Search Results (17,792)

Electronic devices play an extremely important role in the aerospace field. Aluminum nitride (AlN) is a promising ceramic material for high-reliability electronic packaging structures that are subjected to impact loads during service. Quasi-static and dynamic flexural tests were conducted to determine the rate-dependent flexural strengths of AlN ceramics. The impact response of the AlN substrates was investigated using experimental tests and a smeared fixed-crack numerical model. The critical velocity of the impactor and the failure mode of the ceramic plate can be accurately predicted using the Drucker–Prager criterion with the scaled fracture-strength parameter. The radial cracks on the ceramic plate upon impact were well reproduced via the proposed novel numerical technique, showing better accuracy compared to the widely used Johnson–Holmquist II (JH-2) model. The effect of impactor nose shape and deflection angles were further investigated to better illustrate the low-velocity impact response of AlN ceramic substrates. Based on the dynamic flexural-strength testing results, this study achieves the prediction of low-speed impact response for AlN ceramic structures, thereby providing technical support for the impact reliability analysis of aerospace ceramic-packaging devices. Full article

Compressive strength and Young’s modulus are key design parameters in rock engineering, essential for understanding the mechanical behavior of carbonate rocks. Understanding the mechanical behavior of carbonate rocks under varying load conditions is crucial for geotechnical stability analysis. In this paper, empirical relationships are developed to predict the mechanical properties of carbonate rocks. A series of uniaxial and triaxial compression experiments were conducted on carbonate rocks including limestone, dolostone, and granite from Wyoming. In addition, experimental data on different carbonate rocks from the literature are compiled and integrated into this study to evaluate the goodness of fit of our proposed empirical relationships in the prediction of compressive strength and Young’s modulus of carbonate rocks. Regression analysis was used to develop predictive models for the uniaxial compressive strength (UCS), Young’s modulus (E), and triaxial compressive strength (${\sigma }_1$) incorporating parameters such as the porosity (n) and confining pressure (${\sigma }_3$). The results indicated that the UCS and Young’s modulus showed a power relationship with porosity (n), whereas the ${\sigma }_1$ showed a linear relationship with n and ${\sigma }_3$. Furthermore, an analytical model expanded from the wing crack model was applied to predict the ${\sigma }_1$ of limestone based on the coefficient of friction, the initial level of damage, the initial flaw size, and the fracture toughness of the rock. The model showed a good predictability of the ${\sigma }_1$ with a mean bias (i.e., the ratio of the measured to the predicted strength) of 1.07, indicating its reliability in accurately predicting the rock strength. This predictability is crucial for making informed engineering decisions, design optimization, and improving safety protocols in practical applications such as structural analysis and manufacturing processes. Full article

Cemented tailings backfill (CTB) plays an important role in mine filling operations. In order to study the long-term stability of CTB under the dynamic disturbance of deep wells, ultrafine cemented tailings backfill was taken as the research object, and the true triaxial hydraulic fracturing antireflection-wetting dynamic experimental system of coal and rock was used to carry out a static true triaxial compression test, a true triaxial compression test under unidirectional disturbance, and a true triaxial compression test under bidirectional disturbance. At the same time, the acoustic emission monitoring and positioning tests of the CTB were carried out during the compression test. The evolution law of the mechanical parameters and deformation and failure characteristics of CTB under different confining pressures is analyzed, and the damage constitutive model of the filling body is established using stochastic statistical theory. The results show that the compressive strength of CTB increases with an increase in intermediate principal stress. According to the change process of the acoustic emission ringing count over time, the triaxial compression test can be divided into four stages: the initial active stage, initial calm stage, pre-peak active stage, and post-peak calm stage. When the intermediate principal stress is small, the specimen is dominated by shear failure. With an increase in the intermediate principal stress, the specimen changes from brittle failure to plastic failure. The deformation and failure strength of CTB are closely related to its loading and unloading methods. Under a certain stress intensity, compared with unidirectional unloading, bidirectional unloading produces a greater deformation of the rock mass, and the failure strength of the rock mass is higher. This study only considers the confining pressure within the compressive limit of the specimen. Future research can be directed at a wider range of stresses to improve the applicability and reliability of the research results. Full article

