Search Results (134)

The decommissioning of offshore oil rigs presents complex environmental challenges and opportunities, particularly in the context of energy transition goals and marine ecosystem protection. This study applies a Life Cycle Assessment (LCA) approach to evaluate the energy and environmental impacts associated with two different decommissioning approaches: full removal and partial removal. The analysis considers greenhouse gas emissions, energy consumption, material recovery, and long-term waste management. The study demonstrates important energy savings through the recovery and recycling of steel, which offsets energy-intensive operations such as cutting and marine transport. In addition, the analysis underscores the potential of integrating decommissioned infrastructure into offshore renewable energy systems, highlighting synergies with circular economy principles and the decarbonization of offshore operations. The findings highlight the importance of site-specific assessments and integrated policy frameworks to guide environmentally sound decommissioning decisions in offshore energy infrastructure. The analysis shows that full removal results in 14,300 kg CO₂ eq emissions during cutting and transport, compared to 3090 kg CO₂ eq for partial removal. Meanwhile, steel recycling generates environmental benefits of −3.80 × 10⁶ kg CO₂ eq for full removal and −1.17 × 10⁶ kg CO₂ eq for partial removal. Full article

The metallic shaped charge liner (SCL) is widely utilized in the defense industry, oil perforation, cutting, and other industrial fields due to the powerful penetration performance. However, quantitative law and underlying mechanisms of material properties affecting SCL penetration performance are unclear. Based on the real and virtual material properties, by combining numerical simulation with machine learning, the influence of material properties on SCL penetration performance was systematically studied. The findings in the present work provided new insights into the penetration mechanism and corresponding influencing factors of the metal jet. It indicated that penetration depth was dominated by the melting point, specific heat, and density of the SCL materials rather than the conventionally perceived plasticity and sound velocity. Average perforation diameter was dominated by the density and plasticity of the SCL materials. Particularly, the temperature rise and thermal softening effect of the SCL controlled by the melting point and specific heat have a significant effect on the “self-consumption” of the metal jet and further on the penetration ability. Additionally, the density of the SCL influences the penetration depth deeply via dynamic pressure of the jet, but the influence of density on penetration depth decreases with the increase in density. The correlation between the key properties and penetration performance was obtained according to a quadratic polynomial regression algorithm, by which the penetration potential of SCL materials can be quantitatively evaluated. Overall, the present study provides a new SCL material evaluation and design method, which can help to expand the traditional penetration regime of the SCL in terms of the penetration depth and perforation and is expected to be used for overcoming the pierced and lateral enhancement trade-off. Full article

This paper studies the influence of the pick structure on the cutting characteristics of the cutting head when cutting rocks with a tunneling–bolting combined machine. A simulated model of the breaking of soft rock with a cutting pick was established. Dynamic simulation of the cutting head during the cutting process enabled the force characteristics to be obtained. The validity of the simulation was verified by carrying out cutting experiments. A numerical simulation of the pick parameters made it possible to analyze the influence of the pick’s included angle, taper angle, and established angle on the cutting performance. The results showed that the average values for the cutting resistance and traction resistance when the cutting head cut rocks were 14.21 kN and 7.19 kN, respectively. An included angle of between 70° and 75° was found to be most suitable. Within a specific range, the cutting force was found to increase with an increase in the taper angle. An established angle between 40° and 45° proved to have the highest cutting efficiency. At present, the results have been applied to the Shendong Coalmine. Thus, the proposed model provides a sound theoretical basis for the optimal design of the cutting head. Full article

