Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “oscillation”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Analytic Estimation Method of Forced Oscillation Amplitude Under Stochastic Continuous Disturbances

This paper proposes an analytic method for the amplitude estimation of the forced oscillation under stochastic continuous disturbances (SCDs). There is considerable interest in the integration of intermittent renewable energy resources into a power system, which leads to the power system in an environment with SCDs. Thus, the forced oscillation issues under SCDs are of concern. In this paper, the SCDs are described as continuous-time stochastic processes, and then the systems under SCDs are modeled by stochastic differential algebraic equations. Furthermore, by employing stochastic theory, an efficient analytic method for calculating the statistics of system states during the forced oscillation is proposed. Moreover, a novel forced oscillation phenomenon, which presents system states oscillate with stationary distributions under SCDs, is clearly characterized and theoretically explained. Based on the proposed analytic method, a scheme is put forth to estimate amplitudes of system states during forced oscillation under SCDs. Finally, compared to Monte Carlo simulation, the proposed scheme has two significant advantages. First, the proposed scheme offers a fast and effective solution for engineering applications. Second, the impact mechanism of SCDs on forced oscillation in power system is clearer, by the proposed scheme.

42 ENGINEERING↗
DOE OSTI2019

Extraction of Neutrino Oscillation Parameters using a Simultaneous Fit of $\nu_{\mu}$ Disappearance and $\nu_{e}$ Appearance data with the NOvA Experiment

This thesis presents the analyses and results of the $\nu_{\mu} \rightarrow \nu_{\mu}$ disappearance and $\nu_{\mu} \rightarrow \nu_{e}$ appearance due to neutrino oscillations using 8.85 $\times$ 10$^{20}$ protons on target (POT) equivalent of data collected by the NOvA experiment. The data analyzed in this thesis was collected from February 06, 2014 to February 20, 2017. NOvA is an accelerator-based, long-baseline neutrino oscillation experiment and uses the two detector set-up to study the phenomenon of neutrino oscillation using a beam of muon neutrinos produced at Fermilab. One NOvA detector is placed within the Fermilab campus, 100 m underground, at a distance of 1 km from the neutrino source and is called the Near Detector (ND). The ND is 300 ton in mass and smaller in size than the Far Detector (FD) which is 14 kton in mass and is placed 810 km away from the neutrino source in Ash River, Minnesota (MN). Both ND and FD are made of the same material and are functionally identical. The ND being closer to the neutrino source, analyzes the neutrino beam before the neutrinos oscillate and the FD analyzes the neutrinos after oscillations. The ND is used to predict the signal and background expectations in the FD. The similarity in the ND and FD help to reduce the systematic uncertainties in the FD prediction. The combined oscillation fit to the $\nu_{\mu} \rightarrow \nu_{\mu}$ disappearance and $\nu_{\mu} \rightarrow \nu_{e}$ appearance gives the best fit values of the $\Delta m^{2}_{32}$, $\sin^{2}{\theta_{32}}$ and $\delta_{CP}$ oscillation parameters and are presented in this thesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Latest Three Flavor Neutrino Oscillation Results from the NOvA Experiment.

NOvA, is a two-detector, long-baseline neutrino oscillation experiment located at Fermilab, Batavia, IL, USA. It is designed primarily to constrain neutrino oscillation parameters such as the atmospheric mass squared splitting, $\Delta m^2_{32}$, the mixing angle, $\theta_{23}$, neutrino mass hierachy, and the CP-violating phase, $\delta_{CP}$, using $\nu_\mu \ (\bar{\nu}_\mu)$ disappearance and $\nu_e \ (\bar{\nu}_e)$ appearance data. NOvA receives a high purity instense beam of neutrinos and anti-neutrinos from Fermilab's Neutrinos at Main Injector (NuMI) beamline. The NOvA near detector (ND) observes un-oscillated $\nu_\mu \ (\bar{\nu}_\mu)$ and beam $\nu_e \ (\bar{\nu}_e)$ events, while the far detector (FD), which is situated 810 km away from the near detector, records un-oscillated $\nu_\mu \ (\bar{\nu}_\mu)$ and oscillated $\nu_e \ (\bar{\nu}_e)$ events. The best fit values of the oscillation parameters are extracted by performing a joint fit of the far detector predicted events to data from $\nu_\mu \to \nu_\mu$, $\bar{\nu}_\mu \to \bar{\nu}_\mu$, $\nu_\mu \to \nu_e$, and $\bar{\nu}_\mu \to \bar{\nu}_e$ oscillation channels. We present latest joint fit results from NOvA based on a neutrino-beam exposure of $27.24 \times 10^{20}$ POT and an anti-neutrino beam exposure of $12.55\times 10^{20}$ POT and improved simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Three-Flavor Neutrino Oscillations at NOvA

