Search Results (3,829)

The utilization of “green” hydrogen in transportation areas gives rise to production- and supply infrastructure-related challenges; therefore, its wider application in automotive transport would lead to higher demand with cost reduction and a faster expansion of the hydrogen refuelling network. This study presents energy and environmental performance indicators analyses of a Nissan Qashqai J10 engine during the Worldwide Harmonised Light Vehicles Test Cycle (WLTC), replacing conventional fossil gasoline with dual-fuel (D-F) gasoline and hydrogen. Numerical modelling was conducted using AVL Cruise™ (Version R2022.2) software, utilizing the torque, fuel consumption, and environmental performance data of the HR16DE engine obtained through experimental testing across a wide range of loads and speeds on an engine test bench. The experimental investigation was carried out in two stages: using pure gasoline (G100); injecting a hydrogen additive into the intake air, constituting 5% of the gasoline mass (G95H5). Following similar stages, numerical modelling was conducted using the vehicle’s technical specifications to calculate engine load and speed throughout the WLTC range. Instant fuel consumption and pollutant emissions (CO, CH, NO_x) were determined for various driving modes using experimental data maps. CO₂ emissions were calculated considering fuel composition and consumption. By integrating the instant values, the total and specific fuel consumption and emissions were calculated. As a result, this study identified the effect of a 5% hydrogen additive in improving engine energy efficiency, reducing incomplete combustion products and lowering greenhouse gas (CO₂) emissions under various driving modes. Finally, the results were compared with the requirements of EU standards. Full article

Cold forming offers high dimensional accuracy, energy and cost efficiency in the mass production of highly stressed components but is also associated with high tribological loads. Complex lubrication systems are required to ensure smooth production. As environmental standards rise, traditional zinc phosphate-based lubricants are to be replaced by less harmful single-layer systems. However, these new lubricants are temperature-sensitive, which requires precise knowledge of the temperatures in the forming zone for optimal design. Due to high compressive stress, conventional measuring methods cannot measure temperatures directly in the forming zone. In this work, lubricants are expanded into a temperature sensor using thermochromic pigments so that temperatures can be measured directly in the forming zone. This work outlines the selection and integration of the indicators, the development of a calibration method for thermochromic lubricants to characterize the correlation between colour value and temperature. It is shown that the lubricant behaviour does not deteriorate up to concentrations of 10%. The transfer of the measurement methodology from the laboratory application to the industrial multi-stage process has been successfully implemented and local temperature peaks are measured directly in the contact zone and correspond to the simulation results. The results of the work show an approach to closing the gap identified in existing research work, namely that the temperature cannot be measured directly in the forming zone during cold forging. The measuring system developed can be transferred to various processes in the future and contribute to the identification of correlations between temperature, lubricant failure and wear. Full article

Chagas disease remains a significant public health concern, with limited treatment options and an urgent need for novel preventive strategies. Extracellular vesicles (EVs) from Trypanosoma cruzi have been shown to modulate host immune responses, often favoring parasite persistence. In this study, we characterized EVs derived from the non-pathogenic trypanosomatids Trypanosoma rangeli and Phytomonas serpens and evaluated their potential as immunogens capable of inducing cross-protection against T. cruzi infection. Isolated EVs were characterized by Nanoparticle Tracking Analysis (NTA) and electron microscopy. A comparative proteomic analysis of EVs was performed using Mass Spectrometry-Based Proteomic Analysis (LC-MS/MS). The effects of EVs on immunomodulation and T. cruzi infection were assessed through in vitro and in vivo assays, using peripheral blood mononuclear cells (PBMCs) and BALB/c mice. The proteomic analysis identified shared proteins between the EVs of T. rangeli, P. serpens, and T. cruzi, including immunogenic candidates such as calpain-like cysteine peptidase and elongation factor 2. In vitro, pre-stimulation with the T. rangeli EVs reduced infection rates of the host cells by T. cruzi. In vivo, immunization with the EVs from T. rangeli and P. serpens led to a significant reduction in parasitemia in the BALB/c mice challenged with T. cruzi, though this did not translate into improved survival compared to controls. Interestingly, the EVs from T. cruzi also reduced parasitemia but did not confer protection against mortality. These findings suggest that while non-pathogenic trypanosomatid EVs exhibit potential immunogenic properties and can reduce parasitic load, their efficacy in preventing disease progression remains limited. Further research is needed to explore the mechanisms underlying these effects and to optimize EV-based strategies for protective immunity against Chagas disease. Full article

