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Search Results (249)

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Keywords = contact instability

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17 pages, 1509 KiB  
Article
Nanocellulose Application for Metal Adsorption and Its Effect on Nanofiber Thermal Behavior
by Wanderson Ferreira Braz, Lucas Tonetti Teixeira, Rogério Navarro and Omar Ginoble Pandoli
Metals 2025, 15(8), 832; https://doi.org/10.3390/met15080832 - 25 Jul 2025
Viewed by 329
Abstract
Carboxylate (TCNF) and sulfonated (SCNC) cellulose nanofibers were synthesized and used as adsorbents for metallic cations in aqueous solutions: Na+ and Hg2+ (SCNC); Mg2+ and Hg2+ (TCNF). ICP-OES analysis of the liquid phase revealed metal removal efficiencies at room [...] Read more.
Carboxylate (TCNF) and sulfonated (SCNC) cellulose nanofibers were synthesized and used as adsorbents for metallic cations in aqueous solutions: Na+ and Hg2+ (SCNC); Mg2+ and Hg2+ (TCNF). ICP-OES analysis of the liquid phase revealed metal removal efficiencies at room temperature of 89.3% (Hg2+) and 100% (Mg2+) for TCNF, 35.2% (Hg2+) and 63.3% (Na+) for SCNC after 3 h of contact. Interestingly, the nanofibers exhibited a distinct thermal degradation profile (characterized by two main events) compared to that of cellulose, suggesting that their nanostructured morphology and surface functionalization may enhance thermal instability. Additionally, the presence of metals at its surface notably altered the thermal degradation kinetics, as observed for mercury and magnesium in TCNF. Finally, the results for SCNC strongly suggest that the mechanism for thermal degradation can also change, as observed for mercury and sodium, expressed through the appearance of a new DTG peak located around 300 °C. Full article
(This article belongs to the Special Issue Advances in Recycling of Valuable Metals—2nd Edition)
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17 pages, 9414 KiB  
Article
Influence of High-Speed Flow on Aerodynamic Lift of Pantograph at 400 km/h
by Zhao Xu, Hongwei Zhang, Wen Wang and Guobin Lin
Infrastructures 2025, 10(7), 188; https://doi.org/10.3390/infrastructures10070188 - 17 Jul 2025
Viewed by 264
Abstract
This study examines pantograph aerodynamic lift at 400 km/h, and uncovers the dynamic behaviors and mechanisms that influence pantograph–catenary performance. Using computational fluid dynamics (CFD) with a compressible fluid model and an SST k-ω turbulence model, aerodynamic characteristics were analyzed. Simulation data at [...] Read more.
This study examines pantograph aerodynamic lift at 400 km/h, and uncovers the dynamic behaviors and mechanisms that influence pantograph–catenary performance. Using computational fluid dynamics (CFD) with a compressible fluid model and an SST k-ω turbulence model, aerodynamic characteristics were analyzed. Simulation data at 300, 350, and 400 km/h showed lift fluctuation amplitude increases with speed, peaking near 50 N at 400 km/h. Power spectral density (PSD) energy, dominated by low frequencies, peaked around 10 dB/Hz in the low-frequency band, highlighting exacerbated lift instability. Component analysis revealed the smallest lift-to-drag ratio and most significant fluctuations at the head, primarily due to boundary-layer separation and vortex shedding from its non-streamlined design. Turbulence energy analysis identified the head and base as main turbulence sources; however, base vibrations are absorbed by the vehicle body, while the head causes pantograph–catenary vibrations due to direct contact. These findings confirm that aerodynamic instability at the head is the main cause of contact force fluctuations. Optimizing head design is necessary to suppress fluctuations, ensuring safe operation at 400 km/h and above. Results provide a theoretical foundation for aerodynamic optimization and improved dynamic performance of high-speed pantographs. Full article
(This article belongs to the Special Issue The Resilience of Railway Networks: Enhancing Safety and Robustness)
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23 pages, 11962 KiB  
Article
Model Test on Excavation Face Stability of Shallow-Buried Rectangular Pipe Jacking in Sand Layer
by Yunlong Zhang, Peng Zhang, Yong Xu and Jiahao Mei
Appl. Sci. 2025, 15(14), 7847; https://doi.org/10.3390/app15147847 - 14 Jul 2025
Viewed by 200
Abstract
This study addresses the critical challenge of excavation face instability in rectangular pipe jacking through systematic physical model tests. Utilizing a half-section symmetry apparatus with non-contact photogrammetry and pressure monitoring, the study investigates failure mechanisms under varying overburden ratios and sand densities. Key [...] Read more.
