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  • Polymer and Materials Science  (4)
  • Aerodynamics  (3)
  • Collision  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Morphological characterization of polyetheretherketone-carbon fiber composites (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 505-520 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of processing conditions on the morphology of polyetheretherketone (PEEK) graphite reinforced composites (APC-2) has been characaterized. Differential scanning calorimetry was utilized to examine the effect of quench rate on recrystallization where a change in mechanism was observed at a rate of 5°C/min. Optical microscopy revealed a decrease in spherulite size and a reduced degree of transcrystallinity at the graphic fiber surface with increasing quench rates. Dynamic mechanical analysis indicated a change in relaxational processes in the Tg region with varying quench rates.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330218
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic collision avoidance and constraint violation compensation (1995)
    Springer
    Nonlinear dynamics 7 (1995), S. 385-401 
    Details
    ISSN: 1573-269X
    Keywords: Collision ; dynamics ; constraints ; multibody ; obstable avoidance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper uses concepts in multibody dynamics, together with a collision detection algorithm to study the dynamics of collision avoidance. Obstacle avoidance of a mechanical system in motion is expressed in terms of distances, relative velocities and relative accelerations between potentially colliding bodies. The generalized control forces (constraint forces) used to adjust the system dynamics are based on an n-timestep collision avoidance algorithm. Constraint violations resulting from sudden changes in motion direction are compensated for by feeding back the errors of position and velocity constraints to assure asymptotic stability. The procedures developed are illustrated through a maneuver in space of a robotic manipulator used for grasp and deployment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046310
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Energy spectra of electrons transmitted through aluminium filmsResearch sponsored by the National Science Council of the Republic of China.Paper presented at the Quantitative Surface Analysis (QSA-4) Conference, Teddington, UK, November 1986. (1988)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 11 (1988), S. 64-68 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The transmission of electrons through aluminium films has been studied. Several physical quantities including the energy loss, the pathlength, the angular deflection and their distributions were calculated. Theoretical models have been used to estimate the inelastic and elastic differential cross-sections for electrons in aluminium. The calculated spectra were compared with available experimental data.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740110108
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  • 4
    Electronic Resource
    Electronic Resource
    Electron inelastic mean free paths in several solids for 200 eV ≤ E ≤ 10 keV (1982)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 4 (1982), S. 52-55 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Values of k and p are given for predicting inelastic mean free paths for electrons with energies from 200 eV to 10 keV from the simple formula λ = kEp, based on theoretical calculations for ten elemental and compound solids. These results indicate that in the energy range 400 eV ≤ E ≤ 2000 eV, the value of p lies in the range 0.65-0.80. For Si and SiO2, presentation of the available experimental data and theoretical results illustrate the differences which exist in the values of electron mean free paths.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740040205
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  • 5
    Electronic Resource
    Electronic Resource
    Surface excitation parameters of low-energy electrons crossing solid surfaces (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 682-688 
    Details
    ISSN: 0142-2421
    Keywords: surface ; surface excitation ; surface effect ; electron ; inelastic mean free path ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The surface excitation parameter, which describes the influence of surface excitations by electrons for the vacuum side in electron spectroscopies, has been calculated for electrons of 200-2000 eV energies crossing surfaces of Cu, Ag, Au, Fe, Pd, Ni, MgO and SiO2. These calculations were performed for both incident and escaping electrons by the use of dielectric response theory. Spatially varying differential inverse mean free paths for surface excitations as a function of electron distance from the surface were found. The results showed that small differences existed in the surface excitation parameter among different metals but large differences occurred between metals and semiconductors or insulators. Calculated surface excitation parameters were fitted very well to a simple formula, i.e. Ps=aE-b, where Ps is the surface excitation parameter and E is the electron energy. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Euler solutions for self-generated rotor blade-vortex interactionsPresented as AIAA paper 90-1588 at the AIAA 20th Fluids and Plasma Dynamics Conference, Buffalo, New York, June 1990. (1992)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 15 (1992), S. 427-451 
    Details
    ISSN: 0271-2091
    Keywords: Aerodynamics ; Rotor ; Blade-vortex ; Interactions ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A finite-difference procedure has been developed for the prediction of three-dimensional rotor blade-vortex interactions. The interaction velocity field was obtained through a non-linear superposition of the rotor flow field, computed using the unsteady three-dimensional Euler equations, and the embedded vortex wake flow field, computed using the law of Biot-Savart. In the Euler model, near wake rotational effects were simulated using the surface velocity ‘transpiration’ approach. As a result, a modified surface boundary condition was prescribed and enforced at each time step of the computations to satisfy the tangency boundary condition. For supercritical interactions using an upstream-generated vortex, accuracy of the numerical results were found to rely on the user-specified vortex core radius and vortex strength. For the more general self-generated subcritical interactions, vortex wake trajectories were computed using the lifting-line helicopter/rotor trim code CAMRAD. For these interactions, accuracy of the results were found to rely heavily on the CAMRAD-predicted vortex strength, vortex orientation with respect to the blade, and to a large extent on the user-specified vortex core radius. Results for the one-seventh scale model OLS rotor and for a non-lifting rectangular blade having a NACA0012 section are presented. Comparisons with the experimental windtunnel data are also made.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650150405
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  • 7
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    Flow Field Around a Hovering Rotor (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A lifting surface hover code developed by the Analytical Method Inc. (AMI) was used to compute the average and unsteady velocity flow field of an isolated rotor without ground effect. The predicted velocity field compares well with experimental data obtained by hot-wire anemometry and by Laser Doppler Velocimetry. A subroutine 'DOWNWASH' was written to predict the velocity field at any given point in the wake for a given blade position.
    Keywords: Aerodynamics
    Type: NASA-TM-110426 , NAS 1.15:110426 , A-975370 , USAATCOM-TR-96-A-012
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Preliminary Study of a Model Rotor in Descent (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Within a program designed to develop experimental techniques for measuring the trajectory and structure of vortices trailing from the tips of rotor blades, the present preliminary study focuses on a method for quantifying the trajectory of the trailing vortex during descent flight conditions. This study also presents rotor loads and blade surface pressures for a range of tip-path plane angles and Mach numbers. Blade pressures near the leading edge and along the outer radius are compared with data obtained on the same model rotor, but in open jet facilities. A triangulation procedure based on two directable laser-light sheets, each containing an embedded reference, proved effective in defining the spatial coordinates of the trailing vortex. When interrogating a cross section of the flow that contains several trailing vortices, the greatest clarity was found to result when the flow is uniformly seeded. Surface pressure responses during blade-vortex interactions appeared equally sensitive near the leading edge and along the outer portion of the blade, but diminished rapidly as the distance along the blade chord increased. The pressure response was virtually independent of whether the tip-path plane angle was obtained through shaft tilt or cyclic pitch. Although the shape and frequency of the pressure perturbations on the advancing blade during blade-vortex interaction are similar to those obtained in open-jet facilities, the angle of the tip-path plane may need to be lower than the range covered in this study.
    Keywords: Aerodynamics
    Type: NASA/TM-2000-208785 , NAS 1.15:208785 , A-99V0024 , AFDD/TR-99-A-001
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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