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Surface Tension (surface + tension)
Kinds of Surface Tension Terms modified by Surface Tension Selected AbstractsSurface Tension and Viscosity of the Ni-based Superalloy CMSX-4 Measured by the Oscillating Drop Method in Parabolic Flight Experiments,ADVANCED ENGINEERING MATERIALS, Issue 5 2007K. Higuchi The surface tension and the viscosity of the Ni-based superalloy CMSX-4 were measured by the oscillating drop method on electromagnetically levitated specimen under reduced gravity conditions on a parabolic flight. The twenty seconds of reduced gravity available in a single parabola proved sufficient for melting, heating into the stable liquid and free cooling to solidification. [source] An Examination of Surface Tension of Binary Lithium Borate Melts as a Function of Composition and TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Xiumei Shi Surface tensions of xLi2O,(1,x)B2O3 melts, where 0,x,0.68, have been measured systematically with a ring method from respective liquidus temperatures up to about 1450 K. For all of the investigated melts, the relationship between surface tension and temperature can be well described by quadratic polynomial functions. With increasing Li2O content, surface tension monotonously increased, whereas the temperature coefficient of surface tension increased slowly up to about x=0.1, changed sign from positive to negative at about x=0.2, and then remained negative with further increasing Li2O content. Together with the physical properties reported in our previous work, such as density, temperature coefficient of density, and volume expansion coefficient, etc., both surface tension and temperature coefficient of surface tension have been comparatively plotted as a function of Li/B molar ratio. Differentiated from the inflections of slope in the plots of physical properties vs. Li/B molar ratio, three characteristic regions have been found in the melts of this system. Within different regions, different effects of temperature and concentration on the physical properties of melts have been observed. [source] Density, Surface Tension, and Viscosity of PbO-B2O3 -SiO2 Glass MeltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Shigeru Fujino The density, surface tension, and viscosity of the melts from the PbO-B2O3 -SiO2 system have been measured at temperatures in the range 1073,1473 K. The effect of composition on these properties was also investigated. The density of the melt was found to increase linearly with increasing PbO content. Molar volume was derived from the density data, and its deviation from the additivity of partial molar volumes was calculated. These deviations in molar volume from those obtained from additivity rules have been used along with the ratio of various coordination numbers of boron (as reported by Bray) to discuss the structure of the melts. The surface tension was found to decrease with decreasing SiO2/B2O3 ratio, and to increase in the range of the PbO content between 30 and 60 mol%, showing a maximum at ,60 mol% PbO, and then decreased with further additions. This result suggested that the surface tension would be affected primarily by the B2O3 content in the range of the PbO content between 30,60 mol%, and mainly by the PbO content in the range of the PbO content >60 mol%, respectively. The viscosity of the melt was found to decrease linearly with increasing PbO content. The results obtained indicate that the increase in viscosity with B2O3 was half that of SiO2 (on a molar basis), and an empirical equation has been proposed for the viscosity as a function of mole fraction. [source] Effect of Sodium Halide on Dynamic Surface Tension of a Cationic SurfactantCHINESE JOURNAL OF CHEMISTRY, Issue 8 2005Lü Feng-Feng Abstract The equilibrium and dynamic surface tension (DST) of the novel cationic surfactant, 3-(p -nonylphenoxy)-2-hydroxylpropyl trimethyl ammonium bromide, abbreviated as RTAB, were studied. The effect of sodium halide such as NaCl, NaBr and NaI on the DST behavior of the RTAB solution below its CMC was studied in detail. Due to the preferential adsorption, the effect of hydration and salting out, the ability to reduce the DST values at the same concentration was in the order of NaI>NaBr>NaCl. Attributed to its high surface activity, the equilibrium time of the DST of the surfactant solution was insensitive to the ionic strength. [source] The Living: Surface TensionsARCHITECTURAL DESIGN, Issue 3 2010Jordan Geiger Abstract ,Our work begins with the premise of a dynamic world. Political and cultural conditions change: what if the walls and windows morphed in response?' New York-based team The Living, led by David Benjamin and Soo-in Yang, have developed a practice of deep, open-source interfaces of participation. Jordan Geiger describes how for The Living their home city and its environs is a site of evolving