Volume oscillation and acoustical scattering of a gas bubble

The exact solution of a gas bubble’ volume was obtained based on volume oscillation of a gas bubble. The volume pulsation, acoustic impedance, scattering pressure of a gas bubble, acoustical power of scattering and acoustical scattering cross section of a single bubble are researched in a small amplitude acoustic field. The results show that a big bubble oscillates more violently than that of a small bubble in a weak acoustic field if the linear resonance does not happen. The occurrence of a linear resonance response of a single bubble leads to the volume oscillation and the scattering ability of a gas bubble become stronger. Additionally, the scattering cross section does not depend on the driving pressure. The amplitude of scattering pressure of a big bubble can reach the magnitude compared to the driving pressure when the resonance response occurs.

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Mass Determination by Direct Measurement of Electron Scattering

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100114827 ◽

1975 ◽

Vol 33 ◽

pp. 240-241

Author(s):

M. K. Lamvik ◽

A. V. Crewe

Keyword(s):

Cross Section ◽

Electron Scattering ◽

Mass Density ◽

Variable Mass ◽

Scattering Cross Section ◽

Mass Determination ◽

Number Density ◽

Cross Sectional ◽

Thin Slice ◽

Scattering Cross

If a molecule or atom of material has molecular weight A, the number density of such units is given by n=Nρ/A, where N is Avogadro's number and ρ is the mass density of the material. The amount of scattering from each unit can be written by assigning an imaginary cross-sectional area σ to each unit. If the current I0 is incident on a thin slice of material of thickness z and the current I remains unscattered, then the scattering cross-section σ is defined by I=IOnσz. For a specimen that is not thin, the definition must be applied to each imaginary thin slice and the result I/I0 =exp(-nσz) is obtained by integrating over the whole thickness. It is useful to separate the variable mass-thickness w=ρz from the other factors to yield I/I0 =exp(-sw), where s=Nσ/A is the scattering cross-section per unit mass.

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Absolute inner-shell cross section determination for EELS analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010473x ◽

1988 ◽

Vol 46 ◽

pp. 534-535

Author(s):

P.A. Crozier

Keyword(s):

Cross Section ◽

Cross Sections ◽

Absolute Cross Section ◽

Specimen Thickness ◽

Mass Thickness ◽

Scattering Cross ◽

Before And After ◽

Estimated Error ◽

Scattering Cross Sections ◽

Electron Microscopist

Absolute inelastic scattering cross sections or mean free paths are often used in EELS analysis for determining elemental concentrations and specimen thickness. In most instances, theoretical values must be used because there have been few attempts to determine experimental scattering cross sections from solids under the conditions of interest to electron microscopist. In addition to providing data for spectral quantitation, absolute cross section measurements yields useful information on many of the approximations which are frequently involved in EELS analysis procedures. In this paper, experimental cross sections are presented for some inner-shell edges of Al, Cu, Ag and Au.Uniform thin films of the previously mentioned materials were prepared by vacuum evaporation onto microscope cover slips. The cover slips were weighed before and after evaporation to determine the mass thickness of the films. The estimated error in this method of determining mass thickness was ±7 x 107g/cm2. The films were floated off in water and mounted on Cu grids.

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