Search Results (126)

During the process of flexible aerial refueling, the flexible structure of the hose drogue assembly is affected by internal and external interference, such as docking maneuvering, deformation of the hose, attitude changes, and body vibrations, causing the hose to swing and the whipping phenomenon, which greatly limits the success rate and safety of aerial refueling operations. Based on a 2.4 m transonic wind tunnel, high-speed wind tunnel test technology of a flexible aerial refueling hose–drogue system was established to carry out experimental research on the coupling characteristics of aerodynamics and multi-body dynamics. Based on the aid of Videogrammetry Model Deformation (VMD), high-speed photography, dynamic balance, and other wind tunnel test technologies, the dynamic characteristics of the hose–drogue system in a high-speed airflow and during the approach of the receiver are obtained. Adopting flexible multi-body dynamics, a dynamic system of the tanker, hose, drogue, and receiver is modeled. The cable/beam model is based on an arbitrary Lagrange–Euler method, and the absolute node coordinate method is used to describe the deformation, movement, and length variation in the hose during both winding and unwinding. The aerodynamic forces of the tanker, receiver, hose, and drogue are modeled, reflecting the coupling influence of movement of the tanker and receiver, the deformation of the hose and drogue, and the aerodynamic forces on each other. The tests show that during the approach of the receiver (distance from 1000 mm to 20 mm), the sinking amount of the drogue increases by 31 mm; due to the offset of the receiver probe, the drogue moves sideways from the symmetric plane of the receiver. Meanwhile, the oscillation magnitude of the drogue increases (from 33 to 48 and from 48 to 80 in spanwise and longitudinal directions, respectively). The simulation results show that the shear force induced by the oscillation of the hose and the propagation velocity of both the longitudinal and shear waves are affected by the hose stiffness and Mach number. The results presented in this work can be of great reference to further increase the safety of aerial refueling. Full article

In high-elevation mining areas, the roadbeds of certain surface ore haul roads are predominantly composed of sandstone. These sandstones are exposed to cold climatic conditions for long periods and are highly susceptible to erosion by the effects of freeze–thaw, which can degrade their support properties. This paper investigates the mechanism of strength deterioration of sandstone containing prefabricated cracks under cyclic loading and unloading after experiencing freeze–thaw. Sandstone specimens containing prefabricated cracks were prepared and subjected to 0, 20, 40, 60, and 80 freeze–thaw cycle tests. The strength changes were tested, and the crack extension process was analyzed using numerical simulation techniques. The study results show the following: 1. The wave propagation speed within the sandstone is more sensitive to changes in the number of freeze–thaw cycles. In contrast, mass damage shows significant changes only when more freeze–thaw cycles are experienced. 2. As the number of freeze–thaw cycles increases, the frequency of energy release from the numerical model accelerates. 3. The trend of the Cumulative Strain Difference (${\epsilon }_c$) reflects that the plastic strain difference between numerical simulation and actual measurement gradually decreases with increasing stress cycle level. 4. With the increase in freeze–thaw cycles, the damage morphology of the specimen undergoes a noticeable change, which is gradually transformed from monoclinic shear damage to X-shaped conjugate surface shear damage. 5. The number of tensile cracks dominated throughout the cyclic loading and unloading process, but with the increase in freeze–thaw cycles, the percentage of shear cracks increased. As the freeze–thaw cycles increase, sandstones are more inclined to undergo shear damage. These findings are important guidelines for road design and maintenance in alpine mining areas. Full article

