Acoustic Temperature Measurement Research Articles

The interplay of temperature and circadian periodicity in winter activity of non-cavernous hibernator, Nyctalusnoctula

Winter activity of hibernating mammals is likely to be influenced by climate change. Our study focuses on Nyctalus noctula, a non-cavernous hibernator using artificial roosts in a recently colonized winter region. Using continuous acoustic monitoring and temperature measurements inside and outside the roosts, we found that bats exhibit a circadian cycle (active at night, resting during the day) even during hibernation season. Activity duration and intensity changed in response to ambient temperature, photoperiod, and hibernation progression. Warm ambient temperatures led to increased nighttime activity, extending the duration of the active phase. As photoperiod increased, the rest phase lengthened, while the overall magnitude of activity decreased from the beginning to the end of the hibernation period. Below 0 °C vocal activity was nearly zero indicating a minimal probability of bat activity during both day and night. The species recent success in extending its hibernation range northward may be attributed to its flexible adjustment to prevailing environmental conditions. Nevertheless, it remains uncertain whether engaging in daily activity at temperatures above 0 °C confers any advantages at northern latitudes to prevent premature energy depletion. The persistence of circadian activity during winter could be a relic behavior, adapted from historical patterns of wintering in insect-rich and warm southern latitudes.

Calibration-free temperature monitoring of pulverized coal powder based on the dual-mode acoustic tomography

Accurate temperature measurement of the pulverized coal powder is crucial in detecting and preventing coal spontaneous combustion. Compared to other temperature measurement techniques, acoustic tomography using low frequency sound waves has the advantage of high penetration ability for non-intrusive temperature measurement inside the pulverized coal powder. Additionally, by employing an array of acoustic transducers mounted around the coal powder, the entire sensing area can be covered, enabling a comprehensive temperature distribution analysis through tomographic reconstructions. However, the main drawback of the acoustic temperature measurement is the model complexity in describing the dependence of acoustic sound speed on temperature in the porous pulverized coal powder. Accurate calibration is required to determine the model parameters for temperature retrieval, however, which is difficult for in situ industrial application. To solve this problem, we proposed a calibration-free temperature monitoring method based on the dual-mode acoustic tomography for pulverized coal. The three-parameter JCAL model is used to characterize the acoustic propagation in coal powder. The temperature and micro-structure parameters can be jointly retrieved from the reconstructed sound slowness and attenuation distributions at different frequencies. The feasibility and effectiveness of the proposed method are validated in the simulation study. Results show that the dual-mode acoustic tomography can provide calibration-free simplicity for pulverized coal temperature measurement, which has a great potential for industrial applications.

Time Delay Estimation for Acoustic Temperature Measurement of Loose Coal Based on Quadratic Correlation PHAT-β Algorithm

The acoustic temperature measurement method has a broad application prospect due to its advantages of high precision, non-contact, etc. It is expected to become a new method for hidden fire source detection in mines. The acoustic time of flight (TOF) can directly affect the accuracy of acoustic temperature measurement. We proposed a quadratic correlation-based phase transform weighting (PHAT-β) algorithm for estimating the time delay of the acoustic temperature measurement of a loose coal. Validation was performed using an independently built experimental system for acoustic temperature measurement of loose coals under multi-factor coupling. The results show that the PHAT-β algorithm estimated acoustic TOF values closest to the reference line as the sound travelling distance increased. The results of coal temperature inversion experiments show that the absolute error of the PHAT-β algorithm never exceeds 1 °C, with a maximum value of 0.862 °C. Using the ROTH weighted error maximum, when the particle of the coal samples is 3.0–5.0 cm, the absolute error maximum is 4.896 °C, which is a difference of 3.693 °C from the error minimum of 1.203 °C in this particle size interval. The accuracy of six algorithms was ranked as PHAT-β > GCC > PHAT > SCOT > HB > ROTH, further validating the accuracy and reliability of the PHAT-β algorithm.

