Search Results (36,066)

Selective laser melting (SLM) technology is a high-end dual-use technology that is implemented in aerospace and medical equipment, as well as the automotive industry and other military and civilian industries, and is urgently needed for major equipment manufacturing and national defense industries. This paper examines the challenges of uncontrollable service states and the inability to ensure service safety of SLM metal parts under nonlinear and complex operating conditions. An overview of the prediction of the service status of SLM metal parts was introduced, and an effective approach solving the problem was provided in this paper. In this approach, the cross-scale coupling mechanism between mesoscopic damage evolution and macroscopic service state evolution is clarified by tracking the mesoscopic damage evolution process of SLM metal parts based on ultrasonic nonlinear responses. The failure mechanism is organically integrated with hidden information from monitoring big data, and a “chimeric” model to accurately evaluate the service status of SLM metal parts is constructed. Combining nonlinear ultrasound technology with big data and artificial intelligence to construct a “chimeric” model and consummate the corresponding methods and theories for evaluating the service status of SLM metal parts is an effective way to reveal the mesoscopic damage evolution and service status evolution mechanisms of SLM metal parts under complex factor coupling, and to accurately describe and characterize the service status of parts under complex operating conditions. The proposed approach will provide a theoretical basis and technical guarantee for the precise management of SLM parts’ service safety in key equipment fields such as aerospace, medical equipment, and the automotive industry. Full article

Since the advent of rare-earth permanent magnet (PM) materials, PM synchronous machines (PMSMs) have become popular in power generation, industrial drives, and e-mobility. However, rare-earth PMs in PMSMs are prone to temperature- and operation-related irreversible demagnetization. Additionally, faults can endanger components like inverters, batteries, and mechanical structures. Designing a fault-tolerant machine requires considering these risks during the PMSM design phase. Traditional transient finite element analysis is time-consuming, but fast analytical simulation methods provide viable alternatives. This paper evaluates methods for analyzing dynamic three-phase short-circuit (3PSC) events in PMSMs. Experimental measurements on a PMSM prototype serve as benchmarks. The results show that accounting for machine saturation reduces discrepancies between measured and predicted outcomes by 20%. While spatial harmonic content and sub-transient reactance can be neglected in some cases, caution is required in other scenarios. Eddy currents in larger machines significantly impact 3PSC dynamics. This work provides a quick assessment based on general machine parameters, improving fault-tolerant PMSM design. Full article

The design of medical-grade compression garments is essential for therapeutic efficacy, requiring precise pressure distribution on specific body areas. This study evaluates the effectiveness of virtual fit technology, focusing on CLO3D, in designing these garments. Simulated strain and pressure values from CLO3D were compared to experimental measurements, alongside the development of a CP model using CLO3D’s digitized stretch stiffness (Youn’s CP model). Using a 3D-scanned manikin, the mechanical behavior of eight knit fabrics, including composite structures, was assessed under strain of 5%, 10%, 15%, and 20%. The results showed that CLO3D’s built-in pressure simulation overestimated the pressure, especially in plaited fabrics such as SJP and INTP, with discrepancies of up to 10 kPa at strain levels above 15%. In contrast, the experimental pressure measurements using the Kikuhime and PPS sensors varied within 0.13 to 2.59 kPa. Youn’s CP model provided a closer fit to the experimental data, with deviations limited to within 1.9 kPa. This finding highlights the limitations of CLO3D for precision-required applications and underscores the need for more advanced, customized algorithms in virtual fit technology to ensure reliable compression garment design, particularly in medical contexts, where precise pressure control is critical for patient outcomes. Full article

The recent advancements in wearable exoskeletons have highlighted their effectiveness in assisting humans for both rehabilitation and augmentation purposes. These devices interact with the user; therefore, their actuators and power transmission mechanisms are crucial for enhancing physical human–robot interaction (pHRI). The advanced progression of 3D printing technology as a valuable method for creating lightweight and efficient gearboxes enables the exploration of multiple reducer designs. However, to the authors’ knowledge, only sporadic implementations with relatively low reduction ratios have been reported, and the respective experimental validations usually vary, preventing a comprehensive evaluation of different design and implementation choices. In this paper, we design, develop, and examine experimentally multiple 3D-printed gearboxes conceived for wearable assistive devices. Two relevant transmission ratios (1:30 and 1:80) and multiple designs, which include single- and double-stage compact cam cycloidal drives, compound planetary gearboxes, and cycloidal and planetary architectures, are compared to assess the worth of 3D-printed reducers in human–robot interaction applications. The resulting prototypes were examined by evaluating their weight, cost, backdrivability, friction, regularity of the reduction ratio, gear play, and stiffness. The results show that the developed gearboxes represent valuable alternatives for actuating wearable exoskeletons in multiple applications. Full article

