Increasing Aspect Ratio Research Articles

Impact of collector aspect ratio on the energy and exergy efficiency of a louvered fin solar air heater

Solar air heaters have huge applications in renewable energy utilization segments concerning the issues of space heating, drying, and ventilation systems. Performance prediction of such systems largely depends upon the design of the collector itself. The present study has highlighted the influence of various aspect ratios of the collector on the thermal and exergy performance of louvered finned solar or air heaters. In this context, an experimental analysis has been carried out to compare the performance of LFSAH with conventional PSAH. These results show that an increase in aspect ratios enhances thermal efficiencies of heat transfer and the systems. An aspect ratio of 4:1 showed the maximum thermal efficiencies as 81.63 % for LFSAH and 68.13 % for PSAH. On the other hand, at larger mass flow rates, the exergetic efficiency of LFSAH becomes lower owing to the larger friction and exergy losses and sometimes even lower than that of PSAH. The novelties of the present study are in emphasizing the importance of aspect ratio in optimizing solar air heater design and providing relevant insight for better energy use.

Study of the effect of interfacial damage and friction on stress transfer in short fiber-reinforced composites

The purpose of this study is to investigate the influence of different stages of different interfaces evolution under external forces on stress transfer within composite materials, which is crucial for analyzing reinforcement mechanisms in composite materials. Analytical solutions are derived to explore the impact of these distinct phases, both at the interfaces along the fiber length direction and at the fiber ends, on the complex stress distribution profiles within composite materials. Furthermore, the frictional effect at the interface serves to impede the debonding process in the composite. Under the same load, the debonding length of the interface decreases as the frictional effect increases. The increase in fiber aspect ratio (AR) effectively reduces the length of the damage and debonding interface and increases the axial fiber stress. Additionally, the theoretical results agree well with numerical simulation and experimental results. In essence, this model provides analytical solutions that are instrumental for analyzing stress transfer in fiber-reinforced composites during different stages of interface evolution.

Experimental study of flame morphology in slope buildings under the influence of aspect ratio and ambient wind

Slope structures are commonly used in buildings, but such slope structures can exacerbate the rate of fire spread, complicate building fire safety and suppression, and lead to injuries, deaths, and property damage. Particularly, the thermal hazards posed by ambient wind on sloped fires remain unquantified. In this study, a propane burner was used to simulate the flame morphology behavior of a sloped building fire. 480 tests were conducted with varying aspect ratios (1∼8) of the fire source, different ambient winds (0 m/s∼3.5 m/s), and slope inclination angles (0°∼40°). Results demonstrate that the flame length initially increases and then decreases with an increment in ambient wind velocity. Moreover, with an increased aspect ratio of the fire source (length-to-width ratio), the turning point at which the flame length peaks shift to occur at a lower wind velocity threshold. The tilt angle and height of the flame change (respectively increases and decreases) significantly at lower ambient wind speeds and they tend to asymptotically approach respective constant values. As the ambient wind is further promoted. Existing physical models of flame morphology do not consider the combined effects of fire source aspect ratio, slope inclination angle, and ambient wind. A new slope entrainment restriction factor (EF) was proposed based on an analysis of the upward and leeward entrainment volumes. Using this factor, new models for flame morphology (including flame length, flame tilt angle, and flame height) were established. The accuracy and generalizability of the new flame models have been validated using reference data.

1D MXenes: Synthesis, Properties, and Applications.

The fascinating properties and versatile nature of 2D MXenes have generated significant interest in the scientific community. This has led to extensive research on expanding these materials into 1D and 0D forms. This review investigates the synthesis, properties, and applications of 1D MXenes, elucidating their potential across various fields. 1D MXenes, including nanowires, nanoribbons, nanorods, and nanotubes, inherit the remarkable properties of their 2D counterparts while also exhibiting unique anisotropic characteristics that enhance their performance in various applications. The review explores various methods for synthesizing 1D MXenes and examines their structural, electronic, and optical properties. The transition from 2D to 1D results in MXenes that offer superior properties, which are advantageous for various next-generation systems. The increased aspect ratio and surface area of 1D MXenes broaden their usage in energy storage, photothermal therapy, oxygen evolution reactions (OER), hydrogen evolution reactions (HER), oxygen reduction reactions (ORR), microwave absorption, filtration membranes, gas sensors, metal detection, etc. The review also addresses the challenges associated with 1D MXenes, such as limited synthesis methods, scalable production, size customization, preservation of structural integrity, and stability. Furthermore, potential opportunities and future directions in the field of 1D MXenes have also been proposed.

