scholarly journals Acoustic Coupling between Resonator Tubes in Quartz-Enhanced Photoacoustic Spectrophones Employing a Large Prong Spacing Tuning Fork

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4109 ◽  
Author(s):  
Stefano Dello Russo ◽  
Marilena Giglio ◽  
Angelo Sampaolo ◽  
Pietro Patimisco ◽  
Giansergio Menduni ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Sound Field ◽  
Tube Length ◽  
Photoacoustic Detection ◽  
Flexural Mode ◽  
Acoustic Coupling ◽  
Custom Made ◽  
Theoretical Predictions ◽  
Infrared Spectral ◽  
Tube Exit

A theoretical model describing the acoustic coupling between two resonator tubes in spectrophones exploiting custom-made quartz tuning forks (QTFs) is proposed. The model is based on an open-end correction to predict the optimal tube length. A calculation of the sound field distribution from one tube exit allowed for the estimation of the optimal radius as a function of the QTF prong spacing and the sound wavelength. The theoretical predictions have been confirmed using experimental studies employing a custom QTF with a fundamental flexural mode resonance frequency of 15.8 kHz and a quality factor of 15,000 at atmospheric pressure. The spacing between the two prongs was 1.5 mm. Spectrophones mounting this QTF were implemented for the quartz-enhanced photoacoustic detection of water vapor in air in the mid-infrared spectral range.

scholarly journals Water Level Sensing in a Steel Vessel Using A0 and Quasi-Scholte Waves

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Peng Guo ◽  
Bo Deng ◽  
Xiang Lan ◽  
Kaili Zhang ◽  
Hongyuan Li ◽  
...  
Keyword(s):  
Water Level ◽  
Guided Waves ◽  
Mode Conversion ◽  
Experimental Studies ◽  
Low Frequency ◽  
Steel Vessel ◽  
Theoretical Predictions ◽  
Travelling Time ◽  
The Comparative Study ◽  
Group Velocities

This paper presents a water level sensing method using guided waves of A0 and quasi-Scholte modes. Theoretical, numerical, and experimental studies are performed to investigate the properties of both the A0 and quasi-Scholte modes. The comparative study of dispersion curves reveals that the plate with one side in water supports a quasi-Scholte mode besides Lamb modes. In addition, group velocities of A0 and quasi-Scholte modes are different. It is also found that the low-frequency A0 mode propagating in a free plate can convert to the quasi-Scholte mode when the plate has one side in water. Based on the velocity difference and mode conversion, a water level sensing method is developed. For the proof of concept, a laboratory experiment using a pitch-catch configuration with two piezoelectric transducers is designed for sensing water level in a steel vessel. The experimental results show that the travelling time between the two transducers linearly increases with the increase of water level and agree well with the theoretical predictions.

The Peak Overpressure Field Resulting From Shocks Emerging From Circular Shock Tubes

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
A. J. Newman ◽  
J. C. Mollendorf
Keyword(s):  
Shock Tube ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Polar Angle ◽  
Field Measurements ◽  
Initial Development ◽  
Theoretical Predictions ◽  
Mach Numbers ◽  
Tube Exit ◽  
Semi Empirical

A simple semi-empirical model for predicting the peak overpressure field that results when a shock emerges from a circular shock tube is presented and validated. By assuming that the shape of the expanding shock remains geometrically similar after an initial development period, an equation that describes the peak overpressure field in the horizontal plane containing the shock tube’s centerline was developed. The accuracy of this equation was evaluated experimentally by collecting peak overpressure field measurements along radials from the shock tube exit at 0 deg, 45 deg, and 90 deg over a range of shock Mach numbers from 1.15 to 1.45. It was found that the equation became more accurate at higher Mach numbers with percent differences between experimental measurements and theoretical predictions ranging from 1.1% to 3.6% over the range of Mach numbers considered. (1) Shocks do propagate in a geometrically similar manner after some initial development length over the range of Mach numbers considered here. (2) The model developed here gives reasonable predictions for the overpressure field from a shock emerging from a circular shock tube. (3) Shocks are expected to be completely symmetric with respect to the shock tube’s centerline, and hence, a three dimensional overpressure field may be predicted by the model developed here. (4) While there is a range of polar angle at which the shock shape may be described as being spherical with respect to the shock tube’s exit, this range does not encompass the entirety of the half space in front of the shock tube, and the model developed here is needed to accurately describe the entire peak overpressure field.

scholarly journals The Effect of Cooling Water Mass Flow Rate Variations on the Heat Pipe Solar Collector Performance

2017 ◽  
Vol 5 (2) ◽  
pp. 31-41
Author(s):  
Abdulsalam D. M. Hassan ◽  
Rwaa Alaa Hussein
Keyword(s):  
Flow Rate ◽  
Solar Collector ◽  
Experimental Studies ◽  
Cooling Water ◽  
Percentage Increase ◽  
Cover Glass ◽  
Language Version ◽  
Theoretical Predictions ◽  
Useful Heat ◽  
Water Mass Flow Rate