forms of public space whether on land, air or water. Copyright © 2010 John Wiley & Sons, Ltd. [source] Dynamic Surface Tensions of Fluorous Surfactant SolutionsCHINESE JOURNAL OF CHEMISTRY, Issue 4 2005Gao Yan-An Abstract Dynamic surface properties of aqueous solutions of cationic fluorous surfactant CF3CF2CF2O(CF(CF3)CF2O)2CF(CF3)CONH(CH2)3N+(C2H5)2CH3I - (abbrev. FC-4 ) were reported. The critical micelle concentration (cmc) (3.6×10 -5 mol/L) and equilibrium surface tensions ,eq were measured by Krüss K12 tension apparatus. Dynamic surface tension ,(t) was measured in the range of 15 ms to 200 s using the MBP tensiometer. The surface excess ,, as a function of concentration, was obtained from equilibrium tensiometry using the Gibbs equation. Data from these experiments were combined to analyze the ,(t) decays according to the asymptotic Ward and Tordai equation. The results show that at the initial adsorption stage, the dynamic surface tension data were all consistent with this diffusion-controlled mechanism, and at the end of the adsorption process, there were some evidences for an adsorption barrier, suggesting a mixed diffusion-controlled adsorption mechanism. Using measured quantities, the barrier strength was estimated as between 25 and 35 kJ/mol at 25 °C. The surface pressure plays an important role in contributing to the barrier. [source] Confinement effects on the morphology of photopatterned porous polymer monoliths for capillary and microchip electrophoresis of proteinsELECTROPHORESIS, Issue 14 2008Mei He Abstract We find that the morphology of porous polymer monoliths photopatterned within capillaries and microchannels is substantially influenced by the dimensions of confinement. Porous polymer monoliths were prepared by UV-initiated free-radical polymerization using either the hydrophilic or hydrophobic monomers 2-hydroxyethyl methacrylate or butyl methacrylate, cross-linker ethylene dimethacrylate and different porogenic solvents to produce bulk pore diameters between 3.2 and 0.4,µm. The extent of deformation from the bulk porous structure under confinement strongly depends on the ratio of characteristic length of the confined space to the monolith pore size. The effects are similar in cylindrical capillaries and D-shaped microfluidic channels. Bulk-like porosity is observed for a confinement dimension to pore size ratio >10, and significant deviation is observed for a ratio <5. At the extreme limit of deformation a smooth polymer layer ,300 nm thick is formed on the surface of the capillary or microchannel. Surface tension or wetting also plays a role, with greater wetting enhancing deformation of the bulk structure. The films created by extreme deformation provide a rapid and effective strategy to create robust wall coatings, with the ability to photograft various surface chemistries onto the coating. This approach is demonstrated through cationic films used for electroosmotic flow control and neutral hydrophilic coatings for electrophoresis of proteins. [source] Numerical simulation of bubble and droplet deformation by a level set approach with surface tension in three dimensionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2010Roberto Croce Abstract In this paper we present a three-dimensional Navier,Stokes solver for incompressible two-phase flow problems with surface tension and apply the proposed scheme to the simulation of bubble and droplet deformation. One of the main concerns of this study is the impact of surface tension and its discretization on the overall convergence behavior and conservation properties. Our approach employs a standard finite difference/finite volume discretization on uniform Cartesian staggered grids and uses Chorin's projection approach. The free surface between the two fluid phases is tracked with a level set (LS) technique. Here, the interface conditions are implicitly incorporated into the momentum equations by the continuum surface force method. Surface tension is evaluated using a smoothed delta function and a third-order interpolation. The problem of mass conservation for the two phases is treated by a reinitialization of the LS function employing a regularized signum function and a global fixed point iteration. All convective terms are discretized by a WENO scheme of fifth order. Altogether, our approach exhibits a second-order convergence away from the free surface. The discretization of surface tension requires a smoothing scheme near the free surface, which leads to a first-order convergence in the smoothing region. We discuss the details of the proposed numerical scheme and present the results of several numerical experiments concerning mass conservation, convergence of curvature, and the application of our solver to the simulation of two rising bubble problems, one with small and one with large jumps in material parameters, and the simulation of a droplet deformation due to a shear flow in three space dimensions. Furthermore, we compare our three-dimensional results with those of quasi-two-dimensional and two-dimensional simulations. This comparison clearly shows the need for full three-dimensional simulations of droplet and bubble deformation to capture the correct physical behavior. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fountain flow revisited: The effect of various fluid mechanics parametersAICHE JOURNAL, Issue 5 2010Evan Mitsoulis Abstract Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady-state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure-dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure-shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure-dependence of the viscosity. Contour plots of the primary variables (velocity-pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Impact of surface tension and viscosity on solids motion in a conical high shear mixer granulatorAICHE JOURNAL, Issue 12 2009Xianfeng Fan Abstract Surface tension and viscosity are the important properties of liquid binders affecting wet granulation processes. They could be used to control solids flow pattern and relative motion of particles for controlling wetting, granule growth, consolidation, and breakage. This study aims to investigate experimentally the impacts of the two properties with a conical high shear granulator. The results show significant effects of viscosity and surface tension on solids flow pattern and relative motion of particles. The relative importance of the two parameters, the surface tension and the viscosity, are found to vary with the axial and radial positions in the granulator. For example, the viscosity force decreases with an increase in the bed height in the axial direction (vertical plane). The viscosity force between particles coated with PEG4000 solution is in mN order, whereas that between particles coated with ethanol and water is in ,N order. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Stabilization of lysozyme by benzyl alcohol: Surface tension and thermodynamic parametersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2010Monu Kumari Goyal Abstract The aim of the study was to understand the effect of benzyl alcohol on biological activity, aggregation behavior, denaturant and heat-induced unfolding of lysozyme. Compatibility studies of lysozyme carried out with a number of anti-microbial preservatives, indicated benzyl alcohol to be the best suppressor of protein aggregation against heat stress. The effect of this preservative was checked at various pH values ranging from 4.0 to 9.0. In spite of reducing the thermal denaturation temperature (Tm) at all pH values, benzyl alcohol had a stabilizing effect on lysozyme in terms of retaining the biological activity when the enzyme was incubated at 75°C. The reduction in Tm with increasing benzyl alcohol concentration was correlated with decreasing surface tension of surrounding medium. A detailed thermodynamic study of lysozyme in the presence of benzyl alcohol was carried out at pH 6.2. Change in Gibb's free energy of thermal unfolding at 25°C was found to remain constant in the presence of benzyl alcohol, indicating no interaction of benzyl alcohol with the native protein at room temperature. Both the enthalpy and entropy change at mid point of thermal unfolding were found to increase in the presence of benzyl alcohol indicating the stabilization of partially unfolded state. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4149,4161, 2010 [source] Surface tension of poly(ester urethane)s and poly(ether urethane)sPOLYMER INTERNATIONAL, Issue 3 2007Mihaela Lupu Abstract The correlation between the surface tension parameters and the chemical composition of poly(ester urethane) and poly(ether urethane) thin films with different soft and hard segments, both before and after plasma treatment, was investigated. Calculations are based on the geometric mean approach of Owens and Wendt (Owens DK and Wendt RC, J Appl Polym Sci13:1741 (1969)), Rabel (Rabel W, Physikalische Blätter33:151 (1977)) and Kälble (Kälble DH, J Adhesion1:102 (1969)), on the Lifshitz,van der Waals acid/base approach of van Oss and co-workers (van Oss CJ, Good RJ and Chaudhury MK, Langmuir4:884 (1988); van Oss CJ, Ju L, Chaudhury MK and Good RJ, Chem Rev88:927 (1988); van Oss CJ, Interfacial Forces in Aqueous Media. Marcel Dekker, New York (1994)) and on the theoretical methods involving quantitative structure,property relationships (Bicerano J, JMS Rev Macromol Chem PhysC36:161 (1996)). For all investigated films, the polar terms contribute significantly to the total surface tensions, as due to the large electron donor, , interactions. Plasma treatment alters the surface energy of samples by changing their surface polarity and hydrophilicity. The hydrophilicity trends for polyurethanes were also studied by means