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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.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Excited-state uncertainties in lattice-QCD calculations of hadron masses and scattering phase shifts

Lattice QCD has historically produced energy results interpretable as either estimates relying on implicit assumptions about asymptotic behavior or one-sided upper bounds. New Lanczos methods providing two-sided bounds with less-restrictive assumptions are introduced and quantified in a high-statistics calculation with unphysical quark masses. Two-sided bounds without spectral assumptions provide sub-percent constraints on the nucleon mass. Other bounds, which assume all states in a given energy window are resolved, provide meaningful two-sided constraints on nucleon-nucleon scattering phase shifts.

Detmold, William [MIT, Cambridge, CTP]↗
NASA NTRS1997

Common path point diffraction interferometer using liquid crystal phase shifting

A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.

Mercer, Carolyn R.↗
NASA NTRS1993

On the performance of Trellis coded modulation with octal phase shift keying over the TDRSS channel

As the National Aeronautics and Space Administration moves into the 21st century with programs like Space Station Freedom, a manned mission to Mars, and the new Landsat mission, transmission demands on the Tracking and Data Relay Satellite System (TDRSS) will very likely exceed the available bandwidth. The Manual Lujan, Jr. Center for Space Telemetering and Telecommunications Systems (CSTTS) at New Mexico State University (NMSU) is studying techniques for increasing the data rate capabilities of TDRSS. These techniques include the use of advanced bandwidth efficient modulation formats to increase the data rate that can be sustained in a TDRSS transponder and the use of lossless bandwidth compression of the data to be transmitted to lower the data rate required from the user spacecraft. Based upon current technology the most promising bandwidth efficient modulation technique is Trellis Coded Modulation (TCM) operating with Octal Phase shift Keying (8PSK). Trellis Coded Modulation coding with 8PSK carrier modulation has the capability to increase the data rate which can be transmitted through the TDRSS spacecraft by a factor of 2 to 2.5 times that available with todays coded QPSK systems with only a small penalty in link performance relative to the existing systems. However, before NASA can safely employ TCM coding it is necessary to prove that this complex format can perform on the real TDRSS link as it does in labs and simulation studies. This proof-of-concept test over a live satellite channel was the objective of the construction and testing performed under this task of the NMSU NASA grant referenced above. In conjunction with NASA, NMSU's CSTTS has constructed a system to test a new candidate TDRSS modulation scheme, TCM 8PSK, that can enhance the information throughput of the TDRSS spacecraft. The test system for this project which was constructed over a period of 18 months by NMSU consisted of two racks of commercial and univeristy-designed and -built equipment. This project has included modifications of an existing White Sands Ground Terminal (WSGT) High Rate QPSK Demodulator to demodulate 8PSK as well as the construction of other support hardware. Also, two TCM codecs (coder/decoders) have been constructed to implement two levels of bandwidth efficiency. One was designed and built by the research team at NMSU while the other was created by the University of Notre Dame with the University of South Australia. The NMSU codec achieves a 2-to-1 increase in data rate per unit bandwidth with a coding gain relative to QPSK of about 3dB. The Notre Dame/South Australia codec achieves a 2.5-to-1 increase in data rate per unit of occupied bandwidth and a coding gain of about 2dB.

Osborne, William P.↗
NASA NTRS1978

Differential encoding for multiple amplitude and phase shift keying systems

Because of the symmetry in most two-dimensional signal constellations, ambiguities exist at the receiver as to the exact phase orientation of the received signal set. In PSK systems, this ambiguity is resolved by the use of differential encoding. This paper presents differential encoding techniques which can be used with a variety of symmetric signal sets to remove their phase ambiguity. While not proven to be optimum, the techniques do have low performance penalties relative to the uncoded performance. The key to reducing the performance penalty is to use the minimum amount of differential encoding necessary to resolve the ambiguity. Examples of encoding techniques for several common signal constellations are given, including their performance penalties.

Weber, W. J., III↗
NASA NTRS1992

Temporal averaging in a turbulent environment - Compensation for phase drifts in phase shifting interferometry

In an effort to improve the signal to noise in an interference experiment, we have developed a method to remove systematic phase drift between data sets acquired over long time intervals. Using this technique, it is possible to average repeatedly acquired phase measurements and improve the phase estimate without sacrificing spatial resolution. Results from tests using real-time phase stepping holographic interferometry applied to cantilever bending of a piezoelectric bimorph indicate that white noise has been reduced from 3 to less than 1 deg (lambda/360) by averaging 36 phase compensated data sets before object bending and 36 data sets after bending.

Ovryn, B.↗
NASA NTRS1973

Phase shift keyed, pulse code modulated signal synchronizer

Signal is demodulated and synchronized by three loop circuits: ''Q'' loop uses quadrature signal to stabilize frequency; ''B'' loop acts on baseboard signal to stabilize phase; and decoding ''I'' loop acts on in-phase signal. Synchronizer may be used to eliminate false-lock.