Study on energy harvest performance of a flapping hydrofoil with swept leading edges by numerical methods

Inspired by the superior hydrodynamic performance of fish tails with swept shapes, whether a flapping hydrofoil with swept leading edges has higher energy harvesting efficiency attracts our great attention. By solving Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras model, a numerical study on flapping swept hydrofoils was conducted. Results show that, compared to a flapping rectangular hydrofoil, a flapping swept hydrofoil has higher efficiency under almost all operating conditions. When the aspect ratio is 4.0, using a hydrofoil with a sweep angle of 10° increases the efficiency by nearly 9%. As the sweep angle increases, the efficiency increases first and then decreases, so there exists an optimal value. As the aspect ratio increases, the optimal sweep angle decreases. When the taper ratio is around 0.6, the efficiency is or is close to the maximum value. Compared with a single horseshoe vortex around flapping rectangular hydrofoils, the double horseshoe vortices around flapping swept hydrofoils and the advance of their formation time are the reasons for the efficiency improvement. The study confirms that a flapping swept hydrofoil turbine has higher efficiency than a flapping rectangular hydrofoil especially when the aspect ratio is from 2.0 to 5.0 and clarifies the reasons for the efficiency improvement.

Pre-aged and paint-baked strengthening response on the prolonged natural-aged Al-Mg-Si-Cu aluminum alloys

This study investigates the response of pre-aging and paint-baking on the microstructure evolution and precipitation kinetics in prolonged natural aged Al-Mg-Si-Cu aluminum alloys using differential scanning calorimetry (DSC), transmission electron microscopy/scanning transmission electron microscopy (TEM/STEM), small-angle X-ray scattering (SAXS), and mechanical tensile testing. The prolonged natural aged samples for 14 days contained a higher fraction of rod-like GP zones with a size of ∼1.1 nm and ∼5.5 nm in diameter and length, respectively. After pre-ageing treatment at 80°C for 1 h, some of the existing GP zones grew, exhibiting an increased aspect ratio from 5.0 to 7.7, while others dissolved, leading to a decrease in UTS strength from 211.3 ± 2.1 MPa to 193.6 ± 2.4 MPa. In the direct paint-baked samples (at 180°C for 30 mins), the partial dissolution and size reduction of GP zones promoted the formation of rod-like Lp-phase precipitates, which grew on (020)Al habit plane, and characterized by Cu-rich layered convex units along the [020]Al direction. In samples subjected to combined pre-aging and paint-baking treatments, the formation of rod-like β" phases within the aluminium matrix as well as disk-like θ' and Q′ phases along the dislocations played an important role in co-precipitation strengthening. Moreover, the presence of co-existing θ'/Q′ along pre-existing dislocations acted as effective barriers, mitigating lattice strain during tensile deformation. This resulted in a higher UTS of 233.0 ± 5.8 MPa and improved elongation of 29.1 ± 3.0 %.

