Search Results (3,491)

In the present work, the turbulent wake of a circular cylinder in a confined flow environment at a blockage ratio of 14% is experimentally investigated in a wind tunnel consisting of a parallel test section followed by a constant-area distorting duct, under subcritical Re inlet conditions. The initial stage of wake development, extending from the bluff body to the end of the parallel section, is analyzed, with the use of hot-wire anemometry and laser-sheet visualization. The near field reveals partial similarity to unbounded wakes, with the principal difference being a modification of the Kármán vortex street topology, attributed to altered vortex dynamics under confinement. Further downstream, the mean and fluctuating velocity distributions of the confined wake gradually evolve toward channel-flow characteristics. To elucidate this transition, wake measurements are systematically compared with channel flow data obtained in the same configuration under identical inlet conditions and with reference channel-flow datasets from the literature. Experimental results show that a vortex-transportation mechanism exists due to confinement effect, resulting in the progressive crossing and realignment of counter-rotating vortices toward the tunnel centerline. Although wake flow characteristics are preserved, suppression of classical periodic shedding is clearly depicted. Furthermore, it is shown that the confined near-wake spectral peak persists up to x₁/d~60 as in the free case and then vanishes as the spectra broadens. Coincidentally, the confined wake exhibits a narrower halfwidth than its free wake counterpart, while a centerline shift of the shed vortices is observed. Farfield wake-flow maintains strong anisotropy, while a weaker downstream growth of the streamwise integral scale is observed when compared to channel flow. Together, these findings explain how confinement reforms the nearfield topology and reorganizes momentum transport as the flow evolves to channel-like flow. Full article

Blast damage to structural members poses serious risks to both buildings and people, making it important to understand how these elements behave under extreme loads. Columns in reinforced concrete (RC) structures are especially critical, as their sudden failure can trigger progressive collapse, unlike beams or slabs that have more redundancy. This state-of-the-art review brings together the current knowledge of the blast response of RC columns, focusing on their failure patterns, dynamic behavior, and key loading mechanisms. The studies covered include experiments, high-fidelity numerical simulations, emerging machine learning approaches, and analytical models for columns of different shapes (square, rectangular, circular) and strengthening methods, such as fiber reinforcement, steel-concrete composite confinement, and advanced retrofitting. Composite columns are also reviewed to compare their hybrid confinement and energy-absorption advantages over conventional RC members. Over forty specific studies on RC columns were analyzed, comparing the results based on geometry, reinforcement detailing, materials, and blast conditions. Both near-field and contact detonations were examined, along with factors like axial load, standoff distance, and confinement. This review shows that RC columns respond very differently to blasts depending on their shape and reinforcement. Square, rectangular, and circular sections fail in distinct ways. Use of ultra-high-performance concrete, steel fibers, steel-concrete composite, and fiber-reinforced polymer retrofits greatly improves peak and residual load capacity. Ultra-high-performance concrete can retain a significantly higher fraction of axial load (often >70%) after strong blasts, compared to ~40% in conventional high-strength RC under similar conditions. Larger sections, closer stirrups, higher transverse reinforcement, and good confinement reduce spalling, shear failure, and mid-height displacement. Fiber-reinforced polymer and steel-fiber wraps typically improve residual strength by 10–15%, while composite columns with steel cores remain stiff and absorb more energy post-blast. Advanced finite element simulations and machine learning models now predict displacements, damage, and residual capacity more accurately than older methods. However, gaps remain. Current design codes of practice simplify blast loads and often do not account for localized damage, near-field effects, complex boundary conditions, or pre-existing structural weaknesses. Further research is needed on cost-effective, durable, and practical retrofitting strategies using advanced materials. This review stands apart from conventional literature reviews by combining experimental results, numerical analysis, and data-driven insights. It offers a clear, quantitative, and comparative view of RC column behavior under blast loading, identifies key knowledge gaps, and points the way for future design improvements. Full article

