scholarly journals Experimental Study of Raman Spectra of Some Aromatic Hydrocarbons

2020 ◽  
Vol 65 (4) ◽  
pp. 284
Author(s):  
B. Eshchanov ◽  
Sh. Otajonov ◽  
G. Mukhamedov ◽  
I. Doroshenko ◽  
O. Karpova ◽  
...  
Keyword(s):  
Experimental Study ◽  
Aromatic Hydrocarbons ◽  
Low Frequency ◽  
Semiempirical Method ◽  
Wide Frequency Range ◽  
Torsional Vibrations ◽  
Benzene Derivatives ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Potential Barriers

The vibrational spectra of liquid aromatic hydrocarbons – bromobenzene, dioxane, toluene – are studied in a wide frequency range by means of Raman spectroscopy. The manifestation of torsional vibrations of individual groups of atoms is established from the obtained data on the low-frequency spectra. The possibility of using a semiempirical method for calculating the potential barriers of methyl and halide groups in benzene derivatives is shown.

scholarly journals Diagnostics of concrete plate in bending with ultrasonic waves modulated by low frequency oscillations

2013 ◽  
Vol 12 (1) ◽  
pp. 243-250
Author(s):  
Błażej Meronk ◽  
Krzysztof Wilde
Keyword(s):  
Experimental Study ◽  
Low Frequency ◽  
Ultrasonic Waves ◽  
Modulation Method ◽  
Frequency Spectra ◽  
Concrete Plate ◽  
Low Frequency Oscillations ◽  
Damaged Zone ◽  
Nonlinear Acoustic ◽  
Concrete Elements

The paper presents the experimental study on the inter-modulation method for the diagnostics of concrete elements. The tests were conducted on a concrete plate subjected to ultrasonic waves and low frequency vibrations. The nonlinear acoustic effects, recorded in the experiments, made it possible to detect the presence of damaged zones. Further studies are necessary to establish the relation between the sidebanes of frequency spectra and the size of the damaged zone.

Analysis of Sound Absorption Properties of Three-Leaf Microperforated Panel Absorbers without a Rigid Backing

2014 ◽  
Vol 937 ◽  
pp. 465-471
Author(s):  
Xiao Ling Gai ◽  
Xian Hui Li ◽  
Rui Wu ◽  
Bin Zhang ◽  
Jun Juan Zhao
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Wide Frequency Range ◽  
Structure Design ◽  
Frequency Region ◽  
Theoretical Development ◽  
Frequency Range ◽  
Absorption Properties ◽  
High Frequency Region ◽  
Energy Dissipated

Microperforated panel (MPP) absorbers have been developed rapidly and used in many fields in recent years. First, based on the Maa’s theory, the theoretical development of MPP is reviewed in this paper. Furthermore, structure design and processing technology of MPP are introduced. Finally, the further development of MPP is discussed. Based on the MPP theory and electro-acoustical equivalent circuit principle, sound absorption properties of three-leaf microperforated panel (TMPP) absorbers without a rigid backing are studied to broaden the sound absorption bandwidth of MPP structure. Simulation results show that TMPP absorbers without a rigid backing have two resonance peaks and the energy dissipated coefficient remains constant in the low frequency range. The resonance frequency moves toward low frequency region with the increasing of the distance, thickness and pore diameter of MPP and moves toward high frequency region with the increasing of the perforation when other parameters keep invariant. The energy dissipated coefficient more than 0.5 over 8 octaves by choosing proper parameters. In conclusion, TMPP absorbers without a rigid backing have good sound absorption properties in a wide frequency range.

Some measurements in the self-preserving jet

1969 ◽  
Vol 38 (3) ◽  
pp. 577-612 ◽  
Author(s):  
I. Wygnanski ◽  
H. Fiedler
Keyword(s):  
Low Frequency ◽  
Convection Velocity ◽  
Hot Wire ◽  
Frequency Range ◽  
Mean Velocity ◽  
Frequency Spectra ◽  
Velocity Fluctuations ◽  
Taylor’S Hypothesis ◽  
Velocity Turbulence ◽  
Made In

The axisymmetric turbulent incompressible and isothermal jet was investigated by use of linearized constant-temperature hot-wire anemometers. It was established that the jet was truly self-preserving some 70 diameters downstream of the nozzle and most of the measurements were made in excess of this distance. The quantities measured include mean velocity, turbulence stresses, intermittency, skewness and flatness factors, correlations, scales, low-frequency spectra and convection velocity. The r.m.s. values of the various velocity fluctuations differ from those measured previously as a result of lack of self-preservation and insufficient frequency range in the instrumentation of the previous investigations. It appears that Taylor's hypothesis is not applicable to this flow, but the use of convection velocity of the appropriate scale for the transformation from temporal to spatial quantities appears appropriate. The energy balance was calculated from the various measured quantities and the result is quite different from the recent measurements of Sami (1967), which were obtained twenty diameters downstream from the nozzle. In light of these measurements some previous hypotheses about the turbulent structure and the transport phenomena are discussed. Some of the quantities were obtained by two or more different methods, and their relative merits and accuracy are assessed.

