Variational principles in chemical equilibria: Complex chemical systems with interacting subsystems
Zilbergleyt, B
2010-01-01
The goal of the paper is to derive a revised condition of global equilibrium in complex chemical systems as variational principle in formalism of recently developed discrete thermodynamics (DTD) of chemical equilibria. In classical approach the problem of complex equilibrium is solved by minimization of the system Gibbsâ free energy subject to logistic constraints. DTD demands any isolated system to comprise smaller subentities, which individual equilibria are based on the balance of internal and external thermodynamic forces, acting against them. The internal forces are equal to the subsystems thermodynamic affinities, while external forces originate from subsystems mutual interactions. Those interactions impose additional constraints on the mother system Gibbsâ free energy minimum. Basic expression of discrete thermodynamics, being multiplied by subsystems deviations from their âtrueâ thermodynamic equilibria, is naturally identical to dâAlembertâs principle. A thermodynamic ve...
Structures and Chemical Equilibria of Some N-Heterocycles Containing Amide Linkages
Directory of Open Access Journals (Sweden)
N. H. Abd El Moneim
2003-05-01
Full Text Available Structures and chemical equilibria of 5-carboxy-2-thiouracil (1, 5,6-diphenyl-3-hydroxy-1,2,4-triazine (2, 1-phenyl-3-methyl-5-pyrazolone (3 and 2-mercapto-4,6-dimethylpyrimidine hydrochloride (4 are reported. Their electronic transitions are assigned and pK values are evaluated and discussed.
van Bennekom, Joost G.; Winkelman, Jozef G. M.; Venderbosch, Robertus H.; Nieland, Sebastiaan D. G. B.; Heeres, Hero J.
2012-01-01
A solution method was developed to calculate the simultaneous phase and chemical equilibria in high-pressure methanol synthesis (P = 20 MPa, 463
Vapor-Liquid and Chemical Equilibria in the Ethanol + Acetic Acid System at 348.15 K.
Czech Academy of Sciences Publication Activity Database
Bernatová, Svatoslava; Aim, Karel; Wichterle, Ivan
2007-01-01
Roč. 52, 1 (2007) , s. 20-23. ISSN 0021-9568 R&D Projects: GA ČR(CZ) GA203/03/1588 Institutional research plan: CEZ:AV0Z40720504 Keywords : phase equilibria * chemical equilibria * esterification Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.729, year: 2007
Chemical exchange equilibria in isotope separation. Part I : Evaluation of separation factors
International Nuclear Information System (INIS)
The theory of chemical exchange equilibria as applied to the isotope separation processes and the isotope effects on equilibrium constants of different exchange reactions has come a long way since its inception by Urey and Rittenberg. An attempt has been made to bring relevant information together and present a unified approach to isotopic chemical exchange equilibrium constant evaluation and its implications to separation processes. (auth.)
Thermodynamic modeling of chemical equilibria in metal extraction
International Nuclear Information System (INIS)
Models of equilibrium extraction data are being developed for use in computer simulations of metal extraction processes. The correlations are based on chemical mass action principles in which the effects of metal complexation and aqueous phase activity coefficients are considered. Activity coefficients in mixed electrolyte solutions at high ionic strengths are calculated using methods available in the literature. This modeling approach is demonstrated for HNO3 extraction with both the PIREX and TRUEX solvents and for Am3+ extraction by octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide, which is the primary extractant in the TRUEX solvent. 27 refs., 4 figs., 4 tabs
International Nuclear Information System (INIS)
Described are some phase equilibria and chemical thermodynamics of systems relevant to the production and operation of the so-called ''advanced'' fast breeder reactor fuels. The systems discussed include UPu carbides, nitrides, oxycarbides and carbonitrides. Some examples of the application of these phase equilibria to the preparation, fabrication and behaviour of the materials in temperature gradients appropriate to reactor conditions are presented. Finally, aspects of the complex four and five component, U-C-O-N and U-Pu-C-O-N systems are discussed, a detailed knowledge of which is required for an analysis of advanced fuel behaviour
Chemical equilibria between C-S-H and ettringite, at 20 and 85 deg. C
International Nuclear Information System (INIS)
Mixes of C-S-H and ettringite were synthesized in suspension systems and their equilibria were studied at 20 and 85 deg. C. Concentrations in solution (calcium, sulfate, aluminium) were measured and the mineralogical state of the systems was studied by means of X-ray diffraction. The equilibria between C-S-H and ettringite are described. The relative importance of sulfate bound to the C-S-H is evaluated. The kinetics of ettringite reprecipitation from a 'C-S-H-ettringite' system at 85 deg. C placed at 20 deg. C are also evaluated
Ranjbar, Faranak; Jalali, Mohsen
2015-11-01
In this study, the reclamation of a calcareous sodic soil with the exchangeable sodium percentage (ESP) value of 26.6% was investigated using the cheap and readily available chemical and organic materials including natural bentonite and zeolite saturated with calcium (Ca2+), waste calcite, three metal oxide nanoparticles functionalized with an acidic extract of potato residues, and potato residues. Chemical amendments were added to the soil at a rate of 2%, while potato residues were applied at the rates of 2 and 4% by weight. The ESP in the amended soils was reduced in the range of 0.9-4.9% compared to the control soil, and the smallest and the largest decline was respectively observed in treatments containing waste calcite and 4% of potato residues. Despite the reduction in ESP, the values of this parameter were not below 15% at the end of a 40-day incubation period. So, the effect of solutions of varying sodium adsorption ratio (SAR) values of 0, 5, 10, 20, 30, 40, and 50 on sodium (Na+) exchange equilibria was evaluated in batch systems. The empirical models (simple linear, Temkin, and Dubinin-Radushkevich) fitted well to experimental data. The relations of quantity to intensity (Q/I) revealed that the potential buffering capacity for Na+ (PBCNa) varied from 0.275 to 0.337 ((cmolc kg(-1)) (mmol L(-1))(-1/2)) in the control soil and amended soils. The relationship between exchangeable sodium ratio (ESR) and SAR was individually determined for the control soil and amended soils. The values of Gapon selectivity coefficient (KG) of Na+ differed from the value suggested by U.S. Salinity Laboratory (USSL). The PHREEQC, a geochemical computer program, was applied to simulate Na+ exchange isotherms by using the mechanistic cation exchange model (CEM) along with Gaines-Thomas selectivity coefficients. The simulation results indicated that Na+ exchange isotherms and Q/I and ESR-SAR relations were influenced by the type of counter anions. The values of K G increased in
DEFF Research Database (Denmark)
Hansen, Poul Erik; Borisov, Eugeny V.; Lindon, John C.
2015-01-01
The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on 1H and 13C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in th...
Phase equilibria constraints on the chemical and physical evolution of the campanian ignimbrite
Fowler, S.J.; Spera, F.J.; Bohrson, W.A.; Belkin, H.E.; de Vivo, B.
