband envelopes. The principal components analysis (PCA) method is used for the feature selection in order to remove the relevant information and reduce the dimension of original feature variables. Using the selected features as inputs, an artificial neural network (ANN) is constructed to identify the complex bond fault pattern. By analyzing experimental data with the proposed feature extraction method and neural network, the results demonstrate the advantages of the proposed feature extraction method and the constructed artificial neural network in detecting and identifying bond quality.

Waveform selectivity at the same frequency.

PubMed

Wakatsuchi, Hiroki; Anzai, Daisuke; Rushton, Jeremiah J; Gao, Fei; Kim, Sanghoon; Sievenpiper, Daniel F

2015-04-13

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. Each material behaves differently in accordance with the frequency of an incoming electromagnetic wave due to the frequency dispersion or the resonance of the periodic structures. This indicates that if the frequency is fixed, the material always responds in the same manner unless it has nonlinearity. However, such nonlinearity is controlled by the magnitude of the incoming wave or other bias. Therefore, it is difficult to distinguish different incoming waves at the same frequency. Here we present a new concept of circuit-based metasurfaces to selectively absorb or transmit specific types of waveforms even at the same frequency. The metasurfaces, integrated with schottky diodes as well as either capacitors or inductors, selectively absorb short or long pulses, respectively. The two types of circuit elements are then combined to absorb or transmit specific waveforms in between. This waveform selectivity gives us another degree of freedom to control electromagnetic waves in various fields including wireless communications, as our simulation reveals that the metasurfaces are capable of varying bit error rates in response to different waveforms.

The development of two Broadband Vibration Energy Harvesters (BVEH) with adaptive conversion electronics

NASA Astrophysics Data System (ADS)

Clingman, Dan J.; Thiesen, Jack

2017-04-01

Historically, piezoelectric vibration energy harvesters have been limited to operation at a single, structurally resonant frequency. A piezoceramic energy harvester, such as a bimorph beam, operating at structural resonance exchanges energy between dynamic and strain regimes. This energy exchange increases the coupling between piezoceramic deformation and electrical charge generation. Two BVEH mechanisms are presented that exploit strain energy management to reduce inertial forces needed to deform the piezoceramic, thus increasing the coupling between structural and electrical energy conversion over a broadband vibration spectrum. Broadband vibration excitation produces a non-sinusoidal electrical wave form from the BVEH device. An adaptive energy conversion circuit was developed that exploits a buck converter to capture the complex waveform energy in a form easily used by standard electrical components.

Energy efficient neural stimulation: coupling circuit design and membrane biophysics.

PubMed

Foutz, Thomas J; Ackermann, D Michael; Kilgore, Kevin L; McIntyre, Cameron C

2012-01-01

The delivery of therapeutic levels of electrical current to neural tissue is a well-established treatment for numerous indications such as Parkinson's disease and chronic pain. While the neuromodulation medical device industry has experienced steady clinical growth over the last two decades, much of the core technology underlying implanted pulse generators remain unchanged. In this study we propose some new methods for achieving increased energy-efficiency during neural stimulation. The first method exploits the biophysical features of excitable tissue through the use of a centered-triangular stimulation waveform. Neural activation with this waveform is achieved with a statistically significant reduction in energy compared to traditional rectangular waveforms. The second method demonstrates energy savings that could be achieved by advanced circuitry design. We show that the traditional practice of using a fixed compliance voltage for constant-current stimulation results in substantial energy loss. A portion of this energy can be recuperated by adjusting the compliance voltage to real-time requirements. Lastly, we demonstrate the potential impact of axon fiber diameter on defining the energy-optimal pulse-width for stimulation. When designing implantable pulse generators for energy efficiency, we propose that the future combination of a variable compliance system, a centered-triangular stimulus waveform, and an axon diameter specific stimulation pulse-width has great potential to reduce energy consumption and prolong battery life in neuromodulation devices.

Precision measurement of electric organ discharge timing from freely moving weakly electric fish.

PubMed

Jun, James J; Longtin, André; Maler, Leonard

2012-04-01

Physiological measurements from an unrestrained, untethered, and freely moving animal permit analyses of neural states correlated to naturalistic behaviors of interest. Precise and reliable remote measurements remain technically challenging due to animal movement, which perturbs the relative geometries between the animal and sensors. Pulse-type electric fish generate a train of discrete and stereotyped electric organ discharges (EOD) to sense their surroundings actively, and rapid modulation of the discharge rate occurs while free swimming in Gymnotus sp. The modulation of EOD rates is a useful indicator of the fish's central state such as resting, alertness, and learning associated with exploration. However, the EOD pulse waveforms remotely observed at a pair of dipole electrodes continuously vary as the fish swims relative to the electrodes, which biases the judgment of the actual pulse timing. To measure the EOD pulse timing more accurately, reliably, and noninvasively from a free-swimming fish, we propose a novel method based on the principles of waveform reshaping and spatial averaging. Our method is implemented using envelope extraction and multichannel summation, which is more precise and reliable compared with other widely used threshold- or peak-based methods according to the tests performed under various source-detector geometries. Using the same method, we constructed a real-time electronic pulse detector performing an additional online pulse discrimination routine to enhance further the detection reliability. Our stand-alone pulse detector performed with high temporal precision (<10 μs) and reliability (error <1 per 10(6) pulses) and permits longer recording duration by storing only event time stamps (4 bytes/pulse).

Simulating Gravitational Wave Emission from Massive Black Hole Binaries

NASA Technical Reports Server (NTRS)

Centrella, Joan

2008-01-01

The final merger of two black holes releases a tremendous amount of energy and is one of the brightest sources in the gravitational wave sky. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of very strong gravitational fields, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute these waveforms using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. In the past few years, this situation has changed dramatically, with a series of amazing breakthroughs. This talk will focus on the recent advances that are revealing these waveforms. highlighting their astrophysical consequences and the dramatic new potential for discovery that arises when merging black holes will be observed using gravitational waves.

Observing Mergers of Nonspinning Black Hole Binaries with LISA

NASA Technical Reports Server (NTRS)

McWilliams S.; Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly Bernard J.; Thorpe, J. Ira; vanMeter, James R.

2008-01-01

Recent advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black hole coalescence. We present the application of nonspinning numerical relativity waveforms to the search for and precision measurement of black hole binary coalescences using LISA. In particular, we focus on the advances made in moving beyond the equal mass, nonspinning case into other regions of parameter space, focusing on the case of nonspinning holes with ever-increasing mass ratios. We analyze the available unequal mass merger waveforms from numerical relativity, and compare them to two models, both of which use an effective one body treatment of the inspiral, but which use fundamentally different approaches to the treatment of the merger-ringdown. We confirm the expected mass ratio scaling of the merger, and investigate the changes in waveform behavior and their observational impact with changing mass ratio. Finally, we investigate the potential contribution from the merger portion of the waveform to measurement uncertainties of the binary's parameters for the unequal mass case.

Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields

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

Noe, II, G. Timothy; Katayama, Ikufumi; Katsutani, Fumiya

Here, we have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers inmore » the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.« less

Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields

DOE PAGES

Noe, II, G. Timothy; Katayama, Ikufumi; Katsutani, Fumiya; ...

2016-12-22

Here, we have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers inmore » the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.« less

Study on characteristic frequencies of ELF emissions and estimation of ion constituents in the vicinity of magnetic equator

NASA Astrophysics Data System (ADS)

Matsuda, S.; Kasahara, Y.; Goto, Y.

2012-12-01

The AKEBONO satellite has been operated continuously over 2 cycles of solar activity. Long-term observation data obtained by the AKEBONO satellite is very valuable to clarify plasma dynamics in the magnetosphere. Recently, the mechanism of wave-particle interaction around the radiation belt has attracted considerable attention. The ELF receiver, which is a sub-system of the VLF instruments onboard AKEBONO, measures waveforms below 50Hz for one component of electric field and three components of magnetic field, or waveforms below 100Hz for one component of electric and magnetic field, respectively. It was reported that ion cyclotron waves were observed near magnetic equator by the receiver [1] . It is well known that ion cyclotron wave generally propagates with a left-handed circularly polarization, but there exists right-handed polarized ion cyclotron wave below a characteristic frequency called 'crossover' in the presence of two or more kinds of ions such as oxygen and helium ions besides proton. As the crossover frequency can be derived theoretically from relative constituents of ions in plasma, it is possible to estimate the ion constituents by identifying the crossover frequency observationally. In this study, we analyze polarization of the ion cyclotron waves observed around the magnetic equator by the ELF receiver onboard AKEBONO, and report an example of ion cyclotron wave whose polarization changes from left-handed to right-handed at crossover frequency. As a next step, we estimate the ion constituents according to the polarization analysis. Furthermore, these phenomena sometimes have characteristic lower cut-off frequencies changing along the trajectories of Akebono. According to our work, it was found that the cutoff frequency is frequently in agreement with 1/n of proton's cyclotron frequency, where "n" is integer. The lower cut-off of ion cyclotron wave can be theoretically derived considering certain ion constituents of the background cold plasma. However, it remains several different interpretations depending on the species of ions and their ion constituents. In this study, we set up the following two hypotheses which shall satisfy dozens of such phenomena observed in 1989 and 1990: 1) Constituents of major ions in the plasmasphere (i.e., H^{+}, He^{+}) happened to coincide the condition that gives observed lower cut-off frequency along the trajectory. 2) There exists minor ions (i.e., D^{+}, T^{+}) that have cyclotron frequencies at 1/n of proton's cyclotron frequency. We examine the validity of the above hypotheses referring electron density and Dst index of the corresponding period. The present study could be a promising technique to estimate ion constituents from plasma wave observation by Akebono in the radiation belt. It is also noted that it can be also applicable to the ERG mission, which is expected to provide important clues for solving plasma dynamics in the Earth's radiation belt by means of integrated observation of electric and magnetic fields, particles and waves. [1] Y. Kasahara, A. Sawada, M. Yamamoto, I. Kimura, S. Kokubun, and K. Hayashi, Ion Cyclotron Emissions Observed by the Satellite Akebono in the vicinity of the Magnetic Equator, Radio Science, 27, 347-362, 1992.

