Energy Attenuation Coefficient Research Articles

Numerical and experimental study of attenuation inspection during FDM with ultrasonic leaky waveguide

ABSTRACT This work proposes an ultrasonic leaky waveguide (ULWG) for in-situ structural integrity inspection during fused deposition modeling (FDM). Since the ultrasonic wave propagation speed (m·s−1) is much higher than the deposition speed (mm·s−1), a quasi-static finite element model is first established to simulate the wave propagation during this dynamic process. The amplitude and energy attenuation coefficients (α and ζ) are chosen as the inspection features. Processing parameters including deposition layer thickness and number, inspection frequency, plate thickness and interface impedance are explored. For the first layer printing, a thinner thickness, higher frequency and proper interface impedance will enable a better inspection with high sensitivity. For multilayer printing, the multimodal dispersion curves change continuously and α oscillation is observed due to waveform aliasing that ζ is more reliable. Printing failures such as detachment can be predicted as well from the model established. The ULWG is then integrated into a commercial FDM machine to capture the attenuation coefficients of an “S” shape sample. The poor adhesion, local and global detachments, path planning impact can all be revealed by ζ experimentally. Moreover, being consistent to the simulation, the fluctuation of α in multilayer printing increases, which prevents a further printing evaluation.

The application of the K-class system in mine seismicity

As seismology has evolved, scientists have developed various earthquake magnitude scales tailored for specific scenarios, including Richter magnitude (ML) for local, moderate quakes, moment magnitude (Mw) for large-scale seismic events, energy magnitude (Me), which correlates directly with the total energy released, and duration magnitude (MD) for quickly assessing shallow or nearby seismic activities. Despite these advances, these scales were not specifically designed to address the unique challenges posed by mine earthquakes, particularly in coal mine environments where seismic events are typically of lower energy and lower perceptibility but have potentially significant impacts. This study applies the K-class magnitude system for the first time to address significant discrepancies in magnitude values for the same seismic events in mine earthquakes, particularly in coal mines when different formulas are used. However, because current seismic monitoring systems in domestic coal mines continue to employ a variety of magnitude scales, we have developed a corrected Richter scale (MLc) specifically tailored to the geological conditions of coal mines. This adaptation facilitates the conversion to and from the K class, enhancing the accuracy and relevance of seismic assessments in these environments. Therefore, we conducted continuous blasting experiments at the Dongtan Coal Mine and derived the corrected Richter magnitude MLc. Based on data analysis, we fitted the energy attenuation coefficient and compared the K values with four types of traditional magnitude results. Finally, we derived the conversion relationship between the K class and the corrected Richter magnitude MLc, establishing a mine earthquake measurement system. The successful application of the K class in coal mines suggests its potential to be extended to the entire field of induced microseismicity, including mining-induced microseismicity, shale gas extraction-induced microseismicity, and oil extraction-induced microseismicity, providing valuable insights and tools for a broader range of geophysical research and industry practices.

Research on rockburst prevention systems based on the attenuation law of coal and rock vibration wave energy

During the coal and rock mass fracture process, elastic properties are released and vibration waves are radiated outward. The energy attenuation characteristics of these waves can describe the cumulative damage and elastic energy accumulation of the mass. To investigate coal and rock mass failure characteristics and energy attenuation rules during rockburst, numerical simulation and laboratory testing were utilized to study the energy transfer laws under various parameters. Six variables, including elastic modulus, Poisson’s ratio, bulk density, cohesion, internal friction angle, and void ratio, were selected to simulate the rockburst energy release process under different parameter combinations by adding surface pressure to the model. The coal and rock mass energy attenuation coefficient was obtained by fitting the node energy straight line using the least squares method. The six variables’ influence on vibration wave energy transfer was obtained using analytic hierarchy process program written in MATLAB, and a comprehensive calculation formula was proposed. Using the energy attenuation coefficient, the rock layer energy diffusion distance was calculated and compared with the roof collapse rock layer step distance, resulting in the roof rock layer cutting distance determination. By roof rock strata precutting, rockburst occurrence can be prevented, ensuring safe and efficient coal mine production.

