Spreading Rate Research Articles

Spreading of a thin droplet on a soft substrate

A thin liquid droplet spreads on a soft viscoelastic substrate with arbitrary rheology. Lubrication theory is applied to the governing field equations in the liquid and solid domains, which are coupled through the free boundary at the solid–liquid interface, to derive a set of reduced equations that describe the spreading dynamics. Fourier transform techniques and the finite difference method are used to construct a solution for the dynamic liquid–gas and solid–liquid interface shapes, as well as the macroscopic contact angle. Substrate properties affect the spreading dynamics through the contact angle and internal droplet flow fields, and these mechanisms are revealed. Increased substrate softness increases the spreading rate, whereas increased viscoelasticity decreases the spreading rate. For the case of a purely elastic substrate, the spreading power-law exponent recovers Tanner's law in the rigid limit and increases with substrate softness.

Efficacy of Two Tank-Mix Adjuvants to Control Mango Thrips Using a UAV Sprayer

Thrips have become some of the most challenging pests to control in mango production due to their short developmental time, hidden locations and resistance to pesticides, in the tropical regions of China. To improve pesticides efficacy, the tank-mix adjuvants Qi Gong (QG) and the thrips attractant Lv Dian (LD) were added when using an unmanned aerial vehicle (UAV) to control thrips. The surface tension, contact angle on mango leaves, droplet size, spreading rate, and drying time of the two tank-mix adjuvants were determined. The effects of the two tank-mix adjuvants using a UAV sprayer on the droplet coverage and control efficacy against thrips on mango inflorescences were tested through field trials. The results showed that both QG and LD could reduce the surface tension of the liquid and the contact angle on mango leaves and could increase the spreading performance. The droplet coverage in the upper layer of the canopy was about 2% higher than that in the lower layer, and the coverage at the top of the panicle was 5% higher than that at the bottom. QG improved the deposition coverage of mango inflorescences by about 31.5%. The addition of QG increased the efficacy by 18.24% and 8.03%, respectively, at florescence and the young fruit stage. The addition of the LD increased the efficacy by 24.56% and 14.38%, respectively, at florescence and the young fruit stage. These test results can provide a scientific basis for the control of mango thrips with UAVs.

THE METHOD OF IDENTIFYING THE TYPE OF UNMANNED OF THE AVIATION COMPLEX BY ITS RADIO SIGNALS

The article proposes a method for determining the type of unmanned aerial complex (UAC) based on its radio signals, which is based on a comparison of the estimated parameters of the UAV radio signals with known values stored in the database. The following characteristics and parameters of the signal are proposed as recognition features: the appearance of the amplitude-frequency spectrum (AFS) and spectrogram of the radio signal; radio line frequency range; accumulated ASF width; ASF width of the frequency element; spread spectrum parameters (hop duration; rate of frequency hopping spectrum spreading (FHSS); number of FHSS frequencies; FHSS frequency grid step); modulation parameters (symbol rate; modulation index); the position of the autocorrelation function (ACF) peaks; constant symbol sequences. Peculiarities of definition and application of the indicated recognition features are analyzed. It is shown that the most informative features are modulation parameters and constant symbol sequences. In order to increase the probability of correct recognition of UAC, in addition to the indicated features, it is suggested to use the power of received radio signals and the direction of the radio emission sources. A combination of two well-known approaches was used to make a decision about the type of UAC: the decision tree method and the minimum metric method. The application of the first made it possible to reduce the computational complexity due to the exclusion of operations for radio signals parameters evaluating that do not correspond to the decisions made at the previous stages. The minimum metric method was chosen taking into account the simplicity of its implementation and ensuring the possibility of expanding the list of known UAC radio signals without significantly changing the developed recognition method. The proposed method consists of six stages, in which recognition features corresponding to the signal spectral characteristics, spread spectrum parameters, modulation parameters, constant symbol sequences, power of the received radio signal and bearing on the UAV are determined in turn. The indicated features are compared with the known ones stored in the UAC radio signal database using the minimum metric method. In case of coincidence of the estimated and known information, a decision is made about the type of UAC, and the remaining stages are not performed. Verification of the developed method was carried out by applying it to the analysis of radio signals of known UAC, in particular, “Orlan-10”, “Supercam S350”, “Lancet”, “Eleron-3SV”.