High-speed rupture during the initiation of the 2015 Bonin Islands deep earthquake

NASA Astrophysics Data System (ADS)

Zhan, Z.; Ye, L.; Shearer, P. M.; Lay, T.; Kanamori, H.

2015-12-01

Among the long-standing questions on how deep earthquakes rupture, the nucleation phase of large deep events is one of the most puzzling parts. Resolving the rupture properties of the initiation phase is difficult to achieve with far-field data because of the need for accurate corrections for structural effects on the waveforms (e.g., attenuation, scattering, and site effects) and alignment errors. Here, taking the 2015 Mw 7.9 Bonin Islands earthquake (depth = 678 km) as an example, we jointly invert its far-field P waves at multiple stations for the average rupture speed during the first second of the event. We use waveforms from a closely located aftershock as empirical Green's functions, and correct for possible differences in focal mechanisms and waveform misalignments with an iterative approach. We find that the average initial rupture speed is over 5 km/s, significantly higher than the average rupture speed of 3 km/s later in the event. This contrast suggests that rupture speeds of deep earthquakes can be highly variable during individual events and may define different stages of rupture, potentially with different mechanisms.

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

Calabrese, G.; Capineri, L., E-mail: lorenzo.capineri@unifi.it; Granato, M.

This paper describes the design of a system for the characterization of magnetic hysteresis behavior in soft ferrite magnetic cores. The proposed setup can test magnetic materials exciting them with controlled arbitrary magnetic field waveforms, including the capability of providing a DC bias, in a frequency bandwidth up to 500 kHz, with voltages up to 32 V peak-to-peak, and currents up to 10 A peak-to-peak. In order to have an accurate control of the magnetic field waveform, the system is based on a voltage controlled current source. The electronic design is described focusing on closed loop feedback stabilization and passivemore » components choice. The system has real-time hysteretic loop acquisition and visualization. The comparisons between measured hysteresis loops of sample magnetic materials and datasheet available ones are shown. Results showing frequency and thermal behavior of the hysteresis of a test sample prove the system capabilities. Moreover, the B-H loops obtained with a multiple waveforms excitation signal, including DC bias, are reported. The proposal is a low-cost and replicable solution for hysteresis characterization of magnetic materials used in power electronics.« less

DBD tranformerless power supplies: impact of the parasitic capacitances on the power transfer.

NASA Astrophysics Data System (ADS)

Diop, M. A.; Belinger, A.; Piquet, H.

2017-04-01

A new transformerless power supply for DBD application is presented here. The power supply is built with 10kV SiC MOSFET. This high voltage switches allow holding the high voltage required by the DBD. An analytical study of the converter’s operation is presented to deduce the power transmitted to the DBD. A comparison between the experimental and theoretical electrical waveforms is shown. The experimental waveforms are particularly affected by all the parasitic capacitances. When all the switches are in OFF state, oscillations cause over-voltages across the switches. An analysis of the effect of each capacitance is presented and demonstrates that the parasitic capacitances of the switches and of the inductance play a key role in the actual power transfer.

Toward rational design of electrical stimulation strategies for epilepsy control

PubMed Central

Sunderam, Sridhar; Gluckman, Bruce; Reato, Davide; Bikson, Marom

2009-01-01

Electrical stimulation is emerging as a viable alternative for epilepsy patients whose seizures are not alleviated by drugs or surgery. Its attractions are temporal and spatial specificity of action, flexibility of waveform parameters and timing, and the perception that its effects are reversible unlike resective surgery. However, despite significant advances in our understanding of mechanisms of neural electrical stimulation, clinical electrotherapy for seizures relies heavily on empirical tuning of parameters and protocols. We highlight concurrent treatment goals with potentially conflicting design constraints that must be resolved when formulating rational strategies for epilepsy electrotherapy: namely seizure reduction versus cognitive impairment, stimulation efficacy versus tissue safety, and mechanistic insight versus clinical pragmatism. First, treatment markers, objectives, and metrics relevant to electrical stimulation for epilepsy are discussed from a clinical perspective. Then the experimental perspective is presented, with the biophysical mechanisms and modalities of open-loop electrical stimulation, and the potential benefits of closed-loop control for epilepsy. PMID:19926525

Mathematical Formulation of the Remote Electric and Magnetic Emissions of the Lightning Dart Leader and Return Stroke

NASA Astrophysics Data System (ADS)

Thiemann, Edward M. B.

Lightning detection and geolocation networks have found widespread use by the utility, air traffic control and forestry industries as a means of locating strikes and predicting imminent recurrence. Accurate lightning geolocation requires detecting VLF radio emissions at multiple sites using a distributed sensor network with typical baselines exceeding 150 km, along with precision time of arrival estimation to triangulate the origin of a strike. The trend has been towards increasing network accuracy without increasing sensor density by incorporating precision GPS synchronized clocks and faster front-end signal processing. Because lightning radio waveforms evolve as they propagate over a finitely conducting earth, and that measurements for a given strike may have disparate propagation path lengths, accurate models are required to determine waveform fiducials for precise strike location. The transition between the leader phase and return stroke phase may offer such a fiducial and warrants quantitative modeling to improve strike location accuracy. The VLF spectrum of the ubiquitous downward negative lightning strike is able to be modeled by the transfer of several Coulombs of negative charge from cloud to ground in a two-step process. The lightning stepped leader ionizes a plasma channel downward from the cloud at a velocity of approximately 0.05c, leaving a column of charge in its path. Upon connection with a streamer, the subsequent return stroke initiates at or near ground level and travels upward at an average but variable velocity of 0.3c. The return stroke neutralizes any negative charge along its path. Subsequent dart leader and return strokes often travel smoothly down the heated channel left by a preceding stroke, lacking the halting motion of the preceding initial stepped leader and initial return stroke. Existing lightning models often neglect the leader current and rely on approximations when solving for the return stroke. In this thesis, I present an analytic solution to Maxwell's Equations for the lightning leader followed by a novel return stroke model. I model the leader as a downward propagating boxcar function of uniform charge density and constant velocity, and the subsequent return stroke is modeled as an upward propagating boxcar with a time dependent velocity. Charge conservation is applied to ensure self-consistency of the driving current and charge sources, and physical observations are used to support model development. The resulting transient electric and magnetic fields are presented at various distances and delay times and compared with measured waveforms and previously published models.

Computation of an ESD-induced E-field Envirnoment and Definition of a Current Injector Test set-up at Equipment Level

NASA Astrophysics Data System (ADS)

Marque, J. P.; Issac, F.; Parmantier, J. P.; Bertuol, S.

1998-11-01

The ESD-induced electromagnetic field on a S/C is computed using the 3D PIC code GEODE. Typical E-field waveforms are deduced and a new susceptibility test at equipment level is proposed as an alternative to the plane wave approach.

SPE-5 Ground-Motion Prediction at Far-Field Geophone and Accelerometer Array Sites and SPE-5 Moment and Corner-Frequency Prediction

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

Yang, Xiaoning; Patton, Howard John; Chen, Ting

2016-03-25

This report offers predictions for the SPE-5 ground-motion and accelerometer array sites. These predictions pertain to the waveform and spectral amplitude at certain geophone sites using Denny&Johnson source model and a source model derived from SPE data; waveform, peak velocity and peak acceleration at accelerometer sites using the SPE source model and the finite-difference simulation with LLNL 3D velocity model; and the SPE-5 moment and corner frequency.

Probing Behavior of Dichelops furcatus (F.) (Heteroptera: Pentatomidae) on Wheat Plants Characterized by Electropenetrography (EPG) and Histological Studies

PubMed Central

Lucini, Tiago

2017-01-01

The stink bug Dichelops furcatus (F.) (Heteroptera: Pentatomidae) has increased in abundance in recent years on the wheat, Triticum aestivum L., crop cultivated in the southern region of Brazil. To investigate the probing (stylet penetration) behaviors and nonprobing behaviors of D. furcatus on wheat plants, the electrical penetration graph or electropenetrography (EPG) technique was applied. Nine EPG waveforms (types/subtypes) were identified and described on stem and on ear head of wheat plants, as follows: Z, Np, Df1a, Df1b, Df2, Df3a, Df3b, Df4a, and Df4b. For the waveforms Df1, Df2, Df3, and Df4, stylets were severed to determine, via histological studies, the location of the stylet tip and/or salivary sheath tip in plant tissue. Waveform Z was visually correlated with the bug standing still on the plant surface, whereas during Np the bug was walking. Df1a and Df1b represent initial stylet insertion, deep penetration of the stylets into the plant tissue, and secretion of salivary sheath. Df2 represents xylem sap ingestion on stem and on ear head. Waveforms Df3a and Df4a were related to the cell rupturing feeding strategy (laceration and maceration tactics) on stem and on ear head (seed endosperm), respectively. Waveforms Df3b and Df4b represent ingestion of cellular contents derived from cell rupturing activities on stem and on ear head (seed endosperm), respectively. With this fundamental knowledge in hand, future studies can use EPG to develop novel pest management solutions. PMID:28931161

Comparison of Discrete-return ranging and Full-waveform digitization for Bathymetric Lidar Mapping of a Shallow Water Bay

NASA Astrophysics Data System (ADS)

Starek, M. J.; Fernandez-diaz, J.; Pan, Z.; Glennie, C. L.; Shrestha, R. L.; Gibeaut, J. C.; Singhania, A.

