Articles de revues : « Laws of wetting »

1

Voinov, O. V. « Asymptotic laws of wetting hydrodynamics ». Doklady Physics 50, n^o 7 (juillet 2005) : 380–84. http://dx.doi.org/10.1134/1.2005365.

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Fondecave, R., et F. Brochard Wyart. « Wetting laws for polymer solutions ». Europhysics Letters (EPL) 37, n^o 2 (10 janvier 1997) : 115–20. http://dx.doi.org/10.1209/epl/i1997-00120-y.

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Fan, Qianwen, Liangjun Fei, Penghui Zhao, Fangyuan Shen et Yalin Gao. « Study on Soil Water and Nitrogen Transport Characteristics of Unidirectional Intersection Infiltration with Muddy Water Fertilization Film Hole Irrigation ». Agriculture 14, n^o 12 (17 décembre 2024) : 2314. https://doi.org/10.3390/agriculture14122314.

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This study investigated the effects of film hole diameter and soil bulk density on the unidirectional intersection infiltration laws of muddy water fertilization film hole irrigation. Indoor soil box infiltration experiments were conducted. The thickness of the sediment layer, cumulative infiltration amount per unit area, vertical wetting front transport distance, moisture distribution in the wetting body, and nitrate and ammonium nitrogen transport laws were observed and analyzed. The results indicated that both the thickness of the sediment layer and the cumulative infiltration per unit area are inversely correlated with film hole diameter and soil bulk density. Conversely, the vertical wetting front transport distance and nitrogen content are positively correlated with film hole diameter, while exhibiting a negative correlation with soil bulk density. Notably, the initial point of intersection for the moist body was located below the soil surface, with the peak vertical soil moisture content at the intersection approximately 1.5 cm beneath the surface. The distribution pattern of soil nitrate nitrogen at the conclusion of infiltration mirrored that of water content, characterized by a sharp decline near the wetting front. In contrast, soil ammonium nitrogen content decreased significantly in the shallow soil layer as soil depth increased, without a corresponding abrupt decrease near the wetting front. These findings may provide a theoretical foundation for future research on the intersection infiltration laws of muddy water fertilization through film hole irrigation.

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Wang, Boxin, Ruichang Fang, Xu Chai et Qing Wang. « Transportation Laws for Carbonate and Sulfate Ions in Concrete Based on Compartment Model ». Advances in Civil Engineering 2020 (23 juillet 2020) : 1–10. http://dx.doi.org/10.1155/2020/1769186.

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Transportation of carbonate and sulfate ions in concrete under the drying-wetting cycle environment is similar to the ingression and elimination of medicine in human body. Given this similarity, such a process is described dynamically using the classic compartment model in pharmacokinetics. The compartment model was applied to predict the content of carbonate and sulfate ions in different regions of concrete. Factors such as water-cement ratio, salt category, carbonate-ion and sulfate-ion attack depth, and drying-wetting cycle were synthetically considered in the compartment model. In conjunction with the prediction value of the compartment model, the experiment data uniformly distributed two sides of the model curve, and the difference is within the accepted range, thus verifying the reliability of the model prediction consequence. The compartment model in this article provides references for predicting the drying-wetting varied cycles and ions attack depth of concrete under carbonate and sulfate ions attack.

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Parmigiani, A., C. Huber, O. Bachmann et B. Chopard. « Pore-scale mass and reactant transport in multiphase porous media flows ». Journal of Fluid Mechanics 686 (30 septembre 2011) : 40–76. http://dx.doi.org/10.1017/jfm.2011.268.

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AbstractReactive processes associated with multiphase flows play a significant role in mass transport in unsaturated porous media. For example, the effect of reactions on the solid matrix can affect the formation and stability of fingering instabilities associated with the invasion of a buoyant non-wetting fluid. In this study, we focus on the formation and stability of capillary channels of a buoyant non-wetting fluid (developed because of capillary instabilities) and their impact on the transport and distribution of a reactant in the porous medium. We use a combination of pore-scale numerical calculations based on a multiphase reactive lattice Boltzmann model (LBM) and scaling laws to quantify (i) the effect of dissolution on the preservation of capillary instabilities, (ii) the penetration depth of reaction beyond the dissolution/melting front, and (iii) the temporal and spatial distribution of dissolution/melting under different conditions (concentration of reactant in the non-wetting fluid, injection rate). Our results show that, even for tortuous non-wetting fluid channels, simple scaling laws assuming an axisymmetrical annular flow can explain (i) the exponential decay of reactant along capillary channels, (ii) the dependence of the penetration depth of reactant on a local Péclet number (using the non-wetting fluid velocity in the channel) and more qualitatively (iii) the importance of the melting/reaction efficiency on the stability of non-wetting fluid channels. Our numerical method allows us to study the feedbacks between the immiscible multiphase fluid flow and a dynamically evolving porous matrix (dissolution or melting) which is an essential component of reactive transport in porous media.

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Andreotti, Bruno, et Jacco H. Snoeijer. « Statics and Dynamics of Soft Wetting ». Annual Review of Fluid Mechanics 52, n^o 1 (5 janvier 2020) : 285–308. http://dx.doi.org/10.1146/annurev-fluid-010719-060147.

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The laws of wetting are well known for drops on rigid surfaces but change dramatically when the substrate is soft and deformable. The combination of wetting and the intricacies of soft polymeric interfaces have provided many rich examples of fluid–structure interactions, both in terms of phenomenology and from a fundamental perspective. In this review we discuss experimental and theoretical progress on the statics and dynamics of soft wetting. In this context we critically revisit the foundations of capillarity, such as the nature of solid surface tension, the microscopic mechanics near the contact line, and the dissipative mechanisms that lead to unexpected spreading dynamics.

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Wallmeyer, Bernhard, Sarah Trinschek, Sargon Yigit, Uwe Thiele et Timo Betz. « Collective Cell Migration in Embryogenesis Follows the Laws of Wetting ». Biophysical Journal 114, n^o 1 (janvier 2018) : 213–22. http://dx.doi.org/10.1016/j.bpj.2017.11.011.

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Henkel, Christopher, Jacco H. Snoeijer et Uwe Thiele. « Gradient-dynamics model for liquid drops on elastic substrates ». Soft Matter 17, n^o 45 (2021) : 10359–75. http://dx.doi.org/10.1039/d1sm01032h.

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The presented simple long-wave gradient-dynamics model for soft wetting recovers the double transition for static drops and spreading laws on elastic substrates. It allows one to consider the influence of substrate softness on coarsening.

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Erofeev, Daniil A., et Leonid N. Mashlyakovsky. « FABRICATION AND APPLICATION OF HYDROPHOBIC SILICON CONTAINING POLYURETHANE COATINGS. PART TWO. (REVIEW) ». Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 64 (2023) : 40–51. http://dx.doi.org/10.36807/1998-9849-2023-64-90-40-51.

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It is well known, that water drops tend to easily flow down from lotus leaves because of low wetting degree. In the first part of the review, we discussed the basic concept of wetting theory and different limits of existing models. The unsolved questions in the theory of wetting did not slow the development of methods of hydrophobic coatings fabrication. At present, coatings with low wetting degree are implemented in different industry fields. However, fabrication of coatings with stable hydrophobic properties is still difficult. That problem is especially serious for highly- and superhydrophobic coatings. The second part of the review describes the methods of fabrication of hydrophobic, highly- and superhydrophobic polyurethane coatings. We briefly mention the chemical reactions, which lead to polyurethanes obtaining, methods of hydrophobic coatings fabrication, and their application fields. Special attention is focused on the analysis of the surface parameters in order to establish general laws for producing hydrophobic, highly-hydrophobic and super-hydrophobic polyurethane silicon coatings

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Leibler, Ludwik, et Ahmed Mourran. « Wetting on Grafted Polymer Films ». MRS Bulletin 22, n^o 1 (janvier 1997) : 33–37. http://dx.doi.org/10.1557/s0883769400032310.

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Studying the properties of endanchored polymer layers has been a fashionable occupation for numerous physicists, chemists, and material scientists for more than 10 years. Theoreticians have realized that grafted macromolecules are nice statistical objects wriggling around under thermal motion, which give rise to nontrivial long-range entropic effects. These can be described by elegant scaling laws and analogies with quantum or classical mechanics. For experimenters the area turned out to be a marvelous playground in which both very simple and sophisticated techniques such as x-ray or neutron scattering and reflectivity, nuclear magnetic resonance (NMR), Rutherford backscattering, and optical and atomic force microscopy (AFM) have been used to discover interesting and subtle phenomena. All this effort was also motivated by the importance of grafted layers in applications such as paints, adhesives, lubricants, colloidal stabilizers, and composite materials. By anchoring a thin, soft polymer layer to a solid surface, one can tune the surface properties. In this short article, we will discuss how the wetting and spreading of liquids and polymer melts can be profoundly altered by the presence of such protective layers.