This study addresses the critical challenge of excavation face instability in rectangular pipe jacking through systematic physical model tests. Utilizing a half-section symmetry apparatus with non-contact photogrammetry and pressure monitoring, the study investigates failure mechanisms under varying overburden ratios and sand densities. Key findings reveal that support pressure evolution follows a four-stage trajectory: rapid decline (elastic deformation), slow decline (soil arching development), slow rise (arch degradation), and stabilization (global shear failure). The minimum support pressure ratio Pmin decreases by 39–58% in loose sand but only 10–37% in dense sand due to enhanced arching effects. Distinctive failure mechanisms include the following: (1) failure angles exceeding 70°, substantially larger than theoretical predictions; (2) bimodal ground settlement characterized by without settlement followed by abrupt collapse, contrasting with gradual transitions in circular excavations; (3) trapezoidal settlement surfaces with equilibrium arch angles ranging 41°–48°. These new discoveries demonstrate that real-time support pressure monitoring is essential for risk mitigation, as ground deformation exhibits severe hysteresis preceding catastrophic rapid collapse. The experimental framework provides fundamental insights into optimizing excavation face support design in shallow-buried rectangular tunneling. Full article
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19 pages, 5413 KiB  
Article
A Dual-Signal Ratiometric Optical Sensor Based on Natural Pine Wood and Platinum(II) Octaethylporphyrin with High Performance for Oxygen Detection
by Zhongxing Zhang, Yujie Niu, Hongbo Mu, Jingkui Li, Jinxin Wang and Ting Liu
Sensors 2025, 25(13), 3967; https://doi.org/10.3390/s25133967 - 26 Jun 2025
Viewed by 279
Abstract
Optical oxygen sensors have attracted considerable attention owing to their high sensitivity, rapid response, and broad applicability. However, their test results may be affected by fluctuations in the pump light source and instability of the detection equipment. In this study, the intrinsic luminescence [...] Read more.
Optical oxygen sensors have attracted considerable attention owing to their high sensitivity, rapid response, and broad applicability. However, their test results may be affected by fluctuations in the pump light source and instability of the detection equipment. In this study, the intrinsic luminescence of pine wood was utilized as the reference signal, and the luminescence of platinum(II) octaethylporphyrin (PtOEP) was employed as the oxygen indication signal, to fabricate a dual-signal ratiometric oxygen sensor PtOEP/PDMS@Pine. The ratio of the luminescence of pine wood to that of PtOEP was defined as the optical parameter (OP). OP increased linearly with oxygen concentration ([O2]) in the range of 10–100 kPa, and a calibration curve was obtained. The sensor exhibits excellent anti-interference capabilities, effectively resisting fluctuations from laser sources and detection equipment. It also displays stable hydrophobicity with a contact angle of 118.3° and maintains excellent photostability under continuous illumination. The sensor exhibited long-term stability within 90 days and robust recovery performance during cyclic tests, wherein the response time and recovery time were determined to be 1.4 s and 1.7 s, respectively. Finally, the effects of temperature fluctuations and photobleaching on the sensor’s performance have been effectively corrected, enabling accurate oxygen concentration measurements in complex environments. Full article
(This article belongs to the Section Optical Sensors)
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19 pages, 6159 KiB  
Article
Artificial Neural Networks for Impact Strength Prediction of Composite Barriers
by Yuyi Zhang, Andrey Logachev, Aleksandr Smirnov and Nikita Kazarinov
Materials 2025, 18(13), 3001; https://doi.org/10.3390/ma18133001 - 24 Jun 2025
Viewed by 325
Abstract
This study considers the impact and penetration of composite targets by steel projectiles. Firstly, experiments on the impact of homogeneous polymethyl methacrylate (PMMA) targets were simulated using the finite element method (FEM) and the incubation time fracture criterion (ITFC). Next, targets were assumed [...] Read more.
