Cross-sectional Radius Research Articles

Size-Dependent Wetting Contact Angles at the Nanoscale Defined by Equimolar Surfaces and Surfaces of Tension

The wetting characteristics of fluids play a crucial role in various fields of interface and surface science. Contact angle serves as a fundamental indicator of wetting behavior. However, accurate quantification of wetting phenomena even at the macroscale often poses challenges, particularly due to the hysteresis between receding and advancing contact angles. The complexity increases further at the nanoscale, where the significant volume of the interphase region causes ambiguity in defining the “dividing surface.” In this study, we use molecular dynamics simulations to investigate the wetting dynamics of a “cylindrical nanodroplet” and an argon nanofilm. Through analysis of microscopic density distribution maps and tension tensor distributions within the Gibbs framework, we identified equimolar and tension surfaces at both liquid-gas and liquid-solid interfaces. Our results show over 10% discrepancies between equilibrium contact angles calculated for equimolar surfaces and those based on tension surfaces in the case of the cylindrical nanodroplet. We observed a clear dependence of wetting contact angles on the cross-sectional radius of cylindrical droplets with a straight three-phase contact line. As the radius decreases, the differences between contact angles at equimolar and tension surfaces increase, while for larger droplets, these differences diminish and become negligible.

Longitudinal Fracture Analysis with Taking into Account the Elongation Speed of Inhomogeneous Rod Subjected to Centric Tension

The present theoretical study deals with longitudinal fracture of a structural component representing inhomogeneous rod that is loaded in centric tension at its lower end. The upper end of the rod is clamped. The rod is continuously inhomogeneous in radial direction. Besides, the rod exhibits non-linear elastic mechanical behaviour. The parameters involved in the non-linear constitutive law used when analyzing the longitudinal fracture behaviour are smooth functions of the running radius of the rod cross-section. The basic aim of the paper is to analyze the longitudinal fracture with taking into account the influence of the rod elongation speed. The case when the elongation varies with time at a constant speed is treated in detail. The necessary equations for deriving the parameters of the stressed and strained state of the rod are formulated. The problem for determination of strain energy release rate (SEER) for the longitudinal crack in the rod is solved with considering the effect of the elongation speed.

Modeling the Conditions of Occurrence and State of Radial Cracks in Rock Specimens Under Axial Compression with Lateral Pressure

This paper presents a model for predicting the thickness of the cracked surface layer in rock specimens subjected to axial compression with lateral pressure. The study focuses on radial cracks that are most prominently open on the lateral surface, manifesting as axial (or longitudinal) cracks on this surface. The research employs methods for analyzing mechanical and geotechnical systems. The proposed model determines the conditions under which damage to the surface layer decreases depending on Poisson’s ratio and lateral pressure. Radial cracks typically precede spalling, making it crucial to examine the conditions of their initiation and the potential for influencing their development, and this holds significant importance for mining and underground construction practices. A comparison indicated that the predicted values and those reported in the literature for the thickness of the damaged surface layer in rock pillars are within a similar range, varying from 44% to 70% of the initial cross-sectional radius. Although this study focuses on rock materials, the proposed model also offers potential applications in examining crack formation in cement and geopolymer concretes, serving as artificial analogs of rock, thereby helping to mitigate the risk of structural failure in building systems.

Effect of geometric defects on the mechanical properties of additive manufactured Ti6Al4V lattice structures

Lattice structures realized by additive manufacturing (AM) have the great potential for a broad range of engineering applications. However, the lattice structures are involved in geometric defects. This paper focuses the effect of geometric defects on the mechanical properties of Ti6Al4V lattice structures manufactured by laser powder bed fusion (L-PBF), three cell topologies, i.e., body centered cubic with vertical struts (BCCZ), face centered cubic with vertical struts (FCCZ), and face and body centered cubic with vertical struts (FBCCZ) were studied. X-ray computed tomography was used to extract the shape and the distribution of process-induced geometric defects of these three kinds of samples. Probability density distributions of geometric defects in each layer were also established to analyze the effect of the printing sequence on geometric defects. Then these distributions of geometric defects were inputted into Abaqus to build the modified statistical models to study the effect of geometric defects on mechanical properties. It is shown that the deviation of the cross-section radius exhibits normal distribution and the deviation of the center axis offset exhibits logarithmic distribution. And the middle layer of the sample has a better manufacturing precision. The modified statistical model can predict the mechanical properties within an error of 5 %. The strut thickness deviation had a more significant effect on the mechanical properties than the strut waviness.

