Search Results (1,789)

Heracleum sosnowskyi is considered to be a dangerous invasive plant species that has successfully naturalized within a variety of plant communities across numerous countries. As a result of its superior competitiveness, the alien species is able to displace the indigenous species from their native habitats, thus changing the ecosystems and decreasing biodiversity. The phytochemicals present in the H. sosnowskyi aqueous extracts were revealed using GC/MS and HPLC/DAD/TOF techniques. Isopsoralen, methoxsalen, (iso)pimpinellin and/or bergapten were determined to be major compounds in the leaf, inflorescence and root extracts. Glutaric, quinic, linolenic, (iso)chlorogenic and other polyphenolic acids were identified in the extracts. Furthermore, a number of furanocoumarins, including hermandiol, bakuchicin, candinols (A and C) and candibirin F, and coumarins, umbelliferone and yunngnins (A and B), were identified in the roots. Additionally, the presence of flavonoids, including astragalin, quercetin 7,3,4-trimethyl ether, nicotiflorin and rutin, has been detected in the flower and leaf extracts. Allelopathic effects of H. sosnowskyi aqueous extracts were tested on four model plants, lettuce (Lactuca sativa L.) and three native Lithuanian meadow herbs, perennial ryegrass (Lolium perenne L.), timothy (Phleum pratense L.) and white clover (Trifolium repens L.), using the Petri dish method. H. sosnowskyi flower and leaf extracts demonstrated the strongest inhibitory effects on the germination and growth of the tested plant seeds. At the highest relative concentrations, 0.5 and 1.0, extracts of Sosnowsky’s hogweed inflorescences inhibited timothy seedling growth by 95.47% (from 19.64 ± 2.57 mm to 0.89 ± 0.73 mm) and 100%, respectively. The leaf extracts exhibited the strongest inhibitory effects on white clover seedlings. The highest relative concentrations tested (0.5 and 1.0) suppressed clover seedling growth by 94.66% (from 41.22 ± 2.53 mm to 2.20 ± 0.63 mm) and 100%, respectively. Additionally, the germination rate and vigor index of model plants were assessed. The research is of significance for the regulation and monitoring of the spreading of aggressive H. sosnowskyi plants. Moreover, it is important for the development of natural herbicides based on active phytotoxic compounds from these plants. Full article

The high-speed motion of a vehicle underwater induces cavitation, and the resulting cavity alters the surface pressure distribution and flow field characteristics. This study employs a numerical approach combining the $\mathrm{k}-\omega$ SST (Shear Stress Transport) turbulence model, the VOF (Volume of Fluid) multiphase flow model, the Schnerr–Sauer cavitation model, and the overlapping mesh technique. The numerical method is validated through the good agreement between simulation results and experimental data for both cavity shape and vehicle trajectory, with a maximum relative error of 6.1% in vertical displacement. The results indicate that during the launch-tube exit phase, with $\sigma =0.235$ and $\mathrm{Fr}=47.9$, the vehicle acceleration causes the pressure at its shoulder to drop below the saturated vapor pressure, initiating cavitation. Under transverse flow (intensity U = 0.016–0.05), the cavity becomes asymmetric. Specifically, the axial length and radial thickness on the back side are significantly larger than those on the face side, and this asymmetry intensifies with increasing transverse flow intensity. Furthermore, after exiting the launcher, the vehicle’s trajectory and attitude deflect towards the back side and the deflection amplitude increases, with horizontal displacement and attitude angle variation positively correlated with transverse flow intensity. Full article

This paper investigates the impact of lubrication and thermal effects on the performance of single-metal seals in roller cone bits, and it establishes the geometric, material, and operating parameter models for the single-metal seal. Based on the theory of statistics, the Greenwood–Williamson (G–W) model is employed to predict the contact stress of micro-protrusions on the sealing pair surface. This study establishes a Thermal Elastohydrodynamic Lubrication (TEHL) coupling model for single-metal seals, which utilizes the deformation matrix method to characterize the microscopic deformation of the sealing interface. The central difference method is applied to solve the oil film thickness and temperature distribution in the axial and film thickness directions of the sealing surface. The results indicate that the sealing zone is predominantly under rough peak contact pressure, operating in a mixed-lubrication state. Oil film thickness negatively correlates with static contact pressure, and seal pressure and pre-compression displacement significantly influence lubrication performance. Experiments validate the numerical simulation results, with a mean relative error of less than 15%, confirming the model’s effectiveness. This study offers a theoretical basis for optimizing single-metal seal design, enhancing the reliability and lifespan of roller cone bits in harsh conditions. Full article