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Legrand, Quentin, Stephane Benayoun et Stephane Valette. « Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces : Study of the Links between Morphology and Wettability ». Biomimetics 6, n^o 2 (8 juin 2021) : 38. http://dx.doi.org/10.3390/biomimetics6020038.

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This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

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Diduk, I. I., et G. A. Bagliuk. « The Influence of the Chemical Composition and Temperature of Molten Rocks on Laws Wetting Their Platinum-Rhodium Plate Spinneret ». Фізика і хімія твердого тіла 16, n^o 2 (15 juin 2015) : 398–402. http://dx.doi.org/10.15330/pcss.16.2.398-402.

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The results of investigation of platinum-rhodium substrate wetting by the melts of ten different compositions of rocks and the values of their surface tension and adhesion in a wide temperature range. It is shown that the highest values of surface tension and adhesion observed for basalt melts, whereas neutral aluminosilicate glass melts, which do not containiron oxide compounds are characterized by a high value of the contact angle and the lowest values of surface forces. Doping of ZrO2in the meltcompositionsignificantly increases angles of wetting and surface tension and adhesion throughout the temperature range as compared with the same melts without zirconia.

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Tang, Liansheng, Zihua Cheng, Hao Wang et Yang Chen. « Effects of Drying and Wetting Process on the Tensile Strength of Granite Residual Soil ». Water 15, n^o 15 (2 août 2023) : 2801. http://dx.doi.org/10.3390/w15152801.

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The tensile strength of granite residual soil has different changing laws during the wetting and drying process which often appears after rainfall. The microscopic relationship between tensile strength, bond force, and absorbed suction was studied using a self-developed soil tensile strength tester. The results show the following. (1) The change in tensile strength with saturation is a convex curve with a peak; according to the drying and wetting path, there are differences in peak value and amplitude of variation. (2) The sample with a higher fine particle content has a structure that is denser and has fewer pores, while an increase in gravel content will significantly reduce the tensile strength of the soil. (3) Absorbed suction and bond forces are important factors that control tensile strength in the drying process. The bond force contributes more than 70%, the tensile strength is in invariable constant saturation, and the wetting process is mainly controlled by absorbed suction.

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Zhang, Zhuo. « Research on Permeability Regularities in Subgrade behind the Bridge Abutment ». Applied Mechanics and Materials 178-181 (mai 2012) : 1676–80. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.1676.

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On the hypothesis of that the compacted soil was isotropic body and water movement complied with porous model of Green-Ampt, the permeability models in subgrade behind the bridge abutment with crack that is full of water were put forward by Darcy laws. In order to test the reasonableness of theoretical analysis, the flow mode test was conducted in the lab. The test results show that there is a linear relationship between horizontal length of wetting front on top of subgrade with the square root of time, in the sections at the bottom of crack, it is two time function relationship between vertical distance with horizontal length of wetting front. The test results are consistent with theoretical analysis.

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Alberti, Giovanni, et Antonio DeSimone. « Wetting of rough surfaces : a homogenization approach ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 461, n^o 2053 (8 janvier 2005) : 79–97. http://dx.doi.org/10.1098/rspa.2004.1364.

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The contact angle of a drop in equilibrium on a solid is strongly affected by the roughness of the surface on which it rests. We study the roughness–induced enhancement of the hydrophobic or hydrophilic properties of a solid surface through homogenization theory. By relying on a variational formulation of the problem, we show that the macroscopic contact angle is associated with the solution of two cell problems, giving the minimal energy per unit macroscopic area for a transition layer between the rough solid surface and a liquid or vapour phase. Our results are valid for both chemically heterogeneous and homogeneous surfaces. In the latter case, a very transparent structure emerges from the variational approach: the classical laws of Wenzel and Cassie–Baxter give bounds for the optimal energy, and configurations of minimal energy are those leading to the smallest macroscopic contact angle in the hydrophobic case, to the largest one in the hydrophilic case.

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Dorbolo, Stéphane. « The wetting properties of frosted glass ». Papers in Physics 13 (1 décembre 2021) : 130006. http://dx.doi.org/10.4279/pip.130006.

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Frosted glass is a common, low cost material. Its roughness can be used to control how it is wet by water. In this paper, the wetting properties of silicone oil and water are investigated. For the oil, wetting is total since the oleophilic character of the glass is enhanced by its roughness. Due to the remarkable optical properties of frosted glass, the spreading of oil droplets on its surface was recorded over three months. Frosted glass is a parahydrophilic surface because of its large contact angle hysteresis (up to 80° ). The behaviour of oil and water droplets was compared on a long piece of inclined frosted glass. The trajectories (and the spreading) of the droplets were studied and phenomenological laws were deduced to describe the dependence of the droplet speed on the initial volume of the droplet and the angle of inclination. Such dependences of speed at long travel distances (100 times the capillary length) were deduced and rationalised with a simple model that takes into account the thickness of the wake. Moreover, we analysed the flow inside the wake of water droplets sliding on inclined frosted glass. Suggestions are given on how to exploit drainage of the water droplet wake and the high hysteresis of water within the framework of open microfluidics.

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Joanny, Jean-François, et Sriram Ramaswamy. « A drop of active matter ». Journal of Fluid Mechanics 705 (26 avril 2012) : 46–57. http://dx.doi.org/10.1017/jfm.2012.131.

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AbstractWe study theoretically the hydrodynamics of a fluid drop containing oriented filaments endowed with active contractile or extensile stresses and placed on a solid surface. The active stresses alter qualitatively the wetting properties of the drop, leading to new spreading laws and novel static drop shapes. Candidate systems for testing our predictions include cytoskeletal extracts with motors and ATP, suspensions of bacteria or pulsatile cells, or fluids laden with artificial self-propelled colloids.

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Traskine, Vladimir, Z. Skvortsova, Laurent Barrallier, Polina Volovitch et Alexandre Pertsov. « Wetting of Stressed Grain Boundaries in Polycrystals and Rheological Behaviour of Resulting Materials ». Defect and Diffusion Forum 258-260 (octobre 2006) : 409–14. http://dx.doi.org/10.4028/www.scientific.net/ddf.258-260.409.

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Orientational patterns of wetted grain boundaries (GB's) in stressed NaCl polycrystals have been used for describing the GB penetration process on the basis of combined interfacial and mechanical energy balance considerations. The response of the internally wetted polycrystals to static loading has been shown to obey “pressure solution” constitutive laws involving dissolution at stressed surfaces, diffusive transport of dissolved matter and precipitation at less stressed surfaces. Direct experimental evidence for pressure solution mechanism is presented.

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Kim, Jungchul, Myoung-Woon Moon et Ho-Young Kim. « Dynamics of hemiwicking ». Journal of Fluid Mechanics 800 (29 juin 2016) : 57–71. http://dx.doi.org/10.1017/jfm.2016.386.

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Hemiwicking refers to the spreading of a liquid on a rough hydrophilic surface driven by capillarity. Here, we construct scaling laws to predict the velocity of hemiwicking on a rough substrate and experimentally corroborate them with various arrangements and dimensions of micropillar arrays. At the macroscopic scale, where the wetting front appears parallel to the free surface of the reservoir, the wicking distance is shown to grow diffusively, i.e. like $t^{1/2}$ with $t$ being time. We show that our model is consistent with pillar arrays of a wide range of pitch-to-height ratios, either square or skewed. At the microscopic scale, where the meniscus extension from individual pillars at the wetting front is considered, the extension distance begins to grow like $t$ but the spreading slows down to behave like $t^{1/3}$ when the meniscus is far from the pillar. Our microscopic flow modelling allows us to find pillar spacing conditions under which the assumption of densely spaced pillars is valid.

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Bostwick, J. B. « Spreading and bistability of droplets on differentially heated substrates ». Journal of Fluid Mechanics 725 (17 mai 2013) : 566–87. http://dx.doi.org/10.1017/jfm.2013.196.