Using Adhesive Micropatterns and AFM to Assess Cancer Cell Morphology and Mechanics.

The mechanical properties of living cells reflect their physiological and pathological state. In particular, cancer cells undergo cytoskeletal modifications that typically make them softer than healthy cells, a property that could be used as a diagnostic tool. However, this is challenging because cells are complex structures displaying a broad range of morphologies when cultured in standard 2D culture dishes. Here, we use adhesive micropatterns to impose the cell geometry and thus standardize the mechanics and morphologies of cancer cells, which we measure by atomic force microscopy (AFM), mechanical nanomapping, and membrane nanotube pulling. We show that micropatterning cancer cells leads to distinct morphological and mechanical changes for different cell lines. Micropatterns did not systematically lower the variability in cell elastic modulus distribution. These effects emerge from a variable cell spreading rate associated with differences in the organization of the cytoskeleton, thus providing detailed insights into the structure-mechanics relationship of cancer cells cultured on micropatterns. Combining AFM with micropatterns reveals new mechanical and morphological observables applicable to cancer cells and possibly other cell types.

Tectonically assisted emplacement of oceanic intraplate volcanoes: The Bathymetrists Seamounts, central Atlantic

The origin of broad intraplate volcanic provinces has been related to deep mantle plumes or shallow lithospheric processes, e.g., underlying large fault systems. One example of an understudied intraplate volcanic province is the Bathymetrists Seamounts (BSM) in the central-eastern Atlantic, an area with dense and extended fracture zones, but the BSM has been associated with a mantle plume origin. Extensive bathymetric mapping and seafloor sampling show that most BSM-seamounts resemble flat-topped guyots capped by carbonate platforms. Vesicular, volcanoclastic samples imply that their tops formed near sea level, followed by reef formation during cessation of volcanism and crustal subsidence. Erosion determines the seamount irregularity proportional to their sizes. Strong ellipticity of some seamounts is related to multiple vents that erupted along fractures. The orientation of the volcanoes, carbonate platforms, and morphological lineaments of the BSM show particular trends that reveal information on their origin and formation mechanisms. Geomorphological analyses indicate a structural control on volcano emplacement related to underlying lithospheric faults resembling a Riedel shear pattern. The stress field corresponding to their orientations is related to a NE-SW tensional setting, fitting to the prevalent tectonic setting ~56–38 Ma years ago that coincides with the BSM formation and an increase in spreading rates. A change in movement of the African plate during this time, together with the reactivation of fracture zones of the strongly sheared equatorial Atlantic, created pathways in the lithosphere and possibly enhanced magmatism. The seamounts do not show distinct differences in erosion state, morphology, carbonate platform depth, or Mn-crust thickness, in contrast to what would be expected for an age progression within the seamount chain. Our observations, therefore, do not support a plume mantle source. While the magmatic source remains undefined, we show that tectonic pathways determined the shape of the seamounts and enabled the broad emplacement of the Bathymetrists seamount chain.

Modeling Wind‐Blown Umbrella Clouds in Lagrangian Dispersion Models

AbstractThe ash and gas released by large explosive volcanic eruptions rises to its neutral buoyancy level in the atmosphere, then spreads laterally to form an umbrella cloud. Density stratification of the atmosphere generates buoyancy forces in the cloud, which drive the outward spread. Although umbrella clouds are often modeled as circular axisymmetric structures, in practice they are usually influenced quite strongly by the meteorological wind, with spread in the upwind direction halted by the oncoming wind, and different rates of spreading in the downwind and crosswind directions. In this work, we derive a simple parametrization of non‐axisymmetric umbrella cloud spreading from a much more complex physically based shallow‐layer intrusion model. The new parametrization is quick to evaluate and so is suitable for use in operational Volcanic Ash Transport and Dispersion Models (VATDMs). In contrast to previous parametrizations, in which there is assumed to be no interaction between a circular umbrella cloud and the meteorological wind, here the umbrella cloud is influenced by the wind and adopts a shape determined by the balance of buoyant spreading and downwind drag forces. We apply the new scheme to four historical case studies of eruptions at Puyehue 2011, Pinatubo 1991, Ulawun 2019, and Calbuco 2015. The results are compared with VATDM simulations using a conventional circular umbrella cloud parametrization. Using the new scheme, good descriptions of cloud spread are recovered and the prediction of horizontal ash distribution is improved relative to the axisymmetric parametrization.