Accurate immobilization is critical in head and neck (H&N) radiotherapy to ensure precise dose delivery while minimizing irradiation of surrounding healthy tissues. However, conventional thermoplastic masks cannot secure 100% replicas of the patient’s surface and are often limited by mechanical weakness, patient discomfort, and workflow inefficiencies. Recently, the best replicas of the patient’s face have been obtained by exploring personal CT or MRI scans of patients that are used for manufacturing of immobilization masks. This study aimed to design and evaluate customizable immobilization masks using acrylonitrile butadiene styrene (ABS)-based composites reinforced with bismuth oxide (Bi₂O₃) and to compare their mechanical performance against commercial thermoplastic masks. ABS and ABS/Bi₂O₃ composite filaments (5, 10, and 20 wt%) were fabricated and characterized by tensile testing. A patient-specific virtual mask was modeled and subjected to finite element analysis (FEA) under clinically relevant loading scenarios, including neck flexion and lateral bending. Results were benchmarked against two commercial thermoplastic masks. ABS and ABS-based composites exhibited significantly higher stiffness (1.7–2.5 GPa) and yield strength (20–25 MPa) compared to commercial thermoplastics (0.25–0.3 GPa, ~7 MPa; p < 0.001). FEA simulations revealed markedly reduced displacement in ABS masks (1–5 mm at 2 mm thickness; <1 mm at 4 mm thickness) relative to commercial masks, which exceeded 20 mm under lateral load. Hybrid configurations with reinforced edges further optimized rigidity while limiting material usage. Customized ABS-based immobilization masks outperform conventional thermoplastics in mechanical stability and displacement control, with the potential to reduce planning margins and improve patient comfort. In addition, ABS-based masks can be recycled, and Bi₂O₃-filled composites can be reused for printing new immobilization masks, thus contributing to a reduced amount of plastic waste. These findings support their promise as next-generation immobilization devices for precision radiotherapy, warranting further clinical validation, workflow integration and sustainable implementation within a circular economy. Full article

This study evaluates the environmental outcomes of integrating anaerobic digestion (AD) with pyrolysis (Py) and hydrothermal carbonization (HTC) to treat cattle slurry and grass silage in an Irish agricultural context. A consequential life cycle assessment (CLCA) was carried out for six scenarios based on 1 t of feedstock (0.4:0.6 cattle slurry/grass silage on a VS basis): two standalone AD systems (producing bioelectricity and biomethane) and four integrated AD–Py/HTC systems with different product utilisation pathways. Across all impact categories, the integrated systems performed better than standalone AD. This improvement is mainly due to the surplus bioenergy (electricity, biomethane, hydrocarbon fuel, hydrochar) that replaces marginal fossil energy (hard coal, natural gas and heavy fuel oil), together with the displacement of mineral NPK fertilisers by digestate-derived biochar and HTC process water. Among the configurations, the AD–HTC bioelectricity scenario (S4) achieved the best overall performance, driven by higher hydrochar yields, a favourable heating value, and a lower pretreatment energy demand compared with Py-based options. Across the integrated scenarios, climate change, freshwater eutrophication, and fossil depletion impacts were reduced by up to 84%, 86%, and 99%, respectively, relative to the fossil-based reference system, while avoiding digestate and fertiliser application reduced terrestrial acidification by up to 74%. Overall, the results show that the cascading utilisation of digestate via AD–Py/HTC can simultaneously enhance bioenergy production and nutrient recycling, providing a robust pathway for low-emission management of agricultural residues. These findings are directly relevant to Ireland’s renewable energy and circular economy targets and are transferable to other livestock-intensive regions seeking to valorise slurry and grass-based residues as low-carbon energy and biofertiliser resources. Full article

