A comparison of the spectral features of the collision-induced light scattering by the molecular gases CH4 and CF4 and by argon

1977 ◽  
Vol 55 (22) ◽  
pp. 1962-1969 ◽  
Author(s):  
F. Barocchi ◽  
M. Zoppi ◽  
D. P. Shelton ◽  
G. C. Tabisz
Keyword(s):  
Light Scattering ◽  
High Frequency ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Detailed Comparison ◽  
Absolute Intensity ◽  
Molecular Spectra ◽  
Similar Data ◽  
Unknown Parameters ◽  
Three Body

The collision-induced light scattering from compressed gaseous CH4 and CF4 has been observed at room temperature at densities up to 100 and 166 amagats, respectively. Absolute intensity measurements have been made and the two- and three-body components to the spectra have been identified. A detailed comparison is made with similar data on argon and significant differences emerge between the atomic and molecular cases. The two-body molecular spectra contain an excess of intensity over predictions of the dipole–induced-dipole (DID) model; the argon intensity is less than predicted. At low frequency, the two- and three-body spectra of all species are dominated by the DID interaction. At high frequency the two-body molecular spectra decay much more slowly than the profile due to argon. A moment analysis has been performed wherein the pair polarizability is assumed to be of the form, β(r) = 6α2/r3 + B/rp. The unknown parameters B and p are determined from the experimental zeroth and second moments of the spectra. For the molecules B is found to be greater than unity and p is 7.2 for CH4 and 8.5 for CF4. The difference in the values of B and p, together with the fact the shape of the high frequency tail is not consistent with pure translational broadening, lead to the suggestion that the internal degrees of freedom of the molecules are playing a role in the scattering process.

On the Assignment and Directional Dispersion of Polar Phonon Modes in K3Cu(CN)4 and K3Ag(CN)4

1974 ◽  
Vol 29 (7) ◽  
pp. 1011-1016
Author(s):  
W. Nitsch ◽  
H. J. Falge ◽  
R. Claus
Keyword(s):  
Light Scattering ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Region ◽  
Longitudinal Vibrations ◽  
Phonon Modes ◽  
High Frequency Region ◽  
Single Crystalline ◽  
Scattering Measurements ◽  
Stretching Vibrations

Polar phonon modes in single crystalline K3Cu(CN)4 and K3Ag(CN)4 have been experimentally studied by light scattering. Measurements at 293, 82 and 6 K made possible assignments in the low frequency region from 0 to about 700 cm-1 and the high frequency region from 2030 to about 2100 cm-1 originating from the C≡N stretching vibrations. Directional dispersion due to the anisotropy of K3Cu(CN)4 has been studied and allowed the identification of the transversal and longitudinal vibrations in the high frequency region. IR-reflectivity measurements, partly on the basis of the ATR-method, have been used in order to support the assignments in this region.

scholarly journals Simulation of Motion Interactions of a 2-DOF Linear Piezoelectric Impact Drive Mechanism with a Single Friction Interface

2018 ◽  
Vol 8 (8) ◽  
pp. 1400 ◽  
Author(s):  
Haojie Xia ◽  
Liling Han ◽  
Chengliang Pan ◽  
Huakun Jia ◽  
Liandong Yu
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Piezoelectric Actuators ◽  
Friction Model ◽  
Duty Ratio ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Coupled Motion ◽  
Drive Mechanism

A two-degrees-of-freedom (2-DOF) linear piezoelectric impact drive mechanism (PIDM) is actuated by two independent piezoelectric actuators (PAs). The coupled motion interactions of a two orthogonal DOF linear PIDM with a single friction interface are introduced and analyzed. A complete dynamic model of the 2-DOF PIDM is established with the Karnopp friction model considering the distribution of friction in the x-axis and y-axis. The output displacements of the 2-DOF PIDM and two corresponding independent 1-DOF PIDMs are investigated numerically. When the two input exciting signals of a 2-DOF PIDM have the same driving voltage of 100 V with a duty ratio of 98% at 10 Hz and two 1-DOF PIDMs are driving under the same conditions, the step displacements in the two axes of 2-DOF PIDM are improved compared to the corresponding 1-DOF PIDM. When the two input exciting signals of a 2-DOF PIDM have the same driving voltages of 100 V with a duty ratio of 98% but the driving frequency is 10 Hz in the x-axis and 20 Hz in the y-axis, the results show that the displacement of high frequency achieves a slight decrease and displacement of low frequency shows a large increase compared to the two corresponding 1-DOF PIDMs.

Development of Low-Frequency Tone Burst versus the Click Auditory Brainstem Response

2005 ◽  
Vol 16 (02) ◽  
pp. 114-121 ◽  
Author(s):  
Raymond M. Hurley ◽  
Annette Hurley ◽  
Charles I. Berlin
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Tone Burst ◽  
Auditory Brainstem ◽  
Similar Data ◽  
Frequency Sensitivity ◽  
Frequency Tone ◽  
Brainstem Response ◽  
Threshold Testing ◽  
Wave Latency

Often ABR threshold testing employs clicks to assess high-frequency hearing, and low-frequency tone bursts to assess low-frequency sensitivity. While a maturation effect has been shown for click stimuli, similar data are lacking for low-frequency toneburst stimuli. Thus, 305 infants ranging in conceptional age (CA) from 33 weeks to 74 weeks were tested. Absolute latencies were measured for wave V at 55, 35, and 25 dB nHL in response to a click and for wave V500 in response to a 500 Hz tone burst. Major wave latency in response to 500 Hz tone bursts decreases with age and do not stabilize by 70 weeks CA. Likewise, waves III and V latencies in response to clicks decrease with age, as has been reported by others, and do not stabilize by 70 weeks CA. Wave I latency produced by clicks did not decrease with age, being mature by 33 weeks CA.

