Submicron drops from flapping bursting bubbles Jiang, Xinghua; Rotily, Lucas; Villermaux, Emmanuel ...
Proceedings of the National Academy of Sciences - PNAS,
01/2022, Letnik:
119, Številka:
1
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Tiny water drops produced from bubble bursting play a critical role in forming clouds, scattering sunlight, and transporting pathogens from water to the air. Bubbles burst by nucleating a hole at ...their cap foot and may produce jets or film drops. The latter originate from the fragmentation of liquid ligaments formed by the centripetal destabilization of the opening hole rim. They constitute a major fraction of the aerosols produced from bubbles with cap radius of curvature (
) > ∼0.4 × capillary length (
). However, our present understanding of the corresponding mechanisms does not explain the production of most submicron film drops, which represent the main number fraction of sea spray aerosols. In this study, we report observations showing that bursting bubbles with
< ∼0.4
are actually mainly responsible for submicron film drop production, through a mechanism involving the flapping shear instability of the cap with the outer environment. With this proposed pathway, the complex relations between bubble size and number of drops produced per bubble can be better explained, providing a fundamental framework for understanding the production flux of aerosols and the transfer of substances mediated by bubble bursting through the air-water interface and the sensitivity of the process to the nature of the environment.
In this work, the study of traversable wormholes in f(R) massive gravity with the function f(R) = R + α1 Rn, where α1 and n are arbitrary constants, is considered. We choose the shape function of the ...form b(r) = rexp(−α(r − r0)) with α and r0 being an arbitrary constant and a radius of the wormhole throat, respectively. Here α affects the radius of curvature of the wormhole. We consider a spherically symmetric and static wormhole metric and derive field equations. Moreover, we visualize the wormhole geometry using embedding diagrams. Furthermore, we check the null, weak, dominant, and strong energy conditions at the wormhole throat with a radius r0 invoking three types of redshift functions, Φ = constant, γ1/r, log (1 + γ2/r) with γ1 and γ2 are arbitrary real constants. We also compute the volume integral quantifier to calculate the amount of the exotic matter near the constructed wormhole throat.
Justification of the parameters of the disc plough Tukhtakuziev, A; Ishmuradov, Sh U; Xudoyberdiyev, M A
IOP Conference Series: Earth and Environmental Science,
10/2021, Letnik:
868, Številka:
1
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Tillage is one of the most energy-intensive processes. Therefore, it is important to develop energy-efficient and resource-efficient, as well as high-performance disc plough. Based on this, a disk ...plough was developed and its parameters were researched. According to results of theoretical research, to ensure quality tillage, disc plow should be equipped with discs with a diameter of 65 cm and a radius of curvature of 70 cm, and they should be installed at least 38 and 17 angles respectively, relative to direction of movement and verticality.
Strain gradient polarization in graphene Kundalwal, S.I.; Meguid, S.A.; Weng, G.J.
Carbon (New York),
June 2017, 2017-06-00, 20170601, Letnik:
117
Journal Article
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Flexoelectricity phenomenon is the response of electric polarization to an applied strain gradient and is developed as a consequence of crystal symmetry in all materials. In this study, we show that ...the presence of strain gradient in non-piezoelectric graphene sheet does not only affect the ionic positions, but also the asymmetric redistribution of the electron density, which induce strong polarization in the graphene sheet. Using quantum mechanics calculations, the resulting axial and normal piezoelectric coefficients of the graphene sheet were determined using two loading conditions: (i) a graphene sheet containing non-centrosymmetric pores subjected to an axial load, and (ii) a pristine graphene sheet subjected to a bending moment. Particular emphases were placed on the role of edge and corner states of pores arising due to the functionalization. We also investigated the electronic structure of graphene sheet under different in-plane strain distributions using quantum mechanics calculations and tight-binding approach. The findings of our work reveal that the respective axial and normal electromechanical couplings in graphene can be engineered by changing the size of non-centrosymmetric pores and radii of curvature. Our fundamental study highlights the possibility of using graphene sheets in nanoelectromechanical systems as sensors or actuators.
