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  • 1
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    A CALCULATIONAL PROCEDURE FOR ESTIMATING SPACE RADIATION EXPOSURE DURING LUNAR MISSIONS (1962)
    In:  CASI
    Details
    Publication Date: 2006-10-26
    Description: Estimation of space radiation exposure during lunar mission - spacecraft shielding
    Keywords: STRUCTURAL MECHANICS
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  • 2
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    Comparison of measured and calculated dynamic loads for the Mod-2 2.5 mW wind turbine system (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Boeing Company, under contract to the Electric Power Research Institute (EPRI), has completed a test program on the Mod-2 wind turbines at Goodnoe Hills, Washington. The objectives were to update fatigue load spectra, discern site and machine differences, measure vortex generator effects, and to evaluate rotational sampling techniques. This paper shows the test setup and loads instrumentation, loads data comparisons and test/analysis correlations. Test data are correlated with DYLOSAT predictions using both the NASA interim turbulence model and rotationally sampled winds as inputs. The latter is demonstrated to have the potential to improve the test/analysis correlations. The paper concludes with an assessment of the importance of vortex generators, site dependence, and machine differences on fatigue loads. The adequacy of prediction techniques used are evaluated and recommendations are made for improvements to the methodology.
    Keywords: STRUCTURAL MECHANICS
    Type: DASCON Engineering, Collected Papers on Wind Turbine Technology; p 139-152
    Format: application/pdf
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  • 3
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    Investigation of crew performance in a multi-vehicle supervisory control task (1986)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: Crew information processing and decision making in a supervisory control task which is loosely based on the mission of future generation helicopters is measured and represented. Subjects control the motion and activities of their own vehicle and direct the activities of four additional craft. The task involves searching an uncertain environment for cargo and enemies, returning cargo to home base and destroying enemies while attempting to avoid destruction of the scout and the supervised vehicles. A series of experiments with two-person crews and one-person crews were performed. Resulting crew performance was modeled with the objective of describing and understanding the information processing strategies utilized. Of particular interest are problem simplification strategies under time stress and high work load, simplification and compensation in the one-person cases, crew coordination in the two-person cases, and the relationship between strategy and errors in all cases. The results should provide some insight into the effective use of aids, particularly aids based on artificial intelligence, for similar tasks. The simulation is described which is used for the study and some preliminary results from the first two-person crew study are discussed.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: NASA. Ames Research Center, 21st Annual Conference on Manual Control; 1 p
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  • 4
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    The effects of stimulus modality and task integrality: Predicting dual-task performance and workload from single-task levels (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The influence of stimulus modality and task difficulty on workload and performance was investigated. The goal was to quantify the cost (in terms of response time and experienced workload) incurred when essentially serial task components shared common elements (e.g., the response to one initiated the other) which could be accomplished in parallel. The experimental tasks were based on the Fittsberg paradigm; the solution to a SternBERG-type memory task determines which of two identical FITTS targets are acquired. Previous research suggested that such functionally integrated dual tasks are performed with substantially less workload and faster response times than would be predicted by suming single-task components when both are presented in the same stimulus modality (visual). The physical integration of task elements was varied (although their functional relationship remained the same) to determine whether dual-task facilitation would persist if task components were presented in different sensory modalities. Again, it was found that the cost of performing the two-stage task was considerably less than the sum of component single-task levels when both were presented visually. Less facilitation was found when task elements were presented in different sensory modalities. These results suggest the importance of distinguishing between concurrent tasks that complete for limited resources from those that beneficially share common resources when selecting the stimulus modalities for information displays.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: 21st Annual Conference on Manual Contol; 15 p
    Format: application/pdf
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  • 5
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    Theoretical analysis of HVAC duct hanger systems (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Several methods are presented which, together, may be used in the analysis of duct hanger systems over a wide range of frequencies. The finite element method (FEM) and component mode synthesis (CMS) method are used for low- to mid-frequency range computations and have been shown to yield reasonably close results. The statistical energy analysis (SEA) method yields predictions which agree with the CMS results for the 800 to 1000 Hz range provided that a sufficient number of modes participate. The CMS approach has been shown to yield valuable insight into the mid-frequency range of the analysis. It has been demonstrated that it is possible to conduct an analysis of a duct/hanger system in a cost-effective way for a wide frequency range, using several methods which overlap for several frequency bands.
    Keywords: STRUCTURAL MECHANICS
    Type: COSMIC, 15th NASTRAN (R) Users' Colloquium; p 222-249
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  • 6
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    Assessing the Subjective Workload of Directional Orientation Tasks (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The impact of various flight-related tasks on the workload imposed by the requirement to compute new headings, course changes, and reciprocal headings was investigated. Eight pilots were presented with a series of heading-change tasks in a laboratory setting. Two levels of difficulty of each of three tasks were presented verbally and spatially. Performance was measured by evaluating the speed and accuracy of the responses. The subjective responses and objective measures of performance reflected a strong association between subjective experience and objective behavior. The reciprocal calculations were performed quickly and accurately throughout and were considered to be minimally loading. Subjective workload, percent correct and response times for the two course-change tasks varied significantly as a function of level of difficulty and display format, with no discernable speed/accuracy trade off.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: 20th Ann. Conf. on Manual Control, Vol. 2; p 85-96
    Format: text
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  • 7
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    Combined discrete network. Continuous control modelling of operator behavior (1982)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The situation in which an operator is faced with a continuous control task plus one or more discrete information processing tasks is discussed. A modelling approach which has the capability of realistically representing both types of tasks and the resulting interactions is sought. The modelling approach utilizes discrete network models for the cognitive tasks and elements of an open-loop - closed-loop control representation for the continuous task. the approach is demonstrated through its application to a simulated Digital Avionics Information System in which subjects were required to perform retrieval and processing tasks as well as flight control. This model differs from conventional model in that system status sampling is not necessarily continuous or periodic. Rather, the pilot is assumed to read system status displays only as time permits and operate in a so-called open-loop preprogrammed fashion between sampling.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: NASA. Ames Research Center 16th Ann. Conf. on Manual Control; p 448-463
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  • 8
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    Bending strength of large thin-walled pressure- stabilized cylinder beyond onset of compressive skin wrinkling. (1966)
    In:  Other Sources
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    Publication Date: 2018-12-01
    Description: Ultimate bending moment capability of thin walled pressure stabilized cylinder with typical axial loads demonstrated to be 50 percent greater than bending moment at which compressive wrinkling occurs
    Keywords: STRUCTURAL MECHANICS
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  • 9
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    Finite element analysis of partly wrinkled membranes (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The development of a nonlinear numerical algorithm for the analysis of stresses and displacements in partly wrinkled flat membranes, and its implementation on the SAP VII finite-element code are described. A comparison of numerical results with exact solutions of two benchmark problems reveals excellent agreement, with good convergence of the required iterative procedure. An exact solution of a problem involving axisymmetric deformations of a partly wrinkled shallow curved membrane is also reported.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 20; 1-3; 631-639
    Format: text
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  • 10
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    Finite element analysis of wrinkling membranes (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The development of a nonlinear numerical algorithm for the analysis of stresses and displacements in partly wrinkled flat membranes, and its implementation on the SAP VII finite-element code are described. A comparison of numerical results with exact solutions of two benchmark problems reveals excellent agreement, with good convergence of the required iterative procedure. An exact solution of a problem involving axisymmetric deformations of a partly wrinkled shallow curved membrane is also reported.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-172325 , NAS 1.26:172325 , USC-CE-83-05
    Format: application/pdf
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