Friction pendulum bearings are widely used seismic isolation devices for bridges, with their behavior governed by friction during excitation. Sliding velocity and contact pressure are among the factors that substantially affect the friction coefficient. Common friction models include the Coulomb model, which assumes constant friction and neglects both sliding velocity and contact pressure, and the velocity-dependent model, which ignores contact pressure. This study investigates the impact of neglecting contact pressure on bridge response by additionally employing a velocity-pressure-dependent friction model and comparing the effects of these three models on the bridge response. Five 3-span box-girder RC bridges were modeled in OpenSees (v3.5.0) using Coulomb, velocity-dependent, and velocity-pressure-dependent friction models. Deck height variations were introduced to account for axial load changes on bearings. Nonlinear time history analyses were performed to evaluate seismic responses. The study also explored the effects of substructure-to-superstructure mass ratio and variations in the experimentally obtained rate parameter of velocity-dependent and velocity-pressure-dependent models. Results indicate that the velocity-pressure-dependent model provides more consistent predictions, while the rate parameter has negligible effects. The velocity-pressure-dependent model increases isolator displacement by nearly 2.5 times compared to the Coulomb and velocity-dependent models. Differences in responses are influenced more by the mass ratio than by the deck aspect ratio. Full article

The inversion of the ground stress field in rock masses is critical for accurate tunnel and underground engineering design. This study addresses the challenge of accurately capturing both the primary and secondary stress field components in rock masses. The ground stress field consists of the primary stress field, generated by applied tectonic loads, and a secondary stress field, which cannot be fully explained by these loads and is attributed to long-term tectonic processes. This unexplained secondary stress field is often non-random in nature. To improve the accuracy of the ground stress field inversion, we propose prioritizing the use of a regression model with a constant term. This model better accounts for the secondary stress field by capturing long-term tectonic influences. The constant term in the regression model is shown to represent the non-random secondary stress field, which cannot be explained by applied tectonic loads. Furthermore, we define two key conditions for applying this regression model: (1) the constant term should not exceed the maximum measured stress and preferably should not surpass the minimum measured stress, and (2) the residual sum of squares of the regression model with a constant term should be smaller than that of the model without a constant term. By incorporating the constant term, the model improves the representation of both primary and secondary stress fields, offering a more accurate inversion of the ground stress field, especially when the stress field contribution from independent variables is incomplete. Full article

Background/Objectives: The novel pyrazoloquinolinone ligand CW-02-79 shows a unique profile of selective binding to σ2 receptors, but its poor solubility in both water and lipids makes its research and development a burdensome task. We aimed to develop a phospholipid-complex-based nanoemulsion formulation containing CW-02-79 suitable for intravenous administration in preclinical research. Methods: The decorated and undecorated nanoemulsions were formulated and subjected to detailed physiochemical characterization. The delivery and exposure to CW-02-79 from selected nanoemulsions were examined in the in vitro blood–brain barrier model based on human-induced pluripotent stem-cell-derived microvascular endothelial cells, astrocytes, and pericytes, and in vivo neuropharmacokinetic study in rats, respectively. Results: The developed biocompatible nanoemulsions loaded with a CW-02-79—phospholipid complex at a mass ratio of 1:10 exhibited a small droplet size and narrow size distribution, with satisfactory physicochemical stability during steam sterilization and short-term storage at 25 °C. The analysis of protein binding interactions revealed that the PEGylated nanoemulsions had fewer observable interactions compared to the undecorated nanoemulsions, especially when 0.2% DSPE-PEG2000 and 0.1% DSPE-PEG2000-mannose were combined. An in vitro BBB study demonstrated that a substantial part of CW-02-79 present in the applied nanoemulsion is able to permeate the barrier. The quantification of CW-02-79 in plasma/brain homogenate and calculated pharmacokinetic parameters confirmed good systemic and brain availability after intravenous administration. There were subtle differences in the pharmacokinetic parameters in favor of a dual surface-functionalized nanoemulson containing the glucose transporter-1-targeting ligand (mannose). Conclusions: The developed and characterized nanoemulsions enable substantial brain exposure to CW-02-79 as a prerequisite for a pharmacologically and clinically relevant selective modulation of σ2 receptors. Full article