This study considers the impact and penetration of composite targets by steel projectiles. Firstly, experiments on the impact of homogeneous polymethyl methacrylate (PMMA) targets were simulated using the finite element method (FEM) and the incubation time fracture criterion (ITFC). Next, targets were assumed to be composed of cells with weakened mechanical properties, forming a composite barrier. The composite impact problems were then used to demonstrate an approach, which can be applied to overcome the typical difficulties for impact simulations—high demands on computing resources, long computation times, and potential numerical instabilities arising from high stresses in the contact zone and high strain rates. The approach is based on the use of artificial neural networks (ANNs) trained on arrays of numerical results obtained via finite element method. Full article
(This article belongs to the Section Advanced Composites)
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30 pages, 29722 KiB  
Article
Modeling Possible G-Quadruplexes and i-Motifs at DNA–DNA Contact Sites: Strategy, Classification, and Examples
by Vladimir B. Tsvetkov
Int. J. Mol. Sci. 2025, 26(13), 5979; https://doi.org/10.3390/ijms26135979 - 21 Jun 2025
Cited by 1 | Viewed by 446
Abstract
Tetrahelical DNA structures, such as G-quadruplexes (G4s) or i-motifs (iMs), are adopted by sequences comprising several G/C tracts, exist in equilibria with respective duplexes, and may contribute to genomic instability upon helicase deficiency. To understand genomic rearrangements resulting from the juxtaposition of G/C-rich [...] Read more.
Tetrahelical DNA structures, such as G-quadruplexes (G4s) or i-motifs (iMs), are adopted by sequences comprising several G/C tracts, exist in equilibria with respective duplexes, and may contribute to genomic instability upon helicase deficiency. To understand genomic rearrangements resulting from the juxtaposition of G/C-rich DNA duplexes, models of possible intermediate structures are needed. In this study, a general strategy for creating and verifying in silico 3D models of tetrahelical DNA was proposed. This strategy was used to investigate contacts of two or more duplexes with n G3/C3 tracts (n = 2–6) separated by T/A nucleotides. The revealed viable structures of DNA–DNA contacts include stacks of right-handed and left-handed G-quadruplexes (G4s), Holliday structure-resembling assemblies with the G4 and iM opposite each other on the borders of the central “hole”, etc. Based on molecular dynamic simulations, the most probable variants were determined by estimating the contributions to the free energy. The results may be used to clarify the mechanisms of strand exchange and other rearrangements upon DNA breaks near prolonged G/C-rich sites in living systems. Additionally, they provide a balanced view on the polymorphic versus programmed DNA assemblies in artificial systems. Full article
(This article belongs to the Collection State-of-the-Art Macromolecules in Russia)
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14 pages, 4572 KiB  
Article
Synergistic Enhancement of Near-Infrared Electrochromic Performance in W18O49 Nanowire Thin Films via Copper Doping and Langmuir–Blodgett Assembly
by Yueyang Wu, Honglong Ning, Ruiqi Luo, Muyun Li, Zijian Zhang, Rouqian Huang, Junjie Wang, Mingyue Peng, Runjie Zhuo, Rihui Yao and Junbiao Peng
Inorganics 2025, 13(6), 200; https://doi.org/10.3390/inorganics13060200 - 14 Jun 2025
Viewed by 879
Abstract
The development of high-performance electrochromic materials demands innovative approaches to simultaneously control the nanoscale architecture and the electronic structure. We present a dual-modification strategy that synergistically combines copper doping with the Langmuir–Blodgett (LB) assembly to overcome the traditional performance trade-offs in tungsten oxide-based [...] Read more.
The development of high-performance electrochromic materials demands innovative approaches to simultaneously control the nanoscale architecture and the electronic structure. We present a dual-modification strategy that synergistically combines copper doping with the Langmuir–Blodgett (LB) assembly to overcome the traditional performance trade-offs in tungsten oxide-based electrochromic systems. Cu-doped W18O49 nanowires with varying Cu concentrations (0–12 mol%) were synthesized hydrothermally and assembled into thin films via the LB technique, with LB precursors characterized by contact angle, surface tension, viscosity, and thermogravimetric-differential scanning calorimetry (TG-DSC) analyses. The films were systematically evaluated using scanning electron microscopy, X-ray photoelectron spectroscopy, chronoamperometry, and transmittance spectroscopy. Experimental results reveal an optimal Cu-doping concentration of 8 mol%, achieving a near-infrared optical modulation amplitude of 76.24% at 1066 nm, rapid switching kinetics (coloring/bleaching: 5.0/3.0 s), and a coloration efficiency of 133.00 cm2/C. This performance is speculated to be a balance between Cu-induced improvements in ion intercalation kinetics and LB-ordering degradation caused by lattice strain and interfacial charge redistribution, while mitigating excessive doping effects such as structural deterioration and thermodynamic instability. The work establishes a dual-modification framework for designing high-performance electrochromic interfaces, emphasizing the critical role of surface chemistry and nanoscale assembly in advancing adaptive optoelectronic devices like smart windows. Full article
(This article belongs to the Special Issue Optical and Quantum Electronics: Physics and Materials)
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29 pages, 1756 KiB  
Review
Emerging Age-Specific Therapeutic Approaches for Dry Eye Disease
by Tatiana Suárez-Cortés and Itxaso Herrera
J. Clin. Med. 2025, 14(12), 4147; https://doi.org/10.3390/jcm14124147 - 11 Jun 2025
Viewed by 716
Abstract
Dry eye disease (DED) is a common, multifactorial disorder of the ocular surface. Although DED can affect individuals at any age, its prevalence, clinical manifestations, underlying mechanisms, and optimal management strategies differ considerably across the lifespan. In children, symptoms are frequently associated with [...] Read more.
