Search Results (5,831)

In the internal force analysis of plane frames, traditional mechanics solutions require the cumbersome derivation of equations and complex numerical calculations, a process that is both time-consuming and error-prone. While general-purpose Finite Element Analysis (FEA) software offers rapid and precise calculations, it is limited by tedious modeling pre-processing and a steep learning curve, making it difficult to meet the demand for rapid and intelligent solutions. To address these challenges, this paper proposes a deep learning-based automatic solution method for plane frames, enabling the extraction of structural information from printed plane structural schematics and automatically completing the internal force analysis and visualization. First, images of printed plane frame schematics are captured using a smartphone, followed by image pre-processing steps such as rectification and enhancement. Second, the YOLOv8 algorithm is utilized to detect and recognize the plane frame, obtaining structural information including node coordinates, load parameters, and boundary constraints. Finally, the extracted data is input into a static analysis program based on the Matrix Displacement Method to calculate the internal forces of nodes and elements, and to generate the internal force diagrams of the frame. This workflow was validated using structural mechanics problem sets and the analysis of a double-span portal frame structure. Experimental results demonstrate that the detection accuracy of structural primitives reached 99.1%, and the overall solution accuracy of mechanical problems in the final test set exceeded 90%, providing a more convenient and efficient computational method for the analysis of plane frames. Full article

The first hydrogenation behavior of the gas atomized Ti_48.8Fe_46.0Mn_5.2 alloy was systemically investigated. The as-received powder showed no hydrogen absorption due to the long air exposure before the hydrogenation tests. To overcome this, 5 passes of cold rolling were employed as an activation strategy. Cold rolling introduced cracks and defects that facilitated hydrogen diffusion, enabling the alloy to successfully absorb hydrogen. The influences of temperature, constant driving force, and hydrogen pressure on the first hydrogenation were evaluated. The results indicated that the first hydrogenation follows an Arrhenius behavior ($\mathrm{k}=\mathrm{A}{\mathrm{e}}^{-{\displaystyle \frac{{\mathrm{E}}_{\mathrm{a}}}{\mathrm{R}\mathrm{T}}}}$), and average activation energy was calculated as 71 kJ/mol H₂. The pre-exponential factor (A) was found to be pressure-dependent, following the equation A = A₀ (P/P₀)^1.8, where A₀ = 2.6 × 10⁶ s⁻¹. Full article

In the design of shaking table tests concerning saturated sand–pile interactions, quantitatively achieving similarity in liquefaction responses between the model and the prototype has long been a challenging task. In addition, the dynamic shear modulus of the prepared model soil often fails to satisfy the ideal similarity conditions, which further exacerbates the difficulty of realizing liquefaction response similarity. To address the above issues, the authors have proposed a liquefaction similarity law for saturated sand–pile shaking table tests under horizontal excitation, considering the dynamic shear modulus error of the model soil. To further verify the accuracy of the proposed liquefaction similarity law, investigate its simulation capability, and evaluate its applicability under different conditions, this paper establishes and validates numerical models of saturated sand–pile dynamic interaction systems based on shaking table test results and conducts a series of parametric analyses via numerical simulation. The results indicate that when the proposed similarity law is applied, the acceleration similarity ratio should be set to 1, which can satisfy both gravity similarity and elastic force similarity simultaneously. A comparison with the artificial mass similarity law demonstrates the distinct advantages of the proposed similarity law. Finally, the applicability of the proposed similarity law under different parametric conditions is verified, and the influence of various parameters on the accuracy of the back-calculated results using the similarity law is investigated. Full article

Recently, due to the expansion of telecommunication and power networks, as well as other structures, the demand for designing efficient and durable tall supporting columns has increased. Efficient steel columns are well known, including prestressed stayed beam–column systems. However, because of their relatively high cost, designers often turn to reinforced concrete structures, which are not only relatively cheaper but also sufficiently strong and resistant to aggressive external influences. Nevertheless, the large self-weight of reinforced concrete structures and considerable material consumption encourage the search for new efficient solutions. One such solution is the use of spun reinforced concrete structures. Compared to conventional reinforced concrete structures, these solutions not only reduce material consumption but also increase durability. This study examines an innovative prestressed stayed beam–column structure consisting of a spun reinforced concrete core and supporting prestressed steel tension ties. The behavior of such a composite structure is analyzed, and calculations of internal forces and displacements are presented. The rational parameters of the composing elements of this new prestressed stayed beam–column structure are discussed, and their influence on the stress–strain state of the structure is evaluated. Expressions are provided for calculating the rational bending moments of the spun reinforced concrete core. The obtained solutions make it possible to select rational cross-sections of the core and ties, as well as the required prestressing of the tension ties, without iterative calculations. Full article