Performance Analysis of Infrasound Sensor InSAS2008

2012 ◽  
Vol 591-593 ◽  
pp. 201-204 ◽  
Author(s):  
Hao Nan Feng ◽  
Yi Chun Yang
Keyword(s):  
Performance Analysis ◽  
Performance Indicators ◽  
Mechanical Design ◽  
Nonlinear Effects ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Temperature Variations ◽  
Chinese Academy Of Sciences ◽  
Academy Of Sciences

It is known that earthquakes generate infrasound. The frequency spectra of the infrasound signals associated with earthquakes are concentrated within a wide frequency range (0.002-0.02 Hz), and have spectral tail extending up to the frequencies 0.1-1 Hz. Therefore, the dynamic characteristics of infrasound sensors should be chosen so as to capture main features of such signals. In this paper, the characteristics of infrasound sensor InSAS2008 developed by Institute of acoustics, Chinese academy of sciences, are described. Its performance indicators are listed and its frequency response is analyzed. The special construction in the mechanical design is developed to overcome drift problem caused by temperature variations. In addition, the infrasound sensor is not affected by nonlinear effects. The calibration results show that infrasound sensor works within a wide and flat frequency band.

Microstructure and Electrical Properties of Calcium Copper Titanate Ceramics

2007 ◽  
Vol 561-565 ◽  
pp. 551-555 ◽  
Author(s):  
Lai Jun Liu ◽  
Hui Qing Fan
Keyword(s):  
Electrical Properties ◽  
Dielectric Permittivity ◽  
High Frequency ◽  
Low Frequency ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Cell Parameters ◽  
Grain Sizes ◽  
Calcium Copper Titanate ◽  
Titanate Ceramics

The effect of stoichiometry, i.e. Ca/Cu ratios (CaCu3xTi4O12, x = 0.8, 0.9, 1.0, 1.1 and 1.2) on the microstructure and electrical properties was investigated. The grain sizes of CaCu3xTi4O12 composition increased sharply with the increase of copper, from ~1 μm with x = 0.8 to ~50 μm with x = 1.2. The real part of dielectric permittivity changed dramatically, the pellet with x = 1.0 had the highest dielectric permittivity ~160, 000 at 1 kHz. Furthermore, the dielectric permittivity of all pellets was impressively large values (between 10, 000 to 1, 000,000 at 100 Hz) and was nearly constant over a wide frequency range between 100 Hz to ~100 MHz. However, the dielectric permittivity of CaCu3xTi4O12 composition is not consistent with the amount of copper and cell parameters and grain sizes. Impedance spectroscopy exhibited that the CaCu3xTi4O12 composition had two semicircle at least at high frequency (~ 107 Hz) and low frequency (<100 Hz), respectively. The grain and grain boundary of the compositions had different impedance and relaxation behavior.

scholarly journals How well are FREQUENCY SENSITIVITIES OF grasshopper ears tuned to species-specific song spectra?

1996 ◽  
Vol 199 (7) ◽  
pp. 1631-1642
Author(s):  
J Meyer ◽  
N Elsner
Keyword(s):  
High Frequency ◽  
Broad Band ◽  
Low Frequency ◽  
Attachment Site ◽  
The Body ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Interspecific Differences ◽  
Tympanal Membrane ◽  
Species Specific

Grasshoppers of 20 acridid species were examined using spectral analysis, laser vibrometry and electrophysiology to determine whether the song spectra, the best frequencies of tympanal-membrane vibrations and the threshold curves of the tympanal nerves are adapted to one another. The songs of almost all species have a relatively broad-band maximum in the region between 20 and 40 kHz and a narrower peak between 5 and 15 kHz. There are clear interspecific differences in the latter, which are not correlated with the length of the body or of the elytra. At the site of attachment of the low-frequency receptors (a-cells), the tympanal membrane oscillates with maximal amplitude in the region from 5 to 10 kHz. At the attachment site of the high-frequency receptors (d-cells), there is also a maximum in this region as well as another around 15-20 kHz. The tympanal nerve is most sensitive to tones between 5 and 10 kHz, with another sensitivity maximum between 25 and 35 kHz. The species may differ from one another in the position of the low-frequency peaks of the membrane oscillation, of the nerve activity and of the song spectra. No correlation was found between the characteristic frequency of the membrane oscillation and the area of the tympanal membrane. Within a given species, the frequency for maximal oscillation of the membrane at the attachment site of the low-frequency receptors and the frequency for maximal sensitivity of the tympanal nerve are in most cases very close to the low-frequency peak in the song spectrum. In the high-frequency range, the situation is different: here, the position of the peak in the song spectrum is not correlated with the membrane oscillation maximum at the attachment site of the high-frequency receptors, although there is a correlation between the song spectrum and the sensitivity of the tympanal nerve. On the whole, therefore, hearing in acridid grasshoppers is quite well adjusted to the frequency spectra of the songs, partly because the tympanal membrane acts as a frequency filter in the low-frequency range.

