Blast-induced vibrations from newly constructed tunnels may adversely affect adjacent existing tunnel structures. To ensure the safety of the existing tunnel, it is essential to investigate its dynamic response under blast disturbances. Based on an expansion project for a highway double-arch tunnel, this study employed the dynamic finite element program LS-DYNA to analyze the vibration velocity and effective stress in the tunnel lining subjected to blast vibrations. The distribution characteristics of vibration velocity and effective stress at different locations of tunnel lining were obtained. A relationship model between the peak particle velocity (PPV) and effective stress was established. According to the maximum tensile stress theory, a safety criterion based on vibration velocity was determined. To facilitate field monitoring, a correlation between the vibration velocity at the arch waist and foot was established, leading to a proposed safety threshold for the arch foot vibration velocity. Furthermore, a statistical relationship was developed between the charge weight per hole in the upper bench cut and the vibration velocity at the arch foot to guide blasting design. Using the arch foot vibration velocity as the safety standard, the maximum permissible charge weight to ensure the structural safety of the existing tunnel was recommended.

With the rapid expansion of high-speed railway (HSR) networks, the vibration impact on adjacent energy infrastructure has become a critical safety concern. However, existing research lacks a comprehensive evaluation of buried sour gas pipelines specifically in tunnel-undercrossing scenarios. This research investigates the dynamic response characteristics of a sour natural gas pipeline under train-induced vibration loads using a case study in Chongqing. A three-dimensional dynamic coupling model of the track lining soil pipeline system was established based on FLAC-3D. The study innovatively quantifies the vibration superposition effect during bidirectional train encounters and assesses safety using fatigue life and velocity thresholds. Results indicate that pipeline vibration is predominantly vertical. As train speed increases from 250 km/h to 350 km/h, the response exhibits a non-linear rapid growth within the 300–350 km/h range. Under bidirectional encounters, the peak displacement reaches 2.00 times that of unilateral passage, representing the most critical load condition. The maximum peak vibration velocity is 0.1 mm/s, far below the 2 mm/s safety threshold, ensuring structural integrity under current operational standards.

This study evaluated the effectiveness of dynamic ultrasound in diagnosing rotational vertebral artery syndrome (RVAS) and its potential as a screening tool. From January 2022 to September 2024, 98 participants (49 suspected RVAS patients and 49 asymptomatic controls) underwent vertebral artery ultrasound in neutral and rotated head positions. Blood flow velocity and resistance index (RI) changes in the V2 and V3 artery segments were compared. Diagnostic performance and compression thresholds were assessed using independent t tests and receiver operating characteristic (ROC) analysis. An additional pilot study group of 10 participants (5 patients with suspected RVAS and 5 asymptomatic controls) was included to assess the diagnostic thresholds and the role of dynamic ultrasound in RVAS detection. Significant hemodynamic changes were observed in the RVAS group after neck rotation but not in controls. In the V2 segment, velocity decreased from 51.76 ± 14.64 cm/s (neutral) to 44.61 ± 21.01 cm/s (rotated, P = .014). In the V3 segment, velocity increased from 69.37 ± 18.32 cm/s (neutral) to 161.18 ± 51.32 cm/s (rotated, P < .001). RI rose from 0.69 ± 0.06 to 0.76 ± 0.15 (P = .001). ROC analysis identified thresholds of V3 velocity >74.68 cm/s and V3 RI >0.71 for RVAS diagnosis (area under the curve = 0.80, sensitivity = 67.3%, specificity = 85.7%). In the pilot study group, the sensitivity was 80%, and the specificity was 100%. Dynamic ultrasound effectively detects positional hemodynamic changes and serves as a valuable tool for RVAS diagnosis. Identified thresholds support its clinical utility, advocating broader adoption to improve early detection and management.

Physics-based unified formulation for predicting clear-water equilibrium scour depth and scour threshold velocity around piles

ABSTRACTThe primary aim of this study was to generate sport‐specific movement category velocity thresholds for elite rugby sevens male and female players. Match activity data were collected via Global Positioning Systems (GPS) (10 Hz) from 19 male and 11 female players during 88 competitive international fixtures during the 2022/2023 and 2023/2024 seasons. A two‐stage unsupervised clustering method was applied. The elbow method, a technique used to determine the optimal number of clusters in a dataset, was first applied to identify the number of movement categories. Spectral clustering was then used to define the velocity thresholds corresponding to each category. For both male and female rugby sevens, four movement categories were identified with varying velocity thresholds. The male movement category velocity thresholds were low (0.0–2.05 m.s−1), moderate (2.06–4.26 m.s−1), high (4.27–7.20 m.s−1) and very high (> 7.20 m.s−1). Although the female movement category velocity thresholds were low (0.0–1.87 m.s−1), moderate (1.88–3.74 m.s−1), high (3.75–5.97 m.s−1) and very high (> 5.97 m.s−1). A comparison of the total distance covered in the respective gender‐specific zones revealed that females covered a significantly less distance in the low‐velocity movement category (p = 0.02) and a significantly more distance in the very‐high‐velocity movement category (p < 0.001). This work informs customised movement categories that allow for better physical load assessments in male and female rugby sevens and the provision of sport‐specific and gender‐specific conditioning programmes.

