Search NASA⌕ Search

SEARCH · Search NASA

Results for “network alignment”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Parallel access alignment network with barrel switch implementation for d-ordered vector elements

An alignment network between N parallel data input ports and N parallel data outputs includes a first and a second barrel switch. The first barrel switch fed by the N parallel input ports shifts the N outputs thereof and in turn feeds the N-1 input data paths of the second barrel switch according to the relationship X=k.sup.y modulo N wherein x represents the output data path ordering of the first barrel switch, y represents the input data path ordering of the second barrel switch, and k equals a primitive root of the number N. The zero (0) ordered output data path of the first barrel switch is fed directly to the zero ordered output port. The N-1 output data paths of the second barrel switch are connected to the N output ports in the reverse ordering of the connections between the output data paths of the first barrel switch and the input data paths of the second barrel switch. The second switch is controlled by a value m, which in the preferred embodiment is produced at the output of a ROM addressed by the value d wherein d represents the incremental spacing or distance between data elements to be accessed from the N input ports, and m is generated therefrom according to the relationship d=k.sup.m modulo N.

Barnes, George H.↗
NASA NTRS1993

Neural-network-directed alignment of optical systems using the laser-beam spatial filter as an example

This report describes an effort at NASA Lewis Research Center to use artificial neural networks to automate the alignment and control of optical measurement systems. Specifically, it addresses the use of commercially available neural network software and hardware to direct alignments of the common laser-beam-smoothing spatial filter. The report presents a general approach for designing alignment records and combining these into training sets to teach optical alignment functions to neural networks and discusses the use of these training sets to train several types of neural networks. Neural network configurations used include the adaptive resonance network, the back-propagation-trained network, and the counter-propagation network. This work shows that neural networks can be used to produce robust sequencers. These sequencers can learn by example to execute the step-by-step procedures of optical alignment and also can learn adaptively to correct for environmentally induced misalignment. The long-range objective is to use neural networks to automate the alignment and operation of optical measurement systems in remote, harsh, or dangerous aerospace environments. This work also shows that when neural networks are trained by a human operator, training sets should be recorded, training should be executed, and testing should be done in a manner that does not depend on intellectual judgments of the human operator.

Decker, Arthur J.↗
NASA NTRS2012

Disruption of an Aligned Dendritic Network by Bubbles During Re-Melting in a Microgravity Environment

The quiescent Microgravity environment can be quite dynamic. Thermocapillary flow about "large" static bubbles on the order of 1mm in diameter was easily observed by following smaller tracer bubbles. The bubble induced flow was seen to disrupt a large dendritic array, effectively distributing free branches about the solid-liquid interface. "Small" dynamic bubbles were observed to travel at fast velocities through the mushy zone with the implication of bringing/detaching/redistributing dendrite arm fragments at the solid-liquid interface. Large and small bubbles effectively re-orient/re-distribute dendrite branches/arms/fragments at the solid liquid interface. Subsequent initiation of controlled directional solidification results in growth of dendrites having random orientations which significantly compromises the desired science.

Grugel, Richard N.↗
NASA NTRS1970

Solar electric propulsion system evaluation

Solar electric propulsion system performance consisting of thrustors with thrust vector aligning actuators, switching network and flight type power conditioner

Costogue, E. N.↗
NASA NTRS1992

Self-Aligning Optical Measurement Systems

The paper discusses how to teach a system of neural networks to respond to the alignment clues used by a human operator in performing routine, initial alignments. A paradigm is proposed for automating the alignment of the components of optical measurement systems. The paradigm which was tested on a spatial filter has proved to be successful for optical alignment.

Decker, Arthur J.↗
NASA NTRS1991

Neural nets for aligning optical components in harsh environments: Beam smoothing spatial filter as an example

The goal is to develop an approach to automating the alignment and adjustment of optical measurement, visualization, inspection, and control systems. Classical controls, expert systems, and neural networks are three approaches to automating the alignment of an optical system. Neural networks were chosen for this project and the judgements that led to this decision are presented. Neural networks were used to automate the alignment of the ubiquitous laser-beam-smoothing spatial filter. The results and future plans of the project are presented.