Investigation on high temperature point detection of spontaneous combustion of loose coal based on optimal acoustic signal

Selecting sound source signals in acoustic temperature measurement technology is particularly important and is a key to improving the accuracy of acoustic temperature measurements. Pseudorandom, linearly swept, and pulsed signals are selected as research objects for this study. The decay of the three signals as they propagate through a loose coal, the frequency band and the period of the linearly swept signal are analyzed. The results showed that the attenuation coefficient of the linear sweep signal is less sensitive to temperature, and the attenuation coefficient of the low-frequency sound wave is smaller. When the lower limit of the frequency band of the sweep signal is closer to the upper limit of the frequency band, the main peak value of the cross-correlation coefficient is smaller. The main peak of the cross-correlation curve of low-band narrowband signals is greater than that of high-band narrowband signals. The cross-correlation effect is more significant for the 600–1000 Hz sweep signal. Moreover, the strongest effect is determined when the period is 0.1 s. Finally, the temperature of anthracite loose coal was measured according to the optimal signal. The maximum absolute error in the measurement results was 1.23 °C, and the maximum relative error was 4.22%.

Study on the Location Determination of Building Fire Points Based on Acoustic CT Temperature Measurement

Rapid perception of the location of the fire point is crucial to building fire emergency response in the process of building fire emergency response, which can help firefighters direct fire-fighting operations, effectively control fire sources, and provide strong evidence for the analysis and investigation of fire causes. This paper uses acoustic CT temperature measurement technology to determine the fire source location of a building fire and verifies its validity and applicability as follows: we construct various fire point numerical models based on the fire dynamics simulator (FDS) and obtain temperature data at different times; neural network means were used to obtain the time-of-flight (TOF) of an acoustic wave traveling; the large ill-conditioned matrix equation of acoustic flight under different meshing schemes was constructed and solved based on the simultaneous algebraic reconstruction technique (SART) and least squares QR-decomposition (LSQR), and then reconstruction temperature data under each scheme were obtained. Through the error analysis, the reconstruction effect of each reconstruction scheme is evaluated, and then the applicability of the location coordinate determination of the fire point is analyzed. The results show that the determination of the fire location under the conditions of various fire points in the building space can be realized by acoustic CT temperature measurement technology.

Initial exploration on potential fire hazards detection from coal spontaneous combustion applied by acoustic wave

Coal spontaneous combustion often wastes resources and causes environmental pollution. Rapid and accurate identification of high temperature areas in coal is essential to reducing such combustion and environmental pollution. The acoustic thermometry method has the benefits of large temperature measurement space, non-contact, and high interference resistance. Determining the attenuation characteristics of acoustic waves in loose coal is the basis and premise for realizing acoustic temperature measurement. Four types of bituminous coal were scanned by computer tomography equipment. A self-designed acoustic attenuation test device was used to test coal samples under different temperatures and particle sizes. The study result demonstrates that the distribution characteristics of loose coal voids are mainly related to the particle size. The smaller the particle size range, the more uniform the void distribution. As the size of the coal particles increases, the voids become larger. The acoustic attenuation coefficients of four coal samples showed an increasing trend as frequency increased. The influence of coal particle size distribution on the acoustic attenuation coefficient was greater than that of temperature and metamorphic degree. The peak values of coal sound attenuation for different particle sizes were around 400, 700, 1100, and 1600 Hz. This indicated that the distribution of voids was the main factor affecting the propagation of acoustic waves. By analysing the attenuation mechanism of the acoustic wave in loose coal, the attenuation of acoustic temperature measurement signal was caused by the combined effect of loose coal on acoustic wave absorption and scattering. The study results provide theoretical support for the realization of acoustic wave detection of high temperature point in loose coal spontaneous combustion.

