Search NASA⌕ Search

SEARCH · Search NASA

Results for “Waveform Sampling”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Tunable electron beam pulser for picoseconds stroboscopic microscopy in transmission electron microscopes

For two decades, time-resolved transmission electron microscopes (TEM) have relied on pulsed-laser photoemission to generate electron bunches to explore sub-microsecond to sub-picosecond dynamics. Despite the vast successes of photoemission time-resolved TEMs, laser-based systems are inherently complex, thus tend not to be turn-key. In this paper, we report on the successful retrofit of a commercial 200 keV TEM, without an external laser, capable of producing continuously tunable pulsed electron beams with repetition rates from 0.1 GHz up to 12 GHz and a tunable bunch length from tens of nanoseconds down to 10 ps. This innovation enables temporal access into previously inaccessible regimes: i.e., high repetition rate stroboscopic experiments. Combination of a pair of RF-driven traveling wave stripline elements, quadrupole magnets, and a variable beam aperture enables operation of the instrument in (1) continuous waveform (CW) mode as though the instrument was never modified (i.e. convention TEM operation mode, where the electrons from the emission cathode randomly arrive at the sample without resolvable time information), (2) stroboscopic (pump-probe) mode, and (3) pulsed beam mode for dose rate sensitive materials. In order to analyze the effect of a pulsed beam on image quality, we examined Au nanoparticles using bright field, high-resolution TEM imaging and selected area diffraction in both continuous and pulsed-beam mode. Furthermore, in comparison of conventional TEMs, the add-on beam pulser enables the observation of ultrafast dynamic behavior in materials that are reversible under synchronized excitation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

DSP Implementation of a Novel Recurrent Neural Network Controller into a TI Solar Microinverter

Single-phase grid-tied inverters are widely used to integrate small-scale renewable energy sources and distributed generations to the utility grid. A novel Recurrent Neural Network (RNN) current controller is introduced to solve the resonant problem associated with LCL based inverters. The well-trained RNN controller was validated through a Texas Instruments (TI) LCL filter based solar microinverter kit that contains a C2000 TI microcontroller. The inverter closed current loop test without the grid connection was conducted in a laboratory setup to verify the RNN contoller functionality. The laboratory waveform results verified that the RNN current controller produced the strong tracking of the measured inverter AC current to its reference value even at a low sampling frequency of 5KHz. The proposed RNN current controller also proved to perform better than the built-in three-pole-three-zero (3P3Z) current controller provided by TI and produce lower values of Total Harmonic Distortion (THD).

digital signal processor↗
DOE OSTI2024

A Time-Domain Protection Approach for AC Transmission Systems With Grid-Forming Resources

Ac transmission protection must reliably detect, classify, and locate short-circuit faults from voltage and current measurements. At present, these functionalities, which have been classically engineered using phasors approaches, are being challenged by the dynamic behavior and fault-current limits of converter-based generation. This paper tackles these challenges by engineering a time-domain protection approach that leverages the classical Bergeron model in a new manner. Low- and high-impedance faults are detected and classified by ascertaining how well line voltage and current measurements match the Bergeron equations. Faults are located by posing a novel one-variable optimization problem, whereas voltage and current waveforms at the fault location are estimated by unveiling rigorous relationships. The proposed elements are secure against external faults, measurement errors, and variation of line parameters and sampling time. Furthermore, these advances are tested via electromagnetic transient simulations and are significant to satisfy IEEE and North American Electric Reliability Corporation requirements.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

Improved Quantitative Dynamic Range of Time-of-Flight Mass Spectrometry by Simultaneously Waveform-Averaging and Ion-Counting Data Acquisition

Two different types of data acquisition methods, “averaging mode” and “ion-counting mode”, have been used in a time-of-flight (TOF) mass spectrometry. The most common method is an averaging mode that sums waveform signals obtained from each flight cycle. While it is possible to process many ions arriving at the same TOF in one flight cycle, low-abundance ions are difficult to measure because ion signals are overwhelmed by noises from the detection system. An ion-counting mode is suitable for the detection of such low-concentration ions, but counting loss occurs when two or more ions arrive at the detector within the dead time of the acquisition system. In this study, we introduce a technique that combines two methods to measure target ions with a high concentration difference, i.e., averaging mode and ion-counting mode are used simultaneously for high abundant and trace ions, respectively. By processing waveforms concurrently during data acquisition, one can choose to analyze either or both types of data to achieve a highly quantitative mass spectrum over a wide range of sample concentrations. The result of the argon isotope analysis shows that this method provides a more accurate determination of the isotope ratio compared to averaging mode alone at one-twentieth of the analysis time required by ion-counting alone. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