Enhancement in kerosene droplet–coal particle collision and adsorption by bubble trailing vortex in coal slurry conditioning: Energy evolution of collision process

AbstractUnderstanding the collision between kerosene droplets and coal particles in the bubble trailing vortex region is crucial for enhancing slurry conditioning. We found the area of the bubble trailing vortex region increased as the bubble size increased via the Fluent 6.3.26 software. A kerosene droplet velocity range of 0.074–0.106 m/s and a coal particle velocity range of 0.062–0.104 m/s were obtained if a bubble had a diameter of 0.3 mm. We employed a high‐speed motion acquisition system and observed the collision process, which was divided into two stages: Compression and Rebound. The critical motion distance increased as the kerosene droplet size increased, and sufficient kerosene droplet motion distance and enough kinetic energy normally resulted in a rebound phenomenon. The attenuation energy was almost positively linear to the initial energy, and the energy attenuation coefficient of the collision process was fitted to 0.626. Our results can provide valuable insight into mineral separation.

Relation between quadrupole ultrasonic resonance and shear viscoelasticity of polymer droplets with different glass transition temperatures

Abstract When observing the ultrasonic signal transmitted through a suspension of particles dispersed in a liquid, a peak is observed in the frequency spectrum of the attenuation coefficient of the ultrasonic energy. This peak mainly reflects shear elasticity, even though longitudinal ultrasound is used. Hence, the shear modulus of a single particle dispersed in a liquid can be obtained in a non-contact manner. In this study, we used ultrasound to analyze the process of polymer particle formation from an oil-in-water emulsion, in which a polymer solution containing an organic solvent is used as the oil phase, and the organic solvent is evaporated in water. Furthermore, the liquid-to-solid transition was quantified for microparticles consisting of various polymeric materials (liquid, rubber, and glass), and the relationship between the glass transition temperature, peak behavior of ultrasonic attenuation coefficient, and shear modulus was clarified.

Synthesis and Bioapplication of Emerging Nanomaterials of Hafnium.

A significant amount of progress in nanotechnology has been made due to the development of engineered nanoparticles. The use of metallic nanoparticles for various biomedical applications has been extensively investigated. Biomedical research is highly focused on them because of their inert nature, nanoscale structure, and similar size to many biological molecules. The intrinsic characteristics of these particles, including electronic, optical, physicochemical, and surface plasmon resonance, that can be altered by altering their size, shape, environment, aspect ratio, ease of synthesis, and functionalization properties, have led to numerous biomedical applications. Targeted drug delivery, sensing, photothermal and photodynamic therapy, and imaging are some of these. The promising clinical results of NBTXR3, a high-Z radiosensitizing nanomaterial derived from hafnium, have demonstrated translational potential of this metal. This radiosensitization approach leverages the dependence of energy attenuation on atomic number to enhance energy-matter interactions conducive to radiation therapy. High-Z nanoparticle localization in tumor issue differentially increases the effect of ionizing radiation on cancer cells versus nearby healthy ones and mitigates adverse effects by reducing the overall radiation burden. This principle enables material multifunctionality as contrast agents in X-ray-based imaging. The physiochemical properties of hafnium (Z = 72) are particularly advantageous for these applications. A well-placed K-edge absorption energy and high mass attenuation coefficient compared to elements in human tissue across clinical energy ranges leads to significant attenuation. Chemical reactivity allows for variety in nanoparticle synthesis, composition, and functionalization. Nanoparticles such as hafnium oxide exhibit excellent biocompatibility due to physiochemical inertness prior to incidence with ionizing radiation. Additionally, the optical and electronic properties are applicable in biosensing, optical component coatings, and semiconductors. The wide interest has prompted extensive research in design and synthesis to facilitate property fine-tuning. This review summarizes synthetic methods for hafnium-based nanomaterials and applications in therapy, imaging, and biosensing with a mechanistic focus. A discussion and future perspective section highlights clinical progress and elaborates on current challenges. By focusing on factors impacting applicational effectiveness and examining limitations this review aims to support researchers and expedite clinical translation of future hafnium-based nanomedicine.

