Increasing Aspect Ratio Research Articles

Computational study on the uptake of soft nanoparticles and nanoparticle cluster by cells

Nanoparticles (NPs) and exosomes used to transport therapeutic drug molecules to cells have attracted considerable attention in biopharmaceuticals. However, soft NPs entering cells with different angles are hard to be simulated by traditional theoretical endocytic models, let alone clustering of NPs with varied shapes. Here, the endocytic model based on the co-rotational grid method is implemented. The endocytosis of a single soft NP and a nanoparticle cluster (NPC) are investigated. Both the actin force and the dynamic assembly of the clathrin coat have been considered. The results show that NP size is the main factor affecting the internalization efficiency, followed by the aspect ratio, and finally the entry angle. The increase in NP size, aspect ratio, and entry angle will lead to a decrease in internalization efficiency. However, the final configuration of the endocytic vesicle and the internalization efficiency are both independent of the entry angle for NPs with an equivalent radius greater than 15 nm. Besides, a large entry angle can assist a large soft NP in successfully entering cells. The increase in NP stiffness also reduces the internalization efficiency considering the actin force required during endocytosis. The transformation of the NP from the inclined configuration to the vertical configuration is mainly due to NP deformation. Compared with a single NP, NPC has a lower internalization efficiency. The results provide new mechanistic insights into the endocytosis of soft NPs and NPCs.

Evolution of mesoscale structure in fluidized beds with non-spherical dry and wet particles

Instantaneous force distributions at bubble boundaries in non-spherical dry and wet particle systems. • The force distributions at bubble boundaries are analyzed to explain the influence mechanism of different shapes of bubbles in non-spherical dry and wet particle systems. • The effects of particle aspect ratio and liquid viscosities are investigated through the force analysis and factorial analysis. • With the increase of the particle aspect ratio, the bubble equivalent diameter gradually increases. • As the liquid viscosity increases, the bubble frequency gradually decreases. Fluidized beds with non-spherical dry and wet particles are widely used in industrial processes, and the mesoscale structure in the bed has an important influence. In this study, CFD-DEM simulations are performed to evaluate the flow behaviors and mesoscale structure in fluidized beds with non-spherical dry and wet particles. The accuracy of the model is validated by comparison with the results of the particle image velocimetry experiment. The force distributions at bubble boundaries are analyzed to explain the influence mechanism of different shapes of bubbles in non-spherical dry and wet particle systems. The factor analysis indicates the interaction of particle shape and viscous liquid on the translational and rotational kinetic energy of particles. When the bed height is low, as the particle aspect ratio increases, the bubble equivalent diameter gradually increases. In addition, as the liquid viscosity increases, the particle and bubble granular temperature gradually decrease, indicating the reduction of particle velocity fluctuate and the decrease of turbulent kinetic energy of bubble. These findings have guiding significance for the fluidization of non-spherical dry and wet particles and can be used to optimize related industrial processes.

Influence of the Aspect Ratio on the Free Convection Heat Transmission Properties of a Container Containing Porous Materials

Nowadays, many industrial and modern applications depend on heat transport in porous zones. An experimental study of the natural convection heat transfer in a corrugated cavity with dimensions of (200, 250, 300) mm in length, a width of 200 mm, a depth of 27 mm, and an amplitude of 30 mm was filled with porous materials: glass balls (3, 6, 10) mm and alumina balls (6) mm, where the water was the working fluid. The top surface was exposed to the environment, while the bottom surface was subjected to constant heat flux (300, 500, 700, 900, 1100 W/m2), The front face, back face, and sides were insulated. In this study, temperature distribution, modified Rayleigh number, and Nusselt number values are foremost criteria, which are presented for three levels of aspect ratio. The influence of various aspect ratios on heat transfer is investigated. The results showed that the heat transfer coefficient decreases with the increase in aspect ratio. The highest value is when aspect ratio = 1. The enhanced Rayleigh number decreases as the aspect ratio increases by 10%.