The thermal performance of FPHPSC has been studied experimentally and theoretically. The collector consists of copper absorber plate, single glass cover, glass wool insulation and aluminum case. Ten wickless heat pipes of 12.7 mm inner diameter. The experimental studies of collector performance have been performed on four different CWMFR (0.03, 0.04, 0.05 and 0.06) kg/s. The relation between the amount of useful heat, instantaneous collector efficiency and solar intensity is discussed. The collector are tested under the climate condition of Kut city (32.6 latitude and 45.7 longitude). It is investigated that the increasing of CWMFR increase the efficiency of the collector. The percentage increase in the efficiency of the solar collector is in order of (13%), when the cooling water mas flow rate changes from 0.03 kg/sec to 0.06 kg/sec at (45o) collector tilt angle. A computer program based on VISUAL BASIC language (version 6) used for the theoretical analysis. The experimental results are in agreement reasonably with the theoretical predictions.

scholarly journals EFFICIENT ACOUSTIC COMPOSITE PANELS BASED ON GRAPHITE

2021 ◽  
Vol 6 (4) ◽  
pp. 82-90
Author(s):  
E. Fanina
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Sound Field ◽  
Fire Retardant ◽  
Pyramidal Cells ◽  
Sound Insulation ◽  
Composite Panels ◽  
Thin Membrane ◽  
Reverberation Time ◽  
Acoustic Characteristics

A set of experimental studies is carried out to determine the acoustic characteristics of three-dimensional panels of fixed thickness made of carbon-based composite material installed in the opening between the reverberation chambers. Sound insulation indices are determined when they are excited by a diffuse sound field in wide frequency ranges. The reverberation time in model chambers with different partition configurations is calculated. The optimal configuration of the partition with pyramidal cells to reduce the reverberation time in the rooms is determined. The use of graphite in the form of thin membrane applied to various surfaces can significantly reduce the sound pressure levels in the room and increase the sound insulation indices of air noise. In addition to thin membrane, graphite can be used as an additive in composite materials for sound insulation purposes. It is shown that the characteristics of such panels are quite universal. The measured acoustic characteristics of composite panels are compared with similar characteristics of traditional materials. It is determined that the composition belongs to the I group of fire-retardant efficiency and can be recommended for use as a fire-retardant material. The developed acoustic material is an effective absorbing agent that solves problems in architectural acoustics, echo cancellation in construction and architecture. Similar to metamaterials, natural and artificial graphites allow to solve these problems with small volumes and masses using simple and inexpensive technologies.

Simulation of gas transport due to cardiogenic oscillations

1985 ◽  
Vol 58 (4) ◽  
pp. 1331-1339 ◽  
Author(s):  
A. S. Slutsky ◽  
M. C. Khoo ◽  
R. Brown
Keyword(s):  
Gas Transport ◽  
Nitrogen Concentration ◽  
Experimental Studies ◽  
Bronchial Tree ◽  
High Frequency Ventilation ◽  
Gas Mixing ◽  
Theoretical Predictions ◽  
Anatomical Dead Space ◽  
Frequency Ventilation ◽  
Cardiogenic Oscillations

We simulated gas transport due to cardiogenic oscillations (CO) using a model developed to quantify the gas mixing due to high-frequency ventilation (16). The basic components of the model are 1) gas mixing by augmented transport, 2) symmetrical lung morphometry, and 3) a Lagrangian (moving) reference frame. The theoretical predictions of the model are in general agreement with published experimental studies that have examined the effect of CO on the nitrogen concentration obtained by intrapulmonary gas sampling and the effect of CO on regional and total anatomical dead space. Further, the model predicts that augmentation of gas transport due to CO is less, nearer to the alveolar regions of the lung, and that the effect of CO during normal tidal breathing is negligible, but that CO may contribute up to approximately 10% of the alveolar ventilation in patients with severe hypoventilation. The agreement between experimental and theoretical results suggests that it may not be necessary to invoke gas transport mechanisms specific to an asymmetrical bronchial tree to explain the major proportion of gas transport due to CO.

Properties of Magnetic Features from the Analysis of Near-Infrared Spectral Lines

1994 ◽  
Vol 154 ◽  
pp. 393-405
Author(s):  
Sami K. Solanki
Keyword(s):  
Near Infrared ◽  
Velocity Structure ◽  
Spectral Lines ◽  
The Past ◽  
Diagnostic Potential ◽  
Theoretical Predictions ◽  
Infrared Spectral ◽  
Magnetic Features

An overview is given of the structure and the physics of magnetic features in solar plages, as derived from observations of near-infrared lines. First, the diagnostic potential of near-infrared lines is compared with that of lines in the visible and at 12 μm. Then, the results on the magnetic and velocity structure of magnetic features obtained from 1.5 μm lines are described, discussed and compared with results of observations in the visible and with theoretical predictions. Finally, the past and present achievements of near-infrared investigations of Zeeman-split lines are summarized.

scholarly journals The Effects of Stress on Second Harmonics in Plate-Like Structures

