Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “sequencer”

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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Sequencing device utilizing planetary gear set

A planetary (epicyclic) gear set is provided with a reversible rotating input shaft and individual outputs shafts actuated, respectively, by the ring gear and planet gear carrier. Latch means is positioned to selectively and automatically stop the ring gear or carrier member while releasing the other to provide the desired sequential output operation. The output shafts are reversed in sequence and direction of rotation by reversing rotational direction of the input shaft.

Appleberry, W. T.↗
NASA NTRS1979

Investigation of Proposed Process Sequence for the Array Automated Assembly Task, Phase 2

The technological readiness of the proposed process sequence was reviewed. Process steps evaluated include: (1) plasma etching to establish a standard surface; (2) forming junctions by diffusion from an N-type polymeric spray-on source; (3) forming a p+ back contact by firing a screen printed aluminum paste; (4) forming screen printed front contacts after cleaning the back aluminum and removing the diffusion oxide; (5) cleaning the junction by a laser scribe operation; (6) forming an antireflection coating by baking a polymeric spray-on film; (7) ultrasonically tin padding the cells; and (8) assembling cell strings into solar circuits using ethylene vinyl acetate as an encapsulant and laminating medium.

Mardesich, N.↗
NASA NTRS1978

Chemical condensation sequences in supernova ejecta

Equilibrium condensation is investigated for composition and pressures representative of supernova (SN) ejecta. The results are compared with those obtained for the solar nebula, and the distribution of elements among the various gaseous species and solid phases is computed for solar and SN-shell condensation sequences. The data are applied to problems concerning the observed mass fractionations of Si, Mg, and O in Allende, as well as to the strong depletion of heavy-element abundances in the interstellar medium. The results indicate that dust grains from a SN could have introduced isotopic anomalies into the solar nebula, that many minerals produced in SN ejecta are the same as those predicted to be stable in the solar nebula, and that the observed depletion of heavy elements in the interstellar gas could be due to dust formation in SN ejecta.

Lattimer, J. M.↗
NASA NTRS1978

Upper limits on extreme ultraviolet radiation from nearby main sequence and subgiant stars

Flux upper limits for 44-800 A radiation were measured in a sample of nearby main sequence stars and one subgiant star with the aid of the Apollo-Soyuz grazing incidence telescope. Comparisons of emission measure upper limits with three different methods for predicting coronal properties cannot yet determine which, if any, are valid. Data for Alpha Centauri A and B are consistent with recent HEAO-1 soft X-ray measurements which suggest that the surface flux of coronal emission from the Alpha Cen system is comparable to that of the 'normal' sun.

Ayres, T. R.↗
NASA NTRS1979

Orbital configuration assignment of 4S/e/ doubly excited states of lithium isoelectronic sequence

Results of Hartree-Fock and multiconfiguration Hartree-Fock calculations using only two configurations (degenerate in zero order within the context of the nuclear-charge-expansion perturbation method) for 4S(e) doubly excited states of lithium isoelectronic sequence are used to propose an orbital configuration classification of these states extending the similar classification by Holoien and Geltman for 4S(e) states of lithium only.

Ali, M. A.↗
NASA NTRS1978

Evolution of early life inferred from protein and ribonucleic acid sequences

The chemical structures of ferredoxin, 5S ribosomal RNA, and c-type cytochrome sequences have been employed to construct a phylogenetic tree which connects all major photosynthesizing organisms: the three types of bacteria, blue-green algae, and chloroplasts. Anaerobic and aerobic bacteria, eukaryotic cytoplasmic components and mitochondria are also included in the phylogenetic tree. Anaerobic nonphotosynthesizing bacteria similar to Clostridium were the earliest organisms, arising more than 3.2 billion years ago. Bacterial photosynthesis evolved nearly 3.0 billion years ago, while oxygen-evolving photosynthesis, originating in the blue-green algal line, came into being about 2.0 billion years ago. The phylogenetic tree supports the symbiotic theory of the origin of eukaryotes.

