Search Results (10,147)

Geopolymers represent a promising material platform for extrusion-based 3D printing; however, current research remains largely focused on mix design, rheology, printability, buildability, and the relationship between process parameters and the resulting microstructure. This article therefore compares the behaviour of two 3D-printed geopolymer composite truss beams with reference cementitious composite beams developed within the 3D STAR project. The geopolymer elements, 2932 mm long, were designed for the same material volume and target geometry as the reference CC element; however, because of mixture spreading, they reached cross-sections of only approximately 140/250 mm and 170/250 mm. The first beam was printed without setting acceleration, while the second was locally treated with a hot-air gun. In four-point bending, GC-2 was loaded first and reached 22 kN, while GC-1 was loaded second and reached 29 kN; the reference cementitious beams reached 31 and 40 kN. The CC elements failed by rupture of the tensile reinforcement, while the GC elements failed by joint failure followed by deformation and local disintegration of the composite. The study thus shows that the main difference between the two systems lies not only in the achieved load-bearing capacity, but also in stiffness, the shape of the load-displacement diagrams, and the failure mechanism. Full article

Shale gas is a major unconventional energy resource in China. Its low porosity and permeability require large-scale volumetric fracturing to create conductive fracture networks. However, most induced fractures are propped discontinuously because shale reservoirs are geometrically complex. Fracture conductivity and proppant placement efficiency therefore directly control stimulation performance. Following SY/T 6302-2009, this study used linear flow-through experiments and a large-scale visual fracture simulation system to investigate the effects of proppant particle-size distribution, injection sequence, flow rate, and closure pressure on fracture conductivity and placement. The results show that the 20/40:40/70 mesh dual-particle-size combination at a 3:2 ratio provides the best overall performance. A fine-particle content of no more than 16.7% limits conductivity loss and improves the match between particle size and fracture aperture. Multilayer placement at fracture corners distributes high-stress loading and maintains conductivity. Injecting 70–140 mesh fine proppant before 40–70 mesh coarse proppant at 3.6 m³/h improves transport distance, coverage, and placement uniformity. The optimized scheme maintains stable conductivity at closure stresses of 10–80 MPa and achieves at least 95% propped-area coverage. These findings provide experimentally supported parameters for discontinuous propping and can inform shale gas fracturing design. Full article

The influence of blade number and rotor solidity on cyclorotor hover performance remains insufficiently understood because previous studies have generally varied these parameters simultaneously or investigated them through separate one-factor analyses. This work examines their independent effects using a two-dimensional unsteady Reynolds–Averaged Navier–Stokes model in which blade number (2–8) and rotor solidity (0.24–0.60) are varied independently across 26 geometrically feasible design points, at constant rotor radius and rotational speed. The model is validated against published experimental data for the same rotor before the parametric analysis is performed. At fixed rotational speed, increasing solidity raises both the thrust and power coefficients and lowers power loading. Because power loading is disk-loading-dependent even for an ideal rotor, however, this apparent penalty largely reflects a change in operating point rather than a loss of aerodynamic efficiency: compared at matched disk loading, efficiency varies only weakly with solidity except in the corner of the design space that combines high solidity with a long blade chord, and an interior efficiency optimum emerges near $\sigma \approx 0.36$ for blade counts $N=4$–8, reconciling the present results with the chord-to-radius optimum reported in the literature. Blade number has only a secondary influence on mean performance at constant solidity, consistent with classical rotor theory; azimuthally resolved loads, however, show peak-to-mean thrust ratios of 3–4 for two- and three-bladed rotors, a design constraint invisible in cycle-averaged metrics. Full article