Wide Frequency Characterization of Magnetic Properties of Commercial LTCC Ferrite Material

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000224-000231
Author(s):  
Nelu Blaž ◽  
Andrea Marić ◽  
Goran Radosavljević ◽  
Nebojša Mitrović ◽  
Ibrahim Atassi ◽  
...  
Keyword(s):  
Dispersion Model ◽  
Low Frequency ◽  
Hysteresis Loops ◽  
Wide Frequency Range ◽  
Complex Permeability ◽  
Frequency Range ◽  
Dispersion Parameters ◽  
Simple Method ◽  
Microwave Engineering ◽  
Characterization Procedure

Complex magnetic permeability and hysteresis characteristic are key parameters that determine properties of ferrite components. This paper offers effective, accurate and simple method for complex permeability determination of LTCC (Low Temperature Co-fired Ceramic) ferrite sample at wide frequency range (up to 1 GHz). Presented research can be found to be of importance in fields of ferrite components design and application, as well as RF and microwave engineering. The characterization sample is a stack of LTCC tapes forming a toroidal shape structure. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing applied for the sample fabrication. Permeability is determined in the frequency range from 10 kHz to 1 GHz and characterization procedure is divided in two segments - for low and high frequencies. Low frequency measurements (from 10 kHz to 1000 kHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and Vector Network Analyzer were used for the higher frequency range (from 1000 kHz to 1 GHz). Hysteresis properties of this material are also determined. B-H hysteresis loops were measured with BROCKHAUS Tester MPG 100D system using the maximum excitation of 2 kA/m and frequencies of 50 Hz, 500 Hz and 1000 Hz. In addition, we presented another important factor in the practical design, the temperature variation of the permeability dispersion parameters. Obtained results show good agreement with datasheet values given by the manufacturer at lower frequencies and are in good correlation with results extracted from developed dispersion model at higher frequencies.

LOW FREQUENCY MODES PROBED BY TIME-DOMAIN OPTICAL KERR EFFECT SPECTROSCOPY

1996 ◽  
Vol 10 (11) ◽  
pp. 1229-1272 ◽  
Author(s):  
S. KINOSHITA ◽  
Y. KAI ◽  
T. ARIYOSHI ◽  
Y. SHIMADA
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Kerr Effect ◽  
Low Frequency ◽  
Great Accuracy ◽  
Wide Frequency Range ◽  
Optical Kerr Effect ◽  
Spectroscopic Techniques ◽  
Frequency Range ◽  
Debye Relaxation

The principle and application of ultrafast optical Kerr effect (OKE) spectroscopy have been reviewed. This spectroscopy is shown to be very useful to investigate low frequency modes in disordered materials and the obtained data are directly comparable with frequency-domain light scattering spectroscopy. Experimental study to show the consistency between the time- and frequency-domain spectroscopy has been performed for liquid nitrobenzene and the excellent agreement is attained over three orders of magnitude in frequency range. It is also shown that the result obtained by the OKE measurement is consistent with that obtained by four wave mixing spectroscopy. Combination of these spectroscopic techniques is particularly suited for the investigation of low frequency modes because a wide frequency range is covered with great accuracy. Several remarks concerning the OKE spectroscopy are presented such as the breakdown of Debye relaxation model and various interference effects which may distort the time-domain data.

Molecular relaxation in Chitosan films in GHz frequency range

2014 ◽  
Vol 1613 ◽  
pp. 83-88
Author(s):  
Siva Kumar-Krishnan ◽  
Evgen Prokhorov ◽  
Gabriel Luna-Barcenas
Keyword(s):  
Activation Energy ◽  
Low Frequency ◽  
Bound Water ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Temperature Range ◽  
A Value ◽  
Chitosan Films ◽  
First Time

ABSTRACTThe molecular relaxations behavior of chitosan (CS) films in the wide frequency range of 0.1-3x109 Hz (by using three different impedance analyzers) have been investigated in the temperature range of -100C to 120°C using Dielectric Spectroscopy (DS). Additionally to the low frequency molecular relaxations such as α and β relaxations, for the first time, high frequency (1-3 GHz) relaxation process has been observed in the chitosan films. This relaxation exhibits Arrhenius-type dependence in the temperature range of -100 C to 54°C with negative activation energy -2.7 kJ/mol. At temperatures above 54°C, the activation energy changes from -2.7 kJ/mol to +4.4 kJ/mol. Upon cooling, the activation energy becomes negative again with a value of -1.2 kJ/mol. The bound water between chitosan molecules strongly modifies molecular motion and the relaxation spectrum, giving rise to a new relaxation at the frequency at ca. 1 GHz. In situ FTIR analysis has shown that this relaxation related to the changes in vibration of the –OH, NH and –CO functional groups.

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