All-optical sampling of few-cycle infrared pulses using tunneling in a solid

Recent developments in ultrafast laser technology have resulted in novel few-cycle sources in the mid-infrared. Accurately characterizing the time-dependent intensities and electric field waveforms of such laser pulses is essential to their applications in strong-field physics and attosecond pulse generation, but this remains a challenge. Recently, it was shown that tunnel ionization can provide an ultrafast temporal “gate” for characterizing high-energy few-cycle laser waveforms capable of ionizing air. Here, we show that tunneling and multiphoton excitation in a dielectric solid can provide a means to measure lower-energy and longer-wavelength pulses, and we apply the technique to characterize microjoule-level near- and mid-infrared pulses. The method lends itself to both all-optical and on-chip detection of laser waveforms, as well as single-shot detection geometries.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Parameter Estimation for Gravitational-wave Bursts with the BayesWave Pipeline

We provide a comprehensive multi-aspect study of the performance of a pipeline used by the LIGO-Virgo Collaboration for estimating parameters of gravitational-wave bursts. We add simulated signals with four different morphologies (sine-Gaussians (SGs), Gaussians, white-noise bursts, and binary black hole signals) to simulated noise samples representing noise of the two Advanced LIGO detectors during their first observing run. We recover them with the BayesWave (BW) pipeline to study its accuracy in sky localization, waveform reconstruction, and estimation of model-independent waveform parameters. BW localizes sources with a level of accuracy comparable for all four morphologies, with the median separation of actual and estimated sky locations ranging from 25.°1 to 30.°3. This is a reasonable accuracy in the two-detector case, and is comparable to accuracies of other localization methods studied previously. As BW reconstructs generic transient signals with SG wavelets, it is unsurprising that BW performs best in reconstructing SG and Gaussian waveforms. The BW accuracy in waveform reconstruction increases steeply with the network signal-to-noise ratio (S/N{sub net}), reaching a 85% and 95% match between the reconstructed and actual waveform below S/N{sub net}≈20 and S/N{sub net}≈50, respectively, for all morphologies. The BW accuracy in estimating central moments of waveforms is only limited by statistical errors in the frequency domain, and is also affected by systematic errors in the time domain as BW cannot reconstruct low-amplitude parts of signals that are overwhelmed by noise. The figures of merit we introduce can be used in future characterizations of parameter estimation pipelines.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Temperature effects on the nanoscale thermoelastic response of a SiO2 membrane

We crossed two femtosecond extreme ultraviolet (EUV) pulses on a 100 nm thick amorphous membrane of SiO2, generating transient gratings (TGs) of light intensity with 84 nm spatial periodicity. The EUV TG excitation gave rise to the efficient generation of Lamb waves (LWs) and of a temperature grating, whose dynamics was studied at two different initial sample temperatures, 50 and 300 K. The short penetration depth of the EUV excitation pulses turned into a strong non-uniformity in the actual temperature as a function of the depth from the sample surface. At the lowest temperature, the LW frequencies presented a sizable shift in time due to the thermal equilibration along the membrane thickness. The analysis of the EUV TG waveforms allowed us to determine the decay time of the thermal grating and the sound attenuation coefficient, both found in reasonable agreement with the literature. The results show how EUV TG can provide information of non-equilibrium thermoelastic dynamics in thin membranes transparent to optical radiation.

