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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Classification and machine recognition of severe weather patterns

Forecasting and warning of severe weather conditions are treated from the vantage point of pattern recognition by machine. Pictorial patterns and waveform patterns are distinguished. Time series data on sferics are dealt with by considering waveform patterns. A severe storm patterns recognition machine is described, along with schemes for detection via cross-correlation of time series (same channel or different channels). Syntactic and decision-theoretic approaches to feature extraction are discussed. Active and decayed tornados and thunderstorms, lightning discharges, and funnels and their related time series data are studied.

Wang, P. P.↗
NASA NTRS1977

Adaptation to delayed auditory feedback

Delayed auditory feedback disrupts the production of speech, causing an increase in speech duration as well as many articulatory errors. To determine whether prolonged exposure to delayed auditory feedback (DAF) leads to adaptive compensations in speech production, 10 subjects were exposed in separate experimental sessions to both incremental and constant-delay exposure conditions. Significant adaptation occurred for syntactically structured stimuli in the form of increased speaking rates. After DAF was removed, aftereffects were apparent for all stimulus types in terms of increased speech rates. A carry-over effect from the first to the second experimental session was evident as long as 29 days after the first session. The use of strategies to overcome DAF and the differences between adaptation to DAF and adaptation to visual rearrangement are discussed.

Katz, D. I.↗
NASA NTRS1978

Programmable formatting of program text: Experiences drawn from the TAMPR system

The TAMPR System originated as an approach to the problem of automating the routine modifications of FORTRAN source programs required to adapt them to a variety of uses or environments. Three steps are involved: (1) A FORTRAN source program is processed by the TAMPR Recognizer, yielding essentially a parse tree called the abstract form, (2) the Transformation Interpreter applies IGT's (Intragrammatical Transformations) to the abstract form as tree operations, and (3) the abstract form is then reconverted to source program form by the Formatter. By ensuring that the transformations are applied only to the correct syntactic entities and only in the intended contexts, the use of the abstract form greatly simplifies establishing the reliability of the overall process.

Dritz, K. W.↗
NASA NTRS1979

Low density bismaleimide-carbon microballoon composites

A process is described for the preparation of composite laminate.structures of glass cloth preimpregnated with polybismaleimide resin and adhered to a polybismaleimide glass or aromatic polyamide paper honeycomb cell structure that is filled or partially filled with a syntactic foam consisting of a mixture of bismaleimide resin and carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic microballoons and subsequently bonded using a 2% bismaleimide solution. The laminate structures are cured for two hours at 477 deg K and are adhered to the honeycomb bismaleimide adhesive using a pressure of 700 KN/sq m pressure at 450 deg K. The laminate composite is then post-cured for two hours at 527 deg K to produce a composite laminate having a density in the range from about 95 kilograms per cubic meter to 130 kilograms per cubic meter.

Kourtides, D. A.↗
NASA NTRS1979

Design development of an advanced composite aileron

This paper summarizes the design development of an advanced composite inboard aileron for the L-1011 commercial transport aircraft. Design details of the composite aileron are reported. Results of tests which substantiate the structural integrity of the design are also presented. The composite aileron is a multi-rib assembly with graphite/epoxy tape-syntactic core sandwich covers, a graphite/epoxy tape front spar, and graphite/epoxy fabric ribs. This structure is a direct replacement for the current metal aileron with a weight savings of 28.7 percent (40.3 lb.). Engineering cost estimates indicate that the composite structure will be cost competitive with the metal structure it is replacing.

Griffin, C. F.↗
NASA NTRS1981

Basic research planning in mathematical pattern recognition and image analysis

Fundamental problems encountered while attempting to develop automated techniques for applications of remote sensing are discussed under the following categories: (1) geometric and radiometric preprocessing; (2) spatial, spectral, temporal, syntactic, and ancillary digital image representation; (3) image partitioning, proportion estimation, and error models in object scene interference; (4) parallel processing and image data structures; and (5) continuing studies in polarization; computer architectures and parallel processing; and the applicability of "expert systems" to interactive analysis.

