Search Results (13,043)

The purpose of this paper is to study the shear performance of reinforced concrete corbels under a synergistic change in the main stirrup inclination angle to explore the synergistic mechanism of the main reinforcement and the stirrup inclination angle, and to evaluate the applicability of existing design specifications. The shear performance test was carried out by designing RC corbel specimens with an inclination angle of the main reinforcement and stirrup. The test results show that a 15° inclination scheme significantly improves the shear performance: the yield load is increased by 28.3%, the ultimate load is increased by 23.6%, the strain of the main reinforcement of the 15° specimen is reduced by 51.3%, the stirrup shows a delayed yield (the yield load is increased by 11.6%) and lower strain level (250 kN is reduced by 23.7%), and the oblique reinforcement optimizes the internal force transfer path and delays the reinforcement yield. A CDP finite element model was established for verification, and the failure mode and crack propagation process of the corbel were accurately reproduced. The prediction error of ultimate load was less than 2.27%. Based on the test data, the existing standard method is tested and a modified formula of the triangular truss model based on the horizontal inclination angle of the tie rod is proposed. The prediction ratio of the bearing capacity is highly consistent with the test value. A function correlation model between the inclination angle of the steel bar and the bearing capacity is constructed, which provides a quantitative theoretical tool for the optimal design of RC corbel inclination parameters. Full article

Canvases and preparation layers consist of diverse materials that respond differently to mechanical stress. In a canvas painting, elongations and shrinkages can cause deformations—either recoverable or permanent—as well as shear stresses and potential cracks, which may weaken the overall structure. This study aims to better understand the interaction between the canvas and preparatory strata in terms of mechanical behavior. To achieve this, a set of canvases and the same types of canvases with preparation layers were selected. Two types of linen and two types of polycotton were chosen to represent contemporary materials currently available in fine-art stores. Additionally, an accelerated aging process was applied to the samples to compare their mechanical response before and after aging. By examining the mechanical behavior of both primed and unprimed canvases through dynamometric tests, a method to evaluate the mechanical degradation attributable to the ground layer has been developed and explained in detail. This method is applicable to cases with similar characteristics. Analysis of the force/elongation graphs for the ground layer allows for the calculation of how this layer evolves with increasing elongation and how the mechanical degradation worsens. The results highlight the differing mechanical behaviors among the analyzed canvas types in both the warp and weft directions, as well as the degradation values resulting from both the aging process and the dynamometric testing of the canvases and ground layers. Full article

Red blood cell (RBC), accounting for approximately 45% of total blood volume, are essential for oxygen delivery and carbon dioxide removal. Their unique biconcave morphology, high surface area-to-volume ratio, and remarkable deformability enable them to navigate microvessels narrower than their resting diameter, ensuring efficient microcirculation. RBC deformability is primarily determined by membrane viscoelasticity, cytoplasmic viscosity, and cell geometry, all of which can be altered under various physiological and pathological conditions. Reduced deformability is a hallmark of numerous diseases, including sickle cell disease, malaria, diabetes mellitus, sepsis, ischemia–reperfusion injury, and storage lesions in transfused blood. As these mechanical changes often precede overt clinical symptoms, RBC deformability is increasingly recognized as a sensitive biomarker for disease diagnosis, prognosis, and treatment monitoring. Over the past decades, diverse techniques have been developed to measure RBC deformability. These include single-cell methods such as micropipette aspiration, optical tweezers, atomic force microscopy, magnetic twisting cytometry, and quantitative phase imaging; bulk approaches like blood viscometry, ektacytometry, filtration assays, and erythrocyte sedimentation rate; and emerging microfluidic platforms capable of high-throughput, physiologically relevant measurements. Each method captures distinct aspects of RBC mechanics, offering unique advantages and limitations. This review synthesizes current knowledge on the pathophysiological significance of RBC deformability and the methods for its measurement. We discuss disease contexts in which deformability is altered, outline mechanical models describing RBC viscoelasticity, and provide a comparative analysis of measurement techniques. Our aim is to guide the selection of appropriate approaches for research and clinical applications, and to highlight opportunities for developing robust, clinically translatable diagnostic tools. Full article