This paper introduces an acoustic-based monitoring system for high-speed CNC drilling, aimed at optimizing processes and enabling real-time machine state detection. High-fidelity acoustic sensors capture sound signals during drilling operations, allowing the identification of critical events such as tool engagement, material breakthrough, and tool withdrawal. Advanced signal processing techniques, including spectrogram analysis and Fast Fourier Transform, extract dominant frequencies and acoustic patterns, while machine learning algorithms like DBSCAN clustering classify operational states such as cutting, breakthrough, and returning. Experimental studies on materials including acrylic, PTFE, and hardwood reveal distinct acoustic profiles influenced by material properties and drilling conditions. Smoother sound patterns and lower dominant frequencies characterize PTFE drilling, whereas hardwood produces higher frequencies and rougher patterns due to its density and resistance. These findings demonstrate the correlation between acoustic emissions and machining dynamics, enabling non-invasive real-time monitoring and predictive maintenance. As AI power increases, it is expected to extract in-situ process information and achieve higher resolution, enhancing precision in data interpretation and decision-making. A key contribution of this project is the creation of an open sound library for drilling processes, fostering collaboration and innovation in intelligent manufacturing. By integrating big data concepts and intelligent algorithms, the system supports continuous monitoring, anomaly detection, and process optimization. This AI-ready hardware enhances the accuracy and efficiency of drilling operations, improving quality, reducing tool wear, and minimizing downtime. The research establishes acoustic monitoring as a transformative approach to advancing CNC drilling processes and intelligent manufacturing systems. Full article

Background: To develop and validate the Tinnitus Qualities and Impact Questionnaire (TQIQ), a new tool for evaluating the perceived qualities of tinnitus sound. Method: The study was part of two clinical trials on internet-based tinnitus interventions, using cross-sectional (n = 380) and pretest–posttest data (n = 280). Participants completed various questionnaires online, including the newly developed TQIQ and measures of tinnitus severity (Tinnitus Functional Index; TFI), anxiety (Generalized Anxiety Disorder 7; GAD-7), depression (Patient Health Questionnaire 9; PHQ-9), insomnia (Insomnia Severity Index; ISI), and health-related quality of life (EQ-5D-5L Visual Analog Scale; VAS). The psychometric properties of the TQIQ were assessed, including construct validity, internal consistency reliability, floor and ceiling effects, interpretability, and responsiveness to treatment. Results: Exploratory factor analysis resulted in two factors that accounted for 57% of the variance—internal and external tinnitus qualities. Overall, 92% convergent validity predictions were confirmed; TQIQ total scores strongly (≥0.6) or moderately (0.30 to 0.59) correlated with the TFI, GAD-7, PHQ-9, and ISI. The known-groups validity prediction was confirmed as individuals with an overall TFI score > 50 (severe) obtained significantly higher TQIQ scores. All internal consistency reliability statistics were within the required range (Cronbach’s α > 0.8). Floor and ceiling effects were negligible. ROC established clinically important cut-off scores, enhancing the interpretability of tinnitus severity classification. Finally, 89% convergent validity predictions were confirmed; TQIQ and TFI change scores were moderately correlated, indicating good responsiveness of the former to treatment. Conclusions: The TQIQ has adequate psychometric properties, providing a standardized measure for the assessment of characteristics of tinnitus sound in clinical practice. Full article

This study compares the hard turning performance under dual-nozzle minimum quantity lubrication (MQL) using mineral oil and 1-butyl-3-methylimidazolium chloride-based ionic fluids. Key performance indicators, including tool life (based on tool wear), surface roughness, cutting power, cutting temperature, cutting sound, carbon emission, and circularity error, were evaluated to assess manufacturing sustainability. The results revealed that ionic fluid-assisted MQL significantly outperformed mineral oil, improving tool life by 28.75% and reducing surface roughness by 5.58%, attributed to the superior lubrication and cooling ability of ionic fluids. Additionally, after 85 min of machining, the power consumption and carbon emission were greatly reduced under ionic fluid conditions, indicating a lower environmental impact. For precision machining concerns, the ionic fluid proved more favorable, as circularity error under mineral oil conditions was 2.67 times higher than with ionic fluids. The weighted Pugh matrix awarded ionic fluid a higher sustainability score (+7) than mineral oil (+1), establishing it as the superior cooling option for hard turning, enhancing sustainability in machining difficult-to-cut metals. Full article

