A density gradient theory based method for surface tension calculations
DEFF Research Database (Denmark)
Liang, Xiaodong; Michelsen, Michael Locht; Kontogeorgis, Georgios
2016-01-01
The density gradient theory has been becoming a widely used framework for calculating surface tension, within which the same equation of state is used for the interface and bulk phases, because it is a theoretically sound, consistent and computationally affordable approach. Based on the observation...... that the optimal density path from the geometric mean density gradient theory passes the saddle point of the tangent plane distance to the bulk phases, we propose to estimate surface tension with an approximate density path profile that goes through this saddle point. The linear density gradient theory, which...... assumes linearly distributed densities between the two bulk phases, has also been investigated. Numerical problems do not occur with these density path profiles. These two approximation methods together with the full density gradient theory have been used to calculate the surface tension of various...
Theoretical calculations of the surface tension of Ag(1-x)-Cu(x) liquid alloys
International Nuclear Information System (INIS)
Aqra, Fathi; Ayyad, Ahmed
2011-01-01
Highlights: → A thermodynamic model for calculating the surface tension, and its temperature and composition dependences, of liquid binary alloys is described. → The model does not require the prior knowledge of the surface concentration and Gibbs energy. → The surface tension of the liquid Ag-Cu binary alloys has been calculated as a function of temperature and concentration. → The calculated values agree well with existing experimental data. - Abstract: The surface tension of silver-copper binary liquid alloys is calculated, in the frame work of Eyring theory. The calculations were made for different compositions (mole fraction, x Cu = 0, 0.2, 0.4, 0.6, 0.8 and 1), in the temperature range 1100-1800 K. The surface tension decreases with temperature increase, at a fixed copper fraction x Cu , and increases with increasing copper content. The calculated results are appropriately compared with existing literature data.
Density-functional calculations of the surface tension of liquid Al and Na
Stroud, D.; Grimson, M. J.
1984-01-01
Calculations of the surface tensions of liquid Al and Na are described using the full ionic density functional formalism of Wood and Stroud (1983). Surface tensions are in good agreement with experiment in both cases, with results substantially better for Al than those found previously in the gradient approximation. Preliminary minimization with respect to surface profile leads to an oscillatory profile superimposed on a nearly steplike ionic density disribution; the oscillations have a wavellength of about a hardsphere diameter.
A finite-density calculation of the surface tension of isotropic-nematic interfaces
International Nuclear Information System (INIS)
Moore, B.G.; McMullen, W.E.
1992-01-01
The surface tension of the isotropic-nematic interface in a fluid of intermediate-sized hard particles is studied and calculated. The transition from isotropic to nematic is fixed to occur in a continuous fashion by varying the biaxiality of the model particles. A reversal in the preferred orientation of the bulk nematic relative to the isotropic-nematic interface suggests an oblique orientation of the bulk nematic. 32 refs., 8 figs
Surface Tension Confines Cryogenic Liquid
Castles, Stephen H.; Schein, Michael E.
1989-01-01
New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.
Surface tension modelling of liquid Cd-Sn-Zn alloys
Fima, Przemyslaw; Novakovic, Rada
2018-06-01
The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd-Sn-Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd-Sn-Zn and constituent binaries has also been calculated.
Axelrod's model with surface tension
Pace, Bruno; Prado, Carmen P. C.
2014-06-01
In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.
Surface tension and related thermodynamic quantities of aqueous electrolyte solutions
Matubayasi, Norihiro
2013-01-01
Surface tension provides a thermodynamic avenue for analyzing systems in equilibrium and formulating phenomenological explanations for the behavior of constituent molecules in the surface region. While there are extensive experimental observations and established ideas regarding desorption of ions from the surfaces of aqueous salt solutions, a more successful discussion of the theory has recently emerged, which allows the quantitative calculation of the distribution of ions in the surface region. Surface Tension and Related Thermodynamic Quantities of Aqueous Electrolyte Solutions provides a d
Dynamical modeling of surface tension
International Nuclear Information System (INIS)
Brackbill, J.U.; Kothe, D.B.
1996-01-01
In a recent review it is said that free-surface flows ''represent some of the difficult remaining challenges in computational fluid dynamics''. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin. This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin are discussed
The law of corresponding states and surface tension of metals
International Nuclear Information System (INIS)
Digilov, R.
2001-01-01
Full Text: Surface tension of liquid metals is one of fundamental and most important quantities in theory and practice of material processing and its temperature dependence leads to the well-known Marangoni convection. Although currently methods are sufficiently precise to measure the surface tension, there are uncertainties in experimental data and its temperature dependence mainly due to impurity, which even a trace of it strongly affects the results of measurements. The theoretical treatment from the first principles is unwieldy and not always permits one to calculate the surface tension with certainty. Another active research field deals with empirical correlation between the surface tension and bulk thermodynamic properties, which we interpret as a simple consequence of the law of corresponding states. In order to relate the surface tension and to bulk properties of liquid metals the reduced formula is derived by scaling with the melting point T m (0) at p = 0 and atomic volume Ω 0 2/3 at T = 0 K as macroscopic parameters for scaling ε and a characterizing the interatomic potential in metals. The reduced surface tension and the reduced surface entropy obtained in high temperature limit are discussed and compared with the experiment. The reduced temperature coefficient of the surface tension found is a universal constant for the metals of the same structure. It is shown that pressure dependence of the surface tension, so called baric coefficient of the surface tension, can be described by pressure dependence of scaling parameters T m (p) and Ω 0 (p). (author)
Nonzero Ideal Gas Contribution to the Surface Tension of Water.
Sega, Marcello; Fábián, Balázs; Jedlovszky, Pál
2017-06-15
Surface tension, the tendency of fluid interfaces to behave elastically and minimize their surface, is routinely calculated as the difference between the lateral and normal components of the pressure or, invoking isotropy in momentum space, of the virial tensor. Here we show that the anisotropy of the kinetic energy tensor close to a liquid-vapor interface can be responsible for a large part of its surface tension (about 15% for water, independent from temperature).
Density and surface tension of ionic liquids.
Kolbeck, C; Lehmann, J; Lovelock, K R J; Cremer, T; Paape, N; Wasserscheid, P; Fröba, A P; Maier, F; Steinrück, H-P
2010-12-30
We measured the density and surface tension of 9 bis[(trifluoromethyl)sulfonyl]imide ([Tf(2)N](-))-based and 12 1-methyl-3-octylimidazolium ([C(8)C(1)Im](+))-based ionic liquids (ILs) with the vibrating tube and the pendant drop method, respectively. This comprehensive set of ILs was chosen to probe the influence of the cations and anions on density and surface tension. When the alkyl chain length in the [C(n)C(1)Im][Tf(2)N] series (n = 1, 2, 4, 6, 8, 10, 12) is increased, a decrease in density is observed. The surface tension initially also decreases but reaches a plateau for alkyl chain lengths greater than n = 8. Functionalizing the alkyl chains with ethylene glycol groups results in a higher density as well as a higher surface tension. For the dependence of density and surface tension on the chemical nature of the anion, relations are only found for subgroups of the studied ILs. Density and surface tension values are discussed with respect to intermolecular interactions and surface composition as determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The absence of nonvolatile surface-active contaminants was proven by ARXPS.
Effect of potential attraction term on surface tension of ionic liquids
Vaziri, N.; Khordad, R.; Rezaei, G.
2018-03-01
In this work, we have studied the effect of attraction term of molecular potential on surface tension of ionic liquids (ILs). For this purpose, we have introduced two different potential models to obtain analytical expressions for the surface tension of ILs. The introduced potential models have different attraction terms. The obtained surface tensions in this work have been compared with other theoretical methods and also experimental data. Using the calculated surface tension, the sound velocity is also estimated. We have studied the structural effects on the surface tensions of imidazolium-based ionic liquids. It is found that the cation alkyl chain length and the anion size play important roles to the surface tension of the selected ionic liquids. The calculated surface tensions show a good harmony with experimental data. It is clear that the attraction term of molecular potential has an important role on surface tension and sound velocity of our system.
Surface tension of normal and heavy water
International Nuclear Information System (INIS)
Straub, J.; Rosner, N.; Grigull, V.
1980-01-01
A Skeleton Table and simple interpolation equation for the surface tension of light water was developed by the Working Group III of the International Association for the Properties of Steam and is recommended as an International Standard. The Skeleton Table is based on all known measurements of the surface tension and individual data were weighted corresponding to the accuracy of the measurements. The form of the interpolation equation is based on a physical concept. It represents an extension of van der Waals-equation, where the exponent conforms to the 'Scaling Laws'. In addition for application purposes simple relations for the Laplace-coefficient and for the density difference between the liquid and gaseous phases of light water are given. The same form of interpolation equation for the surface tension can be used for heavy water, for which the coefficients are given. However, this equation is based only on a single set of data. (orig.) [de
Surface Tension Measurements with a Smartphone
Goy, Nicolas-Alexandre; Denis, Zakari; Lavaud, Maxime; Grolleau, Adrian; Dufour, Nicolas; Deblais, Antoine; Delabre, Ulysse
2017-01-01
Smartphones are increasingly used in higher education and at university in mechanics, acoustics, and even thermodynamics as they offer a unique way to do simple science experiments. In this article, we show how smartphones can be used in fluid mechanics to measure surface tension of various liquids, which could help students understand the concept…
Exact analytical density profiles and surface tension
Indian Academy of Sciences (India)
journal of. May 2005 physics pp. 785–801. Classical charged fluids at equilibrium near ... is provided by the excess surface tension for an air–water interface, which is determined ... the potential drop created by the electric layer which appears as soon as the fluid has ...... radii, by symmetry, the charge density profile is flat,.
Quantum surface tension in ideal gases
International Nuclear Information System (INIS)
Sisman, A.
2005-01-01
Due to wave character of atoms, an ideal gas confined in a finite domain exhibits Casimir like size effects. These effects become appreciable in a domain with at least one dimension in the order of micron. On this scale, thermodynamic state functions of an ideal gas become shape and size dependent and some new effects appear. In the literature, only some domains of regular shapes have been considered. In this study, the results are generalized to a domain of an arbitrary shape by using Weyl s conjecture for density of states. It is seen that free energy expression of an ideal Maxwellian gas consists of a classical volume dependent term and also a quantum originated surface dependent term, which causes a quantum surface tension. In a rectangular box filled by an ideal gas and separated by a movable wall into two parts, it is shown that a lateral force appears on the movable wall due to quantum surface tension
Surface tension in soap films: revisiting a classic demonstration
International Nuclear Information System (INIS)
Behroozi, F
2010-01-01
We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)
Surface tension in soap films: revisiting a classic demonstration
Energy Technology Data Exchange (ETDEWEB)
Behroozi, F [Department of Physics, University of Northern Iowa, Cedar Falls, IA 50614 (United States)], E-mail: behroozi@uni.edu
2010-01-15
We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)
Surface tension confined liquid cryogen cooler
Castles, Stephen H. (Inventor); Schein, Michael E. (Inventor)
1989-01-01
A cryogenic cooler is provided for use in craft such as launch, orbital, and space vehicles subject to substantial vibration, changes in orientation, and weightlessness. The cooler contains a small pore, large free volume, low density material to restrain a cryogen through surface tension effects during launch and zero-g operations and maintains instrumentation within the temperature range of 10 to 140 K. The cooler operation is completely passive, with no inherent vibration or power requirements.
Generalized surface tension bounds in vacuum decay
Masoumi, Ali; Paban, Sonia; Weinberg, Erick J.
2018-02-01
Coleman and De Luccia (CDL) showed that gravitational effects can prevent the decay by bubble nucleation of a Minkowski or AdS false vacuum. In their thin-wall approximation this happens whenever the surface tension in the bubble wall exceeds an upper bound proportional to the difference of the square roots of the true and false vacuum energy densities. Recently it was shown that there is another type of thin-wall regime that differs from that of CDL in that the radius of curvature grows substantially as one moves through the wall. Not only does the CDL derivation of the bound fail in this case, but also its very formulation becomes ambiguous because the surface tension is not well defined. We propose a definition of the surface tension and show that it obeys a bound similar in form to that of the CDL case. We then show that both thin-wall bounds are special cases of a more general bound that is satisfied for all bounce solutions with Minkowski or AdS false vacua. We discuss the limit where the parameters of the theory attain critical values and the bound is saturated. The bounce solution then disappears and a static planar domain wall solution appears in its stead. The scalar field potential then is of the form expected in supergravity, but this is only guaranteed along the trajectory in field space traced out by the bounce.
Surface tension of H2O and D2O
International Nuclear Information System (INIS)
Vargaftik, N.B.; Voljak, L.D.; Volkov, B.N.
1975-01-01
There is a great number of works on surface tension of clean water (H 2 O) at temperatures up to 100 deg C and very few above the boiling point. Works on surface tension of heavy water (D 2 O) are insufficient. A review of works on surface tension of both kinds of water is given
Surface tension of liquid Al-Cu binary alloys.
Schmitz, Julianna; Brillo, Jürgen; Egry, Ivan; Schmid-Fetzer, Rainer
2009-01-01
Surface tension data of liquid Al–Cu binary alloys have been measured contactlessly using the technique of electromagnetic levitation. A digital CMOS-camera (400 fps) recorded image sequences of the oscillating liquid sample and surface tensions were determined from analysis of the frequency spectra. Measurements were performed for samples covering the entire range of composition and precise data were obtained in a broad temperature range. It was found that the surface tensions can ...
On relation between the quark-gluon bag surface tension and the colour tube string tension
International Nuclear Information System (INIS)
Bugaev, K.A.; Zinovjev, G.M.
2010-01-01
We revisit the bag phenomenology of deconfining phase transition aiming to replenish it by introducing systematically the bag surface tension. Comparing the free energies of such bags and the strings confining the static quark-antiquark pair, we express the string tension in terms of the bag surface tension and the bulk pressure in order to estimate the bag characteristics using the lattice QCD (LQCD) data. Our analysis of the bag entropy density demonstrates that the surface tension coefficient is amazingly negative at the cross-over (continuous transition). The approach developed allows us to naturally account for an origin of a pronounced maximum (observed in the LQCD studies) in the behaviour of heavy quark-antiquark pair entropy. The vicinity of the (tri-)critical endpoint is also analyzed to clarify the meaning of vanishing surface tension coefficient.
Fowler's approximation for the surface tension and surface energy of Lennard-Jones fluids revisited
International Nuclear Information System (INIS)
Mulero, A; Galan, C; Cuadros, F
2003-01-01
We present a detailed study of the validity of Fowler's approximation for calculating the surface tension and the surface energy of Lennard-Jones fluids. To do so, we consider three different explicit analytical expressions for the radial distribution function (RDF), including one proposed by our research group, together with very accurate expressions for the liquid and vapour densities, also proposed by our group. The calculation of the surface tension from the direct correlation function using both the Percus-Yevick and the hypernetted-chain approximations is also considered. Finally, our results are compared with those obtained by other authors by computer simulations or through relevant theoretical approximations. In particular, we consider the analytical expression proposed by Kalikmanov and Hofmans (1994 J. Phys.: Condens. Matter 6 2207-14) for the surface tension. Our results indicate that the values for the surface energy in Fowler's approximation obtained by other authors are adequate, and can be calculated from the RDF models. For the surface tension, however, the values considered as valid in previous works seem to be incorrect. The correct values can be obtained from our model for the RDF or from the Kalikmanov and Hofmans expression with suitable inputs
Density functional theory of simple polymers in a slit pore. III. Surface tension
International Nuclear Information System (INIS)
Hooper, Justin B.; McCoy, John D.; Curro, John G.; Swol, Frank van
2000-01-01
In a previous study of tangent hard-site chains near a surface, the inhomogeneous density profiles were found through density functional theory. In the current study, the surface tensions of these systems are found from the results of the previous study through a thermodynamic integration. The calculated surface tensions are then compared to those found directly through computer simulation. Both the surface tension and surface excess for polymeric systems are shown to differ qualitatively from those of atomic systems, although certain similarities are seen at high densities. (c) 2000 American Institute of Physics
Dadashev, R. Kh.; Dzhambulatov, R. S.; Mezhidov, V. Kh.; Elimkhanov, D. Z.
2018-05-01
Concentration dependences of the surface tension and density of solutions of three-component acetone-ethanol-water systems and the bounding binary systems at 273 K are studied. The molar volume, adsorption, and composition of surface layers are calculated. Experimental data and calculations show that three-component solutions are close to ideal ones. The surface tensions of these solutions are calculated using semi-empirical and theoretical equations. Theoretical equations qualitatively convey the concentration dependence of surface tension. A semi-empirical method based on the Köhler equation allows us to predict the concentration dependence of surface tension within the experimental error.
Surface tension, hydrophobicity, and black holes: The entropic connection
International Nuclear Information System (INIS)
Callaway, D.J.
1996-01-01
The geometric entropy arising from partitioning space in a fluid open-quote open-quote field theory close-quote close-quote is shown to be linearly proportional to the area of an excluded region. The coefficient of proportionality is related to surface tension by a thermodynamic argument. Good agreement with experimental data is obtained for a number of fluids. The calculation employs a density-matrix formalism developed previously for studying the origin of black hole entropy. This approach may lead to a practical technique for the evaluation of thermodynamic quantities with important entropic components. copyright 1996 The American Physical Society
Measurement for Surface Tension of Aqueous Inorganic Salt
Directory of Open Access Journals (Sweden)
Jiming Wen
2018-03-01
Full Text Available Bubble columns are effective means of filtration in filtered containment venting systems. Here, the surface tension has a significant influence on bubble size distribution and bubble deformation, which have a strong impact on the behavior of the bubble column. The influence of aqueous inorganic compounds on the surface tension depends on the electrolytic activity, Debye length, entropy of ion hydration, and surface deficiencies or excess. In this work, the surface tensions of same specific aqueous solutions have been measured by different methods including platinum plate method, platinum ring method, and maximum bubble pressure method. The measured surface tensions of both sodium hydroxide and sodium thiosulfate are less than that of water. As solution temperature ranges from 20 to 75°C, the surface tension of 0.5 mol/L sodium hydroxide solution decreases from 71 to 55 mN/m while that of 1 mol/L solution decreases from 60 to 45 mN/m. Similarly during the same temperature range, the surface tension of 0.5 mol/L sodium thiosulfate decreases from 70 to 38 mN/m, and that of 1 mol/L sodium thiosulfate is between 68 and 36 mN/m. The analysis for the influence mechanism of aqueous inorganic on surface tension is provided. In addition, experimental results show that the surface tension of solid aerosol suspension liquid has no obvious difference from that of distilled water.
Surface tension and related thermodynamic parameters of alcohols using the Traube stalagmometer
International Nuclear Information System (INIS)
Dilmohamud, B A; Seeneevassen, J; Rughooputh, S D D V; Ramasami, P
2005-01-01
An apparatus was devised using the Traube Stalagmometer for the determination of the surface tension of the alcohols methanol, ethanol, propan-1-ol and butan-1-ol. Measurements were made under atmospheric pressure at temperatures between 288.15 K and 313.15 K. The surface tension values were correlated with temperature and surface thermodynamic parameters, namely surface entropy and surface enthalpy, were also calculated. The results obtained are in agreement with the literature and they are promising for the use of this low cost arrangement for accurate measurement of surface tension. Surface tension values were obtained with a maximum error of 0.5 mN m -1 and a maximum standard deviation of 0.8 mN m -1 . We recommend this arrangement for students in advanced university courses and it can also be used for research work
Prediction of surface tension of binary mixtures with the parachor method
Directory of Open Access Journals (Sweden)
Němec Tomáš
2015-01-01
Full Text Available The parachor method for the estimation of the surface tension of binary mixtures is modified by considering temperature-dependent values of the parachor parameters. The temperature dependence is calculated by a least-squares fit of pure-solvent surface tension data to the binary parachor equation utilizing the Peng-Robinson equation of state for the calculation of equilibrium densities. A very good agreement between experimental binary surface tension data and the predictions of the modified parachor method are found for the case of the mixtures of carbon dioxide and butane, benzene, and cyclohexane, respectively. The surface tension is also predicted for three refrigerant mixtures, i.e. propane, isobutane, and chlorodifluoromethane, with carbon dioxide.
Surface tension and density of fusible metal melt with sulphur and selenium
International Nuclear Information System (INIS)
Najdich, Yu.V.; Krasovskij, Yu.P.; Chuvashov, Yu.N.
1990-01-01
Surface tension and density at 970 K have been determined for melts of Ga, In, Sn and Pb with S and Se. High surface activity of chalcogens in the melts has been found. A maximal adsorption of the active components and their ultimate surface activity that correlate with thermodinamical strength of the corresponding sulfides and selenides have been calculated
International Nuclear Information System (INIS)
Rafati, Amir Abbas; Ghasemian, Ensieh
2009-01-01
Surface properties of binary mixtures of (n-alkyl acetates + heptane, benzene, and toluene) have been measured by surface tension method at T = 298.15 K and atmospheric pressure. Also, the surface tension has been predicted based on the Suarez method. This method combines a model for the description of surface tension of liquid mixtures with a group contribution method for the calculation of activity coefficient. The mean relative standard deviations obtained from the comparison of experimental (measured) and calculated surface tension values for the eight binary systems are less than 1.5%, which leads to concluding that the model shows a good accuracy in different situations in comparison with other predicted equations. In addition, the relative Gibbs adsorption and the surface mole fraction have been evaluated using this model. The surface tension deviations were calculated from experimental results and have been fitted to the Redlich-Kister type polynomial relation
Evaluation on Dorsey Method in Surface Tension Measurement of Solder Liquids Containing Surfactants
Zhao, Xingke; Xie, Feiming; Fan, Jinsheng; Liu, Dayong; Huang, Jihua; Chen, Shuhai
2018-06-01
With the purpose of developing a feasible approach for measuring the surface tension of solders containing surfactants, the surface tension of Sn-3Ag-0.5Cu-xP solder alloys, with various drop sizes as well as different phosphorus (P) content, was evaluated using the Dorsey method based on the sessile drop test. The results show that the accuracy of the surface tension calculations depends on both of sessile drop size and the liquid metal composition. With a proper drop size, in the range of 4.5 mm to 5.3 mm in equivalent spherical diameters, the deviation of the surface tension calculation can be limited to 1.43 mN·m-1 and 6.30 mN·m-1 for SnAgCu and SnAgCu-P, respectively. The surface tension of SnAgCu-xP solder alloys decreases quickly to a minimum value when the P content reaches 0.5 wt% and subsequently increases slowly with the P content further increasing. The formation of a P-enriched surface layer and Sn4P3 intermetallic phases is regarded to be responsible for the decreasing and subsequent increasing of surface tension, respectively.
Surface tension of compositions of polyhexametyleneguanidine hydrochloride - surfactants
Directory of Open Access Journals (Sweden)
S. Kumargaliyeva
2012-12-01
Full Text Available We made up songs bactericidal polyhexamethyleneguanidine hydrochloride (metacyde with the surface-active substances - anionic sodium dodecylsulfate, cationic cetylpyridinium bromide, and nonionic Tween-80 and measured the surface tension of water solutions. The study showed that the composition metacyde with surface-active agents have a greater surface activity than the individual components.
Experiment and model for the surface tension of amine–ionic liquids aqueous solutions
International Nuclear Information System (INIS)
Zhang, Pan; Du, LeiXia; Fu, Dong
2014-01-01
Highlights: • The surface tensions of MEA/DEA–ionic liquids aqueous solutions were measured. • The experiments were modeled satisfactorily by using a thermodynamic equation. • The temperature dependence of the surface tension was illustrated. • The effects of the mass fractions of MEA/DEA and ionic liquids were demonstrated. - Abstract: The surface tension (γ) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4 ])–monoethanolamine (MEA), 1-butyl-3-methylimidazolium bromide ([Bmim][Br])–MEA, [Bmim][BF 4 ]–diethanolamine (DEA) and [Bmim][Br]–DEA aqueous solutions was measured by using the BZY-1 surface tension meter. The temperature ranged from (293.2 to 323.2) K. The mass fraction of amines and ionic liquids (ILS) respectively ranged from 0.15 to 0.30 and 0.05 to 0.10. A thermodynamic equation was proposed to model the surface tension of amines–ILS aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fraction of amines and ILS on the surface tension were demonstrated on the basis of experiments and calculations
Surface tension alteration on calcite, induced by ion substitution
DEFF Research Database (Denmark)
Sakuma, Hiroshi; Andersson, Martin Peter; Bechgaard, Klaus
2014-01-01
The interaction of water and organic molecules with mineral surfaces controls many processes in nature and industry. The thermodynamic property, surface tension, is usually determined from the contact angle between phases, but how does one understand the concept of surface tension at the nanoscale...... preferentially as ion pairs at solution-calcite interfaces. Mg2+ incorporation weakens organic molecule adhesion while strengthening water adsorption so Mg2+ substitution renders calcite more water wet. When Mg2+ replaces 10% of surface Ca2+, the contact angle changes dramatically, by 40 to 70, converting...
Some remarks on the solid surface tension determination from contact angle measurements
Energy Technology Data Exchange (ETDEWEB)
Zdziennicka, Anna; Szymczyk, Katarzyna; Krawczyk, Joanna; Jańczuk, Bronisław, E-mail: bronislaw.janczuk@poczta.umcs.lublin.pl
2017-05-31
Graphical abstract: Surface tension of PE, nylon 6 and quartz from different approaches to the interface tension. - Highlights: • New values of water and formamide surface tension components were established. • Quartz surface tension depends on its crystal face. • Usefulness of different approaches for solid surface tension determination was tested. - Abstract: The measurements of water, formamide and diiodomethane contact angle (θ) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), nylon 6, quartz and silica were performed. Based on the θ values of these liquids obtained on PTFE, the Lifshitz-van der Waals and acid-base and/or dispersion and polar components of their surface tension (ST) were determined. In turn, the θ values for water, formamide and diiodomethane on PMMA were applied to calculate the electron-acceptor and electron-donor parameters of the Lewis acid-base component of the formamide ST. For this calculation the same values of the electron-acceptor and electron-donor parameters for water ST were used. Taking into account the values of components and parameters of water, formamide and diiodomethane ST obtained by us, van Oss et al. and from the water(formamide)-n-alkane and water-diiodomethane interface tension, the components and parameters of studied solids ST were calculated. To this end different approaches to the interface tension were considered. The obtained values were compared with those in the literature. It was concluded that for determination of solid ST components and parameters, those of water, formamide and diiodomethane ST obtained from the θ measurements on the model solids should be used.
Effects of surface tension on tray point efficiencies
Energy Technology Data Exchange (ETDEWEB)
Chen, G.X.; Afacan, A.; Chuang, K.T. (Alberta Univ., Edmonton, AB (Canada))
1994-08-01
Sieve tray efficiencies for the distillation of methanol/water, acetic acid/water, and cyclohexane/n-heptane mixtures were measured as a function of composition under fixed vapor and liquid rates in a 0.15 m diameter distillation column. The three binary distillation systems used in the study had a wide range of surface tensions measured as a function of composition. From the efficiencies measured, the number of vapor- and liquid-phase transfer units (Ng and Nl) was determined and the effects of surface tension on Ng and Nl were identified. To further verify the results obtained from the distillation column, bubble sizes in froths for air/water, air/methanol, and air/(water + surfactant) systems with different surface tensions were measured. The results show that surface tension has a significant effect on tray efficiency and the number of transfer units. Bubble sizes in the tray froths were mainly determined by surface tension, and bubble breakup and coalescence occur in the froths. 45 refs., 15 figs., 1 tab.
Nanofluidic bubble pump using surface tension directed gas injection
Tas, Niels Roelof; Berenschot, Johan W.; Lammerink, Theodorus S.J.; Elwenspoek, Michael Curt; van den Berg, Albert
2002-01-01
A new concept for liquid manipulation has been developed and implemented in surface-micromachined fluid channels. It is based on the surface tension directed injection of a gas into the liquid flow through micrometer-sized holes in the microchannel wall. The injected gas is directed to an exhaust by
Contact Angles and Surface Tension of Germanium-Silicon Melts
Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)
2001-01-01
Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.
Modeling of surface tension effects in venturi scrubbing
Ott, Robert M.; Wu, Tatsu K. L.; Crowder, Jerry W.
A modified model of venturi scrubber performance has been developed that addresses two effects of liquid surface tension: its effect on droplet size and its effect on particle penetration into the droplet. The predictions of the model indicate that, in general, collection efficiency increases with a decrease in liquid surface tension, but the range over which this increase is significant depends on the particle size and on the scrubber operating parameters. The predictions further indicate that the increases in collection efficiency are almost totally due to the effect of liquid surface tension on the mean droplet size, and that the collection efficiency is not significantly affected by the ability of the particle to penetrate the droplet.
Surface tension and density of Si-Ge melts
Ricci, Enrica; Amore, Stefano; Giuranno, Donatella; Novakovic, Rada; Tuissi, Ausonio; Sobczak, Natalia; Nowak, Rafal; Korpala, Bartłomiej; Bruzda, Grzegorz
2014-06-01
In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method.
Surface tension in microsystems engineering below the capillary length
Lambert, Pierre
2014-01-01
This book describes how surface tension effects can be used by engineers to provide mechanical functions in miniaturized products (<1 mm). Even if precursors of this field such as Jurin or Laplace already date back to the 18th century, describing surface tension effects from a mechanical perspective is very recent. The originality of this book is to consider the effects of capillary bridges on solids, including forces and torques exerted both statically and dynamically by the liquid along the 6 degrees-of-freedom. It provides a comprehensive approach to various applications, such as capillary adhesion (axial force), centering force in packaging and micro-assembly (lateral force) and recent developments such as a capillary motor (torque). It devises how surface tension can be used to provide mechanical functions such as actuation (bubble-actuated compliant table), sealing and tightness, energy harvesting, nanodispending.
International Nuclear Information System (INIS)
Amore, S.; Brillo, J.; Egry, I.; Novakovic, R.
2011-01-01
The surface tension of liquid Cu-Ti alloys has been measured by using the containerless technique of electromagnetic levitation and theoretically calculated in the framework of the compound formation model. Measurements have been carried out on alloys covering the entire range of composition and over the temperature range 1275-2050 K. For all investigated alloys the surface tension can be described by a linear function of the temperature with negative slope. Due to the presence of different intermetallic compounds in the solid state the surface properties of liquid Cu-Ti alloys are satisfactory described by the compound formation model.
Surface tension mediated conversion of light to work
Okawa, David; Pastine, Stefan J; Zettl, Alexander K; Frechet, Jean M. J
2014-12-02
Disclosed are a method and apparatus for converting light energy to mechanical energy by modification of surface tension on a supporting fluid. The apparatus comprises an object which may be formed as a composite object comprising a support matrix and a highly light absorptive material. The support matrix may comprise a silicon polymer. The highly light absorptive material may comprise vertically aligned carbon nanotubes (VANTs) embedded in the support matrix. The composite object is supported on a fluid. By exposing the highly light absorptive material to light, heat is generated, which changes the surface tension of the composite object, causing it to move physically within the fluid.
Surface tension estimation of high temperature melts of the binary alloys Ag-Au
Dogan, Ali; Arslan, Hüseyin
2017-11-01
Surface tension calculation of the binary alloys Ag-Au at the temperature of 1381 K, where Ag and Au have similar electronic structures and their atomic radii are comparable, are carried out in this study using several equations over entire composition range of Au. Apparently, the deviations from ideality of the bulk solutions, such as activities of Ag and Au are small and the maximum excess Gibbs free energy of mixing of the liquid phase is for instance -4500 J/mol at XAu = 0.5. Besides, the results obtained in Ag-Au alloys that at a constant temperature the surface tension increases with increasing composition while the surface tension decreases as the temperature increases for entire composition range of Au. Although data about surface tension of the Ag-Au alloy are limited, it was possible to make a comparison for the calculated results for the surface tension in this study with the available experimental data. Taken together, the average standard error analysis that especially the improved Guggenheim model in the other models gives the best agreement along with the experimental results at temperature 1383 K although almost all models are mutually in agreement with the other one.
Relationship between surface tension and refractive index in binary non-electrolyte mixtures
International Nuclear Information System (INIS)
Acevedo, I.L.; Pedrosa, G.C.; Katz, M.
1990-01-01
Lorentz-Lorenz equation for molecular refraction has been combined with Sugden's parachor equation for binary non-electrolyte mixtures at 298.15 K. The obtained equation has been shown successful in calculating values of surface tensions, by measuring refractive indices of the binary mixtures at the same mole fractions. The estimated error decreases when the mixtures present possible isorefractives. (Author) [es
Fowler's approximation for the surface tension and surface energy of Lennard-Jones fluids revisited
Energy Technology Data Exchange (ETDEWEB)
Mulero, A [Departamento de Fisica, Universidad de Extremadura, 06071-Badajoz (Spain); Galan, C [Departamento de Fisica, Universidad de Extremadura, 06071-Badajoz (Spain); Cuadros, F [Departamento de Fisica, Universidad de Extremadura, 06071-Badajoz (Spain)
2003-04-16
We present a detailed study of the validity of Fowler's approximation for calculating the surface tension and the surface energy of Lennard-Jones fluids. To do so, we consider three different explicit analytical expressions for the radial distribution function (RDF), including one proposed by our research group, together with very accurate expressions for the liquid and vapour densities, also proposed by our group. The calculation of the surface tension from the direct correlation function using both the Percus-Yevick and the hypernetted-chain approximations is also considered. Finally, our results are compared with those obtained by other authors by computer simulations or through relevant theoretical approximations. In particular, we consider the analytical expression proposed by Kalikmanov and Hofmans (1994 J. Phys.: Condens. Matter 6 2207-14) for the surface tension. Our results indicate that the values for the surface energy in Fowler's approximation obtained by other authors are adequate, and can be calculated from the RDF models. For the surface tension, however, the values considered as valid in previous works seem to be incorrect. The correct values can be obtained from our model for the RDF or from the Kalikmanov and Hofmans expression with suitable inputs.
Schroeder, Craig; Zheng, Wen; Fedkiw, Ronald
2012-01-01
-implicit and fully-coupled viscosity, pressure, and Lagrangian forces. We apply our new framework for forces on a Lagrangian mesh to the case of a surface tension force, which when treated explicitly leads to a tight time step restriction. By applying surface tension
Dynamic Bubble Surface Tension Measurements in Northwest Atlantic Seawater
Kieber, D. J.; Long, M. S.; Keene, W. C.; Kinsey, J. D.; Frossard, A. A.; Beaupre, S. R.; Duplessis, P.; Maben, J. R.; Lu, X.; Chang, R.; Zhu, Y.; Bisgrove, J.
2017-12-01
Numerous reports suggest that most organic matter (OM) associated with newly formed primary marine aerosol (PMA) originates from the sea-surface microlayer. However, surface-active OM rapidly adsorbs onto bubble surfaces in the water column and is ejected into the atmosphere when bubbles burst at the air-water interface. Here we present dynamic surface tension measurements of bubbles produced in near surface seawater from biologically productive and oligotrophic sites and in deep seawater collected from 2500 m in the northwest Atlantic. In all cases, the surface tension of bubble surfaces decreased within seconds after the bubbles were exposed to seawater. These observations demonstrate that bubble surfaces are rapidly saturated by surfactant material scavenged from seawater. Spatial and diel variability in bubble surface evolution indicate corresponding variability in surfactant concentrations and/or composition. Our results reveal that surface-active OM is found throughout the water column, and that at least some surfactants are not of recent biological origin. Our results also support the hypothesis that the surface microlayer is a minor to negligible source of OM associated with freshly produced PMA.
Evaluation of tension stiffening effect on the crack width calculation of flexural RC members
Directory of Open Access Journals (Sweden)
Said M. Allam
2013-06-01
Full Text Available Building codes consider the tension stiffening when calculating the crack width of the flexural members. A simple analytical procedure is proposed for the determination of forces, stresses and strains acting on a reinforced concrete section subjected to flexure considering the concrete contribution in tension up to tensile concrete strain corresponding to the cracking strength of concrete. This analytical method gives the minimum value (lower bound of tension stiffening. Also, a commercial Finite Element Program (ABAQUS 2007 was used to perform non-linear analysis in order to evaluate the total contribution of the tensioned concrete in carrying loads which may be considered as the upper bound of tension stiffening. In addition, a comparison is carried out among the different codes using four reinforced concrete rectangular models to compare and evaluate the tension stiffening with proposed analytical lower bound tension stiffening and upper bound as obtained by ABAQUS. The models include different percentages of flexural steel ratio. The comparison revealed that the codes’ equations always consider tension stiffening lying between lower and upper bound of tension stiffening proposed in this study. Also, the study showed that the tension stiffening decreases with the increase of the percentage of the flexural reinforcement ratio.
A micro surface tension pump (MISPU) in a glass microchip.
Peng, Xing Yue Larry
2011-01-07
A non-membrane micro surface tension pump (MISPU) was fabricated on a glass microchip by one-step glass etching. It needs no material other than glass and is driven by digital gas pressure. The MISPU can be seen working like a piston pump inside the glass microchip under a microscope. The design of the valves (MISVA) and pistons (MISTON) was based on the surface tension theory of the micro surface tension alveolus (MISTA). The digital gas pressure controls the moving gas-liquid interface to open or close the input and output MISVAs to refill or drive the MISTON for pumping a liquid. Without any moving parts, a MISPU is a kind of long-lasting micro pump for micro chips that does not lose its water pumping efficiency over a 20-day period. The volumetric pump output varied from 0 to 10 nl s(-1) when the pump cycle time decreased from 5 min to 15 s. The pump head pressure was 1 kPa.
Surface tension and density of liquid In-Sn-Zn alloys
Pstruś, Janusz
2013-01-01
Using the dilatometric method, measurements of the density of liquid alloys of the ternary system In-Sn-Zn in four sections with a constant ratio Sn:In = 24:1, 3:1, 1:1, 1:3, for various Zn additions (5, 10, 14, 20, 3 5, 50 and 75 at.% Zn) were performed at the temperature ranges of 500-1150 K. Density decreases linearly for all compositions. The molar volume calculated from density data exhibits close to ideal dependence on composition. Measurements of the surface tension of liquid alloys have been conducted using the method of maximum pressure in the gas bubbles. There were observed linear dependences on temperature with a negative gradients dσ/dT. Generally, with two exceptions, there was observed the increase of surface tension with increasing content of zinc. Using the Butler's model, the surface tension isotherms were calculated for temperatures T = 673 and 1073 K. Calculations show that only for high temperatures and for low content of zinc (up to about 35 at.%), the modeling is in very good agreement with experiment. Using the mentioned model, the composition of the surface phase was defined at two temperatures T = 673 and 973 K. Regardless of the temperature and of the defined section, the composition of the bulk is very different in comparison with the composition of the surface.
Kremer, J.; Kilzer, A.; Petermann, M.
2018-01-01
Oscillations of small liquid drops around a spherical shape have been of great interest to scientists measuring physical properties such as interfacial tension and viscosity, over the last few decades. A powerful tool for contactless positioning is acoustic levitation, which has been used to simultaneously determine the surface tension and viscosity of liquids at ambient pressure. In order to extend this acoustic levitation measurement method to high pressure systems, the method is first evaluated under ambient pressure. To measure surface tension and viscosity using acoustically levitated oscillating drops, an image analysis method has to be developed and factors which may affect measurement, such as sound field or oscillation amplitude, have to be analyzed. In this paper, we describe the simultaneous measurement of surface tension and viscosity using freely decaying shape oscillations of acoustically levitated droplets of different liquids (silicone oils AK 5 and AK 10, squalane, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) in air. These liquids vary in viscosity from 2 to about 30 mPa s. An acoustic levitation system, including an optimized standing wave acoustic levitator and a high-speed camera, was used for this study. An image analysis was performed with a self-written Matlab® code. The frequency of oscillation and the damping constant, required for the determination of surface tension and viscosity, respectively, were calculated from the evolution of the equatorial and polar radii. The results and observations are compared to data from the literature in order to analyze the accuracy of surface tension and viscosity determination, as well as the effect of non-spherical drop shape or amplitude of oscillation on measurement.
Sresht, Vishnu; Lewandowski, Eric P; Blankschtein, Daniel; Jusufi, Arben
2017-08-22
A molecular modeling approach is presented with a focus on quantitative predictions of the surface tension of aqueous surfactant solutions. The approach combines classical Molecular Dynamics (MD) simulations with a molecular-thermodynamic theory (MTT) [ Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992 , 8 , 2680 ]. The MD component is used to calculate thermodynamic and molecular parameters that are needed in the MTT model to determine the surface tension isotherm. The MD/MTT approach provides the important link between the surfactant bulk concentration, the experimental control parameter, and the surfactant surface concentration, the MD control parameter. We demonstrate the capability of the MD/MTT modeling approach on nonionic alkyl polyethylene glycol surfactants at the air-water interface and observe reasonable agreement of the predicted surface tensions and the experimental surface tension data over a wide range of surfactant concentrations below the critical micelle concentration. Our modeling approach can be extended to ionic surfactants and their mixtures with both ionic and nonionic surfactants at liquid-liquid interfaces.
Liquid metal actuator driven by electrochemical manipulation of surface tension
Russell, Loren; Wissman, James; Majidi, Carmel
2017-12-01
We examine the electrocapillary properties of a fluidic actuator composed of a liquid metal droplet that is submerged in electrolytic solution and attached to an elastic beam. The beam deflection is controlled by electrochemically driven changes in the surface energy of the droplet. The metal is a eutectic gallium-indium alloy that is liquid at room temperature and forms an nm-thin Ga2O3 skin when oxidized. The effective surface tension of the droplet changes dramatically with oxidation and reduction, which are reversibly controlled by applying low voltage to the electrolytic bath. Wetting the droplet to two copper pads allows for a controllable tensile force to be developed between the opposing surfaces. We demonstrate the ability to reliably control force by changing the applied oxidizing voltage. Actuator forces and droplet geometries are also examined by performing a computational fluid mechanics simulation using Surface Evolver. The theoretical predictions are in qualitative agreement with the experimental measurements and provide additional confirmation that actuation is driven by surface tension.
Analytical description of concentration dependence of surface tension in multicomponent systems
Energy Technology Data Exchange (ETDEWEB)
Dadashev, R; Kutuev, R [Complex Science Research Institute of the Science Academy of the Chechen Republic, 21 Staropromisl. shosse, Grozny 364096 (Russian Federation); Elimkhanov, D [Science Academy of the Chechen Republic (Russian Federation)], E-mail: edzhabrail@mail.ru
2008-02-15
From the basic fundamental thermodynamic expressions the equation of isotherms of the surface tension of a ternary system is received. Various assumptions concerning the concentration dependence of molar areas are usually made when the equation is derived. The dependence of the molar areas is calculated as an additive function of the structure of a volumetric phase or the structure of a surface layer. To define the concentration dependence of the molar areas we used a stricter thermodynamic expression offered by Butler. In the received equation the dependence of molar areas on the structure of the solution is taken into account. Therefore, the equation can be applied for the calculation of surface tension over a wide concentration range of the components. Unlike the known expressions, the equation includes the surface tension properties of lateral binary systems, which makes the accuracy of the calculated values considerably higher. Thus, among the advantages of the offered equation we can point out the mathematical simplicity of the received equation and the fact that the equation includes physical parameters the experimental definition of which does not present any special difficulties.
Surface tension propulsion of fungal spores by use of microdroplets
Noblin, Xavier; Yang, Sylvia; Dumais, Jacques
2010-01-01
Many edible mushrooms eject their spores (about 10 microns in size) at high speed (about 1 m/s) using surface tension forces in a few microseconds. Basically the coalescence of a droplet with the spore generates the necessary momentum to eject the spore. We have detailed this mechanism in \\cite{noblin2}. In this article, we give some details about the high speed movies (up to 250000 fps) of mushrooms' spores ejection attached to this submission. This video was submitted as part of the Gallery...
Density and surface tension of melts of zirconium and hafnium fluorides with lithium fluoride
International Nuclear Information System (INIS)
Katyshev, S.F.; Artemov, V.V.; Desyatnik, V.N.
1988-01-01
A study was conducted to determine the temperature dependence of the density and surface tension of melts of LiF-ZrF 4 and LiF-HfF 4 . Density and surface tension were determined by the method of maximum pressure in an argon bubble. On the basis of experimental data over the entire concentration range the molar volumes and their relative deviations from the additive molar volumes were calculated for 1100 0 K. The positive deviations of the molar volumes from additivity in the LiF-HfF 4 system (22.45%) were greater than in the LiF-ZrF 4 system (15.75%). This indicated that the reaction with lithium fluoride is intensified with the switch to the hafnium fluoride. Results also demonstrated that the fluorides are surface-active components in the molten mixtures
A Comparison of Effective Tension Calculation for Design Belt Conveyor between CEMA and DIN Standard
Directory of Open Access Journals (Sweden)
Satria Iman
2018-01-01
Full Text Available In the present era, many industries are demanding material transfer equipment that works maximally and cheaply. Belt Conveyor is one of the most efficient material transfer equipment compared to heavy equipment or other transportation equipment, because it can transport the material in large capacity. When designing conveyor belts, many industries want large transport capacity at low cost. One of the cost savings can be done with low motor power consumption. Many standards describe the effective tension calculation on the conveyor belt in detail with the parameters, since the effective tension calculation results are essential for determining motor power. This paper aims to analyze the effective tension on conveyor belts using CEMA 5th, CEMA 6th and DIN 22101 standards with case studies of 1000 TPH carrying capacity and 3 m/s conveyor speed. The difference between CEMA and DIN when determining the effective tension is on the use of coefficient of friction, because DIN uses a global coefficient of friction while CEMA uses different friction coefficients on idler, belt and material. This difference in coefficient of friction results in different ways of calculating the resistance being the accumulation of the effective tension. The result is an effective tension value using DIN 22101 standard of 22,148.16 N with motor power consumption of 66.5 kW, while effective tension value using CEMA 5th standard is 32.201.66 N with motor power consumption 96.47 kW, and effective tension value using CEMA 6th standard is 29,686.48 N with 89.06 kW motor power consumption.
Account for the surface tension in hydraulic modeling of the weir with a sharp threshold
Directory of Open Access Journals (Sweden)
Medzveliya Manana Levanovna
Full Text Available In the process of calculating and simulating water discharge in free channels it is necessary to know the flow features in case of small values of Reynolds and Weber numbers. The article considers the influence of viscosity and surface tension on the coefficient of a weir flow with sharp threshold. In the article the technique of carrying out experiments is stated, the equation is presented, which considers the influence of all factors: pressure over a spillway threshold, threshold height over a course bottom, speed of liquid, liquid density, dynamic viscosity, superficial tension, gravity acceleration, unit discharge, the width of the course. The surface tension and liquid density for the applied liquids changed a little. In the rectangular tray (6000x100x200 spillway with a sharp threshold was established. It is shown that weir flow coefficient depends on Reynolds number (in case Re < ~ 2000 and Webers number. A generalized expression for determining weir flow coefficient considering the influence of the forces of viscosity and surface tension is received.
Superfluid 3He A-B surface tension
International Nuclear Information System (INIS)
Bartkowiak, M.; Haley, R.P.; Fisher, S.N.; Guenault, A.M.; Pickett, G.R.; Skyba, P.
2003-01-01
We have made two different measurements of interfacial energies below 300 μK, at zero pressure and in magnetic fields up to 400 mT. A variable magnetic field profile allows us to stabilize and precisely manipulate the position of the A-B interface. First, we can derive the difference in wall wetting energies from the behaviour of the phase boundary as it enters and exits a stack of glass capillary tubes. Secondly, we can measure the surface tension from the level of over- or under-magnetization needed to force the interface through an aperture. These are the first surface energy measurements in high magnetic fields in the zero-temperature limit. Our results are in surprising agreement with earlier measurements at high pressure close to T c
Improvement of gas entrainment prediction method. Introduction of surface tension effect
International Nuclear Information System (INIS)
Ito, Kei; Sakai, Takaaki; Ohshima, Hiroyuki; Uchibori, Akihiro; Eguchi, Yuzuru; Monji, Hideaki; Xu, Yongze
2010-01-01
A gas entrainment (GE) prediction method has been developed to establish design criteria for the large-scale sodium-cooled fast reactor (JSFR) systems. The prototype of the GE prediction method was already confirmed to give reasonable gas core lengths by simple calculation procedures. However, for simplification, the surface tension effects were neglected. In this paper, the evaluation accuracy of gas core lengths is improved by introducing the surface tension effects into the prototype GE prediction method. First, the mechanical balance between gravitational, centrifugal, and surface tension forces is considered. Then, the shape of a gas core tip is approximated by a quadratic function. Finally, using the approximated gas core shape, the authors determine the gas core length satisfying the mechanical balance. This improved GE prediction method is validated by analyzing the gas core lengths observed in simple experiments. Results show that the analytical gas core lengths calculated by the improved GE prediction method become shorter in comparison to the prototype GE prediction method, and are in good agreement with the experimental data. In addition, the experimental data under different temperature and surfactant concentration conditions are reproduced by the improved GE prediction method. (author)
On the modelling of semi-insulating GaAs including surface tension and bulk stresses
Energy Technology Data Exchange (ETDEWEB)
Dreyer, W.; Duderstadt, F.
2004-07-01
Necessary heat treatment of single crystal semi-insulating Gallium Arsenide (GaAs), which is deployed in micro- and opto- electronic devices, generate undesirable liquid precipitates in the solid phase. The appearance of precipitates is influenced by surface tension at the liquid/solid interface and deviatoric stresses in the solid. The central quantity for the description of the various aspects of phase transitions is the chemical potential, which can be additively decomposed into a chemical and a mechanical part. In particular the calculation of the mechanical part of the chemical potential is of crucial importance. We determine the chemical potential in the framework of the St. Venant-Kirchhoff law which gives an appropriate stress/strain relation for many solids in the small strain regime. We establish criteria, which allow the correct replacement of the St. Venant-Kirchhoff law by the simpler Hooke law. The main objectives of this study are: (i) We develop a thermo-mechanical model that describes diffusion and interface motion, which both are strongly influenced by surface tension effects and deviatoric stresses. (ii) We give an overview and outlook on problems that can be posed and solved within the framework of the model. (iii) We calculate non-standard phase diagrams, i.e. those that take into account surface tension and non-deviatoric stresses, for GaAs above 786 C, and we compare the results with classical phase diagrams without these phenomena. (orig.)
International Nuclear Information System (INIS)
Mohammad, Abubaker A.; Alkhaldi, Khaled H.A.E.; AlTuwaim, Mohammad S.; Al-Jimaz, Adel S.
2013-01-01
Highlights: ► Physical properties of binary mixtures of DMF+1-pentanol, 1-hexanol, or 1-heptanol. ► Viscosity and surface tension were measured. ►Δη, Δσ σ and G ∗E were calculated using the experimental data. ► H σ and S σ were determined using the surface tension data. ► Semi-empirical relations were used to estimate the viscosity of liquid mixtures. - Abstract: Viscosity η and surface tension σ were measured for binary mixtures of N,N-dimethylformamide DMF with pentan-1-ol, hexan-1-ol, and heptan-1-ol at T = (298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure over the entire mole fraction range. Deviations in viscosity Δη and surface tension Δσ were calculated using experimental results. Moreover, the values of the excess Gibbs free energy of activation G ∗E , surface enthalpy H σ and surface entropy S σ of these mixtures were determined. Viscosity measurements of the binary systems were correlated with Grunberg and Nissan, the three-body and four-body McAllister expressions. Viscosity deviation, surface tension deviation and excess Gibbs energy of activation functions were fitted to the method of Redlich–Kister (R–K) polynomial to estimate the coefficients and standard deviations. The effects of chain length of alkan-1-ols and temperature on the thermodynamic properties of binary systems were studied.
DEFF Research Database (Denmark)
Ollila, O. H. S.; Lamberg, A.; Lehtivaara, M.
2012-01-01
) are essentially lipid droplets surrounded by specific proteins, their main function being to transport cholesterol. Interfacial tension and surface pressure of these particles are of great interest because they are related to the shape and the stability of the droplets and to protein adsorption at the interface....... Here we use coarse-grained molecular-dynamics simulations to consider a number of related issues by calculating the interfacial tension in protein-free lipid droplets, and in HDL and LDL particles mimicking physiological conditions. First, our results suggest that the curvature dependence......Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively...
Calculated surface-energy anomaly in the 3d metals
DEFF Research Database (Denmark)
Aldén, M.; Skriver, Hans Lomholt; Mirbt, S.
1992-01-01
Local-spin-density theory and a Green’s-function technique based on the linear muffin-tin orbitals method have been used to calculate the surface energy of the 3d metals. The theory explains the variation of the values derived from measurements of the surface tension of liquid metals including...... the pronounced anomaly occurring between vanadium and nickel in terms of a decrease in the d contribution caused by spin polarization....
International Nuclear Information System (INIS)
Evans, R.; Kumaravadivel, R.