NOvA, is a two-detector, long-baseline neutrino oscillation experiment located at Fermilab, Batavia, IL, USA. It is designed primarily to constrain neutrino oscillation parameters such as the atmospheric mass squared splitting, $\Delta m^2_{32}$, the mixing angle, $\theta_{23}$, neutrino mass hierachy, and the CP-violating phase, $\delta_{CP}$, using $\nu_\mu \ (\bar{\nu}_\mu)$ disappearance and $\nu_e \ (\bar{\nu}_e)$ appearance data. NOvA receives a high purity 900 KW instense beam of neutrinos and anti-neutrinos from Fermilab's Neutrinos at Main Injector (NuMI) beamline. NOvA used functionally identical finely granulated liquid scintillation detectors, both situated 14.6 mrad off-axis to the beam direction. The NOvA near detector observes un-oscillated $\nu_\mu \ (\bar{\nu}_\mu)$ and beam $\nu_e \ (\bar{\nu}_e)$ events, while the far detector, which is situated 809 km away from the near detector, records un-oscillated $\nu_\mu \ (\bar{\nu}_\mu)$ and oscillated $\nu_e \ (\bar{\nu}_e)$ events. We will discuss the neutrino oscillation analysis strategy at NOvA and the latest three-flavor oscillation results from 10 years of NOvA data in this talk.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Measurement Adequacy for Monitoring Data Center Oscillations

Artificial intelligence (AI) training data centers with periodic load profiles can induce sustained grid oscillations across a wide frequency range, making accurate monitoring essential for reliable power system operation. This report evaluates the adequacy of existing measurement systems for monitoring such oscillations, focusing on phasor measurement units (PMUs) and point-on-wave (POW) measurement systems. The analysis shows that while PMUs are highly effective for monitoring low-frequency electromechanical oscillations, they have inherent limitations in accurately representing higher-frequency oscillations due to constraints imposed by reporting rates and the bandwidth of phasor estimation filters. Even when configured with higher reporting rates, the filtering inherent in the phasor estimation process can significantly attenuate oscillation magnitudes, potentially leading to underestimation of oscillatory behavior. This has important implications for compliance and performance monitoring of large loads. To address the limitations associated with PMU-based monitoring, the report examines the use of high-resolution POW measurements, which can capture oscillations across a broader frequency range. However, continuous POW monitoring introduces practical challenges related to large data volumes, communication bandwidth, and real-time data processing. For this reason, the report also discusses emerging approaches that use POW measurements as a complementary capability alongside PMUs to improve observability of oscillations from large data center loads.

47 OTHER INSTRUMENTATION↗
NASA NTRS1975

Electron plasma oscillations associated with type 3 radio emissions and solar electrons

An extensive study of the IMP-6 and IMP-8 plasma and radio wave data was performed to try to find electron plasma oscillations associated with type III radio noise bursts and low-energy solar electrons. It is shown that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare the electric field strength is relatively small. Electromagnetic radiation, believed to be similar to the type III radio emission, is observed coming from the region of the more intense electron plasma oscillations upstream. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation.

Gurnett, D. A.↗
NASA NTRS1979

Thrust oscillations of the Space Shuttle solid rocket Booster motor during static tests

Thrust oscillations have occurred during static tests of Space Shuttle Booster solid rocket motors. These oscillations in measured axial thrust occurred primarily near 15 Hz; these oscillations late in the motor burn reach magnitudes up to approximately + or - 3% of motor thrust. The phenomenon has consistently occurred on the four demonstration motors which have been static tested and appears to be associated with small amplitude, 15 Hz pressure oscillations inside the motor. The source of the pressure oscillations is thought to be associated with the fundamental longitudinal acoustic resonance of the motor at 15 Hz. These thrust oscillations potentially can impact the design of the Space Shuttle vehicle structure. The demonstration motors have been instrumented with an array of transducers to aid in understanding the phenomenon. In addition to measuring axial and lateral thrust of the motor, pressure transducers were located to measure chamber pressure oscillations at the forward dome. Accelerometers and extensometers have measured motions of the structure. A modal survey was conducted on a fired motor to identify its structural dynamic characteristics, and these data were used to validate mathematical models of the motor in the static test facility.