Study on propagation mechanism and attenuation law of acoustic emission waves for damage of prestressed steel strands

The study of acoustic emission waves propagation mechanism and attenuation laws for damage of prestressed steel strands is the theoretical basis for acoustic emission health monitoring of prestressed steel strands such as stay cables, slings, suspenders, and concrete structures. Firstly, the propagation mechanism of acoustic emission waves in prestressed steel strands is studied using numerical simulation methods. Secondly, the amplitude and energy attenuation laws of acoustic emission waves caused by damage of prestressed steel strands are analyzed by experimental research, and the amplitude and energy attenuation models of the influence of prestress level are constructed. Finally, the constructed acoustic emission attenuation models are analyzed in combination with practical engineering. The results show that numerical simulation visualizes the propagation path of acoustic emission waves in prestressed steel strands; With the increase of prestress levels, the acoustic emission frequency distribution of prestressed steel strands damage ranges from 100 to 200 kHz, with a dominant frequency of 160 kHz, the acoustic emission amplitude and energy attenuation coefficients decrease, and the amplitude attenuation is slower than the energy attenuation; The acoustic emission amplitude attenuation of prestressed steel strands damage in prestressed hollow slab beams is 5 times faster than that of steel strands without surrounding media.

Snow Suppresses Seismic Signals From Steamboat Geyser

AbstractGeyser and volcano monitoring suffer from temporal, geographic, and instrumental biases. We present a recording bias identified through multiyear monitoring of Steamboat Geyser in Yellowstone National Park, USA. Eruptions of Steamboat are the tallest of any geyser in the world and they produce broadband signals at two nearby stations in the Yellowstone National Park Seismograph Network. In winter, we observe lower eruption signal amplitudes at these seismometers. Instead of a source effect, we find that environmental conditions affect the recorded signals. Lower amplitudes for 23–45 Hz frequencies are correlated with greater snow depths at the station 340 m away from Steamboat, and we calculate an energy attenuation coefficient of 0.21 ± 0.01 dB per cm of snow. More long‐term monitoring is needed at geysers to track changes over time and identify recording biases that may be missed during short, sporadic studies.

A Data-driven approach to predicting neutron penetration through media

A novel methodology is developed to predict the neutron permeation through media, enabling easier selection of shields and attenuators. The methodology relies on generalized metrics parametrized from MCNP®6.2 simulations where the average neutron energy and relative intensity are tallied through various media. This work builds on previously developed neutron energy attenuation coefficients by discussing accompanying neutron permeation coefficients. Both metrics are used to accurately predict the intensity of neutrons penetrating any medium and the average penetrating neutron energy, allowing for a simplified and generalized approach to predicting neutron penetration. Benchmarks with increasing complexity are used to demonstrate the applicability of the metrics to any geometry and medium. The benchmarks revealed 1.29–3.25% deviation from results in higher fidelity simulations. The data-driven methodology enables streamlined approaches to analyze complex neutron-attenuating media and presents a computationally efficient alternative to iterative neutronics simulations for optimizing neutron shielding and moderation setups.

Axial stress measurement for tightened bolt based on the effect of stress on ultrasonic wave attenuation

ABSTRACT Accurate assessment and monitoring of axial stress during the service life of the bolt connection is of great significance in ensuring the stability and reliability of the aerospace structure. The current acoustoelastic method requires both transverse and longitudinal mode waves and is less sensitive to small-size bolts, resulting in relatively larger errors in the evaluation of axial stress. In this paper, an axial stress measurement method with only a single longitudinal/transverse transducer for tightened bolts based on a novel attenuation-based model is introduced. The ultrasonic responses under axial preload in different frequency bands are comprehensively reflected through the energy attenuation coefficient matrix. In addition, an experimental method for selecting the optimal frequency band is given. Furthermore, the semi-permanent coupling method is proposed to provide a stable coupling condition to verify the feasibility of the attenuation-based model. Loading tests and ultrasonic tests were conducted on two kinds of strength-grade materials to obtain the calibration curves of both the longitudinal and transverse attenuation models. The experimental results show that the energy attenuation coefficient is positively correlated with the axial stress in a specific frequency range and the calibrated curve has a high fitting rate with a quadratic fitting function. The average relative error of the prediction results is less than 7.5%, which is better than the conventional acoustoelastic effect model.

