Search Results (188)

This study analyzes the impact of geometric variations induced by the manufacturing process on the aerodynamic efficiency of an airfoil used in the design of a 3 kW wind turbine blade. For this purpose, a computational fluid dynamics (CFD) analysis was implemented, and the results were compared with those obtained using QBlade software. After blade fabrication, experimental evaluation was performed using the laser triangulation technique, enabling the reconstruction of the deformed airfoils and their comparison with the original geometry. Additional CFD simulations were carried out on the manufactured airfoil to quantify the loss of aerodynamic efficiency due to geometrical deformations. The results show that the geometric deviations significantly affect the aerodynamic coefficients, generating a decrease in the lift coefficient and an increase in the drag coefficient, which negatively impacts the airfoil aerodynamic efficiency. A 14.9% reduction in the rotor power coefficient was observed with the deformed airfoils compared to the original design. This study emphasizes the importance of quality control in wind turbine blade manufacturing processes and its impact on turbine power performance. In addition, the findings can contribute to the development of design compensation strategies to mitigate the adverse effects of geometric imperfections on the aerodynamic performance of wind turbines. Full article

Respiratory pathogens are significant causes of morbidity and mortality worldwide. Since the emergence of SARS-CoV-2 in 2019 and the mitigation measures implemented to control the pandemic, other respiratory viruses’ transmission and circulation patterns were substantially disrupted. We leveraged the influenza hospitalization surveillance in Tanzania to understand the distribution of respiratory viruses shortly after nonpharmaceutical interventions (NPIs) were lifted. A total of 475 samples that tested negative for SARS-CoV-2 and influenza from March through May 2022 were included in this study. The samples were tested for 16 virus targets using Anyplex II RV16 multiplex assays. The findings indicate that most hospitalizations (74%) were among children under 15 years, with human bocavirus (HBoV) being the most prevalent (26.8%), followed by rhinovirus (RV, 12.3%), parainfluenza viruses (PIVs1–4, 10.2%), respiratory syncytial virus (RSV, 8.7%), adenovirus (AdV, 4.3%), and metapneumovirus (MPV, 2.9%). Notably, 54% of respiratory hospitalizations had no viruses detected. The findings highlight the broad circulation of respiratory viruses shortly after NPIs were lifted in Tanzania. Surveillance for respiratory pathogens beyond influenza and SARS-CoV-2 can inform public health officials of emerging threats in the country and should be considered an important pandemic preparedness measure at a global level. Full article

This study innovatively proposes a pipeline-type pneumatic lift sediment removal device for cleaning pollutants at the bottom of fish breeding tanks and conducts hydrodynamic characteristic analysis on its core component, the pneumatic lift pipeline structure, which consists of a horizontal circular tube with multiple micro-orifices at the bottom and an upward-inclined circular tube. The pipeline has an inner diameter of 20 mm and a vertical length of 1.2 m, with the orifice at one end of the horizontal tube connected to the gas supply line. During operation, compressed gas enters the horizontal tube, generating negative liquid pressure that draws solid–liquid mixtures from the tank bottom into the pipeline, while buoyant forces propel the gas–liquid–solid mixture upward for discharge through the outlet. Under a constant gas flow rate, numerical simulations investigated efficiency variations through three operational scenarios: ① different pipeline orifice diameters, ② varying orifice quantities and spacings, and ③ adjustable pipeline bottom clearance heights. The results indicate that in scenario ①, an orifice diameter of 4 mm demonstrated optimal efficiency; in scenario ②, the eight-orifice configuration achieved peak efficiency; and scenario ③ showed that the proper adjustment of the bottom clearance height enhances pneumatic efficiency, with maximum efficiency observed at a clearance of 10 mm between sediment suction pipe and tank bottom. Full article