Medical phantoms are essential to imaging calibration, clinician training, and the validation of therapeutic procedures. However, most ultrasound phantoms prioritize acoustic realism while neglecting the viscoelastic and anisotropic properties of fibrous soft tissues. This gap limits their effectiveness in modeling realistic biomechanical behavior, especially in wave-based diagnostics and therapeutic ultrasound. Current materials like gelatine and agarose fall short in reproducing the complex interplay between the solid and fluid components found in biological tissues. To address this, we developed a soft, anisotropic composite whose dynamic mechanical properties resemble fibrous biological tissues such as skin and skeletal muscle. This material enables wave propagation and vibration studies in controllably anisotropic media, which are rare and highly valuable. We demonstrate the tunability of damping and stiffness aligned with fiber orientation, providing a versatile platform for modeling soft-tissue dynamics and validating biomechanical simulations. The phantoms achieved Young’s moduli of 7.16–11.04 MPa for skin and 0.494–1.743 MPa for muscles, shear wave speeds of 1.51–5.93 m/s, longitudinal wave speeds of 1086–1127 m/s, and sound absorption coefficients of 0.13–0.76 dB/cm/MHz, with storage, loss, and complex moduli reaching 1.035–6.652 kPa, 0.1831–0.8546 kPa, and 2.138–10.82 kPa. These values reveal anisotropic response patterns analogous to native tissues. This novel natural fibrous composite system affords sustainable, low-cost ultrasound phantoms that support both mechanical fidelity and acoustic realism. Our approach offers a route to next-gen tissue-mimicking phantoms for elastography, wave propagation studies, and dynamic calibration across diverse clinical and research applications. Full article

Background/Objectives: Recently, shear wave elastography (SWE) and dispersion (SWD) targeting the pancreas have been attempted as noninvasive procedures to evaluate personalized conditions. This study aimed to analyze the feasibility of utilizing them for evaluating the individual need of introducing insulin therapy, combined with the C-peptide index (CPI), in patients with type 2 diabetes mellitus (T2DM). Methods: This study involved 51 patients with T2DM aged ≥20 years old and 20 control subjects without impaired glucose tolerance (CTRL). T2DM were divided into non-insulin-treated (non-INS) and insulin-treated (INS) groups. Their background data, shear wave speed (SWS), and dispersion slope (DS) of the pancreas were obtained on the same day. Results: Pancreatic SWS was higher in T2DM than in CTRL (p < 0.0001), with an AUC of 0.840, sensitivity of 89.1%, and specificity of 70.6%, using a Youden index cutoff of 1.31 m/s. INS and non-INS were discriminated with the cutoff value of 1.70 m/s (p = 0.031, AUC 0.736, sensitivity 55.6% and specificity 89.2%). Pancreatic DS of INS and non-INS was 13.52 and 12.16 (m/s)/kHz, respectively (p = 0.046). Using 12.38 (m/s)/kHz as the cutoff, AUC was 0.718, with sensitivity of 88.9%, specificity of 56.8% and negative predictive value of 95.5%. CPI had AUC of 0.724, sensitivity of 66.7% and specificity of 83.3% with the cutoff of 0.63. With combination of SWS and CPI, all patients with SWS < 1.70 m/s and CPI > 0.476 belonged to non-INS. Conclusions: Simultaneous non-invasive SWE and CPI evaluation showed the feasibility for estimating personalized insulin initiation needs in T2DM, integrating biophysical and hormonal perspectives. Further investigation with a larger, multi-center study population is warranted to enhance the level of evidence. Full article

This study addresses the dynamic response control of deep-water jacket offshore platforms under typhoon and misaligned wave loads by proposing a Tuned Mass Damper (TMD)-based vibration suppression strategy. Typhoon loading is predicted using the Weather Research and Forecasting (WRF) model to simulate maximum wind speed and direction, a customized exponential wind profile fitted to WRF results, and a spectral model calibrated with field-measured data. Correspondingly, typhoon wave loading is calculated using stochastic wave theory with the Joint North Sea Wave Project (JONSWAP) spectrum. A rigorous Finite Element Model (FEM) incorporating soil–structure interaction (SSI) and water-pile interaction is implemented in the Opensees platform. The SSI is modeled using nonlinear Beam on Nonlinear Winkler Foundation (BNWF) elements (PySimple1, TzSimple1, QzSimple1). Numerical simulations demonstrate that the TMD effectively mitigates dynamic platform responses under aligned typhoon and wave conditions. Specifically, the maximum deck acceleration in the X-direction is reduced by 26.19% and 31.58% under these aligned loads, with a 17.7% peak attenuation in base shear. For misaligned conditions, the TMD exhibits pronounced control over displacements in both X- and Y-directions, achieving reductions of up to 29.4%. Sensitivity studies indicated that the TMD’s effectiveness is more significantly impacted by stiffness detuning than mass detuning. It should be emphasized that the effectiveness verification of linear TMD is limited to the load levels within the design limits; for the load conditions that trigger extreme structural nonlinearity, its performance remains to be studied. This research provides theoretical and practical references for multi-directional coupled vibration control of deep-water jacket platforms in extreme marine environments. Full article

