Search Results (451)

To investigate the influence of dry connection methods on the seismic behavior of assembled composite walls, four assembled composite walls were designed and tested. Various dry connection techniques were adopted for the horizontal interfaces, namely sleeve grouting connection, welding connection, box connection, and bolted connection. The failure process, failure mode, bearing capacity, rigidity, steel bar strain, and energy absorption performance of the specimens were investigated through quasi-static cyclic loading tests. The results indicate that all types of connectors can effectively transfer loads and satisfy the conceptual design principle of “strong joint and weak component”. The damage evolution of the specimens is essentially identical, and the limiting drift angles all exceed 1/90. In addition, the shear resistance of the specimens with different connection methods is preliminarily analyzed and estimated. Full article

Traditional fixed-tilt photovoltaic (PV) support structures commonly employ inclined beams, double columns, and diagonal braces to resist and transfer horizontal loads. However, this conventional design is characterized by an excessive number of structural components, elevated steel consumption, and suboptimal installation efficiency. To address these limitations, this study proposes a novel unbraced double-column PV support system incorporating hat-shaped inclined beams and T-shaped connectors. The proposed configuration eliminates diagonal bracing while maintaining structural integrity through an efficient load-transfer mechanism, thereby achieving improved standardization, reduced steel consumption, and enhanced constructability. The structural performance of the proposed system was rigorously evaluated through full-scale load-bearing experiments and comprehensive finite element analysis (FEA). The global response, including ultimate load capacity, failure modes, and deformation characteristics, was comprehensively evaluated. The results demonstrate that the proposed system exhibits favorable mechanical behavior and sufficient load-carrying capacity under combined loading conditions. Furthermore, the finite element model was validated against experimental results, showing good agreement in terms of stiffness, deformation patterns, and ultimate response, thereby confirming its reliability for structural analysis. Full article

Achieving precise docking, reliable locking and damage-free emergency unlocking under complex ocean current conditions remains a key challenge for deep-water multi-way quick connectors (MQCs). This study proposes a novel MQC prototype characterised by a tiered tolerance guidance mechanism, an innovative L-shaped spatial helical cam locking system, and a real-time visual attitude indicator. Using Ansys 2023 R2 and its tools, the safe operating limits were determined through explicit non-linear finite element collision analysis. The results demonstrate that, under a controlled docking speed of 10 mm/s, the hierarchical guidance mechanism successfully accommodated extreme initial misalignments (25 mm lateral offset, 5° horizontal rotation and 15° axial rotation), whilst keeping the peak collision stress within the elastic limit. Furthermore, the L-shaped locking guide was analysed using a fifth-order polynomial motion law and a macro-micro elastoplastic Hertzian contact mechanics model, effectively eliminating rigid-flexible impact forces. Under extreme separation loads of 10,000 psi, the maximum equivalent plastic strain at the base of the locking shaft was strictly controlled at 0.00926. This is well below the failure threshold of 0.0865 specified by ASME, providing a substantial safety margin and completely preventing local yielding. Crucially, the emergency release strategy based on precision locating pins was validated through full-scale prototype testing. Destructive tests conducted under simulated severe jamming conditions demonstrated clean, damage-free disengagement under shear torques ranging from 2100 Nm to 2200 Nm. This threshold ensures that accidental triggering will absolutely not occur during routine operations (1400 Nm) and establishes a safe underwater robotic (ROV) operating speed of ≤4 r/min. This study provides a robust theoretical framework and empirical data for the future design of yield-resistant subsea connectors and safe emergency recovery. Full article

The aim of this in vitro study is to evaluate the stress distribution of different provisional materials designed with different connector dimensions using finite element analysis. Two adjacent prepped maxillary molars were designed digitally. Two-unit connected fixed dental prostheses (FDPs) were designed with four different connector dimensions (2 × 3, 3 × 3, 3 × 4, 4 × 4 mm (width × length)). The tested materials included polymethyl methacrylate (PMMA), bis-acrylate composite, and polyetheretherketone (PEEK). A total of 24 two-unit FDPs were tested using FEA in Autodesk Fusion 360. The study demonstrated a non-linear relationship between connector size and performance, with the 3 × 4 mm design exhibiting optimal stress distribution and the highest safety factors. Among materials, PMMA showed the greatest resistance to deformation, while PEEK provided the highest safety margins against yielding in optimal connectors. The 2 × 3 mm bis-acrylate composite configuration presented a critical failure risk, with stresses exceeding the material yield strength by 25-fold. Force angulation (0° vs. 10°) showed minimal effect on overall displacement patterns. Within the study limitations, the 3 × 4 mm connector demonstrated optimal performance across all materials. PEEK provided the highest safety factor in well-designed connectors, while bis-acrylate composite posed the greatest failure risk, particularly in smaller dimensions. Full article