2013-12-01

Researchers with the National Center for Airborne Laser Mapping (NCALM) at the University of Houston (UH) and the Coastal and Marine Geospatial Sciences Lab (CMGL) of the Harte Research Institute at Texas A&M University-Corpus Christi conducted a coordinated airborne and field-based survey of the Redfish Bay State Scientific Area to investigate the capabilities of shallow water bathymetric lidar for benthic mapping. Redfish Bay, located along the middle Texas coast of the Gulf of Mexico, is a state scientific area designated for the purposes of protecting and studying the native seagrasses. The mapped region is very shallow (< 1 m in most locations) and consists of a variety of benthic cover including sandy bottom, oyster reef, subaqueous vegetation, and submerged structures. For this survey, UH acquired high resolution (2.5 shots per square meter) bathymetry data using their new Optech Aquarius 532 nm green lidar. The field survey conducted by CMGL used an airboat to collect in-situ radiometer measurements, GPS position, depth, and ground-truth data of benthic type at over 80 locations within the bay. The return signal of an Aquarius lidar pulse is analyzed in real time by a hardware-based constant fraction discriminator (CFD) to detect returns from the surface and determine ranges (x,y,z points). This approach is commonly called discrete-return ranging, and Aquarius can record up to 4 returns per an emitted laser pulse. In contrast, full-waveform digitization records the incoming energy of an emitted pulse by sampling it at very high-frequency. Post-processing algorithms can then be applied to detect returns (ranges) from the digitized waveform. For this survey, a waveform digitizer was simultaneously operated to record the return waveforms at a rate of 1GHz with 12 bit dynamic range. High-resolution digital elevation models (DEMs) of the topo-bathymetry were derived from the discrete-return and full-waveform data to evaluate the relative and absolute accuracy using the collected ground-truth data. Results of this evaluation will be presented including an overview of the method used to extract peaks from the waveform data. Potential advantages and disadvantages of the different ranging modes in terms of observed accuracy, increased processing load, and information gain will also be discussed.

Studies of earthquakes and microearthquakes using near-field seismic and geodetic observations

NASA Astrophysics Data System (ADS)

O'Toole, Thomas Bartholomew

The Centroid-Moment Tensor (CMT) method allows an optimal point-source description of an earthquake to be recovered from a set of seismic observations, and, for over 30 years, has been routinely applied to determine the location and source mechanism of teleseismically recorded earthquakes. The CMT approach is, however, entirely general: any measurements of seismic displacement fields could, in theory, be used within the CMT inversion formulation, so long as the treatment of the earthquake as a point source is valid for that data. We modify the CMT algorithm to enable a variety of near-field seismic observables to be inverted for the source parameters of an earthquake. The first two data types that we implement are provided by Global Positioning System receivers operating at sampling frequencies of 1,Hz and above. When deployed in the seismic near field, these instruments may be used as long-period-strong-motion seismometers, recording displacement time series that include the static offset. We show that both the displacement waveforms, and static displacements alone, can be used to obtain CMT solutions for moderate-magnitude earthquakes, and that performing analyses using these data may be useful for earthquake early warning. We also investigate using waveform recordings - made by conventional seismometers deployed at the surface, or by geophone arrays placed in boreholes - to determine CMT solutions, and their uncertainties, for microearthquakes induced by hydraulic fracturing. A similar waveform inversion approach could be applied in many other settings where induced seismicity and microseismicity occurs..

Airborne detection of oceanic turbidity cell structure using depth-resolved laser-induced water Raman backscatter

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne laser-induced, depth-resolved water Raman backscatter is useful in the detection and mapping of water optical transmission variations. This test, together with other field experiments, has identified the need for additional field experiments to resolve the degree of the contribution to the depth-resolved, Raman-backscattered signal waveform that is due to (1) sea surface height or elevation probability density; (2) off-nadir laser beam angle relative to the mean sea surface; and (3) the Gelbstoff fluorescence background, and the analytical techniques required to remove it. When converted to along-track profiles, the waveforms obtained reveal cells of a decreased Raman backscatter superimposed on an overall trend of monotonically decreasing water column optical transmission.

Acoustic dipole radiation based electrical impedance contrast imaging approach of magnetoacoustic tomography with magnetic induction.

PubMed

Sun, Xiaodong; Fang, Dawei; Zhang, Dong; Ma, Qingyu

2013-05-01

Different from the theory of acoustic monopole spherical radiation, the acoustic dipole radiation based theory introduces the radiation pattern of Lorentz force induced dipole sources to describe the principle of magnetoacoustic tomography with magnetic induction (MAT-MI). Although two-dimensional (2D) simulations have been studied for cylindrical phantom models, layer effects of the dipole sources within the entire object along the z direction still need to be investigated to evaluate the performance of MAT-MI for different geometric specifications. The purpose of this work is further verifying the validity and generality of acoustic dipole radiation based theory for MAT-MI with two new models in different shapes, dimensions, and conductivities. Based on the theory of acoustic dipole radiation, the principles of MAT-MI were analyzed with derived analytic formulae. 2D and 3D numerical studies for two new models of aluminum foil and cooked egg were conducted to simulate acoustic pressures and corresponding waveforms, and 2D images of the scanned layers were reconstructed with the simplified back projection algorithm for the waveforms collected around the models. The spatial resolution for conductivity boundary differentiation was also analyzed with different foil thickness. For comparison, two experimental measurements were conducted for a cylindrical aluminum foil phantom and a shell-peeled cooked egg. The collected waveforms and the reconstructed images of the scanned layers were achieved to verify the validation of the acoustic dipole radiation based theory for MAT-MI. Despite the difference between the 2D and 3D simulated pressures, good consistence of the collected waveforms proves that wave clusters are generated by the abrupt pressure changes with bipolar vibration phases, representing the opposite polarities of the conductivity changes along the measurement direction. The configuration of the scanned layer can be reconstructed in terms of shape and size, and the conductivity boundaries are displayed in stripes with different contrast and bipolar intensities. Layer effects are demonstrated to have little influence on the collected waveforms and the reconstructed images of the scanned layers for the two new models. The experimental results have good agreements with numerical simulations, and the reconstructed 2D images provide conductivity configurations in the scanned layers of the aluminum foil and the egg models. It can be concluded that the acoustic pressure of MAT-MI is produced by the divergence of the induced Lorentz force, and the collected waveforms comprise wave clusters with bipolar vibration phases and different amplitudes, providing the information of conductivity boundaries in the scanned layer. With the simplified back projection algorithm for diffraction sources, collected waveforms can be used to reconstruct 2D conductivity contrast image and the conductivity configuration in the scanned layer can be obtained in terms of shape and size in stripes with the spatial resolution of the acoustic wavelength. The favorable results further verify the validity and generality of the acoustic dipole radiation based theory and suggest the feasibility of MAT-MI as an effective electrical impedance contrast imaging approach for medical imaging.

Sensitivity Kernels for the Cross-Convolution Measure: Eliminate the Source in Waveform Tomography

NASA Astrophysics Data System (ADS)

Menke, W. H.

2017-12-01

We use the adjoint method to derive sensitivity kernels for the cross-convolution measure, a goodness-of-fit criterion that is applicable to seismic data containing closely-spaced multiple arrivals, such as reverberating compressional waves and split shear waves. In addition to a general formulation, specific expressions for sensitivity with respect to density, Lamé parameter and shear modulus are derived for a isotropic elastic solid. As is typical of adjoint methods, the kernels depend upon an adjoint field, the source of which, in this case, is the reference displacement field, pre-multiplied by a matrix of cross-correlations of components of the observed field. We use a numerical simulation to evaluate the resolving power of a topographic inversion that employs the cross-convolution measure. The estimated resolving kernel shows is point-like, indicating that the cross-convolution measure will perform well in waveform tomography settings.

Strategies to minimize cognitive side effects with ECT: aspects of ECT technique.

PubMed

Prudic, Joan

2008-03-01

The adverse cognitive effects of electroconvulsive therapy are important limitations in the use of this treatment that continues to be a significant therapeutic strategy after 7 decades of use. Among the approaches to mitigation of these side effects are considerations involving the prescription and manipulation of the electrical stimulus itself. The impact of the following electrical factors on the cognitive outcomes of electroconvulsive therapy are surveyed: efficiency of the stimulus as expressed in electrical waveform; targeting of the stimulus, the major concept underlying electrode placement; stimulus dosing; and frequency and number of treatments. The current state of development of knowledge in these areas is summarized, and methods to achieve the best cognitive outcomes without sacrificing clinical efficacy are discussed. Future trends in the further optimization of the electrical stimulus are briefly mentioned.

Measurement and numerical simulation of high intensity focused ultrasound field in water

NASA Astrophysics Data System (ADS)

Lee, Kang Il

2017-11-01

In the present study, the acoustic field of a high intensity focused ultrasound (HIFU) transducer in water was measured by using a commercially available needle hydrophone intended for HIFU use. To validate the results of hydrophone measurements, numerical simulations of HIFU fields were performed by integrating the axisymmetric Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation from the frequency-domain perspective with the help of a MATLAB-based software package developed for HIFU simulation. Quantitative values for the focal waveforms, the peak pressures, and the size of the focal spot were obtained in various regimes of linear, quasilinear, and nonlinear propagation up to the source pressure levels when the shock front was formed in the waveform. The numerical results with the HIFU simulator solving the KZK equation were compared with the experimental data and found to be in good agreement. This confirms that the numerical simulation based on the KZK equation is capable of capturing the nonlinear pressure field of therapeutic HIFU transducers well enough to make it suitable for HIFU treatment planning.

Adaptive multi-step Full Waveform Inversion based on Waveform Mode Decomposition

NASA Astrophysics Data System (ADS)

Hu, Yong; Han, Liguo; Xu, Zhuo; Zhang, Fengjiao; Zeng, Jingwen

2017-04-01

Full Waveform Inversion (FWI) can be used to build high resolution velocity models, but there are still many challenges in seismic field data processing. The most difficult problem is about how to recover long-wavelength components of subsurface velocity models when seismic data is lacking of low frequency information and without long-offsets. To solve this problem, we propose to use Waveform Mode Decomposition (WMD) method to reconstruct low frequency information for FWI to obtain a smooth model, so that the initial model dependence of FWI can be reduced. In this paper, we use adjoint-state method to calculate the gradient for Waveform Mode Decomposition Full Waveform Inversion (WMDFWI). Through the illustrative numerical examples, we proved that the low frequency which is reconstructed by WMD method is very reliable. WMDFWI in combination with the adaptive multi-step inversion strategy can obtain more faithful and accurate final inversion results. Numerical examples show that even if the initial velocity model is far from the true model and lacking of low frequency information, we still can obtain good inversion results with WMD method. From numerical examples of anti-noise test, we see that the adaptive multi-step inversion strategy for WMDFWI has strong ability to resist Gaussian noise. WMD method is promising to be able to implement for the land seismic FWI, because it can reconstruct the low frequency information, lower the dominant frequency in the adjoint source, and has a strong ability to resist noise.