Background/Objectives: Limited surgical invasiveness is desirable in elderly patients with femur fracture. Serum cytokines have been considered as a possible marker but with inconclusive evidence. The present study aimed to assess the systemic inflammatory response to surgical trauma through the serum levels of several cytokines (IL1β, IL6, IL8, and IL-10), inflammatory markers (c reactive protein—CRP), and muscular damage markers (creatinkinase—CK) at different time intervals in a consecutive series of patients affected by pertrochanteric fractures (PFs) and treated by two different surgical devices (intramedullary nailing (IM) vs. dynamic hip screw plate—DHS). Methods: A total of 60 consecutive patients (45 female and 15 male, mean age 85.6 years) with PFs (AO31A1.2-2.2) were randomly assigned to two groups according to the surgical procedure used (IM vs. DHS). Specimens of venous blood were collected 1 h preoperatively and at 24, 48, and 72 h postoperatively. Commercial ELISA kits were used. Results: In the adjusted linear mixed model, the serum levels of IL-1β, IL-8, IL-10, CRP, and CK revealed no statistically significant correlation with the type of surgical intervention performed. A significant (p < 0.001) correlation was found for IL-6 values in patients undergoing IM, showing higher serum values than patients receiving DHSs in all postoperative blood sample collections. Conclusions: The results of this study reveal that the use of DHSs may have less biological impact than IM in frail elderly due to a more limited secretion of IL-6 cytokines deriving from the preservation of the femoral medullary canal, representing a possible guide for the choice of the surgical device. Full article

This work provides a detailed description of the procedures employed to characterize the mechanical behaviour of two materials present in a coach’s exterior panels, including glass-fibre-reinforced polymer (GFRP) and neat DCPD (dicyclopentadiene)-based polymers. Tensile tests were conducted at quasi-static, intermediate 1 s^-1, 10 s^-1, and high strain rates 150 s^-1, 250 s^-1 to obtain a comprehensive understanding of their behaviour. The results indicate positive and significant dependence on the strain rate. Additionally, GFRP demonstrates superior energy absorption capacity for higher strain rates, unlike DCPD, which exhibits a higher energy absorption capacity for QS tests. In the case of DCPD, raising the strain rate to 10 s^-1 the maximum stress was not affected but decreased the elongation at fracture. At higher strain rates, there was an increase in maximum stress alongside greater elongation. DCPD maintained consistent stiffness across all rates ranging between 2087 MPa and 2389 MPa, and the tests disclosed a failure mode characterized by numerous surface-transverse fissures. Regarding GFRP, a more pronounced variation in stiffness is observed, decreasing from 11,005 MPa to 4532 MPa at 133 s⁻¹, recovering to 7288 MPa at 252 s⁻¹. In addition, the maximum stress and failure elongation tends to increase with the strain rate increase. The detailed analysis of these results provides valuable insights into the mechanical behaviour of these materials under different loading conditions. Full article

Osteoporosis is characterized by an imbalance between osteoblastic bone formation and osteoclastic bone resorption, leading to an increased risk of fractures. The water-soluble matrix (WSM) of nacre exhibits osteoinductive properties in osteoblastic cells, both in vitro and in vivo. However, its release from natural nacre remains challenging due to its solid and compact surface. This study aimed to prepare nano-nacre particles with smaller diameters than intact aragonite crystals to enhance WSM release and to investigate its effects on osteoblast differentiation. Size analysis and SEM imaging showed that the nano-nacre particles had an average size of about 600 nm. Furthermore, their effects on osteoblast differentiation and mineralization were evaluated through qPCR and ARS assay. The results showed that WSM significantly upregulated key osteogenic genes, including RUNX2, ALP, and OCN, in a dose- and time-dependent manner over 14 days, with fold-changes ranging from 1.6 to 3.6. Additionally, the mineralization effects showed calcium deposition levels comparable to those of the positive group. These findings suggest that WSM may be a promising soluble factor for osteoblast differentiation and mineralization. Therefore, understanding the effects of the WSM from H. diversicolor nano-nacre particles on osteoblasts in vitro may provide evidence suggesting that it could be a promising anti-osteoporosis agent. Full article

In this research, a nitrogenized shell layer was formed on the surface of Ti powder in a high-temperature N₂ environment, resulting in core–shell-structured Ti@Ti_xN powder. Using this as a reinforcement, Ti@Ti_xN/Al composite was successfully designed and fabricated via pressure infiltration method. The Ti_xN layer consists of a double-layered spherical shell structure, with TiN as the outer layer and Ti₂N as the inner layer. After the composite was fabricated, no intermetallic compounds between Ti and Al were observed at the interface, as the Ti_xN layer effectively prevented the reaction between Ti and Al. The tensile strength, yield strength, and elongation of the Ti@Ti_xN/Al composite were 173 ± 7.7 MPa, 115 ± 8.1 MPa, and 7.5 ± 0.55%, respectively. Both the strength and hardness were significantly improved compared to the pure Al matrix. Observations of the tensile fracture surface revealed severe interfacial debonding at the interface, and the reinforcement did not exhibit significant coordinated deformation with the matrix. This suggests that future research could focus on strengthening the matrix by adding alloying elements and improving the interfacial bonding to enhance the performance of the composite. Full article