The large-scale integration of variable renewable energy sources (RES) such as solar and wind into transmission networks poses significant challenges to grid stability, operational efficiency, and economic dispatch. Battery Energy Storage Systems (BESS) offer a flexible solution, but their optimal placement remains critical to maximizing technical and economic benefits. This paper presents a multi-index, scenario-based framework for optimal BESS siting in a modified IEEE 118-bus transmission system under high renewable penetration. Six complementary indices are employed: Voltage Deviation Index (VDI), Fast Voltage Stability Index (FVSI), Line Congestion Index (LCI), Bus Congestion Index (BCI), Z-bus Sensitivity Index (ZBSI), and nodal price difference (Δλ). Eight extreme scenarios, combining high/low solar, wind, and hydro generation under peak load, are used to identify vulnerable buses. Five weighting case studies reflect different stakeholder priorities: voltage stability, congestion relief, energy arbitrage, loss reduction, and equal weightage. Results show that the congestion relief case achieves the lowest daily operating cost (approx. $8000 less than the base case) and the highest net economic benefit, while the loss reduction case delivers the greatest reduction in active (34 MW) and reactive (169 MVAr) power losses, compared to the base case. The proposed framework demonstrates that integrating technical and market-based indicators enables more robust and economically attractive BESS placement. This work provides a practical, data-driven planning tool for grid operators and investors aiming to enhance transmission system sustainability under high-RES variability. Full article

High penetration of renewable energy reduces power-system inertia and increases the need for fast-frequency-support resources. This study proposes an integrated virtual synchronous machine (VSM) control framework for clusters of variable-frequency air conditioners (VFACs). The proposed method incorporates synchronous-machine-like inertia and damping into compressor-side power control, aggregates heterogeneous VFACs using fuzzy C-means clustering, and adaptively adjusts virtual inertia according to grid-frequency variations. Virtual-storage flexibility is further incorporated into coordinated frequency regulation. Simulations on the IEEE two-machine, five-node system verify the effectiveness of the proposed framework. Under a representative 3 MW load-increase disturbance, the frequency deviation from the nominal value is reduced from 0.11 Hz to 0.04 Hz. The results indicate that large-scale VFAC clusters can provide fast and coordinated demand-side frequency support while improving system frequency stability. Full article

Precast reinforced concrete (RC) large-panel buildings (LPBs) are a common residential construction typology in urban areas of Eastern European countries, including Albania. Due to the ageing of these buildings, which date back to the 1970s, and the country’s high seismic hazard, it is very important to assess their seismic safety. This study presents a code-based seismic assessment of a five-storey case-study building in Tirana, Albania’s capital, for which limited information was available and was solely based on the original construction specifications (due to the absence of in situ material testing). A 3D finite-element numerical model was developed using LIRA-SAPR 2024 R2 (version 24.2.0.0) software, and seismic analyses were performed using both multi-modal (response spectra) analysis and the equivalent static analysis procedures according to the current Albanian seismic design code (KTP-N.2-89) and the Eurocode 8 framework (including EN 1998-1 and EN 1998-3). Two different seismic hazard levels were considered to assess the effect of a significantly higher seismic hazard level (compared to the original design) on the seismic safety of older existing LPBs. A demand-to-capacity (DCR) assessment revealed significant structural deficiencies, at both the individual wall-panel level and the wall-assembly level. The representative interior load-bearing wall panel has inadequate flexural and shear capacity, with a DCR of 5.13 for flexure due to a very low vertical reinforcement ratio. The assessment also indicates that the vertical panel joint (D4) is the most critical component of the investigated wall assembly, since its shear capacity is governed by the tensile failure of the steel plate that connects the adjacent wall panels, corresponding to a DCR value of 13.89, indicating very high seismic vulnerability. The seismic assessment of the investigated case-study building may be useful for informing future efforts related to seismic assessment and retrofitting of similar LPBs in Albania and Eastern European countries. Full article