1976-01-01
A simple scheme for determining the ion density profile and the surface tension of a liquid metal is described. Assuming that the interaction between metallic pseudo-ions is of the form introduced by Evans, an approximate expression for the excess free energy of the system is derived using the thermodynamic perturbation theory of Weeks, Chandler and Anderson. This excess free energy is then minimized with respect to a parameter which specifies the ion density profile, and the surface tension is given directly. From a consideration of the dependence of the interionic forces on the electron density it is predicted that the ions should take up a very steep density profile at the liquid metal surface. This behaviour is contrasted with that to be expected for rare-gas fluids in which the interatomic forces are density-independent. The values of the surface tension calculated for liquid Na, K and Al from a simplified version of the theory are in reasonable agreement with experiment. (author)
Backward flow in a surface tension driven micropump
International Nuclear Information System (INIS)
Ju, Jongil; Park, Joong Yull; Lee, Sang-Hoon; Kim, Kyung Chun; Kim, Hyundong; Berthier, Erwin; Beebe, David J
2008-01-01
A surface tension driven micropump harnessing the pressure difference generated by drops of different curvature radii proves to be a simple and attractive passive method to drive fluid flow in microdevices. Here we observed the appearance of backward flow when the initial sizes of the droplets at the inlet and outlet ports are similar. To explain this phenomenon several hypotheses have been investigated. Consideration of the inertia of the fluid in the channel revealed that it alone is insufficient to explain the observed backward flow. We discovered that rotational flow inside the outlet droplet could be a source of inertia, explaining the generation of the backward flow. In addition, we have experimentally determined that the ratio of the volumes of the initial outlet drop and inlet drop correlates with the occurrence of the backward flow. (note)
International Nuclear Information System (INIS)
Bagheri, Ahmad; Fazli, Mostafa; Bakhshaei, Malihe
2016-01-01
Highlights: • Surface tension of DMSO + alcohol (methanol, ethanol and isopropanol) at various temperatures was measured. • The surface tension data of binary mixtures were correlated with four equations. • Intermolecular interaction of DMSO with alcohol was discussed. • The surface mole fraction of alcohol increase with increasing the length of alcohol chain. - Abstract: Surface tension of binary mixtures of methanol, ethanol and isopropanol with DMSO (dimethyl sulfoxide) was measured over the whole range of composition at atmospheric pressure of 82.5 kPa within the temperatures between (298.15 and 328.15) K. The experimental measurements were used to calculate in surface tension deviations (Δσ). The sign of Δσ for all temperatures is negative (except of methanol/DMSO system) because of the factors of hydrogen bonding and dipole–dipole interactions in the DMSO-alcohol systems. Surface tension values of the binary systems were correlated with FLW, MS, RK and LWW models. The mean standard deviation obtained from the comparison of experimental and calculated surface tension values for binary systems with three models (FLW, MS and RK) at various temperatures is less than 0.83. Also, the results of the LWW model were used to account for the interaction energy between alcohols and DMSO in binary mixtures. The temperature dependence of σ (surface tension) at fixed composition of solutions was used to estimate surface enthalpy, H s , and surface entropy, S s . The results obtained show that the values of the thermodynamic parameters for alcohol/DMSO mixtures decrease with increasing alkyl chain length of alcohol. Finally, the results are discussed in terms of surface mole fraction and lyophobicity using the extended Langmuir (EL) isotherm.
Using the surface tension to estimate the condensate density of superfluid 4He
International Nuclear Information System (INIS)
Campbell, L.J.
1983-01-01
Distortion of the condensate wavefunction at the free surface of superfluid 4 He contributes to the surface tension in proportion to the condensate fraction n 0 (T). Using this to resolve the present discrepancy between the measured and predicted temperature dependencies of the surface tension gives n 0 (T) in good agreement with results from neutron and x-ray scattering measurements. This picture is also consistent with the measured 3 He- 4 He interfacial tension
Calculation of the Stiffness in the Roll Tensioning of the Circular Saw Blade
Directory of Open Access Journals (Sweden)
Linh Vo Tung
2016-01-01
Full Text Available The circular blade has been widely used in some projects such as cutting stone, wood and other projects. Owing to its particularity and wide use, it has an important position in cutting industry. Roll tensioning is considered as an effective method which can be used to improve the stiffness and performance of the circular saw blade. The effect of rolling position and width in the roll tensioning is obvious. In this paper the calculation of the maximum stiffness at different rolling position and width in the rolling were carried out through the finite -element. The results show that three ideal points are found. And when rolling position is Ø950mm and rolling width is 20mm, the maximum stiffness of the circular saw blade whose minimum deformation is 0.028mm is found. The roll tensioning can increase the stiffness of the saw blade. It will provide a theoretical basis and guidance for the actual production.
The behavior of surface tension on steady-state rotating fluids in the low gravity environments
Hung, R. J.; Leslie, Fred W.
1987-01-01
The effect of surface tension on steady-state rotating fluids in a low gravity environment is studied. All the values of the physical parameters used in these calculations, except in the low gravity environments, are based on the measurements carried out by Leslie (1985) in the low gravity environment of a free-falling aircraft. The profile of the interface of two fluids is derived from Laplace's equation relating the pressure drop across an interface to the radii of curvature which has been applied to a low gravity rotating bubble that contacts the container boundary. The interface shape depends on the ratio of gravity to surface tension forces, the ratio of centrifugal to surface tension forces, the contact radius of the interface to the boundary, and the contact angle. The shape of the bubble is symmetric about its equator in a zero-gravity environment. This symmetry disappears and gradually shifts to parabolic profiles as the gravity environment becomes non-zero. The location of the maximum radius of the bubble moves upward from the center of the depth toward the top boundary of the cylinder as gravity increases. The contact radius of interface to the boundary r0 at the top side of cylinder increases and r0 at the bottom side of the cylinder decreases as the gravity environment increases from zero to 1 g.
Surface crack growth in cylindrical hollow specimen subject to tension and torsion
Directory of Open Access Journals (Sweden)
V. Shlyannikov
2015-07-01
Full Text Available The subject for studies is an aluminium cylindrical hollow specimen with external axial and part circumferential semi-elliptical surface crack undergoing fatigue loads. Both the optical microscope measurements and the crack opening displacement (COD method are used to monitor and calculate both crack depth and crack length during the tests. The variation of crack growth behaviour is studied under cyclic axial tension, pure torsion and combined tension+torsion fatigue loading. For the particular surface flaw geometries considered, the elastic and plastic in-plane and out-of-plane constraint parameters, as well as the governing parameter for stress fields in the form of In-integral and plastic stress intensity factor, are obtained as a function of the aspect ratio, dimensionless crack length and crack depth. The combined effect of tension and torsion loading and initial surface flaw orientation on the crack growth for two type of aluminium alloys is made explicit. The experimental and numerical results of the present study provided the opportunity to explore the suggestion that fatigue crack propagation may be governed more strongly by the plastic stress intensity factor rather than the magnitude of the elastic SIFs alone. One advantage of the plastic SIF is its sensitivity to combined loading due to accounting for the plastic properties of the material.
Tensioned Fabric Structures with Surface in the Form of Chen-Gackstatter
Directory of Open Access Journals (Sweden)
Yee Hooi Min
2016-01-01
Full Text Available Form-finding has to be carried out for tensioned fabric structure in order to determine the initial equilibrium shape under prescribed support condition and prestress pattern. Tensioned fabric structures are normally designed to be in the form of equal tensioned surface. Tensioned fabric structure is highly suited to be used for realizing surfaces of complex or new forms. However, research study on a new form as a tensioned fabric structure has not attracted much attention. Another source of inspiration minimal surface which could be adopted as form for tensioned fabric structure is very crucial. The aim of this study is to propose initial equilibrium shape of tensioned fabric structures in the form of Chen-Gackstatter. Computational form-finding using nonlinear analysis method is used to determine the Chen-Gackstatter form of uniformly stressed surfaces. A tensioned fabric structure must curve equally in opposite directions to give the resulting surface a three dimensional stability. In an anticlastic doubly curved surface, the sum of all positive and all negative curvatures is zero. This study provides an alternative choice for structural designer to consider the Chen-Gackstatter applied in tensioned fabric structures. The results on factors affecting initial equilibrium shape can serve as a reference for proper selection of surface parameter for achieving a structurally viable surface.
A waveless free surface flow past a submerged triangular obstacle in presence of surface tension
Directory of Open Access Journals (Sweden)
Hakima Sekhri
2016-07-01
Full Text Available We consider the Free surface flows passing a submerged triangular obstacle at the bottom of a channel. The problem is characterized by a nonlinear boundary condition on the surface of unknown configuration. The analytical exact solutions for these problems are not known. Following Dias and Vanden Broeck [6], we computed numerically the solutions via a series truncation method. These solutions depend on two parameters: the Weber number $\\alpha$ characterizing the strength of the surface tension and the angle $\\beta$ at the base characterizing the shape of the apex. Although free surface flows with surface tension admit capillary waves, it is found that solution exist only for values of the Weber number greater than $\\alpha_0$ for different configurations of the triangular obstacle.
Surface Tension Driven Instability in the Regime of Stokes Flow
Yao, Zhenwei; Bowick, Mark; Xing, Xiangjun
2010-03-01
A cylinder of liquid inside another liquid is unstable towards droplet formation. This instability is driven by minimization of surface tension energy and was analyzed first by [1,2] and then by [3]. We revisit this problem in the limit of small Laplace number, where the inertial of liquids can be completely ignored. The stream function is found to obey biharmonic equation, and its analytic solutions are found. We rederive Tomotika's main results, and also obtain many new analytic results about the velocity fields. We also apply our formalism to study the recent experiment on toroidal liquid droplet[4]. Our framework shall have many applications in micro-fluidics. [1] L.Rayleigh, On The Instability of A Cylinder of Viscous Liquid Under Capillary Force, Scientific Papers, Cambridge, Vol.III, 1902. [2] L.Rayleigh, On The Instability of Cylindrical Fluid Surfaces, Scientific Papers, Cambridge, Vol.III, 1902. [3] S.Tomotika, On the Instability of a Cylindrical Thread of a Viscous Liquid surround by Another Viscous Fluid, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Volume 150, Issue 870, pp. 322-337. [4] E.Pairam and A.Fern'andez-Nieves, Generation and Stability of Toroidal Droplets in a Viscous Liquid, Physical Review Letters 102, 234501 (2009).
Theory of the surface dipole layer and of surface tension in liquids of charged particles
International Nuclear Information System (INIS)
Senatore, G.; Tosi, M.P.
1980-01-01
The problem of the surface density profiles and of the surface tension of a two-component liquid of charged particles in equilibrium with its vapour is examined. The exact equilibrium conditions for the profiles are given in terms of the inverse response functions of the inhomogeneous fluid, and alternative exact expressions for the surface tension are derived. The use of a density gradient expansion reduces the problem to knowledge of properties of a homogeneous charged fluid on a uniform neutralizing background, in which the total particle density and the charge density are independent variables. Additional simplifications are discussed for special cases for which a perturbative treatment of the surface charge density profile can be developed, and in particular for nearly symmetric ionic liquids and for simple liquid metals. (author)
Life time calculations for LCF loading combined with tensional hold periods
International Nuclear Information System (INIS)
Bocek, M.; Armas, A.; Piel, D.
1983-01-01
The life time in high amplitude strain cycling with tensional hold periods is analysed presuming that creep failure damage is life determining. The life fraction rule (LFR) is used to calculate the life time consumpted during the dwell period in strain controlled tests as well as during tensional hold time stress cycles. It follows from the present investigation that stress relaxation occurring during the strain hold periods plays the dominant influence upon the relationship between life and dwell time. For strong stress relaxation (e.g. high temperature) less damage is accumulated as compared to suppressed relaxation (low temperature). The damage in stress relaxation is calculated by means of the LFR and the results are compared to experiments conducted on Zircaloy-4 and the austenitic stainless stell Type AISI 304. From the very good agreement between both it is concluded that under the loading conditions considered, creep failure damage is the main life determining damage contribution. (orig.)
Dynamic surface tension measurements of ionic surfactants using maximum bubble pressure tensiometry
Ortiz, Camilla U.; Moreno, Norman; Sharma, Vivek
Dynamic surface tension refers to the time dependent variation in surface tension, and is intimately linked with the rate of mass transfer of a surfactant from liquid sub-phase to the interface. The diffusion- or adsorption-limited kinetics of mass transfer to interfaces is said to impact the so-called foamability and the Gibbs-Marangoni elasticity of surfaces. Dynamic surface tension measurements carried out with conventional methods like pendant drop analysis, Wilhelmy plate, etc. are limited in their temporal resolution (>50 ms). In this study, we describe design and application of maximum bubble pressure tensiometry for the measurement of dynamic surface tension effects at extremely short (1-50 ms) timescales. Using experiments and theory, we discuss the overall adsorption kinetics of charged surfactants, paying special attention to the influence of added salt on dynamic surface tension.
Wetting and surface tension of bismate glass melt
International Nuclear Information System (INIS)
Shim, Seung-Bo; Kim, Dong-Sun; Hwang, Seongjin; Kim, Hyungsun
2009-01-01
Lead oxide glass frits are used widely in the electronics industry for low-temperature firing. On the other hand, one of the low-sintering and low-melting lead-free glass systems available, the bismate glass system, is considered to be an alternative to lead oxide glass. In order to extend the applications of Bi 2 O 3 glasses, this study examined the thermophysical properties of low-melting Bi 2 O 3 -B 2 O 3 -ZnO-BaO-Al 2 O 3 -SiO 2 glass frits with various ZnO/B 2 O 3 ratios. The fundamental thermal properties, such as glass transition temperature and softening point, were examined by differential thermal analysis and a glass softening point determination system. The wetting angles, viscosities and surface tension of the various bismate glasses on an alumina substrate were measured using hot-stage microscopy and the sessile drop method. These thermophysical properties will be helpful in understanding the work of adhesion and the liquid spread kinetics of glass frits.
Mapping surface tension induced menisci with application to tensiometry and refractometry.
Mishra, Avanish; Kulkarni, Varun; Khor, Jian-Wei; Wereley, Steve
2015-07-28
In this work, we discuss an optical method for measuring surface tension induced menisci. The principle of measurement is based upon the change in the background pattern produced by the curvature of the meniscus acting as a lens. We measure the meniscus profile over an inclined glass plate and utilize the measured meniscus for estimation of surface tension and refractive index.
Prediction of viscosities and surface tensions of fuels using a new corresponding states model
DEFF Research Database (Denmark)
Queimada, A.J.; Rolo, L.I.; Caco, A.I.
2006-01-01
While some properties of diesels are cheap, easy and fast to measure, such as densities, others such as surface tensions and viscosities are expensive and time consuming. A new approach that uses some basic information such as densities to predict viscosities and surface tensions is here proposed......) 2005 Elsevier Ltd. All rights reserved....
Incorporating contact angles in the surface tension force with the ACES interface curvature scheme
Owkes, Mark
2017-11-01
In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).
Surface tension and Wulff shape for a lattice model without spin flip symmetry.
Bodineau, T
2003-01-01
We propose a new definition of surface tension and check it in a spin model of the Pirogov-Sinai class where the spin flip symmetry is broken. We study the model at low temperatures on the phase transitions line and prove: (i) existence of the surface tension in the thermodynamic limit, for any orientation of the surface and in all dimensions $d\\ge 2$; (ii) the Wulff shape constructed with such a surface tension coincides with the equilibrium shape of the cluster which appears when fixing the total spin magnetization (Wulff problem).
Schroeder, Craig
2012-02-01
We present a method for applying semi-implicit forces on a Lagrangian mesh to an Eulerian discretization of the Navier Stokes equations in a way that produces a sparse symmetric positive definite system. The resulting method has semi-implicit and fully-coupled viscosity, pressure, and Lagrangian forces. We apply our new framework for forces on a Lagrangian mesh to the case of a surface tension force, which when treated explicitly leads to a tight time step restriction. By applying surface tension as a semi-implicit Lagrangian force, the resulting method benefits from improved stability and the ability to take larger time steps. The resulting discretization is also able to maintain parasitic currents at low levels. © 2011.
Surface tension effects on vertical upward annular flows in a small diameter pipe
Energy Technology Data Exchange (ETDEWEB)
Sadatomi, Michio, E-mail: sadatomi@mech.kumamoto-u.ac.jp [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Kawahara, Akimaro [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Suzuki, Aruta [Plant Design & Engineering Dept., Environment, Energy & Plant Headquarters, Hitachi Zosen Corporation, 7-89, Nankokita 1-chome, Suminoe-ku, Osaka, 559-8559 (Japan)
2016-12-15
Highlights: • Surface tension effects were clarified on annular flow in a small diameter pipe. • The mean liquid film thickness became thinner with decreasing of surface tension. • The liquid droplet fraction and the interfacial shear stress became higher with it. • New prediction methods for the above parameters were developed and validated. - Abstract: Experiments were conducted to study the surface tension effects on vertical upward annular flows in a 5 mm I.D. pipe using water and low surface tension water with a little surfactant as the test liquid and air as the test gas. Firstly, the experimental results on the mean liquid film thickness, the liquid droplet fraction and the interfacial shear stress in annular flows together with some flow pictures are presented to clarify the surface tension effects. From these, the followings are clarified: In the low surface tension case, the liquid film surface becomes rough, the liquid film thickness thin, the liquid droplet fraction high, and the interfacial shear stress high. Secondary, correlations in literatures for the respective parameters are tested against the present data. The test results show that no correlation for the respective parameters could predict well the present data. Thus, correlations are revised by accounting for the surface tension effects. The results of the experiments, the correlations tests and their revisions mentioned above are presented in the present paper.
Performance Calculation of Floating Wind Turbine Tension Leg Platform in the South China Sea
Directory of Open Access Journals (Sweden)
Hai Feng Wang
2015-10-01
Full Text Available The harvesting of wind energy is expected to increase greatly in the future because of its stability, abundance, and renewability in large coastal states such as China. The floating support structure will likely become the major structural form for wind turbines in the future due to its cost advantages when the water depth reaches 50 m. The 5MW wind turbine model from National Renewable Energy Lab (NREL and the modified tension leg platform model proposed by Harbin Institute of Technology (HIT were applied to certain sea conditions in the South China Sea in order to consider the effects of external load coupling actions. In this study, the internal force, mooring system force, as well as the acceleration, displacement and velocity of the floating structure of the modified HIT Tension Leg Platform (HIT-TLP were calculated. During this process, the physical parameters of its tension leg structure at a specific frequency domain were obtained to find the technical reserves for its practical application in the future.
General approach for solving the density gradient theory in the interfacial tension calculations
DEFF Research Database (Denmark)
Liang, Xiaodong; Michelsen, Michael Locht
2017-01-01
Within the framework of the density gradient theory, the interfacial tension can be calculated by finding the density profiles that minimize an integral of two terms over the system of infinite width. It is found that the two integrands exhibit a constant difference along the interface for a finite...... property evaluations compared to other methods. The performance of the algorithm with recommended parameters is analyzed for various systems, and the efficiency is further compared with the geometric-mean density gradient theory, which only needs to solve nonlinear algebraic equations. The results show...... that the algorithm is only 5-10 times less efficient than solving the geometric-mean density gradient theory....
A Computational Study of Richtmyer-Meshkov Instability with Surface Tension
Francois, Marianne; Velechovsky, Jan; Jibben, Zach; Masser, Thomas; LANL Collaboration
2017-11-01
We have added the capability to model surface tension in our adaptive mesh refinement compressible flow solver, xRage. Our surface tension capability employs the continuum surface force to model surface tension and the height function method to compute curvatures. We have verified our model implementation for the static and oscillating droplets test cases and the linear regime of the Rayleigh-Taylor instability. With this newly added capability, we have performed a numerical study of the effects of surface tension on single-mode and multi-mode Richtmyer-Meshkov instability. This work was performed under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52 - 06NA25396.
Surface tension anomalies in room temperature ionic liquids-acetone solutions
Abe, Hiroshi; Murata, Keisuke; Kiyokawa, Shota; Yoshimura, Yukihiro
2018-05-01
Surface tension anomalies were observed in room temperature ionic liquid (RTIL)-acetone solutions. The RTILs are 1-alkyl-3-methylimidazorium iodide with [Cnmim][I] in a [Cnmim][I]-x mol% acetone. The maximum value of the surface tension appeared at 40 mol% acetone, although density decreased monotonically with an increase in acetone concentration. A small alkyl chain length effect of the Cnmim+ cations was observed in the surface tension. By the Gibbs adsorption isotherm, it was found that I- anion-mediated surface structure became dominant above 40 mol%. In the different [Cnmim][TFSI]-acetone mixtures, normal decay of the surface tension was observed on the acetone concentration scale, where TFSI- is bis(trifluoromethanesulfonyl)imide.
Energy Technology Data Exchange (ETDEWEB)
Fechter, Stefan, E-mail: stefan.fechter@iag.uni-stuttgart.de [Institut für Aerodynamik und Gasdynamik, Universität Stuttgart, Pfaffenwaldring 21, 70569 Stuttgart (Germany); Munz, Claus-Dieter, E-mail: munz@iag.uni-stuttgart.de [Institut für Aerodynamik und Gasdynamik, Universität Stuttgart, Pfaffenwaldring 21, 70569 Stuttgart (Germany); Rohde, Christian, E-mail: Christian.Rohde@mathematik.uni-stuttgart.de [Institut für Angewandte Analysis und Numerische Simulation, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Zeiler, Christoph, E-mail: Christoph.Zeiler@mathematik.uni-stuttgart.de [Institut für Angewandte Analysis und Numerische Simulation, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)
2017-05-01
The numerical approximation of non-isothermal liquid–vapor flow within the compressible regime is a difficult task because complex physical effects at the phase interfaces can govern the global flow behavior. We present a sharp interface approach which treats the interface as a shock-wave like discontinuity. Any mixing of fluid phases is avoided by using the flow solver in the bulk regions only, and a ghost-fluid approach close to the interface. The coupling states for the numerical solution in the bulk regions are determined by the solution of local two-phase Riemann problems across the interface. The Riemann solution accounts for the relevant physics by enforcing appropriate jump conditions at the phase boundary. A wide variety of interface effects can be handled in a thermodynamically consistent way. This includes surface tension or mass/energy transfer by phase transition. Moreover, the local normal speed of the interface, which is needed to calculate the time evolution of the interface, is given by the Riemann solution. The interface tracking itself is based on a level-set method. The focus in this paper is the description of the two-phase Riemann solver and its usage within the sharp interface approach. One-dimensional problems are selected to validate the approach. Finally, the three-dimensional simulation of a wobbling droplet and a shock droplet interaction in two dimensions are shown. In both problems phase transition and surface tension determine the global bulk behavior.
The interfacial surface tension of a quark-gluon plasma fireball in a ...
Indian Academy of Sciences (India)
surface tension with the cube of the critical transition temperature is in overall ... more rigorous structures may be built depending on the phenomenological success .... k +dk in a spherically symmetric situation, and gi is the degeneracy factor ( ...
International Nuclear Information System (INIS)
Bowring, R.W.; Garton, D.A.; Kinneir, J.H.
1961-09-01
Values of surface tension were obtained over the temperature range from near the melting point to near the normal boiling point of each substance. A capillary rise method was used employing a closed glass U-tube apparatus. The accuracy was ± 3% near the melting point falling to ± 5% near the normal boiling point. Values of the parachor calculated from the experimental data were in excellent agreement with those calculated from the molecular structure using the method proposed by Sugden. The surface tension in each case decreased with ascending temperature from near 30 to 40 dynes/cm close to the melting point to 13 to 15 dynes/cm near the normal boiling point. (author)
Critical Assessment of the Surface Tension determined by the Maximum Pressure Bubble Method
Benedetto, Franco Emmanuel; Zolotucho, Hector; Prado, Miguel Oscar
2015-01-01
The main factors that influence the value of surface tension of a liquid measured with the Maximum Pressure Bubble Method are critically evaluated. We present experimental results showing the effect of capillary diameter, capillary depth, bubble spheroidicity and liquid density at room temperature. We show that the decrease of bubble spheroidicity due to increase of capillary immersion depth is not sufficient to explain the deviations found in the measured surface tension values. Thus, we pro...
Kalantarian, Ali; Ninomiya, Hiromasa; Saad, Sameh M.I.; David, Robert; Winklbauer, Rudolf; Neumann, A. Wilhelm
2009-01-01
Biological tissues behave in certain respects like liquids. Consequently, the surface tension concept can be used to explain aspects of the in vitro and in vivo behavior of multicellular aggregates. Unfortunately, conventional methods of surface tension measurement cannot be readily applied to small cell aggregates. This difficulty can be overcome by an experimentally straightforward method consisting of centrifugation followed by axisymmetric drop shape analysis (ADSA). Since the aggregates ...
International Nuclear Information System (INIS)
Mjalli, Farouq S.; Vakili-Nezhaad, Gholamreza; Shahbaz, Kaveh; AlNashef, Inas M.
2014-01-01
Highlights: • Critical temperatures of eight common DES were calculated using two methods. • Density and surface tension were calculated using the Rackett and Guggenheim equations. • The Rackett method should be used in the low temperature range only. • The Eötvos and Guggenheim methods gave best density and surface tension predictions. - Abstract: The recent continuing interest in deep eutectic solvents (DES) as ionic liquids analogues and their successful applications in different areas of separation necessities the existence of reliable physical and thermodynamic properties database. The scarcity of data on the physical properties of such solvents, increases the need for their prediction using reliable methods. In this study, first the critical temperatures of eight DES systems have been calculated based on the Eötvos empirical equation using the experimental data of the density and surface tension at various temperatures, then the density and surface tension values of these systems were predicted from the calculated critical temperatures. For the density prediction the Eötvos and Guggenheim equations were combined to introduce a simple power law equation using the estimated critical temperatures from the Eötvos and the Modified Lydersen–Joback–Reid group contribution methods. Finally, the estimated critical temperatures by these two methods were used in the Guggenheim empirical equation to calculate the surface tension of the DES systems. The prediction quality of the two physical properties under investigation were compared and proper recommendations were postulated
Energy Technology Data Exchange (ETDEWEB)
Mjalli, Farouq S., E-mail: farouqsm@yahoo.com [Petroleum and Chemical Engineering Department, Sultan Qaboos University, 123 Sultanate of Oman (Oman); Vakili-Nezhaad, Gholamreza; Shahbaz, Kaveh [School of Engineering, Taylor' s University, 47500 Selangor (Malaysia); AlNashef, Inas M. [Chemical Engineering Department, King Saud University, Riyadh 11421 (Saudi Arabia)
2014-01-10
Highlights: • Critical temperatures of eight common DES were calculated using two methods. • Density and surface tension were calculated using the Rackett and Guggenheim equations. • The Rackett method should be used in the low temperature range only. • The Eötvos and Guggenheim methods gave best density and surface tension predictions. - Abstract: The recent continuing interest in deep eutectic solvents (DES) as ionic liquids analogues and their successful applications in different areas of separation necessities the existence of reliable physical and thermodynamic properties database. The scarcity of data on the physical properties of such solvents, increases the need for their prediction using reliable methods. In this study, first the critical temperatures of eight DES systems have been calculated based on the Eötvos empirical equation using the experimental data of the density and surface tension at various temperatures, then the density and surface tension values of these systems were predicted from the calculated critical temperatures. For the density prediction the Eötvos and Guggenheim equations were combined to introduce a simple power law equation using the estimated critical temperatures from the Eötvos and the Modified Lydersen–Joback–Reid group contribution methods. Finally, the estimated critical temperatures by these two methods were used in the Guggenheim empirical equation to calculate the surface tension of the DES systems. The prediction quality of the two physical properties under investigation were compared and proper recommendations were postulated.
Bechert, M.; Scheid, B.
2017-11-01
The draw resonance effect appears in fiber spinning processes if the ratio of take-up to inlet velocity, the so-called draw ratio, exceeds a critical value and manifests itself in steady oscillations of flow velocity and fiber diameter. We study the effect of surface tension on the draw resonance behavior of Newtonian fiber spinning in the presence of inertia and gravity. Utilizing an alternative scaling makes it possible to visualize the results in stability maps of highly practical relevance. The interplay of the destabilizing effect of surface tension and the stabilizing effects of inertia and gravity lead to nonmonotonic stability behavior and local stability maxima with respect to the dimensionless fluidity and the dimensionless inlet velocity. A region of unconditional instability caused by the influence of surface tension is found in addition to the region of unconditional stability caused by inertia, which was described in previous works [M. Bechert, D. W. Schubert, and B. Scheid, Eur. J. Mech B 52, 68 (2015), 10.1016/j.euromechflu.2015.02.005; Phys. Fluids 28, 024109 (2016), 10.1063/1.4941762]. Due to its importance for a particular group of fiber spinning applications, a viscous-gravity-surface-tension regime, i.e., negligible effect of inertia, is analyzed separately. The mechanism underlying the destabilizing effect of surface tension is discussed and established stability criteria are tested for validity in the presence of surface tension.
International Nuclear Information System (INIS)
Bagheri, Ahmad; Moradian, Zohreh
2014-01-01
Highlights: • Surface tension of non-ideal binary systems of alcohol/DMSO determined. • The surface tension data of binary mixtures were correlated with five equations. • The interaction energy values were calculated by using LWW model. • The U 12 value shows different behavior for two systems with increasing temperature. - Abstract: Surface tension of binary mixtures of tert-butyl alcohol (TBA) and iso-amyl alcohol (IAA) with DMSO (dimethyl sulfoxide) were measured over the entire concentration range at pressure of 82.5 kPa at temperatures between (298.15 and 328.15) K. Correlating the surface tension and surface tension deviation of the above mentioned binary systems was performed with empirical and thermodynamic based models. The average relative error obtained from the comparison of experimental and calculated surface tension values for the two binary systems with five models at various temperatures is less than 2%. The effect of temperature on the interaction energy values in binary mixtures has been used to obtain information about solute structural effects on DMSO. Also, the experimental data were used to evaluate the nature and type of intermolecular interactions in binary mixtures
Measurement of the surface tension by the method of maximum gas bubble pressure
International Nuclear Information System (INIS)
Dugne, Jean
1971-01-01
A gas bubble method for measuring surface tension was studied. Theoretical investigations demonstrated that the maximum pressure can be represented by the envelope of a certain family of curves and that the physical nature of the capillary tube imposes an upper limit to its useful radius. With a given tube and a specified liquid, the dynamic evolution of the gas bubble depends only upon the variation of the mass of gas contained with time; this fact may restrict the choice of tubes. The use of one single tube requires important corrections. Computer treatment of the problem led to some accurate equations for calculating γ. Schroedinger equations and Sudgen's table are examined. The choice of tubes, the necessary corrections, density measurement, and the accuracy attainable are discussed. Experiments conducted with water and mercury using the sessile drop method and continuous recording of the pressure verified the theoretical ideas. (author) [fr
Beatrici, Anderson; Santos Baptista, Leandra; Mauro Granjeiro, José
2018-03-01
Regenerative Medicine comprises the Biotechnology, Tissue Engineering and Biometrology for stem cell therapy. Starting from stem cells extracted from the patient, autologous implant, these cells are cultured and differentiated into other tissues, for example, articular cartilage. These cells are reorganized into microspheres (cell spheroids). Such tissue units are recombined into functional tissues constructs that can be implanted in the injured region for regeneration. It is necessary the biomechanical characterization of these constructed to determine if their properties are similar to native tissue. In this study was carried out the modeling of the calculation of uncertainty of the surface tension of cellular spheroids with the use of the Young-Laplace equation. We obtained relative uncertainties about 10%.
Energy Technology Data Exchange (ETDEWEB)
Melchior, Tobias
2011-10-26
In the context of CO{sub 2}-emission-induced global warming, greenhouse gases resulting from the production of electricity in coal-fired power plants gain increasing attention. One possible way to reduce such emissions is to gasify coal instead of burning it. The corresponding process is referred to as Integrated Gasification Combined Cycle and allows for the separation of CO{sub 2} before converting a synthesis gas into electrical energy. However, further improvements in efficiency and availability of this plant technology are needed to render the alternative generation of electricity sensible from an economic point of view. One corresponding approach introduces hot gas cleaning facilities to the gasification plant which guarantee a removal of slag particles from the synthesis gas at high temperatures. The development of such filters depends on the availability of data on the material properties of the coal ash slags to be withdrawn. In this respect, the surface tension is a relevant characteristic. Currently, the surface tension of real coal ash slags as well as of synthetic model systems was measured successfully by means of the sessile drop and the maximum bubble pressure method. With regard to the sessile drop technique, those experiments were conducted in a gasification-like atmosphere at temperatures of up to 1500 C. Furthermore, the pressure inside the experimental vessel was raised to 10 bar in order to allow for deriving the influence of this variable on the surface tension. In contrast, maximum bubble pressure trials were realised at atmospheric pressure while the gas atmosphere assured inert conditions. For performing sessile drop measurements, a corresponding apparatus was set up and is described in detail in this thesis. Three computer algorithms were employed to calculate surface tensions out of the photos of sessile drops and their individual performance was evaluated. A very good agreement between two of the codes was found while the third one
Rehner, Philipp; Gross, Joachim
2018-04-01
The curvature dependence of interfacial properties has been discussed extensively over the last decades. After Tolman published his work on the effect of droplet size on surface tension, where he introduced the interfacial property now known as Tolman length, several studies were performed with varying results. In recent years, however, some consensus has been reached about the sign and magnitude of the Tolman length of simple model fluids. In this work, we re-examine Tolman's equation and how it relates the Tolman length to the surface tension and we apply non-local classical density functional theory (DFT) based on the perturbed chain statistical associating fluid theory (PC-SAFT) to characterize the curvature dependence of the surface tension of real fluids as well as mixtures. In order to obtain a simple expression for the surface tension, we use a first-order expansion of the Tolman length as a function of droplet radius Rs, as δ(Rs) = δ0 + δ1/Rs, and subsequently expand Tolman's integral equation for the surface tension, whereby a second-order expansion is found to give excellent agreement with the DFT result. The radius-dependence of the surface tension of increasingly non-spherical substances is studied for n-alkanes, up to icosane. The infinite diameter Tolman length is approximately δ0 = -0.38 Å at low temperatures. For more strongly non-spherical substances and for temperatures approaching the critical point, however, the infinite diameter Tolman lengths δ0 turn positive. For mixtures, even if they contain similar molecules, the extrapolated Tolman length behaves strongly non-ideal, implying a qualitative change of the curvature behavior of the surface tension of the mixture.
Surface tension and contact angles: Molecular origins and associated microstructure
Davis, H. T.
1982-01-01
Gradient theory converts the molecular theory of inhomogeneous fluid into nonlinear boundary value problems for density and stress distributions in fluid interfaces, contact line regions, nuclei and microdroplets, and other fluid microstructures. The relationship between the basic patterns of fluid phase behavior and the occurrence and stability of fluid microstructures was clearly established by the theory. All the inputs of the theory have molecular expressions which are computable from simple models. On another level, the theory becomes a phenomenological framework in which the equation of state of homogeneous fluid and sets of influence parameters of inhomogeneous fluids are the inputs and the structures, stress tensions and contact angles of menisci are the outputs. These outputs, which find applications in the science and technology of drops and bubbles, are discussed.
Surface Tension of Multi-phase Flow with Multiple Junctions Governed by the Variational Principle
International Nuclear Information System (INIS)
Matsutani, Shigeki; Nakano, Kota; Shinjo, Katsuhiko
2011-01-01
We explore a computational model of an incompressible fluid with a multi-phase field in three-dimensional Euclidean space. By investigating an incompressible fluid with a two-phase field geometrically, we reformulate the expression of the surface tension for the two-phase field found by Lafaurie et al. (J Comput Phys 113:134–147, 1994) as a variational problem related to an infinite dimensional Lie group, the volume-preserving diffeomorphism. The variational principle to the action integral with the surface energy reproduces their Euler equation of the two-phase field with the surface tension. Since the surface energy of multiple interfaces even with singularities is not difficult to be evaluated in general and the variational formulation works for every action integral, the new formulation enables us to extend their expression to that of a multi-phase (N-phase, N ≥ 2) flow and to obtain a novel Euler equation with the surface tension of the multi-phase field. The obtained Euler equation governs the equation for motion of the multi-phase field with different surface tension coefficients without any difficulties for the singularities at multiple junctions. In other words, we unify the theory of multi-phase fields which express low dimensional interface geometry and the theory of the incompressible fluid dynamics on the infinite dimensional geometry as a variational problem. We apply the equation to the contact angle problems at triple junctions. We computed the fluid dynamics for a two-phase field with a wall numerically and show the numerical computational results that for given surface tension coefficients, the contact angles are generated by the surface tension as results of balances of the kinematic energy and the surface energy.
Determination of surface tension coefficient of liquids by diffraction of light on capillary waves
International Nuclear Information System (INIS)
Nikolić, D; Nešić, Lj
2012-01-01
This paper describes a simple technique for determining the coefficient of the surface tension of liquids, based on laser light diffraction on capillary waves. Capillary waves of given frequency are created by an exciter needle acting on the surface of liquid and represent a reflective diffraction grating, the constant of which (the wavelength of capillary waves) can be determined based on a known incidence angle of light (grazing angle). We obtain the coefficient of the surface tension of liquids by applying the dispersion relation for capillary waves and analyze the difficulties that arise when setting up and conducting the experiment in detail. (paper)
Temporal instability of viscous liquid microjets with spatially varying surface tension
Energy Technology Data Exchange (ETDEWEB)
Furlani, E P [Integrated Materials and Microstructures Laboratory, Electronic Imaging Products, Eastman Kodak Company, Rochester, NY 14650-2121 (United States)
2005-01-07
A linear theory is developed for the temporal instability of a viscous liquid microjet of Newtonian fluid with a spatially periodic variation of surface tension imposed along its length. The variation of surface tension induces Marangoni flow within the jet that leads to breakup and drop formation. An analytical expression is derived for the behaviour of the free surface of the microjet. This expression is useful for parametric analysis of jet instability and breakup as a function of jet radius, wavelength and fluid properties.
Temporal instability of viscous liquid microjets with spatially varying surface tension
International Nuclear Information System (INIS)
Furlani, E P
2005-01-01
A linear theory is developed for the temporal instability of a viscous liquid microjet of Newtonian fluid with a spatially periodic variation of surface tension imposed along its length. The variation of surface tension induces Marangoni flow within the jet that leads to breakup and drop formation. An analytical expression is derived for the behaviour of the free surface of the microjet. This expression is useful for parametric analysis of jet instability and breakup as a function of jet radius, wavelength and fluid properties
Bubble extinction in Hele-Shaw flow with surface tension and kinetic undercooling regularization
International Nuclear Information System (INIS)
Dallaston, Michael C; McCue, Scott W
2013-01-01
We perform an analytic and numerical study of an inviscid contracting bubble in a two-dimensional Hele-Shaw cell, where the effects of both surface tension and kinetic undercooling on the moving bubble boundary are not neglected. In contrast to expanding bubbles, in which both boundary effects regularize the ill-posedness arising from the viscous (Saffman–Taylor) instability, we show that in contracting bubbles the two boundary effects are in competition, with surface tension stabilizing the boundary, and kinetic undercooling destabilizing it. This competition leads to interesting bifurcation behaviour in the asymptotic shape of the bubble in the limit it approaches extinction. In this limit, the boundary may tend to become either circular, or approach a line or ‘slit’ of zero thickness, depending on the initial condition and the value of a nondimensional surface tension parameter. We show that over a critical range of surface tension values, both these asymptotic shapes are stable. In this regime there exists a third, unstable branch of limiting self-similar bubble shapes, with an asymptotic aspect ratio (dependent on the surface tension) between zero and one. We support our asymptotic analysis with a numerical scheme that utilizes the applicability of complex variable theory to Hele-Shaw flow. (paper)
International Nuclear Information System (INIS)
Behroozi, F.; Mohazzabi, P.; McCrickard, J.
1995-01-01
The familiar catenary is the shape assumed by a chain or string as it hangs from two points. The mathematical equation of the catenary was first published more than three hundred years ago by Leibnitz and Huygen, among others. Here we consider the shapes assumed by a hanging string in the presence of gravity and surface tension. The surface tension is introduced by suspending the string from a thin horizontal rod while the area bounded by the string and the rod is covered with a soap film. The string then assumes new and wonderful shapes depending on the relative strength of the surface tension and the weight per unit length of the string. When surface tension dominates, the string is pulled inward, assuming a convex shape similar to the Greek letter γ. On the other hand, when gravity is dominant the string is pulled outward and assumes a concave shape best described as a distorted catenary. However, when the gravitational force normal to the string matches the surface tension, the string takes a linear configuration similar to the letter V. Under suitable conditions, the string can be made to assume any of the three configurations by adjusting the separation of its end points. The equations that describe the shape of the string are derived by minimizing the total energy of the system and are presented for the three principal configurations
Kalantarian, Ali; Ninomiya, Hiromasa; Saad, Sameh M I; David, Robert; Winklbauer, Rudolf; Neumann, A Wilhelm
2009-02-18
Biological tissues behave in certain respects like liquids. Consequently, the surface tension concept can be used to explain aspects of the in vitro and in vivo behavior of multicellular aggregates. Unfortunately, conventional methods of surface tension measurement cannot be readily applied to small cell aggregates. This difficulty can be overcome by an experimentally straightforward method consisting of centrifugation followed by axisymmetric drop shape analysis (ADSA). Since the aggregates typically show roughness, standard ADSA cannot be applied and we introduce a novel numerical method called ADSA-IP (ADSA for imperfect profile) for this purpose. To examine the new methodology, embryonic tissues from the gastrula of the frog, Xenopus laevis, deformed in the centrifuge are used. It is confirmed that surface tension measurements are independent of centrifugal force and aggregate size. Surface tension is measured for ectodermal cells in four sample batches, and varies between 1.1 and 7.7 mJ/m2. Surface tension is also measured for aggregates of cells expressing cytoplasmically truncated EP/C-cadherin, and is approximately half as large. In parallel, such aggregates show a reduction in convergent extension-driven elongation after activin treatment, reflecting diminished intercellular cohesion.
Design of an experimental apparatus for measurement of the surface tension of metastable fluids
Vinš, V.; Hrubý, J.; Hykl, J.; Blaha, J.; Šmíd, B.
2013-04-01
A unique experimental apparatus for measurement of the surface tension of aqueous mixtures has been designed, manufactured, and tested in our laboratory. The novelty of the setup is that it allows measurement of surface tension by two different methods: a modified capillary elevation method in a long vertical capillary tube and a method inspired by the approach of Hacker (National Advisory Committee for Aeronautics, Technical Note 2510, 1-20, 1951), i.e. in a short horizontal capillary tube. Functionality of all main components of the apparatus, e.g., glass chamber with the capillary tube, temperature control unit consisting of two thermostatic baths with special valves for rapid temperature jumps, helium distribution setup allowing pressure variation above the liquid meniscus inside the capillary tube, has been successfully tested. Preliminary results for the surface tension of the stable and metastable supercooled water measured by the capillary elevation method at atmospheric pressure are provided. The surface tension of water measured at temperatures between +26 °C and -11 °C is in good agreement with the extrapolated IAPWS correlation (IAPWS Release on Surface Tension of Ordinary Water Substance, September 1994); however it disagrees with data by Hacker.
Modeling the surface tension of complex, reactive organic-inorganic mixtures
Schwier, A. N.; Viglione, G. A.; Li, Z.; McNeill, V. Faye
2013-11-01
Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as heterogeneous reactivity, ice nucleation, and cloud droplet formation. We present new experimental data for the surface tension of complex, reactive organic-inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2-6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two semi-empirical surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well described by a weighted Szyszkowski-Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling of aerosol systems because the Henning model (using data obtained from organic-inorganic systems) and Tuckermann approach provide similar modeling results and goodness-of-fit (χ2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.
Spreading of oil films on water in the surface tension regime
Energy Technology Data Exchange (ETDEWEB)
Camp, D.W.
1985-01-01
Surface tension forces will cause an oil to spread over water if the tension of the oil film (the summed surface and interfacial tensions for bulk oil films, or the equilibrium spreading tension for monomolecular films) is less than the surface tension of water. For oil films spreading in a 40 cm long channel, measurements are made of leading edge position and lateral profiles of film thickness, velocity, and tension as a function of time. Measurements of the tension profiles, important for evaluating proposed theories, is made possible by the development of a new technique based on the Wilhelmy method. The oils studied were silicones, fatty acids and alcohols, and mixtures of surfactants in otherwise nonspreading oils. The single-component oils show an acceleration zone connecting a slow-moving inner region with a fast-moving leading monolayer. The dependence of film tension on film thickness for spreading single-component oils often differs from that at equilibrium. The mixtures show a bulk oil film configuration which extends to the leading edge and have velocity profiles which increase smoothly. The theoretical framework, similarity transformation, and asymptotic solutions of Foda and Cox for single-component oils were shown to be valid. An analysis of spreading surfactant-oil mixtures is developed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows accurate prediction of detailed spreading behavior for any spreading oil.
International Nuclear Information System (INIS)
Yan Hong; Wei Jiu-An; Cui Shu-Wen; Zhu Ru-Zeng
2013-01-01
The expressions of the radius and the surface tension of surface of tension R s and γ s in terms of the pressure distribution for nanoscale liquid threads are of great importance for molecular dynamics (MD) simulations of the interfacial phenomena of nanoscale fluids; these two basic expressions are derived in this paper. Although these expressions were derived first in the literature [Kim B G, Lee J S, Han M H, and Park S, 2006 Nanoscale and Microscale Thermophysical Engineering, 10, 283] and used widely thereafter, the derivation is wrong both in logical structure and physical thought. In view of the importance of these basic expressions, the logic and physical mistakes appearing in that derivation are pointed out. (condensed matter: structural, mechanical, and thermal properties)
The surface tension of pure liquids. Thermodynamic components and corresponding states
Lyklema, J.
1999-01-01
From the temperature dependency of surface and interfacial tensions the surface excess energy and entropy per unit area can be obtained. The excess energy is a liquid-specific property; it varies over about three decades between liquid helium and molten metals. On the other hand, the excess entropy
Performing chemical reactions in virtual capillary of surface tension ...
Indian Academy of Sciences (India)
The flow paths were fabricated by making parallel lines using permanent marker pen ink or other polymer on glass surfaces. Two mirror image patterned glass plates were then sandwiched one on top of the other, separated by a thin gap - created using a spacer. The aqueous liquid moves between the surfaces by capillary ...
International Nuclear Information System (INIS)
Ishikawa, Takehiko; Paradis, Paul-Francois; Yoda, Shinichi
2004-01-01
Surface tension and viscosity of liquid rhenium, which have hardly been measured due to the extremely high melting temperature of rhenium, were measured using an electrostatic levitation method combined with the oscillation drop technique. Sample position instability problems caused by the photon pressure of the heating lasers and by sample evaporation were solved by modifying the electrodes design. Good sample stability allowed the measurements of the surface tension and the viscosity over wide temperature ranges including the undercooled states. Over the 2800-3600 K interval, the surface tension of rhenium was measured as σ(T)=2.71x10 3 -0.23(T-T m ), where T m is the melting temperature, 3453 K. At T m , the datum agrees well with the literature values. Similarly, on the same temperature range, the viscosity was determined as η(T)=0.08 exp[1.33x10 5 /(RT)] (mPa s)
A hybrid model to predict the onset of gas entrainment with surface tension effects
International Nuclear Information System (INIS)
Saleh, W.; Bowden, R.C.; Hassan, I.G.; Kadem, L.
2008-01-01
The onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink. Through use of the Kelvin-Laplace equation the model included the effects of surface tension. The resulting model required further knowledge of the flow field, specifically the dip radius of curvature prior to the onset of gas entrainment. The dip shape and size was investigated experimentally and correlations were provided to characterize the dip in terms of the discharge Froude number. The experimental correlation was used in conjunction with the theoretical model to predict the critical height. The results showed that by including surface tension effects the predicted critical height showed excellent agreement with experimental data. Surface tension reduces the critical height through the Bond number
Predicting the minimum liquid surface tension activity of pseudomonads expressing biosurfactants.
Mohammed, I U; Deeni, Y; Hapca, S M; McLaughlin, K; Spiers, A J
2015-01-01
Bacteria produce a variety of biosurfactants capable of significantly reducing liquid (aqueous) surface tension (γ) with a range of biological roles and biotechnological uses. To determine the lowest achievable surface tension (γMin ), we tested a diverse collection of Pseudomonas-like isolates from contaminated soil and activated sludge and identified those expressing biosurfactants by drop-collapse assay. Liquid surface tension-reducing ability was quantitatively determined by tensiometry, with 57 isolates found to significantly lower culture supernatant surface tensions to 24·5-49·1 mN m(-1) . Differences in biosurfactant behaviour determined by foaming, emulsion and oil-displacement assays were also observed amongst isolates producing surface tensions of 25-27 mN m(-1) , suggesting that a range of structurally diverse biosurfactants were being expressed. Individual distribution identification (IDI) analysis was used to identify the theoretical probability distribution that best fitted the surface tension data, which predicted a γMin of 24·24 mN m(-1) . This was in agreement with predictions based on earlier work of published mixed bacterial spp. data, suggesting a fundamental limit to the ability of bacterial biosurfactants to reduce surface tensions in aqueous systems. This implies a biological restriction on the synthesis and export of these agents or a physical-chemical restriction on their functioning once produced. Numerous surveys of biosurfactant-producing bacteria have been conducted, but only recently has an attempt been made to predict the minimum liquid surface tension these surface-active agents can achieve. Here, we determine a theoretical minimum of 24 mN m(-1) by statistical analysis of tensiometry data, suggesting a fundamental limit for biosurfactant activity in bacterial cultures incubated under standard growth conditions. This raises a challenge to our understanding of biosurfactant expression, secretion and function, as well as
International Nuclear Information System (INIS)
Ghasemian, Ensieh; Najafi, Mojgan; Rafati, Amir Abbas; Felegari, Zahra
2010-01-01
Surface and bulk properties of 1-hexyl-3-methylimidazolium chloride [C 6 mim][Cl] as an ionic liquid (IL) have been investigated by surface tension and electrical conductivity techniques at various temperatures. Results reveal that the ionic liquid behaves as surfactant-like and aggregates in aqueous solution. Critical aggregation concentration (cac) values obtained by conductivity and surface tension measurements are in good agreement with values found in the literature. A series of important and useful adsorption parameters including cac, surface excess concentration (Γ), and minimum surface area per molecule (A min ) at the air + water interface were estimated from surface tension in the presence and absence of different electrolytes. Obtained data show that the surface tension as well as the cac of [C 6 mim][Cl] is reduced by electrolytes. Also, values of surface excess concentration (Γ) show that the IL ions in the presence of electrolyte have much larger affinity to adsorption at the surface and this affinity increased in aqueous electrolyte solution in the order of I - > Br - > Cl - for counter ion of salts that was explained in terms of a larger repulsion of chloride anions from interface to the bromide and iodide anion as well as difference in their excess polarizability.
A new corresponding state-based correlation for the surface tension of organic fatty acids
Zhang, Cuihua; Tian, Jianxiang; Zheng, Mengmeng; Yi, Huili; Zhang, Laibin; Liu, Shuzhen
2018-01-01
In this paper, we proposed a new corresponding state-based correlation for organic fatty (aliphatic, carboxylic and polyfunctional) acids. By using the recently published surface tension data of the 99 acids [A. Mulero and I. Cachadiña, J. Phys. Chem. Ref. Data 45 (2016) 033105] and comparing with the recently published other corresponding state correlations, we found that this correlation reproduces the lowest absolute average deviation (AAD) values for 82 acids out of the 99 acids. It can reproduce the surface tension data with AAD less than 10% for 89 out of the 99 acids.
Cuenot, Stéphane; Frétigny, Christian; Demoustier-Champagne, Sophie; Nysten, Bernard
2004-04-01
The effect of reduced size on the elastic properties measured on silver and lead nanowires and on polypyrrole nanotubes with an outer diameter ranging between 30 and 250 nm is presented and discussed. Resonant-contact atomic force microscopy (AFM) is used to measure their apparent elastic modulus. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The latter is comparable to the macroscopic modulus of the materials. The increase of the apparent elastic modulus for the smaller diameters is attributed to surface tension effects. The surface tension of the probed material may be experimentally determined from these AFM measurements.
Kou, Jisheng; Sun, Shuyu
2014-01-01
The gradient theory for the surface tension of simple fluids and mixtures is rigorously analyzed based on mathematical theory. The finite element approximation of surface tension is developed and analyzed, and moreover, an adaptive finite element method based on a physical-based estimator is proposed and it can be coupled efficiently with Newton's method as well. The numerical tests are carried out both to verify the proposed theory and to demonstrate the efficiency of the proposed method. © 2013 Elsevier B.V. All rights reserved.
Kou, Jisheng
2014-01-01
The gradient theory for the surface tension of simple fluids and mixtures is rigorously analyzed based on mathematical theory. The finite element approximation of surface tension is developed and analyzed, and moreover, an adaptive finite element method based on a physical-based estimator is proposed and it can be coupled efficiently with Newton\\'s method as well. The numerical tests are carried out both to verify the proposed theory and to demonstrate the efficiency of the proposed method. © 2013 Elsevier B.V. All rights reserved.
A simple laboratory experiment to measure the surface tension of a liquid in contact with air
International Nuclear Information System (INIS)
Riba, Jordi-Roger; Esteban, Bernat
2014-01-01
A simple and accurate laboratory experiment to measure the surface tension of liquids has been developed, which is well suited to teach the behaviour of liquids to first- or second-year students of physics, engineering or chemistry. The experimental setup requires relatively inexpensive equipment usually found in physics and chemistry laboratories, since it consists of a used or recycled burette, an analytical balance and a stereoscopic microscope or a micrometer. Experimental data and error analysis show that the surface tension of distilled water, 1-butanol and glycerol can be determined with accuracy better than 1.4%. (paper)
Interrelation of surface tension, optical turbidity, and color of operational transformer oils
International Nuclear Information System (INIS)
L’vov, S. Yu.; Lyut’ko, E. O.; Lankau, Ya. V.; Komarov, V. B.; Seliverstov, A. F.; Bondareva, V. N.; L’vov, Yu. N.; L’vov, M. Yu.; Ershov, B. G.