Simulation Research on the Control Method of Bow-Collapse in Gear Cold Roll-Beating

Bow-collapse is a type of geometric defect in the gear cold roll-beating process. In order to effectively control bow-collapse and improve material utilization, this paper calculates the cross-section radius of the blank according to the volume invariance principle of metal plastic deformation, and then performs FE simulation of the cold roll-beating process by using the cyclic beating of adjacent tooth spaces and intermittent blank feeding method. The flow state of metal particles is investigated, revealing that the movement of metal particles along the axial direction of the blank is the main reason for the formation of bow-collapse. This paper proposes a method to correct the cross-section radius of the blank and thus control for bow-collapse, where the loss coefficient K characterizes the state of metal particle loss in an infinitesimal thickness region on the cross-section. The analytical equation for calculating the corrected value of the cross-section radius is derived, and the corrected value is calculated. Conducted on the modified blank, cold roll-beating FE simulation results show that bow-collapse is effectively controlled, and the loss coefficient K correctly reflects the loss state of metal particles on the cross-section. The simulation results also show that after cold roll-beating, the gear teeth with standard face width and tooth depth can be obtained after two turning end faces and turning tip circle processes. The bow-collapse control method proposed in this paper effectively improves material utilization.

Dependence of coronal mass ejections on the morphology and toroidal flux of their source magnetic flux ropes

Context. Coronal mass ejections (CMEs) stand as intense eruptions of magnetized plasma from the Sun, and they play a pivotal role in driving significant changes of the heliospheric environment. Deducing the properties of CMEs from their progenitors in solar source regions is crucial for space weather forecasting. Aims. The primary objective of this paper is to establish a connection between CMEs and their progenitors in solar source regions, enabling us to infer the magnetic structures of CMEs before their full development. Methods. We created a dataset comprising a magnetic flux rope series with varying projection shapes (S-, Z-, and toroid-shaped), sizes, and toroidal fluxes using the Regularized Biot-Savart Laws (RBSL). These flux ropes were inserted into solar quiet regions with the aim of imitating the eruptions of quiescent filaments. Thereafter, we simulated the propagation of these flux ropes from the solar surface to a distance of 25 R⊙ with our global coronal magnetohydrodynamic (MHD) model COCONUT. Results. Our parametric survey revealed significant impacts of source flux ropes on the consequent CMEs. Regarding the flux-rope morphology, we find that the projection shape (e.g., sigmoid or torus) can influence the magnetic structures of CMEs at 20 R⊙, albeit with minimal impacts on the propagation speed. However, these impacts diminish as source flux ropes become fat. In terms of toroidal flux, our simulation results demonstrate a pronounced correlation with the propagation speed of CMEs as well as the successfulness in erupting. Conclusions. This work builds the bridge between the CMEs in the outer corona and their progenitors in solar source regions. Our parametric survey suggests that the projection shape, cross-section radius, and toroidal flux of source flux ropes are crucial parameters in predicting magnetic structures and the propagation speed of CMEs, providing valuable insights for space weather prediction. On the one hand, the conclusion drawn here could be instructive in identifying the high-risk eruptions with the potential to induce stronger geomagnetic effects (Bz and propagation speed). On the other hand, our findings hold practical significance for refining the parameter settings of launched CMEs at 21.5 R⊙ in heliospheric simulations, such as with EUHFORIA, based on observations for their progenitors in solar source regions.

