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Copyright of Artvin Çoruh Üniversitesi Orman Fakültesi Dergisi is the property of Artvin Coruh University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Preventive maintenance through monitoring and early detection is important for trees that are structurally weak due to internal decay. Once internal decay has occurred, recovery of lost strength is irreversible. The decaying tree becomes vulnerable to external impacts, which may lead to breakage or windthrow. The Yoshino cherry (Cerasus×yedoensis (Matsum.) "Somei-yoshino") accounts for a high proportion of landscape trees in Asia. Testing the reliability of noninvasive sonic tomography (SoT) to estimate internal defects could facilitate structural stability evaluation and proactive preventive management. We performed noninvasive SoT and invasive resistance microdrilling to detect and quantify internal defects in old and large Yoshino cherry trees. Generally, SoT reflected the areas and location of severe structural defects, showing a correlation with the resistance microdrilling results (R² = 0.542, p < .001). However, when cracks were present in disks, the SoT overestimated defects and errors mainly observed in the transition zone (green). Based on these findings, when evaluating the SoT, careful decisions are needed to distinguish between actual defects and broad sonic shadows. Furthermore, additional evidence from drilling resistance is required to differentiate between incipient decay and cracks. The results of this study provide valuable insights for enhancing the interpretation of sonic tomograms. Study Implications : We suggest defect boundaries in sonic tomograms should be redefined to improve the accuracy of interpretation for any new species being studied. Careful drilling resistance measurements should be taken, especially in transition zones (green areas in tomogram) and incipient decay zone (light brown areas). Noninvasive sonic tomograms only reflect acoustic properties of the tested cross-section of a tree and cannot be considered an actual representation of the internal conditions until the readings are calibrated to destructive sampling results. [ABSTRACT FROM AUTHOR]

Acoustic tomography utilizes sensor arrays to collect sound wave signals, enabling non-contact measurement of physical parameters within an area of interest. Compared to optical technologies, acoustic tomography offers the advantages of low cost, low maintenance, and easy installation. Current research in acoustic tomography mainly focuses on reconstruction algorithms for temperature fields, while monitoring the composition and concentration of gases is significant for ensuring safety and improving efficiency, such as in scenarios like boiler furnaces and aviation engine nozzles. In excitable gases, the speed of sound exhibits an S-shaped curve that changes with frequency, a characteristic that could be potentially useful for acoustic tomography. Therefore, this study primarily discusses the quantitative calculation of gas concentration and temperature based on the dispersion of the speed of sound. By employing graphic processing and pattern matching methods, a coupled relationship of the dispersion of the speed of sound with gas concentration and temperature is established. The projection intersection method is used to calculate the concentration and temperature of binary and ternary gas mixtures. Combined with the inversion method, a joint reconstruction method for gas concentration fields and temperature fields based on the dispersion of the speed of sound is developed. The feasibility of the proposed simultaneous reconstruction method for temperature and concentration fields is validated using numerical simulations. Additionally, an acoustic tomography experimental system was set up to conduct reconstruction experiments for binary gas concentration fields and temperature fields, confirming the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The reconstruction algorithms play an important role in acoustic thermometry and are a research hotspot. This paper proposes a novel reconstruction method to improve the accuracy of temperature field reconstruction methods based on acoustic tomography. First, three mesh models are constructed by using the finite element method, which overcomes the defects of oversimplified classical discretization models. Secondly, the coefficient matrix A of the acoustic thermometry forward problem is calculated offline, and then the temperature values of several points in the measurement are obtained by solving the inverse problem using the improved regularization method based on singular value decomposition. Finally, the temperature profile of the entire region is obtained through interpolation. The correctness and feasibility of the proposed method are validated through simulations and experimental testing with three different temperature fields. Results show that the proposed method has satisfactory reconstruction accuracy and provides a different solution for reconstructing the ultrasound temperature field.

Thermal exchange of underwater water mass caused by marine heat wave is a hot point of research recently. In particular, because the water temperature observation along hot water mass transportation is hard work. Acoustic tomography is an advanced method to measure water temperature variations via sound signal transmission with multi-station network sensing. The 5 kHz frequency acoustic tomography used for observing water temperature variations caused by ocean heat waves is interesting work. In this paper, the numerical simulation of hot water mass is completed first, then floatation and diffusion of hot water mass in a simulation are monitored by acoustic tomography. A new inversion optimization method is proposed to obtain hot water mass transportation variations at two-dimensional temperature vertical profile. The proposed inversion method adds a regularized mode matrix and the optimization method adds the model correlation matrix to improve the results quality. The accuracy of inversion optimization results is compared and discussed, where the mean temperature error is less than 0.4 °C. Sensing water temperature variation of marine heat waves is verified via acoustic signal transmission and improved inversion optimization method. The water dynamical process observation is an application of acoustic tomography, which can be further used observe underwater environmental characteristics. [ABSTRACT FROM AUTHOR]

The article aimed to show the fundamental possibility of constructing a computational digital twin of the acoustic tomograph within the framework of a unified physics–mathematical model based on the Navier–Stokes equations. The authors suggested that the size of the modeling area is quite small, sound waves are waves of "small" disturbance, and given that a person consists of more than 60% water, human organs can be modeled using a liquid model, taking into account their density. During numerical experiments, we obtained the pressure registered in the receivers that are located on the side walls of the tomograph. The differences in pressure values are shown depending on the configuration of inclusions in the mannequin imitating internal organs. The results show that the developed technology can be used to probe the human body in medical acoustic tomographs and determine the acoustic parameters of the human body to detect neoplasms. [ABSTRACT FROM AUTHOR]

