Effect Of Curvature Research Articles

Bracing requirements and design for a single column considering semi-rigid connections and initial curvature

The use of bracing has been widely recognized as an effective technique to increase the strength of columns by reducing their effective length. This paper presents an assessment of the bracing requirements for a semi-rigidly connected column, which is laterally braced at the mid-height. By utilizing the proposed half-length column model, the effects of column stiffness and initial curvature on the brace strength and stiffness requirements are investigated. The results indicate that the column’s initial curvature coefficient increases with a higher applied load, but decreases with increased column end connection stiffness. The required brace stiffness requirement stipulated in AISC 360-22 should be increased when considering the effect of column’s initial curvature. Following the design concepts of AISC 360-22 and CSA S16-19, equations for assessing the bracing requirements for a semi-rigidly connected column are proposed. These equations are validated against the finite element analysis results, demonstrating their ability to accurately assess the bracing requirements for semi-rigidly connected columns. These equations can be adopted in current engineering practice.

Surface curvature modulation of the boron nitride nanocage to boost formaldehyde adsorption and catalytic oxidation

Development of efficient catalysts for formaldehyde (HCHO) oxidation is of importance in indoor air pollution treatment. However, the robust design criteria remain greatly challenging because of the poor recognization of structure-function relationships. Herein, by means of density functional theory (DFT) calculations, we proposed a surface modulation strategy to optimize the surface polar bonding state of BN, proving a curvature tuned B–N–B active sites and its relationship with catalytic activity. The results indicated that HCHO can be efficiently adsorbed by the curved BN nanocage with exceptional chemisorption efficiency (up to 97 %) and even under high coverage (two molecules, 86 %). Moreover, the distortion of BN nanocage facilitates the electron transfer from electron-rich O atom of HCHO to B 2p orbital, and then transfer to O2 via the B–N polar bond, leading to the implementation of HCHO chemisorption and O2 activation. Thus, a multi-channel for interactive electron transfer was spatially built for the HCHO oxidation on BN nanocage. Finally, a novel BN nanocage initiated advanced HCHO oxidation mechanism, combining the curvature and polarity catalytic effects, is systematically investigated based on reaction-kinetic studies. These findings shed new light on the rational design of HCHO oxidation catalysts and broadened the applications of BN-based materials.

Three-dimensional non-Abelian Bloch oscillations and higher-order topological states

Recently, higher-order topological insulators (HOTIs) have been introduced, and were shown to host topological corner states under the theoretical framework of Benalcazar-Bernevig-Hughes. Here we unveil some topological effects in HOTIs by studying the three-dimensional (3D) non-Abelian Bloch oscillations (BOs). In HOTIs, BOs with a multiplied period occur when a force with a special direction is applied due to the effect of the non-Abelian Berry curvature. Along the direction of the oscillations we find a higher-order topological state that goes beyond the theoretical framework of multipole moments. The emergence of such a higher-order topological state coincides with the appearance of the 3D non-Abelian BOs. That is, the 3D non-Abelian BOs can be used as a tool to probe higher-order topological states. These phenomena are observed experimentally with designed electric circuit networks. Our work opens up a way to detect topological phases theoretically and experimentally.

Cryo-TEM Reveals the Influence of Multivalent Charge and PEGylation on Shape Transitions in Fluid Lipid Assemblies: From Vesicles to Discs, Rods, and Spheres.

Lipids, and cationic lipids in particular are of interest as delivery vectors for hydrophobic drugs such as the cancer therapeutic paclitaxel, and the structures of lipid assemblies affect their efficacy. We investigated the effect of incorporating the multivalent cationic lipid MVL5 (+5e) and poly(ethylene glycol)-lipids (PEG-lipids), alone and in combination, on the structure of fluid-phase lipid assemblies of the charge-neutral lipid 1,2-dioleoyl-sn-glycero-phosphocholine (DOPC). This allowed us to elucidate lipid-assembly structure correlations in sonicated formulations with high charge density, which are not accessible with univalent lipids such as the well-studied DOTAP (+1e). Cryogenic transmission electron microscopy (cryo-TEM) allowed us to determine the structure of the lipid assemblies, revealing diverse combinations of vesicles and disc-shaped, worm-like, and spherical micelles. Remarkably, MVL5 forms an essentially pure phase of disc micelles at 50 mol % MVL5. At a higher (75 mol %) content of MVL5, short- and intermediate-length worm-like micellar rods were observed, and in ternary mixtures with PEG-lipid, longer and highly flexible worm-like micelles formed. Independent of their length, the worm-like micelles coexisted with spherical micelles. In stark contrast, DOTAP forms mixtures of vesicles, disc micelles, and spherical micelles at all studied compositions, even when combined with PEG-lipids. The observed similarities and differences in the effects of charge (multivalent versus univalent) and high curvature (multivalent charge versus PEG-lipid) on the assembly structure provide insights into parameters that control the size of fluid lipid nanodiscs, relevant for future applications.

