Search Results (332)

Objective: To evaluate the predictive value of umbilical artery half peak systolic velocity deceleration time (UA hPSV-DT) for composite adverse perinatal outcomes (CAPO) in pregnancies complicated by gestational diabetes mellitus (GDM). Methods: In this prospective observational study, 120 singleton pregnancies in the third trimester were enrolled: 30 insulin-regulated GDM (IRGDM), 30 diet-regulated GDM (DRGDM), and 60 healthy controls. UA hPSV-DT and standard Doppler indices were measured using a standardized protocol by a single perinatologist. An abnormal UA hPSV-DT was defined as <5th percentile for gestational age. Maternal metabolic parameters, fetal biometry, and neonatal outcomes were recorded. The primary outcome was CAPO, defined as the presence of one or more adverse perinatal events. Results: Median UA hPSV-DT values were significantly lower in IRGDM (171 ms) and DRGDM (184 ms) compared with controls (227 ms) (p = 0.006). Abnormal UA hPSV-DT occurred in 43.3% of GDM cases and was associated with higher estimated fetal weight and abdominal circumference percentiles, increased amniotic fluid, elevated OGTT values, higher HbA1c, and more frequent insulin therapy (p < 0.01 for all). In GDM pregnancies, CAPO occurred in 73.1% of the abnormal UA hPSV-DT group versus 11.8% of the normal group (p < 0.001). ROC analysis identified a cut-off of < 181 ms for predicting CAPO (AUC 0.741, 70.3% sensitivity, 66.7% specificity). Conclusions: UA hPSV-DT is a novel, reproducible Doppler parameter that independently predicts adverse perinatal outcomes in GDM pregnancies, even when conventional UA Doppler indices are normal. Incorporating UA hPSV-DT into routine surveillance may improve risk stratification and guide management to optimize perinatal outcomes. Full article

The fatigue constitutive model under cyclic loading is of vital importance for studying the fatigue deformation characteristics of soft rocks. In this paper, based on the classical Bingham model, a modified Bingham fatigue model for describing the fatigue deformation characteristics of soft rocks under cyclic loading was developed. Firstly, the traditional constant-viscosity component was replaced by an improved nonlinear viscoelastic component related to the number of cycles. The elastic component was replaced by an improved nonlinear elastic component that decays as the number of cycle loads increases. Meanwhile, by decomposing the cyclic dynamic loads into static loads and alternating loads, a one-dimensional nonlinear viscoelastic-plastic Bingham fatigue model was developed. Furthermore, a rock fatigue yield criterion was proposed, and by using an associated flow rule compatible with this criterion, the one-dimensional fatigue model was extended to a three-dimensional constitutive formulation under complex stress conditions. Finally, the applicability of the developed Bingham fatigue model was verified through fitting with experimental data, and the parameters of the model were identified. The model fitting results show high consistency with experimental data, with correlation coefficients exceeding 0.978 and 0.989 under low and high dynamic stress conditions, respectively, and root mean square errors (RMSEs) below 0.028. Comparative analysis between theoretical predictions and existing soft rock fatigue test data demonstrates that the developed Bingham fatigue model more effectively captures the complete fatigue deformation process under cyclic loading, including the deceleration, constant velocity, and acceleration phases. With its simplified component configuration and straightforward combination rules, this model provides a valuable reference for studying fatigue deformation characteristics of rock materials under dynamic loading conditions. Full article

Flow dynamics were characterized and stable zones in diversions were quantified using physical modeling, in situ experiments, and 3D numerical simulations. ADV (1 cm spatial resolution) and water-level probes (0.01 cm spatial resolution) were used in the physical experiments in a rectangular channel. ADCP (resolution of 50 cm) was employed for in situ validation at a northern China hub. Numerical simulations using ANSYS 2022R2 Fluent software with RNG k-ε and VOF showed little error (<15%) compared to the experiments. The results quantified the diversion zone into four sub-regions: acceleration (length 0.8–1.2 h); stabilization (1.2–3.5 h); diffusion deceleration (3.5–5.0 h); and stagnation (localized eddies, diameter 0.3–0.8 d). The stable zone length was dominantly controlled by the nonlinear coupling of geometric (B_s/B_m, 42%) and hydraulic (Fr, 28%) parameters. Upstream and downstream stable zone empirical models showed high accuracy (R² = 0.83 and 0.76, p < 0.01), with an average relative error <15%. Based on the proposed zoning principles and flow characteristics, measurement facilities in the irrigation area are presented. These tools enhance irrigation diversion design and management for improved water efficiency. Full article