To investigate the influence mechanism of hanger damage and arch-beam combined parameters on the failure behavior of tied-arch bridges, this study employs an advanced damage failure model within the LS-DYNA. A comprehensive simulation of the entire failure process was conducted, considering the coupled effects of hanger damage parameters and structural parameters of the arch-beam system, using a tied-arch bridge as the engineering case. The primary innovation of this study lies in overcoming the limitations of previous research, which has largely been confined to single hanger failure or static parameter analysis, by achieving, for the first time, dynamic tracking and quantitative identification of structural failure paths under the coupled influence of multiple parameters. The results demonstrate that both the severity and spatial distribution pattern of hanger damage significantly influence the structural failure mechanism. When damage is either uniformly distributed across the bridge or relatively concentrated—particularly when long hangers experience severe degradation—the structure becomes susceptible to cascading stress redistribution, substantially increasing the risk of global progressive collapse. This finding provides a theoretical foundation for developing risk-informed maintenance and repair strategies for hangers. It is therefore recommended that practical maintenance efforts prioritize monitoring the condition of long hangers and regions with concentrated damage. Furthermore, variations in arch-beam combined parameters are shown to have a significant effect on the structure’s collapse resistance. For the case bridge studied herein, the original design parameters achieve an optimal balance between anti-collapse performance and economic efficiency, underscoring the importance of rational parameter selection in enhancing system robustness. This work offers both theoretical insights and numerical tools for evaluating and optimizing the collapse-resistant performance of under-deck tied-arch bridges, contributing meaningful engineering value toward improving the safety and durability of similar structures. Full article

The fabrication of highly loaded and uniformly dispersed metal oxide nanoparticles (NPs) is much desired but still remains a great challenge. Herein, the NiO NPs exclusively confined in mesoporous silica SBA-15 were obtained by using nickel nitrate hydrate as a precursor through a facile solvent-free preparation method, which comprised manual grinding of Ni(NO₃)₂·6H₂O with SBA-15 and subsequent air calcination. Characterization results from X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that aggregation-free NiO nanoparticles with sizes of 3–5 nm were obtained at loading as high as 20 wt.% (weight%). Further increasing the NiO loading to 30 wt.% led to partial agglomeration of discrete nanoparticles to rod-like particles, while no external particles were observed. By comparing the sample derived from nickel acetate with exclusively external NiO particles, it was established that the pore confinement provided NiO nanoparticles with high thermal stability. Lastly, the catalytic performance of the prepared sample was evaluated in the model reaction of ammonia decomposition to CO_x-free H₂, and the stable NH₃ conversion of 93.7% was achieved at the weight hourly space velocity (WHSV) value of 30,000 mL·g⁻¹·h⁻¹ and at high temperature of 650 °C for 60 h, demonstrating the great potential of the solvent-free method in preparing thermally stable and robust supported catalysts. Full article

Thyroid cancer (TC) represents the most prevalent endocrine malignancy, with papillary thyroid cancer (PTC) comprising approximately 80% of cases and accounting for the majority of annual incidence and mortality. PTC is generally confined to the thyroid gland and demonstrates an excellent prognosis after surgery, with a five-year survival rate exceeding 90%. Nevertheless, recurrence can occur, and the ten-year survival rate for the advanced PTC is below 50%. Even after effective successful surgical intervention, many still require ongoing surveillance, additional treatment, and lifelong thyroid hormone replacement, while facing the potential adverse effects such as hormone fluctuations, surgical complications, and sequelae of radioactive iodine exposure. Naturally occurring compounds have demonstrated anti-cancer properties and hence the potential to be used as therapeutic options, impacting the same drivers and pathways involved in the tumorigenesis of thyroid cancer. This narrative review focuses on the natural compounds’ convergence on molecular nodes of PI3K/Akt, MAPK, and JAK/STAT to overcome therapeutic resistance and restore apoptosis, highlighting their potential in advanced and recurrent PTC. Full article