Urban networks are a key force in reshaping regional resilience patterns. However, existing research has not yet systematically elucidated, from a physical–virtual integration perspective, the underlying mechanisms through which composite urban networks shape multidimensional urban resilience in regions confronted with severe environmental and infrastructural challenges. Northwest China, characterized by its extreme arid climate, pronounced core–periphery structure, and heavy reliance on overland transportation, provides an important empirical context for examining the unique relationship between network centrality and the mechanisms of resilience formation. Based on the panel data of 33 prefecture-level cities in northwest China from 2011 to 2023, this article empirically examines the impact of the composite urban network constructed by traffic and information flows on urban resilience from the perspective of network node centrality using a two-way fixed-effects model. It is found that (1) the spatial evolution of urban resilience in northwest China is characterized by “core leadership—gradient agglomeration”: provincial capitals demonstrate significantly the highest resilience levels, while non-provincial cities are predominantly characterized by medium resilience and contiguous distribution, and the growth rate of low-resilience cities is faster, which pushes down the relative gap in the region, but the absolute gap persists; (2) the urban network in this region is characterized by a highly centralized topology, which improves the efficiency of resource allocation yet simultaneously introduces systemic vulnerability due to its over-reliance on a limited number of core hubs; (3) urban network centrality exerts a significant positive impact on resilience enhancement (β = 0.002, p < 0.01) and the core nodes of the city through the control of resources to strengthen the economic, ecological, social, and infrastructural resilience; (4) multi-dimensional factors synergistically drive the resilience, with the financial development level, economic density, and informationization level as a positive pillar. The population size and rough water utilization significantly inhibit the resilience of the region. Accordingly, the optimization path of “multi-center resilience network reconstruction, classified measures to break resource constraints, regional wisdom, and collaborative governance” is proposed to provide theoretical support and a practical paradigm for the construction of resilient cities in northwest China. Full article

The seismic bearing capacity of water-saturated composite foundations adjacent to slopes is critical for engineering safety, yet it is significantly influenced by complex factors such as earthquakes and heavy rainfall. This paper establishes a failure mechanism model that involves both reinforced and non-reinforced zones, comprehensively considering the synergistic effects of seismic force, pore water pressure and group pile replacement rate, and thus addressing the issue that existing models struggle to account for the coupling effects of multiple factors. Based on the principle of virtual work, a general solution for ultimate bearing capacity is derived, and the optimal solution is obtained using the MATLAB R2023a exhaustive method. Findings reveal that pile group support substantially enhances bearing capacity: the improvement becomes more pronounced with higher soil strength parameters (φ, c) and replacement ratios. When the seismic acceleration coefficient increases from 0 to 0.3, the bearing capacity of the unreinforced foundation decreases by approximately 61.6% (from 134.71 kPa to 51.83 kPa), while group pile support can increase the bearing capacity by 433.2%. Notably, when soil strength is inherently high, the marginal benefit of pile group reinforcement diminishes. A case study in Fuzhou validates through numerical simulation that pile groups improve foundation stability by altering energy dissipation distribution, with the discrepancy between theoretical calculations and simulation results within 10%. The research results can directly guide the design of saturated composite foundations near slopes in earthquake-prone areas (such as Fujian and Guangdong) and enhance the seismic safety reserve by optimizing the replacement rate of group piles (recommended to be 0.2~0.3). Full article

The barbell back squat, a prevalent lower-limb resistance exercise characterized by a closed kinetic chain and multi-joint movement, results in the greatest knee joint range of motion. Variations in thigh and shank lengths and their ratios may influence knee joint mechanics. This study investigated the effects of thigh and shank lengths and their ratios on knee kinematics and kinetics during the barbell back squat. Fifty resistance-trained adult men participated. Kinematic and kinetic data were collected using an eight-camera motion capture system and two force plates. Correlation and simple linear regression analyses were conducted to evaluate the relationships between thigh and shank length parameters and knee joint mechanics. Greater thigh length was significantly associated with increased anterior knee displacement and knee extension moment. Additionally, longer shank length and a higher shank-to-thigh ratio were associated with greater knee abduction and internal rotation angles. Consequently, increased thigh length may contribute to greater anterior knee displacement, while increased shank length may be associated with increased knee abduction and internal rotation. Accordingly, trainers and trainees should evaluate individual thigh and shank lengths. For participants with relatively longer shank and thigh segments, compensatory knee movements should be closely monitored to mitigate the risk of musculoskeletal injuries. Full article