Modeling lidar waveforms with time-dependent stochastic radiative transfer theory for remote estimations of forest structure

NASA Astrophysics Data System (ADS)

Kotchenova, Svetlana Y.; Shabanov, Nikolay V.; Knyazikhin, Yuri; Davis, Anthony B.; Dubayah, Ralph; Myneni, Ranga B.

2003-08-01

Large footprint waveform-recording laser altimeters (lidars) have demonstrated a potential for accurate remote sensing of forest biomass and structure, important for regional and global climate studies. Currently, radiative transfer analyses of lidar data are based on the simplifying assumption that only single scattering contributes to the return signal, which may lead to errors in the modeling of the lower portions of recorded waveforms in the near-infrared spectrum. In this study we apply time-dependent stochastic radiative transfer (RT) theory to model the propagation of lidar pulses through forest canopies. A time-dependent stochastic RT equation is formulated and solved numerically. Such an approach describes multiple scattering events, allows for realistic representation of forest structure including foliage clumping and gaps, simulates off-nadir and multiangular observations, and has the potential to provide better approximations of return waveforms. The model was tested with field data from two conifer forest stands (southern old jack pine and southern old black spruce) in central Canada and two closed canopy deciduous forest stands (with overstory dominated by tulip poplar) in eastern Maryland. Model-simulated signals were compared with waveforms recorded by the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) over these regions. Model simulations show good agreement with SLICER signals having a slow decay of the waveform. The analysis of the effects of multiple scattering shows that multiply scattered photons magnify the amplitude of the reflected signal, especially that originating from the lower portions of the canopy.

Stereotyped high-frequency oscillations discriminate seizure onset zones and critical functional cortex in focal epilepsy.

PubMed

Liu, Su; Gurses, Candan; Sha, Zhiyi; Quach, Michael M; Sencer, Altay; Bebek, Nerses; Curry, Daniel J; Prabhu, Sujit; Tummala, Sudhakar; Henry, Thomas R; Ince, Nuri F

2018-01-30

High-frequency oscillations in local field potentials recorded with intracranial EEG are putative biomarkers of seizure onset zones in epileptic brain. However, localized 80-500 Hz oscillations can also be recorded from normal and non-epileptic cerebral structures. When defined only by rate or frequency, physiological high-frequency oscillations are indistinguishable from pathological ones, which limit their application in epilepsy presurgical planning. We hypothesized that pathological high-frequency oscillations occur in a repetitive fashion with a similar waveform morphology that specifically indicates seizure onset zones. We investigated the waveform patterns of automatically detected high-frequency oscillations in 13 epilepsy patients and five control subjects, with an average of 73 subdural and intracerebral electrodes recorded per patient. The repetitive oscillatory waveforms were identified by using a pipeline of unsupervised machine learning techniques and were then correlated with independently clinician-defined seizure onset zones. Consistently in all patients, the stereotypical high-frequency oscillations with the highest degree of waveform similarity were localized within the seizure onset zones only, whereas the channels generating high-frequency oscillations embedded in random waveforms were found in the functional regions independent from the epileptogenic locations. The repetitive waveform pattern was more evident in fast ripples compared to ripples, suggesting a potential association between waveform repetition and the underlying pathological network. Our findings provided a new tool for the interpretation of pathological high-frequency oscillations that can be efficiently applied to distinguish seizure onset zones from functionally important sites, which is a critical step towards the translation of these signature events into valid clinical biomarkers.awx374media15721572971001. © The Author(s) (2018). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Waveform Design for Wireless Power Transfer

NASA Astrophysics Data System (ADS)

Clerckx, Bruno; Bayguzina, Ekaterina

2016-12-01

Far-field Wireless Power Transfer (WPT) has attracted significant attention in recent years. Despite the rapid progress, the emphasis of the research community in the last decade has remained largely concentrated on improving the design of energy harvester (so-called rectenna) and has left aside the effect of transmitter design. In this paper, we study the design of transmit waveform so as to enhance the DC power at the output of the rectenna. We derive a tractable model of the non-linearity of the rectenna and compare with a linear model conventionally used in the literature. We then use those models to design novel multisine waveforms that are adaptive to the channel state information (CSI). Interestingly, while the linear model favours narrowband transmission with all the power allocated to a single frequency, the non-linear model favours a power allocation over multiple frequencies. Through realistic simulations, waveforms designed based on the non-linear model are shown to provide significant gains (in terms of harvested DC power) over those designed based on the linear model and over non-adaptive waveforms. We also compute analytically the theoretical scaling laws of the harvested energy for various waveforms as a function of the number of sinewaves and transmit antennas. Those scaling laws highlight the benefits of CSI knowledge at the transmitter in WPT and of a WPT design based on a non-linear rectenna model over a linear model. Results also motivate the study of a promising architecture relying on large-scale multisine multi-antenna waveforms for WPT. As a final note, results stress the importance of modeling and accounting for the non-linearity of the rectenna in any system design involving wireless power.

Modeling Gravitational Radiation Waveforms from Black Hole Mergers

NASA Technical Reports Server (NTRS)

Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.

2006-01-01

Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.

Effects of different excitation waveforms on detection and characterisation of delamination in PV modules by active infrared thermography

NASA Astrophysics Data System (ADS)

Sinha, Archana; Gupta, Rajesh

2017-10-01

Delamination significantly affects the performance and reliability of photovoltaic (PV) modules. Recently, an active infrared thermography approach using step heating has been exploited for the detection and characterisation of delamination in PV modules. However, step heating takes longer observation time and causes overheating problems. This paper presents the effects of different thermal excitation waveforms namely rectangular, half-sine and short pulse, on the detection and characterisation of delamination in PV module by experiments and simulations. For simulation, a 3-dimensional electro-thermal model of heat conduction, based on resistance-capacitance network approach, has been exploited to study the variation in maximum thermal contrast and peak contrast time with the delamination thickness and heating parameters. Results show that the rectangular waveform provides better detection of delamination due to higher absolute contrast, while the half-sine waveform allows better characterisation of delamination in the PV modules with low-cost and low-power heat source. The high-energy short pulse enabled quick visualisation of delamination, but has limited practical implementation. The advantages and limitations of each waveform have been highlighted to assess the specific requirement for appropriate choice in the non-destructive thermographic inspection of delamination in PV modules at the manufacturing units or outdoor fields.

Processing and evaluation of riverine waveforms acquired by an experimental bathymetric LiDAR

NASA Astrophysics Data System (ADS)

Kinzel, P. J.; Legleiter, C. J.; Nelson, J. M.

2010-12-01

Accurate mapping of fluvial environments with airborne bathymetric LiDAR is challenged not only by environmental characteristics but also the development and application of software routines to post-process the recorded laser waveforms. During a bathymetric LiDAR survey, the transmission of the green-wavelength laser pulses through the water column is influenced by a number of factors including turbidity, the presence of organic material, and the reflectivity of the streambed. For backscattered laser pulses returned from the river bottom and digitized by the LiDAR detector, post-processing software is needed to interpret and identify distinct inflections in the reflected waveform. Relevant features of this energy signal include the air-water interface, volume reflection from the water column itself, and, ideally, a strong return from the bottom. We discuss our efforts to acquire, analyze, and interpret riverine surveys using the USGS Experimental Advanced Airborne Research LiDAR (EAARL) in a variety of fluvial environments. Initial processing of data collected in the Trinity River, California, using the EAARL Airborne Lidar Processing Software (ALPS) highlighted the difficulty of retrieving a distinct bottom signal in deep pools. Examination of laser waveforms from these pools indicated that weak bottom reflections were often neglected by a trailing edge algorithm used by ALPS to process shallow riverine waveforms. For the Trinity waveforms, this algorithm had a tendency to identify earlier inflections as the bottom, resulting in a shallow bias. Similarly, an EAARL survey along the upper Colorado River, Colorado, also revealed the inadequacy of the trailing edge algorithm for detecting weak bottom reflections. We developed an alternative waveform processing routine by exporting digitized laser waveforms from ALPS, computing the local extrema, and fitting Gaussian curves to the convolved backscatter. Our field data indicate that these techniques improved the definition of pool areas dominated by weak bottom reflections. These processing techniques are also being tested for EAARL surveys collected along the Platte and Klamath Rivers where environmental conditions have resulted in suppressed or convolved bottom reflections.

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

NASA Astrophysics Data System (ADS)

Gibson, Andrew R.; Gans, Timo

2017-11-01

The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15-20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity.

Stimulation Efficiency With Decaying Exponential Waveforms in a Wirelessly Powered Switched-Capacitor Discharge Stimulation System.

PubMed

Lee, Hyung-Min; Howell, Bryan; Grill, Warren M; Ghovanloo, Maysam

2018-05-01

The purpose of this study was to test the feasibility of using a switched-capacitor discharge stimulation (SCDS) system for electrical stimulation, and, subsequently, determine the overall energy saved compared to a conventional stimulator. We have constructed a computational model by pairing an image-based volume conductor model of the cat head with cable models of corticospinal tract (CST) axons and quantified the theoretical stimulation efficiency of rectangular and decaying exponential waveforms, produced by conventional and SCDS systems, respectively. Subsequently, the model predictions were tested in vivo by activating axons in the posterior internal capsule and recording evoked electromyography (EMG) in the contralateral upper arm muscles. Compared to rectangular waveforms, decaying exponential waveforms with time constants >500 μs were predicted to require 2%-4% less stimulus energy to activate directly models of CST axons and 0.4%-2% less stimulus energy to evoke EMG activity in vivo. Using the calculated wireless input energy of the stimulation system and the measured stimulus energies required to evoke EMG activity, we predict that an SCDS implantable pulse generator (IPG) will require 40% less input energy than a conventional IPG to activate target neural elements. A wireless SCDS IPG that is more energy efficient than a conventional IPG will reduce the size of an implant, require that less wireless energy be transmitted through the skin, and extend the lifetime of the battery in the external power transmitter.