Dry eye disease (DED) is a common, multifactorial disorder of the ocular surface. Although DED can affect individuals at any age, its prevalence, clinical manifestations, underlying mechanisms, and optimal management strategies differ considerably across the lifespan. In children, symptoms are frequently associated with atopy and allergic disorders and environmental factors, whereas in young adults, digital device usage and contact lens wear are the predominant contributors. In older adults, systemic diseases and polypharmacy significantly elevate the risk of DED. Across all age groups, tear film instability, decreased tear production, and chronic inflammation are central pathogenic features. Key tear biomarkers, such as pro-inflammatory cytokines, have been widely linked to disease development. Cathepsin S and tumor necrosis factor-alpha have recently been implicated in age-related DED. A nuanced understanding of these age-related differences is crucial for improving diagnostic accuracy and tailoring interventions to specific patient populations. This review synthesizes current evidence on DED across age groups, focusing on prevalence, risk factors, pathophysiology, molecular mechanisms, coexisting conditions, biomarkers, and treatment options. Finally, it highlights critical unmet clinical needs in the management of age-related DED. Full article
(This article belongs to the Special Issue Advances in Dry Eye Disease Treatment: 2nd Edition)
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23 pages, 4227 KiB  
Review
Redox Mediators for Li2CO3 Decomposition
by Zixuan Liu, Haoshen Huang, Zhengfei Chen, Haiyong He, Deyu Wang and Zhoupeng Li
Inorganics 2025, 13(6), 192; https://doi.org/10.3390/inorganics13060192 - 8 Jun 2025
Viewed by 553
Abstract
Lithium–air batteries (LABs) possess the highest energy density among all energy storage systems, and have drawn widespread interest in academia and industry. However, many arduous challenges are still to be conquered, one of them is Li2CO3, which is a [...] Read more.
Lithium–air batteries (LABs) possess the highest energy density among all energy storage systems, and have drawn widespread interest in academia and industry. However, many arduous challenges are still to be conquered, one of them is Li2CO3, which is a ubiquitous product in LABs. It is inevitably produced but difficult to decompose; therefore, Li2CO3 is perceived as the “Achilles’ heel of LABs”. Among various approaches to addressing the Li2CO3 issue, developing Li2CO3-decomposing redox mediators (RMs) is one of the most convenient and versatile, because they can be electrochemically oxidized at the gas cathode surface, then they diffuse to the solid-state products and chemically oxidize them, recovering the RMs to a pristine state and avoiding solid-state catalysts’ contact instability with Li2CO3. Furthermore, because of their function mechanism, they can double as catalysts for Li2O2/LiOH decomposition, which are needed in LABs/LOBs anyway regardless of Li2CO3 incorporation due to the sluggish kinetics of oxygen reduction/evolution reactions. This review summarizes the progress in Li2CO3-decomposing RMs, including halides, metal–chelate complexes, and metal-free organic compounds. The insights into and discrepancies in the mechanisms of Li2CO3 decomposition and corresponding catalysis processes are also discussed. Full article
(This article belongs to the Special Issue Novel Research on Electrochemical Energy Storage Materials)
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23 pages, 7184 KiB  
Article
Experimental Investigation of a Passive Compliant Torsional Suspension for Curved-Spoke Wheel Stair Climbing
by Sunbeom Jeong and Youngsoo Kim
Appl. Sci. 2025, 15(11), 5985; https://doi.org/10.3390/app15115985 - 26 May 2025
Viewed by 423
Abstract
Curved-spoke wheels have been proposed as an effective way to overcome stair-like obstacles with smooth, rotation-only motion. However, when the wheel’s contact point shifts, discontinuous changes in its radius of curvature cause abrupt drops in the robot’s linear speed, often leading to reduced [...] Read more.
