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All sources NASA NTRS DOE OSTI

NASA NTRS2008

High-Voltage, Asymmetric-Waveform Generator

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Beegle, Luther W.↗

NASA NTRS1999

Using a Genetic Algorithm to Model Broadband Regional Waveforms for Crustal Structure in the Western United States

In this study, we analyze regional seismograms to obtain the crustal structure in the eastern Great Basin and western Colorado plateau. Adopting a for- ward-modeling approach, we develop a genetic algorithm (GA) based parameter search technique to constrain the one-dimensional crustal structure in these regions. The data are broadband three-component seismograms recorded at the 1994-95 IRIS PASSCAL Colorado Plateau to Great Basin experiment (CPGB) stations and supplemented by data from U.S. National Seismic Network (USNSN) stations in Utah and Nevada. We use the southwestern Wyoming mine collapse event (M(sub b) = 5.2) that occurred on 3 February 1995 as the seismic source. We model the regional seismograms using a four-layer crustal model with constant layer parameters. Timing of teleseismic receiver functions at CPGB stations are added as an additional constraint in the modeling. GA allows us to efficiently search the model space. A carefully chosen fitness function and a windowing scheme are added to the algorithm to prevent search stagnation. The technique is tested with synthetic data, both with and without random Gaussian noise added to it. Several separate model searches are carried out to estimate the variability of the model parameters. The average Colorado plateau crustal structure is characterized by a 40-km-thick crust with velocity increases at depths of about 10 and 25 km and a fast lower crust while the Great Basin has approximately 35- km-thick crust and a 2.9-km-thick sedimentary layer.

Bhattacharyya, Joydeep↗

DOE OSTI2018

Lg-Wave Cross Correlation and Epicentral Double-Difference Location in and near China

In this paper, we perform epicentral relocations for a broad area using cross-correlation measurements made on Lg waves recorded at regional distances on a sparse station network. Using a two-step procedure (pairwise locations and cluster locations), we obtain final locations for 5623 events—3689 for all of China from 1985 to 2005 and 1934 for the Wenchuan area from May to August 2008. These high-quality locations comprise 20% of a starting catalog for all of China and 25% of a catalog for Wenchuan. Of the 1934 events located for Wenchuan, 1662 (86%) were newly detected. The final locations explain the residuals 89 times better than the catalog locations for all of China (3.7302–0.0417 s) and 32 times better than the catalog locations for Wenchuan (0.8413–0.0267 s). The average semimajor axes of the 95% confidence ellipses are 420 m for all of China and 370 m for Wenchuan. The average azimuthal gaps are 205° for all of China and 266° for Wenchuan. 98% of the station distances for all of China are over 200 km. The mean and maximum station distances are 898 and 2174 km. The robustness of our location estimates and various trade-offs and sensitivities is explored with different inversion parameters for the location, such as starting locations for iterative solutions and which singular values to include. Finally, our results provide order-of-magnitude improvements in locations for event clusters, using waveforms from a very sparse far-regional network for which data are openly available.

58 GEOSCIENCES↗

NASA NTRS1985

Acoustic detection of air shower cores

At an altitude of 1890m, a pre-test with an Air shower (AS) core selector and a small acoustic array set up in an anechoic pool with a volume of 20x7x7 cu m was performed, beginning in Aug. 1984. In analyzing the waveforms recorded during the effective working time of 186 hrs, three acoustic signals which cannot be explained as from any source other than AS cores were obtained, and an estimation of related parameters was made.

Gao, X.↗

NASA NTRS1990

Summary of Sonic Boom Rise Times Observed During FAA Community Response Studies over a 6-Month Period in the Oklahoma City Area

The sonic boom signature data acquired from about 1225 supersonic flights, over a 6-month period in 1964 in the Oklahoma City area, was enhanced with the addition of data relating to rise times and total signature duration. These later parameters, not available at the time of publication of the original report on the Oklahoma City sonic boom exposures, are listed in tabular form along with overpressure, positive impulse, positive duration, and waveform category. Airplane operating information along with the surface weather observations are also included. Sonic boom rise times include readings to the 1/2, 3/4, and maximum overpressure values. Rise time relative probabilities for various lateral locations from the ground track of 0, 5, and 10 miles are presented along with the variation of rise times with flight altitude. The tabulated signature data, along with corresponding airplane operating conditions and surface and upper level atmospheric information, are also available on electronic files to provide it in the format for more efficient and effective utilization.