This dataset presents the indoor air temperature collections using the novel technique of Acoustic travel time TOMography (ATOM) in the ultrasonic frequency range. The presented measuring system employs early reflections as sound propagation paths in addition to the travel time of the direct path, effectively combining room acoustics with tomography techniques. The data was collected across various measurement scenarios within the climate chamber laboratory at the Building Physics Department at the Bauhaus-University Weimar. Additionally, the measurements data regarding the phase shift compensating of the utilized preamplifier in the setup are provided. These measurements served to assess the effectiveness of the new ultrasonic measurement system which was presented in the co-published article (Dokhanchi et al., 2024). The developed algorithms provided in this Dataset offers a valuable reference for researchers in the field of acoustic tomography especially those focusing on indoor applications, and the researchers involved in indoor climate monitoring where non-contact indoor air temperature measurements are required.

Diplodia pinea is a fungal pathogen that causes Diplodia shoot blight in pines and is widely spread in red pine (Pinus resinosa) and jack pine (Pinus banksiana) forests in Michigan. The objective of this study was to examine whether infection with D. pinea compromises wood quality in pine stands. Acoustic data was collected using an acoustic tomographer from the stem region at breast height (1.3 m) of red pine and jack pine trees across two categories of forest health condition (control vs. Diplodia-affected), in two latitudinal regions (Lower Peninsula vs. Upper Peninsula), and two levels of initial stand density (low vs. high). The acoustic data was used to infer the wood quality (i.e., density) in these two tree species since material of higher density generally has higher sound velocity rates. Red pine had significantly higher wood quality (i.e., higher sound velocities) in the Upper Peninsula region compared to the Lower Peninsula region. Within each latitudinal region, red pine sound velocities did not show significant differences between forest health condition or initial stand density levels. Jack pine showed no significant differences in sound velocities across the treatment categories. The results indicate that latitudinal region appears to have more impact on red pine wood quality than the influence of forest health condition (presence of Diplodia shoot blight) or initial stand density. All analyzed factors (latitudinal region, forest health condition, and stand density) did not have a significant impact on the wood quality of jack pine.

The health and stability of trees are essential information for the safety of people and property in urban greenery, parks or along roads. The stability of the trees is linked to root stability but essentially also to trunk decay. Currently used internal tree stem decay assessment methods, such as tomography and penetrometry, are reliable but usually time-consuming and unsuitable for large-scale surveys. Therefore, a new method based on close-range remotely sensed data, specifically close-range photogrammetry and iPhone LiDAR, was tested to detect decayed standing tree trunks automatically. The proposed study used the PointNet deep learning algorithm for 3D data classification. It was verified in three different datasets consisting of pure coniferous trees, pure deciduous trees, and mixed data to eliminate the influence of the detectable symptoms for each group and species itself. The mean achieved validation accuracies of the models were 65.5% for Coniferous trees, 58.4% for Deciduous trees and 57.7% for Mixed data classification. The accuracies indicate promising data, which can be either used by practitioners for preliminary surveys or for other researchers to acquire more input data and create more robust classification models. [ABSTRACT FROM AUTHOR]

Acoustic tomography utilizes sensor arrays to collect sound wave signals, enabling non-contact measurement of physical parameters within an area of interest. Compared to optical technologies, acoustic tomography offers the advantages of low cost, low maintenance, and easy installation. Current research in acoustic tomography mainly focuses on reconstruction algorithms for temperature fields, while monitoring the composition and concentration of gases is significant for ensuring safety and improving efficiency, such as in scenarios like boiler furnaces and aviation engine nozzles. In excitable gases, the speed of sound exhibits an S-shaped curve that changes with frequency, a characteristic that could be potentially useful for acoustic tomography. Therefore, this study primarily discusses the quantitative calculation of gas concentration and temperature based on the dispersion of the speed of sound. By employing graphic processing and pattern matching methods, a coupled relationship of the dispersion of the speed of sound with gas concentration and temperature is established. The projection intersection method is used to calculate the concentration and temperature of binary and ternary gas mixtures. Combined with the inversion method, a joint reconstruction method for gas concentration fields and temperature fields based on the dispersion of the speed of sound is developed. The feasibility of the proposed simultaneous reconstruction method for temperature and concentration fields is validated using numerical simulations. Additionally, an acoustic tomography experimental system was set up to conduct reconstruction experiments for binary gas concentration fields and temperature fields, confirming the effectiveness of the proposed method.

By means of an ultrafast optical technique, picosecond acoustic strain pulses in a transparent medium are tomographically visualized at GHz frequencies. The strain distribution in BK7 glass is reconstructed from time-domain reflectivity changes of 415-nm probe light as a function of the optical incidence angle with 1 ps temporal and 120 nm spatial resolutions, enabled by automated angle scanning. The latter resolution is achieved owing to the commensurate acoustic wavelength. Applications include imaging strain, carrier and temperature distributions on ultrashort timescales.