Decker, Arthur J.↗
NASA NTRS2004

Discrete Wavelength-Locked External Cavity Laser

A prototype improved external cavity laser (ECL) was demonstrated in the second phase of a continuing effort to develop wavelength-agile lasers for fiber-optic communications and trace-gas-sensing applications. This laser is designed to offer next-generation performance for incorporation into fiber-optic networks. By eliminating several optical components and simplifying others used in prior designs, the design of this laser reduces costs, making lasers of this type very competitive in a price-sensitive market. Diode lasers have become enabling devices for fiber optic networks because of their cost, compactness, and spectral properties. ECLs built around diode laser gain elements further enhance capabilities by virtue of their excellent spectral properties with significantly increased (relative to prior lasers) wavelength tuning ranges. It is essential to exploit the increased spectral coverage of ECLs while simultaneously insuring that they operate only at precisely defined communication channels (wavelengths). Heretofore, this requirement has typically been satisfied through incorporation of add-in optical components that lock the ECL output wavelengths to these specific channels. Such add-in components contribute substantially to the costs of ECL lasers to be used as sources for optical communication networks. Furthermore, the optical alignment of these components, needed to attain the required wavelength precision, is a non-trivial task and can contribute substantially to production costs. The design of the present improved ECL differs significantly from the designs of prior ECLs. The present design relies on inherent features of components already included within an ECL, with slight modifications so that these components perform their normal functions while simultaneously effecting locking to the required discrete wavelengths. Hence, add-in optical components and the associated cost of alignment can be eliminated. The figure shows the locking feedback signal, and the frequency locking achieved by use of this signal, as a mirror is tilted through a range of angles to tune the ECL through 48 channels. The data for the frequency plot were obtained, simultaneously with the data for the locking-signal plot, by using a scanning Michelson interferometer to precisely determine the ECL wavelength (and, hence, frequency). Given the ability of the Michelson interferometer to obtain highly precise readings, the frequency plot can be taken to be a reliable indication of single-mode operation. The discontinuities in the frequency plot signify the switching of the ECL between channels; in other words, they indicate tuning with locking to discrete frequencies. The peaks of the feedbacklocking signal correspond to the centers, or near centers, of the mirror angle scan through the corresponding channels. Thus, it is clear that when the feedback-locking signal is at a local maximum, the ECL is operating at single frequency at or near the middle frequency of the selected channel. This is all that is required for precisely locking the ECL output wavelength. The locking is achieved without additional external optical components.

Pilgrim, Jeffrey S.↗
NASA NTRS2018

Hi-C2.1 Observations of Solar Jetlets at Edges of Network Lanes

We present high resolution (0.2”) high cadence (5s) extreme ultraviolet (EUV) observations of small-­scale jetlet-­like features and spicule-­like features observed with NASA’s High-­resolution Coronal Imager2.1 (Hi-C) during its 5‐min observing span. We investigate the magnetic setting of 4 on-disk jetlets and 2 on-­disk spicules by using high resolution 172A images from Hi-­‐C and EUV images from Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and line-­of-­sight magnetograms from SDO/Helioseismic and Magnetic Imager (HMI). The jetlets and spicules are at edges of magnetic network lanes. From magnetograms co-­aligned with the Hi-­C and AIA images, we find that the jetlets stem from sites of likely flux cancelation between merging majority-polarity and weaker minority-­polarity flux, but in contrast to larger jetlets observed by IRIS some do not show obvious enhanced brightenings at their base. Based on the similarity of these observations of approx. 4 obvious Hi-­C small jetlets with our previous observations of 10 IRIS larger jetlets and approx. 30 coronal jets in quiet regions and coronal holes, we infer that flux cancelation is probably the essential process in the buildup and triggering of jetlets. Our observations suggest that network jetlet eruptions, large and small, are small-scale analogs of both larger-­scale coronal jet eruptions and the still-­larger-­scale eruptions that makemajor CMEs. For simplicitywe will use termjetlets for jetlet-­like features and spicules for spicule-­like features.

Panesar, Navdeep K.↗
NASA NTRS1984

Heating the sun's lower transition region with fine-scale electric currents

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

Rabin, D.↗
NASA NTRS1988

Investigation of RF excited CW CO2 waveguide lasers local oscillator - RF excitation

A new local oscillator housing was built which seems to have improved laser life. Laser cooling was changed from internal water cooling to the more convenient thermal contact cooling. At the present time, a conclusion can not be made if the 20 percent reduction in power output is the result of poorer cooling or poorer grating alignment. The coupling-starting network was improved from 55 to about 90 percent. It can be adjusted by varying trimmers C sub 1 and C sub 2 to match RF power levels between 10 and 30 W. If the laser admittance changes greatly with laser life rematching will have to be achieved by remote control for space applications. The same holds true if the RF power level has to be changed with a maximum efficiency constraint.