Spatio-temporal instabilities in viscoelastic channel flows: The centre mode

We study in this work the spatio-temporal characteristics of the centre-mode linear instability in viscoelastic channel flows of Oldroyd-B and FENE-P fluids. The linear complex Ginzburg–Landau equation derived using an amplitude expansion method is adopted to determine whether the flow is convectively unstable or absolutely unstable. Comparison of the obtained results with those from the conventional saddle-point searching method shows a favourable agreement. This demonstrates the good predictability of the linear complex Ginzburg–Landau equation which is more suitable for a parametric study in a large space than the conventional method. We found that the centre-mode instability in the viscoelastic channel flow is of a convective nature, i.e., the trailing edge of the wavepacket travels downstream. This could be attributed to the relatively high phase speed, low spreading rate and low growth rate of the instability, collectively preventing a disturbance from travelling upstream. Our results show that stronger polymer elasticity (a greater elastic number or larger polymer concentration) marginally affects the trailing-edge velocity of the centre mode. Decreasing the maximum polymer extensibility in the FENE-P model reduces the spreading rate of the wavepacket and makes the centre-mode disturbance more convective. Theoretical derivations at asymptotically high Reynolds numbers confirm the convective nature of the instabilities from numerical observations. Our results may be conducive to a better understanding of the spatio-temporal instability in viscoelastic experiments.

Machine Learning‐Based New Earthquake Catalog Illuminates On‐Fault and Off‐Fault Seismicity Patterns at the Discovery Transform Fault, East Pacific Rise

AbstractOceanic transform faults connect spreading centers and are imprinted with previous tectonic events. However, their tectonic interactions are not well understood due to limited observations. The Discovery transform fault system at 4°S, East Pacific Rise (EPR), represents a young transform system, offering a unique opportunity to study the interplay between faulting and other tectonic events at an early phases of an oceanic transform system. Discovery regularly hosts M5–6 characteristic earthquakes, and the seafloor north of Discovery includes a 35 km‐long rift zone that records a complex history of rifting, faulting and volcanism, suggesting that the transform faults likely interact with regional tectonic activity. We apply a machine‐learning enabled workflow to locate 21,391 earthquakes recorded during a 1‐year ocean bottom seismometer experiment in 2008. Our results indicate that seismicity on the western Discovery fault is separated into seven patches with distinct aseismic and seismic slip modes. Additionally, we observe a patch of off‐fault seismicity near where seafloor abyssal hills intersect the rift zone. This seismicity may have been caused by varying opening rates as spreading rate decreases from north to south in the rift zone. Our findings suggest that the Discovery system is still evolving, and that system equilibrium has not been reached between rifting and faulting. These results reflect the complex yet rarely observed interactions between fault slip, plate rotation, and rifting which are likely ubiquitous at oceanic transform systems.

IMPACTS OF SLR-UPSCALED NOURISHMENT SCENARIOS ON DECADAL CROSS-SHORE DYNAMICS

Projections of high rates of sea level rise have stimulated proposals for adaptation strategies with increasingly high nourishment volumes. Nourishment strategies involving higher sand volumes can be accomplished by increasing the volume of individual nourishments or by decreasing the time interval between successive nourishments. The optimal placement of the sediment volumes in the cross-shore and alongshore to attain our coastal management goals is still under debate. From a long term, large scale perspective only the added sediment volume may be considered, regardless of the placement. A widely accepted perception is that coastal profiles respond to nourishment by rapid equilibration to an equilibrium shape including the added sand volume. However, the timescale of the redistribution of the sediment may be slower than the desired spreading rate of the added sediment, causing sediment to accumulate at some parts of the profile, while leaving other elevations sediment starved. This research aims to examine decadal-scale coastal profile response to nourishment strategies upscaled with sea level rise (SLR) whereby potential nourishment strategy impacts for beach width (fluctuations), dune growth potential and momentary coastline are mapped.