In addition to the general benefits that all trees provide, historic urban trees contribute significant cultural and affective value to the quality of life in cities. As these trees age, their maintenance requires meticulous and consistent attention to reduce associated risks. The objective of the present study was to identify and estimate the extent of internal damage in the trunk of historic urban trees. Forty-five Eucalyptus robusta trees located in a popular square in the city of Nova Friburgo-RJ, Brazil were evaluated. A visual analysis of the crown, trunk, and root system was performed, followed by complementary evaluations of acoustic tomography and, when necessary, resistography. Mathematical models were adjusted to infer the relationship and influence of dendrometric characteristics (total height, height to the first branch, diameter at 1.30 m above the ground, and crown diameter) and the mean resistographic amplitude on the mean wave propagation velocity acoustic. Most trees presented some form of external lesion on their trunks, and, generally, trees with severe lesions also exhibited alterations in the propagation velocity of acoustic waves and in the perforation resistance profile. The combination of different techniques allows for the identification of areas with possible internal injuries in the trunks of historic urban trees. However, it is worth noting that the extent of these areas varied among the techniques used. [ABSTRACT FROM AUTHOR]

Diplodia pinea is a fungal pathogen that causes Diplodia shoot blight in pines and is widely spread in red pine (Pinus resinosa) and jack pine (Pinus banksiana) forests in Michigan. The objective of this study was to examine whether infection with D. pinea compromises wood quality in pine stands. Acoustic data was collected using an acoustic tomographer from the stem region at breast height (1.3 m) of red pine and jack pine trees across two categories of forest health condition (control vs. Diplodia-affected), in two latitudinal regions (Lower Peninsula vs. Upper Peninsula), and two levels of initial stand density (low vs. high). The acoustic data was used to infer the wood quality (i.e., density) in these two tree species since material of higher density generally has higher sound velocity rates. Red pine had significantly higher wood quality (i.e., higher sound velocities) in the Upper Peninsula region compared to the Lower Peninsula region. Within each latitudinal region, red pine sound velocities did not show significant differences between forest health condition or initial stand density levels. Jack pine showed no significant differences in sound velocities across the treatment categories. The results indicate that latitudinal region appears to have more impact on red pine wood quality than the influence of forest health condition (presence of Diplodia shoot blight) or initial stand density. All analyzed factors (latitudinal region, forest health condition, and stand density) did not have a significant impact on the wood quality of jack pine. [ABSTRACT FROM AUTHOR]

Copyright of Iranian Journal of Soil & Water Researches (IJSWR) is the property of University of Tehran and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A method of high-resolution acoustic tomography of scattering inhomogeneities based on the method of reverse time migration is proposed. An inhomogeneous background medium with a known distribution of refractive inhomogeneities is considered, where it is necessary to detect scattering inhomogeneities. Probing is carried out by broadband arbitrary waveforms. The method of reverse time migration is supplemented with linear filtering of the direct propagation field, which makes it possible to increase the resolution of reconstructed images. The results of numerical modeling and experiment are presented. Sounding was carried out in water at frequencies from 20 to 350 kHz using a signal with linear frequency modulation. The source of the ultrasonic signal was fixed and irradiated the objects under study in the water. The scattered signal was measured in a plane near the surface in water on a rectangular area with a step of less than 2 mm. Signal processing by the proposed method made it possible to reconstruct a three-dimensional image of scattering inhomogeneities with a resolution of about 7 mm. Comparison of the proposed method and the reverse time migration method showed that the proposed method allows obtaining a higher resolution.

Senile trees in historic church gardens have natural, aesthetic, historical, and cultural value. Cutting them down too hastily annihilates the achievements of entire generations. We should try to preserve the greenery surrounding historic churches and integrate it into a clear compositional arrangement with the sacral architecture. The primary purpose of the paper was to describe the process of inventorying 200-year-old trees and to present the revalorization project for the garden around the historic Orthodox church in Horostyta, located in the Lublin Voivodeship, in southeastern Poland. The church complex consists of a wooden 18th-century building, bell tower, garden, and cemetery. Within the church garden's boundaries, there are 15 trees, with two predominant species: Acer pseudoplatanus L. and Tilia cordata Mill. These trees are of varying ages and health conditions. We used acoustic tomography to perform tree health diagnostics. Three trees, for which the initial visual assessment was disturbing, were examined thanks to detailed tomography tests. Then, through a project adapting the church garden to the health conditions of the ancient trees, they were separated from users by flowerbeds and no small architectural objects were placed around them. The presented development concept forms a compromise between tradition and the modern user's needs. In 2007, a general renovation of the temple building was completed. Currently, the presented project for the church garden is being implemented. [ABSTRACT FROM AUTHOR]

Accurate qualitative evaluation of grown and harvested wood is a key issue from the point of view of its subsequent economic evaluation. With the current trend of global climate change and large volumes of wood damaged by harmful agents, automated methods of wood quality assessment are becoming more and more important. The work aimed to verify the applicability and significance of the results of using the acoustic tomograph for the qualitative assessment of selected tree species logs. Ten samples of log sections of non-coniferous and coniferous trees were evaluated, on which an image analysis of qualitative features was performed on a cross-section from their digital photograph and the image output of an acoustic tomograph software. The results were compared with each other and the accuracy of qualitative feature identification by acoustic tomograph was evaluated. At the same time, the results of the image analysis of the qualitative feature were compared with its assessment through STN EN 1309-3. It was shown that, when evaluated according to the Standard, qualitative features were overestimated by an average of 29.19% compared to the acoustic tomograph and by 28.22% compared to the digital photograph. The use of the acoustic tomograph confirmed a good level of accuracy in the identification of qualitative features even on logs of harvested wood, although it is primarily intended for the qualitative evaluation of standing trees. [ABSTRACT FROM AUTHOR]

The online and accurate capture of dynamic changes in furnace temperature distribution is crucial for production efficiency improvement and international environmental policy compliance in power plants. To achieve this, a measurement system with a reliable online reconstruction capability and high temporal resolution is necessary. This paper presents a novel technique that can improve the temporal resolution of the currently existing acoustic tomography (AT) system using frequency division multiplexing (FDM). This method allows for concurrent transmissions of acoustic signals in several different frequency bands instead of a sequential manner, which leads to more efficient channel utilization and allows all acoustic signals to be acquired at the same time, so that a better temporal uniformity of multipath acoustic signals can be realized. Theoretical analysis and experiments have been conducted to verify the effectiveness of this technique. The results prove that the proposed method can significantly improve the temporal resolution of the AT system while maintaining the accuracy and robustness of the reconstruction.