To address the difficulty in accurately evaluating the vertical bearing behavior of prestressed high-strength concrete (PHC) pipe pile-group foundations, this study investigated three single piles and an eight-pile group with a Wang-shaped irregular pile cap through field static loading tests and theoretical analysis. The measured ultimate bearing capacities of single piles D1/D2 and D3 were 7040 and 3000 kN, respectively. For the pile-group foundation, the ultimate bearing state was not reached under the maximum applied load of 15,000 kN, at which the settlement was only 3.52 mm. The pile-head load distribution followed the order corner piles > side piles > inner piles, with corresponding load proportions of approximately 13.9%, 12.9%, and 9.4%. The calibrated API and hyperbolic models predicted the single-pile bearing capacities with errors ranging from 0.23% to 3.40%. The API model better represented the steep-drop portion of the Q-s curve, whereas the hyperbolic model more accurately predicted the initial stiffness and low-load response. For pile-group foundations, the combined equivalent-pier and load-transfer method showed good applicability. The main contribution of this study is to provide field evidence for the vertical bearing and load-transfer behavior of a large-diameter PHC pipe pile group with a Wang-shaped irregular pile cap, extending existing studies that have mainly focused on single piles or conventional symmetric pile groups. The results also provide a quantitative basis for the analysis and design of PHC pipe pile-group foundations in highway bridge engineering. Full article

Tetrapod piled jacket foundations, widely adopted for large-capacity offshore wind turbines, are frequently affected by scour, which substantially alters their lateral mechanical responses. Nevertheless, existing studies on this subject remain limited and mostly adopt simplified uniform scour assumptions that deviate significantly from actual field conditions. This study conducted lateral-loading model tests on scoured tetrapod piled jacket foundations, with the local scour geometry idealized based on the non-uniform scour-hole morphology reported in field monitoring and flume test studies. The evolution law of the lateral bearing capacity of the foundations with scour development is revealed, and the differences in lateral bearing performance under uniform and non-uniform scour are systematically compared. A three-dimensional finite element model is established and validated against test data to verify its accuracy and reliability. Additionally, comprehensive parametric analyses are performed to supplement the experimental results, exploring the influences of flow angles, corresponding scour-hole morphologies and lateral load directions on the lateral bearing performance of tetrapod piled jacket foundations. The pile bearing mechanism and internal force distribution characteristics are further clarified. The research findings can provide a theoretical basis for the safe service of offshore wind turbines supported by tetrapod piled jacket foundations. Full article

As the core equipment for in situ deep-sea scientific research, the design quality and operational performance of the sampling platform determine the efficiency of deep-sea operations, including long-term continuous observation, high-quality sampling and preservation, and in situ experimental studies. To address technical bottlenecks commonly observed in conventional platforms, including track sinkage, excessive motion drag, and low propulsion efficiency, this study proposes the design and development of a novel sampling platform with tracked-propeller dual-mode propulsion, deployable from either a surface vessel or a large manned submersible, capable of high-throughput, multi-sequence fidelity water sampling, in situ sediment incubation, and seabed mudstone sampling in deep sea. Through hydrodynamic performance analysis and design optimization, both lightweight design and drag reduction were achieved. Furthermore, load verification of the main frame under multiple operating conditions was conducted; results demonstrate that the structure meets strength and stiffness requirements and ensures reliability in typical service environments. This study provides a theoretical basis and technical reference for the development of similar deep-sea sampling platforms and holds substantial engineering application value. Full article

Through-going structures are widely distributed in rock masses of underground engineering, and their dip angles act as the core factor affecting the stress field and mechanical response of surrounding rock. To reveal the mechanical mechanism of rock masses containing through-going structures with different dip angles, this study adopts a combined method of theoretical derivation, indoor model testing and numerical simulation. Firstly, a plane strain mechanical model is established to classify Tectonically-induced Stress, Residual Gravitational Stress and engineering-induced stress, and the theoretical formulas for stress components, stress residual coefficient and stress deflection angle are derived. Secondly, rock-like specimens with through-going structures of various dip angles are prepared and biaxial compression tests are carried out to monitor mechanical parameters such as surrounding rock strain and peak strength. Finally, a large-scale numerical model is built by FLAC2D (version 7.0) software to simulate the whole process of stress equilibrium and excavation unloading of rock mass under a normal stress of 20 MPa. Then the data of principal stress, stress components, stress residual coefficient and deflection angle under different dip angles are extracted. The results show that the dip angle of through-going structure exerts a prominent regulatory effect on the rock mass stress field. With the increase of the dip angle, the Tectonically-induced Stress decreases continuously while the Residual Gravitational Stress rises gradually. The variation trend of stress deflection angle is highly consistent with structural dip angle, and the influence of Residual Gravitational Stress on deflection angle is limited. Due to the differences in loading modes and model sizes between indoor tests and numerical simulations, the evolution laws of stress residual coefficient show opposite trends, but both results verify the dominant effect of structural dip angle. Combined with theoretical, experimental and numerical results, the proposed theoretical system can effectively describe the stress evolution law of rock masses with through-going structures, which provides theoretical reference and technical support for the stability analysis of surrounding rock in similar underground engineering. Full article