The invention of telescopic blade technology marks a significant step in wind turbine innovation by enabling dynamic adjustment of blade radius in response to changing wind conditions. Since its proof of concept in 2002, radius control has relied on data from conventional fixed-blade turbines, requiring costly prototype fabrication at the initial step in every new telescopic blade design. The dependency on fixed-blade data presents a gap in cost-effective design strategies. This study proposes an alternative analytical framework that eliminates the need for preliminary fixed-blade prototypes. The method introduces an alternative radius adjustment function and investigates the role of turbine resistive mass in determining critical velocity points. Two theoretical models are developed: a rotating lever model, which conceptualizes the turbine as a lever machine comparing effective wind force against resistive load, and a wheel–axle model, which examines the effective cross-sectional interaction between wind particles and the rotor. The findings indicate that the models can reliably predict critical operational velocities (cut-in, rated, and cut-out) without the need for extensive field trials. By deriving analytical relationships between turbine design parameters and velocity thresholds, the models provide a low-cost, generalizable approach to telescopic blade design. The results demonstrate that optimal generator performance is achieved when the rated angular velocity of the turbine aligns with the site’s average wind speed. The broader implication of this work is a cost-efficient pathway for developing site-specific telescopic turbines, offering design simulation and performance optimization prior to fabrication.

Does a Single Measurement of the Optimal Minimum Velocity Threshold Enable Accurate One-Repetition Maximum Estimations Over Time? The Effect of Training and Detraining

This study employs reactive molecular dynamics (MD) simulations to investigate how key operating conditions, such as loading pressure, temperature, and sliding speed, influence the morphological evolution of iron oxide asperities lubricated by sodium silicate glass at increased temperatures. We systematically analyze the formation of wear particles, atom transfer, worn surface area, and tribological responses, such as shear stress and the coefficient of friction (CoF). Notably, this work presents, for the first time, a detailed investigation of asperity wear evolution as a function of sliding distance. The results show that the number of wear nanoparticles, the number of transferred atoms, and worn area differences all increase with sliding distance with their growth rate peaking at a loading pressure before decreasing. These metrics increase with temperature but exhibit a nonmonotonic trend with sliding speed, initially decreasing before reversing beyond a threshold velocity. Consistent with prior MD findings, shear stress increases while the CoF decreases under higher pressures. Conversely, increasing temperatures lead to a nonlinear reduction in both shear stress and the CoF. Interestingly, variations in sliding speed have a minimal impact on the CoF and shear stress. This work provides fresh insights into the wear behavior of lubricated asperities under extreme conditions, with implications for high-temperature tribological applications.

Traditional monitoring methods often fail to capture the complex kinematics of slow-moving landslides. This study proposes a novel dual-parameter instability criterion integrating displacement vector angles (DVA) and velocity thresholds for landslide stability assessment. Persistent Scatterers InSAR (PSInSAR) technique is used to obtain the displacement information in the Wudongde area. A physics-based early-warning framework is established to quantify spatiotemporal deformation patterns. According to the proposed dual-parameter instability criterion, the results show that when DVA exceeds 26.59° and the velocity exceeds 120 mm/year, the landslide enters the sliding deformation stage. This paper provides a robust tool for regional landslide risk management.

This study presents a comprehensive nonlinear dynamic analysis of curved sandwich beams subjected to high-velocity moving point loads, focusing on their buckling behavior. The sandwich structure comprises carbon nanotube (CNT)-reinforced nanocomposite face sheets and a closed-cell foam core. The effective properties of the nanocomposite faces are determined using the modified rule of mixtures, while the mechanical behavior of the foam core accounts for cell-wall bending, face stretching, and the internal gas pressure, providing a realistic representation of its nonlinear response. The third-order shear deformation theory (TSDT) is adopted to capture transverse shear effects, rotary inertia, and to satisfy the traction-free boundary conditions on the outer surfaces of the beam. Geometric nonlinearity is incorporated through the von Kármán strain-displacement relations. The total potential energy of the system is formulated and discretized using a nonlinear Ritz-based approach, leading to a set of governing equations of motion. These equations are integrated in the time domain using the Hilber–Hughes–Taylor (HHT) method, which enhances numerical stability and introduces controllable numerical dissipation for high-frequency response components, which makes it well-suited for nonlinear transient dynamics. The resulting nonlinear algebraic systems at each time step are solved iteratively using the Newton–Raphson method, ensuring convergence under strong geometric nonlinearities. Furthermore, the Budiansky instability criterion is employed to determine the critical load magnitude and velocity thresholds for dynamic buckling initiation. The proposed formulation effectively captures the complex interaction between geometric nonlinearity, advanced material behavior, and dynamic loading, offering valuable insights into the instability mechanisms of curved sandwich nanocomposite structures under transient localized excitations.