There are many contradictory opinions, and the role of TGF-β1 in the vascular effects of atherosclerosis remains unclear. This study aims to verify whether plasma TGF-β1 concentrations are correlated with changes in echocardiographic and vascular parameters in individuals with early coronary artery disease (CAD), including those with type 2 diabetes mellitus (T2DM). The study group consisted of 100 patients with early-onset CAD. Patients underwent echocardiography and electrocardiography. The thickness of the internal and middle membrane complex of the carotid and brachial arteries, the ankle-brachial index, and the atherosclerotic plaques present were assessed via Doppler ultrasound. No statistically significant correlation of TGF-β1 with diabetes, hypertension, metabolic syndrome, or myocardial infarction was observed, only weak associations with impaired ventricular function. The positive correlations between right and left ventricular parameters and TGF-β1 level, as well as the negative correlations fractional shortening and deceleration time, were found. The last correlation was strong. There is a strong positive correlation between TGF-β1 and QRS II width and QRS V5 width. The positive correlation was found between TGF-β1 and PLA density and thickness of the intima-media. These associations are very weak. In patients with early-onset CAD, high TGF-β1 concentrations are not associated with heart attacks or the associated risk factors. However, these cases are potentially those with stable plaques. Our study indicates a significant association between TGF-β1 levels and left ventricular diastolic dysfunction and arrhythmia risk in these patients. Full article

Nanotechnology has become a transformative field in modern science and engineering, offering innovative approaches to enhance conventional thermal and fluid systems. Heat and mass transfer phenomena, particularly fluid motion across various geometries, play a crucial role in industrial and engineering processes. The inclusion of nanoparticles in base fluids significantly improves thermal conductivity and enables advanced phase-change technologies. The current work examines Powell–Eyring nanofluid’s heat transmission properties on a stretched Riga plate, considering the effects of magnetic fields, porosity, Darcy–Forchheimer flow, thermal radiation, and activation energy. Using the proper similarity transformations, the pertinent governing boundary-layer equations are converted into a set of ordinary differential equations (ODEs), which are then solved using the boundary value problem fourth-order collocation (BVP4C) technique in the MATLAB program. Tables and graphs are used to display the outcomes. Due to their significance in the industrial domain, the Nusselt number and skin friction are also evaluated. The velocity of the nanofluid is shown to decline with a boost in the Hartmann number, porosity, and Darcy–Forchheimer parameter values. Moreover, its energy curves are increased by boosting the values of thermal radiation and the Biot number. A stronger Hartmann number M decelerates the flow (thickening the momentum boundary layer), whereas increasing the Riga forcing parameter Q can locally enhance the near-wall velocity due to wall-parallel Lorentz forcing. Visual comparisons and numerical simulations are used to validate the results, confirming the durability and reliability of the suggested approach. By using a systematic design technique that includes training, testing, and validation, the fluid dynamics problem is solved. The model’s performance and generalization across many circumstances are assessed. In this work, an artificial neural network (ANN) architecture comprising two hidden layers is employed. The model is trained with the Levenberg–Marquardt scheme on reliable numerical datasets, enabling enhanced prediction capability and computational efficiency. The ANN demonstrates exceptional accuracy, with regression coefficients $R\approx 1.0$ and the best validation mean squared errors of $8.52\times {10}^{-10}$, $7.91\times {10}^{-9}$, and $1.59\times {10}^{-8}$ for the Powell–Eyring, heat radiation, and thermophoresis models, respectively. The ANN-predicted velocity, temperature, and concentration profiles show good agreement with numerical findings, with only minor differences in insignificant areas, establishing the ANN as a credible surrogate for quick parametric assessment and refinement in magnetohydrodynamic (MHD) nanofluid heat transfer systems. Full article

Automated vehicles (AVs) are expected to shape the future of transportation and to improve traffic flow and safety. Studies have focused on AVs effects on traffic flow during the transition to full automation, with few examining their influence on human-driven vehicles (HDVs). This study investigated potential changes in HDVs’ driving behavior induced by the presence of AVs with different driving styles (aggressive vs. cautious) at varying market penetration rates (MPRs) (0%, 25%, 50%, and 75%). First, a driving simulator experiment with 160 people (56 females, 104 males) was conducted to collect HDV trajectory data. Then, a microsimulation model was implemented in VISSIM, where HDV behavioral parameters were calibrated using the driving simulator data. Average time headway (THW), relative velocity (RelVel), average acceleration (Acc), average deceleration (Dec), and lane change frequency (LnCh) were used as behavioral metrics. A two-way ANOVA was applied for analysis. Results showed that higher AVs’ MPRs decreased THW, Acc, and Dec in HDVs, while RelVel increased with cautious AVs and decreased with aggressive AVs. Similar trends were observed for LnCh. These findings highlight the need to consider potential HDVs behavioral adaptation during the transition phase, as neglecting it may lead to inaccurate traffic assessments and ineffective policies. Full article