Creating a Mathematical Model from the Realization of the Measuring of a Transient Process of a Mechanical System

2006 ◽  
Vol 113 ◽  
pp. 229-234
Author(s):  
Vytautas Slivinskas ◽  
Kastytis Slivinskas ◽  
Vytautas Bučinskas
Keyword(s):  
Mechanical System ◽  
Transient Process ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Component ◽  
High Frequency Component ◽  
Unknown Parameters ◽  
Prony Method ◽  
Sample Data ◽  
Model Versus

In the paper the method of creating the dynamical model of the mechanical system is considered. The transient process measured after the hammer blow is used as input data. Prony method with its improvements is used for the estimation of unknown parameters of the model. Using the FFT and IFFT procedures the sample data is decomposed into two parts: a high frequency component and a low frequency component. Each part is investigated separately. While the high frequency component was modeled by using a simple six poles model, the low frequency component was modeled by a single multiple pole. The correctness of the model was checked by RMSE criteria. The RMSE of the low frequency component model versus the multiplicity of the pole was investigated. The results show good agreement with experimental data. The full final model was used to get the amplitude-frequency response of the system.

Use of twitch pressures to assess diaphragmatic function and central drive

1994 ◽  
Vol 77 (4) ◽  
pp. 1705-1715 ◽  
Author(s):  
G. T. Ferguson
Keyword(s):  
Phrenic Nerve ◽  
High Frequency ◽  
Rabbit Model ◽  
Low Frequency ◽  
Absolute Intensity ◽  
Validity And Reliability ◽  
Twitch Potentiation ◽  
Diaphragmatic Function ◽  
Nerve Recordings ◽  
Central Drive

Transdiaphragmatic pressures generated by phrenic nerve twitches have been proposed as a means to assess diaphragmatic function and central drive, but their validity and reliability have not been determined. We evaluated diaphragmatic twitch and twitch occlusion measurements in a rabbit model of diaphragmatic contractile dysfunction and diaphragmatic fatigue to determine whether 1) diaphragmatic twitch pressures accurately assess changes in low- and high-frequency diaphragm trains during the development of, and recovery from, contractile fatigue; 2) twitch occlusion measurements accurately quantify the intensity of central drive to the diaphragm; and 3) twitch measurements are affected by thoracoabdominal binding or twitch potentiation. Single-twitch and 20-Hz double- and triple-twitch pressures accurately reflected changes in low-frequency diaphragm train pressures, whereas only 80-Hz triple-twitch pressures accurately reflected changes in high-frequency trains. Twitch occlusion measurements of central drive closely mirrored central drive as reflected by phrenic nerve recordings and only slightly underestimated the absolute intensity of central drive. Thoracoabdominal binding increased twitch and train pressures, and repetitive electrical stimulations further potentiated twitch pressure. However, twitch potentiation and a lack of thoracoabdominal binding had no effect on twitch measurements of diaphragmatic function during the induction and recovery from fatigue or on twitch occlusion measurements of intensity of central drive. Thus, twitch measurements can be used to accurately assess diaphragmatic low- and high-frequency fatigue and to quantify the intensity of central drive to the diaphragm.

Features of Nonlinear Sound Propagation in Vibrationally Excited Gases

2013 ◽  
Vol 38 (3) ◽  
pp. 357-362
Author(s):  
Anna Perelomova ◽  
Magdalena Kusmirek
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Sound Propagation ◽  
Vibrational Excitation ◽  
Low Frequency ◽  
Vibrationally Excited ◽  
Weakly Nonlinear ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Nonlinear Distortions

Abstract Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound

Squirt flow in fully saturated rocks

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Jack Dvorkin ◽  
Gary Mavko ◽  
Amos Nur
Keyword(s):  
High Frequency ◽  
Pore Space ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Confining Pressure ◽  
Biot Theory ◽  
Unknown Parameters ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Dispersion And Attenuation

We estimate velocity/frequency dispersion and attenuation in fully saturated rocks by employing the squirt‐flow mechanism of solid/fluid interaction. In this model, pore fluid is squeezed from thin soft cracks into the surrounding large pores. Information about the compliance of these soft cracks at low confining pressures is extracted from high‐pressure velocity data. The frequency dependence of squirt‐induced pressure in the soft cracks is linked with the porosity and permeability of the soft pore space, and the characteristic squirt‐flow length. These unknown parameters are combined into one expression that is assumed to be a fundamental rock property that does not depend on frequency. The appropriate value of this expression for a given rock can be found by matching our theoretical predictions with the experimental measurements of attenuation or velocity. The low‐frequency velocity limits, as given by our model, are identical to those predicted by Gassmann’s formula. The high‐frequency limits may significantly exceed those given by the Biot theory: the high‐frequency frame bulk modulus is close to that measured at high confining pressure. We have applied our model to D’Euville Limestone, Navajo Sandstone, and Westerly Granite. The model realistically predicts the observed velocity/frequency dispersion, and attenuation.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

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