Maglieri, Domenic J.↗

NASA NTRS2002

Grace Under Pressure

Developed in response to a NASA requirement to remotely measure tension in critical bolts on the International Space Station, the SureBolt(TM) Correlation Bolt Gage is the first ultrasonic system to capture an entire "echo" pulse for determining the change in time of flight of an ultrasonic signal traversing a fastener for tension measurement. The standard SureBolt system hardware has the capability of recording over 1 million bolt tension readings-with their complete waveforms-in Microsoft Excel-compatible format. The user- friendly Tension-Not-Torque(Copyright) software interface offers tension change graphing in real time, and a place to store field notes, special parameters, tension calibration constants, and temperature changes for each measurement. The technology has been used on fasteners as small as fine-threaded, 1-inch bolts, and as large as 18-inch-diameter by 30-foot-long tie rods. SureBolt is finding increased application within NASA and the aerospace industry, as well as in the automotive and nuclear industries.

Source record↗

NASA NTRS2013

Some Fundamental Limits on SAW RFID Tag Information Capacity and Collision Resolution

In this paper, we apply results from multi-user information theory to study the limits of information capacity and collision resolution for SAW RFID tags. In particular, we derive bounds on the achievable data rate per tag as a function of fundamental parameters such as tag time-bandwidth product, tag signal-to-noise ratio (SNR), and number of tags in the environment. We also discuss the implications of these bounds for tag waveform design and tag interrogation efficiency

Barton, Richard J.↗

DOE OSTI2018

Characteristics of Airplanes and Helicopters Recorded by a Dense Seismic Array Near Anza California

We observe frequent air traffic events in continuous seismic waveforms recorded for about 30 days by 1,108 vertical geophones in a tight array on the San Jacinto fault zone. The waveforms of the air traffic events resemble tremor or collections of small earthquakes. However, time-frequency analysis reveals clear Doppler effects that can be modeled with basic equations and fitted well with parameters corresponding to airplanes and helicopters. The flying traces can be inverted by fitting the parameters at each station across the entire array. About 31 air traffic events are detected per day in the relatively remote study area, with peak activity from about 8:00 to 18:00 and significantly fewer events between 23:00 and 4:00 local time. The average event duration is about 200 s, so they cover together>7% of the day. To estimate the total time covered by earthquakes, we derive a scaling relation logτ(M) = 0.41M + 0.89 between earthquake duration and magnitudes using data of 266 earthquakes in the magnitude range 0 ≤ M ≤ 3. The results indicate that in most places, the duration of air traffic events is likely to exceed considerably the total time covered by earthquakes.

58 GEOSCIENCES↗

NASA NTRS1975

Effect of Nozzle Nonlinearities upon Nonlinear Stability of Liquid Propellant Rocket Motors

A three dimensional, nonlinear nozzle admittance relation is developed by solving the wave equation describing finite amplitude oscillatory flow inside the subsonic portion of a choked, slowly convergent axisymmetric nozzle. This nonlinear nozzle admittance relation is then used as a boundary condition in the analysis of nonlinear combustion instability in a cylindrical liquid rocket combustor. In both nozzle and chamber analyses solutions are obtained using the Galerkin method with a series expansion consisting of the first tangential, second tangential, and first radial modes. Using Crocco's time lag model to describe the distributed unsteady combustion process, combustion instability calculations are presented for different values of the following parameters: (1) time lag, (2) interaction index, (3) steady-state Mach number at the nozzle entrance, and (4) chamber length-to-diameter ratio. In each case, limit cycle pressure amplitudes and waveforms are shown for both linear and nonlinear nozzle admittance conditions. These results show that when the amplitudes of the second tangential and first radial modes are considerably smaller than the amplitude of the first tangential mode the inclusion of nozzle nonlinearities has no significant effect on the limiting amplitude and pressure waveforms.

Padmanabhan, M. S.↗

NASA NTRS1991

Characteristics of Winter Lightning Currents Struck an Isolated Tower

To make clear the characteristics of winter lightning flashes, the current waveforms of winter lightning flashes were measured by two resistive shunts which were connected to two lighting rods since the winter of 1981, and another measurement has started using a set of five Rogowsky type coils since the winter of 1982. They were recorded by computer controlled digital recording systems. Up to date, 145 current waveforms of the winter lightning flashes, which have the current amplitude over 1 kA, were obtained by the shunt systems and/or the coils system. They show that winter lightning flashes often have a very long duration or continuing current and sometimes have a very large amplitude over 200 kA in positive flashes. For example, the current parameters that were measured on 9 Jan. 1987 were the maximum current amplitude, +280 kA, maximum current derivative 1.0 x 10(exp 10) A/s, total charge +400 C, and action integral 1.5 x 10(exp 7)(sq. A)(s). The statistical evaluation shows that medium peak values of winter lightning flashes (50 percent values) were about 5 kA for negative and 10 kA for positive, and 5 percent values were about 30 kA for negative and 170 kA for positive. The winter lightning current waveforms are classified into three types: single stroke flashes, monopolar multistroke flashes, and bipolar flashes. Moreover, each flash is subdivided into positive or negative, single peak or multipeak, and with or without continuing current.