High resolution aquifer characterization using crosshole GPR full-waveform tomography

NASA Astrophysics Data System (ADS)

Gueting, N.; Vienken, T.; Klotzsche, A.; Van Der Kruk, J.; Vanderborght, J.; Caers, J.; Vereecken, H.; Englert, A.

2016-12-01

Limited knowledge about the spatial distribution of aquifer properties typically constrains our ability to predict subsurface flow and transport. Here, we investigate the value of using high resolution full-waveform inversion of cross-borehole ground penetrating radar (GPR) data for aquifer characterization. By stitching together GPR tomograms from multiple adjacent crosshole planes, we are able to image, with a decimeter scale resolution, the dielectric permittivity and electrical conductivity of an alluvial aquifer along cross-sections of 50 m length and 10 m depth. A logistic regression model is employed to predict the spatial distribution of lithological facies on the basis of the GPR results. Vertical profiles of porosity and hydraulic conductivity from direct-push, flowmeter and grain size data suggest that the GPR predicted facies classification is meaningful with regard to porosity and hydraulic conductivity, even though the distributions of individual facies show some overlap and the absolute hydraulic conductivities from the different methods (direct-push, flowmeter, grain size) differ up to approximately one order of magnitude. Comparison of the GPR predicted facies architecture with tracer test data suggests that the plume splitting observed in a tracer experiment was caused by a hydraulically low-conductive sand layer with a thickness of only a few decimeters. Because this sand layer is identified by GPR full-waveform inversion but not by conventional GPR ray-based inversion we conclude that the improvement in spatial resolution due to full-waveform inversion is crucial to detect small-scale aquifer structures that are highly relevant for solute transport.

Acizzia solanicola (Hemiptera: Psyllidae) probing behaviour on two Solanum spp. and implications for possible pathogen spread

PubMed Central

Valenzuela, Isabel; Trebicki, Piotr; Powell, Kevin S.; Vereijssen, Jessica; Norng, Sorn

2017-01-01

Piercing-sucking insects are vectors of plant pathogens, and an understanding of their feeding behaviour is crucial for studies on insect population dynamics and pathogen spread. This study examines probing behaviour of the eggplant psyllid, Acizzia solanicola (Hemiptera: Psyllidae), using the electrical penetration graph (EPG) technique, on two widespread and common hosts: eggplant (Solanum melongena) and tobacco bush (S. mauritianum). Six EPG waveforms were observed: waveform NP (non-probing phase), waveform C (pathway phase), G (feeding activities in xylem tissues), D (first contact with phloem tissues), E1 (salivation in the sieve elements) and E2 (ingestion from phloem tissues). Results showed that A. solanicola is predominantly a phloem feeder and time spent in salivation and ingestion phases (E1 and E2) differed between hosts. Feeding was enhanced on eggplant compared to tobacco bush which showed some degree of resistance, as evidenced by shorter periods of phloem ingestion, a higher propensity to return to the pathway phase once in the sieve elements and higher number of salivation events on tobacco bush. We discuss how prolonged phloem feeding could indicate the potential for A. solanicola to become an important pest of eggplant and potential pathogen vector. PMID:28575085

Modulation of distributed feedback (DFB) laser diode with the autonomous Chua's circuit: Theory and experiment

NASA Astrophysics Data System (ADS)

Talla Mbé, Jimmi Hervé; Woafo, Paul

2018-03-01

We report on a simple way to generate complex optical waveforms with very cheap and accessible equipments. The general idea consists in modulating a laser diode with an autonomous electronic oscillator, and in the case of this study, we use a distributed feedback (DFB) laser diode pumped with an electronic Chua's circuit. Based on the adiabatic P-I characteristics of the laser diode at low frequencies, we show that when the total pump is greater than the laser threshold, it is possible to convert the electrical waveforms of the Chua's circuit into optical carriers. But, if that is not the case, the on-off dynamical behavior of the laser permits to obtain many other optical waveform signals, mainly pulses. Our numerical results are consistent with experimental measurements. The work presents the advantage of extending the range of possible chaotic dynamics of the laser diodes in the time domains (millisecond) where it is not usually expected with conventional modulation techniques. Moreover, this new technique of laser diodes modulation brings a general benefit in the physical equipment, reduces their cost and congestion so that, it can constitute a step towards photonic integrated circuits.

Redefinition of the self-bias voltage in a dielectrically shielded thin sheath RF discharge

NASA Astrophysics Data System (ADS)

Ho, Teck Seng; Charles, Christine; Boswell, Rod

2018-05-01

In a geometrically asymmetric capacitively coupled discharge where the powered electrode is shielded from the plasma by a layer of dielectric material, the self-bias manifests as a nonuniform negative charging in the dielectric rather than on the blocking capacitor. In the thin sheath regime where the ion transit time across the powered sheath is on the order of or less than the Radiofrequency (RF) period, the plasma potential is observed to respond asymmetrically to extraneous impedances in the RF circuit. Consequently, the RF waveform on the plasma-facing surface of the dielectric is unknown, and the behaviour of the powered sheath is not easily predictable. Sheath circuit models become inadequate for describing this class of discharges, and a comprehensive fluid, electrical, and plasma numerical model is employed to accurately quantify this behaviour. The traditional definition of the self-bias voltage as the mean of the RF waveform is shown to be erroneous in this regime. Instead, using the maxima of the RF waveform provides a more rigorous definition given its correlation with the ion dynamics in the powered sheath. This is supported by a RF circuit model derived from the computational fluid dynamics and plasma simulations.

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.

Digital ac monitor

DOEpatents

Hart, George W.; Kern, Jr., Edward C.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

Digital ac monitor

DOEpatents

Hart, G.W.; Kern, E.C. Jr.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

Transition in Pulsatile Pipe Flow

NASA Astrophysics Data System (ADS)

Vlachos, Pavlos; Brindise, Melissa

2016-11-01

Transition has been observed to occur in the aorta, and stenotic vessels, where pulsatile flow exists. However, few studies have investigated the characteristics and effects of transition in oscillating or pulsatile flow and none have utilized a physiological waveform. In this work, we explore transition in pipe flow using three pulsatile waveforms which all maintain the same mean and maximum flow rates and range to zero flow, as is physiologically typical. Velocity fields were obtained using planar particle image velocimetry for each pulsatile waveform at six mean Reynolds numbers ranging between 500 and 4000. Turbulent statistics including turbulent kinetic energy (TKE) and Reynolds stresses were computed. Quadrant analysis was used to identify characteristics of the production and dissipation of turbulence. Coherent structures were identified using the λci method. We developed a wavelet-Hilbert time-frequency analysis method to identify high frequency structures and compared these to the coherent structures. The results of this study demonstrate that the different pulsatile waveforms induce different levels of TKE and high frequency structures, suggesting that the rates of acceleration and deceleration influence the onset and development of transition.

Magnetic plethysmograph transducers for local blood pulse wave velocity measurement.

PubMed

Nabeel, P M; Joseph, Jayaraj; Sivaprakasam, Mohanasankar

2014-01-01

We present the design of magnetic plethysmograph (MPG) transducers for detection of blood pulse waveform and evaluation of local pulse wave velocity (PWV), for potential use in cuffless blood pressure (BP) monitoring. The sensors utilize a Hall effect magnetic field sensor to capture the blood pulse waveform. A strap based design is performed to enable reliable capture of large number of cardiac cycles with relative ease. The ability of the transducer to consistently detect the blood pulse is verified by in-vivo trials on few volunteers. A duality of such transducers is utilized to capture the local PWV at the carotid artery. The pulse transit time (PTT) between the two detected pulse waveforms, measured along a small section of the carotid artery, was evaluated using automated algorithms to ensure consistency of measurements. The correlation between the measured values of local PWV and BP was also investigated. The developed transducers provide a reliable, easy modality for detecting pulse waveform on superficial arteries. Such transducers, used for measurement of local PWV, could potentially be utilized for cuffless, continuous evaluation of BP at various superficial arterial sites.

Observing mergers of nonspinning black-hole binaries

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

McWilliams, Sean T.; Baker, John G.; Kelly, Bernard J.

2010-07-15

Advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black-hole coalescence for generic binaries. The state of the art has advanced well beyond the equal-mass case into the unequal-mass and spinning regions of parameter space. We present a study of the nonspinning portion of parameter space, primarily using an analytic waveform model tuned to available numerical data, with an emphasis on observational implications. We investigate the impact of varied mass-ratio on merger signal-to-noise ratios for several detectors, and compare our results with expectations from the test-mass limit. Wemore » note a striking similarity of the waveform phasing of the merger waveform across the available mass ratios. Motivated by this, we calculate the match between our 1:1 (equal-mass) and 4:1 mass-ratio waveforms during the merger as a function of location on the source sky, using a new formalism for the match that accounts for higher harmonics. This is an indicator of the amount of degeneracy in mass-ratio for mergers of moderate-mass-ratio systems.« less

Binary Black Holes, Gravitational Waves, and Numerical Relativity

NASA Technical Reports Server (NTRS)

Centrella, Joan

2007-01-01

Massive black hole (MBH) binaries are found at the centers of most galaxies. MBH mergers trace galaxy mergers and are strong sources of gravitational waves. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of very strong gravitational fields, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute these waveforms using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities. causing them to crash well before the black hole:, in the binary could complete even a single orbit. Recently this situation has changed dramatically, with a series of amazing breakthroughs. This presentation shows how a spacetime is constructed on a computer to build a simulation laboratory for binary black hole mergers. Focus is on the recent advances that that reveal these waveforms, and the potential for discoveries that arises when these sources are observed by LIGO and LISA.