Snow avalanches occur in snow-covered highland mountains and represent one of the most significant natural hazards pertaining to the field of geoscience. Although some insight into the formation of avalanches has been provided, a comprehensive overview or critical review of the latest research is currently lacking. This paper reviews recent advances on the formation process of dry slab avalanches and provides a guiding framework for further research. The formation of avalanches is the consequence of a series of fracture processes in the snowpack, which is usually induced by the failure of a weak layer underlying a snow slab layer. The parameters at each stage of avalanches’ formation are reviewed from theoretical, experimental and simulation perspectives. In terms of the onset of crack propagation, the understanding of the mechanical process has gone through a transition from shear theory, to the anticrack model and supershear. The critical length shows divergent trends with snowpack parameters and slope angles, and there is a lack of consensus in different models. The specific fracture energy is also an essential component in determining fracture propagation. Within cracks’ dynamic propagation, the crack propagation speed includes both the sub-Rayleigh regime and supershear. The crack speed exceeds the shear wave speed in the supershear mode. When the crack propagation reaches a specific distance, the slab undergoes a tensile fracture and the cracking’s arrest. The numerical simulation allows a complete reproduction of the initial failure, the crack’s dynamic propagation and slab fracture. In the future, a unified model is necessary through refining the formative mechanism and integrating it with the avalanche flow. This work offers a comprehensive understanding of the mechanics of the formation and release of avalanches, useful for both modelers and experimentalists. Full article

During winter, strong winds and waves significantly enhance sediment resuspension in the Yellow River Delta. Based on the continuous and high-resolution data on water levels, wave heights, current velocities, and echo intensities collected by the Acoustic Doppler Current Profiler at different depths (5 m and 12 m) in the northern Yellow River Delta simultaneously, this study investigated the sediment resuspension during gale events and tranquil conditions. In deeper waters (12 m), the suspended sediment volume concentration (SSVC) showed a strong correlation with current speed (r = 0.74), while in shallower waters (5 m), the SSVC correlated more closely with wave height (r = 0.72). The thorough analysis of gale events revealed that the maximum wave heights during northwest gales were 23.80% and 34.59% lower than that during northeast gales at deep and shallow stations, respectively, primarily due to the longer wind fetch associated with northeast gales. Conversely, the maximum current velocities during northwest gales were 10.34% and 37.31% higher than that during northeast gales at deep and shallow stations. In deeper waters, the maximum wave–current induced shear stress $({\tau }_{cw}$) and SSVC during northwest gales were 30.38% and 3.70% higher than those during northeast gales, highlighting current-driven resuspension. In contrast, in shallower waters, the maximum ${\tau }_{cw}$ and SSVC during northeast gales were 47.35% and 4.94% higher than those during northwest gales, underscoring the dominance of wave-induced resuspension. Full article