Numerical analysis of the effect of ellipsoidal shape on the freezing behavior of impacting water droplets on cold surfaces

A two-dimensional numerical model that investigates the freezing behavior of ellipsoidal impacting water droplets on cold surfaces was established in this paper, focusing on the spreading behavior, impact force evolution and heat transfer behavior of ellipsoidal water droplets. For cold surfaces with a higher temperature, reducing aspect ratio can reduce the contact time of water droplets on the superhydrophobic surface, which is useful for the rebound of impacting water droplets. Increasing aspect ratio can increase the spreading range of water droplets, especially for hydrophilic surfaces. The evolution of impact force of ellipsoidal water droplets on superhydrophobic surfaces exhibits a double-peak feature. With increase of aspect ratio, the first peak of impact force is gradually decreased, while the second peak is gradually increased. The effect of surface wettability on the first peak of impact force is smaller. The feature of the second peak of impact force decreases with increase of surface wettability and finally disappears. Although water droplet with higher aspect ratio has smaller peak of heat transfer rate, the heat transfer between it and cold surface is greater than that with lower aspect ratio. The stronger the surface wettability, the more obvious this phenomenon is. For some applications where the rapid freezing of impacting water droplets is required, increasing aspect ratio of water droplets seems to be a good choice.

Experimental study of urban microclimate on scaled street canyons with various aspect ratios

Urban geometry influences urban microclimate by changing both radiation and ventilation processes. Full-scale experiments provide significant information on urban microclimate but usually experience difficulty from complicated urban morphologies. It is challenging to quantify the effect of urban geometry on radiative exchange and convective ventilation under real-world atmospheric conditions. Therefore, this study conducted a scaled outdoor measurement to investigate the surface temperatures, wind velocities, and radiative fluxes in street canyons with various aspect ratios. The velocity ratio of 0.25H to 2H (V0.25H/V2H) was adopted to assess convective ventilation. The urban canyon albedo (UCA) and net all-wave radiation (Q∗) were used to quantify the radiative exchange. An increase in aspect ratio resulted in reduced convective ventilation and increased trapping radiation. The V0.25H/V2H of H/W = 2and 3were 25% and 55% smaller than that of H/W = 1, respectively. The mean midday (11:00–13:00) UCA of H/W = 1, 2, 3, and 6 was 0.11, 0.06, 0.05, and 0.03, respectively. Compared with H/W = 1, the H/W = 2, 3, and 6 increased daily total Q∗ by 11.41%, 14.41%, and 19.40%, respectively. The surface temperature was negatively correlated with aspect ratio during the daytime but positively at night. Such high-quality experimental data are useful for validating and improving the unsteady numerical simulation.

Fiber reinforcement on spherical granular beds under triaxial compressions

In this study, triaxial compressions of spherical granular beds that are reinforced by immersed flexible fibers, are simulated using the discrete element method (DEM). The DEM model is calibrated for the simulation studies of flexible fiber reinforced granular beds according to the agreement between experimental and simulation results. It is found that yield stresses of the particle beds increase as fiber concentration or its aspect ratio increases, while the yield stresses are insensitive to fiber flexibility. Configuration of the immersed fibers has a remarkable impact on compressive strength of the beds. Compared to the case with randomly distributed fibers, a vertically-placed fiber bundle augments the maximum yield stresses while exhibits negligible effect on residual stresses. Placing the fibers in a cage or net structure can dramatically enhance the strength of the particle beds, depending on the distances between the individual fibers.

Effects of hot rolling and annealing temperature on microstructure and tensile properties of a Zr-containing Ni-based ODS superalloy