The introduction of Diels–Alder (D-A) bonds into epoxy resins is a promising pathway to convert these unrecyclable materials into sustainable materials. However, D-A bonds make epoxy resins extremely brittle materials and hinder their practical usability. Nonetheless, the reversibility of D-A bonds allows the transition of the material to a de-crosslinked network formed by separated oligomers that can melt above 90–100 °C. This means that D-A epoxy resins can be reprocessed after being cured like thermoplastics. In the present work, a thermoset blend is made by adding spent epoxy particles to a D-A epoxy resin to increase its thermal and mechanical properties and to evaluate a possible reuse of conventional thermoset wastes. The application of hot-pressing to a mixture of epoxy particles and powder of cured D-A epoxy creates a material in which the interaction of the particles with the D-A resin increases the thermal resistance of the material and prevents the D-A epoxy from melting at high temperatures. In addition, the flexural strength is increased by 80% and the chemical resistance against organic solvents is also improved. Full article

Autologous chondrocyte implantation (ACI) and matrix-induced ACI (MACI) have demonstrated improved clinical outcomes and reduced revision rates for treating osteochondral and chondral defects. However, their ability to achieve lasting, fully functional repair remains limited. To overcome these challenges, scaffold-enhanced ACI, particularly utilizing hydrogel-based biomaterials, has emerged as an innovative strategy. These biomaterials are intended to mimic the biological composition, structural organization, and biomechanical properties of native articular cartilage. This review aims to provide comprehensive and up-to-date information on advancements in hydrogel-enhanced ACI from the past decade. We begin with a brief introduction to cartilage biology, mechanisms of cartilage injury, and the evolution of surgical techniques, particularly looking at ACI. Subsequently, we review the diversity of hydrogel scaffolds currently undergoing development and evaluation in preclinical studies for articular cartilage regeneration, emphasizing chondrocyte-laden hydrogels applicable to ACI. Finally, we address the key challenges impeding effective clinical translation, with particular attention to issues surrounding fixation and integration, aiming to inform and guide the future progression of tissue engineering strategies. Full article

Background and Objectives: This study aimed to evaluate the effects of advanced platelet-rich fibrin (A-PRF+) tissue regeneration therapy on clinical periodontal parameters in non-smokers and smoker patients. The anticipated biological mechanisms of A-PRF+ include stimulating angiogenesis, thereby promoting the formation of new blood vessels, which is essential for tissue healing. Additionally, A-PRF+ harnesses the regenerative properties of platelet-rich fibrin, contributing to the repair and regeneration of periodontal tissues. Materials and Methods: The study was conducted on 55 patients, divided into two groups: non-smoker patients (n = 29) and smoker patients (n = 26). A single operator conducted the surgical procedure. Following the administration of local anesthesia with articaine 4% with adrenaline 1:100,000 precise intracrevicular incisions were made, extending towards the adjacent teeth, until the interproximal spaces, with meticulous attention to conserving the interdental gingival tissue to the greatest extent possible. Extended, full-thickness vestibular and oral flaps were carefully lifted, and all granulation tissue was meticulously removed from the defect without altering the bone contour. After debridement of the defects, A-PRF+ was applied. BOP (bleeding on probing), PI (plaque index), CAL (clinical attachment loss), and probing depth (PD) were determined at baseline and six months post-surgery. Results: Significant reductions were observed in PD and CAL after six months. In the non-smokers group, PD decreased from 7.0 ± 1.0 mm to 3.1 ± 0.1 mm (p < 0.001), while in the smokers group, PD decreased from 6.9 ± 1.1 mm to 3.9 ± 0.3 mm (p < 0.001). CAL decreased in the non-smokers group from 5.8 ± 0.7 mm to 2.6 ± 0.2 mm and from 5.7 ± 0.9 mm to 3.2 ± 0.2 mm (p < 0.001) in smokers. Notably, the reductions in CAL and PD were statistically more significant in the non-smokers group. Conclusions: Even though the clinical periodontal improvements were considerable in smoker patients, they did not reach the level observed in non-smoker patients. Full article

Numerical simulation in fluid dynamics can be computationally expensive and difficult to achieve. To enhance efficiency, developing high-performance and accurate surrogate models is crucial, where deep learning shows potential. This paper introduces geometric attention (GeoAttention), a method that leverages attention mechanisms to encode geometry represented by point cloud, thereby enhancing the neural network’s generalizability across different geometries. Furthermore, by integrating GeoAttention with neural field, we propose the geometric attention neural field (GeoANF), specifically for learning representations of airfoil flow fields. The GeoANF embeds observational data independently of the specific discretization process into a latent space, constructing a mapping that relates geometric shape to the corresponding flow fields under given initial conditions. We use the public dataset AirfRANS to evaluate our approach, GeoANF significantly surpasses the baseline models on four key performance metrics, particularly in volume flow field and surface pressure measurements, achieving mean squared errors of 0.0038 and 0.0089, respectively. Full article