In this work, we present a new graphene-based sensor designed to monitor a set of photovoltaic panels on a sound-absorbing screen in terms of their potential mechanical damage. The innovative design of the photovoltaic module and consequently its sound-reflecting and sound-absorbing parameters play a vital role. The light transmittance of the sensor layer composed of graphene flakes in a cellulose matrix, confirmed by optical studies, allows its use directly over the photovoltaic cells. All the sensors are interconnected with metallic connections to reduce their internal resistance on larger surfaces. The sensor state is monitored through the resistance value as a zero-one operation/damaged response. Two sensor damage, scenarios, repetitive scratching, and cutting-out were described. The sensor measurements were performed in the potential ranging from 2.1 to 51.1 V, and the current response allowed to calculate the total resistance. The change in sensor resistance ranged between 9.3 and 24.1%, depending on the damaged area. The resistance for the scratched surface oscillated between 25 and 26 Ω, whereas the cut-out surface showed values more than 1.5 times higher. The proposed sensor based on graphene, cellulose, and ethylene–vinyl acetate allows the registration of immediate information about the destruction or theft of a power node. Full article

As a bionic flow control structure, leading-edge serrations have been proven to effectively suppress the aerodynamic noise of airfoils. Compared with single-wavelength serrations, a greater noise reduction potential can be obtained for airfoils with the double-wavelength serrations because of the phase interference at different tip-to-root ratios. In this study, in order to reduce the aerodynamic noise of a flat plate operating in a steady uniform flow, double-wavelength leading-edge serrations based on Ayton’s analytical model are optimized by the meta-heuristic optimization algorithm. The effects of different double-wavelength serrations on the noise characteristics of the flat plate are investigated. By comparing and analyzing the radiation integral function and quantifying the sound pressure along the leading edge of the flat plate, the local source cut-off effect resulting from the large transition curvature of the root and phase difference superposition is analyzed in detail. The results show that, before the first inflection point, the convex sinusoidal and iron-shaped serrations can significantly reduce the aerodynamic noise of the flat plate. When the concave ogee-shaped serrations are adopted, the reduction of the high-frequency noise is more obviously. Especially when the slits are embedded at the roots of the optimized leading-edge serrated structures, the improved design further promotes an additional noise reduction level of 0.7 dB for the flat plate. Through numerical studies, the coupled noise reduction mechanism of the serration roots and the slits is also revealed. Full article

This study investigates the acoustic characteristics of the alto saxophone by analyzing the spectral content of sound pressure along its bore and examining the influence of register valves. A detailed in situ analysis is presented of internal sound pressure from the mouthpiece to the bell for notes ranging from D₃ to C#₅, using a thin probe microphone needle in the neck and a movable miniature microphone in the body of the saxophone. The findings reveal that the cut-off frequency for lower notes in the first register is located near the third mode, whereas for higher notes, it shifts closer to the fourth mode. This research investigated previous assumptions that the cut-off frequency lies near the sixth mode, instead demonstrating that it occurs at lower modes depending on the note played. In the second register, the cut-off frequency consistently aligns with the second mode for all notes. The results demonstrate that opening the register tone holes alters the sound pressure level (SPL) distribution and shifts the positions of sound pressure valleys, with the first register valve having a more pronounced effect on SPL and mode shape than the second register valve. For the fourth mode in the first register, the register valves exhibit a stronger influence on SPL distribution compared to mode 2. Full article