2011-01-01
Measurements of the acidity, optical turbidity, surface tension, and color of transformer oil from 54 power transformers, autotransformers, and shunt reactors are reported. Changes in surface tension, optical turbidity, and color are found to obey adequate linear correlations, while the acidity has no correlation with any of these properties. Numerical criteria for the maximum permissible state (quality) of the oil with respect to optical turbidity and color are obtained. Recommendations to operating staff are provided for cases in which the criteria for optical turbidity and color are exceeded.
Multi-phase-field method for surface tension induced elasticity
Schiedung, Raphael; Steinbach, Ingo; Varnik, Fathollah
2018-01-01
A method, based on the multi-phase-field framework, is proposed that adequately accounts for the effects of a coupling between surface free energy and elastic deformation in solids. The method is validated via a number of analytically solvable problems. In addition to stress states at mechanical equilibrium in complex geometries, the underlying multi-phase-field framework naturally allows us to account for the influence of surface energy induced stresses on phase transformation kinetics. This issue, which is of fundamental importance on the nanoscale, is demonstrated in the limit of fast diffusion for a solid sphere, which melts due to the well-known Gibbs-Thompson effect. This melting process is slowed down when coupled to surface energy induced elastic deformation.
Kou, Jisheng
2015-08-01
Surface tension significantly impacts subsurface flow and transport, and it is the main cause of capillary effect, a major immiscible two-phase flow mechanism for systems with a strong wettability preference. In this paper, we consider the numerical simulation of the surface tension of multi-component mixtures with the gradient theory of fluid interfaces. Major numerical challenges include that the system of the Euler-Lagrange equations is solved on the infinite interval and the coefficient matrix is not positive definite. We construct a linear transformation to reduce the Euler-Lagrange equations, and naturally introduce a path function, which is proven to be a monotonic function of the spatial coordinate variable. By using the linear transformation and the path function, we overcome the above difficulties and develop the efficient methods for calculating the interface and its interior compositions. Moreover, the computation of the surface tension is also simplified. The proposed methods do not need to solve the differential equation system, and they are easy to be implemented in practical applications. Numerical examples are tested to verify the efficiency of the proposed methods. © 2014 Elsevier B.V.
Danov, Krassimir D.; Stanimirova, Rumyana D.; Kralchevsky, Peter A.; Marinova, Krastanka G.; Stoyanov, Simeon D.; Blijdenstein, Theodorus B.J.; Cox, Andrew R.; Pelan, Eddie G.
2016-01-01
Here, we review the principle and applications of two recently developed methods: the capillary meniscus dynamometry (CMD) for measuring the surface tension of bubbles/drops, and the capillary bridge dynamometry (CBD) for quantifying the bubble/drop adhesion to solid surfaces. Both methods are
Shapes of an Air Taylor Bubble in Stagnant Liquids Influenced by Different Surface Tensions
Lertnuwat, B.
2018-02-01
The aim of this work is to propose an empirical model for predicting shapes of a Taylor bubble, which is a part of slug flows, under different values of the surface tension in stagnant liquids by employing numerical simulations. The k - Ɛ turbulence model was used in the framework of finite volume method for simulating flow fields in a unit of slug flow and also the pressure distribution on a Taylor bubble surface. Assuming that an air pressure distribution inside the Taylor bubble must be uniform, a grid search method was exploited to find an appropriate shape of a Taylor bubble for six values of surface tension. It was found that the shape of a Taylor bubble would be blunter if the surface tension was increased. This was because the surface tension affected the Froude number, controlling the flow around a Taylor bubble. The simulation results were also compared with the Taylor bubble shape, created by the Dumitrescu-and-Taylor model and former studies in order to ensure that they were consistent. Finally, the empirical model was presented from the simulation results.
International Nuclear Information System (INIS)
Li, Lihua; Zhang, Jianbin; Li, Qiang; Guo, Bo; Zhao, Tianxiang; Sha, Feng
2014-01-01
Graphical abstract: Excess property of the binary system 1,2-ethanediamine (EDA) + diethylene glycol (DEG). - Highlights: • Densities and viscosities of EDA + DEG at 298.15–318.150 K were listed. • Thermodynamics data of EDA + DEG at 298.15–318.15 K were calculated. • Surface tension of EDA + DEG at 298.15 K was measured. • Intermolecular interaction of EDA with DEG was discussed. - Abstract: This paper reports density and viscosity data at T = 298.15, 303.15, 308.15, 313.15, and 318.15 K and surface tension data at 298.15 K for the binary system 1,2-ethanediamine (EDA) + diethylene glycol (DEG) as a function of composition under atmospheric pressure. From the experimental density and viscosity data, the excess molar volume and viscosity deviation were calculated, and the results were fitted to a Redlich–Kister equation to obtain the coefficients and to estimate the standard deviations between the experimental and calculated quantities. Based on the kinematic viscosity data, enthalpy of activation for viscous flow, entropy of activation for the viscous flow, and Gibbs energies of activation of viscous flow were calculated. In addition, based on Fourier transform infrared spectra, UV–vis spectra, and electrical conductivity for the system EDA + DEG with various concentrations, intermolecular interaction of EDA with DEG was discussed
Directory of Open Access Journals (Sweden)
D. A. Goncharov
2015-01-01
Full Text Available In this paper we investigate small axisymmetric oscillations of a liquid in an elastic tank. We also take into account the influence of surface tension forces. For this, we turn to the mechanical analogue of the considered mechanical system. To realize the transition to mechanical analogue we use the energy method: postulating the equality of kinetic and potential energy for the investigated mechanical system and the mechanical system analog. Due to this transition we can further investigate the oscillations of a mechanical analogue. As a mechanical analogue, we consider the oscillator in the spring. The mass of the oscillator is calculated as the weight of the fluid to make oscillations. The oscillator spring constant is calculated using the identity of equations, namely, equation of free small oscillations of the oscillator and equation of free small oscillations of the system under investigation: the fluid in the elastic tank. The identity of equations allows us to draw conclusion about the identity of the natural frequencies for the source mechanical system and the system of a mechanical analogue. Next, we take into consideration the action of the surface tension. We record the Laplace condition for excess pressure because of the forces of surface tension. Then we compile the expression for the generalized force, taking into account the phenomenon of the surface tension. Next, we write the equation of oscillations of a mechanical analogue. The surface tension, due to the introduction of the generalized force in the equation for small oscillations of the mechanical analogue will change the natural frequency of the mechanical analogue. The paper presents the appropriate dependencies. The abovementioned allows us to investigate the stability of small motions of fluid in microgravity or low gravity by studying the stability of small motions of mechanical analogue. The latter is especially important due to the design and development of advanced
Xu, Xue-song
2014-12-01
Under complex currents, the motion governing equations of marine cables are complex and nonlinear, and the calculations of cable configuration and tension become difficult compared with those under the uniform or simple currents. To obtain the numerical results, the usual Newton-Raphson iteration is often adopted, but its stability depends on the initial guessed solution to the governing equations. To improve the stability of numerical calculation, this paper proposed separated the particle swarm optimization, in which the variables are separated into several groups, and the dimension of search space is reduced to facilitate the particle swarm optimization. Via the separated particle swarm optimization, these governing nonlinear equations can be solved successfully with any initial solution, and the process of numerical calculation is very stable. For the calculations of cable configuration and tension of marine cables under complex currents, the proposed separated swarm particle optimization is more effective than the other particle swarm optimizations.
Durand, O.; Jaouen, S.; Soulard, L.; Heuzé, O.; Colombet, L.
2017-10-01
We compare, at similar scales, the processes of microjetting and ejecta production from shocked roughened metal surfaces by using atomistic and continuous approaches. The atomistic approach is based on very large scale molecular dynamics (MD) simulations with systems containing up to 700 × 106 atoms. The continuous approach is based on Eulerian hydrodynamics simulations with adaptive mesh refinement; the simulations take into account the effects of viscosity and surface tension, and the equation of state is calculated from the MD simulations. The microjetting is generated by shock-loading above its fusion point a three-dimensional tin crystal with an initial sinusoidal free surface perturbation, the crystal being set in contact with a vacuum. Several samples with homothetic wavelengths and amplitudes of defect are simulated in order to investigate the influence of viscosity and surface tension of the metal. The simulations show that the hydrodynamic code reproduces with very good agreement the profiles, calculated from the MD simulations, of the ejected mass and velocity along the jet. Both codes also exhibit a similar fragmentation phenomenology of the metallic liquid sheets ejected, although the fragmentation seed is different. We show in particular, that it depends on the mesh size in the continuous approach.
DEFF Research Database (Denmark)
Queimada, Antonio; Silva, Filipa A. E.; Caco, Ana I.
2003-01-01
To extend the surface tension database for heavy or asymmetric n-alkane mixtures, measurements were performed using the Wilhelmy plate method. Measured systems included the binary mixtures heptane + eicosane, heptane + docosane and heptane + tetracosane and the ternary mixture heptane + eicosane ...
DEFF Research Database (Denmark)
Queimada, Antonio; Silva, Filipa A.E; Caco, Ana I.
2003-01-01
To extend the surface tension database for heavy or asymmetric n-alkane mixtures, measurements were performed using the Wilhelmy plate method. Measured systems included the binary mixtures heptane + eicosane, heptane + docosane and heptane + tetracosane and the ternary mixture heptane + eicosane...
Generation of Recommendable Values for the Surface Tension of Water Using a Nonparametric Regression
Czech Academy of Sciences Publication Activity Database
Pátek, Jaroslav; Součková, Monika; Klomfar, Jaroslav
2016-01-01
Roč. 61, č. 2 (2016), s. 928-935 ISSN 0021-9568 R&D Projects: GA ČR GA13-00145S Institutional support: RVO:61388998 Keywords : water * surface tension * experimental data * recommended data Subject RIV: BJ - Thermodynamics Impact factor: 2.323, year: 2016
Standard reference data for the air-liquid and vapor-liquid surface tension of benzene
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2013-01-01
Roč. 356, October (2013), s. 329-337 ISSN 0378-3812 R&D Projects: GA ČR GA101/09/0010 Institutional support: RVO:61388998 Keywords : benzene * surface tension * experimental data * standard reference data Subject RIV: BJ - Thermodynamics Impact factor: 2.241, year: 2013 http://www.sciencedirect.com/science/article/pii/S0378381213004196
Directory of Open Access Journals (Sweden)
Yizhak Marcus
2018-01-01
Full Text Available The critical temperatures of two dozen deep eutectic solvents, for only some of which these have been estimated previously, were estimated from the temperature dependences of their surface tensions and densities available in the literature according to the Eötvös and the Guggenheim expressions.
Density, viscosity and surface tension of liquid phase Beckmann rearrangement mixtures
Zuidhof, K.T.; Croon, de M.H.J.M.; Schouten, J.C.; Tinge, J.T.
2015-01-01
We have determined the density, dynamic viscosity, and surface tension of liquid phase Beckmann rearrangement mixtures, consisting of e-caprolactam and fuming oleum. These important properties have been measured in wide ranges of both temperature and molar ratios of acid and e-caprolactam, covering
Surface tension phenomena in the xylem sap of three diffuse porous temperate tree species
K. K. Christensen-Dalsgaard; M. T. Tyree; P. G. Mussone
2011-01-01
In plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. In this study we collected xylem sap from branches of the tree species Populus tremuloides, Betula papyrifera and Sorbus...
On the theory of type-I superconductor surface tension and twinning-plane-superconductivity
International Nuclear Information System (INIS)
Mishonov, T.M.
1990-01-01
A correction is found to the surface tension in type-I superconductors which is proportional to the square root of the Ginsburg-Landau parameter. This correction is essential for obtaining the phase diagram and other thermodynamical variables of the narrow superconducting layer arising near the twinning plane in some metals
DEFF Research Database (Denmark)
Gharagheizi, Farhad; Eslamimanesh, Ali; Sattari, Mehdi
2013-01-01
include critical temperature or temperature/critical volume/acentric factor/critical pressure/reduced temperature/reduced normal boiling point temperature/molecular weight of the compounds. Around 1,300 surface tension data of 118 random compounds are used for developing the first model (a four...
Surface tension of heptane, decane, hexadecane, eicosane, and some of their binary mixtures
DEFF Research Database (Denmark)
Rolo, Lara I.; Caco, Ana I.; Queimada, Antonio
2002-01-01
Surface tension measurements were performed by the Wilhelmy plate method. Measured systems included pure heptane, decane, hexadecane, eicosane, and some of their binary mixtures at temperatures from 293.15 K to 343.15 K with an average absolute deviation of 1.6%. The results were compared with a ...
On Surface Tension for Compact Stars R. Sharma & S. D. Maharaj
Indian Academy of Sciences (India)
Abstract. In an earlier analysis it was demonstrated that general rel- ativity gives higher values of surface tension in strange stars with quark matter than neutron stars.We generate the modified Tolman–Oppenheimer–. Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides ...
Energy Technology Data Exchange (ETDEWEB)
Bertole, Hector; Aguero, Carlos A.; Prado, Pedro O.; Suarez, Juan A. [Universidad Nacional de Mar del Plata, Buenos Aires (Argentina). Facultad de Ingenieria
1997-12-31
This development is a group of tools of calculations and analysis thought to be used in the technical area of an electric power company. It allows the realization of calculations of voltage drop in the networks of half tension and the determination of the break points. It is possible to analyze the readiness of power in the distribution centers and the state of load of the conductors. (author) 8 refs., 7 figs.; e-mail: hbertole at fi.mdp.edu.ar; poprado at fi.mdp.edu.ar
Program for the surface muon spectra calculation
International Nuclear Information System (INIS)
Arkatov, Yu.M.; Voloshchuk, V.I.; Zolenko, V.A.; Prokhorets, I.M.; Soldatov, S.A.
1987-01-01
Program for the ''surface'' muon spectrum calculation is described. The algorithm is based on simulation of coordinates of π-meson birth point and direction of its escape from meson-forming target (MFT) according to angular distribution with the use of Monte Carlo method. Ionization losses of π-(μ)-mesons in the target are taken into account in the program. Calculation of ''surface'' muon spectrum is performed in the range of electron energies from 150 MeV up to 1000 MeV. Spectra of π-mesons are calculated with account of ionization losses in the target and without it. Distributions over lengths of π-meson paths in MFT and contribution of separate sections of the target to pion flux at the outlet of meson channel are calculated as well. Meson-forming target for calculation can be made of any material. The program provides for the use of the MFT itself in the form of photon converter or photon converter is located in front of the target. The program is composed of 13 subprograms; 2 of them represent generators of pseudorandom numbers, distributed uniformly in the range from 0 up to 1, and numbers with Gauss distribution. Example of calculation for copper target of 3 cm length, electron beam current-1 μA, energy-300 MeV is presented
In situ droplet surface tension and viscosity measurements in gas metal arc welding
International Nuclear Information System (INIS)
Bachmann, B; Siewert, E; Schein, J
2012-01-01
In this paper, we present an adaptation of a drop oscillation technique that enables in situ measurements of thermophysical properties of an industrial pulsed gas metal arc welding (GMAW) process. Surface tension, viscosity, density and temperature were derived expanding the portfolio of existing methods and previously published measurements of surface tension in pulsed GMAW. Natural oscillations of pure liquid iron droplets are recorded during the material transfer with a high-speed camera. Frame rates up to 30000 fps were utilized to visualize iron droplet oscillations which were in the low kHz range. Image processing algorithms were employed for edge contour extraction of the droplets and to derive parameters such as oscillation frequencies and damping rates along different dimensions of the droplet. Accurate surface tension measurements were achieved incorporating the effect of temperature on density. These are compared with a second method that has been developed to accurately determine the mass of droplets produced during the GMAW process which enables precise surface tension measurements with accuracies up to 1% and permits the study of thermophysical properties also for metals whose density highly depends on temperature. Thermophysical properties of pure liquid iron droplets formed by a wire with 1.2 mm diameter were investigated in a pulsed GMAW process with a base current of 100 A and a pulse current of 600 A. Surface tension and viscosity of a sample droplet were 1.83 ± 0.02 N m -1 and 2.9 ± 0.3 mPa s, respectively. The corresponding droplet temperature and density are 2040 ± 50 K and 6830 ± 50 kg m -3 , respectively. (paper)
Directory of Open Access Journals (Sweden)
Michelly C. dos Santos
2010-01-01
Full Text Available An undergraduate physical chemistry experiment based on the drop counting method for surface tension measurements is proposed to demonstrate adsorption isotherms of binary aqueous solutions of ethanol, n-propanol, and n-butanol. Excess surface is obtained by the derivative of surface tension taken with respect to alcohol activity, after this activity calculation using van Laar equation. Laboratory class contents are surface tension, excess surface, percolation of hydrogen bonds, micelle, activity, and ideal solution.
Energy Technology Data Exchange (ETDEWEB)
Mosteiro, Laura; Casas, Lidia M. [Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Vigo, Lagoas Marcosende s/n, 36310 Vigo (Spain); Legido, Jose L. [Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Vigo, Lagoas Marcosende s/n, 36310 Vigo (Spain)], E-mail: xllegido@uvigo.es
2009-05-15
This paper reports the results of a new experimental study of thermophysical properties for the ternary mixture of {l_brace}diethyl carbonate + p-xylene + decane{r_brace}. Surface tension has been measured at 298.15 K and, density and speed of sound have been measured in the temperature range T = (288.15 to 308.15) K. Excess molar volumes, excess isentropic compressibilities, and surface tension deviations, have been calculated from experimental data. Surface tension deviations have been correlated with Cibulka equation and Nagata and Tamura equation was used for the other excess properties. Good accuracy has been obtained. These excess magnitudes are discussed qualitatively in terms of the nature and type of intermolecular interactions of the components involved.
Ferreira, D. J. S.; Bezerra, B. N.; Collyer, M. N.; Garcia, A.; Ferreira, I. L.
2018-04-01
The simulation of casting processes demands accurate information on the thermophysical properties of the alloy; however, such information is scarce in the literature for multicomponent alloys. Generally, metallic alloys applied in industry have more than three solute components. In the present study, a general solution of Butler's formulation for surface tension is presented for multicomponent alloys and is applied in quaternary Al-Cu-Si-Fe alloys, thus permitting the Gibbs-Thomson coefficient to be determined. Such coefficient is a determining factor to the reliability of predictions furnished by microstructure growth models and by numerical computations of solidification thermal parameters, which will depend on the thermophysical properties assumed in the calculations. The Gibbs-Thomson coefficient for ternary and quaternary alloys is seldom reported in the literature. A numerical model based on Powell's hybrid algorithm and a finite difference Jacobian approximation has been coupled to a Thermo-Calc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting liquidus temperature, latent heat, alloy density, surface tension and Gibbs-Thomson coefficient for Al-Cu-Si-Fe hypoeutectic alloys to be calculated, as an example of calculation capabilities for multicomponent alloys of the proposed method. The computed results are compared with thermophysical properties of binary Al-Cu and ternary Al-Cu-Si alloys found in the literature and presented as a function of the Cu solute composition.
Spreading of oil on water in the surface-tension regime
Energy Technology Data Exchange (ETDEWEB)
Camp, D.W.; Berg, J.C.
1987-11-01
Data which describe the unidirectional spreading of several pure oils and oil-surfactant mixtures on water in the surface-tension regime are reported. Leading-edge position and profiles of velocity, thickness and film tension are given as functions of time. The data are consistent with the numerical similarity solution of Foda and Cox (1980), although the measured dependence of the film tension on the film thickness often differs from the equilibrium relationship. The configuration of the oil film near the spreading origin may be either a coherent multimolecular layer or a multitude of thinning, outward-moving lenses surrounded by monolayer. The pure oils show an acceleration zone connecting the slow-moving inner region to a fast-moving outer region, while the oil-surfactant mixtures show a much more gradual increase in film velocity.
Single-Step Fabrication of High-Density Microdroplet Arrays of Low-Surface-Tension Liquids.
Feng, Wenqian; Li, Linxian; Du, Xin; Welle, Alexander; Levkin, Pavel A
2016-04-01
A facile approach for surface patterning that enables single-step fabrication of high-density arrays of low-surface-tension organic-liquid microdroplets is described. This approach enables miniaturized and parallel high-throughput screenings in organic solvents, formation of homogeneous arrays of hydrophobic nanoparticles, polymer micropads of specific shapes, and polymer microlens arrays. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Mohammad, Abubaker A.; Alkhaldi, Khaled H.A.E.; AlTuwaim, Mohammad S.; Al-Jimaz, Adel S.
2014-01-01
Highlights: • Effect of temperature and chain length on η and σ of DMF + 1-alkanol binary systems. • Viscosity and surface tension were obtained. • Δη, Δσ and G ∗E were calculated using the experimental data. • H σ and S σ were determined using the surface tension data. • Semi-empirical relations were used to estimate the viscosity of liquid mixtures. - Abstract: Viscosity and surface tension of binary systems of N,N-dimethylformamide DMF with higher 1-alkanols (C 8 –C 10 ) were measured at atmospheric pressure and four different temperatures over the entire range of mole fraction. The experimental measurements were used to calculate the deviations in viscosity and surface tension. Furthermore, the excess Gibbs free energy of activation, surface enthalpy and surface entropy of the (DMF + 1-alkanols) binary mixtures were determined. In addition, the deviation and excess properties were fitted to the method of Redlich–Kister (R–K) polynomial. Viscosity data of the binary systems were correlated with three different expressions (Grunberg and Nissan, the three-body, and four-body McAllister). The effects of the chain length of the higher 1-alkanols and temperature were investigated
Pressure and surface tension of solid-liquid interface using Tara zona density functional theory
International Nuclear Information System (INIS)
Moradi, M.; Kavosh Tehrani, M.
2001-01-01
The weighted density functional theory proposed by Tara zona is applied to study the solid-liquid interface. In the last two decades the weighted density functional became a useful tool to consider the properties of inhomogeneous liquids. In this theory, the role of the size of molecules or the particles of which the matter is composed, was found to be important. In this research we study a hard sphere fluid beside a hard wall. For this study the liquid is an inhomogeneous system. We use the definition of the direct correlation function as a second derivative of free energy with respect to the density. We use this definition and the definition of the weighting function, then we minimize the grand potential with respect to the density to get the Euler Lagrange equation and we obtain an integral equation to find the inhomogeneous density profile. The obtained density profile as a function of the distance from the wall, for different bulk density is pitted in three dimensions. We also calculate the pressure and compare it with the Carnahan-Starling results, and finally we obtained the surface tension at liquid-solid interface and compared it with the results of Monte Carlo simulation
Energy Technology Data Exchange (ETDEWEB)
Sing, Charles E. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Zwanikken, Jos W.; Olvera de la Cruz, Monica [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)
2015-01-21
Polymer mixtures such as blends or block copolymers are of great interest in energy applications and functional materials, and often, one or more of these species contain charges. The traditional fashion in which such materials are studied uses Self-Consistent Field Theory (SCFT) methods that incorporate electrostatics using Poisson-Boltzmann (PB) theory. We adapt a new and rigorous approach that does not rely on the mean-field assumptions inherent in the PB theory and instead uses Liquid State (LS) integral equation theory to articulate charge correlations that are completely neglected in PB. We use this theory to calculate phase diagrams for both blends and block copolyelectrolytes using SCFT-LS and demonstrate how their phase behavior is highly dependent on chain length, charge fraction, charge size, and the strength of Coulombic interactions. Beyond providing phase behavior of blends and block copolyelectrolytes, we can use this theory to investigate the interfacial properties such as surface tension and block copolyelectrolyte lamellar spacing. Lamellar spacing provides a way to directly compare the SCFT-LS theory to the results of experiments. SCFT-LS will provide conceptual and mathematical clarification of the role of charge correlations in these systems and aid in the design of materials based on charge polymers.
International Nuclear Information System (INIS)
Sing, Charles E.; Zwanikken, Jos W.; Olvera de la Cruz, Monica
2015-01-01
Polymer mixtures such as blends or block copolymers are of great interest in energy applications and functional materials, and often, one or more of these species contain charges. The traditional fashion in which such materials are studied uses Self-Consistent Field Theory (SCFT) methods that incorporate electrostatics using Poisson-Boltzmann (PB) theory. We adapt a new and rigorous approach that does not rely on the mean-field assumptions inherent in the PB theory and instead uses Liquid State (LS) integral equation theory to articulate charge correlations that are completely neglected in PB. We use this theory to calculate phase diagrams for both blends and block copolyelectrolytes using SCFT-LS and demonstrate how their phase behavior is highly dependent on chain length, charge fraction, charge size, and the strength of Coulombic interactions. Beyond providing phase behavior of blends and block copolyelectrolytes, we can use this theory to investigate the interfacial properties such as surface tension and block copolyelectrolyte lamellar spacing. Lamellar spacing provides a way to directly compare the SCFT-LS theory to the results of experiments. SCFT-LS will provide conceptual and mathematical clarification of the role of charge correlations in these systems and aid in the design of materials based on charge polymers
Pressure and surface tension of soild-liquid interface using Tarazona density functional theory
Directory of Open Access Journals (Sweden)
M. M.
2000-12-01
Full Text Available The weighted density functional theory proposed by Tarazona is applied to study the solid-liquid interface. In the last two decades the weighted density functional became a useful tool to consider the properties of inhomogeneous liquids. In this theory, the role of the size of molecules or the particles of which the matter is composed, was found to be important. In this resarch we study a hard sphere fluid beside a hard wall. For this study the liquid is an inhomogeneous system. We use the definition of the direct correlation function as a second derivative of free energy with respect to the density. We use this definition and the definition of the weighting function, then we minimize the grand potential with respect to the density to get the Euler Lagrange equation and we obtain an integral equation to find the inhomogeneous density profile. The obtained density profile as a function of the distance from the wall, for different bulk density is plotted in three dimensions. We also calculate the pressure and compare it with the Carnahan-starling results, and finally we obtained the surface tension at liquid-solid interface and compared it with the results of Monte Carlo simulation.
Surface density profile and surface tension of the one-component classical plasma
International Nuclear Information System (INIS)
Ballone, P.; Senatore, G.; Trieste Univ.; Tosi, M.P.; Oxford Univ.
1982-08-01
The density profile and the interfacial tension of two classical plasmas in equilibrium at different densities are evaluated in the square-density-gradient approximation. For equilibrium in the absence of applied external voltage, the profile is oscillatory in the higher-density plasma and the interfacial tension is positive. The amplitude and phase of these oscillations and the magnitude of the interfacial tension are related to the width of the background profile. Approximate representations of the equilibrium profile by matching of its asymptotic forms are analyzed. A comparison with computer simulation data and a critical discussion of a local-density theory are also presented. (author)
International Nuclear Information System (INIS)
Sun Zhongguo; Xi Guang; Chen Xi
2009-01-01
The binary collision of liquid droplets is of both practical importance and fundamental value in computational fluid mechanics. We present a modified surface tension model within the moving particle semi-implicit (MPS) method, and carry out two-dimensional simulations to investigate the mechanisms of coalescence and separation of the droplets during binary collision. The modified surface tension model improves accuracy and convergence. A mechanism map is established for various possible deformation pathways encountered during binary collision, as the impact speed is varied; a new pathway is reported when the collision speed is critical. In addition, eccentric collisions are simulated and the effect of the rotation of coalesced particle is explored. The results qualitatively agree with experiments and the numerical protocol may find applications in studying free surface flows and interface deformation
The Role of Surface Tension in the Crystallization of Metal Halide Perovskites
Zhumekenov, Ayan A.
2017-07-06
The exciting intrinsic properties discovered in single crystals of metal halide perovskites still await their translation into optoelectronic devices. The poor understanding and control of the crystallization process of these materials are current bottlenecks retarding the shift towards single crystal-based optoelectronics. Here we theoretically and experimentally elucidate the role of surface tension in the rapid synthesis of perovskite single crystals by inverse temperature crystallization (ITC). Understanding the nucleation and growth mechanisms enabled us to exploit surface tension to direct the growth of monocrystalline films of perovskites (AMX3, where A = CH3NH3+ or MA; M = Pb2+, Sn2+; X = Br-, I-) on the solution surface. We achieve up to 1 cm2-sized monocrystalline films with thickness on the order of the charge carrier diffusion length (~5-10 µm). Our work paves the way to control the crystallization process of perovskites, including thin film deposition, which is essential to advance the performance benchmarks of perovskite optoelectronics.
Contact angle and surface tension measurements of a five-ring polyphenyl ether
Jones, W. R., Jr.
1986-01-01
Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220 C in room air. The critical surface energy of spreading (gamma /sub c/) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma /sub LV/). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma /sub c/). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.
A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension
Energy Technology Data Exchange (ETDEWEB)
Garrick, Daniel P. [Department of Aerospace Engineering, Iowa State University, Ames, IA (United States); Owkes, Mark [Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT (United States); Regele, Jonathan D., E-mail: jregele@iastate.edu [Department of Aerospace Engineering, Iowa State University, Ames, IA (United States)
2017-06-15
Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge–Kutta method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten–Lax–van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas–liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.
Novel method for the simultaneous estimation of density and surface tension of liquids
International Nuclear Information System (INIS)
Thirunavukkarasu, G.; Srinivasan, G.J.
2003-01-01
The conventional Hare's apparatus generally used for the determination of density of liquids has been modified by replacing its vertical arms (glass tubes) with capillary tubes of 30 cm length and 0.072 cm diameter. When the columns of liquids are drawn through the capillary tubes with reduced pressure at the top of the liquid columns and kept at equilibrium with the atmospheric pressure acting on the liquid surface outside the capillary tubes, the downward pressure due to gravity of the liquid columns has to be coupled with the pressure arising due to the effect of surface tension of the liquids. A fresh expression for the density and surface tension of liquids has been arrived at while equating the pressure balancing system for the two individual liquid columns of the modified Hare's apparatus. The experimental results showed that the proposed method is precise and accurate in the simultaneous estimation of density and surface tension of liquids, with an error of less than 5%
Amrhein, Sven; Bauer, Katharina Christin; Galm, Lara; Hubbuch, Jürgen
2015-12-01
The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species. © 2015 Wiley Periodicals, Inc.
Calculation of Interfacial Tensions of Hydrocarbon-water Systems under Reservoir Conditions
DEFF Research Database (Denmark)
Zuo, You-Xiang; Stenby, Erling Halfdan
1998-01-01
Assuming that the number densities of each component in a mixture are linearly distributed across the interface between the coexisting vapor-liquid or liquid-liquid phases, we developed in this research work a linear-gradient-theory (LGT) model for computing the interfacial tension of hydrocarbon......-brine systems. The new model was tested on a number of hydrocarbon-water/brine mixtures and two crude oil-water systems under reservoir conditions. The results show good agreement between the predicted and the experimental interfacial tension data.......Assuming that the number densities of each component in a mixture are linearly distributed across the interface between the coexisting vapor-liquid or liquid-liquid phases, we developed in this research work a linear-gradient-theory (LGT) model for computing the interfacial tension of hydrocarbon-water...... mixtures on the basis of the SRK equation of state. With this model, it is unnecessary to solve the time-consuming density-profile equations of the gradient-theory model. In addition, a correlation was developed for representing the effect of electrolytes on the interfacial tension of hydrocarbon...
Directory of Open Access Journals (Sweden)
Maria de Fátima Carvalho Costa
1998-06-01
Full Text Available Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac of polymer-surfactant complexes and the critical micellar concentration (cmc of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS mixtures, solutions containing poly(ethylene oxide-SDS, poly(vinylpyrrolidone-SDS and poly(acrylic acid-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe.
Light Meets Water in Nonlocal Media: Surface Tension Analogue in Optics
Horikis, Theodoros P.; Frantzeskakis, Dimitrios J.
2017-06-01
Shallow water wave phenomena find their analogue in optics through a nonlocal nonlinear Schrödinger (NLS) model in 2 +1 dimensions. We identify an analogue of surface tension in optics, namely, a single parameter depending on the degree of nonlocality, which changes the sign of dispersion, much like surface tension does in the shallow water wave problem. Using multiscale expansions, we reduce the NLS model to a Kadomtsev-Petviashvili (KP) equation, which is of the KPII (KPI) type, for strong (weak) nonlocality. We demonstrate the emergence of robust optical antidark solitons forming Y -, X -, and H -shaped wave patterns, which are approximated by colliding KPII line solitons, similar to those observed in shallow waters.
On the Problem of Determining Aggregation Numbers from Surface Tension Measurements.
Rusanov, Anatoly I
2017-11-07
In view of the recent discovery of variable aggregation numbers in the vicinity of the critical micelle concentration (CMC), the mass-action-law theory of the surface tension isotherm of a micellar solution with variable aggregation numbers is formulated both for nonionic and ionic surfactants. It is shown that the shape of the surface tension isotherm should be concave in the logarithmic scale above the CMC. Considering a change in the isotherm slope at the CMC apparent break point, the problems of determining the aggregation number for nonionic micelles and the degree of counterion binding for ionic micelles are discussed. In case of the aggregation number variability near the CMC, finding the aggregation number above the CMC apparent break point is considered and a computational scheme is elaborated, requiring a higher precision for experiment. Some experimental data from the literature are analyzed, and the method of estimating the degree of counterion binding is improved.
Let’s not forget the critical role of surface tension in xylem water relations
Jean-Christophe Domec
2011-01-01
The widely supported cohesionâtension theory of water transport explains the importance of a continuous water column and the mechanism of long-distance ascent of sap in plants (Dixon 1914, Tyree 2003, Angeles et al. 2004). The evaporation of water from the surfaces of mesophyll cells causes the airâwater interface to retreat into the cellulose matrix of the plant cell...
A Synthetic Phased Array Surface Acoustic Wave Sensor for Quantifying Bolt Tension
Directory of Open Access Journals (Sweden)
Rasim Guldiken
2012-09-01
Full Text Available In this paper, we report our findings on implementing a synthetic phased array surface acoustic wave sensor to quantify bolt tension. Maintaining proper bolt tension is important in many fields such as for ensuring safe operation of civil infrastructures. Significant advantages of this relatively simple methodology is its capability to assess bolt tension without any contact with the bolt, thus enabling measurement at inaccessible locations, multiple bolt measurement capability at a time, not requiring data collection during the installation and no calibration requirements. We performed detailed experiments on a custom-built flexible bench-top experimental setup consisting of 1018 steel plate of 12.7 mm (½ in thickness, a 6.4 mm (¼ in grade 8 bolt and a stainless steel washer with 19 mm (¾ in of external diameter. Our results indicate that this method is not only capable of clearly distinguishing properly bolted joints from loosened joints but also capable of quantifying how loose the bolt actually is. We also conducted detailed signal-to-noise (SNR analysis and showed that the SNR value for the entire bolt tension range was sufficient for image reconstruction.
Effect of liquid surface tension on circular and linear hydraulic jumps; theory and experiments
Bhagat, Rajesh Kumar; Jha, Narsing Kumar; Linden, Paul F.; Wilson, David Ian
2017-11-01
The hydraulic jump has attracted considerable attention since Rayleigh published his account in 1914. Watson (1964) proposed the first satisfactory explanation of the circular hydraulic jump by balancing the momentum and hydrostatic pressure across the jump, but this solution did not explain what actually causes the jump to form. Bohr et al. (1992) showed that the hydraulic jump happens close to the point where the local Froude number equals to one, suggesting a balance between inertial and hydrostatic contributions. Bush & Aristoff (2003) subsequently incorporated the effect of surface tension and showed that this is important when the jump radius is small. In this study, we propose a new account to explain the formation and evolution of hydraulic jumps under conditions where the jump radius is strongly influenced by the liquid surface tension. The theory is compared with experiments employing liquids of different surface tension and different viscosity, in circular and linear configurations. The model predictions and the experimental results show excellent agreement. Commonwealth Scholarship Commission, St. John's college, University of Cambridge.
Surface tension and wetting properties of rapeseed oil to biofuel conversion by-products
Muszyński, Siemowit; Sujak, Agnieszka; Stępniewski, Andrzej; Kornarzyński, Krzysztof; Ejtel, Marta; Kowal, Natalia; Tomczyk-Warunek, Agnieszka; Szcześniak, Emil; Tomczyńska-Mleko, Marta; Mleko, Stanisław
2018-04-01
This work presents a study on the surface tension, density and wetting behaviour of distilled glycerol, technical grade glycerol and the matter organic non-glycerin fraction. The research was conducted to expand the knowledge about the physical properties of wastes from the rapeseed oil biofuel production. The results show that the densities of technical grade glycerol (1.300 g cm-3) and distilled glycerol (1.267 g cm-3) did not differ and were significantly lower than the density of the matter organic non-glycerin fraction (1.579 g cm-3). Furthermore, the surface tension of distilled glycerol (49.6 mN m-1) was significantly higher than the matter organic non-glycerin fraction (32.7 mN m-1) and technical grade glycerol (29.5 mN m-1). As a result, both technical grade glycerol and the matter organic non-glycerin fraction had lower contact angles than distilled glycerol. The examined physical properties of distilled glycerol were found to be very close to that of the commercially available pure glycerol. The results suggest that technical grade glycerol may have potential application in the production of glycerol/fuel blends or biosurfactants. The presented results indicate that surface tension measurements are more useful when examining the quality of biofuel wastes than is density determination, as they allow for a more accurate analysis of the effects of impurities on the physical properties of the biofuel by-products.
Two Surface-Tension Formulations For The Level Set Interface-Tracking Method
International Nuclear Information System (INIS)
Shepel, S.V.; Smith, B.L.
2005-01-01
The paper describes a comparative study of two surface-tension models for the Level Set interface tracking method. In both models, the surface tension is represented as a body force, concentrated near the interface, but the technical implementation of the two options is different. The first is based on a traditional Level Set approach, in which the surface tension is distributed over a narrow band around the interface using a smoothed Delta function. In the second model, which is based on the integral form of the fluid-flow equations, the force is imposed only in those computational cells through which the interface passes. Both models have been incorporated into the Finite-Element/Finite-Volume Level Set method, previously implemented into the commercial Computational Fluid Dynamics (CFD) code CFX-4. A critical evaluation of the two models, undertaken in the context of four standard Level Set benchmark problems, shows that the first model, based on the smoothed Delta function approach, is the more general, and more robust, of the two. (author)
Brosius, Nevin; Ward, Kevin; Matsumoto, Satoshi; SanSoucie, Michael; Narayanan, Ranga
2018-01-01
In this work, a method for the measurement of surface tension using continuous periodic forcing is presented. To reduce gravitational effects, samples are electrostatically levitated prior to forcing. The method, called Faraday forcing, is particularly well suited for fluids that require high temperature measurements such as liquid metals where conventional surface tension measurement methods are not possible. It offers distinct advantages over the conventional pulse-decay analysis method when the sample viscosity is high or the levitation feedback control system is noisy. In the current method, levitated drops are continuously translated about a mean position at a small, constant forcing amplitude over a range of frequencies. At a particular frequency in this range, the drop suddenly enters a state of resonance, which is confirmed by large executions of prolate/oblate deformations about the mean spherical shape. The arrival at this resonant condition is a signature that the parametric forcing frequency is equal to the drop's natural frequency, the latter being a known function of surface tension. A description of the experimental procedure is presented. A proof of concept is given using pure Zr and a Ti 39.5 Zr 39.5 Ni 21 alloy as examples. The results compare favorably with accepted literature values obtained using the pulse-decay method.
A thermodynamical model for the surface tension of silicate melts in contact with H2O gas
Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello
2016-01-01
Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.
A Linear Gradient Theory Model for Calculating Interfacial Tensions of Mixtures
DEFF Research Database (Denmark)
Zou, You-Xiang; Stenby, Erling Halfdan
1996-01-01
excellent agreement between the predicted and experimental IFTs at high and moderate levels of IFTs, while the agreement is reasonably accurate in the near-critical region as the used equations of state reveal classical scaling behavior. To predict accurately low IFTs (sigma ... with proper scaling behavior at the critical point is at least required.Key words: linear gradient theory; interfacial tension; equation of state; influence parameter; density profile....
Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy
Deng Zhenghua; Li Huaji; Zhao Wanjun
2013-01-01
Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in...
Evaluation of salivary surface tension in a cohort of young healthy adults.
Foglio-Bonda, P L; Laguini, E; Davoli, C; Pattarino, F; Foglio-Bonda, A
2018-03-01
To determine salivary pH, flow rate (FR) and surface tension (γs) in a cohort of 30 healthy young adults. To acquire cohort biological independent variables (age, gender, weight, height, medications, smoking, pathologies, and allergies) and to correlate them with pH, FR and γs obtained values. Evaluate the possible variation of the γs values during the time after the withdrawal and the influence of the operational abilities of the experimenting operators. Evaluate the relationship between γs, pH and FR and the dependence between pH and FR. Non-stimulated saliva samples were taken in four different time span, for three days, with a drooling method for 15 minutes. The saliva sample was analyzed, in terms of γs, by two different operators (OP1 and OP2), twice consecutive (γs-1 and γs-2) for a total of 360 measurements. The γs was calculated using the du Noüy method. The FR was evaluated by weighing technique and pH by pH indicator papers. The measurements of γs performed by two different operators (OP1, OP2) showed respectively average values of 46.46 mN/m and 43.45 mN/m, while the mean FR was 0.29 ± 0.13 mL/min and the average pH was 7.1 ± 0.43. There were no significant correlations between γs and the biological variables analyzed. We can consider as reference values, in a sample of young adults, γs 45.56 ± 6.51 mN/m.
Khoddami, Seyyedeh Maryam; Talebian, Saeed; Izadi, Farzad; Ansari, Noureddin Nakhostin
2017-05-01
The study aims to evaluate the reliability and the discriminative validity of surface electromyography (sEMG) in the assessment of patients with primary muscle tension dysphonia (MTD). The study design is cross-sectional. Fifteen patients with primary MTD (mean age: 34.07 ± 10.99 years) and 15 healthy volunteers (mean age: 34.53 ± 10.63 years) were included. All participants underwent evaluation of sEMG to record the electrical activity of the thyrohyoid and cricothyroid muscles. The outcome measures were the root mean square (RMS), activity peak, duration, and time to the peak activity, which were obtained during /a/ and /i/ prolongation for test-retest reliability. The test-retest reliability was good to excellent for the RMS and peak activity measures (intraclass correlation coefficient [agreement] [ICC agreement ] = 0.49-0.98). The reliability for the activity duration was poor to excellent (ICC agreement = 0.19-0.9). Poor test-retest reliability was found for the time to peak measure (ICC agreement = 0.15-0.37). The standard error of measurement for all sEMG measures was between 0.41 and 2.05. The smallest detectable change (SDC) was calculated between 1.13 and 5.66. The highest SDC values were obtained for the peak and the lowest SDCs were documented for the duration (5.66 and 1.13, respectively). All sEMG measures were not able to discriminate between the MTD patients and healthy subjects (P > 0.05). The sEMG is a reliable tool to measure the RMS, the peak activity, and the activity duration in primary MTD. However, it is not able to discriminate the patients with primary MTD from healthy subjects. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
D. O. Topping
2007-01-01
Full Text Available In order to predict the physical properties of aerosol particles, it is necessary to adequately capture the behaviour of the ubiquitous complex organic components. One of the key properties which may affect this behaviour is the contribution of the organic components to the surface tension of aqueous particles in the moist atmosphere. Whilst the qualitative effect of organic compounds on solution surface tensions has been widely reported, our quantitative understanding on mixed organic and mixed inorganic/organic systems is limited. Furthermore, it is unclear whether models that exist in the literature can reproduce the surface tension variability for binary and higher order multi-component organic and mixed inorganic/organic systems of atmospheric significance. The current study aims to resolve both issues to some extent. Surface tensions of single and multiple solute aqueous solutions were measured and compared with predictions from a number of model treatments. On comparison with binary organic systems, two predictive models found in the literature provided a range of values resulting from sensitivity to calculations of pure component surface tensions. Results indicate that a fitted model can capture the variability of the measured data very well, producing the lowest average percentage deviation for all compounds studied. The performance of the other models varies with compound and choice of model parameters. The behaviour of ternary mixed inorganic/organic systems was unreliably captured by using a predictive scheme and this was dependent on the composition of the solutes present. For more atmospherically representative higher order systems, entirely predictive schemes performed poorly. It was found that use of the binary data in a relatively simple mixing rule, or modification of an existing thermodynamic model with parameters derived from binary data, was able to accurately capture the surface tension variation with concentration. Thus
The influence of microstructure on surface strain distributions in a nickel micro-tension specimen
International Nuclear Information System (INIS)
Turner, T J; Shade, P A; Schuren, J C; Groeber, M A
2013-01-01
This work presents an integrated experimental and modeling approach for examining the deformation of a pure nickel polycrystal utilizing micro-mechanical testing and a crystal-based elasto-viscoplastic finite-element model (CPFEM). The objective is to study the influence of microstructure on the heterogeneous deformation in polycrystalline materials, and to utilize a modeling framework to explore aspects of the deformation that are difficult or impossible to measure experimentally. To accomplish this, a micro-tension specimen containing 259 grains was created from a pure nickel foil material and deformed in uniaxial tension. After the deformation, the specimen was destructively serial sectioned in concert with electron back scattering diffraction, and these data were used to instantiate a CPFEM simulation. The material parameters in the CPFEM model were calibrated by matching the experimental macroscopic stress-strain response of the micro-tension specimen, and then the simulation results were compared with experimental surface deformations measured with digital image correlation. After validating the simulation results by comparing measured and predicted surface strain distributions, a parametric study of the influence of both crystallographic texture and grain morphology is presented to better understand the influence of microstructure on the development of heterogeneous deformation in the pure nickel polycrystalline material. (paper)
Directory of Open Access Journals (Sweden)
Jyh Jian Chen
2014-03-01
Full Text Available Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.
Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy
Directory of Open Access Journals (Sweden)
Deng Zhenghua
2013-03-01
Full Text Available Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in the formation of surface oxide film. In this present work, the ignition temperature and the surface tension of Mg-9wt.%Al alloy with different Ce concentrations were studied. Surface tensions was measured using the maximum bubble pressure method (MBPM. Ignition temperature was measured using NiCr-NiSi type thermocouples and was monitored and recorded via a WXT-604 desk recording device. The results show that the ignition point of Mg-9wt.%Al alloy can be effectively elevated by adding Ce. The ignition temperature reaches its highest point of 720 ℃ when the addition of Ce is 1wt.%. The surface tension of the molten Mg-9wt.%Al alloy decreases exponentially with the increase of Ce addition at the same temperature. Similarly, the experiment also shows that the surface tension of Mg-9wt.%Al alloy decreases exponentially with the increase of temperature.
Energy Technology Data Exchange (ETDEWEB)
Kikuchi, T.; Hayasaka, K.; Takanohashi, T.; Iino, M. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science
1996-10-28
The behavior and properties of associated bodies were studied through measurement of surface tension considering acetone-soluble fraction relatively light among various solvent extracts of coal. In experiment, the acetone-soluble fraction was extracted from the substances extracted from Upper Freeport coal as standard specimen using the mixed solvent of carbon disulfide (CS2) and N-methyl-2-pyrrolidinone (NMP), and it was dissolved into NMP after drying. Surface tension was measured by Wilhelmy method. The experimental results are as follows. Equilibrium surface tension is equal to the surface tension of pure solvent in a low concentration range of solution, and decreases with an increase in concentration approaching a fixed value at 0 in log concentration, nearly showing an S curve. Adsorption of species with non-polar aromatic ring of the acetone-soluble fraction on a solution surface probably decreases surface tension. Change with time in surface tension is observed which suggests fast initial reaction and slow subsequent reaction. 4 figs.
Calculation of the interfacial tension of the methane-water system with the linear gradient theory
DEFF Research Database (Denmark)
Schmidt, Kurt A. G.; Folas, Georgios; Kvamme, Bjørn
2007-01-01
The linear gradient theory (LGT) combined with the Soave-Redlich-Kwong (SRK EoS) and the Peng-Robinson (PR EoS) equations of state has been used to correlate the interfacial tension data of the methane-water system. The pure component influence parameters and the binary interaction coefficient...... for the mixture influence parameter have been obtained for this system. The model was successfully applied to correlate the interfacial tension data set to within 2.3% for the linear gradient theory and the SRK EoS (LGT-SRK) and 2.5% for the linear gradient theory and PE EoS (LGT-PR). A posteriori comparison...... of data not used in the parameterisation were to within 3.2% for the LGT-SRK model and 2.7% for the LGT-PR model. An exhaustive literature review resulted in a large database for the investigation which covers a wide range of temperature and pressures. The results support the success of the linear...
On a Hele-Shaw flow with a time-dependent gap in the presence of surface tension
International Nuclear Information System (INIS)
Savina, T V; Nepomnyashchy, A A
2015-01-01
The introduction of surface tension into a Hele-Shaw problem makes it more realistic from the physical viewpoint, but more difficult from the mathematical viewpoint. In this paper we discuss a Hele-Shaw flow with a time-dependent gap taking into account the surface tension of the free boundary. We use the Schwarz function method to find asymptotic solutions for the interior problem in the case when the initial shape of the droplet is a weakly distorted circle. (paper)
A waveless two-dimensional flow in a channel against an inclined wall with surface tension effect
International Nuclear Information System (INIS)
Merzougui, Abdelkrim; Mekias, Hocine; Guechi, Fairouz
2007-01-01
Surface tension effect on a two-dimensional channel flow against an inclined wall is considered. The flow is assumed to be steady, irrotational, inviscid and incompressible. The effect of surface tension is taken into account and the effect of gravity is neglected. Numerical solutions are obtained via series truncation procedure. The problem is solved numerically for various values of the Weber number α and for various values of the inclination angle β between the horizontal bottom and the inclined wall
A waveless two-dimensional flow in a channel against an inclined wall with surface tension effect
Energy Technology Data Exchange (ETDEWEB)
Merzougui, Abdelkrim [Departement de Mathematiques, Faculte des sciences, Universite Mohamed Boudiaf, M' sila, 28000 (Algeria); Mekias, Hocine [Departement de Mathematiques, Faculte des sciences, Universite Farhat Abbas Setif 19000 (Algeria); Guechi, Fairouz [Departement de Mathematiques, Faculte des sciences, Universite Farhat Abbas Setif 19000 (Algeria)
2007-11-23
Surface tension effect on a two-dimensional channel flow against an inclined wall is considered. The flow is assumed to be steady, irrotational, inviscid and incompressible. The effect of surface tension is taken into account and the effect of gravity is neglected. Numerical solutions are obtained via series truncation procedure. The problem is solved numerically for various values of the Weber number {alpha} and for various values of the inclination angle {beta} between the horizontal bottom and the inclined wall.
Annotated bibliography for liquid metal surface tensions of groups III-A, IV-A, and V-A metals
International Nuclear Information System (INIS)
Murtha, M.J.; Burnet, G.
1976-04-01
An annotated bibliography has been prepared which includes summaries of 82 publications dating from 1920 and dealing with the measurement of the surface tensions of Groups III-A, IV-A, and V-A metals in the liquid state. The bibliography is organized by key element investigated, and contains a tabulation of correlations for surface tension as a function of temperature. A brief discussion dealing with variables and methods has been included
Use of local and global limit load solutions for plates with surface cracks under tension
Energy Technology Data Exchange (ETDEWEB)
Lei, Y. [British Energy Generation Ltd, Barnett Way, Bamwood, Gloucester GL4 3RS (United Kingdom)], E-mail: yuebao.lei@british-energy.com
2007-09-15
Some available experimental results for the ductile failure of plates with surface cracks under tension are reviewed. The response of crack driving force, J, and the ligament strain near the local and global limit loads are investigated by performing elastic-perfectly plastic finite element (FE) analysis of a plate with a semi-elliptical crack under tension. The results show that a ligament may survive until the global collapse load is reached when the average ligament strain at the global collapse load, which depends on the uniaxial strain corresponding to the flow stress of the material and the crack geometry, is less than the true fracture strain of the material obtained from uniaxial tension tests. The FE analysis shows that ligament yielding corresponding to the local limit load has little effect on J and the average ligament strain, whereas approach to global collapse corresponds to a sharp increase in both J and the average ligament strain. The prediction of the FE value of J using the reference stress method shows that the global limit load is more relevant to J-estimation than the local one.
Use of local and global limit load solutions for plates with surface cracks under tension
International Nuclear Information System (INIS)
Lei, Y.
2007-01-01
Some available experimental results for the ductile failure of plates with surface cracks under tension are reviewed. The response of crack driving force, J, and the ligament strain near the local and global limit loads are investigated by performing elastic-perfectly plastic finite element (FE) analysis of a plate with a semi-elliptical crack under tension. The results show that a ligament may survive until the global collapse load is reached when the average ligament strain at the global collapse load, which depends on the uniaxial strain corresponding to the flow stress of the material and the crack geometry, is less than the true fracture strain of the material obtained from uniaxial tension tests. The FE analysis shows that ligament yielding corresponding to the local limit load has little effect on J and the average ligament strain, whereas approach to global collapse corresponds to a sharp increase in both J and the average ligament strain. The prediction of the FE value of J using the reference stress method shows that the global limit load is more relevant to J-estimation than the local one
DEFF Research Database (Denmark)
Zuo, You-Xiang; Stenby, Erling Halfdan
1997-01-01
.26% at low pressure, and that of naphtha reformate cuts was 3.6%. In addition, the gradient theory was used to predict interfacial tensions for binary systems in the near-critical region. The results show excellent agreement between the predicted and experimental IFTs at high and moderate levels, while....... A consistent procedure for the estimation of properties associated to lumped systems. Fluid Phase Equilibria, 87: 89-197] was used to lump a mixture into one pseudocomponent, and its IFTs were calculated by means of the method of pure fluids. On the basis of the SRK EOS, the overall AAD of mixtures was 3...