of the free energy of hydration between compounds and water. Preliminary blood contact tests of the selected polyurethane sample with higher hydrophilicity were developed for biomedical applications. Copyright © 2006 Society of Chemical Industry [source] Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air DistributorTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007M. Abid Akhtar Abstract Two- and three-dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume-of-fluid approach. The effect of hole-size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k-, turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement. On a effectué des simulations numériques bi et tridimensionnelles dans un réacteur à colonne à bulles à l'échelle de laboratoire à l'aide d'une approche volume-de-fluide. L'effet de la taille du trou et de la vitesse de gaz superficielle sur la distribution de tailles des bulles et leurs trajectoires a été étudié dans un réacteur cylindrique de 20 cm de diamètre et de 1 m de hauteur. Toutes les simulations ont été réalisées selon un mode transitoire à l'aide du logiciel FLUENT. La tension de surface entre deux phases a été modélisée comme une force volumique avec une valeur constante. La turbulence a été modélisée par la méthode de turbulence k-,. Une comparaison entre les prédictions des simulations et les études expérimentales mentionnées montre un bon accord. [source] An Examination of Surface Tension of Binary Lithium Borate Melts as a Function of Composition and TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Xiumei Shi Surface tensions of xLi2O,(1,x)B2O3 melts, where 0,x,0.68, have been measured systematically with a ring method from respective liquidus temperatures up to about 1450 K. For all of the investigated melts, the relationship between surface tension and temperature can be well described by quadratic polynomial functions. With increasing Li2O content, surface tension monotonously increased, whereas the temperature coefficient of surface tension increased slowly up to about x=0.1, changed sign from positive to negative at about x=0.2, and then remained negative with further increasing Li2O content. Together with the physical properties reported in our previous work, such as density, temperature coefficient of density, and volume expansion coefficient, etc., both surface tension and temperature coefficient of surface tension have been comparatively plotted as a function of Li/B molar ratio. Differentiated from the inflections of slope in the plots of physical properties vs. Li/B molar ratio, three characteristic regions have been found in the melts of this system. Within different regions, different effects of temperature and concentration on the physical properties of melts have been observed. [source] Phospholipase A2 is present in meconium and inhibits the activity of pulmonary surfactant: an in vitro studyACTA PAEDIATRICA, Issue 4 2001AJJ Schrama Atelectasis, a major contributor to pulmonary dysfunction in meconium aspiration syndrome (MAS), is produced by bronchiolar obstruction and surfactant inactivation. It has been shown that substances in meconium, e.g. fatty acids, inhibit surfactant activity. However, the role of the enzyme phospholipase A2 (PLA2), which hydrolyses surfactant in adult respiratory distress syndrome (ARDS), has not yet been studied. Our objective was to investigate whether PLA2 is present in meconium and inhibits pulmonary surfactant activity in vitro. Therefore, the presence of PLA2 activity in meconium, collected from 10 newborns, was measured by the formation of lysophosphatidylcholine after incubation of meconium with radioactively labelled dipalmitoylphosphati-dylcholine. Meconium was fractionated by Sephadex G-100 column chromatography and the fractions were assayed for PLA2 activity. Also, their effect on the surface tension of surfactant (Curosurf) was measured using a pulsating bubble surfactometer (PBS). PLA2 activity was present in all meconium samples. Addition of meconium to surfactant significantly increased surface tension (mean ± SD: 17 ± 1.6 mN/m to 24.3 ± 6.7 mN/m, p= 0.0001) and only the addition of the PLA2 containing fraction from meconium to surfactant also significantly increased surface tension (mean 1.7 ± 1.6mN/m to 19.0 ± 3.58 mN/m, p < 0.0001). Conclusion: PLA2 is present in meconium and inhibits the activity of pulmonary surfactant in vitro. Therefore, PLA2 in meconium may contribute to surfactant inactivation and alveolar ateectasis in MAS. [source] Periostin promotes a fibroblastic lineage pathway in atrioventricular valve progenitor cellsDEVELOPMENTAL DYNAMICS, Issue 5 2009Russell A. Norris Abstract Differentiation of prevalvular mesenchyme into valve fibroblasts is an integral step towards the development of functionally mature cardiac valves. Although clinically relevant, little is known regarding the molecular and cellular