Fluidized bed-chemical vapor deposition (FB-CVD) technology stands as a cross-cutting achievement of fluidized bed technology in chemical engineering and chemical vapor deposition (CVD) in materials science, finding applications in particle coating, granulation, and material preparation. As compared to conventional CVD technology, FB-CVD distinguishes itself through enhanced heat/mass transfer efficiency, achieving a uniform coating layer while maintaining low production costs. Given the related research on FB-CVD micro-nano particle coating, the mechanism of particle fluidization and chemical vapor deposition, and the difficulty of micro-nano particle agglomeration were summarized. The process intensification of micro-nano particle fluidization assisted by particle design and external force field, such as vibration field, magnetic field, and sound field, and micro-nano particle chemical vapor deposition coating were summarized. In particular, applications of FB-CVD micro-nano particle coating are introduced. Finally, the opportunities and challenges faced by FB-CVD micro-nano particle coating technology are discussed, and the development prospect of this technology is prospected. This review is beneficial for the researchers of the fluidization field, and also the particle coating technology. Full article

High-precision noise radiation characterization is essential for designing circular saw blades aimed at vibration and noise reduction. However, previous studies have generally overlooked the effects of thermal stress, centrifugal force, and cutting force on the acoustic performance of saw blades during the cutting process. This paper proposes a multi-physics field coupling analysis method based on FEM/BEM joint simulation technology. By performing thermal-force coupling analysis to obtain the sawing vibration response, the resulting vibration acceleration is introduced into the acoustic–solid coupling model to predict the frequency-domain characteristics and spatial distribution of sawing noise. The validity of the simulation results is verified through sawing noise test experiments. The study shows that the circular saw blade radiates the most noise when sawing in the mid-frequency band from 500 Hz to 8000 Hz, while the noise radiation efficiency is lower in both the low-frequency band and the high-frequency band. The multi-physical field coupling simulation method can significantly improve the calculation accuracy of the frequency-domain characteristics of sawing noise. The vibration noise of the circular saw blade shows clear directional distribution at different excitation frequencies, while the directionality of the experimentally measured noise is less distinct. Furthermore, based on the noise radiation characteristics, this study explores the design strategies of noise reduction slots and sound barriers, which provide references for the noise control and vibration damping design of circular saw blades. Full article

The acoustic emissions of ventilation systems and their subcomponents contribute to the perceived overall comfort in indoor environments and are, therefore, the subject of research. In contrast to fans, there is little research on the aeroacoustic properties of air diffusers (often referred to as outlets). This study investigates a commercially available ceiling swirl diffuser. Using a hybrid approach, a detailed three-dimensional large-eddy simulation is coupled with a perturbed wave equation to capture the aeroacoustic processes within the diffuser. The flow model is validated for the investigated operating point of 470 m³/h using laser-optical and acoustic measurements. To identify the noise sources, the acoustic pressure is sampled with various receivers and on cut sections to evaluate the cross-power spectral density, and the sound-pressure level distribution on cut sections is evaluated. It is found that the plenum attenuates the noise near its acoustic eigenmodes and thus dominates other noise sources by several orders of magnitude. By implementing the plenum walls as sound-absorbing, the overall sound-pressure level is predicted to decrease by nearly 10 dB/Hz. Other relevant geometric features are the mounting beam and the guide elements, which are responsible for flow-borne noise emissions near 698 Hz and 2699 Hz, respectively. Full article