International Nuclear Information System (INIS)
Maroto, J A; Nieves, F J de las; Quesada-Perez, M
2004-01-01
A classical experience in a physics student laboratory is to determine the surface tension of a liquid versus the temperature and to check the linear appearance of the obtained graph. In this work we show a simple method to estimate the critical temperature of three liquids by using experimental data of surface tension at different temperatures. By a logarithm fitting between surface tension and temperature, the critical temperature can be determined and compared with data from the literature. For two liquids (butanol and nitrobenzene) the comparison is acceptable but the differences are too high for the third liquid (water). By discussing the results it seems to be clear that the difference between the critical temperature of the liquid and the maximum temperature of the surface tension measurements is the determining factor in obtaining acceptable results. From this study it is possible to obtain more information on the liquid characteristics from surface tension measurements that are currently carried out in a student laboratory. Besides, in this paper it is shown how to select the most suitable liquids which provide both acceptable values for the critical temperature and measurements of the surface tension at moderate temperatures. The complementary use of numerical methods permits us to offer a complete experience for the students with a simple laboratory experiment which we recommend for physics students in advanced university courses
Zhang, Zhen-yu; Zhang, Hui-sheng
2004-11-01
Surface tension effects on the behavior of a pure vapor cavity or a cavity containing some noncondensible contents, which is growing, collapsing, and rebounding axisymmetrically near a rigid wall, are investigated numerically by the boundary integral method for different values of dimensionless stand-off parameter gamma, buoyancy parameter delta, and surface tension parameter beta. It is found that at the late stage of the collapse, if the resultant action of the Bjerknes force and the buoyancy force is not small, surface tension will not have significant effects on bubble behavior except that the bubble collapse time is shortened and the liquid jet becomes wider. If the resultant action of the two force is small enough, surface tension will have significant and in some cases substantial effects on bubble behavior, such as changing the direction of the liquid jet, making a new liquid jet appear, in some cases preventing the bubble from rebound before jet impact, and in other cases causing the bubble to rebound or even recollapse before jet impact. The mechanism of surface tension effects on the collapsing behavior of a cavity has been analyzed. The mechanisms of some complicated phenomena induced by surface tension effects are illustrated by analysis of the computed velocity fields and pressure contours of the liquid flow outside the bubble at different stages of the bubble evolution.
Investigations of surface-tension effects due to small-scale complex boundaries
Feng, Jiansheng
In this Ph.D. dissertation, we have investigated some important surface-tension phenomena including capillarity, wetting, and wicking. We mainly focus on the geometric aspects of these problems, and to learn about how structures affect properties. . In the first project (Chapter 2), we used numerical simulations and experiments to study the meniscus of a fluid confined in capillaries with complicated cross-sectional geometries. In the simulations, we computed the three-dimensional shapes of the menisci formed in polygonal and star-shaped capillaries with sharp or rounded corners. Height variations across the menisci were used to quantify the effect of surface tension. Analytical solutions were derived for all the cases where the cross-sectional geometry was a regular polygon or a regular star-shape. Power indices that characterize the effects of corner rounding were extracted from simulation results. These findings can serve as guide for fabrications of unconventional three-dimensional structures in Capillary Force Lithography experiments. Experimental demonstrations of the working principle was also performed. Although quantitative matching between simulation and experimental results was not achieved due to the limitation of material properties, clear qualitative trends were observed and interesting three-dimensional nano-structures were produced. A second project (Chapter 3) focused on developing techniques to produce three-dimensional hierarchically structured superhydrophobic surfaces with high aspect ratios. We experimented with two different high-throughput electron-beam-lithography processes featuring single and dual electron-beam exposures. After a surface modification procedure with a hydrophobic silane, the structured surfaces exhibited two distinct superhydrophobic behaviors---high and low adhesion. While both types of superhydrophobic surfaces exhibited very high (approximately 160° water advancing contact angles, the water receding contact angles on
Short-Time Structural Stability of Compressible Vortex Sheets with Surface Tension
Stevens, Ben
2016-11-01
Assume we start with an initial vortex-sheet configuration which consists of two inviscid fluids with density bounded below flowing smoothly past each other, where a strictly positive fixed coefficient of surface tension produces a surface tension force across the common interface, balanced by the pressure jump. We model the fluids by the compressible Euler equations in three space dimensions with a very general equation of state relating the pressure, entropy and density such that the sound speed is positive. We prove that, for a short time, there exists a unique solution of the equations with the same structure. The mathematical approach consists of introducing a carefully chosen artificial viscosity-type regularisation which allows one to linearise the system so as to obtain a collection of transport equations for the entropy, pressure and curl together with a parabolic-type equation for the velocity which becomes fairly standard after rotating the velocity according to the interface normal. We prove a high order energy estimate for the non-linear equations that is independent of the artificial viscosity parameter which allows us to send it to zero. This approach loosely follows that introduced by Shkoller et al. in the setting of a compressible liquid-vacuum interface. Although already considered by Coutand et al. [10] and Lindblad [17], we also make some brief comments on the case of a compressible liquid-vacuum interface, which is obtained from the vortex sheets problem by replacing one of the fluids by vacuum, where it is possible to obtain a structural stability result even without surface tension.
Effect of increased surface tension and assisted ventilation on /sup 99m/Tc-DTPA clearance
International Nuclear Information System (INIS)
Jefferies, A.L.; Kawano, T.; Mori, S.; Burger, R.
1988-01-01
Experiments were performed to determine the effects of conventional mechanical ventilation (CMV) and high-frequency oscillation (HFO) on the clearance of technetium-99m-labeled diethylenetriamine pentaacetate (/sup 99m/Tc-DTPA) from lungs with altered surface tension properties. A submicronic aerosol of /sup 99m/Tc-DTPA was insufflated into the lungs of anesthetized, tracheotomized rabbits before and 1 h after the administration of the aerosolized detergent dioctyl sodium sulfosuccinate (OT). Rabbits were ventilated by one of four methods: 1) spontaneous breathing; 2) CMV at 12 cmH2O mean airway pressure (MAP); 3) HFO at 12 cmH2O MAP; 4) HFO at 16 cmH2O MAP. Administration of OT resulted in decreased arterial PO2 (PaO2), increased lung wet-to-dry weight ratios, and abnormal lung pressure-volume relationships, compatible with increased surface tension. /sup 99m/Tc-DTPA clearance was accelerated after OT in all groups. The post-OT rate of clearance (k) was significantly faster (P less than 0.05) in the CMV at 12 cmH2O MAP [k = 7.57 +/- 0.71%/min (SE)] and HFO at 16 cmH2O MAP (k = 6.92 +/- 0.61%/min) groups than in the spontaneously breathing (k = 4.32 +/- 0.55%/min) and HFO at 12 cmH2O MAP (4.68 +/- 0.63%/min) groups. The clearance curves were biexponential in the former two groups. We conclude that pulmonary clearance of /sup 99m/Tc-DTPA is accelerated in high surface tension pulmonary edema, and this effect is enhanced by both conventional ventilation and HFO at high mean airway pressure
International Nuclear Information System (INIS)
Sanzi, H.C.
1987-01-01
This paper presents the results obtained from the tensions state and the displacements field of thermal origin, generated by a caloric source during the welding process. All the surfaces in contact with heavy water in a PHWR plant (Reactor of Pressurized Heavy Water) must be of austenitic stainless steel according to standard DIN 1.4550 or must be internally covered with this material. In the case of the primary loop components, -as the steam generator-, the walls of ferritic steel are covered with an austenitic stainless steel cladding. This cladding is applied by the welding process of immersed arc. Special attention is given during calculation, on the deformation produced in the holes of the bolts that link the entrance with the external lead. The distribution of nodal temperatures, as a function of time, is determined by a two-dimensional finite elements model during the welding process and the tension state and the displacement, by means of computational programs, were afterwards calculated. (Author)
Wu, Jie; Yu, Sheng-Tao; Jiang, Bo-nan
1996-01-01
In this paper a numerical procedure for simulating two-fluid flows is presented. This procedure is based on the Volume of Fluid (VOF) method proposed by Hirt and Nichols and the continuum surface force (CSF) model developed by Brackbill, et al. In the VOF method fluids of different properties are identified through the use of a continuous field variable (color function). The color function assigns a unique constant (color) to each fluid. The interfaces between different fluids are distinct due to sharp gradients of the color function. The evolution of the interfaces is captured by solving the convective equation of the color function. The CSF model is used as a means to treat surface tension effect at the interfaces. Here a modified version of the CSF model, proposed by Jacqmin, is used to calculate the tension force. In the modified version, the force term is obtained by calculating the divergence of a stress tensor defined by the gradient of the color function. In its analytical form, this stress formulation is equivalent to the original CSF model. Numerically, however, the use of the stress formulation has some advantages over the original CSF model, as it bypasses the difficulty in approximating the curvatures of the interfaces. The least-squares finite element method (LSFEM) is used to discretize the governing equation systems. The LSFEM has proven to be effective in solving incompressible Navier-Stokes equations and pure convection equations, making it an ideal candidate for the present applications. The LSFEM handles all the equations in a unified manner without any additional special treatment such as upwinding or artificial dissipation. Various bench mark tests have been carried out for both two dimensional planar and axisymmetric flows, including a dam breaking, oscillating and stationary bubbles and a conical liquid sheet in a pressure swirl atomizer.
Collective probabilities algorithm for surface hopping calculations
International Nuclear Information System (INIS)
Bastida, Adolfo; Cruz, Carlos; Zuniga, Jose; Requena, Alberto
2003-01-01
General equations that transition probabilities of the hopping algorithms in surface hopping calculations must obey to assure the equality between the average quantum and classical populations are derived. These equations are solved for two particular cases. In the first it is assumed that probabilities are the same for all trajectories and that the number of hops is kept to a minimum. These assumptions specify the collective probabilities (CP) algorithm, for which the transition probabilities depend on the average populations for all trajectories. In the second case, the probabilities for each trajectory are supposed to be completely independent of the results from the other trajectories. There is, then, a unique solution of the general equations assuring that the transition probabilities are equal to the quantum population of the target state, which is referred to as the independent probabilities (IP) algorithm. The fewest switches (FS) algorithm developed by Tully is accordingly understood as an approximate hopping algorithm which takes elements from the accurate CP and IP solutions. A numerical test of all these hopping algorithms is carried out for a one-dimensional two-state problem with two avoiding crossings which shows the accuracy and computational efficiency of the collective probabilities algorithm proposed, the limitations of the FS algorithm and the similarity between the results offered by the IP algorithm and those obtained with the Ehrenfest method
Richard, David; Speck, Thomas
2018-06-14
Combining three numerical methods (forward flux sampling, seeding of droplets, and finite-size droplets), we probe the crystallization of hard spheres over the full range from close to coexistence to the spinodal regime. We show that all three methods allow us to sample different regimes and agree perfectly in the ranges where they overlap. By combining the nucleation work calculated from forward flux sampling of small droplets and the nucleation theorem, we show how to compute the nucleation work spanning three orders of magnitude. Using a variation of the nucleation theorem, we show how to extract the pressure difference between the solid droplet and ambient liquid. Moreover, combining the nucleation work with the pressure difference allows us to calculate the interfacial tension of small droplets. Our results demonstrate that employing bulk quantities yields inaccurate results for the nucleation rate.
Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Marinova, Krastanka G; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Cox, Andrew R; Pelan, Eddie G
2016-07-01
Here, we review the principle and applications of two recently developed methods: the capillary meniscus dynamometry (CMD) for measuring the surface tension of bubbles/drops, and the capillary bridge dynamometry (CBD) for quantifying the bubble/drop adhesion to solid surfaces. Both methods are based on a new data analysis protocol, which allows one to decouple the two components of non-isotropic surface tension. For an axisymmetric non-fluid interface (e.g. bubble or drop covered by a protein adsorption layer with shear elasticity), the CMD determines the two different components of the anisotropic surface tension, σs and σφ, which are acting along the "meridians" and "parallels", and vary throughout the interface. The method uses data for the instantaneous bubble (drop) profile and capillary pressure, but the procedure for data processing is essentially different from that of the conventional drop shape analysis (DSA) method. In the case of bubble or drop pressed against a substrate, which forms a capillary bridge, the CBD method allows one to determine also the capillary-bridge force for both isotropic (fluid) and anisotropic (solidified) adsorption layers. The experiments on bubble (drop) detachment from the substrate show the existence of a maximal pulling force, Fmax, that can be resisted by an adherent fluid particle. Fmax can be used to quantify the strength of adhesion of bubbles and drops to solid surfaces. Its value is determined by a competition of attractive transversal tension and repulsive disjoining pressure forces. The greatest Fmax values have been measured for bubbles adherent to glass substrates in pea-protein solutions. The bubble/wall adhesion is lower in solutions containing the protein HFBII hydrophobin, which could be explained with the effect of sandwiched protein aggregates. The applicability of the CBD method to emulsion systems is illustrated by experiments with soybean-oil drops adherent to hydrophilic and hydrophobic substrates in
Standard practice for fracture testing with surface-crack tension specimens
American Society for Testing and Materials. Philadelphia
2003-01-01
1.1 This practice covers the design, preparation, and testing of surface-crack tension (SCT) specimens. It relates specifically to testing under continuously increasing force and excludes cyclic and sustained loadings. The quantity determined is the residual strength of a specimen having a semielliptical or circular-segment fatigue crack in one surface. This value depends on the crack dimensions and the specimen thickness as well as the characteristics of the material. 1.2 Metallic materials that can be tested are not limited by strength, thickness, or toughness. However, tests of thick specimens of tough materials may require a tension test machine of extremely high capacity. The applicability of this practice to nonmetallic materials has not been determined. 1.3 This practice is limited to specimens having a uniform rectangular cross section in the test section. The test section width and length must be large with respect to the crack length. Crack depth and length should be chosen to suit the ultimate pu...
Chen, Shulei; Liu, Kun; Liu, Cunbin; Wang, Dongyang; Ba, Dechun; Xie, Yuanhua; Du, Guangyu; Ba, Yaoshuai; Lin, Qiao
2016-12-01
Surface tension and viscosity act as important roles on the fluid flow in microchannel channels. In order to understand the influencing mechanism, three dimensional numerical simulations as well as experimental investigations were carried out on the slug formation and transfer in a rectangle T-junction microchannel. The simulation showed that the increasing Capillary number (Ca) resulted in the decreasing slug volume. Due to the existence of film thickness and corner flow, the characteristic length of slug was not the same trend completely. The results also showed that the pressure of junction point fluctuated periodically in the process of slug formation, which can reflect the slug formation period and the effect of the various conditions on pressure change. Two other pressure monitoring points were located in vertical channel and main channel and they monitored the pressure of two phase flow respectively. The increasing surface tension resulted in an increasing of total pressure, the interface pressure drop of two phases and the period of slug formation. The frequency of slug formation and two phases total pressure increased with the viscosity of continuous phase.
An accessible micro-capillary electrophoresis device using surface-tension-driven flow
Mohanty, Swomitra K.; Warrick, Jay; Gorski, Jack; Beebe, David J.
2010-01-01
We present a rapidly fabricated micro-capillary electrophoresis chip that utilizes surface-tension-driven flow for sample injection and extraction of DNA. Surface-tension-driven flow (i.e. passive pumping) injects a fixed volume of sample that can be predicted mathematically. Passive pumping eliminates the need for tubing, valves, syringe pumps, and other equipment typically needed for interfacing with microelectrophoresis chips. This method requires a standard micropipette to load samples before separation, and remove the resulting bands after analysis. The device was made using liquid phase photopolymerization to rapidly fabricate the chip without the need of special equipment typically associated with the construction of microelectrophoresis chips (e.g. cleanroom). Batch fabrication time for the device presented here was 1.5 h including channel coating time to suppress electroosmotic flow. Devices were constructed out of poly-isobornyl acrylate and glass. A standard microscope with a UV source was used for sample detection. Separations were demonstrated using Promega BenchTop 100 bp ladder in hydroxyl ethyl cellulose (HEC) and oligonucleotides of 91 and 118 bp were used to characterize sample injection and extraction of DNA bands. The end result was an inexpensive micro-capillary electrophoresis device that uses tools (e.g. micropipette, electrophoretic power supplies, and microscopes) already present in most labs for sample manipulation and detection, making it more accessible for potential end users. PMID:19425002
Surface tension driven aggregation of organic nanowires via lab in a droplet.
Gu, Jianmin; Yin, Baipeng; Fu, Shaoyan; Feng, Man; Zhang, Ziming; Dong, Haiyun; Gao, Faming; Zhao, Yong Sheng
2018-06-05
Directing the architecture of complex organic nanostructures is desirable and still remains a challenge in areas of materials science due to their structure-dependent collective optoelectronic properties. Herein, we demonstrate a simple and versatile solution strategy that allows surface tension to drive low-dimensional nanostructures to aggregate into complex structures via a lab in a droplet technique. By selecting a suitable combination of a solvent and an anti-solvent with controllable surface tension difference, the droplets can be automatically cracked into micro-droplets, which provides an aggregation force directed toward the centre of the droplet to drive the low-dimensional building blocks to form the special aggregations during the self-assembly process. This synthetic strategy has been shown to be universal for organic materials, which is beneficial for further optimizing the optoelectronic properties. These results contribute to gaining an insightful understanding on the detailed growth mechanism of complex organic nanostructures and greatly promoting the development of organic nanophotonics.
Directory of Open Access Journals (Sweden)
M.C. Teixeira
2017-02-01
Full Text Available The aim of this study was the assessment of the physicochemical stability of d-α-tocopherol formulated in medium chain triglyceride nanoemulsions, stabilized with Tween®80 and Lipoid®S75 as surfactant and co-surfactant, respectively. d-α-tocopherol was selected as active ingredient because of its well-recognized interesting anti-oxidant properties (such as radical scavenger for food and pharmaceutical industries. A series of nanoemulsions of mean droplet size below 90 nm (polydispersity index < 0.15 have been produced by high-pressure homogenization, and their surface electrical charge (zeta potential, pH, surface tension, osmolarity, and rheological behavior, were characterized as a function of the d-α-tocopherol loading. In vitro studies in Caco-2 cell lines confirmed the safety profile of the developed nanoemulsions with percentage of cell viability above 90% for all formulations.
A novel technique for including surface tension in PLIC-VOF methods
Energy Technology Data Exchange (ETDEWEB)
Meier, M.; Yadigaroglu, G. [Swiss Federal Institute of Technology, Nuclear Engineering Lab. ETH-Zentrum, CLT, Zurich (Switzerland); Smith, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Thermal-Hydraulics
2002-02-01
Various versions of Volume-of-Fluid (VOF) methods have been used successfully for the numerical simulation of gas-liquid flows with an explicit tracking of the phase interface. Of these, Piecewise-Linear Interface Construction (PLIC-VOF) appears as a fairly accurate, although somewhat more involved variant. Including effects due to surface tension remains a problem, however. The most prominent methods, Continuum Surface Force (CSF) of Brackbill et al. and the method of Zaleski and co-workers (both referenced later), both induce spurious or 'parasitic' currents, and only moderate accuracy in regards to determining the curvature. We present here a new method to determine curvature accurately using an estimator function, which is tuned with a least-squares-fit against reference data. Furthermore, we show how spurious currents may be drastically reduced using the reconstructed interfaces from the PLIC-VOF method. (authors)
Surface tension-induced high aspect-ratio PDMS micropillars with concave and convex lens tips
Li, Huawei
2013-04-01
This paper reports a novel method for the fabrication of 3-dimensional (3D) Polydimethylsiloxane (PDMS) micropillars with concave and convex lens tips in a one-step molding process, using a CO2 laser-machined Poly(methyl methacrylate) (PMMA) mold with through holes. The PDMS micropillars are 4 mm high and have an aspect ratio of 251. The micropillars are formed by capillary force drawing up PDMS into the through hole mold. The concave and convex lens tips of the PDMS cylindrical micropillars are induced by surface tension and are controllable by changing the surface wetting properties of the through holes in the PMMA mold. This technique eliminates the requirements of expensive and complicated facilities to prepare a 3D mold, and it provides a simple and rapid method to fabricate 3D PDMS micropillars with controllable dimensions and tip shapes. © 2013 IEEE.
Surface tension-induced high aspect-ratio PDMS micropillars with concave and convex lens tips
Li, Huawei; Fan, Yiqiang; Yi, Ying; Foulds, Ian G.
2013-01-01
This paper reports a novel method for the fabrication of 3-dimensional (3D) Polydimethylsiloxane (PDMS) micropillars with concave and convex lens tips in a one-step molding process, using a CO2 laser-machined Poly(methyl methacrylate) (PMMA) mold with through holes. The PDMS micropillars are 4 mm high and have an aspect ratio of 251. The micropillars are formed by capillary force drawing up PDMS into the through hole mold. The concave and convex lens tips of the PDMS cylindrical micropillars are induced by surface tension and are controllable by changing the surface wetting properties of the through holes in the PMMA mold. This technique eliminates the requirements of expensive and complicated facilities to prepare a 3D mold, and it provides a simple and rapid method to fabricate 3D PDMS micropillars with controllable dimensions and tip shapes. © 2013 IEEE.
New sensitive micro-measurements of dynamic surface tension and diffusion coefficients
DEFF Research Database (Denmark)
Kinoshita, Koji; Ortiz, Elisa Parra; Needham, David
2017-01-01
Currently available dynamic surface tension (DST) measurement methods, such as Wilhelmy plate, droplet- or bubble-based methods, still have various experimental limitations such as the large size of the interface, convection in the solution, or a certain “dead time” at initial measurement....... These limitations create inconsistencies for the kinetic analysis of surfactant adsorption/desorption, especially significant for ionic surfactants. Here, the “micropipette interfacial area-expansion method” was introduced and validated as a new DST measurement having a high enough sensitivity to detect diffusion...... for surface excess concentration. We found that the measured diffusion coefficient of 1-Octanol, 7.2 ± 0.8 × 10−6 cm2/s, showed excellent agreement with the result from an alternative method, “single microdroplet catching method”, to measure the diffusion coefficient from diffusion-controlled microdroplet...
Surface tension and wetting behaviour of Bi-In-Sn alloys
International Nuclear Information System (INIS)
Ervina Efzan Mohd Noor; Ahmad Badri Ismail; Soong, T.K.; Chin, Y.T.; Luay Bakir Hussain
2007-01-01
Concerns about possible landfill contamination, influent discharge from production process are one of the reasons convert from lead-containing electronics to lead-free containing. The surface and interfacial properties of Bi-In-Sn lead-free solder system as a basic system of multicomponent alloys proposed as lead-free solder materials have been studied. The surface tension of Bi-In-Sn lead-free solder system of melting temperature 60 degree Celsius has been measured the temperature range 80 degree Celsius and 140 degree Celsius. The study of the wetting behaviour of Bi-In-Sn lead-free solder system on a Cu substrate has been performed by measuring contact angle on various metal substrates by Optical Microscopy with software. (author)
Tice, Ian
2018-04-01
This paper concerns the dynamics of a layer of incompressible viscous fluid lying above a rigid plane and with an upper boundary given by a free surface. The fluid is subject to a constant external force with a horizontal component, which arises in modeling the motion of such a fluid down an inclined plane, after a coordinate change. We consider the problem both with and without surface tension for horizontally periodic flows. This problem gives rise to shear-flow equilibrium solutions, and the main thrust of this paper is to study the asymptotic stability of the equilibria in certain parameter regimes. We prove that there exists a parameter regime in which sufficiently small perturbations of the equilibrium at time t=0 give rise to global-in-time solutions that return to equilibrium exponentially in the case with surface tension and almost exponentially in the case without surface tension. We also establish a vanishing surface tension limit, which connects the solutions with and without surface tension.
Directory of Open Access Journals (Sweden)
Shantonu Biswas
2016-03-01
Full Text Available This publication provides an overview and discusses some challenges of surface tension directed fluidic self-assembly of semiconductor chips which are transported in a liquid medium. The discussion is limited to surface tension directed self-assembly where the capture, alignment, and electrical connection process is driven by the surface free energy of molten solder bumps where the authors have made a contribution. The general context is to develop a massively parallel and scalable assembly process to overcome some of the limitations of current robotic pick and place and serial wire bonding concepts. The following parts will be discussed: (2 Single-step assembly of LED arrays containing a repetition of a single component type; (3 Multi-step assembly of more than one component type adding a sequence and geometrical shape confinement to the basic concept to build more complex structures; demonstrators contain (3.1 self-packaging surface mount devices, and (3.2 multi-chip assemblies with unique angular orientation. Subsequently, measures are discussed (4 to enable the assembly of microscopic chips (10 μm–1 mm; a different transport method is introduced; demonstrators include the assembly of photovoltaic modules containing microscopic silicon tiles. Finally, (5 the extension to enable large area assembly is presented; a first reel-to-reel assembly machine is realized; the machine is applied to the field of solid state lighting and the emerging field of stretchable electronics which requires the assembly and electrical connection of semiconductor devices over exceedingly large area substrates.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, K [Yokohama National Univ., Yokohama (Japan). Faculty of Engineering; Akiba, H [Toyo Construction Co. Ltd., Tokyo (Japan)
1997-12-31
The effect of surface tension on free surface flow around floating models is discussed experimentally and numerically. Three-dimensional free surface flow around vertical circular cylinders floating in a circulating water channel was visually observed, where a surface-active agent was added to water. The results are analyzed using Weber number. The numerical analysis was done for vertical cylinder and CY100 models using the Rankine source method. Weber number of at least around 120 is necessary to eliminate the effect of surface tension from free surface flow around the CY100 model. The numerical analysis for the cylinder model needs simulation with wavelength shorter than that of free surface wave used by the Rankine source method. The model for the resistance test should be at least around 7m long to eliminate the effect of surface tension at Froude number of 0.1 or higher. 15 refs., 12 figs., 2 tabs.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, K. [Yokohama National Univ., Yokohama (Japan). Faculty of Engineering; Akiba, H. [Toyo Construction Co. Ltd., Tokyo (Japan)
1996-12-31
The effect of surface tension on free surface flow around floating models is discussed experimentally and numerically. Three-dimensional free surface flow around vertical circular cylinders floating in a circulating water channel was visually observed, where a surface-active agent was added to water. The results are analyzed using Weber number. The numerical analysis was done for vertical cylinder and CY100 models using the Rankine source method. Weber number of at least around 120 is necessary to eliminate the effect of surface tension from free surface flow around the CY100 model. The numerical analysis for the cylinder model needs simulation with wavelength shorter than that of free surface wave used by the Rankine source method. The model for the resistance test should be at least around 7m long to eliminate the effect of surface tension at Froude number of 0.1 or higher. 15 refs., 12 figs., 2 tabs.
International Nuclear Information System (INIS)
Jacome, Paulo A.D.; Landim, Mariana C.; Garcia, Amauri; Furtado, Alexandre F.; Ferreira, Ivaldo L.
2011-01-01
Highlights: → Surface tension and the Gibbs-Thomson coefficient are computed for Al-based alloys. → Butler's scheme and ThermoCalc are used to compute the thermophysical properties. → Predictive cell/dendrite growth models depend on accurate thermophysical properties. → Mechanical properties can be related to the microstructural cell/dendrite spacing. - Abstract: In this paper, a solution for Butler's formulation is presented permitting the surface tension and the Gibbs-Thomson coefficient of Al-based binary alloys to be determined. The importance of Gibbs-Thomson coefficient for binary alloys is related to the reliability of predictions furnished by predictive cellular and dendritic growth models and of numerical computations of solidification thermal variables, which will be strongly dependent on the thermophysical properties assumed for the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled to a specific interface of a computational thermodynamics software in order to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Fe, Al-Ni, Al-Cu and Al-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.
Energy Technology Data Exchange (ETDEWEB)
Jacome, Paulo A.D.; Landim, Mariana C. [Department of Mechanical Engineering, Fluminense Federal University, Av. dos Trabalhadores, 420-27255-125 Volta Redonda, RJ (Brazil); Garcia, Amauri, E-mail: amaurig@fem.unicamp.br [Department of Materials Engineering, University of Campinas, UNICAMP, PO Box 6122, 13083-970 Campinas, SP (Brazil); Furtado, Alexandre F.; Ferreira, Ivaldo L. [Department of Mechanical Engineering, Fluminense Federal University, Av. dos Trabalhadores, 420-27255-125 Volta Redonda, RJ (Brazil)
2011-08-20
Highlights: {yields} Surface tension and the Gibbs-Thomson coefficient are computed for Al-based alloys. {yields} Butler's scheme and ThermoCalc are used to compute the thermophysical properties. {yields} Predictive cell/dendrite growth models depend on accurate thermophysical properties. {yields} Mechanical properties can be related to the microstructural cell/dendrite spacing. - Abstract: In this paper, a solution for Butler's formulation is presented permitting the surface tension and the Gibbs-Thomson coefficient of Al-based binary alloys to be determined. The importance of Gibbs-Thomson coefficient for binary alloys is related to the reliability of predictions furnished by predictive cellular and dendritic growth models and of numerical computations of solidification thermal variables, which will be strongly dependent on the thermophysical properties assumed for the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled to a specific interface of a computational thermodynamics software in order to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Fe, Al-Ni, Al-Cu and Al-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.
International Nuclear Information System (INIS)
Choo, R.T.C.; Szekely, J.; David, S.A.
1992-01-01
By combining a mathematical model of the welding arc and of the weld pool, calculations are presented here to describe the free surface temperature of weld pools for spot welding operations. The novel aspects of the treatment include the calculation of the heat and current fluxes falling on the free weld pool surface from first principles, a realistic allowance for heat losses due to vaporization, and a realistic allowance for the temperature dependence of the surface tension. The most important finding reported in this article is that the free surface temperature of weld pools appears to be limited by Marangoni convection, rather than heat losses due to vaporization. Furthermore, it was found that once thermocapillary flow can produce high enough surface velocities (>25 cm/s), the precise nature of the relationship between temperature and surface tension will become less important
Leong, Kai-Yang; Wang, Feng
2018-04-01
The surface tension of nanoscale droplets of water was studied with molecular dynamics simulations using the BLYPSP-4F water potential. The internal pressure of the droplet was measured using an empirical correlation between the pressure and density, established through a series of bulk simulations performed at pressures from 1 to 1000 bars. Such a procedure allows for reliable determination of internal pressure without the need to calculate the local virial. The surface tension, estimated with the Young-Laplace relation, shows good agreement with the Tolman equation with a Tolman length of -0.48 Å. The interface of a liquid water droplet is shown to be around 1.1-1.3 nm thick depending on radii. The fairly thick interface region puts a lower limit on the size of droplets that still have a bulk-like interior.
Pendent_Drop: An ImageJ Plugin to Measure the Surface Tension from an Image of a Pendent Drop
Directory of Open Access Journals (Sweden)
Adrian Daerr
2016-01-01
Full Text Available The pendent drop method for surface tension measurement consists in analysing the shape of an axisymmetric drop hanging from a capillary tube. This software is an add-on for the public domain image processing software ImageJ which matches a theoretical profile to the contour of a pendent drop, either interactively or by automatically minimising the mismatch. It provides an estimate of the surface tension, drop volume and surface area from the best matching parameters. It can be used in a headless setup. It is hosted on http://fiji.sc/List_of_update_sites with the source code on https://github.com/adaerr/pendent-drop
Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min
2017-08-28
The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.
The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids
Hu, Bin; Kieweg, Sarah L.
2012-01-01
Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability. PMID:23687391
Bakhshi, Nafiseh; Soleimanian-Zad, Sabihe; Sheikh-Zeinoddin, Mahmoud
2017-06-01
Currently, screening of microbial biosurfactants (BSs) is based on their equilibrium surface tension values obtained using static surface tension measurement. However, a good surfactant should not only have a low equilibrium surface tension, but its dynamic surface tension (DST) should also decrease rapidly with time. In this study, screening of BSs produced by Lactobacillus plantarum subsp. plantarum PTCC 1896 (probiotic) was performed based on their DST values measured by Wilhelmy plate tensiometry. The relationship between DST and structural and functional properties (anti-adhesive activity) of the BSs was investigated. The results showed that the changes in the yield, productivity and structure of the BSs were growth medium and incubation time dependent (p<0.05). Structurally different BSs produced exhibited identical equilibrium surface tension values. However, differences among the structure/yield of the BSs were observed through the measurement of their DST. The considerable dependence of DST on the concentration and composition of the BS proteins was observed (p<0.05). Moreover, the anti-adhesive activity of the BS was found to be positively correlated with its DST. The results suggest that the DST measurement could serve as an efficient method for the clever screening of BSs producer/production condition, and consequently, for the investigation of probiotic features of bacteria, since the anti-adhesive activity is an important criterion of probiotics. Copyright © 2017 Elsevier Inc. All rights reserved.
Dynamics of two-phase interfaces and surface tensions: A density-functional theory perspective
Yatsyshin, Petr; Sibley, David N.; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim
2016-11-01
Classical density functional theory (DFT) is a statistical mechanical framework for the description of fluids at the nanoscale, where the inhomogeneity of the fluid structure needs to be carefully accounted for. By expressing the grand free-energy of the fluid as a functional of the one-body density, DFT offers a theoretically consistent and computationally accessible way to obtain two-phase interfaces and respective interfacial tensions in a ternary solid-liquid-gas system. The dynamic version of DFT (DDFT) can be rigorously derived from the Smoluchowsky picture of the dynamics of colloidal particles in a solvent. It is generally agreed that DDFT can capture the diffusion-driven evolution of many soft-matter systems. In this context, we use DDFT to investigate the dynamic behaviour of two-phase interfaces in both equilibrium and dynamic wetting and discuss the possibility of defining a time-dependent surface tension, which still remains in debate. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from the Engineering and Physical Sciences Research Council of the UK via Grants No. EP/L027186 and EP/L020564.
Modeling of a Curvilinear Planar Crack with a Curvature-Dependent Surface Tension
Zemlyanova, A. Y.; Walton, J. R.
2012-01-01
An approach to modeling fracture incorporating interfacial mechanics is applied to the example of a curvilinear plane strain crack. The classical Neumann boundary condition is augmented with curvature-dependent surface tension. It is shown that the considered model eliminates the integrable crack-tip stress and strain singularities of order 1/2 present in the classical linear fracture mechanics solutions, and also leads to the sharp crack opening that is consistent with empirical observations. Unlike for the case of a straight crack, for a general curvilinear crack some components of the stresses and the derivatives of the displacements may still possess weaker singularities of a logarithmic type. Generalizations of the present study that lead to complete removal of all crack-tip singularities, including logarithmic, are the subject of a future paper. © 2012 Society for Industrial and Applied Mathematics.
A multiscale method for compressible liquid-vapor flow with surface tension*
Directory of Open Access Journals (Sweden)
Jaegle Felix
2013-01-01
Full Text Available Discontinuous Galerkin methods have become a powerful tool for approximating the solution of compressible flow problems. Their direct use for two-phase flow problems with phase transformation is not straightforward because this type of flows requires a detailed tracking of the phase front. We consider the fronts in this contribution as sharp interfaces and propose a novel multiscale approach. It combines an efficient high-order Discontinuous Galerkin solver for the computation in the bulk phases on the macro-scale with the use of a generalized Riemann solver on the micro-scale. The Riemann solver takes into account the effects of moderate surface tension via the curvature of the sharp interface as well as phase transformation. First numerical experiments in three space dimensions underline the overall performance of the method.
Effect of surface tension on the behavior of adhesive contact based on Lennard-Jones potential law
Zhu, Xinyao; Xu, Wei
2018-02-01
The present study explores the effect of surface tension on adhesive contact behavior where the adhesion is interpreted by long-range intermolecular forces. The adhesive contact is analyzed using the equivalent system of a rigid sphere and an elastic half space covered by a membrane with surface tension. The long-range intermolecular forces are modeled with the Lennard‒Jones (L‒J) potential law. The current adhesive contact issue can be represented by a nonlinear integral equation, which can be solved by Newton‒Raphson method. In contrast to previous studies which consider intermolecular forces as short-range, the present study reveals more details of the features of adhesive contact with surface tension, in terms of jump instabilities, pull-off forces, pressure distribution within the contact area, etc. The transition of the pull-off force is not only consistent with previous studies, but also presents some new interesting characteristics in the current situation.
Yu, Fengyi; Wei, Yanhong
2018-05-01
The effects of surface tension anisotropy and welding parameters on initial instability dynamics during gas tungsten arc welding of an Al-alloy are investigated by a quantitative phase-field model. The results show that the surface tension anisotropy and welding parameters affect the initial instability dynamics in different ways during welding. The surface tension anisotropy does not influence the solute diffusion process but does affect the stability of the solid/liquid interface during solidification. The welding parameters affect the initial instability dynamics by varying the growth rate and thermal gradient. The incubation time decreases, and the initial wavelength remains stable as the welding speed increases. When welding power increases, the incubation time increases and the initial wavelength slightly increases. Experiments were performed for the same set of welding parameters used in modeling, and the results of the experiments and simulations were in good agreement.
Elastic-Plastic J-Integral Solutions or Surface Cracks in Tension Using an Interpolation Methodology
Allen, P. A.; Wells, D. N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
Tong, Jing; Yang, Hong-Xu; Liu, Ru-Jing; Li, Chi; Xia, Li-Xin; Yang, Jia-Zhen
2014-11-13
With the use of isothermogravimetrical analysis, the enthalpies of vaporization, Δ(g)lH(o)m(T(av)), at the average temperature, T(av) = 445.65 K, for the ionic liquids (ILs) 1-alkyl-3-methylimidazolium propionate [C(n)mim][Pro](n = 4, 5, 6) were determined. Using Verevkin's method, the difference of heat capacities between the vapor phase and the liquid phase, Δ(g)lC(p)(o)m, for [C(n)mim][Pro](n = 2, 3, 4, 5, 6), were calculated based on the statistical thermodynamics. Therefore, with the use of Δ(g)lC(p)(o)m, the values of Δ(g)lH(o)m(T(av)) were transformed into Δ(g)lH(o)m(298), 126.8, 130.3, and 136.5 for [C(n)mim][Pro](n = 4, 5, 6), respectively. In terms of the new scale of polarity for ILs, the order of the polarity of [C(n)mim][Pro](n = 2, 3, 4, 5, 6) was predicted, that is, the polarity decreases with increasing methylene. A new model of the relationship between the surface tension and the enthalpy of vaporization for aprotic ILs was put forward and used to predict the surface tension for [C(n)mim][Pro](n = 2, 3, 4, 5, 6) and others. The predicted surface tension for the ILs is in good agreement with the experimental one.
Pseudopotentials for calculating the bulk and surface properties of solids
International Nuclear Information System (INIS)
Cohen, M.L.
1983-01-01
A survey is presented describing research in condensed matter physics using pseudopotentials to calculate electronic, structural, and vibrational properties of solids. Semiconductors are emphasized, and both bulk and surface calculations are discussed. (author) [pt
Sauer, Dorothea; McGinity, James W
2009-06-01
Limited information on thermally cured dry-powder coatings used for solid dosage forms has been available in the literature. The aim of this study was to characterize the film formation process of Eudragit L 100-55 dry-powder coatings and to investigate the influence of film additives on melt viscosity and surface tension. The coating process employed no liquids and the plasticizer was combined with the polymer using hot melt extrusion. Thermoanalytical methods including differential scanning calorimetry and thermogravimetric analysis (TGA) were used to investigate the thermal properties of the dry-coating formulations. The rheological behavior of the coating formulations were characterized with the extrusion torque, and the surface energy parameters were determined from contact angle measurements. The influence of the level of triethyl citrate (TEC) as plasticizer and polyethylene glycol (PEG) 3350 in the polymer film on film formation was investigated using a digital force tester. TGA confirmed thermal stability of all coating excipients at the investigated curing conditions. Increasing TEC levels and the addition of PEG 3350 as a low melting excipient in the coating reduced the viscosity of the polymer. Plasticization of the polymer with TEC increased the surface free energy, whereas the admixture of 10% PEG 3350 did not affect the surface free energy of Eudragit L 100-55. The spreading coefficient of the polymers over two sample tablet formulations was reduced with increasing surface free energy. During the curing process, puncture strength, and elongation of powder-cast films increased. The effect of curing time on the mechanical properties was dependent on the plasticizer content. The incorporation of TEC and PEG 3350 into the Eudragit L 100-55 powder coating formulation improved film formation. Mechanical testing of powder-cast films showed an increase of both elongation and puncture strength over the curing process as criterion for polymer particle fusion
Pline, Alexander D.; Werner, Mark P.; Hsieh, Kwang-Chung
1991-01-01
The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the United States Microgravity Laboratory-1 (USML-1) Spacelab mission planned for June, 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electric, two dimensional Particle Image Velocimetry (PIV) technique called Particle Displacement Tracking (PDT), which uses a simple space domain particle tracking algorithm. Results using the ground based STDCE hardware, with a radiant flux heating mode, and the PDT system are compared to numerical solutions obtained by solving the axisymmetric Navier Stokes equations with a deformable free surface. The PDT technique is successful in producing a velocity vector field and corresponding stream function from the raw video data which satisfactorily represents the physical flow. A numerical program is used to compute the velocity field and corresponding stream function under identical conditions. Both the PDT system and numerical results were compared to a streak photograph, used as a benchmark, with good correlation.
International Nuclear Information System (INIS)
Oliveira, M.B.; Domínguez-Pérez, M.; Cabeza, O.; Lopes-da-Silva, J.A.; Freire, M.G.; Coutinho, J.A.P.
2013-01-01
Highlights: • Novel data for the surface tensions of mixtures [C 4 mim][NTf 2 ] + [C 4 C 1 mim]/[C 3 mpy]/[C 3 mpyr]/[C 3 mpip][NTf 2 ] are presented. • γ were determined at a fixed temperature, 298.2 K, and at atmospheric pressure, for the whole composition range. • Surface tension deviations showed the near ideal behavior of the selected mixtures. • Gibbs adsorption isotherms showed the surface preferential adsorption of one ionic liquid over the other. -- Abstract: While values for thermophysical properties of ionic liquids are becoming widely available, data for ionic liquid mixtures are still scarce. In an effort to overcome this limitation and understand the behavior of ionic liquid mixtures, novel data for the surface tension of mixtures composed of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 4 mim][NTf 2 ], with other ionic liquids with a common anion, namely 1-butyl-2,3-dimethylimidazolium, [C 4 C 1 mim] + , 3-methyl-1-propylpyridinium, [C 3 mpy] + , 1-methyl-1-propylpyrrolidinium, [C 3 mpyr] + , and 1-methyl-1-propylpiperidinium, [C 3 mpip] + , were measured at T = 298.2 K and atmospheric pressure over the entire composition range. From the surface tension deviations derived from the experimental results, it was possible to infer that the cation alkyl chain length of the second ionic liquid constituting the mixture has a stronger influence in the ideal mixture behavior than the type of family the ionic liquid cation belongs to. The Gibbs adsorption isotherms, estimated from the experimental values, show that the composition of the vapor–liquid interface is not the same as that of the bulk and that the interface is richer in the ionic liquid with the lowest surface tension, [C 4 mim][NTf 2
Coffman, Kirsten E; Taylor, Bryan J; Carlson, Alex R; Wentz, Robert J; Johnson, Bruce D
2016-01-15
Alveolar-capillary membrane conductance (D(M,CO)) and pulmonary-capillary blood volume (V(C)) are calculated via lung diffusing capacity for carbon monoxide (DL(CO)) and nitric oxide (DL(NO)) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θ(CO)) and the D(M,NO)/D(M,CO) ratio (α-ratio), are controversial. This study systematically determined optimal θ(CO) and α-ratio values to be used in the single-FiO2 method that yielded the most similar D(M,CO) and V(C) values compared to the 'gold-standard' multiple-FiO2 method. Eleven healthy subjects performed single breath DL(CO)/DL(NO) maneuvers at rest and during exercise. D(M,CO) and V(C) were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θ(CO) equations and a range of previously reported α-ratios. The RP θ(CO) equation (Reeves, R.B., Park, H.K., 1992. Respiration Physiology 88 1-21) and an α-ratio of 4.0-4.4 yielded DM,CO and VC values that were most similar between methods. The RP θ(CO) equation and an experimental α-ratio should be used in future studies. Copyright © 2015 Elsevier B.V. All rights reserved.
Zehnder, Matthias; Schicht, Olivier; Sener, Beatrice; Schmidlin, Patrick
2005-08-01
The aim of this study was to evaluate the effect of reducing surface tension in endodontic chelator solutions on their ability to remove calcium from instrumented root canals. Aqueous solutions containing 15.5% EDTA, 10% citric acid, or 18% 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP) were prepared with and without 1% (wt/wt) polysorbate (Tween) 80 and 9% propylene glycol. Surface tension in these solutions was measured using the Wilhelmy method. Sixty-four extracted, single-rooted human teeth of similar length were instrumented and irrigated with a 1% sodium hypochlorite solution and then randomly assigned (n = 8 per group) to receive a final one-minute rinse with 5 ml of test solutions, water, or the pure aqueous Tween/propylene glycol solution. Calcium concentration in eluates was measured using atomic absorption spectrometry. Incorporation of wetting agents resulted in a reduction of surface tension values by approximately 50% in all tested solutions. However, none of the solutions with reduced surface tension chelated more calcium from canals than their pure counterparts (p > 0.05).
Huck-Iriart, Cristia´n; De-Candia, Ariel; Rodriguez, Javier; Rinaldi, Carlos
2016-01-01
In this work, we described an image processing procedure for the measurement of surface tension of the air-liquid interface using isothermal capillary action. The experiment, designed for an undergraduate course, is based on the analysis of a series of solutions with diverse surfactant concentrations at different ionic strengths. The objective of…
Galan Sanchez, L.M.; Espel, J.R.; Onink, S.A.F.; Meindersma, G.W.; Haan, de A.B.
2009-01-01
Density, viscosity, and surface tension data sets of 13 ionic liquids formed by imidazolium, pyridinium, or pyrrolidinium cations paired with dicyanamide (DCA), tetrafluoroborate (BF4¯), thiocyanate (SCN¯),methylsulfate (MeSO4¯), and trifluoroacetate (TFA) anions are reported. The properties were
Pishkar, Leila; Taheri, Saba; Makarem, Somayeh; Alizadeh Zeinabad, Hojjat; Rahimi, Arash; Saboury, Ali Akbar; Falahati, Mojtaba
2017-02-01
In this study, a novel method to probe molecular interactions and binding of human hemoglobin (Hb) with nanodiamond (ND) was introduced based on the surface tension measurement. This method complements conventional techniques, which are basically done by zeta potential and dynamic light scattering (DLS) measurements, near and far circular dichroism (CD) spectroscopy, intrinsic and extrinsic fluorescence spectroscopy. Addition of ND to Hb solution increased the surface tension value of Hb-ND complex relative to those of Hb and ND molecules. The zeta potential values reveled that Hb and ND provide identical charge distribution at pH 7.5. DLS measurements demonstrated that Hb, ND, and ND-Hb complex have hydrodynamic radiuses of 98.37 ± 4.57, 122.07 ± 7.88 nm and 62.27 ± 3.70 at pH of 7.5 respectively. Far and near UV-CD results indicated the loss of α-helix structure and conformational changes of Hb, respectively. Intrinsic fluorescence data demonstrated that the fluorescence quenching of Hb by ND was the result of the static quenching. The hydrophobic interaction plays a pivotal role in the interaction of ND with Hb. Fluorescence intensity changes over time revealed conformational change of Hb continues after the mixing of the components (Hb-ND) till 15 min, which is indicative of the denaturation of the Hb relative to the protein control. Extrinsic fluorescence data showed a considerable enhancement of the ANS fluorescence intensity of Hb-ND system relative to the Hb till 60 nM of ND, likely persuaded by greater exposure of nonpolar residues of Hb hydrophobic pocket. The remarkable decrease in T m value of Hb in Hb-ND complex exhibits interaction of Hb with ND conducts to conformational changes of Hb. This study offers consequential discrimination into the interaction of ND with proteins, which may be of significance for further appeal of these nanoparticles in biotechnology prosecution.
KINEMATICAL FEATURES OF FORMATION OF A FLANGE WITH MINIMUM TENSION OF A TRANSIENT TOROIDAL SURFACE
Directory of Open Access Journals (Sweden)
M. I. Sidorenko
2018-01-01
Full Text Available The technology of plastic forming of wide flanges in tube billets with the predicted length of the transitional toroidal section between the outer plane of the flange and the internal cavity of the pipe is proposed. The procedure for calculating the length of this section is given. In order to eliminate the toroidal portion in the flange formed during the flanging of the pipe, it is proposed to perform its plastic shaping by depositing the cylindrical part of the workpiece. Equations for calculating the extent of the free surface on the toroidal part of the workpiece when it is shaped, depending on the coefficient of contact friction and the presence of a radial support of the flange are obtained. The variant of forming in the flange the toroidal section in the stamp with the compensation cavity is proposed. Equations for calculating the deformation force and the extent of the free surface are given.
Kozhevnikov, Danil A.; Sheremet, Mikhail A.
2018-01-01
The effect of surface tension on laminar natural convection in a vertical cylindrical cavity filled with a weak evaporating liquid has been analyzed numerically. The cylindrical enclosure is insulated at the bottom, heated by a constant heat flux from the side, and cooled by a non-uniform evaporative heat flux from the top free surface having temperature-dependent surface tension. Governing equations with corresponding boundary conditions formulated in dimensionless stream function, vorticity, and temperature have been solved by finite difference method of the second-order accuracy. The influence of Rayleigh number, Marangoni number, and aspect ratio on the liquid flow and heat transfer has been studied. Obtained results have revealed that the heat transfer rate at free surface decreases with Marangoni number and increases with Rayleigh number, while the average temperature inside the cavity has an opposite behavior; namely, it growths with Marangoni number and reduces with Rayleigh number.
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Ali Khazaei
2014-07-01
Full Text Available In this work, artificial neural network (ANN has been employed to propose a practical model for predicting the surface tension of multi-component mixtures. In order to develop a reliable model based on the ANN, a comprehensive experimental data set including 15 ternary liquid mixtures at different temperatures was employed. These systems consist of 777 data points generally containing hydrocarbon components. The ANN model has been developed as a function of temperature, critical properties, and acentric factor of the mixture according to conventional corresponding-state models. 80% of the data points were employed for training ANN and the remaining data were utilized for testing the generated model. The average absolute relative deviations (AARD% of the model for the training set, the testing set, and the total data points were obtained 1.69, 1.86, and 1.72 respectively. Comparing the results with Flory theory, Brok-Bird equation, and group contribution theory has proved the high prediction capability of the attained model.
Wu, You; Kharge, Angana Banerjee; Perlman, Carrie E
2014-10-01
With proteinaceous-liquid flooding of discrete alveoli, a model of the edema pattern in the acute respiratory distress syndrome, lung inflation over expands aerated alveoli adjacent to flooded alveoli. Theoretical considerations suggest that the overexpansion may be proportional to surface tension, T. Yet recent evidence indicates proteinaceous edema liquid may not elevate T. Thus whether the overexpansion is injurious is not known. Here, working in the isolated, perfused rat lung, we quantify fluorescence movement from the vasculature to the alveolar liquid phase as a measure of overdistension injury to the alveolar-capillary barrier. We label the perfusate with fluorescence; micropuncture a surface alveolus and instill a controlled volume of nonfluorescent liquid to obtain a micropunctured-but-aerated region (control group) or a region with discrete alveolar flooding; image the region at a constant transpulmonary pressure of 5 cmH2O; apply five ventilation cycles with a positive end-expiratory pressure of 0-20 cmH2O and tidal volume of 6 or 12 ml/kg; return the lung to a constant transpulmonary pressure of 5 cmH2O; and image for an additional 10 min. In aerated areas, ventilation is not injurious. With discrete alveolar flooding, all ventilation protocols cause sustained injury. Greater positive end-expiratory pressure or tidal volume increases injury. Furthermore, we determine T and find injury increases with T. Inclusion of either plasma proteins or Survanta in the flooding liquid does not alter T or injury. Inclusion of 2.7-10% albumin and 1% Survanta together, however, lowers T and injury. Contrary to expectation, albumin inclusion in our model facilitates exogenous surfactant activity. Copyright © 2014 the American Physiological Society.
Walker, R. D., Jr.
1973-01-01
Results of experiments on electron microscopy of fuel cell components, thermal decomposition of Teflon by thermogravimetry, surface area and pore size distribution measurements, water transport in fuel cells, and surface tension of KOH solutions are described.
International Nuclear Information System (INIS)
Moosavi, Majid; Khashei, Fatemeh; Sharifi, Ali; Mirzaei, Mojtaba
2017-01-01
Highlights: • Surface tension and density of three GDILs were measured at different temperatures. • Surface entropy and surface enthalpy indicate the surface ordering in these GDILs. • Parachors and critical temperatures of these systems were estimated. • Results of GDILs were compared with the results of corresponding traditional MILs. • Relations between surface tension, density and viscosity of GDILs were demonstrated. - Abstract: Surface tensions and densities of three imidazolium-based geminal dicationic ionic liquids (GDILs) with the bis(trifluoromethylsulfonyl)imide, [NTf 2 ] − , as a common anion, have been measured at ambient pressure at different temperatures in the range from 296.00 to 353.15 K. The surface thermodynamic functions such as surface entropy and surface enthalpy were derived from the temperature dependence of surface tension which indicated the surface ordering in these GDILs. As well as the parachor, the critical temperatures of these systems have been estimated using the Guggenheim and Eotvos correlations. In each case, the results of GDILs have been compared with the results of corresponding traditional monocationic ILs (MILs). Also, the relations between the surface tension and density and also surface tension and viscosity data have been demonstrated and discussed.