Piezoelectric-actuated nanopositioning stages commonly employ flexure amplification mechanisms to enlarge output displacement and are widely used in optical measurement, micro and nano manufacturing, and other precision engineering fields. However, existing methods still have limitations in computational efficiency, hinge modeling accuracy, and displacement prediction under external loading. To address these limitations, this paper proposes a generalized compliant-chain modeling method in which flexure hinges are treated as compliant units connected by rigid elements, improving computational efficiency relative to repeated finite element modeling. A multi-configuration hinge model (MCH model) is established to analyze the effects of hinge configurations and mechanism parameters on key performance indices, thereby improving prediction accuracy and extending the design space. A load-induced displacement loss model (LDL model) is further developed to characterize output displacement loss under external loading and improve the applicability of the method to loaded conditions and integrated systems involving multiple flexure mechanisms. Finite element simulations and experiments are conducted to validate the proposed models. The results show that the prediction errors of the amplification ratio and stiffness are both within 5%, while the designed mechanism achieves a high amplification ratio of 17.55. These results indicate that the proposed method provides competitive prediction accuracy and displacement amplification performance among similar flexure amplification mechanisms. The proposed method provides an effective modeling and design tool for amplification mechanisms requiring large stroke and high load capacity. Full article

Local installation errors in stern-tube bearings can substantially affect shaft alignment, yet conventional calculations often represent these errors only as nominal support displacements. This study extends the three-moment-equation framework by explicitly parameterising vertical and lateral offsets of the aft stern bearing within the compatibility equations for a multi-supported shaft beam. The method is benchmarked against published bearing-elevation data. Relative to the reference calculation, the mean absolute error (MAE) and root-mean-square error (RMSE) are 0.043 and 0.055 mm, respectively; relative to the reported installation elevations, the corresponding values are 0.229 and 0.281 mm. The method is then applied to the shafting system of a large container ship to evaluate changes in shaft deformation and slope, bearing clearance, maximum pressure, bearing load, shear force, bending moment, and support stiffness. For this case, the vertical offset is the dominant disturbance: an increase from 0 to 0.1 mm raises the maximum aft-bearing pressure by 12.19% and reduces its support stiffness by 14.39%. The effects of lateral offset remain limited up to 0.3 mm, whereas a secondary contact region develops at approximately 0.4 mm. This transition is case-specific and should not be interpreted as a universal tolerance limit. The method is intended as a rapid preventive tool for assessing installation tolerances; however, its pressure and stiffness predictions require further validation of the contact model and additional experimental evidence. Full article

Increasing frequency and intensity of heat events pose significant challenges for the production and early establishment of urban trees. This study evaluated whether horticultural interventions could mitigate heat stress and improve growth of young red maple (Acer rubrum ‘FranksRed’) under full-sun conditions representative of urban planting environments. Six treatments (control, canopy misting, paclobutrazol, propiconazole, kaolin clay, and potassium phosphite) were evaluated over two growing seasons in the Willamette Valley, Oregon, which were characterized by hot, dry summers and episodic heat waves. Canopy temperature, soil volumetric water content, and growth were monitored using high-resolution sensor networks and analyzed using mixed-effects modeling to account for repeated measures and environmental covariates. Across both years, mean canopy temperature largely tracked ambient conditions, and treatment effects on absolute temperature were modest. However, canopy misting reduced daily canopy temperature amplitude (ΔT) and maintained the highest soil volumetric water content, while both misting and kaolin consistently reduced exposure to the highest canopy temperature thresholds. Although these reductions in cumulative thermal exposure were not statistically significant, they coincided with improved tree growth. The chemical treatments produced smaller, context-dependent effects. Despite modest temperature differences, stem caliper increased by 10–20% under misting relative to the control (p < 0.05). Growth responses indicate that small changes in canopy thermal exposure and soil water availability can translate into meaningful differences in early tree performance. These results demonstrate that the absence of strong treatment effects on mean canopy temperature does not preclude biologically relevant outcomes. Management strategies that modify canopy thermal dynamics or plant water relations may improve growth and establishment potential of young trees under increasingly extreme thermal conditions, even when ambient heat loads cannot be fully mitigated. Full article