Preliminary Study on Reconstruction of Building Thermal Field Based on Iterative Algorithm Acoustic CT

Real-time acquisition and visualization of temperature anomalies in building spaces and 3D temperature field data during fires are of vital importance for fire danger warnings, early rescue operations, evacuation commands, and subsequent fire accident investigations. Taking into account the non-contact, global (planar and spatial), and high efficiency advantages of acoustic CT temperature measurement technology, this study involved the conducting of exploratory preliminary research in order to provide new ideas for the real-time global perception of information on building fires. The detailed research objective was as follows: obtain the temperature data at any time of a fire based on Fire Dynamics Simulator (FDS) and fit them to form the base temperature distribution diagram at that time. The large ill-conditioned matrix equation of acoustic flight under the scheme of multi-grid division was then constructed. The discrete temperature data of each grid in the building space was obtained by solving the matrix equation based on algebraic reconstruction algorithm (ART) and joint algebraic reconstruction algorithm (SART). The three-dimensional temperature field reconstruction of building space was realized by the interpolation of discrete temperature data. The reconstruction effect of each scheme was evaluated through the error analysis between the reconstruction data and the basic data. The results show that the real-time reconstruction of a 3D temperature field of a building thermal field can be realized based on acoustic CT temperature measurement technology, and the reconstruction algorithm and grid division scheme have a significant control effect on the reconstruction effect.

Optical and acoustic phonon temperature measurements using electron nanoprobe and electron energy loss spectroscopy

Measuring temperature at a high spatial resolution is a fundamental technique for investigating local static and dynamic thermal properties in various materials and devices. Here, we report temperature measurement by electron energy loss spectroscopy using monochromated electron probes of 1--2 nm diameter and large scattering vectors of electrons and based on the principle of detailed balancing between the annihilation and creation of phonons. Temperatures defined by optical and acoustic phonons are evaluated separately. We demonstrate that the use of acoustic phonons is advantageous for low-temperature measurements with higher accuracy. The scheme is applied to evaluating local temperatures in a diamond nanowire during Joule heating. We also discuss the Joule heating mechanism and key factors for improving temperature measurement accuracy.

Sound absorption characteristics of loose bituminous coal porous media with different metamorphic degrees

With the advantages of high applicability and reliability, the acoustic detection method has been widely used in the field of temperature measurement, positioning, and flaw detection. To apply acoustic temperature measurement techniques to the detection of high temperature points of loose coal spontaneous combustion, the basic acoustic properties of loose coal need to be clarified. Four bituminous coals with different degrees of metamorphosis were selected for the study. The stacking structural characteristics of loose coal were studied by industrial computerized tomography. The sound absorption coefficient of loose coal was tested based on the sound absorption test system. The results revealed that with the increase of particle size, the voids of loose coal gradually became larger and the connectivity became better. The distribution characteristics of voids in loose coal were intrinsic to the variation in sound absorption coefficients. The sound absorption coefficient was more influenced by the particle size and stack thickness than by the degree of deterioration. Except for the particle size of less than 0.9 mm and the stacked thickness of 2 cm coal samples, the absorption coefficients of the coal samples increased gradually with decreasing particle size at the same acoustic frequency, and the peak absorption coefficients gradually shifted towards lower frequencies with increasing thickness. The peak frequency range of the absorption coefficient was calculated to provide a basis for the selection of the frequency band of the acoustic temperature measurement signal for loose coal.

Acoustic Limescale Layer and Temperature Measurement in Ultrasonic Flow Meters

Guided acoustic waves are commonly used in domestic water meters to measure the flow rate. The accuracy of this measurement method is affected by factors such as variations in temperature and limescale deposition inside of the pipe. In this work, a new approach using signals from different sound propagation paths is used to determine these quantities and allow for subsequent compensation. This method evaluates the different propagation times of guided Lamb waves in flow measurement applications. A finite element method-based model is used to identify the calibration curves for the device under test. The simulated dependencies on temperature and layer thickness are validated by experimental data. Finally, a test on simulated data with varying temperatures and limescale depositions proves that this method can be used to separate both effects. Based on these values, a flow measurement correction scheme can be derived that provides an improved resolution of guided acoustic wave-based flow meters.

