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  • 1
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    Investigations of High Pressure Acoustic Waves in Resonators with Seal-Like Features (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: 1) Standing waves with maximum pressures of 188 kPa have been produced in resonators containing ambient pressure air; 2) Addition of structures inside the resonator shifts the fundamental frequency and decreases the amplitude of the generated pressure waves; 3) Addition of holes to the resonator does reduce the magnitude of the acoustic waves produced, but their addition does not prohibit the generation of large magnitude non-linear standing waves; 4) The feasibility of reducing leakage using non-linear acoustics has been confirmed.
    Keywords: Acoustics
    Type: 2003 NASA Seal/Secondary Air System Workshop, Volume 1; 239-271; NASA/CP-2004-212963/VOL1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Effect of Forcing Function on Nonlinear Acoustic Standing Waves (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Nonlinear acoustic standing waves of high amplitude have been demonstrated by utilizing the effects of resonator shape to prevent the pressure waves from entering saturation. Experimentally, nonlinear acoustic standing waves have been generated by shaking an entire resonating cavity. While this promotes more efficient energy transfer than a piston-driven resonator, it also introduces complicated structural dynamics into the system. Experiments have shown that these dynamics result in resonator forcing functions comprised of a sum of several Fourier modes. However, previous numerical studies of the acoustics generated within the resonator assumed simple sinusoidal waves as the driving force. Using a previously developed numerical code, this paper demonstrates the effects of using a forcing function constructed with a series of harmonic sinusoidal waves on resonating cavities. From these results, a method will be demonstrated which allows the direct numerical analysis of experimentally generated nonlinear acoustic waves in resonators driven by harmonic forcing functions.
    Keywords: Acoustics
    Type: Paper 4aPAa2 , 145th Acoustic Society of America Conference; Apr 28, 2003 - May 02, 2003; Nashville, TN; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Screech Tones of Supersonic Jets from Bevelled Rectangular Nozzles (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: It is known experimentally that an imperfectly expanded rectangular jet from a thin-lip convergent nozzle emits only a single dominant screech tone. The frequency of the screech tone decreases continuously with increase in jet Mach number. However, for a supersonic jet issued from a bevelled nozzle or a convergent-divergent nozzle with straight side walls, the shock cell structure and the screech frequency pattern are fairly complicated and have not been predicted before. In this paper, it is shown that the shock cell structures of these jets can be decomposed into waveguide modes of the jet flow. The screech frequencies are related to the higher-order waveguide modes following the weakest-link screech tone theory. The measured screech frequencies are found to compare well with the predicted screech frequency curves.
    Keywords: Acoustics
    Type: NASA-CR-205131 , AIAA Paper 95-0143 , NAS 1.26:205131 , Aerospace Sciences Meeting & Exhibit; Jan 06, 1997 - Jan 10, 1997; Reno, NV; United States
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  • 4
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    Crystal structures of AB sub 3 and A sub 2 B sub 7 rare earth-nickel phases. (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Crystal structures of Ni-rich rare earth/Ni phases, including high temperature forms
    Keywords: MATERIALS, METALLIC
    Type: ; ADEMIE DES SCIENCES
    Format: text
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  • 5
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    NbZn - A mu-phase. (1968)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Mu phase lattice constants and cell volume in Nb-Zn system
    Keywords: MATERIALS, METALLIC
    Type: ; TROPHYSICAL JOURNAL
    Format: text
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  • 6
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    The Nd-Rh system (1970)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Phase diagram of Nd-Rh system determined by powder X ray diffraction, metallography and differential thermal analysis methods
    Keywords: MATERIALS, METALLIC
    Type: ; ADEMIE DES SCIENCES
    Format: text
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  • 7
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    Alloy chemistry of sigma /beta-U/-related phases. III - Sigma-phases with non- transition elements (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Sigma phase occurrence in transition/nontransition elements alloys, discussing solid solubility limits
    Keywords: MATERIALS, METALLIC
    Type: ; ADEMIE DES SCIENCES
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  • 8
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    Alloy chemistry of sigma/beta u/-related phases. I. (1968)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Refractory metal alloys related phases in ternary systems, noting atomic radius and shell electron concentration effects
    Keywords: MATERIALS, METALLIC
    Type: ; ADEMIE DES SCIENCES
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  • 9
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    Alloy chemistry of sigma /beta-U/-related phases. II (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Extension characteristics of delta and sigma related phases in Mo-Ni ternary systems and evaluation of unit cell dimension variations on alloying
    Keywords: MATERIALS, METALLIC
    Type: ; YAL SOCIETY (
    Format: text
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  • 10
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    The lanthanum-rhodium system. (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: La-Rh system study by powder X ray diffraction, metallographic and differential thermal analysis, constructing equilibrium diagram and determining crystal structure data
    Keywords: MATERIALS, METALLIC
    Type: ; VUE TECHNIQUE CECLES
    Format: text
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