摘要:

The ultrasonic absorption and velocity of dilute solutions of methyl, chloro‐, and bromocyclohexane in xylene have been measured over the range 0.6 to 25 Mc and 65° to 95°C. The frequency dependence of the absorption in all cases is that of a single relaxation process. The concentration dependence of the relaxation parameters is consistent with the mechanism being the interchange of axial and equatorial chair isomers, while the temperature dependence yields a difference in enthalpy and entropy between isomers of methyl cyclohexane of 3.54±0.7 kcal/mole and 4.04±1.1 cal/mole °C, respectively, and an activation energy for the conversion of axial into equatorial isomers of 10.94±0.8 kcal/mole for methyl cyclohexane and 12±2 kcal/mole for chloro‐ and bromo‐cyclohexane. There is no significant change in these values for methyl cyclohexane when the solvent is changed to nitrobenzene orn‐butyl alcohol, indicating that intermolecular processes do not make an appreciable contribution, and that the difference in volume between isomers can be neglected in the calculations. The conversion of axial into equatorial isomers is found to be uni‐molecular, and a mode of vibration of the molecule similar to either theA1gorEumodes of cyclohexane is suggested for the path of this reaction.

ISSN:0001-4966    

DOI:10.1121/1.1908618

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The problem considered is the behavior of a gas bubble in a liquid saturated with dissolved gas when oscillating pressures are imposed on the system. This situation is encountered in experiments on cavitation and in the propagation of sonic and ultrasonic waves in liquids. Since gas diffuses into the bubble during the expansion half‐cycle in which the pressure drops below its mean value, and diffuses out of the bubble during the compression half‐cycle in which the pressure rises above its mean value, there is no net transfer of mass into or out of the bubble in first order. There is, however, in second order a net inflow of gas into the bubble which is called rectified diffusion. The equations which determine the system include the equation of state of the gas in the bubble, the equation of motion for the bubble boundary in the liquid, and the equation for the diffusion of dissolved gas in the liquid. In the solution presented here, the acoustic approximation is made; that is, the amplitude of the pressure oscillation is taken to be small. It is also assumed that the gas in the bubble remains isothermal throughout the oscillations; this assumption is valid provided the oscillation frequency is not too high. Under these conditions one finds for the mean rate of gas flow into the bubble the expression〈dm/dt〉 = (8π/3)DC∞R0(ΔP/P0)2, whereDis the diffusivity of the dissolved gas in the liquid,C∞is the equilibrium dissolved gas concentration for the mean ambient pressureP0,R0is the mean radius of the bubble, and ΔPis the amplitude of the acoustic pressure oscillations. It may be remarked that the most important contribution to the rectification effect comes from the convection contribution to the diffusion process.

ISSN:0001-4966    

DOI:10.1121/1.1908621

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The general equations for a small displacement superimposed on a finite deformation of a perfectly elastic material of arbitrary symmetry are derived anew. These equations are the basis of an analysis of plane waves of small amplitude propagating in an initially deformed and stressed elastic material. Certain restrictions on the energy function of finite elasticity theory are determined. These restrictions, which provide necessary and sufficient conditions that a homogeneously deformed material admit plane waves, are then compared with other restrictions obtained from themostatic equilibrium considerations. Compatibility conditions, which are necessary and sufficient that data on sound wave propagation in elastic materials be compatible with classical elasticity theory upon suitable assignment of the material symmetry, are derived. Finally, it is shown how the variation of sound speeds with initial stress and the measured magnitude of the acoustoelastic effect can be used to determine the third‐order elastic constants of an isotropic material and as a partial confirmation and experimental check of the theory.

ISSN:0001-4966    

DOI:10.1121/1.1908623

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

This paper presents the results of an experimental investigation of the scattering of acoustic energy from finite circular cylinders in water. Photographs are shown of the pulses scattered in the backward direction in the plane normal to the longitudinal axis and in the plane containing the longitudinal axis of a cylinder. The echo structure exhibits characteristics dependent upon the corners of the cylinder where there is a sharp change in the slope of the projected area and discontinuities between air, brass, and water. The photographs of pulses returned from the cylinders in the plane normal to the longitudinal axes imply the existence of surface waves which travel around (the) circumferences of the cylinders. Distribution‐in‐angle diagrams of acoustic energy scattered in the plane perpendicular to the longitudinal axes of solid and hollow air‐filled cylinders were taken for changes in cylinder length, changes in pulse length, and changes in acoustic radii. Length modes of vibration do not affect significantly the energy scattered perpendicular to the longitudinal axis. When pulses, which are long compared to the diameter of the cylinder, are used, the scattered energy distribution is dependent upon the composition and the acoustic radius of the cylinder.

ISSN:0001-4966    

DOI:10.1121/1.1908625

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The effects of surface waves on sound propagated from a continuous wave source over a range of 300 it in water of depth 10 ft have been examined. It is found that the surface waves induce regular amplitude and phase fluctuations in the received signal. The dependence of the amount of amplitude and phase fluctuation on crest to trough height of the surface waves has been obtained for acoustic frequencies in the range 1 to 10 kc. Frequency spectra of the fluctuations, for values of the ratio of sound wavelength (λ) to wave height (A) above 18, are the same as the surface wave spectra. For values of λ/Aless than 18 the fluctuation spectra are broader and show well defined second and sometimes third harmonic components. Wave packet experiments in which the bow wave of a small boat is propagated across the length of the otherwise calm duct surface show that in the case of the uniformly rough surface the fluctuations are produced only by surface waves near the source and near the receiver.

ISSN:0001-4966    

DOI:10.1121/1.1908628

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908630

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A new formula for the speed of sound in sea water was recently published by Mackenzie. This letter compares the new formula with a more familiar formula, since the new one contains more terms and conveys the impression of being a much better approximation.

ISSN:0001-4966    

DOI:10.1121/1.1908633

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP