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A benchmark problem is formulated which is well suited for the validation of mesoscopic phase-field models for grain-boundary migration in polycrystals. First, an analytical steady-state solution of the sharp moving boundary problem is derived for a symmetric lamellar structure, which is valid for arbitrary bulk driving forces and triple junction angles. Characteristic quantities are identified to reduce the parameter space which in turn allows a systematic comparison of simulations and analytical results. Various multiphase-field (MPF) formulations are compared which approximate the sharp interface problem in terms of a diffuse regularization. An interfacial thickness convergence study reveals that the model error is largely dependent on the ratio of bulk to interfacial stabilizing force as well as the underlying model formulation. An additional grid convergence study highlights the efficiency of a more advanced discretization scheme. The results can be used to guide the selection of appropriate models and to estimate the interface thickness and spatial resolution required to achieve a given accuracy target. The post-processing framework consists of a fully automated determination of well-defined metrics from the phase field simulation data, eliminating human bias and facilitating reproducibility. The corresponding code is made openly available to assist the materials science and engineering community in validating MPF, multi-order parameter and similar model developments. We believe that this work provides a reliable benchmark procedure to better understand the potentials and limitations of current MPF models as well as alternative approaches. [ABSTRACT FROM AUTHOR]

This study seeks to investigate the influence of cement and Arabic gum on the physico-mechanical and microstructural properties of cementitious composites. The influence of varying quantities of Arabic gum on the hydration, fluidity, mechanical performance and microstructure of cement paste was investigated. The influence of Arabic gum on slant shear performance and capillary water absorption was also investigated. The results indicate that the workability of cement was diminished as a result of the ability of Arabic gum to make the cement paste cohesive. It is evident that when the gum Arabic concentration increases from 147 to 174 mm, the resultant slump value for various w/b ratios drops. The adsorption characteristics showed that for a 15 mg g ^−1 dosage at 60, 45, 30, and 15 min, respectively, 1.43, 1.32, 1.25, and 1.03 mg g ^−1 are achieved. For 1% gum Arabic substitution, the highest flexural strength percentage growth is achieved at 38.46%, 23.74%, and 17.29% at 7, 14, and 28 days, respectively. In addition, the inclusion of Arabic gum improved the slant shear strength of cement composite, making it ideal for use as a building repair material with significant application potential. Experiments on the bonding behavior of the produced cementitious composite with the old mortar reveal that the shear bond strength was greatly increased, demonstrating the compatibility between the old and new cement composites. The microstructure and the porosity of the cement matrix also showed denser and compact matrix making them durable to attain better service life.

A two-mode phase field crystal (PFC) model is employed to investigate the equilibrium configurations of a range of grain boundaries in fcc-structured materials. A total of 80 different symmetrical tilt grain boundaries are evaluated by PFC simulations in 3D and the results are shown to agree well with data taken from the literature, both regarding the variation of grain boundary energy and also in terms of the resulting grain boundary structures. This verification complements existing PFC studies which are almost exclusively focused either on grain boundaries found in 2D systems or in bcc lattices in 3D. The present work facilitates application of PFC in the analysis of grain boundary mechanics in an extended range of materials, in particular such mechanics that take place at extended time scales not tractable for molecular dynamics (MD) simulations. In addition to the verification of predicted grain boundary energies and structures, wavelet transforms of the density field are used in the present work to obtain phase fields from which it is possible to identify grain boundary fluctuations that provide the means to evaluate grain boundary stiffness based on the capillarity fluctuation method. It is discussed how PFC provides benefits compared to alternative methods, such as MD simulations, for this type of investigations. [ABSTRACT FROM AUTHOR]

Liquid properties are relevant for the understanding of fundamental and applied sciences. Among these properties, those that can be traced back and explained through the surface tension are particularly interesting to study and reconstruct in educational terms. Traditional educational treatment of surface tension is often obscure or too complex, sometimes superficial or completely neglected. The aim of the research here described is to discuss in detail a mesoscopic model of liquids and show quantitative results obtained by a computer simulation approach. Looking at the educational aspect, the main advantage of this approach is that it allows the student/teacher to control the simulation parameters and understand step by step how the physical quantities influence the investigated system. Some of the main properties of capillarity phenomena (meniscus formation, capillary rise, etc) are analysed through the simulation of a liquid in a tray with a capillary tube inside, where a value of surface tension is obtained. [ABSTRACT FROM AUTHOR]