Contact Time of Droplet Impact on Superhydrophobic Cylindrical Surfaces with a Ridge.

This study investigates whether adding ridges to a superhydrophobic cylindrical surface can reduce contact times compared to those of ridged flat or cylindrical surfaces, inspired by the shortened contact time achieved by adding ridges to flat surfaces. The study focuses on studying azimuthal ridges on the cylinder through experimentation, emphasizing the impact dynamics and contact time characteristics under varying We (Weber number) and D* (dimensionless droplet diameter). Within the ultralow Weber number range (ULWR), low Weber number range (LWR), and medium Weber number range (MWR), the contact time is longer than on ridged flat surfaces. In the high Weber number range (HWR), the opposite is observed: increased inertial forces lead to the rupture of the liquid film above the ridges due to Rayleigh-Plateau instability. As a result, the primary droplet splits into two sections with curvature effects promoting its recoiling and rebounding. This study introduces a criterion, defined as C = We/D*, and finds that when C exceeds 2.42, not only is the contact time shorter than on ridged flat or cylindrical surfaces, but it also further decreases with an increase in We or a decrease in D*. The contact time characteristics observed in the HWR offer potential applications in areas such as anti-icing.

A unified thermal-field emission theory for metallic nanotips

The role of curvature effects, in the thermal-field (TF) emission of electrons from nanotips, has been investigated. It is found that for field emitter tips having tip radius of curvature Ra<50 nm, the error on using the planar tunneling potential to evaluate the current density is significant compared to the curvature-corrected potential. Furthermore, the error is found to be strongly temperature dependent at low apex fields, whereas at high fields, it is only moderate. For emitter tips having tip radius Ra≥5 nm, a unified expression for current density applicable for field, thermal-field, and thermionic emission is obtained. In the analysis, a single linearization point corresponding to the peak of the normal energy distribution of electrons is chosen, about which the Gamow exponent is expanded. The temperature-dependent curvature-corrected current density equation is numerically validated against a benchmark that performs the current density integral with the Kemble form of the Wentzel–Kramers–Brillouin transmission coefficient up to the peak of the tunneling potential, while above the barrier, the Morse transmission coefficient is used. The agreement is found to be good. It is inferred that the curvature plays a significant role in field and thermal-field emission, whereas in thermionic emission, it is not as important. In the limit where the apex radius of curvature Ra→∞, it is able to retrieve the Murphy–Good equation as well as the Richardson–Laue–Dushman equation in their respective limits.

Curvature-enhanced membrane asymmetry slows down protein diffusion

Diffusion of transmembrane proteins plays a vital role in various cellular processes, such as endocytosis, raft formation and signal transduction. Current understanding of protein diffusion dynamics in lipid membranes is mostly based on hydrodynamic analyses, in which lipid membrane is simply treated as a thin layer of viscous liquid, same for highly curved ones. Therefore, how the mechanical state of highly curved membranes may affect the transmembrane protein diffusion remains unclear. In this study, we employed molecular dynamics (MD) simulations to analyse membrane curvature effect on the diffusion of cylindrically shaped Aquaporin-0 (AQP0) protein. Slowing down of protein diffusion with the increase in membrane curvature was observed. The possible contributions from membrane tension and asymmetric pressure profile were systematically investigated by simulating the protein diffusion dynamics in planar membranes with various tension levels or with various lipid number ratios between the two leaflets, respectively. We found no significant effect of membrane tension on AQP0 diffusion. Instead, the asymmetric pressure profile present in highly curved bilayer membranes was identified as a key factor that contributes to the slowing down of transmembrane protein diffusion. Our work thus contributes to a more complete picture of transmembrane protein diffusion on highly curved biological membranes.

Oblique water entry of a curved foil with varying speed

The hydrodynamic problem of a curved foil entering into water obliquely with varying speed is investigated through the boundary element method in time domain, and fully nonlinear boundary conditions on the deforming free surface are adopted. The process of foil entry begins with a single point at the lower edge; posing numerical challenges due to the extremely small wetted area, we utilize the stretched co-ordinate system method to address this. An auxiliary method is adopted to solve for pressure distribution. The whole process of the attached flow forming along the curved body and then detaching from the top edge is considered. We engage in extensive discussions on the effects of curvature, gravity, and acceleration, exploring their physical significance and potential applications, particularly within the context of surface-piercing propellers.