Núñez-Rojas, Edgar; Aguilar-Pineda, Jorge Alberto; Pérez de la Luz, Alexander; de Jesús González, Edith Nadir; Alejandre, José
2018-02-08
The transferable potential for a phase equilibria force field in its united-atom version, TraPPE_UA, is evaluated for 41 polar liquids that include alcohols, thiols, ethers, sulfides, aldehydes, ketones, and esters to determine its ability to reproduce experimental properties that were not included in the parametrization procedure. The intermolecular force field parameters for pure components were fit to reproduce experimental boiling temperature, vapor-liquid coexisting densities, and critical point (temperature, density, and pressure) using Monte Carlo simulations in different ensembles. The properties calculated in this work are liquid density, heat of vaporization, dielectric constant, surface tension, volumetric expansion coefficient, and isothermal compressibility. Molecular dynamics simulations were performed in the gas and liquid phases, and also at the liquid-vapor interface. We found that relative error between calculated and experimental data is 1.2% for density, 6% for heat of vaporization, and 6.2% for surface tension, in good agreement with the experimental data. The dielectric constant is systematically underestimated, and the relative error is 37%. Evaluating the performance of the force field to reproduce the volumetric expansion coefficient and isothermal compressibility requires more experimental data.
International Nuclear Information System (INIS)
Kawahara, Akimaro; Sadatomi, Michio; Higuchi, Tatsuya
2009-01-01
Two-phase diversion cross-flow between tight lattice subchannels has been investigated experimentally and analytically. For hydraulically non-equilibrium flows with the pressure difference between the subchannels, experiments were conducted using a vertical multiple-channel with two subchannels simplifying a triangle tight lattice rod bundle. To know the effects of the reduced surface tension on the diversion cross-flow, water and water with a surfactant were used as the test liquids. Data were obtained on the axial variations in the pressure difference between the subchannels, gas and liquid flow rates and void fraction in each subchannel for slug-churn and annular flows. In the analysis, flow redistribution processes due to the diversion cross-flow have been calculated by our subchannel analysis code based on a two-fluid model. From a comparison between the experiment and the code calculation, the code was found to be valid against the present data if the improved constitutive equations of wall and interfacial friction reported in our previous paper were incorporated to account for the reduced surface tension effects. (author)
Onaizi, Sagheer A
2018-03-01
The dynamic adsorption of the anionic biosurfactant, surfactin, at the air-water interface has been investigated in this work and compared to those of two synthetic surfactants: the anionic sodium dodecylbenzenesulfonate (SDBS) and the nonionic octaethylene glycol monotetradecyl ether (C 14 E 8 ). The results revealed that surfactin adsorption at the air-water interface is purely controlled by diffusion mechanism at the initial stage of the adsorption process (i.e., [Formula: see text]), but shifts towards a mixed diffusion-barrier mechanism when surface tension approaches equilibrium (i.e., [Formula: see text]) due to the development of an energy barrier for adsorption. Such energy barrier has been found to be a function of the surfactin bulk concentration (increases with increasing surfactin concentration) and it is estimated to be in the range of 1.8-9.5 kJ/mol. Interestingly, such a trend (pure diffusion-controlled mechanism at [Formula: see text] and mixed diffusion-barrier mechanism at [Formula: see text]) has been also observed for the nonionic C 14 E 8 surfactant. Unlike the pure diffusion-controlled mechanism of the initial surfactin adsorption, which was the case in the presence and the absence of the sodium ion (Na + ), SDBS showed a mixed diffusion-barrier controlled at both short and long time, with an energy barrier of 3.0-9.0 and 3.8-18.0 kJ/mol, respectively. Such finding highlights the nonionic-like adsorption mechanism of surfactin despite its negative charge.
Liu, Shanqiu; Eijkelenkamp, Rik; Duvigneau, Joost; Vancso, G Julius
2017-11-01
Core-shell nanoparticles consisting of silica as core and surface-grafted poly(dimethylsiloxane) (PDMS) as shell with different diameters were prepared and used as heterogeneous nucleation agents to obtain CO 2 -blown poly(methyl methacrylate) (PMMA) nanocomposite foams. PDMS was selected as the shell material as it possesses a low surface energy and high CO 2 -philicity. The successful synthesis of core-shell nanoparticles was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The cell size and cell density of the PMMA micro- and nanocellular materials were determined by scanning electron microscopy. The cell nucleation efficiency using core-shell nanoparticles was significantly enhanced when compared to that of unmodified silica. The highest nucleation efficiency observed had a value of ∼0.5 for nanoparticles with a core diameter of 80 nm. The particle size dependence of cell nucleation efficiency is discussed taking into account line tension effects. Complete engulfment by the polymer matrix of particles with a core diameter below 40 nm at the cell wall interface was observed corresponding to line tension values of approximately 0.42 nN. This line tension significantly increases the energy barrier of heterogeneous nucleation and thus reduces the nucleation efficiency. The increase of the CO 2 saturation pressure to 300 bar prior to batch foaming resulted in an increased line tension length. We observed a decrease of the heterogeneous nucleation efficiency for foaming after saturation with CO 2 at 300 bar, which we attribute to homogenous nucleation becoming more favorable at the expense of heterogeneous nucleation in this case. Overall, it is shown that the contribution of line tension to the free energy barrier of heterogeneous foam cell nucleation must be considered to understand foaming of viscoelastic materials. This finding emphasizes the need for new strategies including the use of
Wit, PJ; vanderMei, HC; Busscher, HJ
1997-01-01
By allowing an air-bubble to pass through a parallel plate flow chamber with negatively charged, colloidal polystyrene particles adhering to the bottom collector plate of the chamber, the detachment of adhering particles stimulated by surface tension forces induced by the passage of a liquid-air
Influence of Zinc on the Surface Tension, Density and Molar Volume of (Ag-Sneut +Zn Liquid Alloys
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Gąsior W.
2016-03-01
Full Text Available The dilatometric and maximum bubble pressure methods were applied for the measurements of the density and surface tension of liquid (Ag-Sneut +Zn lead-free solders. The experiments were carried out in the temperature range from 515 to 1223 K for the alloys of the zinc concentration equaling 0.01, 0.02, 0.04, 0.05, 0.1 and 0.2 of the mole fraction. It was found that the temperature dependence of both the density and the surface tension could be thought as linear, so they were interpreted by straight line equations. The experimental data of the molar volume of the investigated alloys were described by the polynomial dependent on the composition and temperature.
Zemlyanova, A. Y.
2013-03-08
A problem of an interface crack between two semi-planes made out of different materials under an action of an in-plane loading of general tensile-shear type is treated in a semi-analytical manner with the help of Dirichlet-to-Neumann mappings. The boundaries of the crack and the interface between semi-planes are subjected to a curvature-dependent surface tension. The resulting system of six singular integro-differential equations is reduced to the system of three Fredholm equations. It is shown that the introduction of the curvature-dependent surface tension eliminates both classical integrable power singularity of the order 1/2 and an oscillating singularity present in a classical linear elasticity solutions. The numerical results are obtained by solving the original system of singular integro-differential equations by approximating unknown functions with Taylor polynomials. © 2013 The Author.
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H. Hammami
2017-08-01
Full Text Available Introduction: During last century, population explosion has been pressing man to produce more supplies of food by consuming more energy in agroecosystems like applying chemical management strategies. herbicides have increasingly become a key component of weed management programs. In Iran, using herbicides led to increasing wheat yield about 20% and 22% in rainfed and irrigated farms respectively (20. Nonetheless, herbicides have also a negative impact on environment. A tool for reducing the herbicide usage which allows to decreasing their cost and side effects is the use of adjuvants. They increase the effectiveness of the post-emergence herbicides. Some adjuvants have toxic effects on living organisms such as Polyethoxylated tallowamine adjuvants that they are very toxic in fairy shrimp (Thamnocephalus platyurus (6. Vegetable oils are not phytotoxic and likely are degraded and metabolized quickly in the environment (8. Sethoxydim is an acetyl coenzyme A carboxylase (ACCase inhibitor that is considered to be a key enzyme in lipid biosynthesis. Similar to other foliar applied herbicides, it need to be associated with an adjuvant for more effective control. Vegetable oils can be developed characteristics of sethoxydim solution such as surface tension and spry drop diffusion. Therefore, the objective of this research is to determine the effect of vegetable oils on the surface tension, diffusion and efficiency of sethoxydim to control wild oat (Avena ludoviciana Durieu.. Materials and Metods: To evaluate the effect of vegetable oils on properties of sethoxydim solution, a series of experiments were separately conducted at Ferdowsi University of Mashhad and Khorasan Science and Technology Park in 2012. For evaluating the effect of vegetable oils on surface tension of distilled water and sethoxydim solution and the sethoxydim efficiency on wild oat control, three experiments were conducted as factorial based on completely randomized design. In other
Calculation of nuclear electromagnetic pulse propagation along the earth's surface
International Nuclear Information System (INIS)
Liang Rui; Zheng Yi; Song Lijun; Zhang Xueqin; Lip Peng
2010-01-01
It calculates the LF/VLF wave of NEMP propagation along the earth's surface. The earth-wave and the sky-wave are taken into account in the calculation. With the distance increase, the earth wave attenuates fast than the sky wave, and the time difference between the earth wave and the sky wave is reduced. (authors)
Improved density functional calculations for atoms, molecules and surfaces
International Nuclear Information System (INIS)
Fricke, B.; Anton, J.; Fritzsche, S.; Sarpe-Tudoran, C.
2005-01-01
The non-collinear and collinear descriptions within relativistic density functional theory is described. We present results of both non-collinear and collinear calculations for atoms, diatomic molecules, and some surface simulations. We find that the accuracy of our density functional calculations for the smaller systems is comparable to good quantum chemical calculations, and thus this method provides a sound basis for larger systems where no such comparison is possible. (author)
3D electric field calculation with surface charge method
International Nuclear Information System (INIS)
Yamada, S.
1992-01-01
This paper describes an outline and some examples of three dimensional electric field calculations with a computer code developed at NIRS. In the code, a surface charge method is adopted because of it's simplicity in the mesh establishing procedure. The charge density in a triangular mesh is assumed to distribute with a linear function of the position. The electric field distribution is calculated for a pair of drift tubes with the focusing fingers on the opposing surfaces. The field distribution in an acceleration gap is analyzed with a Fourier-Bessel series expansion method. The calculated results excellently reproduces the measured data with a magnetic model. (author)
Model calculation for energy loss in ion-surface collisions
International Nuclear Information System (INIS)
Miraglia, J.E.; Gravielle, M.S.
2003-01-01
The so-called local plasma approximation is generalized to deal with projectiles colliding with surfaces of amorphous solids and with a specific crystalline structure (plannar channeling). Energy loss of protons grazingly colliding with aluminum, SnTe alloy, and LiF surfaces is investigated. The calculations agree quite well with previous theoretical results and explain the experimental findings of energy loss for aluminum and SnTe alloy, but they fall short to explain the data for LiF surfaces
Variant of a volume-of-fluid method for surface tension-dominant two ...
Indian Academy of Sciences (India)
2013-12-27
Dec 27, 2013 ... face tension-dominant two-phase flows are explained. ... for one particular fluid inside a cell as its material volume divided by the total ... the reconstructed interface and the velocity field, and the final part ..... Welch S W J and Wilson J 2000 A volume of fluid based method for fluid flows with phase change. J.
Energy Technology Data Exchange (ETDEWEB)
Behroozi, F [Department of Physics, University of Northern Iowa, Cedar Falls, IA 50614 (United States); Behroozi, P S, E-mail: behroozi@uni.edu [Department of Physics, Stanford University, Stanford, CA 94305 (United States)
2011-09-15
A chain assumes the well-known shape known as a catenary when it hangs loosely from two points in a gravitational field. The correct solution of the catenary was one of the early triumphs of the newly invented calculus of variations at the end of the 17th century. Here we revisit the catenary and show that, for a chain hanging from a horizontal rod, three new and distinct configurations are possible if a soap film covers the area bounded by the chain and the rod. We first review the general problem and discuss the conditions under which the chain assumes a concave, triangular or convex configuration. The deciding factor is the strength of surface tension relative to the gravitational force per unit length of the chain. The conditions under which the chain assumes the shape of a perfect triangle are discussed in greater detail and analysed to obtain the tension along the chain. The triangular configuration is especially intriguing to undergraduates and may be used as a simple experiment to obtain the surface tension of the soap solution by measuring just one angle of the triangle.
International Nuclear Information System (INIS)
Behroozi, F; Behroozi, P S
2011-01-01
A chain assumes the well-known shape known as a catenary when it hangs loosely from two points in a gravitational field. The correct solution of the catenary was one of the early triumphs of the newly invented calculus of variations at the end of the 17th century. Here we revisit the catenary and show that, for a chain hanging from a horizontal rod, three new and distinct configurations are possible if a soap film covers the area bounded by the chain and the rod. We first review the general problem and discuss the conditions under which the chain assumes a concave, triangular or convex configuration. The deciding factor is the strength of surface tension relative to the gravitational force per unit length of the chain. The conditions under which the chain assumes the shape of a perfect triangle are discussed in greater detail and analysed to obtain the tension along the chain. The triangular configuration is especially intriguing to undergraduates and may be used as a simple experiment to obtain the surface tension of the soap solution by measuring just one angle of the triangle.
Proceedings of the colloquium: The response of liquids to dynamic tension
International Nuclear Information System (INIS)
Jones, A.V.
1978-01-01
The contributed papers are: - Tension pulses in a liquid column; - A generalized cavitationn model for liquids; - Transmission of a tension pulse through water; - Current status of the equation of state in Lagrangian codes; - The effects of the reflection of an underwater shock at a free surface; - The calculation of the propagation of tension and recompaction waves
Dynamical behavior of surface tension on rotating fluids in low and microgravity environments
Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.
1989-01-01
Consideration is given to the time-dependent evolutions of the free surface profile (bubble shapes) of a cylindrical container, partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry in low and microgravity environments. The dynamics of the bubble shapes are calculated for four cases: linear time-dependent functions of spin-up and spin-down in low and microgravity, linear time-dependent functions of increasing and decreasing gravity at high and low rotating cylinder speeds, time-dependent step functions of spin-up and spin-down in low gravity, and sinusoidal function oscillation of the gravity environment in high and low rotating cylinder speeds. It is shown that the computer algorithms developed by Hung et al. (1988) may be used to simulate the profile of time-dependent bubble shapes under variations of centrifugal, capillary, and gravity forces.
Surface tension of decane binary and ternary mixtures with eicosane, docosane, and tetracosane
DEFF Research Database (Denmark)
Queimada, Antonio; Cao, A.I.; Marrucho, I.M.
2005-01-01
-C24H50 and the ternary n-C10H22 + n-C20H42 + n-C24H50 were measured from 293.15 K (or above the solution melting temperature) up to 343.15 K. An average absolute deviation of 1.3% was obtained in comparison with pure component literature data. No mixture information for the reported systems was found......A tensiometer operating on the Wilhelmy plate method was employed to measure liquid-vapor interfacial tensions of three binary mixtures and one ternary mixture of decane with eicosane, docosane, and tetracosane. Tensions of binary mixtures n-C10H22 + n-C20H42, n-C10H22 + n-C22H46, and n-C10H22 + n...
Surface Tension of Supercooled Water Determined by Using a Counterpressure Capillary Rise Method
Czech Academy of Sciences Publication Activity Database
Vinš, Václav; Fransen, M. A. L. J.; Hykl, Jiří; Hrubý, Jan
2015-01-01
Roč. 119, č. 17 (2015), s. 5567-5575 ISSN 1520-6106 R&D Projects: GA MŠk LG13056; GA ČR GJ15-07129Y Institutional support: RVO:61388998 Keywords : capillary tube * interfacial tension * metastable liquid * supercooled liquid Subject RIV: BJ - Thermodynamics Impact factor: 3.187, year: 2015 http://pubs.acs.org/doi/abs/10.1021/acs.jpcb.5b00545
Energy Technology Data Exchange (ETDEWEB)
Boogar, Rahman Sadeghi; Gheshlaghi, Reza; Mahdavi, Mahmood Akhavan [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)
2013-01-15
A microchannel was fabricated with glass tubes to investigate the effect of viscosity, surface tension, and flow rate on the liquid-liquid two-phase flow regime. Water and gasoil were selected as aqueous and organic working fluids, respectively. The two fluids were injected into the microchannel and created either slug or parallel profile depending on the applied conditions. The range of Reynolds and capillary numbers was chosen in such a way that neither inertia nor interfacial tension forces were negligible. Xanthan gum was used to increase viscosity and Triton X-100 (TX-100) and Sodium Dodecyl Sulfate (SDS) were used to reduce the interfacial tension. The results demonstrated that higher value of viscosity and flow rate increased interfacial area, but slug flow regime remained unchanged. The two surfactants showed different effects on the flow regime and interfacial area. Addition of TX-100 did not change the slug flow but decreased the interfacial area. In contrast, addition of SDS increased interfacial area by decreasing the slug’s length in the low concentrations and by switching from slug to parallel regime at high concentrations.
DESIGN AND CALCULATION OF AERODROMECOAING WITH HEATED SURFACE LAYERS
Directory of Open Access Journals (Sweden)
Vadim G. Piskunov
2009-04-01
Full Text Available The developed constructions with heated by surface layers for aerodromes and auto roads when developed composition of electroconductive concrete reinforced with chemical electrical conductive fibres being used was researched. The experimentally obtained characteristics of ended conductive concrete reinforced with fibers were presented. Calculation by developed heated construction of shell was made.
Kabir, Kamaluddeen; Deeni, Yusuf Y; Hapca, Simona M; Moore, Luke; Spiers, Andrew J
2018-02-01
Bacterial biosurfactants have a wide range of biological functions and biotechnological applications. Previous analyses had suggested a limit to their reduction of aqueous liquid surface tensions (γMin), and here we confirm this in an analysis of 25 Pseudomonas spp. strains isolated from soil which produce high-strength surfactants that reduce surface tensions to 25.2 ± 0.1-26.5 ± 0.2 mN m-1 (the surface tension of sterile growth medium and pure water was 52.9 ± 0.4 mN m-1 and 72.1 ± 1.2 mN m-1, respectively). Comparisons of culture supernatants produced using different growth media and semi-purified samples indicate that the limit of 24.2-24.7 mN m-1 is not greatly influenced by culture conditions, pH or NaCl concentrations. We have used foam, emulsion and oil-displacement behavioural assays as a simple and cost-effective proxy for in-depth biochemical characterisation, and these suggest that there is significant structural diversity amongst these surfactants that may reflect different biological functions and offer new biotechnological opportunities. Finally, we obtained a draft genome for the strain producing the highest strength surfactant, and identified a cluster of non-ribosomal protein synthase genes that may produce a cyclic lipopeptide (CLP)-like surfactant. Further investigation of this group of related bacteria recovered from the same site will allow a better understanding of the significance of the great variety of surfactants produced by bacterial communities found in soil and elsewhere. © FEMS 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Calculation of the surface free energy of fcc copper nanoparticles
International Nuclear Information System (INIS)
Jia Ming; Lai Yanqing; Tian Zhongliang; Liu Yexiang
2009-01-01
Using molecular dynamics simulations with the modified analytic embedded-atom method we calculate the Gibbs free energy and surface free energy for fcc Cu bulk, and further obtain the Gibbs free energy of nanoparticles. Based on the Gibbs free energy of nanoparticles, we have investigated the heat capacity of copper nanoparticles. Calculation results indicate that the Gibbs free energy and the heat capacity of nanoparticles can be divided into two parts: bulk quantity and surface quantity. The molar heat capacity of the bulk sample is lower compared with the molar heat capacity of nanoparticles, and this difference increases with the decrease in the particle size. It is also observed that the size effect on the thermodynamic properties of Cu nanoparticles is not really significant until the particle is less than about 20 nm. It is the surface atoms that decide the size effect on the thermodynamic properties of nanoparticles
Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds
International Nuclear Information System (INIS)
Lee, H.A.; Chien, P.S.J.
1982-10-01
Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups
Vinš, Václav; Hošek, Jan; Hykl, Jiří; Hrubý, Jan
2015-05-01
New experimental apparatus for measurement of the surface tension of liquids under the metastable supercooled state has been designed and assembled in the study. The measuring technique is similar to the method employed by P.T. Hacker [NACA TN 2510] in 1951. A short liquid thread of the liquid sample was sucked inside a horizontal capillary tube partly placed in a temperature-controlled glass chamber. One end of the capillary tube was connected to a setup with inert gas which allowed for precise tuning of the gas overpressure in order of hundreds of Pa. The open end of the capillary tube was precisely grinded and polished before the measurement in order to assure planarity and perpendicularity of the outer surface. The liquid meniscus at the open end was illuminated by a laser beam and observed by a digital camera. Application of an increasing overpressure of the inert gas at the inner meniscus of the liquid thread caused variation of the outer meniscus such that it gradually changed from concave to flat and subsequently convex shape. The surface tension at the temperature of the inner meniscus could be evaluated from the overpressure corresponding to exactly planar outer meniscus. Detailed description of the new setup together with results of the preliminary tests is provided in the study.
International Nuclear Information System (INIS)
Kim, Jae Kwan; Cho, Hye Sung; Jung, Ho-Sup; Suh, Kahp-Yang; Lim, Kipil; Kim, Ki-Bum; Choi, Dae-Geun; Jeong, Jun-Ho
2012-01-01
We report on nanoimprinting of polymer thin films at 30 nm scale resolution using two types of ultraviolet (UV)-curable, flexible polymer molds: perfluoropolyether (PFPE) and polyurethane acrylate (PUA). It was found that the quality of nanopatterning at the 30 nm scale is largely determined by the combined effects of surface tension and the coefficient of thermal expansion of the polymer mold. In particular, the polar component of surface tension may play a critical role in clean release of the mold, as evidenced by much reduced delamination or broken structures for the less polarized PFPE mold when patterning a relatively hydrophilic PMMA film. In contrast, such problems were not notably observed with a relatively hydrophobic PS film for both polymer molds. In addition, the demolding characteristic was also influenced by the coefficient of thermal expansion so that no delamination or uniformity problems were observed when patterning a UV-curable polymer film at room temperature. These results suggest that a proper polymeric mold material needs to be chosen for patterning polymer films under different surface properties and processing conditions, providing insights into how a clean demolding characteristic can be obtained at 30 nm scale nanopatterning. (paper)
A dielectric matrix calculation of the surface-plasmon energy for the silicon (100) surface
International Nuclear Information System (INIS)
Forsyth, A.J.; Smith, A.E.; Josefsson, T.W.
1996-01-01
Full text: As an extension of previous work, we present preliminary calculations for the dielectric properties of the silicon (100) surface. In particular, the |q|→0 and |q|=2π/a(1,0,0) surface loss function, and corresponding surface plasmon energies have been calculated within a simple model for the silicon surface. The results have been obtained from the Adler and Wiser dielectric matrix (DM). The bandstructure used for the calculation was based on the highly successful empirical pseudopotential method of Cohen and Chelikovsky. We have used a 59 plane wave basis for the bandstructure, and have chosen a DM size of 59 x 59. Results are compared and contrasted with volume plasmon calculations, free electron calculations and experiment
Directory of Open Access Journals (Sweden)
Griese Matthias
2007-10-01
Full Text Available Abstract Background Deleted in Malignant Brain Tumors 1 (DMBT1 is a secreted scavenger receptor cysteine-rich protein that binds various bacteria and is thought to participate in innate pulmonary host defense. We hypothesized that pulmonary DMBT1 could contribute to respiratory distress syndrome in neonates by modulating surfactant function. Methods DMBT1 expression was studied by immunohistochemistry and mRNA in situ hybridization in post-mortem lungs of preterm and full-term neonates with pulmonary hyaline membranes. The effect of human recombinant DMBT1 on the function of bovine and porcine surfactant was measured by a capillary surfactometer. DMBT1-levels in tracheal aspirates of ventilated preterm and term infants were determined by ELISA. Results Pulmonary DMBT1 was localized in hyaline membranes during respiratory distress syndrome. In vitro addition of human recombinant DMBT1 to the surfactants increased surface tension in a dose-dependent manner. The DMBT1-mediated effect was reverted by the addition of calcium depending on the surfactant preparation. Conclusion Our data showed pulmonary DMBT1 expression in hyaline membranes during respiratory distress syndrome and demonstrated that DMBT1 increases lung surface tension in vitro. This raises the possibility that DMBT1 could antagonize surfactant supplementation in respiratory distress syndrome and could represent a candidate target molecule for therapeutic intervention in neonatal lung disease.
International Nuclear Information System (INIS)
Ghatee, Mohammad Hadi; Bahrami, Maryam; Khanjari, Neda
2013-01-01
Highlights: • Characterization of high purity synthesized alkyl quaternary ammonium ionic liquids. • Measurement of temperature dependent surface tension, density, viscosity and critical point. • Systematic increase of surface energy and surface entropy having plateau at high chain length. • Accurate application of VFT and fluidity equations to temperature dependent viscosities. • Particular variation of fluidity exponent with a plateau at high alkyl chain length. -- Abstract: In this work five quaternary ammonium-based ionic liquids with bis(trifluoromethylsulfonyl)imide anion were synthesized and their density, viscosity and surface tensions were measured in the temperature range (298 to 373) K. Surface tensions were measured by capillary rise method using a homemade capillary apparatus, in which the liquid/vapor can be brought into equilibrium practically. Measurements of viscosities and surface tensions were performed under water–vapor free atmosphere. The surface tension of quaternary ammonium-based ILs decreases as the alkyl chain length increases. Also surface energy and surface entropy are found as increasing functions of alkyl chain length with a plateau at high lengths in the surface. The viscosities measured by capillary viscometer fit in VFT equation, indication of non-Arrhenius ionic liquids. Viscosities are also fitted quite accurately in the relation we have developed recently as the fluidity equation with the characteristics exponent ϕ. Values of ϕ for ionic liquids are close to one another and tend to the limiting value, almost 0.328, asymptotically as the alkyl chain length increases. The critical temperatures predicted via the temperature dependent surface tensions decrease with increasing alkyl chain length of the cation. The trend of predicted critical temperature of these ionic liquids conforms to those of imidazolium-based ILs
Denisova, Irina Vlad.
2015-03-01
The paper deals with the motion of two immiscible viscous fluids in a container, one of the fluids being compressible while another one being incompressible. The interface between the fluids is an unknown closed surface where surface tension is neglected. We assume the compressible fluid to be barotropic, the pressure being given by an arbitrary smooth increasing function. This problem is considered in anisotropic Sobolev-Slobodetskiǐ spaces. We show that the L 2-norms of the velocity and deviation of compressible fluid density from the mean value decay exponentially with respect to time. The proof is based on a local existence theorem (Denisova, Interfaces Free Bound 2:283-312, 2000) and on the idea of constructing a function of generalized energy, proposed by Padula (J Math Fluid Mech 1:62-77, 1999). In addition, we eliminate the restrictions for the viscosities which appeared in Denisova (Interfaces Free Bound 2:283-312, 2000).
Alekseenko, Elena; Kuznetsov, Konstantin; Roux, Bernard
2016-04-01
Wind stress on the free surface is the main driving force behind the circulation of the upper part of the ocean, which in hydrodynamic models are usually defined in terms of the coefficient of surface tension (Zhang et al., 2009, Davies et al., 2003). Moreover, wave motion impacts local currents and changes sea level, impacts the transport and the stratification of the entire water column. Influence of surface waves at the bottom currents is particularly pronounced in the shallow coastal systems. However, existing methods of parameterization of the surface tension have significant limits, especially in strong wind waves (Young et al., 2001, Jones et al., 2004) due to the difficulties of measuring the characteristics of surface waves in stormy conditions. Thus, the formula for calculating the coefficient of surface tension in our day is the actual problem in modeling fluid dynamics, particularly in the context of strong surface waves. In the hydrodynamic models usually a coefficient of surface tension is calculated once at the beginning of computation as a constant that depends on the averaged wind waves characteristic. Usually cases of strongly nonlinear wind waves are not taken into account, what significantly reduces the accuracy of the calculation of the flow structures and further calculation of the other processes in water basins, such as the spread of suspended matter and pollutants. Thus, wave motion influencing the pressure on the free surface and at the bottom must be considered in hydrodynamic models particularly in shallow coastal systems. A method of reconstruction of a free-surface drag coefficient based on the measured in-situ bottom pressure fluctuations is developed and applied in a three-dimensional hydrodynamic model MARS3D, developed by the French laboratory of IFREMER (IFREMER - French Research Institute for Marine Dynamics). MARS3D solves the Navier-Stokes equations for incompressible fluid in the Boussinesq approximation and with the
Nguyen, Phuc Nghia; Trinh Dang, Thuan Thao; Waton, Gilles; Vandamme, Thierry; Krafft, Marie Pierre
2011-10-04
The adsorption dynamics of a series of phospholipids (PLs) at the interface between an aqueous solution or dispersion of the PL and a gas phase containing the nonpolar, nonamphiphilic linear perfluorocarbon perfluorohexane (PFH) was studied by bubble profile analysis tensiometry. The PLs investigated were dioctanoylphosphatidylcholine (DiC(8)-PC), dilaurylphosphatidylcholine, dimyristoylphosphatidylcholine, and dipalmitoylphosphatidylcholine. The gas phase consisted of air or air saturated with PFH. The perfluorocarbon gas was found to have an unexpected, strong effect on both the adsorption rate and the equilibrium interfacial tension (γ(eq)) of the PLs. First, for all of the PLs, and at all concentrations investigated, the γ(eq) values were significantly lower (by up to 10 mN m(-1)) when PFH was present in the gas phase. The efficacy of PFH in decreasing γ(eq) depends on the ability of PLs to form micelles or vesicles in water. For vesicles, it also depends on the gel or fluid state of the membranes. Second, the adsorption rates of all the PLs at the interface (as assessed by the time required for the initial interfacial tension to be reduced by 30%) are significantly accelerated (by up to fivefold) by the presence of PFH for the lower PL concentrations. Both the surface-tension reducing effect and the adsorption rate increasing effect establish that PFH has a strong interaction with the PL monolayer and acts as a cosurfactant at the interface, despite the absence of any amphiphilic character. Fitting the adsorption profiles of DiC(8)-PC at the PFH-saturated air/aqueous solution interface with the modified Frumkin model indicated that the PFH molecule lay horizontally at the interface. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Calculation of surface acoustic waves in a multilayered piezoelectric structure
International Nuclear Information System (INIS)
Zhang Zuwei; Wen Zhiyu; Hu Jing
2013-01-01
The propagation properties of the surface acoustic waves (SAWs) in a ZnO—SiO 2 —Si multilayered piezoelectric structure are calculated by using the recursive asymptotic method. The phase velocities and the electromechanical coupling coefficients for the Rayleigh wave and the Love wave in the different ZnO—SiO 2 —Si structures are calculated and analyzed. The Love mode wave is found to be predominantly generated since the c-axis of the ZnO film is generally perpendicular to the substrate. In order to prove the calculated results, a Love mode SAW device based on the ZnO—SiO 2 —Si multilayered structure is fabricated by micromachining, and its frequency responses are detected. The experimental results are found to be mainly consistent with the calculated ones, except for the slightly larger velocities induced by the residual stresses produced in the fabrication process of the films. The deviation of the experimental results from the calculated ones is reduced by thermal annealing. (semiconductor physics)
Direct Observation of Domain-Wall Surface Tension by Deflating or Inflating a Magnetic Bubble
Zhang, Xueying; Vernier, Nicolas; Zhao, Weisheng; Yu, Haiming; Vila, Laurent; Zhang, Yue; Ravelosona, Dafiné
2018-02-01
The surface energy of a magnetic domain wall (DW) strongly affects its static and dynamic behaviors. However, this effect is seldom directly observed, and some of the related phenomena are not well understood. Moreover, a reliable method to quantify the DW surface energy is still absent. Here, we report a series of experiments in which the DW surface energy becomes a dominant parameter. We observe that a semicircular magnetic domain bubble can spontaneously collapse under the Laplace pressure induced by DW surface energy. We further demonstrate that the surface energy can lead to a geometrically induced pinning when the DW propagates in a Hall cross or from a nanowire into a nucleation pad. Based on these observations, we develop two methods to quantify the DW surface energy, which can be very helpful in the estimation of intrinsic parameters such as Dzyaloshinskii-Moriya interactions or exchange stiffness in magnetic ultrathin films.
Longford, Francis G. J.; Essex, Jonathan W.; Skylaris, Chris-Kriton; Frey, Jeremy G.
2018-06-01
We present an unexpected finite size effect affecting interfacial molecular simulations that is proportional to the width-to-surface-area ratio of the bulk phase Ll/A. This finite size effect has a significant impact on the variance of surface tension values calculated using the virial summation method. A theoretical derivation of the origin of the effect is proposed, giving a new insight into the importance of optimising system dimensions in interfacial simulations. We demonstrate the consequences of this finite size effect via a new way to estimate the surface energetic and entropic properties of simulated air-liquid interfaces. Our method is based on macroscopic thermodynamic theory and involves comparing the internal energies of systems with varying dimensions. We present the testing of these methods using simulations of the TIP4P/2005 water forcefield and a Lennard-Jones fluid model of argon. Finally, we provide suggestions of additional situations, in which this finite size effect is expected to be significant, as well as possible ways to avoid its impact.
... tight band around your head. A tension headache (tension-type headache) is the most common type of headache, and ... Headache after a head injury, especially if the headache gets worse ... tension or stress. But research suggests muscle contraction isn't the ...
Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb
Wang, Yazhen; Regel, Liya L.; Wilcox, William R.
2000-01-01
We extended the previous analysis of detached solidification of InSb based on the moving meniscus model. We found that for steady detached solidification to occur in a sealed ampoule in zero gravity, it is necessary for the growth angle to exceed a critical value, the contact angle for the melt on the ampoule wall to exceed a critical value, and the melt-gas surface tension to be below a critical value. These critical values would depend on the material properties and the growth parameters. For the conditions examined here, the sum of the growth angle and the contact angle must exceed approximately 130, which is significantly less than required if both ends of the ampoule are open.
Manjunatha, N.; Sumithra, R.
2018-04-01
The problem of surface tension driven two component magnetoconvection is investigated in a Porous-Fluid system, consisting of anincompressible two component electrically conducting fluid saturatedporous layer above which lies a layer of the same fluid in the presence of a uniform vertical magnetic field. The lower boundary of the porous layeris rigid and the upper boundary of the fluid layer is free with surfacetension effects depending on both temperature and concentration, boththese boundaries are insulating to heat and mass. At the interface thevelocity, shear and normal stress, heat and heat flux, mass and mass fluxare assumed to be continuous suitable for Darcy-Brinkman model. Theeigenvalue problem is solved in linear, parabolic and inverted parabolictemperature profiles and the corresponding Thermal Marangoni Numberis obtained for different important physical parameters.
Energy Technology Data Exchange (ETDEWEB)
Dreyer, Wolfgang [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany); Kimmerle, Sven-Joachim [Humboldt-Univ. Berlin (Germany). Dept. of Mathematics
2009-07-01
Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first class of models treats the diffusion-controlled regime of interface motion, while the second class is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. We consider homogenised models, where different length scales of the experimental situation have been exploited in order to simplify the equations. These homogenised models generalise the well-known Lifshitz-Slyozov-Wagner model for Ostwald ripening. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation. (orig.)
Sasaki, Satoshi; Iida, Yoshinori
2009-06-01
The effect of kinematic viscosity and surface tension of the solution was investigated by adding catalase, glucose oxidase, or glucose on the bubble movement in a catalase-hydrogen peroxide system. The kinematic viscosity was measured using a Cannon-Fenske kinematic viscometer. The surface tension of the solution was measured by the Wilhelmy method using a self-made apparatus. The effects of the hole diameter/cell wall thickness, catalase concentration, glucose concentration, and glucose oxidase concentration on the kinematic viscosity, surface tension, and bubble take-off period were investigated. With our system, the effects of the changes in the solution materiality on the bubble take-off period were proven to be very small in comparison to the change in the oxygen-producing rate.
International Nuclear Information System (INIS)
Moh, Jeong Hah; Cho, Y. I.
2014-01-01
This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady
The effect of surface tension on the contraction coefficient of a jet
International Nuclear Information System (INIS)
Gasmi, A; Mekias, H
2003-01-01
Two-dimensional free surface potential flow issued from an opening of a container is considered. The flow is assumed to be inviscid and incompressible. The mathematical problem, which is characterized by the nonlinear boundary condition on the free surface of an unknown equation, is solved via a series truncation. We computed solutions for all Weber numbers. Our problem is an extension of the work done by Ackerberg and Liu (1987 Phys. Fluids 30 289-96), the results confirm and extend their results
International Nuclear Information System (INIS)
Siewert, E; Schein, J; Forster, G
2013-01-01
The metal transfer is a fundamental process in gas metal arc welding, which substantially determines the shape of the weld seam and strongly influences arc formation and stability. In this investigation the material transfer from the wire electrode (anode) to the workpiece (cathode) is analysed experimentally with high accuracy using various innovative diagnostic techniques for a pulsed gas metal arc welding (PGMAW) process. A high-speed two-colour pyrometer, a calorimeter, thermocouples, a stereo optical setup and a droplet oscillation technique are used to analyse a precisely defined PGMAW process. Thus, results obtained are verified by different measurement techniques and enable a comprehensive description of the material transfer procedure. The surface temperature of both electrodes as well as the droplet temperature, enthalpy and surface tension were determined. Furthermore, the geometry of the arc, wire, droplets and weld pool were extracted in three dimensions in order to describe the interaction between the material transfer and the formation of the weld seam. The experiments are performed using argon as shielding gas and pure iron as filler and base material to reduce complex chemical processes. It turned out that the wire feed rate has the biggest influence on droplet temperature and detachment. A correlation between weld pool formation and weld pool surface temperature gradient was observed, which is mainly a function of welding speed and wire feed rate. The experimental results obtained provide a detailed data pool for use in modelling. (paper)
Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, Fred W.
1989-01-01
Time-dependent evolutions of the profile of the free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low- and microgravity environments, (2) linear functions of increasing and decreasing gravity environments at high- and low-rotating cylinder speeds, and (3) step functions of spin-up and spin-down in a low-gravity environment.
Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.
1988-01-01
Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) step functions of spin-up and spin-down in a low gravity environment, and (3) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds.
J-integral and limit load analysis of semi-elliptical surface cracks in plates under tension
International Nuclear Information System (INIS)
Lei, Y.
2004-01-01
Systematic detailed non-linear finite element (FE) analyses are described for semi-elliptical surface cracks in plates under tension. Limit load solutions are obtained from the FE J results through the reference stress method. The results show that the type of the relationship between J and the limit load mainly depends on the ratio a/t, where a is the crack depth and t the thickness of the plate. For a/t≤0.5, J for any position along the crack front can be predicted by the reference stress method using a single limit load value, except for the points very close to the plate surface. For a/t=0.8, J can only be approximately estimated because no single limit load value can be found to satisfy all the FE J solutions along the crack front. However, for all cases considered, the maximum J value along the crack front can still be predicted by using the global limit load in the reference stress method. The limit load data obtained from this work can be well predicted by a global limit load equation developed by Goodall and Webster
Sarma, Rajkumar; Mondal, Pranab Kumar
2018-04-01
We investigate Marangoni instability in a thin liquid film resting on a substrate of low thermal conductivity and separated from the surrounding gas phase by a deformable free surface. Considering a nonmonotonic variation of surface tension with temperature, here we analytically derive the neutral stability curve for the monotonic and oscillatory modes of instability (for both the long-wave and short-wave perturbations) under the framework of linear stability analysis. For the long-wave instability, we derive a set of amplitude equations using the scaling k ˜(Bi) 1 /2 , where k is the wave number and Bi is the Biot number. Through this investigation, we demonstrate that for such a fluid layer upon heating from below, both monotonic and oscillatory instability can appear for a certain range of the dimensionless parameters, viz., Biot number (Bi ) , Galileo number (Ga ) , and inverse capillary number (Σ ) . Moreover, we unveil, through this study, the influential role of the above-mentioned parameters on the stability of the system and identify the critical values of these parameters above which instability initiates in the liquid layer.
Calculation of Operations Efficiency Factors for Mars Surface Missions
Layback, Sharon L.
2014-01-01
enough time to capture variations in relay asset interactions, Earth/Mars time phasing, and seasonal variations in holidays). This model is used to estimate the ops efficiency factor for each operations configuration. The second model in a separate Excel spreadsheet is a scenario model, which uses the sol types to rack up the total number of "scenario sols" for that scenario (in other words, the ideal number of sols it would take to perform the scenario objectives). Then, the number of sols requiring ground in the loop is calculated based on the soil types contained in the given scenario. Next, the scenario contains a description of what sequence of operations configurations is used, for how many days each, and this is used with the corresponding ops efficiency factors for each configuration to calculate the "ops duration" corresponding to that scenario. Finally, a margin is applied to determine the minimum surface lifetime required for that scenario. Typically, this level of analysis has not been performed until much later in the mission, and has not been able to influence mission design. Further, the notion of moving to sustainable operations during Prime Mission - and the effect that that move would have on surface mission productivity and mission objective choices - has not been encountered until the most recent rover missions (MSL and Mars 2018).
Czech Academy of Sciences Publication Activity Database
Klomfar, Jaroslav; Součková, Monika; Pátek, Jaroslav
2015-01-01
Roč. 385, January (2015), s. 62-71 ISSN 0378-3812 R&D Projects: GA ČR GA13-00145S Institutional support: RVO:61388998 Keywords : ionic liquid * density * surface tension * odd-even effect Subject RIV: BJ - Thermodynamics Impact factor: 1.846, year: 2015
Surface tension-induced PDMS micro-pillars with controllable tips and tilt angles
Li, Huawei; Fan, Yiqiang; Conchouso Gonzalez, David; Foulds, Ian G.
2013-01-01
This paper reports a novel method to fabricate three-dimensional (3D) polydimethylsiloxane (PDMS) micro-pillars using a CO2 laser-machined poly(methyl methacrylate) (PMMA) mold with through-holes. This method eliminates the requirements of expensive and complicated facilities to fabricate a 3D mold. The micro-pillars were formed by the capillary force that draws PDMS into the through-holes of the PMMA mold. The tilt angles of the micro-pillars depend on the tilt angles of the through-holes in the mold, and the concave and convex micro-lens tip shapes of the PDMS micro-pillars can be modified by changing the surface wettability of the PMMA through-holes.
Surface tension-induced PDMS micro-pillars with controllable tips and tilt angles
Li, Huawei
2013-12-21
This paper reports a novel method to fabricate three-dimensional (3D) polydimethylsiloxane (PDMS) micro-pillars using a CO2 laser-machined poly(methyl methacrylate) (PMMA) mold with through-holes. This method eliminates the requirements of expensive and complicated facilities to fabricate a 3D mold. The micro-pillars were formed by the capillary force that draws PDMS into the through-holes of the PMMA mold. The tilt angles of the micro-pillars depend on the tilt angles of the through-holes in the mold, and the concave and convex micro-lens tip shapes of the PDMS micro-pillars can be modified by changing the surface wettability of the PMMA through-holes.
International Nuclear Information System (INIS)
Royl, P.
1984-02-01
The transient cavity pressurization in an ULOF driven TOP excursion has been analyzed for the SPX-1 reactor with an equation of state that allows to simulate the contribution of small froth gas bubbles to the pressure build-up in a fuel pin with inclusion of restraints from surface tension. Calculations were performed for various bubble parameters. Estimates are made for effective gas availabilities at fuel melting which can be used in a cavity model with an ideal gas equation to arrive at similar pressure transients
Viscosity and surface tension effects during multiphase flow in propped fractures
Dzikowski, Michał; Dąbrowski, Marcin
2017-04-01
Geological sequestration of CO2 was proposed as an important mechanism to reduce its emission into atmosphere. CO2 exhibits a higher affinity to organic matter than methane molecules and, potentially, it could be pumped and stored in shale reservoirs while enhancing late stage shale gas production. A successful analysis of CO2 sequestration in low matrix permeability rocks such as shales requires a thorough understanding of multiphase flow in stimulated rock fractures, which provide most significant pathways for fluids in such systems. Multiphase fracture flows are also of great relevance to brine, oil and gas migration in petroleum systems, water and stream circulation in geothermal reservoirs, and chemical transport of non-aqueous phase liquids in shallow hydrogeological systems, particularly in partially saturated zones. There are various physical models that describe phenomena taking place during multiphase flow through porous media. One of key aspects that need to be considered are pore-scale effects related to capillarity. Unfortunately, detailed models that describe motion and evolution of phase or component boundary require direct numerical simulations and spatial resolutions that are hard to reach when considering industrial relevant systems. Main aim of the presented work was the development of reduced 2.5D models based on Brinkman approximation of thin domain flow that would be able to capture local scale phenomena without expensive 3D simulations. Presented approach was designed specifically to tackle incompressible and immiscible systems and is based on Continuous Surface Force approach presented by Brackbill et al., implemented using Lattice Boltzmann Method. Presented approach where firstly validated against standard test cases with known classical solution and known experimental data. In the second part, we present and discuss two component, immiscible permeability data for rough and propped fracture obtained with our code for a rage of proppants
Investigation of wettability to evaluate the morphology and surface tension wood filler
Directory of Open Access Journals (Sweden)
S. T. Antipov
2017-01-01
Full Text Available In this paper, we propose a new scheme of a highly efficient line for preparing safflower grains for processing consisting of an air-sieve separator, a magnetic separator, an ovary, a puppet, and a stone picker. The new after vortex separator is a vibroseparator for separating the products close in physical properties, grinding Machine with a duo-aspirator, a photoseparator and a device for moisture-thermal treatment. Advantages of the proposed line for preparation of safflower grain for processing are that an additional plant in front of the photocarerator of the grinding machine and duo-espirator allows the crest to separate and remove or refine the shell of the seed in the form of a shell layer for more efficient subsequent spectral point analysis, which determines the grain composition for the purpose of sorting it On the basis of chemical composition and color in the photo separator, and sequential placement after the stone separator of a vibro separator for separation of products close in physical properties, a grinding machine with a duo-aspirator, a photoseparator and a device for moisture-thermal treatment, provides an intensification of the technological process of efficient separation of safflower from impurities and its preparation for further processing and Due to the rational layout of equipment.A highly efficient photocell separator is also provided, the advantages of which are that the installation of a storage and vibrating feeder in relation to the slanting tray from the back side and the execution of a smooth curved transition to the vibrating feeder in the upper part of the pitcher allows improving the separation of grain products by reducing the amplitude of grain oscillations, Caused by a rebound from the surface of the tray during the loading of the sorted material from the vibrating feeder.
Calculation of Operations Efficiency Factors for Mars Surface Missions
Laubach, Sharon
2014-01-01
The duration of a mission--and subsequently, the minimum spacecraft lifetime--is a key component in designing the capabilities of a spacecraft during mission formulation. However, determining the duration is not simply a function of how long it will take the spacecraft to execute the activities needed to achieve mission objectives. Instead, the effects of the interaction between the spacecraft and ground operators must also be taken into account. This paper describes a method, using "operations efficiency factors", to account for these effects for Mars surface missions. Typically, this level of analysis has not been performed until much later in the mission development cycle, and has not been able to influence mission or spacecraft design. Further, the notion of moving to sustainable operations during Prime Mission--and the effect that change would have on operations productivity and mission objective choices--has not been encountered until the most recent rover missions (MSL, the (now-cancelled) joint NASA-ESA 2018 Mars rover, and the proposed rover for Mars 2020). Since MSL had a single control center and sun-synchronous relay assets (like MER), estimates of productivity derived from MER prime and extended missions were used. However, Mars 2018's anticipated complexity (there would have been control centers in California and Italy, and a non-sun-synchronous relay asset) required the development of an explicit model of operations efficiency that could handle these complexities. In the case of the proposed Mars 2018 mission, the model was employed to assess the mission return of competing operations concepts, and as an input to component lifetime requirements. In this paper we provide examples of how to calculate the operations efficiency factor for a given operational configuration, and how to apply the factors to surface mission scenarios. This model can be applied to future missions to enable early effective trades between operations design, science mission
Strotman, Lindsay N; Lin, Guangyun; Berry, Scott M; Johnson, Eric A; Beebe, David J
2012-09-07
Extraction and purification of DNA is a prerequisite to detection and analytical techniques. While DNA sample preparation methods have improved over the last few decades, current methods are still time consuming and labor intensive. Here we demonstrate a technology termed IFAST (Immiscible Filtration Assisted by Surface Tension), that relies on immiscible phase filtration to reduce the time and effort required to purify DNA. IFAST replaces the multiple wash and centrifugation steps required by traditional DNA sample preparation methods with a single step. To operate, DNA from lysed cells is bound to paramagnetic particles (PMPs) and drawn through an immiscible fluid phase barrier (i.e. oil) by an external handheld magnet. Purified DNA is then eluted from the PMPs. Here, detection of Clostridium botulinum type A (BoNT/A) in food matrices (milk, orange juice), a bioterrorism concern, was used as a model system to establish IFAST's utility in detection assays. Data validated that the DNA purified by IFAST was functional as a qPCR template to amplify the bont/A gene. The sensitivity limit of IFAST was comparable to the commercially available Invitrogen ChargeSwitch® method. Notably, pathogen detection via IFAST required only 8.5 μL of sample and was accomplished in five-fold less time. The simplicity, rapidity and portability of IFAST offer significant advantages when compared to existing DNA sample preparation methods.
Surface passivation for tight-binding calculations of covalent solids
International Nuclear Information System (INIS)
Bernstein, N
2007-01-01
Simulation of a cluster representing a finite portion of a larger covalently bonded system requires the passivation of the cluster surface. We compute the effects of an explicit hybrid orbital passivation (EHOP) on the atomic structure in a model bulk, three-dimensional, narrow gap semiconductor, which is very different from the wide gap, quasi-one-dimensional organic molecules where most passivation schemes have been studied in detail. The EHOP approach is directly applicable to minimal atomic orbital basis methods such as tight-binding. Each broken bond is passivated by a hybrid created from an explicitly expressed linear combination of basis orbitals, chosen to represent the contribution of the missing neighbour, e.g. a sp 3 hybrid for a single bond. The method is tested by computing the forces on atoms near a point defect as a function of cluster geometry. We show that, compared to alternatives such as pseudo-hydrogen passivation, the force on an atom converges to the correct bulk limit more quickly as a function of cluster radius, and that the force is more stable with respect to perturbations in the position of the cluster centre. The EHOP method also obviates the need for parameterizing the interactions between the system atoms and the passivating atoms. The method is useful for cluster calculations of non-periodic defects in large systems and for hybrid schemes that simulate large systems by treating finite regions with a quantum-mechanical model, coupled to an interatomic potential description of the rest of the system
Directory of Open Access Journals (Sweden)
D. Topping
2010-11-01
Full Text Available Calculating the equilibrium composition of atmospheric aerosol particles, using all variations of Köhler theory, has largely assumed that the total solute concentrations define both the water activity and surface tension. Recently however, bulk to surface phase partitioning has been postulated as a process which significantly alters the predicted point of activation. In this paper, an analytical solution to calculate the removal of material from a bulk to a surface layer in aerosol particles has been derived using a well established and validated surface tension framework. The applicability to an unlimited number of components is possible via reliance on data from each binary system. Whilst assumptions regarding behaviour at the surface layer have been made to facilitate derivation, it is proposed that the framework presented can capture the overall impact of bulk-surface partitioning. Demonstrations of the equations for two and five component mixtures are given while comparisons are made with more detailed frameworks capable at modelling ternary systems at higher levels of complexity. Predictions made by the model across a range of surface active properties should be tested against measurements. Indeed, reccomendations are given for experimental validation and to assess sensitivities to accuracy and required level of complexity within large scale frameworks. Importantly, the computational efficiency of using the solution presented in this paper is roughly a factor of 20 less than a similar iterative approach, a comparison with highly coupled approaches not available beyond a 3 component system.
Energy Technology Data Exchange (ETDEWEB)
Maleewong, Montri; Asavanant, Jack [Chulalongkorn University, Department of Mathematics and Advanced Virtual Intelligence Computing Center, Bangkok (Thailand); Grimshaw, Roger [Loughborough University, Department of Mathematical Sciences, Loughborough (United Kingdom)
2005-08-01
We consider steady free surface two-dimensional flow due to a localized applied pressure distribution under the effects of both gravity and surface tension in water of constant depth, and in the presence of a uniform stream. The fluid is assumed to be inviscid and incompressible, and the flow is irrotational. The behavior of the forced nonlinear waves is characterized by three parameters: the Froude number, F, the Bond number, {tau}>1/3, and the magnitude and sign of the pressure forcing parameter {epsilon}. The fully nonlinear wave problem is solved numerically by using a boundary integral method. For small amplitude waves and F<1 but not too close to 1, linear theory gives a good prediction for the numerical solution of the nonlinear problem in the case of bifurcation from the uniform flow. As F approaches 1, the nonlinear terms need to be taken account of. In this case the forced Korteweg-de Vries equation is found to be an appropriate model to describe bifurcations from an unforced solitary wave. In general, it is found that for given values of F<1 and {tau}>1/3, there exists both elevation and depression waves. In some cases, a limiting configuration in the form of a trapped bubble occurs in the depression wave solutions. (orig.)