This study is concerned with the large time behaviour of the three-dimensional isentropic compressible Navier–Stokes–Korteweg equations, which are used to model viscous and compressible fluids with internal capillarity. Based on the fact that the rarefaction wave is nonlinearly stable to the one-dimensional isentropic compressible Navier–Stokes–Korteweg equations, the planar rarefaction wave to the three-dimensional isentropic compressible Navier–Stokes–Korteweg equations is first constructed. Then it is shown that the planar rarefaction wave is asymptotically stable in the case that the initial data are a suitably small perturbation of the planar rarefaction wave and the strength of the rarefaction wave is small. The proof is based on the delicate energy method. The result indicate that the planar rarefaction wave of the inviscid Euler system is stable for the three-dimensional isentropic compressible fluids with physical viscosities and internal capillarity. [ABSTRACT FROM AUTHOR]

The present paper deals with the Cauchy problem of a compressible generic two-fluid model with capillarity effects in any dimension N ⩾ 2. We first study the unique global solvability of the model in spaces with critical regularity indices with respect to the scaling of the associated equations. Due to the presence of the capillary terms, we exploit the parabolic properties of the linearized system for all frequencies which enables us to apply contraction mapping principle to show the unique global solvability of strong solutions close to a stable equilibrium state. Furthermore, under a mild additional decay assumption involving only the low frequencies of the data, we establish the optimal time decay rates for the constructed global solutions. [ABSTRACT FROM AUTHOR]

The article presents experiments that emphasize surface-tension force and explain show the force is exerted on an external object, its magnitude and its direction. The first experiment used a circular wire frame, wherein the two ends of a piece thread are connected to the circumference of the frame. The frame is dipped into soap solution. Two threads were used in the second experiment. A rectangular wire frame with a small and light wire slider is made in the third experiment. The third experiment showed that the force exerted by any of the films does not defend on their area but on their common border with the slider.

This paper reports on the effective use of capillary self-alignment for low-cost and time-efficient assembly of heterogeneous foil components into a smart electronic identification label. Particularly, we demonstrate the accurate (better than 50 µm) alignment of cm-sized functional foil dies. We investigated the role played by the assembly liquid, by the size and the weight of assembling dies and by their initial offsets in the self-alignment performance. It was shown that there is a definite range of initial offsets allowing dies to align with high accuracy and within approximately the same time window, irrespective of their initial offset. [ABSTRACT FROM AUTHOR]

The paper focuses on a model describing the spreading of an insoluble surfactant on a thin viscous film with capillary effects taken into account. The governing equation for the film height is a degenerate parabolic of fourth order and coupled to a second order parabolic equation for the surfactant concentration. It is shown that nonnegative weak solutions exist [ABSTRACT FROM AUTHOR]

Atmospheric pressure ionization waves (IWs) propagating in flexible capillary tubes are a unique way of transporting a plasma and its active species to remote sites for applications such as biomedical procedures, particularly in endoscopic procedures. The propagation mechanisms for such IWs in tubes having aspect ratios of hundreds to thousands are not clear. In this paper, results are discussed from a numerical investigation of the fundamental properties of ionization waves generated by nanosecond voltage pulses inside a 15 cm long, 600µm wide (aspect ratio 250), flexible dielectric channel. The channel, filled with a Ne/Xe = 99.9/0.1 gas mixture at 1 atm, empties into a small chamber separated from a target substrate by 1 cm. The IWs propagate through the entire length of the channel while maintaining similar strength and magnitude. Upon exiting the channel into the chamber, the IW induces a second streamer discharge at the channel-chamber junction. This streamer then propagates across the chamber and impinges upon the target. The average speeds of the capillary-bounded IW are about 5 × 107 cm s-1 and 1 × 108 cm s-1 for positive and negative polarities, respectively. The propagation speed is sensitive to the curvature of the channel. In both cases, the peak in ionization tends to be located along the channel walls and alternates from side-to-side depending on the direction of the local instantaneous electric field and curvature of the channel. The ionization region following the IW extends up to several centimeters inside the channel, as opposed to being highly localized at the ionization front in unconstrained, atmospheric pressure IWs. The maximum speed of the IW in the chamber is about twice that in the channel. [ABSTRACT FROM AUTHOR]

A commercial current monitor has been used to measure the current associated with plasma bullets created in both the positive and negative half cycles of the sinusoidal driving voltage sustaining a plasma jet. The maximum values of the positive bullet current are typically ∼750µA and persist for 10µs, while the peaks in the negative current of several hundred µA are broad, persisting for about 40µs. From the time delay of the current peaks with increasing distance from the jet nozzle, an average bullet propagation speed has been measured; the positive and negative bullets travel at 17.5 km s-1 and 3.9 km s-1 respectively. The net space charge associated with the bullet(s) has also been calculated; the positive and negative bullets contain a similar net charge of the order of 10-9 C measured at all monitor positions, with estimated charged particle densities nb of ∼1010-1011 cm-3 in the bullet. [ABSTRACT FROM AUTHOR]

An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107-108 cm s-1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications. [ABSTRACT FROM AUTHOR]

We present observations of the emission characteristics of the plasma processes of a low inductance, sub Joule, compact capillary discharge, when operated in nitrogen at up to 600 Hz. A quarter period of under 10 ns is achieved allowing currents of order 5 kA. Four geometries are explored: two lengths, 21 and 36 mm, and two internal diameters, 1.6 and 3.2 mm. Transient hollow cathode fast electrons are associated with enhanced soft x-ray emission at shorter wavelengths with measured output energies of NVI at 28.8Å as compared with a Maxwellian plasma. Time-integrated spectroscopy together with filtered diode signals, and with spatial resolution, reveals a small axial emitting plasma close to the anode. Optical time-resolved spectroscopy gives larger scale plasma parameters both of the anode and the cathode plasmas. This volume plasma covers the range 2-8 eV, while the x-ray emitting plasma covers 10-20 eV, according to geometry. Nitrogen metastable emission is also observed in the hollow cathode volume prior to breakdown. Both internal wall diameter and capillary length affect both the spectrum and the x-ray emitting volume as does the axial pressure gradient. Electron beams from the transient hollow cathode are associated in model spectra with the observed NVI, OVI and Al VII-X ionization stages. Operating conditions that affect the spectral purity and discharge characteristics include the internal pressure gradient and nitrogen to helium mix ratio. We discuss the suitability of the capillary geometries as a soft x-ray source and in the context of available computer models. [ABSTRACT FROM AUTHOR]

Our research goal is to carry out two-dimensional (2D) and three-dimensional (3D) measurements of the velocity distribution within a single vessel. We modified a non-invasive beam laser Doppler velocimeter using near-infrared light, and linearized the laser to carry out simultaneous multipoint measurements. We also scanned the measurement line in the direction of depth to allow 3D imaging of vascular blood flow in opaque areas in vivo. We used micro multipoint laser Doppler velocimetry (LDV) and a device with improved spatial resolution from 250 to 125 µm. We compared actual and calculated values using a rotating disk with an attached microwire. To demonstrate the effectiveness of the proposed system, blood flowing at a constant rate through a glass capillary and the velocity distribution of flow in the capillary were measured and mapped. The average flow velocity was calculated from the cross-sectional area and flow rate in the glass capillary, and we compared the calculated and measured values. To obtain an image of blood flow velocity in vivo, we measured both 2D and 3D flow velocity distributions in mouse mesenteric vessels. [ABSTRACT FROM AUTHOR]

The capillary rise/fall of a liquid within a thin capillary tube is described by the well-established Jurin's law. The liquid reaches an equilibrium height/depth as the capillary pressure is balanced by the hydrostatic pressure. When the adhesion force at the three-phase contact line is counteracted by the liquid weight, the liquid column also stabilizes. Both descriptions evidently coincide although they are based on different physical quantities. Most undergraduate textbooks do not mention why these two routes draw two identical results; besides, the proofs become conceptually incorrect. We review the underlying ideas in Jurin's law and the two possible derivations. [ABSTRACT FROM AUTHOR]

Based on a recent loopless mounting method, a simplified loopless and bufferless crystal mounting method is developed for macromolecular crystallography. This simplified crystal mounting system is composed of the following components: a home-made glass capillary, a brass seat for holding the glass capillary, a flow regulator, and a vacuum pump for evacuation. Compared with the currently prevalent loop mounting method, this simplified method has almost the same mounting procedure and thus is compatible with the current automated crystal mounting system. The advantages of this method include higher signal-to-noise ratio, more accurate measurement, more rapid flash cooling, less x-ray absorption and thus less radiation damage to the crystal. This method can be extended to the flash-freeing of a crystal without or with soaking it in a lower concentration of cryoprotectant, thus it may be the best option for data collection in the absence of suitable cryoprotectant. Therefore, it is suggested that this mounting method should be further improved and extensively applied to cryocrystallographic experiments. [ABSTRACT FROM AUTHOR]

Following the concept developed in Part 1 of this study [Y. Wang, J. Electrochem. Soc., 156, B 1124 (2009)], this paper deals with the two-phase transport in the porous-media channel for polymer electrolyte fuel cells (PEFCs). Two-phase flow in the channel plays a crucial role in both reactant supply and water removal for a high humidity operation. Based on the two-fluid description, we developed a two-phase transport model for the PEFC channel, and we further analytically obtained the profiles of the phase velocities, liquid/gas volume fractions, and pressures for both liquid and gas phases along the channel. We find that the impact of the capillary action can be neglected for the liquid transport along the channel. The prediction of liquid saturation profiles varies considerably when using different models of the relative permeabilities. A maximum liquid saturation of approximately 20% is predicted, which avoids the occurrence of a high transport resistance for gaseous reactants. Pores in the porous-media channel cannot be completely occupied by liquid due to the dominant interfacial forces among the phases. These benefits make the proposed porous channel approach superior to the traditional hollow channels in terms of two-phase transport characteristics. [ABSTRACT FROM AUTHOR]

The transmissions of oxygen ions through Al2O3 nanocapillaries each 50 nm in diameter and 10 mm in length at a series of different tilt angles are measured, where the ions with energies ranging from 10 to 60 keV and charge states from 1 up to 6 are involved. The angular distribution and the transmission yields of transported ions are investigated. Our results indicate both the existence of a guiding effect when ions pass through the capillary and a significant dependence of the ion transmission on the energy and the charge state of the ions. The guiding effects are observed to be enhanced at lower projectile energies and higher charge states. Meanwhile, the results also exhibit that the transmission yields increase as the tilt angle decreases at a given energy and charge state. [ABSTRACT FROM AUTHOR]

The heating produced by a focused laser has been shown to provide a range of manipulation tools on droplets in microfluidic situations, through the generation of thermocapillary flows whose net result is to produce a force on the drop. In particular, droplets of water in oil that are produced in microchannels can be blocked in a special test section. Here, the manipulation of the flow within the droplet is explored through spatial and temporal modulation of the laser pattern used to block the drop. When a stationary pattern of two laser spots is used, the flow preserves the mirror symmetry inside the drop, as happens in the case of two alternating spots if the frequency of the switching is higher than the response rate of the fluid. Lower frequency switching produces a time periodic flow that breaks the mirror symmetry and which leads to efficient mixing inside the droplet. The mixing that is produced by this alternating flow is studied both experimentally and using numerical simulations of particle trajectories from measured velocity fields. This mixing can be optimized for certain parameter ranges, namely by varying the distance between the spots and the forcing frequency. [ABSTRACT FROM AUTHOR]

A recent experiment showed that cylindrical segments of water filling a hydrophilic stripe on an otherwise hydrophobic surface display a capillary instability when their volume is increased beyond the critical volume at which their apparent contact angle on the surface reaches 90° (Gau et al 1999 Science 283 46-9). Surprisingly, the fluid segments did not break up into droplets—as would be expected for a classical Rayleigh-Plateau instability—but instead displayed a long-wavelength instability where all excess fluid gathered in a single bulge along each stripe.We consider here the dynamics of the flow instability associated with this setup. We perform a linear stability analysis of the capillary flow problem in the inviscid limit. We first confirm previous work showing that all cylindrical segments are linearly unstable if (and only if) their apparent contact angle is larger than 90°. We then demonstrate that the most unstable wavenumber for the surface perturbation decreases to zero as the apparent contact angle of the fluid on the surface approaches 90°, allowing us to re-interpret the creation of bulges in the experiment as a zero-wavenumber capillary instability. A variation of the stability calculation is also considered for the case of a hydrophilic stripe located on a wedge-like geometry. [ABSTRACT FROM AUTHOR]

To enhance durability and cold-start performance of polymer electrolyte fuel cells (PEFCs), residual water in the fuel cell components must be minimized during operation and after shutdown. A transient two-phase mathematical and computational model is developed to describe water redistribution in the PEFC components after shutdown, which for the first time includes thermo-osmotic flow in the membrane. The model accounts for capillary and phase-change induced flow in the porous media and thermo-osmotic and diffusive flow in the polymer membrane. In the porous media, liquid-water flow is dominated by capillary transport until irreducible saturation is achieved, after which water removal is dominated by phase-change induced flow. In the membrane, thermo-osmotic flow can significantly help or hinder water drainage from the catalyst layer, depending on the situation. During shutdown to the frozen state, residual water at the cathode can be controlled, and freeze damage can be avoided, through balancing the phase-change induced flux in the diffusion media with the net balance of thermo-osmosis and diffusion flux in the membrane. [ABSTRACT FROM AUTHOR]

A microtribometer is used to measure and compare pull-off forces and friction forces exerted on (a) micro-dimpled silicon surfaces, (b) bare silicon surfaces, and (c) octadecyltrichlorosilane (OTS) treated silicon surfaces at different relative humidity (RH) levels separately. It is found that above a critical RH level, the capillary pull-off force increases abruptly and that the micro-dimple textured surface has a lower critical RH value as well as a higher pull-off force value than the other two surfaces. A micro topography parameter, namely sidewall area ratio, is found to play a major role in controlling the capillary pull-off force. Furthermore, micro-dimpled silicon surface is also proved to be not sensitive to variation in RH level, and can realize a stable and decreased friction coefficient compared with un-textured silicon surfaces. The reservoir-like function of micro dimples is considered to weaken or avoid the breakage effect of liquid bridges at different RH levels, thereby maintaining a stable frictional behaviour. [ABSTRACT FROM AUTHOR]

