Showing papers on "Acoustic interferometer published in 1976"
TL;DR: In this paper, the authors proposed a delay-line light-modulation scheme for a wideband, instantaneous spectrum (ISV) modulator with a delay line light-emitting diode (LED).
Abstract: [78] L. B. Lambert, “Wide-Band, Instantaneous Spectrum An[81] D. L. Hecht, “Acousto-Optic Nonlinearities in Multi-Frequency alyzers Em loying Delay-Line Light Modulators,” IRE Inf . Acousto-Optic Diffraction,” Tnt’l. Quantum Electron Conf., Conv. Rec., fit. 6, Vol. 10, Mar. 1962, pp. 69-78. [79] R. W. Damon, W. T. Maloney, and D. H. McMahon, “Ink:; [82] A. J. DeMaria and G. E. Danielson, “Internal Laser Modulation San Francisco, June 1974.
52 citations
01 May 1976
TL;DR: A review of the current state of knowledge concerning waveguiding structures for acoustic surface waves is presented in this article, where the stress is on the various types of waveguide and their properties, in order to provide a guide for the applications-oriented engineer.
Abstract: A review is presented of the current state of knowledge concerning waveguiding structures for acoustic surface waves. The stress is on the various types of waveguide and their properties, in order to provide a guide for the applications-oriented engineer. Related matters which are treated more briefly include the reasons for using waveguides, and some applications, both actual and potential.
47 citations
Journal Article•
14 citations
01 Jan 1976
12 citations
01 May 1976
TL;DR: In this article, an analytical model is developed to determine the velocity of surface acoustic waves in strained media, and it is shown that the SAW propagation may depend significantly on the velocity change with strain.
Abstract: An analytical model is developed to determine the velocity of surface acoustic waves in strained media. It is shown that, in addition to the variations in path length, the SAW propagation may depend significantly on the velocity change with strain.
11 citations
01 Jan 1976
8 citations
TL;DR: In this article, the authors measured the dispersion relation of test waves in plasmas with ion acoustic turbulence and found that the phase velocity of the test wave becomes smaller than the ion acoustic velocity for frequencies near the peak frequency of the turbulence spectrum.
Abstract: By measuring the dispersion relation of test waves in plasmas with ion acoustic turbulence, we find that the phase velocity of the ion acoustic wave becomes smaller than the ion acoustic velocity for frequencies near the peak frequency of the turbulence spectrum.
7 citations
TL;DR: In this paper, the authors deal with two applications of phase-measuring interferometers: the accurate measurement of position (astrometry), and the determination of source structure, in particular, mapping observations.
Abstract: Publisher Summary This chapter deals with two applications of phase-measuring interferometers: the accurate measurement of position (astrometry), and the determination of source structure, in particular, mapping observations. In both cases, the determination of the difference in phase between incoming signals (the interferometer phase) is crucial. Essential features for the interpretation of measurements of interferometer phase are a known baseline and stable electrical lengths for the various local oscillator and signal paths. The effective baseline may be varied, either by tracking the source over a range of hour angles so that the orientation and projected length of the baseline change, or by using movable elements in the interferometer. Both methods may be employed in the same instrument. In a tracking interferometer, the difference in electrical paths from the source to the two antennas changes continuously. The variation in path difference across the field of view of the interferometer is illustrated in the chapter. The disturbing effects of tropospheric irregularities under calm and disturbed conditions are discussed and an overview of Green Bank three-element interferometer is also presented.
5 citations
TL;DR: In this article, the sound absorption performance of an acoustic absorber consisting of a stretched circular membrane placed a short distance in front of a fiberglass blanket was both measured and predicted.
Abstract: The sound absorption performance of an acoustic absorber consisting of a stretched circular membrane placed a short distance in front of a fiberglass blanket was both measured and predicted. Both theoretical and experimental analyses were restricted to plane acoustic waves. Theoretical predictions indicated that the membrane–blanket combination would have a sound power absorption coefficient nearly equal to the sound power absorption coefficient of the blanket alone if the incident acoustic plane wave drove the membrane at one of its resonance frequencies. Theoretical analysis also predicted that the sound power absorption coefficient would approach zero when the membrane was driven at an antiresonance frequency by the incident acoustic plane wave. Experimental agreement with theoretical predictions was good for several membrane–blanket combinations. The results show that membrane–blanket combinations can be effective acoustic absorbers in frequency ranges which do not include the antiresonance frequencie...
01 Jan 1976
TL;DR: In this paper, the velocity and absorption of ultrasonic waves in the mesomorphic states of four cholesteric liquid crystals, namely, cholesteryl nonanoate, decanoate and linoleate, were measured by a pulse technique and velocity by an acoustic interferometer at a single frequency of 2 MHz.
