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  • 1
    Electronic Resource
    Electronic Resource
    “Legal Aspects of the Sino-Indian Boeder Dispute” (1962)
    Cambridge : Cambridge University Press
    The @China quarterly 9 (1962), S. 193-199 
    Details
    ISSN: 0305-7410
    Source: Cambridge Journals Digital Archives
    Topics: Linguistics and Literary Studies , History , Political Science , Sociology , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0305741000025303
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    “The Road Divides” (1967)
    Cambridge : Cambridge University Press
    The @China quarterly 32 (1967), S. 132-135 
    Details
    ISSN: 0305-7410
    Source: Cambridge Journals Digital Archives
    Topics: Linguistics and Literary Studies , History , Political Science , Sociology , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S030574100004724X
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    “Mao at Seventy” (1964)
    Cambridge : Cambridge University Press
    The @China quarterly 18 (1964), S. 214-214 
    Details
    ISSN: 0305-7410
    Source: Cambridge Journals Digital Archives
    Topics: Linguistics and Literary Studies , History , Political Science , Sociology , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0305741000042004
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    Paper (German National Licenses)
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  • 4
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    An optical particle detector for evaluating film quality (1968)
    American Chemical Society
    Details
    Publication Date: 1968-03-01
    Print ISSN: 0021-9584
    Electronic ISSN: 1938-1328
    Topics: Chemistry and Pharmacology , Education
    Published by American Chemical Society
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    PAPER CURRENT
  • 5
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    Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core (1996)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: Sound transmission through an infinite cylindrical sandwich shell is studied in the context of the transmission of airborne sound into aircraft interiors. The cylindrical shell is immersed in fluid media and excited by an oblique incident plane sound wave. The internal and external fluids are different and there is uniform airflow in the external fluid medium. An explicit expression of transmission loss is derived in terms of modal impedance of the fluids and the shell. The results show the effects of (a) the incident angles of the plane wave; (b) the flight conditions of Mach number and altitude of the aircraft; (c) the ratios between the core thickness and the total thickness of the shell; and (d) the structural loss factors on the transmission loss. Comparisons of the transmission loss are made among different shell constructions and different shell theories.
    Keywords: Structural Mechanics
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    NASA TECHNICAL REPORTS
  • 6
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    Modeling of Sound Transmission through Shell Structures with Turbulent Boundary Layer Excitation (1996)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The turbulent boundary layer (TBL) pressure field is an important source of cabin noise during cruise of high subsonic and supersonic commercial aircraft. The broadband character of this excitation field results in an interior noise spectrum that dominates the overall sound pressure level (SPL) and speech interference metrics in the forward and midcabins of many aircraft. In the authors' previous study, sound transmission through an aircraft fuselage, modeled by two concentric cylindrical sandwich shells and excited by a TBL statistical model was investigated analytically. An assessment of point and global structural vibration levels and resulting interior noise levels was obtained for different TBL models, flight conditions and fuselage structural designs. However, due to the complication of the shell structure, the important noise transmission mechanisms were difficult to discern. Previous experience has demonstrated that a fundamental understanding of the range of modes (or wavenumbers) generated by the TBL source both in the structure and the acoustic cavity is key to the development of both active and passive control technologies. In an initial effort to provide this insight, the objective of this paper is to develop an analytical model of sound transmission through a simple unstiffened cylindrical aluminum shell excited by a TBL pressure field. The description of the turbulent pressure field is based on the Corcos formulation for the cross-spectral density (CSD) of the pressure fluctuations. The coupled shell and interior and exterior acoustic equations are solved for the structural displacement and the interior acoustic response using a Galerkin approach to obtain analytical solutions. Specifically, this study compares the real part of the normalized CSD of the TBL excitation field, the structural displacement and the interior acoustic field. Further the modal compositions of the structural and cavity response are examined and some inference of the dominant mechanism of noise transmission is made.