We measure the transmission of O6+ ions with a higher energy of 60keV (in turn a higher value of Ep/q) through capillaries in an uncoated Al2O3 membrane, and obtain agreements with previously reported results in general angular distribution of the transmitted ions and the transmission profile width variation with capillary tilt angle. The transmission fractions as a function of the tilt angle can be fitted to the semi-empirical Gaussian-like function well. Due to using uncoated capillary membrane, our Psc is larger than that using gold-coated one, in spite of our larger value of Ep/q, which suggests a larger equilibrium charge Q[?] in our experiment. [ABSTRACT FROM AUTHOR]

Thermocapillary convection coupling with the evaporation effect of evaporating liquids is studied experimentally. This study focused on an evaporation liquid layer in a rectangular cavity subjected to a horizontal temperature gradient when the top evaporating surface is open to air, while most previous works only studied pure thermocapillary convection without evaporation. Two liquids with different evaporating rates are used to study the coupling of evaporation and thermocapillary convection, and the interfacial temperature profiles for different temperature gradients are measured. The experimental results indicate evidently the influence of evaporation effect on the thermocapillary convection and interfacial temperature profiles. The steady multicellular flow and the oscillatory multicellular flow in the evaporation liquid layer are observed by using the particle-image-velocimetry method. [ABSTRACT FROM AUTHOR]

To understand capillary interactions between probe tips and nanoparticles under ambient conditions, a theoretical model of capillary forces between them is developed based on the geometric relations. It is found that the contribution of surface tension force to the total capillary force attains to similar order of magnitude as the capillary pressure force in many cases. It is also shown that the tip shape and the radial distance of the meniscus have great influence on the capillary force. The capillary force decreases with the increasing separation distances, and the variance of the contact angles may change the magnitudes of capillary forces several times at large radial distances. The applicability of the symmetric meniscus approximation is discussed. [ABSTRACT FROM AUTHOR]

The carbonyl iron flakes are fabricated by high-energy ball milling. The effective permeability is measured and calculated for the composite consisting of flakes embedded in a nonmagnetic matrix. The magnetic flakes with a shape anisotropy and random spatial distribution of normal direction are considered to calculate the complex permeability of magnetic flake materials. Its analytical model is derived from the Landau-Lifshitz-Gilbert equation and Bruggeman's effective medium theory. The calculated results agree well with the experiment. [ABSTRACT FROM AUTHOR]

As a result of capillary forces, animal hairs, carbon nanotubes or nanowires of a periodically or randomly distributed array often assemble into hierarchical structures. In this paper, the energy method is adopted to analyse the capillary adhesion of microsized hairs, which are modelled as clamped microcantilevers wetted by liquids. The critical conditions for capillary adhesion of two hairs, three hairs or two bundles of hairs are derived in terms of Young's contact angle, elastic modulus and geometric sizes of the beams. Then, the hierarchical capillary adhesion of hairs is addressed. It is found that for multiple hairs or microcantilevers, the system tends to take a hierarchical structure as a result of the minimization of the total potential energy of the system. The level number of structural hierarchy increases with the increase in the number of hairs if they are sufficiently long. Additionally, we performed experiments to verify our theoretical solutions for the adhesion of microbeams. [ABSTRACT FROM AUTHOR]

The limited working distance of the high numerical aperture microscope objectives used in conventional optical tweezers makes it difficult to trap objects at the liquid-air interface. Since with a weakly focused optical beam the gradient forces are not sufficient to overcome the axial scattering force, we investigated the possibility of the use of surface tension forces generated when the object is pushed against the liquid-air interface by a weakly focused optical beam to balance the axial scattering force. In contrast to the expected trapping of objects at the focal point of the trap beam the objects were observed to get trapped in an annular region about the trap beam. The experimental results and their analysis reveal that, apart from optical and surface tension forces, the laser-induced heating of the interface and the resulting thermocapillary effect are responsible for the observed trapping of objects. [ABSTRACT FROM AUTHOR]

Capillary force may cause adhesion of devices at micro- and nano-scales. Considering the fact that large deformation is often involved in adhesion of microbeams, we analysed the capillary adhesion of two beams using finite deformation elasticity theory. The critical adhesion condition can be obtained from the present method as a function of the bending stiffness, Young's contact angle, the spacing of the two beams as well as the surface tensions of the solid and liquid phases. The solution for the capillary adhesion of a beam with a rigid substrate is also given. The results from the finite deformation analysis are compared with that of infinitesimal deformation method in order to show the necessity of accounting for the nonlinear effect associated with large deflection. The method adopted in this study can also be used to solve other adhesion problems associated with van der Waals force or electrostatic force. [ABSTRACT FROM AUTHOR]