Real-Time Estimation of Human Arm Dynamic Parameters Based on Optical

Abstract A flexible optical intensity sensor is designed in this study to address the poor adaptability of fixed-value parameters in exoskeleton research, which makes it difficult to handle system changes and uncertainties. The light transmission portion of the sensor is made of TPU and PET, exhibiting flexibility and bendable deformation characteristics, as well as good sensitivity, anti-interference capability, and stability. The flexible optical sensor is fixed on the side of the binding device, which is installed on the biceps brachii to collect the optical intensity loss signals after sensor bending. By utilizing this method, parameters such as the cross-sectional radius, arm centroid, and moment of inertia can be estimated in real-time. Finally, the estimated radius values are compared with theoretical values, and the accuracy is verified by combining the kinematic model. Experimental results demonstrate that the proposed method achieves a parameter information error of less than 8.63% and a stability better than 4.3%. Compared to the traditional fixed parameter method, the stability has improved by 25.06%, and the accuracy has improved by 9.04%.

Proposal for variability-induced effective radius of elliptical gate-all-around junctionless transistors and its applicability in hydrogen gas sensors

Nano-ribbons with gate-all-around (GAA) architecture have been predicted to serve as next-generation on-chip transistors, among which, the junctionless transistor (JLT) has emerged as a promising candidate, mitigating few limitations of conventional inversion-mode metal–oxide–semiconductor field-effect transistors (MOSFETs). Due to imperfect fabrication process, the GAA architecture is often subject to cross-sectional variabilities. This work presents an analytical model for the effective radius of elliptical cross-section of the channel region having a non-circular oxide surrounding it, resulting in various structural configurations having non-uniform oxide thickness. To demonstrate the impact of cross-sectional variability of GAA-JLTs, few performance parameters, such as, drain current, threshold voltage, and so on, have been evaluated using our proposed formulation for the effective radius and the results were found to agree well with TCAD simulations. As a case study, we have emphasized on the applicability of our proposed model in variability-induced GAA-JLT-based hydrogen sensors using few sensitivity metrics. Our computations show substantial changes in the sensing device as the cross-section deviates from the ideal circular one. Our computations reveal that incorporating the effects of radius variability in the device model along with proper tuning of operating conditions can enhance the performance and accuracy of such sensors.

Slender phoretic loops and knots

We present an asymptotic theory for solving the dynamics of slender autophoretic loops and knots. Our formulation is valid for nonintersecting three-dimensional center lines, with arbitrary chemical patterning and varying (circular) cross-sectional radius, allowing a broad class of slender active loops and knots to be studied. The theory is amenable to closed-form solutions in simpler cases, allowing us to analytically derive the swimming speed of chemically patterned tori, and the pumping strength (stresslet) of a uniformly active slender torus. Using simple numerical solutions of our asymptotic equations, we then elucidate the behavior of many exotic active particle geometries, such as a bumpy uniformly active torus that spins and a Janus trefoil knot, which rotates as it swims forwards. Published by the American Physical Society 2024

Lift modeling, load and vibration analysis of Magnus rotors

The method of theoretical combined with numerical simulation is employed to study the lift model and the optimal position of viscoelastic supports for the rotating cylindrical sail (short for Magnus rotor or rotor sail). Initially, using a numerical simulation method to modify the Magnus rotor lift model established based on the Kutta-Joukowski theory obtained a lift/drag model for the rotor. Subsequently, the lift/drag model is utilized as an external load, considering the rotor as a rotating cantilever beam with fixed support at one end. The finite element method is employed to study the vibration characteristics of the drive shaft under external excitation, analyzing the deflection characteristics of the cantilever beam, the stiffness of elastic support, and the span variation on the vibration characteristics of the drive shaft for different cross-sectional radii. Finally, for the investigated large-scale Magnus rotor, a modified lift model and the optimal design position for viscoelastic supports and the dimensions of the drive shaft are provided. Simulation results demonstrate that by appropriately adding viscoelastic supports to the structure, the vibrational deflection of the drive shaft's steady-state response can be significantly suppressed.