Mason, D. R.↗
NASA NTRS1982

No warmup crystal oscillator

During warmup, crystal oscillators often show a frequency offset as large as 1 part in 10 to the 5th power. If timing information is transferred to the oscillator and then the oscillator is allowed to warmup, a timing error greater than 1 millisecond will occur. For many applications, it is unsuitable to wait for the oscillator to warmup. For medium accuracy timing requirements where overall accuracies in the order of 1 millisecond are required, a no warmup crystal concept was developed. The concept utilizes two crystal oscillator, used sequentially to avoid using a crystal oscillator for timing much higher frequency accuracy once warmed up. The accuracy achieved with practical TCXOs at initial start over a range of temperatures is discussed. A second design utilizing two oven controlled oscillators is also discussed.

Phillips, D. H.↗
NASA NTRS1984

A comparison of IMPATT oscillator power and frequency above 100 GHz with results derived from theoretical models

This investigation is concerned with a comparison of measured 117-GHz IMPATT oscillator frequency and output power with results derived from theoretical circuit models. It is pointed out that previous millimeter-wave oscillator models are unsuitable for studying circuit behavior, such as oscillator tuning as a function of waveguide short position or other circuit parameters. In the current study, oscillator circuit modeling techniques, successfully applied at X-band, are applied for the first time to a millimeter-wave IMPATT oscillator circuit. Attention is given to an oscillator circuit description, an IMPATT diode circuit model, a circuit model, and an oscillator analysis.

Bates, B. D.↗
NASA NTRS1991

Oscillations of rotating neutron stars

A perturbation technique is used to compute the rotational corrections to the nonradial oscillation spectrum of a realistic neutron star model. The l = l(0) oscillations are coupled to l = l(0) + or - 1 oscillations by the Coriolis force. To calculate the rotational corrections to the quadrupole, l(0) = 2, oscillation modes, previous calculations of the nonradial oscillation spectrum of this neutron star model are extended to include l(0) = 1 and l(0) = 3 modes, as well as many higher overtones at each value of l(o). As an example of this technique, the rotational corrections to two quadrupole toroidal modes are computed. For these modes the coupling to the spheroidal class of oscillations produced by the Coriolis force introduces a nonzero radial component to the velocity field, as well as a nonvanishing Lagrangian density perturbation. This result is used to compute the neutrino damping rates for these toroidal modes of a rotating neutron star. The neutrino damping time can approach the gravitational radiation damping time in rotating neutron stars if the central temperature is high enough. The rotationally induced coupling of spheroidal oscillations to toroidal modes can also produce significant displacements at the stellar surface in some of the toroidal modes. The damping rates due to this process for the rotationally corrected toroidal modes are estimated. The coupling of surface motions to the toroidal modes also have interesting implications for channeling energy, e.g., that associated with a glitch in the crust, to the surface of the star. Perhaps this might produce observable effects in the pulsar emission process or a gamma-ray burst event.

Strohmayer, Tod E.↗
NASA NTRS1991

Latitudinal and longitudinal oscillations of cloud features on Neptune

Voyager observations suggest that three of Neptune's major cloud features oscillate in latitude by 2 to 4 deg and that two of them simultaneously oscillate in longitude by 7.8 and 98 deg about their mean drift longitudes. The observations define most convincingly the two orthogonal oscillations of the second dark spot (near 53 deg south). These oscillations have similar periods near 800 hours and approximately satisfy a simple advective model in which a latitudinal oscillation produces a phase-shifted longitudinal oscillation proportional to the local wind shear. The latitudinal motion of the Great Dark Spot can be fit with an oscillation period of about 2550 hours, whereas its dominant longitudinal motion, if oscillatory at all, has such a long period that it is not well constrained by the Voyager data.