Considering that capillary force is one of the most important forces between nanoparticles and atomic force microscope (AFM) tips in ambient atmosphere, we develop an analytic approach on the capillary force between an AFM tip and a nanoparticle. The results show that the capillary forces are considerably affected by the geometry of the AFM tip, the humidity of the environment, the vertical distance between the AFM tip and the nanoparticle, as well as the contact angles of the meniscus with an AFM tip and a nanoparticle. It is found that the sharper the AFM tip, the smaller the capillary force. The analyses and results are expected to be helpful for the quantitative imaging and manipulating of nanoparticles by AFMs. [ABSTRACT FROM AUTHOR]

The absorption of water from a slurry into an absorbent substrate is analysed using Sharp Front theory. The analysis describes the relationship between the sorptivity S of the substrate, the desorptivity R of the slurry and the transfer sorptivity A between slurry and substrate, and leads to the relationship 1/A2 = 1/R2 + 1/S2. Experimental data are presented which validate this equation for the practically important case of the absorption of water from soft mortar mixes by fired clay bricks. A unique feature of the experimental work is the measurement of the desorptivity of the mortars at a pressure equal to the wetting front capillary pressure of the clay brick substrate. Analysis of the experimental data also enables, for the first time, the calculation of the capillary potential at the slurry/substrate interface. The analysis has relevance to many aspects of ceramic and mineral processing, industrial filtration and construction engineering. [ABSTRACT FROM AUTHOR]

In the context of developing a mercury-free lamp for automotive lighting an optimization of lamp design and plasma radiation was performed. In contrast to existing quartz lamps, a new lamp design was chosen consisting of a sapphire capillary combined with ceramic parts and pure tungsten electrodes. The lamps consist of metal halides and between 1 and 20 bar of xenon. They were operated with an electronic ballast at input powers between 20 and 40 W. Besides an optimization of the tube materials, thermography and plasma diagnostics were performed to understand the processes inside the lamp and to find optimal operation conditions. In addition to experimental diagnostics, a simulation of self-reversed sodium spectral lines was performed to verify plasma parameters, particularly the xenon pressure which could not be determined from the experiment. Additionally, tendencies of the influence of single components could be estimated by modelling. [ABSTRACT FROM AUTHOR]

This paper presents a model for the computation of capillary forces (applied to water capillary condensation). For simple geometries (planes, spheres, cones, etc), this model complies well with the literature results. But the literature only provides results for simple shapes and meniscii geometries. Our model allows the computation of capillary force for non-axisymmetrical shapes, with a meniscus fulfilling the Kelvin equation (i.e. we do not assume the profile of the meniscus).Currently the model takes into account the contact angles, the relative humidity, temperature and the geometrical description of the problem.The complexity of the problem can result from object shape (modelling for example an AFM tip) and/or from geometrical configuration. Using the model, this article shows that the tilt angle of a tip cannot be neglected when computing capillary forces. It is also shown that the difference between a cone and a pyramid has a significant effect on the computation of the force. The authors propose a simplified formula to determine capillary forces for a range of tips from existing results for similar tips.Eventually, the paper also shows that this geometrical effect can be used to control the force between a tip and an object, allowing to pick it up and release it. [ABSTRACT FROM AUTHOR]

The high-friction limit in Euler–Korteweg equations for fluid mixtures is analyzed. The convergence of the solutions towards the zeroth-order limiting system and the first-order correction is shown, assuming suitable uniform bounds. Three results are proved: the first-order correction system is shown to be of Maxwell–Stefan type and its diffusive part is parabolic in the sense of Petrovskii. The high-friction limit towards the first-order Chapman–Enskog approximate system is proved in the weak-strong solution context for general Euler–Korteweg systems. Finally, the limit towards the zeroth-order system is shown for smooth solutions in the isentropic case and for weak-strong solutions in the Euler–Korteweg case. These results include the case of constant capillarities and multicomponent quantum hydrodynamic models. [ABSTRACT FROM AUTHOR]