Yukihiro Goto↗

DOE OSTI2025

PickerXL, A Large Deep Learning Model to Measure Arrival Times from Noisy Seismic Signals

Precisely measuring seismic arrival times is a labor-intensive task but is critical for both earthquake monitoring and subsurface imaging. Recently published deep learning models have demonstrated superior performance compared to traditional automatic approaches for picking arrival times. Although existing deep learning models have shown promising results, further advancements are necessary as their performance is not yet satisfactory especially when applied to new regions and station networks. Increasing model size has led to improved performance in other machine learning applications. Here, we aimed to investigate whether enlarging deep learning models can increase performance on accepted benchmarks. We trained three models of varying sizes, small (1X), medium (4X), and large (16X), using globally distributed local and regional earthquake signals and background noise waveforms from a benchmark dataset, Stanford Earthquake Dataset. Our results indicate that the largest model (PickerXL) outperforms both the smaller models and Seisbench implementation of the PhaseNet model, which has the same number of parameters as our small model. The PickerXL model’s enhanced capacity to extract complex patterns from seismograms contributes to its superior arrival picking abilities compared to the smaller model.

Chai, Chengping [Oak Ridge National Laboratory (OR↗

DOE OSTI2023

On-Sensor Data Filtering using Neuromorphic Computing for High Energy Physics Experiments

This work describes the investigation of neuromorphic computing-based spiking neural network (SNN) models used to filter data from sensor electronics in high energy physics experiments conducted at the High Luminosity Large Hadron Collider. We present our approach for developing a compact neuromorphic model that filters out the sensor data based on the particle's transverse momentum with the goal of reducing the amount of data being sent to the downstream electronics. The incoming charge waveforms are converted to streams of binary-valued events, which are then processed by the SNN. We present our insights on the various system design choices - from data encoding to optimal hyperparameters of the training algorithm - for an accurate and compact SNN optimized for hardware deployment. Our results show that an SNN trained with an evolutionary algorithm and an optimized set of hyperparameters obtains a signal efficiency of about 91% with nearly half as many parameters as a deep neural network.

R. Kulkarni, Shruti↗

DOE OSTI2018

Parameters and Tolerances for the Booster Dipole Power Supplies

In this technical note we discuss the parameters and tolerances for the booster dipole power supplies. We first discuss the requirements on the current ramp profile for the cases of energy ramps at 1 and 2 Hz. Then we determine the voltage waveforms that correspond to these current ramps. Using the booster magnet lattice and the actual power supply circuit layouts we then calculate the orbit distortion and tune spread caused by the magnetic field amplitude errors in the combined-function dipole magnets at the time of injection and extraction and establish the requirements on the value of the magnetic field amplitude errors at these points along the ramp. We then conclude the note by translating these requirements into the amplitude and time tolerances for the dipole power supplies.

42 ENGINEERING↗

NASA NTRS1990

Source parameters of earthquakes and intraplate deformation beneath the Shillong Plateau and the northern Indoburman ranges

The fault-plane solutions and focal depths are determined for 17 earthquakes beneath the Shillong Plateau and the northern Indoburman ranges by combining results from the inversion of long-period P and SH waveforms and amplitudes, from polarities of first motions, and from the identification of pP and sP phases on short-period seismograms. Fault-plane solutions of 15 earthquakes show mixtures of thrust and strike-slip faulting, but the P axes for these events are nearly horizontal and consistently oriented N-NE-S-SW. All of these earthquakes occurred at depths greater than 29 km. Beneath the Shillong Plateau, one event occurred at a depth of 52 km. The relatively large depths for earthquakes in an intraplate setting suggest that the Indian lithosphere in this area is especially cold.