Microwave irradiation of rocks can reduce the strength of rocks and ease their subsequent excavation. Exploring the combination of microwave and cutting tools for rock breaking under different conditions is important to the practical engineering application of microwaves. Based on a true triaxial microwave-assisted dual-mode mechanical rock-breaking test system, high-power microwave irradiation of rocks was investigated under different true triaxial stresses, durations of microwave irradiation, and cutting tool conditions such as mechanical drilling tools and tunnel boring machine (TBM) hobs. This research provides important data support for improving the rock-breaking efficiency of mine mining and tunneling as well as mechanical cutting tools and TBM hobs. In this experiment, Chifeng basalt with a relatively high strength was adopted as the research object. A 15 kW (2.45-GHz) open high-power microwave device was used to irradiate 200 mm × 200 mm × 200 mm cubic Chifeng basalt samples under conditions of different burial depths, and a cone drill bit was used for staged excavation. After microwave irradiation of Chifeng basalt measuring 400 mm × 400 mm × 400 mm, a 4-inch (102 mm) rotary cutter was employed to conduct round-by-circle cutting and rock-breaking tests in the microwave irradiation area. The results show that under true triaxial stress, the law of rock breaking by microwave irradiation combined with cone drill bits is as follows: the cutting force shows a trend of increasing–decreasing–increasing again–decreasing again. After microwave irradiation combined with hob cutting, the effective range of the influence of the hob is within the third cutting circle, with a range of diameters of approximately 200 mm. The results also indicate that the open microwave device can pre-crack rocks under deep stress, and there is obvious crack propagation. This research has good applicability to microwave-combined cantilever road-headers and TBM as well as in the mining field, and has a promising development prospect. Full article

Marking techniques are employed to guarantee the identification and traceability of biomedical materials. This study investigated the impact of laser and mechanical marking processes on the tribological performance of ISO 5832-1 austenitic stainless steel (SS), specifically examining corrosion resistance, the coefficient of friction, and wear volume in ball-cratering wear tests. The laser marking was performed using a nanosecond Q-switched Nd:YAG laser. Cytotoxicity tests assessed the biocompatibility of the biomaterial. Non-marked surfaces were also evaluated for comparison. A phosphate-buffered saline solution (PBS) served as both the lubricant and corrosion medium. The surface finishing was analyzed using optical microscopy and scanning electron microscopy coupled with a field-emission gun (SEM-FEG), combined with an energy-dispersive X-ray spectrometer. The oxide film was examined through X-ray photoelectron spectroscopy (XPS). Wear tests lasted 10 min, with PBS drops applied every 10 s at 75 rpm; solid balls of AISI 316L stainless steel (SS) and polypropylene (PP), each 1 inch in diameter, were used as counter-bodies. Corrosion resistance was assessed using electrochemical methods. Results showed variations in roughness and microstructure due to laser marking. The tribological behaviour was influenced by the type of marking process, and the wear amount depended on the normal force and ball nature. None of the samples was considered cytotoxic, although laser-marked surfaces exhibited the lowest cellular viability among the tested surfaces and the lowest corrosion resistance. Full article

Aiming at the problem of lacking accurate and reliable contact and bonding parameters in the discrete element simulation of whole cotton stalk harvesting equipment, this study proposed a reverse modeling method for cotton roots combining the Discrete Element Method (DEM) with 3D laser scanning. This method systematically constructed a general discrete element model and completed its parameter calibration. Firstly, cotton root samples were collected and measured to obtain key morphological parameters, providing a basis for selecting representative roots and performing 3D reverse reconstruction. Subsequently, mechanical parameters and contact parameters of the cotton roots were measured and calibrated through mechanical tests and stacking angle tests. Furthermore, based on the Hertz–Mindlin with Bonding contact model, a structured root sample model was established using a layered particle combination strategy. The bonding parameters were then optimized and calibrated through shear and tensile mechanical simulation experiments. Finally, a discrete element model of the root–soil complex was established based on the optimal parameter set. The reliability of the model was validated by comparing the simulation results with physical field tests of root extraction force. The results indicated that in the contact parameter validation test, the relative error between the simulated stacking angle and the measured value was only 0.43%, demonstrating the high accuracy of the model in simulating contact characteristics. In the bonding parameter calibration validation tests, the relative errors between the simulation results and measured values for shear and tensile mechanics were 1.22% and 1.40%, respectively, indicating that the model parameters could accurately simulate shear strength and tensile strength. Finally, in the root extraction force validation test, the relative error between the simulated extraction force and the field-measured value was 3.76%, further confirming the model’s applicability for analyzing the complex interaction mechanisms between roots and soil. The findings of this study can provide key models and parameter support for the digital design, operation process simulation, and performance optimization of whole cotton stalk harvesting equipment. Full article