A Ni-based ODS superalloy with composition of Ni-20Cr-0.5Ti-0.3Al-0.6Y2O3-0.6Zr (in mass%) was prepared by mechanical alloying and hot isostatic pressing. Hot rolling was carried out at 1100 °C with different reduction ratio (40 %, 50 % and 60 %) and different annealing temperature (1200 °C, 1250 °C and 1300 °C) to investigate their influence on nanoscale oxides, grain and high temperature tensile properties. The results showed that high-density nanoscale oxides Y4Zr3O12 are formed in the Zr-containing Ni-based ODS alloy. Hot rolling and annealing result in the slight increase of oxide size and decrease of oxide density. The growth rate of oxides obeys fifth-law, which is called pipe diffusion along dislocation. The diffusion activity energy is derived as 827 kJ/mol. Average oxide size decreases and number density increases by decreasing rolling reduction ratio or annealing temperature. The size of columnar grain and grain aspect ratio increase with increase of annealing temperature which results into enhanced ultimate tensile strength and improved ductility at 800 °C. In addition, increasing rolling reduction ratio refines grain size and reduces grain aspect ratio in the alloy. The strength of the alloy annealed at 1300 °C with a reduction ratio of 50 % is the highest which is approximately 300 MPa at 800 °C.

The effect of nozzle geometry on the flow and heat transfer of pulsed impinging jet on the concave surface

The main aim of this paper is to investigate the effect of nozzle geometry on the flow and heat transfer from a pulsed jet into a concave surface. Experiments have been carried out for pulsed circular jet and numerical simulations were done for circular, elliptical, rectangular and square geometries. Numerical solution was performed for the frequency ranges of 25Hz to 100Hz, the jet Reynolds number of 7000, the dimensionless nozzle distance to concave surfaces of 2 and 5. Numerical results show a consistent agreement with experimental results and previous works. Accordingly, the geometry of nozzle directly affects the air entrainment ratio. In addition, with the increase of aspect ratio of the nozzle, average Nusselt number (Nuave) decreases. By pulsating the inlet jet with pulse frequency of 100Hz, the average Nu number for circular/square and elliptical/rectangular jets increases 22% and 15%, respectively. Generally, the pulsation causes a reduction and an increase of the Nuave at low and high frequencies, respectively, compared to that of the steady jet. At low frequencies, the Nuave of circular jet decreases significantly in comparison to that of the square and elliptical jets. However, at high frequencies, circular jet shows higher Nuave compared to other ones. As the distance between the jet and the concave surface increases, the effect of the nozzle shape on Nuave decreases.

The effect of aspect ratio on the inception of primary instabilities in the laminar regime wake of a D-shaped cylinder

A numerical investigation was performed to study the wake dynamics of a D-shaped cylinder, and the effect of the aspect ratio of the cylinder on the onset of primary instabilities was explored. The aspect ratio ( L/D) is varied by increasing the cylinder’s length ( L) while keeping the cylinder’s diameter ( D) constant. Five aspect ratios ranging from 1 to 3 in increments of 0.5 were considered for the present study. The essential variables are the Reynolds number (Re) and the aspect ratio (AR). The primary instability analysis was performed using the Stuart-Landau equation to determine the critical Reynolds number value where the instability sets in. At low Reynolds number, the flow is steady and symmetric; at critical Reynolds number, the flow experiences Hopf bifurcation resulting in a time-periodic flow. As the aspect ratio was increased, the critical Reynolds number over which the primary instability sets in was found to increase linearly in the present study. Increasing the aspect ratio leads to significant modification of the flow topology and force coefficients. For aspect ratio two, the wake is more streamlined and narrower leading to a drag reduction of 14.49%. The drag reduction magnitude diminishes with a further increase in aspect ratio due to increased surface area resulting in more friction drag. The phase diagram and Fast Fourier transform (FFT) analysis revealed a reduction in vortex shedding activity, and velocity fluctuations in the wake.

Fatigue characterization analysis of a submerged fishing farm platform through spectral-based fracture mechanics

This study proposes a general direct calculation approach for fatigue crack growth evaluation and life predictions through a spectral-based fracture mechanics method. First, equivalent damage accumulation rates are introduced to describe the crack propagation characteristics under short-term sea states, integrating wave spectrum and fracture mechanics. Subsequently, a general fatigue crack growth program is integrated to realize automatic crack growth, accurate stress intensity factor (SIF) calculation and reliable fatigue life prediction through coupling analysis of meter-scale structures and millimeter-scale cracks. Finally, a parameter study is implemented to explore the influence of wave direction and initial crack size/shape on the fatigue performance of the fishing farm platform. Results indicate that the remaining fatigue life is evidently longer under 90° wave direction than that under 0 and 45°, which can be well characterized through SIF transfer functions. Critical fatigue life decreases with the increase of crack size and aspect ratio with the shortest duration of 12.8 years, demonstrating that residual fatigue life is closely associated with initial crack state. Fatigue failure is more predominant at lower tubular joints with the critical fatigue life ranging from 15 to 30 years, indicating the self-developed program possesses good universality and applicability in dealing with fatigue issues.