The paper presents an innovative approach to producing structural connectors for bamboo constructions using recycled plastic. This solution enhances the sustainability of bamboo structures while simultaneously promoting the valorization of plastics waste. The aim is to conduct a preliminary investigation in the possible use of high-density polyethylene (HDPE) as a structural material. Two connectors’ geometries have been developed, both specifically devised for bamboo truss systems: a paddle-shaped design and an oval-shaped design. In both designs, a series of circularly arranged holes enables flexible orientation of the connected elements. The connectors are fabricated melting layers of rough-milled HDPE, sourced from waste materials, which are cast in a mold incorporating an agave braid as a reinforcement. The manufacturing process is intentionally low-tech and accessible, relying only on basic tools and equipment for milling, melting, and casting. This approach makes the proposed connectors particularly suitable for adoption in developing countries. To assess their performance, physical and mechanical tests were conducted on the base material, evaluating density, void content, and tensile strength. The tensile strength of the finished connectors results in an average value of 12.73 MPa, with a standard deviation of 2.34 MPa and a coefficient of variation CV of 18.4%, consistent with the results of tests reported in the literature. Although the sample size is limited, the obtained data are sufficient to assess the feasibility of the proposed solution, demonstrating a reasonable reliability of both the molding process and the mechanical performance of the connector. Full article

Cross-laminated timber (CLT), an engineered timber product with distinctive features, has significantly broadened the applicability of timber structures. The self-tapping screws (STSs) with excellent anchorage performance have become one of the primary connectors used in CLT structures. However, the long-term withdrawal resistance is susceptible to environmental factors such as temperature and humidity fluctuations, which may lead to reduced CLT density and corrosion-induced degradation of the steel components. These effects represent a critical life-cycle challenge to the structural integrity and safety of timber connections. This study aims to investigate the withdrawal resistance of STSs in CLT under material aging effects. To achieve this, a two-step experimental program was designed. First, the effects of two artificial accelerated aging methods (ASTM D1037 and improved version of ASTM D1037) on the withdrawal resistance of STSs in glued laminated timber (glulam) were compared to validate the feasibility of the improved protocol. This comparison was necessary to ensure that the improved protocol produces a degradation pattern without altering the failure mechanism. Subsequently, a series of CLT specimens with embedded STSs were subjected to 0, 3 and 6 aging cycles to investigate the withdrawal behavior including aging characterization, failure modes, load–displacement curves, withdrawal capacity, and stiffness. The results indicate that the failure mode of CLT joint with STSs under the improved aging scheme was the consistent pull-out of STSs, identical to that observed in the glulam, confirming mechanistic consistency. After three and six aging cycles, the normalized withdrawal capacity retention rates were 104.98% and 95.36%, respectively. The stiffness is more significantly affected by aging. The corresponding normalized stiffness retention rates were 85.60% and 80.94%, respectively. As the number of aging cycles increased, the occurrence of wood fiber tearing became more pronounced and the ratio of the corresponding load to the peak load decreased. Furthermore, ensuring adequate distance from the vertical glue layer was found to lead to greater long-term resilience and withdrawal capacity. Full article

This survey provides a comprehensive guide to Multimodal Large Language Models (MLLMs) with a focus on vision–language tasks, including image captioning, visual question answering, cross-modal retrieval, visual grounding, multi-image reasoning, long-video understanding, and embodied AI. We examine architectures, training pipelines, and practical applications, covering visual encoders, language model backbones, connector modules, contrastive pre-training, instruction tuning, and preference alignment. We also foreground first-principles constraints—information bottlenecks, data-processing limits, and statistical co-occurrence bias—that shape architecture, robustness, and evaluation. This survey centers on vision–language systems and does not cover audio-only models or code-generation tools without visual inputs. Through task-level analysis and system-level case studies, we examine prominent MLLM implementations while addressing key challenges in scalability, memory, energy use, inference cost, robustness, and cross-modal learning. We present a unified taxonomy of the MLLM design space, a comparative overview of representative models and evaluation benchmarks, and a discussion of open problems. Concluding with ethical considerations and responsible AI development, this survey offers theoretical frameworks and practical insights for researchers, practitioners, and students working at the intersection of natural language processing and computer vision. Full article