Deformation and breakup of a ferrofluid droplet in shear flow under magnetic field

Effects of magnetic field applied perpendicular to a shear plane in shear flow on the deformation of a ferrofluid droplet are numerically investigated. The boundary integral method is employed to solve the two-phase Stokes flow under a uniform magnetic field. When the magnetic field is applied perpendicular to the shear plane, the deformation of the droplet in the shear plane decreases. The magnetic field causes the droplet to elongate in the y-direction, and its cross-sectional radius in shear plane decreases. Consequently, the apparent capillary number in the shear plane decreases, thereby suppressing the droplet deformation. Droplet breakup is also suppressed by imposing a magnetic field perpendicular to the shear plane, thereby increasing the critical capillary numbers. The critical capillary numbers for the magnetic Bond numbers Bo = 2.0 and 4.0 increase to approximately 110% and 130%, respectively, than those without magnetic field. Furthermore, an equation for the theoretical prediction of the droplet deformation under a magnetic field in shear flow is presented, which is based on the small deformation theory, the decrease in the cross-sectional radius, and the boundary conditions at the droplet interface. The theoretical prediction agrees well with the numerical results for the variation in the magnetic susceptibility of the droplet as well as the viscosity ratio between the external fluid and the ferrofluid droplet under a small deformation. The critical capillary numbers under a magnetic field can also be predicted by using the numerical results without a magnetic field.

Non-reflective Propagation of Kink Waves in Magnetic-Flux Tubes in the Solar Atmosphere

We study the non-reflective propagation of kink waves in inhomogeneous magnetic-flux tubes. We use the thin-tube and zero-beta plasma approximations. The wave equation with the variable velocity is reduced to the Euler–Poisson–Darboux equation. This equation contains one dimensionless parameter. There are two infinite sequences of this parameter, one monotonically increasing and the other monotonically decreasing, when exact analytical solutions for the Euler–Poisson–Darboux equation can be obtained. For the monotonically increasing sequences the Euler–Poisson–Darboux equation becomes the equation describing spherically symmetric waves in multi-dimensional spaces. The general results are applied to kink-wave propagation in coronal magnetic loops. We consider a coronal magnetic loop of a half-circular shape. We find that for a fixed loop height there is a one-parametric family of dependences of the loop cross-sectional radius on the coordinate along the loop corresponding to the non-reflective kink-wave propagation.

Effects of Geometry Design Parameters on the Fatigue Failure of a Drive Axle Housing using Finite Element Analysis

The current paper investigates the effects of geometric design parameters on the fatigue failure of the drive axle housing using the Finite Element Method (FEM). The study examines the effects of various factors on the fatigue life of the drive axle housing, such as axle housing wall thickness, housing cross-sectional rounding radius, and rounding radius of the central part of the housing. Based on the known material properties and dynamic loads, a CAD/FEM model of the drive axle housing was developed, and a structural analysis was carried out. Based on the results of the structural analysis, critical places on the housing were determined, and fatigue analysis and lifetime prediction were performed. Through a series of simulations, the study reveals that increasing housing wall thickness can significantly improve fatigue performance. Similarly, increasing the rounding radius at the housing cross-section, as well as the rounding radius at the central part of the housing can also lead to improved fatigue performance. However, the effect of increasing the value of these two radii is not as significant as the effect of the wall thickness. These findings give useful information regarding the design and manufacture of drive axle housings for vehicles, intending to reduce the likelihood of fatigue failure.

Experimental Investigation of Water Infiltration Law in Loess with Black Locust (Robinia pseudoacacia) Roots

Physical model experiments are increasingly applied in the study of the water infiltration law in loess with roots. In the past, due to differences in study objects and the limitations of measuring techniques, the infiltration law in loess with roots is rarely evaluated by using appropriate indoor physical model experimental data. In order to investigate the law of water infiltration in loess with roots, we designed a new soil column experimental device that can automatically collect data and images. By comparing the soil column experiment data of loess, we analyzed variables in root contents (the ratio of root mass to dry soil mass) and root types. Roots with diameters of 0–2 mm, 2–5 mm, and 5–10 mm are defined as type I, type II, and type III, respectively. It was found that the water infiltration rate, water-holding capacity, and saturated permeability coefficient increase with the increase in root content. In loess containing different root types, the root types were found to improve the rate of water infiltration, water-holding capacity, and saturated permeability coefficient in the soil. The root types were ranked in descending order in terms of their impact: root type II had the highest improvement, followed by root type III, and then root type I. The phenomenon of circumferential flow existed when water infiltrated loess with roots. Root content and root type would affect the radius of circumferential flow, infiltration path, and cross-section. When calculating the saturated permeability coefficient of loess with roots, ignoring the effect of circumferential flow would lead to a higher result.