Characterization of Blast Wave Parameters in the Detonation Locus and Near Field for Shaped Charges

Understanding physical phenomena such as blast shock waves produced by controlled explosions are relevant for issues appearing in the fields of military and civilian activities. The current study analyzes detonations of cylindrical and 3D cone-shaped charges through experimental trials and numerical simulations. In order to accomplish such goals, the work is divided into three sections, which include (a) numerical studies on spherical charges to define an accurate model; (b) numerical and experimental studies to assess the influence of cylindrical and 3D cone-shaped charges on incident peak pressure and the shape of shock wave propagation; and (c) numerical studies to define the magnitude of incident peak pressure as a function of orientation, L/D aspect ratio and scaled distance. Validation studies proved that the applied model was reasonably accurate. Furthermore, relevant findings included the observation that when the L/D aspect ratio decreases, more release energy is concentrated in the axial direction for a 3D cone-shaped charge, while as the aspect ratio increases, more release energy is concentrated in the radial direction for a cylindrical-shaped charge. Additionally, the blast shock wave produced a great quantity of energy for the explosive charge with the largest surface. Finally, the orientation has less influence than the L/D aspect ratio on the incident pressure contours. Therefore, cylindrical charges have the potential of inflicting great damage when used as confined charges, and 3D charges are able to cut solid materials in case of a direct contact.

Aerodynamics and three-dimensional effect of a translating bristled wing at low Reynolds numbers

The smallest insects fly with bristled wings at very low Reynolds numbers (Re) and use the drag of the wings to provide the weight-supporting force and thrust. Previous studies used two-dimensional (2-D) models to study the aerodynamic force and the detailed flow field of the bristled wings, neglecting the three-dimensional (3-D) effect caused by the finite span. At high Re, the 3-D effect is known to decrease the aerodynamic force on a body, compared with the 2-D case. However, the bristled wing operates at very low Re, for which the 3-D effect is unknown. Here, a 3-D model of the bristled wing is constructed to numerically investigate the detailed flow field and the aerodynamic force of the wing. Our findings are as follows: The 3-D effect at low Re increases the drag of the bristled wing compared with that of the corresponding 2-D wing, which is contrary to that of the high-Re case. The drag increase is limited to the tip region of the bristles and could be explained by the increase of the flow velocity around the tip region. The spanwise length of the drag-increasing region (measuring from the wing tip) is about 0.23 chord length and does not vary as the wing aspect ratio increases. The amount of the drag increment in the tip region does not vary as the wing aspect ratio increases either, leading to the decrease of the drag coefficient with increasing aspect ratio.

Self-assembled calcium pyrophosphate nanostructures for targeted molecular delivery.

Nanostructured, inorganic microspheres have many industrial applications, including catalysis, electronics, and particularly drug delivery, with several advantages over their organic counterparts. However, many current production methods require high energy input, use of harmful chemicals, and extensive processing. Here, the self-assembly of calcium pyrophosphate into nanofibre microspheres is reported. This process takes place at ambient temperature, with no energy input, and only salt water as a by-product. The formation of these materials is examined, as is the formation of nanotubes when the system is agitated, from initial precipitate to crystallisation. A mechanism of formation is proposed, whereby the nanofibre intermediates are formed as the system moves from kinetically favoured spheres to thermodynamically stable plates, with a corresponding increase in aspect ratio. The functionality of the nanofibre microspheres as targeted enteric drug delivery vehicles is then demonstrated in vitro and in vivo, showing that the microspheres can pass through the stomach while protecting the activity of a model protein, then release their payload in intestinal conditions.