Research on the Cooperation of Emergency Response Subjects for the Shortage of Urban Natural Gas Energy

This paper deals with the urgent problem of urban natural gas shortage. In order to improve emergency efficiency, enhance emergency efforts, and reduce urban disaster losses, the differential game theory is firstly applied for constructing a tripartite dynamic game model. Then, based on the Hamilton–Jacobi–Bellman (HJB) equation, the optimal effort degree, natural gas energy shortage, and maximum urban loss are obtained in three cases, i.e., spontaneous governance mode, superior dominant mode, and cooperative mode. The results show that the effort of provincial government, local government, and natural gas emergency enterprise is positively related to the emergency shadow, the impact of effort and natural gas energy attenuation coefficient of provincial government, local government, and enterprise, but it is negatively related to the emergency cost coefficient and the discount rate. From the perspective of emergency shortage and total urban loss, the government-enterprise cooperation mode turns out to be the best emergency mode, while the spontaneous governance mode remains the worst. At the same time, the government implements subsidies and incentives for nongovernmental organizations involved in emergency response, which is more conducive to the emergency of natural gas shortage in heavily suffering cities.

Estimation method of coal channel Q value based on frequency shift phenomenon of transmitting channel wave

Currently, the transmitting channel wave technique mainly uses the attenuation coefficient of the channel wave total energy to explore the geological structure of the coal seam face. In the case of weak geophone coupling and intense geological anomaly, the channel wave energy will be attenuated severely, which significantly affects the stability and accuracy of the result. The Q value of the coal channel is a critical parameter to evaluate the energy attenuation characteristics of the channel wave. The Q value is typically estimated by using the attenuation coefficient of the body wave, but the special coal channel model hinders the estimation of the Q value of the coal seam. According to the linear attenuation characteristics of the centroid frequency of the transmitting channel wave, a new method was proposed to assess the quality factor (Q) of the coal channel by using the centroid frequency change of the channel wave signal. The expected frequency was calculated as its centroid frequency according to the energy ratio of each frequency point through the spectral analysis of the channel wave signal. Combined with the transmission tomography technology, the imaging of the coal seam face based on the transmitting channel wave Q value was established. According to the sudden change of the Q value of the coal channel near the geological structure of the coal seam face, a geological interpretation method based on the abnormal Q value was proposed. The two-dimensional numerical simulation demonstrated that the centroid frequency of the transmitting channel wave signal decayed linearly with the propagation distance and the geological structure increased the frequency shift. Furthermore, three-dimensional numerical simulation validated the feasibility and effectiveness of the Q value inversion method. Field Experimental results showed that the algorithm exhibited improved stability and accuracy. This work proposed a novel frequency-domain inversion method of the transmitting channel wave that directly uses the frequency shift characteristics of the channel wave to estimate the Q value of the coal channel, which offers a new strategy in the data processing of channel wave.

A New Axial Stress Measurement Method for High-Strength Short Bolts Based on Stress-Dependent Scattering Effect and Energy Attenuation Coefficient.

The accurate estimation of axial stresses is a major problem for high-strength bolted connections that needs to be overcome to improve the assembly quality and safety of aviation structures. However, the conventional acoustoelastic effect based on velocity-stress dependence is very weak for short bolts, which leads to large estimation errors. In this article, the effect of axial stress on ultrasonic scattering attenuation is investigated by calculating the change in the energy attenuation coefficient of ultrasonic echoes after applying axial preload. Based on this effect, a stress-dependent attenuation estimation model is developed to measure the bolt axial stress. In addition, the spectrum of the first and second round-trip echoes is divided into several frequency bands to calculate the energy attenuation coefficients, which are used to select the frequency band sensitive to the axial stress changes. Finally, the estimation model between axial stress and energy attenuation coefficients in the sensitive frequency band is established under 20 steps of axial preloads. The experimental results show that the energy attenuation coefficient in the sensitive band corresponds well with axial stress. The average relative error of the predicted axial stress is 6.28%, which is better than that of the conventional acoustoelastic effect method. Therefore, the proposed approach can be used as an effective method to measure the axial stress of short bolts in the assembly of high-strength connections.