Dayhoff, M. O.↗
NASA NTRS1978

Petrology of a sequence of pyroclastic rocks from the valley of Taurus-Littrow /Apollo 17 landing site/

Thirteen samples of core 74001/2, collected at Shorty Crater by Apollo 17, have been analyzed. The samples, taken from the core section below 5.5 cm and representing most of the major stratigraphic units described by Nagle (1978), consist entirely of whole and fragmented orange and black droplets. The grain shape, degree of crystallinity, breakage, vesicularity, predominant olivine shapes, and phenocryst content of about 18,000 droplets were investigated. The crystalline droplets were found to contain olivine and ilmenite as major phases and pyroxene, Cr-spinel and metallic Fe as minor phases. The grain shape, degree of crystallization, olivine shape and olivine composition suggest that a wide range of cooling rates is represented. The upper part of the core section (above 5.5 cm) has undergone in situ reworking by micrometeorites. The 74001/2 samples are believed to be from an ultramafic pyroclastic deposit brought to the surface by the Shorty Crater impact and originally formed by a lava fountain active in the Taurus-Littrow valley 3.5 b.y. ago. The sequence represented in the sample was most likely deposited over a very short period of time.

Heiken, G.↗
NASA NTRS1978

A candidate low-cost processing sequence for terrestrial silicon solar cell panel

Manufacturing sequence for silicon solar cells using Czochralsky crystal growing techniques in order to produce at a rate of 20 MW per year on a 24-hour per day basis is discussed. Cost analysis of the manufacturing is presented and consideration is given to the following processing decision categories of the manufacturing of an unencapsulated solar cell from a silicon wafer: (1) treatment of the optical surface; (2) formation of the junction(s); and (3) metallization of electrical collectors. The manufacturing of encapsulated solar modules from solar cells, using two glass plates, a low iron front surface, and a standard float glass back plate, is described. Totaling the three major activities of wafer making, cell manufacturing, and module fabrication, the resulting contribution to module price will be 1.945 $/watt.

Bickler, D. B.↗
NASA NTRS1979

Binary classification of real sequences by discrete-time systems

This paper considers a novel approach to coding or classifying sequences of real numbers through the use of (generally nonlinear) finite-dimensional discrete-time systems. This approach involves a finite-dimensional discrete-time system (which we call a real acceptor) in cascade with a threshold type device (which we call a discriminator). The proposed classification scheme and the exact nature of the classification problem are described, along with two examples illustrating its applicability. Suggested approaches for further research are given.

Kaliski, M. E.↗
NASA NTRS1979

Proton collisional excitation in the lowest lying 3P terms of ions in the Be and Mg isoelectronic sequences

Proton collisional excitation cross sections and rate constants are presented for transitions between the 3P(J) fine-structure levels of the lowest-lying sp configurations in a number of astrophysically important ions belonging to the Be and Mg isoelectronic sequences. The calculations were made by direct integration of the Schroedinger equation resulting from semiclassical Coulomb excitation theory. The cross sections and rate constants for the 3P(J) transitions in the lowest-lying P(2) configurations are expected to be similar to those for the corresponding sp configuration transitions, and this is illustrated for C III. For the high-temperature ion Ca XVII alpha particle excitation is shown to be unimportant for situations involving ordinary values of the He/H abundance ratio. A simple, but apparently accurate method for determining certain radial integrals for low-lying excited configurations is proposed.

Landman, D. A.↗
NASA NTRS1979

Viking adaptive mission sequence and control operations

Viking mission operations were required to provide an adaptive sequencing capability in which future observations could be influenced by the latest information about Mars as it was obtained and analyzed. The mission operations strategy that was developed met this requirement and provided the capability to respond smoothly and efficiently to spacecraft subsystem anomalies with minimum impact on the science data gathering process. A description of the major elements of this adaptive man-in-the-loop control system is provided. Specific cases showing how it was utilized to enhance scientific return and to respond to spacecraft anomalies are also provided.

Larman, B. T.↗
NASA NTRS1980

Granulation in a main-sequence F-type star

The modal approach developed by Nelson and Musman (1977) is used to investigate convection in an F-type main-sequence star (effective temperature of 7300 K, g = 10,000 cm per sec per sec). The convective velocities and intensity contrasts are found to be larger than in the sun. Even though the convective flux is less than 1% of the total flux at a mean optical depth of unity, the spectral-energy distribution is strongly reddened as a result of the fluctuating opacity. This has important implications in the conversion scale from observed colors to effective temperature. The scale of the surface granulation is expected to be in the range 1000-5000 km. Calculations of the combined H-He I and He II convection zones support the prediction of Toomre et al. (1976) that the stable region between the zones is well mixed

Nelson, G. D.↗
NASA NTRS1980

Particle flux decrease-increase events at synchronous orbit and the temporal sequence of aurora during substorms

