Search Results (20,628)

Vacuum arc remelting (VAR) is essential for producing premium titanium alloys, where an externally applied alternating magnetic field enables circumferential stirring to control ingot homogeneity. However, current magnetic field parameter design relies on empirical trial-and-error approaches, lacking systematic theoretical guidance. To address this issue, this study establishes a comprehensive multi-physics framework through a two-dimensional axisymmetric swirl model integrating electromagnetic, fluid dynamics, thermal, and solute transport phenomena. Our findings demonstrate that both the magnetic field strength and period exhibit optimal operating ranges, which directly influence ingot homogeneity. As magnetic field strength increases progressively, ingot uniformity shows a distinctive non-monotonic response—initially improving before subsequently deteriorating. Correspondingly, with increasing stirring period, macrosegregation undergoes a distinct three-stage evolution: initial mitigation, subsequent aggravation, and final alleviation. These phenomena originate from the small-scale circulatory flow generated by the external magnetic field on the surface of the VAR molten pool. The interactions among the flow, the solute diffusion layer, and the mushy zone collectively alter elemental diffusion behavior, ultimately determining the homogeneity of the ingot. This study provides a theoretical foundation for precise control of ingot homogeneity in titanium alloy VAR processes and demonstrates significant potential for engineering applications. Full article

Human squat motion is commonly analyzed using inverse dynamics, where joint moments are computed from experimentally measured kinematics. Such analyses typically assume that the observed motion is mechanically feasible and do not explicitly account for limitations of joint moment capacity. In this study, a computational framework is proposed for the load-constrained reconstruction of squat motion that integrates kinematic motion generation with a mechanical model of moment-limited joints. The human body is represented as a multi-segment system consisting of feet, shanks, thighs, pelvis, and torso. Joint behavior is modeled using nonlinear rotational springs with bounded moment capacity, allowing elastic response followed by allowing bounded moment response and redistribution of mechanical demand as critical moment levels are approached. A reference squat trajectory is first generated kinematically, after which a constrained optimization problem is solved at each motion frame to obtain a mechanically admissible posture under external loading. The objective function combines trajectory tracking with joint energy contributions, while gravitational loading from a barbell applied at the shoulders introduces external work. The formulation enables automatic correction of the reference motion when joint moment limits are exceeded, resulting in mechanically admissible squat postures. Numerical examples illustrate the evolution of pelvis trajectory, torso inclination, lower-limb segment angles, and reconstructed body configurations throughout the squat cycle. The results confirm that joint moment capacity directly influences the reconstructed motion and leads to load-dependent adaptation of squat posture. Full article

The mechanical behavior of aqueduct structures exhibits highly complex characteristics during prestress tensioning, making it difficult for the traditional double-control method to accurately predict and real-time control the key stresses. To improve the construction safety of prestressed tensioning and the prediction accuracy of structural prestress responses, this study develops a rapid structural mechanical property prediction method based on machine learning. Taking prestressed aqueducts as the research object, a system of “finite element simulation—sample generation—machine learning prediction” is established. Firstly, multiple groups of tensioning parameter combinations are designed via Latin hypercube sampling, and the stress responses are obtained through finite element analysis to form a high-quality training sample library. Subsequently, critical structural features are extracted based on mesh reconstruction, and stress prediction models are established using the K-Nearest Neighbors (KNN) and Random Forest algorithms respectively; the prediction performance of both models is compared and validated against finite element simulation results. Furthermore, the prediction outputs of the optimal machine learning model were used to analyze the stress distribution and potential stress concentration issues of the structure during the tensioning process. The comparative analysis results indicate that the Random Forest model performs best in terms of stress prediction accuracy and stability, and its prediction results are highly consistent with those of the finite element method. Compared with traditional finite element condition analysis, the machine learning model can complete multi-condition stress prediction in a shorter time. Leveraging its high-efficiency prediction capability, local high-stress areas of the structure in the tensioning construction scheme can be identified, thereby providing effective optimization schemes to improve the stress distribution. The mechanical response prediction method for the prestress tensioning process of aqueducts, with machine learning as the core, constructed in this paper realizes the rapid and reliable prediction of key stresses throughout the entire prestress tensioning process. This method can be applied to assist in optimizing tensioning construction schemes and construction monitoring, providing a practical technical solution for safety control of aqueduct structures during the prestress construction stage. Full article