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AbstractAn axisymmetric drop spreads on a radially heated, partially wetting solid substrate in a rotating geometry. The lubrication approximation is applied to the field equations for this thin viscous drop to yield an evolution equation that captures the dependence of viscosity, surface tension, gravity, centrifugal forces and thermocapillarity. We study the quasi-static spreading regime, whereby droplet motion is controlled by a constitutive law that relates the contact angle to the contact-line speed. Non-uniform heating of the substrate can generate both vertical and radial temperature gradients along the drop interface, which produce distinct thermocapillary forces and equivalently flows that affect the spreading process. For the non-rotating system, competition between surface chemistry (wetting) and thermocapillary flows induced by the thermal gradients gives rise to bistability in certain regions of parameter space in which the droplets converge to an equilibrium shape. The centrifugal forces that develop in a rotating geometry enlarge the bistability regions. Parameter regimes in which the droplet spreads indefinitely are identified and spreading laws are computed to compare with experimental results from the literature.

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Zhang, Zhenjie, Tianyi Zhao et Qingbang Meng. « A Novel Model of Counter-Current Imbibition in Interacting Capillaries with Different Size Distribution ». Energies 15, n^o 17 (29 août 2022) : 6309. http://dx.doi.org/10.3390/en15176309.

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The imbibition phenomenon widely exists in nature and industrial applications. It is of great significance to study the mechanism of imbibition and the influence laws of related factors. In this paper, based on the assumption of interacting capillaries, a capillary bundle model of counter-current imbibition is established. In addition, the characteristics of imbibition and the influences of capillary size and fluid viscosity are analyzed. The results show that water is imbibed into the smaller capillaries and expelled from the larger capillaries. The rate of the meniscus in water-imbibition capillaries is proportional to the square root of time. In the interacting capillaries, oil production by counter-current imbibition decreases and then increases gradually with the increase of the capillary diameter difference. When the total cross-sectional area of the capillary remains unchanged, the cross-sectional area of the total water-imbibition capillaries is affected by the size distribution of the capillaries. The larger the viscosity of the non-wetting phase, the more uneven the imbibition front, the lower the imbibition efficiency. The higher the viscosity of the wetting phase, the more uniform the imbibition front, and the higher the imbibition efficiency.

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Yuan, Quanzi, et Ya-Pu Zhao. « Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface ». Journal of Fluid Mechanics 716 (25 janvier 2013) : 171–88. http://dx.doi.org/10.1017/jfm.2012.539.

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AbstractDynamic wetting of a droplet on lyophilic pillars was explored using a multiscale combination method of experiments and molecular dynamics simulations. The excess lyophilic area not only provided excess driving force, but also pinned the liquid around the pillars, which kept the moving contact line in a dynamic balance state every period of the pillars. The flow pattern and the flow field of the droplet on the pillar-arrayed surface, influenced by the concerted effect of the liquid–solid interactions and the surface roughness, were revealed from the continuum to the atomic level. Then, the scaling analysis was carried out employing molecular kinetic theory. Controlled by the droplet size, the density of roughness and the pillar height, two extreme regimes were distinguished, i.e. $R\sim {t}^{1/ 3} $ for the rough surface and $R\sim {t}^{1/ 7} $ for the smooth surface. The scaling laws were validated by both the experiments and the simulations. Our results may help in understanding the dynamic wetting of a droplet on a pillar-arrayed lyophilic substrate and assisting the future design of pillar-arrayed lyophilic surfaces in practical applications.

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Xue, Baoyong, Ping Yao, Xiaolong Zou, Qian Liu et Yanlong Zhao. « DAMAGE CHARACTERISTICS OF RECYCLED ASPHALT MIXTURES UNDER THE EROSION EFFECT OF SNOW-MELTING SALT ». DYNA 96, n^o 4 (1 juillet 2021) : 379–87. http://dx.doi.org/10.6036/10174.

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The erosion effect of snow-melting salt will degrade the durability of recycled asphalt pavement, but the damage characteristics of recycled asphalt mixture triggered by the erosion effect of snow-melting salt remain unclear. To solve the snow-melting salt-induced durability degradation of asphalt pavement, two commonly used snow-melting salts, NaCl and CaCl2, were selected to carry out the saline water immersion, salt-drying and -wetting cyclic and salt-freezing and -thawing cyclic splitting tests on recycled asphalt mixture, and the attenuation laws of splitting strengths and its damage characteristics under the erosion effect of snow-melting salts were analyzed. Results demonstrate that with the increase in soaking time, salt-drying and -wetting cycles and salt-freezing and -thawing cycles, the splitting strength of the recycled asphalt mixture maintain a declining trend, and the attenuation rate of splitting strength is elevated. The damage degree of the recycled asphalt mixture presents a nonlinear growth trend during saline water immersion, salt-drying and -wetting cycles, and salt-freezing and -thawing cycles. Under the same conditions, the damage degree after the action of NaCl solution is higher than that after the action of CaCl2 solution, and meanwhile, within the range of test concentration, the damage degree after the action of low-concentration saline solution is higher than that after the action of high-concentration saline solution. Conclusions provide a significant reference for the composition design and maintenance decisions of recycled asphalt pavement materials in cold regions. Keywords: road engineering; salt erosion; recycled asphalt mixture; damage characteristics; splitting strength

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Deng, Hongwei, Shiyu Zhou, Songtao Yu, Yao Liu et Jingbo Xu. « Evolution of Pore Structure and Mechanical Characteristics of Red Sandstone Under Drying–Wetting Cycles ». Minerals 15, n^o 2 (7 février 2025) : 158. https://doi.org/10.3390/min15020158.

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Red sandstone is widely distributed in southern China. Due to the significant difference in mechanical properties before and after hydration and its poor water stability, red sandstone often triggers landslide accidents. In this paper, red sandstone from an open pit slope in Jiangxi Province was taken as the research object. Two variables, namely the initial saturation degree (25%, 50%, 75%, and 100%) and the number of wetting–drying cycles (0, 10, 20, 30, and 40), were set. With the help of nuclear magnetic resonance, the Brazilian disc test, and fractal theory, the relationships among its meso-structure, macroscopic fracture mechanics characteristics, and deterioration mechanism were analyzed. The research results are as follows: (1) Wetting–drying cycles have a significant impact on the pore structure and fracture mechanics characteristics of red sandstone. Moreover, the higher the initial saturation degree, the more obvious the deterioration effect of the wetting–drying cycles on the rock mass. (2) After further subdividing the pores according to their size for research, it was found that sandstone is mainly composed of mesopores, and the deterioration laws of different types of pores after the wetting–drying cycles are different. The porosities of total pores and macropores increase, while the proportions of mesopores and micropores decrease. The fractal dimensions of macropores and total pores of each group of rock samples are all within the range of 2–3, and the fractal dimension value increases with the increase in the number of wetting–drying cycles, showing significant and regular fractal characteristics. Micropores and some mesopores do not possess fractal characteristics. The fractal dimension of rock samples basically satisfies the rule that the larger the pore diameter, the larger the fractal dimension and the more complex the pore structure. (3) Both the type I and type II fracture toughness of rock samples decrease with the increase in the number of cycles, and the decrease is the most significant when the initial saturation degree is 100%. After 40 cycles, the decreases in type I and type II fracture toughness reach 23.578% and 30.642%, respectively. The fracture toughness is closely related to the pore structure. The porosity and fractal dimension of rock samples and their internal macropores are linearly negatively correlated with the type II fracture toughness. The development of the macropore structure is the key factor affecting its fracture mechanics performance. (4) After the wetting–drying cycles, the internal pores of red sandstone continue to develop. The number of pores increases, the pore diameter enlarges, and the proportion of macropores rises, resulting in internal damage to the rock mass. When bearing loads, the expansion and connection of internal cracks intensify, ultimately leading to the failure of the rock mass. The research results can provide important reference for the stability analysis of sandstone slope engineering.

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Martínez, M. A., F. Velasco et J. Abenojar. « Behaviour of Fluids in Porous Materials ». Materials Science Forum 802 (décembre 2014) : 303–8. http://dx.doi.org/10.4028/www.scientific.net/msf.802.303.

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The pore structure and the presence of open and close porosity has always made difficult the study of the interaction between fluids and porous materials, being complicated the analysis of liquids wettability and permeability, capillarity or speed of wetting, among others. This work tries to deal with these problems in a simple way, from a theoretical point of view, applying hydrostatic laws and the effect of capillarity to address the effect of open porosity. Moreover, surface roughness of these materials is the consequence of surface finishing (e.g. polishing) and porosity. This work also faces this aspect of wettability of surfaces, important to understand sealing conditions or lubricant retention in powder metallurgical components. From a practical point of view, the speed of fluids through metallic filters is compared to that through metallic meshes.

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Abid, Maysoon B., Safa N. Hamad et Sabah M. Hussain. « ANALYTICAL SOLUTION OF UNSATURATED SOIL WATER FLOW FROM A POINT SOURCE ». Journal of Engineering 18, n^o 1 (10 mai 2023) : 95–106. http://dx.doi.org/10.31026/j.eng.2012.01.07.

