Search Results (3,688)

To clarify the heat transfer and flow characteristics of arc plasma in a DC magnesium electrofusion furnace under short-arc conditions, a two-dimensional axisymmetric magnetohydrodynamic (MHD) model was developed. Coupled electromagnetic, thermal, and flow fields were solved using COMSOL Multiphysics 6.3, and the model was validated against Bowman’s free-arc experimental data. Results show that the arc is electromagnetically constricted into a contracted column, with high-temperature and high-velocity regions concentrated near the arc center. Unlike conventional long arcs, the short arc reaches the anode before the jet fully diffuses, causing momentum to be concentrated on the anode surface and generating pronounced pressure peaks. Higher current increases the arc temperature and jet velocity, thereby strengthening the pressure and shear stresses exerted on the molten pool. In contrast, increasing the arc length reduces the arc temperature, flow velocity, and surface forces, weakening both momentum transfer and heat transfer to the molten pool. Overall analysis reveals that arc length has a more significant effect on arc–molten pool interactions than current and is the dominant parameter governing short-arc behavior. These findings provide guidance for optimizing operating conditions and improving energy utilization in magnesium electrofusion furnaces. Full article

Accurate hemodynamic assessment is essential for characterizing vascular function and pathology. While computational fluid dynamics (CFD) provides the means to simulate blood flow, each anatomical variation requires its own dedicated simulation, which in turn demands substantial computational resources and domain expertise. Accelerating blood flow simulations to enable real-time or near real-time predictions could significantly enhance clinical decision-making and personalized treatment planning. We evaluated single and multi-case physics-informed neural networks (PINNs) in predicting steady-state blood flow in parameterized two-dimensional (2D) stenotic vascular geometries. The PINN was trained without the use of labeled data, utilizing the parameterized incompressible steady state continuity and Navier–Stokes equations. The degree of stenosis was set to vary from 20% to 60% and the Reynolds number ($Re$) from 500 to 1750. To measure the accuracy, CFD ground truth data were generated using COMSOL Multiphysics^® version 6.4. Results show that PINNs accurately predict both axial and vertical velocity fields, with low global and localized errors. Pressure predictions were generally insufficient, particularly in mild to moderate stenoses at low $Re$, with the median throat-pressure error reaching 38.8%. Pressure is anchored by a single outlet condition, and its non-dimensional scale varies by a factor of 142 across cases, so a few dominate the training objective; hard boundary-condition enforcement improved the field but not the pressure drop. These findings highlight that while current PINNs can reliably reproduce velocity fields, their ability to capture localized pressure dynamics remains limited, indicating the need for more robust formulations. Full article

Ammonia (NH₃) emissions from intensive livestock farming are a major contributor to the formation of secondary particulate matter (PM_2.5) in northern Italy, particularly during winter, when high humidity and low temperatures promote ammonium nitrate formation. This phenomenon is further exacerbated by the extensive use of maize monoculture, which leaves the soil bare for most of the winter season, thereby reducing aerodynamic roughness and limiting dry deposition processes. This study evaluates the potential of winter cover crops to enhance atmospheric ammonia removal by increasing dry deposition velocities. Drawing on established deposition models and regional air-quality data, we estimate that replacing bare soil with autumn–winter vegetation can increase deposition velocities by up to an order of magnitude (from <0.1 to ≈1 cm s⁻¹). In hotspot areas of the Cuneo–Turin plain, where winter NH₃ concentrations regularly exceed 30 µg m⁻³, cover crops can generate additional deposition fluxes of approximately 30–70 kg NH₃ ha⁻¹ yr⁻¹. Applied to the 90,000 ha of intensive monoculture identified in the study area, this corresponds to a potential removal of ~2800 t NH₃ yr⁻¹, equivalent to 8–9% of total agricultural emissions in Piedmont. These reductions would also decrease the availability of precursors for secondary PM_2.5 formation. Existing regional rural-development measures provide a suitable policy framework, but they are currently underutilized, indicating substantial potential for large-scale implementation. Full article