Fucoidan from brown seaweed Tubinaria decurrens: Structure and structure - anticancer activity relationship

The aims of this study are to determine the structure of a fucoidan from brown seaweed Turbinaria decurrens, to investigate its anticancer activity and structure–activity relationship. SEC-MALLS, IR, ESI-MS and NMR spectra analysis indicated that dominant structure of the fucoidan, with a Mw 122.6 KDa, has a backbone of (1 → 3)– and (1 → 4)–α–L–Fucp residues, branched at C–4, sulfate groups are attached at C–2, C–3 and C–4; branches are (1 → 4)–β–D–Galp residues and sulfated at C–2. The fucoidan was hydrolyzed by HCl aqueous solution to obtain hydrolyzed fucoidans. It is assumed that native and hydrolyzed fucoidans have a rod-like conformation in solution with cross–sectional radius of gyration (Rgc) ranged from 0.53 to 1.52 nm as estimated from SAXS measurements. The fucoidans show great anticancer activity against HT29 human colon cancer cell line with IC50 ranging from 5.41 ± 0.36 to 73.52 ± 2.54 μg/mL. Anticancer activity of the fucoidan could be significantly improved by lowering molecular weight, furthermore, fucoidan required small molecular weight, small molecular weight distribution and rod–like structure with a short branch length for high anticancer activity.

Investigating the binding and mechanical properties of carbon nanotube-encapsulated Si nanowires: A perspective from atomic simulations

Atomic simulations using classical mechanics formalism are used to investigate the interfacial binding between CNTs and silicon nanowires as well as mechanical properties of the CNTs encapsulated silicon nanowires systems. The simulations provide the effect of temperature, systems' cross-sectional radius, interfacial distance, applied tension on their binding degree and deformation behaviors. The simulation results reveal that the spacing and interfaces between CNT and nanowire significantly affect thermal stability and the degree of interfacial binding in the systems. The Lode-Nadai values' distributions in the systems provide insight into the loading states on the atoms both in CNTs and silicon nanowires during tension. The atomic hydrostatic pressures can be used to identify stress-transfer paths in the systems during the elasticity, plasticity, and fracture stages.

Microbiota response of pectin determined by its structural characteristics during in vitro fecal fermentation: A comparative study of various pectin sources

To identify the key structural properties of pectic polysaccharides that affect their gut fermentation behavior, structural characteristics and fecal fermentation ability of acid-extractable pectins obtained from 8 kinds of fruit and vegetable were compared. Results showed that the peach pectin presented a single molecular weight (Mw) distribution with large Mw (706.3 kDa), and the broccoli pectin owned high contents of arabinose (99.62 mg/g) and galactose (129.11 mg/g). Fermentation with these two pectins for 24 h improved the relative abundance of Bifidobacterium (13.42 % and 13.04 %, respectively), which had positive relation (p < 0.001) with Mw, arabinose and galactose. Hawthorn pectin was featured with low Mw, which also exhibited high linearity (6.96), supporting the relative abundance of Bacteroides (40.04 %) after fermentation. It had positive relation (p < 0.05) with linearity, acetate and butyrate. Tomato pectin was characterized by tri-Mw distribution with small polydispersity index (1.231, 1.120 and 1.106, respectively). Moreover, it displayed a compact and curved conformation in terms of smaller radius of gyration (Rg, 7.88 nm) and larger cross-sectional radius (Rc, 5.28 nm). Tomato pectin generated the highest content of short-chain fatty acids (61.59 mmol/L) among all the pectins after fermentation. Meanwhile, Ruminococcus was detected as key genera in the tomato pectin substrate, which was positively correlated (p < 0.05) with acetate, propionate, Rg and Rc. The correlation analysis further confirmed that Rg and arabinose content of the pectin have the greatest impact on the microbiota modification, followed by Rc and polydispersity index, promoting a deep understanding of the relationship between pectin structure and gut fermentation.