2007-01-01
The Campanian Ignimbrite is a > 200 km3 trachyte-phonolite pyroclastic deposit that erupted at 39.3 ?? 0.1 ka within the Campi Flegrei west of Naples, Italy. Here we test the hypothesis that Campanian Ignimbrite magma was derived by isobaric crystal fractionation of a parental basaltic trachyandesitic melt that reacted and came into local equilibrium with small amounts (5-10 wt%) of crustal rock (skarns and foid-syenites) during crystallization. Comparison of observed crystal and magma compositions with results of phase equilibria assimilation-fractionation simulations (MELTS) is generally very good. Oxygen fugacity was approximately buffered along QFM+1 (where QFM is the quartz-fayalite-magnetite buffer) during isobaric fractionation at 0.15 GPa (???6 km depth). The parental melt, reconstructed from melt inclusion and host clinopyroxene compositions, is found to be basaltic trachyandesite liquid (51.1 wt% SiO2, 9.3 wt% MgO, 3 wt% H2O). A significant feature of phase equilibria simulations is the existence of a pseudo-invariant temperature, ???883??C, at which the fraction of melt remaining in the system decreases abruptly from ???0.5 to < 0.1. Crystallization at the pseudo-invariant point leads to abrupt changes in the composition, properties (density, dissolved water content), and physical state (viscosity, volume fraction fluid) of melt and magma. A dramatic decrease in melt viscosity (from 1700 Pa s to ???200 Pa s), coupled with a change in the volume fraction of water in magma (from ??? 0.1 to 0.8) and a dramatic decrease in melt and magma density acted as a destabilizing eruption trigger. Thermal models suggest a timescale of ??? 200 kyr from the beginning of fractionation until eruption, leading to an apparent rate of evolved magma generation of about 10-3 km3/year. In situ crystallization and crystal settling in density-stratified regions, as well as in convectively mixed, less evolved subjacent magma, operate rapidly enough to match this apparent
International Nuclear Information System (INIS)
The value of the electrochemical technique Reverse Pulse Voltammetry (RPV) for the characterization of chemical equilibria in solution is theoretically investigated. For this, the RPV response of the square scheme is studied at spherical and disc electrodes of any size assuming that the chemical reactions are at equilibrium. When the effective diffusion coefficients of the oxidized and reduced species are the same, analytical solutions are reported for both electrode geometries. Otherwise, a rigorous analytical solution is derived for spherical electrodes whereas the case of microdiscs is addressed by numerical simulations. The theory for the square scheme enables the study of the RPV response in very different situations, including the cases where the electrochemical and/or chemical transformations alter significantly the species diffusivity such as in electron transfer processes in room temperature ionic liquids or in the association of the electroactive species with (bio) macromolecules and nanoparticles. It is found that, when medium-size (disc or spherical) microelectrodes are employed, the RPV method enables the simultaneous determination of the effective diffusion coefficients of the oxidized and reduced species as well as the apparent formal potential. These magnitudes make it possible a sound physicochemical characterization of the system
The use of available chemical equilibria software for the prediction of the performance of EKR
Villén Guzmán, María; Gómez-Lahoz, C.; García Rubio, Ana; Paz García, José Manuel; Vereda Alonso, Carlos; García Herruzo, Francisco; Rodríguez Maroto, José Miguel
2014-01-01
Risk assessment aims for the prediction of the mobility of contaminants, and these are usually based in lab essays together with mathematical modelling. Also the feasibility studies of most techniques, require similar tools. Frequently the lab characterization is based in the chemical fractionation of the contaminants based on their mobility under different chemical reagents. Probably the most frequent fractionation technique for heavy metal contaminated soils is the BCR [1]. The use of ch...
Thermodynamic modeling of chemical equilibria in liquid-liquid extraction of lutetium
International Nuclear Information System (INIS)
The extraction equilibrium data of lutetium from sodium succinate solution with Aliquat 336 in benzene is systematically investigated. The aqueous phase metal complexation and polymerization in the organic phase are taken into account in obtaining extraction coefficients, stability constants, hydrolysis constants, solubility product, and extraction constants. A thermodynamic model of the above equilibrium extraction data is developed for use in computer simulation of the extraction process. The correlations are based on chemical mass action principles in which the metal complexation in the aqueous phase, polymerization in the organic phase, precipitation in the aqueous phase, and aqueous phase activity coefficients are considered. Extraction behavior of other lanthanides from a succinate medium is also discussed
Spalding, B P; Spalding, I R
2001-01-15
Strontium-90 is a major hazardous contaminant of radioactive wastewater and its processing sludges at many Department of Energy (DOE) facilities. In the past, such contaminated wastewater and sludge have been disposed in soil seepage pits, lagoons, or cribs often under highly perturbed alkaline conditions (pH > 12) where 90Sr solubility is low and its adsorption to surrounding soil is high. As natural weathering returns these soils to near-neutral or slightly acidic conditions, the adsorbed and precipitated calcium and magnesium phases, in which 90Sr is carried, change significantly in both nature and amounts. No comprehensive computational method has been formulated previously to quantitatively simulate the dynamics of 90Sr in the soil-groundwater environment under such dynamic and wide-ranging conditions. A computational code, the Hydrologic Utility Model for Demonstrating Integrated Nuclear Geochemical Environmental Responses (HUMDINGER), was composed to describe the changing equilibria of 90Sr in soil based on its causative chemical reactions including soil buffering, pH-dependent cation-exchange capacity, cation selectivity, and the precipitation/dissolution of calcium carbonate, calcium hydroxide, and magnesium hydroxide in response to leaching groundwater characteristics including pH, acid-neutralizing capacity, dissolved cations, and inorganic carbonate species. The code includes a simulation of one-dimensional transport of 90Sr through a soil column as a series of soil mixing cells where the equilibrium soluble output from one cell is applied to the next cell. Unamended soil leaching and highly alkaline soil treatments, including potassium hydroxide, sodium silicate, and sodium aluminate, were simulated and compared with experimental findings using large (10 kg) soil columns that were leached with 90Sr-contaminated groundwater after treatment. HUMDINGER's simulations were in good agreement with dynamic experimental observations of soil exchange capacity
Development of a self-standing numerical tool to solve chemical equilibria in nuclear materials
International Nuclear Information System (INIS)
Many numerical codes are available to provide a prediction of nuclear fuel behaviour under normal and abnormal conditions. These codes typically require a method of capturing chemical phenomena and phase equilibrium in a system with many components. The integration of existing thermochemical software is complicated by the need to pass information through input and output operations between various programs since the source code is generally unavailable. Accordingly, fuel behaviour codes typically rely on empirical correlations to incorporate fuel physical chemistry knowledge for lack of a thermochemical solver that can be directly implemented within the code. The empirical correlations generally do not convey with high fidelity the original thermodynamic analysis. A numerical tool is being constructed to provide the equilibrium compositions of species and related thermochemical properties in multiphase-multicomponent systems through the process of Gibbs energy minimization. Standard Gibbs energies of formation for pure species are used along with models that describe the mixing of solute species dissolved in various non-ideal solution phases. Mass constraints are observed with the use of an internal linear equation solver employing Gaussian elimination. An impediment to many existing thermochemical codes is the inability of handling a sufficiency of components necessary to capture all of the fission products possibly produced. Furthermore, the ability to customize Gibbs energy formulations directly in the source code is a great convenience. For instance, it may be desirable to introduce thermodynamic models representing the non-ideal mixing of solute atoms using mathematical expressions that do not conform to the expectation of standard software. Thermodynamic models representing the non-stoichiometry of solid and liquid uranium dioxide can benefit from such sophisticated mathematical expressions. The programming is currently being applied to advance a
Kandori, Michihiro
1988-01-01
This paper provides a way to formulate a general equilibrium model with both infinite time horizon and continuous uncertainty by 2.space, and provides a si mple proof of the equiva-lence of equilibria in complete markets, inc omplete markets with sequential trading, and incomplete markets with one-shot trades in single consumer economies. The proof is general in the sense that it does not assume time-homogeneous structure nor smo othness of preferences. The result guarantees that one can avoi...
Energy Technology Data Exchange (ETDEWEB)
Dutrow, Barbara
2008-08-13
Our research evaluates the hypothesis that feedback amongst thermal-chemical-mechanical processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with feedback. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of feedback to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or feedback, and
Transport and isomorphic equilibria
Energy Technology Data Exchange (ETDEWEB)
Boozer, A.H.
1981-07-01
It is shown that large classes of plasma equilibria can have identical drift orbits and associated transport. Such equilibria are named isomorphic. In particular, the neoclassical transport coefficients are given for all equilibria in which the magnetic field strength depends on one helicity.