Chemerin is a multifunctional adipokine involved in metabolic regulation, inflammation, and vascular homeostasis, but its relationship with arterial stiffness remains uncertain. We investigated the association between circulating chemerin and carotid–femoral pulse wave velocity (cfPWV) and explored individual chemerin–PWV discordance in participants from the Brisighella Heart Study (n = 1304). Multivariable linear regression was adjusted for age, sex, body mass index, mean arterial pressure, resting heart rate, current smoking, and estimated glomerular filtration rate. Chemerin was correlated with cfPWV in unadjusted analysis (Spearman’s ρ = 0.073; p = 0.009). After adjustment, each one-standard-deviation increase in chemerin was associated with a nonsignificant 0.093 m/s higher cfPWV (95% confidence interval, −0.026 to 0.212; p = 0.126). Residual-based classification identified 132 participants with higher-than-expected chemerin and lower-than-expected cfPWV and 151 with higher-than-expected values of both measures. No investigated factor remained associated with membership in the former group after false-discovery-rate correction. Cross-fitting showed 95.6% agreement in phenotype classification. Circulating chemerin was not independently associated with central arterial stiffness, while residual analysis revealed stable but clinically unvalidated patterns of chemerin–cfPWV discordance. Full article

The Small Island Developing States (SIDS) face a myriad of energy challenges due to their dependence on imported fossil fuels and increased rates of natural disasters, resulting in high electricity costs and grid instability. Marine current energy continues to be an emerging energy technology because of high installation and maintenance costs; however, the large resource availability makes it a promising resource for islands. This study is a techno-economic evaluation of a novel bridge-supported marine current energy system designed for shallow-water deployment, using the U.S. Virgin Islands as a case study. A bridge support structure is proposed that will allow for ease of installation and maintenance within local systems. The National Renewable Energy Laboratory (NREL) Reference Model 4 was used as the framework for the technical design and cost estimates and was adjusted based on economies-of-scale relationships. We develop an estimate for the levelized cost of energy (LCOE) for installations for a range of deployments and perform sensitivity analysis over current velocity correction factors, turbine size, and interest rate. The results indicate that a three-unit installation for this case study will achieve an LCOE of $1.13/kWh, while 100-unit deployments can reduce the LCOE to $0.31/kWh. The technology becomes economically competitive with the present electricity cost in the U.S. Virgin Islands—$0.42/kWh—at an installed capacity of approximately 10 MW. These findings demonstrate the potential of bridge-supported marine current energy systems to strengthen energy security and support the renewable energy transition in the Caribbean and other Small Island Developing States. Full article

Close-range UAV visual servoing near overhead ground wires requires simultaneous regulation of the target’s lateral position, apparent width, and orientation angle in the image. Owing to flight-control response lag and visual-processing delay, current image changes may reflect the combined effects of multiple historical control inputs. To address this issue, this paper proposes a multi-history-weighted projection-adaptive Jacobian control method (MHW-PAJ-CLF). For each visual channel, the method takes a weighted sum of the parameter corrections associated with different historical inputs based on response prediction errors and input magnitudes and updates the local Jacobian matrix online under projection bounds. The online estimate is then blended with the nominal model. Control Lyapunov function-based quadratic programming (CLF-QP) uses the blended model to generate velocity and yaw-rate commands, coordinating the regulation of the three visual errors under input constraints. Comparative experiments were conducted on the RflySim–PX4 hardware-in-the-loop platform. The proposed method achieves a mean success rate of 75.50%, exceeding that of the best baseline by 11.05 percentage points. In tests with additional visual-feedback delay and command–response lag, the proposed method achieves lower overall tracking error than single-history PAJ-CLF, indicating that multi-history weighting helps improve visual tracking under time delays. Full article