Abstract: This paper reports experimental results for the velocity and absorption of ultrasonic waves in the mesomorphic states of four cholesteric liquid crystals, namely, cholesteryl nonanoate, decanoate, oleate, and linoleate. The absorption has been measured by a pulse technique and velocity by an acoustic interferometer, both at a single frequency of 2 MHz. The results obtained for these materials furnish distinct similarities with the behavior of pure normal materials in the critical region. Anomalous increase in absorption and decrease in velocity observed across the isotropic–mesomorphic transition temperature in each case are interpreted in terms of pretransitional effect.
01 Jan 1976
TL;DR: In this paper, a two-beam interferometer of the Michelson type for optical wave-length comparison was built at the Institut National de Metrologie (INM).
Abstract: We have built at the Institut National de Metrologie (INM) a two beam interferometer, of Michelson type, for optical wave-length comparison. It is in vacuum and the separating plate works at Brewster’s angle. Its main quality is to give a flat field of interference at a path difference chosen for measurements (temporarily 250 mm), hence providing a large flux. The standard line of krypton provides a signal-to-noise ratio which allows us to work with a continuous scanning of path difference and a time constant less than 10−1 second.
TL;DR: 本文は線形素子としてのフィルターなどの特性改善に将来重要性を増すと思われる 増幅�arrow子, £1,000,000を述べる.
Abstract: 弾性表面波は機器の小型化と, 波の発生・検出・制御等の容易さという点で機能素子として多くの適用が考えられる.本文は線形素子としてのフィルター, およびフィルターなどの特性改善に将来重要性を増すと思われる増幅素子, 非線形効果の積極的応用としてのコンボルバー, イメージ素子などについて最近の動向を述べる.
Journal Article•
TL;DR: In this article, a linear coupling between electrostatic ion cyclotron waves and ion acoustic waves near the second harmonic frequency was detected experimentally in an argon plasma, which is nearly in accordance with the theoretical results.
Abstract: By investigating the dispersion relation of electrostatic ion waves in a magnetic field, a linear coupling is found between electrostatic ion cyclotron waves and ion acoustic waves near the second harmonic ion cyclotron frequency. The coupling between the two modes are also detected experimentally in an argon plasma, which is nearly in accordance with the theoretical results.
TL;DR: In this paper, it was shown that ion acoustic waves can be refracted in thermal and density gradients, and possible implications of the mechanism for turbulent heating experiments are pointed out.
01 Jan 1976
TL;DR: A new determination of the gas constant was made using a method in which the velocity of sound in argon was measured by means of an acoustic interferometer operated close to the triple point of water as discussed by the authors.
Abstract: A New Determination of The Gas Constant has been made using a method in which the velocity of sound in argon was measured by means of an acoustic interferometer operated close to the triple point of water. Ninety eight independent velocity measurements were made over a pressure range from 30 to 200 kPa to enable the velocity at zero pressure to be obtained by extrapolation. Using this experimental value, a new value for the gas constant of 8316.00 ± 0.17 J K−1 kmole−1 was deduced. This is higher than the old value for R, obtained from measurements of the density of oxygen, by 191 ppm.
TL;DR: Clark et al. as mentioned in this paper investigated the effects of the phase reversal which occurs when large-amplitude acoustic waves are reflected by a pressure-release boundary and showed that sawtooth waves will deform back into sinusoidal waves under these conditions.
Abstract: Effects of the phase reversal which occurs when large‐amplitude acoustic waves are reflected by a pressure‐release boundary have been investigated experimentally. Large‐amplitude, waterborne acoustic waves were generated by an induction type of electroacoustic transducer. Instantaneous pressure distributions associated with the propagating acoustic waves were determined by a whole field optical measurement method described elsewhere [Whole Field Measurements of Acousto‐Optic Refraction, J. A. Clark, J. Sound Vib. 46, 306–310 (1976)]. Nonlinear deformations of the acoustic waves were analyzed both before and after reflection at the pressure‐release boundary in order to verify theoretical predictions that large‐amplitude sawtooth waves will deform back into sinusoidal waves under these conditions. [Research supported by ONR.]
TL;DR: The use of hyperbolic-type heat transfer equations in an acoustic wave is considered in this article, where Acoustic dispersion is calculated Theoretical results are compared with experimental data on the coefficient of absorption for ultrasonic waves in castor oil.
Abstract: The use of hyperbolic-type heat-transfer equations in an acoustic wave is considered Acoustic dispersion is calculated Theoretical results are compared with experimental data on the coefficient of absorption for ultrasonic waves in castor oil
01 Oct 1976
TL;DR: In this paper, the cristalline constants are used to calculate the slowness curve of acoustic surface wave (a.s.w) devices, such as delay lines, acoustic lenses, apodized filters, helical long delay lines.
Abstract: Diffraction effects are important in many acoustic surface wave (a.s. w) devices : delay lines, acoustic lenses, apodized filters, helical long delay lines... If the slowness curve (i.e dependance of the slowness with propagation direction) is known, theoritical prediction of these effects can be done. But in some important cases, such as Li Nb 03, the cristalline constants are not known with a sufficient precision to permit an accurate computation of the slowness curve. Two global experimental methods can be used to determine the slowness.