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  • 1
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    Application Explorer Mission 2 (AEM 2), Stratospheric Aerosol and Gas Experiment (SAGE) (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Washington Upper Atmosphere Res. Program; p 234-235
    Format: text
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  • 2
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    Laboratory characterization of direct readout Si:Sb and Si:Ga infrared detector arrays (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Highlights of recent results obtained at Ames Research Center in performance evaluations of infrared detector arrays are presented. Antimony- and gallium-doped silicon direct readout 58x62 element hybrid devices from Ames' ongoing detector technology development program are described. The observed characteristics meet most of the performance goals specified by the Space Infrared Telescope Facility (SIRTF) instrument teams and compare favorably with the best performance reported for discrete non-integrating extrinsic silicon detectors. Initial results of radiation environment testing are reported, and non-ideal behavior demonstrated by these test devices is discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Proceedings of the Third Infrared Detector Technology Workshop; p 403-412
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  • 3
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    Some approaches to substructure coupling with damping (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Time-domain and frequency-domain methods for coupling substructures with general linear damping are discussed. A time-domain method is presented which employs a state variable representation of each substructure. Also presented is a method which employs frequency-domain coupling together with DFT and FFT transformations to obtain transient response solutions.
    Keywords: STRUCTURAL MECHANICS
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  • 4
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    Modal vector estimation for closely-spaced-frequency modes (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Identification of modal parameters is made more difficult if the system has repeated frequencies or even closely spaced frequencies. This paper discusses the problems associated with closely-spaced-frequency modes and describes two related methods for dealing with these problems. It is demonstrated that proper identification of the system parameters of such systems requires information from multiple inputs and/or multiple outputs. The analytical basis for the 'minimum coincident response method' is outlined, and examples of the use of these two techniques to extract model parameters are presented.
    Keywords: STRUCTURAL MECHANICS
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  • 5
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    A review of time-domain and frequency-domain component mode synthesis method (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Hurty (1965) has conducted a dynamic analysis of structural systems using component modes. The component mode synthesis (CMS) procedure considered by him represents a form of substructure coupling analysis which is often utilized in structural dynamics. Time-domain CMS methods employing real modes are discussed, taking into account real component modes, normal modes, redundant constraint modes, rigid-body modes, attachment modes, inertia-relief modes, statically-complete interface mode sets, dynamic component mode supersets, component modal models, the coupling of components, and the classification of methods. Attention is also given to the experimental determination of component mode synthesis parameters, time-domain CMS methods for damped systems, and frequency-domain CMS methods for damped systems.
    Keywords: STRUCTURAL MECHANICS
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  • 6
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    Application of component mode synthesis in structural dynamics (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The principal analytical techniques used for component mode synthesis (CMS) of undamped systems and their application to structural dynamics are discussed. In the CMS, a system is divided into components or substructures, and for each of these components, the number of degrees of freedom is reduced by expressing the physical coordinates in terms of a reduced set of component modal coordinates. Among a number of component modes, a new form of component mode, called an applied force attachment mode, is described. Consideration is given to literature studies of damped structures and recent combined analytical/experimental studies.
    Keywords: STRUCTURAL MECHANICS
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  • 7
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    Digital multishaker modal testing (1983)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A review of several modal testing techniques is made, along with brief discussions of their advantages and limitations. A new technique is presented which overcomes many of the previous limitations. Several simulated experiments are included to verify the validity and accuracy of the new method. Conclusions are drawn from the simulation studies and recommendations for further work are presented. The complete computer code configured for the simulation study is presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-170951 , NAS 1.26:170951 , CAR-83-1
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  • 8
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    Multishaker modal testing (1985)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A component mode synthesis method for damped structures was developed and modal test methods were explored which could be employed to determine the relevant parameters required by the component mode synthesis method. Research was conducted on the following topics: (1) Development of a generalized time-domain component mode synthesis technique for damped systems; (2) Development of a frequency-domain component mode synthesis method for damped systems; and (3) Development of a system identification algorithm applicable to general damped systems. Abstracts are presented of the major publications which have been previously issued on these topics.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-178507 , NAS 1.26:178507 , CAR-85-3
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  • 9
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    A substructure coupling procedure applicable to general linear time-invariant dynamic systems (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A substructure synthesis procedure applicable to structural systems containing general nonconservative terms is presented. In their final form, the nonself-adjoint substructure equations of motion are cast in state vector form through the use of a variational principle. A reduced-order mode for each substructure is implemented by representing the substructure as a combination of a small number of Ritz vectors. For the method presented, the substructure Ritz vectors are identified as a truncated set of substructure eigenmodes, which are typically complex, along with a set of generalized real attachment modes. The formation of the generalized attachment modes does not require any knowledge of the substructure flexible modes; hence, only the eigenmodes used explicitly as Ritz vectors need to be extracted from the substructure eigenproblem. An example problem is presented to illustrate the method.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-178510 , NAS 1.26:176144 , CAR-84-1
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  • 10
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    Modal analysis using a Fourier analyzer, curve-fitting, and modal tuning (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The proposed modal test program differs from single-input methods in that preliminary data may be acquired using multiple inputs, and modal tuning procedures may be employed to define closely spaced frquency modes more accurately or to make use of frequency response functions (FRF's) which are based on several input locations. In some respects the proposed modal test proram resembles earlier sine-sweep and sine-dwell testing in that broadband FRF's are acquired using several input locations, and tuning is employed to refine the modal parameter estimates. The major tasks performed in the proposed modal test program are outlined. Data acquisition and FFT processing, curve fitting, and modal tuning phases are described and examples are given to illustrate and evaluate them.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-161886 , CAR-81-1
    Format: application/pdf
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