Curved-spoke wheels have been proposed as an effective way to overcome stair-like obstacles with smooth, rotation-only motion. However, when the wheel’s contact point shifts, discontinuous changes in its radius of curvature cause abrupt drops in the robot’s linear speed, often leading to reduced payload stability and slip. As a result, maintaining reliable stair climbing becomes more difficult. At higher speeds, these sudden changes become stronger, further reducing dynamic stability. To address these issues, we propose a passive Compliant Spiral Torsional Suspension (C-STS) attached to the wheel’s drive axis. Through camera-based marker tracking, we analyzed wheel trajectories under various stiffness and speed conditions. In particular, we define the deceleration caused by the velocity drop during contact transitions as our dynamic stability metric and demonstrate that the C-STS significantly reduces this deceleration across low-, medium-, and high-speed climbing, based on comparisons both with and without the suspension. It also raises the average velocity, likely due to a brief release of stored elastic energy, and lowers the net torque requirement. Our findings show that the proposed C-STS greatly improves dynamic stability and suggest its potential for enhancing stair-climbing performance in curved-wheel-based robotic systems. Furthermore, our approach may extend to other reconfigurable wheels facing similar instabilities. Full article
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24 pages, 531 KiB  
Article
Linguistic Contact, Transcoding and Performativity: Linguistic and Cultural Integration of Italian Immigrants in the Río de la Plata
by Virginia Sciutto
Languages 2025, 10(6), 121; https://doi.org/10.3390/languages10060121 - 26 May 2025
Viewed by 625
Abstract
From the late 19th to the early 20th century, Argentina experienced a wave of mass migration due to political, economic, and social instability in Europe. This study examines how idiomatic expressions in Argentine Spanish incorporate Italianisms and Rioplatense slang (lunfardismos), focusing on linguistic [...] Read more.
From the late 19th to the early 20th century, Argentina experienced a wave of mass migration due to political, economic, and social instability in Europe. This study examines how idiomatic expressions in Argentine Spanish incorporate Italianisms and Rioplatense slang (lunfardismos), focusing on linguistic contact, transcoding, and performativity. The integration of these lexical and phraseological elements occurred through direct borrowings, phraseological calques, and neological formations influenced by both languages, shaped by continuous interactions between immigrant and local communities. Based on a corpus of 179 phraseological units (PUs) from the Diccionario fraseológico del habla argentina. Frases, dichos y locuciones (DiFHA), compiled by Barcia and Pauer, the study analyzes semantic and structural changes resulting from this exchange. The findings highlight linguistic contact, reflecting the interaction between Italian and Rioplatense Spanish; transcoding, illustrating the adaptation of linguistic elements to a new sociocultural context; and performativity, demonstrating how these expressions acquire distinct meanings in daily communication. By examining these phraseological units, the research reveals how language embodies Argentina’s migratory and cultural history, showing how linguistic contact enriches communication and identity through the interaction of different communities. Full article
11 pages, 528 KiB  
Article
Impact of Multiple Sclerosis on Load Distribution, Plantar Pressures, and Ankle Dorsiflexion Range of Motion in Women
by Sara Zúnica-García, Esther Chicharro-Luna, Alba Gracia-Sánchez, Isabel Jiménez-Trujillo, Jonatan García-Campos and Ángel P. Sempere
Healthcare 2025, 13(11), 1231; https://doi.org/10.3390/healthcare13111231 - 23 May 2025
Viewed by 410
Abstract
Alterations in static plantar pressure distribution serve as important indicators of gait and balance impairments in individuals with Multiple Sclerosis (MS). In addition, the identification of altered patterns of plantar load distribution, along with restricted ankle dorsiflexion, may serve as early markers of [...] Read more.