Transport and isomorphic equilibria
International Nuclear Information System (INIS)
It is shown that large classes of plasma equilibria can have identical drift orbits and associated transport. Such equilibria are named isomorphic. In particular, the neoclassical transport coefficients are given for all equilibria in which the magnetic field strength depends on one helicity
Determination of CTX equilibria
International Nuclear Information System (INIS)
The method by which we determine the magnetic field equilibrium for CTX in a nonperturbing manner is presented. Measurements of flux conserver image currents are combined with calculations from a numerical model of the equilibrium. Results give equilibria which differ significantly from the minimum energy state, but the equilibria data are well-described by a model where j/B has a linear dependence on the poloidal flux function. The observation of non-disruptive rotating internal kink distortions (with toroidal mode numbers n = 1, 2 and 3) within the equilibria and theoretical MHD thresholds for the onset of these modes corroborate the inferred equilibria
International Nuclear Information System (INIS)
Highlights: ► Quaternary (liquid + liquid) equilibria are measured for ionic liquids, cyclohexane, pyridine and thiophene. ► Extraction of thiophene and pyridine from cyclohexane using ionic liquids is investigated. ► Three different ionic liquids are investigated. ► The experimental data can be successfully correlated using NRTL and UNIQUAC models. ► The experimental data are in moderate agreement with a priori predictions made using the COSMO-SAC model. -- Abstract: 1-Ethyl 3-methylimidazolium acetate [EMIM][OAc], 1-ethyl 3-methylimidazolium ethylsulfate [EMIM][EtSO4] and 1-ethyl 3-methylimidazolium methylsulfonate [EMIM][MeSO3] are found to be effective for the selective removal of a five member ring sulfur compound, viz. thiophene, and a six member ring nitrogen compound, viz. pyridine from a hydrocarbon, viz. cyclohexane at room temperature and atmospheric pressure. The liquid liquid equilibrium (LLE) data for the quaternary mixtures of ionic liquid (1) + thiophene (2) + pyridine (3) + cyclohexane (4) are experimentally determined. The experimental tie line data are successfully correlated with the Non Random Two Liquid (NRTL) and UNIversal QUAasi-Chemical (UNIQUAC) models, which provide a good correlation of the experimental data with root mean square deviation (RMSD) values less than unity for all the studied systems. The results suggest that the structure and size of the anion greatly affects the extractive performance of ionic liquids. The reliability of experimental data is ascertained by applying the quantum chemical based COnductor like Screening Model-Segment Activity Coefficient (COSMO-SAC) model. The goodness of the fit is determined by calculating the RMSD values. The RMSD values obtained for [EMIM][OAc], [EMIM][EtSO4] and [EMIM][MeSO3] are 10.4%, 8.1% and 12.2%, respectively
Meyer, Danilo; Neumann, Piotr; Koers, Eline; Sjuts, Hanno; Lüdtke, Stefan; Sheldrick, George M.; Ficner, Ralf; Tittmann, Kai
2012-01-01
Thiamin diphosphate, the vitamin B1 coenzyme, plays critical roles in fundamental metabolic pathways that require acyl carbanion equivalents. Studies on chemical models and enzymes had suggested that these carbanions are resonance-stabilized as enamines. A crystal structure of this intermediate in pyruvate oxidase at 1.1 Å resolution now challenges this paradigm by revealing that the enamine does not accumulate. Instead, the intermediate samples between the ketone and the carbanion both inter...
Learning efficient correlated equilibria
Borowski, Holly P.
2014-12-15
The majority of distributed learning literature focuses on convergence to Nash equilibria. Correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However, there are no existing distributed learning algorithms that converge to specific correlated equilibria. In this paper, we provide one such algorithm which guarantees that the agents\\' collective joint strategy will constitute an efficient correlated equilibrium with high probability. The key to attaining efficient correlated behavior through distributed learning involves incorporating a common random signal into the learning environment.
Institutions, Equilibria and Efficiency
DEFF Research Database (Denmark)
Competition and efficiency is at the core of economic theory. This volume collects papers of leading scholars, which extend the conventional general equilibrium model in important ways. Efficiency and price regulation are studied when markets are incomplete and existence of equilibria in such...
Czech Academy of Sciences Publication Activity Database
Aim, Karel; Wichterle, Ivan
2010, s. 210. ISBN N. [International Conference on Properties and Phase Equilibria for Product and Process Design PPEPPD 2010 /20./. Suzhou (CN), 16.05.2010-21.05.2010] Institutional research plan: CEZ:AV0Z40720504 Keywords : esterification reactions * vapor-liquid equilibria * chemical equilibria Subject RIV: CF - Physical ; Theoretical Chemistry http://www.ppeppd2010.cn/
Resurrecting Equilibria Through Cycles
DEFF Research Database (Denmark)
Barnett, Richard C.; Bhattacharya, Joydeep; Bunzel, Helle
equilibria because they asymptotically violate some economic restriction of the model. The literature has always ruled out such paths. This paper studies a pure-exchange monetary overlapping generations economy in which real balances cycle forever between momentary equilibrium points. The novelty is to show...... that segments of the offer curve that have been previously ignored, can in fact be used to produce asymptotically valid cyclical paths. Indeed, a cycle can bestow dynamic validity on momentary equilibrium points that had erstwhile been classified as dynamically invalid....
Adsorption analysis equilibria and kinetics
Do, Duong D
1998-01-01
This book covers topics of equilibria and kinetics of adsorption in porous media. Fundamental equilibria and kinetics are dealt with for homogeneous as well as heterogeneous particles. Five chapters of the book deal with equilibria and eight chapters deal with kinetics. Single component as well as multicomponent systems are discussed. In kinetics analysis, we deal with the various mass transport processes and their interactions inside a porous particle. Conventional approaches as well as the new approach using Maxwell-Stefan equations are presented. Various methods to measure diffusivity, such
Equilibria in saturated bentonite
International Nuclear Information System (INIS)
It has been proposed that smectite clays, the predominant minerals in bentonite, are metastable solid solutions whose compositional heterogeneity prevents strict adherence to fixed ion activities and activity ratios characterizing invariant equilibria among stoichiometric phases. This is analysis of exceptionally well-constrained experimental data using a solid solution model defined by the phase rule and estimated ideal site-mixing are approached among smectite solid solutions and coexist metastably with respect to aSiO2(aq). Irreducible uncertainties are generated in the model by analytical and conceptual deficiencies in understanding compositional variability in smectite. However, their estimated effects on smectite's stability are relatively small, and are comparable to the effects of experimental uncertainty in standard Gibbs energies on the stabilities of stoichiometric minerals. An alternate analysis of the data further confirms that smectite does not behave like a stoichiometric phase. Ion-exchange models for this clay mineral may therefore be thermodynamically ill defined because stoichiometric behavior is assumed implicitly under limiting conditions of fixed sites. Ion exchange is a pragmatic simplification enabling empirical analysis of some experimental data. However, its empirical, rather than thermodynamic, basis should not be overextended to conditions that are beyond an experimentally calibrated range
Directory of Open Access Journals (Sweden)
Delavar M.
2012-01-01
Full Text Available In this study, adsorption of methane as the main constituent of natural gas was firstly studied on the pristine multi-walled carbon nanotubes (MWCNTs and then purification and chemical treatments of MWCNTs was performed to enhance the natural gas adsorption capacity. MWCNTs were chemically treated using different methods in this research. The results revealed that chemical treatment of the MWCNTs in presence of H2SO4/HNO3 acidic mixture in 3:1 volume ratio, enhanced considerably natural gas adsorption capacity (an optimal up to 45 mmol/g at temperature of 298.15 K and the pressure of 50 bar compared to the pristine MWCNTs (about 27 mmol/g at the same operating conditions. This effect can be attributed to the opening of the nanotubes caps with a major alteration in its structural properties due to chemical treatment. The experimental data of adsorption were almost equally well described by Langmuir, Freundlich and Sips equations to determine the model isotherms. The best fit was obtained by the Sips model isotherm with the r-squared value near to unity. Furthermore, using the experimental data obtained in different temperatures the isosteric heat of natural gas adsorption onto pristine MWCNTs was also calculated in the interested range of pressures and temperatures using the thermodynamic-based Clausius-Clapeyron equation from the Sips isotherm model. The results revealed an energetically heterogeneous surface of MWCNTs in natural gas adsorption. Also the natural gas adsorption process was kinetically studied through pseudo-second order and intra-particle diffusion models which indicated the intra-particular diffusion is rate limiting step in adsorption of methane on MWCNTs.