To investigate model applicability for the seismic analysis of shield tunnels in adverse geological sections, this study compares the beam–spring model (BSM) and mass–beam–spring model (MBSM). The Shantou Bay subsea shield tunnel, located in a Seismic Fortification Intensity Degree 8 region (PGA = 0.15 g), is used as the case study. Based on the Response Displacement Method, numerical simulations were conducted via ABAQUS and Python (Version 2.7) scripts to evaluate dynamic responses under unidirectional and tri-directional ground motions. Results indicate that while both models capture longitudinal response patterns, significant amplitude differences exist. Specifically, by accounting for soil inertial effects and shear transfer, the MBSM yields peak relative displacements, joint openings, and internal forces at soft–hard rock interfaces that are approximately 60–130% higher than those of the BSM. Furthermore, tri-directional input significantly amplifies structural responses, exhibiting distinct abrupt changes at geological transition zones. These findings provide a vital reference for the seismic design of shield tunnels traversing complex geological conditions. Full article

To address the combined demands of lightweighting, modular construction, and durability in ultra-tall wind-turbine towers, a segmental prestressed concrete-filled steel-tube (PCFST) chord for lattice towers is investigated in this study. A finite-element approach is validated against published tests on CFST columns, showing close agreement in load–displacement response and failure modes. Based on this validation, a finite-element model of the segmental PCFST chord is developed to clarify load-bearing mechanisms and parameters under axial compression and tension. The results show that, in compression, the concrete core governs the response; after steel yielding, the tube undergoes multiaxial stress redistribution—rising hoop stress and falling axial stress—consistent with von Mises yielding and dilation of confined concrete. In tension, load sharing is dominated by the steel tube and tendons, with limited concrete contribution. Parametric analyses indicate that end stiffeners markedly improve tensile behavior: with eight stiffeners, initial stiffness and peak tensile load increase by 1.8 times and 1.3 times relative to no stiffener, while effects in compression are minor. Increasing initial prestress improves tensile performance but shows diminishing returns beyond a moderate level and reduces compressive yield capacity. Increasing flange thickness enhances tensile performance with negligible compressive effect, whereas greater tube thickness increases both capacities and the initial stiffness. Full article

This study establishes a systematic and reproducible workflow for topology optimization (TO) of indexable face milling cutter bodies with integrated internal coolant channels, designed for Additive Manufacturing (AM) of metallic parts. Grounded in Design for Additive Manufacturing (DfAM) principles, the workflow combines displacement-based TO and computational fluid dynamics analysis to generate simulation-driven tool geometries tailored to the constraints of AM. By leveraging iterative design knowledge, the proposed methodology enhances the scalability and repeatability of the design process, reducing development time and supporting rapid adaptation across various tool geometries. AM is explicitly exploited to integrate support-free internal coolant channels directed toward the insert cutting edge, thereby achieving a 20% mass reduction relative to the initial milling tool designs, and improving material usage efficiency at the design stage. The workflow yields numerically optimized geometries that maintain simulated global stiffness under the considered loading conditions and exhibit coolant flow distributions that effectively target the exposed cutting edges. These simulation results demonstrate the feasibility of an AM oriented, workflow-based approach for the numerical design of milling tools with internal cooling, mass reduction and provide a focused basis for subsequent experimental validation and comparison with conventionally manufactured counterparts. Full article