Study on dynamic behaviors from non-circular dense granular jet impact

Dynamic behaviors of non-circular dense granular jets impacting a sufficiently large target are studied by experiment and DEM simulation. Effects of the granular jet velocity, particle diameter, and aspect ratio on the anisotropic pattern were investigated. Results show that the anisotropy of particle concentration of the granular sheet is enhanced with increasing aspect ratio. Interestingly, despite the significant differences in flux, the particle velocities are approximately consistent along the long and short axes. Unlike liquid, a dead zone is present in the impact zone, and the axial-to-radial transformation of the velocity is achieved by similar circular motion along the dead zone. Because the dead zone is adaptively adjusted with the cross section, the particle fluxes are anisotropic. Frequent collisions and frictions contribute to the homogenization of velocity in azimuths. Increasing particle diameter causes the enhancement of velocity fluctuations, the circular motion cannot be maintained and particles become scattered and isotropic. • The anisotropy in velocity and flux of particles from non-circular dense particle jet impact is characterized. • The effects of the velocity, aspect ratio, and particle diameter on anisotropy are assessed. • The mechanism of the anisotropy of the granular sheet is simulated by DEM.

Experimental study on burning behavior of n-heptane in ice cavities with different aspect ratios

In situ burning is a widely used method in oil spill cleanup. This paper aims to study the burning behavior of n-heptane in ice cavities with aspect ratios ranging from 1 to 10. The depth and opening area of ice cavities were 9 cm and about 100 cm2, respectively, for all cases before ignition. Results show that the dynamic variation process of burning zone is different in square cavities and cavities with aspect ratio larger than one. For square cavities, the flame accumulates in the middle area of the cavity after ignition. For cavities with aspect ratio larger than one, at the early stage, there are unevenly distributed clusters of pulsating flames; and afterwards, the flames at different positions are gradually connected as a whole. A ring-shaped flame is observed in all cases before the extinguishing, and through theoretical analysis, it is believed that this phenomenon may be caused by the surface tension driven flow inside the water layer. In each case, at the same height, invasion lengths, i.e., horizontal distance between the cavity edge before and after burning, along the short and long sides are basically the same (average relative standard deviation: 1.60 %). And the invasion lengths show a non-monotonic trend of increasing first and then decreasing slightly with height in all cases. In addition, at the same height, the opening area of cavity increases as aspect ratio increases. For cavities with the same initial fuel layer thickness and fuel volume, the variation of aspect ratio results in little change in the growth and decay rate of mass loss rate, with the maximum relative standard deviation of 8.84 %. Heat is lost via thermal radiative penetration, conduction of fuel layer to ice walls, and conduction of fuel layer to water. Based on calculation, it is found the sharp decrease of mass loss rate cannot only be attributed to conductive heat loss, thermal radiative penetration is also an important part, which even accounts for about one-third of the total heat loss.

Parametric finite element study of novel corrugated steel deck for two-way action in steel-concrete composite floors

Composite construction using steel and concrete is a widely adopted flooring construction technique. Past literature has reported ample research in the development of composite one-way slabs. However, there is a lack of understanding of two-way action in these composite slabs. It has prevented the applicability of two-way steel-concrete composite slabs in floor construction. The performance of a novel deck composed of corrugated hat sections placed orthogonally at equal spacing on a corrugated base sheet has been investigated for achieving two-way action in steel-concrete composite slab construction. Non-linear finite element (FE) models were developed and researched for feasibility in two-way action using the commercial FE package ABAQUS. The decks were analyzed in the construction stage, that is, in the absence of concrete, to isolate the properties of the new steel deck. Various parameters such as depth and spacing of hat section, angle of hat section webs and aspect ratio of the decks were investigated to establish a suitable configuration for two-way action. The effect of the parameters on the load-deflection relationship and distribution of load in two directions were studied to optimize the two-way action. Decks were also analyzed for one-way action to benchmark the change in behavior of the corresponding two-way decks. Obtained numerical results showed that the proposed corrugated deck is efficient in two-way action and could be adopted in two-way steel-concrete composite slabs. The distribution of loads in both directions improved with a decrease in hat-section spacing but increased aspect ratio and depth.