Detachment of leading-edge vortex enhances wake capture force production

During stroke reversals, insect wings interact with their own wake flow from the preceding half-stroke, resulting in an unsteady aerodynamic mechanism known as ‘wing–wake interaction’ or ‘wake capture’. To better elucidate this mechanism, we numerically solved the incompressible Navier–Stokes equations at Reynolds numbers $10^2$ and $10^3$ . Simulations were conducted for wing planforms defined using the beta function distribution with varying aspect ratios ( $AR=2\unicode{x2013}6$ ) and radial centroid locations ( $\hat {r}_1=0.4\unicode{x2013}0.6$ ), whilst employing representative normal hovering kinematics. The wake development from the considered flapping wing planforms was investigated, and the wake capture contribution to aerodynamic force production was quantified by comparing the force generation between the fifth and first stroke cycles at multiple sections along the wingspan. Our results revealed that on the inboard wing region experiencing an attached leading-edge vortex (LEV) structure, wing–wake interaction is dominated by an unsteady downwash effect, resulting in a reduction in local force production. However, in regions closer to the wingtip experiencing detachment of the LEV, wing–wake interaction is dominated by an unsteady upwash effect, leading to an increase in local force production. Consequently, the global wake capture force production is controlled by the extent of LEV detachment, which primarily increases with the increase of wing aspect ratio. This suggests that for normal hovering flapping wings, the typical loss in translational force production due to wingtip stall is partially mitigated by wake capture effects.

Recirculation through western boundary currents varies nonlinearly with the ocean basin's aspect ratio

Recirculation gyres adjacent to western boundary currents (WBCs) in the ocean enhance the poleward transport of these currents. While it is well-established that the WBC in a barotropic ocean strengthens with increase in basin's aspect ratio (the meridional-to-zonal extent ratio), how intensity of the recirculation through the western boundary layer varies with this parameter remains unexplored. I address this using the non-dimensional form of the nonlinear, wind-driven Stommel–Munk model of westward intensification that comprises three parameters—the aspect ratio (δ), the damping coefficient (ϵ), and the β-Rossby number (Rβ). Here, ϵ is set by the ratio of Rayleigh friction coefficient (or eddy viscosity) to the meridional gradient of the Coriolis frequency and the basin's zonal dimension, while Rβ is proportional to wind stress amplitude and quantifies the strength of nonlinearity. In the weak-to-moderate nonlinearity limit (Rβ<∼ϵ), perturbation analysis reveals that recirculation varies concavely with aspect ratio, suggesting existence of an optimal aspect ratio (δopt) for which the recirculation is maximum and for typical values of ϵ (10−3−10−2), δopt follows the power-law relation δopt=4.3ϵ. Numerical simulations further validate the existence of δopt. For large ϵ (>5×10−3), the power-law predicts δopt for the numerical solutions rather accurately, but does not hold for smaller ϵ (2×10−3) due to increased importance of nonlinear terms. Nevertheless, the nonlinear variation in recirculation through the western boundary layer with aspect ratio is observed for all ϵ values and may contribute to the heterogeneous increase in the WBC's transport across different ocean basins in a warming climate.

Osteogenic differentiation of bone mesenchymal stem cells on linearly aligned triangular micropatterns.

Mesenchymal stem cells (MSCs) hold promise for regenerative medicine, particularly for bone tissue engineering. However, directing MSC differentiation towards specific lineages, such as osteogenic, while minimizing undesired phenotypes remains a challenge. Here, we investigate the influence of micropatterns on the behavior and lineage commitment of rat bone marrow-derived MSCs (rBMSCs), focusing on osteogenic differentiation. Linearly aligned triangular micropatterns (TPs) and circular micropatterns (CPs) coated with fibronectin were fabricated to study their effects on rBMSC morphology and differentiation and the underlying mechanobiological mechanisms. TPs, especially TP15 (15 μm), induced the cell elongation and thinning, while CPs also promoted the cell stretching, as evidenced by the decreased circularity and increased aspect ratio. TP15 significantly promoted osteogenic differentiation, with increased expression of osteogenic genes (Runx2, Spp1, Alpl, Bglap, Col1a1) and decreased expression of adipogenic genes (Pparg, Cebpa, Fabp4). Conversely, CPs inhibited both osteogenic and adipogenic differentiation. Mechanistically, TP15 increased Piezo1 activity, cytoskeletal remodeling including the aggregates of F-actin and myosin filaments at the cell periphery, YAP1 nuclear translocation, and integrin upregulation. Piezo1 inhibition suppressed the osteogenic genes expression, myosin remodeling, and YAP1 nuclear translocation, indicating Piezo1-mediated the mechanotransduction in rBMSCs on TPs. TP15 also induced osteogenic differentiation of BMSCs from aging rats, with upregulated Piezo1 and nuclear translocation of YAP1. Therefore, triangular micropatterns, particularly TP15, promote osteogenesis and inhibit adipogenesis of rBMSCs through Piezo1-mediated myosin and YAP1 pathways. Our study provides novel insights into the mechanobiological mechanisms governing MSC behaviors on micropatterns, offering new strategies for tissue engineering and regenerative medicine.

Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engineering in Optoelectronics Devices.

The growth kinetics of vertical III-V nanowires (NWs) were clarified long ago. The increasing aspect ratio of NWs results in an increase in the surface area, which, in turn, enhances the material collection. The group III adatom diffusion from the NW sidewalls to the top sustains a superlinear growth regime. In this work, we report on the growth of different GaAs nanostructures by selective area MOVPE on GaAs (111)B substrates. We show that the opening dimensions and geometry qualitatively alter the morphology and height evolution of the structures. We compare the time evolution of vertical GaAs NWs stemming from circular holes and horizontal GaAs nanomembranes (NMs) growing from one-dimensional (1D) rectangular slits on the same substrate. While NW heights grow exponentially with time, NMs surprisingly exhibit sublinear kinetics. The absence of visible atomic steps on the top facets of both NWs and NMs suggests layer-by-layer growth in the mononuclear mode. We interpret these observations within a self-consistent growth model, which links the diffusion flux of Ga adatoms to the position- and shape-dependent nucleation rate on top of NWs and NMs. Specifically, the island nucleation rate is lower on top of the NMs than that on the NWs, resulting in the total diffusion flux being directed from the top facet to the sidewalls. This gives a sublinear height evolution for the NMs. These results open innovative perspectives for shape engineering of III-V nanostructures and new avenues for the design of optoelectronics and photonic devices.

Optimizing the Morphology and Solidification Behavior of Fe-Rich Phases in Eutectic Al-Si-Based Alloys with Different Fe Contents by Adding Mn Elements.

A high Fe content easily produces Fe-rich phases with a harmful morphology, resulting in a huge detrimental effect on the properties and recycling ability of Al-Si alloys. Therefore, finding ways to effectively transform Fe-rich phases to form a beneficial phase or shape is of great significance. Accordingly, Al-Si-based alloys with Fe contents ranging from 0.1 wt.% to 2.0 wt.% were modified by different Mn additions. Moreover, experiments combined with simulations were utilized to comprehensively analyze the mechanism of Mn on the morphology and microstructural evolution of Fe-rich phases from different perspectives. The current findings determine that adding different Fe contents changes the phase-transition reactions in alloys. Without Mn, and by increasing the Fe content from 0.1 wt.% to 2.0 wt.%, the Fe-rich phases gradually convert from a skeleton-shaped α-Al8Fe2Si (<0.25 wt.%) to β-Al9Fe2Si2 with a fibrous (0.5 wt.%), needle-like (1.0 wt.%) and plate-like shape without curvatures (2.0 wt.%). The maximum length and mean aspect ratio increase from 12.01 μm to 655.66 μm and from 1.96 to 84.05, while the mean curvature decreases from 8.66 × 10-2 μm-1 to 8.25 × 10-4 μm-1. The addition of 0.35 wt.% Mn promotes a new Chinese-character and petal-shaped α-Al15(FeMn)3Si2, with an atomic ratio of Fe and Mn of 1:1 when the Fe content is lower than 0.5 wt.%, while it transforms to β-Al15(FeMn)3Si2 with an atomic ratio of 5:1, presenting as a refined plate-like shape with a certain curvature, as the Fe content increases to 2.0 wt.%. Mn alters the phase reactions and increases the threshold of the Fe content required for β-Al15(FeMn)3Si2, limiting the formation and growth of them simultaneously in time and space. The enrichment of Mn atoms and solute diffusion at the growth front of β-Al15(FeMn)3Si2, as well as the strong atomic-binding ability, can deflect the growth direction of β-Al15(FeMn)3Si2 for it to have a certain curvature. Additionally, the enriched Mn atoms easily form α-Al15(FeMn)3Si2 and cause the long β-Al15(FeMn)3Si2 to be broken and refined to further reduce the damages caused to the alloy's performance. Ultimately, the maximum length and mean aspect ratio can be effectively reduced to 46.2% and 42.0%, respectively, while the mean curvature can be noticeably increased by 3.27 times with the addition of Mn.

