Search Results (190)

Background: Previous research from our group demonstrated that novel hemodynamic indices can predict 3–5-year mortality risk in myocardial infarction survivors. Building on these findings, we assessed the long-term prognostic value of these markers over a 10-year follow-up period. Methods: We conducted a prospective study involving 569 consecutive acute coronary syndrome (ACS) patients admitted within 12 h of symptom onset, all presenting with >50% coronary artery stenosis. Hemodynamic indices were assessed using echocardiography to measure ejection fraction (EF), global longitudinal peak systolic strain (GLPSS), and ventricular–arterial coupling (VA coupling). Excess aortic pressure (excess_PTI) was evaluated via radial tonometry, while local arterial stiffness was assessed by pulse wave velocity (PWV) through carotid ultrasonography. The primary outcome was all-cause mortality over a 10-year follow-up period. Results: Over a median follow-up of 3249 days, 172 patients reached the primary endpoint (death). Deceased individuals were older and exhibited lower EF, impaired VA coupling, higher excess_PTI, and a lower PWV/GLPSS index compared to survivors. In multivariate Cox proportional hazards analysis, EF, VA coupling, excess_PTI, and PWV/GLPSS index were independently associated with all-cause mortality over a 10-year follow-up period. Conclusions: This study highlights the significant long-term prognostic value of novel hemodynamic indices, including VA coupling, PWV/GLPSS index, and excess_PTI, in predicting 10-year all-cause mortality in ACS patients. Full article

With the advancement of scientific research, understanding the physical parameters governing acoustic wave propagation in sea ice has become increasingly important. Among these parameters, shear wave velocity plays a crucial role. However, as measurements progressed, it became apparent that there was a large discrepancy between measured values of shear waves and predictions based on empirical formulas or existing models. These inconsistencies stem primarily from the complex internal structure of natural sea ice, which significantly influences its physical behavior. Research reveals that shear wave velocity is not only influenced by bulk properties such as density, temperature, and stress state but is also sensitive to microstructural features, including air bubbles, inclusions, and ice crystal orientation. Compared to longitudinal wave velocity, the characterization of shear wave velocity is far more challenging due to these inherent complexities, underscoring the need for more precise measurement and modeling techniques. To address the challenges posed by the complex internal structure of natural sea ice and improve prediction accuracy, this study introduces a novel, integrated approach combining simulation, measurement, and inversion intelligent learning model. First, a laboratory-based method for generating sea ice layers under controlled formation conditions is developed. The produced sea ice layers align closely with measured values for Poisson’s ratio, multi-year sea ice density, and uniaxial compression modulus, particularly in the high-temperature range. Second, enhancements to shear wave velocity measurement equipment have been implemented. The improved device achieves measurement accuracy exceeding 1%, offers portability, and meets the demands of high-precision experiments conducted in harsh polar environments. Finally, according to the characteristics of small sample data. The ANN neural network was improved to a deep residual neural network with the addition of Squeeze-and-Excitation Attention (SE-ResNet) to predict longitudinal and transverse wave velocities. This prediction method improves the accuracy of shear and longitudinal wave velocity prediction by 24.87% and 39.59%, respectively, compared to the ANN neural network. Full article