Materials Science↗
DOE OSTI2022

Report on Depth-Dependent Q from Frequency-Dependent Lg Q

As a phase that travels through the crustal waveguide, Lg samples the velocity and attenuation structure of the crust. We have developed methods (Pasyanos et al., 2009a; Pasyanos et al., 2009b) to estimate Qp and Qs of the crust and upper mantle from the amplitudes of regional phases, and have applied it to a number of regions around the world, and over a broad frequency band (0.5 - 10 Hz). In prior attenuation modeling, Lg phase amplitudes are able to effectively distinguish the high Q (low attenuation) of old stable cratonic crust from the low Q (high attenuation) of more recently active tectonic regions. For a variety of purposes (e.g. waveform modeling, seismic hazard, etc.), it is useful to have more information on the depth-dependence of the Q structure in the crust. One obvious candidate for doing this is using the frequency-dependence information of Lg Q, in the manner of surface waves. Unfortunately, however, Lg samples the whole of the crust without much differentiation with respect to frequency that is characteristic of fundamental mode surface waves. Lg is generally thought to be the sum of supercritically reflected S-waves trapped in the crustal waveguide (e.g. Xie and Lay, 1994). The phase can also be modeled as a superposition of surface waves. At lower frequencies, it is primarily composed of fundamental and low-order surface waves, while at higher frequencies, it is comprised purely of many high-order surface waves. The low-order surface waves that comprise Lg in low frequency bands (< 1 Hz) are preferentially sensitive to shallow earth structure, such as sedimentary basins and upper crust, while high-order surface waves have a more homogenized sensitivity to the whole crust. Furthermore, at the lower frequencies, we might expect to see some differentiation in the sensitivity between early Lg (herein referred to as Lg1) and late Lg (referred to as Lg2) where the latter is comprised of lower-order surface waves and, hence, shallower structure. Therefore, we might expect to see the signature of shallow features, primarily the lower Q of sediments as compared to crystalline crust, at lower frequencies and in later arriving Lg amplitudes.

58 GEOSCIENCES↗
DOE OSTI2019

Experimental Study of the Rare Neutral-Kaon Decays at J-PARC (Final Technical Report)

Understanding the origin of CP violation is currently one of the most forefront issues in elementary particle physics. Together with a better understanding of quark mixing and neutrino mixing phenomena, it is one of the central goals of particle physics, and has been pursued vigorously in many experiments. The very rare decay $K_L \to \pi ^0 v\bar{v}$ provides one of the best probes for understanding the original of CP violation in the quark sector. Particularly, theoretical uncertainties are very small in the Standard Model (SM) calculations, and the value therefore most suitable to be tested for beyond SM contributions. J-PARC E14 (also known as KOTO) aims to reach Standard Model sensitivity and beyond with Stage-1 and Stage-2. KOTO acquired 100 hours beam data in May 2013 and the result has been accepted for publication. From 2015-16, KOTO increased the data set by a factor of twenty, which will allow a limit to be set at the Grossman-Nir bound. This bound is valid in virtually any extension of the Standard Model. By comparing this model-independent bound and SM prediction, it is clear that there is considerable room for new physics. Analysis on these collected data sets shows neutron interactions which mimic the two-photon signal could become a potential background. To discriminate neutron background from the photon signal, one important tool, as shown in current data, is to perform detailed waveform analysis of the signal from the phototubes. To fully capture the calorimeter pulse shape with best fidelity from 100 out of the 2700 channels of CsI, we built the 500 MSPS (Mega Samples Per Second) with 14-bit digitizers. With KOTO Stage-2 currently in the planning stages, we started R&D work on a full width, but length scalable photon veto barrel detector with detailed layout of active detector elements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Understanding Photon / Free Carrier Interaction in LVP Signals on Ultra-Thin Silicon ICs.

This project investigated a recently patented Sandia technology known as visible light Laser Voltage Probing (LVP). In this effort we carefully prepared well understood and characterized samples for testing. These samples were then operated across a range of configurations to minimize the possibility of superposition of multiple photon carrier interactions as data was taken with conventional and visible light LVP systems. Data consisted of LVP waveforms and Laser Voltage Images (LVI). Visible light (633 nm) LVP data was compared against 1319 nm and 1064 nm conventional LVP data to better understand the similarities and differences in mechanisms for all wavelengths of light investigated. The full text can be obtained by reaching the project manager, Ed Cole or the Cyber IA lead, Justin Ford.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Three-dimensional NDE of VHTR core components via simulation-based testing. Final report

