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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Steady-state analysis of a faulted three-phase four-wire system supplying induction motors with neutrals connected and other single-phase line-to-neutral loads

Four wire Wye connected ac power systems exhibit peculiar steady state fault characteristics when the fourth wire of three phase induction motors is connected. The loss of one phase of power source due to a series or shunt fault results in currents higher than anticipated on the remaining two phases. A theoretical approach to compute the fault currents and voltages is developed. A FORTRAN program is included in the appendix.

Wood, M. E.↗
NASA NTRS1984

Space station architecture, module, berthing hub, shell assembly, berthing mechanism and utility connection channel

The geometric form of a space station is presented that includes a description of a plurality of modules and berthing hubs, joined by interconnections which are sideways connectable. The modules and hubs are fastened together in a triangular configuration in three dimensions. The interconnections include a pair of opposed, axially aligned, flanged ports and a clamp latch formed from a plurality of sections hinged along their length and extending circumferentially around the flanged ports. A hermetic seal is formed between the ports. A utilities connection channel extends between the ports. The channel has a shell with utilities connectors movable between an extended position to mating connectors in the modules and a withdrawn position. Assembly sequence and common module shell structure is detailed.

Cohen, M. M.↗
NASA NTRS1986

Rotating Connection for Electrical Cables

Cable reel provides electrical connections between fixed structure and rotating one. Reel carries power and signal lines while allowing rotating structure to turn up to 360 degrees with respect to fixed structure. Reel replaces sliprings. Can be used to electrically connect arm of robot with body. Reel releases cable to rotating part as it turns and takes up cable as rotating part comes back to its starting position, without tangling, twisting, or kinking.

Manges, D. R.↗
NASA NTRS1986

Determining Internal Connections in Capacitors

Simple electrical test shows which terminals connected to outer capacitor foil. Test makes it unnecessary to resort to X-ray inspection to distinguish terminals. When outer foil of capacitor is attached to ungrounded signal-generator output lead, oscilloscope displays higher waveform amplitude. When outer foil is joined to grounded signalgenerator output lead, waveform amplitude is lower. Test also used to determine internal connections in multiple-element capacitors.

Ott, F. M.↗
NASA NTRS1986

Quick-Connect Heavy-Duty Fastener

Attaching device combines fast connection and disconnection with high strength. T-shaped stud engages groove in receptacle after one-quarter turn. Further turning tightens nut on receptacle. Like quarter-turn attaching devices, connected and disconnected quickly. Like threaded devices, adjusted to desired preload, withstand high loads, and accommodate wide range of grip lengths.

Moore, D. M.↗
NASA NTRS1986

Combining and connecting linear, multi-input, multi-output subsystem models

The mathematical background for combining and connecting linear, multi-input, multi-output subsystem models into an overall system model is provided. Several examples of subsystem configurations are examined in detail. A description of a MATRIX (sub x) command file to aid in the process of combining and connecting these subsystem models is contained.

Duke, E. L.↗
NASA NTRS1986

Inclusion of elastically connected members in exact buckling and frequency calculations

A standard stiffness matrix procedure which permits any combination of rigid, elastic, pinned or sliding connections of the degrees of freedom at the ends of a member to the nodes of its parent structure is described, in order to show how easily it can be extended to allow an existing algorithm to be used to ensure that no eigenvalues of the parent structure can be missed even when 'exact' member theory is used. The eigenvalues are the natural frequencies of undamped free vibration analyses or the critical load factors of buckling problems. The method preserves the exactness of the member theory and an efficient method for computer application is indicated. The theory also permits any combination of rigid, elastic, pinned or sliding connections between the freedoms of a substructure and those of its parent structure.

Williams, F. W.↗
NASA NTRS1987

Reverse time migration: A seismic processing application on the connection machine

The implementation of a reverse time migration algorithm on the Connection Machine, a massively parallel computer is described. Essential architectural features of this machine as well as programming concepts are presented. The data structures and parallel operations for the implementation of the reverse time migration algorithm are described. The algorithm matches the Connection Machine architecture closely and executes almost at the peak performance of this machine.

Fiebrich, Rolf-Dieter↗
NASA NTRS1987

Solving very large, sparse linear systems on mesh-connected parallel computers

The implementation of Pan and Reif's Parallel Nested Dissection (PND) algorithm on mesh connected parallel computers is described. This is the first known algorithm that allows very large, sparse linear systems of equations to be solved efficiently in polylog time using a small number of processors. How the processor bound of PND can be matched to the number of processors available on a given parallel computer by slowing down the algorithm by constant factors is described. Also, for the important class of problems where G(A) is a grid graph, a unique memory mapping that reduces the inter-processor communication requirements of PND to those that can be executed on mesh connected parallel machines is detailed. A description of an implementation on the Goodyear Massively Parallel Processor (MPP), located at Goddard is given. Also, a detailed discussion of data mappings and performance issues is given.