In this study, through RH water model simulation experiments, the effects of precipitation bubbles on the two-phase flow pattern, liquid steel flow behavior, and flow characteristics in an RH reactor during the whole decarburization process were comparatively investigated and analyzed by using quasi-counts that reflected the similarity of the precipitation bubble phenomenon. The experimental results show that an increase in precipitation bubbles is positively related to an increase in circulating flow rate, a reduction in mixing time, and an increase in gas content and negatively related to the residence time of liquid steel in the vacuum chamber. The two-phase flow pattern of the rising tube under the influence of precipitation bubbles includes bubble flow, slug flow, mixing flow, and churn flow. Under the influence of precipitation bubbles, the liquid surface spattering inside the vacuum chamber is reduced, the fluctuation amplitude is reduced, the efficiency of liquid steel processing is improved, it is not easy for cold steel to form, and the fluctuation frequency is increased, which is conducive to increasing the surface area of the vacuum chamber; the bubbles’ rising, aggregating, and crushing behavior increases the stirring effect inside the vacuum chamber, which is conducive to improving the decarburization and mass transfer rate. Under the influence of the precipitated bubbles, the concentration gradient between the ladle and the vacuum chamber is increased, which accelerates the mixing speed of the liquid steel in the ladle, and the volume of the dead zone is reduced by 50%. The lifting gas flow rate can be appropriately reduced in the plant. Full article

Nitrogen oxides (NO_x) are key precursors of tropospheric ozone and particulate matter. The sparse local observations make it challenging to understand NO_x cycling across the Tibetan Plateau (TP), which plays a crucial role in regional and global atmospheric processes. Here, we utilized Geostationary Environment Monitoring Spectrometer (GEMS) data to examine the tropospheric NO₂ vertical column density (Ω_NO2) spatiotemporal variability over TP, a pristine environment marked with natural sources. GEMS observations revealed that the Ω_NO2 over TP is generally low compared with surrounding regions with significant surface emissions, such as India and the Sichuan basin. A spatial decreasing trend of Ω_NO2 is observed from the south and center to the north over Tibet. Unlike the surrounding regions, the TP exhibits opposing seasonal patterns and a negative correlation between the surface NO₂ and Ω_NO2. In the Lhasa and Nam Co areas within Xizang, the highest Ω_NO2 in spring contrasts with the lowest surface concentration. Diurnally, a midday increase in Ω_NO2 in the warm season reflects some external sources affecting the remote area. Trajectory analysis suggests strong convection lifted air mass from India and Southeast Asia into the upper troposphere over the TP. These findings highlight the mixing interplay of nonlocal and local NO_x sources in shaping NO₂ variability in a high-altitude environment. Future research should explore these transport mechanisms and their implications for atmospheric chemistry and climate dynamics over the TP. Full article

Background/Objectives: Clinical experience indicates that the determination of interleukin 6 (IL-6) in human blood can vary depending on time span between sample collection and centrifugation. Here, we evaluated confounding effects in various blood specimens. Methods: The blood of healthy individuals and critically ill patients was collected in EDTA-, heparin-, and serum collection tubes. Tubes were facultatively incubated (20 °C, 24–48 h) before centrifugation, and IL-6 was measured in the supernatant. Results: The preincubation of the blood collection tubes increased the IL-6 values in heparin plasma (in 17/20 samples up to 50-fold) and serum (in 17/20 samples up to 12-fold). These changes were relevant since the normal values were thereby lifted above the upper confidence limit in 12/20 heparin plasma samples and 4/20 serum samples. These IL-6 increases were probably due to in vitro synthesis as opposed to the release of preformed IL-6 from blood cells because subjecting uncentrifuged collection tubes to mechanical cell lyses had negligible effects on IL-6, while incubation with microbial stimulators dramatically increased these values. In the case of EDTA blood, collection tube preincubation induced IL-6 decreases in 17/20 samples from healthy individuals and 20/23 samples from critically ill patients. Conclusions: IL-6 determination in heparin plasma and serum is compromised by delayed centrifugation. This effect is relevant for normal values. It increased the number of false high results by >50%. The delayed centrifugation of EDTA blood decreased the IL-6 values, which caused a single false-negative result in 1/43 healthy and critically ill people. The false-negative rate is possibly higher in EDTA blood from non-critically ill out-patients, exhibiting moderately increased IL-6 levels. Full article