Thermal exchange of underwater water mass caused by marine heat wave is a hot point of research recently. In particular, because the water temperature observation along hot water mass transportation is hard work. Acoustic tomography is an advanced method to measure water temperature variations via sound signal transmission with multi-station network sensing. The 5 kHz frequency acoustic tomography used for observing water temperature variations caused by ocean heat waves is interesting work. In this paper, the numerical simulation of hot water mass is completed first, then floatation and diffusion of hot water mass in a simulation are monitored by acoustic tomography. A new inversion optimization method is proposed to obtain hot water mass transportation variations at two-dimensional temperature vertical profile. The proposed inversion method adds a regularized mode matrix and the optimization method adds the model correlation matrix to improve the results quality. The accuracy of inversion optimization results is compared and discussed, where the mean temperature error is less than 0.4 °C. Sensing water temperature variation of marine heat waves is verified via acoustic signal transmission and improved inversion optimization method. The water dynamical process observation is an application of acoustic tomography, which can be further used observe underwater environmental characteristics.

The acoustic tomography (AT) velocity field reconstruction technique has become a research hotspot in recent years due to its noninvasive nature, high accuracy, and real-time measurement advantages. However, most of the existing studies are limited to the reconstruction of the velocity field in a rectangular area, and there are very few studies on a circular area, mainly because the layout of acoustic transducers, selection of acoustic paths, and division of measured regions are more difficult in a circular area than in a rectangular area. Therefore, based on AT and using the reconstruction algorithm of the Markov function and singular value decomposition (MK-SVD), this paper proposes a measured regional division optimization algorithm for velocity field reconstruction in a circular area. First, an acoustic path distribution based on the multipath effect is designed to solve the problem of the limited emission angle of the acoustic transducer. On this basis, this paper proposes an adaptive optimization algorithm for measurement area division based on multiple sub-objectives. The steps are as follows: first, two optimization objectives, the condition number of coefficient matrix and the uniformity of acoustic path distribution, were designed. Then, the weights of each sub-objective are calculated using the coefficient of variation (CV). Finally, the measured regional division is optimized based on particle swarm optimization (PSO). The reconstruction effect of the algorithm and the anti-interference ability are verified through the reconstruction experiments of the model velocity field and the simulated velocity field.

The article aimed to show the fundamental possibility of constructing a computational digital twin of the acoustic tomograph within the framework of a unified physics–mathematical model based on the Navier–Stokes equations. The authors suggested that the size of the modeling area is quite small, sound waves are waves of “small” disturbance, and given that a person consists of more than 60% water, human organs can be modeled using a liquid model, taking into account their density. During numerical experiments, we obtained the pressure registered in the receivers that are located on the side walls of the tomograph. The differences in pressure values are shown depending on the configuration of inclusions in the mannequin imitating internal organs. The results show that the developed technology can be used to probe the human body in medical acoustic tomographs and determine the acoustic parameters of the human body to detect neoplasms.

Backscattered wave acoustic tomography using wideband probing signals makes it possible to obtain three-dimensional (3D) images of scattering inhomogeneities. Signal processing based on the reverse time migration (RTM) method allows one to take into account the influence of background refractive obstacles of the medium to minimize distortions of reconstructed tomographic images. We propose a noniterative method of acoustic tomography in an immersion medium based on RTM approach supplemented with linear signal preprocessing to enhance resolution of reconstructing tomography images. The visualization of scattering objects is based on wave inversion from the measurement area considering the probing wave field specially distorted to perform regularized back convolution. The applicability of the proposed method for visualizing scattering objects in water is shown analytically, numerically and experimentally. The proposed method is resistant to noise according to regularization. The results obtained show the agreement between the numerical and analytical solution. Using the example of sounding with linear frequency modulation signals, it is demonstrated that the proposed method allows increasing the resolution of tomographic images in comparison with conventional RTM. The novelty of the proposed method is the preliminary filtration of the forward propagation wave in the course of solving the inverse problem. This approach improves the resolution of tomographic images and allows considering the influence of obstacles. [ABSTRACT FROM AUTHOR]

The comparative study of two globally convergent numerical methods for acoustic tomography is carried out in two dimensions. These are the boundary control method and the quasi-reversibility method. The novelty is that in the latter a nonlinear inverse problem is reduced to a family of the linear integral equation of the first kind via the Lavrentiev approach and this reduction is used within the quasi-reversibility method. The analysis of its stability is carried out via Carleman estimates. The computational effectiveness of these methods is tested in the numerical experiments with the smooth and discontinuous coefficients to be recovered from the tomographic data. [ABSTRACT FROM AUTHOR]