Attenuation characteristics of impact-induced seismic wave in deep tunnels: An in situ investigation based on pendulum impact test

The radiated seismic energy is an important index for the intensity assessment of microseismic (MS) events and the early warning of dynamic disasters. However, the energy of MS signals is significantly attenuated due to the heterogeneity and viscous damping of rock media. Therefore, the study on attenuation characteristics of MS signals in underground engineering has practical significance for the accurately estimation of radiated seismic energy. Based on a pendulum impact test facility and MS monitoring system, an in situ investigation was carried out to explore attenuation characteristics at a deep tunnel. The results show that the seismic energy and peak particle velocity (PPV) attenuation are exponentially related to the propagation distance. The attenuation coefficient of energy is larger than that of PPV. With the increase in the input impact-energy, the seismic energy attenuation coefficient decreases as a power function. An empirical relationship between energy attenuation coefficient and wave impedance of rock mass was established in this scenario. Moreover, the time-frequency characteristics and energy distribution laws of impact-induced signals were investigated by the continuous wavelet transform (CWT) and wavelet packet analyses, respectively. The dominant frequency of signals decreases gradually as the propagation distance increases. Based on the energy attenuation characteristics, a new method was proposed to calculate the released source energy of MS events in the field. This study can provide an insight into energy attenuation characteristics of seismic waves and references for attenuation correction in seismic energy calculation.

Attenuation characteristics analysis of seismic energy and its application to risk assessment in underground coal mines

Seismic energy analysis is the basis of coal burst risk assessment. The prerequisite for utilizing seismic energy to quantify coal burst hazards is the accurate understanding of seismic energy attenuation. Thereby the characteristics of seismic energy attenuation were first systematically investigated in this paper. Based on the seismic data and 24 coal burst records during the period of sixteen months, a risk assessment method including three indexes (Static Intensity Index (SII), Dynamic Intensity Index (DII), and Risk Assessment Index (RAI)) was derived from seismic energy attenuation. In consideration of the static and dynamic response, the superposition effects of seismic energy were proposed to improve the performance of risk assessment. Results show that residual seismic energy (RSE) is relatively correlated with seismic energy, source radius, and energy attenuation coefficient; the higher seismic energy, source radius, and lower energy attenuation coefficient would result in higher coal burst risk. The case study demonstrated that SII could effectively predict the damaged area, but its prediction efficiency of high-magnitude events (HMEs) is relatively low; DII could predict damaged areas and HMEs, but may lead to risk overestimation; and RAI could efficiently predict the damaged area and HMEs. The sensitivity of the monitoring system and seismicity activeness could be the two main restrictions of the proposed method, leading to low efficiency or even false risk assessment. This paper sheds light on seismic energy utilization to risk prediction in underground coal mines. Highlights The attenuation response characteristics of seismic energy to different factors including seismic energy, source radius, and attenuation coefficient were investigated. A new assessment method based on seismic energy attenuation calculation was proposed to assess coal burst risks. Three seismic-based indexes considering static and dynamic response and their superposition effects were proposed to assess coal burst risk. Sensitivity of monitoring system and seismicity activeness could be the two main restrictions leading to low accuracy or even false in risk assessing, which implies that the proposed method could also have false judgements in the place where rare seismicity is monitored.

Connection Between Damping Torque Analysis and Energy Flow Analysis in Damping Performance Evaluation for Electromechanical Oscillations in Power Systems

The damping performance evaluation for electro-mechanical oscillations in power systems is crucial for the stable operation of modern power systems. In this paper, the connection between two commonly-used damping performance evaluation methods, i.e., the damping torque analysis (DTA) and energy flow analysis (EFA), are systematically examined and revealed for the better understanding of the oscillatory damping mechanism. First, a concept of the aggregated damping torque coefficient is proposed and derived based on DTA of multi-machine power systems, which can characterize the integration effect of the damping contribution from the whole power system. Then, the pre-processing of measurements at the terminal of a local generator is conducted for EFA, and a concept of the frequency-decomposed energy attenuation coefficient is defined to screen the damping contribution with respect to the interested frequency. On this basis, the frequency spectrum analysis of the energy attenuation coefficient is employed to rigorously prove that the results of DTA and EFA are essentially equivalent, which is valid for arbitrary types of synchronous generator models in multi-machine power systems. Additionally, the consistency between the aggregated damping torque coefficient and frequency-decomposed energy attenuation coefficient is further verified by the numerical calculation in case studies. The relationship between the proposed coefficients and the eigenvalue (or damping ratio) is finally revealed, which consolidates the application of the proposed concepts in the damping performance evaluation.