Naclerio, F, Larumbe-Zabala, E, Chapman, M, Gonzalez-Frutos, P, and Triplett, NT. Comparable workout output by using velocity feedback or perceived exertion in male and female recreationally resistance trained individuals. J Strength Cond Res XX(X): 000-000, 2025-We compared an objective (velocity feedback [VEL]) vs. a subjective (rating of perceived exertion [RPE]) autoregulatory method to estimate velocity drop thresholds associated with low (10%), moderate (20%) metabolic fatigue, and muscular endurance (40%) during continuous sets in the back squat (BSQ) exercise using either 50% or 75% of the 1 repetition maximum (1RM). After five sessions of familiarization and determining the 1RM, 19 male subjects (24.5 ± 6 years) and 9 female subjects (30.4 ± 8 years) underwent two identical 6-day testing sessions over 2 weeks (12 sessions) using the VEL (first 6 sessions) or the RPE method (last 6 sessions). The assessments of velocity thresholds and relative loads were randomized for each 6-day testing period. The average velocity (AV) and the OMNI-RES (0-10) scale scores were measured for every repetition of each set. Under VEL, sets ended after completing two consecutive repetitions below the target threshold. A linear mixed-effects model setting velocity thresholds, method, and their interaction as fixed effects, and subjects as random components, was conducted. Although no significant differences between methods were identified for the percentage of velocity decrease and the total number of repetitions completed per set, compared with VEL, under the RPE method, fewer repetitions were completed below the thresholds for both 50 and 75% 1RM (p < 0.01 and g > 1 in all cases). In conclusion, both methods, VEL and RPE, seem useful for estimating velocity changes during continuous sets of BSQ. However, the RPE method allowed for fewer unnecessary repetitions when squatting until 10, 20, and 40% of velocity decrease.

Fitas, A, Gomes, M, Santos, P, Pezarat-Correia, P, and Mendonca, GV. Sex differences in the back-squat one-repetition maximum estimation accuracy relying on the average optimal minimum velocity threshold. J Strength Cond Res XX(X): 000-000, 2025-The prediction of 1-repetition maximum (1RM) using the submaximal load-velocity relationship (LVR) is highly relevant in the field of strength and conditioning. The average optimal minimum velocity threshold (MVT)-velocity that minimizes the differences between actual and predicted 1RM-was recently proposed to overcome the limitations inherent to the individual optimal MVT: necessity of 1RM direct determination and the lack of knowledge regarding its longitudinal reliability. However, 1RM estimation accuracy based on this methodology has yet to be tested in female subjects. Individual LVRs of the Smith machine pause back squat were obtained in 16 male subjects and 16 female subjects. Estimations of 1RM were made based on sex specific average actual MVTs (1RM velocity) and average optimal MVTs (mean value of the individual actual and optimal MVTs). The accuracy of 1RM predictions was examined using absolute percentage error and Bland-Altman plots. Cross-validation was performed using a leave-one-out approach. Relative 1RM, the slope of the LVR, and the optimal MVT were similar in both sexes. In male subjects, 1RM estimation accuracy was similar regardless of the MVT used. In female subjects, however, the average optimal MVT reduced the absolute percentage error from 8.7 to 6.4% compared with the average actual MVT. However, wide limits of agreement (LoA) were found between actual and estimated 1RM using both approaches (∼15 and ∼10 kg, for male and female subjects, respectively). The average optimal MVT improves female subjects' 1RM estimation accuracy. Despite these findings, the width of the LoA may result in misestimations that are unacceptable for practical use.

Enhancement of disturbance on oleaginous microalgal growth applying in semi-open photobioreactors: Dynamic response of physiological characteristics, application of wastewater cultivation.