Four-dimensional (4D) printing integrates additive manufacturing with stimuli-responsive materials to fabricate biomedical implants and functional healthcare devices that undergo programmed, time-dependent changes in shape or function. Unlike static 3D-printed constructs, 4D-printed systems can respond to clinically relevant stimuli such as temperature, hydration, pH, light (including near-infrared), magnetic fields, or electrical inputs. These triggers drive defined actuation mechanisms, most commonly thermomechanical shape-memory recovery, swelling-induced morphing, and magnetothermal activation. This review synthesizes the principal material platforms used for biomedical 4D printing, including shape-memory polymers and alloys, hydrogels, liquid-crystal elastomers, and responsive composites, and links material choice to device behavior and translational feasibility. Applications are discussed across self-expanding stents, cardiac occluders, tissue-engineered constructs, implantable drug delivery systems, and adaptive wearables. Key translational challenges include sterilization compatibility, manufacturing reproducibility and quality control, safe stimulus delivery, predictable biodegradation and long-term biocompatibility, and regulatory pathway definition. Full article

The gravitational field represents the fundamental stress field in geotechnical engineering. Its influence on soil mechanical behavior is manifested not only through variations in stress magnitude but also through stress gradient effects. However, existing soil mechanics frameworks and classical continuum-based numerical methods cannot characterize the intrinsic mechanical response of granular media under stress gradient conditions. Based on a previously established higher-order continuum theory incorporating stress gradient effects, this study develops a multiscale coupled Finite Element Method–Discrete Element Method (FEM–DEM) numerical framework. The method is implemented using Esys-escript in conjunction with the open-source discrete element platform Yade. By embedding representative volume elements (RVEs) at the finite element level and introducing gravity-induced stress gradients within the RVE using the discrete element method, stress gradient transfer and multiscale coupling are achieved. The proposed method is validated through numerical simulations of triaxial compression and trapdoor tests. The results demonstrate that the method can capture the microscale mechanisms associated with stress gradient effects and effectively resolve the constitutive solution difficulty encountered in the previously proposed generalized continuum framework incorporating stress gradients. The developed framework provides a new numerical tool for investigating the mechanical behavior of granular media under stress gradient conditions, with potential applications in geotechnical problems governed by gravitational fields, including deep underground engineering and extraterrestrial environments with non-conventional gravity. Full article

Optogenetic modulation employs light-sensitive proteins known as opsins to regulate cellular activity. A unique therapeutic application of this technique involves modulating pain perception by selectively targeting neural pathways within the spinal cord. Multi-Characteristic Opsin (MCO) represents an innovative optogenetic actuator capable of activation across a broad spectrum of light wavelengths, exhibiting a slow depolarizing phase that resembles natural photoreceptors. This study examines the current advancements in spinal optogenetic modulation utilizing MCO for pain management. Due to its high sensitivity, MCO facilitates minimally invasive, remotely controlled optogenetic modulation of spinal neurons. This approach enables the regulation of extensive spatial regions, provided the MCO channel receives sufficient light intensity to surpass the activation threshold. Nano-enhanced optical delivery (NOD) successfully transfected spinal neurons with the GAD67-MCO2-mCherry construct, as confirmed by membrane-localized mCherry fluorescence with DAPI-labeled nuclei. Using this platform, 5 Hz spinal optogenetic stimulation produced a significant reduction in formalin-evoked pain behaviors, demonstrating frequency-specific modulation of spinal pain circuits. Neither 2 Hz nor 10 Hz stimulation yielded comparable analgesic effects, underscoring the importance of precise stimulation parameters. The therapeutic impact also depended on transfection efficiency: reducing the fGNR–plasmid concentration diminished MCO expression and weakened the analgesic response. Together, these results show that effective spinal optogenetic pain modulation requires both optimal stimulation frequency and robust gene delivery. Full article

Based on an extended Theory of Planned Behavior (ETPB), this study investigated how perceived social sustainability shaped individuals’ intentions to use fitness facilities. Specifically, it examined the moderating role of social sustainability in the relationships between key TPB determinants and fitness facility use intention. Survey data were collected from 195 adults living in metropolitan areas and were analyzed using partial least squares structural equation modeling (PLS-SEM). The results revealed that perceived social sustainability exerted a dual moderating influence on intention formation by strengthening the effect of subjective norm while attenuating the effect of perceived behavioral control on use intention. Higher levels of perceived social sustainability (SS) strengthened the relationship between subjective norm (SN) and fitness facility use intention with a medium effect size, while attenuating the relationship between perceived behavioral control (PBC) and use intention with a small effect size. In contrast, no significant moderating effect was observed in the relationship between attitude and use intention. These findings suggest that value-oriented considerations related to social responsibility and community well-being enhanced socially driven motivations while reducing the relative influence of control-based factors. By demonstrating the conditional effects of perceived social sustainability within the TPB framework, this study extended existing research on health-related behavioral intentions. The findings further highlight the importance of incorporating community-oriented and socially responsible practices into fitness facility management to foster sustainable user engagement. Full article