The search for new natural, sustainable, economical and biodegradable reinforcements for composite materials has increased in recent years, highlighting the importance of fibers from the natural environment. This work evaluates the use of tururi fibrous fabric as a reinforcement in a polymer matrix, using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry and scanning electron microscopy. The mechanical and fractographic performance of composites reinforced with 2.5, 5.0 and 7.5% mass fraction of tururi in a polyester matrix is also investigated. The FTIR and XRD results identified groups characteristic of natural fibers and the presence of elemental constituents such as cellulose, hemicellulose and lignin. Thermogravimetry indicated good thermal stability near 246 °C. The morphology of the fibrous fabric is irregular and formed by tangles of threads. The mechanical behavior of the composites in bending revealed a variation in stress with the increase in the percentage of fabric in the matrix, explained by defects and failures due to low interfacial adhesion between the phases. Impact tests indicated that increasing the percentage of fabric in the matrix improves impact energy absorption, reflecting better adhesion and load distribution. Thus, the development of this natural composite is promising for applications in green and sustainable products. Full article

The stress level of a rotating component is of vital importance in order to ensure its safe operation. The primary source of stress for this type of component is the induced centrifugal stress, which depends on the material, rotational speed, and the distribution of the mass. The reduction of stress has been a topic of study for some time; however, the advent of additive technologies has prompted a new wave of research into the design and manufacture of centrifugal impellers for gas turbine engines, incorporating internal lattice structures (LSs). These structures offer benefits in terms of material savings and load reduction by decreasing the centrifugal force. The present work analyzes the stress–strain state of a turbine centrifugal impeller for six different designs, distinguished by the presence or absence of LSs of various geometries, achievable only through additive technologies. The analysis was conducted on a turbine impeller, which serves as an example of a promising small-scale gas turbine engine (SSGTE). The effectiveness of LSs was assessed through their unloading effect; furthermore, an approach to identify their optimal location within the impeller was demonstrated. Full article

This paper presents a comprehensive analysis of the dynamics and design of oleo-pneumatic shock absorbers for the landing gear of carrier-based Unmanned Aerial Vehicles (UAVs). Carrier-based operations impose unique challenges due to high-impact landings, necessitating robust landing gear systems capable of withstanding significant g-forces. The study investigates the performance of landing gears designed for carrier operations under various sink rates, utilizing computer simulations to model the dynamics of both sprung and unsprung masses. The design process for an oleo-pneumatic main landing gear of an 8500 kg UAV includes detailed calculations for stroke, shock absorber strut sizing, spring and damping characteristics, and impact force analysis. The research employs both isothermal and adiabatic models to evaluate the variation in pneumatic pressure and air spring force under static and dynamic loadings, revealing the nonlinear behavior of the shock absorber. The damping characteristics are thoroughly analyzed, demonstrating the superior performance of oleo-pneumatic systems in vibration damping. The simulation results confirm that the current design effectively mitigates impact forces, maintaining vertical accelerations within the design constraints and ensuring structural integrity during landing maneuvers. Key findings include the ability of the shock absorber to handle high sink rates typical of carrier-based operations, with calculated vertical accelerations and force values indicating robust performance. The study identifies areas for future research, such as the development of automated loads and stress analysis tools for rapid weight quantification, exploration of active control systems for vibration alleviation, and potential benefits of multi-service applications for landing gear designs. By addressing the challenges of performance and robustness in carrier-based operations, this research advances landing gear technology for UAVs, enhancing their safety and efficiency in various operation environments. The insights gained provide a solid foundation for optimizing landing gear systems, ensuring reliable performance under demanding conditions. Full article

Red sandstone is widely distributed in southern China. Due to the significant difference in mechanical properties before and after hydration and its poor water stability, red sandstone often triggers landslide accidents. In this paper, red sandstone from an open pit slope in Jiangxi Province was taken as the research object. Two variables, namely the initial saturation degree (25%, 50%, 75%, and 100%) and the number of wetting–drying cycles (0, 10, 20, 30, and 40), were set. With the help of nuclear magnetic resonance, the Brazilian disc test, and fractal theory, the relationships among its meso-structure, macroscopic fracture mechanics characteristics, and deterioration mechanism were analyzed. The research results are as follows: (1) Wetting–drying cycles have a significant impact on the pore structure and fracture mechanics characteristics of red sandstone. Moreover, the higher the initial saturation degree, the more obvious the deterioration effect of the wetting–drying cycles on the rock mass. (2) After further subdividing the pores according to their size for research, it was found that sandstone is mainly composed of mesopores, and the deterioration laws of different types of pores after the wetting–drying cycles are different. The porosities of total pores and macropores increase, while the proportions of mesopores and micropores decrease. The fractal dimensions of macropores and total pores of each group of rock samples are all within the range of 2–3, and the fractal dimension value increases with the increase in the number of wetting–drying cycles, showing significant and regular fractal characteristics. Micropores and some mesopores do not possess fractal characteristics. The fractal dimension of rock samples basically satisfies the rule that the larger the pore diameter, the larger the fractal dimension and the more complex the pore structure. (3) Both the type I and type II fracture toughness of rock samples decrease with the increase in the number of cycles, and the decrease is the most significant when the initial saturation degree is 100%. After 40 cycles, the decreases in type I and type II fracture toughness reach 23.578% and 30.642%, respectively. The fracture toughness is closely related to the pore structure. The porosity and fractal dimension of rock samples and their internal macropores are linearly negatively correlated with the type II fracture toughness. The development of the macropore structure is the key factor affecting its fracture mechanics performance. (4) After the wetting–drying cycles, the internal pores of red sandstone continue to develop. The number of pores increases, the pore diameter enlarges, and the proportion of macropores rises, resulting in internal damage to the rock mass. When bearing loads, the expansion and connection of internal cracks intensify, ultimately leading to the failure of the rock mass. The research results can provide important reference for the stability analysis of sandstone slope engineering. Full article