mechanisms by which this process proceeds. Genes that are regulated in a spatio-temporal pattern during valve remodeling are candidates for affecting this differentiation process. Based on its expression pattern, we have focused our studies on the role of the matricellular gene, periostin, in regulating the differentiation of cushion mesenchymal cells into valve fibroblasts. Herein, we demonstrate that periostin expression is coincident with and regulates type I collagen protein production, a major component of mature valve tissue. Adenoviral-mediated knock-down of periostin in atrioventricular mesenchyme resulted in a decrease in collagen I protein expression and aberrant induction of myocyte markers indicating an alteration in AV mesenchyme differentiation. In vitro analyses using a novel "cardiotube" assay further demonstrated that expression of periostin regulates lineage commitment of valve precursor cells. In these cells, expression of periostin and collagen I are regulated, in part, by TGF,-3. We further demonstrate that TGF,-3, through a periostin/collagen pathway, enhances the viscoelastic properties of AV cushion tissue surface tension and plays a crucial role in regulating valve remodeling. Thus, data presented here demonstrate that periostin, a TGF,-3 responsive gene, functions as a crucial mediator of chick AV valve maturation via promoting mesenchymal-to-fibroblast differentiation while blocking differentiation of alternative cell types (myocytes). Developmental Dynamics 238:1052,1063, 2009. © 2009 Wiley-Liss, Inc. [source] Synthesis and characterization of imidazolinium surfactants derived from tallow fatty acids and diethylenetriamineEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 10 2008Divya Bajpai Abstract This paper describes the synthesis of long-chain dialkylamido imidazolines based on tallow fatty acids and diethylenetriamine, followed by their quaternization. Imidazolines were obtained by non-solvent microwave synthesis using calcium oxide as support, which were then quaternized by using dimethyl sulfate as a quaternizing agent and iso -propanol as a solvent, to produce cationic imidazolinium salts. The synthesized cationic imidazoline surfactants were evaluated for yield and cationic content. The instrumental techniques, viz. FT-IR and 1H-NMR, verified the formation of imidazolines and their subsequent quaternization. The surface-active and performance properties of the cationic imidazolines in terms of critical micelle concentration, surface tension, dispersibility, emulsion stability, softening, rewettability and antistatic properties were also reported. [source] Challenges in Measuring of Physical Properties of Liquid Phases for Material and Process Optimisation,ADVANCED ENGINEERING MATERIALS, Issue 4 2007S. Akbari The exact knowledge of thermo-physical properties of molten phases is crucial to modern metallurgy. It leads to optimized process windows including better metal/slag separation, suitable slag selection or reduced slag/refractory wetting. The most important properties are melting and boiling point, electrical- and thermal conductivity, melting and transition enthalpies, wetting angle, density, viscosity and surface tension. The aim of this paper is to present opportunities, methods and uncertainties of characterization of this kind of materials. This will be examplified by measuring three physical properties (density, viscosity and surface tension). [source] Particle-Stabilized Materials: Dry Oils and (Polymerized) Non-Aqueous FoamsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Ryo Murakami Abstract Oil (liquids with low surface tension and practically immiscible with water) drops can be dispersed in air if relatively oleophobic particles are available. However, such particles with oil-repellent surfaces cannot simply be prepared by controlling the particle surface chemistry alone. Herein the preparation of oil-in-air materials (oil marbles, dry oils) by changing the wetting behavior of particles by tuning the oil properties, which allows the formation of the metastable Cassie,Baxter wetting state of particle assemblies on oil drop surfaces, is presented. The oil-in-air materials can be converted to air-in-oil materials (non-aqueous foams) by tailoring the oil properties, as the robustness of the metastable Cassie,Baxter state of the particle assemblies critically depends on the particle wettability. This conversion implies the phase inversion of dispersed systems consisting of air and oils. It is also shown that particle-stabilized non-aqueous foams can be utilized as template to produce macroporous polymers. [source] Hexagonal Network Organization of Dye-Loaded Zeolite,L Crystals by Surface-Tension Driven Autoassembly,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2006S. Yunus Abstract Highly fluorescent dye-loaded zeolite,L crystals, approximately 1.4,,m long and 650,nm in