This study aims to examine the relationship between competition-derived GPS metrics and explosive power, as expressed by the countermovement jump (CMJ), and their influence on neuromuscular fatigue in professional male soccer players. In this observational–longitudinal study, GPS-derived data were collected during 15 official competitions from the same seven players (age = 26.03 ± 4.59 y, height = 180.0 ± 0.076 cm, body mass = 77.88 ± 9.90 kg). CMJ assessments were performed at matchday − 1 (MD + 2) and matchday + 2 (MD + 2) of each competition. CMJ height was significantly decreased from MD − 1 to MD + 2 (p < 0.05). While no significant correlations were found between MD − 1 CMJ values and the examined GPS metrics (total distance covered (TDC), high-speed running distance (HSR-D (m)), sprint-running distance (SR-D (m)), and number of high-intensity accelerations/decelerations (HIA (n)/HID (n), respectively), a significant negative relationship emerged between MD + 2 CMJ height and HIA (n) and HID (n) (p < 0.05). Linear mixed-effects measures revealed the impact of several parameters in three different models: (a) HIA (n) × HID (n) × HSR (m) × SR-D (m), (b) HIA (n) × HID (n) × SR-D (m), and (c) HID (n) × SR-D (m), with univariate testing highlighting significant effects of HIA (n) and HID (n) (p < 0.05). In conclusion, no association was evident between MD − 1 CMJ values and competition GPS metrics, while HIA (n) and DIA (n) were associated with post-competition explosive-power values at MD + 2. Moreover, CMJ reduction from MD − 1 to MD + 2, serving as a competition-induced neuromuscular fatigue indicator, was found to be related to HIA (n) and HID (n) volumes either individually or in association with HSR (m) and SR-D (m) distances, suggesting those to impact post-competition fatigue kinetics. Full article

This study explores the behavior of phantom dark energy within the framework of Weyl-type $f(Q,T)$ gravity, considering a spatially flat FLRW universe under observational constraints. The field equations are analytically solved for a dust-like fluid source. To determine the present values of the model parameters, we utilize observational data from the Hubble parameter measurements via cosmic chronometers (CC) and the apparent magnitude data from the Pantheon compilation of Type Ia supernovae (SNe Ia). With these obtained parameter values, we analyze the model’s physical characteristics by evaluating the effective and dark energy equation of state parameters ${\omega }_{eff}$ and ${\omega }_{de}$, the deceleration parameter $q\left(z\right)$, and energy conditions. Additionally, we conduct the $O_m$ diagnostic test for the model. We estimate the transition redshift $z_t\le 0.5342, 0.6334$ and the present age of the universe $t_0=13.46, 13.49$ Gyrs with $H_0=67.4\pm 3.6, 68.8\pm 1.9$ Km/s/Mpc, ${\mathsf{\Omega }}_{m0}={0.41}_{-0.24}^{+0.13}, {0.299}_{-0.077}^{+0.042}$, and ${\omega }_{eff}=-0.6447,-0.696$, ${\omega }_{de}=-1.0347,-1.0284$. We find a transit phase accelerating and physically acceptable phantom dark energy model of the universe. Full article

A novel honeycomb with gradient-thickness cell walls (HGTCWs) is fabricated through chemical etching to achieve progressive thickness reduction in the cell walls. This engineered honeycomb demonstrates superior energy absorption by effectively eliminating the peak load during the linear elastic stage of the load–displacement curve under impact loading, thereby preventing premature structural failure caused by excessive instantaneous loads. To systematically investigate the impact compression mechanics, energy absorption characteristics, and key influencing factors of aluminum HGTCWs, a three-factor orthogonal array of low-velocity impact experiments was designed. The design of experimental parameters for the impact test has taken into account the impact mass, impact velocity, and etching height. Comparative analysis assessed how these factors influence energy absorption performance. Results reveal that chemical etching-induced thickness gradient modification effectively suppresses peak load generation. Load–displacement curves exhibit distinct bilinear characteristics: an initial single linear phase when compression displacement is below the etching height, followed by a dual-linear phase with an inflection point at the gradient height. Time–velocity profiles during impact primarily consist of an initial nonlinear deceleration phase followed by a linear deceleration phase. Range analysis and analysis of variance identify impact velocity as the dominant factor influencing the energy absorption characteristics of HGTCWs. Full article