Efficient two-dimensional simulation of primary reference fuel ignition under engine-relevant thermal stratification

Despite vast research on engine knock, there remains a limited understanding of the interaction between reaction front propagation, pressure oscillations, and fuel chemistry. To explore this through computational fluid dynamics, the adoption of advanced numerical methods is necessary. In this context, the current study introduces ARCFoam, a computational framework that combines dynamic mesh balancing, chemistry balancing, and adaptive mesh refinement with an explicit, density-based solver designed for simulating high-speed flows in OpenFOAM. First, the validity and performance of the solver are assessed by simulating directly initiated detonation in a hydrogen/air mixture. Second, the study explores the one/two-dimensional (1D/2D) hotspot ignition for the primary reference fuel and illuminates the impact of transitioning to 2D simulations on the predicted combustion modes. The 2D hotspot simulations reveal a variety of 2D physical phenomena, including the appearance of converging shock/detonation fronts as a result of negative temperature coefficient (NTC) behavior and shock wave reflection-induced detonation. The main results of the paper are as follows: (1) NTC chemistry is capable of drastically changing the anticipated reaction front propagation mode by manipulating the local/global reactivity distribution inside and outside the hotspot, (2) subsonic hotspot ignition can induce detonation (superknock) through the generation of shock waves and subsequent wall reflections, and (3) while the 1D framework predicts the initial combustion mode within the hotspot, significant differences between 1D and 2D results may emerge in scenarios involving ignition-to-detonation transitions and curvature effect on shock/detonation front propagation.

Synergy of defect engineering and curvature effect for porous graphite carbon nitride nanotubes promoted photocatalytic hydrogen evolution

AbstractGraphite carbon nitride (g‐C3N4) nanotubes have received extensive attention due to its unique morphology and electronic migration. Herein, the defective porous g‐C3N4 nanotube (DTCN) is prepared through a simple thermal reduction process. The construction of N vacancy and tubular structure can synergistically promote the separation of photogenerated charge carriers. As a result, DTCN demonstrates a higher photocatalytic hydrogen evolution rate (1440 μmol·g−1·h−1), which is 5 times higher than that of the initial g‐C3N4 nanotube (TCN). Importantly, combined with density functional theory calculations and experimental results, it is the first time to prove that the synergy of curvature effect and N vacancy of nanotubes can enhance the adsorption energy of hydrogen and decrease the work function, resulting in more superior photocatalytic performance than the layered structure. This work provides more in‐depth comprehension for the photocatalytic mechanism of nanotube materials, which has inspirational significance for the design of the g‐C3N4 photocatalyst with high performance.

Efficacy of corneal curvature on the accuracy of 8 intraocular lens power calculation formulas in 302 highly myopic eyes.

To investigate the effect of corneal curvature (K) on the accuracy of 8 intraocular lens formulas in highly myopic eyes. Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China. Retrospective consecutive case series. 302 eyes (302 patients) were analyzed in subgroups based on the K value. The mean refractive error, mean absolute error (MAE), median absolute error (MedAE), root-mean-square absolute prediction error (RMSAE) and proportions of eyes within ±0.25 diopter (D), ±0.50 D, ±0.75 D, ±1.00 D were statistical analyzed. Emmetropia Verifying Optical (EVO) 2.0, Kane, and Radial Basis Function (RBF) 3.0 had the lower MAE (≤0.28) and RMSAE (≤0.348) and highest percentage of eyes within ±0.50 D (≥83.58%) in the flat (K ≤ 43 D) and steep K (K > 45 D) groups. Hoffer QST had the lowest MedAE (0.19), RMSAE (0.351) and the highest percentage of eyes within ±0.50 D (82.98%) in the normal K group (43 < K ≤ 45 D). When axial length (AL) ≤28 mm, all formulas showed close RMSAE values (0.322 to 0.373) in flat K group. When AL >28 mm, RBF 3.0 achieved the lowest MAE (≤0.24), MedAE (≤0.17) and RMSAE (≤0.337) across all subgroups. EVO 2.0, Kane, and RBF 3.0 were the most accurate in highly myopic eyes with a flat or steep K. Hoffer QST is recommended for long eyes with normal K values. RBF 3.0 showed the highest accuracy when AL >28 mm, independent of corneal curvature.