Research of correlation between aspect ratio and descent rate-Based on paper-plane using experiment

The aspect ratio is important to airplane performance because it affects the aircrafts performance by changing the geometry of the aerofoil, which affects the lift the aerofoil can generate. An experiment of testing 5 planes with different wing aspect ratio has performed in order to figure out the relationship between aspect ratio and descent rate. The experiment is based on small scale model. Before the experiment, analysis based on physics computation show some advantage of small scale model. The wing of the model airplane is made of paper, and the fuselage is made from paperboard. The plane is released at a certain height by a rubber band which allow the plane to glide. Finally, the experiment shows that although the increase in aspect ratio can improve the performance of the plane, the performance will get worst as aspect ratio increases after a critical aspect ratio. Computation of the average descent rate and comparison in gliding distance of different wing aspect ratio obtained by the experiments show the optimal value of AR is 5.1.

Finite element method for natural convection flow of Casson hybrid (Al2O3–Cu/water) nanofluid inside H-shaped enclosure

The fundamental problem in electronic cooling systems is the implementation of a cavity such that it can be used to provide localized cooling to specific components, such as CPUs or GPUs, enhancing their performance and longevity. It can also be used in microfluidic devices for controlled drug delivery, where precise control of fluid flow is crucial. The present article numerically explores the free convection non-Newtonian Casson hybrid nanofluid phenomena that occur within an H-shaped cavity while heated from the middle. The heating efficiency and heat flow in a cavity are influenced by perpendicular hot walls that connect two vertical closed channels. A numerical solution is obtained by implementing the Galerkin finite element method to solve the partial differential equation. The numerical outcomes are depicted on the contour of streamlines and isotherms for different parameters in the following ranges: 0.1 ≤ η ≤ 0.4, 0.005≤ϕhp≤0.020, 0.1 ≤ γ ≤ 2, and 103 ≤ Ra ≤ 106 at fixed Pr = 6.2. In addition, line graphs show rate of heat transfer within the enclosure using the average Nusselt number for these parameters. Increased aspect ratios (η = 0.4) result in a minimal rate of heat transfer enhancement, whereas decreasing η leads to a significantly higher average Nusselt number and maximum heat transfer within the cavity. The convective rate of heat transfer increases with the presence of hybrid nanoparticles inside an H-shaped cavity for all Rayleigh numbers. The rotation of the Casson hybrid nanofluid also rises as the volume ratio of nanoparticles increases. For a fixed aspect ratio (A.R) of 0.1, the heat dissipation is 6.91% at a lower ϕhp value of 0.005 at a fixed Ra value of 105. However, it increases to 7.072% for a higher ϕhp value of 0.02 at Ra = 105. With increasing Ra number, ϕhp, and γ, the number NuAve increases.

Investigation of wake dynamics near the cylinder with the variation of length-to-diameter ratio

The study investigates the impact of drag forces on underwater pipeline structures at junctions where diameter changes occur, utilizing three-dimensional numerical simulations to analyze flow patterns around dual-step cylinders at a Reynolds number of 5000. The numerical model is validated against benchmark studies for a plain circular cylinder at heating condition, demonstrating strong agreement. Subsequently, cylinder temperatures were varied to assess their influence on drag force. The study further explores the effect of varying the aspect ratio L/D from 1 to 3 on drag reduction. Analysis of the flow structures is conducted, focusing on vortex patterns, velocity fields, and force coefficients surrounding the cylinders. Additionally, streamwise and crosswise velocities are analyzed at different sectional planes of the step cylinder. Results indicate that the drag force diminishes with increasing aspect ratio, correlating with formation length (Lf). At lower aspect ratios, step-induced vortices migrate toward the wall, while at higher aspect ratios, they drift midway. This research provides insights for designing stepped diameter cylinder systems in the subcritical regime, contributing to optimized underwater pipeline structures.