Bryant, J.↗
NASA NTRS1981

A model for the control mode man-computer interface dialogue

A four stage model is presented for the control mode man-computer interface dialogue. It consists of context development, semantic development syntactic development, and command execution. Each stage is discussed in terms of the operator skill levels (naive, novice, competent, and expert) and pertinent human factors issues. These issues are human problem solving, human memory, and schemata. The execution stage is discussed in terms of the operators typing skills. This model provides an understanding of the human process in command mode activity for computer systems and a foundation for relating system characteristics to operator characteristics.

Chafin, R. L.↗
NASA NTRS1981

Enlightened Use of Passive Voice in Technical Writing

The passive voice as a normal, acceptable, and established syntactic form in technical writing is defended. Passive/active verb ratios, taken from sources including 'antipassivist' text books, are considered. The suitability of the passive voice in technical writing which involves unknown or irrelevant agents is explored. Three 'myths' that the passive (1) utilizes an abnormal and artificial word order, (2) is lifeless, and (3) is indirect are considered. Awkward and abnormal sounding examples encountered in text books are addressed in terms of original context. Unattractive or incoherent passive sentences are explained in terms of inappropriate conversion from active sentences having (1) short nominal or pronominal subjects or (2) verbs with restrictions on their passive use.

Trammell, M. K.↗
NASA NTRS1981

Toward defining good writing: A rhetorical analysis of the words, sentences, and paragraphs in 16 industrial scripts

The assumption that teachers of technical writing agree on a definition of good writing was found to be without basis. Resolution of disagreements arising from close reading and textual analysis is described. Writing samples from corporate sources including IBM, ALCOA, Exxon, Weyerhaeuser, Bell Labs, Underwriters Laboratories, Dow Chemical, and US Steel were requested. A mixture of informative and persuasive examples, and examples directed at lay and specialist audiences were received. Analyses of 16 writing samples are reported. Analysis of word level, sentence level, and paragraph level, was completed. Syllabism, verb selection, nominalizations, vocabulary choices, t-units, subordination, sentence and clause length, syntactic order, patterns, development, topic sentences, propositional order, and transitions were analyzed.

Freisinger, R. R.↗
NASA NTRS1984

Repairable Encapsulated Electronic Modules

Packaging technique seals electronic modules as effectively as potting in epoxy, yet permits removal of encapsulant when component change necessary. Technique encloses module in thin, rigid epoxy/fiberglass shell containing lightweight syntactic foam.

Dozois, P. C.↗
NASA NTRS1983

Top-down methodology for human factors research

User computer interaction as a conversation is discussed. The design of user interfaces which depends on viewing communications between a user and the computer as a conversion is presented. This conversation includes inputs to the computer (outputs from the user), outputs from the computer (inputs to the user), and the sequencing in both time and space of those outputs and inputs. The conversation is viewed from the user's side of the conversation. Two languages are modeled: the one with which the user communicates with the computer and the language where communication flows from the computer to the user. Both languages exist on three levels; the semantic, syntactic and lexical. It is suggested that natural languages can also be considered in these terms.

Sibert, J.↗
NASA NTRS1979

Advanced manufacturing development of a composite empennage component for L-1011 aircraft

Work in process verification and tooling development continued. The decision was made to redesign the ribs to a more producible design. The bead was eliminated and the truss ribs changed to plain C sections. The solid web rib stiffeners were eliminated as well as the beads and the webs are now reinforced with a syntactic core. Syntectic is an epoxy containing glass microballoons. Two cover specimens were successfully tested. The first specimen (H27) was designed to verify the stability and compression strength of the cover when it is hot and wet. Failure occurred at 120 percent of design ultimate load. As the failure appeared to be fixture induced and was limited to one end of the panel, the remainder of the panel will be tested. The second specimen (H28) was designed to verify the failsafe aspects of the design. The test verified the design. Preparation of the PRVT test facility is nearing completion and all ten spar durability specimens were installed in the test chambers.