The mechanical properties of corn stalks play a crucial role in the design of packing and harvesting equipment. Complete and damaged stalks were used to simulate stalk mixtures during the collection process. This study measured the mechanical characteristics of complete stalks and damaged stalks through experiments. A discrete element method (DEM) model was established which incorporated both the skin and core tissues of the samples. The compression behavior of the stalks was analyzed with the EDEM 2022 software. The results indicate that the complete stalks exhibited both a plastic and second plastic stage, while the damaged stalks fractured immediately upon reaching peak stress. The models of the complete and damaged stalks were validated through a radial compression test. An analysis of the relative errors and particle velocities enabled the quantification of experimental accuracy, ensured the reliability of the experimental data, and revealed the dynamic behavior mechanism of the materials under mechanical loading. The simulation results show that the maximum compression force is 254.11 N and 33.1 N, with a 1.5% and 12.3% relative error compared to the experiment. The particle velocity in the core part is the largest, which is 9.83 × 10⁴ mm/s and 3.51 × 10⁵ mm/s. This study can provide a theoretical reference for researching the mechanical behavior and compressive failure of stalks. Full article

Graphene was directly grown on SiO₂/Si substrates using microwave plasma-enhanced chemical vapor deposition (PECVD) to investigate how synthesis-driven variations in structure and doping influence carrier transport. The effects of synthesis temperature, plasma power, deposition time, gas flow, and pressure on graphene’s structure and electronic properties were systematically studied. Raman spectroscopy revealed non-monotonic changes in layer number, defect density, and doping levels, reflecting the complex interplay between growth, etching, and self-doping mechanisms. The surface morphology and conductivity were assessed by atomic force microscopy (AFM). Charge carrier mobility, extracted from graphene-based field-effect transistors, showed strong correlations with Raman features, including the intensity ratios and positions of the Two-dimension (2D) and G peaks. Importantly, mobility did not correlate with defect density but was linked to reduced self-doping and a weaker graphene–substrate interaction rather than intrinsic structural disorder. These findings suggest that charge transport in PECVD-grown graphene is predominantly limited by interfacial and doping effects. This study offers valuable insights into the synthesis–structure–property relationship, which is crucial for optimizing graphene for electronic and sensing applications. Full article

Seed rope direct seeding technology is a precision seeding method that can accurately mix and arrange multiple varieties based on specific grain spacing and quantity, making it suitable for precision breeding and variety comparison studies. As seed ropes serve as the crucial seed encapsulation material in seed rope direct seeding, this study employed a multi-faceted approach to investigate the dynamic degradation of nonwoven fabric and paper material seed ropes under diverse environmental conditions as well as their adhesion properties with Ultisols, Oxisols, and the Substrate in this seeding technique. Firstly, the degradation dynamics were systematically analyzed using image-based surface area detection, breaking force measurement, and organic carbon content analysis. Secondly, the process of seed rope laying was simulated by modeling the sliding friction and adhesion forces during the detachment of soil slurry. The laying motion was simulated considering both sliding friction (during the uniform-speed interaction between the seed rope and soil slurry) and adhesion (during upward detachment), providing crucial reference values for optimizing the rope-breaking mechanism in field applications. The study yielded several significant findings: In natural environments, Wood pulp paper seed rope degrades significantly faster than nonwoven fabric, with a degradation cycle of only 5.68 days in winter (approximately 34% of the degradation cycle of nonwoven fabric) and 4.70 days in summer (approximately 78% of the degradation cycle of nonwoven fabric). The main effect of seed viability on the degradation rate of seed tapes was not statistically significant. The degradation of Wood pulp paper seed rope was relatively predictable in indoor settings but exhibited notable fluctuations outdoors. The peak friction occurred at 35% soil moisture content, with values of 1.22 N for Wood pulp paper seed rope and 2.08 N for nonwoven fabric when interacting with Oxisols; nonwoven ropes demonstrated stronger adhesion than Wood pulp paper seed rope in the Substrate (at moisture contents of 25–30% and 40–45%) and Oxisols (at 35–45% moisture). In Ultisols, nonwoven fabric only showed superior adhesion compared to Wood pulp paper seed rope at 35–45% moisture, while Wood pulp paper seed rope exhibited better adhesion in other moisture ranges. Full article