Background/Objectives: Mechanical shocks generated by the recoil of hand-held power screwdrivers are a significant biomechanical stressor for the operator’s hand–arm complex. Currently, vibration exposure is measured at the tool-handle level, while operator-centered practical measures remain limited. This study proposes a computational methodology to quantify relative reductions in mechanical shock and biomechanical load across different workstations. Using wearable inertial measurement units, ratios of transmitted torque and worst-case wrist joint power were calculated directly at the operator’s upper limb, without direct force measurement. Methods: The methodology was tested with 30 participants performing standardized fastening tasks across five configurations: one unsupported and four with distinct support arms, paired with an electric and pneumatic in-line screwdriver. Results: Workstation configuration had a significant main effect on both the peak angular acceleration and the peak wrist angular velocity (p < 0.001 for both variables). Compared with the unsupported condition, all support-arm configurations substantially reduced the mechanical shock transmitted to the operator, decreasing the estimated transmitted torque by 71–81% and the worst-case wrist joint power by more than 95% (p < 0.001 for all pairwise comparisons). The articulated arm induced higher kinematic responses than telescopic and Cartesian designs. Age was the only significant covariate for hand peak angular acceleration (p = 0.039). Conclusions: The proposed methodology provides a simplified operator-centered approach for assessing mechanical shock transmission during screwdriving operations using wearable IMUs. This methodology may serve as a preliminary screening tool to support workstation design and ergonomic investigations. However, the present findings do not establish a direct relationship between the proposed indices and musculoskeletal disorder risk, and further validation against established ergonomic and clinical outcomes is required. Full article

Background: Cigarette smoking alters carotid plaque composition. Two-dimensional ultrasound shear-wave elastography (2D-SWE) is a promising non-invasive imaging technique for quantifying plaque stiffness. This prospective study aimed to determine whether carotid plaque stiffness assessed using 2D-SWE is associated with smoking status. Methods: A total of 132 carotid plaques were evaluated from 93 patients who underwent carotid ultrasound 2D-SWE. Demographic and clinical data were collected, and patients were classified as current cigarette smokers (n = 45) and non-smokers (n = 48). A total of 65 carotid plaques in smokers and 67 in non-smokers were evaluated. Plaque stiffness was quantified using shear-wave velocity (m/s), with three SWE measurements obtained from each plaque. Demographic and clinical characteristics and plaque stiffness were compared according to smoking status, and correlations between smoking status and plaque stiffness were evaluated. Results: A total of 396 SWE measurements were obtained from 132 carotid plaques (195 in cigarette smokers and 201 in non-smokers). Plaques in smokers demonstrated significantly greater stiffness than those in non-smokers, as indicated by shear-wave velocity (smokers: median 4.17 m/s, interquartile range (IQR) 1.94 vs. non-smokers: median 2.91 m/s, IQR 1.81, Z = −5.36, p < 0.001). Smoking was positively correlated with shear-wave velocity (r = 0.27, p < 0.001). No significant differences were observed between smokers and non-smokers in age, sex, hypertension, or diabetes mellitus. Conclusions: Cigarette smoking was associated with increased carotid plaque stiffness measured using ultrasound 2D-SWE. These findings suggest that SWE may provide a quantitative imaging marker of smoking-related differences in carotid plaque composition. Larger studies incorporating smoking duration and cumulative exposure are warranted to determine their clinical significance. Full article

Current all-optical chiral sorting approaches are ineffective for nanoscale drug molecules with weak chirality, as their faint optical response cannot maintain the chiral sorting mechanism. To overcome this physical limitation, the theoretical study proposes a core–shell composite chiral sensing microsphere, in which a drug crystal core is encapsulated by a nematic liquid crystal shell, acting as a chirality-amplifying carrier for optofluidic detection. Using a sodium ibuprofen nanocrystal as a representative weakly chiral drug, the optimal core–shell sensing structure was determined to consist of a nematic liquid crystal E7 shell with a radius of 19 μm and a sodium ibuprofen crystal core with a radius of 9.5 μm. This optimized configuration amplifies the molecular chirality parameter from 10⁻⁶ to 6.5 × 10⁻³ and yields the maximum transverse separation velocity of 1.19 μm/s. Hydrodynamic calculations demonstrate that when the optimized composite sensing microsphere accumulates an absolute transverse displacement greater than 19 μm within a microfluidic channel, the maximum longitudinal flow velocity of the system reaches 2.4 μm/s, satisfying the geometric threshold required for continuous sensing and sorting. This study provides a design strategy to advance optofluidic sensing and sorting systems for nanoscale chiral drugs. Full article