Calculations of oxide formation on low-index Cu surfaces
Energy Technology Data Exchange (ETDEWEB)
Lian, Xin; Liu, Renlong, E-mail: lrl@cqu.edu.cn, E-mail: henkelman@utexas.edu [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Xiao, Penghao; Yang, Sheng-Che; Henkelman, Graeme, E-mail: lrl@cqu.edu.cn, E-mail: henkelman@utexas.edu [Department of Chemistry and the Institute for Computational and Engineering Sciences, University of Texas at Austin, Austin, Texas 78712-0165 (United States)
2016-07-28
Density-functional theory is used to evaluate the mechanism of copper surface oxidation. Reaction pathways of O{sub 2} dissociation on the surface and oxidation of the sub-surface are found on the Cu(100), Cu(110), and Cu(111) facets. At low oxygen coverage, all three surfaces dissociate O{sub 2} spontaneously. As oxygen accumulates on the surfaces, O{sub 2} dissociation becomes more difficult. A bottleneck to further oxidation occurs when the surfaces are saturated with oxygen. The barriers for O{sub 2} dissociation on the O-saturated Cu(100)-c(2×2)-0.5 monolayer (ML) and Cu(100) missing-row structures are 0.97 eV and 0.75 eV, respectively; significantly lower than those have been reported previously. Oxidation of Cu(110)-c(6×2), the most stable (110) surface oxide, has a barrier of 0.72 eV. As the reconstructions grow from step edges, clean Cu(110) surfaces can dissociatively adsorb oxygen until the surface Cu atoms are saturated. After slight rearrangements, these surface areas form a “1 ML” oxide structure which has not been reported in the literature. The barrier for further oxidation of this “1 ML” phase is only 0.31 eV. Finally the oxidized Cu(111) surface has a relatively low reaction energy barrier for O{sub 2} dissociation, even at high oxygen coverage, and allows for facile oxidation of the subsurface by fast O diffusion through the surface oxide. The kinetic mechanisms found provide a qualitative explanation of the observed oxidation of the low-index Cu surfaces.
Scholz, Norman; Behnke, Thomas; Resch-Genger, Ute
2018-01-01
Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key parameter indicating the formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence parameters for signal detection and compared the results with conductometric and surface tension measurements. Based upon these results, requirements, advantages, and pitfalls of each method are discussed. Our study underlines the versatility of fluorometric methods that do not impose specific requirements on surfactants and are especially suited for the quantification of very low CMC values. Conductivity and surface tension measurements yield smaller uncertainties particularly for high CMC values, yet are more time- and substance consuming and not suitable for every surfactant.
Czech Academy of Sciences Publication Activity Database
Klomfar, Jaroslav; Součková, Monika; Pátek, Jaroslav
2011-01-01
Roč. 56, č. 8 (2011), s. 3454-3462 ISSN 0021-9568 R&D Projects: GA ČR GA101/09/0010; GA AV ČR IAA200760701 Institutional research plan: CEZ:AV0Z20760514 Keywords : surface tension * density * dicyanamide * experimental data Subject RIV: BJ - Thermodynamics Impact factor: 1.693, year: 2011 http://pubs.acs.org/doi/abs/10.1021/je200502j
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2012-01-01
Roč. 333, NOV 15 2012 (2012), s. 38-46 ISSN 0378-3812 R&D Projects: GA ČR GA101/09/0010 Institutional research plan: CEZ:AV0Z20760514 Keywords : ionic liquid * tris(pentaﬂuoroethyl)triﬂuorophosphate * density * surface tension Subject RIV: BJ - Thermodynamics Impact factor: 2.379, year: 2012 http://www.sciencedirect.com/science/article/pii/S037838121200310X
Czech Academy of Sciences Publication Activity Database
Klomfar, Jaroslav; Součková, Monika; Pátek, Jaroslav
2017-01-01
Roč. 431, January (2017), s. 24-33 ISSN 0378-3812 R&D Projects: GA ČR GA13-00145S Institutional support: RVO:61388998 Keywords : ionic liquid * pyridinium-based cation * bis(triﬂuoromethylsulfonyl)imide anion * density-temperature relation * surface tension-temperature relation * recommended property values Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 2.473, year: 2016
International Nuclear Information System (INIS)
Rahul Banerjee; Khan, M.; Mandal, L.K.; Roy, S.; Gupta, M.R.
2010-01-01
Complete text of publication follows. The Rayleigh-Taylor (R-T) instability and Richtmyer-Meshkov (R-M) instability are well known problems in the formation of some astrophysical structures such as the supernova remnants in the Eagle and Crab nebula. A core collapse supernova is driven by an externally powerful shock, and strong shocks are the breeding ground of hydrodynamic instability such as Rayleigh-Taylor instability or Richtmyer-Meshkov instability. These instabilities are also important issues in the design of targets for inertial confinement fusion (ICF). In an ICF target, a high density fluid is frequently accelerated by the pressure of a low density fluid and after ablation the density quickly decays. So, small ripples at such an interface will grow. Under potential flow model, the perturbed interface between heavier fluid and lighter fluid form bubble and spike like structures. The bubbles are in the form of columns of lighter fluid interleaved by falling spike of heavy fluid. In this paper, we like to presented the effect of viscosity and surface tension on Rayleigh-Taylor instability and Richtmyer-Meshkov instability under the non-linear Layzer's approach and described the displacement curvature, growth and velocity of the tip of the bubble as well as spike. It is seen that, in absence of surface tension the lowering of the asymptotic velocity of the tip of the bubble which is formed when the lighter fluid penetrates into the denser fluid and thus encounters the viscous drag due to the denser fluid, which depends only on the denser fluid's viscosity coefficient. On the other hand the asymptotic velocity of the tip of the spike formed as the denser fluid penetrates into the lighter fluid is reduced by an amount which depends only on the viscosity coefficient of the lighter fluid and the spike is resisted by the viscous drag due to the lighter fluid. However, in presence of surface tension the asymptotic velocity of the tip of the bubble (spike) and
Surface incompressibility from semiclassical relativistic mean field calculations
International Nuclear Information System (INIS)
Patra, S.K.; Centelles, M.; Vinas, X.; Estal, M. del
2002-01-01
By using the scaling method and the Thomas-Fermi and extended Thomas-Fermi approaches to relativistic mean field theory the surface contribution to the leptodermous expansion of the finite nuclei incompressibility K A has been self-consistently computed. The validity of the simplest expansion, which contains volume, volume-symmetry, surface, and Coulomb terms, is examined by comparing it with self-consistent results of K A for some currently used nonlinear σ-ω parameter sets. A numerical estimate of higher-order contributions to the leptodermous expansion, namely, the curvature and surface-symmetry terms, is made
Ziegler, D K
1978-05-01
Headache is an extremely common symptom, and many headaches undoubtedly have a relationship to stressful situations. The clear definition, however, of a "tension headache" complex and its differentiation from migraine in some patients is difficult. The problems are in the identification of a specific headache pattern induced by stress or "tension" and the relationship of the symptom to involuntary contraction of neck and scalp muscles. Treatment consists of analgesics and occasionally mild tranquilizers. Psychotherapy consists of reassurance and often other supportive measures, including modification of life styles. Various feedback techniques have been reported of value, but their superiority to suggestion and hypnosis is still problematic.
Numerical Calculation of Distribution of Induced Carge Density on Planar Confined Surfaces
International Nuclear Information System (INIS)
Bolotov, V.; Druzhchenko, R.; Karazin, V.; Lominadze, J.; Kharadze, F.
2007-01-01
The calculation method of distribution of induced charge density on planar surfaces, including fractal structures of Sierpinski carpet type, is propesed. The calculation scheme is based on the fact that simply connected conducting surface of arbitrary geometry is an equipotential surface. (author)
Kinetic-energy functionals studied by surface calculations
DEFF Research Database (Denmark)
Vitos, Levente; Skriver, Hans Lomholt; Kollár, J.
1998-01-01
The self-consistent jellium model of metal surfaces is used to study the accuracy of a number of semilocal kinetic-energy functionals for independent particles. It is shown that the poor accuracy exhibited by the gradient expansion approximation and most of the semiempirical functionals in the lo...... density, high gradient limit may be subtantially improved by including locally a von Weizsacker term. Based on this, we propose a simple one-parameter Pade's approximation, which reproduces the exact Kohn-Sham surface kinetic energy over the entire range of metallic densities....
Surface regulated arsenenes as Dirac materials: From density functional calculations
International Nuclear Information System (INIS)
Yuan, Junhui; Xie, Qingxing; Yu, Niannian; Wang, Jiafu
2017-01-01
Highlights: • The presence of Dirac cones in chemically decorated buckled arsenene AsX (X = CN, NC, NCO, NCS, and NCSe) has been revealed. • First-principles calculations show that all these chemically decorated arsenenes are kinetically stable in defending thermal fluctuations in room temperature. - Abstract: Using first principle calculations based on density functional theory (DFT), we have systematically investigated the structure stability and electronic properties of chemically decorated arsenenes, AsX (X = CN, NC, NCO, NCS and NCSe). Phonon dispersion and formation energy analysis reveal that all the five chemically decorated buckled arsenenes are energetically favorable and could be synthesized. Our study shows that wide-bandgap arsenene would turn into Dirac materials when functionalized by -X (X = CN, NC, NCO, NCS and NCSe) groups, rendering new promises in next generation high-performance electronic devices.
Diffraction efficiency calculations of polarization diffraction gratings with surface relief
Nazarova, D.; Sharlandjiev, P.; Berberova, N.; Blagoeva, B.; Stoykova, E.; Nedelchev, L.
2018-03-01
In this paper, we evaluate the optical response of a stack of two diffraction gratings of equal one-dimensional periodicity. The first one is a surface-relief grating structure; the second, a volume polarization grating. This model is based on our experimental results from polarization holographic recordings in azopolymer films. We used films of commercially available azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]), shortly denoted as PAZO. During the recording process, a polarization grating in the volume of the material and a relief grating on the film surface are formed simultaneously. In order to evaluate numerically the optical response of this “hybrid” diffraction structure, we used the rigorous coupled-wave approach (RCWA). It yields stable numerical solutions of Maxwell’s vector equations using the algebraic eigenvalue method.
Maiti, Amitesh; McGrother, Simon
2004-01-01
Dissipative particle dynamics (DPD) is a mesoscale modeling method for simulating equilibrium and dynamical properties of polymers in solution. The basic idea has been around for several decades in the form of bead-spring models. A few years ago, Groot and Warren [J. Chem. Phys. 107, 4423 (1997)] established an important link between DPD and the Flory-Huggins χ-parameter theory for polymer solutions. We revisit the Groot-Warren theory and investigate the DPD interaction parameters as a function of bead size. In particular, we show a consistent scheme of computing the interfacial tension in a segregated binary mixture. Results for three systems chosen for illustration are in excellent agreement with experimental results. This opens the door for determining DPD interactions using interfacial tension as a fitting parameter.
Czech Academy of Sciences Publication Activity Database
Jungwirth, Pavel; Tobias, D. J.
2015-01-01
Roč. 448, Jun 15 (2015), s. 593 ISSN 0021-9797 Institutional support: RVO:61388963 Keywords : surface tension * Gibbs adsorption equation * hydroxide * water Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.782, year: 2015
Das, Subir K; Egorov, Sergei A; Virnau, Peter; Winter, David; Binder, Kurt
2018-06-27
Results from Monte Carlo simulations of wall-attached droplets in the three-dimensional Ising lattice gas model and in a symmetric binary Lennard-Jones fluid, confined by antisymmetric walls, are analyzed, with the aim to estimate the dependence of the contact angle [Formula: see text] on the droplet radius [Formula: see text] of curvature. Sphere-cap shape of the wall-attached droplets is assumed throughout. An approach, based purely on 'thermodynamic' observables, e.g. chemical potential, excess density due to the droplet, etc, is used, to avoid ambiguities in the decision which particles belong (or do not belong, respectively) to the droplet. It is found that the results are compatible with a variation [Formula: see text], [Formula: see text] being the contact angle in the thermodynamic limit ([Formula: see text]). The possibility to use such results to estimate the excess free energy related to the contact line of the droplet, namely the line tension, at the wall, is discussed. Various problems that hamper this approach and were not fully recognized in previous attempts to extract the line tension are identified. It is also found that the dependence of wall tensions on the difference of chemical potential of the droplet from that at the bulk coexistence provides effectively a change of the contact angle of similar magnitude. The simulation approach yields precise estimates for the excess density due to wall-attached droplets and the corresponding free energy excess, relative to a system without a droplet at the same chemical potential. It is shown that this information suffices to estimate nucleation barriers, not affected by ambiguities on droplet shape, contact angle and line tension.
International Nuclear Information System (INIS)
Rukavishnikova, I.V.; Lokett, V.N.; Burukhin, A.S.; Stepanov, V.P.
2006-01-01
The density and interphase tension of molten mixtures of lithium fluoride with potassium, rubidium, and cesium bromides were measured over the temperature range 1120-1320 K in the region of limited mutual solubility by the hydrostatic weighing and meniscus weight methods. The dependences of properties on the size ratio between the mixed ions were determined. The critical order parameters for systems with the predominantly ionic character of interparticle interactions were estimated [ru
Energy Technology Data Exchange (ETDEWEB)
Su, Jun [Department of Polymer Science and Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); College of Mechanics Engineering, Nanjing Institute of Industry Technology, Nanjing, 210023 (China); Zhang, Jun, E-mail: zhangjun@njtech.edu.cn [Department of Polymer Science and Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China)
2016-12-01
Graphical abstract: - Highlights: • The non-polar and short vinyl groups can greatly reduce G′ of HDPE composites. • Long chains on BaTiO{sub 3} surface enhance the interaction of BaTiO{sub 3} with HDPE. • Polar amino groups on BaTiO{sub 3} surface raise the interaction of BaTiO{sub 3} with HDPE. • Polar amino groups can boost the dielectric constant of HDPE composites. • The potential use in electronic equipment of the KH550 composites is obtained. - Abstract: In this work, three types of coupling agents: isopropyl trioleic titanate (NDZ105), vinyltriethoxysilane (SG-Si151), 3-aminopropyltriethoxysilane (KH550) were applied to modify the surface tension of Barium titanate (BaTiO{sub 3}) particles. The Fourier transform infrared (FT-IR) spectra confirm the chemical adherence of coupling agents to the particle surface. The long hydrocarbon chains in NDZ105 can cover the particle surface and reduce the polar surface tension of BaTiO{sub 3} from 37.53 mJ/m{sup 2} to 7.51 mJ/m{sup 2}, turning it from hydrophilic to oleophilic properties. The short and non-polar vinyl groups in SG-Si151 does not influence the surface tension of BaTiO{sub 3}, but make BaTiO{sub 3} have both hydrophilic and oleophilic properties. The polar amino in KH550 can keep BaTiO{sub 3} still with hydrophilic properties. It is found that SG-Si151 modified BaTiO{sub 3} has the lowest interaction with HDPE matrix, lowering the storage modulus of HDPE composites to the greatest extent. As for mechanical properties, the polar amino groups in KH550 on BaTiO{sub 3} surface can improve the adhesion of BaTiO{sub 3} with HDPE matrix, which increases the elongation at break of HDPE composites to the greatest extent. In terms of electrical properties, the polar amino groups on surface of BaTiO{sub 3} can boost the dielectric properties of HDPE/BaTiO{sub 3} composites and decrease the volume resistivity of HDPE/BaTiO{sub 3} composites. The aim of this study is to investigate how functional groups
Hot-electron-mediated desorption rates calculated from excited-state potential energy surfaces
DEFF Research Database (Denmark)
Olsen, Thomas; Gavnholt, Jeppe; Schiøtz, Jakob
2009-01-01
We present a model for desorption induced by (multiple) electronic transitions [DIET (DIMET)] based on potential energy surfaces calculated with the delta self-consistent field extension of density-functional theory. We calculate potential energy surfaces of CO and NO molecules adsorbed on variou...
Buffoni, Boris; Groves, Mark D.; Wahlén, Erik
2018-06-01
Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3}) has recently been given. In this article we present an existence theory for the physically more realistic case {0 point of the reduced functional is found by minimising it over its natural constraint set.
Czech Academy of Sciences Publication Activity Database
Vinš, Václav; Planková, Barbora; Hrubý, Jan
2013-01-01
Roč. 34, č. 5 (2013), s. 792-812 ISSN 0195-928X R&D Projects: GA AV ČR IAA200760905; GA ČR(CZ) GPP101/11/P046; GA ČR GA101/09/1633 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : chemical polarity * gradient theory * surface tension Subject RIV: BJ - Thermodynamics Impact factor: 0.623, year: 2013 http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10765-012-1207-z
Barman, Biraj Kumar; Rajbanshi, Biplab; Yasmin, Ananya; Roy, Mahendra Nath
2018-05-01
The formation of the host-guest inclusion complexes of ionic liquids namely [BMIm]Cl and [HMIm]Cl with α-CD and β-CD were studied by means of physicochemical and spectroscopic methods. Conductivity and surface tension study were in good agreement with the 1H NMR and FT-IR studies which confirm the formation of the inclusion complexes. The Density and viscosity study also supported the formation of the ICs. Further the stoichiometry was determined 1:1 for each case and the association constants and thermodynamic parameters derived supported the most feasible formation of the [BMIm]Cl- β-CD inclusion complex.
A calculation of the surface recombination rate constant for hydrogen isotopes on metals
International Nuclear Information System (INIS)
Baskes, M.J.
1980-01-01
The surface recombination rate constant for hydrogen isotopes on a metal has been calculated using a simple model whose parameters may be determined by direct experimental measurements. Using the experimental values for hydrogen diffusivity, solubility, and sticking coefficient at zero surface coverage a reasonable prediction of the surface recombination constant may be made. The calculated recombination constant is in excellent agreement with experiment for bcc iron. A heuristic argument is developed which, along with the rate constant calculation, shows that surface recombination is important in those metals in which hydrogen has an exothermic heat of solution. (orig.)
International Nuclear Information System (INIS)
Jamet, Didier; Torres, David; Brackbill, J.U.
2002-01-01
Errors in the computation of fluid flows with surface tension are examined. These errors cause large parasitic flows when the capillary number is large and have often been attributed to truncation error in underresolved interfacial regions. A study using the second-gradient method reveals that when truncation error is eliminated in the computation of energy exchanges between surface and kinetic energies so that energy is strictly conserved, the parasitic currents are reduced to round-off. The results are based on general thermodynamic arguments and can be used to guide improvements in other methods, such as the continuum-surface-force (CSF) method, which is commonly used with the volume-of-fluid (VOF) method
Jamet, D; Brackbill, J U
2002-01-01
Errors in the computation of fluid flows with surface tension are examined. These errors cause large parasitic flows when the capillary number is large and have often been attributed to truncation error in underresolved interfacial regions. A study using the second-gradient method reveals that when truncation error is eliminated in the computation of energy exchanges between surface and kinetic energies so that energy is strictly conserved, the parasitic currents are reduced to round-off. The results are based on general thermodynamic arguments and can be used to guide improvements in other methods, such as the continuum-surface-force (CSF) method, which is commonly used with the volume-of-fluid (VOF) method.
Tension Tests of Copper Thin Films
Energy Technology Data Exchange (ETDEWEB)
Park, Kyung Jo; Kim, Chung Youb [Chonnam Nat’l Univ., Gwangju (Korea, Republic of)
2017-08-15
Tension tests for copper thin films with thickness of 12 μm were performed by using a digital image correlation method based on consecutive digital images. When calculating deformation using digital image correlation, a large deformation causes errors in the calculated result. In this study, the calculation procedure was improved to reduce the error, so that the full field deformation and the strain of the specimen could be accurately and directly measured on its surface. From the calculated result, it can be seen that the strain distribution is not uniform and its variation is severe, unlike the distribution in a common bulk specimen. This might result from the surface roughness introduced in the films during the fabrication process by electro-deposition.
Surface impedance of superconductors in wide frequency ranges for wake field calculations
International Nuclear Information System (INIS)
Davidovskii, V.G.
2006-01-01
The problem of the surface impedance of superconductors in wide frequency ranges for calculations of wake fields, generated by bunches of charged particles moving axially inside a metallic vacuum chambers, is solved. The case of specular electron reflection at the superconductor surface is considered. The expression for the surface impedance of superconductors suitable for numerical computation is derived [ru
Calculated orientation dependence of surface segregations in Pt50Ni50
DEFF Research Database (Denmark)
Abrikosov, I. A.; Ruban, Andrei; Skriver, Hans Lomholt
1994-01-01
We present local-density calculations of surface segregation profiles in a random Pt50Ni50 alloy. We find that the concentration profiles of the three low-index surfaces oscillate and that the two most closely packed surfaces, i.e., (111) and (100), are enriched by Pt while Ni is found to segrega...
Zhelezny, Vitaly; Geller, Vladimir; Semenyuk, Yury; Nikulin, Artem; Lukianov, Nikolai; Lozovsky, Taras; Shymchuk, Mykola
2018-03-01
This paper presents results of an experimental study of the density, saturated vapor pressure, surface tension and viscosity of Al_2O_3 nanoparticle colloidal solutions in isopropyl alcohol. Studies of the thermophysical properties of nanofluids were performed at various temperatures and concentrations of Al_2O_3 nanoparticles. The paper gives considerable attention to a turbidimetric analysis of the stability of nanofluid samples. Samples of nanofluids remained stable over the range of parameters of the experiments, ensuring the reliability of the thermophysical property data for the Al_2O_3 nanoparticle colloidal solutions in isopropyl alcohol. The studies show that the addition of Al_2O_3 nanoparticles leads to an increase of the density, saturated vapor pressure and viscosity, as well as a decrease for the surface tension of isopropyl alcohol. The information reported in this paper on the various thermophysical properties for the isopropyl alcohol/Al_2O_3 nanoparticle model system is useful for the development of thermodynamically consistent models for predicting properties of nanofluids and correct modeling of the heat exchange processes.
Directory of Open Access Journals (Sweden)
S. Ekström
2009-02-01
Full Text Available A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono- and polysaccharides and polyols such as the 2-methyltetrols, methylerythritol and methyltreitol. Because of their high solubility these compounds are considered as potentially efficient CCN material. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Köhler curves for C3-C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what was expected, none of these compounds displayed a higher CCN efficiency than organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as saccharides and polyols would not contribute more to cloud formation than other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, in contrary to recently suggested.
SGFM applied to the calculation of surface band structure of V
International Nuclear Information System (INIS)
Baquero, R.; Velasco, V.R.; Garcia Moliner, F.
1986-07-01
The surface Green function matching (SGFM) method has been developed recently to deal with a great variety of problems in a unified way. The method was first developed for continuum systems. The recent advances for discrete structures can deal with surfaces, interfaces, quantum wells, superlattices, intercalated layered compounds, and other systems. Several applications of this formalism are being carried out. In the present note we will describe how the formalism applies to the calculation of the electronic surface band structure of vanadium which is a quite interesting transition metal with very active magnetic properties at the surface, in particular at the (100) surface. It is straightforward, on the basis of the calculation presented here, to obtain the magnetic moment on the surface, for example, through the method followed by G. Allan or the surface paramagnon density which should be particularly enhanced at this surface as compared to the bulk
Hayashi, Nobuhiko; Terauchi, Masaharu; Aya, Youichirou; Kanayama, Shutetsu; Nishitani, Hikaru; Nakagawa, Tohru; Takase, Michihiko
2017-09-01
We are developing a thin and lightweight CPV module using small size lens system made from poly methyl methacrylate (PMMA) with a short focal length and micro-solar cells to decrease the transporting and the installing costs of CPV systems. In order to achieve high conversion efficiency in CPV modules using micro-solar cells, the micro-solar cells need to be mounted accurately to the irradiated region of the concentrated sunlight. In this study, we have successfully developed self-align method thanks to the surface tension of the melted solder even utilizing commercially available surface-mounting technology (SMT). Solar cells were self-aligned to the specified positions of the circuit board by this self-align method with accuracy within ±10 µm. We actually fabricated CPV modules using this self-align method and demonstrated high conversion efficiency of our CPV module.
International Nuclear Information System (INIS)
Yan Han; Gan Zhiyin; Song Xiaohui; Chen Zhaohui; Xu Jingping; Liu Sheng
2009-01-01
First-principles calculations of magnesium adsorption at the Ga-terminated and N-terminated {0 0 0 1} basal plane wurtzite gallium nitride surfaces have been carried out to explain the atomic-scale insight into the initial adsorption processes of magnesium doping in gallium nitride. The results reveal that magnesium adsorption on N-terminated surfaces is preferred than that on Ga-terminated surfaces. Furthermore, the surface diffusivity of magnesium atom on the N-terminated surface is much lower than that on the Ga-terminated surface, which is due to both the larger average adsorption energies and the lower adsorption distance on N-terminated surface than that on Ga-terminated surface. The results indicate that the p-type doping on the Ga-terminated surface will be better distributed than that on the N-terminated surface.
International Nuclear Information System (INIS)
Ramanujan, R.V.
2003-01-01
The concept of the dividing surface has been extensively used to define the relationships between thermodynamic quantities at the interface between two phases; it is also useful in calculations of interfacial energy (γ). However, in the original formulation, the two phases are continuum phases, the atomistic nature of the interface was not considered. It is, therefore, useful to examine the use of the dividing surface in the context of atomistic interfacial energy calculations. The case of a planar fcc:hcp interface is considered and the dividing surface positions which are useful in atomistic interfacial energy calculations are stated, one position equates γ to the excess internal energy, the other position allows us to use the Gibbs adsorption equation. An example of a calculation using the convenient dividing surface positions is presented
Full charge-density calculation of the surface energy of metals
DEFF Research Database (Denmark)
Vitos, Levente; Kollár, J..; Skriver, Hans Lomholt
1994-01-01
of a spherically symmetrized charge density, while the Coulomb and exchange-correlation contributions are calculated by means of the complete, nonspherically symmetric charge density within nonoverlapping, space-filling Wigner-Seitz cells. The functional is used to assess the convergence and the accuracy......We have calculated the surface energy and the work function of the 4d metals by means of an energy functional based on a self-consistent, spherically symmetric atomic-sphere potential. In this approach the kinetic energy is calculated completely within the atomic-sphere approximation (ASA) by means...... of the linear-muffin-tin-orbitals (LMTO) method and the ASA in surface calculations. We find that the full charge-density functional improves the agreement with recent full-potential LMTO calculations to a level where the average deviation in surface energy over the 4d series is down to 10%....
The calculation of surface free energy based on embedded atom method for solid nickel
International Nuclear Information System (INIS)
Luo Wenhua; Hu Wangyu; Su Kalin; Liu Fusheng
2013-01-01
Highlights: ► A new solution for accurate prediction of surface free energy based on embedded atom method was proposed. ► The temperature dependent anisotropic surface energy of solid nickel was obtained. ► In isotropic environment, the approach does not change most predictions of bulk material properties. - Abstract: Accurate prediction of surface free energy of crystalline metals is a challenging task. The theory calculations based on embedded atom method potentials often underestimate surface free energy of metals. With an analytical charge density correction to the argument of the embedding energy of embedded atom method, an approach to improve the prediction for surface free energy is presented. This approach is applied to calculate the temperature dependent anisotropic surface energy of bulk nickel and surface energies of nickel nanoparticles, and the obtained results are in good agreement with available experimental data.
Lowe, Benjamin M.; Skylaris, Chris-Kriton; Green, Nicolas G.; Shibuta, Yasushi; Sakata, Toshiya
2018-04-01
Continuum-based methods are important in calculating electrostatic properties of interfacial systems such as the electric field and surface potential but are incapable of providing sufficient insight into a range of fundamentally and technologically important phenomena which occur at atomistic length-scales. In this work a molecular dynamics methodology is presented for interfacial electric field and potential calculations. The silica–water interface was chosen as an example system, which is highly relevant for understanding the response of field-effect transistors sensors (FET sensors). Detailed validation work is presented, followed by the simulated surface charge/surface potential relationship. This showed good agreement with experiment at low surface charge density but at high surface charge density the results highlighted challenges presented by an atomistic definition of the surface potential. This methodology will be used to investigate the effect of surface morphology and biomolecule addition; both factors which are challenging using conventional continuum models.
International Nuclear Information System (INIS)
Kim, Jung-Ha; Hill, Robin; Kuncic, Zdenka
2012-01-01
The Monte Carlo (MC) method has proven invaluable for radiation transport simulations to accurately determine radiation doses and is widely considered a reliable computational measure that can substitute a physical experiment where direct measurements are not possible or feasible. In the EGSnrc/BEAMnrc MC codes, there are several user-specified parameters and customized transport algorithms, which may affect the calculation results. In order to fully utilize the MC methods available in these codes, it is essential to understand all these options and to use them appropriately. In this study, the effects of the electron transport algorithms in EGSnrc/BEAMnrc, which are often a trade-off between calculation accuracy and efficiency, were investigated in the buildup region of a homogeneous water phantom and also in a heterogeneous phantom using the DOSRZnrc user code. The algorithms and parameters investigated include: boundary crossing algorithm (BCA), skin depth, electron step algorithm (ESA), global electron cutoff energy (ECUT) and electron production cutoff energy (AE). The variations in calculated buildup doses were found to be larger than 10% for different user-specified transport parameters. We found that using BCA = EXACT gave the best results in terms of accuracy and efficiency in calculating buildup doses using DOSRZnrc. In addition, using the ESA = PRESTA-I option was found to be the best way of reducing the total calculation time without losing accuracy in the results at high energies (few keV ∼ MeV). We also found that although choosing a higher ECUT/AE value in the beam modelling can dramatically improve computation efficiency, there is a significant trade-off in surface dose uncertainty. Our study demonstrates that a careful choice of user-specified transport parameters is required when conducting similar MC calculations. (note)
International Nuclear Information System (INIS)
Ma, Shu-Cui; Wang, Zhi-Gang; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia
2015-01-01
Highlights: • To examine surface hydroxyl functional groups of the calcined diatomite by TGA-DSC, FTIR, and XPS. • To calculate the optimized log K 1 , log K 2 and log C values and the surface species distribution of each surface reactive site using ProtoFit and PHREEQC, respectively. - Abstract: The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation–deprotonation behavior was determined by continuous acid–base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m 2 /g and large numbers of surface hydroxyl functional groups (i.e. ≡Si-OH, ≡Fe-OH, and ≡Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K 1 , log K 2 ) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation–deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent
Energy Technology Data Exchange (ETDEWEB)
Ma, Shu-Cui [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China); Wang, Zhi-Gang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Ji-Lin, E-mail: zjl@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Sun, De-Hui [Changchun Institute Technology, Changchun 130012 (China); Liu, Gui-Xia, E-mail: liuguixia22@163.com [Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China)
2015-02-01
Highlights: • To examine surface hydroxyl functional groups of the calcined diatomite by TGA-DSC, FTIR, and XPS. • To calculate the optimized log K{sub 1}, log K{sub 2} and log C values and the surface species distribution of each surface reactive site using ProtoFit and PHREEQC, respectively. - Abstract: The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation–deprotonation behavior was determined by continuous acid–base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m{sup 2}/g and large numbers of surface hydroxyl functional groups (i.e. ≡Si-OH, ≡Fe-OH, and ≡Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K{sub 1}, log K{sub 2}) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation–deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.
Mitochondrial Respiration and Oxygen Tension.
Shaw, Daniel S; Meitha, Karlia; Considine, Michael J; Foyer, Christine H
2017-01-01
Measurements of respiration and oxygen tension in plant organs allow a precise understanding of mitochondrial capacity and function within the context of cellular oxygen metabolism. Here we describe methods that can be routinely used for the isolation of intact mitochondria, and the determination of respiratory electron transport, together with techniques for in vivo determination of oxygen tension and measurement of respiration by both CO 2 production and O 2 consumption that enables calculation of the respiratory quotient [CO 2 ]/[O 2 ].
Calculating the sensitivity of wind turbine loads to wind inputs using response surfaces
DEFF Research Database (Denmark)
Rinker, Jennifer M.
2016-01-01
at a low computational cost. Sobol sensitivity indices (SIs) can then be calculated with relative ease using the calibrated response surface. The proposed methodology is demonstrated by calculating the total sensitivity of the maximum blade root bending moment of the WindPACT 5 MW reference model to four......This paper presents a methodology to calculate wind turbine load sensitivities to turbulence parameters through the use of response surfaces. A response surface is a high-dimensional polynomial surface that can be calibrated to any set of input/output data and then used to generate synthetic data...... turbulence input parameters: a reference mean wind speed, a reference turbulence intensity, the Kaimal length scale, and a novel parameter reflecting the nonstationarity present in the inflow turbulence. The input/output data used to calibrate the response surface were generated for a previous project...
Study on the surface hydroxyl group on solid breeding materials by ab-initio calculations
Energy Technology Data Exchange (ETDEWEB)
Tanaka, Satoru; Taniguchi, Masaki [Tokyo Univ. (Japan). Faculty of Engineering
1996-10-01
The nature of -OH on the surface of Li{sub 2}O was analyzed with the ab-initio quantum chemical calculation technique. Calculation results showed that the stretching vibration of O-H is affected by the chemical species around the -OH. (author)
Inoue, N.; Kitada, N.; Irikura, K.
2013-12-01
A probability of surface rupture is important to configure the seismic source, such as area sources or fault models, for a seismic hazard evaluation. In Japan, Takemura (1998) estimated the probability based on the historical earthquake data. Kagawa et al. (2004) evaluated the probability based on a numerical simulation of surface displacements. The estimated probability indicates a sigmoid curve and increases between Mj (the local magnitude defined and calculated by Japan Meteorological Agency) =6.5 and Mj=7.0. The probability of surface rupture is also used in a probabilistic fault displacement analysis (PFDHA). The probability is determined from the collected earthquake catalog, which were classified into two categories: with surface rupture or without surface rupture. The logistic regression is performed for the classified earthquake data. Youngs et al. (2003), Ross and Moss (2011) and Petersen et al. (2011) indicate the logistic curves of the probability of surface rupture by normal, reverse and strike-slip faults, respectively. Takao et al. (2013) shows the logistic curve derived from only Japanese earthquake data. The Japanese probability curve shows the sharply increasing in narrow magnitude range by comparison with other curves. In this study, we estimated the probability of surface rupture applying the logistic analysis to the surface displacement derived from a surface displacement calculation. A source fault was defined in according to the procedure of Kagawa et al. (2004), which determined a seismic moment from a magnitude and estimated the area size of the asperity and the amount of slip. Strike slip and reverse faults were considered as source faults. We applied Wang et al. (2003) for calculations. The surface displacements with defined source faults were calculated by varying the depth of the fault. A threshold value as 5cm of surface displacement was used to evaluate whether a surface rupture reach or do not reach to the surface. We carried out the
DEFF Research Database (Denmark)
Greeley, Jeffrey Philip; Nørskov, Jens Kehlet
2007-01-01
A simple procedure is introduced to use periodic Density Functional Theory calculations to estimate trends in the thermodynamics of surface alloy dissolution in acidic media. With this approach, the dissolution potentials for solute metal atoms embedded in the surface layer of various host metals...
Ma, Shu-Cui; Wang, Zhi-Gang; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia
2015-02-01
The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation-deprotonation behavior was determined by continuous acid-base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m2/g and large numbers of surface hydroxyl functional groups (i.e. tbnd Si-OH, tbnd Fe-OH, and tbnd Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K1, log K2) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation-deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.
Rojewska, Monika; Biadasz, Andrzej; Kotkowiak, Michał; Olejnik, Anna; Rychlik, Joanna; Dudkowiak, Alina; Prochaska, Krystyna
2013-10-01
The adsorption properties of surfactant mixtures containing two types of quaternary derivatives of lysosomotropic substances: alkyl N,N-dimethylalaninates methobromides and alkyl N,N-dimethylglycinates methobromides were studied. Quantitative and qualitative description of the adsorption process was carried out on the basis of experimentally obtained equilibrium surface tension isotherms. The results indicated that most of the systems studied revealed synergistic effect both in adsorption and wetting properties. In vitro studies on human cancer cells were undertaken and the data obtained showed that the mixtures suppressed the cancer cells' proliferation more effectively than individual components. Results of preliminary research on the interaction of catanionic mixtures with phospholipids suggested a possibility of a strong penetration of cell membranes by the mixtures investigated. Copyright © 2013 Elsevier B.V. All rights reserved.
Lin, Bojie; Miao, Yong; Wang, Jin; Fan, Zhexiang; Du, Lijuan; Su, Yongsheng; Liu, Bingcheng; Hu, Zhiqi; Xing, Malcolm
2016-03-09
Human dermal papilla (DP) cells have been studied extensively when grown in the conventional monolayer. However, because of great deviation from the real in vivo three-dimensional (3D) environment, these two-dimensional (2D) grown cells tend to lose the hair-inducible capability during passaging. Hence, these 2D caused concerns have motivated the development of novel 3D culture techniques to produce cellular microtissues with suitable mimics. The hanging-drop approach is based on surface tension-based technique and the interaction between surface tension and gravity field that makes a convergence of liquid drops. This study used this technique in a converged drop to form cellular spheroids of dermal papilla cells. It leads to a controllable 3Dspheroid model for scalable fabrication of inductive DP microtissues. The optimal conditions for culturing high-passaged (P8) DP spheroids were determined first. Then, the morphological, histological and functional studies were performed. In addition, expressions of hair-inductive markers including alkaline phosphatase, α-smooth muscle actin and neural cell adhesion molecule were also analyzed by quantitative RT-PCR, immunostaining and immunoblotting. Finally, P8-DP microtissues were coimplanted with newborn mouse epidermal cells (EPCs) into nude mice. Our results indicated that the formation of 3D microtissues not only endowed P8-DP microtissues many similarities to primary DP, but also confer these microtissues an enhanced ability to induce hair-follicle (HF) neogenesis in vivo. This model provides a potential to elucidate the native biology of human DP, and also shows the promising for the controllable and scalable production of inductive DP cells applied in future follicle regeneration.
Calculating the sensitivity of wind turbine loads to wind inputs using response surfaces
International Nuclear Information System (INIS)
Rinker, Jennifer M.
2016-01-01
This paper presents a methodology to calculate wind turbine load sensitivities to turbulence parameters through the use of response surfaces. A response surface is a highdimensional polynomial surface that can be calibrated to any set of input/output data and then used to generate synthetic data at a low computational cost. Sobol sensitivity indices (SIs) can then be calculated with relative ease using the calibrated response surface. The proposed methodology is demonstrated by calculating the total sensitivity of the maximum blade root bending moment of the WindPACT 5 MW reference model to four turbulence input parameters: a reference mean wind speed, a reference turbulence intensity, the Kaimal length scale, and a novel parameter reflecting the nonstationarity present in the inflow turbulence. The input/output data used to calibrate the response surface were generated for a previous project. The fit of the calibrated response surface is evaluated in terms of error between the model and the training data and in terms of the convergence. The Sobol SIs are calculated using the calibrated response surface, and the convergence is examined. The Sobol SIs reveal that, of the four turbulence parameters examined in this paper, the variance caused by the Kaimal length scale and nonstationarity parameter are negligible. Thus, the findings in this paper represent the first systematic evidence that stochastic wind turbine load response statistics can be modeled purely by mean wind wind speed and turbulence intensity. (paper)
The Equilibrium Spreading Tension of Pulmonary Surfactant
Dagan, Maayan P.; Hall, Stephen B.
2015-01-01
Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γe) with the bulk phase from which they form. For individual phospholipids, γe is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γe therefo...
Directory of Open Access Journals (Sweden)
Uğur YALÇIN
2004-02-01
Full Text Available In this study, quasi-optical scattering of finite source electromagnetic waves from a dielectric coated cylindrical surface is analysed with Physical Optics (PO approach. A linear electrical current source is chosen as the finite source. Reflection coefficient of the cylindrical surface is derived by using Geometrical Theory of Diffraction (GTD. Then, with the help of this coefficient, fields scattered from the surface are obtained. These field expressions are used in PO approach and surface scattering integral is determined. Evaluating this integral asymptotically, fields reflected from the surface and surface divergence coefficient are calculated. Finally, results obtained in this study are evaluated numerically and effects of the surface impedance to scattered fields are analysed. The time factor is taken as j te? in this study.
Ammonia synthesis over a Ru(0001) surface studied by density functional calculations
DEFF Research Database (Denmark)
Logadottir, Ashildur; Nørskov, Jens Kehlet
2003-01-01
In this paper we present DFT studies of all the elementary steps in the synthesis of ammonia from gaseous hydrogen and nitrogen over a ruthenium crystal. The stability and configurations of intermediates in the ammonia synthesis over a Ru(0001) surface have been investigated, both over a flat...... surface and over a stepped surface. The calculations show that the step sites on the surface are much more reactive than the terrace sites. The DFT results are then used to study the mechanism of promotion by alkalies over the Ru(0001) and to determine the rate-determining step in the synthesis of ammonia...
Liu, Shanqiu; Eijkelenkamp, Rik; Duvigneau, Joost; Vancso, G. Julius
2017-01-01
Core-shell nanoparticles consisting of silica as core and surface-grafted poly(dimethylsiloxane) (PDMS) as shell with different diameters were prepared and used as heterogeneous nucleation agents to obtain CO2-blown poly(methyl methacrylate) (PMMA) nanocomposite foams. PDMS was selected as the shell
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2016-01-01
Roč. 100, September (2016), s. 79-88 ISSN 0021-9614 R&D Projects: GA ČR GA13-00145S Institutional support: RVO:61388998 Keywords : 1-Cn-3-methylimidazolium cation * tetrafluoroborate anion * density–temperature relation * surface tension–temperature relation * recommended property values Subject RIV: BJ - Thermodynamics Impact factor: 2.726, year: 2016
DEFF Research Database (Denmark)
Christensen, N. Egede; Feuerbacher, B.
1974-01-01
is obtained from an ad hoc potential based on a Dirac-Slater atomic calculation for the ground-state configuration and with full Slater exchange in the atomic as well as in the crystal potential. The selection of this best potential is justified by comparing the calculated band structure to Fermi...... of states. The present work includes a crude estimate of this surface density of states, which is derived from the bulk band structure by narrowing the d bands according to an effective number of neighbors per surface atom. Estimates of surface relaxation effects are also included.......The electronic energy-band structure of tungsten has been calculated by means of the relativistic-augmented-plane-wave method. A series of mutually related potentials are constructed by varying the electronic configuration and the amount of Slater exchange included. The best band structure...
Calculation of the flux density of gamma rays above the surface of Venus and the Earth
International Nuclear Information System (INIS)
Surkov, Yu.A.; Manvelyan, O.S.
1987-01-01
In this article the authors present the results of calculating the flux density of unscattered gamma rays as a function of height above the surfaces of Venus and the Earth. At each height they calculate the areas which will collect a certain fraction of the gamma rays. The authors calculate the spectra of scattered gamma rays, as well as their integrated fluxes at various heights above the surface of Venus. They consider how the atmosphere will affect the recording of gamma rays. Their results enable them to evaluate the optimal conditions for measuring the gamma-ray fields above the surfaces of Venus and the Earth and to determine the area of the planet which can be investigated in this way. These results are also necessary if they are to determine the elemental composition of the rock from the characteristic recorded spectrum of gamma radiation
Ab Initio Calculations for the BaTiO3 (001) Surface Structure
Institute of Scientific and Technical Information of China (English)
XUE Xu-Yan; WANG Chun-Lei; ZHONG Wei-Lie
2004-01-01
@@ The ab initio method within the local density approximation is applied to calculate cubic BaTiO3 (001) surface relaxation and rumpling for two different terminations (BaO and TiO2). Our calculations demonstrate that cubic perovskite BaTiO3 crystals possess surface polarization, accompanied by the presence of the relevant electric field.We analyse their electronic structures (band structure, density of states and the electronic density redistribution with emphasis on the covalency effects). The results are also compared with that of the previous ab initio calculations. Considerable increases of Ti-O chemical bond covalency nearby the surface have been observed.The band gap reduces especially for the TiO2 termination.
Magnetic properties of polar ZnO surfaces from ab-initio calculations
Energy Technology Data Exchange (ETDEWEB)
Fischer, Guntram; Adeagbo, Waheed; Hergert, Wolfram [University Halle, Halle (Germany); Ernst, Arthur [Max-Planck-Institute of Microstructure Physics, Halle (Germany); Sanchez, Nadia; Mu noz, Carmen [Instituto de Ciencia de Materiales de Madrid, Madrid (Spain); Szotek, Zdzislawa; Temmerman, Walter [Daresbury Laboratory, Warrington (United Kingdom)
2011-07-01
We have investigated a magnetic moment formation of three oxygen-terminated polar ZnO surfaces. Specifically, these are the (000-1) surface, the (0001) surface with an oxygen atom on top of the Zn atom [(0001)-t], and the (0001) surface with an oxygen atom in a threefold hollow site [(0001)-h]. In this study we have used a multi-code approach allowing us to relax the surface structure and calculate the Heisenberg exchange parameters via a magnetic force theorem. Also, the influence of applying self-interaction corrections (SIC) to the oxygen p orbitals has been investigated. Our calculations show that all three surfaces are magnetic. In addition, we find that applying SIC is necessary to correctly describe the top oxygen atom of the (0001)-h and (0001)-t surfaces, for both of which we find Curie temperatures to be larger than room temperature. The latter have been derived from Monte Carlo simulations based on the calculated exchange parameters.
Energy Technology Data Exchange (ETDEWEB)
Gharaei, R.; Hadikhani, A. [Hakim Sabzevari University, Department of Physics, Sciences Faculty, Sabzevar (Iran, Islamic Republic of)
2017-07-15
For the first time the influence of the surface energy coefficient γ and temperature T on the parameterization of the fusion barriers is systematically analyzed within the framework of the proximity formalism, namely proximity 1977, proximity 1988 and proximity 2010 models. A total of 114 fusion reactions with the condition 39 ≤ Z{sub 1}Z{sub 2} ≤ 1520 for the charge product of their participant nuclei have been studied. We present γ-dependent and T -dependent pocket formulas which reproduce the theoretical and empirical data of the fusion barrier height and position for our considered reactions with good accuracy. It is shown that the quality of the γ-dependent formula enhances by increasing the strength of the surface energy coefficient. Moreover, the obtained results confirm that imposing the thermal effects improves the agreement between the parameterized and empirical data of the barrier characteristics. (orig.)
Calculation of gamma-ray flux density above the Venus and Earth surfaces
International Nuclear Information System (INIS)
Surkov, Yu.A.; Manvelyan, O.S.
1987-01-01
Calculational results of dependence of flux density of nonscattered gamma-quanta on the height above the Venus and Earth planet surfaces are presented in the paper. Areas, where a certain part of gamma quanta is accumulated, are calaculted for each height. Spectra of scattered gamma quanta and their integral fluxes at different heights above the Venera planet surface are calculated. Effect of the atmosphere on gamma radiation recorded is considered. The results obtained allow to estimate optimal conditions for measuring gamma-fields above the Venus and Earth planet surfaces, to determine the area of the planet surface investigated. They are also necessary to determine the elementary composition of the rock according to the characteristic gamma radiation spectrum recorded
Iron -chromium alloys and free surfaces: from ab initio calculations to thermodynamic modeling
International Nuclear Information System (INIS)
Levesque, M.
2010-11-01
Ferritic steels possibly strengthened by oxide dispersion are candidates as structural materials for generation IV and fusion nuclear reactors. Their use is limited by incomplete knowledge of the iron-chromium phase diagram at low temperatures and of the phenomena inducing preferential segregation of one element at grain boundaries or at surfaces. In this context, this work contributes to the multi-scale study of the model iron-chromium alloy and their free surfaces by numerical simulations. This study begins with ab initio calculations of properties related to the mixture of atoms of iron and chromium. We highlight complex dependency of the magnetic moments of the chromium atoms on their local chemical environment. Surface properties are also proving sensitive to magnetism. This is the case of impurity segregation of chromium in iron and of their interactions near the surface. In a second step, we construct a simple energy model for high numerical efficiency. It is based on pair interactions on a rigid lattice to which are given local chemical environment and temperature dependencies. With this model, we reproduce the ab initio results at zero temperature and experimental results at high temperature. We also deduce the solubility limits at all intermediate temperatures with mean field approximations that we compare to Monte Carlo simulations. The last step of our work is to introduce free surfaces in our model. We then study the effect of ab initio calculated bulk and surface properties on surface segregation.Finally, we calculate segregation isotherms. We therefore propose an evolution model of surface composition of iron-chromium alloys as a function of bulk composition. which are given local chemical environment and temperature dependencies. With this model, we reproduce the ab initio results at zero temperature and experimental results at high temperature. We also deduce the solubility limits at all intermediate temperatures with mean field approximations that
Directory of Open Access Journals (Sweden)
E. O. Fors
2010-06-01
Full Text Available HUmic-LIke Substances (HULIS have been identified as major contributors to the organic carbon in atmospheric aerosol. The term "HULIS" is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rondônia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA at relative humidity (RH <100%, and a cloud condensation nucleus counter (CCNC at RH >100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m and 31% (50.3 mN/m for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m and 13% (63.3 mN/m.
Zhao, Hongxia; Yang, Yong; Shu, Xin; Wang, Yanwei; Ran, Qianping
2018-04-09
First-principle calculations, especially by the density functional theory (DFT) methods, are becoming a power technique to study molecular structure and properties of organic/inorganic interfaces. This review introduces some recent examples on the study of adsorption models of organic molecules or oligomers on mineral surfaces and interfacial properties obtained from first-principles calculations. The aim of this contribution is to inspire scientists to benefit from first-principle calculations and to apply the similar strategies when studying and tailoring interfacial properties at the atomistic scale, especially for those interested in the design and development of new molecules and new products. Copyright © 2017. Published by Elsevier B.V.
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2015-01-01
Roč. 83, April (2015), s. 52-60 ISSN 0021-9614 R&D Projects: GA ČR GA13-00145S; GA ČR GA101/09/0010 Institutional support: RVO:61388998 Keywords : density * surface tension * 1-alkyl-3-methylimidazolium iodide * group contribution method * parachor Subject RIV: BJ - Thermodynamics Impact factor: 2.196, year: 2015
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2015-01-01
Roč. 406, November (2015), s. 181-193 ISSN 0378-3812 R&D Projects: GA ČR GA13-00145S Institutional support: RVO:61388998 Keywords : ionic liquid * surface tension-temperature relation * density -temperature relation * cyano-funcionalized anion Subject RIV: BJ - Thermodynamics Impact factor: 1.846, year: 2015
Directory of Open Access Journals (Sweden)
Chen X.
2006-11-01
Full Text Available Le problème considéré ici est celui de l'évaluation des efforts excitateurs de deuxième ordre (en mode somme, c'est-à-dire prenant place aux sommes deux à deux des fréquences de houle sur des plates-formes à lignes tendues. Ces efforts sont tenus pour responsables de comportements résonnants (en roulis, tangage et pilonnement observés lors d'essais en bassin et pourraient réduire sensiblement la durée de vie en fatigue des tendons. Des résultats sont tout d'abord présentés pour une structure simplifiée, consistant en 4 cylindres verticaux reposant sur le fond marin. L'intérêt de cette géométrie est que tous les calculs peuvent être menés à terme de façon quasi analytique. Les résultats obtenus permettent d'illustrer le haut degré d'interaction entre les colonnes, et la faible décroissance du potentiel de diffraction de deuxième ordre avec la profondeur. On présente ensuite des résultats pour une plate-forme réelle, celle de Snorre. Tension Leg Platforms (TLP's are now regarded as a promising technology for the development of deep offshore fields. As the water depth increases however, their natural periods of heave, roll and pitch tend to increase as well (roughly to the one-half power, and it is not clear yet what the maximum permissible values for these natural periods can be. For the Snorre TLP for instance, they are only about 2. 5 seconds, which seems to be sufficiently low since there is very limited free wave energy at such periods. Model tests, however, have shown some resonant response in sea states with peak periods of about 5 seconds. Often referred to as springing , this resonant motion can severely affect the fatigue life of tethers and increase their design loads. In order to calculate this springing motion at the design stage, it is necessary to identify and evaluate both the exciting loads and the mechanisms of energy dissipation. With the help of the French Norwegian Foundation a joint effort was
Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.
1988-01-01
Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).
The FLUFF code for calculating finned surface heat transfer -description and user's guide
International Nuclear Information System (INIS)
Fry, C.J.
1985-08-01
FLUFF is a computer code for calculating heat transfer from finned surfaces by convection and radiation. It can also represent heat transfer by radiation to a partially emitting and absorbing medium within the fin cavity. The FLUFF code is useful not only for studying the behaviour of finned surfaces but also for deriving heat fluxes which can be applied as boundary conditions to other heat transfer codes. In this way models of bodies with finned surfaces may be greatly simplified since the fins need not be explicitly represented. (author)
International Nuclear Information System (INIS)
Fradera, J.; Cuesta-López, S.
2013-01-01
Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM ® CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium nucleation
Caleman, Carl; van Maaren, Paul J; Hong, Minyan; Hub, Jochen S; Costa, Luciano T; van der Spoel, David
2012-01-10
The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats
Energy Technology Data Exchange (ETDEWEB)
Fradera, J., E-mail: jfradera@ubu.es; Cuesta-López, S., E-mail: scuesta@ubu.es
2013-12-15
Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM{sup ®} CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium
Calculation of the surface energy of hcp-metals with the empirical electron theory
International Nuclear Information System (INIS)
Fu Baoqin; Liu Wei; Li Zhilin
2009-01-01
A brief introduction of the surface model based on the empirical electron theory (EET) and the dangling bond analysis method (DBAM) is presented in this paper. The anisotropy of spatial distribution of covalent bonds of hexagonal close-packed (hcp) metals such as Be, Mg, Sc, Ti, Co, Zn, Y, Zr, Tc, Cd, Hf, and Re, has been analyzed. And under the first-order approximation, the calculated surface energy values for low index surfaces of these hcp-metals are in agreement with experimental and other theoretical values. Correlated analysis showed that the anisotropy of surface energy of hcp-metals was related with the ratio of lattice constants (c/a). The calculation method for the research of surface energy provides a good basis for models of surface science phenomena, and the model may be extended to the surface energy estimation of more metals, alloys, ceramics, and so on, since abundant information about the valence electronic structure (VES) is generated from EET.