Imageability is a cognitive measure of environmental differentiation and place memory. However, the existing literature focuses mainly on static morphological descriptions or subjective perception, without systematic quantitative studies of how physical environment and behavioral activity jointly generate the imageability of characteristic districts. This limits active responses to the rise of “placelessness” in numerous cities. Based on the S-O-R theory, this study proposes a “visual–activity” two-channel mediation model. Based on 65 typical characteristic districts in Wuhan, and using multi-source data in the research, PLS-SEM was employed to systematically study the process that influences imageability in urban environments. It was found that (1) behavioral activity serves as the core mediating link between the physical environment and imageability; (2) scenic beauty exerts a partial mediating effect between visual sensitivity and imageability; (3) vitality exerts a full mediating effect between activity support and imageability. This study is expected to provide a scientific foundation for design refinements, quality enhancement, and place identity construction in urban characteristic districts oriented toward perceptual experience in the post-industrial era. Full article

Rolling bearings operate under complex contact conditions, and their tribological and dynamic behaviors are highly sensitive to their lubrication performance. Based on previous studies on surface texturing, three types of representative textures (wholly distributed dimples, locally distributed dimples, and grooves) with optimized parameters were fabricated on the shaft washers using the laser marking method. This was done to investigate the synergistic effect of surface textures and polytetrafluoroethylene (PTFE) nano-additives on the tribological and friction-induced vibration performance of cylindrical roller thrust bearings under starved lubrication. Lubricating oils containing various mass fractions (0.5 wt%, 1.0 wt%, and 3.0 wt%) of PTFE nano-additives were prepared and employed. The coefficients of friction (COFs), wear losses, worn morphologies, and time/frequency-domain vibration responses were analyzed. The results show that the appropriate integration of surface textures and solid lubricant additives can establish a highly effective synergy for rolling bearings under starved lubrication. PTFE nano-additives significantly improved the tribological performance of the smooth bearings and those with dimples (both wholly distributed and locally distributed), with the optimal performance observed at a mass fraction of 3.0 wt%. In contrast, the tribological performance of the groove-textured bearings noticeably deteriorated with the addition of PTFE nano-particles, especially at higher mass fractions. The bearing with wholly distributed dimples exhibited the best overall tribological performance at a mass fraction of 3.0 wt%, achieving a 61.8% reduction in the average COF, a 99.6% reduction in wear loss, and significantly suppressed vibration amplitudes. Full article

The corporate social responsibility (CSR) approach from a managerial point of view has become a topic of interest especially in the European ex-Communist countries. This paper explores the intentions of Romanian managers of small and medium-sized enterprises and multinational corporations operating in Romania to implement corporate socially responsible practices (CSRPs). To this end, a quantitative research methodology based on an online survey was employed, and partial least squares structural equation modeling was used to analyze the data. The results show that the research model based on the Theory of Planned Behavior (TPB) has been validated. The values of composite reliability and Cronbach’s alpha exceed 0.7, the value of average variance extracted exceeds 0.5, while the values of average block variance inflation factor and average full collinearity are below 3.3. The findings also indicate that the intention of managers to integrate CSRP within their business organizations is mostly influenced by the stakeholder pressure, suggesting that the attainment of social approval is a crucial driver of responsible behavior, rather than other constructs related to the TPB. The study concludes that while negative attitudes towards CSR do not significantly affect managers’ intentions to engage in CSRP, positive attitudes exert a favorable influence. Full article

Many existing reinforced concrete (RC) structures have undergone increases in service loads due to changes in use, functional upgrades, and evolving design codes. This highlights the need for reliable requalification methods that account for long-term degradation mechanisms, particularly those related to sustained loading and creep. This study investigates the residual flexural behavior of RC beams after long-term loading and evaluates its effects on stiffness and ultimate strength. Three RC beams were loaded to 43% of their short-term yielding moment and kept under sustained load for 210 days, while three identical specimens were maintained as unloaded references. Afterward, all beams were subjected to repeated four-point loading–unloading cycles to detect changes in stiffness, strength, and cyclic response. The results indicate that long-term loading did not significantly affect the beams’ ultimate load-carrying capacity compared with the reference specimens. However, the long-term-loaded beams exhibited a clear reduction in initial stiffness. This difference was most evident during the first loading cycle and gradually decreased in subsequent cycles. To interpret these findings, a layered fiber model was developed to simulate cyclic behavior while incorporating time-dependent concrete effects. The model successfully reproduced the main experimental trends, reinforcing the reliability of both the testing program and the analytical approach. The study enhances understanding of stiffness degradation in RC elements subjected to increased service loads. Full article