The term “pristine emulsion” is used for differentiating emulsions that consist of only water and oil with no surfactant from the Pickering emulsions, which are also surfactant-free but stabilized with colloidal particles. We review 22 papers dedicated to such emulsions prepared from a wide variety of liquids. We studied here the evolution of one such emulsion, hexadecane-in-water at 4% vl, over a long period of time, from days to weeks. We discovered that the droplet size grows with time, with a rate that depends on mixing conditions, which supports a coalescence hypothesis. However, this coalescence is unusual because the size reaches a certain constant value, which contradicts typical coalescence behavior. To explain this peculiarity and such emulsification in general, we employ a theoretical model that was developed for explaining pristine nano-bubble stability. We hypothesize the existence of a layer of structured water molecules at the interface, following Eastoe and Ellis (Adv in Colloid and Interface Sci., 134–135, 89–95, 2007) and others. We point out that the Electric Double Layer exerts a force on the water dipole moments in this layer (dielectrostatic force) that compensates Kelvin’s pressure. The droplet size calculated using this model is close to the measured size. The second factor associated with this layer is the repulsion of the water dipole moments, which we show can compensate for the surface tension tangential to the interface. After ruling out alternative hypotheses with our data, we conclude that the model suggested for explaining the stability of nano-bubbles is also consistent with our results for these “pristine emulsions”. Full article

Understanding the dynamics of atmospheric ions, the carriers of electrons and ions in the global electric circuit (GEC), is necessary to fully understand Earth’s atmospheric electricity. Because atmospheric ions are too small to be influenced by gravity, the gravitational settling of aerosol particle in fair weather has not been considered as a driving force in the GEC model. However, the attachment of these particles to other coarse particles can cause them to move in gravity’s direction. In this study, the influence of the gravitational settling of various bioaerosol particles with electrostatic force on the GEC is calculated. The results show the importance of considering bioaerosol particles in the GEC model, and that pollen grains can carry the order of 0.1% of ions and electrons carried by atmospheric ions due to their weight and charging efficiencies. Also, the reduction in atmospheric conductivity in the presence of bioaerosol particles was calculated. Bioaerosol particles can reduce atmospheric conductivity by an order of $0.01\%$ due to pollen and by an order of $0.1\%$ due to microbes. Full article

The purpose of this study was to investigate voluntary force modulation accuracy during the isometric mid-thigh pull (IMTP) and to investigate biological sex and relative strength as factors relating to error. Strength-trained males (n = 18) and females (n = 18) completed ascending (ASC) (25%, 50%, 75%) or descending (DESC) (75%, 50%, 25%) submaximal testing followed by maximal testing. Subjects rested before completing the opposite submaximal testing sequence. External feedback was not provided during testing. Measured and intended (INT) forces were analyzed with two-way repeated-measures ANOVAs with within- (ASC, DESC, and INT) and between-subject factors (male or female). Independent-samples t-tests analyzed differences in error between males and females. Pearson correlations were calculated to investigate associations between relative strength and error. Statistically significant differences were observed between INT and measured force at every intensity (p < 0.05); however, differences in error were not significant between males and females (p > 0.05). Statistically non-significant small relationships were observed between relative strength and error (p > 0.05). Subjects demonstrate error in force modulation during the IMTP, with the greatest error occurring at lower relative intensity. However, these results indicate that biological sex and relative strength may not influence force modulation accuracy. Full article

This study proposes a data quality-driven channel selection methodology to improve hand gesture recognition performance in multi-channel wearable Human–Machine Interface (HMI) systems. The methodology centers around calculating (i) five data quality indices for both surface electromyography (sEMG) and pressure-based force myography (pFMG) signals and (ii) establishing a relationship between these data quality indices and the accuracy of gesture recognition for applications typified by prosthetic hand control. Machine learning (ML)-based and correlation-based methods were used to select three optimal channel/pair configurations from an eight-channel/pair system. Evaluations on the UOW and Ninapro DB2 datasets showed that the proposed methods consistently outperformed random channel selection, with the ML-based approach achieving the best results (76.36% for sEMG, 71.59% for pFMG, and 88.2% for fused sEMG-pFMG on the UOW dataset and 70.28% on Ninapro DB2). Notably, using three pairs of strategically selected sEMG-pFMG channels generated 88.2%, which is comparable to the 88.38% accuracy obtained with a full eight-channel sEMG system on the UOW dataset, highlighting the efficacy of our channel selection methodologies. These results highlight the value of data quality indices for sensor selection and provide a foundation for developing more efficient wearable HMI systems. Full article