Introduction: Shear wave elastography (SWE) has been widely used to assess the mechanical properties of peripheral nerves, including the sciatic nerve. However, the relationship between sciatic nerve stiffness and posterior chain flexibility remains unclear. Therefore, we aimed to examine differences in sciatic nerve stiffness and shear wave speed (SWS) based on limb dominance and hamstring flexibility, and to explore their association with posterior chain mobility assessed through AKE and ASLR tests in healthy individuals. Methods: An observational study was conducted on 25 healthy, physically active participants (49 lower limbs). Sciatic nerve stiffness was measured using SWE at a standardized location in the posterior thigh. Posterior chain flexibility was assessed using the Active Knee Extension (AKE) and Active Straight Leg Raise (ASLR) tests. Participants were categorized based on hamstring flexibility, and comparisons were made between dominant and non-dominant limbs. Results: Participants with limited hamstring flexibility exhibited significantly higher AKE and ASLR values (p < 0.001) and showed an increased stiffness and SWS towards greater sciatic nerve (p = 0.05), although correlations between SWE values and flexibility tests were not significant. No significant differences were found between dominant and non-dominant limbs in AKE (p = 0.28), ASLR (p = 0.47), SWE (p = 0.38), or SWS (p = 0.34) values. Conclusions: Although no significant correlations were found between SWE parameters and flexibility tests, individuals with limited posterior chain mobility exhibited higher sciatic nerve stiffness in healthy participants. Full article

Background/Objectives: The quadratus lumborum (QL) muscle is a key structure involved in patients with low back pain (LBP). Since the discriminative capability of morphological descriptors is uncertain and considering the high prevalence of myofascial trigger points and the poor reliability of manual palpation in this condition, developing a reliable procedure for assessing the QL’s tenderness is needed for facilitating the diagnosis and monitoring changes over time. We aimed to analyze the intra- and inter-examiner reliability of SWE for calculating the QL tenderness in patients with LBP. Methods: Using a convex transducer, longitudinal shear wave elastography (SWE) images of the QL muscle were acquired bilaterally twice in 52 volunteers with moderate LBP and disability by one experienced examiner and one novel examiner to measure shear wave speed and Young’s modulus as stiffness metrics. Results: Intra-examiner reliability estimates demonstrated high consistency independently of the examiner’s experience (intraclass correlation coefficients (ICCs) > 0.930) for both metrics. However, experienced examiners showed smaller minimal detectable changes. Additionally, inter-examiner reliability was lower, with ICCs ranging from 0.57 to 0.68, and significant differences in mean values between examiners (p < 0.01) were found. Conclusions: This procedure exhibited excellent intra-examiner reliability for assessing QL muscle stiffness in patients suffering LBP, indicating high repeatability of measurements when performed by the same examiner. In addition, experienced examiners demonstrated greater sensitivity in detecting real changes not attributed to measurement errors. However, inter-examiner reliability was moderate, highlighting the need for consistent examiner use to avoid measurement variability and averaging multiple measurements to enhance the accuracy. Full article

The thumb and transverse carpal ligament (TCL) have an anatomical connection and biomechanical interaction. Understanding the in vivo mechanics of this interaction is valuable for the study of hand and wrist biomechanics. The objective of this study was to quantify this biomechanical interaction using shear wave elastography. The hands and forearms of healthy volunteers (n = 11) were submerged in water. A pinch meter was placed between the thumb and index finger. An ultrasound transducer was placed at the distal carpal tunnel to image the cross section. Ultrasound and shear wave elastography images were taken for pinch forces of 0, 10, 20, and 30 N. The shear wave speed (SWS) was measured on the TCL. Repeated measures ANOVAs were used for comparisons (α = 0.05). SWS increased with increasing pinch force (p = 0.007). The SWS changed by 0.27 m/s [95% CI: (−0.01 m/s, 0.55 m/s); p = 0.0572], 0.54 m/s [95% CI: (0.07 m/s, 1.01 m/s); p = 0.0294] and 0.83 m/s [95% CI: (0.27 m/s, 1.39 m/s); p = 0.0079] when the pinch force was increased from 0 to 10 N, 0 to 20 N and 0 to 30 N. TCL SWS increases with in vivo loading. Full article