The dynamic response of ancient multi-drum columns, commonly found in historical monuments, is characterized by complex nonlinear mechanisms including rocking, sliding, and wobbling. Unlike modern monolithic columns, these structures consist of large, unbonded stone drums that rotate and interact dynamically during ground motion, resulting in highly nonlinear behavior due to intermittent impacts and evolving contact surfaces. The objective of this study is to evaluate the influence of the friction coefficient at the interfaces on the dynamic response of multi-drum columns. Two structural configurations are considered: (i) simple free-standing multi-drum columns, and (ii) multi-drum columns connected with iron dowels, replicating ancient Greek construction techniques. The columns analyzed are representative of the colonnade system of the Gymnasium of Ancient Messene, Greece. Sinusoidal base excitations with varying characteristics are applied, and parametric study is conducted by varying the interfacial friction coefficient. The results indicate that in the first configuration, low friction promotes interfacial sliding, leading to enhanced energy dissipation, a softened rocking response, and a reduced overturning frequency range. In the second configuration, variations in friction have a limited effect on the collapse frequency range, because at lower friction levels strong excitations lead to dowel reinsertion failure over a wide frequency range. Full article

This study aimed to explore athletes’ experiences of transitioning out of sport following spinal cord injury (SCI). Using a multiple-case study design, three former nondisabled competitive athletes participated in one-on-one semi-structured interviews. The participants’ interview responses were informed by quantitative measure data collected prior to the interviews using the Athletic Identity Measurement Scale, the Social Support Questionnaire-6, and the Satisfaction with Life Scale. The thematic analysis of the interviews revealed that participants experienced a range of cognitive, emotional, social, and behavioral influences during the transition process. These influences contributed to outcome-related appraisals of post-SCI transition. Balanced self-identity, adaptive sport participation, and peer-mentor relationships were common factors influencing athletes’ transition with spinal cord injury. The results partially support the conceptual model of adaptation to career transition and extend it to account for athletes’ experiences following SCI. The results also benefit rehabilitation professionals and athletes with spinal cord injury by providing insight into psychosocial factors and resources that may influence the transition experience. Full article

This experiment aimed to evaluate physiological and behavioral responses of crossbred Dehong dairy buffaloes to heat stress (HS) in comparison with those in a thermoneutral (TN) environment. Twelve crossbred dairy buffaloes at similar lactation stages were randomly allocated to two groups of six animals each. Six buffaloes were exposed to HS conditions and the other six to TN conditions in an open loose-housing barn without individual stalls. Respiration rates were manually recorded at 08:00 h, 13:00 h, and 18:00 h. Duration and frequency of behaviors (standing, lying, feeding, and drinking) were continuously monitored using digital cameras for 20 consecutive days. Compared with the TN group, HS-exposed buffaloes exhibited markedly higher respiration rates (p < 0.001) and feeding frequencies (p < 0.05), but significantly shorter feeding duration throughout the observation period (p < 0.05). No significant differences were observed in the time spent standing, lying, or drinking between the two groups (p ≥ 0.05). Under HS conditions, buffaloes preferred a vertical lying posture to reduce exposure to intense solar radiation. These results suggest that crossbred Dehong dairy buffaloes can adapt to heat stress by modulating their physiological and behavioral strategies. The observed changes in physiological indices and behavioral patterns provide fundamental data for further elucidating the heat stress adaptation mechanisms in dairy buffaloes. Full article

Accumulating evidence indicates that a hypomagnetic field (HMF, <5 μT) has a significant impact on various organ systems in animals. However, the cellular and molecular mechanisms underlying these biological effects remain unclear. Understanding the molecular mechanisms underlying mammalian responses to a HMF is crucial for addressing health and safety concerns associated with HMF exposure. In this study, we investigated the changes in intracellular protein phosphorylation under HMF conditions and validated the functional mechanisms by which HMF-induced protein phosphorylation affects cell behavior. We found that U2OS cells can rapidly sense changes in magnetic fields, leading to alterations in protein phosphorylation levels within the cell. The quantitative phosphoproteomics results revealed that the exposure of U2OS cells to the HMF environment for 0.5 h and 3 days resulted in the alteration of 1101 and 1543 phosphosites, respectively. Notably, HMF exposure enhanced the phosphorylation of β-Catenin at Ser552, and this increased phosphorylation-promoted U2OS proliferation and migration. Furthermore, quantitative proteomics showed that exposure to a HMF for 3 days upregulated the expression of LOX and FN1, while the knockdown of LOX or FN1 suppressed the proliferation and migration of the U2OS cells. These results suggest that a HMF enhances U2OS cell proliferation and migration by promoting β-Catenin phosphorylation and upregulating FN1 and LOX expression. Full article