A next generation, simulation-driven-and-enabled testing platform is developed for the 3D detection and characterization of defects and damage in nuclear graphite and composite structures in Very High Temperature Reactors (VHTRs). The proposed work addresses the critical need for the development of high-fidelity Non-Destructive Examination (NDE) technologies for as-manufactured and replaceable in-service VHTR components. Centered around the novel use of elastic (sonic and ultrasonic) waves, this project deploys a robust, non-iterative inverse solution for the 3D defect reconstruction together with a non-contact, laser-based approach to the measurement of experimental waveforms in VHTR core components. In particular, this research (1) deploys three-dimensional Scanning Laser Doppler Vibrometry (3D SLDV) as a means to accurately and remotely measure 3D displacement waveforms over the accessible surface of a VHTR core component excited by mechanical vibratory source; (2) implements a powerful new inverse technique, based on the concept of Topological Sensitivity (TS), for non-iterative elastic waveform tomography of internal defects - that permits robust 3D detection, reconstruction and characterization of discrete damage (e.g. holes and fractures) in nuclear graphite from limited-aperture NDE measurements; (3) implements state-of-the art computational (finite element) model that caters for accurately simulating elastic wave propagation in 3D blocks of nuclear graphite; (4) integrates the SLDV testing methodology with the TS imaging algorithm into a non-contact, high-fidelity NDE platform for the 3D reconstruction and characterization of defects and damage in VHTR core components; and (5) applies the proposed methodology to VHTR core component samples (both two- and three-dimensional) with a priori induced, discrete damage in the form of holes and fractures. Overall, the newly established SLDV-TS testing platform represents a next-generation NDE tool that surpasses all existing techniques for the 3D ultrasonic imaging of material damage from non-contact, limited-aperture waveform measurements. Outlook. The next stage in the development of this technology includes items such as (a) non-contact generation of mechanical vibrations in VHTR components via thermal expansion created by high-intensity laser; (b) development and incorporation of Synthetic Aperture Focusing Technique (SAFT) for elevating the accuracy of 3D imaging in highly noisy environments with minimal accessible surface; (c) further analytical and computational developments to facilitate the reconstruction of diffuse damage (e.g. microcracks) in nuclear graphite as they lead to the dispersion of elastic waves, (d) concept of model updating for accurate tracking of the evolution of material damage via periodic inspections; (d) adoption of the Bayesian framework to obtain information on the certainty of obtained images; and (e) optimization of the computational scheme toward real-time, model-based imaging of damage in VHTR core components.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Capture Cross Section Measurements in {sup nat}Fe and {sup 181}Ta from 1 to 2000 keV Using a New C6D6 Detector Array

A new array of four C6D6 detectors has been developed at the Rensselaer Polytechnic Institute Gaerttner LINAC center for the purposes of measuring neutron capture cross sections in the keV resonance region with low sensitivity to scattered neutrons. The new detection apparatus incorporates low-mass, low cross-section materials to reduce neutron sensitivity, and uses digital data acquisition equipment to enable saving of the full waveform output of each detector module for offline analysis. Capture yields are determined by applying the total energy method and pulse height weighting technique during the analysis of the saved data. Measurements have been performed on samples of iron and tantalum using the new system, with results consistent with existing data libraries. (authors)

42 ENGINEERING↗
DOE OSTI2014

SU-E-T-217: Intrinsic Respiratory Gating in Small Animal CT

Purpose: Preclinical animal models of lung cancer can provide a controlled test-bed for testing dose escalation or function-based-treatment-planning studies. However, to extract lung function, i.e. ventilation, one needs to be able to image the lung at different phases of ventilation (in-hale / ex-hale). Most respiratory-gated imaging using micro-CT involves using an external ventilator and surgical intervention limiting the utility in longitudinal studies. A new intrinsic respiratory retrospective gating method was developed and tested in mice. Methods: A fixed region of interest (ROI) that covers the diaphragm was selected on all projection images to estimate the mean intensity (M). The mean intensity depends on the projection angle and diaphragm position. A 3-point moving average (A) of consecutive M values: Mpre, Mcurrent and Mpost, was calculated to be subtracted from Mcurrent. A fixed threshold was used to enable amplitude based sorting into 4 different phases of respiration. Images at full-inhale and end-exhale phases of respiration were reconstructed using the open source OSCaR. Lung volumes estimated at the 2 phases of respiration were validated against literature values. Results: Intrinsic retrospective gating was accomplished without the use of any external breathing waveform. While projection images were acquired at 360 different angles. Only 138 and 104 projections were used to reconstruct images at full-inhale and end-exhale. This often results in non-uniform under-sampled angular projections leading to some minor streaking artifacts. The calculated expiratory, inspiratory and tidal lung volumes correlated well with the values known from the literature. Conclusion: Our initial result demonstrates an intrinsic gating method that is suitable for flat panel cone beam small animal CT systems. Reduction in streaking artifacts can be accomplished by oversampling the data or using iterative reconstruction methods. This initial experience will enable freebreathing small animal micro-CT imaging to fuel longitudinal studies of lung function.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Monitoring Noble Gases (Xe and Kr) and Aerosols (Cs and Rb) in a Molten Salt Reactor Surrogate Off-Gas Stream Using Laser-Induced Breakdown Spectroscopy (LIBS)