Stress Concentration Factor in vessels with circular crosshole: Continuous parameters analysis

In this paper, a parametric study of the Stress Concentration Factor (SCF) has been carried out in cylindrical pressure vessels with circular holes. A three-dimensional finite element analysis has been carried out performing a variation of dimensionless parameters (thickness ratio, size ratio and aspect ratio) exploring a wider range than other investigations. It is observed that the maximum value of the SCF increases as the hole size ratio and the aspect ratio increase, although the location of the maximum SCF is located from the internal area of the vessel to the external part depending on the geometric configuration, defining thus three differentiated zones. Additionally, in the final part of the document, a fit model is defined to determine the value of the maximum SCF for different continuous values of the defined dimensionless parameters. This model allows to quickly calculate or locate from a contour map the maximum value of SCF for a specific geometry of pressure vessel.

Study on dispersion and wave velocity in 2D elliptic granular crystals by a micromechanics-based micromorphic model

This study considers two-dimensional elliptic granular crystals respectively with different aspect ratios. Using a micromechanics-based micromorphic model, macroscopic micromorphic constitutive modulus tensors of elliptic granular crystals are obtained. Two modes of Taylor expansion of relative displacements are used to establish contact relation between particles. This study obtains micromorphic transverse-rotational and longitudinal waves. Obvious dispersions of micromorphic waves are given in 2D elliptic granular crystals. With increase of aspect ratio, width of frequency band gap increases when wave propagates along [Formula: see text] direction but decreases when wave propagates along [Formula: see text] direction. Two modes of Taylor expansion of relative displacements only have influence on dispersions and frequency band gap of transverse-rotational waves. Velocities of longitudinal and transverse-rotational waves first decrease to zero, keep zero for a range of frequency and then increase to a larger wave velocity with increase of frequency for different aspect ratios. The situation with a larger aspect ratio leads to larger transverse-rotational and longitudinal velocities, and ratio between transverse-rotational and longitudinal velocities decreases from 0.7 to 0.59, when wave propagates along [Formula: see text] direction. However, it leads to smaller transverse-rotational and longitudinal velocities, and ratio between two velocities decreases from 0.88 to 0.56, when wave propagates along [Formula: see text] direction.

Evaporation of liquid coating a fiber

We investigate theoretically and numerically the diffusion-limited evaporation of a liquid deposited on a fiber in two configurations: a sleeve and an axisymmetric barrel-shaped droplet. For a sleeve, the local flux depends on both the aspect ratio and the smallest length of the problem. By using analytical calculations and 3D finite elements simulations, we predict a divergence of this flux further localized at the edge as the aspect ratio increases. The evaporation of axisymmetric drops on a fiber is studied with numerical simulations. For sufficiently large volumes, we evidence that the evaporation rate is almost independent of the wetting properties of the liquid, even for small contact angles, and that the droplets evaporate as spheres of the same volume.

In Vitro Colonic Fermentation Profiles and Microbial Responses of Cellulose Derivatives with Different Colloidal States.

Although cellulose derivatives are widely applied in the food industry, the effects of their structural properties on colonic health is unknown. Here, four types of cellulose derivatives, including microcrystalline cellulose (MCC), TEMPO-oxidized nanofibrillated cellulose (TOCNF), TEMPO-oxidized nanocrystalline cellulose (TOCNC), and carboxymethyl cellulose (CMC) were selected to investigate their in vitro fermentation profiles. TOCNF exhibited the highest production of total short-chain fatty acids (SCFAs), followed by TOCNC. The results suggested that reduced particle size and increased aspect ratio improved the fermentability of insoluble cellulose derivatives. MCC and CMC were barely fermented with similar total SCFAs production as the blank. 16S rRNA sequencing revealed that the fermentation of cellulose derivatives resulted in divergent microbial community structures. Moreover, Bacteroides cellulosilyticus showed high specificity to utilize TOCNF and TOCNC. The findings demonstrated that the colloidal states of cellulose derivatives, such as size and solubility, were important factors governing microbial community composition and metabolites.