Source record↗
NASA NTRS1981

Advanced manufacturing development of a composite empennage component for L-1011 aircraft. Phase 2: Design and analysis

The composite fin design consists of two one-piece cocured covers, two one-piece cocured spars and eleven ribs. The lower ribs are truss ribs with graphite/epoxy caps and aluminum truss members. The upper three ribs are a sandwich design with graphite/epoxy face sheets and a syntactic epoxy core. The design achieves a 27% weight saving compared to the metal box. The fastener count has been reduced from over 40,000 to less than 7000. The structural integrity of the composite fin was verified by analysis and test. The static, fail-safe and flutter analyses were completed. An extensive test program has established the material behavior under a range of conditions and critical subcomponents were tested to verify the structural concepts.

Jackson, A. C.↗
NASA NTRS1981

Advanced composite aileron for L-1011 transport aircraft: Aileron manufacture

The fabrication activities of the Advanced Composite Aileron (ACA) program are discussed. These activities included detail fabrication, manufacturing development, assembly, repair and quality assurance. Five ship sets of ailerons were manufactured. The detail fabrication effort of ribs, spar and covers was accomplished on male tools to a common cure cycle. Graphite epoxy tape and fabric and syntactic epoxy materials were utilized in the fabrication. The ribs and spar were net cured and required no post cure trim. Material inconsistencies resulted in manufacturing development of the front spar during the production effort. The assembly effort was accomplished in subassembly and assembly fixtures. The manual drilling system utilized a dagger type drill in a hydraulic feed control hand drill. Coupon testing for each detail was done.

Dunning, E. G.↗
NASA NTRS1983

Development of phosphorylated adhesives

The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame.

Bilow, N.↗
NASA NTRS1984

Computer vision for real-time orbital operations. Center directors discretionary fund

Machine vision research is examined as it relates to the NASA Space Station program and its associated Orbital Maneuvering Vehicle (OMV). Initial operation of OMV for orbital assembly, docking, and servicing are manually controlled from the ground by means of an on board TV camera. These orbital operations may be accomplished autonomously by machine vision techniques which use the TV camera as a sensing device. Classical machine vision techniques are described. An alternate method is developed and described which employs a syntactic pattern recognition scheme. It has the potential for substantial reduction of computing and data storage requirements in comparison to the Two-Dimensional Fast Fourier Transform (2D FFT) image analysis. The method embodies powerful heuristic pattern recognition capability by identifying image shapes such as elongation, symmetry, number of appendages, and the relative length of appendages.

Vinz, F. L.↗
NASA NTRS1986

Fuzzy automata and pattern matching

A wide-ranging search for articles and books concerned with fuzzy automata and syntactic pattern recognition is presented. A number of survey articles on image processing and feature detection were included. Hough's algorithm is presented to illustrate the way in which knowledge about an image can be used to interpret the details of the image. It was found that in hand generated pictures, the algorithm worked well on following the straight lines, but had great difficulty turning corners. An algorithm was developed which produces a minimal finite automaton recognizing a given finite set of strings. One difficulty of the construction is that, in some cases, this minimal automaton is not unique for a given set of strings and a given maximum length. This algorithm compares favorably with other inference algorithms. More importantly, the algorithm produces an automaton with a rigorously described relationship to the original set of strings that does not depend on the algorithm itself.

Setzer, C. B.↗
NASA NTRS1985

PCG: A prototype incremental compilation facility for the SAGA environment, appendix F

A programming environment supports the activity of developing and maintaining software. New environments provide language-oriented tools such as syntax-directed editors, whose usefulness is enhanced because they embody language-specific knowledge. When syntactic and semantic analysis occur early in the cycle of program production, that is, during editing, the use of a standard compiler is inefficient, for it must re-analyze the program before generating code. Likewise, it is inefficient to recompile an entire file, when the editor can determine that only portions of it need updating. The pcg, or Pascal code generation, facility described here generates code directly from the syntax trees produced by the SAGA syntax directed Pascal editor. By preserving the intermediate code used in the previous compilation, it can limit recompilation to the routines actually modified by editing.

Kimball, Joseph John↗