Evaluation of fabric liquid and moisture management properties at simulated skin and sweat temperatures using an advanced novel sweating simulator

The moisture management performance of fabrics under profuse sweating (i.e. the ability to sweat absorb, spread, evaporate, drip, and dry) is crucial to the wearer’s comfort and performance, and should therefore be accurately and realistically tested for quality evaluation and product development. However, it is challenging to measure these properties simultaneously under realistic conditions using current evaluation techniques or testing standards. In this article an advanced version of the novel sweating simulator (NSS) is presented with which the skin temperature, sweat temperature, active body posture, and varying sweating rates can be simulated and multiple fabric moisture management properties including liquid sweat accumulation rate, multi-directional spreading rates, variations in downflow rates caused by increasing liquid accumulation, discharge rate, evaporation rate, drying rate, and drying time can be measured concurrently and in real-time during the simulated sweating and drying phases. The high accuracy and excellent reproducibility of NSS measurements were demonstrated through testing eight different kinds of commercial moisture management fabrics to show the potential applications of the NSS. It is believed that the novel sweating simulator, owing to its comprehensive testing capability, will play a key role in the development of next-generation moisture management fabrics for numerous apparel and technical applications.

SHI1I2R competitive information spreading model in online and offline two-layer networks in emergencies

Previous research on information propagation has primarily focused on either online social networks or offline social networks. Additionally, there remains a gap in understanding the propagation of competitive information in emergency scenarios. This paper introduces an SHI1I2R information spreading model to investigate the dynamics of competitive information dissemination and interactions in online and offline two-layer networks during emergencies. To enhance the accuracy of information propagation modeling, we depart from the conventional assumption of constant spreading and decay rates and instead propose nonlinear spreading and interest decay rates within the SHI1I2R model. Employing a microscopic Markov chain approach, we conduct theoretical analysis and derive the spreading threshold of information in two-layer networks. Subsequently, we perform numerical simulations to validate the effectiveness of the SHI1I2R model and explore the factors influencing information propagation. Our findings indicate that information spreads more rapidly and extensively in two-layer networks compared to one-layer networks. Furthermore, the final scale of information dissemination and the speed of propagation follow the order: random network > small-world network > scale-free network > regular network.

Large silicic magma chambers at the Moho depth characterize the multi-level plumbing system of back-arc spreading ridges

The plumbing system of volcanoes in crustal convergent settings consists of vertically superimposed, sill-like reservoirs. The shallower reservoirs are generally filled by less dense and SiO2-richer magmas. The plumbing systems of spreading ridges are supposed to be simpler and characterized by prevailing sub-parallel vertical dykes. Here, we present the results of thermo-barometric determinations from minerals and modelling of potential field data at the Marsili spreading ridge in the Southern Tyrrhenian Sea back-arc oceanic basin. The Marsili plumbing system consists of sill-like, large SiO2-rich magma reservoirs located at the Moho depth and sub-vertical basaltic dykes crossing the whole oceanic crust. The formation of deep-seated silicic reservoirs is associated with a decrease in the back-arc spreading rate. The geometry of the plumbing system of spreading ridges may be not dissimilar from that of volcanoes at convergent margins.

Effect of hydrophilic chain length on the impact and wetting behavior of nonionic surfactants regulating droplets on hydrophobic surfaces

Regulation of the droplet impact and wetting behavior of hydrophobic surfaces is a difficult problem to solve. The addition of surfactants is commonly used to improve droplet retention by modifying interfacial properties. The effect of the surfactant structure on the regulation of droplet rebound and wetting behavior needs further research. In this study, the physicochemical properties and regulation of droplet behavior for nonionic surfactants with different hydrophilic chain lengths were investigated. The results indicate that with an increasing hydrophilic chain (Epoxyethane (EO) numbers) length, Isodecyl polyoxyethylene ether (XL) surfactant solutions could better regulate the droplet impact behavior on hydrophobic surfaces and better suppress droplet rebound. This mainly attributed to a faster diffusion of surfactant molecules to newly formed interfaces, thus leading to better wetting reversal and deposition of substrates. Additionally, it was found that with the reduction of the hydrophilic chain length, XL surfactant solutions could better regulate droplet wetting, mainly attributed to its critical micelle concentration and surface tension, creating greater Marangoni forces during spreading and leading to faster spreading rates and larger spreading areas. The results from this study promote understanding of the mechanism for regulation of impact behavior and surfactant solution wetting on hydrophobic surfaces by regulating the EO chain length. This provides an effective strategy in regulating droplet deposition on hydrophobic surfaces and provides the basic data or guidance for the use of nonionic surfactants as tank-mixing adjuvants in unmanned aerial vehicle plant protection.