Sromovsky, Lawrence A.↗
NASA NTRS1992

A quasioptical resonant-tunneling-diode oscillator operating above 200 GHz

We have fabricated and characterized a quasioptically stabilized resonant-tunneling-diode (RTD) oscillator having attractive performance characteristics for application as a radiometric local oscillator. The fundamental frequency of the oscillator is tunable from about 200 to 215 GHz, the instantaneous linewidth is between 10 and 20 kHz, and the output power across the tuning band is about 50 micro-W. The narrow linewidth and fine tuning of the frequency are made possible by a scanning semiconfocal open cavity which acts as the high-Q resonator for the oscillator. The cavity is compact, portable, and insensitive to vibration and temperature variation. The total dc power consumption (RTD plus bias supply) is only 10 mW. The present oscillator provides the highest power obtained to date from an RTD above 200 GHz. We attribute this partly to the use of the quasioptical resonator, but primarily to the quality of the RTD. It is fabricated from the In(0.53)Ga(0.47)As/AlAs materials system, which historically has yielded the best overall resonant-tunneling characteristics of any material system. The RTD active area is 4 sq microns, and the room-temperature peak current density and peak-to-valley current ratio are 2.5x10(exp 5) A cm(exp -2) and 9, respectively. The RTD is mounted in a WR-3 standard-height rectangular waveguide and is contacted across the waveguide by a fine wire that protrudes through a via hole in a Si3N4 'honeycomb' overlayer. We estimate that the theoretical maximum frequency of oscillation of this RTD is approximately 1.1 THz, and that scaled-down versions of the same quasioptical oscillator design should operate in a fundamental mode up to frequencies of at least 500 GHz.

Brown, E. R.↗
NASA NTRS1992

A new kind of oscillation in the persistent emission of the Rapid Burster

We present a study of a new kind of oscillation found in the persistent emission after some type II bursts from the Rapid Burster observed during 1985 August with EXOSAT. All 95 bursts observed were longer than 30 s. Ten of them were followed by these oscillations. The frequency of the oscillations ranged from 39 to 56 mHz. A period decrease (by 30-50 percent) over a time-scale of about 100 s was observed in seven cases. The fractional rms variation of the oscillations ranged from 5 to 15 percent. In eight cases, about 4-Hz quasi-periodic oscillations with fractional rms values from 6 to 19 percent were observed simultaneously with the new oscillations. There is a high probability that the two forms of oscillation are related to one another.

Lubin, Lori M.↗
NASA NTRS1993

Dynamics of the solar chromosphere. I - Long-period network oscillations

We analyze differences in solar oscillations between the chromospheric network and internetwork regions from a 1 hr sequence of spectrograms of a quiet region near disk center. The spectrograms contain Ca II H, Ca I 422.7 nm, and various Fe I blends in the Ca II H wing. They permit vertical tracing of oscillations throughout the photosphere and into the low chromosphere. We find that the rms amplitude of Ca II H line center Doppler fluctuations is about 1.5 km/s for both network and internetwork, but that the character of the oscillations differs markedly in these two regions. Within internetwork areas the chromospheric velocity power spectrum is dominated by oscillations with frequencies at and above the acoustic cutoff frequency. They are well correlated with the oscillations in the underlying photosphere, but they are much reduced in the network. In contrast, the network Ca II H line center velocity and intensity power spectra are dominated by low-frequency oscillations with periods of 5-20 min. Their signature is much clearer in our Ca II H line center measurements than in previously used diagnostics which are contaminated by signals from deeper layers. We find that these long-period oscillations are not correlated with underlying photospheric disturbances, and we discuss their nature.

Lites, B. W.↗
NASA NTRS1993

The source of 5 minute period photospheric umbral oscillations

We observed the oscillations in the umbrae of two sunspots, using the MCCD imaging spectrograph at the Mees Solar Observatory on Haleakala, Maui. We perform four spatial analyses of the umbral velocity and find that (1) there is more power traveling toward the center of the umbrae than leaving the center of the umbrae (this provides a direct measure of the absorption of p-modes by the sunspot umbrae); (2) the umbral oscillations display power in the same spatial and temporal frequency band as the quiet-sun oscillations; (3) Fourier-Bessel analysis of one umbra shows no obvious resonant frequencies which might represent natural oscillation modes; and (4) the centers of the umbrae have less rms velocity at high spatial wavenumber than the edges of the umbrae. We conclude: (1) the photospheric umbral oscillations are driven by a source external to the sunspot, the global p-mode oscillations; (2) there are no resonant frequencies in the oscillations; and (3) the absorption of acoustic waves occurs inside the umbrae.