International Nuclear Information System (INIS)
A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges with the external environment. By the utilization of a geochemical code associated to a thermodynamical database and coupled to a 3D transport model, this approach authorizes the study of all aggressive solution. The approach has been validated by the comparison of experimental observations to simulated degradations for three different environments (pure water, mineralized water, seawater) and on three different materials (CEM I Portland cement with 0.25, 0.4 and 0.5 water-to cement ratio). The microstructural approach permits also to have access to mechanical properties evolutions. During chemical aggressions, the cement matrix evolution is traduced in a microstructure evolution. This one is represented from 3D images similarly to the models developed at NIST (National Institute of Standards and Technology). A new finite-element model, validated on previous tests or models, evaluates the stiffness of the cement paste, using as a mesh these microstructures. Our approach identifies and quantifies the major influence of porosity and its spatial
Lithium Alkyl Exchange Equilibria
International Nuclear Information System (INIS)
Kinetic analyses of two types of exchange reactions of organo- lithium reagents, both alkyl and aryl types, RLi, have been made: (1) halogen-metal interchange with alkyl and aryl halides, R'X, and (2) hydrogen-metal interchange (commonly called metallation) with aromatic hydrocarbons, R'H. Rates of these RLi + R'X ⇄ RX + R'Li; (1) . RLi + R'H ⇄ RH+ R'Li (2) reactions have been determined, conditions under which the systems attain equilibrium have been established, and the positions of equilibrium measured, all as functions of the reactants, solvents and catalysts employed. Concerning halogen-lithium interchange between alkyl groups (1), the conclusion is reached that equilibration proceeds to yield the less sterically demanding alkyl group attached to lithium. The data show, for example, that isobutyllithium is much less stable than n-butyllithium, and again, that 2,6-dimethyl- phenyllithium is much less stable than phenyllithium. The exchange is general with iodides, occurs with some bromides and does not occur with chlorides. The exchange is quite slow in hydrocarbon media and is catalysed by relatively small amounts of ethers. In the presence of the optically active methyl ether of menthol, methyl iodide exchanges with racemic s-butyllithium to give optically active s-butyl iodide. In work with the second reaction, hydrogen-lithium interchange (2), nuclear magnetic resonance spectrometry has been used for rate studies. Catalysts (Lewis bases) have been evolved for establishing equilibria in rather unreactive systems, e.g. phenyllithium can be demonstrated to exchange with benzene by labelling the latter radioactivity. From the correlations of structure and reactivity found in this study, the conclusion is reached that the basic alkyllithium structure is dimeric, R2Li2 The arrangement of the groups within this dimer satisfactorily explain the special steric effects noted in organolithium reagent stability. (author)
Phase equilibria in polyethylene systems
Hemmingsen, Pål Viggo
2000-01-01
The background for this work is a need to better understand the production of high density polythylene (HDPE). HDPE particles grow in a loop slurry reactor, and particle swelling and slurry viscosity are critical parts in the process. This thesis is concerned with the thermodynamic aspects of liquid and solid polyethylene, and liquid-liquid and solid-liquid equilibria in solvent-polyethylene systems. It also covers studies of vapor-liquid and solid-liquid equilibria in solvent-n-alkane system...
Helical ITER hybrid scenario equilibria
International Nuclear Information System (INIS)
Numerical computations of ITER equilibria in the hybrid scenario using a three-dimensional (3D) magnetohydrodynamic equilibrium code with nested magnetic flux surfaces demonstrate the formation of internal 3D helical cores similar to saturated ideal internal kink modes under reversed magnetic shear conditions when the minimum value of the inverse rotational transform is in the neighbourhood of unity.
Thermodynamic Equilibria and Extrema Analysis of Attainability Regions and Partial Equilibria
Gorban, Alexander N; Kaganovich, Boris M; Keiko, Alexandre V; Shamansky, Vitaly A; Shirkalin, Igor A
2006-01-01
This book discusses mathematical models that are based on the concepts of classical equilibrium thermodynamics. They are intended for the analysis of possible results of diverse natural and production processes. Unlike the traditional models, these allow one to view the achievable set of partial equilibria with regards to constraints on kinetics, energy and mass exchange and to determine states of the studied systems of interest for the researcher. Application of the suggested models in chemical technology, energy and ecology is illustrated in the examples.
Equilibria, Fixed Points, and Complexity Classes
Yannakakis, Mihalis
2008-01-01
Many models from a variety of areas involve the computation of an equilibrium or fixed point of some kind. Examples include Nash equilibria in games; market equilibria; computing optimal strategies and the values of competitive games (stochastic and other games); stable configurations of neural networks; analysing basic stochastic models for evolution like branching processes and for language like stochastic context-free grammars; and models that incorporate the basic primitives of probability and recursion like recursive Markov chains. It is not known whether these problems can be solved in polynomial time. There are certain common computational principles underlying different types of equilibria, which are captured by the complexity classes PLS, PPAD, and FIXP. Representative complete problems for these classes are respectively, pure Nash equilibria in games where they are guaranteed to exist, (mixed) Nash equilibria in 2-player normal form games, and (mixed) Nash equilibria in normal form games with 3 (or ...
Separating equilibria in continuous signalling games.
Bergstrom, Carl T.; Számadó, Szabolcs; Lachmann, Michael
2002-01-01
Much of the literature on costly signalling theory concentrates on separating equilibria of continuous signalling games. At such equilibria, every signaller sends a distinct signal, and signal receivers are able to exactly infer the signaller's condition from the signal sent. In this paper, we introduce a vector-field solution method that simplifies the process of solving for separating equilibria. Using this approach, we show that continuous signalling games can have low-cost separating equi...
Multiple equilibria in radiative-convective atmospheres
Rennó, Nilton O.
2011-01-01
A one-dimensional, radiative-convective model is used to study the equilibria conditions of moist atmospheres. We show that when the hydrologic cycle is included in the model a subcritical bifurcation occurs, leading to 2 linearly stable solutions to the radiative-convective equilibria. In this case, when the net forcing is larger than a critical value, two equilibria are possible. Furthermore, a finite amplitude instability can lead to a runaway greenhouse regime when the solar forcing is la...
Phase equilibria basic principles, applications, experimental techniques
Reisman, Arnold
2013-01-01
Phase Equilibria: Basic Principles, Applications, Experimental Techniques presents an analytical treatment in the study of the theories and principles of phase equilibria. The book is organized to afford a deep and thorough understanding of such subjects as the method of species model systems; condensed phase-vapor phase equilibria and vapor transport reactions; zone refining techniques; and nonstoichiometry. Physicists, physical chemists, engineers, and materials scientists will find the book a good reference material.
Fixed points and economic equilibria
Urai, Ken
2014-01-01
This book presents a systematic approach to problems in economic equilibrium based on fixed-point arguments and rigorous set-theoretical (axiomatic) methods. It describes the highest-level research on the classical theme, fixed points and economic equilibria, in the theory of mathematical economics, and also presents basic results in this area, especially in the general equilibrium theory and non-co-operative game theory. The arguments also contain distinguishable developments of the main theme in the homology theory for general topological spaces, in the model theory and mathematical logic, a
Reflectivity method for geomechanical equilibria
Kuvshinov, Boris N.
2007-08-01
It is shown that the block LU decomposition of the transfer and scattering matrix convert these matrices into each other. This allows to introduce a generalization of the Kennett reflectivity method, which is applicable to arbitrary systems of linear differential equations. The introduced method is convenient to analyse equilibria, where the governing matrix is degenerate. The resulting algorithm is compact and numerically stable. To illustrate the concept, we consider elastic equilibrium of a layered medium. We also derive closed-form expressions for a quasi-stationary poroelastic case taking into account solid-fluid and electrokinetic coupling.
Phase equilibria in asymmetric mixtures
International Nuclear Information System (INIS)
The simplified version of the Perturbed Hard-Chain Theory (SPHCT) is used to compute the phase equilibria and Henry's constants for mixtures in which the molecules are highly asymmetric both in shape and in the intermolecular potential. These mixtures include binary systems such as CO2/hydrocarbons and hydrocarbons/hydrocarbons, which are of particular interest for the oil industry. For this type of mixtures a single parameter (which is calculated from available experimental data of liquid-vapor equilibrium) is introduced. The approach yields results which compare well with the experimental behavior reported in the literature (Author)
Contemporaneous Perfect Epsilon-Equilibria
2003-01-01
We examine contemporaneous perfect epsilon-equilibria, in which a player’s actions after every history, evaluated at the point of deviation from the equilibrium, must be within epsilon of a best response. This concept implies, but is stronger than, Radner’s ex ante perfect epsilon-equilibrium. A strategy profile is a contemporaneous perfect epsilon-equilibrium of a game if it is a subgame perfect equilibrium in a perturbed game with nearly the same payoffs, with the converse holding for pure ...
Existence of Multiagent Equilibria with Limited Agents
Bowling, M; 10.1613/jair.1332
2011-01-01
Multiagent learning is a necessary yet challenging problem as multiagent systems become more prevalent and environments become more dynamic. Much of the groundbreaking work in this area draws on notable results from game theory, in particular, the concept of Nash equilibria. Learners that directly learn an equilibrium obviously rely on their existence. Learners that instead seek to play optimally with respect to the other players also depend upon equilibria since equilibria are fixed points for learning. From another perspective, agents with limitations are real and common. These may be undesired physical limitations as well as self-imposed rational limitations, such as abstraction and approximation techniques, used to make learning tractable. This article explores the interactions of these two important concepts: equilibria and limitations in learning. We introduce the question of whether equilibria continue to exist when agents have limitations. We look at the general effects limitations can have on agent b...