Analysis of motor fan radiated sound and vibration waveform by automatic pattern recognition technique using "Mahalanobis distance"

NASA Astrophysics Data System (ADS)

Toma, Eiji

2018-06-01

In recent years, as the weight of IT equipment has been reduced, the demand for motor fans for cooling the interior of electronic equipment is on the rise. Sensory test technique by inspectors is the mainstream for quality inspection of motor fans in the field. This sensory test requires a lot of experience to accurately diagnose differences in subtle sounds (sound pressures) of the fans, and the judgment varies depending on the condition of the inspector and the environment. In order to solve these quality problems, development of an analysis method capable of quantitatively and automatically diagnosing the sound/vibration level of a fan is required. In this study, it was clarified that the analysis method applying the MT system based on the waveform information of noise and vibration is more effective than the conventional frequency analysis method for the discrimination diagnosis technology of normal and abnormal items. Furthermore, it was found that due to the automation of the vibration waveform analysis system, there was a factor influencing the discrimination accuracy in relation between the fan installation posture and the vibration waveform.

Observing Mergers of Non-Spinning Black-Hole Binaries

NASA Technical Reports Server (NTRS)

McWilliams, Sean T.; Boggs, William D.; Baker, John G.; Kelly, Bernard J.

2010-01-01

Advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black-hole coalescence for generic binaries. The state of the art has advanced well beyond the equal-mass case into the unequal-mass and spinning regions of parameter space. We present a study of the nonspinning portion of parameter space, primarily using an analytic waveform model tuned to available numerical data, with an emphasis on observational implications. We investigate the impact of varied m8BS ratio on merger signal-to-noise ratios (SNR) for several detectors, and compare our results with expectations from the test-mass limit. We note a striking similarity of the waveform phasing of the merger waveform across the available mass ratios. Motivated by this, we calculate the match between our equal-mass and 4:1 mass-ratio waveforms during the merger as a function of location on the source sky, using a new formalism for the match that accounts for higher harmonics. This is an indicator of the amount of degeneracy in mass ratio for mergers of moderate mass ratio systems.

Binary Black Holes, Gravitational Waves, and Numerical Relativity

NASA Technical Reports Server (NTRS)

Centrella, Joan

2007-01-01

This viewgraph presentation reviews the massive black hole (MBH) binaries that are found at the center of most galaxies, "astronomical messenger", gravitational waves (GW), and the use of numerical relativity understand the features of these phenomena. The final merger of two black holes releases a tremendous amount of energy and is one of the brightest sources in the gravitational wave sky. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of very strong gravitational fields, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute these waveforms using the methods of numerical relativity.. This talk will take you on this quest for the holy grail of numerical relativity, showing how a spacetime is constructed on a computer to build a simulation laboratory for binary black hole mergers. We will focus on the recent advances that are revealing these waveforms, and the dramatic new potential for discoveries that arises when these sources will be observed by LIGO and LISA.

Acoustic Nondestructive Evaluation of Aircraft Paneling Using Piezoelectric Sensors

DTIC Science & Technology

2012-12-01

Electromagnetic Materials Team of the U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Clinical Trials Monitoring Branch, for...connected to this clip. This electrical connection ensures single-point grounding, which has been implemented to avoid electromagnetic interference...waveform of each sensor features an electromagnetic pick-up signature that is aligned with the transduced signal but phase shifted by 180. We know to

Proceedings of Tunnel Detection Symposium on Subsurface Exploration Technology (4th) held in Golden, Colorado on 26 - 29 Apr 1993

DTIC Science & Technology

1993-04-29

characteristics such as intuition, telepathy , ESP, PSI, subconscious creativity and the likz. "Don’t do it Ruskey," they told me, "give them nuts and bolts." Nuts...basic shape of the homogeneous media response ( i.e. the primary wave). The synthetic waveforms 72 show good conformance with the field data. The minor...as a fracture halo surrounding the tunnel which is unaccounted for in the simulation. Figure 5 shows a suite of synthetic waveforms for an air tilled

Electric organ discharge diversification in mormyrid weakly electric fish is associated with differential expression of voltage-gated ion channel genes.

PubMed

Nagel, Rebecca; Kirschbaum, Frank; Tiedemann, Ralph

2017-03-01

In mormyrid weakly electric fish, the electric organ discharge (EOD) is used for species recognition, orientation and prey localization. Produced in the muscle-derived adult electric organ, the EOD exhibits a wide diversity across species in both waveform and duration. While certain defining EOD characteristics can be linked to anatomical features of the electric organ, many factors underlying EOD differentiation are yet unknown. Here, we report the differential expression of 13 Kv1 voltage-gated potassium channel genes, two inwardly rectifying potassium channel genes, two previously studied sodium channel genes and an ATPase pump in two sympatric species of the genus Campylomormyrus in both the adult electric organ and skeletal muscle. Campylomormyrus compressirostris displays a basal EOD, largely unchanged during development, while C. tshokwe has an elongated, putatively derived discharge. We report an upregulation in all Kv1 genes in the electric organ of Campylomormyrus tshokwe when compared to both skeletal muscle and C. compressirostris electric organ. This pattern of upregulation in a species with a derived EOD form suggests that voltage-gated potassium channels are potentially involved in the diversification of the EOD signal among mormyrid weakly electric fish.

Detection of inter-turn short-circuit at start-up of induction machine based on torque analysis

NASA Astrophysics Data System (ADS)

Pietrowski, Wojciech; Górny, Konrad

2017-12-01

Recently, interest in new diagnostics methods in a field of induction machines was observed. Research presented in the paper shows the diagnostics of induction machine based on torque pulsation, under inter-turn short-circuit, during start-up of a machine. In the paper three numerical techniques were used: finite element analysis, signal analysis and artificial neural networks (ANN). The elaborated numerical model of faulty machine consists of field, circuit and motion equations. Voltage excited supply allowed to determine the torque waveform during start-up. The inter-turn short-circuit was treated as a galvanic connection between two points of the stator winding. The waveforms were calculated for different amounts of shorted-turns from 0 to 55. Due to the non-stationary waveforms a wavelet packet decomposition was used to perform an analysis of the torque. The obtained results of analysis were used as input vector for ANN. The response of the neural network was the number of shorted-turns in the stator winding. Special attention was paid to compare response of general regression neural network (GRNN) and multi-layer perceptron neural network (MLP). Based on the results of the research, the efficiency of the developed algorithm can be inferred.

Multi-parameter Full-waveform Inversion for Acoustic VTI Medium with Surface Seismic Data

NASA Astrophysics Data System (ADS)

Cheng, X.; Jiao, K.; Sun, D.; Huang, W.; Vigh, D.

2013-12-01

Full-waveform Inversion (FWI) attracts wide attention recently in oil and gas industry as a new promising tool for high resolution subsurface velocity model building. While the traditional common image point gather based tomography method aims to focus post-migrated data in depth domain, FWI aims to directly fit the observed seismic waveform in either time or frequency domain. The inversion is performed iteratively by updating the velocity fields to reduce the difference between the observed and the simulated data. It has been shown the inversion is very sensitive to the starting velocity fields, and data with long offsets and low frequencies is crucial for the success of FWI to overcome this sensitivity. Considering the importance of data with long offsets and low frequencies, in most geologic environment, anisotropy is an unavoidable topic for FWI especially at long offsets, since anisotropy tends to have more pronounced effects on waves traveled for a great distance. In VTI medium, this means more horizontal velocity will be registered in middle-to-long offset data, while more vertical velocity will be registered in near-to-middle offset data. Up to date, most of real world applications of FWI still remain in isotropic medium, and only a few studies have been shown to account for anisotropy. And most of those studies only account for anisotropy in waveform simulation, but not invert for those anisotropy fields. Multi-parameter inversion for anisotropy fields, even in VTI medium, remains as a hot topic in the field. In this study, we develop a strategy for multi-parameter FWI for acoustic VTI medium with surface seismic data. Because surface seismic data is insensitivity to the delta fields, we decide to hold the delta fields unchanged during our inversion, and invert only for vertical velocity and epsilon fields. Through parameterization analysis and synthetic tests, we find that it is more feasible to invert for the parameterization as vertical and horizontal velocities instead of inverting for the parameterization as vertical velocity and epsilon fields. We develop a hierarchical approach to invert for vertical velocity first but hold epsilon unchanged and only switch to simultaneous inversion when vertical velocity inversion are approaching convergence. During simultaneous inversion, we observe significant acceleration in the convergence when incorporates second order information and preconditioning into inversion. We demonstrate the success of our strategy for VTI FWI using synthetic and real data examples from the Gulf of Mexico. Our results show that incorporation of VTI FWI improves migration of large offset acquisition data, and produces better focused migration images to be used in exploration, production and development of oil fields.

Acoustic bubble: Controlled and selective micropropulsion and chemical waveform generator

NASA Astrophysics Data System (ADS)

Ahmed, Daniel

The physics governing swimming at the microscale---where viscous forces dominate over inertial---is distinctly different than that at the macroscale. Devices capable of finely controlled swimming at the microscale could enable bold ideas such as targeted drug delivery, non-invasive microsurgery, and precise materials assembly. Progress has already been made towards such artificial microswimmers using several means of actuation: chemical reactions and applied magnetic, electric or acoustic fields. However, the prevailing goal of selective actuation of a single microswimmer from within a group, the first step towards collaborative, guided action by a group of swimmers, has so far not been achieved. Here I present a new class of microswimmer that accomplishes for the first time selective actuation (Chapter 1). The swimmer design eschews the commonly-held design paradigm that microswimmers must use non-reciprocal motion to achieve propulsion; instead, the swimmer is propelled by oscillatory motion of an air bubble trapped within the swimmer's polymer body. This oscillatory motion is driven by a low-power biocompatible acoustic field to the ambient liquid, with meaningful swimmer propulsion occurring only at resonance frequencies of the bubble. This acoustically-powered microswimmer performs controllable rapid translational and rotational motion even in highly viscous liquid. By using a group of swimmers each with a different bubble size (and thus different resonance frequencies) selective actuation of a single swimmer from among the group can be readily achieved. Cellular response to chemical microenvironments depends on the spatiotemporal characteristics of the stimulus, which is central to many biological processes including gene expression, cell migration, differentiation, apoptosis, and intercellular signaling. To date, studies have been limited to digital (or step) chemical stimulation with little control over the temporal counterparts. Microfluidic approaches have offered a higher level of sophistication in terms of liquid manipulation, however, due to low Reynolds number associated with these methods, precise temporal manipulation has remained a challenge. Furthermore, varying the sample concentration rapidly and controllably, an important task for a plethora of chemical and biological studies, has proven to be extremely difficult. Here I demonstrate (Chapter 3) a novel approach for generating chemical waveforms that permits continuous modulation of the signal characteristics including the shape, frequency, amplitude (sample concentration), and duty cycle, with frequencies reaching up to 30 Hz. Furthermore, using multiple bubbles of different sizes in a single microchannel, we show fast switching between multiple distinct stimuli, wherein the waveform of each stimulus is independently controlled. Using our device, we characterized the frequency-dependent activation and internalization of the -adrenergic receptor (beta2-AR), a prototypic G-protein coupled receptors (GPCRs) due to epinephrine. We determined that beta2-AR internalization due to epinephrine occurs on timescales between 100 ms and 5sec. The chemical waveform generation and switching method presented herein is expected to be useful for understanding the dynamics of fast biomolecular processes.