In recent years, the actuarial literature involving machine learning in insurance pricing has flourished. However, most actuarial machine learning research focuses on property and casualty insurance, while using such techniques in health insurance is yet to be explored. In this paper, we discuss the use of neural networks to set the price of health insurance coverage following the structure of a classical frequency-severity model. In particular, we propose negative multinomial neural networks to jointly model the frequency of possibly correlated medical claims and Gamma neural networks to estimate the expected claim severity. Using a case study based on real-world health insurance data, we highlight the overall better performance of the neural network models with respect to more established regression models, both in terms of accuracy (frequency models achieve an average out-of-sample deviance of 8.54 compared to 8.61 for classical regressions) and risk diversification, as indicated by the ABC lift metric, which is $5.62\times {10}^{-3}$ for neural networks versus $8.27\times {10}^{-3}$ for traditional models. Full article

Although grouting technology has been widely applied for lifting and rectifying tilted structures, theoretical research remains underdeveloped and lags behind the practical demands of engineering applications. In this study, a self-developed experimental setup was utilized to conduct model tests on the lifting and rectification of a raft foundation in saturated silty clay. The evolution patterns of ground surface displacement, excess pore water pressure, and foundation-additional pressure induced by grouting were systematically analyzed. Furthermore, the influence of grouting depth and injection rate on surface displacement, excess pore water pressure, foundation-additional pressure, and grouting parameters (grout volume and pressure) was investigated. The key findings are summarized as follows: The grouting efficiency (η) ranged between 0.72 and 0.81. A power-exponential dual-function model was proposed to quantify the spatiotemporal evolution of excess pore water pressure, achieving a distance–decay power function with R² > 0.89 and a time-dependent dissipation exponential function with $R^2$ > 0.94. The maximum surface uplift displacement decreased by 20.6% and 8.9% with increasing grouting rates, respectively. The dissipation time of excess pore water pressure exhibited a negative correlation with the grouting rate, and grouting efficiency declined as excess pore water pressure dissipated. The maximum foundation-additional pressure occurred directly above the grouting center and gradually diminished as the horizontal distance from the grouting location increased. Variations in surface displacement, excess pore water pressure, and additional base pressure induced by grouting were systematically analyzed. Full article

To address the negative impacts in recovering large areas of residual plastic film from corn stubble in the Hexi irrigation area—such as the residual film containing substantial amounts of soil, corn stubble, and corn straw, and high power consumption during the operation process—in this study, a combined operation machine was designed for corn straw crushing and residual film recovery. The machine consisted of a double-wing, single-blade shovel for lifting the film and cutting corn stubble, a corn straw-crushing and returning device for reducing the residual film impurity rate, an eccentric teeth shifting cylinder for picking up residual film, a device for shifting residual film, and a collection device for bundling residual film. The key components of the combined operation machine were designed based on an agronomic model for corn planting and the mechanized operation requirements in the Hexi irrigation area. The optimal combination of operating parameters was devised based on theoretical calculations and single- and multifactor simulation tests. The results showed that when the angle of entry of the film-lifting shovel was 25.14°, the rotational speed of the eccentric teeth shifting cylinder was 80.96 rpm, and the forward velocity of the machine was 4.03 km/h, while the rate of recovery of residual film was 92.56%. The field test showed that the residual film contained 16.65% impurities, and the qualified rate of corn straw crushing was 88.51%, with a relative error of 0.65% from the optimized value. The experimental results provide theoretical support and a design reference for research on the mechanized recycling of residual film in large areas of corn stubble. Full article