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Water flow into unsaturated porous media is governed by the Richards’ partial differential equation expressing the mass conservation and Darcy’s laws. The Richards’ equation may be written in three forms,where the dependent variable is pressure head or moisture content, and the constitutive relationships between water content and pressure head allow for conversion of one form into the other. In the present paper, the “moisture-based" form of Richards’ equation is linearized by applying Kirchhoff’s transformation, whichcombines the soil water diffusivity and soil water content. Then the similarity method is used to obtain the analytical solution of wetting front position. This exact solution is obtained by means of Lie’s method of infinitesimal transformation groups. The predicted results of the analytical solution agreed well with available results of experiments and numerical solutions.

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GLASNER, K. B. « Variational models for moving contact lines and the quasi-static approximation ». European Journal of Applied Mathematics 16, n^o 6 (23 novembre 2005) : 713–40. http://dx.doi.org/10.1017/s0956792505006406.

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This paper proposes the use of a variational framework to model fluid wetting dynamics. The central problem of infinite energy dissipation for a moving contact line is dealt with explicitly rather than by introducing a specific microscopic mechanism which removes it. We analyze this modelling approach in the context of the quasi-steady limit, where contact line motion is slower than bulk relaxation. We find that global effects enter into Tanner-type laws which relate line velocity to apparent contact angle through the role that energy dissipation plays in the bulk of the fluid. A comparison is made to the dynamics of lubrication equations that include attractive and repulsive intermolecular interactions. A Galerkin-type approximation method is introduced which leads to reduced-dimensional dynamical descriptions. Computations are conducted using these low-dimensional approximations, and a substantial connection to lubrication equation dynamics is found.

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Wen, Tao, Yankun Wang, Huiming Tang, Junrong Zhang et Mingyi Hu. « Damage Evolution and Failure Mechanism of Red-Bed Rock under Drying–Wetting Cycles ». Water 15, n^o 15 (25 juillet 2023) : 2684. http://dx.doi.org/10.3390/w15152684.

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The rock mass on the bank slope of the Three Gorges Reservoir (TGR) area often suffers from a drying–wetting cycle (DWC). How the DWCs significantly affect the mechanical properties and the stability of the rock mass is worth comprehensively investigating. In this study, the influence of the DWC on the mechanical properties of red-bed rock, mainly purplish red argillaceous siltstone, is explored in detail. Triaxial compression tests were conducted on siltstones that were initially subjected to different DWCs. The results show that DWCs lead to a decrease in mechanical properties such as peak stress, residual stress, and elastic modulus, while an increase in confining pressure (CP) levels leads to an increase in these mechanical properties. Significant correlations are found between the energy parameters and the DWC or the CP. Notably, the total absorption energy (TAE) demonstrates a positive correlation with the CP, but the capability of siltstones to absorb energy shows a negative correlation with DWC. Moreover, the study also examines the damage evolution laws of rocks under different DWCs by proposing a damage variable (DV). Results demonstrate that the effect of the CP on the DV is more pronounced than that of DWCs. A novel brittleness index (BI) was also proposed for estimating rock brittleness through damage strain rate analysis. The effectiveness of the proposed BI is validated by evaluating the effects of DWCs and CP on rock brittleness. Finally, the failure mechanism of the rocks under water–rock interaction is revealed. The weakening of mechanical properties occurs due to the formation of microcracks in response to DWCs. These findings provide valuable guidance for the long-term stability assessment of bank slope engineering projects under DWCs.

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Щуцька, Г. В., et Н. П. Супрун. « Вологоперенос в багатошарових перев'язочних засобах ». Bulletin of the Kyiv National University of Technologies and Design. Technical Science Series 126, n^o 5 (12 février 2019) : 63–71. http://dx.doi.org/10.30857/1813-6796.2018.5.7.

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Prediction on the base of analysis of the laws of moisture transfer the property of multilayer packages of wound dressing to carry out the transfer of drugs and metabolic fluids in such systems.In the course of experimental studies of penetration of moisture through the packages of wound coatings, in which in different variants of the arrangement of used samples with different raw material composition and density (nonwoven cotton fabrics and linen fabric), were determined parameters of distribution of the liquid and the dimensions of the wetted zone in the upper, lower and middle layers.It has been found that, starting with a certain thickness, most of the liquid accumulates within the package, which changes the general shape of the wetting zone. The surfaces of wetted zones for different package variants, which show a fairly pronounced maximum inside the material, are obtained. The analysis of the dynamics of the change of the wetted zone surface allowed to formulate the problem of determining the location of additional material in the multilayer wound covering. This gives the opportunity to accumulate the highest moisture content inside the material package, which improves the quality of wound dressings. A study on the effects of additional wetting in multi-layer packets of textile medical materials has revealed for the first time the effect of increasing the concentration of fluid inside such systems, which we called "paradox of internal concentration". This effect appear in the fact that at certain ratios of discrete environmental parameters, the maximum propagation of the liquid occurs not on the material surface, but at a certain depth, in the place of location of the material of high density. The appearance of the effect is determined by the parameter that binds the geometric properties of the material and the discrete parameters of the liquid passing. Practical significance. The investigated processes of wetting of multilayer dressing materials can be used to predict conditions of their real functioning, proceeding from the requirements of operational situation. This allows solving problems of durability of bandages. The criterion of longevity may be the prevention of the exhaust outlet to the surface or the restriction of the exhaust emission area on the outer surface of the wound dressing in certain volumes.

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Zhang, Qing Zhang, Xiang Lin Gu, Wei Ping Zhang et Qing Hua Huang. « Study on Effect of Soaking Time on the Transmission of Chloride Ion in Concrete under Drying-Wetting Cycles ». Advanced Materials Research 261-263 (mai 2011) : 61–68. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.61.

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Acceleration penetration tests of chloride ion were conducted for typical diurnal and semidiurnal tidal types in China with consideration of various values of soaking time. It was found that the content of chloride ion from shallow area near the surface of concrete to the pure diffusion area of concrete reduced more significantly with the depth than that in the pure diffusion area of concrete. Based on Fick’s second law, the variation laws of chloride ion content at the edge of the pure diffusion area and chloride ion diffusion coefficient in the pure diffusion area under different soaking time ratios were identified by using the chloride ion content distributions that were established based on the test results of concrete in the pure diffusion area. It was found that the chloride ion content and the apparent chloride ion diffusion coefficient in pure diffusion area may be very high when the ratio of soaking time ratio is between 0.3 and 0.42 or 0.6 and 0.7 for diurnal tidal type and 0.83 for semidiurnal tidal type, which will cause severe erosion in concrete structures in tidal zone.

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Guo, Zhong-qun, Yuan-ming Lai, Jie-fang Jin, Jian-rong Zhou, Zheng Sun et Kui Zhao. « Effect of Particle Size and Solution Leaching on Water Retention Behavior of Ion-Absorbed Rare Earth ». Geofluids 2020 (26 mai 2020) : 1–14. http://dx.doi.org/10.1155/2020/4921807.

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Soil-water characteristic curve reflects water retention behavior of unsaturated soil mass. Particle size and mineral composition can influence water retention behavior of soil mass significantly. To discuss effects of particle size and solution leaching on water retention behavior of ion-absorbed rare earth, soil-water characteristic tests of samples with different particle sizes before and after the solution leaching were carried out by using a pressure plate instrument. Soil-water characteristic curves during drying and wetting were analyzed. A fitting analysis on test data was implemented by the Fredlund&Xing 3 parameter model, the Fredlund&Xing 4 parameter model, and the Van Genuchten model to discuss variation laws of soil-water characteristic parameters in different models. Effects of particle size and solution leaching on water retention behavior of ion-absorbed rare earth as well as action mechanism were investigated. Results demonstrate that given the same matric suction, soil water content decreases gradually with the increase of particle size and content of coarse particles, thus decreasing water retention capacity of soil accordingly. Given the same volumetric water content, matric suction is inversely proportional to particle size. During drying and wetting, the amplitude of variation decreases gradually with the increase of particle size and content of coarse particles. The soil water content after solution leaching is smaller than that before under the same matric suction, indicating that solution leaching can decrease water retention capacity of soil. This is mainly because thickness of the double diffuse layer and pore water pressure are increased as a response to the ion exchange, thus decreasing matric suction.

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Chen, Sitong, Xueke Wang, Tong Zhu et Xiaofeng Xie. « Interaction of Vibration and Air Flow-Accelerating Droplet Emission from the Gas Diffusion Layer of Proton Exchange Membrane Fuel Cell ». International Journal of Photoenergy 2019 (10 décembre 2019) : 1–12. http://dx.doi.org/10.1155/2019/1674134.