A systematic temporal correlation has been found between the energetic particle intensity variations measured at 6.6 earth radii and the development of large scale auroral features. The intensification and equatorward drift of eastwest oriented stable discrete homogeneous auroral arc systems coincide with the decrease in energetic particle intensity at 6.6 earth radii as the nightside magnetosphere develops into a more tail-like configuration. The subsequent major breakup of the aurora coincides with the recovery in particle intensity as the field returns to a more dipolar configuration. Since this prominent decrease-increase sequence must be related to the intensification or inward convection of the tail current plasma sheet configuration followed by its diversion or dissipation, the auroral correlation documented here closely links the auroral particle precipitation to the plasma sheet and tail current dynamics.

Erickson, K. N.↗
NASA NTRS1979

Aerospace Ground Equipment for model 4080 sequence programmer. A standard computer terminal is adapted to provide convenient operator to device interface

The Aerospace Ground Equipment (AGE) provides an interface between a human operator and a complete spaceborne sequence timing device with a memory storage program. The AGE provides a means for composing, editing, syntax checking, and storing timing device programs. The AGE is implemented with a standard Hewlett-Packard 2649A terminal system and a minimum of special hardware. The terminal's dual tape interface is used to store timing device programs and to read in special AGE operating system software. To compose a new program for the timing device the keyboard is used to fill in a form displayed on the screen.

Nissley, L. E.↗
NASA NTRS1981

Determination of load sequence effects on the degradation and failure of composite materials

A theoretical model was established to predict the fatigue behavior of composite materials, with emphasis placed on predictions of the degradation of residual strength and residual stiffness during fatigue cycling. The model parameters were evaluated from three test series including static strength fatigue life and residual strength tests. The tests were applied to two graphite/epoxy laminates. Load sequence effects were emphasized for both laminates and the predicted results agreed quite well with subsequent verification tests. Dynamic as well as static stiffness reduction data were collected by use of a PDP11-03 computer, which performed quite satisfactorily and permitted the recording of a substantial amount of dynamic stiffness reduction data.

Yang, J. N.↗
NASA NTRS1981

Reduction of the two dimensional stationary Navier-Stokes problem to a sequence of Fredholm integral equations of the second kind

Present approaches to solving the stationary Navier-Stokes equations are of limited value; however, there does exist an equivalent representation of the problem that has significant potential in solving such problems. This is due to the fact that the equivalent representation consists of a sequence of Fredholm integral equations of the second kind, and the solving of this type of problem is very well developed. For the problem in this form, there is an excellent chance to also determine explicit error estimates, since bounded, rather than unbounded, linear operators are dealt with.

Gabrielsen, R. E.↗
NASA NTRS1981

Observations of energetic helium ions in the earth's radiation belts during a sequence of geomagnetic storms

Observations of energetic (MeV) helium ions made with Explorer 45 during a sequence of magnetic storms during June through December of 1972 are presented. It is noted that the first of these storms started on June 17 and had a Dst index excursion to -190 gamma and that the MeV helium ions were perturbed primarily beyond 3 earth radii in the equatorial radiation belts with a typical flux increase of an order of magnitude at L equal to 4. The second storm period was in August and was associated with very major solar flare activity. While the Dst extremum was at best 35 gamma less than the June storm, this period can be characterized as irregular (or multi-storm) with strong compression of the magnetosphere and very large (order of magnitude) MeV helium ion flux enhancements down to L approximately equal to 2. After this injection, the trapped helium ion fluxes showed positive spherical slope with the peak beyond 3.15 MeV at L equal to 2.5; at the lowest observable L shells, little flux decay was seen during the remainder of the year.

Spjeldvik, W. N.↗
NASA NTRS1981

Load sequence effects on the fatigue of unnotched composite materials

A more comprehensive version of an earlier fatigue and residual strength degradation model is proposed to predict the effect of load sequence on the statistical fatigue behavior of composite laminates. The model, which reduces to various fatigue models proposed in the literature by means of approximations, is verified by a survey of experiments on glass/epoxy laminates. It is shown that the correlation between the model and the test results under dual stress levels is reasonable, and that a simplified version of the model is verified by experiments on graphite/epoxy laminates in which the correlation between theoretical predictions and results under dual stress levels is satisfactory. The model is also shown capable of predicting the effect of proof loads on the fatigue behavior of composite materials.

Yang, J. N.↗