Shear wave elastography (SWE) is an advanced ultrasound technique that assesses tissue stiffness by measuring shear wave speed (SWS) produced after an acoustic impulse. It includes bidimensional (2D-SWE) and focal point (pSWE) methods, allowing qualitative and quantitative analysis of tissue stiffness. This study aimed to describe the elastographic features of testicular abnormalities in dogs, supported by histological findings. Eighteen dogs with testicular abnormalities underwent B-mode ultrasound, power and color Doppler ultrasound, 2D-SWE, and pSWE before orchiectomy. Five cryptorchid testes were excluded and thirty-one testes (12 normal, 7 with leydigomas, 6 with seminomas, 1 with a round cell tumor, and 5 with orchitis) were examined. Normal testes, lesions, and adjacent healthy tissues (no evident ultrasound changes, NEUC) were sampled. Testicular abnormalities presented SWS values of 1.05–4.89 m/s (2D-SWE) and 1.35–5.31 m/s (pSWE). Significant differences were observed among normal testes, NEUC areas, and those with orchitis, leydigomas, and seminomas by both 2D-SWE and pSWE. Normal testes were significantly softer than ones with leydigomas, seminomas, and orchitis, and NEUC areas also had different SWS values compared to those with tumors and orchitis (p < 0.05). However, SWE techniques lacked specificity in differentiating between orchitis and tumors. Diagnostic accuracy of SWE techniques for testicular lesions remains challenging and requires further investigation to fully address its clinical potential. Full article

Alcohol-related liver disease (ALD) is a major cause of global morbidity and mortality, progressing from steatosis to cirrhosis and hepatocellular carcinoma. While liver biopsy remains the gold standard for identifying liver disease, non-invasive methods like shear wave dispersion (SWD) elastography offer promising alternatives. This scoping review evaluates SWD’s potential in the study of ALD, comparing it to metabolic dysfunction-associated steatotic liver disease (MASLD). SWD measures changes in shear wave speed in relation to liver viscosity and necroinflammation. Studies in MASLD suggest that SWD effectively correlates with fibrosis and inflammation stages, but its application in ALD remains underexplored. Both ALD and MASLD show similar inflammatory and fibrotic pathways, despite having different etiologies and histological features. This review emphasizes the necessity to identify ALD-specific SWD reference values and verify SWD’s ability to improve diagnosis and disease progression. Prospective studies comparing SWD findings with histological benchmarks in ALD are essential for establishing its clinical utility. Incorporating SWD into clinical practice could revolutionize the non-invasive evaluation of ALD, offering a safer, cost-effective, and repeatable diagnostic tool. Full article

Multiparametric ultrasound (mpUS) enhances prostate cancer (PCa) diagnosis by using multiple imaging modalities. Tissue-mimicking materials (TMM) phantoms, favoured over animal models for ethical and consistency reasons, were created using polyvinyl alcohol (PVA) with varying molecular weights (Mw). Methods: Four PVA samples, varying in Mw with constant concertation, were mixed with glycerol, silicon carbide (SiC), and aluminium oxide (Al₂O₃). Phantoms with varying depth and inclusion sizes were created and tested using shear-wave elastography (SWE). An mpUS phantom was developed to mimic prostate tissue, including isoechoic and hypoechoic inclusions and vessels. The phantom was scanned using supersonic ultrasound, strain elastography, and Doppler ultrasound. Validation was performed using radical prostatectomy data and shear-wave elastography. Results: The acoustic properties varied with enhancers like glycerol and Al₂O₃. Low Mw PVA samples had a speed of sound ranging from 1547.50 ± 2 to 1553.70 ± 2.2 m/s and attenuation of 0.61 ± 0.062 to 0.63 ± 0.05 dB/cm/MHz. High Mw PVA samples ranged from 1555 ± 2.82 to 1566 ± 4.5 m/s and 0.71 ± 0.02 to 0.73 ± 0.046 dB/cm/MHz. Young’s modulus ranged from 11 ± 2 to 82.3 ± 0.5 kPa across 1 to 10 freeze-thaw cycles. Inclusion size, depth, and interaction statistically affect the SWE measurements with p-value = 0.056327, p-value = 8.0039 × 10⁻⁸, and p-value = 0.057089, respectively. SWE showed isoechoic inclusions, prostate tissue, and surrounding tissue only. The Doppler velocity was measured in three different inner diameters. Conclusion: PVA mixed with enhancer materials creates an mpUS phantom with properties that mimic normal and abnormal prostate tissue, blood vessels, and soft tissue, facilitating advanced diagnostic training and validation. Full article

