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Results for “phase slippage”

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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7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Performance of a finite phase state bit-synchronization loop with and without sequential filters

A discrete phase state bit-synchronization loop is proposed for synchronization and detection of a binary nonreturn-to-zero (NRZ) process. The general loop model is developed for 11 and 17 phase states with optional sequential loop filter. Loop performance is considered in terms of the phase error density function, rms phase error, and mean time to bit slippage. It is shown that satisfactory loop performance can be achieved at -3 dB SNR through use of sequential loop filters.

Ransom, J. J.↗
NASA NTRS1988

Artificial intelligence approaches to software engineering

Artificial intelligence approaches to software engineering are examined. The software development life cycle is a sequence of not so well-defined phases. Improved techniques for developing systems have been formulated over the past 15 years, but pressure continues to attempt to reduce current costs. Software development technology seems to be standing still. The primary objective of the knowledge-based approach to software development presented in this paper is to avoid problem areas that lead to schedule slippages, cost overruns, or software products that fall short of their desired goals. Identifying and resolving software problems early, often in the phase in which they first occur, has been shown to contribute significantly to reducing risks in software development. Software development is not a mechanical process but a basic human activity. It requires clear thinking, work, and rework to be successful. The artificial intelligence approaches to software engineering presented support the software development life cycle through the use of software development techniques and methodologies in terms of changing current practices and methods. These should be replaced by better techniques that that improve the process of of software development and the quality of the resulting products. The software development process can be structured into well-defined steps, of which the interfaces are standardized, supported and checked by automated procedures that provide error detection, production of the documentation and ultimately support the actual design of complex programs.

Johannes, James D.↗
NASA NTRS1993

A continuum theory of a lubrication problem with solid particles

The governing equations for a two-dimensional lubrication problem involving the mixture of a Newtonian fluid with solid particles at an arbitrary volume fraction are developed using the theory of interacting continuua (mixture theory). The equations take the interaction between the fluid and the particles into consideration. Provision is made for the possibility of particle slippage at the boundaries. The equations are simplified assuming that the solid volume fraction varies in the sliding direction alone. Equations are solved for the velocity of the fluid phase and that of the solid phase of the mixture flow in the clearance space of an arbitrary shaped bearing. It is shown that the classical pure fluid case can be recovered as a special case of the solutions presented. Extensive numerical solutions are presented to quantify the effect of particulate solid for a number of pertinent performance parameters for both slider and journal bearings. Included in the results are discussions on the influence of particle slippage on the boundaries as well as the role of the interacting body force between the fluid and solid particles.

Dai, Fuling↗
NASA NTRS1972

Use of propagation corrections for VLF timing

The theory of VLF timing from phase measurements is briefly reviewed with attention to both frequency and epoch. Propagational aspects are noted without specific attention to predictional details. Cycle slippage is described. Application of propagation corrections to VLF timing is described, with particular attention to the use of available skywave corrections published for the OMEGA Navigation System.

Swanson, E. R.↗
NASA NTRS1973

An analytical investigation of acquisition techniques and system integration studies for a radar aircraft guidance research facility, phase 2

A review of user requirements and updated instrumentation plans are presented for the aircraft tracking and guidance facility at NASA Wallops Station. User demand has increased as a result of new flight research programs; however, basic requirements remain the same as originally reported. Instrumentation plans remain essentially the same but with plans for up- and down-link telemetry more firm. With slippages in the laser acquisition schedule, added importance is placed on the FPS-16 radar as the primary tracking device until the laser is available. Limited simulation studies of a particular Kalman-type filter are also presented. These studies simulated the use of the filter in a helicopter guidance loop in a real-time mode. Disadvantages and limitations of this mode of operation are pointed out. Laser eyesafety calculations show that laser tracking of aircraft is readily feasible from the eyesafety viewpoint.

Thompson, W. S.↗
NASA NTRS1979

Automated array assembly, phase 2

Tasks of scaling up the tandem junction cell (TJC) from 2 cm x 2 cm to 6.2 cm and the assembly of several modules using these large area TJC's are described. The scale-up of the TJC was based on using the existing process and doing the necessary design activities to increase the cell area to an acceptably large area. The design was carried out using available device models. The design was verified and sample large area TJCs were fabricated. Mechanical and process problems occurred causing a schedule slippage that resulted in contract expiration before enough large-area TJCs were fabricated to populate the sample tandem junction modules (TJM). A TJM design was carried out in which the module interconnects served to augment the current collecting buses on the cell. No sample TJMs were assembled due to a shortage of large-area TJCs.

Carbajal, B. G.↗
NASA NTRS1978

A1 moonquakes - Source distribution and mechanism

Two novel analysis techniques have been used to study focal mechanisms of A1 moonquakes, which occur at the most active of the 80 deep-moonquake source regions identified to date. The first is the cross-spectral analysis of matching signal waveforms. Cross phase spectra clearly show relative polarity of signals and give precise time relationships between signals, thus enabling accurate detemination of relative source locations within the source region. The second is the analysis of amplitude ratios, which reveal the patterns of P- and S-wave radiations around the source region. A1 moonquake foci are found to be concentrated in a nearly horizontal planar region less than 1 km in diameter. Their focal mechanism may be described by slippages along a horizontal plane with the slip direction rotating with and predominantly controlled by the shifting tidal stress field. Thus, A1 moonquakes represent a process of simple storage and release of tidal energy with no evidence for a release of accumulated tectonic stress.

Nakamura, Y.↗