Hochuli, U.↗
NASA NTRS2011

Enabling the Capture and Sharing of NASA Technical Expertise Through Communities of Practice

Historically, engineers at the National Aeronautics and Space Administration (NASA) had few opportunities or incentives to share their technical expertise across the Agency. Its center- and project- focused culture often meant that knowledge never left organizational and geographic boundaries. With increasingly complex missions, the closeout of the Shuttle Program, and a new generation entering the workforce, developing a knowledge sharing culture became critical. To address this need, the Office of the Chief Engineer established communities of practice on the NASA Engineering Network. These communities were strategically aligned with NASA's core competencies in such disciplines as avionics, flight mechanics, life support, propulsion, structures, loads and dynamics, human factors, and guidance, navigation, and control. This paper describes the process used to identify and develop communities, from establishing simple websites that compiled discipline-specific resources to fostering a knowledge-sharing environment through collaborative and interactive technologies. It includes qualitative evidence of improved availability and transfer of knowledge. It focuses on pivotal capabilities that increased knowledge exchange such as a custom-made Ask An Expert system, community contact lists, publication of key resources, and submission forms that allowed any user to propose content for the sites. It discusses the peer relationships that developed through the communities and the leadership and infrastructure that made them possible.

Topousis, Daria E.↗
NASA NTRS1990

Method and apparatus for transmitting data

A method and apparatus for transmitting a byte-organized serial data stream from a transmitting station to a receiving station that may employ byte boundaries different than the transmitting station. The technique includes sending N different data streams from the remote terminal, where N is the number of different framing alignments that may be imposed on the unframed data stream by the network. The different data streams are chosen so that one will be framed by the network as the intended data stream regardless of which framing alignment is actually imposed.

Schroeder, George L.↗
NASA NTRS2012

A Human View Model for Socio-Technical Interactions

The Human View was developed as an additional architectural viewpoint to focus on the human part of a system. The Human View can be used to collect and organize data in order to understand how human operators interact and impact the other elements of a system. This framework can also be used to develop a model to describe how humans interact with each other in network enabled systems. These socio-technical interactions form the foundation of the emerging area of Human Interoperability. Human Interoperability strives to understand the relationships required between human operators that impact collaboration across networked environments, including the effect of belonging to different organizations. By applying organizational relationship concepts from network theory to the Human View elements, and aligning these relationships with a model developed to identify layers of coalition interoperability, the conditions for different levels for Human Interoperability for network enabled systems can be identified. These requirements can then be captured in the Human View products to improve the overall network enabled system.

Handley, Holly A.↗
NASA NTRS1984

Plasma and magnetospheric research

Research activities on the following topics were summarized: (1) software for the Space Plasma computer Analysis Network (SPAN), (2) plasmaspheric field-aligned temperature gradients, (3) the shift in spacecraft potential as a function of plasma density, (4) plasma flow, (5) the Fabry-Perot interferometer, and (6) the Differential Ion Flux Probe (DIFP).

Comfort, R. H.↗
NASA NTRS1994

Earth Rotation Parameters from DSN VLBI: 1994

In this report, Earth Rotation Parameter (ERP) estimates ahve been obtained from an analysis of Deep Space Network (DSN) VLBI data that directly aligns its celestial and terrestrial reference frames with those of the International Earth Rotation Service (IERS).

Earth rotation TEMPO↗
NASA NTRS1980

TRISCAN: A method of precision antenna positioning

The triangle (antenna) scan (TRISCAN) is a method of improving the alignment between the boresight of the Deep Space Network antennas and a particular target, spacecraft, or radio source (star). For stars, the method works in conjunction with the noise adding radiometer and the antenna pointing system to form estimates of the alignment offset coordinates. This information is then used to position the antenna for improved target alignment. A comparison with CONSCAN is included since a CONSCAN study led to TRISCAN development.

Bunce, R. C.↗