To understand the macroscopic fracture behavior of shale under different confining pressures, it is necessary to study the process of microcrack propagation from a microscopic perspective. In this study, a cohesive zone model for heterogeneous shale based on mineral distribution was constructed. Numerical simulation experiments were conducted under different confining pressures to investigate the effects of confining pressure on the extension of microcracks under tensile and shear loading from three perspectives: microcrack morphology, acoustic emission characteristics, and mechanical responses of different minerals. This study reveals the influence of different confining pressures on the extension of microcracks under tensile and shear loading conditions in shale and their microscopic mechanisms, which holds theoretical and practical significance for the exploitation of deeply buried shale gas. Full article

In scaled laser-driven magnetized liner inertial fusion (MagLIF), externally applied magnetic fields improve energy coupling by suppressing electron thermal conduction, enhancing Joule heating, and increasing $\alpha$-particle energy deposition. However, confinement can be significantly degraded by magnetic flux transport, dominated by resistive diffusion, and more critically, the Nernst effect. One-dimensional magnetohydrodynamic simulations demonstrate that increasing the applied field generally enhances neutron yield, but when the Nernst effect is included, the benefit of stronger magnetization diminishes. Stagnation is achieved at 2.72 ns, yielding a peak temperature of 2.17 keV and a neutron production of $1.2\times {10}^{12}$. When the Nernst effect is taken into account, the neutron yield decreases by 57.3% compared with the case without it under an initial magnetic field of 10 T. During the implosion, the magnetic field in the fuel gradually diffuses outward into the outer liner. By stagnation, the magnetic flux of fuel has decreased by 33.8%. Based on the characteristics of the Nernst effect, an optimized initial magnetic field of approximately 6 T is identified, which yields an about 2.5 times higher neutron yield than the unmagnetized case. These findings emphasize the key role of magnetic–energy coupling in target performance and provide guidance for the design and scaling of magnetized targets. Full article

Shear strength plays a critical role in the rutting resistance of asphalt pavements. In this study, a three-dimensional discrete element method (DEM) model was developed in PFC^3D to systematically investigate the effects of aggregate and void characteristics on the shear resistance of asphalt mixtures under triaxial loading. The simulation results exhibited excellent agreement with laboratory triaxial tests across varying confining pressures and mixture gradations, confirming the reliability of the DEM approach. Both aggregate and void characteristics were found to exert significant influences on shear deformation. Uniform aggregate distributions and higher friction coefficients enhanced interparticle interlocking, thereby increasing cohesion, internal friction angle, and shear resistance. In contrast, elevated air-void contents or nonuniform void distributions significantly degraded shear performance, whereas a well-distributed void size range (1–4 mm) optimized aggregate skeleton interlocking and load-transfer efficiency. These findings provide micromechanical insights into the mechanisms governing shear resistance and offer practical guidance for designing asphalt mixtures with improved rutting resistance. Full article

The development of compact, energy-efficient integrated lasers operating at 1.3 µm re-mains a critical focus in silicon photonics, essential for advancing data communications and optical interconnect technologies. This paper presents a numerical study of distributed Bragg reflector (DBR) hybrid III-V-on-silicon lasers, analyzing design trade-offs and optimization strategies based on supermode theory. The III-V section of the design incorporates InAs/(Al)GaAs quantum dots (QDs), which offer improved temperature insensitivity at the cost of more complex III-V/Si optical coupling, due to the high refractive index of (Al)GaAs. Consequently, many current laser designs rely on silicon waveguides with a thickness exceeding 220 nm, which helps coupling but limits their compatibility with standard CMOS technologies. To address this challenge, we perform detailed simulations focusing on 220-nm-thick silicon waveguides. We first examine how the mode profiles jointly depend on the silicon waveguide dimensions and the geometry and composition of the III-V stack. Based on this analysis, we propose a novel epitaxial design that enables effective III-V/Si coupling, with the optical mode strongly confined within the III-V waveguide in the gain section and efficiently transferred to the silicon waveguide in the passive sections. Moreover, the final design is shown to be robust to fabrication-induced deviations from nominal parameters. Full article