Full-waveform Inversion of Crosshole GPR Data Collected in Strongly Heterogeneous Chalk: Challenges and Pitfalls

NASA Astrophysics Data System (ADS)

Keskinen, Johanna; Looms, Majken C.; Nielsen, Lars; Klotzsche, Anja; van der Kruk, Jan; Moreau, Julien; Stemmerik, Lars; Holliger, Klaus

2015-04-01

Chalk is an important reservoir rock for hydrocarbons and for groundwater resources for many major cities. Therefore, this rock type has been extensively investigated using both geological and geophysical methods. Many applications of crosshole GPR tomography rely on the ray approximation and corresponding inversions of first break traveltimes and/or maximum first-cycle amplitudes. Due to the inherent limitations associated with such approaches, the resulting models tend to be overly smooth and cannot adequately capture the small-scale heterogeneities. In contrast, the full-waveform inversion uses all the information contained in the data and is able to provide significantly improved images. Here, we apply full-waveform inversion to crosshole GPR data to image strong heterogeneity of the chalk related to changes in lithology and porosity. We have collected a crosshole tomography dataset in an old chalk quarry in Eastern Denmark. Based on core data (including plug samples and televiewer logging data) collected in our four ~15-m-deep boreholes and results from previous related studies, it is apparent that the studied chalk is strongly heterogeneous. The upper ~7 m consist of variable coarse-grained chalk layers with numerous flint nodules. The lower half of the studied section appears to be finer-grained and contains less flint. However, still significant porosity variations are also detected in the lower half. In general, the water-saturated (watertable depth ~2 m) chalk is characterized by high porosities, and thus low velocities and high attenuation, while the flint is essentially non-porous and has correspondingly high velocities and low attenuation. Together these characteristics form a strongly heterogeneous medium, which is challenging for the full-waveform inversion to recover. Here, we address the importance of (i) adequate starting models, both in terms of the dielectric permittivity and the electrical conductivity, (ii) the estimation of the source wavelet, (iii) and the effects of data sampling density when imaging this rock type. Moreover, we discuss the resolution of the bedding recovered by the full-waveform approach. Our results show that with proper estimates of the above-mentioned prior parameters, crosshole GPR full-waveform tomography provides high-resolution images capturing a high degree of variability that standard methods cannot resolve in chalk. This in turn makes crosshole full-waveform inversion a promising tool to support time-lapse flow modelling.

Observations of lightning processes using VHF radio interferometry

NASA Technical Reports Server (NTRS)

Rhodes, C. T.; Shao, X. M.; Krehbiel, P. R.; Thomas, R.

1991-01-01

A single station, multiple baseline radio interferometer was used to locate the direction of VHF radiation from lightning discharges with microsec time resolution. Radiation source directions and electric field waveforms were analyzed for various types of breakdown events. These include initial breakdown and K type events of in-cloud activity, and the leaders of initial and subsequent strokes to ground and activity during and following return strokes. Radiation during the initial breakdown of a flash and in the early stages of initial leaders to ground is found to be similar. In both instances, the activity consists of localized bursts of radiation that are intense and slow moving. Motion within a given burst is unresolved by the interferometer. Radiation from in-cloud K type events is essentially the same as that from dart leaders; in both cases it is produced at the leading edge of a fast moving streamer that propagates along a well defined, often extensive path. K type events are sometimes terminated by fast field changes that are similar to the return stroke initiated by dart leaders; such K type events are the in-cloud analog of the dart leader return stroke process.

Variable speed wind turbine generator with zero-sequence filter

DOEpatents

Muljadi, Eduard

1998-01-01

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

Variable Speed Wind Turbine Generator with Zero-sequence Filter

DOEpatents

Muljadi, Eduard

1998-08-25

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

Variable speed wind turbine generator with zero-sequence filter

DOEpatents

Muljadi, E.

1998-08-25

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility. 14 figs.

Development of an integrated surface stimulation device for systematic evaluation of wound electrotherapy.

PubMed

Howe, D S; Dunning, J; Zorman, C; Garverick, S L; Bogie, K M

2015-02-01

Ideally, all chronic wounds would be prevented as they can become life threatening complications. The concept that a wound produces a 'current of injury' due to the discontinuity in the electrical field of intact skin provides the basis for the concept that electrical stimulation (ES) may provide an effective treatment for chronic wounds. The optimal stimulation waveform parameters are unknown, limiting the reliability of achieving a successful clinical therapeutic outcome. In order to gain a more thorough understanding of ES for chronic wound therapy, systematic evaluation using a valid in vivo model is required. The focus of the current paper is development of the flexible modular surface stimulation (MSS) device by our group. This device can be programed to deliver a variety of clinically relevant stimulation paradigms and is essential to facilitate systematic in vivo studies. The MSS version 2.0 for small animal use provides all components of a single-channel, programmable current-controlled ES system within a lightweight, flexible, independently-powered portable device. Benchtop testing and validation indicates that custom electronics and control algorithms support the generation of high-voltage, low duty-cycle current pulses in a power-efficient manner, extending battery life and allowing ES therapy to be delivered for up to 7 days without needing to replace or disturb the wound dressing.

Global and local waveform simulations using the VERCE platform

NASA Astrophysics Data System (ADS)

Garth, Thomas; Saleh, Rafiq; Spinuso, Alessandro; Gemund, Andre; Casarotti, Emanuele; Magnoni, Federica; Krischner, Lion; Igel, Heiner; Schlichtweg, Horst; Frank, Anton; Michelini, Alberto; Vilotte, Jean-Pierre; Rietbrock, Andreas

2017-04-01

In recent years the potential to increase resolution of seismic imaging by full waveform inversion has been demonstrated on a range of scales from basin to continental scales. These techniques rely on harnessing the computational power of large supercomputers, and running large parallel codes to simulate the seismic wave field in a three-dimensional geological setting. The VERCE platform is designed to make these full waveform techniques accessible to a far wider spectrum of the seismological community. The platform supports the two widely used spectral element simulation programs SPECFEM3D Cartesian, and SPECFEM3D globe, allowing users to run a wide range of simulations. In the SPECFEM3D Cartesian implementation the user can run waveform simulations on a range of pre-loaded meshes and velocity models for specific areas, or upload their own velocity model and mesh. In the new SPECFEM3D globe implementation, the user will be able to select from a number of continent scale model regions, or perform waveform simulations for the whole earth. Earthquake focal mechanisms can be downloaded within the platform, for example from the GCMT catalogue, or users can upload their own focal mechanism catalogue through the platform. The simulations can be run on a range of European supercomputers in the PRACE network. Once a job has been submitted and run through the platform, the simulated waveforms can be manipulated or downloaded for further analysis. The misfit between the simulated and recorded waveforms can then be calculated through the platform through three interoperable workflows, for raw-data access (FDSN) and caching, pre-processing and finally misfit. The last workflow makes use of the Pyflex analysis software. In addition, the VERCE platform can be used to produce animations of waveform propagation through the velocity model, and synthetic shakemaps. All these data-products are made discoverable and re-usable thanks to the VERCE data and metadata management layer. We demonstrate the functionality of the VERCE platform with two use cases, one using the pre-loaded velocity model and mesh for the Maule area of Chile using the SPECFEM3D Cartesian workflow, and one showing the output of a global simulation using the SPECFEM3D globe workflow. It is envisioned that this tool will allow a much greater range of seismologists to access these full waveform inversion tools, and aid full waveform tomographic and source inversion, synthetic shakemap production and other full waveform applications, in a wide range of tectonic settings.

Software-type Wave-Particle Interaction Analyzer on board the ARASE satellite

NASA Astrophysics Data System (ADS)

Katoh, Y.; Kojima, H.; Hikishima, M.; Takashima, T.; Asamura, K.; Miyoshi, Y.; Kasahara, Y.; Kasahara, S.; Mitani, T.; Higashio, N.; Matsuoka, A.; Ozaki, M.; Yagitani, S.; Yokota, S.; Matsuda, S.; Kitahara, M.; Shinohara, I.

2017-12-01

Wave-Particle Interaction Analyzer (WPIA) is a new type of instrumentation recently proposed by Fukuhara et al. (2009) for direct and quantitative measurements of wave-particle interactions. WPIA computes an inner product W(ti) = qE(ti)·vi, where ti is the detection timing of the i-th particle, E(ti) is the wave electric field vector at ti, and q and vi is the charge and the velocity vector of the i-th particle, respectively. Since W(ti) is the gain or the loss of the kinetic energy of the i-th particle, by accumulating W for detected particles, we obtain the net amount of the energy exchange in the region of interest. Software-type WPIA (S-WPIA) is installed in the ARASE satellite as a software function running on the mission data processor. S-WPIA on board the ARASE satellite uses electromagnetic field waveform measured by Waveform Capture (WFC) of Plasma Wave Experiment (PWE) and velocity vectors detected by Medium-Energy Particle Experiments - Electron Analyzer (MEP-e), High-Energy Electron Experiments (HEP), and Extremely High-Energy Electron Experiment (XEP). The prime target of S-WPIA is the measurement of the energy exchange between whistler-mode chorus emissions and energetic electrons in the inner magnetosphere. It is essential for S-WPIA to synchronize instruments in the time resolution better than the time scale of wave-particle interactions. Since the typical frequency of chorus emissions is a few kHz in the inner magnetosphere, the time resolution better than 10 micro-sec should be realized so as to measure the relative phase angle between wave and velocity vectors with the accuracy enough to detect the sign of W correctly. In the ARASE satellite, a dedicated system has been developed in order to realize the required time resolution for the inter-instruments communications. In this presentation, we show the principle of the WPIA and its significance as well as the implementation of S-WPIA on the ARASE satellite.