Urban vitality is a critical metric for measuring the quality of sustainable development and overall competitiveness, serving as the core kinetic energy for urban survival and growth. As a key link for land–sea resource coordination and internal–external economic circulation, the urban vitality of China’s coastal regions is of great significance for promoting regional coordinated development. Focusing on 130 cities in China’s coastal regions, this study constructs an evaluation system encompassing five dimensions: economy, society, culture, environment, and population. Utilizing the AHP–entropy combined weighting method, the urban vitality index (UVI) for 2023 is calculated based on a scientific measurement of each dimension’s vitality level. Additionally, spatial autocorrelation and the multiscale geographically weighted regression (MGWR) model are employed to examine the spatial evolution patterns and multidimensional driving mechanisms in depth. The results indicate the following: (1) Coastal regions exhibit significant spatial heterogeneity in vitality, characterized by a distinct south–north gradient (high in the south and low in the north). Geographically, the distribution of overall vitality is highly uneven: high-value clusters are concentrated in southern coastal urban agglomerations—notably the Pearl River Delta and the Yangtze River Delta—whereas northern coastal areas, with the exception of the Shandong Peninsula, generally demonstrate relatively low vitality levels. Administrative rank has a significant effect on vitality agglomeration; the average vitality of provincial capitals and above is approximately four times that of other cities. (2) Environmental vitality performs best but shows significant spatial polarization. High-value areas for economic and population vitality are concentrated in the Yangtze River Delta, Pearl River Delta, and Shandong Peninsula urban agglomerations, while social and cultural vitality only stand out in megacities such as Shenzhen, Guangzhou, and Shanghai. (3) Urban vitality exhibits strong spatial correlation and path dependence. Coastal urban vitality shows a significant positive spatial autocorrelation, with H-H (high–high) clusters primarily concentrated in the Yangtze River Delta and Pearl River Delta, indicating a high degree of spatial aggregation and regional synergy in urban vitality. Conversely, L-L (low–low) “depressed cities” are distributed in contiguous blocks in the north and peripheral areas, indicating that regional collaborative driving forces need to be further strengthened. (4) Multifactor driving mechanisms show obvious spatial heterogeneity and scale effects. The MGWR model results reveal that the medical insurance coverage rate, human capital level, and annual average PM 2.5 concentration are the dominant factors driving coastal urban vitality. Their influence intensity shows significant north–south differences across geographical locations, and the contribution of nonspatial factors is overall higher than that of traditional built environment factors. These findings provide a scientific reference for formulating precise and differentiated regional vitality enhancement strategies, optimizing coastal resource allocation, and promoting high-quality land–sea coordinated development. Full article

The results of experimental tests of six various water-lubricated bearings are described. Tests were performed under conditions typical for marine stern tube bearings. The acquired low-friction coefficient values indicated that the bearings operated in the fluid friction regime over a wide range of sliding speeds and loads. Due to elastic deformations of the flexible non-metal bushings, it was not possible to measure the lubricant film thickness to confirm this phenomenon. Studying measured hydrodynamic pressure distribution profiles, and thanks to lifting force calculation, it was proven that hydrodynamic phenomena occur between strongly deformed, rough surfaces lubricated by a low-viscosity fluid. Full article

Accurate modelling of agricultural vehicles is essential for optimizing drivetrain performance and energy efficiency, particularly as hybrid systems become more prevalent in sustainable farming. This study presents an experimental validation of a vehicle physical model using the Claas Xerion 3800 tractor. Coast-down tests were conducted to determine the rolling resistance coefficient, while GPS and diagnostic data were used to capture real-world vehicle dynamics and fuel consumption. The rolling resistance coefficient was calculated using two-stage aggregation method of multiple run data, yielding a statistically robust result. Simulation outputs showed close agreement with measured longitudinal responses, including vehicle acceleration, traction force, and fuel usage, with a 2.1% deviation in total fuel consumption. These findings demonstrate that the proposed modelling approach reliably replicates the vehicle’s macroscopic longitudinal dynamics and support its application in drivetrain optimization, hybrid system integration, and energy-efficient vehicle design studies. The validated framework contributes to the development of context-aware simulations capable of reflecting real-world off-road conditions and operational variability. Full article

The Hong Kong Tseung Kwan O Cross Bay Link project adopted Self-Propelled Modular Transporter (SPMT) for the first time for the floating-state loading and transportation of large-span prestressed concrete box girders, allowing the 75 m box girders to be placed on the SPMT fixture in a multi-point support manner. To prevent concrete cracking during transportation, this paper studies the stress and deformation characteristics of large-span box girders under a multi-support system through a combination of theoretical research, numerical calculation, and field testing. Based on crack control of box girders, a SPMT vehicle arrangement and segmented jacking method are proposed. The results show that the SPMT vehicle group arrangement range at both ends of the box girder should be controlled within 1/3 of the box girder span; during the jacking process of the box girder, the torsion of the box girder caused by the differential oil pressure in segmented jacking should be controlled, and synchronous jacking should be adopted as much as possible; the SPMT vehicle arrangement and jacking should control the support force to be smaller closer to the mid-span. The research results have been successfully applied in the Hong Kong Tseung Kwan O project and can provide technical reference for similar projects. Full article