Современная группирующаяся низкомагнитудная сейсмичность срединно-океанического хребта Гаккеля

Earthquakes at mid-ocean ridges (MOR) reflect the active magmatic and tectonic processes that form new oceanic crust. Active spreading processes of ultraslow ridges, with spreading rates of less than 20 mm/yr, are still poorly understood compared to the MOR in the Atlantic and Pacific oceans, with spreading rates of more than 25 mm/yr. Thanks to the installation of stationary seismic stations in the 21st century on the Arctic archipelagos of Franz Josef Land and Severnaya Zemlya, it became possible to record and study low-magnitude grouping earthquakes within the Gakkel Ridge, including swarm sequences of earthquakes. This article presents the first results of registration, location and study of swarm sequences of low-magnitude earthquakes within the Gakkel Ridge for the period from 2012 to 2022. It is shown that swarm sequences are recorded to a greater extent in the western volcanic and eastern volcanic segments of the ridge, while no such sequences were found within the central amagmatic segment. The structure formation of this part of the ridge is dominated by tectonic rather than magmatic and metamorphic processes. Two large swarm of low-magnitude earthquakes that occurred in the eastern volcanic segment of the ridge are considered in detail.

The Spreading Characteristics of Droplets Impacting Wheat Leaves Based on the VOF Model

Given the problem that droplets cannot stay on the surfaces of leaves and wet them effectively, resulting in high levels of pesticide input and environmental pollution, this work studied the dynamic behaviors of droplets with different diameters (400–550 um) falling on the surfaces of wheat leaves from different heights (2–16 cm) using contact angle-measuring instruments and a high-speed camera. The VOF method in Fluent software was used to establish a numerical model of droplets impacting the surfaces of wheat leaves. The results show that with an increase in the initial diameter and initial velocity of a droplet, the maximum diameter of the droplet during the spreading process also gradually increases. After a droplet impacts a wheat leaf, the droplet-spreading diameter first increases and then decreases. The maximum droplet spreading rate, βmax, increases with an increase in the Weber number, βmax ∈We14, which is consistent with the existing theory. The results of this study lay a foundation for studying the spread of droplets on the surfaces of leaves, which is conducive to improving the rate of pesticide utilization.

Liquid Oxygen/Gaseous Methane Single-Element Shear Coaxial Flame Dynamics

An experimental study was conducted to visualize the dynamics and spectra of single-element shear coaxial liquid oxygen (LOX)/gaseous methane flames at high but still subcritical pressure for the LOX, and at supercritical temperature for the methane. High-speed shadowgraphs were employed to image and track the flame and jet dynamics close to the liquid oxygen’s post region. High-speed OH* and CH* chemiluminescence were also simultaneously collected along the same line of sight as the shadowgraphs. The results were compared to previous LOX/hydrogen results using the same injector at the same momentum flux ratios. The initial temperature of the methane was varied between 200 and 300 K. The LOX/methane flames were found to share many features in common with the LOX/hydrogen flames previously studied, but there were notable differences. The spreading rate of the LOX/hydrogen flames was larger than that of LOX/methane flames. The amplitude of the spreading rate fluctuations for hydrogen was also larger, although the relative spreading rate fluctuations normalized by the average spreading rates were about the same. Despite the differences, a wave amplification mechanism found previously to be active for shear coaxial LOX/hydrogen flames was found to also be active for LOX/methane flames. Overall, both the LOX/methane flames and the LOX/hydrogen were both found to be spectrally fairly quiet.

Spreading rate, opening time, and kinematic history of the Ayu Trough

Spreading rate, opening time, and kinematic history of the Ayu Trough

Diameter-Optimum Spreading for the Impinging of Water Nanodroplets on Solid Surfaces.