Two-dimensional unconfined seepage flow toward a highway cut slope

The unconfined gravity-flow system near a free-outflow boundary such as a highway cut slope was investigated by using a higher-order numerical model. Unlike the Dupuit–Forchheimer equation, which is applicable mainly to a hydraulic flow problem, the proposed model accounts for the effects of the vertical component of the flow for a full treatment of the problem of plane phreatic flow. The model equations were numerically solved by means of a finite-difference scheme. Their accuracy was then verified using the solutions of the full two-dimensional potential-flow method and rigorous mathematical approaches, revealing that for a face slope flatter than 70º, the differences between the solutions of the model and the earlier approaches for the relative seepage-face height were nearly negligible. The comparison results also demonstrated the substantial effects of the slope of the downstream face on this height and the seepage discharge. Furthermore, the accuracies of the model predictions for the phreatic-surface profile and the distributions of the piezometric head at different vertical sections are much better than the earlier method, which approximates the trapezoidal-shaped aquifer by its equivalent rectangular one. Such a satisfactory performance may be attributed to the model’s higher-order correction factor for the effects of the phreatic-surface curvature and steep slope.

The effects of imposed swirling flow on the transport and deposition of particulate pollutants in the 90° industrial duct bends: An Eulerian-Lagrangian approach

Duct bend is one of the important parts of ventilation and dust removal systems, and particles deposited in curved ducts can reduce system efficiency or cause erosion on the bend wall. To investigate whether particle deposition is affected by imposed swirl on fluid flow, this article combines the RSM turbulence model and the Discrete Phase Model (DPM) to predict the deposition efficiency of particles in the bend under high Reynolds number conditions. The results show that the imposed swirl flow modifies the secondary flow initially dominated by the pressure gradient caused by the curvature effect. With the gradual increase of the swirl number ( S n), the deposition efficiency of the particles gradually decreased. However, when the swirl number is low ( S n ≤ 0.17), particles with smaller Stokes numbers are more susceptible to the intensity of turbulence. The higher the turbulence intensity near the wall, the easier it is for low inertia particles ( St ≤ 0.456) to deposit. The higher swirl intensity dominates the centrifugal force, reduces the turbulent intensity in the central region of the duct, improves the stability of the airflow and makes it easier for particles with larger inertia ( St ≥ 0.811) to pass through the bend.

Non-Abelian magnetic field and curvature effects on pair production

Non-Abelian magnetic field and curvature effects on pair production

The curvature effect: Approach-avoidance tendencies in response to interior design stimuli

Previous research suggests that curved vs. angular interior environments trigger affective (e.g., preference) and behavioural (e.g., approach-avoidance) responses. Yet, behavioural responses have mainly been assessed through explicit evaluations, such as self-reports. We aimed to investigate this phenomenon more ‘implicitly’ using a battery of reaction time (RT) paradigms, particularly focusing on approach-avoidance tendencies.Online participants (initial N = 219) undertook four randomized tasks involving 20 photo-realistic living room images matched for contours (angular vs. curved) and styles (modern vs. classic). We intended to capture attentional (Dot Probe Task [DPT]), motoric (Approach Avoidance Task [AAT]), as well as associative-semantic (Implicit Association Task [IAT]) and -motoric (Stimulus Response Compatibility Task [SRCT]) biases towards contours.The DPT and AAT showed no significant effects. However, we observed a significant congruency effect in the IAT (F(1,192) = 97.51, p < .001, ƞ2 = 0.074), whereby images were assigned faster into categories when those were curved-approach and angular-avoid (instead of curved-avoid, angular-approach). Additionally, we found a significant direction x contour interaction (F(1,179) = 7.08, p = .009, ƞ2 = 0.004) in the SRCT, attributable to within-curvature differences (faster approach compared to avoidance). Moreover, within-directions comparisons revealed a faster avoidance of angular than curved conditions.Our findings confirmed an effect of contours on approach-avoidance tendencies using RT paradigms. We identified semantic associations between curvature and approach and angularity and avoidance behaviour. Furthermore, we demonstrated differential approach (faster) – avoidance (slower) representations in relation to curvature rather than an avoidance of angularity. These findings may hint towards (partially) automatic responses to contours in interior design, which in addition to self-reports, should be further researched concerning criterion validity, such as in correlation with physiological and psychological reactions to built spaces.

Refocusing of the optical branched flow on a rough curved surface

The phenomenon of branched flow has attracted researchers since its inception, with recent observations of the light branching on soap bubbles. However, previous studies have primarily focused on the flat spacetime, overlooking the effect of surface curvature on branched flows. In this paper, we explore the branched flow phenomenon of light on a rough curved surface called constant Gaussian curvature surfaces (CGCSs). Compared with flat space, a CGCS demonstrates that the first branching point advances due to the focusing effect of the positive curvature of the surface. Furthermore, unlike on flat space, optical branches on curved surfaces do not consistently become chaotic during its transmission in a random potential field. On the contrary, the “entropy” decreases at specific positions, which reveals a sink flow phenomenon following the generation of branched flows. This result highlights the time inversion characteristics of CGCSs. Lastly, we demonstrated that the anomalous entropy reduction is related to the transverse and longitudinal coherence transformations of light. We suppose these efforts would fuel further investigation of the thermodynamic evolution and spatiotemporal inversion of random caustics, as well as their future application in the information transmission of random potentials in curved spacetime.