Grouted sleeve connectors are critical components in precast concrete structural joints. This study investigates the effects of grouting defect location, quantity, and grout strength on the bond–slip constitutive relationship at the steel–grout interface in fully grouted sleeves. Fifteen centrally loaded pull-out specimens were designed using the controlled variable method and tested under monotonic tension. Failure modes, ultimate load, bond stress, and slip characteristics were analyzed. Numerical modeling was performed using ABAQUS, and a mathematical bond–slip constitutive model was developed. The experimental results show that all specimens with a single defect failed by tensile fracture of the reinforcing bar, whereas those with multiple defects exhibited bar pull-out failure, which most significantly degraded connection performance. Grout strength positively correlated with interfacial bond performance. Deviation of the water-to-binder ratio from the standard value reduced grout strength, leading to decreases in bond strength, ultimate load, and slip. The apparent increase in bond stress under multiple defects was attributed to the reduced effective anchorage area rather than enhanced interfacial bonding, resulting in the lowest actual ultimate load among all scenarios. The established bond–slip constitutive model achieved a coefficient of determination R² ≥ 0.96, indicating excellent fit. The finite element simulations agreed well with test data and accurately reproduced the bond–slip response under various defect conditions. The proposed constitutive model and finite element modeling approach provide a theoretical and quantitative basis for performance assessment of grouted sleeve connectors in engineering practice. Full article

Copper busbar inserts are critical components of high-voltage connectors in new energy vehicles. The interfacial contact stress between the insert and the polymer directly affects the sealing reliability and service life of the connector. To address the interfacial stress concentration caused by the mismatch in thermal expansion coefficients between metal and polymer, this study employs COMSOL Multiphysics 6.2 simulations to investigate the regulation laws of arc-shaped and trapezoidal microstructures on the interfacial stress of copper–polyphenylene sulfide (PPS)/polypropylene (PP). The response surface methodology (RSM) is introduced to verify simulation reliability and optimize parameters. The simulation results indicate that both structures can effectively reduce interfacial stress, and the stress exhibits a significant nonlinear relationship with the structural parameters. Due to its high temperature resistance and polar thioether bond, PPS demonstrates better interfacial compatibility than PP. Under the same structural position, the maximum stress reduction exceeds 20% (from 0.689 MPa to 0.539 MPa). Moreover, the arc-shaped structure is more effective in alleviating stress concentration than the trapezoidal structure. At the same position, compared to the trapezoidal surface, the arc-shaped surface reduces the valley contact stress of PPS from 0.527 MPa to 0.5 MPa (a decrease of 5.12%) and that of PP from 0.679 MPa to 0.605 MPa (a decrease of 10.9%). The optimal parameters are as follows: an arc-shaped radius width of 1.0 mm, a depth of 0.8 mm; a trapezoidal bottom base of 2.0 mm, a height of 1.2 mm. This study provides a basis for the interface design of metal–polymer composite components and holds significant engineering value for the reliability optimization of high-voltage connectors. Full article

During the global transition toward cleaner energy infrastructure, floating photovoltaic (FPV) systems have emerged as a research focus in renewable energy technologies due to their distinctive spatial utilization advantages. This study examines the hydrodynamic performance of a novel FPV system comprising multiple floating modules connected via flexible connectors to a circular frame. Three distinct connection schemes among the floating modules were designed for comparative analysis. To ensure computational accuracy, a numerical model was established and validated against existing experimental data from a 2 × 3 scaled array. Although the validation setup differs from the novel configurations proposed in this study, the results confirm the reliability of the adopted numerical method. Based on this validated model, time-domain analyses were conducted to evaluate the six-degree-of-freedom (6-DOF) motions of the FPV, as well as the dynamic responses of the flexible connectors and mooring system under various wave periods, heights, and directions. The study shows that the motion differences in FPV under different connection schemes are mainly observed in short wave periods and oblique waves. At a wave direction of 45°, the maximum differences in surge and sway motions among the schemes reach 0.2 m. The disparity in mooring tension and connector tension for different connection schemes increases as the wave period decreases and the wave height increases. Specifically, the maximum difference in connector tension attains 10 kN under a wave period of 9 s and a wave direction of 45°, while the peak difference in mooring chain tension reaches 13 kN at a wave direction of 90°. The dynamic responses of the connectors and mooring chains in the second connection scheme are superior to those of the other two schemes. The numerical simulations identify the optimal connection scheme. The results provide theoretical guidance for the design and practical application of FPV system. Full article

The use of 3D-printed parts is becoming increasingly widespread, including in the furniture industry. Furniture products are subjected to various loads during use. Therefore, it is important to know their maximum allowable static loads and their maximum allowable cyclic loads, which are lower and depend on design and material properties. In this study, simple 3D FFF printed connectors intended as shelf connectors and made of three different materials (ABS, PLA, Wood–PLA) were subjected to different forces under static and cyclic loading until failure. Connectors made of ABS withstand the highest static load (346 N), followed by connectors made of PLA (195 N) and Wood–PLA (136 N). The fatigue behaviour of the tested connectors also depended on the material used. Connectors made of ABS exhibit the highest static load, but the stresses must be significantly lower under cyclic loading. For example, connectors made of ABS can withstand 50,000 cycles with a load of less than 25% of their maximum static load, while connectors made of PLA can withstand the same number of cycles with a load of 44% of their maximum static load. Connectors made of Wood–PLA achieved 50,000 cycles at a load of 63% of their maximum load. PLA and Wood–PLA were more durable relative to their maximum strength, even though ABS could carry heavier absolute loads. These findings could support the design of material-efficient furniture connectors with respect to their expected maximum loads and required durability; however, the results should be interpreted as preliminary and indicative of comparative trends rather than statistically validated fatigue data. Full article