A reconstruction algorithm is proposed, based on multi-dictionary learning (MDL), to improve the reconstruction quality of acoustic tomography for complex temperature fields. Its aim is to improve the under-determination of the inverse problem by the sparse representation of the sound slowness signal (i.e., reciprocal of sound velocity). In the MDL algorithm, the K-SVD dictionary learning algorithm is used to construct corresponding sparse dictionaries for sound slowness signals of different types of temperature fields; the KNN peak-type classifier is employed for the joint use of multiple dictionaries; the orthogonal matching pursuit (OMP) algorithm is used to obtain the sparse representation of sound slowness signal in the sparse domain; then, the temperature distribution is obtained by using the relationship between sound slowness and temperature. Simulation and actual temperature distribution reconstruction experiments show that the MDL algorithm has smaller reconstruction errors and provides more accurate information about the temperature field, compared with the compressed sensing and improved orthogonal matching pursuit (CS-IMOMP) algorithm, which is an algorithm based on compressed sensing and improved orthogonal matching pursuit (in the CS-IMOMP, DFT dictionary is used), the least square algorithm (LSA) and the simultaneous iterative reconstruction technique (SIRT). [ABSTRACT FROM AUTHOR]

• Acoustic tomography technology is used for temperature distribution reconstruction. • Combines sparse reconstruction algorithms with deep learning networks. • A sparse reconstruction model is proposed for the reconstruction of temperature distribution. • A dual-domain feature fusion network is proposed to integrate image and signal features. • The accuracy of reconstruction is improved by mining the feature of time-of-flight. Addressing the challenges encountered by deep convolutional neural networks in reconstructing the temperature distribution of acoustic tomography, such as limited single feature extraction scale and suboptimal utilization of original measurement information, we propose a novel algorithm termed the dual-domain feature fusion network (DDFF-Net) for acoustic tomography temperature distribution reconstruction. Initially, the algorithm acquires the initial temperature distribution by solving the sparse reconstruction model of acoustic tomography thermometry. Subsequently, DDFF-Net is constructed to perform multi-scale feature extraction and fusion reconstruction of the image domain and signal domain. By fully mining the original measurement information, the reconstruction accuracy of the temperature distribution is improved. Numerical simulations and experimental tests were conducted, and comparative analysis with other algorithms was conducted. Numerical simulation results show that DDFF-Net has the smallest average relative error and root mean square error, which are 0.13 % and 0.16 % respectively. In the experimental test, DDFF-Net has the smallest average error in reconstructing the temperature of the thermocouple sampling point, which is 0.34 %. In summary, the DDFF-Net algorithm effectively extracts and integrates feature information from both image and signal domains, facilitating precise reconstruction of temperature distribution. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • A calibration-free temperature measurement technique for pulverized coal. • 3-parameter JCAL model is used to characterize acoustic property of coal powder. • Multi-frequency dual-mode acoustic tomography is used for data acquisition. • Jointly retrieval of temperature and micro-structure parameters. • Good qualitative accuracy in imaging the temperature distribution. [ABSTRACT FROM AUTHOR]

The health and stability of trees are essential information for the safety of people and property in urban greenery, parks or along roads. The stability of the trees is linked to root stability but essentially also to trunk decay. Currently used internal tree stem decay assessment methods, such as tomography and penetrometry, are reliable but usually time-consuming and unsuitable for large-scale surveys. Therefore, a new method based on close-range remotely sensed data, specifically close-range photogrammetry and iPhone LiDAR, was tested to detect decayed standing tree trunks automatically. The proposed study used the PointNet deep learning algorithm for 3D data classification. It was verified in three different datasets consisting of pure coniferous trees, pure deciduous trees, and mixed data to eliminate the influence of the detectable symptoms for each group and species itself. The mean achieved validation accuracies of the models were 65.5% for Coniferous trees, 58.4% for Deciduous trees and 57.7% for Mixed data classification. The accuracies indicate promising data, which can be either used by practitioners for preliminary surveys or for other researchers to acquire more input data and create more robust classification models.

In this paper, we analyzed the results of experimental data processing in the study of regularities of propagation and transformation of low-frequency harmonic signals at the boundary of the "sea−land−sea" system. Harmonic signals at a carrier frequency of 33 Hz were generated by a low-frequency hydroacoustic radiator in Vityaz Bay. Then, they passed along the shelf of decreasing depth, transformed into seismoacoustic signals of the upper layer of the Earth's crust and the bedrocks of Shultz Cape and excited hydroacoustic signals at the corresponding frequency in the shelf waters in the open part of the Sea of Japan. When processing the experiment results, we obtained the vertical distributions of the pressure field, caused by an acoustic low-frequency signal passing through the upper layer of the Earth's crust. We presented the distributions of hydroacoustic and seismoacoustic energies. The obtained experimental data were compared with the simulations by the model, developed strictly according to the experiment scheme and the geological structure of the area. In the discussion of the obtained results, we explained a probable mechanism of acoustic energy propagation and the nature of the vertical distributions of the pressure field formation. [ABSTRACT FROM AUTHOR]