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In order to explore the influence of vibration that the vehicles are often subjected on water management of PEMFC, the dynamic characteristics of vibrating droplet on gas diffusion layer (GDL) surface were investigated through a high-speed image technology. The operating condition of vertical and horizontal excitations separately or coupled with air flow under different frequencies and amplitudes are applied on the substrate, so that the laws for the transition from Wenzel-Cassie regime to Cassie regime and the contact angle, the deformation rate for the width and height are obtained. It is observed that the wetting diameter of the droplet is smaller than the initial value under vertical vibration, making it easier for the gas to discharge the water droplets from the PEMFC. For the horizontal excitation, the droplet is pulled apart when the applied energy exceeded the cohesive energy at elevated frequency and amplitude. Moreover, as to the interaction of vibration and air flow, the droplet was more likely to move forward under the gas-driven force.

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Miao, Fasheng, Yiping Wu, Linwei Li, Huiming Tang et Feng Xiong. « Weakening laws of slip zone soils during wetting–drying cycles based on fractal theory : a case study in the Three Gorges Reservoir (China) ». Acta Geotechnica 15, n^o 7 (5 décembre 2019) : 1909–23. http://dx.doi.org/10.1007/s11440-019-00894-8.

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Amarsid, Lhassan, Ahmad Awdi, Abdoulaye Fall, Jean-Noël Roux et François Chevoir. « Viscous effects in sheared unsaturated wet granular materials ». Journal of Rheology 68, n^o 4 (20 mai 2024) : 523–37. http://dx.doi.org/10.1122/8.0000824.

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We report on experiments and discrete element simulations of homogeneous, simple, normal stress-controlled, shear flows of model unsaturated granular materials: assemblies of frictional spherical particles bonded by a small quantity of a wetting liquid. The rheology of such unsaturated granular materials in the dense flow regime was characterized in recent publications of our group, in terms of internal friction coefficient μ∗ and solid fraction Φ, depending on the reduced pressure P∗ comparing capillary forces to controlled normal stress, and on inertial number I. The present study extends this description to the influence of the liquid viscosity on material rheology in the low saturation regime. The quantitative agreement of simulations with experiments is confirmed for the quasistatic limit, and our numerical results, despite some quantitative differences, capture the correct trends in the regime dominated by viscous forces. Rheological properties are then determined, to a large extent, by the same viscous numberIv as used to formulate constitutive laws in saturated, dense suspensions. More precisely, a visco-inertial numberJ, combining Iv with inertial number I as J=Iv+2I2, appears apt to describe the rheological laws, as expressed by the internal friction coefficient and the solid fraction, measured in the laboratory or in the simulations, as well as the numerically investigated internal state of the flowing material. Simulations provide insight into the role of viscous forces: predominantly tensile, they contribute to the increase with shear rate of the macroscopic friction coefficient μ∗ through a direct positive contribution to shear stress, a negative contribution to normal stresses (enhancing the strength of the contact network), and microstructural changes affecting the network of contacts and liquid bridges.

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Zhai, Yaming, Wuerkaixi Kurexi, Ce Wang, Chengli Zhu, Zhanyu Zhang et Yi Li. « Modelling Soil Water Infiltration and Wetting Patterns in Variable Working-Head Moistube Irrigation ». Agronomy 13, n^o 12 (4 décembre 2023) : 2987. http://dx.doi.org/10.3390/agronomy13122987.

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Moistube irrigation is an efficient method that accurately irrigates and fertilizes agricultural crops. Investigation into the mechanisms of infiltration behaviors under an adjusted working head (WKH) benefits a timely and artificially regulating moisture condition within root zones, as adapted to evapotranspiration. This study explores the laws of Moistube irrigated soil water movement under constant and adjusted working heads. Lysimeter experiments were conducted to measure Moistube irrigation cumulative infiltration, infiltration rate, and to observe wetting front area and water content distribution using digital image processing and time domain reflectometry, respectively. Treatments of constant heads (0, 1, and 2 m), increasing heads (0 to 1, 0 to 2 and 1 to 2 m) and deceasing heads (1 to 0, 2 to 0 and 2 to 1 m) were designed. The results show that (1) under constant heads, the cumulative infiltration increases linearly over time. The infiltration rate and cumulative infiltration are positively correlated with the pressure head. When WKH is increased or decreased, the infiltration rate and cumulative infiltration curves significantly change, followed by a gradual stabilization. The more the head is increased or decreased, the more evident this tendency will be. (2) When WKH is increased, the wetting front migration rate and the wetted soil moisture content marked increase; when WKH is decreased, the wetting front migration rate sharply decelerates, and the water content of the wetted soil slowly grows. They both tend to equilibrium with time. (3) By regarding the same cumulative infiltration of increased WKH and constant WKH treatments as a similar initial condition, we proposed a cumulative infiltration empirical model for Moistube irrigation under variable working head. Additionally, we treat the Moistube as a clayey porous medium and construct a HYDRUS-2D numerical model to predict the infiltration behaviors under variable WKH. The validity of the two models were well proven, with MRE and NRMSE close to 0 and NSE greater than 0.867, indicating good agreements with the experimental results. This model breaks through the limitation of constant boundary of traditional numerical model and applies variable head boundary to the boundary of the Moistube pipe, which can also effectively simulate the response mechanism of Moistube irrigation to variable WKH. The research results further confirmed the feasibility of manually adjusting the WKH to regulate the discharge of the Moistube pipe and soil moisture state. Based on the HYDRUS-2D numerical model simulation results and the root distribution and water demand of typical facility crops, the selection range of placement depth and the adjustable range of WKH of Moistube irrigation were proposed. The research results provide a theoretical reference for manual adjustment or automatic control of Moistube irrigation WKH to adapt to real-time crop water demand in agricultural production.

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Wei, Hsien-Hung, Heng-Kwong Tsao et Kang-Ching Chu. « Slipping moving contact lines : critical roles of de Gennes’s ‘foot’ in dynamic wetting ». Journal of Fluid Mechanics 873 (20 juin 2019) : 110–50. http://dx.doi.org/10.1017/jfm.2019.352.

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In the context of dynamic wetting, wall slip is often treated as a microscopic effect for removing viscous stress singularity at a moving contact line. In most drop spreading experiments, however, a considerable amount of slip may occur due to the use of polymer liquids such as silicone oils, which may cause significant deviations from the classical Tanner–de Gennes theory. Here we show that many classical results for complete wetting fluids may no longer hold due to wall slip, depending crucially on the extent of de Gennes’s slipping ‘foot’ to the relevant length scales at both the macroscopic and microscopic levels. At the macroscopic level, we find that for given liquid height $h$ and slip length $\unicode[STIX]{x1D706}$, the apparent dynamic contact angle $\unicode[STIX]{x1D703}_{d}$ can change from Tanner’s law $\unicode[STIX]{x1D703}_{d}\sim Ca^{1/3}$ for $h\gg \unicode[STIX]{x1D706}$ to the strong-slip law $\unicode[STIX]{x1D703}_{d}\sim Ca^{1/2}\,(L/\unicode[STIX]{x1D706})^{1/2}$ for $h\ll \unicode[STIX]{x1D706}$, where $Ca$ is the capillary number and $L$ is the macroscopic length scale. Such a no-slip-to-slip transition occurs at the critical capillary number $Ca^{\ast }\sim (\unicode[STIX]{x1D706}/L)^{3}$, accompanied by the switch of the ‘foot’ of size $\ell _{F}\sim \unicode[STIX]{x1D706}Ca^{-1/3}$ from the inner scale to the outer scale with respect to $L$. A more generalized dynamic contact angle relationship is also derived, capable of unifying Tanner’s law and the strong-slip law under $\unicode[STIX]{x1D706}\ll L/\unicode[STIX]{x1D703}_{d}$. We not only confirm the two distinct wetting laws using many-body dissipative particle dynamics simulations, but also provide a rational account for anomalous departures from Tanner’s law seen in experiments (Chen, J. Colloid Interface Sci., vol. 122, 1988, pp. 60–72; Albrecht et al., Phys. Rev. Lett., vol. 68, 1992, pp. 3192–3195). We also show that even for a common spreading drop with small macroscopic slip, slip effects can still be microscopically strong enough to change the microstructure of the contact line. The structure is identified to consist of a strongly slipping precursor film of length $\ell \sim (a\unicode[STIX]{x1D706})^{1/2}Ca^{-1/2}$ followed by a mesoscopic ‘foot’ of width $\ell _{F}\sim \unicode[STIX]{x1D706}Ca^{-1/3}$ ahead of the macroscopic wedge, where $a$ is the molecular length. It thus turns out that it is the ‘foot’, rather than the film, contributing to the microscopic length in Tanner’s law, in accordance with the experimental data reported by Kavehpour et al. (Phys. Rev. Lett., vol. 91, 2003, 196104) and Ueno et al. (Trans. ASME J. Heat Transfer, vol. 134, 2012, 051008). The advancement of the microscopic contact line is still led by the film whose length can grow as the $1/3$ power of time due to $\ell$, as supported by the experiments of Ueno et al. and Mate (Langmuir, vol. 28, 2012, pp. 16821–16827). The present work demonstrates that the behaviour of a moving contact line can be strongly influenced by wall slip. Such slip-mediated dynamic wetting might also provide an alternative means for probing slippery surfaces.