The Physics and Manipulation of Dean Vortices in Single- and Two-Phase Flow in Curved Microchannels: A Review.

Microchannels with curved geometries have been employed for many applications in microfluidic devices in the past decades. The Dean vortices generated in such geometries have been manipulated using different methods to enhance the performance of devices in applications such as mixing, droplet sorting, and particle/cell separation. Understanding the effect of the manipulation method on the Dean vortices in different geometries can provide crucial information to be employed in designing high-efficiency microfluidic devices. In this review, the physics of Dean vortices and the affecting parameters are summarized. Various Dean number calculation methods are collected and represented to minimize the misinterpretation of published information due to the lack of a unified defining formula for the Dean dimensionless number. Consequently, all Dean number values reported in the references are recalculated to the most common method to facilitate comprehension of the phenomena. Based on the converted information gathered from previous numerical and experimental studies, it is concluded that the length of the channel and the channel pathline, e.g., spiral, serpentine, or helix, also affect the flow state. This review also provides a detailed summery on the effect of other geometric parameters, such as cross-section shape, aspect ratio, and radius of curvature, on the Dean vortices' number and arrangement. Finally, considering the importance of droplet microfluidics, the effect of curved geometry on the shape, trajectory, and internal flow organization of the droplets passing through a curved channel has been reviewed.

An efficient multi-objective optimization framework for thin-walled tubular deployable composite boom

As a crucial structural component in space applications such as solar sails and solar arrays, the thin-walled tubular deployable composite booms (DCBs) demonstrate extensive utilization by employing stored elastic strain energy to achieve folding and deploying functions. This paper introduces a multi-objective optimization framework that integrates an analytical model with a genetic algorithm. By utilizing a multi-objective evolutionary algorithm based on de-composition (MOEA/D), the optimization objectives of minimizing folding moment and maximizing bending stiffness are pursued. Multiple constraints associated with failure avoidance, laminate stacking sequence design principles, and the folding moment range of actuator in the folding mechanism are considered in the optimization. The multi-objective optimization design of the tubular DCBs is performed to obtain the optimal combinations of cross-sectional radius, central angle, and ply scheme. Experimental validation confirms the efficacy of the optimization results. Additionally, an in-depth analysis on the influence of genetic algorithm types, hyperparameters, and different design variables on the optimization outcomes is thoroughly discussed. The findings of this study offer significantly insights for the practical engineering applications of tubular DCBs.

Triboelectric nanogenerator based on a water droplet spring with a concave spherical surface for harvesting wave energy and detecting pressure

Abstract Triboelectric nanogenerator (TENG) has strong application potential in collecting nano energy and detecting micro motion. In this study, a TENG based on a water droplet spring with a concave spherical surface was proposed. The dispersive-aggregative triboelectric nanogenerator (DA-TENG) added the water droplet to the concave spherical surface which was covered with circular copper foil electrode and polytetrafluoroethylene. External loading/unloading caused water droplet dispersion/aggregation. Therefore, the solid and liquid electrodes could generate voltage by contacting and separating. Meanwhile, DA-TENG design parameters were optimized to find optimal output conditions, including the water droplet volume, the cross-sectional radius of the concave spherical surface, the force area of the elastic membrane, and the excitation frequency of the shaker. In addition, the voltage signal generated by volunteers pressing DA-TENG could show the keyboard usage habits of different people and thus serve as a basis for personnel identification, which suggested DA-TENG could be used as a self-powered pressure detector. Finally, DA-TENG was designed as a harvesting wave energy device. Under a 6 MΩ load, a unit of work could produce a peak current of 1.7 μA and an effective power of 8.82 μW; three units could produce a peak current of 5.3 μA.