We consider the flow of a viscous fluid (power-law, non-Newtonian) injected into a gap of height H between two horizontal plates. When the viscosity of the ambient (displaced) fluid is negligible, the injected fluid forms a tail-slug in contact with both plates connected (at a moving grounding line) to a leading gravity current (GC) whose interface does not touch the top of the gap. Surface tension menisci may appear at the grounding line and nose of the GC. Such systems, of interest in the injection molding industry, have been investigated recently in the framework of the lubrication theory for the volume $\mathcal{V}=q{t}^{\alpha }$ (q and $\alpha$ are positive constants and t is time). Similarity appears for certain values of $\alpha$. The similarity solution of the lubrication model requires manipulations and numerical calculations, which obscure the underlying mechanisms and defy reliable interpretation, because the flow is dependent on four coupled parameters: viscosity exponent n, as well as J, $\sigma$, and ${\sigma }_N$ (the height ratio of the unconfined GC, grounding line meniscus, and nose meniscus to H, respectively). Here we present a significantly simpler box-model analysis, which provides straightforward insights and facilitates the quantitative predictions. Comparisons with the rigorous lubrication-model solution and with previously published data demonstrate that the box model provides a reliable physical description of the system, as well as a fairly accurate prediction of the propagation, for a wide range of parameters. Full article

This study quantified mercury (Hg) levels in the body hair of domestic and wild animals in four Brazilian states, Paraná, Mato Grosso do Sul, Goiás, and Minas Gerais, by analyzing 169 samples from sows, piglets, free-range pigs, and wild animals. The highest mean Hg concentration (274.93 ± 48.14 µg/kg) was found in wild animals in the Pantanal (MSSilvestre, Mato Grosso do Sul), followed by Minas Gerais (245.09 ± 40.27 µg/kg) and Paraná (193.0 ± 42.45 µg/kg). Levels at the GO, MGM, MSLiv, and PRV sites were significantly lower (p ≤ 0.05), according to the Scott–Knott test. Statistical analysis using ANOVA indicated significant variation in Hg levels between locations (F = 2.36; p ≤ 0.05), with homogeneity of variance (Levene’s test, p = 0.1772). Animals raised in confinement had lower levels than wild animals, which, due to extensive movement and contact with diverse environments, exhibited greater bioaccumulation. Lactating sows showed greater sensitivity than piglets, demonstrating an effect of animal category on metal absorption. The main sources of mercury are anthropogenic activities, such as mining and industrial processes, responsible for the environmental release of the metal. Although the detected levels do not pose an immediate risk to animal health or meat quality, they highlight the need for continuous monitoring, given mercury’s ability to bioaccumulate and affect ecosystems and food security. This work contributes to the understanding of environmental exposure to mercury in Brazil, reinforcing the urgency of effective mitigation strategies to preserve biodiversity and public health. Full article

With the rapid development of coastal and nearshore engineering projects in China, geotextile pipe and bag (GPB) structures have been increasingly applied in marine land reclamation and coastal protection works. To better understand the mechanical behavior of GPB structures on soft soil foundations, this study conducts a systematic investigation into the mechanical properties of both soft soils and GPBs using a physical model test system. By integrating numerical simulations, the stress–deformation characteristics of GPB structures on soft soils and the evolution of pore pressure are further analyzed. The results indicate that the compression curve of soft soil exhibits significant nonlinearity, with silt showing higher apparent compressibility than silty clay. Experimental data yielded the compression coefficient λ and rebound coefficient μ for both soil types. As consolidation pressure increases, deviatoric stress in the soft soil rises notably, demonstrating typical strain-hardening behavior. Based on these findings, the critical state effective stress ratio M was determined for both soil types. The study also establishes the development laws of cohesion c and friction angle φ during soil consolidation, as well as the variation of pore water pressure under different confining pressures. Interface tests clarify the relationships between cohesion and friction angle at the interfaces between geotextile pipe bags and sand, and between adjacent pipe bag layers. Numerical simulations reveal that the reclamation construction process significantly influences structural horizontal displacement. Significant stress concentration occurs at the toe of the slope, while the central portion of the pipe-bag structure experiences maximum tensile stress—still within the material’s allowable stress limit. The installation of drainage boards effectively accelerates pore pressure dissipation, achieving nearly complete consolidation within one year after construction. This research provides a scientific foundation and practical engineering guidance for assessing the overall stability and safety of (GPB) structures on soft soil foundations in coastal regions. Full article