Late-stage sandstone reservoirs often exhibit flow behavior markedly different from early performance, reducing recovery. This study quantifies two-phase flow in Jilin Oilfield sandstone cores to support production optimization. An oil–water displacement apparatus was built and unsteady-state relative-permeability tests were performed on core plugs from multiple well blocks. Permeability, pressure gradient, water saturation, and displacement efficiency were tracked over a range of injection multiples. Water-phase relative-permeability curves classify three seepage types: concave-down (12 cores, 2.10–46.17 mD), linear (7 cores, 1.58–12.23 mD), and concave-up (3 cores, 8.74–30.73 mD). Permeability is strongly negatively correlated with irreducible water saturation (R² = 0.84) and positively correlated with residual oil saturation (R² = 0.58), two-phase flow interval (R² = 0.51), and movable oil saturation (R² = 0.89); other relationships are weak. An increasing pressure gradient markedly improves displacement efficiency in low-permeability cores. Higher injection multiples further raise displacement efficiency across all permeability classes, but gains diminish with increasing permeability. Displacement efficiency also increases with water cut when used as a flooding-stage indicator in these unsteady-state tests. Full article

Tunnel boring machine (TBM) hydraulic cylinders operate under pronounced start–stop shocks and load uncertainties, making it difficult to simultaneously achieve smooth start-up and high-precision tracking. This paper proposes a two-phase switching adaptive sliding mode control (ASMC) strategy for TBM hydraulic actuation. Phase I targets a soft start by introducing smooth gating and a ramped start-up mechanism into the sliding surface and equivalent control, thereby suppressing pressure spikes and displacement overshoot induced by oil compressibility and load transients. Phase II targets precise tracking, combining adaptive laws with a forgetting factor design to maintain robustness while reducing chattering and steady-state error. We construct a state-space model that incorporates oil compressibility, internal/external leakage, and pump/valve dynamics, and provide a Lyapunov-based stability analysis proving bounded stability and error convergence under external disturbances. Comparative simulations under representative TBM conditions show that, relative to conventional PID Controller and single ASMC Controller, the proposed method markedly reduces start-up pressure/velocity peaks, overshoot, and settling time, while preserving tracking accuracy and robustness over wide load variations. The results indicate that the strategy can achieve the unity of smooth start and high-precision trajectory of TBM hydraulic cylinder without additional sensing configuration, offering a practical path for high-performance control of TBM hydraulic actuators in complex operating environments. Full article

Pile foundations are critical load-bearing components in bridge structures, particularly in soft, high-moisture soils susceptible to external disturbances. This study investigated the impact of large-scale soil excavation on the stability of adjacent pile foundations through comprehensive field monitoring of a newly constructed bridge during both the bridge construction and channel excavation phases. The close proximity of the excavation site to the pile caps facilitated a detailed assessment of soil–structure interaction. The results indicate that the pile axial force peaked at the pile head and decreased progressively with depth, consistent with the load transfer mechanism of friction piles. Notably, a distinct variation in axial force was observed at the bedrock interface, attributed to reduced relative displacement between the pile and the surrounding soil. Furthermore, channel water filling raised the local groundwater table, which increased the buoyancy and reduced negative skin friction, thereby decreasing the pile axial force. The study also highlighted the sensitivity of pile deformation in soft soil to unbalanced earth pressure. Asymmetric excavation and surface surcharge loading were identified as critical factors compromising pile stability and overall structural safety. These findings provide valuable insights for construction practices and offer effective strategies to mitigate adverse excavation effects, ensuring long-term structural stability. Full article

The delisting of Binance USD (BUSD) constitutes a major regulatory intervention in the stablecoin market and provides a unique opportunity to examine how targeted regulation affects liquidity allocation, market concentration, and short-run systemic risk in crypto-asset markets. Using daily data for 2023 and a linear and nonlinear Local Projections event-study framework, this paper analyzes the dynamic market responses to the BUSD delisting across major stablecoins and cryptocurrencies. The results show that liquidity displaced from BUSD is reallocated primarily toward USDT and USDC, leading to a measurable increase in stablecoin market concentration, while decentralized and algorithmic stablecoins absorb only a limited share of the shock. At the same time, Bitcoin and Ethereum experience temporary liquidity contractions followed by a relatively rapid recovery, suggesting conditional resilience of core crypto-assets. Overall, the findings document how a regulatory-induced exit of a major stablecoin reshapes short-run market dynamics and concentration patterns, highlighting potential trade-offs between regulatory enforcement and market structure. The paper contributes to the literature by providing the first empirical analysis of the BUSD delisting and by illustrating the usefulness of Local Projections for studying regulatory shocks in cryptocurrency markets. Full article