Frequent building fires seriously threaten the safety of steel structures. According to the data, fire accidents account for about 35% of the total number of production safety accidents. The collapse of steel structures accounted for 42% of the total collapse. The early warning problem of steel structure fire collapse is imminent. This study aims to address this challenge by establishing a novel early warning framework, which is used to quantify the critical early warning threshold of steel frames based on elastic modulus degradation and its correlation with ultrasonic wave velocity under different collapse modes. The sequential thermal–mechanical coupling numerical method is used in the study. Firstly, Pyrosim is used to simulate the high-fidelity fire to obtain the real temperature field distribution, and then it is mapped to the Abaqus finite element model as the temperature load for nonlinear static analysis. The critical point of structural instability is identified by monitoring the mutation characteristics of the displacement and the change rate of the key nodes in real time. The results show that when the steel frame collapses inward as a whole, the three-level early warning elastic modulus thresholds of the beam are 153.6 GPa, 78.6 GPa, and 57.5 GPa, respectively. The column is 168.7 GPa, 122.4 GPa, and 72.6 GPa. Then the three-level warning threshold of transverse and longitudinal wave velocity is obtained. The three-stage shear wave velocity warning thresholds of the fire column are 2828~2843 m/s, 2409~2434 m/s, and 1855~1874 m/s, and the three-stage longitudinal wave velocity warning thresholds are 5742~5799 m/s, 4892~4941 m/s, and 3804~3767 m/s. The core innovation of this study is to quantitatively determine a three-level early warning threshold system, which corresponds to the three stages of significant degradation initiation, local failure, and critical collapse. Based on the theoretical relationship, these elastic modulus thresholds are converted into corresponding ultrasonic wave velocity thresholds. The research results provide a direct and reliable scientific basis for the development of new early warning technology based on acoustic emission real-time monitoring and fill the gap between the mechanism research and engineering application of steel structure fire resistance design. Full article

With the global low-carbon energy transition, accurate prediction of thermal and physical parameters of deep rock masses is critical for geothermal resource development. To address the insufficient generalization ability of machine learning models caused by scarce measured data on granite thermal conductivity, this study focused on granites from the Gonghe Basin and Songliao Basin in Qinghai Province. A data augmentation strategy combining cubic spline interpolation and Gaussian noise injection (with noise intensity set to 10% of the original data feature range) was proposed, expanding the original 47 samples to 150. Thermal conductivity prediction models were constructed using Support Vector Machine (SVM), Random Forest (RF), and Backpropagation Neural Network(BPNN). Results showed that data augmentation significantly improved model performance: the RF model exhibited the best improvement, with its coefficient of determination R² increasing from 0.7489 to 0.9765, Root Mean Square Error (RMSE) decreasing from 0.1870 to 0.1271, and Mean Absolute Error (MAE) reducing from 0.1453 to 0.0993. The BPNN and SVM models also improved, with R² reaching 0.9365 and 0.8743, respectively, on the enhanced dataset. Feature importance analysis revealed porosity (with a coefficient of variation of 0.88, much higher than the longitudinal wave velocity’s 0.27) and density as key factors, with significantly higher contributions than longitudinal wave velocity. This study provides quantitative evidence for data augmentation and machine learning in predicting rock thermophysical parameters, promoting intelligent geothermal resource development. Full article

Background and Objectives: Type 2 diabetes mellitus (T2DM) is associated with subclinical cardiovascular changes, such as increased arterial stiffness and myocardial dysfunction. Vitamin D deficiency has been recognized as a potential contributing factor to vascular disease; however, its impact on early cardiac changes associated with T2DM remains poorly understood. Our aim was to evaluate the association between serum levels of 25-hydroxyvitamin D3 [25(OH)D3], arterial stiffness, and left ventricular global longitudinal strain (LV GLS) in patients with T2DM who do not have a clinically evident cardiovascular disease. Material and methods: This cross-sectional study evaluated the carotid intima–media thickness (IMT), aortic pulse wave velocity (PWVao), LV GLS, and serum 25(OH)D3 levels in patients diagnosed with T2DM (n = 65) compared to healthy control subjects (n = 55). Independent predictors of arterial stiffness were identified by a multivariate logistic regression analysis. Results: Patients with T2DM showed a significant increase in IMT and PWVao, a reduction in LV GLS, and low levels of 25(OH)D3 compared to subjects in the control group (all p < 0.05). Both vitamin D deficiency and T2DM were found to be independently associated with an increased arterial stiffness, with odds ratios of 2.4 and 4.8, respectively. A significant inverse relationship was identified between 25(OH)D3 levels and markers of arterial stiffness, as well as LV GLS, suggesting a possible association between the vitamin D status and the early onset of cardiovascular dysfunction. Conclusions: Patients with T2DM show early signs of heart and blood vessel problems, even with an ejection fraction that remains within normal limits. There is a significant correlation between vitamin D deficiency and increased arterial stiffness, along with impaired LV GLS, indicating its possible involvement in cardiovascular complications associated with diabetes. These findings support the utility of integrating vascular, myocardial, and vitamin D assessments in early cardiovascular risk stratification for T2DM patients. Full article