Abstract Hyperbolic encounters play a crucial role in diverse dynamical systems, from asteroid flybys ($\mu \lesssim \times {{10}^{ - 6}}$) to galaxy encounters ($0.3 \lesssim \mu \le 0.5$). This paper proposes an analytical framework for material exchange in the hyperbolic restricted three-body problem, showing that the opening of the neck region near L1​ is governed by a time-dependent energy boundary. By introducing the novel libration point energy curve (LPEC) as an analytical generalisation of the zero-velocity curve, a global energy criterion is established for material exchange between primary bodies without requiring extensive numerical integration. It is found that the derived critical velocity threshold provides a clear analytical condition for the transition between confined and exchangeable motion, while the novel concept of conditional Hill stability introduces a combined time and energy constraint determining when exchange remains dynamically feasible. Analysis reveals that increasing mass ratio reduces the conditional Hill stable domain, whereas a larger eccentricity expands it in both time and energy dimensions. In asteroid flybys, it is found that feasible spacecraft trajectories occur only when the velocity remains near the critical velocity threshold​, with periapsis being the optimal epoch for asteroid exploration. Analytical results in galaxy encounters demonstrate that higher mass ratios and periapsis passages enhance material exchange, consistent with the development of tidal bridges between galaxies. These findings provide an analytical framework that links the energy topology of hyperbolic encounters with observable transfer phenomena, offering new insight for both asteroid mission design and tidal structure formation in galaxy encounters.

ABSTRACT A physical framework is constructed to characterize the viscoelastic‐plastic response, crack damage, and ignition characteristics of polymer‐bonded explosives (PBXs) under low‐velocity impact conditions. This approach enhances the existing viscoelastic statistical crack mechanics model (Visco‐SCRAM) through multiple key advancements. Damage progression is determined using the generalized Griffith criterion for instability, focusing on the most critical (i.e., maximally unstable) crack size instead of an orientation‐averaged crack dimension. The collective effect of numerous microcracks on the dynamic mechanical response of microcrack‐containing materials is captured in a statistical sense through a dominant microcrack represented as an internal variable. A confined Steven test simulation is conducted to validate the model and to investigate the mechanical and thermal responses of PBXs. The analysis reveals that although the radius has a minimal effect on the temperature rise of the specimen, the thickness plays a significant role in determining the velocity threshold, the location of the hot spot, and the extent of temperature increase. The simulation results show that the critical impact velocities are 45 m/s for the oval projectile, 95 m/s for the flat projectile, and 24 m/s for the pin projectile. A comprehensive analysis is provided regarding the differences in temperature rise among the three types of projectiles. Moreover, the study demonstrates that frictional work is the dominant ignition mechanism during low‐velocity impacts. This research presents a new perspective for understanding and predicting the ignition behavior of PBX under such impact conditions.

Cliff-top boulder deposits are rare but striking geomorphic features found along high-energy coastlines. Their formation mechanisms—whether from storm waves or tsunamis–remain a subject of scientific debate. This study examines tsunami-induced boulder transport on the steep southern coast of Mallorca Island (Western Mediterranean), integrating detailed morphometric analysis with high-resolution simulations using a non-linear numerical model. Boulder characteristics, including volume, elevation, distance from cliff edges, and orientation, were mapped and used to compute mobilization thresholds under subaerial, submerged, and joint-bounded block (JBB) conditions. Our simulations tested 360 tsunami scenarios varying in wave height, period, and direction. Results show that wave height alone is insufficient to explain boulder transport; instead, velocity thresholds–particularly for saltation and JBB lifting—provide more accurate indicators. The model successfully replicates tsunami propagation, cliff impact, and inland flooding, revealing that only long-period, high-magnitude waves from southern directions exceed the thresholds needed to displace the observed boulders. Boulder deposits differ across the study area: smaller, higher-elevation blocks in the western sector are only mobilized by a narrow range of extreme tsunami conditions, while larger, lower-elevation eastern boulders respond to a broader spectrum. Storm wave simulations failed to reach or displace the boulders, strengthening the tsunami hypothesis. These findings highlight the critical role of numerical modeling in tsunami hazard assessment and call for re-evaluation of other cliff-top deposits globally. The methodology presented here demonstrates a robust, multidisciplinary approach to interpreting boulder emplacement and contributes to refining coastal hazard mapping in tsunami-prone regions.