Directory of Open Access Journals (Sweden)
Carlos Estrela
2005-06-01
Full Text Available The purpose of this study was to evaluate the surface tension of calcium hydroxide (CH associated with different substances (deionized distilled water, camphorated paramonochlorophenol, 2% chlorhexidine digluconate, Otosporin, 3% sodium lauryl ether sulphate; Furacin, PMC Furacin using tensiometer. The action of the substances studied on the dentinal structure enhances the property of surface tension. This method consists in the application of force to separate a platinum ring immersed in the substances. Thus, torsion was applied to the screw until the platinum ring separated during substances testing. Considering the methodology applied, the following can be concluded: distilled water alone or associated with CH presented a high surface tension (70.00 and 68.40 dynes/cm; calcium hydroxide in association with anionic detergent showed low surface tension (31.60 dynes/cm; camphorated paramonochlorophenol plus CH presented low surface tension (37.50 dynes/cm; 2% chlorhexidine associated with calcium hydroxide showed high surface tension values (58.00 dynes/cm; Otosporin plus calcium hydroxide showed low surface tension (35.40 dynes/cm; paramonochlorophenol Furacin mixed with calcium hydroxide presented surface tension equal to 45.50 dynes/cm; sodium hypochlorite presented high surface tension (75.00 dynes/cm. Antimicrobial agents more indicated in endodontics, i.e. CH, chlorhexidine and hypochlorite, presented the highest surface tension.Estudou-se a tensão superficial do hidróxido de cálcio associado a diferentes substâncias (água destilada deionizada, paramonoclorofenol canforado, digluconato de clorexidina 2%, Otosporin, sulfato éter lauril sódio 3%, furacin, PMC furacin usando tensiômetro. O modelo experimental consistiu na aplicação de uma força para separar um anel de platina imerso na superfície das substâncias, exercido por um tensiômetro. Considerando a metodologia aplicada, pode-se concluir: a água destilada isolada ou
Energy Technology Data Exchange (ETDEWEB)
Wang, Zhiying; Li, Yikai; Huang, Biao; Gao, Deming [Beijing Institute of Technology, Beijing (China)
2016-06-15
We numerically investigated the rising of bubbles in a quiescent liquid layer. The numerical simulation is performed by solving the incompressible, multiphase Navier-Stokes equations via computational code in axisymmetric coordinates using a Coupled level-set and volume-of-fluid (CLSVOF) method. The numerical results show that the CLSVOF method with a novel algebraic relation between F and f for axisymmetric two-phase flows not only can predict the bubble surface accurately, but also overcome the deficiency in preserving volume conservation. The effects of the Reynolds number Re and the Bond number Bo on the bubble deformation and its motion are investigated. The results show that with the increasing of Re (10 < Re < 150), the bubble shape transfers from oblate ellipsoidal cap to toroidal when Bo = 116. With the increasing of Bo (10 < Bo < 700), the bubble shape transfers from oblate ellipsoidal to toroidal when Re = 30. Although the toroidal bubble shapes are reached in these two cases, the transition modes are different. For the case Bo = 116, the bubble front is pierced by an upward jet from the rear of the bubble. While for the case Re = 30, the rear of the bubble is pierced by a downward jet from the front part.
International Nuclear Information System (INIS)
Ma, Ting; Zhang, Zhongjie
2014-01-01
Irregular surface topography has revolutionized how seismic traveltime is calculated and the data are processed. There are two main schemes for dealing with an irregular surface in the seismic first-arrival traveltime calculation: (1) expanding the model and (2) flattening the surface irregularities. In the first scheme, a notional infill medium is added above the surface to expand the physical space into a regular space, as required by the eikonal equation solver. Here, we evaluate the chosen propagation velocity in the infill medium through ray path tracking with the eikonal equation-solved traveltime field, and observe that the ray paths will be physically unrealistic for some values of this propagation velocity. The choice of a suitable propagation velocity in the infill medium is crucial for seismic processing of irregular topography. Our model expansion criterion for dealing with surface topography in the calculation of traveltime and ray paths using the eikonal equation highlights the importance of both the propagation velocity of the infill physical medium and the topography gradient. (paper)
Calculation of Pressure Distribution at Rotary Body Surface with the Vortex Element Method
Directory of Open Access Journals (Sweden)
S. A. Dergachev
2014-01-01
Full Text Available Vortex element method allows to simulate unsteady hydrodynamic processes in incompressible environment, taking into account the evolution of the vortex sheet, including taking into account the deformation or moving of the body or part of construction.For the calculation of the hydrodynamic characteristics of the method based on vortex element software package was developed MVE3D. Vortex element (VE in program is symmetrical Vorton-cut. For satisfying the boundary conditions at the surface used closed frame of vortons.With this software system modeled incompressible flow around a cylindrical body protection elongation L / D = 13 with a front spherical blunt with the angle of attack of 10 °. We analyzed the distribution of the pressure coefficient on the body surface of the top and bottom forming.The calculate results were compared with known Results of experiment.Considered design schemes with different number of Vorton framework. Also varied radius of VE. Calculation make possible to establish the degree of sampling surface needed to produce close to experiment results. It has been shown that an adequate reproducing the pressure distribution in the transition region spherical cylindrical surface, on the windward side requires a high degree of sampling.Based on these results Can be possible need to improve on the design scheme of body's surface, allowing more accurate to describe the flow vorticity in areas with abrupt changes of geometry streamlined body.
International Nuclear Information System (INIS)
Shang Yanlong; Cai Qi; Chen Lisheng; Zhang Yangwei
2012-01-01
In this paper, the combined method of response surface and importance sampling was applied for calculation of parameter failure probability of the thermodynamic system. The mathematics model was present for the parameter failure of physics process in the thermodynamic system, by which the combination arithmetic model of response surface and importance sampling was established, then the performance degradation model of the components and the simulation process of parameter failure in the physics process of thermodynamic system were also present. The parameter failure probability of the purification water system in nuclear reactor was obtained by the combination method. The results show that the combination method is an effective method for the calculation of the parameter failure probability of the thermodynamic system with high dimensionality and non-linear characteristics, because of the satisfactory precision with less computing time than the direct sampling method and the drawbacks of response surface method. (authors)
International Nuclear Information System (INIS)
Kawamura, T.; Ono, T.; Yamamura, Y.
1994-08-01
Physical sputtering yields from the carbon surface irradiated by the boundary plasma are obtained with the use of a Monte Carlo simulation code ACAT. The yields are calculated for many random initial energy and angle values of incident protons or deuterons with a Maxwellian velocity distribution, and then averaged. Here the temperature of the boundary plasma, the sheath potential and the angle δ between the magnetic field line and the surface normal are taken into account. A new fitting formula for an arrangement of the numerical data of sputtering yield is introduced, in which six fitting parameters are determined from the numerical results and listed. These results provide a way to estimate the erosion of carbon materials irradiated by boundary plasma. The particle reflection coefficients for deuterons and their neutrals from a carbon surface are also calculated by the same code and presented together with, for comparison, that for the case of monoenergetic normal incidence. (author)
FreeSASA: An open source C library for solvent accessible surface area calculations.
Mitternacht, Simon
2016-01-01
Calculating solvent accessible surface areas (SASA) is a run-of-the-mill calculation in structural biology. Although there are many programs available for this calculation, there are no free-standing, open-source tools designed for easy tool-chain integration. FreeSASA is an open source C library for SASA calculations that provides both command-line and Python interfaces in addition to its C API. The library implements both Lee and Richards' and Shrake and Rupley's approximations, and is highly configurable to allow the user to control molecular parameters, accuracy and output granularity. It only depends on standard C libraries and should therefore be easy to compile and install on any platform. The library is well-documented, stable and efficient. The command-line interface can easily replace closed source legacy programs, with comparable or better accuracy and speed, and with some added functionality.
An improved method for calculation of interface pressure force in PLIC-VOF methods
International Nuclear Information System (INIS)
Sefollahi, M.; Shirani, E.
2004-08-01
Conventional methods for the modeling of surface tension force in Piecewise Linear Interface Calculation-Volume of Fluid (PLIC-VOF) methods, such as Continuum Surface Force (CSF), Continuum Surface Stress (CSS) and also Meier's method, convert the surface tension force into a body force. Not only do they include the force in the interfacial cells but also in the neighboring cells. Thus they produce spurious currents. Also the pressure jump, due to the surface tension, is not calculated accurately in these methods. In this paper a more accurate method for the application of interface force in the computational modeling of free surfaces and interfaces which use PLIC-VOF methods is developed. This method is based on the evaluation of the surface tension force only in the interfacial cells and not the neighboring cells. Also the normal and the interface surface area needed for the calculation of the surface tension force is calculated more accurately. The present method is applied to a two-dimensional motionless drop of liquid and a bubble of gas as well as a non-circular two-dimensional drop, which oscillates due to the surface tension force, in an initially stagnant fluid with no gravity force. The results are compared with the results of the cases when CSF, CSS and Meier's methods are used. It is shown that the present method calculates pressure jump at the interface more accurately and produces less spurious currents comparing to CSS an CSF models. (author)
use of the RESRAD-BUILD code to calculate building surface contamination limits
International Nuclear Information System (INIS)
Faillace, E.R.; LePoire, D.; Yu, C.
1996-01-01
Surface contamination limits in buildings were calculated for 226 Ra, 230 Th, 232 Th, and natural uranium on the basis of 1 mSv y -1 (100 mrem y -1 ) dose limit. The RESRAD-BUILD computer code was used to calculate these limits for two scenarios: building occupancy and building renovation. RESRAD-BUILD is a pathway analysis model designed to evaluate the potential radiological dose incurred by individuals working or living inside a building contaminated with radioactive material. Six exposure pathways are considered in the RESRAD-BUILD code: (1) external exposure directly from the source; (2) external exposure from materials deposited on the floor; (3) external exposure due to air submersion; (4) inhalation of airborne radioactive particles; (5) inhalation of aerosol indoor radon progeny; and (6) inadvertent ingestion of radioactive material, either directly from the sources or from materials deposited on the surfaces. The code models point, line, area, and volume sources and calculates the effects of radiation shielding, building ventilation, and ingrowth of radioactive decay products. A sensitivity analysis was performed to determine how variations in input parameters would affect the surface contamination limits. In most cases considered, inhalation of airborne radioactive particles was the primary exposure pathway. However, the direct external exposure contribution from surfaces contaminated with 226 Ra was in some cases the dominant pathway for building occupancy depending on the room size, ventilation rates, and surface release fractions. The surface contamination limits are most restrictive for 232 Th, followed by 230 Th, natural uranium, and 226 Ra. The results are compared with the surface contamination limits in the Nuclear Regulatory Commission's Regulatory Guide 1.86, which are most restrictive for 226 Ra and 230 Th, followed by 232 Th, and are least restrictive for natural uranium
Onischuk, A A; Purtov, P A; Baklanov, A M; Karasev, V V; Vosel, S V
2006-01-07
Zinc and silver vapor homogeneous nucleations are studied experimentally at the temperature from 600 to 725 and 870 K, respectively, in a laminar flow diffusion chamber with Ar as a carrier gas at atmospheric pressure. The size, shape, and concentration of aerosol particles outcoming the diffusion chamber are analyzed by a transmission electron microscope and an automatic diffusion battery. The wall deposit is studied by a scanning electron microscope (SEM). Using SEM data the nucleation rate for both Zn and Ag is estimated as 10(10) cm(-3) s(-1). The dependence of critical supersaturation on temperature for Zn and Ag measured in this paper as well as Li, Na, Cs, Ag, Mg, and Hg measured elsewhere is analyzed. To this aim the classical nucleation theory is extended by the dependence of surface tension on the nucleus radius. The preexponent in the formula for the vapor nucleation rate is derived using the formula for the work of formation of noncritical embryo [obtained by Nishioka and Kusaka [J. Chem. Phys. 96, 5370 (1992)] and later by Debenedetti and Reiss [J. Chem. Phys. 108, 5498 (1998)
Xiao, Jingwen; Liu, Fang; Garamus, Vasil M; Almásy, László; Handge, Ulrich A; Willumeit, Regine; Mu, Bozhong; Zou, Aihua
2014-04-01
The interactions among neutral polymer polyacrylamide (PAM) and the biosurfactant Surfactin and four betaines, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SDDAB), N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (STDAB), N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SHDAB), and N-dodecyl-N,N-dimethyl-2-ammonio-acetate (C12BE), in phosphate buffer solution (PBS) have been studied by surface tension measurements, small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and rheological experiments. It has been confirmed that the length of alkyl chain is a key parameter of interaction between betaines and PAM. Differences in scattering contrast between X-ray and neutrons for surfactants and PAM molecules provide the opportunity to separately follow the changes of structure of PAM and surfactant aggregates. At concentrations of betaines higher than CMC (critical micelle concentration) and C2 (CMC of surfactant with the presence of polymer), spherical micelles are formed in betaines and betaines/PAM solutions. Transition from spherical to rod-like aggregates (micelles) has been observed in solutions of Surfactin and Surfactin/SDDAB (αSurfactin = 0.67 (molar fraction)) with addition of 0.8 wt % of PAM. The conformation change of PAM molecules only can be observed for Surfactin/SDDAB/PAM system. Viscosity values follow the structural changes suggested from scattering measurements i.e., gradually increases for mixtures PAM → Surfactin/PAM → Surfactin/SDDAB/PAM in PBS.
Calculated electronic structure of chromium surfaces and chromium monolayers on iron
International Nuclear Information System (INIS)
Victora, R.H.; Falicov, L.M.
1985-01-01
A self-consistent calculation of the magnetic and electronic properties of the chromium (100) and (110) surfaces and of a chromium monolayer on the (100) and (110) iron surfaces is presented. It is found that (i) the (100) chromium surface is ferromagnetic with a greatly enhanced spin polarization (3.00 electrons); (ii) a substantial enhancement of the spin imbalance exists several (>5) layers into the bulk; (iii) the (110) chromium surface is antiferromagnetic with a large (2.31) spin imbalance; (iv) the (100) chromium monolayer on ferromagnetic iron is ferromagnetic, with a huge spin imbalance (3.63), and aligned antiferromagnetically with respect to the bulk iron; (v) the (110) chromium monolayer on ferromagnetic iron is also ferromagnetic, with a spin imbalance of 2.25 and antiferromagnetically aligned to the iron. The spin imbalance of chromium on iron (100) is possibly the largest of any transition-metal system
Energy Technology Data Exchange (ETDEWEB)
Meier, Patrick; Oschetzki, Dominik; Rauhut, Guntram, E-mail: rauhut@theochem.uni-stuttgart.de [Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Berger, Robert [Clemens-Schöpf Institut für Organische Chemie and Biochemie, Technische Universität Darmstadt, Petersenstrasse 22, 64287 Darmstadt (Germany)
2014-05-14
A transformation of potential energy surfaces (PES) being represented by multi-mode expansions is introduced, which allows for the calculation of anharmonic vibrational spectra of any isotopologue from a single PES. This simplifies the analysis of infrared spectra due to significant CPU-time savings. An investigation of remaining deviations due to truncations and the so-called multi-level approximation is provided. The importance of vibrational-rotational couplings for small molecules is discussed in detail. In addition, an analysis is proposed, which provides information about the quality of the transformation prior to its execution. Benchmark calculations are provided for a set of small molecules.
Practical Calculation of Thermal Deformation and Manufacture Error uin Surface Grinding
Institute of Scientific and Technical Information of China (English)
周里群; 李玉平
2002-01-01
The paper submits a method to calculate thermal deformation and manufacture error in surface grinding.The author established a simplified temperature field model.and derived the thermal deformaiton of the ground workpiece,It is found that there exists not only a upwarp thermal deformation,but also a parallel expansion thermal deformation.A upwarp thermal deformation causes a concave shape error on the profile of the workpiece,and a parallel expansion thermal deformation causes a dimension error in height.The calculations of examples are given and compared with presented experiment data.
Directory of Open Access Journals (Sweden)
Ceme Ferreira Jordy
1995-09-01
Full Text Available Eletromiograma de superfície foi realizado no crânio e pescoço, durante stress provocado por frio, em 100 pacientes sofrendo cefaléia crônica isolada. Os resultados de diagnóstico obtidos com a eletromiografia revelaram erro de 24% a 32% na avaliação clínica da cefaléia tensional segundo os critérios anamnésicos referendados pelo Comitê de Classificação das Cefaléias, da Sociedade Internacional de Cefaléia (1988. A eletromiografia durante stress é proposta como novo critério de diagnóstico da Cefaléia tensional.We report the use of surface scalp and neck electromyography during experimental stress state in a series of 100 out-patients suffering from chronic tension headache. Results revealed a 24% to 32% of diagnostic errors in the diagnostic obtained by routine anamnestic procedures and following the criteria recommended by the Headache Classification Commitee of the International Headache Society (1988. The electromyography with stress is proposed as a new diagnostic criterion for tension headache.
International Nuclear Information System (INIS)
Spiers, F.W.; Whitwell, J.R.; Beddoe, A.H.
1978-01-01
The method of calculating dose factors for the haemopoietic marrow and endosteal tissues in human trabecular bone, used by Whitwell and Spiers for volume-seeking radionuclides, has been developed for the case of radionuclides which are deposited as very thin layers on bone surfaces. The Monte Carlo method is again used, but modifications to the computer program are made to allow for a surface rather than a volume source of particle emission. The principal change is the introduction of a surface-orientation factor which is shown to have a value of approximately 2, varying slightly with bone structure. Results are given for β-emitting radionuclides ranging from 171 Tm(anti Esub(β) = 0.025 MeV) to 90 Y(anti Esub(β) = 0.93 MeV), and also for the α-emitter 239 Pu. It is shown that where the particle ranges are short compared with the dimensions of the bone structures the dose factors for the surface seekers are much greater than those for the volume seekers. For long range particles the dose factors for surface- and volume-seeking radionuclides converge. Comparisons are given relating the dose factors calculated in this paper on the basis of measured bone structures to those of other workers based on single plane geometry. (author)
First Principles Calculations of Oxygen Adsorption on the UN(001) Surface
International Nuclear Information System (INIS)
Zhukovskii, Yuri F.; Bocharov, Dmitry; Kotomin, Eugene Alexej; Evarestov, Robert; Bandura, A.V.
2009-01-01
Fabrication, handling and disposal of nuclear fuel materials require comprehensive knowledge of their surface morphology and reactivity. Due to unavoidable contact with air components (even at low partial pressures), UN samples contain considerable amount of oxygen impurities affecting fuel properties. In this study we focus on reactivity of the energetically most stable (001) substrate of uranium nitride towards the atomic oxygen as one of initial stages for further UN oxidation. The basic properties of O atoms adsorbed on the UN(001) surface are simulated here combining the two first principles calculation methods based on the plane wave basis set and that of the localized orbitals.
SLOWNESS SURFACE CALCULATION FOR DIFFERENT MEDIA USING THE SYMBOLIC MATHEMATICS LANGUAGE MAPLE®
Directory of Open Access Journals (Sweden)
Piedrahita Carlos
2004-06-01
Full Text Available Starting from the equation in different media, we obtain the different type of waves that can exists in such media. The evaluation of the eigenvalues and eigenvectors let us construct the slowness surfaces. In general complex calculations case have to be made. In this work, routines were implemented in the symbolic language MAPLE® and the slowness surfaces were plotted. This work is relevant for the modelling of equivalent media that simulates natural fractured reservoirs, like those common in the Colombian foothills. It is important to understand the seismic response of this reservoirs for exploration of this areas.
DEFF Research Database (Denmark)
Clausen, Johan Christian; Damkilde, Lars; Andersen, Lars Vabbersgaard
2015-01-01
Purpose – The purpose of this paper is to present several methods on how to deal with yield surface discontinuities. The explicit formulations, first presented by Koiter (1953), result in multisingular constitutive matrices which can cause numerical problems in elasto-plastic finite element...... documented in the literature all present “easy” calculation examples, e.g. low friction angles and few elements. The amendments presented in this paper result in robust elasto-plastic computations, making the solution of “hard” problems possible without introducing approximations in the yield surfaces...... calculations. These problems, however, are not documented in previous literature. In this paper an amendment to the Koiter formulation of the constitutive matrices for stress points located on discontinuities is proposed. Design/methodology/approach – First, a review of existing methods of handling yield...
Hu, Liang; Zhao, Nannan; Gao, Zhijian; Mao, Kai; Chen, Wenyu; Fu, Xin
2018-05-01
Determination of the distribution of a generated acoustic field is valuable for studying ultrasonic transducers, including providing the guidance for transducer design and the basis for analyzing their performance, etc. A method calculating the acoustic field based on laser-measured vibration velocities on the ultrasonic transducer surface is proposed in this paper. Without knowing the inner structure of the transducer, the acoustic field outside it can be calculated by solving the governing partial differential equation (PDE) of the field based on the specified boundary conditions (BCs). In our study, the BC on the transducer surface, i.e. the distribution of the vibration velocity on the surface, is accurately determined by laser scanning measurement of discrete points and follows a data fitting computation. In addition, to ensure the calculation accuracy for the whole field even in an inhomogeneous medium, a finite element method is used to solve the governing PDE based on the mixed BCs, including the discretely measured velocity data and other specified BCs. The method is firstly validated on numerical piezoelectric transducer models. The acoustic pressure distributions generated by a transducer operating in an homogeneous and inhomogeneous medium, respectively, are both calculated by the proposed method and compared with the results from other existing methods. Then, the method is further experimentally validated with two actual ultrasonic transducers used for flow measurement in our lab. The amplitude change of the output voltage signal from the receiver transducer due to changing the relative position of the two transducers is calculated by the proposed method and compared with the experimental data. This method can also provide the basis for complex multi-physical coupling computations where the effect of the acoustic field should be taken into account.
Response surfaces and sensitivity analyses for an environmental model of dose calculations
Energy Technology Data Exchange (ETDEWEB)
Iooss, Bertrand [CEA Cadarache, DEN/DER/SESI/LCFR, 13108 Saint Paul lez Durance, Cedex (France)]. E-mail: bertrand.iooss@cea.fr; Van Dorpe, Francois [CEA Cadarache, DEN/DTN/SMTM/LMTE, 13108 Saint Paul lez Durance, Cedex (France); Devictor, Nicolas [CEA Cadarache, DEN/DER/SESI/LCFR, 13108 Saint Paul lez Durance, Cedex (France)
2006-10-15
A parametric sensitivity analysis is carried out on GASCON, a radiological impact software describing the radionuclides transfer to the man following a chronic gas release of a nuclear facility. An effective dose received by age group can thus be calculated according to a specific radionuclide and to the duration of the release. In this study, we are concerned by 18 output variables, each depending of approximately 50 uncertain input parameters. First, the generation of 1000 Monte-Carlo simulations allows us to calculate correlation coefficients between input parameters and output variables, which give a first overview of important factors. Response surfaces are then constructed in polynomial form, and used to predict system responses at reduced computation time cost; this response surface will be very useful for global sensitivity analysis where thousands of runs are required. Using the response surfaces, we calculate the total sensitivity indices of Sobol by the Monte-Carlo method. We demonstrate the application of this method to one site of study and to one reference group near the nuclear research Center of Cadarache (France), for two radionuclides: iodine 129 and uranium 238. It is thus shown that the most influential parameters are all related to the food chain of the goat's milk, in decreasing order of importance: dose coefficient 'effective ingestion', goat's milk ration of the individuals of the reference group, grass ration of the goat, dry deposition velocity and transfer factor to the goat's milk.
Patterson, C H
2012-09-07
Surface phonons, conductivities, and loss functions are calculated for reconstructed (2×1), p(2×2) and c(4×2) clean Si(001) surfaces, and (2×1) H and D covered Si(001) surfaces. Surface conductivities perpendicular to the surface are significantly smaller than conductivities parallel to the surface. The surface loss function is compared to high resolution electron energy loss measurements. There is good agreement between calculated loss functions and experiment for H and D covered surfaces. However, agreement between experimental data from different groups and between theory and experiment is poor for clean Si(001) surfaces. Formalisms for calculating electron energy loss spectra are reviewed and the mechanism of electron energy losses to surface vibrations is discussed.
International Nuclear Information System (INIS)
Malandra, L.J.; Beer, R.W.; Salton, R.B.; Spiegelman, S.R.; Cognevich, M.L.
1982-01-01
A quick-acting stud tensioner, for facilitating the loosening or tightening of a stud nut on a reactor vessel stud, has gripper jaws which when the tensioner is lowered into engagement with the upper end of the stud are moved inwards to grip the upper end and which when the tensioner is lifted move outward to release the upper end. (author)
Metadyn View: Fast web-based viewer of free energy surfaces calculated by metadynamics
Hošek, Petr; Spiwok, Vojtěch
2016-01-01
Metadynamics is a highly successful enhanced sampling technique for simulation of molecular processes and prediction of their free energy surfaces. An in-depth analysis of data obtained by this method is as important as the simulation itself. Although there are several tools to compute free energy surfaces from metadynamics data, they usually lack user friendliness and a build-in visualization part. Here we introduce Metadyn View as a fast and user friendly viewer of bias potential/free energy surfaces calculated by metadynamics in Plumed package. It is based on modern web technologies including HTML5, JavaScript and Cascade Style Sheets (CSS). It can be used by visiting the web site and uploading a HILLS file. It calculates the bias potential/free energy surface on the client-side, so it can run online or offline without necessity to install additional web engines. Moreover, it includes tools for measurement of free energies and free energy differences and data/image export.
Direct Monte Carlo dose calculation using polygon-surface computational human model
International Nuclear Information System (INIS)
Jeong, Jong Hwi; Kim, Chan Hyeong; Yeom, Yeon Su; Cho, Sungkoo; Chung, Min Suk; Cho, Kun-Woo
2011-01-01
In the present study, a voxel-type computational human model was converted to a polygon-surface model, after which it was imported directly to the Geant4 code without using a voxelization process, that is, without converting back to a voxel model. The original voxel model was also imported to the Geant4 code, in order to compare the calculated dose values and the computational speed. The average polygon size of the polygon-surface model was ∼0.5 cm 2 , whereas the voxel resolution of the voxel model was 1.981 × 1.981 × 2.0854 mm 3 . The results showed a good agreement between the calculated dose values of the two models. The polygon-surface model was, however, slower than the voxel model by a factor of 6–9 for the photon energies and irradiation geometries considered in the present study, which nonetheless is considered acceptable, considering that direct use of the polygon-surface model does not require a separate voxelization process. (author)
Density functional studies: First principles and semiempirical calculations of clusters and surfaces
International Nuclear Information System (INIS)
Sinnott, S.B.
1993-01-01
In the research presented here, various theoretical electronic structure techniques are utilized to analyze widely different systems from silicon clusters to transition metal solids and surfaces. For the silicon clusters, first principles density functional methods are used to investigate Si N for N = 2-8. The goal is to understand the different types of bonding that can occur in such small clusters where the coordination of the atoms differs substantially from that of the stable bulk tetrahedral bonding. Such uncoordinated structures can provide a good test of more approximate theories that can be used eventually to model silicon surfaces, of obvious technological importance. For the transition metal systems, non-self-consistent electronic structure methods are used to provide an understanding of the driving force for surface relaxations. An in-depth analysis of the results is presented and the physical basis of surface relaxation within the theory is discussed. In addition, the limitations inherent in calculations of metal surface relaxation are addressed. Finally, in an effort to increase understanding of approximate methods, a novel non-self-consistent density functional electronic structure method is developed that is ∼1000 times faster computationally than more sophisticated methods. This new method is tested for a variety of systems including diatomics, mixed clusters, surfaces and bulk lattices. The strengths and weaknesses of the new theory are discussed in detail, leading to greater understanding of non-self-consistent density functional theories as a whole
Ma, Xia-Xia; Li, Ze-Sheng
2018-01-01
Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O2 and perovskite based on the first-principles calculation. The results show that O2 is adsorbed on the (100) surface of MAPbI3 perovskite mainly by Van der Waals force. O2 adsorption makes the MAPbI3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO2). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O2 to form superoxide. The theoretical power conversion efficiency of the system with and without O2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O2 adsorption is slightly lower than that of the system without O2 adsorption. This result indicates that avoiding the introduction of O2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.
On the calculation of principle curvatures of the left-ventricular surfaces.
Claus, Piet; Choi, Hon Fai; D'hooge, Jan; Rademakers, Frank E
2008-01-01
A local description of the shape of the left ventricle is relevant in assessing the process of adverse ventricular remodeling, associated with most cardiac pathologies, and in monitoring reverse remodeling by therapy. To quantify local shape of the left ventricle, one can calculate the curvature of its epicardial or endocardial surface. The 3D geometry of the heart and especially the ventricles, can typically be described using finite element meshes. From a mathematical point of view these meshes provide a local parametrization of the surface in the 3-dimensional space. We discuss the analytic derivation of the principle curvatures of the left-ventricular surfaces given their smooth finite-element meshes and apply this derivation to assess the regional shape of the normal porcine left ventricle.
Calculation of reasonable exemption levels for surface contamination by measuring overall gamma ray
International Nuclear Information System (INIS)
Ogino, Haruyuki; Hattori, Takatoshi
2008-01-01
The present regulation on surface contamination [Bq/cm 2 ] is determined from a simple radiological model for the most hazardous radionuclides (Pu-239 for alpha emitters and Sr-90 for beta emitters) and its extremely conservative model is applied for all other alpha and beta emitters. In this study, reasonable exemption levels for surface contamination are calculated for each radionuclide by adopting an original radiological dose evaluation method for surface contamination that can be applied in radiation safety, transport safety and waste safety. Furthermore, a new concept of judging the exemption by estimating the overall contamination [Bq] on the objects from the measurement of gamma ray has been designed and a reasonable value was derived. We conclude that the overall exemption levels obtained by gamma ray measurement can be one order smaller than those obtained by the conventional method for some radionuclides, such as Mn-54, Co-60, Nb-94, Cs-134, Cs-137, Eu-152 and Eu-154. (author)
Surface complexation modeling calculation of Pb(II) adsorption onto the calcined diatomite
Ma, Shu-Cui; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia
2015-12-01
Removal of noxious heavy metal ions (e.g. Pb(II)) by surface adsorption of minerals (e.g. diatomite) is an important means in the environmental aqueous pollution control. Thus, it is very essential to understand the surface adsorptive behavior and mechanism. In this work, the Pb(II) apparent surface complexation reaction equilibrium constants on the calcined diatomite and distributions of Pb(II) surface species were investigated through modeling calculations of Pb(II) based on diffuse double layer model (DLM) with three amphoteric sites. Batch experiments were used to study the adsorption of Pb(II) onto the calcined diatomite as a function of pH (3.0-7.0) and different ionic strengths (0.05 and 0.1 mol L-1 NaCl) under ambient atmosphere. Adsorption of Pb(II) can be well described by Freundlich isotherm models. The apparent surface complexation equilibrium constants (log K) were obtained by fitting the batch experimental data using the PEST 13.0 together with PHREEQC 3.1.2 codes and there is good agreement between measured and predicted data. Distribution of Pb(II) surface species on the diatomite calculated by PHREEQC 3.1.2 program indicates that the impurity cations (e.g. Al3+, Fe3+, etc.) in the diatomite play a leading role in the Pb(II) adsorption and dominant formation of complexes and additional electrostatic interaction are the main adsorption mechanism of Pb(II) on the diatomite under weak acidic conditions.
Directory of Open Access Journals (Sweden)
Mohammad-Reza Ahmadian-Yazdi
2018-02-01
Full Text Available Perovskite solar cells (PSCs are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2 substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2 are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.
Ahmadian-Yazdi, Mohammad-Reza; Rahimzadeh, Amin; Chouqi, Zineb; Miao, Yihe; Eslamian, Morteza
2018-02-01
Perovskite solar cells (PSCs) are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2) substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2) are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.
Santos, Cherry S; Baldelli, Steven
2009-01-29
The gas-liquid interface of halide-free 1,3-dialkylimidazolium alkyl sulfates [RMIM][R-OSO(3)] with R chain length from C(1)-C(4) and C(8) has been studied systematically using the surface-specific sum frequency generation (SFG) vibrational spectroscopy and surface tension measurements. From the SFG spectra, vibrational modes from the methyl group of both cation and anion are observed for all ionic liquid samples considered in the present study. These results suggest the presence of both ions at the gas-liquid interface, which is further supported by surface tension measurements. Surface tension data show a decreasing trend as the alkyl chain in the imidazolium cation is varied from methyl to butyl chain, with a specific anion. A similar trend is observed when the alkyl chain of the anion is modified and the cation is fixed.
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2012-01-01
Roč. 48, MAY 2012 (2012), s. 267-275 ISSN 0021-9614 R&D Projects: GA ČR GA101/09/0010 Institutional research plan: CEZ:AV0Z20760514 Keywords : ionic liquid s * tris(pentafluoroethyl)trifluorophosphate * surface tension * group contribution method * density Subject RIV: BJ - Thermodynamics Impact factor: 2.297, year: 2012 http://www.sciencedirect.com/science/article/pii/S0021961411004770
Czech Academy of Sciences Publication Activity Database
Klomfar, Jaroslav; Součková, Monika; Pátek, Jaroslav
2014-01-01
Roč. 59, July (2014), s. 2263-2274 ISSN 0021-9568 R&D Projects: GA ČR GA13-00145S; GA ČR GA101/09/0010 Institutional support: RVO:61388998 Keywords : trihexyl(tetradecyl)phosphonium cation * 1-hexyl-3-methylimidazolium hexafluorophosphate * bis(trifluoromethylsulfonyl)imide anion * dicyanamide anion * experimental pvT data * surface tension * internal pressure Subject RIV: BJ - Thermodynamics Impact factor: 2.037, year: 2014
Directory of Open Access Journals (Sweden)
Ibrahim S. Khattab
2017-02-01
Full Text Available Density, viscosity, surface tension and molar volume of propylene glycol + water mixtures at 293, 298, 303, 308, 313, 318, and 323 K are reported, compared with the available literature data and the Jouyban–Acree model was used for mathematical correlation of the data. The mean relative deviation (MRD was used as an error criterion and the MRD values for data correlation of density, viscosity, surface tension and molar volume at different investigated temperatures are 0.1 ± 0.1%, 7.6 ± 6.4%, 3.4 ± 3.7%, and 0.4 ± 0.4%, respectively. The corresponding MRDs for the predicted properties after training the model using the experimental data at 298 K are 0.1 ± 0.2%, 12.8 ± 9.3%, 4.7 ± 4.1% and 0.6 ± 0.5%, respectively for density, viscosity, surface tension, and molar volume data.
International Nuclear Information System (INIS)
Ulissi, Zachary W.; Medford, Andrew J.; Bligaard, Thomas; Nørskov, Jens K.
2017-01-01
Surface reaction networks involving hydrocarbons exhibit enormous complexity with thousands of species and reactions for all but the very simplest of chemistries. We present a framework for optimization under uncertainty for heterogeneous catalysis reaction networks using surrogate models that are trained on the fly. The surrogate model is constructed by teaching a Gaussian process adsorption energies based on group additivity fingerprints, combined with transition-state scaling relations and a simple classifier for determining the rate-limiting step. The surrogate model is iteratively used to predict the most important reaction step to be calculated explicitly with computationally demanding electronic structure theory. Applying these methods to the reaction of syngas on rhodium(111), we identify the most likely reaction mechanism. Lastly, propagating uncertainty throughout this process yields the likelihood that the final mechanism is complete given measurements on only a subset of the entire network and uncertainty in the underlying density functional theory calculations.
International Nuclear Information System (INIS)
Ohya, Kaoru; Kawata, Jun; Mori, Ichiro
1990-01-01
Incidence angle dependences of secondary electron emission from a carbon surface by low energy electron and hydrogen atom are calculated using Monte Carlo simulations on the kinetic emission model. The calculation shows very small increase or rather decrease of the secondary electron yield with oblique incidence. It is explained in terms of not only multiple elastic collisions of incident particles with the carbon atoms but also small penetration depth of the particles comparable with the escape depth of secondary electrons. In addition, the two types of secondary electron emission are distinguished by using the secondary electron yield statistics; one is the emission due to trapped particles in the carbon, and the other is that due to backscattered particles. The high-yield component of the statistics on oblique incidence is more suppressed than those on normal incidence. (author)
Surface water management: a user's guide to calculate a water balance using the CREAMS model
International Nuclear Information System (INIS)
Lane, L.J.
1984-11-01
The hydrologic component of the CREAMS model is described and discussed in terms of calculating a surface water balance for shallow land burial systems used for waste disposal. Parameter estimates and estimation procedures are presented in detail in the form of a user's guide. Use of the model is illustrated with three examples based on analysis of data from Los Alamos, New Mexico and Rock Valley, Nevada. Use of the model in design of trench caps for shallow land burial systems is illustrated with the example applications at Los Alamos
International Nuclear Information System (INIS)
Agamaliyev, Z.A.; Tahirov, V.I.; Hasanov, Z.Y.; Quliyev, A.F.
2007-01-01
A binary solid solution single crystal growth method has been worked out. Cylinder feeding alloy with complex content distribution and truncated cone crucible are used. Second component distribution coefficient is more than unit. Content distribution along grown crystal is found by solving continuity equation. After reaching dynamic equilibrium state second component concentration in grown crystal is saturated the value of which is less than the average ona in the feeding alloy. Using the method Ge-Si perfect single crystals has been grown. Calculation method of melt surface displacement velocity has been offered as well
International Nuclear Information System (INIS)
Laletin, N.I.; Sultanov, N.V.; Boyarinov, V.F.
1992-01-01
Estimation is fulfilled of an influence of scattering anisotropy on K ef the TRX and BAPL assemblies by the WIMS-D4 program in the transport (TA) and linear-anisotropic (LAA) approximations. It is shown that account for the scattering anisotropy in the LAA in comparison with TA decreases K ef by 0.8% for TRX assemblies and by 0.5-0.6% for BAPL ones. For more detailed account for the scattering anisotropy in calculations of cylindrical and cluster cells in the one-velocity approximation is developed a technique for account for the anisotropy in the methods of surface pseudosources
Calculating the Maximum Density of the Surface Packing of Ions in Ionic Liquids
Kislenko, S. A.; Moroz, Yu. O.; Karu, K.; Ivaništšev, V. B.; Fedorov, M. V.
2018-05-01
The maximum density of monolayer packing on a graphene surface is calculated by means of molecular dynamics (MD) for ions of characteristic size and symmetry: 1-butyl-3-methylimidazolium [BMIM]+, tetrabutylammonium [TBA]+, tetrafluoroborate [BF4]-, dicyanamide [DCA]-, and bis(trifluoromethane) sulfonimide [TFSI]-. The characteristic orientations of ions in a closely packed monolayer are found. It is shown that the formation of a closely packed monolayer is possible for [DCA]- and [BF4]- anions only at surface charges that exceed the limit of the electrochemical stability of the corresponding ionic liquids. For the [TBA]+ cation, a monolayer structure can be observed at the charge of nearly 30 μC/cm2 attainable in electrochemical experiment.
Calculated Fermi surface properties of LaSn3 and YSn3 under pressure
International Nuclear Information System (INIS)
Kanchana, V.
2012-01-01
The electronic structure, Fermi surface and elastic properties of the iso-structural and iso-electronic LaSn 3 and YSn 3 intermetallic compounds are studied under pressure within the frame work of density functional theory including spin-orbit coupling. The LaSn 3 Fermi surface consists of two sheets, of which the second is very complex. Under pressure a third sheet appears around compression V/V 0 =0.94, while a small topology changes in the second sheet is seen at compression V/V 0 =0.90. This may be in accordance with the anomalous behavior in the superconducting transition temperature observed in LaSn 3 , which has been suggested to reflect a Fermi surface topological transition, along with a non-monotonic pressure dependence of the density of states at the Fermi level. The similar behavior is not observed in YSn 3 for which the Fermi surface includes three sheets already at ambient conditions, and the topology remains unchanged under pressure. The reason for the difference in behavior between LaSn 3 and YSn 3 is the role of spin-orbit coupling and the hybridization of La-4f state with the Sn-p state in the vicinity of the Fermi level, which is well explained using the band structure calculation. The elastic constants and related mechanical properties are calculated at ambient as well as at elevated pressures. The elastic constants increase with pressure for both compounds and satisfy the conditions for mechanical stability under pressure. (author)
Theoretical investigation of lead vapor adsorption on kaolinite surfaces with DFT calculations
Energy Technology Data Exchange (ETDEWEB)
Wang, Xinye [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Huang, Yaji, E-mail: heyyj@seu.edu.cn [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Pan, Zhigang [College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Wang, Yongxing; Liu, Changqi [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China)
2015-09-15
Highlights: • Al surface after dehydroxylation is active while Si surface is inert. • The active sites are the unsaturated Al atoms and O atoms losing H atom. • PbO is the most suitable species for adsorption. • Increasing the activities of Al atoms can enhance the performance of kaolinite. • Produce of amorphous silica is a potential path to enhance the performance of kaolinite. - Abstract: Kaolinite can be used as the in-furnace sorbent/additive to adsorb lead (Pb) vapor at high temperature. In this paper, the adsorptions of Pb atom, PbO molecule and PbCl{sub 2} molecule on kaolinie surfaces were investigated by density functional theory (DFT) calculation. Si surface is inert to Pb vapor adsorption while Al surfaces with dehydroxylation are active for the unsaturated Al atoms and the O atoms losing H atoms. The adsorption energy of PbO is much higher than that of Pb atom and PbCl{sub 2}. Considering the energy barriers, it is easy for PbO and PbCl{sub 2} to adsorb on Al surfaces but difficult to escape. The high energy barriers of de–HCl process cause the difficulties of PbCl{sub 2} to form PbO·Al{sub 2}O{sub 3}·2SiO{sub 2} with kaolinite. Considering the inertia of Si atoms and the activity of Al atoms after dehydroxylation, calcination, acid/alkali treatment and some other treatment aiming at amorphous silica producing and Al activity enhancement can be used as the modification measures to improve the performance of kaolinite as the in-furnace metal capture sorbent.
Calculation of three-dimensional fluid flow with multiple free surfaces
International Nuclear Information System (INIS)
Vander Vorst, M.J.; Chan, R.K.C.
1978-01-01
This paper presents a method for computing incompressible fluid flows with multiple free surfaces which are not restricted in their orientation. The method is presented in the context of the three-dimensional flow in a Mark I reactor pressure suppression system immediately following a postulated loss of coolant accident. The assumption of potential flow is made. The numerical method is a mixed Eulerian-Lagrangian formulation with the interior treated as Eulerian and the free surfaces as Lagrangian. The accuracy of solution hinges on the careful treatment of two important aspects. First, the Laplace equation for the potential is solved at interior points of the Eulerian finite difference mesh using a three-dimensional ''irregular star'' so that boundary conditions can be imposed at the exact position of the free surface. Second, the Lagrangian free surfaces are composed of triangular elements, upon each vertex of which is applied the fully nonlinear Bernoulli equation. One result of these calculations is the transient load on the suppression vessel during the vent clearing and bubble formation events of a loss of coolant accident
International Nuclear Information System (INIS)
Gibson, J.A.B.; Wrixon, A.D.
1979-01-01
Surface contamination is often measured as an indication of the general spread of radioactive contamination in a particular place. Derived working limits, (DWLs) for surface contamination provide figures against which to assess the significance of measurements. Derived working limits for surface contamination were first established for use in the nuclear energy industry. They were designed to cope with a wide range of unspecified radionuclides and were therefore based on the assumption that the contamination was due to the presence of the most hazardous radionuclides, e.g. 90 Sr, 210 Pb, 226 Ra and 239 Pu. While this assumption may still be appropriate when the radionuclide mixture is unknown, there are now many specialized uses of particular low-toxicity radionuclides in universities, hospitals and general industry. If it is known that only a particular radionuclide is present, the general DWL can be replaced by a more specific value. The methods for calculating DWLs for some of the more commonly employed low-toxicity radionuclides are described. The exposure pathways considered are (a) external radiation of the skin and inhalation of airborne material from contaminated surfaces in active areas; (b) external irradiation of the skin and ingestion from contaminated skin. Some consideration is given to the effect of the revised dose equivalent limits in the most recent recommendations of ICRP. (author)
Calculation of high-dimensional fission-fusion potential-energy surfaces in the SHE region
International Nuclear Information System (INIS)
Moeller, Peter; Sierk, Arnold J.; Ichikawa, Takatoshi; Iwamoto, Akira
2004-01-01
We calculate in a macroscopic-microscopic model fission-fusion potential-energy surfaces relevant to the analysis of heavy-ion reactions employed to form heavy-element evaporation residues. We study these multidimensional potential-energy surfaces both inside and outside the touching point.Inside the point of contact we define the potential on a multi-million-point grid in 5D deformation space where elongation, merging projectile and target spheroidal shapes, neck radius and projectile/target mass asymmetry are independent shape variables. The same deformation space and the corresponding potential-energy surface also describe the shape evolution from the nuclear ground-state to separating fragments in fission, and the fast-fission trajectories in incomplete fusion.For separated nuclei we study the macroscopic-microscopic potential energy, that is the ''collision surface'' between a spheroidally deformed target and a spheroidally deformed projectile as a function of three coordinates which are: the relative location of the projectile center-of-mass with respect to the target center-of-mass and the spheroidal deformations of the target and the projectile. We limit our study to the most favorable relative positions of target and projectile, namely that the symmetry axes of the target and projectile are collinear
Directory of Open Access Journals (Sweden)
H. Hernández Herrera
2004-09-01
Full Text Available En el trabajo se presenta el cálculo de las tensiones de cortante en la sección de la garganta para las uniones soldadassometidas a flexión con costuras de filete de sección transversal asimétrica cuando el plano de carga no pasa por el centrode flexión o no coincide con los ejes centroidales principales de inercia. Los resultados obtenidos por las expresiones decálculo propuestas se comparan con los obtenidos por el Método de los Elementos Finitos demostrando de esta manera lavalidez de las mismas.Palabras claves: Flexión, uniones soldadas, soldadura de filete.___________________________________________________________________________Abstract.In this paper is presented the bending shear stresses calculation in the throat area for asymmetric welded joints with filletweldings, when the load plane does not go by the flexion center or it do not coincide with the mains inertia centroidal axes.The results obtained by the proposed expressions are compared with those obtained by the Finite Elements Methoddemonstrating by this way the validity of the same ones.Key words: Bending, welded joints, fillet weldings.
Iwamatsu, Masao
2016-09-20
The free-energy barrier of filling a spherical cavity having an inner wall of various wettabilities is studied. The morphology and free energy of a lens-shaped droplet are determined from the minimum of the free energy. The effect of line tension on the free energy is also studied. Then, the equilibrium contact angle of the droplet is determined from the generalized Young's equation. By increasing the droplet volume within the spherical cavity, the droplet morphology changes from spherical with an equilibrium contact angle of 180° to a lens with a convex meniscus, where the morphological complete drying transition occurs. By further increasing the droplet volume, the meniscus changes from convex to concave. Then, the lens-shaped droplet with concave meniscus spreads over the whole inner wall, resulting in an equilibrium contact angle of 0° to leave a spherical bubble, where the morphological complete wetting transition occurs. Finally, the whole cavity is filled with liquid. The free energy shows a barrier from complete drying to complete wetting as a function of droplet volume, which corresponds to the energy barrier between the Cassie and Wenzel states of the superhydrophobic surface with spherical cavities. The free-energy maximum occurs when the meniscus of the droplet becomes flat, and it is given by an analytic formula. The effect of line tension is expressed by the scaled line tension, and this effect is largest at the free-energy maximum. The positive line tension increases the free-energy maximum, which thus increases the stability of the Cassie superhydrophobic state, whereas the negative line tension destabilizes the superhydrophobic state.
Calculation of electrical potentials on the surface of a realistic head model by finite differences
International Nuclear Information System (INIS)
Lemieux, L.; McBride, A.; Hand, J.W.
1996-01-01
We present a method for the calculation of electrical potentials at the surface of realistic head models from a point dipole generator based on a 3D finite-difference algorithm. The model was validated by comparing calculated values with those obtained algebraically for a three-shell spherical model. For a 1.25 mm cubic grid size, the mean error was 4.9% for a superficial dipole (3.75 mm from the inner surface of the skull) pointing in the radial direction. The effect of generator discretization and node spacing on the accuracy of the model was studied. Three values of the node spacing were considered: 1, 1.25 and 1.5 mm. The mean relative errors were 4.2, 6.3 and 9.3%, respectively. The quality of the approximation of a point dipole by an array of nodes in a spherical neighbourhood did not depend significantly on the number of nodes used. The application of the method to a conduction model derived from MRI data is demonstrated. (author)
Synthesis of ZnO nanoparticles for oil-water interfacial tension reduction in enhanced oil recovery
Soleimani, Hassan; Baig, Mirza Khurram; Yahya, Noorhana; Khodapanah, Leila; Sabet, Maziyar; Demiral, Birol M. R.; Burda, Marek
2018-02-01
Nanoparticles show potential use in applications associated with upstream oil and gas engineering to increase the performance of numerous methods such as wettability alteration, interfacial tension reduction, thermal conductivity and enhanced oil recovery operations. Surface tension optimization is an important parameter in enhanced oil recovery. Current work focuses on the new economical method of surface tension optimization of ZnO nanofluids for oil-water interfacial tension reduction in enhanced oil recovery. In this paper, zinc oxide (ZnO) nanocrystallites were prepared using the chemical route and explored for enhanced oil recovery (EOR). Adsorption of ZnO nanoparticles (NPs) on calcite (111) surface was investigated using the adsorption locator module of Materials Studio software. It was found that ZnO nanoparticles show maximum adsorption energy of - 253 kcal/mol. The adsorption of ZnO on the rock surface changes the wettability which results in capillary force reduction and consequently increasing EOR. The nanofluids have been prepared by varying the concentration of ZnO nanoparticles to find the optimum value for surface tension. The surface tension (ST) was calculated with different concentration of ZnO nanoparticles using the pendant drop method. The results show a maximum value of ST 35.57 mN/m at 0.3 wt% of ZnO NPs. It was found that the nanofluid with highest surface tension (0.3 wt%) resulted in higher recovery efficiency. The highest recovery factor of 11.82% at 0.3 wt% is due to the oil/water interfacial tension reduction and wettability alteration.
Calculating the Jc, B, T surface for commercial niobium tin conductors using a reduced state model
International Nuclear Information System (INIS)
Green, M.A.
1993-07-01
This report presents a method for calculating the J c , B, T critical surface for commercial grade niobium tin given an effective T c and B c2 and J c over a range of magnetic inductions B. Given the effective T c and B c2 and J c , one can estimate the J c over a range of magnetic inductions from 0.1 T to 0.8 times effective B c2 and a range of temperatures from 1.5 K to about 14 K. The effects of conductor strain can also be estimated using the method. A comparison between calculated values of J c and measurements is illustrated for a number of cases. The method presented in this report can be used to estimate the performance of niobium tin in magnets at temperatures different from those where measured data is available. The method of calculating the J c can also be used to estimate the effects of superconductor magnetization on the field quality at low fields
Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.
2015-11-01
Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G0W0, GW0 to partially self-consistent sc-GW0, as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW0-BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations.
International Nuclear Information System (INIS)
Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.
2015-01-01
Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G 0 W 0 , GW 0 to partially self-consistent sc-GW 0 , as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW 0 -BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations
First-principles calculation of adsorption of shale gas on CaCO3 (100) surfaces.
Luo, Qiang; Pan, Yikun; Guo, Ping; Wang, Zhouhua; Wei, Na; Sun, Pengfei; Liu, Yuxiao
2017-06-16
To demonstrate the adsorption strength of shale gas to calcium carbonate in shale matrix, the adsorption of shale gas on CaCO3 (100) surfaces was studied using the first-principles method, which is based on the density functional theory (DFT). The structures and electronic properties of CH4, C2H6, CO2 and N2 molecules were calculated by the generalized gradient approximation (GGA), for a coverage of 1 monolayer (ML). Under the same conditions, the density of states (DOS) of CaCO3 (100) surfaces before and after the adsorption of shale gas molecules at high-symmetry adsorption sites were compared. The results showed that the adsorption energies of CH4, C2H6, CO2 and N2 on CaCO3 (100) surfaces were between 0.2683 eV and -0.7388 eV. When a CH4 molecule was adsorbed at a hollow site and its 2 hydrogen atoms were parallel to the long diagonal (H3) on the CaCO3 (100) surface, it had the most stable adsorption, and the adsorption energy was only -0.4160 eV. The change of adsorption energy of CH4 was no more than 0.0535 eV. Compared with the DOS distribution of CH4 before adsorption, it shifted to the left overall after adsorption. At the same time, the partial density of states (PDOS) curves of CaCO3 (100) surfaces before and after adsorption basically overlapped. This work showed that the adsorption effect of shale gas on calcium carbonate is very weak, and the adsorption is physisorption at the molecular level.
Indentation of a floating elastic sheet: geometry versus applied tension.