Gamma-Ray Attenuation Characteristics of Some Essential Amino Acids for 57Co, 192Ir, 18F, and 116mIn Sources

Purpose: In different tissues of the body, proteins are important parts that are made up of building blocks called amino acids. Considering the wide applications of radioactive sources in industry and medicine, the need to study the attenuation characteristics of amino acids is determined. Materials and Methods: To study the attenuation characteristics of five types of amino acids, MCNPX Monte Carlo code and XMuDat program were used. Linear and mass attenuation coefficients, half and tenth value layers, mean free path, effective atomic and electronic cross-sections, effective atomic numbers and effective electron densities were calculated. 57Co, 192Ir, 18F, and 116mIn gamma sources were considered for this study. To validate the theoretical results, the obtained values were compared with the available experimental data. Results: The difference between the theoretical and experimental results was less than 11%. The results showed that with increasing photon energy, the linear and mass attenuation coefficients and effective atomic and electronic cross-sections decreased, while the half and tenth value layers and mean free path quantities increased. Furthermore, the linear attenuation coefficients, the effective atomic and electronic cross-sections, as well as the effective atomic number values increased with increasing amino acid density, while the effective electron density behaves independently of the amino acid density. Conclusion: The presented theoretical methods produced data similar to experimental results with fair accuracy, so by using these methods, attenuation properties of other amino acids can be obtained over a wide range of energies.

A novel method for the design and selection of neutron-attenuating media

A new methodology for designing neutron shields and selecting moderators using sets of generalized metrics is presented. The metrics were derived from many MCNP®6.2 simulations. Neutron and photon statistics were tracked at the outer surface of a sphere for each of the materials in each simulation to derive neutron energy attenuation coefficients that can accurately track the exponential energy decrement of neutrons in media. Neutron penetration probabilities as well as a normalized measure of the number of collisions were also obtained as a measure of the number of neutrons that penetrate the media and the number of collisions the neutrons undergo, respectively. Finally, the penetrative photon generation probability and their average energy were also obtained, allowing for photon dose rate computations. Attempts at generalizing each of the derived metrics are also discussed, showing the limitations of such simplifications. The methodology allows more streamlined approaches for analyzing complex neutron attenuating media.

Discrimination and application of the properties of the in-seam seismic wave in the collapse column of the working face

During in-seam wave seismic exploration of working face, the anomaly has serious diversification, and sometimes it is difficult to accurately determine the nature of the anomaly. Due to the large differences in the collapse column shape of the working face, especially when there are multiple sets of collapsed columns, it is difficult to effectively distinguish its nature. This has been an unresolved problem since the tunnel wave earthquake was introduced. Based on the analysis of the characteristics of the collapse column in the working face, the forward simulation analysis of the collapse column is carried out. Based on the field application case, the BPT algorithm and the SIRT algorithm in the calculation process of the energy attenuation coefficient tomography overlay inversion calculation are studied. Through analyzing the amplitude and frequency dispersion characteristics of the verification of the collapse column anomaly, a method for identifying the seismic properties of the working face collapse column groove wave is proposed, which effectively improves the accuracy of the in-seam wave seismic detection.

Experimental research on the acoustic transmission characteristics of refractory materials

The damage acoustic emission (AE) signal of refractories can be used to evaluate the classification and degree of the phase damage, which is different from the traditional damage location study in AE. In the analysis of AE signal, considering the nonuniformity of refractory inner structure, results of damage source inspection are usually affected by the signal transmission path. Therefore, the influence of transmitting path should be studied first. Piezoceramic material, capable of actuation and sensing, is commonly used to build AE probes. In this paper, two kinds of industrial refractories were selected as research objects and AE probes were chosen to generate emission acoustic signals. The relative amplitude attenuation coefficient and the relative energy attenuation coefficient were consequently designed as discriminant indicators to study the propagation characteristics of stress wave under different transmission paths and thicknesses. Results indicate that energy attenuation is higher than amplitude attenuation. Meanwhile, signal attenuation is principally proportional to transmission distance without directional selectivity. The above conclusions provide strong support to arrange AE sensors for nondestructive testing in refractory industry.