Background: The purpose of this study was to examine the relationships between the characteristics of force development and electromyographic activity of the quadriceps muscles in the isometric mid-shin pull (MSP) and the countermovement jump (CMJ) performed under different conditions. Methods: Fifteen resistance-trained individuals (age = 25.9 ± 4.0 y; body mass = 73.2 ± 11.7 Kg; stature = 172.3 ± 9.5 cm) were tested for MSP and for the following CMJs: regular CMJ (CMJ); elastic band-assisted CMJ (CMJ_AB); elastic band-resisted CMJ (CMJ_RB); weighted vest CMJ (CMJ_V) in random order, using a force plate. Peak force (PF) and peak rate of force development (PRFD) were calculated in all the assessments, while peak velocity and power were calculated only in the CMJs. In addition, during all the tests, electromyographic activity of the vastus lateralis (EMG_VL) and of vastus medialis (EMG_VM) was detected. Results: Higher PF was registered in MSP compared to the CMJs (p < 0.001). PRFD and EMG_VL were significantly more elevated in the CMJs compared to the MSP (p < 0.05). No significant correlations were noted between the PRFD measured in MSP and in CMJs, while the PRFD in MSP was largely correlated with PP in CMJs (r = 0.68/0.83). Conclusions: Results of the present study showed that CMJs promote PRFD and the excitation of the vastus lateralis, to a greater extent compared to MSP. Regular CMJ performed at body mass may represent the best option for power development, and small variations in loads allowed by weighted vests or elastic bands do not seem to alter the characteristics of force development. Full article

Background: Polymer-coated mesoporous silica nanoparticles have attracted immense research interest in stimuli-responsive drug delivery systems due to their drug-releasing ability on demand at specific sites in response to external or internal signals. However, the relationships between the coated-copolymer encapsulation and drug delivery performance in the hybrid nanocomposites was rarely reported. Therefore, the main objectives of the present work are to explore the cell uptake, cellular internalization, cytotoxicity, and hemolysis performance of the fluorescent hybrid materials with different polymer-encapsulated amounts. Methods: Using (2-(2-aminoethyl)-6-(dimethylamino)-1H-benzo[de]isoquinoline-1,3(2H)-dione)-doped poly[(N-isopropylacrylamide)-co-(acrylic acid)] (PAN) as a shell and bimodal mesoporous silicas (BMMs) as a core, the dual pH- and temperature-responsive mesoporous PAN@M-BMMs with the fluorescent performances were synthesized via a radical polymerization approach. The effects of the PAN-coated thicknesses on their physicochemical properties and structural features were demonstrated via XRD and SAXS patterns, SEM and TEM images, FT-IR spectra, and TG analysis. Their mass fractal (D_m) evolutions were elucidated on the basis of the SAXS patterns and fluorescence spectra. Results: The D_m values increased from 2.74 to 2.87 with an increase of the PAN-coated amount from 17 to 26.5% along with the particle size from 76.1 to 85.6 nm and blue-shifting of their fluorescent emission wavelength from 470 to 444 nm. Meanwhile, the PAN@M-BMMs exhibited a high ibuprofen (IBU) loading capacity (13.8%) and strong dual pH-/temperature-responsive drug-releasing performances (83.1%) at pH 7.4 and 25 °C, as comparison with that (17.9%) at pH 2.0 and 37 °C. The simulated results confirmed that the adsorption energy decreased from −67.18 kJ/mol for pure BMMs to −116.76 kJ/mol for PAN@M-BMMs, indicating the PAN-grafting on the surfaces of the BMMs core was beneficial to improve its IBU-adsorption capacity. Its uptake in the HeLa cell line was performed via microplate readers, confocal microscopy, flow cytometry, and ICP measurement, showing a low cytotoxicity at a concentration up to 100 µg/mL. Specially, P_0.2AN@M-BMMs had a superior cellular uptake and fluorescence properties via the time-dependent uptake experiments, and exhibited the highest silicon content via the cellular internalization analysis, as compared to other carriers. Hemolysis tests confirmed the hemolysis rates below 5%. Conclusions: These demonstrations verified that PAN@M-BMMs should be a promising biomedical application prospect. Full article