Sthenoteuthis oualaniensis is one of the most commercially important marine cephalopod species distributed throughout tropical and subtropical waters of the Indo-Pacific Seas. The Indian Ocean is a main fishing ground for S. oualaniensis with a high population density. To explore the distribution of S. oualaniensis in the east equatorial Indian Ocean, four surveys were carried out using light-lift-net fishing vessels. Meanwhile, marine environmental data were also collected, including the sea surface temperature, sea temperature at 100 m depth, mixed layer depth, sea surface chlorophyll-a concentration, sea surface height, and eddy kinetic energy. Generalized Additive Models were used to analyze the relationship between the catch per unit effort (CPUE) for S. oualaniensis and environmental factors. The results showed that the average CPUE of S. oualaniensis was 14.55 kg/h in the four surveys, which was considerably lower than in the South China Sea and Northwest Indian Ocean. In terms of seasonal distribution, the high-CPUE stations were closer to the continental shelf in spring, while they shifted towards the deeper and offshore water in autumn, demonstrating a seasonal migration trend. Pearson correlation analysis showed that CPUE reflected a significant negative correlation with both sea temperature at 100 m depth and eddy kinetic energy (p < 0.001). The Generalized Additive Models revealed that sea surface height was the most significant factor affecting CPUE with a variance explanation of 30.1%. Furthermore, the optimal CPUE prediction model was established by stepwise regression, which contains two factors, sea surface height and eddy kinetic energy, with a variance explanation of 34.9%. This study provides insights into the environmental factors influencing the distribution of S. oualaniensis, which is essential for the sustainable utilization and management of this species. Full article

In order to explore the inducing mechanism of negative damping of bending–torsional coupling flutter, an ideal plate with a width of 0.45 m was taken as the research object. The changes in frequency, critical wind speed, aerodynamic stiffness, and aerodynamic damping were systematically analyzed by using the “incentive-feedback” mechanism theory. The source of modal damping and the inducing mechanism of bending–torsional coupling flutter were identified. The research results show that the torsional modal damping of the ideal plate mainly comes from the aerodynamic positive damping of the torsional velocity self-excitation ($A_2^{*}$) and the aerodynamic negative damping of the torsional displacement incentive feedback ($A_1^{*}{H}_3^{*}$). Among them, the aerodynamic negative damping of the item ($A_1^{*}{H}_3^{*}$) causes the torsional mode damping to be negative, and the ideal plate undergoes bending–torsion-coupled flutter under the drive of the torsional mode aerodynamic negative damping. The reason why the aerodynamic damping of the item ($A_1^{*}{H}_3^{*}$) is negative depends on two aspects: one is that the flutter derivatives $A_1^{*}$ and $H_3^{*}$ have opposite signs; the second is that the torsional displacement self-excited lift excites the vertical vibration to produce negative stiffness $-m_h{\omega }_{s\alpha }^2$. This results in the phase difference between the torsional displacement self-excited lift and the vertical displacement response in the range of (90–180°). Full article

This study investigates the aerodynamic effects of wing membrane elasticity inspired by bats, which exhibit exceptional maneuverability and stability. By mimicking bat wing folding and flapping motions, a 2-DOF flapping mechanism was developed to examine the impact of wing membrane elasticity. Polydimethylsiloxane (PDMS) membranes with tunable elastic properties were fabricated by adjusting the ratio of the curing agent (B agent), with the 1/50 ratio exhibiting the greatest extensibility and the lowest Young’s modulus. Experimental results demonstrate that wing membrane elasticity significantly influences aerodynamic performance. During flapping, increased elasticity led to larger camber changes, enhancing vertical lift through stronger leading-edge vortices, as confirmed by PIV flow field measurements. However, when elasticity became excessively high, as in the 1/50 membrane, the lift benefit diminished, and horizontal force decreased, indicating a trade-off between vertical and horizontal aerodynamic performance. Additionally, the folding mechanism was found to be critical for drag reduction, reducing nearly 50% of negative horizontal forces during flight. By integrating adjustable wing membrane properties and a bioinspired flapping mechanism, this research provides valuable insights into the aerodynamic characteristics of bat flight. These findings not only enhance the understanding of flapping wing aerodynamics but also offer guidance for the design of efficient and agile bioinspired aerial vehicles. Full article