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

The deep carbonate reservoirs in the Tarim Basin, Xinjiang, China, are widely developed with multi-scale complex reservoir spaces such as fractures, pores, and karst caves under the coupling of abnormal high pressure, diagenesis, karst, and tectonics and have strong heterogeneity. Among them, fracture–cavity carbonate reservoirs are one of the main reservoir types. Revealing the petrophysical characteristics of fracture–cavity carbonate reservoirs can provide a theoretical basis for the log interpretation and geophysical prediction of deep reservoirs, which holds significant implications for deep hydrocarbon exploration and production. In this study, based on the mineral composition and complex pore structure of carbonate rocks in the Tarim Basin, we comprehensively applied classical petrophysical models, including Voigt–Reuss–Hill, DEM (Differential Effective Medium), Hudson, Wood, and Gassmann, to establish a fracture–cavity petrophysical model tailored to the target block. This model effectively characterizes the complex pore structure of deep carbonate rocks and addresses the applicability limitations of conventional models in heterogeneous reservoirs. The discrepancies between the model-predicted elastic moduli, longitudinal and shear wave velocities (Vp and Vs), and laboratory measurements are within 4%, validating the model’s reliability. Petrophysical template analysis demonstrates that P-wave impedance (Ip) and the Vp/Vs ratio increase with water saturation but decrease with fracture density. A higher fracture density amplifies the fluid effect on the elastic properties of reservoir samples. The Vp/Vs ratio is more sensitive to pore fluids than to fractures, whereas Ip is more sensitive to fracture density. Regions with higher fracture and pore development exhibit greater hydrocarbon storage potential. Therefore, this petrophysical model and its quantitative templates can provide theoretical and technical support for predicting geological sweet spots in deep carbonate reservoirs. Full article

Background: Age-related vascular stiffening increases cardiovascular risk by altering ventricular–arterial coupling (VAC). Physical activity, a modifiable factor, may improve cardiovascular health. This pilot study evaluated the relationship between physical activity evaluation and VAC, measured by the carotid–femoral pulse wave velocity to global longitudinal strain (cfPWV/GLS) ratio, in a Romanian primary care cohort. Methods: The prospective cohort analysis was performed on 81 adults (49 females, mean age 50.27 ± 12.93 years). Physical activity was quantified through anamnesis using metabolic equivalents (METs) according with Compendium of Physical Activities, and patients were stratified into four groups: G1 (METs < 1.5, n = 39), G2 (METs = 1.5–2.9, n = 2), G3 (METs = 3–5.9, n = 23), and G4 (METs ≥ 6, n = 17). Demographic and echocardiographic data were recorded to explore associations between physical activity and VAC. Results: The cfPWV/GLS ratio differed significantly across groups (p = 0.012), with the lowest values present in the moderate-intensity group (G3). VAC ≥ 0.391 can predict sedentary lifestyles (AUC = 0.730; CI: 0.617–0.833, p > 0.001). Multivariate analysis revealed that age, arterial age, and hypertension independently predict VAC. Conclusions: Higher physical activity is inversely associated with VAC (cfPWV/GLS ratio) and can predict sedentary lifestyles. Encouraging moderate-to-vigorous exercise in primary care may improve cardiovascular function and aid prevention. Full article

In this study, a correction procedure for ship mass and its longitudinal location of center of gravity suitable for a simulation environment is proposed in OpenFOAM v6.0. The concept is implemented ensuring static equilibrium and an approximately zero-pitch moment on the ship before the simulation. The viscous flow field around the ship in calm water is simulated using the VOF (Volume of Fluid) free surface two-phase and SST (Shear Stress Transport) k–ω turbulence models. Using static mesh, the resistance error of medium and fine grids is 4%, on average, against the experimental value. As the sinkage and trim are predicted using dynamic mesh, the increasing ship’s resistance causes larger errors, except for the container ship. Through the proposed correction, the ship’s vertical motions are significantly improved, and the resistance error decreases for the dynamic simulation. For the container ship, the error of resistance and motion achieved is less than 1%. The sinkage and trim errors improve tremendously for the tanker and bulk carrier, and the resistance errors are reduced slightly, by less than 3%. In the end, the detailed flow field is analyzed, as well as the ship wave-making pattern and the nominal wake velocity distribution, and these are compared with the measurement data available. The characteristics of the flow phenomena are successfully modeled. The resistance value for each hull form satisfies the requirement of Verification and Validation, and the uncertainty values are estimated. Full article