Deep mining is often accompanied by complex geological conditions, which can cause damage to the coal seam roof surrounding rock, thereby reducing its safety and stability. Therefore, analyzing the long-term mechanical behavior of multiscale damaged sandstone under deep mining conditions is of great significance. To describe the long-term deformation and damage evolution of multiscale damaged sandstone under deep mining conditions, this work establishes a fractional-order multiscale damage creep model by incorporating fractional calculus and damage mechanics theory into the Nishihara model. The model parameters were determined by fitting the creep data of damaged sandstone using the least squares method. The results demonstrate that the proposed model can accurately simulate the complete creep process, including the decelerated, steady-state, and accelerated stages. Compared with the classical integer-order multiscale damage creep model, the fractional-order model can better capture the time-dependent behavior of materials and thus shows superior performance in characterizing the nonlinear features of the accelerated creep stage. Furthermore, through sensitivity analysis of the parameters reveals the influence of key parameters on different creep stages, thereby validating the model’s effectiveness and reliability. This model provides a solid theoretical foundation for evaluating the long-term stability of coal mine roof strata in deep mining environments. Full article

The phenomenon of arable land non-agriculturalization has become increasingly severe, posing significant threats to the security of arable land resources and ecological sustainability. This study focuses on Dachang Hui Autonomous County in Langfang City, Hebei Province, a region located at the edge of the Beijing–Tianjin–Hebei metropolitan cluster. In recent years, the area has undergone accelerated urbanization and industrial transfer, resulting in drastic land use changes and a pronounced contradiction between arable land protection and the expansion of construction land. The study period is 2016–2023, which covers the key period of the Beijing–Tianjin–Hebei synergistic development strategy and the strengthening of the national arable land protection policy, and is able to comprehensively reflect the dynamic changes of arable land non-agriculturalization under the policy and urbanization process. Multi-temporal Sentinel-2 imagery was utilized to construct a multi-dimensional feature set, and machine learning classifiers were applied to identify arable land non-agriculturalization with optimized performance. GIS-based analysis and the geographic detector model were employed to reveal the spatio-temporal dynamics and driving mechanisms. The results demonstrate that the XGBoost model, optimized using Bayesian parameter tuning, achieved the highest classification accuracy (overall accuracy = 0.94) among the four classifiers, indicating its superior suitability for identifying arable land non-agriculturalization using multi-temporal remote sensing imagery. Spatio-temporal analysis revealed that non-agriculturalization expanded rapidly between 2016 and 2020, followed by a deceleration after 2020, exhibiting a pattern of “rapid growth–slowing down–partial regression”. Further analysis using the geographic detector revealed that socioeconomic factors are the primary drivers of arable land non-agriculturalization in Dachang Hui Autonomous County, while natural factors exerted relatively weaker effects. These findings provide technical support and scientific evidence for dynamic monitoring and policy formulation regarding arable land under urbanization, offering significant theoretical and practical implications. Full article

This paper describes the complex process of rock crushing removal by AWJ impact from the microscopic perspective. The acceleration and deceleration mechanism of abrasive particles throughout the whole process of single abrasive particles impacting rocks, the spherical cavity expansion mechanism of the abrasive particles’ impact on the rock, and the elastic contact force of the collision between the abrasive particles and rock were investigated; a mathematical model of AWJ’s impact on the rock crushing removal conditions was established; and the threshold values of the jet impact parameters were obtained. The mathematical model of the rock crushing removal conditions was verified through numerical simulation and jet impact experiments. The research results show that the theoretical value of the jet impact velocity that meets the conditions for limestone crushing removal is greater than or equal to 36 m/s, and the theoretical value of the pressure is greater than or equal to 2.7 MPa. Numerical simulation was used to obtain the displacement of marked points, stress, and strain variation in marked elements of rock under different impact velocities. The effect of impact rock breaking obtained through the experiment demonstrates the correspondence between the test pressure and the theoretical pressure, which verifies the accuracy of the mathematical model of the rock crushing removal conditions. Full article