Objectives: The aim of this study was to determine and compare the capability of several B-mode ultrasound (US) and shear wave elastography (SWE) metrics to differentiate subjects with chronic non-specific neck pain from asymptomatic subjects. Methods: A diagnostic accuracy study recruiting a sample of patients with chronic neck pain and asymptomatic controls was conducted. Data collection included sociodemographic information (i.e., gender, age, height, weight and body mass index), clinical information (pain intensity assessed using the Visual Analogue Scale and pain-related disability using the Neck Disability Index) and B-mode ultrasound and shear wave elastography features of the cervical multifidus muscle (cross-sectional area, perimeter, mean echo intensity, fat infiltration, shear wave speed and Young’s modulus). After analyzing between-group differences for left/right sides, cases and controls, and males and females, the area under the receiver operating characteristic (ROC) curve, the optimal cut-off point, the sensitivity, the specificity, the positive likelihood ratio (LR) and negative LR for each metric were calculated. A total of 316 individuals were recruited in this study (n = 174 cases with neck pain and n = 142 asymptomatic controls). Results: No significant differences (p > 0.05) were found between cases and controls for most variables, except for fatty infiltration, which was significantly higher in chronic neck pain cases (p < 0.001). Gender differences were significant across all US and SWE metrics (all, p < 0.001 except p = 0.015 for fatty infiltrates). A slight asymmetry was observed between the left and right sides for area (p = 0.038). No significant interactions between group, gender and side (all metrics, p > 0.008) were identified. Fatty infiltration was the most effective discriminator, with a ROC value of 0.723, indicating acceptable discrimination. The optimal cut-off point for fatty infiltration was 25.77, with a moderate balance between sensitivity (59.8%) and specificity (20.5%). However, its positive likelihood ratio (LR) of 0.75 suggests limited usefulness in confirming the condition. Conclusions: Fatty infiltration was significantly higher in individuals with chronic idiopathic neck pain compared to those without symptoms, while other muscle metrics were similar between both groups. However, since fat infiltration had moderate diagnostic accuracy and the other metrics showed poor discriminatory power, US cannot be used solely to discriminate patients with idiopathic neck pain. Full article

The solar atmosphere is a complex, coupled, highly dynamic plasma environment, which shows rich structuring due to the presence of gravitational and magnetic fields. Several features of the Sun’s atmosphere can serve as guiding media for magnetohydrodynamic (MHD) waves. At the same time, these waveguides may contain flows of various magnitudes, which can then destabilise the waveguides themselves. MHD waves were found to be ubiquitously present in the solar atmosphere, thanks to the continuous improvement in the spatial, temporal, and spectral resolution of both space-born and ground-based observatories. These detections, coupled with recent theoretical advancements, have been used to obtain diagnostic information about the solar plasma and the magnetic fields that permeate it, by applying the powerful concept of solar magneto-seismology (SMS). The inclusion of asymmetric shear flows in the MHD waveguide models used may considerably affect the seismological results obtained. Further, they also influence the threshold for the onset of the Kelvin–Helmholtz instability, which, at high enough relative flow speeds, can lead to energy dissipation and contribute to the heating of the solar atmosphere—one of the long-standing and most intensely studied questions in solar physics. Full article