Alterations in static plantar pressure distribution serve as important indicators of gait and balance impairments in individuals with Multiple Sclerosis (MS). In addition, the identification of altered patterns of plantar load distribution, along with restricted ankle dorsiflexion, may serve as early markers of postural instability and gait dysfunction in women with MS. Objectives: To assess differences in static plantar pressure, load distribution, and ankle dorsiflexion range of motion between women diagnosed with MS and women without the condition. Methods: A cross-sectional observational study was conducted between April and December 2024. Women with MS were recruited from patient associations in the provinces of Alicante and Murcia, as well as from the neurology outpatient clinic at the Doctor Balmis University Hospital (Alicante, Spain). Static postural assessment was performed using the Neo-Plate® pressure platform, which measured maximum and mean plantar pressure (kPa), load distribution (%), contact surface area (cm2), and anterior–posterior weight distribution between the forefoot and rearfoot. The ankle dorsiflexion range of motion was assessed with a universal two-arm goniometer. All parameters were compared with those of a group of women without a diagnosis of MS. Results: Compared to women without MS, participants with MS showed a significantly greater load on the right forefoot (25.75% vs. 23.41%, p = 0.021), and reduced load on the right (23.09% vs. 26.01%, p = 0.004) and left rearfoot (26.60% vs. 30.85%, p = 0.033). Total forefoot loading was significantly higher (52.33% vs. 46.40%, p < 0.001), and rearfoot loading was lower (47.64% vs. 52.42%, p = 0.006) in the MS group. Ankle dorsiflexion range of motion was also significantly reduced in women with MS, both with the knee flexed (5.95° ± 4.50 and 6.76° ± 4.69 vs. 15.45° ± 5.04 and 14.90° ± 5.43) and extended (2.69° ± 3.69 and 3.12° ± 3.83 vs. 8.17° ± 3.41 and 8.60° ± 3.31), with all differences reaching statistical significance (p < 0.001). Conclusions: Women with MS present significant alterations in static plantar load distribution, with increased forefoot and decreased rearfoot loading, as well as markedly reduced ankle dorsiflexion, in comparison to women without the disease. These findings suggest the presence of postural imbalances associated with MS, potentially affecting functional stability and mobility. Full article
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20 pages, 8369 KiB  
Article
Mechanical Response of Pipeline Leakage to Existing Tunnel Structures: Insights from Numerical Modeling
by Ruichuan Zhao, Linghui Li, Xiaofei Chen and Sulei Zhang
Buildings 2025, 15(11), 1771; https://doi.org/10.3390/buildings15111771 - 22 May 2025
Cited by 1 | Viewed by 345
Abstract
Pipeline leakage can induce ground surface settlements and structural responses in existing tunnels. A thorough understanding of pipeline–tunnel interactions is crucial for optimizing urban underground design and establishing construction guidelines. As urban underground spaces undergo rapid, large-scale development, their layouts have grown increasingly [...] Read more.
Pipeline leakage can induce ground surface settlements and structural responses in existing tunnels. A thorough understanding of pipeline–tunnel interactions is crucial for optimizing urban underground design and establishing construction guidelines. As urban underground spaces undergo rapid, large-scale development, their layouts have grown increasingly complex. Previous studies have mainly focused on the leakage propagation range and the resulting strata instability during tunnel excavation, while paying limited attention to the effects of pipeline leakage on existing tunnels. This study systematically investigated the mechanical response of existing tunnel structures to pipeline leakage under different layout configuration conditions using numerical modeling. A two-dimensional numerical model was developed to simulate the pipeline leakage process and its impact on adjacent tunnels. The research established a correlation between surrounding rock strength parameters and the saturation degree while examining the evolution patterns of leakage effects in various tunnel–pipeline arrangements. The analysis specifically focused on the mechanical influence of horizontal pipeline–tunnel distance, quantitatively determining the relationships among pipeline–tunnel spacing, leakage duration, and structural internal force. The horizontal pipeline–tunnel distance did not influence the development of the leakage zone above the tunnel vault but significantly altered the seepage path length and interface contact area. The complete encapsulation of the tunnel periphery by the leakage zone required progressively longer durations with increasing horizontal offsets: 16 days (0 m), 20 days (3 m), and 33 days (6 m). Corresponding circumferential contact ratios at 10 days were measured at 68.9%, 56.4%, and 30.6%, respectively. Furthermore, prolonged seepage duration led to increased ground subsidence with expanded affected areas, while the maximum settlement decreased proportionally with greater horizontal separation from the tunnel. These findings provide valuable insights for planning, designing, and maintaining “old tunnel-new pipeline” systems in urban underground development. Full article
(This article belongs to the Special Issue Design, Construction and Maintenance of Underground Structures)
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16 pages, 3292 KiB  
Article
Contact-Angle-Guided Semi-Cured Slot-Die Coating Eliminates Air Entrapment in LED Multilayer Films
by Zikeng Fang, Jiaqi Wan, Chenghang Li, Henan Li and Ying Yan
Polymers 2025, 17(11), 1436; https://doi.org/10.3390/polym17111436 - 22 May 2025
Viewed by 497
Abstract
LED polymer multilayer films offer clear advantages over single-layer coatings, such as minimized particle settling, finer control over particle distribution, and more precise spectral tuning. However, the standard “coat–dry–coat” process for these multilayer systems often traps air bubbles, degrading film quality and uniformity. [...] Read more.