Magnesium phosphate cement (MPC), a cementitious material that hardens through an acid–base reaction, is theoretically expected to exhibit strong acid resistance. However, studies on the durability of MPC in acidic environments remain limited. This study aims to systematically evaluate the acid resistance of MPC in common inorganic acid solutions across various pH levels. By measuring changes in compressive strength, mass loss, apparent changes, pH changes, and the microstructure evolution of MPC under acidic conditions, the mechanisms and influencing factors of its acid resistance are revealed. The results indicate that at pH levels of 1.0 and 2.0, MPC’s resistance to H₂SO₄ and HCl erosion is markedly superior compared to its performance against H₃PO₄, as evidenced by compressive strength retention, mass loss, and visible erosion. At pH levels above 2.0, MPC demonstrates robust resistance to all tested corrosive media, with compressive strength retention ranging from 68.9% to 86.9%, irrespective of the acid source. Although new corrosion products form in these acidic environments, the adverse effects of NH₄/P loss from struvite, along with the redissolution of corrosion products due to their higher solubility, increase porosity and subsequently reduce the mechanical strength. Nevertheless, considering that strength retention is significantly higher than that of other cement-based materials reported in the literature, MPC still exhibits good acid resistance and is suitable for environments requiring enhanced resistance to acid corrosion. Full article

The accurate prediction of PM_2.5 concentration across extensive temporal and spatial scales is essential for air pollution control and safeguarding public health. To address the challenges of the uneven coverage and limited number of traditional PM_2.5 ground monitoring networks, the low inversion accuracy of PM_2.5 concentration, and the incomplete understanding of its spatiotemporal dynamics, this study proposes a refined PM_2.5 concentration estimation model, Bi-LSTM-SA, integrating multi-source remote sensing data. First, utilizing multi-source remote sensing data, such as MODIS aerosol optical depth (AOD) products, meteorological data, and PM_2.5 monitoring sites, AERONET AOD was used to validate the accuracy of the MODIS AOD data. Variables including temperature (TEMP), relative humidity (RH), surface pressure (SP), wind speed (WS), and total precipitation (PRE) were selected, followed by the application of the variance inflation factor (VIF) and Pearson’s correlation coefficient (R) for variable screening. Second, to effectively capture temporal dependencies and emphasize key features, an improved Long Short-Term Memory Network (LSTM) model, Bi-LSTM-SA, was constructed by combining a bidirectional LSTM (Bi-LSTM) model with a self-adaptive attention mechanism (SA). This model was evaluated through ablation and comparative experiments using three cross-validation methods: sample-based, temporal, and spatial. The effectiveness of this method was demonstrated on Beijing–Tianjin–Hebei urban agglomeration, achieving a coefficient of determination (R²) of 0.89, root mean squared error (RMSE) of 12.76 μg/m³, and mean absolute error (MAE) of 8.27 μg/m³. Finally, this model was applied to predict PM_2.5 concentration on Beijing–Tianjin–Hebei urban agglomeration in 2023, revealing the characteristics of its spatiotemporal evolution. Additionally, the results indicated that this model performs exceptionally well in hourly PM_2.5 concentration forecasting and can be used for PM_2.5 concentration hourly prediction tasks. This study provides technical support for the large-scale, accurate remote sensing inversion of PM_2.5 concentration and offers fundamental insights for regional atmospheric environmental protection. Full article

Structural components with curved edges are common in many engineering designs. Fatigue cracks, corrosion and other types of defects and mechanical damage often initiate from (or are located close to) edges. Damage and defect detection in the presence of complex geometry represents a significant challenge for non-destructive testing (NDT). To address this challenge, this paper investigates the fundamental mode of the quasi-symmetric edge-guided wave (QES0) propagating along a curved edge, as well as its scattering characteristics in the presence of different types of edge defects. The finite element (FE) approach is used to investigate the propagation and mode shapes of the QES0. It was found that the wave attenuation dramatically increases when the radius-to-thickness ratio is less than 20. Moreover, the mode shapes are significantly affected by the waveguide curvature as well as the excitation frequency. Additionally, to evaluate the sensitivity of QES0 to edge defects, different sizes of edge defects were investigated with the FE model, which validated against experimental results. The validated FE model was further employed to quantify the dependence of the amplitude of scattered waves for different types of edge defects. These studies indicate that the amplitude of scattered wave is very sensitive to the presence of edge defects. The main outcome of this work is the demonstrated ability of the QES0 wave mode to propagate over long distances and a high sensitivity of this mode to different types of edge defects, which manifest its great potential for detecting and characterising damage near the curved edges of structural components. Full article