Background and Objectives: Analysing the characteristics of the mandibular bone through panoramic radiographs could be useful as a prescreening tool for detecting individuals with osteoporosis. The aims of this study were to evaluate the possible associations between the mandibular cortical index (MCI) and bone mineral density (BMD) in various bone regions, to investigate whether BMD better identifies moderate–severe mandibular erosion or severe mandibular erosion, and to establish BMD cut-off points to identify individuals with moderate or severe mandibular cortical erosion. Methods: This study analysed 179 Spanish Caucasian women between September 2021 and June 2024. Bone measurements, including amplitude-dependent speed of sound (Ad-SOS), the ultrasound bone profiler index (UBPI), and the bone transmission time (BTT), were obtained via dual energy X-ray absorptiometry (DXA) for the femoral neck, lumbar spine, and trochanter and quantitative bone ultrasound (QUS) for the phalanx. The MCI was calculated via the Klemetti index from panoramic radiographs. Results: According to the Klemetti index classification, lower QUS measurements in the phalanx and DXA measurements in the femoral neck, trochanter, and lumbar spine were found in women with poorer mandibular cortical bone quality. Our results revealed that, compared with moderate cortical erosion, all the BMD measures had better AUCs when identifying severe cortical erosion. Moreover, femoral neck BMD had the largest area under the curve (AUC = 0.719) for detecting severe mandibular cortical erosion, suggesting a cut-off of <0.703 gr/cm². Finally, predictor analysis of osteoporosis revealed that moderate and severe mandibular cortical erosion, compared with an uninjured mandibular cortical area, was independently associated with a diagnosis of osteoporosis. Conclusions: In conclusion, MCI was associated with BMD measurements assessed by QUS and DXA in various bone regions. Our results suggest that the Klemetti index could be used as a predictor of osteoporosis and fracture risk. Full article

Compared to vibration sensors, microphones offer several advantages, including non-contact detection, high sensitivity, low cost, and ease of installation. To address the challenges posed by the complex components and significant interference in rolling bearing sound signals, we proposed a fault diagnosis method for rolling bearing acoustic signals based on Secretary Bird Optimization Algorithm (SBOA)-optimized Feature Mode Decomposition (FMD). Initially, a microphone is utilized to collect sound data while the bearing operates, followed by the application of S-FMD (Secretary Bird Optimization Algorithm-optimized Feature Mode Decomposition) to decompose the sound signal and extract components that may contain fault information related to the bearing. The SBOA is employed to adaptively optimize four influencing parameters of FMD: mode number n, filter length L, frequency band cutting number K, and cycle period m. By minimizing envelope entropy as the objective function, we achieve FMD of the bearing sound signal with the assistance of the SBOA. Additionally, this paper introduces an Integrated Signal Evaluation Index (ISEI) to extract potential bearing failure characteristics from the filtered components. Simulation experiments and test results indicate that, compared to Empirical Mode Decomposition, Complementary Ensemble Empirical Mode Decomposition, fixed-parameter FMD, and adaptive variational mode decomposition methods, the proposed approach more effectively extracts weak characteristic information related to early faults in bearing sound signals. Full article

A multilayer structure is a type of construction consisting of outer layers and a core, which is mainly characterized by high strength and specific stiffness, as well as the ability to dampen vibration and sound. This structure combines the high strength of traditional materials (mainly metals) and composites. Currently, sandwich structures in any configurations (types of core) are one of the main directions of technology development and research. This paper evaluates the surface quality of II- and III-layer sandwich structures that are a combination of aluminum alloy and CFRP (Carbon Fiber-Reinforced Polymer) after the machining. The effect of depth of cut (a_e) on the surface roughness of the II- and III-layer sandwich structures after the milling process was investigated. The surface homogeneity was also investigated. It was expressed by the I_Ra and I_Rz surface homogeneity indices formed from the Ra and Rz surface roughness parameters measured separately for each layer of the materials forming the sandwich structure. It was noted that the lowest surface roughness (Ra = 0.03 µm and Rz = 0.20 µm) was obtained after the milling of the II-layer sandwich structure using a_e = 0.5 mm, while the highest was obtained for the III-layer structure and a_e = 1.0 mm (Ra = 1.73 µm) and a_e = 0.5 mm (Rz = 10.98 µm). The most homogeneous surfaces were observed after machining of the II-layer structure and using the depth of cut a_e = 2.0 mm (I_Ra = 0.28 and I_Rz = 0.06), while the least homogeneous surfaces were obtained after milling of the III-layer structure and the depths of cut a_e = 0.5 mm (I_Ra = 0.64) and a_e = 2.0 mm (I_Rz = 0.78). The obtained results may be relevant to surface engineering and combining hybrid sandwich structures with other materials. Full article