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Kanduč, Matej, et Roland R. Netz. « From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces ». Proceedings of the National Academy of Sciences 112, n^o 40 (21 septembre 2015) : 12338–43. http://dx.doi.org/10.1073/pnas.1504919112.

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Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can—if strong enough—give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface–surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles.

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Xu, Hanwen, Zhiang Liu, Man Yu et Xuning Sun. « How to Live the Advertisement of Family Planning Products in the Age of "Sex" Change ». International Journal of Education and Humanities 6, n^o 2 (18 décembre 2022) : 173–76. http://dx.doi.org/10.54097/ijeh.v6i2.3680.

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In China, advertising of family planning products rarely transmits the information of family planning products to the public through mass platforms such as television. In addition to policy prohibitions, it is now mostly the pressure of public opinion. Another reason is that the TV advertising investment is large, and the coincidence rate between the TV audience and the current major consumers of family planning products is not high, so it is not necessary for advertisers to put advertisements on the TV platform. Although the advertising of family planning products often wanders on the edge of the prohibition of advertising laws and regulations, there is no way to walk along the river without wetting your shoes. If you don't pay more attention to the advertising of family planning products, it will violate the advertising laws and regulations, which will have a negative impact on the enterprise as well as the society. Although both good and bad advertisements can bring a lot of traffic to enterprises, from the perspective of advertising law and professional ethics, the publicity effect of an excellent advertising work is far greater than that of an advertisement. Advertising should not ignore the moral value of the advertising works in order to pursue the publicity effect. Although it is an advertisement for family planning products, creative breakthroughs should be made as far as possible during the production, rather than violations or even illegal acts. The advertising of family planning products should conform to the advertising laws and regulations, and the advertising producers of family planning products should uphold professional ethics, so as not to let the advertising of family planning products become "rotten", and the era of "sex" change for the sake of this is another layer of public fear of the advertising of family planning products. This article combines the development of family planning product advertising with its gains and losses to make an advertising creation plan suitable for the survival in the age of "sex" color change, summarizes the future development direction of this kind of advertising, and at the same time, finds a solution to the current predicament and existing problems of this kind of advertising.

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Peng, Youliang, Liangjun Fei, Renming Xue, Fangyuan Shen, Runqiao Zhen et Qian Wang. « Effect of Muddy Water Characteristics on Infiltration Laws and Stratum Compactum Soil Particle Composition under Film Hole Irrigation ». Agriculture 14, n^o 8 (16 août 2024) : 1377. http://dx.doi.org/10.3390/agriculture14081377.

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To investigate the impact of sediment on water infiltration and soil structure under muddy water irrigation conditions, indoor muddy water film hole infiltration experiments were conducted. Four different muddy water sediment concentrations (3%, 6%, 9%, 12%) and four typical sediment particle size distributions (which were quantified by the physical clay content with a particle size of less than 0.01 mm, d0.01: 9.13%, 16.46%, 27.34%, 44.02%) were employed to examine how muddy water properties affect infiltration law and the stratum compactum soil particle composition under film hole irrigation. The results showed that as the muddy water sediment concentration and physical clay content increased, the wetting front migration distance, cumulative infiltration amount, and soil water content gradually decreased simultaneously. The Kostiakov infiltration model effectively captured the changes in soil water infiltration during muddy water film hole irrigation, exhibiting a strong fit with a high coefficient of determination (R2 > 0.9). With higher muddy water sediment concentration, the deposition layer thickness increases within the same infiltration time. Conversely, higher physical clay content leads to a decrease in deposition layer thickness. The characteristics of the muddy water have a significant impact on the particle composition of the soil in the stratum compactum caused by film hole irrigation. The deposition layer has a lower relative content of fine soil particles compared to muddy water, but this content increases with higher muddy water sediment concentration and physical clay content. In the stranded layer soil, fine particles have a higher relative content than the original soil. Fine particle content increases notably with higher muddy water sediment concentration and physical clay content. The stranded layer soil particles exhibit a higher fractal dimension than the original soil, and as the infiltrated soil layer depth increases, the soil fractal dimension decreases until it matches the original soil. The fractal dimension increased with the increase in muddy water sediment concentration and physical clay content in muddy water irrigation conditions under the same soil layer depth. This research findings could serve as a theoretical foundation for understanding soil water movement under muddy water irrigation conditions.

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Murillo, J., S. Martinez-Aranda, A. Navas-Montilla et P. García-Navarro. « Adaptation of flux-based solvers to 2D two-layer shallow flows with variable density including numerical treatment of the loss of hyperbolicity and drying/wetting fronts ». Journal of Hydroinformatics 22, n^o 5 (17 juillet 2020) : 972–1014. http://dx.doi.org/10.2166/hydro.2020.207.

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Abstract An important feature of the two-layer shallow flow model is that the resulting system of equations cannot be expressed in conservation-law form. Here, the HLLS and ARoe solvers, derived initially for systems of conservation laws, are reformulated and applied to the two-layer shallow flows in a great variety of problems. Their resulting extension and combination allows us to overcome the loss of the hyperbolic character, ensuring energy or exactly balanced property, guarantees positivity of the solution, and provides a correct drying/wetting advance front without requiring tuning parameters. As a result, in those cases where the rich description of internal and external waves cannot be provided by the ARoe solver, HLLS is applied. Variable density is considered in each layer as a result of a bulk density driven by the mixture of different constituents. A wide variety of test cases is presented confirming the properties of this combination, including exactly balanced scenarios in subcritical and subcritical-transcritical scenarios, dam-break problems over bed variations and wet/dry fronts, non-hyperbolic conditions, transcritical exchange flow with loss of hyperbolicity. Despite the complexity of the test cases presented here, accurate and stable simulations are guaranteed, ensuring positivity of the solution without decreasing the time step.

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Incollingo, Sara, Alessio Ferrari et Guido Musso. « Numerical investigation on water exchange of shale samples ». E3S Web of Conferences 195 (2020) : 02025. http://dx.doi.org/10.1051/e3sconf/202019502025.

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Interest in the hydraulic and mechanical characterization of shales has grown in recent years, because of their application in the context of energy geotechnics. In the frame of nuclear waste disposal shales are considered as host formations for the placements of nuclear waste at high depths. In the frame of hydrocarbon production they are considered as unconventional reservoirs, from which extracting natural gas. Understanding how fluids flow through shales is then a key aspect for both fields of application. This paper focuses on the analysis of the transport of water vapour through laboratory samples. After reviewing the balance and flow laws that govern the transport of fluid in unsaturated porous media, a simplified model is put forward. The model was implemented in a commercial finite element code, and it was used to reproduce the results of a literature study on wetting and drying of Opalinus Clay shale samples, imposed through the vapour equilibrium technique. Back analysis of the water content and volume strains of these specimens suggests that existing models underestimate the actual flow rate of water vapour which takes place at low suctions. The current interpretation also seems to be consistent with microstructural investigations on the interconnection between large pores of this material.

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Liu, Dingzhu, Jinbo Tang, Hao Wang, Yang Cao, Nazir Ahmed Bazai, Huayong Chen et Daochuan Liu. « A New Method for Wet-Dry Front Treatment in Outburst Flood Simulation ». Water 13, n^o 2 (18 janvier 2021) : 221. http://dx.doi.org/10.3390/w13020221.