Local scour around bridge piers poses significant challenges to the stability and safety of bridge structures. Local scour results from the combined effects of increased longitudinal flow velocity, the direct impact of the flow in front of the pier, and the suction effect of horseshoe vortices. This study utilizes a three-dimensional mathematical model to simulate the flow field around the pier, employing the SWASH (simulating waves till shore) model. Experimental observations in a bed load flume were conducted to analyze the contribution of different factors to local scour. The results indicate that the scour depth caused predominantly by the flow accounts for approximately 75–80% of the total scour depth. Analysis of the longitudinal flow velocity distribution suggests that the scour depth due to the redistribution of longitudinal flow velocity generally accounts for 15–30% of the total scour depth. These findings provide insights into the local scour mechanism and have implications for the design and maintenance of bridge foundations. Full article

To investigate the pore structure evolution characteristics and damage mechanism of sandstone subjected to treatment with freeze–thaw cycles, quantitative analyses were conducted on the longitudinal wave velocity (LWV) and T₂ spectrum of sandstone before and after 10, 20, 30, and 40 freeze–thaw cycles, using longitudinal wave velocity testing, low-field nuclear magnetic resonance (NMR) testing, and fractal theory. The results show that, with the increase in the number of freeze–thaw cycles, the LWV of sandstone gradually decreases, the amplitude of the saturated T₂ spectrum gradually increases, the amplitude of the centrifugal T₂ spectrum gradually decreases, the total porosity and effective porosity increase, and the residual porosity decreases. After undergoing freeze–thaw cycles, sandstone exhibits obvious fractal characteristics in both the total porosity NMR fractal dimension and the effective porosity NMR fractal dimension, and the growth rates of both decrease exponentially with the increase in the number of freeze–thaw cycles. The magnitude of the fractal dimensions reflects the complexity of the pore structure, with smaller fractal dimensions indicating better pore connectivity. In summary, the damage evolution mechanism of sandstone under freeze–thaw cycles is characterized by the gradual expansion and interconnection of internal closed micro-pores (cracks), along with increased total porosity and effective porosity, leading to enhanced freeze–thaw damage. Full article

Nonlinear elastic properties of polymers and polymer-based composites are essential for accurate prediction of their response to dynamic loads, which is crucial in a wide range of applications. These properties can be affected by strain rate, temperature, and pressure. The temperature susceptibility of nonlinear elastic moduli of polymers remains poorly understood. We have recently observed a significant frequency dependence of the nonlinear elastic (Murnaghan) moduli of polystyrene. In this paper we expanded this analysis by the temperature dependence. The measurement methodology was based on the acousto-elastic effect, and involved analysis of the dependencies of velocities of longitudinal and shear single-frequency ultrasonic waves in the sample on the applied static pressure. Measurements were performed at different temperatures in the range of 25–65 °C and at different frequencies in the range of 0.7–3 MHz. The temperature susceptibility of the nonlinear moduli l and m was found to be two orders of magnitude larger than that of linear moduli $\lambda$ and $\mu$. At the same time, the observed variations of n modulus with temperature were low and within the measurement tolerance. The observed tendencies can be explained by the shift of nonlinear moduli towards higher frequencies with increasing temperature. Full article