Box, Finn; Vella, Dominic; Style, Robert W; Neufeld, Jerome A
2017-10-01
The localized loading of an elastic sheet floating on a liquid bath occurs at scales from a frog sitting on a lily pad to a volcano supported by the Earth's tectonic plates. The load is supported by a combination of the stresses within the sheet (which may include applied tensions from, for example, surface tension) and the hydrostatic pressure in the liquid. At the same time, the sheet deforms, and may wrinkle, because of the load. We study this problem in terms of the (relatively weak) applied tension and the indentation depth. For small indentation depths, we find that the force-indentation curve is linear with a stiffness that we characterize in terms of the applied tension and bending stiffness of the sheet. At larger indentations, the force-indentation curve becomes nonlinear and the sheet is subject to a wrinkling instability. We study this wrinkling instability close to the buckling threshold and calculate both the number of wrinkles at onset and the indentation depth at onset, comparing our theoretical results with experiments. Finally, we contrast our results with those previously reported for very thin, highly bendable membranes.
Ma, J.; Liu, Q.
2018-02-01
This paper presents an improved short circuit calculation method, based on pre-computed surface to determine the short circuit current of a distribution system with multiple doubly fed induction generators (DFIGs). The short circuit current, injected into power grid by DFIG, is determined by low voltage ride through (LVRT) control and protection under grid fault. However, the existing methods are difficult to calculate the short circuit current of DFIG in engineering practice due to its complexity. A short circuit calculation method, based on pre-computed surface, was proposed by developing the surface of short circuit current changing with the calculating impedance and the open circuit voltage. And the short circuit currents were derived by taking into account the rotor excitation and crowbar activation time. Finally, the pre-computed surfaces of short circuit current at different time were established, and the procedure of DFIG short circuit calculation considering its LVRT was designed. The correctness of proposed method was verified by simulation.
Research on Calculation of the IOL Tilt and Decentration Based on Surface Fitting
Directory of Open Access Journals (Sweden)
Lin Li
2013-01-01
Full Text Available The tilt and decentration of intraocular lens (IOL result in defocussing, astigmatism, and wavefront aberration after operation. The objective is to give a method to estimate the tilt and decentration of IOL more accurately. Based on AS-OCT images of twelve eyes from eight cases with subluxation lens after operation, we fitted spherical equation to the data obtained from the images of the anterior and posterior surfaces of the IOL. By the established relationship between IOL tilt (decentration and the scanned angle, at which a piece of AS-OCT image was taken by the instrument, the IOL tilt and decentration were calculated. IOL tilt angle and decentration of each subject were given. Moreover, the horizontal and vertical tilt was also obtained. Accordingly, the possible errors of IOL tilt and decentration existed in the method employed by AS-OCT instrument. Based on 6–12 pieces of AS-OCT images at different directions, the tilt angle and decentration values were shown, respectively. The method of the surface fitting to the IOL surface can accurately analyze the IOL’s location, and six pieces of AS-OCT images at three pairs symmetrical directions are enough to get tilt angle and decentration value of IOL more precisely.
Research on calculation of the IOL tilt and decentration based on surface fitting.
Li, Lin; Wang, Ke; Yan, Yan; Song, Xudong; Liu, Zhicheng
2013-01-01
The tilt and decentration of intraocular lens (IOL) result in defocussing, astigmatism, and wavefront aberration after operation. The objective is to give a method to estimate the tilt and decentration of IOL more accurately. Based on AS-OCT images of twelve eyes from eight cases with subluxation lens after operation, we fitted spherical equation to the data obtained from the images of the anterior and posterior surfaces of the IOL. By the established relationship between IOL tilt (decentration) and the scanned angle, at which a piece of AS-OCT image was taken by the instrument, the IOL tilt and decentration were calculated. IOL tilt angle and decentration of each subject were given. Moreover, the horizontal and vertical tilt was also obtained. Accordingly, the possible errors of IOL tilt and decentration existed in the method employed by AS-OCT instrument. Based on 6-12 pieces of AS-OCT images at different directions, the tilt angle and decentration values were shown, respectively. The method of the surface fitting to the IOL surface can accurately analyze the IOL's location, and six pieces of AS-OCT images at three pairs symmetrical directions are enough to get tilt angle and decentration value of IOL more precisely.
Error rate of automated calculation for wound surface area using a digital photography.
Yang, S; Park, J; Lee, H; Lee, J B; Lee, B U; Oh, B H
2018-02-01
Although measuring would size using digital photography is a quick and simple method to evaluate the skin wound, the possible compatibility of it has not been fully validated. To investigate the error rate of our newly developed wound surface area calculation using digital photography. Using a smartphone and a digital single lens reflex (DSLR) camera, four photographs of various sized wounds (diameter: 0.5-3.5 cm) were taken from the facial skin model in company with color patches. The quantitative values of wound areas were automatically calculated. The relative error (RE) of this method with regard to wound sizes and types of camera was analyzed. RE of individual calculated area was from 0.0329% (DSLR, diameter 1.0 cm) to 23.7166% (smartphone, diameter 2.0 cm). In spite of the correction of lens curvature, smartphone has significantly higher error rate than DSLR camera (3.9431±2.9772 vs 8.1303±4.8236). However, in cases of wound diameter below than 3 cm, REs of average values of four photographs were below than 5%. In addition, there was no difference in the average value of wound area taken by smartphone and DSLR camera in those cases. For the follow-up of small skin defect (diameter: <3 cm), our newly developed automated wound area calculation method is able to be applied to the plenty of photographs, and the average values of them are a relatively useful index of wound healing with acceptable error rate. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Impact of thermoplastic mask on X-ray surface dose calculated with Monte Carlo code
International Nuclear Information System (INIS)
Zhao Yanqun; Li Jie; Wu Liping; Wang Pei; Lang Jinyi; Wu Dake; Xiao Mingyong
2010-01-01
Objective: To calculate the effects of thermoplastic mask on X-ray surface dose. Methods: The BEAMnrc Monte Carlo Code system, designed especially for computer simulation of radioactive sources, was performed to evaluate the effects of thermoplastic mask on X-ray surface dose.Thermoplastic mask came from our center with a material density of 1.12 g/cm 2 . The masks without holes, with holes size of 0.1 cm x 0.1 cm, and with holes size of 0. 1 cm x 0.2 cm, and masks with different depth (0.12 cm and 0.24 cm) were evaluated separately. For those with holes, the material width between adjacent holes was 0.1 cm. Virtual masks with a material density of 1.38 g/cm 3 without holes with two different depths were also evaluated. Results: Thermoplastic mask affected X-rays surface dose. When using a thermoplastic mask with the depth of 0.24 cm without holes, the surface dose was 74. 9% and 57.0% for those with the density of 1.38 g/cm 3 and 1.12 g/cm 3 respectively. When focusing on the masks with the density of 1.12 g/cm 3 , the surface dose was 41.2% for those with 0.12 cm depth without holes; 57.0% for those with 0. 24 cm depth without holes; 44.5% for those with 0.24 cm depth with holes size of 0.1 cm x 0.2 cm;and 54.1% for those with 0.24 cm depths with holes size of 0.1 cm x 0.1 cm.Conclusions: Using thermoplastic mask during the radiation increases patient surface dose. The severity is relative to the hole size and the depth of thermoplastic mask. The surface dose change should be considered in radiation planning to avoid severe skin reaction. (authors)
Vries, de W.; Bakker, D.J.
1996-01-01
Methodologies are described for calculating critical loads of lead, cadmium, copper, zinc, nickel, chromium and mercury for soils and surface waters. The aspects which are discussed are: selection of a computation model, determination of environmental-quality criteria for the metals, collection of
Directory of Open Access Journals (Sweden)
Debashish Chowdhury
2012-01-01
Full Text Available Tension type headaches are common in clinical practice. Earlier known by various names, the diagnosis has had psychological connotations. Recent evidence has helped clarify the neurobiological basis and the disorder is increasingly considered more in the preview of neurologists. The classification, clinical features, differential diagnosis and treatment of tension type headache are discussed in this paper.
Tensions in Distributed Leadership
Ho, Jeanne; Ng, David
2017-01-01
Purpose: This article proposes the utility of using activity theory as an analytical lens to examine the theoretical construct of distributed leadership, specifically to illuminate tensions encountered by leaders and how they resolved these tensions. Research Method: The study adopted the naturalistic inquiry approach of a case study of an…
Oxide-cathode activation and surface temperature calculation of electron cooler
International Nuclear Information System (INIS)
Li Jie; Yang Xiaodong; Mao Lijun; Li Guohong; Yuan Youjin; Liu Zhanwen; Zhang Junhui; Yang Xiaotian; Ma Xiaoming; Yan Tailai
2011-01-01
The pollution on electron gun ceramic insulation of electron cooler restricted the operation of electron cooler at HIRFL-CSR main ring. To cool and accumulate ion beam well, the pollution was cleared and a new oxide-coated cathode was assembled. The processes of cathode replacement,vacuum chamber baking-out, and thermal decomposition of coating binders and alkaline earth metal carbonates, and cathode activation are presented. The electron gun perveance of 10.6 μA/V 1.5 was attained under the heating power of 60 W. The typical surface temperature of oxide-coated cathode that is calculated through grey-body radiation is 1 108 K which shows a comparable result to the experimental measurement 1 078 K. The perveance growth of electron gun during the electron cooler operation is also explained by partial activation of the cathode. (authors)
The calculation of the surface dose in examinations following cardiac catheterization
International Nuclear Information System (INIS)
Ewen, K.
1995-01-01
It is inevitable in examinations requiring patient exposure to high doses that the investigators and medical assistants receive high wholebody doses on account of fray radiation and, occasionally, also high partial body doses (hands) on account of the useful beam range. A number of different circumstances are adding up to create this extreme situation. In this connection, a mathematical method for the calculation of the surface dose (cutaneous dose rate) is described that is based on sets of parameters commonly used in diagnostic radiology: Set I of parameters: Tube voltage - current strength of tube - distance between focus and skin; - set II of parameters: Incidence dose rate of image intensifier - distance between focus and skin -distance between image intensifier and plane of ray incidence (skin). (orig./VHE) [de
Determination of the step dipole moment and the step line tension on Ag(0 0 1) electrodes
International Nuclear Information System (INIS)
Beltramo, G.L.; Ibach, H.; Linke, U.; Giesen, M.
2008-01-01
Using impedance spectroscopy, we determined the step dipole moment and the potential dependence of the step line tension of silver electrodes in contact with an electrolyte: (0 0 1) and vicinal surfaces (1 1 n) with n = 5, 7, 11 in 10 mM ClO 4 - -solutions were investigated. The step dipole moment is determined from the shift of the potential of zero charge (pzc) as a function of the surface step density. The dipole moment per step atom was found to be 3.5 ± 0.5 x 10 -3 e A. From the pzc and the potential dependence of the capacitance curves, the potential dependence of the surface tension of the vicinal surfaces is determined. The line tension of the steps is then calculated from the difference between the surface tensions of stepped (1 1 n) and the nominally step-free (0 0 1) surfaces. The results are compared to a previous study on Au(1 1 n) surfaces. For gold, the step line tension decreases roughly linear with potential, whereas a parabolic shape is observed for silver
International Nuclear Information System (INIS)
Shokuhi Rad, Ali; Zareyee, Daryoush; Peyravi, Majid; Jahanshahi, Mohsen
2016-01-01
Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.
Energy Technology Data Exchange (ETDEWEB)
Shokuhi Rad, Ali, E-mail: a.shokuhi@gmail.com [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Zareyee, Daryoush [Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Peyravi, Majid; Jahanshahi, Mohsen [Faculty of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)
2016-12-30
Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.
Coles, Phillip; Yurchenko, Sergei N.; Polyansky, Oleg; Kyuberis, Aleksandra; Ovsyannikov, Roman I.; Zobov, Nikolay Fedorovich; Tennyson, Jonathan
2017-06-01
We present a new spectroscopic potential energy surface (PES) for ^{14}NH_3, produced by refining a high accuracy ab initio PES to experimental energy levels taken predominantly from MARVEL. The PES reproduces 1722 matched J=0-8 experimental energies with a root-mean-square error of 0.035 cm-1 under 6000 cm^{-1} and 0.059 under 7200 cm^{-1}. In conjunction with a new DMS calculated using multi reference configuration interaction (MRCI) and H=aug-cc-pVQZ, N=aug-cc-pWCVQZ basis sets, an infrared (IR) line list has been computed which is suitable for use up to 2000 K. The line list is used to assign experimental lines in the 7500 - 10,500 cm^{-1} region and previously unassigned lines in HITRAN in the 6000-7000 cm^{-1} region. Oleg L. Polyansky, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Lorenzo Lodi, Jonathan Tennyson, Andrey Yachmenev, Sergei N. Yurchenko, Nikolai F. Zobov, J. Mol. Spec., 327 (2016) 21-30 Afaf R. Al Derzia, Tibor Furtenbacher, Jonathan Tennyson, Sergei N. Yurchenko, Attila G. Császár, J. Quant. Spectrosc. Rad. Trans., 161 (2015) 117-130
Haqiqi, M. T.; Yuliansyah; Suwinarti, W.; Amirta, R.
2018-04-01
Short Rotation Coppice (SRC) system is an option to provide renewable and sustainable feedstock in generating electricity for rural area. Here in this study, we focussed on application of Response Surface Methodology (RSM) to simplify calculation protocols to point out wood chip production and energy potency from some tropical SRC species identified as Bauhinia purpurea, Bridelia tomentosa, Calliandra calothyrsus, Fagraea racemosa, Gliricidia sepium, Melastoma malabathricum, Piper aduncum, Vernonia amygdalina, Vernonia arborea and Vitex pinnata. The result showed that the highest calorific value was obtained from V. pinnata wood (19.97 MJ kg-1) due to its high lignin content (29.84 %, w/w). Our findings also indicated that the use of RSM for estimating energy-electricity of SRC wood had significant term regarding to the quadratic model (R2 = 0.953), whereas the solid-chip ratio prediction was accurate (R2 = 1.000). In the near future, the simple formula will be promising to calculate energy production easily from woody biomass, especially from SRC species.
Calculating the optical properties of defects and surfaces in wide band gap materials
Deák, Peter
2018-04-01
The optical properties of a material critically depend on its defects, and understanding that requires substantial and accurate input from theory. This paper describes recent developments in the electronic structure theory of defects in wide band gap materials, where the standard local or semi-local approximations of density functional theory fail. The success of the HSE06 screened hybrid functional is analyzed in case of Group-IV semiconductors and TiO2, and shown that it is the consequence of error compensation between semi-local and non-local exchange, resulting in a proper derivative discontinuity (reproduction of the band gap) and a total energy which is a linear function of the fractional occupation numbers (removing most of the electron self-interaction). This allows the calculation of electronic transitions with accuracy unseen before, as demonstrated on the single-photon emitter NV(-) center in diamond and on polaronic states in TiO2. Having a reliable tool for electronic structure calculations, theory can contribute to the understanding of complicated cases of light-matter interaction. Two examples are considered here: surface termination effects on the blinking and bleaching of the light-emission of the NV(-) center in diamond, and on the efficiency of photocatalytic water-splitting by TiO2. Finally, an outlook is presented for the application of hybrid functionals in other materials, as, e.g., ZnO, Ga2O3 or CuGaS2.
International Nuclear Information System (INIS)
He, Kun; Wang, Xinying; Lu, Jiayu; Cui, Quansheng; Pang, Lei; Di, Dongxu; Zhang, Qiaogen
2015-01-01
To obtain the energy deposition curve is very important in the fields to which nanosecond pulse dielectric barrier discharges (NPDBDs) are applied. It helps the understanding of the discharge physics and fast gas heating. In this paper, an equivalent circuit model, composed of three capacitances, is introduced and a method of calculating the energy deposition curve is proposed for a nanosecond pulse surface dielectric barrier discharge (NPSDBD) plasma actuator. The capacitance C d and the energy deposition curve E R are determined by mathematically proving that the mapping from C d to E R is bijective and numerically searching one C d that satisfies the requirement for E R to be a monotonically non-decreasing function. It is found that the value of capacitance C d varies with the amplitude of applied pulse voltage due to the change of discharge area and is dependent on the polarity of applied voltage. The bijectiveness of the mapping from C d to E R in nanosecond pulse volumetric dielectric barrier discharge (NPVDBD) is demonstrated and the feasibility of the application of the new method to NPVDBD is validated. This preliminarily shows a high possibility of developing a unified approach to calculate the energy deposition curve in NPDBD. (paper)
Martínez, G M; Rennó, N; Fischer, E; Borlina, C S; Hallet, B; de la Torre Juárez, M; Vasavada, A R; Ramos, M; Hamilton, V; Gomez-Elvira, J; Haberle, R M
2014-08-01
The analysis of the surface energy budget (SEB) yields insights into soil-atmosphere interactions and local climates, while the analysis of the thermal inertia ( I ) of shallow subsurfaces provides context for evaluating geological features. Mars orbital data have been used to determine thermal inertias at horizontal scales of ∼10 4 m 2 to ∼10 7 m 2 . Here we use measurements of ground temperature and atmospheric variables by Curiosity to calculate thermal inertias at Gale Crater at horizontal scales of ∼10 2 m 2 . We analyze three sols representing distinct environmental conditions and soil properties, sol 82 at Rocknest (RCK), sol 112 at Point Lake (PL), and sol 139 at Yellowknife Bay (YKB). Our results indicate that the largest thermal inertia I = 452 J m -2 K -1 s -1/2 (SI units used throughout this article) is found at YKB followed by PL with I = 306 and RCK with I = 295. These values are consistent with the expected thermal inertias for the types of terrain imaged by Mastcam and with previous satellite estimations at Gale Crater. We also calculate the SEB using data from measurements by Curiosity's Rover Environmental Monitoring Station and dust opacity values derived from measurements by Mastcam. The knowledge of the SEB and thermal inertia has the potential to enhance our understanding of the climate, the geology, and the habitability of Mars.
Giusti, Fabrice; Popot, Jean-Luc; Tribet, Christophe
2012-07-17
Amphipols (APols) are short amphiphilic polymers designed to handle membrane proteins (MPs) in aqueous solutions as an alternative to small surfactants (detergents). APols adsorb onto the transmembrane, hydrophobic surface of MPs, forming small, water-soluble complexes, in which the protein is biochemically stabilized. At variance with MP/detergent complexes, MP/APol ones remain stable even at extreme dilutions. Pure APol solutions self-associate into well-defined micelle-like globules comprising a few APol molecules, a rather unusual behavior for amphiphilic polymers, which typically form ill-defined assemblies. The best characterized APol to date, A8-35, is a random copolymer of acrylic acid, isopropylacrylamide, and octylacrylamide. In the present work, the concentration threshold for self-association of A8-35 in salty buffer (NaCl 100 mM, Tris/HCl 20 mM, pH 8.0) has been studied by Förster resonance energy transfer (FRET) measurements and tensiometry. In a 1:1 mol/mol mixture of APols grafted with either rhodamine or 7-nitro-1,2,3-benzoxadiazole, the FRET signal as a function of A8-35 concentration is essentially zero below a threshold concentration of 0.002 g·L(-1) and increases linearly with concentration above this threshold. This indicates that assembly takes place in a narrow concentration interval around 0.002 g·L(-1). Surface tension measurements decreases regularly with concentration until a threshold of ca. 0.004 g·L(-1), beyond which it reaches a plateau at ca. 30 mN·m(-1). Within experimental uncertainties, the two techniques thus yield a comparable estimate of the critical self-assembly concentration. The kinetics of variation of the surface tension was analyzed by dynamic surface tension measurements in the time window 10 ms-100 s. The rate of surface tension decrease was similar in solutions of A8-35 and of the anionic surfactant sodium dodecylsulfate when both compounds were at a similar molar concentration of n-alkyl moieties. Overall, the
International Nuclear Information System (INIS)
Dembinski, W.; Zlotowski, T.
1973-01-01
A computer program written in FORTRAN language for calculations of final results of specific surface analysis based on BET theory has been described. Two gases - nitrogen and krypton were used. A technical description of measuring apparaturs is presented as well as theoretical basis of the calculations together with statistical analysis of the results for uranium compounds powders. (author)
A new approach for calculation of volume confined by ECR surface and its area in ECR ion source
International Nuclear Information System (INIS)
Filippov, A.V.
2007-01-01
The volume confined by the resonance surface and its area are important parameters of the balance equations model for calculation of ion charge-state distribution (CSD) in the electron-cyclotron resonance (ECR) ion source. A new approach for calculation of these parameters is given. This approach allows one to reduce the number of parameters in the balance equations model
SU-F-T-371: Development of a Linac Monte Carlo Model to Calculate Surface Dose
Energy Technology Data Exchange (ETDEWEB)
Prajapati, S; Yan, Y; Gifford, K [UT MD Anderson Cancer Center, Houston, TX (United States)
2016-06-15
Purpose: To generate and validate a linac Monte Carlo (MC) model for surface dose prediction. Methods: BEAMnrc V4-2.4.0 was used to model 6 and 18 MV photon beams for a commercially available linac. DOSXYZnrc V4-2.4.0 calculated 3D dose distributions in water. Percent depth dose (PDD) and beam profiles were extracted for comparison to measured data. Surface dose and at depths in the buildup region was measured with radiochromic film at 100 cm SSD for 4 × 4 cm{sup 2} and 10 × 10 cm{sup 2} collimator settings for open and MLC collimated fields. For the 6 MV beam, films were placed at depths ranging from 0.015 cm to 2 cm and for 18 MV, 0.015 cm to 3.5 cm in Solid Water™. Films were calibrated for both photon energies at their respective dmax. PDDs and profiles were extracted from the film and compared to the MC data. The MC model was adjusted to match measured PDD and profiles. Results: For the 6 MV beam, the mean error(ME) in PDD between film and MC for open fields was 1.9%, whereas it was 2.4% for MLC. For the 18 MV beam, the ME in PDD for open fields was 2% and was 3.5% for MLC. For the 6 MV beam, the average root mean square(RMS) deviation for the central 80% of the beam profile for open fields was 1.5%, whereas it was 1.6% for MLC. For the 18 MV beam, the maximum RMS for open fields was 3%, and was 3.1% for MLC. Conclusion: The MC model of a linac agreed to within 4% of film measurements for depths ranging from the surface to dmax. Therefore, the MC linac model can predict surface dose for clinical applications. Future work will focus on adjusting the linac MC model to reduce RMS error and improve accuracy.
Shi, Baoli; Wang, Yue; Jia, Lina
2011-02-11
Inverse gas chromatography (IGC) is an important technique for the characterization of surface properties of solid materials. A standard method of surface characterization is that the surface dispersive free energy of the solid stationary phase is firstly determined by using a series of linear alkane liquids as molecular probes, and then the acid-base parameters are calculated from the dispersive parameters. However, for the calculation of surface dispersive free energy, generally, two different methods are used, which are Dorris-Gray method and Schultz method. In this paper, the results calculated from Dorris-Gray method and Schultz method are compared through calculating their ratio with their basic equations and parameters. It can be concluded that the dispersive parameters calculated with Dorris-Gray method will always be larger than the data calculated with Schultz method. When the measuring temperature increases, the ratio increases large. Compared with the parameters in solvents handbook, it seems that the traditional surface free energy parameters of n-alkanes listed in the papers using Schultz method are not enough accurate, which can be proved with a published IGC experimental result. © 2010 Elsevier B.V. All rights reserved.
Calculation of rectal dose surface histograms in the presence of time varying deformations
International Nuclear Information System (INIS)
Roeske, John C.; Spelbring, Danny R.; Vijayakumar, S.; Forman, Jeffrey D.; Chen, George T.Y.
1996-01-01
Purpose: Dose volume (DVH) and dose surface histograms (DSH) of the bladder and rectum are usually calculated from a single treatment planning scan. These DVHs and DSHs will eventually be correlated with complications to determine parameters for normal tissue complication probabilities (NTCP). However, from day to day, the size and shape of the rectum and bladder may vary. The purpose of this study is to compare a more accurate estimate of the time integrated DVHs and DSHs of the rectum (in the presence of daily variations in rectal shape) to initial DVHs/DSHs. Methods: 10 patients were scanned once per week during the course of fractionated radiotherapy, typically accumulating a total of six scans. The rectum and bladder were contoured on each of the studies. The model used to assess effects of rectal contour deformation is as follows: the contour on a given axial slice (see figure) is boxed within a rectangle. A line drawn parallel to the AP axis through the rectangle equally partitions the box. Starting at the intersection of the vertical line and the rectal contour, points on the contour are marked off representing the same rectal dose point, even in the presence of distortion. Corresponding numbered points are used to sample the dose matrix and create a composite DSH. The model assumes uniform stretching of the rectal contour for any given axial cut, and no twist of the structure or vertical displacement. A similar model is developed for the bladder with spherical symmetry. Results: Normalized DSHs (nDSH) for each CT scan were calculated as well as the time averaged nDSH over all scans. These were compared with the nDSH from the initial planning scan. Individual nDSHs differed by 8% surface area irradiated at the 80% dose level, to as much as 20% surface area in the 70-100% dose range. DSH variations are due to position and shape changes in the rectum during different CT scans. The spatial distribution of dose is highly variable, and depends on the field
Energy Technology Data Exchange (ETDEWEB)
Pal, Sougata; Jasper-Toennies, Torben; Hack, Michael; Pehlke, Eckhard [Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel (Germany)
2011-07-01
The structure and electronic properties of the ZnO(0001) and ZnO(000 anti 1) surfaces as studied by density functional calculations are presented. The stability of the surface has already been investigated by various groups. The electronic surface band structure, however, in particular the existence of surface states and the differences between experimental band dispersion for both terminations, still appears to pose open problems. To address these issues, we compare Kohn Sham band structures and electrostatic potentials close to the surface for the relaxed (1 x 1)-surface, (2 x 2) vacancy reconstructions, and surfaces with pits. In particular the effect of the bending of the electrostatic potential at the surface on the eigenstates is quantified. Comparing the adsorption energies of Fe atoms for various adsorption sites on ZnO(000 anti 1), the fcc hollow position turned out to be energetically favorable. The oxidation state of the Fe atom is derived from the projected density of states.
The small surface oscillations of the gluon tube: The elongated bag
International Nuclear Information System (INIS)
Laperashvili, L.V.
1986-01-01
We investigate surface oscillations on a bag tube, inside of which is spanned a longitudinal color electric field, and calculate the masses for such vibrations conceived of as quasi-particles on the string. This represents the bag tube for several suggestive values of the parameters in the bag model. Contrary to similar calculations by Vladimirsky, we consider the case where there is a surface tension and we consider higher than zero angular momentum modes. The nonzero angular momentum modes have zero mass in the case of zero surface tension (when higher quantum corrections are ignored). Our considerations point towards the surface tension not being zero. (orig.)
National Aeronautics and Space Administration — To design and fabricate a light weight (few oz), very small (~2 inch length) parachute cord tension sensor demonstrator device.A major challenge for the CPAS (The...
Leadership. Using Creative Tension.
Cook, David L.
1986-01-01
Leadership involves maintaining a balance of the variables which comprise leadership. Love and fear, types of power, success and effectiveness, and driving and restraining forces are discussed as sources of the creative tension a leader uses to influence others. (MT)
DEFF Research Database (Denmark)
la Cour, M; Kiilgaard, Jens Folke; Eysteinsson, T
2000-01-01
To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide.......To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide....
Spontaneous tension haemopneumothorax
Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey
2008-01-01
Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such c...
Effects of Cu intercalation on the graphene/Ni(111) surface: density-functional calculations
International Nuclear Information System (INIS)
Kwon, Se Gab; Kang, Myung Ho
2012-01-01
The Cu-intercalated graphene/Ni(111) surface has been studied by using density-functional theory calculations. We find that (1) the intercalation-induced decoupling between graphene and the Ni(111) substrate begins sharply at a Cu coverage of about 0.75 ML, (2) at the optimal Cu coverage of 1 ML, graphene recovers an almost ideal Dirac-cone band structure with no band gap, and (3) the Dirac point is located at 0.17 eV below the Fermi level, indicating a small charge transfer from the substrate. Cu thus plays essentially the same role as Au in realizing quasi-free-standing graphene by intercalation. Our charge character analysis shows that the Dirac-cone bands near the Fermi level reveal a weakening of their π character when crossing the Ni d bands, suggesting that the resulting low Dirac-cone intensity could possibly be the origin of the recent photoemission report of a relatively large band gap of 0.18 eV.
Magnetism of CrO overlayers on Fe(001)bcc surface: first principles calculations
Félix-Medina, Raúl Enrique; Leyva-Lucero, Manuel Andrés; Meza-Aguilar, Salvador; Demangeat, Claude
2018-04-01
Riva et al. [Surf. Sci. 621, 55 (2014)] as well as Calloni et al. [J. Phys.: Condens. Matter 26, 445001 (2014)] have studied the oxydation of Cr films deposited on Fe(001)bcc through low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy. In the present work we perform a density functional approach within Quantum Expresso code in order to study structural and magnetic properties of CrO overlayers on Fe(001)bcc. The calculations are performed using DFT+U. The investigated systems include O/Cr/Fe(001)bcc, Cr/O/Fe(001)bcc, Cr0.25O0.75/Fe(001)bcc, as well as the O coverage Ox/Cr/Fe(001)bcc (x = 0.25; 0.50). We have found that the ordered CrO overlayer presents an antiferromagnetic coupling between Cr and Fe atoms. The O atoms are located closer to the Fe atoms of the surface than the Cr atoms. The ground state of the systems O/Cr/Fe(001)bcc and Cr/O/Fe(001)bcc corresponds to the O/Cr/Fe(001)bcc system with a magnetic coupling c(2 × 2). The effect of the O monolayer on Cr/Fe(001)bcc changes the ground state from p(1 × 1) ↓ to c(2 × 2) and produces an enhancement of the magnetic moments. The Ox overlayer on Cr/Fe(001)bcc produces an enhancement of the Cr magnetic moments.
The Plastic Tension Field Method
DEFF Research Database (Denmark)
Hansen, Thomas
2005-01-01
This paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used for predicting the failure load or, as a design method, to determine the optimal amount of internal web stiffeners. The new method is called the plastic tension field...... method. The method is based on the theory of plasticity and is analogous to the so-called diagonal compression field method developed for reinforced concrete beams with transverse stirrups, which is adopted in the common European concrete code (Eurocode 2). Many other theories have been developed...
Tension perturbations of black brane spacetimes
International Nuclear Information System (INIS)
Traschen, Jennie; Fox, Daniel
2004-01-01
We consider black brane spacetimes that have at least one spatial translation Killing field that is tangent to the brane. A new parameter, the tension of a spacetime, is defined. The tension parameter is associated with spatial translations in much the same way that the ADM mass is associated with the time translation Killing field. In this work, we explore the implications of the spatial translation symmetry for small perturbations around a background black brane. For static-charged black branes we derive a law which relates the tension perturbation to the surface gravity times the change in the horizon area, plus terms that involve variations in the charges and currents. We find that as a black brane evaporates the tension decreases. We also give a simple derivation of a first law for black brane spacetimes. These constructions hold when the background stress-energy is governed by a Hamiltonian, and the results include arbitrary perturbative stress-energy sources
Dobosz, Alexandra; Gancarz, Tomasz
2018-03-01
The data for the physicochemical properties viscosity, density, and surface tension obtained by different experimental techniques have been analyzed for liquid Al-Zn, Ag-Sn, Bi-Sn, Cu-Sn, and Sn-Zn eutectic alloys. All experimental data sets have been categorized and described by the year of publication, the technique used to obtain the data, the purity of the samples and their compositions, the quoted uncertainty, the number of data in the data set, the form of data, and the temperature range. The proposed standard deviations of liquid eutectic Al-Zn, Ag-Sn, Bi-Sn, Cu-Sn, and Sn-Zn alloys are 0.8%, 0.1%, 0.5%, 0.2%, and 0.1% for the density, 8.7%, 4.1%, 3.6%, 5.1%, and 4.0% for viscosity, and 1.0%, 0.5%, 0.3%, N/A, and 0.4% for surface tension, respectively, at a confidence level of 95%.
Kim, Ji-Su; Kim, Byung-Kook; Kim, Yeong-Cheol
2015-10-01
We investigated the effect of Cu alloying on S poisoning of Ni surfaces and nanoparticle morphologies using ab-initio thermodynamics calculations. Based on the Cu segregation energy and the S adsorption energy, the surface energy and nanoparticle morphology of pure Ni, pure Cu, and NiCu alloys were evaluated as functions of the chemical potential of S and the surface orientations of (100), (110), and (111). The constructed nanoparticle morphology was varied as a function of chemical potential of S. We find that the Cu added to Ni for NiCu alloys is strongly segregated into the top surface, and increases the S tolerance of the NiCu nanoparticles.
Combined tension and bending testing of tapered composite laminates
O'Brien, T. Kevin; Murri, Gretchen B.; Hagemeier, Rick; Rogers, Charles
1994-11-01
A simple beam element used at Bell Helicopter was incorporated in the Computational Mechanics Testbed (COMET) finite element code at the Langley Research Center (LaRC) to analyze the responce of tappered laminates typical of flexbeams in composite rotor hubs. This beam element incorporated the influence of membrane loads on the flexural response of the tapered laminate configurations modeled and tested in a combined axial tension and bending (ATB) hydraulic load frame designed and built at LaRC. The moments generated from the finite element model were used in a tapered laminated plate theory analysis to estimate axial stresses on the surface of the tapered laminates due to combined bending and tension loads. Surfaces strains were calculated and compared to surface strains measured using strain gages mounted along the laminate length. The strain distributions correlated reasonably well with the analysis. The analysis was then used to examine the surface strain distribution in a non-linear tapered laminate where a similarly good correlation was obtained. Results indicate that simple finite element beam models may be used to identify tapered laminate configurations best suited for simulating the response of a composite flexbeam in a full scale rotor hub.
Zhang, Yiou; Zhang, Jingzhao; Tse, Kinfai; Wong, Lun; Chan, Chunkai; Deng, Bei; Zhu, Junyi
Determining accurate absolute surface energies for polar surfaces of semiconductors has been a great challenge in decades. Here, we propose pseudo-hydrogen passivation to calculate them, using density functional theory approaches. By calculating the energy contribution from pseudo-hydrogen using either a pseudo molecule method or a tetrahedral cluster method, we obtained (111)/(-1-1-1) surfaces energies of Si, GaP, GaAs, and ZnS with high self-consistency. Our findings may greatly enhance the basic understandings of different surfaces and lead to novel strategies in the crystal growth. We would like to thank Su-huai Wei for helpful discussions. Computing resources were provided by the High Performance Cluster Computing Centre, Hong Kong Baptist University. This work was supported by the start-up funding and direct Grant with the Project.
Energy Technology Data Exchange (ETDEWEB)
MartInez-Casado, R [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Miret-Artes, S [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, Serrano 123, 28006 Madrid (Spain); Meyer, B [Interdisziplinaeres Zentrum fuer Molekulare Materialien ICMM and Computer-Chemie-Centrum CCC, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Naegelsbachstrasse 25, 91052 Erlangen (Germany); Traeger, F [Lehrstuhl fuer Physikalische Chemie I, Ruhr-Universitaet Bochum, 44801 Bochum (Germany); Woell, Ch, E-mail: r.martinezcasado@imperial.ac.u [Institut fuer Funktionelle Grenzflaechen, Karlsruher Institut fuer Technologie KIT, Kaiserstrasse 12, 76131 Karlsruhe (Germany)
2010-08-04
Diffraction intensities of a molecular He beam scattered off the clean and water-covered ZnO(101-bar0) surface have been simulated using a new potential model in conjunction with the close-coupling formalism. The effective corrugation functions for the systems He-ZnO(101-bar0) and He-H{sub 2}O/ZnO(101-bar0) have been obtained from density functional theory calculations within the Esbjerg-Noerskov approximation. Using these data a potential model is constructed consisting of a corrugated Morse potential at small He-surface distances and a semiempiric attractive part at larger distances. The diffraction patterns obtained from close-coupling calculations agree with the experimental data within about 10%, which opens the possibility to simulate He diffraction from surfaces of any structural complexity and to verify surface and adsorbate structures proposed theoretically by employing this kind of analysis.
Spontaneous tension haemopneumothorax.
Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey
2008-10-31
We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported.Aetiology and current approach to spontaneous haemothorax are discussed briefly.
Spontaneous tension haemopneumothorax
Directory of Open Access Journals (Sweden)
Itam Sarah
2008-10-01
Full Text Available Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported. Aetiology and current approach to spontaneous haemothorax are discussed briefly.
International Nuclear Information System (INIS)
Delchambre, E; Counsell, G; Kirk, A
2009-01-01
The non-uniformity of the target temperature due to micrometric hot spots (Hermann et al 2004 Phys. Scr. T 111 98) is an explanation for the experimental fact that near-infrared measurements yield higher temperature values than mid-infrared measurements (Hildebrandt et al 2003 InfraMation 2003 Proc. (Las Vegas, USA, October 2003), Delchambre et al 2005 J. Nucl. Mater. 337-339 1069). The issue of micrometric hot spot disturbance in the surface temperature (T surf ) measurement and heat load calculation is addressed in this paper. The theoretical investigation at 3, 5 and 12 μm and experiments in the range 3.5-5 μm indicate that the surface state can play an important role in the non-uniform heating surface and consequently in the overestimation of the bulk temperature. The contribution of the hot spots to temperature measurements and flux calculations has been simulated at different wavelengths. Calculations show that (1) the overestimation of the bulk temperature decreases with the wavelength and (2) the overestimation depends on the temperature difference, ΔT, between the bulk and the micrometric hot spots. In addition, experiments have been carried out in order to compare the flux calculations at different wavelengths on different graphite (polished, dusty). The results obtained are very sensitive to the surface state pointing out the difficulties in improving the heat flux calculation model, since the surface state can change during the plasma discharges. This paper shows that the problem of non-homogenous surface temperature can be significantly diminished on working at longer wavelengths.
DEFF Research Database (Denmark)
Aldén, M.; Abrikosov, I. A.; Johansson, B.
1994-01-01
of the frozen-core and atomic-sphere approximation but, in addition, includes the dipole contribution to the intersphere potential. Within the concept of complete screening, we identify the surface core-level binding-energy shift with the surface segregation energy of a core-ionized atom and use the Green......'s-function impurity technique in a comprehensive study of the surface core-level shifts (SCLS) of the 4d and 5d transition metals. In those cases, where observed data refer to single crystals, we obtain good agreement with experiment, whereas the calculations typically underestimate the measured shift obtained from...
Hsieh, Po-Fan; Wang, Yu-De; Huang, Chi-Ping; Wu, Hsi-Chin; Yang, Che-Rei; Chen, Guang-Heng; Chang, Chao-Hsiang
2016-07-01
We proposed a mathematical formula to calculate contact surface area between a tumor and renal parenchyma. We examined the applicability of using contact surface area to predict renal function after partial nephrectomy. We performed this retrospective study in patients who underwent partial nephrectomy between January 2012 and December 2014. Based on abdominopelvic computerized tomography or magnetic resonance imaging, we calculated the contact surface area using the formula (2*π*radius*depth) developed by integral calculus. We then evaluated the correlation between contact surface area and perioperative parameters, and compared contact surface area and R.E.N.A.L. (Radius/Exophytic/endophytic/Nearness to collecting system/Anterior/Location) score in predicting a reduction in renal function. Overall 35, 26 and 45 patients underwent partial nephrectomy with open, laparoscopic and robotic approaches, respectively. Mean ± SD contact surface area was 30.7±26.1 cm(2) and median (IQR) R.E.N.A.L. score was 7 (2.25). Spearman correlation analysis showed that contact surface area was significantly associated with estimated blood loss (p=0.04), operative time (p=0.04) and percent change in estimated glomerular filtration rate (p contact surface area and R.E.N.A.L. score independently affected percent change in estimated glomerular filtration rate (p contact surface area was a better independent predictor of a greater than 10% change in estimated glomerular filtration rate compared to R.E.N.A.L. score (AUC 0.86 vs 0.69). Using this simple mathematical method, contact surface area was associated with surgical outcomes. Compared to R.E.N.A.L. score, contact surface area was a better predictor of functional change after partial nephrectomy. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
Soil heat flux at the surface (G0) is strongly influenced by whether the soil is shaded or sunlit, and therefore can have large spatial variability for incomplete vegetation cover, such as across the interrows of row crops. Most practical soil-plant-atmosphere energy balance models calculate G0 as a...
2010-07-01
... Manufacturing Standards for Aluminum Recreational Boat Surface Coating Operations § 63.5752 How do I calculate... fraction of organic HAP in coating i, kilograms of organic HAP per kilogram of coating. p = number of..., activator, or additive k, kilograms per liter. Wk= mass fraction of organic HAP in thinner, activator, or...
Croteau, T; Bertram, A K; Patey, G N
2008-10-30
Grand canonical Monte Carlo calculations are used to determine water adsorption and structure on defect-free kaolinite surfaces as a function of relative humidity at 235 K. This information is then used to gain insight into ice nucleation on kaolinite surfaces. Results for both the SPC/E and TIP5P-E water models are compared and demonstrate that the Al-surface [(001) plane] and both protonated and unprotonated edges [(100) plane] strongly adsorb at atmospherically relevant relative humidities. Adsorption on the Al-surface exhibits properties of a first-order process with evidence of collective behavior, whereas adsorption on the edges is essentially continuous and appears dominated by strong water lattice interactions. For the protonated and unprotonated edges no structure that matches hexagonal ice is observed. For the Al-surface some of the water molecules formed hexagonal rings. However, the a o lattice parameter for these rings is significantly different from the corresponding constant for hexagonal ice ( Ih). A misfit strain of 14.0% is calculated between the hexagonal pattern of water adsorbed on the Al-surface and the basal plane of ice Ih. Hence, the ring structures that form on the Al-surface are not expected to be good building-blocks for ice nucleation due to the large misfit strain.
Folta, Bernarr
This paper discusses the rationale and teaching methods for a six-week unit, for a high school freshman English Class, on perception, semantics, and writing, which places special focus on developing tension in student writing. The first four objectives of the course focus on perception and the next two focus on semantics. The seventh…
DEFF Research Database (Denmark)
Celik, Tim Holst
on the statesituated tension-filled functional relationship between legitimation and accumulation, the study both historically and theoretically reworks this approach and reapplies it for the post-1970s/1990s governance period. It asks whether and to what extent governance has served as a distinctive post- 1970s/1990s...
Egenvall, Agneta; Eisersiö, Marie; Rhodin, Marie; van Weeren, P.R.; Roepstorff, Lars
2015-01-01
Riders generally use reins as a means for communication with the horse. At present, the signalling pattern is poorly understood. The aim of this study was to illustrate and analyse the rein tension patterns in a number of rider/horse combinations across a variety of exercises in the canter gait. Our
DEFF Research Database (Denmark)
Kiilgaard, Jens Folke; Pedersen, D B; Eysteinsson, T
2004-01-01
The authors have previously reported that carbonic anhydrase inhibitors such as acetazolamide and dorzolamide raise optic nerve oxygen tension (ONPO(2)) in pigs. The purpose of the present study was to investigate whether timolol, which belongs to another group of glaucoma drugs called beta...
Necessary Tension in Marine Risers Tension des colonnes montantes en mer
Directory of Open Access Journals (Sweden)
Lubinski A.
2006-11-01
Full Text Available The tension governing transverse static and dynamic deflections in a riser is not the actual tension but the so-called « effective tension » The concept of effective tension and effective compression is thoroughly explained, and means for calculating effective forces are given. Numerical examples are worked out for risers whose length is between 152 m (520 ft and 920 m (3020 ft. The reciprocal of maximum bending moment of the vicinity of the hall joint is plotted versus the effective tension of the ball joint. Bending moments used were obtained through use of static and dynamic computer programs applied ta a variety of conditions of wave loading, use or non-use of buoyant moterial sleeves, etc. The most important parameters affecting riser performance are the effective La tension régissant les déflections transversales statiques et dynamiques d'une colonne montante n'est pas la tension réelle mais ce qu'on appelle « la tension effective ». Le concept de tension ou de compression effective est expliqué en détail et la façon de calculer les forces effectives est indiquée dans cet article. Des exemples numériques sont développés pour des colonnes montantes de longueur comprise entre 152 m (520 ft et 920 m (3 020 ft. On a tracé la courbe de l'inverse du moment fléchissant en fonction de la tension effective à l'articulation. Les moments fléchissants utilisés ont été calculés par ordinateur en utilisant des programmes dynamiques et statiques pour des conditions variées d'action des vagues, la colonne montante étant ou non munie de manchettes de flottabilité, etc. Les deux paramètres les plus importants qui affectent le bon comportement d'une colonne montante sont la tension effective et la charge latérale.
Directory of Open Access Journals (Sweden)
Simon Mitternacht
2016-02-01
Full Text Available Calculating solvent accessible surface areas (SASA is a run-of-the-mill calculation in structural biology. Although there are many programs available for this calculation, there are no free-standing, open-source tools designed for easy tool-chain integration. FreeSASA is an open source C library for SASA calculations that provides both command-line and Python interfaces in addition to its C API. The library implements both Lee and Richards’ and Shrake and Rupley’s approximations, and is highly configurable to allow the user to control molecular parameters, accuracy and output granularity. It only depends on standard C libraries and should therefore be easy to compile and install on any platform. The library is well-documented, stable and efficient. The command-line interface can easily replace closed source legacy programs, with comparable or better accuracy and speed, and with some added functionality.
Nandi, Prithwish Kumar; Valsakumar, M C; Chandra, Sharat; Sahu, H K; Sundar, C S
2010-09-01
We calculate properties like equilibrium lattice parameter, bulk modulus and monovacancy formation energy for nickel (Ni), iron (Fe) and chromium (Cr) using Kohn-Sham density functional theory (DFT). We compare the relative performance of local density approximation (LDA) and generalized gradient approximation (GGA) for predicting such physical properties for these metals. We also make a relative study between two different flavors of GGA exchange correlation functional, namely PW91 and PBE. These calculations show that there is a discrepancy between DFT calculations and experimental data. In order to understand this discrepancy in the calculation of vacancy formation energy, we introduce a correction for the surface intrinsic error corresponding to an exchange correlation functional using the scheme implemented by Mattsson et al (2006 Phys. Rev. B 73 195123) and compare the effectiveness of the correction scheme for Al and the 3d transition metals.
Coulomb string tension, asymptotic string tension, and the gluon chain
Greensite, Jeff; Szczepaniak, Adam P.
2014-01-01
We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.
Oxide nanostructures on a Nb surface and related systems: experiments and ab initio calculations
International Nuclear Information System (INIS)
Kuznetsov, Mikhail V; Razinkin, A S; Ivanovskii, Alexander L
2011-01-01
This review discusses the state of the art in two related research areas: the surfaces of niobium and of its related group IV-VI transition metals, and surface (primarily oxide) nanostructures that form on niobium (and group IV-VI d-metals) due to gas adsorption or impurity diffusion from the bulk. Experimental (X-ray photoelectron spectroscopy, photoelectron diffraction, scanning tunneling microscopy) and theoretical (ab initio simulation) results on d-metal surfaces are summarized and reviewed. (reviews of topical problems)
Self-consistent density functional calculation of the image potential at a metal surface
International Nuclear Information System (INIS)
Jung, J; Alvarellos, J E; Chacon, E; GarcIa-Gonzalez, P
2007-01-01
It is well known that the exchange-correlation (XC) potential at a metal surface has an image-like asymptotic behaviour given by -1/4(z-z 0 ), where z is the coordinate perpendicular to the surface. Using a suitable fully non-local functional prescription, we evaluate self-consistently the XC potential with the correct image behaviour for simple jellium surfaces in the range of metallic densities. This allows a proper comparison between the corresponding image-plane position, z 0 , and other related quantities such as the centroid of an induced charge by an external perturbation. As a by-product, we assess the routinely used local density approximation when evaluating electron density profiles, work functions, and surface energies by focusing on the XC effects included in the fully non-local description
A Modified Approach in Modeling and Calculation of Contact Characteristics of Rough Surfaces
Directory of Open Access Journals (Sweden)
J.A. Abdo
2005-12-01
Full Text Available A mathematical formulation for the contact of rough surfaces is presented. The derivation of the contact model is facilitated through the definition of plastic asperities that are assumed to be embedded at a critical depth within the actual surface asperities. The surface asperities are assumed to deform elastically whereas the plastic asperities experience only plastic deformation. The deformation of plastic asperities is made to obey the law of conservation of volume. It is believed that the proposed model is advantageous since (a it provides a more accurate account of elasticplastic behavior of surfaces in contact and (b it is applicable to model formulations that involve asperity shoulder-to shoulder contact. Comparison of numerical results for estimating true contact area and contact force using the proposed model and the earlier methods suggest that the proposed approach provides a more realistic prediction of elastic-plastic contact behavior.
Adsorption of Ti on LiAlH4 surfaces studied by band structure calculations
International Nuclear Information System (INIS)
Loevvik, O.M.
2004-01-01
LiAlH 4 is a potential light-weight hydrogen storage material if hydrogenation can be made reversible. In NaAlH 4 this may be done by adding small amounts of Ti, but the same effect has not yet been observed in LiAlH 4 . To understand these mechanisms, detailed studies of the materials with and without the additive are necessary. In this study, two-dimensional slabs representing the open (0 1 0) and densely packed (1 0 1) surfaces of LiAlH 4 have been used to model adsorption of titanium atoms on those surfaces. The results show that the Ti atom tends to move below the surface towards interstitial sites rather than binding to a Li ion or AlH 4 complex at the surface
Self-consistent density functional calculation of the image potential at a metal surface
Energy Technology Data Exchange (ETDEWEB)
Jung, J [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Alvarellos, J E [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Chacon, E [Instituto de Ciencias de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain); GarcIa-Gonzalez, P [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain)
2007-07-04
It is well known that the exchange-correlation (XC) potential at a metal surface has an image-like asymptotic behaviour given by -1/4(z-z{sub 0}), where z is the coordinate perpendicular to the surface. Using a suitable fully non-local functional prescription, we evaluate self-consistently the XC potential with the correct image behaviour for simple jellium surfaces in the range of metallic densities. This allows a proper comparison between the corresponding image-plane position, z{sub 0}, and other related quantities such as the centroid of an induced charge by an external perturbation. As a by-product, we assess the routinely used local density approximation when evaluating electron density profiles, work functions, and surface energies by focusing on the XC effects included in the fully non-local description.
Three-Dimensional Elasto-Plastic Calculations Using Yield Surfaces with Corner Discontinuities
DEFF Research Database (Denmark)
Clausen, Johan; Andersen, Lars; Damkilde, Lars
2009-01-01
This paper presents a simple and efficient way of dealing with the corners found in many yield surfaces, especially in geotechnical engineering. The efficiency of the method is demonstrated through three-dimensional computational examples.......This paper presents a simple and efficient way of dealing with the corners found in many yield surfaces, especially in geotechnical engineering. The efficiency of the method is demonstrated through three-dimensional computational examples....
Calculation of Reflectance and Transmittance of Coating With Optically Rough Surfaces
International Nuclear Information System (INIS)
El-Depsy, A.; Shawky, A.M.
2011-01-01
For ideal surfaces, components of the reflected beam are related to the components of the incident beam by Fresnel reflection equation. The surfaces encountered in engineering applications deviate from ideal as a result of roughness, oxidization and contamination; hence the Radiative properties of these real surfaces differ greatly from those predicted by electromagnetic theory. In regard to problems of radiative heat transfer; the roughness of surfaces may be divided into two categories: (1) small surface irregularities such that the incident radiation cannot undergo more than a single reflection, (2) deep cavities in which the incident radiation undergoes multi-reflection. The normally incident radiation from rough surface having small irregularities is reflected partly specularly and partly diffusely [1]. Kubelka-Munk theory (K-M) [2] describes optical characteristics (e.g. reflectance, transmittance and absorbance) by a variety of light scattering media including paints, textiles and papers, and It is widely used in various industrial applications. Moder developments in radiative transfer theory (RTT) enable the derivation of (K-M) parameters from first principles [3]. Kubelka and Munk proposed a theory based on a model of two light fluxes travelling in the forward and backward directions. Subsequently a number of authors refined the theory and compared it with experimental data [4]. Several authors attempted to relate the Kubelka- Munk coefficients to the transport coefficients [5,6
Verification of heat flux and temperature calculation on the control rod outer surface
Taler, Jan; Cebula, Artur
2011-12-01
The paper presents heat transfer calculation results concerning a control rod of Forsmark Nuclear Power Plant (NPP). The part of the control rod, which is the object of interest, is surrounded by a mixing region of hot and cold flows and, as a consequence, is subjected to thermal fluctuations. The paper describes a numerical test which validates the method based on the solution of the inverse heat conduction problem (IHCP). The comparison of the results achieved by two methods, computational fluid dynamics (CFD) simulations and IHCP, including a description of the IHCP method used in the calculation process, shows a very good agreement between the methods.
The tension of framed membranes from computer simulations
DEFF Research Database (Denmark)
Hamkens, Daniel; Jeppesen, Claus; Ipsen, John H.
2018-01-01
the membranes display power-law characteristics for the equation of state, while higher tension levels includes both an extended linear (elastic) as well as a highly non-linear stretching regime. For semi-flexible membranes a transition from extended to buckled conformations takes place at negative frame......Abstract.: We have analyzed the behavior of a randomly triangulated, self-avoiding surface model of a flexible, fluid membrane subject to a circular boundary by Wang-Landau Monte Carlo computer simulation techniques. The dependence of the canonical free energy and frame tension on the frame area...... is obtained for flexible membranes. It is shown that for low bending rigidities the framed membrane is only stable above a threshold tension, suggesting a discontinuous transition from the collapsed (branched polymer) state to a finite tension extended state. In a tension range above this threshold tension...