diameter, are organized in a hexagonal network by a surface-tension-driven autoassembly process. A polydimethylsiloxane (PDMS) film presenting a trigonal ordering of spherical protuberances, including a polystyrene (PS) hexagonal network occupying their interstices, is chosen as the platform for the assembly. The overall wettability and the difference in surface tension between PDMS and PS surfaces are found to offer good conditions for ordering micrometric dye-loaded zeolite,L crystals in a 2D hexagonal network. The resulting film displays a regular hexagonal pattern of polarized fluorescence, reflecting the polarization properties of the dye molecules inserted in the parallel nanochannels of the zeolites. [source] Perpendicularly Aligned, Size-and Spacing-Controlled Nanocylinders by Molecular-Weight Adjustment of a Homopolymer Blended in an Asymmetric Triblock CopolymerADVANCED FUNCTIONAL MATERIALS, Issue 15 2006U. Ahn Abstract Perpendicularly arrayed and size-controlled nanocylinders have been prepared by simply blending an asymmetric polystyrene- block -polyisoprene- block -polystyrene triblock copolymer with polystyrene (the minority component) homopolymers of different molecular weights. The preference for perpendicular orientation or hexagonal ordering of the nanocylinders over a large area in the asymmetric block copolymer can be controlled by adjusting the molecular weight of the blended homopolymer, and the perfection of hexagonal ordering of the perpendicular cylinders can be tuned by using a substrate whose surface tension is much different from that of the majority component of the block copolymer. Such highly controlled nanostructured block-copolymer materials, which have been obtained by a simple method independent of film thickness and interfacial tension between the blocks and the substrates, have wide-ranging commercial potential, e.g., for use in membranes and nanotemplates with size-tunable pores, bandgap-controlled photonic crystals, and other nanotechnological fields demanding a specific nanosize and nanomorphology. [source] The formation of rising liquid thin film on the fluted surface of a horizontal tubeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2005Li Yan Abstract The purpose of this study is to investigate the mechanism of the formation of the rising liquid thin film and its flow characteristics on the fluted surface of a horizontal tube. By analyzing the wetting behaviors of the fluted tube, which was primarily responsible for the formation of the rising liquid thin film, a numerical model of one-phase fluid was established to analyze the distribution of the velocity and thickness of the rising liquid thin film during its evaporation. The behaviors of the flow characteristics were discussed and the results showed that geometric properties of the fluted surface of a horizontal tube and surface tension of the fluid were essential for the formation of a continuous and uniform liquid thin film. Theoretical analysis suggested that the capillary force created by the fluid surface tension was a key value for the formation of the thin film. The heat and mass transfer characteristics of the formed thin film also had an effect on the formation of the rising film. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(6): 396,406, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20075 [source] Cover Picture: Fabrication of Multicomponent Microsystems by Directed Three-Dimensional Self-Assembly (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 5 2005Mater. Abstract Directed three-dimensional self-assembly to assemble and package integrated semiconductor devices is demonstrated by Jacobs and Zheng on p.,732. The self-assembly process uses geometrical shape recognition to identify different components and surface-tension between liquid solder and metal-coated areas to form mechanical and electrical connections. The components (top left) self-assemble in a turbulent flow (center) and form functional multi-component microsystems (bottom right) by sequentially adding parts to the assembly solution. The technique provides, for the first time, a route to enable the realization of three-dimensional heterogeneous microsystems that contain non-identical parts, and connecting them electrically. We have developed a directed self-assembly process for the fabrication of three-dimensional (3D) microsystems that contain non-identical parts and a statistical model that relates the process yield to the process parameters. The self-assembly process uses geometric-shape recognition to identify different components, and surface tension between liquid solder and metal-coated areas to form mechanical and electrical connections. The concept is used to realize self-packaging microsystems that contain non-identical subunits. To enable the realization of microsystems that contain more than two non-identical subunits, sequential