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When utilizing a finite volume method to predict outburst flood evolution in real geometry, the processing of wet-dry front and dry cells is an important step. In this paper, we propose a new approach to process wet-dry front and dry cells, including four steps: (1) estimating intercell properties; (2) modifying interface elevation; (3) calculating dry cell elevations by averaging intercell elevations; and (4) changing the value of the first term of slope limiter based on geometry in dry cells. The Harten, Lax, and van Leer with the contact wave restored (HLLC) scheme was implemented to calculate the flux. By combining the MUSCL (Monotone Upstream–centred Scheme for Conservation Laws)-Hancock method with the minmod slope limiter, we achieved second-order accuracy in space and time. This approach is able to keep the conservation property (C-property) and the mass conservation of complex bed geometry. The results of numerical tests in this study are consistent with experimental data, which verifies the effectiveness of the new approach. This method could be applied to acquire wetting and drying processes during flood evolution on structured meshes. Furthermore, a new settlement introduces few modification steps, so it could be easily applied to matrix calculations. The new method proposed in this study can facilitate the simulation of flood routing in real terrain.

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Xu, Haoping, Wenyuan Xu, Xuewen Zheng et Kai Cao. « A Multistage Analysis of Asphalt Binder Nanocrack Generation and Self-Healing Behavior Based on Molecular Dynamics ». Polymers 14, n^o 17 (30 août 2022) : 3581. http://dx.doi.org/10.3390/polym14173581.

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In order to study the characteristics and laws of nanocrack generation and self-healing behavior of asphalt materials under tensile action, the molecular dynamics (MD) method was used to simulate the continuous “tensile failure—self-healing” process, and this study remedies the shortcomings of existing experimental and observational methods. It is found that the MD-reproduced formation process of asphalt binder nanocrack contains four stages: “tensile extension”, “nanocrack generation”, “crack adding, expanding and penetrating” and “cracking failure”. The influence of tensile conditions on the tensile cracking simulation of an asphalt binder model was analyzed, and it was found that low temperature and high loading rate would increase the tensile strength of the asphalt binder model. In addition, the MD-reproduced healing process of asphalt binder nanocracks can be divided into four stages: “surface approach”, “surface rearrangement”, “surface wetting” and “diffusion”, which is similar to the healing process of polymers. Finally, from the perspective of energy change, the change rule of dominant van der Waals energy in the self-healing process was studied. Based on the existing research, the influence of damage degree on the healing performance of asphalt binder and its mechanism were further analyzed. The research results further enrich the theoretical research on microlevel cracking and healing of asphalt materials, and have certain theoretical value for the further development of self-healing asphalt materials.

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Tang, Ke, Xue-song Mao, Qian Wu, Longqi Liu, Ying Zhao, Wan-jun Huang et Jian-xun Zhang. « The Concrete Performance with Iron Tailings Sand Modified by Polypropylene Fibers under Aggressive Environment ». Advances in Materials Science and Engineering 2020 (9 décembre 2020) : 1–16. http://dx.doi.org/10.1155/2020/4368592.

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This paper aimed to explore the performance of concrete with iron tailings sand modified by polypropylene fibers under aggressive environment. Three kinds of concrete (ordinary concrete, concrete with iron tailings sand (ITS), and concrete with ITS modified by polypropylene fibers) were exposed to drying-wetting cycles in 5% Na2SO4 solution for 28, 56, 84, 112, and 140 days. The performance, such as pores distribution, crack width, corrosion products, mass variation, expansion variation, compressive strength, flexural strength, and the diffusion of sulfate ion were measured at regular time intervals during the whole exposure period to describe the associated evolution laws. The results show that, in the process of the corrosion of sodium sulfate solution, the formation of gypsum and ettringite (AFT) has an important impact on the harmful pores (>0.1 μm), cracks, mass variation, expansion variation, compressive strength, and flexural strength of the three concrete. Polypropylene fibers can refine the pores development and inhabit the crack development of the concrete with ITS, further alleviating the rate of sulfate ion attack on concrete and the rate of increase of corrosion products, so that the mass variation, the expansion variation, and the reduction of compressive strength and flexural strength can be limited effectively. Furthermore, in the concrete with ITS modified by 0.1% polypropylene fibers, the content of sulfate ions diffused is always the lowest.

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Anisimova, Mariya A., Anna G. Knyazeva, Elena N. Korosteleva et Sergey E. Povernov. « Peculiarities of sintering CuO-Al and TiO2-Al powder compositions under conditions of controlled heating ». Himičeskaâ fizika i mezoskopiâ 26, n^o 4 (2024) : 457–70. https://doi.org/10.62669/17270227.2024.4.38.

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Composites obey numerous advantages over traditional materials in various industries in various industries because of their unique properties. The work is aimed at studying the peculiarities of the production of composites under controlled heating conditions and in situ formation of strengthening particles. The experimental results of the most commonly used method that is vacuum sintering for producing composites from aluminium and copper oxide powders as well as aluminium and titanium oxide under the conditions of controlled heating are presented. The distinctive features of the behaviour of the powder systems (oxide + aluminium matrix) depending on oxide type and sintering temperature are shown. Volumetric changes, non-equilibrium phase composition and the problem of poor wetting of initial oxide particles by aluminium melt, which may be the cause of the phase formation delay, were revealed. Diffusion problems illustrating the reasons of possible delay in the formation of diffusion transition layers were analyzed. The analytical solutions of the problems are presented. A model of the diffusion phase formation process is proposed. The model takes into account the condition of non-ideal contact between particles and matrix. Quasi-stationary approximation allows constructing analytical solutions for the concentration distribution in phases. The interface boundary conditions give the coupled ordinary differential equations allowing us to find the laws of motion of the boundaries separating the phases. The equations were solved numerically. The phase retardation is demonstrated when non-ideal contact takes place.

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Chen, Xupeng, Zhuowen Sun et Jianyong Pang. « A Research on Durability Degradation of Mineral Admixture Concrete ». Materials 14, n^o 7 (2 avril 2021) : 1752. http://dx.doi.org/10.3390/ma14071752.

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In order to study the degradation laws and mechanisms of admixture concretes with single-added SO42− and composite of Mg2+ and SO42−, respectively, the durability tests were conducted on three types of mineral admixture concretes (concretes with single-added metakaolin (MK), single-added ultra-fine fly ash (UFA), and composite of metakaolin and ultra-fine fly ash (MF), and one reference concrete. In these tests, the 10% Na2SO4 solution and the 10% MgSO4 solution were used as the erosion medium, and the drying-wetting circle method was applied. It can be seen from the compressive tests and grey relational analysis that the MK admixture can improve the anti-Na2SO4-erosion capability of the concrete significantly, but weaken its anti-MgSO4-erosion capability; the UFA admixture can improve both the anti-Na2SO4-erosion and the anti-MgSO4-erosion capability of the concrete; and the composite admixture has superimposed effects and can enhance erosion resistance against these two erosion mediums. The phase composition and the changes of the macro morphology and the micro structure during the erosion process caused by mono sulfate ions and complex ions has been observed through X-ray diffraction (XRD), FTIR spectrum (FTIR), and scanning electron microscope (SEM), based on which it was determined that the erosion of single-added SO42− ions can produce erosive outputs of ettringite, gypsum, and mirabilite in the concrete, and cause corner scaling or deformation. Mg2+ and SO42− reacted in the concrete and produced brucite, M-S-H, ettringite, and gypsum, etc. The erosion of complex ions can cause scaling of the cement mortar and aggregate from the surface or the desquamation of corners.

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Park, Joung-Man, Dong-Jun Kwon, Zuo-Jia Wang, Joon-Hyung Byun, Hyung-Ik Lee, Jong-Kyoo Park et Lawrence K. DeVries. « Novel method of electrical resistance measurement in structural composite materials for interfacial and dispersion evaluation with nano- and hetero-structures ». MRS Proceedings 1700 (2014) : 37–46. http://dx.doi.org/10.1557/opl.2014.537.

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ABSTRACTInterest in development in the use of nanoparticles in structural composites for the improvement of thermal conductivity, mechanical properties and electrical properties has recently stimulated some research efforts. Such improvements require the introduction of functional groups and the proper selection and concentration of the nanoparticles, as well as their uniform dispersion. The identification and verification of uniformity of dispersion is very important in the efficient processing for improved performance. Recently, new methods for studying and evaluating the interfacial properties between the reinforcing fibers and the epoxy matrix, have been developed. Distinct from FE-SEM observation, electrical resistance methods are being developed which can be applied for to measure interfacial shear strength (IFSS) and degree of dispersion. The main principle, on which the electrical resistance measurement is based, is Kirchhoff’s laws, which considers conductive materials as electrical circuits. In this research, the self sensing character of the conductive carbon nanotubes (CNT) and conventional carbon reinforcing fibers has been successfully used as a method for evaluating the dispersion of nanoparticles and interfacial adhesion. The electrical resistance in these composites was observed to be dependent on differences in wetting and interfacial adhesion between matrix and fillers. In summary, a correlation was observed between the electrical resistance and dispersion and degree of cure. It is felt that these methods, along with the electro-micromechanical methods, provide valuable tools for investigating the role of interfacial behavior on thermal conductivity, electrical and mechanical properties. Optical observations by FE-SEM of degree of dispersion and interfacial adhesion are consistent with the electrical resistance results. Additionally, it may be possible to use electrical resistance circuit analysis to detect the location of and extent of micro-damage within composite materials.

