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  • 1
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    In:  Terra Nova, Warszawa, Army Corps of Engineers, Woodward-Clyde Consultants, vol. 6, no. 48, pp. 133-142, pp. 1013, (ISBN: 0-12-018847-3)
    Publication Date: 1994
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; GeodesyY ; ConvolutionE
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  • 2
    Publication Date: 2013-08-29
    Description: The spatial evolution of disturbances in plane Poiseuille flow and zero pressure gradient boundary layer flow is considered. For disturbances governed by the linearized equations, potential for significant transient growth of the amplitude is demonstrated. The maximum amplification occurs for disturbances with zero or near zero frequencies. Spatial numerical simulations of the transition scenario involving a pair of oblique waves has been conducted for both flows. A fully spectral solver using a simple but efficient fringe region technique allowed the flows to be computed with high resolution into the fully turbulent domain. A modal decomposition of the simulation results indicates that non-linear excitation of the transient growth is responsible for the rapid emergence of low-frequency structures. Physically, this corresponds to streaky flow structures, as seen from the results of a numerical amplitude expansion. Thus, this spatial transition scenario has been found to be similar to the corresponding temporal one. In the boundary layer simulations the streaks are seen to break down from what appears to be a secondary instability.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD, Application of Direct and Large Eddy Simulation to Transition and Turbulence; 13 p
    Format: text
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  • 3
    Publication Date: 2013-08-31
    Description: In the context of an ESTEC technology contract, a Chopping Mechanism was developed and built with the Far Infrared and Submillimeter Telescope (FIRST) astronomy mission as a reference. The task of the mechanism is to tilt the subreflector of the telescope with an assumed mass of 2.5 kg about one chopping axis at nominal frequencies of up to 5 Hz and chopping angles of up to +/- 11.25 mrad with high efficiency (minimum time for position change). The chopping axis is required to run through the subreflector vertex. After performing a concept trade-off also considering the low operational temperatures in the 130 K range, a design using moving magnet actuators was found to be the favorite one. In addition, a bearing concept using flexible pivots was chosen to meet the high chopping accuracy required. With this approach, a very reliable design could be realized, since the actuators work without any mechanical contact between its moving and fixed parts, and the only bearings used are two flexible pivots supporting the subreflector mounting interface. The mechanism was completely built in titanium in a lightweight and stiff design. The moving magnet actuators were designed to meet the stringent requirements for minimum risetime (time necessary to move from one angular position to a new one) in the 20 msec range. The angular position and the corresponding chopping frequency as well can be arbitrarily selected by the user.
    Keywords: OPTICS
    Type: NASA. Lewis Research Center, The 28th Aerospace Mechanisms Symposium; p 167-181; NASA-CP-3260
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: The eigenvalue sensitivity for hydrodynamic stability operators is investigated. Classical matrix perturbation techniques as well as the concept of epsilon-pseudoeigenvalues are applied to show that parts of the spectrum are highly sensitive to small perturbations. Applications are drawn from incompressible plane Couette, trailing line vortex flow and compressible Blasius boundary layer flow. Parametric studies indicate a monotonically increasing effect of the Reynolds number on the sensitivity. The phenomenon of eigenvalue sensitivity is due to the non-normality of the operators and their discrete matrix analogs and may be associated with large transient growth of the corresponding initial value problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-189683 , NAS 1.26:189683 , ICASE-92-33 , AD-A255123
    Format: application/pdf
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  • 5
    Publication Date: 2019-08-28
    Description: NASA has defined a program to address critical laser-induced damage issues peculiar to its remote sensing systems. The Langley Research Center (LaRC), with input from the Goddard Space Flight Center (GSFC), has developed a program plan focusing on the certification of optical materials for spaceflight applications and the development of techniques to determine the reliability of such materials under extended laser exposures. This plan involves cooperative efforts between NASA and optics manufacturers to quantify the performance of optical materials for NASA systems and to ensure NASA's continued application of the highest quality optics possible for enhanced system reliability. A review panel was organized to assess NASA's optical damage concerns and to evaluate the effectiveness of the LaRC proposed program plan. This panel consisted of experts in the areas of laser-induced damage, optical coating manufacture, and the design and development of laser systems for space. The panel was presented information on NASA's current and planned laser remote sensing programs, laser-induced damage problems already encountered in NASA systems, and the proposed program plan to address these issues. Additionally, technical presentations were made on the state of the art in damage mechanisms, optical materials testing, and issues of coating manufacture germane to laser damage.
    Keywords: OPTICS
    Type: NASA-TM-109243 , NAS 1.15:109243 , Sep 10, 1991 - Sep 12, 1991; Newport News, VA; United States
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-13
    Description: The eigenvalue sensitivity for hydrodynamic stability operators is investigated. Classical matrix perturbation techniques as well as the concept of epsilon-pseudospectra are applied to show that parts of the spectrum are highly sensitive to small perturbations. Applications are drawn from incompressible plane Couette flow, trailing line vortex flow, and compressible Blasius boundary-layer flow. Parameter studies indicate a monotonically increasing effect of the Reynolds number on the sensitivity. The phenomenon of eigenvalue sensitivity is due to the nonnormality of the operators and their discrete matrix analogs and may be associated with large transient growth of the corresponding initial value problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Theoretical and Computational Fluid Dynamics (ISSN 0935-4964); 4; 5; p. 227-240.
    Format: text
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  • 7
    Publication Date: 2019-07-13
    Description: The Space Station Freedom (SSF) program requires measurements, by gas detector tubes, of trace contaminants (mainly CO and toluene didsocyanate) in the Node 2 (which is isolated from the trace contaminant control system for about 100 days during the SSF building missions) and Lab A atmosphere prior to the first entry of the crew. This paper discusses the results of an analysis of the levels of trace contaminants that can be expected in the Node 2 atmosphere at 100 days and the aspects of the detector tube design and technology which may need further developent for application in microgravity. Attention is also given to the factors governing the use of detector tubes for monitoring selected contaminants.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: SAE PAPER 921150 , ; 8 p.|SAE, International Conference on Environmental Systems; Jul 13, 1992 - Jul 16, 1992; Seattle, WA; United States
    Format: text
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  • 8
    Publication Date: 2020-12-23
    Type: Article , NonPeerReviewed
    Format: text
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  • 9
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    Institut für Polarökologie Kiel
    In:  Mitteilungen zur Kieler Polarforschung, 7 . pp. 21-27.
    Publication Date: 2017-05-16
    Type: Article , NonPeerReviewed
    Format: text
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  • 10
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    In:  (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 73 pp
    Publication Date: 2021-07-15
    Type: Thesis , NonPeerReviewed
    Format: text
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