Penn, M. J.↗
NASA NTRS1994

A preliminary analysis of low frequency pressure oscillations in hybrid rocket motors

Past research with hybrid rockets has suggested that certain motor operating conditions are conducive to the formation of pressure oscillations, or flow instabilities, within the motor combustion chamber. These combustion-related vibrations or pressure oscillations may be encountered in virtually any type of rocket motor and typically fall into three frequency ranges: low frequency oscillations (0-300 Hz); intermediate frequency oscillations (400-1000 Hz); and high frequency oscillations (greater than 1000 Hz). In general, combustion instability is characterized by organized pressure oscillations occurring at well-defined intervals with pressure peaks that may maintain themselves, grow, or die out. Usually, such peaks exceed +/- 5% of the mean chamber pressure. For hybrid motors, these oscillations have been observed to grow to a limiting amplitude which may be dependent on factors such as fuel characteristics, oxidizer injector characteristics, average chamber pressure, oxidizer mass flux, combustion chamber length, and grain geometry. The approach taken in the present analysis is to develop a modified chamber length, L, instability theory which accounts for the relationship between pressure and oxidizer to fuel concentration ratio in the motor.

Jenkins, Rhonald M.↗
NASA NTRS1994

Low-frequency oscillations in radiative-convective systems

Although eastward propagation has long been considered one of the essential features of the Madden-Julian waves, recent observations have revealed a stationary or quasi-stationary component in the oscillations, particularly in measures of the diabatic heating rate. Wave-CISK theories of the low-frequency oscillations have struggled to explain the observed period and vertical structure of the waves. On the other hand, theoretical and numerical studies have shown that low-frequency waves strongly resembling the observed oscillations can be excited by specified low-frequency oscillations of the convective heating. A problem with the latter set of theories is that the cause of the oscillatory heating has not been satisfactorily explained. It is proposed here that the observed low-frequency wave motions are the response to forcing by an essentially stationary, self-excited oscillating heat source that is produced by nonlinear interactions among radiation, cumulus convection, and the surface fluxes of sensible heat and moisture. Feedback of the large-scale motions on the latent heating is not required. Results from two very different one-dimensional models are presented to support this hypothesis. The physical processes included in the models are essentially the same, that is, radiation, cumulus convection, and the surface fluxes of sensible heat and moisture; the first model is highly simplified, however, while the second includes relatively sophisticated parameterizations of all the relevant physical processes. Results from both models show low-frequency oscillations of the latent heating, temperature, and moisture. Experiments show that the oscillations are favored by a warm sea surface and weak surface wind speeds, consistent with the observed conditions over the Indian Ocean and the tropical western Pacific Ocean.

Hu, QI↗
NASA NTRS2010

Effects of Temperature on the Performance and Stability of Recent COTS Silicon Oscillators

Silicon oscillators have lately emerged to serve as potential replacement for crystal and ceramic resonators to provide timing and clock signals in electronic systems. These semiconductor-based devices, including those that are based on MEMS technology, are reported to be resistant to vibration and shock (an important criteria for systems to be deployed in space), immune to EMI, consume very low current, require few or no external components, and cover a wide range of frequency for analog and digital circuits. In this work, the performance of five recently-developed COTS silicon oscillator chips from different manufacturers was determined within a temperature range that extended beyond the individual specified range of operation. In addition, restart capability at extreme temperatures, i.e. power switched on while the device was soaking at extreme (hot or cold) temperature, and the effects of thermal cycling under a wide temperature range on the operation of these silicon oscillators were also investigated. Performance characterization of each oscillator was obtained in terms of its output frequency, duty cycle, rise and fall times, and supply current at specific test temperatures. The five different oscillators tested operated beyond their specified temperature region, with some displaying excellent stability throughout the whole test temperature range. Others experienced some instability at certain temperature test points as evidenced by fluctuation in the output frequency. Recovery from temperature-induced changes took place when excessive temperatures were removed. It should also be pointed out that all oscillators were able to restart at the extreme test temperatures and to withstand the limited thermal cycling without undergoing any significant changes in their characteristics. In addition, no physical damage was observed in the packaging material of any of these silicon oscillators due to extreme temperature exposure and thermal cycling. It is recommended that additional and more comprehensive testing under long term cycling be carried out to fully establish the reliability of these devices and to determine their suitability for use in space exploration missions under extreme temperature conditions.

Patterson, Richard L.↗