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Zuluaga, Elizabeth, et Larry W. Lake. « Modeling of Experiments on Water Vaporization for Gas Injection Using Traveling Waves ». SPE Journal 13, n^o 02 (1 juin 2008) : 248–56. http://dx.doi.org/10.2118/91393-pa.

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Summary Dry gas injected into wells will vaporize water from near the wellbore. The vaporization starts from the well and proceeds outward. Gas flowing to producers is in equilibrium with the reservoir brine, but water will be vaporized because the pressure drop that occurs toward the wellbore increases the ability of the gas to contain water. Thus, there are different mechanisms for injection and production. For both gas injection and gas production, vaporization concentrates solids in the brine that will precipitate into the formation when sufficiently concentrated. This paper reports on a combined experimental and theoretical analysis on the vaporization portion of this problem for dry gas injection. Experiments have been performed previously to determine the rate of water vaporization from Berea core samples at uniform initial water saturation (Zuluaga and Monsalve 2003). These experiments were performed by injecting dry methane into core samples that contained immobile water to represent water vaporization in a gas injector. Effluent water concentration curves showed two vaporization periods: a constant rate period and a falling rate period. The existence of a constant rate period means that the mass transfer within the core is occurring at conditions of local equilibrium. We interpret the falling rate period as the result of a moving capillary transition zone in which the amount of water vaporized decreases slowly because of capillary pressure effects. The falling rate period is the consequence of capillary imbibition of a wetting phase at very small saturation. We interpret the vaporization results with two traveling wave solutions. The first, which can be solved analytically, assumes that the capillary diffusion coefficient, D, and the volume fraction of water in the gaseous phase, Cwg, are constant. For this case, the results of the traveling wave solution are matched to the results of laboratory experiments by adjusting D. The second traveling-wave solution must be solved through numerical integration. In this case, the relative permeability scaling exponent is adjusted to match the laboratory experiments. The fitting provides insights into the nature of wetting phase flow at small saturation. Lastly, the experimental and mathematical procedure discussed in this paper is certainly a new method to obtain relative permeability exponents for the wetting phase at very low values of wetting-phase saturation (down to theoretically zero values). Introduction Dodson and Standing (1944) performed the first experimental study to determine the amount of water vaporized at different pressures and temperatures using PVT cells. They found that the rate of water vaporization increases with temperature and decreases with pressure and solids content in the water. Bette and Heinemann (1989) confirmed vaporization in cores taken from gas injectors in the Arun field. The water content in these cores was very small; in some cases the cores were completely dry. Kamath and Laroche (2000) and Mahadevan and Sharma (2005) performed experiments in permeable media that were initially fully saturated with brine. When gas was used as a displacing fluid, there were two flow regimes: a displacement regimen followed by a vaporization regimen. Using gas as both a displacing agent and a drying agent makes the study of the vaporization alone difficult. Zuluaga and Monsalve (2003) performed vaporization experiments in permeable media at outlet pressures ranging from 1,000 to 2,000 psig and temperatures from 194 to 212°F. The experiments were not displacements, the initial water saturation being set as a nonflowing saturation by a porous plate method. Fig. 1 shows the rate of water production for an experiment performed at 1,500 psig outlet pressure and 194°F. The experiments were perfomed by measuring the accumulated mass of water as it exited the medium and as it was sorbed on a silica substrate. The rate shown in Fig. 1 was obtained by differentiating the cumulative data with respect to time. Two vaporization periods occur: a constant rate period and a falling rate period. These two periods of water vaporization have been extensively reported for drying of solids (ceramic, wood) in the chemical engineering literature (Allerton 1949; Perry and Green 1984; Mujumdar 1987). Our goal is to understand and quantify this behavior. There has been little modeling of water vaporization for flow through permeable media. Most approaches have been based on modifications of existing compositional simulators by incorporating water as a component in the equation of state (Bette and Heinemman 1989; Kurihara et al. 2000). The effect of salinity has been included either with salinity-dependent solubility tables (Morin and Montel 1995) or by adding salt as a component in an equation of state (Lee and Lin 1999). Some have modified material balance equations to account for water vaporization (Humphreys 1991). This study formulates and obtains solutions to the conservational laws describing water vaporization. We study the vaporization for gas injectors as a traveling wave in which capillary imbibition occurs. The solution obtained allows predictions of remaining water saturation with distance and time during both the constant and the falling rate periods (Zuluaga 2005).

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Chang, Baoxin, Benjamin Wherley, Jacqueline Aitkenhead-Peterson, Nadezda Ojeda, Charles Fontanier et Philip Dwyer. « Effect of Wetting Agent on Nutrient and Water Retention and Runoff from Simulated Urban Lawns ». HortScience 55, n^o 7 (juillet 2020) : 1005–13. http://dx.doi.org/10.21273/hortsci14982-20.

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Wetting agents have been widely used in the turf industry for ameliorating hydrophobic soil conditions and improving water use efficiency. However, limited information is available regarding potential benefits of wetting agents on fine textured soil lawns where wettable soils are commonly found, because most prior studies have been conducted in sand-based turf systems. This 2-year field study evaluated the potential for wetting agents to improve turf quality, as well as to reduce runoff losses of water and nutrients from st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] lawns. Over two seasons, turfgrass quality, percent green cover, and soil moisture in plots were evaluated in response to wetting agent and fertilizer treatments. During precipitation events, total runoff volumes were measured, as well as total export of nutrients including NO3-N, NH4-N, total dissolved N, dissolved organic N, dissolved organic C, and PO4-P. No runoff was detected from any treatments when precipitation was less than 13 mm. St. augustinegrass turfgrass quality and soil moisture were slightly improved by wetting agent and fertilizer treatments during the study, but no significant effects of either of the treatments were found on runoff volumes or nutrient exports. Although turf was managed under deficit irrigation levels of 0.3 × reference evapotranspiration, irrigation events were not withheld due to rainfall, and thus, little to no drought stress was observed during the study.

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Hunt, Allen, Boris Faybishenko, Behzad Ghanbarian, Markus Egli et Fang Yu. « Predicting Water Cycle Characteristics from Percolation Theory and Observational Data ». International Journal of Environmental Research and Public Health 17, n^o 3 (23 janvier 2020) : 734. http://dx.doi.org/10.3390/ijerph17030734.

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The fate of water and water-soluble toxic wastes in the subsurface is of high importance for many scientific and practical applications. Although solute transport is proportional to water flow rates, theoretical and experimental studies show that heavy-tailed (power-law) solute transport distribution can cause chemical transport retardation, prolonging clean-up time-scales greatly. However, no consensus exists as to the physical basis of such transport laws. In percolation theory, the scaling behavior of such transport rarely relates to specific medium characteristics, but strongly to the dimensionality of the connectivity of the flow paths (for example, two- or three-dimensional, as in fractured-porous media or heterogeneous sediments), as well as to the saturation characteristics (i.e., wetting, drying, and entrapped air). In accordance with the proposed relevance of percolation models of solute transport to environmental clean-up, these predictions also prove relevant to transport-limited chemical weathering and soil formation, where the heavy-tailed distributions slow chemical weathering over time. The predictions of percolation theory have been tested in laboratory and field experiments on reactive solute transport, chemical weathering, and soil formation and found accurate. Recently, this theoretical framework has also been applied to the water partitioning at the Earth’s surface between evapotranspiration, ET, and run-off, Q, known as the water balance. A well-known phenomenological model by Budyko addressed the relationship between the ratio of the actual evapotranspiration (ET) and precipitation, ET/P, versus the aridity index, ET0/P, with P being the precipitation and ET0 being the potential evapotranspiration. Existing work was able to predict the global fractions of P represented by Q and ET through an optimization of plant productivity, in which downward water fluxes affect soil depth, and upward fluxes plant growth. In the present work, based likewise on the concepts of percolation theory, we extend Budyko’s model, and address the partitioning of run-off Q into its surface and subsurface components, as well as the contribution of interception to ET. Using various published data sources on the magnitudes of interception and information regarding the partitioning of Q, we address the variability in ET resulting from these processes. The global success of this prediction demonstrated here provides additional support for the universal applicability of percolation theory for solute transport as well as guidance in predicting the component of subsurface run-off, important for predicting natural flow rates through contaminated aquifers.

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