2020 ◽  
Vol 10 (15) ◽  
pp. 5124
Author(s):  
Xiaochuan Niu ◽  
Liqiang Zhu ◽  
Zujun Yu
Keyword(s):  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Studies ◽  
Arbitrary Cross Section ◽  
Ultrasonic Guided Waves ◽  
Analysis Method ◽  
Harmonic Mode ◽  
Amplitude Coefficient ◽  
Theoretical Predictions ◽  
Application Potential

Cumulative second harmonic of ultrasonic guided waves is considered to have great application potential in evaluating internal stress of structures. One difficulty with the application is the diversity and complexity of modal response to the stress change in waveguide. At present, there is a lack of relevant theoretical studies and experimental results to guide the applications. In this article, a method is proposed to characterize the amplitude change of cumulative second harmonic mode in a plate under stress through calculating the amplitude coefficient, which can be acquired based on mode shape analysis. The steel plate is taken as an example to demonstrate the analysis method. Experimental studies are presented with results consistent with the theoretical predictions. The results of this study indicate that the amplitudes of different cumulative second harmonic modes may increase or decrease monotonically with the change of stress. Therefore, when the phenomenon of modes mixing occurs in the waveguide, it is necessary to analyze and predict the amplitude of selected cumulative second harmonic mode with the change of stress in advance; otherwise, wrong results may be obtained. The method and conclusions proposed in this paper can also be applicable to waveguide of arbitrary cross-section and have universality.

Infrared Spectroscopy of Hydrogen in ZnO

2004 ◽  
Vol 813 ◽  
Author(s):  
M.D. Mccluskey ◽  
S.J. Jokela
Keyword(s):  
First Principles ◽  
Experimental Studies ◽  
Wide Band ◽  
Shallow Donor ◽  
Great Promise ◽  
Bulk Single Crystal ◽  
First Principles Calculations ◽  
Wide Band Gap ◽  
Theoretical Predictions ◽  
Good Agreement

ABSTRACTZinc oxide (ZnO) has shown great promise as a wide band gap semiconductor with optical, electronic, and mechanical applications. Recent first-principles calculations and experimental studies have shown that hydrogen acts as a shallow donor in ZnO, in contrast to hydrogen's usual role as a passivating impurity. The structures of such hydrogen complexes, however, have not been determined. To address this question, we performed vibrational spectroscopy on bulk, single-crystal ZnO samples annealed in hydrogen (H2) or deuterium (D2) gas. Using infrared (IR) spectroscopy, we have observed O-H and O-D stretch modes at 3326.3 cm−1 and 2470.3 cm−1 respectively, at a sample temperature of 14 K. These frequencies are in good agreement with the theoretical predictions for hydrogen and deuterium in an antibonding configuration, although the bond-centered configuration cannot be ruled out. The IR-active hydrogen complexes are unstable, however, with a dissocation barrier on the order of 1 eV.

Glulam rivet connections under eccentric loading

1987 ◽  
Vol 14 (5) ◽  
pp. 621-630 ◽  
Author(s):  
Erol Karacabeyli ◽  
Ricardo O. Foschi
Keyword(s):  
Failure Modes ◽  
Experimental Studies ◽  
Design Guidelines ◽  
Bearing Failure ◽  
Element Analysis ◽  
Theoretical Predictions ◽  
Failure Loads ◽  
Fracture Theory ◽  
Timber Engineering ◽  
Type Of Failure

Results from theoretical and experimental studies on the strength of glulam rivet connections under eccentric loading are presented. Two failure modes are studied: (1) rivet yielding in bending with simultaneous bearing failure of the wood under the rivet's shank and (2) wood failure around the rivet cluster. The latter is studied using brittle fracture theory and a finite element analysis of the stress distribution in the wood around the rivets.Experimental results are shown to compare well with theoretical predictions for failure loads and type of failure, and design guidelines are proposed. Key words: fasteners, wood connectors, glued-laminated, nails, timber engineering.

An experimental study of the onset of parametrically pumped surface waves in viscous fluids

1995 ◽  
Vol 288 ◽  
pp. 325-350 ◽  
Author(s):  
John Bechhoefer ◽  
Valerie Ego ◽  
Sebastien Manneville ◽  
Brad Johnson
Keyword(s):  
Surface Waves ◽  
Size Effects ◽  
Experimental Studies ◽  
Finite Size ◽  
Finite Depth ◽  
Finite Size Effects ◽  
Polar Fluid ◽  
Faraday Instability ◽  
Theoretical Predictions ◽  
Finite Size Corrections

We measure the threshold accelerations necessary to excite surface waves in a vertically vibrated fluid container (the Faraday instability). Under the proper conditions, the thresholds and onset wavelengths agree with recent theoretical predictions for a laterally infinite, finite-depth container filled with a viscous fluid. Experimentally, we show that by using a viscous, non-polar fluid, the finite-size effects of sidewalls and the effects of surface contamination can be made negligible. We also show that finite-size corrections are of order h/L, where h is the fluid depth and L the container size. Based on these measurements, one can more easily interpret certain unexpected observations from previous experimental studies of the Faraday instability.

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