Air transport, acknowledged as the safest and most efficient mode for long-haul travel, is confronted with diverse challenges aimed at improving its environmental performance. A notable aspect of this effort involves the formation of contrails, arising from the emission of water vapor and condensation nuclei in a cold, ice-supersaturated atmosphere, which represents one of the most difficult-to-predict yet physically quantifiable environmental impacts of air traffic. Adopting the bottom-up principle to evaluate individual contrails for trajectory optimization introduces uncertainties in calculating the radiative forcing of contrails and modeling their life cycle. Former studies for modeling the microphysical life cycle of individual contrails based on a 2D Gaussian plume model could be validated with a photographic contrail tracking method in the mid-latitudes. However, contrails rarely form individually over Central Europe; rather, they form as an accumulation behind many aircraft flying through an ice-supersaturated region. For this reason, the 3D Gaussian plume model has been extended for the co-existence of several contrails. The greater the overlap of the contrails, the greater the competition in ice supersaturation between the contrails and therefore the greater the reduction in lifetime compared to single contrails. Furthermore, with increasing overlap, the number density of ice crystals increases, resulting in smaller ice crystals with shorter lifetimes. The overlap effect is also reflected in the angle between non-parallel contrails. The results can be used for further studies on the optical properties of real co-existing contrails. Full article

The application of steel–concrete composite structures in the pylons of long-span cable-stayed bridges can effectively address the issue of insufficient structural stiffness. Shear connectors are critical load-transfer components in steel–concrete composite segments, where they are typically arranged to ensure coordinated force transmission between steel and concrete. The stud–PBL composite shear connector, as a novel type of connector, has been implemented in engineering practice. However, the collaborative load-bearing performance between studs and PBL connectors remains unclear. Most shear connectors operate within the elastic stage during service, making their elastic stiffness a key evaluation metric. Based on the Winkler elastic foundation beam theory, plane strain theory, and the spring series–parallel model, this study derives the elastic stiffness calculation formulas for stud shear connectors and PBL shear connectors, respectively. The primary focus of this study was the single-layer stud–PBL composite shear connector within the steel–concrete composite section of bridge pylons. Embedded push-out tests were designed and conducted, comprising three main categories and eight subcategories. The load–slip curves for the three types of shear connectors were generated, and the stiffness calculation formula for the stud–PBL composite shear connector was verified through finite element analysis. The comparative push-out tests and finite element simulations demonstrate that the theoretical formula proposed in this study can effectively analyze the elastic stiffness of three types of shear connectors. The elastic stiffness of composite shear connectors can be regarded as the superposition of the elastic stiffness of studs and PBL shear connectors. Compared with single shear connectors, composite shear connectors exhibit superior elastic stiffness and shear resistance, meeting the application requirements of steel–concrete composite bridge pylons. The research findings provide a theoretical basis for the optimal design of shear connectors in large-span cable-stayed bridge composite pylons. Furthermore, the established formula has broad applicability. Full article

Background/Objectives: Musculoskeletal injuries (MSIs) continue to be a significant challenge in military populations. Load carriage is cited as a key contributor to postural stability (PS) impairments and therefore may contribute to injury risk. Therefore, the purpose of the present study was to examine the influence of load per kilogram of body mass (LpBM) on dynamic postural stability index (DPSI) percentage difference between unloaded and loaded conditions, while moderating for biological sex. Methods: Thirty-three recreationally active adults (16 males, 17 females) participated in a cross-sectional study. Each participant performed single-leg landing (SLL) tasks under unloaded and loaded conditions, and DPSI was calculated using ground reaction force data collected over the first three seconds post-landing. The loaded condition (22–23 kg, varies based on helmet and vest size) required individuals to wear a full combat load. A moderated multiple regression with robust standard errors was run to determine whether the relationship between percentage difference in DPSI between unloaded and loaded conditions and LpBM carried is different for female and male participants. Results: There was not a statistically significant moderator effect of the DPSI percentage difference, as evidenced by the addition of the interaction term explaining an additional 0.94% of the total variance, p < 0.643. Follow-up standard multiple regressions revealed that there was a statistically significant positive linear relationship (0.887 ± 0.320) between DPSI percentage difference and LpBM (p = 0.010). It was also observed that females did not have statistically significantly higher DPSI percentage difference than males (1.210 ± 4.392, p = 0.785). Conclusions: The results suggest that as LpBM increases, stability becomes more difficult to maintain. These findings highlight the importance of considering relative load when assessing injury risk and designing load carriage training protocols in tactical populations. Full article