Berthing path planning for ships in the presence of ocean currents is a challenging task. Several relevant methods have been proposed, but they all assume a constant surge velocity for the whole path. This hypothesis makes it impossible to achieve the simultaneous optimization of speed and energy consumption. To deal with this issue, in this paper an optimal control path planning method that considers the characteristics of currents is proposed. Unlike traditional algorithms such as the A* algorithm and genetic algorithm, the proposed improved hp-pseudospectral (IHP) method does not require a constant thrust assumption. In addition, it can obtain the Pareto optimal path under various current environments and optimize the sailing parameters. Specifically, first a multi-objective optimal control path planning model considering the kinematic characteristics of autonomous ships is established. Second, the IHP method is proposed to solve it, which includes dividing the time interval, subdomain collocation, and transformation optimization. Last, the optimality and high efficiency of the proposed method are proved theoretically. Simulation experiments show that the proposed method can provide solutions to this problem where existing algorithms fail and it has strong robustness and high efficiency. Furthermore, the obtained path is superior to those obtained using the existing algorithms in various scenarios; the results show that the proposed method outperforms A* and genetic algorithms in terms of path smoothness, energy efficiency, and computational economy, achieving reductions in travel distance, sailing time, and energy consumption by up to 6.0%, 6.9%, and 4.0%, respectively, compared with A, and by 3.3%, 4.4%, and 1.8%, respectively, compared with the genetic algorithm. Full article

For continuous boundary observation at a prescribed scalar level in unknown marine scalar fields, this paper proposes an isoline tracking method for an autonomous underwater helicopter (AUH) using only noisy local measurements. The method establishes an isoline kinematic relation based on the local scalar value and its rate of change. Without field reconstruction or compensation for unknown terms, it enables the AUH to stably approach the target isoline and maintain tangential motion, with adjustable tracking accuracy. To obtain reliable scalar-rate information from noisy measurements, a finite-time differentiator using current and historical noisy measurements was developed to suppress measurement noise while retaining the required dynamic response. A low-complexity prescribed-time velocity-matching controller was further developed in a direct algebraic form, allowing the contraction time and terminal range of the velocity errors to be specified without imposing restrictive conditions on finite initial errors. Simulation results in a suspended particulate matter scalar field and a temperature field verified the effectiveness of the proposed method. Full article

This article addresses real-time local conflict resolution for a self-planning UAV operating in a three-dimensional dynamic environment with surrounding UAVs. To this end, we develop an SBA–DWA hybrid planning framework in which an improved sticky bacteria algorithm (SBA) is embedded in the dynamic window approach (DWA) to enhance real-time velocity selection for the self-planning UAV. First, a chemotaxis operator with projection is developed to strictly constrain bacterial positions within the convex dynamic window. Furthermore, an anisotropic Gaussian adhesion potential field is proposed to adaptively guide the current population search using historical optimal velocity commands, achieving cross-step memory transfer. Then, a dynamic pruning mechanism is designed to ensure that historical memory does not lead UAVs into infeasible or hazardous regions. The proposed scheme guarantees that the single-step planning latency satisfies stringent real-time requirements. Comparative simulation results demonstrate that the proposed method reduces path length by approximately 30% and planning time by approximately 31% compared with the standard DWA, while achieving a larger minimum inter-vehicle clearance in dense dynamic scenarios. Full article