Measurement of electromagnetic waves in ELF and VLF bands to monitor lightning activity in the Maritime Continent

NASA Astrophysics Data System (ADS)

Yamashita, Kozo; Takahashi, Yukihiro; Ohya, Hiroyo; Tsuchiya, Fuminori; Sato, Mitsuteru; Matsumoto, Jun

2013-04-01

Data of lightning discharge has been focused on as an effective way for monitoring and nowcasting of thunderstorm activity which causes extreme weather. Spatial distribution of lightning discharge has been used as a proxy of the presence or absence of deep convection. Latest observation shows that there is extremely huge lightning whose scale is more than hundreds times bigger than that of averaged event. This result indicates that lightning observation should be carried out to estimate not only existence but also scale for quantitative evaluation of atmospheric convection. In this study, lightning observation network in the Maritime Continent is introduced. This network is consisted of the sensors which make possible to measure electromagnetic wave radiated from lightning discharges. Observation frequency is 0.1 - 40 kHz for the measurement of magnetic field and 1 - 40 kHz for that of electric field. Sampling frequency is 100 kHz. Waveform of electromagnetic wave is recorded by personal computer. We have already constructed observation stations at Tainan in Taiwan (23.1N, 121.1E), Saraburi in Thailand (14.5N, 101.0E), and Pontianak in Indonesia (0.0N, 109.4E). Furthermore, we plan to install the monitoring system at Los Banos in Philippines (14.18, 121.25E) and Hanoi in Viet Nam. Data obtained by multipoint observation is synchronized by GPS receiver installed at each station. By using data obtained by this network, location and scale of lightning discharge can be estimated. Location of lightning is determined based on time of arrival method. Accuracy of geolocation could be less than 10km. Furthermore, charge moment is evaluated as a scale of each lightning discharge. It is calculated from electromagnetic waveform in ELF range (3-30 kHz). At the presentation, we will show the initial result about geolocation for source of electromagnetic wave and derivation of charge moment value based on the measurement of ELF and VLF sferics.

Reducing disk storage of full-3D seismic waveform tomography (F3DT) through lossy online compression

NASA Astrophysics Data System (ADS)

Lindstrom, Peter; Chen, Po; Lee, En-Jui

2016-08-01

Full-3D seismic waveform tomography (F3DT) is the latest seismic tomography technique that can assimilate broadband, multi-component seismic waveform observations into high-resolution 3D subsurface seismic structure models. The main drawback in the current F3DT implementation, in particular the scattering-integral implementation (F3DT-SI), is the high disk storage cost and the associated I/O overhead of archiving the 4D space-time wavefields of the receiver- or source-side strain tensors. The strain tensor fields are needed for computing the data sensitivity kernels, which are used for constructing the Jacobian matrix in the Gauss-Newton optimization algorithm. In this study, we have successfully integrated a lossy compression algorithm into our F3DT-SI workflow to significantly reduce the disk space for storing the strain tensor fields. The compressor supports a user-specified tolerance for bounding the error, and can be integrated into our finite-difference wave-propagation simulation code used for computing the strain fields. The decompressor can be integrated into the kernel calculation code that reads the strain fields from the disk and compute the data sensitivity kernels. During the wave-propagation simulations, we compress the strain fields before writing them to the disk. To compute the data sensitivity kernels, we read the compressed strain fields from the disk and decompress them before using them in kernel calculations. Experiments using a realistic dataset in our California statewide F3DT project have shown that we can reduce the strain-field disk storage by at least an order of magnitude with acceptable loss, and also improve the overall I/O performance of the entire F3DT-SI workflow significantly. The integration of the lossy online compressor may potentially open up the possibilities of the wide adoption of F3DT-SI in routine seismic tomography practices in the near future.

Reducing Disk Storage of Full-3D Seismic Waveform Tomography (F3DT) Through Lossy Online Compression

DOE PAGES

Lindstrom, Peter; Chen, Po; Lee, En-Jui

2016-05-05

Full-3D seismic waveform tomography (F3DT) is the latest seismic tomography technique that can assimilate broadband, multi-component seismic waveform observations into high-resolution 3D subsurface seismic structure models. The main drawback in the current F3DT implementation, in particular the scattering-integral implementation (F3DT-SI), is the high disk storage cost and the associated I/O overhead of archiving the 4D space-time wavefields of the receiver- or source-side strain tensors. The strain tensor fields are needed for computing the data sensitivity kernels, which are used for constructing the Jacobian matrix in the Gauss-Newton optimization algorithm. In this study, we have successfully integrated a lossy compression algorithmmore » into our F3DT SI workflow to significantly reduce the disk space for storing the strain tensor fields. The compressor supports a user-specified tolerance for bounding the error, and can be integrated into our finite-difference wave-propagation simulation code used for computing the strain fields. The decompressor can be integrated into the kernel calculation code that reads the strain fields from the disk and compute the data sensitivity kernels. During the wave-propagation simulations, we compress the strain fields before writing them to the disk. To compute the data sensitivity kernels, we read the compressed strain fields from the disk and decompress them before using them in kernel calculations. Experiments using a realistic dataset in our California statewide F3DT project have shown that we can reduce the strain-field disk storage by at least an order of magnitude with acceptable loss, and also improve the overall I/O performance of the entire F3DT-SI workflow significantly. The integration of the lossy online compressor may potentially open up the possibilities of the wide adoption of F3DT-SI in routine seismic tomography practices in the near future.« less

Method and apparatus for electrospark deposition

DOEpatents

Bailey, Jeffrey A.; Johnson, Roger N.; Park, Walter R.; Munley, John T.

2004-12-28

A method and apparatus for controlling electrospark deposition (ESD) comprises using electrical variable waveforms from the ESD process as a feedback parameter. The method comprises measuring a plurality of peak amplitudes from a series of electrical energy pulses delivered to an electrode tip. The maximum peak value from among the plurality of peak amplitudes correlates to the contact force between the electrode tip and a workpiece. The method further comprises comparing the maximum peak value to a set point to determine an offset and optimizing the contact force according to the value of the offset. The apparatus comprises an electrode tip connected to an electrical energy wave generator and an electrical signal sensor, which connects to a high-speed data acquisition card. An actuator provides relative motion between the electrode tip and a workpiece by receiving a feedback drive signal from a processor that is operably connected to the actuator and the high-speed data acquisition card.

System and method of modulating electrical signals using photoconductive wide bandgap semiconductors as variable resistors

DOEpatents

Harris, John Richardson; Caporaso, George J; Sampayan, Stephen E

2013-10-22

A system and method for producing modulated electrical signals. The system uses a variable resistor having a photoconductive wide bandgap semiconductor material construction whose conduction response to changes in amplitude of incident radiation is substantially linear throughout a non-saturation region to enable operation in non-avalanche mode. The system also includes a modulated radiation source, such as a modulated laser, for producing amplitude-modulated radiation with which to direct upon the variable resistor and modulate its conduction response. A voltage source and an output port, are both operably connected to the variable resistor so that an electrical signal may be produced at the output port by way of the variable resistor, either generated by activation of the variable resistor or propagating through the variable resistor. In this manner, the electrical signal is modulated by the variable resistor so as to have a waveform substantially similar to the amplitude-modulated radiation.

STEREO and Wind Observations of Intense Cyclotron Harmonic Waves at the Earth's Bow Shock and Inside the Magnetosheath

NASA Technical Reports Server (NTRS)

Breneman, A. W.; Cattell, C.

2013-01-01

We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 millivolts/meter peak-peak. A comparison between the short (15 meters) and long (100 meters) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 meters, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

Efficient calculation of full waveform time domain inversion for electromagnetic problem using fictitious wave domain method and cascade decimation decomposition

NASA Astrophysics Data System (ADS)

Imamura, N.; Schultz, A.

2016-12-01

Recently, a full waveform time domain inverse solution has been developed for the magnetotelluric (MT) and controlled-source electromagnetic (CSEM) methods. The ultimate goal of this approach is to obtain a computationally tractable direct waveform joint inversion to solve simultaneously for source fields and earth conductivity structure in three and four dimensions. This is desirable on several grounds, including the improved spatial resolving power expected from use of a multitude of source illuminations, the ability to operate in areas of high levels of source signal spatial complexity, and non-stationarity. This goal would not be obtainable if one were to adopt the pure time domain solution for the inverse problem. This is particularly true for the case of MT surveys, since an enormous number of degrees of freedom are required to represent the observed MT waveforms across a large frequency bandwidth. This means that for the forward simulation, the smallest time steps should be finer than that required to represent the highest frequency, while the number of time steps should also cover the lowest frequency. This leads to a sensitivity matrix that is computationally burdensome to solve a model update. We have implemented a code that addresses this situation through the use of cascade decimation decomposition to reduce the size of the sensitivity matrix substantially, through quasi-equivalent time domain decomposition. We also use a fictitious wave domain method to speed up computation time of the forward simulation in the time domain. By combining these refinements, we have developed a full waveform joint source field/earth conductivity inverse modeling method. We found that cascade decimation speeds computations of the sensitivity matrices dramatically, keeping the solution close to that of the undecimated case. For example, for a model discretized into 2.6x105 cells, we obtain model updates in less than 1 hour on a 4U rack-mounted workgroup Linux server, which is a practical computational time for the inverse problem.