The impinging of water nanodroplets on solid surfaces is crucial to many nanotechnologies. Through large-scale molecular dynamics simulations, the size effect on the spreading of water nanodroplets after impinging on hydrophilic, graphite, and hydrophobic surfaces under low impinging velocities has been systematically studied. The spreading rates of nanodroplets first increase and then decrease and gradually become constant with the increase of nanodroplet diameter. The nanodroplets with the diameters of 17-19 nm possess the highest spreading rates because of the combined effect of the strongest interfacial interaction and the strongest surface interaction within water molecules. The highest water molecule densities, hydrogen bond numbers, and dielectric constants of interface and surface layers mainly contribute to the lowest interface work of adhesion and surface tension values at optimal diameters. These results unveil the nonmonotonic characteristics of spreading velocity, interface work of adhesion and surface tension with nanodroplet diameter for nanodroplets on solid surfaces.

Geophysical investigation of the Mado Megamullion oceanic core complex: implications for the end of back-arc spreading

Detachment faulting is one of the main styles of seafloor spreading at slow to intermediate mid-ocean ridges. However, we have limited insight into its role in back-arc basin formation. We surveyed a remnant back-arc spreading center in the Philippine Sea and determined the detailed features and formation processes of the Mado Megamullion (Mado MM) oceanic core complex (OCC). This was undertaken in the context of back-arc evolution, based on the shipborne bathymetry, magnetics, and gravity with radiometric age dating of the rock samples collected. The Mado MM OCC has a typical OCC morphology with prominent corrugations on the domed surface and positive gravity anomalies, suggesting that there has been an exposure of the lower crust and mantle materials by a detachment fault. The downdip side of the detachment continues to the relict axial rift valley, which has indicated that the Mado MM OCC was formed at the end of the back-arc basin opening. The spreading rate of the basin decreased once when the spreading direction changed after six million years of stable trench perpendicular spreading. The rate then further decreased immediately prior to the end of the spreading when the Mado MM OCC was formed. The existence of other OCC-like structures in the neighboring segment and the previously reported OCCs along the Parece Vela Rift have indicated that the melt-poor, tectonic-dominant spreading is a widespread phenomenon at the terminal phase of back-arc spreading. The decrease in spreading rate in the later stage is consistent with the previous numerical modeling because of the decrease in trench retreat. In the Izu–Bonin–Mariana arc trench system, the rotation of the spreading axis and the resultant axis segmentation have enhanced the lithosphere cooling and constrained mantle upwelling, which caused the tectonic-dominant spreading at the final phase of the basin evolution.

Social and clinical risk factors associated with hospitalized COVID-19 patients in Brussels's deprived and multiethnic areas.

In Belgium, the Brussels-Capital region was severely affected by the COVID-19 epidemic. Various hypotheses were mentioned in order to explain Brussels' excess disease spreading and mortality rate, but socioeconomic risk factors are increasingly recognized. This study's objective was to analyze clinical and social profiles of patients hospitalized for COVID-19, by nationality groups, in two hospitals located in Brussels's deprived and multiethnic areas. Data covered hospitalized COVID-19 patients from two Brussels hospitals (n = 787) between the 1st of March 2020 and the 31st of June 2020. Social data was collected using hospital records, and clinical data was extracted from hospitals' COVID-19 databases. Multivariable logistic regression models were used to estimate the odds ratios (OR) of the association between two outcomes (Intensive Care Unit admission and mortality) and risk factors (social and clinical). Patients from Sub-Saharan Africa were younger, had a higher prevalence of obesity, lacked health insurance, and had the highest proportion of Intensive Care Unit (ICU) admission (27.7%) but the lowest mortality rates than other nationality groups. Patients from North Africa had a higher prevalence of diabetes compared to other nationality groups and a high proportion of European patients came from nursing homes. Patients deprived of health insurance had a higher risk of ICU admission compared to those who had insurance (OR IC95%; 1,9 1.1-3.6, p = 0.03). Other risk factors as sex and obesity were significantly associated to ICU admission and, age and hypertension were significantly associated to mortality. Social and clinical profile of the patients differs between the nationality groups, and some risk factors for Intensive Care Unit admission and mortality were linked to more patients' precarious situation as the availability of health insurance. This study underlines the role of selected social health determinants and the importance of routinely collecting social along with clinical data.