Cloud task scheduling is a critical component of cloud computing systems because it directly affects resource allocation, workload distribution, execution efficiency, and service cost. However, many metaheuristic algorithms suffer from population diversity loss, premature convergence, and an inadequate balance between global exploration and local exploitation when solving complex and large-scale optimization problems. To address these limitations, this study develops an Enhanced Human Urbanization Algorithm (EHUA) for numerical optimization and cloud task scheduling. Inspired by the collaborative resource-allocation behavior of modern logistics networks, three coordinated mechanisms are reformulated within the adventurer–city–citizen structure of the original Human Urbanization Algorithm: a logistics-hub-guided adaptive exploration mechanism, a supply–demand-based dynamic redistribution mechanism, and a cooperative logistics delivery exploitation mechanism. These mechanisms reduce excessive dependence on a single capital, adaptively regulate city search ranges, and strengthen citizen-level solution refinement. The performance of EHUA is evaluated on the CEC2014 and CEC2020 benchmark suites using convergence analysis, box plots, numerical statistics, Wilcoxon signed-rank tests, Friedman rankings, and ablation experiments. EHUA obtains the best mean fitness values on 20 of the 30 CEC2014 functions under both 30- and 50-dimensional settings, on 8 of the 10 CEC2020 functions at 10 dimensions, and on all 10 functions at 20 dimensions, demonstrating strong overall competitiveness and repeatability without implying universal superiority on every problem. EHUA is further applied to cloud task scheduling under workload scales ranging from 100 to 10,000 tasks. Considering comprehensive cost, monetary cost, execution time, and load cost, the proposed method consistently achieves low comprehensive scheduling costs and maintains favorable trade-offs among individual objectives as the workload increases. These results indicate that EHUA provides an effective and scalable optimization framework for complex benchmark problems and cloud task scheduling applications. Full article

Periprosthetic joint infection (PJI) remains one of the most serious complications of arthroplasty, largely due to the formation of microbial biofilms on implant surfaces. Biofilm-associated infections exhibit increased tolerance to antimicrobial therapy and host immune responses, making eradication difficult and often requiring repeated surgical interventions. Consequently, there is a growing need for effective local therapeutic strategies capable of delivering high concentrations of antimicrobial agents directly to the site of infection while minimizing systemic toxicity. Hydrogels have emerged as promising drug delivery platforms for the management of biofilm-associated PJI. Their biocompatibility, injectability, high water content, and tunable physicochemical properties enable controlled and localized release of therapeutic agents within the infected peri-implant environment. This narrative review summarizes recent advances in hydrogel-based approaches, including antibiotic-loaded hydrogels, systems incorporating anti-biofilm enzymes, bacteriophage-loaded formulations, and nanoparticle-enhanced platforms. It also highlights future research directions, with particular emphasis on the need for expanded clinical studies to facilitate the translation of emerging hydrogel-based therapies into clinical practice. Further development of these systems should focus on the incorporation of novel therapeutic agents into hydrogel platforms, aiming to enhance biofilm eradication and improve treatment outcomes in patients with PJI. Particular attention is given to stimuli-responsive (“smart”) hydrogels that release therapeutic payloads in response to infection-related triggers such as pH changes, with emphasis on the need for expanded clinical studies to facilitate the translation of emerging hydrogel-based therapies into clinical practice. Further development of these systems should focus on the incorporation of novel therapeutic agents into hydrogel platforms, aiming to enhance biofilm eradication and improve treatment outcomes in patients with PJI. Full article