self-assembly is introduced, a process that is similar to the formation of heterodimers, heterotrimers, and higher aggregates found in nature, chemistry, and chemical biology. The self-assembly of three-component assemblies is demonstrated by sequentially adding device segments to the assembly solution including two hundred micrometer-sized light-emitting diodes (LEDs) and complementary metal oxide semiconductor (CMOS) integrated circuits. Six hundred AlGaInP/GaAs LED segments self-assembled onto device carriers in two minutes, without defects, and encapsulation units self-assembled onto the LED-carrier assemblies to form a 3D circuit path to operate the final device. The self-assembly process is a well-defined statistical process. The process follows a first-order, non-linear differential equation. The presented model relates the progression of the self-assembly and yield with the process parameters,component population and capture probability,that are defined by the agitation and the component design. [source] Enhancement of pool boiling heat transfer in water and ethanol/water mixtures (effect of surface-active agent)HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2004Toshiaki Inoue Abstract The surface tension of alcohol/water mixtures has been measured over the whole fraction range and then it has been measured when a surface-active agent was added into the mixtures. The effect of the concentration of alcohol and the surface- active agent on surface tension was experimentally clarified, in order to gain base data related to enhancement of the heat transfer coefficient in the mixtures and water. The experiment was also carried out to enhance the boiling heat transfer coefficients of water and alcohol/water mixtures on a horizontal heated fine wire at a pressure of 0.1 MPa by adding a surface-active agent into the tested liquid. The results show, the coefficients were enhanced in lower alcohol concentration (C , 0.5) and low heat flux range which occur just after the onset of boiling. It was also found that the enhancement effect by the surfactant disappears in concentrations over 1000 ppm. Finally, we demonstrated that the surface tension remarkably affects the heat transfer coefficients in nucleate pool boiling. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 229,244, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20010 [source] Heat transfer for Marangoni-driven boundary layer flowHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2002David M. Christopher Abstract Marangoni convection induced by variation of the surface tension with temperature along a surface influences crystal growth melts and other processes with liquid,vapor interfaces, such as boiling in both microgravity and normal gravity in some cases. This paper presents the Nusselt number for Marangoni flow over a flat surface calculated using a similarity solution for both the momentum equations and the energy equation assuming developing boundary layer flow along a surface. Solutions are presented for the surface velocity, the total flow rate, and the Nusselt number for various temperature profiles, Marangoni numbers, and Prandtl numbers. For large bubbles, the predicted boundary layer thickness would be less than the bubble diameter, so the curvature effects could be neglected and this analysis could be used as a first estimate of the effect of Marangoni flow around a vapor bubble. © 2002 Scripta Technica, Heat Trans Asian Res, 31(2): 105,116, 2002; DOI 10.1002/htj.10019 [source] Macroscopic Single-Walled-Carbon-Nanotube Fiber Self-Assembled by Dip-Coating MethodADVANCED MATERIALS, Issue 43 2009Eui Yun Jang Pure macroscopic single-walled-carbon-nanotube (SWNT) fibers are fabricated by using a dip-coating method without any additive or additional electrical equipment or complex apparatus. The present method only utilizes microfluidics, which includes capillary condensation, capillary flow, and surface tension, and results in the self-assembly and self-alignment of SWNT colloids. [source] Infiltration into effluent irrigation-induced repellent soils and the dependence of repellency on ambient relative humidityHYDROLOGICAL PROCESSES, Issue 17 2007R. Wallach Abstract As a result of water scarcity and as a means of wastewater disposal, reuse of treated sewage effluent in irrigated agriculture is practiced worldwide. Among the detrimental aspects of wastewater re-use in agriculture is the possibility that soils will be rendered water repellent. The current study focuses on time dependent variation of infiltration rate in effluent-induced repellent soils, and time dependent variation in water repellency at different levels of ambient relative humidity (RH). The shape of the cumulative infiltration curve of water was found to depend on the repellency degree (concave for wettable and slightly repellent soils, convex for severely repellent