On coral reefs, disturbances commonly generate legacy materials in the form of coral rubble. Rubble morphometrics and the diversity of organisms that bind rubble together can influence recovery trajectories. The quantification of rubble movement threshold velocities has been used to predict rubble bed stability, a precursor to binding. Yet empirical data on bind strength across environmental gradients are needed to inform predictions of whether bound rubble beds will experience routine bind breakage, and thus poor recovery, under varying hydrodynamic regimes. Over 18 mo, we tracked the strength of binding organisms that colonised experimental rubble pairs along environmental gradients on the Great Barrier Reef and used strength to estimate breakage velocity thresholds. The degree of contact between rubble pieces was a key determinant of bind strength, which increased over time and was weakest at inshore sheltered sites, driven by a high proportion of macroalgal binds. Bind strength was a direct reflection of the binding community, with the strongest binds by vermetid snails, bivalves, solitary ascidians, hard corals, and crustose coralline algae. For most offshore and inshore exposed sites, the threshold velocity required to break apart bound rubble increased from ~1 m s -1 after 4 mo of stability and binding succession to ~3 m s -1 by 18 mo, though these thresholds will vary with rubble morphology, arrangement and resulting interstitial spacing. These findings can be used in conjunction with time-series hydrodynamic data to predict the potential for disturbed rubble beds to recover and thus optimise the deployment of reef restoration interventions.

Abstract Large-scale hydrothermal eruptions, although rare, pose significant hazards in geothermal regions. While aquifer lithology is known to influence fluid dynamics and eruption initiation for smaller-scale events, systematic studies linking lithological properties to large-scale eruptions remain limited. Here, we investigate the role of lithological variability in priming and eruption mechanisms at Rotokawa, New Zealand. We measured petrophysical properties and conducted rapid decompression experiments on disrupted aquifer lithologies, including consolidated lacustrine silts, clay-altered vitric tuffs, silicified volcaniclastic sandstones, and silicic-argillic altered paleo-breccia. Lithologies cover a broad range of properties and fragmentation characteristics, namely, density (0.9–1.9 g/cm 3 for bulk, 2.5–3.2 g/cm 3 for skeletal), porosity (3.7–63.5%), permeability (1.2 × 10 −17 –1.2 × 10 11 m 2 ), compressional wave velocity (0.9–5.2 m/s), fragmentation threshold (2–22.5 MPa), energy density (1.3–12.8 MJ/m 3 ), and fragmentation velocity (1–160 m/s). We evaluate contrasting priming scenarios for large hydrothermal eruptions, from rapid lake drainage to influx of deep hot fluids with either localized or widespread mixing. Results indicate that widespread and efficient mixing of hot and cold fluids in clay-altered aquifer lithologies is essential to reach energy thresholds for large-scale eruptions. Lithologies that have undergone argillic alteration are mechanically weakened and promote fragmentation, whereas silicification increases fragmentation thresholds by a factor of 2–3. We propose a conceptual model for the Rotokawa eruption in which initiation and progression are governed by lithology-dependent fragmentation energies, ranging from 1.6 to 8.5 MJ m 3 in lacustrine silts and sands, 1.3–6 MJ m 3 in altered vitric tuffs, 1.6–6.5 MJ m 3 in silicified sandstones, and 1.3–12.8 MJ m 3 in paleo-breccias. These findings refine estimates of the energy required for hydrothermal eruptions and define conditions favoring large-scale events. By improving understanding of priming conditions, eruption mechanisms, and lithological susceptibility, this study enhances forecasting and hazard mitigation strategies in geothermal systems.

Abstract. Snow cornices are a common snow pattern in cold regions, and their fracture and collapse can easily trigger avalanches. Despite numerous observations and experimental simulations on their formation process, the microscopic mechanism of their initial stage of formation remains unclear. In this paper, based on wind-tunnel experiments and high-speed photography, experimental studies on the trajectory of particles surrounding the snow cornice were carried out. The experiment results reveal the distinct differences in particle size, impact velocity, and impact angle between the surface and edge of a cornice. The findings show that edge-deposited particles are generally smaller and more dendritic, attaching mainly through low-velocity saltation and mechanical interlocking, while surface deposition is dominated by larger and faster particles. The different probability distributions of impacting velocities and angles in these two regions are attributed to variations in airflow and local cornice topography. Both surface and edge regions, however, exhibit a characteristic vertical impact velocity threshold of 2–2.5 m s−1, which is the dominant parameter governing particle adherence or rebound. A static adhesion model incorporating particle morphology parameters for edge deposition was developed and experimentally validated, confirming its effectiveness in predicting the influence of particle size and shape on adhesion thresholds. Overall, this research reveals the micro-dynamics underlying initial cornice growth, providing a theoretical basis for avalanche modeling and infrastructure protection in alpine environments, as well as offering a methodological and mechanical framework for studying snow and ice adhesion in both natural and engineered systems.

Neuroinflammation and osteomyelitis in adults with Type 2 diabetes mellitus and peripheral neuropathy without and with foot lesions. What comes first?