This study develops a high-performance water-based mold release agent for polyurethane (PU) foaming applications. We demonstrate that incorporating octamethylcyclotetrasiloxane (D4) into a dimethyl silicone oil emulsion (5 vol% fixed concentration) significantly enhances key performance metrics. By systematically varying D4 content (0–15 vol%), we characterize droplet morphology, particle size distribution, contact angle, and viscosity to elucidate the underlying enhancement mechanism. Our findings reveal the following: (i) Optimal emulsion stability: At 5 vol% D4, the mold release agent exhibits a narrow particle size distribution (6–9 μm). (ii) Efficient processing: Film formation completes within 10 min, reducing demolding force and yielding PU foam with defect-free, non-adherent surfaces. (iii) Storage stability: After 60 days in ambient conditions, performance remains unchanged, with no phase separation observed under thermal stress (60 °C) or refrigeration (2–6 °C). This work explores an alternative pathway to mitigate key limitations—slow film formation and poor shelf-life—offering a prototype for next-generation release agents. Full article

Background and objectives: Knee osteoarthritis (KOA) is a degenerative joint disorder often associated with altered gait mechanics. This systematic review aims to evaluate the effect of rehabilitation treatment on walking, with a focus on gait speed. Material and methods: A systematic search was conducted in PubMed, Scopus, Web of Science, Cochrane, and PEDro databases, following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. Randomised controlled trials published in English between 2015 and 2025, involving patients with KOA undergoing rehabilitation and using computerised gait measurements, including 3D motion capture, force plates, and instrumented treadmills, were included. A meta-analysis was conducted on the selected studies assessing gait speed, with the risk of bias being evaluated using the Cochrane Risk of Bias 2 tool for RCTs. Results: Out of 2143 articles, 7 studies met the inclusion criteria. These studies showed increased gait speed in patients with KOA following exercise therapy, various walking training programmes, massage, or dietary interventions. The meta-analysis revealed a standardised mean difference (SMD) of 1.807, with a 95% confidence interval (CI) of [1.637, 1.977] (p < 0.001). The interventions were associated with improvements in walking parameters and quality of life, as well as reductions in pain and fall risk. Substantial heterogeneity was noted, likely due to variations in intervention types and study populations. Conclusions: The results suggest an overall improvement in gait speed in the intervention groups compared to the control groups. However, only a limited number of studies have investigated the effects of physiotherapy, bath therapy, or mud therapy on gait mechanics in patients with KOA. Full article

Background: Patient discomfort during the initial phase of orthodontic treatment is a common concern and may influence compliance. Archwire selection plays a critical role in modulating pain perception. This study aimed to compare immediate and dynamic pain perception among patients undergoing initial orthodontic leveling using three types of nickel–titanium archwires with different mechanical properties and cross-sectional dimensions. Methods: Forty-eight patients undergoing fixed appliance therapy were enrolled in a single-blind comparative clinical study. Participants completed a two-part, pilot-tested questionnaire assessing immediate (Day 4) and dynamic (Day 8) pain after the first archwire placement. Group differences were analyzed with Kruskal–Wallis and Bonferroni-adjusted Mann–Whitney U tests (α = 0.05). Results: TriTanium^® was consistently associated with lower pain across functional tasks and had significantly lower overall pain than both Bio-Active^® and 0.014-inch single-force round Ni-Ti (Bonferroni-adjusted). Bio-Active^® was intermediate and did not differ from 0.014-inch round; its reduction relative to the round wire showed a non-significant trend. No correlation was found between archwire size and pain intensity. Conclusions: The type and mechanical behavior of the archwire, rather than its cross-sectional dimension, influence patient discomfort during the initial leveling phase. Multiforce shape-memory archwires such as TriTanium^® may offer improved comfort and should be considered when planning early-stage orthodontic treatment. Full article