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Folding DNA into Twisted and Curved Nanoscale Shapes Dietz, Hendrik; Douglas, Shawn M; Shih, William M
Science (American Association for the Advancement of Science),
08/2009, Letnik:
325, Številka:
5941
Journal Article
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We demonstrate the ability to engineer complex shapes that twist and curve at the nanoscale from DNA. Through programmable self-assembly, strands of DNA are directed to form a custom-shaped bundle of ...tightly cross-linked double helices, arrayed in parallel to their helical axes. Targeted insertions and deletions of base pairs cause the DNA bundles to develop twist of either handedness or to curve. The degree of curvature could be quantitatively controlled, and a radius of curvature as tight as 6 nanometers was achieved. We also combined multiple curved elements to build several different types of intricate nanostructures, such as a wireframe beach ball or square-toothed gears.
Abstract
Using the ion mirror image (IMIM) technique, a focused ion beam (FIB) microscope is used to investigate the charging phenomenon of Polymethyl methacrylate (PMMA). The effect of the ...experimental chamber’s finite size is studied using classical scattering theory. We test the widely held belief that the method tests the radius of curvature of the equipotential by performing a thorough calculation of the Ion orbits in the presence of extended sources. We show that, near to the chamber walls, the field lines bend until they are normal to the walls, the field is small, and the ion orbit is unaffected, as well as how to get rid of the “mirror effect”.
A resistive flexible humidity sensor based on multi-walled carbon nanotubes (MWCNTs) was designed and fabricated. Screen and gravure printing processes were used for monolithically fabricating the ...humidity sensor containing interdigitated electrodes (IDE), a sensing layer and a meandering conductive heater. An average thickness and surface roughness of <inline-formula> <tex-math notation="LaTeX">0.99~\mu \text{m} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">0.23~\mu \text{m} </tex-math></inline-formula>, respectively, was registered for the printed MWCNTs sensing layer. The capability of the printed sensor, with heater, was investigated by subjecting it to relative humidity (RH) ranging from 10% to 90%. The response demonstrated an overall resistance change of 55% when the sensor was subjected to 90% RH, when compared to 10% RH. A maximum hysteresis of 5.1%, at 70% RH, was calculated for the resistive response of the sensor. The printed sensors can be bend with radius of curvature of 1.5 inch with literally no effect.
•Forced convection heat transfer of flow past tandem cylinders with rounded corners.•Effects of gap ratio and corner radius of the cylinders are studied.•Flow is stabilized as the cylinders are ...rounded at a large corner radius.•Steady and unsteady gap flows are observed at small and larger gap ratios.•Flow and heat transfer characteristics are determined by the gap flow patterns.
This work presents the first numerical investigation on the forced convection of flow across two tandem cylinders with rounded corners in a channel at Re = 100. Both cylinders have the geometry of a square rounded at all corners with a radius of curvature R, which is non-dimensionalized as R+ = R/D where D is the cylinder diameter, thus the cylinder geometry can be square (R+ = 0.0), partially rounded (R+ = 0.1–0.4) or circular (R+ = 0.5). The two cylinders are separated at a distance in the streamwise direction as characterized by the parameter of gap ratio (GR) chosen at GR = 1(1)8. The objective of this work is to explore the effects of two significant parameters, i.e., gap ratio and corner radius, on the flow unsteadiness and heat transfer characteristics of the tandem arrangement that has not been studied before. The effects of the two parameters are exhibited and analyzed by the instantaneous temperature and vorticity fields, variation of representative aerodynamic and heat transfer quantities, spatial distributions of local heat transfer rate, flow behaviors in the gap and the near-wake regions, and temperature distribution and variation on the channel wall. The results are presented by time-averaged and fluctuating quantities to reflect both mean and pulsating behaviors. We observed that the cylinder geometry determines the unsteadiness of the near-wake flow after the downstream cylinder; the flow is always unsteady for square-like cylinders where the corner radius is small, while the flow can be stabilized by the circular-like cylinders with larger corner radii that the flow fluctuation is greatly weakened or even fully suppressed at small GRs. Numerical results also reveal that the gap flow is steady at small GRs and unsteady at large GRs, as categorized as steady gap flow regime and unsteady gap flow regime. There are drastic variations for the representative characteristic quantities at the critical GR where the gap flow transits from steady to unsteady. The different flow regimes categorized by GR and R+ also substantially determine the flow patterns in the gap and near-wake regions, the mean and fluctuating of heat transfer rate on the cylinder surface and the temperature variation on the channel wall.
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