High-quality measurement of temperature distribution information is of great significance for industrial production. As a typical non-contact temperature measurement method, acoustic tomography (AT) can obtain temperature distribution through reconstruction algorithms. To improve the reconstruction quality, a two-stage algorithm based on virtual observation (VO) and residual network (ResNet) was proposed. This algorithm combines the advantages of VO and ResNet. Aiming at total least squares, the VO method was adopted to reconstruct the ultrasonic time-of-flight (TOF) to obtain the temperature distribution under a coarse grid. Then, ResNet was built to predict the temperature distribution under the refined grid, and the dual-input model was used to improve the network generalization ability. At the same time, the sub-pixel convolution layer was introduced to reduce the network computing dimension, which improves the computing efficiency and the reconstruction quality. The numerical simulation of typical temperature field models was carried out, and the reconstruction results show that the average relative error and root mean square error are less than 0.86% and 1.21%, respectively. The noise immunity and reconstruction spatial resolution are better than traditional algorithms and the previous two-stage algorithm. [ABSTRACT FROM AUTHOR]

On the northeastern shelf of the Black Sea in 2010, a tomographic experiment was carried out on the counterpropagation of phase-shift keyed acoustic signals. During the day, the time responses of the medium were measured during the emission and reception of high-frequency complex phase-shift keyed signals from three bottom-moored transceivers located at the corners of an equilateral triangle with sides of about 1100 m. The transceivers were at a distance of >2 km from Golubaya Bay at a depth of about 40 m. Nearby, a thermistor chain was moored to record internal waves. Based on the data on the temporal variability of the responses of the medium to acoustic signals, information about the internal waves present in the water area was reconstructed using the method of consistent time responses. A temporal sampling of the vertical displacements of the thermocline was obtained, in which short-period waves with a height of 0.5–1 m and a period from 5 to 15–20 min were found. Comparison of acoustic measurements with independent contact measurements of internal waves revealed their good mutual agreement. On the whole, the results of the acoustic experiment showed the possibility of successfully using acoustic tomography to study the dynamics of waters for shallow-water conditions. [ABSTRACT FROM AUTHOR]

The ray statement of the inverse problem of determining three unknown variable coefficients in the linear acoustic equation is studied. These coefficients are assumed to differ from given constants only inside some bounded domain. There are point pulse sources and acoustic receivers on the boundary of this domain. Acoustic signals are measured by a receiver near the moment of time at which the signal from a source arrives at the receiver. It is shown that this information makes it possible to uniquely determine all the three desired coefficients. Algorithmically, the original inverse problem splits into three subproblems solved successively. One of them is a well-known inverse kinematic problem (of determining the speed of sound), while the other two lead to the same integral geometry problem for a family of geodesic lines determined by the speed of sound. [ABSTRACT FROM AUTHOR]

Zelkova serrata (Thunb.) Makino trees, which account for a large proportion of cultural assets and protected trees and have considerable historical and cultural symbolic meaning in South Korea. To verify the reliability of the nondestructive sonic tomography (SoT) method on Z. serrata trees, this study compared the results of SoT with those obtained with the destructive resistance micro-drilling method. With SoT measurement, defects were found in approximately 75% of the target Z. serrata trees and two of these trees were evaluated as having a high risk because their defective portions accounted for approximately 70% or more of the entire cross section. The independent samples t-test indicated that the two methods did not show a significant difference between measurements. Regression analysis indicated that the measurement values of the two methods showed a positive relationship with a high explanatory power of 76%, thus, verifying the reliability of SoT.

The two/three-dimensional distribution image of furnace temperature can be obtained by furnace acoustic tomographic temperature measurement system. The distribution of ultrasonic probes will directly affect its imaging accuracy. Four-side and four-corner distribution of 8, 12 and 16 ultrasonic probes were studied, respectively. Tikhonov regularization algorithm was adopted to obtain the temperature distribution under coarse mesh, and then the local weighted regression method was used to predict the temperature distribution after mesh refinement. Typical temperature field distributions reconstruction was carried out for the 6 probe distributions, and the root mean square error and correlation coefficient were analyzed. The results show that the highest accuracy can be obtained using 16 four-side distribution probes.

Acoustic tomography is a widely used non-contact method for visualizing temperature distribution. A temperature distribution reconstruction algorithm based on an improved sparse reconstruction model and multi-scale feature fusion network is proposed. First, the acoustic temperature measurement sparse reconstruction model is improved by combining the error function (ERF) and the iterative reweighting algorithm, and the alternating direction method of multipliers algorithm (ADMM) is used to solve the model to obtain the initial temperature distribution. Then the feature extraction network is constructed to extract multi-scale features of acoustic time of flight (TOF) as prior information. Finally, the feature fusion reconstruction network is constructed to fuse and reconstruct the initial temperature distribution and multi-scale features to obtain a high-precision temperature distribution. Simulation and experimental tests were conducted respectively, and compared with other algorithms. The results show that the average relative error and root mean square error of the simulated temperature distribution reconstruction are 0.073% and 0.1% respectively, the average reconstruction error of the temperature points set in the experimental test is 0.38%, and the reconstruction errors are lower than other algorithms. The proposed method effectively utilizes prior information to correct sparse reconstruction temperature distribution reconstruction results, significantly improving the quality of temperature distribution reconstruction. [Display omitted] • Acoustic tomography technology is used for temperature distribution reconstruction. • The improved sparse reconstruction model can improve the accuracy of initial temperature distribution reconstruction. • The feature extraction network can perform multi-scale feature extraction on the time-of-flight of acoustic waves. • The feature fusion reconstruction network can improve the utilization of prior information. [ABSTRACT FROM AUTHOR]