Research Progress of the Temperature Monitoring Technology of the Electric Joints in the Ring Main Unit

This article summarizes several existing temperature monitoring methods for cable joints inside the ring main unit, mainly introducing infrared temperature measurement, fluorescent optical fiber detection, passive wireless surface acoustic wave temperature measurement, and wireless temperature sensor measurement. Then, the above methods were compared, and the advantages and disadvantages of each method were clarified. Finally, the research on the temperature monitoring method of the cable joints in the ring main unit is summarized. And the follow-up development direction of the passive wireless surface acoustic wave temperature measurement method in the temperature measurement of the cable joints of the ring main unit is prospected. It provides some reference for the research on the temperature monitoring method of the cable joints inside the ring main unit in the future.

Study on time delay estimation in boiler acoustic temperature measurement based on third correlation PHAT-β

In order to accurately measure the temperature of power plant boiler, a new algorithm of time delay was proposed based on third correlation and phase transform weighting on the basis of the research of traditional cross-correlation method and generalized cross-correlation. Small peaks can be weakened with the help of phase transform weighting and the addition of exponential coefficient β. The simulation result shows that the PHAT-β algorithm based on third correlation can accurately measure the value of time delay estimation compared with first correlation, second correlation and traditional third correlation, so as to improve the accurancy of temperature of power plant boiler.

Investigation of Spherical Roller Bearing and Deep Groove Ball Bearings with Various Defects Using Fft Analyser and Matlab Simulation

The bearing is very essential component in any mechanism. It is always running under high speed and high load conations. Failures in bearings often results in lengthy industrial downtime that has economic consequences. Prompt diagnostics of bearings failure is essential not only for the safe operation of machines, but also for the reduction of maintenance cost of any machine.
 Different methods are used for detection and diagnosis of defects of bearings; they may be broadly classified as vibration and acoustic measurements, temperature measurements and wear debris analysis. The most fundamental tool for bearing diagnosis is vibration analysis. The strength and weakness of vibration represents the location of defects.
 This paper discuss about the bearing failure diagnosis using vibration analysis. Crest factor is defined as the ratio of the peak value of a waveform to its RMS value. Comparative analysis is made between damaged and healthy Rolling and Ball bearings.FFT analyzer and accelerometer is use to perform experimental measurements in axial and radial directions

Вопросы построения струйно-капельных оптических измерительных систем: регистрация сигналов акустической эмиссии и измерение температуры в зоне резания при точении, сверлении и фрезеровании

Вопросы построения струйно-капельных оптических измерительных систем: регистрация сигналов акустической эмиссии и измерение температуры в зоне резания при точении, сверлении и фрезеровании

Numerical approaches for the simulation of a real multiphase flow in a fermentation tank

AbstractIn the context of investigations of multiphase flows, the beer production is currently being investigated, especially fermentation, maturation and storage in cooperation with the local brewery. The university has its own 350 litre fermentation tank with comprehensive acoustic flow and temperature measurement technology for the systematical investigation of the influence of the fermentation activity, distribution of yeast and occurring convection phenomena. This paper deals with the numerical simulation of the fermentation tank and the combination of a numerical approach and an experimental investigation with the two Fluid Eulerian‐Eulerian time‐averaged model [3]. The Eulerian‐Eulerian model allows two sets of governing equations, continuity and momentum equations to be solved for either phase and their interactions are modelled using interface transfer terms for interfacial heat, mass and momentum exchanges. As a result, the numerical solution of a natural convection flow which is superimposed by rising gas bubbles will be presented.

Research of FTRLS Algorithm in Acoustic Signal De-noising

In the acoustic temperature measurement system, the acoustic emission signal is easily affected by the wind field, the ambient noise and so on during the propagation process. Coupled with its own reflection, diffraction and scattering properties, the sensor receive the acoustic signals that are weak, difficult to identify, and even submerged in the background noise. In order to solve the above problem, this paper combines the principle of adaptive filter, and the FTRLS adaptive filter algorithm is designed to deal with linear frequency modulation signal, and the simulation experiment was carried out by MATLAB software. The results show that the noise-disturbing chirp signal can be effectively restored to a certain extent after denoising.