Chen, Wang-Ping↗

NASA NTRS2006

Black Hole Solar Systems Extreme Mass Ratio Inspirals

Waveforms known well enough to detect some EMRIs today. Soon, enough to realize Gair et al estimate of approx. 100's to 1000's of detections to z = 1. Not yet enough to for precision parameter estimation of Barack and Cutler (mass and spin to 10(exp -4)). Some turning to the more exotic: non-Kerr background, gas interaction, third body, ... More status and refs: Drasco, gr-qc/0604115.

general relativity↗

DOE OSTI2018

Quadri-joint inversion: Method and application to the Big Sky 9C 3D data set in northern Montana

The Kevin Dome [Formula: see text] storage project, located in northern Montana, attempted to characterize the Duperow Formation as a potential long-term storage zone for injected [Formula: see text]. A multicomponent (9C) seismic survey was acquired for the Big Sky Carbon Sequestration Partnership over a portion of the Kevin Dome using P- and S-wave sources. Prestack migrated PP, PS, SH, and SV data sets were generated. We then applied several stratigraphic inversion workflows using one or several kinds of seismic wavefield at the same time resulting in joint inversions of each data set. The aim of our study is to demonstrate the benefits of doing quadri-joint inversion of PP-, PS-, SH-, and SV-wavefields for the recovery of the elastic earth parameters, especially the S-wave impedance and density. These are crucial parameters because they can help determine lithology and porefill in the reservoir characterization workflow. Because the inversion workflow always uses the original seismic data recorded in its own time domain, it is necessary to compute registration laws between PP-PS-, PP-SH-, and PP-SV-wavefields using a time shift computation procedure (warping) based on inverted S-wave impedances from inversion of a single wavefield. This generated a significant improvement over methods that rely on attempting to match trace waveforms that may have a different phase, frequency content, and polarity. Finally, we wanted to investigate the reliability of the quadri-joint inversion results in the Bakken/Banff Formations, which have less lateral geologic variation than the underlying Duperow target. This interval shares many of the geophysical characterization challenges common to shale reservoirs in other North American basins. We computed geomechanical parameters, such as Poisson’s ratio and Young’s modulus, which are a proxy for brittleness. Comparison of these results with independent laboratory measurements in the Bakken interval demonstrates the superiority of the quadri-joint inversion method to the traditional inversion using P-wave data only.

Geochemistry & Geophysics↗

DOE OSTI2024

Machine Learning Inference of Random Medium Properties

Earth materials are heterogeneous across a range of spatial scales, but the resolvability of small structures is limited by sparse data coverage, noise, bandlimitedness, and other difficulties. In practice, heterogeneities below a certain size cannot be recovered from seismic data except through statistical medium descriptions, which even then can be difficult to uniquely determine. To improve the characterization of such heterogeneities, we develop a novel supervised machine learning (ML) model that provides insight about the recoverability of statistical medium properties from elastic waveform data and succeeds despite cycle-skipping and other challenges well known from elastic waveform inversion. We demonstrate the approach using random media generated by superimposing self-affine random variations on homogeneous and layered background structures. After training on sparsely-recorded, high-frequency waveforms from hundreds of different random medium realizations, we show the ability of our ML model to recover correlation lengths and other statistical properties of interest to near-surface and crustal seismology, among other fields. For frequency passbands and spatial offsets encountered in seismology, Gaussian correlation lengths and the amplitude of the random variations relative to the background model are recovered even in challenging scenarios involving unknown medium parameters, complex crustal structures, and low signal-to-noise ratio. In comparison, von Kármán correlation lengths, which are related to larger-wavelength variations of the medium than Gaussian correlation lengths, are not as well recovered. These results provide one of the first and most systematic investigations of the recoverability of statistical properties of heterogeneities below the resolution limit of deterministic seismic tomography, and suggest practical ML strategies for high-frequency waveform seismology.

58 GEOSCIENCES↗

DOE OSTI2014

PAPR-Constrained Pareto-Optimal Waveform Design for OFDM-STAP Radar

We propose a peak-to-average power ratio (PAPR) constrained Pareto-optimal waveform design approach for an orthogonal frequency division multiplexing (OFDM) radar signal to detect a target using the space-time adaptive processing (STAP) technique. The use of an OFDM signal does not only increase the frequency diversity of our system, but also enables us to adaptively design the OFDM coefficients in order to further improve the system performance. First, we develop a parametric OFDM-STAP measurement model by considering the effects of signaldependent clutter and colored noise. Then, we observe that the resulting STAP-performance can be improved by maximizing the output signal-to-interference-plus-noise ratio (SINR) with respect to the signal parameters. However, in practical scenarios, the computation of output SINR depends on the estimated values of the spatial and temporal frequencies and target scattering responses. Therefore, we formulate a PAPR-constrained multi-objective optimization (MOO) problem to design the OFDM spectral parameters by simultaneously optimizing four objective functions: maximizing the output SINR, minimizing two separate Cramer-Rao bounds (CRBs) on the normalized spatial and temporal frequencies, and minimizing the trace of CRB matrix on the target scattering coefficients estimations. We present several numerical examples to demonstrate the achieved performance improvement due to the adaptive waveform design.

Sen, Satyabrata↗