Signaling equilibria in sensorimotor interactions.
Leibfried, Felix; Grau-Moya, Jordi; Braun, Daniel A
2015-08-01
Although complex forms of communication like human language are often assumed to have evolved out of more simple forms of sensorimotor signaling, less attention has been devoted to investigate the latter. Here, we study communicative sensorimotor behavior of humans in a two-person joint motor task where each player controls one dimension of a planar motion. We designed this joint task as a game where one player (the sender) possesses private information about a hidden target the other player (the receiver) wants to know about, and where the sender's actions are costly signals that influence the receiver's control strategy. We developed a game-theoretic model within the framework of signaling games to investigate whether subjects' behavior could be adequately described by the corresponding equilibrium solutions. The model predicts both separating and pooling equilibria, in which signaling does and does not occur respectively. We observed both kinds of equilibria in subjects and found that, in line with model predictions, the propensity of signaling decreased with increasing signaling costs and decreasing uncertainty on the part of the receiver. Our study demonstrates that signaling games, which have previously been applied to economic decision-making and animal communication, provide a framework for human signaling behavior arising during sensorimotor interactions in continuous and dynamic environments. PMID:25935748
Motion Control along Relative Equilibria
DEFF Research Database (Denmark)
Nordkvist, Nikolaj
2008-01-01
The subject of this thesis is control of mechanical systems as they evolve along the steady motions called relative equilibria. These trajectories are of interest in theory and applications and have the characterizing property that the system's body-fixed velocity is constant. For example, constant......-speed rotation about a principal axis is a relative equilibrium of a rigid body in three dimensions. We focus our study on simple mechanical control systems on Lie groups, i.e., mechanical systems with the following properties: the configuration manifold is a matrix Lie group, the total energy is equal to the...... Lie group is locally controllable along a relative equilibrium. These conditions subsume the well-known local controllability conditions for equilibrium points. Second, for systems that have fewer controls than degrees of freedom, we present a novel algorithm to control simple mechanical control...
Beam-induced tensor pressure tokamak equilibria
International Nuclear Information System (INIS)
D-shaped tensor pressure tokamak equilibria induced by neutral-beam injection are computed. The beam pressure components are evaluated from the moments of a distribution function that is a solution of the Fokker-Planck equation in which the pitch-angle scattering operator is ignored. The level-psub(perpendicular) contours undergo a significant shift away from the outer edge of the device with respect to the flux surfaces for perpendicular beam injection into broad-pressure-profile equilibria. The psub(parallel) contours undergo a somewhat smaller inward shift with respect to the flux surfaces for both parallel and perpendicular injection into broad-pressure-profile equilibria. For peaked-pressure-profile equilibria, the level pressure contours nearly co-incide with the flux surfaces. (author)
Braided magnetic fields: equilibria, relaxation and heating
Pontin, D I; Russell, A J B; Hornig, G
2015-01-01
We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling. The key results obtained from recent modelling efforts are summarised, in the context of testable predictions for the laboratory. We discuss the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity - as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We discuss the properties of this relaxation, and in particular the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor's hypo...
Braided magnetic fields: equilibria, relaxation and heating
Pontin, D. I.; Candelaresi, S.; Russell, A. J. B.; Hornig, G.
2016-05-01
We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor’s hypothesis.
Nash equilibria via duality and homological selection
Indian Academy of Sciences (India)
Arnab Basu; Samik Basu; Mahan MJ
2014-11-01
Given a multifunction from to the -fold symmetric product Sym$_{k}(X)$, we use the Dold–Thom theorem to establish a homological selection theorem. This is used to establish existence of Nash equilibria. Cost functions in problems concerning the existence of Nash equilibria are traditionally multilinear in the mixed strategies. The main aim of this paper is to relax the hypothesis of multilinearity. We use basic intersection theory, Poincaré duality in addition to the Dold–Thom theorem.
On Uniqueness of Equilibria in the CAPM
Thorsten HENS; Laitenberger, Jörg; Löffler, Andreas
2000-01-01
"- This paper replaces the paper ""Existence and Uniqueness of Equilibria in the CAPM"" -nIn the standard CAPM with a riskless asset we give a sufficient condition for uniqueness. This condition is a joint restriction on the agents' endowments and their preferences which is compatible with non-increasing absolute risk aversion and which is in particular satisfied with constant absolute risk aversion. Moreover in the CAPM without a riskless asset we give an example for multiple equilibria even...
Network Connection Games with Disconnected Equilibria
Brandes, Ulrik; Nick, Bobo
2008-01-01
In this paper we extend a popular non-cooperative network creation game (NCG) to allow for disconnected equilibrium networks. There are n players, each is a vertex in a graph, and a strategy is a subset of players to build edges to. For each edge a player must pay a cost, and the utility is a trade-off between edge costs and shortest path lengths to all other players. We extend the model to a penalized game (PCG), for which we reduce the penalty counted towards the utility for a pair of disconnected players to a finite value. Our analysis concentrates on existence, structure, and cost of disconnected regular and strong Nash equilibria. Although the PCG is not a potential game, pure Nash equilibria always and pure strong equilibria very often exist. We provide tight conditions under which disconnected (strong) Nash equilibria can evolve. Components of these equilibria must be (strong) Nash equilibria of a smaller NCG. However, in contrast to the NCG, for almost all parameter values no tree is a stable componen...
Inefficient equilibria in transition economy
Directory of Open Access Journals (Sweden)
Igor Pospelov
1998-01-01
Full Text Available The paper studies a general equilibrium in an economy where all market participants face a bid-ask spread. The spread may be caused by indirect business taxes, middlemen rent-seeking, delays in payments or liquidity constraints or price uncertainty. Wherever it comes from the spread causes inefficiency of the market equilibrium. We discuss some institutions that can decrease the inefficiency. One is second currency (barter exchange in the inter-firm transactions. It is shown that the general equilibrium in an economy with second currency is effective though is still different from ArrowÃ¢Â€Â“Debreu equilibrium. Another solution can be introduction of mutual trade credit. In the economy with trade credit there are multiple equilibria that are more efficient than original bid-ask spread but still not as efficient as ArrowÃ¢Â€Â“Debreu one, too. The implications for firms' integration and applicability to Russian economy are discussed.
Institute of Scientific and Technical Information of China (English)
大沼郁雄
2005-01-01
It is well known that the magnetic properties such as the Curie temperature TmagC and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tcmag and β of the Ni3 Pt (L12) and NiPt (L10) and Tcmag of the CoPt (L10) and CoPt3 (L12) ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ-FeNi3(L12) and the α-FeCo (B2) ordered compounds have higher Tcmag and β values comparing with the disordered solution phases, γ (A1) and α (A2), respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tcmag and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X(X=Al, Co, Ni, Rh, Si) binary systems.The Gibbs energy of the α(A2), γ(A1) and liquid phases is described by a sub-regular solution approximatior. The ordering contribution to the Gibbs energy ,ΔGmorder, and deviations of magnetic properties, ΔTcmag and Δβ, of the ordered compounds, FeAl(B2), Fe3 Al (D03), FeCo (B2), FeRh (B2), FeSi (B2), Fe3 Si (D03) and FeNi3 (L12) is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.
Relative Equilibria of Identical Point Vortices
Aref, Hassan
2006-11-01
The problem of finding relative equilibria of identical point vortices is classical and was considered by Kelvin and J. J. Thomson almost immediately after the model had been introduced by Helmholtz in 1858. At the time relative equilibria of vortices were proposed as models of atoms. Apart from the intrinsic interest of the problem, and its mathematical challenge, such equilibria have been used as models for stationary states of distributed vortices, and have been observed in rotating superfluids, most recently in spectacular images of BECs. Simple equilibria such as regular polygons (both open and centered) were found and analyzed in the 19th century. Double rings and more recently triple rings have been found analytically. However, the numerically known relative equilibria continue to greatly outnumber those that are analytically known. A major numerical exploration was undertaken by Campell & Ziff in 1978 resulting in what is known as the Los Alamos Catalog. We will explore the results in this catalog and what we have learned since then, and present details on the quest for an analytical understanding of these intriguing states.