A validation of computational fluid dynamics temperature distribution prediction in a pulverized coal boiler with acoustic temperature measurement

The main objective of this work was to examine the capability of CFD (Computational Fluid Dynamics) on properly predicting temperature distribution in the combustion chamber. Numerous approaches were employed to verify CFD models of large-scale utility boilers. Furnace Exit Gas Temperature is one of the key values used for verification studies. Harsh environment and large dimensions inside the furnace make temperature measurement a complex task. Traditionally used suction pyrometry provides only local information. With this technique, while extremely accurate, it is practically impossible to obtain a representative temperature distribution at the furnace exit as measurements in different locations are not taken at the same time. Acoustic Pyrometry technique is the most appropriate for comprehensive CFD flame shape prediction verification. Not only average temperature value in a certain boiler cross-section can be continuously measured but also its complete two-dimensional distribution. CFD code was used to simulate the OP-650 front-fired boiler operation. The boiler is equipped with Acoustic Gas Temperature Measuring system located in a horizontal plane approximately 4 m under the furnace exit. Comparison of simulation results with measurements proves good accuracy of CFD results.

Whales and waves: Humpback whale foraging response and the shoaling of internal waves at Stellwagen Bank

AbstractWe tested the hypothesis that humpback whales aggregate at the southern flank of Stellwagen Bank (SB) in response to internal waves (IWs) generated semidiurnally at Race Point (RP) channel because of the presence of their preferred prey, planktivorous fish, which in turn respond to zooplankton concentrated by the predictable IWs. Analysis of synthetic aperture radar (SAR) images indicates that RP IWs approach the southern flank of SB frequently (∼62% of the images). Published reports of whale sighting data and archived SAR images point to a coarse spatial coincidence between whales and Race Point IWs at SB's southern flank. The responses of whales to IWs were evaluated via sightings and behavior of humpback whales, and IWs were observed in situ by acoustic backscatter and temperature measurements. Modeling of IWs complemented the observations, and results indicate a change of ∼0.4 m/s in current velocity, and ∼1.5 Pa in dynamic pressure near the bottom, which may be sufficient for bottom fish to detect the IWs. However, fish were rare in our acoustic observations, and fish response to the IWs could not be evaluated. RP IWs do not represent the leading edge of the internal tide, and they may have less mass‐transport potential than typical coastal IWs. There was large interannual variability in whale sightings at SB's southern flank, with decreases in both numbers of sightings and proportion of sightings where feeding was observed from 2008 to 2013. Coincidence of whales and IWs was inconsistent, and results do not support the hypothesis.

Two-Dimension Temperature Field Reconstruction in Furnace by Acoustic Method

Acoustic temperature measurement technology is a new temperature measuring technology which is rising in recent years. This paper discusses a kind of reconstruction method of temperature field based on acoustic pyrometer. First , acoustic sensors has been used to obtain measurement data, and the technique of wavelet has been used to denoise in order to improve the accuracy of measurement , secondly, the least-squares algorithm has been used to reconstruct temperature field. Finally, we work out our own acoustic temperature measurement system and has got the satisfying result using our own acoustic pyrometer to detect two-dimension temperature field in the laboratory.

Primary study of temperature distribution measurement in stored grain based on acoustic tomography

A common and traditional method for detecting stored grain deterioration is the measurement of grain temperature. This study proposes a temperature monitoring method for stored grain based on acoustic tomography. A model describing the relationship between grain temperature and sound travel time in stored grain is established. A speed conversion coefficient is defined and used to convert the measured velocity of sound in the stored grain into the sound velocity in free space, which has the same gas components and temperature as those of the stored grain. The influence factors of the speed conversion coefficient are analyzed, and the calibration method of the coefficient is introduced. The time-delay estimation method based on triple correlation and wavelet de-noising and the temperature reconstruction algorithm based on Markov radial basis function and singular value decomposition are used to measure the temperature distribution of the grain bulk. Two experimental systems are built to verify the acoustic model and reconstruct the temperature distribution of grain. The experimental result shows that the acoustic model can be used for temperature measurement in soybeans. The temperature distributions with different hot spot locations in soybeans are all well reconstructed, and the coordinates of the hot spots are reconstructed with better accuracy than that in thermocouple measurement. Thus, acoustic temperature measurement is useful in the early prediction of temperature anomalies in stored grain.