In this study with surrogate materials we show that laser-induced breakdown spectroscopy (LIBS) is a robust tool with promising capability toward monitoring gaseous (Xe and Kr) and aerosol (Cs and Rb) species in an off-gas stream from a molten salt reactor (MSR). MSRs will continually evolve fission products into the cover gas flowing across the reactor headspace. The cover gas entrains Xe and Kr gases, along with aerosol particles, before passing into an off-gas treatment system. Univariate models of Xe and Kr peaks showed a strong correlation to concentration indicated by their coefficients of determination of 0.983 and 0.997, respectively. Multivariate models were built for all four analytes using partial least squares regression coupled with preprocessing steps including normalization, trimming, and/or genetic algorithm derived filters. The models were evaluated by predicting the concentrations of the analytes in four validation samples, in which all calibration models were successfully validated at a confidence interval of 99.9%. Finally, pressure controllers were used to regulate the mass flow rate of Kr flowing into the measurement cell in sinusoidal and stepwise waveforms to test the real-time monitoring capabilities of the regression models. Both univariate and partial least squares Kr models were able to successfully quantify the gas concentration in the real-time evaluation. The root mean squared error of prediction (RMSEP) values for these real-time tests were calculated to be 0.051, 0.060, and 0.121 mol% demonstrating the measurement systems’ capability to perform online monitoring with acceptable accuracy.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Fully Autonomous Multiplet Event Detection: Application to Local-Distance Monitoring of Blood Falls Seismicity

We apply a fully autonomous icequake detection methodology to a single day of high-sample rate (200 Hz) seismic network data recorded from the terminus of Taylor Glacier, ANT that temporally coincided with a brine release episode near Blood Falls (May 13, 2014). We demonstrate a statistically validated procedure to assemble waveforms triggered by icequakes into populations of clusters linked by intra-event waveform similarity. Our processing methodology implements a noise-adaptive power detector coupled with a complete-linkage clustering algorithm and noise-adaptive correlation detector. This detector-chain reveals a population of 20 multiplet sequences that includes ~150 icequakes and produces zero false alarms on the concurrent, diurnally variable noise. Our results are very promising for identifying changes in background seismicity associated with the presence or absence of brine release episodes. We thereby suggest that our methodology could be applied to longer time periods to establish a brine-release monitoring program for Blood Falls that is based on icequake detections.

42 ENGINEERING↗
DOE OSTI2024

Electron Density Measurements Using USPR (Final Scientific/Technical Report)