In order to solve certain issues, such as brittle fracture corrosion and easy failure, which occur under high ambient temperatures and high breakthrough pressures when conventional cement is used to plug rock perforations, a method using a Sn58Bi alloy was adopted in this paper; it was utilized to melt and plug a perforation. Subsequently, the influence of the characteristics of the rock perforation (such as perforation length and diameter) on alloy plugging performance under different conditions and ambient temperatures was studied. The experimental results show that the plugging effect of the Sn58Bi alloy was affected by ambient temperature, plugging diameter, and length. When the plugging length was 100 mm and the perforation diameter was 10 mm, the mechanical plug performance decreased by 24.0% when the ambient temperature increased from 30 °C to 60 °C, and then decreased by 19.0% when the ambient temperature increased to 90 °C. At 30 °C, the mechanical plug performance decreased by 30.4% when the diameter decreased from 10 mm to 8 mm, and decreased by 28.0% when the diameter decreased to 6 mm. When the length was constant and the diameter was decreased from 10 mm to 8 mm and then to 6 mm, the hydraulic plugging effect became better, and the trend increased from 33.7% to 37.2%. Full article

Background/Objectives: Accurate localization of fractured endodontic instruments (FEIs) in periapical radiographs (PAs) remains a significant challenge. This study aimed to evaluate the performance of YOLOv8 and Mask R-CNN in detecting FEIs and root canal treatments (RCTs) and compare their diagnostic capabilities with those of experienced endodontists. Methods: A data set of 1050 annotated PAs was used. Mask R-CNN and YOLOv8 models were trained and evaluated for FEI and RCT detection. Metrics including accuracy, intersection over union (IoU), mean average precision at 0.5 IoU (mAP50), and inference time were analyzed. Observer agreement was assessed using inter-class correlation (ICC), and comparisons were made between AI predictions and human annotations. Results: YOLOv8 achieved an accuracy of 97.40%, a mAP50 of 98.9%, and an inference time of 14.6 ms, outperforming Mask R-CNN in speed and mAP50. Mask R-CNN demonstrated an accuracy of 98.21%, a mAP50 of 95%, and an inference time of 88.7 ms, excelling in detailed segmentation tasks. Comparative analysis revealed no statistically significant differences in diagnostic performance between the models and experienced endodontists. Conclusions: Both YOLOv8 and Mask R-CNN demonstrated high diagnostic accuracy and reliability, comparable to experienced endodontists. YOLOv8’s rapid detection capabilities make it particularly suitable for real-time clinical applications, while Mask R-CNN excels in precise segmentation. This study establishes a strong foundation for integrating AI into dental diagnostics, offering innovative solutions to improve clinical outcomes. Future research should address data diversity and explore multimodal imaging for enhanced diagnostic capabilities. Full article

In this work, the impact resistance of three zirconia ceramics was investigated: two yttria-stabilized zirconia (3Y-TZP and 1.5Y-TZP) and a ceria-stabilized-zirconia (Ce-TZP) composite. The impact resistance was evaluated through drop-ball impact tests on disk-shaped samples. The results are discussed in terms of the materials’ transformability, which was correlated to the size of tetragonal-to-monoclinic (t-m) transformation zones observed after the impact tests and to the volume fraction of the monoclinic content on fractured surfaces. The findings show that impact resistance increases with the ability of the material to undergo t-m transformation. The Ce-TZP composite exhibited the highest transformability and consequently the highest impact resistance, followed by 1.5Y-TZP, and then 3Y-TZP. Full article

This systematic literature review investigates microstrip antenna applications in image acquisition, focusing on their design characteristics, reconstruction algorithms, and application areas. We applied the PRISMA methodology for article selection. From selected studies, classifications were identified based on antenna patch geometry, substrate types, and image reconstruction algorithms. According to inclusion criteria, a significant increase in publications on this topic has been observed since 2013. Considering this trend, our study focuses on a 10-year publication range, including articles up to 2023. Results indicate that medical applications, particularly breast cancer detection, dominate this field. However, emerging areas are gaining attention, including stroke detection, bone fracture monitoring, security surveillance, avalanche radars, and weather monitoring. Our study highlights the need for more efficient algorithms, system miniaturization, and improved models to achieve precise medical imaging. Visual tools such as heatmaps and box plots are used to provide a deeper analysis, identify knowledge gaps, and offer valuable insights for future research and development in this versatile technology. Full article