Obesity is a multifaceted health issue linked to conditions like type 2 diabetes, hypertension, and cardiovascular disease. Bariatric surgery is a well-established method for significant weight loss and health improvement, but maintaining weight loss and recovering post-surgery can be challenging. Probiotics, beneficial live microorganisms, are suggested as potential aids in managing obesity and its complications, but research on their effectiveness in this context is limited and diverse. This study aimed to evaluate the impact of probiotics on obesity in individuals post-bariatric surgery. A meta-umbrella review was conducted, analyzing systematic reviews and meta-analyses of probiotics’ effects. The review included studies from PubMed, Scopus, EMBASE, and Cochrane Library, focusing on weight loss, body composition, and metabolic parameters. Four systematic reviews met the criteria. The findings indicate that probiotics may significantly reduce waist circumference and body weight, and improve lipid and liver markers. However, their effects on glycemic parameters, quality of life, and adverse events were less clear. Overall, probiotics might offer modest benefits in managing weight and improving certain metabolic parameters after bariatric surgery. However, their overall efficacy, especially regarding glycemic control and quality of life, remains uncertain. Further high-quality research is needed to confirm these findings and elucidate the mechanisms involved. Full article

FmocFF (9-fluorenyl methoxycarbonyl-phenylalanine) is an extensively studied low-molecular-weight hydrogel. Although there have been numerous studies on FmocFF hydrogel, its potential to form organogels has not been well explored. In this work, we systematically explore the organogels of FmocFF in a wide range of organic solvents. FmocFF is found to be a robust organogeltor, and the subsequent organogels exhibit diverse gelmorphic behavior exhibiting various degrees of crystallinity and morphology depending on the solvent used. The mechanical strength of the organogels is evaluated using rheology. A novel technique, in situ SHG microscopy, is introduced to study the gel structure in its native state. In addition to the solvent–solute interactions that are typically used to predict gelmorphic behavior, we observed indications that the degree of crystallinity also plays a significant role in determining the mechanical properties and structure of FmocFF organogels. Full article

The poultry industry struggles with oxidative stress affecting gut health and productivity. This study examined using 1-Deoxynojirimycin (DNJ) extracts from mulberry leaves as an antioxidant in broilers feed to combat this issue. We divided 240 broilers, aged 16 days, into six groups, including a control and groups exposed to oxidative stress through H₂O₂ injections, with different supplement levels of DNJ-E (40, 80, 120, and 160 mg/kg of the basal diet) lasting until the broilers reached 42 days old. We evaluated intestinal morphology, ultrastructure, oxidative stress markers, the tight junction, and inflammatory cytokines. Adding 40 mg/kg DNJ-E improved villus height, the villus-to-crypt ratio, and cellular ultrastructure, and increased SOD levels in the jejunum and ileum, as well as CAT levels in the duodenum and jejunum (p < 0.05), compared to the H₂O₂ group. The addition of DNJ had differential effects on oxidative stress, the intestinal barrier, and immune-related genes. Importantly, the dosages of 40 mg/kg and 80 mg/kg resulted in an upregulation of MUC2 mRNA expression (p < 0.05). These findings suggest that DNJ-E holds potential as a beneficial feed additive for enhancing broiler health, particularly at supplementation levels below 80 mg/kg, as higher concentrations may negatively influence intestinal health. Future investigations should aim to elucidate the underlying mechanisms through which DNJ-E operates within the avian gastrointestinal system. Full article

Heavy metal pollution is a worldwide and stringent concern following many decades of industrialization and intensive mining without (in some cases) consideration for environmental protection. This review aims to identify the existing and emerging techniques for heavy metals (HM) removal/recycling from water and wastewater, with an emphasis on cobalt. Unlike many other heavy metals, cobalt has not been considered a detrimental element for the environment and human beings until recently. Thus, several methods and applicable techniques were evaluated to identify the best treatment approaches applicable to cobalt-polluted water and wastewater. The most feasible depollution methods adapted to the source, environment, and economic conditions were investigated and concluded. The operations and processes presented in this paper are conventional and innovative as well, including precipitation, membrane separation, with emphasis on ultrafiltration (UF) and nanofiltration (NF), but also reverse osmosis/forward osmosis (RO/FO), sorption/chemisorption processes, flotation/mechanical separation operations combined with coagulation/flocculation, photocatalysis, and electrochemical processes. For each one, depending on the frequency of use, physicochemical mechanisms and optimal operational conditions were identified to carry out successful cobalt removal and recovery from aqueous environments. Full article