soil). Compared with infiltration rates in the wettable and slightly repellent soils, infiltration rates in the severely repellent soil were very low at the beginning and then increased. When the liquid-vapor surface tension was reduced by means of ethanol addition to the infiltrating solution, the cumulative infiltration curve of the severely repellent soil also became concave. Repellency degree (as measured by WDPT) was found to be essentially constant over a large range of ambient RH values (<10 , ,81%), and to increase sharply at values above 90%. The relative increase in water drop penetration time (WDPT) at high RH was greatest for the least repellent soil (10-fold increase in WDPT), and least for the most repellent soil (2-fold increase in WDPT). At RH > 90%, the time to reach equilibrium with respect to WDPT and soil moisture content was similar. In contrast, at values of ambient RH ranging from < 10 to 81%, WDPT was invariant over the course of reaching equilibrium with respect to moisture content. However, after reaching moisture content equilibrium, WDPT declined with increasing time. Copyright © 2007 John Wiley & Sons, Ltd. [source] Silicon Nanowires: A Review on Aspects of their Growth and their Electrical PropertiesADVANCED MATERIALS, Issue 25-26 2009Volker Schmidt Abstract This paper summarizes some of the essential aspects of silicon-nanowire growth and of their electrical properties. In the first part, a brief description of the different growth techniques is given, though the general focus of this work is on chemical vapor deposition of silicon nanowires. The advantages and disadvantages of the different catalyst materials for silicon-wire growth are discussed at length. Thereafter, in the second part, three thermodynamic aspects of silicon-wire growth via the vapor,liquid,solid mechanism are presented and discussed. These are the expansion of the base of epitaxially grown Si wires, a stability criterion regarding the surface tension of the catalyst droplet, and the consequences of the Gibbs,Thomson effect for the silicon wire growth velocity. The third part is dedicated to the electrical properties of silicon nanowires. First, different silicon nanowire doping techniques are discussed. Attention is then focused on the diameter dependence of dopant ionization and the influence of interface trap states on the charge carrier density in silicon nanowires. It is concluded by a section on charge carrier mobility and mobility measurements. [source] Synthesis of Carbon-Nanotube Composites Using Supercritical Fluids and Their Potential ApplicationsADVANCED MATERIALS, Issue 7 2009Zhimin Liu Abstract Carbon-nanotube (CNT) composites have attracted a lot of attention because of their potential applications in many fields. Here, recent advances in the synthesis of CNT composites using supercritical fluids (SCFs) are highlighted. SCFs exhibit unique features for the synthesis of composites because of their unusual properties, such as low viscosity, high diffusivity, near-zero surface tension, and tunability. Preliminary studies show that SCFs show unusual advantages for the synthesis of CNT composites. The morphologies and structures of the resultant CNT composites can be tuned by changing the solvent properties. The SCF methods not only provide a green route for the synthesis of composites, but also result in nanostructures that have not yet been produced by conventional methods. Moreover, the potential applications of the resultant CNT composites are also discussed. [source] Numerical analysis of Rayleigh,Plesset equation for cavitating water jetsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2007H. Alehossein Abstract High-pressure water jets are used to cut and drill into rocks by generating cavitating water bubbles in the jet which collapse on the surface of the rock target material. The dynamics of submerged bubbles depends strongly on the surrounding pressure, temperature and liquid surface tension. The Rayleigh,Plesset (RF) equation governs the dynamic growth and collapse of a bubble under various pressure and temperature conditions. A numerical finite difference model is established for simulating the process of growth, collapse and rebound of a cavitation bubble travelling along the flow through a nozzle producing a cavitating water jet. A variable time-step technique is applied to solve the highly non-linear second-order differential equation. This technique, which emerged after testing four finite difference schemes (Euler, central, modified Euler and Runge,Kutta,Fehlberg (RKF)), successfully solves the Rayleigh,Plesset (RP) equation for wide ranges of pressure variation and bubble initial sizes and saves considerable computing time. Inputs for this model are the pressure and velocity data obtained from a CFD (computational fluid dynamics) analysis of the jet. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||