Acoustic process tomography is a powerful tool for monitoring multiphase flow and combustion. However, its capability of revealing details of the interrogation zone is restricted by the ill-posed and rank deficiency problems. In each projection, a probing sound beam only passes the pixels along its propagation path, resulting in a large number of zero-valued elements in the measurement matrix. This is more pronounced as the resolution of the imaging zone becomes gradually finer, which is detrimental to image reconstruction. In this study, a mathematically explicable reconstruction algorithm of regularization is proposed by assigning each zero-valued pixel with a combination of the values of the neighboring pixels, ruled by the appropriate regularization factors. The formula to determine the regularization factors is also derived. Simulations are carried out to verify this new approach, and some representative cases are presented. As a result, the ambiguity of the inverse process is removed, and the accuracy of the image reconstruction is significantly improved. The results show the robustness of the algorithm and certain advantages over the standard Tikhonov regularization formula. [ABSTRACT FROM AUTHOR]

Incidence rates of tree damage are increasing because of the increased intensity and frequency of abnormal climate events such as strong winds and heavy rains. Structural defects inside trees are difficult to detect by visual inspection; therefore, it is difficult to respond to them in advance based on prediction. Noninvasive sonic tomography (SoT) is a method that estimates internal defects while minimizing physical damage to trees; however, its accuracy differs depending on the species. Therefore, in this study, we aimed to compare the performance of noninvasive SoT and invasive resistance micro-drilling (RM) in detecting tree damage in oriental white oak (Quercus aliena Blume) distributed in East Asia and performed wood section analysis to verify the accuracy of noninvasive SoT. Linear regression analysis showed that defects in tomograms tended to increase with an increase in the number of defects in the RM profile, but the value of R2 was 0.405, which is lower than that of other tree species. The results from the wood section analysis and SoT were compared; the SoT tomograms appropriately reflected the location and size of the defects with a tendency to overestimate the defects when cracks were present, while the electric resistance tomography was effective for detecting incipient decay. [ABSTRACT FROM AUTHOR]

To improve the ability of the acoustic computed tomography (CT) temperature field reconstruction system for reconstructing various temperature distributions in the measured area, square and circular layouts of transducers were studied. In case of the square layout, the focus was on the placement of the transducers, and in case of the circular layout, the focus was on the division of grids. We proposed the coefficient matrix theory and indexes for studying and evaluating transducers layout. Four typical temperature field models were simulated and reconstructed. Simulation results showed that in a square layout, optimizing the position of transducers can result in better reconstruction quality. In a circular layout, a regular hexagonal grid division was better than an equal-area division, and better reconstruction quality was obtained by choosing the appropriate number of grids. For a small number of transducers, the circular layout of nine transducers with 27 acoustic rays and 91 regular hexagonal grids resulted in better reconstruction quality than the square and circular layout of eight transducers; in each reconstruction, the error was ≤ 5.07%. [ABSTRACT FROM AUTHOR]

In this article we present results of a pilot study focused on the relationship between heartrot in spruce stems caused by Armillaria ostoye and the invasion of Ips typographus. We used an acoustic tomograph taking in the consideration the fact that it has not been employed so far in the Czech Republic for a study like that. Spruce stands not exceeding age of 30 years, which had been weakened by long-term drought period were measured. Th e fungal mycelium of the pathogen was observed in 6.4% of the trees investigated. More than 60% of trees showed no signs of cambioxylophagous insects attack. A relationship between mycelium intergrowth and occurrence of hollows inside the measured trees was confi rmed. Weak relationship between the insects and occurrence of hollows was found in these age-structure spruces. [ABSTRACT FROM AUTHOR]

The importance of urban forests is undeniable when considering their benefits to the environment, such as improving air quality, landscapes and breaking its monotony. However, trees are subject to failures that can cause personal and economic damage. Therefore, it is necessary to know the health conditions of the trees to define their most adequate management. Some tools are used to detect plant health conditions, such as visual analysis, tomography, and drilling resistance. In addition, some formulas based on the cavity and trunk diameter relation or the remaining trunk wall dimension are also used to infer the strength loss of a tree and its consequent risk of falling. However, these formulas have limitations, such as assuming only cavities that are always centered and not considering areas with decay. Therefore, this research evaluates whether ultrasonic tomographic imaging allows us to improve the reach of the equations proposed in the literature to infer the strength loss of trees due to the presence of cavities and decays. The results showed that ultrasonic tomographic imaging allowed the equations to be closer to real conditions of the tree trunk, such as the inclusion of wood strength reduction from decay and the displacement of internal cavities in calculating the reduction in the second moment of area. [ABSTRACT FROM AUTHOR]

Premise of the studyField methodology and image analysis protocols using acoustic tomography were developed and evaluated as a tool to estimate the amount of internal decay and damage of living trees, with special attention to tropical rainforest trees with irregular trunk shapes.Methods and resultsLiving trunks of a diversity of tree species in tropical rainforests in the Republic of Panama were scanned using an Argus Electronic PiCUS 3 Sonic Tomograph and evaluated for the amount and patterns of internal decay. A protocol using ImageJ analysis software was used to quantify the proportions of intact and compromised wood. The protocols provide replicable estimates of internal decay and cavities for trees of varying shapes, wood density, and bark thickness.ConclusionsSonic tomography, coupled with image analysis, provides an efficient, noninvasive approach to evaluate decay patterns and structural integrity of even irregularly shaped living trees.