This paper tests the capability of a simplified model to predict major trends in the dynamic structural response of monopile offshore wind turbines. For this purpose, the results of two numerical models of different levels of complexity are compared: the advanced time-domain multi-physics tool OpenFAST and a simplified static-equivalent model based on beam elements and concentrated masses. The IEA-15-240-RWT reference wind turbine is considered as a benchmarking problem. The comparison between the two structural models is presented in terms of their fundamental frequencies and through the analysis of shear forces and bending moments under wind-only and combined wave and wind load scenarios. The results show that the simplified model can adequately represent the system’s mass and stiffness characteristics, as well as the impact of soil–structure interaction effects on its fundamental frequency. Turbulence and wind velocity have a significant impact on internal forces and on the ability of the simplified model to reproduce their values. Despite the large differences obtained for highly turbulent scenarios, the acceptable accuracy obtained for relevant load scenarios and the conservative nature of the simplified model make it a viable option for preliminary large-scale studies that prioritize efficiency and efficacy over high-precision. Full article

Background: Injury to the anterior cruciate ligament is one of the most common knee injuries. Following anterior cruciate ligament reconstruction, strength deficits and reduced quadriceps and hamstring muscle mass are common. Traditional strengthening protocols recommend the use of heavy loads. However, following surgery, heavy-load exercises are contraindicated to protect the joint and graft. Blood flow restriction resistance training is an alternative that optimizes muscle recovery. The aim of this study was to evaluate the effects of blood flow restriction resistance training on muscle mass and strength after ACLR. Methods: The Pubmed, Cochrane Library, and PEDro databases were used to constitute the corpus of this systematic review. The methodological quality of the studies was assessed with the Cochrane Collaboration’s analysis grid. Results: Thirty-four articles were identified in the initial search, and five randomized controlled trials were included in this review. Not all studies reported significant results regarding strength and muscle mass. Two of these studies observed a significant improvement in strength associated with blood flow restriction resistance training compared with the control group. A significant increase in muscle mass was observed in one study. Conclusions: The blood flow restriction resistance training method shows superior efficacy to training without occlusion, yet this device has not been shown to be more effective than heavy-load resistance training in terms of muscular strength and muscle mass. Blood flow restriction resistance training shows superior efficacy in both these variables when used with low loads. However, there are still few random controlled trials on this subject, and this review presents their limitations and biases. Future research is needed on guidelines for the application of blood flow restriction resistance training in clinical populations. Full article

The wind-induced response of structures is typically studied in wind tunnels either on scaled models or using numerical approaches under similar transient load conditions. In early design phases—where the potential for impactful change is most significant—information is often limited. As a result, studies are frequently conducted on simplified or reduced-resolution structural models. Typical applications for dimensionally reduced engineering models include early design phases, deciding on the need for high-fidelity analyses, and verifying wind tunnel models, which are often constructed using beams with lumped masses. In this contribution, the validity of these approaches is tested. Various limitations intrinsically arising from such modeling assumptions, showcased on a generic high-rise under dynamic wind load conditions, are highlighted. The systematic parametric analysis focuses on the variations in transient structural responses, particularly displacement and accelerations at the top of a building. Various wind loading cases are studied, with the reduction of the resolution taking place either in the original or in modal space. Results indicate that a considerable reduction is possible, but characteristic design values tend to deteriorate in cases of a high reduction, particularly when higher mode contributions are truncated. It is observed that the top-floor acceleration and displacement can be captured with considerable accuracy with three lumped masses for tall buildings. It is critical to study the impact of simplifying models starting at the highest level of detail possible. Here, a three-DoF model was able to capture the displacement up to a deviation of 11% and accelerations up to 20%. These approximate models are useful for initial design stages, optimization, uncertainty quantification, etc., where fast, cheap, and moderately accurate model evaluations are necessary. Full article