This work presents the design and characterization of a thermoregulated, bandwidth-enhanced TEM cell system optimized for bioelectromagnetic experiments on biological cells, with a focus on bioluminescence resonance energy transfer investigations at 700 MHz and 3.5 GHz. Bandwidth improvement, achieved through geometric modifications and optimized connector transitions, resulted in reduced return and insertion losses and improved field uniformity, particularly in the 2.5–6 GHz range. Numerical simulations showed homogeneous electric field and normalized specific absorption rate (SAR) distributions (~1 W/kg) at 700 MHz. At 3.5 GHz, the improved TEM cell provided the most uniform exposure of the biological sample with SAR values of 15 W/kg and 10.5 W/kg, for the bulk and surface (bottom layer), respectively. Experimental SAR measurements using a ~1 mm³ fluoro-optic probe agreed well with simulations. To counteract RF-induced heating, the system incorporated active thermoregulation at 37 °C. At 3.5 GHz and 20 W input power, a 1.5 °C rise over 120 s was effectively mitigated using water-circulation cooling. This work provides a controlled and reliable setup for future studies on the interaction of 5G-band electromagnetic fields with biological systems. Full article

Digital mining has become a tangible reality in recent years and the digital revolution enables and requires data exchange for autonomous machines and operational flow management. LoRa technology and its underground propagation behavior can make an important contribution to this digitalization. This paper presents a Data Mule approach that enabled progress in digitalization at refueling stations in active underground mining areas of a mine near Werra, Germany, operated by the K+S Group. This demonstration aimed to automate manual data collection at fuel gauges by using a dynamic LoRa network. We used specially developed LoRa Data Mule modules for operations over many square kilometers. LoRa was chosen for its industrial functionality and long-range capabilities, particularly in underground environments. The Data Mule modules used were in-house-designed units with underground mining-rated casing and connectors, as well as commercial LoRa boards and custom communication protocols. Connectivity between all systems was realized at travel speeds of 20 to 40 km/h, with connection data successfully relayed for 180 to 770 m, despite 90° turns and no line of sight. It was shown that the LoRa Data Mule approach can be used in a network of remote but active data generation points. Full article

Cu/Ni/Ag composite materials are widely used in the manufacturing of electrical connector contacts due to their excellent electrical conductivity and good wear resistance. During hot plugging and unplugging operations, electrical connectors inevitably generate arc discharge, leading to melting, splashing, and erosion of the contact material, which severely threaten system reliability and service life. To investigate the arc behavior of Cu/Ni/Ag composite electrical connectors during plugging and unplugging, this paper establishes a multiphysics coupling model incorporating electric field, fluid heat transfer, and laminar flow based on the COMSOL simulation software (version 6.2). The model employs a multiphysics coupling approach, incorporating electric field, fluid heat transfer, and laminar flow, to systematically simulate the formation and evolution mechanisms of the arc during plugging and unplugging. The study focuses on analyzing the effects of plugging and unplugging speed, operating voltage, and arc gap distance on the arc, exploring the temporal and spatial evolution characteristics and distribution patterns of arc temperature. The simulation results reveal that the arc temperature follows a radially decreasing gradient, with the core region exceeding 10,000 K. When the operating voltage increases to 1000 V, the arc peak temperature rises to 1.3 × 10⁴ K. As the arc gap distance increases, the arc coverage area expands, and the peak arc temperature increases by approximately 2% to 8%. As the plugging/unplugging speed is increased to 500 mm/s, the peak temperature of the arc increases from 1.19 × 10⁴ K to 1.3 × 10⁴ K. The distribution characteristics of the magnetic field are clearly correlated with the arc temperature field and the electric field intensity distribution and the current density also exhibits typical constriction characteristics. Prolonged arc duration is correlated with an upward trend in peak temperature. Further analysis indicates that the temperature distribution characteristics of the arc are constrained by the competition mechanism of energy deposition and diffusion, while the evolution characteristics of the arc are regulated by the coupling effect of electromagnetic field and mechanical work. The research results provide a theoretical basis and simulation methods for the design of arc-resistant structures in Cu/Ni/Ag composite electrical connectors. Full article