CFD analysis of curvature and inclination effect on steam condensation in the presence of air

Steam-air condensation is one of the critical thermal–hydraulic phenomena in containment under accident conditions. Currently, sufficient experimental research and numerical analysis have been conducted on steam–air condensation outside the tube/plate. However, few studies have investigated the influence of curvature and inclination on condensation characteristics, and the local phenomena and mechanisms that affect the condensation process have not yet been fully revealed. In addition, it is of vital importance to evaluate the coupling effect between curvature and inclination in practical applications. To investigate the above-mentioned effects, numerical simulations were conducted over a wide parameter range (P = 0.2 ∼ 1.6 MPa, ωa = 0.1 ∼ 0.9, ΔT = 20 ∼ 100 K), and the related mechanisms were analyzed in detail. The results showed that there is a strong coupling relationship between curvature effect and inclination effect and the inflection point in the influence of inclination effect on steam condensation characteristics is discovered. Compared to the traditional conclusion that condensation capability gradually increases with the decrease of inclination angle. The effect of inclination on the condensation characteristics can reverse in different curvature regions. When the curvature is greater than 5 m−1, the inclination angle is negatively correlated with the condensation capability. When the curvature is less than 5 m−1, the inclination angle is positively correlated with the condensation capability. Furthermore, the enhancement effect originate from the curvature effect will greatly decrease as the inclination angle increases.

Effects of inflection curvature on flow interference at furcating fracture intersections

Effects of inflection curvature on flow interference at furcating fracture intersections

Modulating Polymer Ultrathin Film Crystalline Fraction and Orientation with Nanoscale Curvature.

We investigated the effect of nanoscale curvature on the structure of thermally equilibrated poly-3-hexylthiophene (P3HT) ultrathin films. The curvature-induced effects were investigated with synchrotron grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Our results demonstrate that nanoscale curvature reduces the polymer crystalline fraction and the crystal length. The first effect is strongest for the lowest curvature and results in a decrease in the out-of-plane thickness of the polymer crystals. On the other hand, the crystal in-plane length decreases with the increase in substrate curvature. Finally, the semi-quantitative analysis of crystal anisotropy shows a marked dependence on the substrate curvature characterized by a minimum at curvatures between 0.00851 nm-1 and 0.0140 nm-1. The results are discussed in terms of a curvature-dependent polymer fraction, which fills the interstices between neighboring particles and cannot crystallize due to extreme space confinement. This fraction, whose thickness is highest at the lowest curvatures, inhibits the crystal nucleation and the out-of-plane crystal growth. Moreover, because of the adhesion to the curved portion of the substrates, crystals adopt a random orientation. By increasing the substrate curvature, the amorphous fraction is reduced, leading to polymer films with higher crystallinity. Finally, when the thickness of the film exceeds the particle diameter, the curvature no longer affects the crystal orientation, which, similarly to the flat case, is predominantly edge on.

Covariant description of the colloidal dynamics on curved manifolds

Brownian motion is a universal characteristic of colloidal particles embedded in a host medium, and it is the fingerprint of molecular transport or diffusion, a generic feature of relevance not only in physics but also in several branches of science and engineering. Since its discovery, Brownian motion, also known as colloidal dynamics, has been important in elucidating the connection between the molecular details of the diffusing macromolecule and the macroscopic information on the host medium. However, colloidal dynamics is far from being completely understood. For instance, the diffusion of non-spherical colloids and the effects of the underlying geometry of the host medium on the dynamics of either passive or active particles are a few representative cases that are part of the current challenges in soft matter physics. In this contribution, we take a step forward to introduce a covariant description of the colloidal dynamics in curved spaces. Without the loss of generality, we consider the case where hydrodynamic interactions are neglected. This formalism will allow us to understand several phenomena, for instance, the curvature effects on the kinetics during spinodal decomposition and the thermodynamic properties of colloidal dispersion, to mention a few examples. This theoretical framework will also serve as the starting point to highlight the role of geometry on colloidal dynamics, an aspect that is of paramount importance to understanding more complex transport phenomena, such as the diffusive mechanisms of proteins embedded in cell membranes.