Why mixed equilibria may not be conventions
DEFF Research Database (Denmark)
Hansen, Pelle Guldborg
2008-01-01
In his Convention (1969) David Lewis defined conventions as behavioural regularities instantiating proper coordination equilibria made salient by precedent and operational by this being common knowledge. While later proponents of game theoretical approaches in the study of convention have agreed on...... dropping Lewis' eccentric ‘coordination' requirement as well as that of common knowledge, they are confused on whether conventions should be regarded as proper thereby precluding mixed equilibria. In this paper I argue that mixed equilibria may not be conventions, but also suggest that the reason for this...... reveals that though common knowledge is not necessary for a convention to operate, it may be utilized as to identify the conventional aspect of a given practice....
Real Indeterminacy of Stationary Monetary Equilibria in Centralized Economies
Kamiya, Kazuya; Kubota, So; Nakajima, Kayuna
2011-01-01
In this paper, we present a new logic of indeterminacy of stationary monetary equilibria. We rst show that, in a class of dynamic Walrasian market models with at money, stationary equilibria are indeterminate; that is, there exists a continuum of stationary equilibria, where the value of money varies across the stationary equilibria. Then we explore the logic of the indeterminacy, and show that it can be applied not only to dynamic Walrasian market models but also to Jean et al. (2010)'s sear...
Effect of temperature on acid–base equilibria in separation techniques. A review
Energy Technology Data Exchange (ETDEWEB)
Gagliardi, Leonardo G.; Tascon, Marcos; Castells, Cecilia B., E-mail: castells@isis.unlp.edu.ar
2015-08-19
Studies on the theoretical principles of acid–base equilibria are reviewed and the influence of temperature on secondary chemical equilibria within the context of separation techniques, in water and also in aqueous-organic solvent mixtures, is discussed. In order to define the relationships between the retention in liquid chromatography or the migration velocity in capillary electrophoresis and temperature, the main properties of acid–base equilibria have to be taken into account for both, the analytes and the conjugate pairs chosen to control the solution pH. The focus of this review is based on liquid–liquid extraction (LLE), liquid chromatography (LC) and capillary electrophoresis (CE), with emphasis on the use of temperature as a useful variable to modify selectivity on a predictable basis. Simplified models were evaluated to achieve practical optimizations involving pH and temperature (in LLE and CE) as well as solvent composition in reversed-phase LC. - Highlights: • The study of theoretical principles of acid–base equilibrium has been reviewed. • The proton transfer process is often present in the analytical separation practice. • The influence of temperature on secondary chemical equilibria is examined. • The focus is laid on liquid chromatography and capillary electrophoresis. • Temperature can be a useful variable to modify selectivity under predictable basis.
Binary Solid-Liquid Phase Equilibria
Ellison, Herbert R.
1978-01-01
Indicates some of the information that may be obtained from a binary solid-liquid phase equilibria experiment and a method to write a computer program that will plot an ideal phase diagram to which the experimental results may be compared. (Author/CP)
Optimal Cartel Equilibria with Imperfect Monitoring
Dilip Abreu; David Pearce; Ennio Stacchetti
1984-01-01
There exist optimal symmetric equilibria in the Green-Porter model [5, 8] having an elementary intertemporal structure. Such an equilibrium is described entirely by two subsets of price space and two quantities, the only production levels used by firms in any contingency. The central technique employed in the analysis is the reduction of the repeated game to a family of static games.
On the stochastic stability of MHD equilibria
International Nuclear Information System (INIS)
The stochastic stability in the large of stationary equilibria of ideal and dissipative magnetohydrodynamics under the influence of stationary random fluctuations is studied using the direct Liapunov method. Sufficient and necessary conditions for stability of the linearized Euler-Lagrangian systems are given. The destabilizing effect of stochastic fluctuations is demonstrated. (orig.)
Phase equilibria of carbohydrates in polar solvents
DEFF Research Database (Denmark)
Jonsdottir, Svava Osk; Rasmussen, Peter
A method for calculating interaction energies and interaction parameters with molecular mechanics methods is extended to predict solid-liquid equilibria (SLE) for saccharides in aqueous solution, giving results in excellent agreement with experimental values. Previously, the method has been shown...
Equilibria with incompressible flows from symmetry analysis
Kuiroukidis, Ap
2015-01-01
We identify and study new nonlinear axisymmetric equilibria with incompressible flow of arbitrary direction satisfying a generalized Grad Shafranov equation by extending the symmetry analysis presented in [G. Cicogna and F. Pegoraro, Phys. Plasmas Vol. 22, 022520 (2015)]. In particular, we construct a typical tokamak D-shaped equilibrium with peaked toroidal current density, monotonically varying safety factor and sheared electric field.
Stability of relative equilibria of three vortices
DEFF Research Database (Denmark)
Aref, Hassan
2009-01-01
Three point vortices on the unbounded plane have relative equilibria wherein the vortices either form an equilateral triangle or are collinear. While the stability analysis of the equilateral triangle configurations is straightforward, that of the collinear relative equilibria is considerably more...... involved. The only comprehensive analysis available in the literature, by Tavantzis and Ting [Phys. Fluids 31, 1392 (1988)], is not easy to follow nor is it very physically intuitive. The symmetry between the three vortices is lost in this analysis. A different analysis is given based on explicit formulas...... for the three eigenvalues determining the stability, including a new formula for the angular velocity of rotation of a collinear relative equilibrium. A graphical representation of the space of vortex circulations is introduced, and the resultants between various polynomials that enter the problem are...
Modeling of Phase Equilibria Containing Associating Fluids
DEFF Research Database (Denmark)
Derawi, Samer; Kontogeorgis, Georgios
terms of an activity coefficient model or an equation of state. Our target in this thesis is to review and develop such models capable of describing qualitatively as well as quantitatively phase equilibria in multicomponent multiphase systems containing non-polar, polar, and associating compounds. The......–known cubic SRK equation of state and the association term proposed by Wertheim, typically employed in models like the various variations of SAFT. CPA has been shown in the past to be a successful model for phase equilibria calculations for systems containing water, hydrocarbons and alcohols. In Chapter 4...... of CPA for the cross-association energy and volume parameters. Different types of such combining rules have been suggested over the past years for association models such as SAFT. These are tested in this work for CPA in terms of their correlation and prediction capabilities for vapor...
Multiple equilibria in a simple elastocapillary system
Taroni, Michele
2012-09-28
We consider the elastocapillary interaction of a liquid drop placed between two elastic beams, which are both clamped at one end to a rigid substrate. This is a simple model system relevant to the problem of surface-tension-induced collapse of flexible micro-channels that has been observed in the manufacture of microelectromechanical systems (MEMS). We determine the conditions under which the beams remain separated, touch at a point, or stick along a portion of their length. Surprisingly, we show that in many circumstances multiple equilibrium states are possible. We develop a lubrication-type model for the flow of liquid out of equilibrium and thereby investigate the stability of the multiple equilibria. We demonstrate that for given material properties two stable equilibria may exist, and show via numerical solutions of the dynamic model that it is the initial state of the system that determines which stable equilibrium is ultimately reached. © 2012 Cambridge University Press.
Set identification in models with multiple equilibria
Marc Henry; Alfred Galichon
2011-01-01
We propose a computationally feasible way of deriving the identified features of models with multiple equilibria in pure or mixed strategies. It is shown that in the case of Shapley regular normal form games, the identified set is characterized by the inclusion of the true data distribution within the core of a Choquet capacity, which is interpreted as the generalized likelihood of the model. In turn, this inclusion is characterized by a finite set of inequalities and efficient and easily imp...
Quality of equilibria in resource allocation games
Jong, de, J.
2016-01-01
In situations where multiple parties are involved, local or selfish decisions result in outcomes that rarely align with what is best for society. In order to evaluate the quality of the resulting outcomes, we first need to predict which outcomes can occur. Game theory offers answers to this question, the Nash equilibrium being the most prominent example: it is an outcome where no party can improve by unilateral deviations. In that sense Nash equilibria are a good description of a stable outco...
Phase equilibria in stratified thin liquid films stabilized by colloidal particles
Blawzdziewicz, J.; Wajnryb, E.
2005-01-01
Phase equilibria between regions of different thickness in thin liquid films stabilized by colloidal particles are investigated using a quasi-two-dimensional thermodynamic formalism. Appropriate equilibrium conditions for the film tension, normal pressure, and chemical potential of the particles in the film are formulated, and it is shown that the relaxation of these parameters occurs consecutively on three distinct time scales. Film stratification is described quantitatively for a hard-spher...