Devising controlled microfluidic liquid transfer in porous diagnostic devices presents challenges in respect to differentiation between surface/film flow and wicking within the bulk of the substrate. Rapid liquid translation is predominantly driven by film flow mechanisms in such devices. However, the more complex needs of in-pore reactivity between test fluids and reactive agents, followed typically by the need to perform chromatographic separation of eluents, demands the often contradictory facility of rapid spatial transport whilst allowing exposure to high internal surface area, i.e. by the mechanism of internal bulk wicking. The key parameters are permeability to saturated flow relatively far behind the wetting front, limiting the delivery rate of liquid to the wetting front, and capillarity within an ideally parallel high surface area pore network. We demonstrate a way to balance these properties using a coating with a discretely bimodal pore structure, whereby bulk flow is controlled by interparticle connectivity and interpore throat size, and capillarity and surface reactivity by ultrafine intraparticle pores. The distance travelled at time t by the wetting front is expressed as a power law function, tp . Evaluating p  provides a measure as to the closeness of dependence on viscous-controlled bulk flow permeability as p  tends to 0.5, i.e.  √t. Deviation from bulk flow dependence indicates the presence of pore wall film flow or inertial plug flow, possibly combined with evaporation and/or material sorption onto the pore wall surface or into the binder matrix. In this context, a variety of coating formulations are evaluated, and wicking rate is shown to vary strongly as a function of the binder impact on interparticle pore connectivity and on the absorption behaviour of the binder itself. Microfibrillated cellulose is shown to be a highly suitable binder for microfluidic diagnostic coatings. Reactivity within the coating is illustrated using charge-driven chromatographic colorant separation. [ABSTRACT FROM AUTHOR]

The issue of constructing interface networks translating under curvature-driven migration is addressed. The translating networks are the main accessory for testing capillarity driven migration mode in grain growth simulations. They also arise in experimental studies of boundary mobility and junction drag. The networks are constructed of pieces of simple translating curves—lines and grim reapers (GRs)—meeting at triple junctions. The primary method of building the networks relies on a certain property of GRs which reduces the construction to simple algebraic operations. At the outset, networks of interfaces having different tensions are considered. More detailed discussion concerns a restricted model in which the migration speed does not depend on the tensions. In this second case, the networks have noteworthy properties: some cell dimensions are directly related to angles at triple junctions, there are simple expressions for area sweeping rates, and there is a convenient and elegant alternative way of constructing these particular networks. [ABSTRACT FROM AUTHOR]

The temperature dependence of the capillary forces at nano-sized contacts is investigated. Two different resistive scanning thermal microscopy (SThM) nanoprobes are used in this study. Measurements of the capillary forces are reported as a function of the probe temperature on hydrophilic samples of different thermal properties. These forces appear to be largely reduced for probe temperatures larger than a threshold temperature, where the value depends on the sample thermal conductance. This could pave the way to an alternative solution to reduce the stiction in nano/ micro-electromechanical (NEMS/MEMS) devices. The dimensions of the water meniscus at the probe–sample contact were then estimated. Moreover, these results help the evaluation of thermal conductance through the water meniscus. It is found, through this work, that the values of the thermal conductance through the water meniscus can represent 6% of those of the contact thermal conductance in the case of the KNT probe (from Kelvin nanotechnology). These values can be equal to 4% of those of thermal conduction in the cantilever–sample air gap in the case of a doped-silicon probe. [ABSTRACT FROM AUTHOR]

A class of invariant transformations is presented for the classical Korteweg capillarity system. The invariance is an extension of a kind originally introduced in an anisentropic gasdynamics context. In a particular instance, application of the invariant transformation leads to a deformed one-parameter class of Kármán–Tsien-type capillarity laws associated with a deformation of an integrable nonlinear Schrödinger-type equation which incorporates a de Broglie–Bohm potential. The latter and another integrable case associated with the classical Boussinesq equation may be linked to the motion of curves in Euclidean and projective space so that both the invariant transformation and the Galilean invariance of the capillarity system may be interpreted in a geometric and soliton-theoretic manner. The work is set in the broader context of other connections of invariant transformations in gasdynamics with soliton theory. [ABSTRACT FROM AUTHOR]

We investigate the role of capillarity stresses on the ion-hammering phenomenon when sub-micrometer colloidal particles are considered. To this end, nearly monodisperse, chemically synthesized silica (SiO2) colloids (100, 300 and 600 nm) were irradiated at room temperature (300 K) with 4 MeV Au ions for fluences up to Ph = 1.8 x 1016 cm [?] 2. It has been taken for granted that the transverse dimension of an ion-deformable amorphous material grows exponentially with the irradiation fluence, L(ph) = L(0)exp[A0Ph]. Here, we show that for sub-micrometer particles the irradiation-induced deformation saturates for larger fluences, L(\phi)\rightarrow const. The saturation fluence depends on the initial dimension of the colloidal nanoparticles: the smaller the dimension of the colloids, the lower the saturation fluence. Experimental data are successfully accounted for by having recourse to a phenomenological model first developed by Klaumunzer and further elaborated by van Dillen. We also estimate the evolution with fluence of the principal stresses inside the particles, s11(ph) = s22(ph) and s33(ph), and we show that they evolve toward a steady-state value following a sigmoidal-like behavior. Furthermore, when stresses induced by the surface curvature become non-negligible the approximation often made that the deformation strain rate, A0 = dL/L dPh, remains constant upon irradiation is no longer valid. We show that A0 evolves with the irradiation fluence, e.g. A_{0} \longrightarrow A(\Phi) , and we relate this behavior to the evolution of the stresses upon irradiation. Finally, this work allows us to define the limits of the ion-hammering effect when the non-hydrostatic capillarity stresses become important. [ABSTRACT FROM AUTHOR]