Eco‐Friendly Chemical Modification of Agave Americana Fibers for Biocomposite Properties Enhancement

AbstractChemical treatments are used to remove hydrophilic OH groups and surface particles from the fiber surface for increasing aspect ratio of fibers and subsequently, mechanical properties. In this paper, the effect of two eco‐friendly chemical treatments on morphology, chemical structure, and thermal stability of Agave Americana fibers (AAFs) is investigated. The first chemical treatment of AAF is based on citric acid (C6H8O7) to substitute OH groups contained in AAF by ester groups, while the second one involves sodium bicarbonate (NaHCO3) to remove the lignin and hemicellulose components with the aim to promote good fiber‐matrix adhesion. Attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) data shows that both treatments are efficient to remove hemicelluloses and a part of lignin contained in AAF resulting in a rough and clean fiber surface. Thermal stability of AAF has clearly increased by NaHCO3 treatment compared to untreated one, unlike C6H8O7, which reduces this property. The study highlights the possibility of substituting conventional polluting chemical treatments with environmentally friendly ones to modify the surface of plant fibers for polymer composites reinforcement.

Prediction of UCS and BTS under freeze-thaw conditions in the NW himalayan rock mass using petrographic analysis and laboratory testing

Repeated freeze-thaw (F&T) cycles substantially harm the durability of rocks, heightening the potential for landslides, rockslides, and avalanches. The current work investigates the effect of the F&T cycle on rock mass (biotite schist) samples. For this purpose, 32 rock samples were prepared and gathered from eight distinct locations in the northwest Himalayan region. For each sample, petrographical analysis and laboratory testing such as uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) are investigated at repeated (0th, 10th, 20th, and 30th) F&T cycles. Additionally, machine learning (ML) sequential models such as recurrent neural networks (RNN), gated recurrent units (GRU), and bi-directional long short-term memory (Bi-LSTM) are constructed to estimate the UCS and BTS under F&T conditions. Petrographical results show no change in the mineral indices, while there is a noticeable increase in aspect ratio but a significant decline in mean grain size with each successive 10th cycle, suggesting sample damage. The study also provides a comprehensive assessment of the ML models' performance, highlighting the Bi-LSTM model's superior accuracy among all models in terms of R2 (0.9850) and RMSLE (0.0100) during the TR stage and R2 (0.9020) and RMSLE (0.0170) during the TS stage for UCS prediction. Similarly, BTS prediction also shows superior precision, recording an R2 (0.7543) and RMSLE (0.0345) during TR and R2 (0.7404) and RMSLE (0.0213) during TS stages. The present study also explores the heatmap, line diagram, regression analysis, 2D kernel density plot, Taylor diagram, and DDR criterion for evaluating the model performance more clearly.

CFD–PBM coupled modeling of liquid–liquid interphase mass transfer behaviors inside the Kenics static mixer

Kenics static mixers (KSM) are commonly used in various industries for its excellent mass transfer performance. It is essential to systematically analyze the relationship between fluid parameters and mass transfer parameters to better understand the mass transfer behaviors between liquid–liquid phases and optimize the mass transfer efficiency of the KSM. In this work, a computational fluid dynamic–population balance model coupled method is utilized and three mass transfer models are compared and analyzed. Further simulations investigate the mass transfer behaviors inside the KSM under different superficial velocities, dispersed phase volume fractions, and aspect ratios. The results show that the increase of superficial velocity leads to the 2.23–14.15–fold increase of volumetric mass transfer coefficient and the 1.71–4.56–fold increase of mass transfer rate. What's more, increasing the dispersed phase volume fraction leads to the significant increase of 15.51 times in volumetric mass transfer coefficient and 34.92 times in mass transfer rate. Moreover, the increase of aspect ratio could result in the reduction of 4.19–1.72 times in volumetric mass transfer coefficient and 1.81–1.17 times in mass transfer rate. This work provides valuable theoretical insights for the optimal design of the KSM and the enhancement of mass transfer performance.