Quantum Nash Equilibria and Quantum Computing
Fellman, Philip Vos; Post, Jonathan Vos
In 2004, At the Fifth International Conference on Complex Systems, we drew attention to some remarkable findings by researchers at the Santa Fe Institute (Sato, Farmer and Akiyama, 2001) about hitherto unsuspected complexity in the Nash Equilibrium. As we progressed from these findings about heteroclinic Hamiltonians and chaotic transients hidden within the learning patterns of the simple rock-paper-scissors game to some related findings on the theory of quantum computing, one of the arguments we put forward was just as in the late 1990's a number of new Nash equilibria were discovered in simple bi-matrix games (Shubik and Quint, 1996; Von Stengel, 1997, 2000; and McLennan and Park, 1999) we would begin to see new Nash equilibria discovered as the result of quantum computation. While actual quantum computers remain rather primitive (Toibman, 2004), and the theory of quantum computation seems to be advancing perhaps a bit more slowly than originally expected, there have, nonetheless, been a number of advances in computation and some more radical advances in an allied field, quantum game theory (Huberman and Hogg, 2004) which are quite significant. In the course of this paper we will review a few of these discoveries and illustrate some of the characteristics of these new "Quantum Nash Equilibria". The full text of this research can be found at http://necsi.org/events/iccs6/viewpaper.php?id-234
Relative Equilibria in the Spherical, Finite Density 3-Body Problem
Scheeres, D J
2016-01-01
The relative equilibria for the spherical, finite density 3 body problem are identified. Specifically, there are 28 distinct relative equilibria in this problem which include the classical 5 relative equilibria for the point-mass 3-body problem. None of the identified relative equilibria exist or are stable over all values of angular momentum. The stability and bifurcation pathways of these relative equilibria are mapped out as the angular momentum of the system is increased. This is done under the assumption that they have equal and constant densities and that the entire system rotates about its maximum moment of inertia. The transition to finite density greatly increases the number of relative equilibria in the 3-body problem and ensures that minimum energy configurations exist for all values of angular momentum.
Ruthenium redox equilibria: 1. Thermodynamic stability of Ru(III and Ru(IV hydroxides
Directory of Open Access Journals (Sweden)
Igor Povar
2016-04-01
Full Text Available On the basis of the selected thermodynamic data for Ru(III and Ru(IV compounds in addition to original thermodynamic and graphical approach used in this paper, the thermodynamic stability areas of sparingly soluble hydroxides as well as the repartition of their soluble and insoluble chemical species towards the solution pH and initial concentrations of ruthenium in heterogeneous mixture solid phase–saturated solution have been investigated. By means of the ΔG–pH diagrams, the areas of thermodynamic stability of Ru(III and Ru(IV hydroxides have been established for a number of analytical concentrations in heterogeneous mixtures. The diagrams of heterogeneous and homogeneous chemical equilibria have been used for graphical representation of complex equilibria in aqueous solutions containing Ru(III and Ru(IV. The obtained results, based on the thermodynamic analysis and graphic design of the calculated data in the form of the diagrams of heterogeneous chemical equilibria, are in good agreement with the available experimental data.
Calculation of Liquid Water-Hydrate-Methane Vapor Phase Equilibria from Molecular Simulations
DEFF Research Database (Denmark)
Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas;
2010-01-01
Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled...... using the TIP4P/ice potential and a united-atom Lennard-Jones potential. respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials. (ii) calculation of the chemical...
On Stable Equilibria in Discrete-Space Social Interaction Models
AKAMATSU Takashi; Fujishima, Shota; Takayama, Yuki
2014-01-01
We investigate the differences and connections between discrete-space and continuous-space social interaction models. Although our class of continuous-space model has a unique equilibrium, we find that discretized models can have multiple equilibria for any degree of discretization, which necessitates a stability analysis of equilibria. We present a general framework for characterizations of equilibria and their stability under a broad class of evolutionary dynamics by using the properties of...
Dudebout, Nicolas
2014-12-15
This paper proves that exogenous empirical-evidence equilibria (xEEEs) in perfect-monitoring repeated games induce correlated equilibria of the associated one-shot game. An empirical-evidence equilibrium (EEE) is a solution concept for stochastic games. At equilibrium, agents\\' strategies are optimal with respect to models of their opponents. These models satisfy a consistency condition with respect to the actual behavior of the opponents. As such, EEEs replace the full-rationality requirement of Nash equilibria by a consistency-based bounded-rationality one. In this paper, the framework of empirical evidence is summarized, with an emphasis on perfect-monitoring repeated games. A less constraining notion of consistency is introduced. The fact that an xEEE in a perfect-monitoring repeated game induces a correlated equilibrium on the underlying one-shot game is proven. This result and the new notion of consistency are illustrated on the hawk-dove game. Finally, a method to build specific correlated equilibria from xEEEs is derived.
Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria
Circone, S.; Kirby, S.H.; Stern, L.A.
2006-01-01
Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.
Entropy and Equilibria in Competitive Systems
Directory of Open Access Journals (Sweden)
A. Y. Klimenko
2013-12-01
Full Text Available This paper investigates the applicability of thermodynamic concepts and principles to competitive systems. We show that Tsallis entropies are suitable for the characterisation of systems with transitive competition when mutations deviate from Gibbs mutations. Different types of equilibria in competitive systems are considered and analysed. As competition rules become more and more intransitive, thermodynamic analogies are eroded, and the behaviour of the system can become complex. This work analyses the phenomenon of punctuated evolution in the context of the competitive risk/benefit dilemma.
High temperature phase equilibria and phase diagrams
Kuo, Chu-Kun; Yan, Dong-Sheng
2013-01-01
High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature
Natural elongation and triangularity of tokamak equilibria
International Nuclear Information System (INIS)
Quasianalytic formulas are calculated for the elongation κ and triangularity δ of the plasma surface of a free-boundary tokamak equilibrium. The final results give κ and δ as functions of five quantities: the inverse aspect ratio ε, the poloidal beta βp, the internal inductance li, and the quadrupole and hexapole moments of the externally applied field. The agreement with numerically computed equilibria is found to be quite good when A≥3, κ≤1.5, and δ≤0.2 and when the plasma is limited by the vacuum vessel wall and not diverted by the presence of a separatrix on the plasma surface
Phase equilibria in Zr-Nb-Sn system
International Nuclear Information System (INIS)
Using system approach to the analysis of phase equilibria in three-component system, as well as totality of author's experimental results and literature data, topology of phase diagram of Zr-Nb-Sn state in the region rich in zirconium is presented. In the system existence of four nonvariant equilibria is ascertained
Correlated Equilibria in Continuous Games: Characterization and Computation
Stein, Noah D.; Parrilo, Pablo A.; Ozdaglar, Asuman
2008-01-01
We present several new characterizations of correlated equilibria in games with continuous utility functions. These have the advantage of being more computationally and analytically tractable than the standard definition in terms of departure functions. We use these characterizations to construct effective algorithms for approximating a single correlated equilibrium or the entire set of correlated equilibria of a game with polynomial utility functions.
The use of radioisotopes for determination of complex equilibria
International Nuclear Information System (INIS)
Radioisotopes can be used for determination of complex equilibria in solution, provided this solution is in equilibrium with another phase. The most versatile systems for studying aqueous solutions use solvent-extraction and ion-exchange methods. These two methods more seen be to universally practical for determining complex equilibria than EMF, spectrophotometric and other more conventional ones. (author)
Three-dimensional magnetohydrodynamic equilibria - I
International Nuclear Information System (INIS)
By using an analytical method, the paper treats the three-dimensional magnetohydrodynamic equilibria of an incompressible, perfectly conducting plasma with an embedded magnetic field in the presence of a gravitational field. We derive a nonlinear second-order partial differential equation for the magnetic potential or stream function. According to the basic equation obtained by us, we analyse a simple example of solutions with the realistic physical property. This set of solutions represents a magnetohydrodynamic equilibrium model for the solar prominence. The results show that the z-component of the inertia force is everywhere upward, adding to upward the Lorentz force and pressure gradient in supporting the plasma weight in a magnetic well. (author)
An Algorithm for Computing All Berge Equilibria
Directory of Open Access Journals (Sweden)
H. W. Corley
2015-01-01
Full Text Available An algorithm is presented in this note for determining all Berge equilibria for an n-person game in normal form. This algorithm is based on the notion of disappointment, with the payoff matrix (PM being transformed into a disappointment matrix (DM. The DM has the property that a pure strategy profile of the PM is a BE if and only if (0,…,0 is the corresponding entry of the DM. Furthermore, any (0,…,0 entry of the DM is also a more restrictive Berge-Vaisman equilibrium if and only if each player’s BE payoff is at least as large as the player’s maximin security level.