Copyright of Journal of Forestry Society of Croatia / Sumarski List Hrvatskoga Sumarskoga Drustva is the property of Forestry Society of Croatia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal Of Sichuan University (Natural Sciences Division) / Sichuan Daxue Xuebao-Ziran Kexueban is the property of Editorial Department of Journal of Sichuan University Natural Science Edition and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A reconstruction algorithm is proposed, based on multi-dictionary learning (MDL), to improve the reconstruction quality of acoustic tomography for complex temperature fields. Its aim is to improve the under-determination of the inverse problem by the sparse representation of the sound slowness signal (i.e., reciprocal of sound velocity). In the MDL algorithm, the K-SVD dictionary learning algorithm is used to construct corresponding sparse dictionaries for sound slowness signals of different types of temperature fields; the KNN peak-type classifier is employed for the joint use of multiple dictionaries; the orthogonal matching pursuit (OMP) algorithm is used to obtain the sparse representation of sound slowness signal in the sparse domain; then, the temperature distribution is obtained by using the relationship between sound slowness and temperature. Simulation and actual temperature distribution reconstruction experiments show that the MDL algorithm has smaller reconstruction errors and provides more accurate information about the temperature field, compared with the compressed sensing and improved orthogonal matching pursuit (CS-IMOMP) algorithm, which is an algorithm based on compressed sensing and improved orthogonal matching pursuit (in the CS-IMOMP, DFT dictionary is used), the least square algorithm (LSA) and the simultaneous iterative reconstruction technique (SIRT).

In this paper, we analyzed the results of experimental data processing in the study of regularities of propagation and transformation of low-frequency harmonic signals at the boundary of the “sea−land−sea” system. Harmonic signals at a carrier frequency of 33 Hz were generated by a low-frequency hydroacoustic radiator in Vityaz Bay. Then, they passed along the shelf of decreasing depth, transformed into seismoacoustic signals of the upper layer of the Earth’s crust and the bedrocks of Shultz Cape and excited hydroacoustic signals at the corresponding frequency in the shelf waters in the open part of the Sea of Japan. When processing the experiment results, we obtained the vertical distributions of the pressure field, caused by an acoustic low-frequency signal passing through the upper layer of the Earth’s crust. We presented the distributions of hydroacoustic and seismoacoustic energies. The obtained experimental data were compared with the simulations by the model, developed strictly according to the experiment scheme and the geological structure of the area. In the discussion of the obtained results, we explained a probable mechanism of acoustic energy propagation and the nature of the vertical distributions of the pressure field formation.

• In previous temperature field reconstructions, the inherent delays introduced by acoustic sensors were often overlooked in the actual measurement of acoustic signals.In this paper, we propose a Spatio-Temporal Feature Extraction (STFE) method that takes into account this delay information to achieve more accurate temperature field reconstruction. • No one has done time-series prediction in the highly dynamic and nonlinear background of temperature field before, especially the location of each path is different, it is more difficult to do time-series prediction with time in different dimensions, and this paper contributes to the time-series prediction in this aspect. • The problem of time resolution of the reconstructed image of the temperature field has been solved after reconstructing the measured time-of -flight (TOF) and, at the same time, a great contribution has been made to both the accuracy and the overall error of the reconstruction of the position of the temperature field. The temperature distribution within a furnace chamber is a key parameter reflecting the combustion condition of the boiler, and acoustic tomography provides an accurate quantitative reconstruction of the temperature distribution within the chamber's overlay. However, during the measurement process of acoustic tomography, the inherent latency in ultrasonic sensor data acquisition is a challenge for the real-time detection of the temperature field. When using ultrasonic sensors to measure the time-of-flight (TOF) of acoustic waves in the furnace chamber, the temperature properties of the chamber are recorded at different time points due to the sequential nature of signal transmission and reception, and the propagation paths of the recordings are different at different moments due to the different installation locations of the sensors, so utilizing this temporal information to reconstruct the temperature field is a complex challenge. The aim of this study is to accurately reconstruct the temperature field at each moment by utilizing the TOF of different attributes. To this end, a sophisticated multi-dimensional time series analytical framework is proposed to elucidate the temperature field dynamics informed by TOF variations by extracting its temporal and spatial features, respectively, to more accurately simulate the evolution process in real engineering. Firstly, the graph structure of each acoustic wave propagation path is established. Spatial correlations are derived from Pearson correlation analysis to form the "equivalent path" matrix. Subsequently, non-negative matrix decomposition is employed to determine the weight of each position. Concurrently, the TOF matrix is utilized to extract temporal features and calculate the time weights corresponding to different temperature field conditions. These two coefficient matrices are reorganized to reconstruct the real-time temperature field for a specific frame. The reconstruction not only precisely delineates the temperature field's variations during the measurement process but also significantly improves the fidelity of reconstruction. Specifically, the position reconstruction accuracy improves by over 4%, with an overall accuracy enhancement exceeding 2%. [ABSTRACT FROM AUTHOR]

The inverse wave problem of tomographic type is considered. It consists in reconstruction of several scatterer's characteristics in the form of spatial distributions for sound speed, medium density, absorption coefficient and power index of its frequency dependence, as well as vector of flow velocity. In the form of a survey material (based on several publications), a sequence of steps is discussed that leads to reconstruction of each individual spatial distribution in the presence of different combinations of the mentioned characteristics. The minimum number of frequencies required for reconstruction is discussed when the complete set of scattering data is available at each of the frequencies. For the first time, two possible approaches to reconstruct the scatterer characteristics in the presence of inhomogeneous spatial distributions of the density and the flow velocity vector are compared, and attention is drawn to the perspectives of reconstruction by functional algorithms in this case. The possibility of separating the sought spatial distributions during the inverse problem solution is illustrated by numerical modeling. [ABSTRACT FROM AUTHOR]