Kobayashi, H. S.↗
NASA NTRS1972

Low phase-shift amplifier

Single-stage MOSFET amplifier is described which is identical to standard neutralized amplifier except that neutralization provided by broadband transformer is applied to AGC gate instead of signal gate. Neutralization of drain-to-control gate capacity minimizes the phase change induced by variation in AGC.

Lutes, G. F.↗
NASA NTRS1985

Source phase shift - A new phenomenon in wave propagation due to anelasticity

The free oscillations of an anelastic earth model due to earthquakes were calculated directly by means of the correspondence principle from wave propagation theory. The formulation made it possible to find the source phase which is not predictable using first order perturbation theory. The predicted source phase was largest for toroidal modes with source components proportional to the radial strain scalar instead of the radial displacement scalar. The source phase increased in relation to the overtone number. In addition, large relative differences were found in the excitation modulus and the phase when the elastic excitation was small. The effect was sufficient to bias estimates of source properties and elastic structure.

Buland, R.↗
NASA NTRS1982

Phase shift errors in the theory and practice of surface intensity measurements

The surface acoustical intensity method (sometimes known as the microphone-accelerometer cross-spectral method) is a relatively new noise source/path identification tool. Several researchers have had difficulties implementing this method because of instrumentation phase mis-match. A simple technique for measuring and correcting instrumentation phase mis-match has been developed. This new technique has been tested recently on a noise source identification problem of practical interest. The results of the experiments indicate that the surface acoustic intensity method produces reliable data and can be applied to a variety of noise source/path problems.

Mcgary, M. C.↗
DOE OSTI2023

Detecting Spin-Bath Polarization with Quantum Quench Phase Shifts of Single Spins in Diamond

Single-qubit sensing protocols can be used to measure qubit-bath coupling parameters. However, for sufficiently large coupling, the sensing protocol itself perturbs the bath, which is predicted to result in a characteristic response in the sensing measurements. Here, we observe this bath perturbation, also known as a quantum quench, by preparing the nuclear spin bath of a nitrogen-vacancy (NV) center in polarized initial states and performing phase-resolved spin-echo measurements on the NV electron spin. These measurements reveal a time-dependent phase determined by the initial state of the bath. We derive the relationship between the sensor phase and the Gaussian spin-bath polarization and apply it to reconstruct both the axial and transverse polarization components. Using this insight, we optimize the transfer efficiency of our dynamic nuclear polarization sequence. This technique for directly measuring bath polarization may assist in preparing high-fidelity quantum memory states, improving nanoscale NMR methods, and investigating non-Gaussian quantum baths.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Transient circadian internal desynchronization after light-dark phase shift in monkeys

In four conscious chair-acclimatized squirrel monkeys (Saimiri sciureus) studied with lights on (600 lx) from 0800 to 2000 hr daily, prominent 24-hr rhythms in feeding, drinking, activity, body temperature, and urinary potassium, sodium, and water excretion were seen. When the monkeys were subjected to 36 hr of darkness followed by 36 hr of light, each variable demonstrated a circadian rhythm which was not passively dependent on the light-dark cycle. After the 24-hr light-dark cycle was abruptly phase-delayed by 8 hr, all the rhythms resynchronized with the new light-dark cycle phase, demonstrating that light-dark cycles are an effective zeitgeber. However, the resynchronization of the rhythms of feeding, drinking, activity, and body temperature was 90% complete within approximately 2 days while the 90% resynchronization of the urinary rhythms took approximately 5 days. These results suggest that the circadian timing system in S. sciureus may consist of several spontaneously oscillating units which can become transiently uncoupled during perturbations of environmental time cues.

Moore-Ede, M. C.↗
DOE OSTI2021

Oval-cycloidal Magnetic Structure with Phase-shift in the Non-centrosymmetric Tetragonal Compound CePdSi 3

CePdSi 3 with H // [100] exhibits multiple metamagnetic transitions. Since there is no frustration in this system, it is suggested that the origin of the multiple metamagnetic transitions is the influence of the antisymmetric spin–orbit interaction. To clarify the magnetic structure under the influence of the antisymmetric spin–orbit interaction, neutron diffraction experiments have been performed using single crystal samples of CePdSi3. There are observed magnetic reflections with incommensurate magnetic propagation vector q=(0.315,0,0) in the phase I. In addition, additional magnetic reflections were also observed in the phase III. The magnetic structure was found to be an oval-cycloidal structure at the phase III in CePdSi 3 , and we discuss the origin of the unusual magnetic structure.

36 MATERIALS SCIENCE↗