    Keywords: Aircraft Design, Testing and Performance
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    NASA TECHNICAL REPORTS
  • 7
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    Sound Transmission through Cylindrical Shell Structures Excited by Boundary Layer Pressure Fluctuations (1996)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: This paper examines sound transmission into two concentric cylindrical sandwich shells subject to turbulent flow on the exterior surface of the outer shell. The interior of the shells is filled with fluid medium and there is an airgap between the shells in the annular space. The description of the pressure field is based on the cross-spectral density formulation of Corcos, Maestrello, and Efimtsov models of the turbulent boundary layer. The classical thin shell theory and the first-order shear deformation theory are applied for the inner and outer shells, respectively. Modal expansion and the Galerkin approach are used to obtain closed-form solutions for the shell displacements and the radiation and transmission pressures in the cavities including both the annular space and the interior. The average spectral density of the structural responses and the transmitted interior pressures are expressed explicitly in terms of the summation of the cross-spectral density of generalized force induced by the boundary layer turbulence. The effects of acoustic and hydrodynamic coincidences on the spectral density are observed. Numerical examples are presented to illustrate the method for both subsonic and supersonic flows.
    Keywords: Acoustics
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    NASA TECHNICAL REPORTS
  • 8
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    Fully-Coupled Fluid/Structure Vibration Analysis Using MSC/NASTRAN (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: MSC/NASTRAN's performance in the solution of fully-coupled fluid/structure problems is evaluated. NASTRAN is used to perform normal modes (SOL 103) and forced-response analyses (SOL 108, 111) on cylindrical and cubic fluid/structure models. Bulk data file cards unique to the specification of a fluid element are discussed and analytic partially-coupled solutions are derived for each type of problem. These solutions are used to evaluate NASTRAN's solutions for accuracy. Appendices to this work include NASTRAN data presented in fringe plot form, FORTRAN source code listings written in support of this work, and NASTRAN data file usage requirements for each analysis.
    Keywords: Acoustics
    Type: NASA-TM-110215 , NAS 1.15:110215
    Format: application/pdf
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  • 9
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    The Influences of Lamination Angles on the Interior Noise Levels of an Aircraft (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of reducing the interior noise levels of an aircraft passenger cabin through optimization of the composite lay up of the fuselage is investigated. MSC/NASTRAN, a commercially available finite element code, is used to perform the dynamic analysis and subsequent optimization of the fuselage. The numerical calculation of sensitivity of acoustic pressure to lamination angle is verified using a simple thin, cylindrical shell with point force excitations as noise sources. The thin shell used represents a geometry similar to the fuselage and analytic solutions are available for the cylindrical thin shell equations of motion. Optimization of lamination angle for the reduction of interior noise is performed using a finite element model of an actual aircraft fuselage. The aircraft modeled for this study is the Beech Starship. Point forces simulate the structure borne noise produced by the engines and are applied to the fuselage at the wing mounting locations. These forces are the noise source for the optimization problem. The acoustic pressure response is reduced at a number of points in the fuselage and over a number of frequencies. The objective function is minimized with the constraint that it be larger than the maximum sound pressure level at the response points in the passenger cabin for all excitation frequencies in the range of interest. Results from the study of the fuselage model indicate that a reduction in interior noise levels is possible over a finite frequency range through optimal configuration of the lamination angles in the fuselage. Noise reductions of roughly 4 dB were attained. For frequencies outside the optimization range, the acoustic pressure response may increase after optimization. The effects of changing lamination angle on the overall structural integrity of the airframe are not considered in this study.
    Keywords: Acoustics
    Type: NASA-TM-110250 , NAS 1.15:110250
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Sound Transmission through Two Concentric Cylindrical Sandwich Shells (1996)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: This paper solves the problem of sound transmission through a system of two infinite concentric cylindrical sandwich shells. The shells are surrounded by external and internal fluid media and there is fluid (air) in the annular space between them. An oblique plane sound wave is incident upon the surface of the outer shell. A uniform flow is moving with a constant velocity in the external fluid medium. Classical thin shell theory is applied to the inner shell and first-order shear deformation theory is applied to the outer shell. A closed form for transmission loss is derived based on modal analysis. Investigations have been made for the impedance of both shells and the transmission loss through the shells from the exterior into the interior. Results are compared for double sandwich shells and single sandwich shells. This study shows that: (1) the impedance of the inner shell is much smaller than that of the outer shell so that the transmission loss is almost the same in both the annular space and the interior cavity of the shells; (2) the two concentric sandwich shells can produce an appreciable increase of transmission loss over single sandwich shells especially in the high frequency range; and (3) design guidelines may be derived with respect to the noise reduction requirement and the pressure in the annular space at a mid-frequency range.
    Keywords: Acoustics
    Format: application/pdf
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