When a microstructure is placed on a droplet, the structure is positioned and remains at a particular position due to capillary forces. By using this phenomenon, two-dimensional arrangements on droplets have been widely developed. In this study, we fabricate a three-dimensional structure (prism shape) by placing two circular plates on a droplet. The paper explains the dynamics of the positioning both experimentally and numerically. Through experiment and simulation, we found that the rotational positioning is determined by surface tension and the two plates are supported by internal pressure and surface tension. The apex angle of the prism can be easily tuned by changing its volume. As described at the end of the paper, a prism composed of a droplet of silicone oil and two transparent circular SU-8 plates is encapsulated by depositing an organic Parylene membrane. The shape of the liquid is fixed, and a non-evaporative and non-deformable prism is formed with a volume of less than 1 mm3. [ABSTRACT FROM AUTHOR]

The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness measured by this new method can reach the order of angstroms with high quality capillaries. [ABSTRACT FROM AUTHOR]

In this paper we investigate both capillary water imbibition and the sorptivity of aerated gypsum plaster, and how these sorption characteristics are related to the pore structure of the material. These characteristics are examined by monitoring mass change using the conventional gravimetric method and by obtaining water content profiles using non-destructive magnetic resonance imaging (MRI) techniques during capillary imbibition of water. Here, three different gypsum samples are investigated: one non-aerated reference gypsum sample and two aerated gypsum samples produced with different volumetric air fractions. The capillary water absorption into the reference sample follows t1/2 kinetics (Fickian diffusion), where t is the time of ingress. However, in the aerated gypsum samples there are deviations from t1/2 kinetics. The MRI results show unambiguously that two wetting fronts advance through the aerated structure; an observation that cannot be made from the gravimetric data alone. The water content profiles of the aerated gypsum samples are therefore analysed by treating them as the sum of two separate absorption processes using sharp front analysis. The capillary water absorption properties of this material are well described as a parallel combination of fast absorption into fine matrix pores and slow absorption into a modified structure of matrix pores inter-connected to air voids introduced into the slurry by aeration. [ABSTRACT FROM AUTHOR]

The rough sea surface covered by an organic film will cause attenuation of capillarity waves, which implies that the organic films play an important role in rough sea surface processes. We focus on a one-dimensional (1D) rough sea surface with the Pierson--Moskowitz (PM) spectrum distributed to the homogeneous insoluble organic slicks. First, the impact of the organic film on the PM surface spectrum is presented, as well as that of the correlation length, the rms height and slope of the rough sea surface. The damping effect of the organic film changes the physical parameters of the rough sea surface. For example, the organic film will reduce the rms height and slopee of the rough sea surface, which results in the attenuation of the high-frequency components of the PM spectrum leading to modification of the surface PM spectrum. Then, the influence of the organic film on the electromagnetic (EM) scattering coefficients from PM rough sea surface covered by the organic film is investigated and discussed in detail, compared with the clean PM rough sea surface through the method of moments. [ABSTRACT FROM AUTHOR]

There are lots of reasons to restrict a low-permeability oil layer to enhance the recovery factor. Based on the research results of non-Darcy flow, microflow of water drive and micro-acting force in low permeability porous media are studied by establishing the expression of fluid viscosity factor. Numerical calculation shows that under the condition of L/S interaction, the radial velocity distribution near the solid wall changes obviously, and the curve form changes from convex to concave. The tinier the capillary radius is, the stronger the L/S interaction is. The larger the n value is, more obviously the flowing velocity decreases. The results will help people to deal with improving recovery factor of low permeability reservoir, and understanding the fluid flow behavior in blood capillary. [ABSTRACT FROM AUTHOR]

We investigate the angular distribution of the transmitted 18 keV negative ions Cl[?] through Al2O3 nanocapillaries of 50 nm in diameter and 10 um in length. Elastic scattering ions and inelastic scattering ions are obtained simultaneously. The experimental result is partially consistent with the guiding effect. We can qualitatively explain our experimental result through a dynamic process. [ABSTRACT FROM AUTHOR]

A novel Whispering-Gallery-Mode (WGM) fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre. [ABSTRACT FROM AUTHOR]