Direct kinematic measurements of cosmic acceleration via the cosmological redshift drift (the Sandage–Loeb effect) provide a powerful, model-independent avenue to map the expansion history of the Universe. In this work, which extends the forecasting framework developed in a recent study, we evaluate the capability of the Square Kilometre Array (SKA) to constrain three physically motivated, quantum-gravity inspired holographic dark energy (HDE) paradigms: Standard HDE (with a future event horizon cutoff), Tsallis HDE (THDE), and Rényi HDE (RHDE). Utilizing simulated neutral hydrogen (HI) 21 cm emission lines from a census of over ${10}^9$ galaxies up to $z=1.0$ and 21 cm absorption lines in $1.8\times {10}^3$ damped Lyman-$\alpha$ (DLA) systems, we simulate mock velocity drift observations ($\dot{v}$) at high spectral resolutions ($\Delta \nu =0.001$ Hz and $0.002$ Hz) over a semi-annual ($\Delta t=0.5$ year) cadence baseline. We contrast these forecasts with current real-world constraints obtained from the joint Markov chain Monte Carlo (MCMC) likelihood analysis of the Pantheon SNe Ia and DESI DR2 BAO compilations. Our results reveal a profound limitation of integrated geometric probes: while current SNe Ia and BAO data suffer from severe parameter degeneracies—leaving the non-additive entropy scaling exponents ($\delta$ and $\alpha$) completely unconstrained as open vertical bands—the simulated SKA redshift drift successfully breaks these degeneracies. From emission-line observations at $0.001$ Hz spectral resolution, we obtain marginalized $1\sigma$ constraints of ${\sigma }_c=\pm 0.021$ for the standard holographic parameter, ${\sigma }_{\delta }=\pm 0.035$ for the Tsallis entropy index, and ${\sigma }_{\alpha }=\pm 0.007$ for the Rényi parameter. Crucially, we identify and resolve a critical duplicate-plotting mathematical error present in the existing redshift-drift literature by providing the mathematically correct physical scaling and peak structures for both the dimensionless redshift drift ($S_z$) and the physical velocity drift ($S_v$). We conclude that the SKA will serve as a premier instrument for testing the holographic principle and non-extensive thermodynamics at cosmological scales. Full article

Despite major advances in exercise physiology, biomechanics, and mechanobiology, exercise science still lacks a clear conceptual definition of the mechanical stimulus experienced by skeletal muscle during resistance training. Current approaches rely on diverse external, internal, and biomechanical variables (e.g., volume-load, force, power, velocity, time under tension, or muscle architecture), yet none individually captures the muscle-specific mechanical exposure relevant to muscular adaptation. This conceptual inconsistency limits comparisons across studies, complicates training prescription, and hinders the development of individualized monitoring strategies. This integrative review critically synthesizes current evidence from mechanobiology, skeletal muscle physiology, biomechanics, and resistance training to examine how mechanical stimuli are currently conceptualized, quantified, and interpreted. Based on this synthesis, we propose a working definition of Mechanical Dose as the cumulative, muscle-specific mechanical exposure experienced over a defined time window, characterized by loading magnitude, rate, duration, frequency, and spatial distribution, and conditioned by contraction mode and muscle–tendon geometry. Rather than representing a directly measurable variable, mechanical dose is presented as a latent conceptual construct that can only be estimated through combinations of biomechanical, physiological, and morphological indicators. Building upon this definition, we introduce an integrative conceptual framework linking external load, movement biomechanics, mechanical dose, mechanotransduction, and tissue adaptation. We further discuss how this framework may guide future research on the interpretation of field-based monitoring, resistance training prescription, recovery management, and future explainable artificial intelligence approaches in sport science. By reframing mechanical dose as the central construct connecting biomechanics and biological adaptation, this review provides a unified conceptual basis for future research and contributes toward a more biologically informed paradigm of exercise prescription and monitoring. Full article

This publication presents results of a numerical study of a controlled flow nozzle blade with a modification added at the leading edge of an annular cascade. The presented three-dimensional shape is compared with one having a constant lean at the leading edge, which is currently used in power plants. The study compares the annular row loss coefficient for a relatively large blade length and for a blade length reduced by half. Calculations are performed for compressible and incompressible flows. Additionally, the blade rows are investigated with different boundary conditions at the inlet and outlet, divided into several groups, in order to evaluate their effectiveness at different secondary-flow intensities. In numerical simulations, a variable velocity distribution, total temperature, and total pressure are set at the inlet, and a mass flow rate or variable static pressure is set at the outlet. For the developed variants, a loss coefficient is calculated, and a comparison is made between the two proposed bladed rows: the first with a straight-line trailing edge and a constant circumferential lean at the leading edge, and the second with a variable lean in the circumferential direction and a reverse sweep at the leading edge. Full article