The effects of different processes for heat treatment on microstructures and mechanical properties of a Ti-Al-V-Cr-Fe-based alloy (TLC002) were investigated based on the Ti-6411 alloy designed by Northwest Institute for Nonferrous Metals Research. The results show that the TLC002 alloy treated with solid solution and aging has high strength and low impact toughness. For the annealed specimens, both strength and impact toughness are high. With the rising annealing temperature from 800 °C to 880 °C, the tensile strength (UTS), yield strength (YS), and impact toughness (α_u2) increase, especially for the α_u2 from 48.7 J/cm² to 86.0 J/cm². The tensile and impact specimens treated with both solid solution and aging and annealing are all typical ductile fractures. Both the size dimension and depth of the dimples for the equiaxed structures are greater than those of the bimodal structures, indicating that the plasticity of the equiaxed structures is superior to that of the bimodal structures. The heat treatment that annealing at 880 °C for 1.5 h and then air cooling leads to qualified mechanical properties and a good match of the strength and plasticity of the TLC002 alloy. Full article

Background/Objectives: Friends and family members of people who are discharged from hospital after a fracture often take on caring roles, since these patients have reduced independence during recovery. Previous literature suggests that these individuals are rarely supported in their adoption of these roles. No studies have previously explored the use of carer training interventions to support friends/family members by health professionals in this setting. This survey study aimed to address this. Methods: A cross-sectional online survey was conducted among health professionals who treat people in hospital following fractures. Respondents were asked about the use of care training for friends/family members of people discharged from hospital after fracture, and whether a clinical trial would be useful to test such carer training interventions. Results: A total of 114 health professionals accessed the survey. Fifty respondents (44%) reported that carer training was not offered in their practice. When it was offered, respondents reported this was not consistently provided. Less than 12% of respondents reported offering carer training to most of their patients following a fracture. What was offered in these instances was largely based on education provision (69%), practical skills in exercise prescription (55%) and manual handling (51%). Ninety-eight percent of respondents reported that a clinical trial would be, or would potentially be, valuable to aid a change in practice to include carer training in routine clinical care. Conclusions: Carer training programmes are not routinely provided in clinical practice for people following a fracture. The results indicate that health professionals see a potential value in these programmes, but further research is recommended to provide an evidence base for these interventions. Full article

Fractured rock masses are extremely common in geological engineering. In order to improve the stability of surrounding rock under dynamic conditions, new grouting materials and their reinforcement characteristics were studied. In this paper, split Hopkinson pressure bar (SHPB) tests were employed to analyze the dynamic mechanical and failure characteristics of grouted fractured rock with nano-grouting material (nano-grouted fractured rock). Simultaneously, high-speed camera tests were utilized to examine the macroscopic dynamic deformation and failure processes. The following was found: (1) Under a relatively low impact air pressure of 0.1 MPa, the mechanical properties of nano-grouted fractured rock are considerably better than those of traditional cement-based grouted rock. However, when the impact air pressure is increased to 0.3 MPa, the superiority of nano-grouting material diminishes, the possible cause of which is explained from the microscopic point of view. This means the nano-grouting material is more suitable for low-engineering-disturbance conditions (e.g., shield construction). (2) Both for the nano- and superfine cement grouting material, the impact fractures initially emerge at the two ends of the original grouted fracture and form a pair of parallel lines. (3) In comparison with 0.1 MPa, the impact pressure of 0.3 MPa leads to more severe damage to the rock specimen. These findings contribute to a deeper understanding of the behavior of nano-grouted fractured rock under dynamic loading and provide valuable insights for relevant engineering applications in the field of rock mechanics and grouting technology. Full article

X80 steel pipelines are widely used in oil and gas transportation, and the quality and fracture behavior of the girth weld have an important influence on the safety and performance of the pipeline. This study presents a comprehensive investigation into the microstructure, mechanical properties, and fracture characteristics of X80 steel welded joints. Through microstructure analysis and mechanical testing, the hardness, impact, and tensile properties of the base metal, heat-affected zone, and weld zone are evaluated. Digital Image Correlation (DIC) technology is employed to scrutinize the strain behavior under quasi-static tensile tests for both smooth and notched round bar specimens, providing a detailed strain distribution analysis. The findings indicate that, while X80 welded joints are well-formed without significant defects, the hardness and impact properties vary across different zones, with the base metal exhibiting the highest impact toughness and the weld zone the lowest. Notched tensile tests reveal that the presence and geometry of notches significantly alter the stress state and deformation characteristics, influencing the fracture mode. The DIC analysis further elucidates the strain concentration and localization behavior in the weld zone, highlighting the importance of notch size in determining the load-bearing capacity and ductility of the welded joints. This study contributes to a deeper understanding of the fracture mechanics in X80 pipeline girth welds and offers valuable insights for the optimization of welding practices and the assessment of pipeline integrity. Full article