This study presents a detailed experimental comparison of the rotordynamic and thermal performance of automotive turbochargers supported by two distinct hydrodynamic bearing configurations: fully floating ring bearings (FFRBs) and semi-floating ring bearings (SFRBs). While both designs are widely used in commercial turbochargers, they exhibit significantly different dynamic behaviors due to differences in ring motion and fluid film interaction. A cold air-driven test rig was employed to assess vibration and temperature characteristics across a range of controlled lubricant conditions. The test matrix included oil supply pressures from 2 bar (g) to 4 bar (g) and temperatures between 30 °C and 70 °C. Rotor speeds reached up to 200 krpm (thousands of revolutions per minute), and data were collected using a high-speed data acquisition system, triaxial accelerometers, and infrared (IR) thermal imaging. Rotor vibration was characterized through waterfall and Bode plots, while jump speeds and thermal profiles were analyzed to evaluate the onset and severity of instability. The results demonstrate that the FFRB configuration is highly sensitive to oil supply parameters, exhibiting strong subsynchronous instabilities and hysteresis during acceleration–deceleration cycles. In contrast, the SFRB configuration consistently provided superior vibrational stability and reduced sensitivity to lubricant conditions. Changes in lubricant supply conditions induced a jump speed variation in floating ring bearing (FRB) turbochargers that was approximately 3.47 times larger than that experienced by semi-floating ring bearing (SFRB) turbochargers. Furthermore, IR images and oil outlet temperature data confirm that the FFRB system experiences greater heat generation and thermal gradients, consistent with higher energy dissipation through viscous shear. This study provides a comprehensive assessment of both bearing types under realistic high-speed conditions and highlights the advantages of the SFRB configuration in improving turbocharger reliability, thermal performance, and noise suppression. The findings support the application of SFRBs in high-performance automotive systems where mechanical stability and reduced frictional losses are critical. Full article

This paper presents a structured and experimentally validated approach to the parameter identification, modeling, and real-time speed control of a brushless DC (BLDC) motor. Electrical parameters, including resistance and inductance, were measured through DC and AC testing under controlled conditions, respectively, while mechanical and electromagnetic parameters such as the back electromotive force (EMF) constant and rotor inertia were determined experimentally using an AVL dynamometer. The back EMF was obtained by operating the motor as a generator under varying speeds, and inertia was identified using a deceleration method based on the relationship between angular acceleration and torque. The identified parameters were used to construct a transfer function model of the motor, which was implemented in MATLAB/Simulink R2024b and validated against real-time experimental data using sinusoidal and exponential input signals. The comparison between simulated and measured speed responses showed strong agreement, confirming the accuracy of the model. A proportional–integral (PI) controller was developed and implemented for speed regulation, using a low-cost National Instruments (NI) USB-6009 data acquisition (DAQ) and a Kelly controller. A first-order low-pass filter was integrated into the control loop to suppress high-frequency disturbances and improve transient performance. Experimental tests using a stepwise reference speed profile demonstrated accurate tracking, minimal overshoot, and robust operation. Although the modeling and control techniques applied are well known, the novelty of this work lies in its integration of experimental parameter identification, real-time validation, and practical hardware implementation within a unified and replicable framework. This approach provides a solid foundation for further studies involving more advanced or adaptive control strategies for BLDC motors. Full article

The aim of this study was to examine the relationship between the external load (EL) and internal load among U15, U17, and U19 youth soccer players and to identify the factors best influencing the rating of perceived exertion (RPE) and session-RPE (s-RPE) from Global Positioning System-derived variables. Data were collected from 50 male youth soccer players over an 11-week in-season period, encompassing a total of 1386 observations (145 training sessions and 33 matches). The findings indicate that during training sessions, the relationship between EL-derived volume variables and s-RPE exhibited moderate-to-very-strong correlations (U15—r ranging from 0.23 to 0.52; U17—r ranging from 0.51 to 0.78; U19—r ranging from 0.34 to 0.61, p < 0.001). The strongest relationships were observed with the total distance, acceleration, deceleration, and player load variables (p < 0.001). However, perceived wellness measures showed weak correlations with almost every EL parameter. Considering matches for all age groups, total distance showed moderate-to-large correlation with s-RPE (ranging from 0.41 to 0.59, p < 0.001). Additionally, RPE and s-RPE were significantly influenced by the variables of total distance, acceleration, deceleration, medium-speed running per minute, sprint distance per minute, and deceleration per minute. Full article