Two genetically engineered Bacillus subtilis strains, BMV9 and BsB6, were evaluated in terms of culture medium (effect of nutrients on surfactin yield) and potential biotechnological applications of surfactin in agriculture and the petrochemical industry. BMV9 (spo0A3; abrB*; ΔmanPA; sfp+) is, to date, the highest surfactin producer reported scientifically, and BsB6 is a sfp+ laboratory derivative strain that has also demonstrated considerable production potential. To assess their performance, fermentation experiments were conducted in shake flasks using two different culture media, a mineral salt medium and a complex medium, each supplemented with 2% (w/v) glucose. Lipopeptides (surfactin and fengycin) were extracted and quantified at multiple time points (up to 48 h) via high-performance thin-layer chromatography (HPTLC). Optical density, residual glucose, and pH were monitored throughout the cultivation. In parallel, microbial growth in both media were also validated in small-scale cultivation approaches. Antifungal activity of culture supernatants and lipopeptide extracts was tested against two Diaporthe species, key phytopathogens in soybean crops. Given the agricultural relevance of these pathogens, the biocontrol potential of lipopeptides represents a sustainable alternative to conventional chemical fungicides. Additionally, oil displacement tests were performed to evaluate the efficacy of surfactin in enhanced oil recovery (EOR), bioremediation, and related petrochemical processes. High-resolution LC-MS/MS analysis enabled structural characterization and relative quantification of the lipopeptides. Overall, these investigations provide a comprehensive comparison of strain production performance and the associated impact of cultivation media, aiming to define the optimal conditions for economically viable surfactin production and to explore its broader biotechnological applications in agriculture and the petrochemical industry. Full article

The free vibration of stiffened plates analyzed using classical plate–beam theoretical theory (PBM) simplified the vibrations of stiffeners parallel to the plane of the stiffened plate as the first-order torsional vibration of the stiffener cross-section. This simplification introduces errors in both the natural frequencies and mode shapes of the structure for stiffened plates with relatively tall stiffeners. To mitigate the issue previously described, this paper proposes an enhanced plate–beam theoretical model (EPBM). The EBPM decouples stiffener deformation into two components: (1) bending deformation along the transverse direction of the stiffened plate, governed by Euler–Bernoulli beam theory, and (2) transverse deformation of the stiffeners, modeled using thin plate theory. Virtual torsional springs are introduced at the stiffener–plate and stiffener–stiffener interfaces via penalty function method to enforce rotational continuity. These constraints are transformed into energy functionals and integrated into the system’s total energy. Displacement trial functions constructed from Chebyshev polynomials of the first kind are solved using the Ritz method. Numerical validation demonstrates that the EBPM significantly improves accuracy over the BPM: errors in free-vibration frequency decrease from 2.42% to 0.63% for the first mode and from 9.79% to 1.34% for the second mode. For constrained vibration, the second-mode error is reduced from 4.22% to 0.03%. This approach provides an effective theoretical framework for the vibration analysis of structures with high stiffeners. Full article

Based on ongoing experimental research, the present manuscript presents the effect of the slippage of a steel reinforcing bar due to corrosion on the chord rotation and deformation of corroded Reinforced Concrete members. The experimental results recorded that the increase in the corrosion level of the steel led to bond strength loss and relative slip between the steel and concrete, which was increased from 1.5 mm in non-corroded conditions to 3.5 mm even at low corrosion levels, up to a 5% steel mass loss. This slippage of corroded reinforcing bars from the anchorage leads to a proportional increase in terms of chord rotation due to pull out resulting in an additional increase in the displacement of the column’s top. In conclusion, the present study highlights the great importance of the contribution of the resulting slippage of a steel reinforcing bar due to corrosion in the calculation of the limit chord rotation (column–beam), a term which is of major importance in the assessment of the structural integrity of old RC structures, which was introduced as an adequacy requirement by both Eurocode 8-3 and the Greek Code of Structural Interventions (KAN.EPE). Full article