LED polymer multilayer films offer clear advantages over single-layer coatings, such as minimized particle settling, finer control over particle distribution, and more precise spectral tuning. However, the standard “coat–dry–coat” process for these multilayer systems often traps air bubbles, degrading film quality and uniformity. This study investigates the air entrainment mechanism in multilayer film formation. Bubbles form when the cured bottom layer exhibits a low contact angle, which destabilizes the advancing liquid front. High-speed microscopy captured these interfacial dynamics, and contact-angle measurements quantified the wetting behavior. Numerical simulations further demonstrated that reduced wettability and vortex formation drive air entrainment. To mitigate air entrainment, a semi-cured slot die coating approach was proposed to modify the surface wettability and suppress the flow instabilities. Incorporating temperature-dependent viscosity into the simulation model improved its predictive accuracy, cutting the error in predicted coating-gap limits from 11.49% to 4.99%. This combined strategy delivers reliable, bubble-free multilayer films and paves the way for more consistent, high-quality LED polymer applications. Full article
(This article belongs to the Special Issue Recent Advances in Polymer Coatings)
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16 pages, 5257 KiB  
Article
Effects of Driving Current Ripple Fluctuations on the Liquefied Layer of the Armature–Rail Interface in Railguns
by Wen Tian, Gongwei Wang, Ying Zhao, Weikang Zhao, Weiqun Yuan and Ping Yan
Energies 2025, 18(10), 2596; https://doi.org/10.3390/en18102596 - 16 May 2025
Viewed by 329
Abstract
During the electromagnetic launching process, the actual current input into the launcher is obtained by controlling the discharge of the pulsed power supply. Generally, the waveform of the pulse current is determined by the discharge characteristics and discharge time of the pulse power [...] Read more.
During the electromagnetic launching process, the actual current input into the launcher is obtained by controlling the discharge of the pulsed power supply. Generally, the waveform of the pulse current is determined by the discharge characteristics and discharge time of the pulse power supply. Due to the limitation of control accuracy, the driving current is not an ideal trapezoidal wave, but there is a certain fluctuation (current ripple) in the flat top portion of the trapezoidal wave. The fluctuation of the current will affect the thickness of the liquefied layer at the armature–rail interface as well as the magnitude of the contact pressure, thereby inducing instability at the armature–rail interface and generating micro-arcs, which result in a reduction in the service life of the rails within the launcher. Consequently, it is imperative to conduct an in-depth analysis of the influence of current ripple on the liquefied layer during electromagnetic launching. In this paper, a thermoelastic magnetohydrodynamic model is constructed by coupling temperature, stress, and electromagnetic fields, which are predicated on the Reynolds equation of the metal liquefied layer at the armature–rail contact interface. The effects of current fluctuations on the melting rate of the surface of the armature, the thickness of the liquefied layer, and the hydraulic pressure of the liquefied layer under four different current ripple coefficients (RCs) were analyzed. The results show the following: (1) The thickness and the pressure of the liquefied layer at the armature–rail interface fluctuate with the fluctuation of the current, and, the larger the ripple coefficient, the greater the fluctuations in the thickness and pressure of the liquefied layer. (2) The falling edge of the current fluctuation leads to a decrease in the hydraulic pressure of the liquefied layer, which results in the instability of the liquefied layer between the armature and rails. (3) As the ripple coefficient increases, the time taken for the liquefied layer to reach a stable state increases. In addition, a launching experiment was also conducted in this paper, and the results showed that, at the falling edge of the current fluctuation, the liquefied layer is unstable, and a phenomenon such as the ejection of molten armature and transition may occur. The results of the experiment and simulations mutually confirm that the impact of current fluctuations on the armature–rail interface increases with increases in the ripple coefficient. Full article
(This article belongs to the Section F1: Electrical Power System)
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