The present controlled experimental research addresses the effects of exposure to nature on workers’ well-being and job performance in a work-confined setting. Ten individuals working in an open-space office inside a Portuguese military bunker were exposed to simulated nature (audio sounds and/or video images of nature). Quantitative physiological (heart rate) and self-reported measures (perceived positive and negative emotions, environment restorativeness, and work performance) were taken. Results indicate that exposure to nature during working time in confined places, through simulating a window with a view of nature and/or by introducing sounds of nature, promotes physiological and emotional well-being at work (heart rate significantly decreases, positive emotions significantly increase, and negative emotions decrease), and significantly increases employees’ perception of workplace restorative qualities. The results on work performance were non-significant. The present findings contribute to the evidence of the restorative effects of nature exposure during work. The research bridges a gap by considering workplaces where real nature exposure is not feasible and examining the evidence on the beneficial biophilic interventions (the restorative effects of simulated nature) within confined environments. The strategy to use videos and audio of nature may improve the structural conditions of work, benefiting well-being in these types of work settings. Full article

ZnO thin films were deposited on soda–lime glass substrates using the chemical spray pyrolysis method at a temperature of 500 °C. After the deposition, the substrates were irradiated with 10 keV H⁺ and Ar⁺ ions using a Colutron ion gun. We investigated the optical, structural, and morphological properties of the irradiated samples using Rutherford Backscattering Spectrometry, Ultraviolet and Visible Spectroscopy, X-ray diffraction, and Scanning Electron Microscopy. Our results showed a slight decrease in the optical band gap of the irradiated samples, which can be attributed to the quantum confinement effect caused by changes in the crystallite size. The diffractograms displayed diffraction peaks corresponding to the characteristic planes of the hexagonal wurtzite phase of ZnO, indicating that the films were polycrystalline with a preferential orientation along the c-axis. We also observed a reduction in the average crystallite size of the samples after ion irradiation. The morphological study showed that the average grain size increased and the shape changed from spherical in the pristine sample to flake-like after irradiation. Additionally, the samples irradiated with Ar⁺ ions exhibited a bimodal distribution in grain size, which is attributed to the defects and nucleation centers generated during the irradiation process. Full article

Cell migration through confined spaces is a critical step in cancer metastasis, yet the spatial regulation of endocytosis and adhesion dynamics during this process remains poorly understood. To investigate this, we adapted a microfluidic platform that generates stable, spatially linear biochemical gradients across 5 μm-tall migration channels. COMSOL simulations and optical calibration using FITC-dextran confirmed that gradients form reliably within 5 min. The microdevice also supports long-term live imaging and is compatible with both spinning disk confocal and total internal reflection fluorescence structured illumination microscopy modalities, enabling high-resolution visualization of adhesion and endocytic structures. By leveraging this platform for spatially restricted drug delivery, we locally applied the endocytic inhibitor Dyngo-4a to either the front or rear of migrating cells. This revealed that front-targeted endocytic inhibition preserved or increased leading-edge enrichment of paxillin and the clathrin adaptor AP-2, whereas rear-targeted inhibition eliminated paxillin polarity and reduced AP-2 polarity. These changes were accompanied by a significant increase in cell migration speed under front-targeted inhibition, while rear-targeted inhibition had no significant effect on speed and neither treatment altered persistence. Together, these findings suggest that endocytic polarity regulates adhesion dynamics and cell migration under confinement, offering a mechanistic insight into processes relevant to cancer cell invasion. Full article