UC Davis has fabricated an ultrashort pulse reflectometer (USPR) diagnostic instrument for electron density profile measurements on compact, short duration, magnetically-confined fusion-energy concept devices such as spheromaks and FRCs. The USPR system transmits extremely short duration (~few nsec) chirped waveforms that together span 29 to 75 GHz. These chirped waveforms illuminate and reflect from the target plasma, with each frequency component reflecting from a different density layer (higher frequencies probe deeper into the plasma before reflecting). The reflected waveforms are split into roughly 42 different frequencies; time-of-flight (TOF) measurements made at each frequency with high resolution (~25 psec measurement resolution which corresponds to ~5 mm). These TOF data may then be inverted via software to generate electron density profiles with high time resolution (~10 μsec). At the heart of the system is a field programmable gate array (FPGA) based controller which collects and processes all of the USPR data in addition to generating all of the control signals required for maximum flexibility. The FPGA controller has the software flexibility to be easily reconfigured for different plasma devices, and the entire system sufficiently compact to be easily and quickly transported between devices. A high speed impulse generator was transformed into a set of three ultrashort pulse transmitter chirps using a combination of dispersive waveguide, frequency doublers and high-pass filters. A mm-wave controller was fabricated to sequentially switch between the three chirps, directing the chirps one-by-one to three different mm-wave assemblies spanning 29-75 GHz. Each mm-wave assembly consists of a high power active multiplier chain which converts the transmitter chirp to higher frequencies, and a broadband mixer which downconverts the reflected waveform to the 2-18 GHz range of the UPSR receiver. The 16-channel receiver (shared by all 3 mm-wave assemblies) was fabricated employing custom TOF modules capable of operating at a high 1 MHz sampling rate. Laboratory testing of the full system revealed the presence of unwanted harmonics from the multiplication process, with interference observed in the downconverted reflections at selected frequency channels that could not be completely filtered out. Additional interference effects arising from internal reflections within the mm-wave assemblies were minimized using a high-speed switch which served to “gate out” much of these reflections. The USPR diagnostic was transported and installed onto the HIT-SIU plasma device, becoming operational on 11/08/2022. Although designed to span 3 distinct mm-wave bands, the HIT-SIU plasmas at this time were sufficiently low density such that only the lowest of the three bands was likely to have strong plasma reflections. The system was then set to operate on only the lowest band (assembly #1), with data collected every 1 μsec rather than 3 μsec which would have been the case when cycling through all three bands. Connected to HIT-SIU, time-varying plasma reflections were observed on 9 of 16 possible frequency channels. Close examination of the data collected revealed issues previously unobserved in laboratory testing, associated with (a) reflections from the small aperture horns required for operation within the HIT-SIU device, and (b) a dependence of the recorded TOF with the threshold voltage of a given channel. Plans were made to address each of these issues before undertaking any future campaigns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Creation of a Robust and Generalizable Machine Learning Classifier for Patient Ventilator Asynchrony

Background: As healthcare increasingly digitizes, streaming waveform data is being made available from an variety of sources, but there still remains a paucity of performant clinical decision support systems. For example, in the intensive care unit (ICU) existing automated alarm systems typically rely on simple thresholding that result in frequent false positives. Recurrent false positive alerts create distrust of alarm mechanisms that can be directly detrimental to patient health. To improve patient care in the ICU, we need alert systems that are both pervasive, and accurate so as to be informative and trusted by providers. Objective: We aimed to develop a machine learning-based classifier to detect abnormal waveform events using the use case of mechanical ventilation waveform analysis, and the detection of harmful forms of ventilation delivery to patients. We specifically focused on detecting injurious subtypes of patient-ventilator asynchrony (PVA).Methods: Using a dataset of breaths recorded from 35 different patients, we used machine learning to create computational models to automatically detect, and classify two types of injurious PVA, double trigger asynchrony (DTA), breath stacking asynchrony (BSA). We examined the use of synthetic minority over-sampling technique (SMOTE) to overcome class imbalance problems, varied methods for feature selection, and use of ensemble methods to optimize the performance of our model. Results: We created an ensemble classifier that is able to accurately detect DTA at a sensitivity/specificity of 0.960/0.975, BSA at sensitivity/specificity of 0.944/0.987, and non-PVA events at sensitivity/specificity of .967/.980. Conclusions: Our results suggest that it is possible to create a high-performing machine learning-based model for detecting PVA in mechanical ventilator waveform data in spite of both intra-patient, and inter-patient variability in waveform patterns, and the presence of clinical artifacts like cough and suction procedures. Our work highlights the importance of addressing class imbalance in clinical data sets, and the combined use of statistical methods and expert knowledge in feature selection.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

A 128-Tap Highly Tunable CMOS IF Finite Impulse Response Filter for Pulsed Radar Applications

A configurable-bandwidth (BW) filter is presented in this paper for pulsed radar applications. Also, to eliminate dispersion effects in the received waveform, a finite impulse response (FIR) topology is proposed, which has a measured standard deviation of an in-band group delay of 11 ns that is primarily dominated by the inherent, fully predictable delay introduced by the sample-and-hold. The filter operates at an IF of 20 MHz, and is tunable in BW from 1.5 to 15 MHz, which makes it optimal to be used with varying pulse widths in the radar. Employing a total of 128 taps, the FIR filter provides greater than 50-dB sharp attenuation in the stopband in order to minimize all out-of-band noise in the low signal-to-noise received radar signal. Fabricated in a 0.18-μm silicon on insulator CMOS process, the proposed filter consumes approximately 3.5 mW/tap with a 1.8-V supply. Finally, a 20-MHz two-tone measurement with 200-kHz tone separation shows IIP3 greater than 8.5 dBm.

42 ENGINEERING↗