In the complex and harsh working environment of wind turbines, the horizontal axis wind turbine blade is increasingly confronted with the issue of surface roughening. It leads to a decrease and instability in the output power of the horizontal axis wind turbine. Vortex generator have emerged as a potential solution to this problem by regulating the flow patterns on the blade surface. This research focuses on exploring the impact of vortex generator on the aerodynamic performance of blades under rough wall condition by wind tunnel experiment and computational fluid dynamics simulation. It is important to improve the aerodynamic performance of horizontal axis wind turbine under rough condition. The results show that vortex generator changes the airfoil aerodynamic performance by slowing the stall angle of attack and increasing the ratio of lift-drag in some angles of attack. vortex generator delays the flow separation of the suction surface under the rough wall condition. It is able to counteract the reduction in the aerodynamic performance of blade under rough wall condition. At tip speed ratio is 5.83, vortex generator increased power coefficient by 47.8% under rough wall condition by reducing the flow separation area of 33% radius and weakening the spanwise flow. The study found that the vortex generator effectively eliminated the negative effects of blade surface roughening on aerodynamic performance, improved the roughness insensitivity of the blade, and has good potential for future applications. Full article

The hydrodynamic coefficients of underwater robots can be used to evaluate their maneuverability and motion stability and to design motion controllers, thereby reducing experimental time and costs. In this paper, an Autonomous Underwater Vehicle (AUV) with a negative-lift profile is designed. The spatially constrained motion method, combined with neural networks, is utilized to identify all the hydrodynamic coefficients in the standard hydrodynamic equations of the AUV. Subsequently, based on the goodness-of-fit, the significance of the hydrodynamic coefficients is evaluated to yield a simplified hydrodynamic equation. Given the cost constraints, it was not feasible to obtain precise experimental data on hydrodynamic coefficients to validate the accuracy of the CFD calculation method. Therefore, the hydrodynamic coefficients were used to construct a dynamic model for the AUV, and an MPC controller was designed based on this model. Finally, simulations and pool tests were conducted on the AUV, and a comparative analysis of the simulation results with the pool test results revealed that although there were certain errors in the calculation of the hydrodynamic coefficients, the controller constructed within this margin of error was still capable of effectively controlling the AUV. This fully demonstrates the feasibility and applicability of using CFD methods to calculate hydrodynamic coefficients and establishing model predictive control methods based on these coefficients in practical applications. Full article

Positive-reinforcement training of laboratory pigs can reduce the reliance on forced manual restraint and anaesthesia for sample collection, reducing stress and physiological disruption. Training regimens for laboratory pigs typically rely on specialised equipment for restraint, such as Panepinto slings, with a time investment that may not be justified for short-term studies. These training regimens also commonly rely on pigs being lifted into sling restraints, which is not practical for studies involving large pigs. We developed and assessed a rapid, three-phase, positive-reinforcement training regimen for both individually housed and group-housed laboratory pigs to facilitate the collection of minimally invasive samples consciously and voluntarily. The time to complete each phase of training in both individually housed and group-housed pigs was recorded. The behaviour of the individually housed pigs was assessed via an ethogram of behaviours exhibited during a human approach test, and stress response was assessed by analysing salivary corticosterone. The rapid, positive-reinforcement training regimen successfully facilitated oral swabbing, rectal swabbing and rectal thermometer insertion from individually housed (within 18 days) and group-housed (within 6 days) pigs. The trained pigs displayed increasing positive behaviours, no or very few negative behaviours and corticosterone levels within normal limits throughout the study. This training regimen provides a practical and welfare-positive tool for the collection of minimally invasive samples from both small and large laboratory pigs, with a low time investment of 2–5 min/pig/day without the need for specialised restraint equipment. Full article