Opsahl, Torstein↗
NASA NTRS1986

Teleparallelism as a universal connection on null hypersurfaces in general relativity

It is shown that a close relationship between the inner geometry of a null hypersurface N3 and the Newman-Penrose (NP) (1962, 1963) spin coefficient formalism exists. Projecting the null complex NP tetrad onto N3, two triads of basis vectors in N3 are obtained. The inner geometry of N3 is based on the assumption that these vectors are parallelly transported along the surface; this gives rise to the teleparallel connection as a metric nonsymmetric affine connection. The gauge freedom for the choice of the basis triads is given by the isotropy subgroup of the local Lorentz group leaving invariant the direction of the null generators of N3, and teleparallelism is determined by the equivalence class of the basis triads with respect to the global gauge group. Nine of the twelve NP coefficients are identified as the triad components of the torsion and the second fundamental form of N3. The resulting generalized Gauss-Codazzi equations are identical to nine of the NP equations, i.e., to the half of the Ricci identities. This result gives a geometrical meaning to the entire formalism. Finally a general proof of Penrose's theorem that the shear of the null generators of N3 is the only initial null datum for a gravitational field on N3 is presented.

Mazur, P. O.↗
NASA NTRS1987

Binary synaptic connections based on memory switching in a-Si:H for artificial neural networks

A scheme for nonvolatile associative electronic memory storage with high information storage density is proposed which is based on neural network models and which uses a matrix of two-terminal passive interconnections (synapses). It is noted that the massive parallelism in the architecture would require the ON state of a synaptic connection to be unusually weak (highly resistive). Memory switching using a-Si:H along with ballast resistors patterned from amorphous Ge-metal alloys is investigated for a binary programmable read only memory matrix. The fabrication of a 1600 synapse test array of uniform connection strengths and a-Si:H switching elements is discussed.

Thakoor, A. P.↗
NASA NTRS1988

Connectivity is the key

Connectivity that would allow users at home to interact with an experiment in space and with facilities and services worldwide is a primary goal of the international Space Station program. The systems supporting such connectivity, including the Space Station Information System, the Technical and Management Information System, and the Software Support Environment, are discussed here. The primary purposes of each system and their operational data are addressed.

Hall, Dana L.↗
NASA NTRS1989

Space station architecture, module, berthing hub, shell assembly, berthing mechanism and utility connection channel

A Space Station includes a plurality of modules, and berthing hubs, joined by interconnections which are sideways connectable. The modules and hubs are fastened together in a trianglar configuration in three dimensions. The interconnections include a pair of opposed, axially aligned, flanged ports, and a clamp latch formed from a plurality of sections hinged along their length and extending circumferentially around the flanged ports. A utilities connection channel extends between ports. The channel has a shell with utilities connectors movable between an extended position to mating connectors in the modules and a withdrawn position. Assembly sequence and common module shell structure is detailed.

Marc M Cohen↗
NASA NTRS1988

Kanerva's sparse distributed memory: An associative memory algorithm well-suited to the Connection Machine

The advent of the Connection Machine profoundly changes the world of supercomputers. The highly nontraditional architecture makes possible the exploration of algorithms that were impractical for standard Von Neumann architectures. Sparse distributed memory (SDM) is an example of such an algorithm. Sparse distributed memory is a particularly simple and elegant formulation for an associative memory. The foundations for sparse distributed memory are described, and some simple examples of using the memory are presented. The relationship of sparse distributed memory to three important computational systems is shown: random-access memory, neural networks, and the cerebellum of the brain. Finally, the implementation of the algorithm for sparse distributed memory on the Connection Machine is discussed.

Rogers, David↗
NASA NTRS1988

Phase connection for geodesy - Results from a 245-km baseline

In an effort to greatly improve the measurement precision of VLBI observables used to determine geodetic baselines, the potential of utilizing fringe phase has been investigated. The 245-km baseline between Mojave and Owens Valley in CA has been most thoroughly studied for this purpose. In trying several different experimental designs, it appears that source scheduling is not the critical factor in determining when phase connection can be established. Normally, instrumental instabilities are also not limiting (although nominal functioning of the instrumentation is essential). The most serious factor in limiting opportunities for phase connection seems to be atmospheric variability. However, when the observation SNR is made large (greater than 50) to give very precise group delays (and hence enhance the chance of resolving phase ambiguities), the improvement in baseline uncertainty obtained using phase delays is only marginal compared with the corresponding group delay solution. For this case, the baseline error budget is dominated by stochastic variations in clock and atmospheric delay contributions rather than by observation noise.

Ray, J. R.↗
NASA NTRS1988

Novel tether-connected two-dimensional structures for low earth orbits

This paper proposes novel tether-connected two-dimensional structures with a size of several hundred square kilometers for low earth orbits. The attitude of these structures is gravitationally stabilized with respect to an earth-oriented reference frame. A stable shape is obtained by utilizing environmental forces such as differential air drag or electrodynamic forces which stiffen the system. Configurations which differ in geometry and in the number of connecting tethers are presented in the paper. The static stability of each configuration is analyzed as a function of design and orbital parameters. A brief discussion of the applications of such tethered systems is provided at the end of the paper.

Lorenzini, Enrico C.↗