Influence of real particle morphology on single particle crushing behavior of rockfill based on FDEM

Particle morphology is critical in affecting the crushing behavior of rockfill materials. In contrast, most current single particle simulations lack satisfactory morphology accuracy, and the resulting crushing modes deviate from observations to some extent. Therefore, we reconstruct the real particle morphology with the spherical harmonic (SH) method and employ the finite-discrete element method (FDEM) to simulate the one-dimensional (1D) compressive crushing process of basalt particles commonly used in rockfill. The influences of four main morphological parameters, i.e. sphericity, aspect ratio, roundness, and convexity, on the single particle strength and the crushing modes are discussed. The results show that with the SH degree set to 15 and a mesh number of 20,480, the FDEM models of reconstructed particles achieve sufficient morphology accuracy and high computational efficiency. Based on the model, the simulation results demonstrate that the aspect ratio has the most significant impact on single particle strength, followed by sphericity. In contrast, roundness and convexity have a weaker effect than the above two parameters. Also, it is revealed that single particle strength decreases with increasing aspect ratio and sphericity, while it increases with higher roundness and convexity. Furthermore, aspect ratio significantly changes the initial crushing position, sphericity dominates post-crushing fragment size and quantity, and roundness mainly affects post-crushing morphology. The model results have been employed in establishing a support vector regression (SVR)-based predicted model, exhibiting good predictive performance and advantages for the optimization of rockfill particles in engineering.

Effect of aspect ratio and axial tensile load on the inflation of cylindrical tubes

We explore the snap-through instability in hyper-elastic cylindrical tubes during inflation, specifically investigating the influences of geometry and imposed axial tensile loads on both the bulging shape profiles and the initiation pressure of the bulge. We perform bulging experiments on latex rubber tubes with different parameters such as the length-to-diameter aspect ratio and axial tension. To complement these experiments, finite element simulations across various geometries and a theoretical analysis of an infinite-length tube are conducted. Our simulations reveal a critical aspect ratio that divides the bulging into two possibilities: short tubes exhibit whole bulging, while longer tubes show localized bulging. Both experimental and simulation findings indicate that as the aspect ratio and axial tensile load increase, the initiation pressure diminishes and then converges. Notably, when the axial tensile load surpasses the shear modulus, it obstructs snap-through in shorter tubes and neutralizes the influence of the aspect ratio on the initiation pressure. The outcomes of this research offer valuable perspectives on modulating the bulging mode and initiation pressure in tubular structures within soft devices, including soft pneumatic actuators and energy harvesters.

In-situ microfibrilization of liquid metal droplets in polymer matrix for enhancing electromagnetic interference shielding and thermal conductivity

Herein, liquid metal microfibers (LMM) were constructed in poly (ε-caprolactone) (PCL) matrix and PCL/carbon nanotubes (CNT) composites via an in-situ microfibrilization of liquid metal (LM) droplets by a layer-by-layer stacking method. The aspect ratios of LMMs in the composites can be easily adjusted by controlling the number layers. The effect of LMM aspect ratios on electromagnetic interference (EMI) shielding effectiveness (SE) and thermal conductivity is discussed. The results show that the EMI SE value and the thermal conductivity increase with increasing aspect ratios of LMMs. In addition, the EMI shielding mechanism of PCL/LMM and PCL/LMM/CNT composites is evaluated comprehensively through the combination of electromagnetic simulation and experimental investigation. The efficiently conductive network can be formed in the composites with LMMs, which enhance EMI SE and thermal conductivity. Furthermore, the electric field distribution on the LMM surface is uneven, which enhances the polarization loss ability to electromagnetic waves.