Background: The Mediterranean diet has long been associated with better cardiovascular health, with evidence suggesting that it may play a key role in reducing arterial stiffness. This research aims to systematically review existing evidence on the association between a Mediterranean diet pattern and arterial stiffness in the general population. Methods: The literature was examined in six electronic databases up until December 2024. The evaluation of the 128 publications based on inclusion criteria resulted in the selection of 16 observational and randomized controlled trials that aligned with the research question. Two researchers simultaneously extracted the data, employing inter-rater reliability (IRR) to assess coder agreement, followed by the κ statistic to evaluate accuracy and precision. According to the PRISMA principles and quality evaluation procedures, all data extraction phases achieved a k coefficient of no less than 0.9. All publications, with the exception of randomized controlled trials (RCTs), were evaluated for bias risk utilizing the NIH Quality Assessment Toolkit. The study protocol was registered with PROSPERO (CRD42024597173). Results: Most studies were observational (ten cross-sectional, three longitudinal), with three RCTs. Studies were primarily conducted in Europe (82%), followed by America (12%) and Australia (6%), with a total of 13,680 participants. The evidence showed an inverse relationship between adherence to the Mediterranean diet and arterial stiffness, with a focus on pulse wave velocity (PWV) and the Augmentation Index (AIx) as outcome measures. Lower but consistent and statistically significant evidence was also found in the cross-tabulation of adherence to the Mediterranean diet and the cardiovascular ankle index (CAVI), a proxy of the overall stiffness of the artery from the origin of the aorta to the ankle. Study quality ranged from moderate to high. Conclusions: The available evidence consistently shows that people who follow a Mediterranean diet may have less stiff arteries and, therefore, a lower cardiovascular risk. However, multifactorial biological pathways still need to be corroborated. Full article

The diversity of commercial tree planting sites, with their distinct environmental conditions, directly influences tree growth and consequently impacts the wood properties in various ways. However, there is limited research evaluating the impact of these variations in nondestructive testing. Therefore, this study aimed to investigate whether edaphoclimatic variations affect parameters obtained through nondestructive tests conducted on standing trees. To this end, 30 specimens were selected from 3 Eucalyptus sp. clones, aged 1, 3, and 4 years, grown in 2 regions, totaling 540 trees. Tree development was monitored quarterly over 12 months. The tests included ultrasound propagation, drilling resistance, and penetration resistance, and the trees were measured for diameter at breast height (DBH) and height. Among the edaphoclimatic factors evaluated, only temperature and soil water storage differed statistically between the two study regions. The higher temperature and lower soil water storage in region 2 promoted tree growth, with these trees showing greater drilling resistance and higher longitudinal wave velocities. In addition, the influence of climatic factors was evidenced by the variation of wave propagation velocity throughout the year. Periods of lower water availability resulted in higher velocities, while periods of greater precipitation were associated with lower velocities. The research results showed that temperature and soil water storage had significant effects on tree growth (DBH and height), as well as ultrasound wave propagation velocity and drilling resistance. Full article

Background: Cardiac amyloidosis (CA) is a progressive disorder characterized by amyloid fibril deposition in the heart, leading to heart failure and arrhythmias. Arterial stiffness, assessed by pulse wave velocity (PWV), is recognized as an adverse consequence of amyloidosis, yet its progression and relationship with myocardial dysfunction remain inadequately explored. This study examines the progression of PWV and its potential association with the deterioration of global longitudinal strain (GLS) in CA patients over a 6-month follow-up period. Methods: This prospective study enrolled 31 patients who were diagnosed with CA, including both the immunoglobulin light chain (AL) and transthyretin (ATTR) forms. All participants underwent a full echocardiographic study and PWV measurements (carotid-femoral [c-f] and carotid-radial [c-r] PWV) at baseline and 6-month follow-up. Age- and sex-matched individuals with similar cardiovascular risk factors were included as a control group. Results: In the CA group, the left ventricular mass index (LVMI) increased significantly from 119.4 ± 52.1 to 124 ± 53.2 g/m² (p = 0.002). Both c-f and c-r PWV showed significant increases at the 6-month follow-up (p < 0.001 and p = 0.005, respectively). The GLS deteriorated significantly from −14 ± 4.4% to −12.8 ± 4.9% (p = 0.018). No significant changes were observed in the control group. A weak correlation (r = 0.3; p = 0.095) was found between increases in PWV and GLS deterioration. Conclusions: Both arterial stiffness and myocardial dysfunction worsen rapidly in CA patients. However, the weak correlation between PWV and GLS suggests that they may evolve through independent mechanisms, necessitating further research to understand their complex interplay in CA. Full article