CONSTRUCTING EXAMPLES WITH 5 EQUILIBRIA FOR SYMMETRIC 3 × 2 CES / LES PURE EXCHANGE ECONOMIES
Institute of Scientific and Technical Information of China (English)
Huang Hui; Shi Xiaojun; Zhang Shunming
2012-01-01
This paper explores the existence of multiple equilibria for symmetric 3 individual,2 good CES / LES pure exchange economies.Analytically,we show that there are no more than 5 equilibria in such economies.The number of equilibria varies from 5 to 3 then to 1.We generalize our analytical results of existence of 1,3,5 equilibria for a wide range of parametrizations.We also provide concrete examples of 1,3,5 equilibria with parameter zones specified.
The freedom to choose neutron star magnetic field equilibria
Glampedakis, Kostas
2016-01-01
Our ability to interpret and glean useful information from the large body of observations of strongly magnetised neutron stars rests largely on our theoretical understanding of magnetic field equilibria. We answer the following question: is one free to arbitrarily prescribe magnetic equilibria such that fluid degrees of freedom can balance the equilibrium equations? We examine this question for various models for neutron star matter; from the simplest single-fluid barotrope to more realistic non-barotropic multifluid models with superfluid/superconducting components, muons and entropy. We do this for both axi- and non-axisymmetric equilibria, and in Newtonian gravity and general relativity. We show that, in axisymmetry, the most realistic model allows complete freedom in choosing a magnetic field equilibrium whereas non-axisymmetric equilibria are never completely arbitrary.
The freedom to choose neutron star magnetic field equilibria
Glampedakis, Kostas; Lasky, Paul D.
2016-08-01
Our ability to interpret and glean useful information from the large body of observations of strongly magnetised neutron stars rests largely on our theoretical understanding of magnetic field equilibria. We answer the following question: is one free to arbitrarily prescribe magnetic equilibria such that fluid degrees of freedom can balance the equilibrium equations? We examine this question for various models for neutron star matter; from the simplest single-fluid barotrope to more realistic non-barotropic multifluid models with superfluid/superconducting components, muons and entropy. We do this for both axi- and non-axisymmetric equilibria, and in Newtonian gravity and general relativity. We show that, in axisymmetry, the most realistic model allows complete freedom in choosing a magnetic field equilibrium whereas non-axisymmetric equilibria are never completely arbitrary.
Learning Equilibria with Partial Information in Decentralized Wireless Networks
Rose, Luca; Lasaulce, Samson; Debbah, Mérouane
2011-01-01
In this article, a survey of several important equilibrium concepts for decentralized networks is presented. The term decentralized is used here to refer to scenarios where decisions (e.g., choosing a power allocation policy) are taken autonomously by devices interacting with each other (e.g., through mutual interference). The iterative long-term interaction is characterized by stable points of the wireless network called equilibria. The interest in these equilibria stems from the relevance of network stability and the fact that they can be achieved by letting radio devices to repeatedly interact over time. To achieve these equilibria, several learning techniques, namely, the best response dynamics, fictitious play, smoothed fictitious play, reinforcement learning algorithms, and regret matching, are discussed in terms of information requirements and convergence properties. Most of the notions introduced here, for both equilibria and learning schemes, are illustrated by a simple case study, namely, an interfe...
Sunspot equilibria in a monetary economy with capital accumulation
Bloise, Gaetano; Francesco MAGRIS
2000-01-01
In this paper, we consider the determinacy of equilibrium prices, interest rate and income in an economy with liquidity constraints and capital accumulation. In particular, we show that, even though no extrinsic uncertainty effects fundamentals, under some conditions, rational expectations equilibria exist in which prices and quantities exhibit repetitive and persistent fluctuations. To prove the existence of such sunspot equilibria, we introduce a technique of general applicability to nonlin...
Determination of 3D Equilibria from Flux Surface Knowledge Only
International Nuclear Information System (INIS)
We show that the method of Christiansen and Taylor, from which complete tokamak equilibria can be determined given only knowledge of the shape of the flux surfaces, can be extended to 3-dimensional equilibria, such as those of stellarators. As for the tokamak case, the given geometric knowledge has a high degree of redundancy, so that the full equilibrium can be obtained using only a small portion of that information
The freedom to choose neutron star magnetic field equilibria
Glampedakis, Kostas; Lasky, Paul D.
2016-01-01
Our ability to interpret and glean useful information from the large body of observations of strongly magnetised neutron stars rests largely on our theoretical understanding of magnetic field equilibria. We answer the following question: is one free to arbitrarily prescribe magnetic equilibria such that fluid degrees of freedom can balance the equilibrium equations? We examine this question for various models for neutron star matter; from the simplest single-fluid barotrope to more realistic ...
Solubility equilibria in chiral systems and their importance for enantioseparation
Lorenz, H; Sapoundjiev, D.; Seidel-Morgenstern, A.
2003-01-01
Ternary solubility equilibria are studied for three chiral systems in various aqueous and nonaqueous solvents. The chosen systems were a pharmaceutical intermediate, threonine and mandelic acid. Measured solubility data are presented and the nature of the ternary solubility phase diagrams is described. On this basis possible procedures for a crystallization based enantioseparation are derived. Also, the impact of solubility equilibria on the resolution of racemates by liquid chromatography is...
Medical Service
2002-01-01
It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546
Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibria fluctuations
International Nuclear Information System (INIS)
A set of reduced ideal MHD equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. It is found that as in the axisymmetric case, general two-dimensional flow equilibria are governed by a second-order quasi-linear partial differential equation for a magnetic flux function, which is coupled to a Bernoulli-type equation for the density. The equation for the magnetic flux function becomes hyperbolic at certain critical flow speeds which follow from its characteristic equation. When the equation is hyperbolic, shock phenomena may exist. As a particular example, unidirectional flow along the lines of symmetry is considered. In this case, the equation mentioned above is always elliptic. An exact solution for the case of helically symmetric unidirectional flow is found and studied to determine flow effects on the magnetic topology. In second part of this thesis, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency. It is shown that the fluid model with resistivity yields spectral densities which are roughly Lorentzian, exhibit equipartition with no apparent cutoff in wavenumber space and a Bohm-type diffusion coefficient. Under certain conditions, the ensuing transport may be comparable to classical values. For a phenomenological cutoff imposed on the spectrum, the typical fluctuating-to-equilibrium magnetic field ratio is found to be of the order of 10 -10
Bhushanavathi, P.; Veeraswamy, B.; Rao, G. Nageswara; Viplavaprasad, U.
2012-01-01
Protonation equilibria of L-proline and L-valine in varying compositions (0.0-60.0% v/v) of 1, 2-Propanediol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1 using sodium chloride. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, Χ2, skewness, and kurtosis. All the protonation constants of proline and valine increased with increasing propan...
Bilinear Relative Equilibria of Identical Point Vortices
DEFF Research Database (Denmark)
Aref, H.; Beelen, Peter; Brøns, Morten
2012-01-01
-axis and n on the x-axis. We define generating polynomials q(z) and p(z), respectively, for each set of vortices. A second-order, linear ODE for p(z) given q(z) is derived. Several results relating the general solution of the ODE to relative equilibrium configurations are established. Our strongest result......A new class of bilinear relative equilibria of identical point vortices in which the vortices are constrained to be on two perpendicular lines, conveniently taken to be the x- and y-axes of a Cartesian coordinate system, is introduced and studied. In the general problem we have m vortices on the y......, obtained using Sturm’s comparison theorem, is that if p(z) satisfies the ODE for a given q(z) with its imaginary zeros symmetric relative to the x-axis, then it must have at least n−m+2 simple, real zeros. For m=2 this provides a complete characterization of all zeros, and we study this case in some detail...
The CHEASE code for toroidal MHD equilibria
International Nuclear Information System (INIS)
CHEASE solves the Grad-Shafranov equation for the MHD equilibrium of a Tokamak-like plasma with pressure and current profiles specified by analytic forms or sets of data points. Equilibria marginally stable to ballooning modes or with a prescribed fraction of bootstrap current can be computed. The code provides a mapping to magnetic flux coordinates, suitable for MHD stability calculations or global wave propagation studies. The code computes equilibrium quantities for the stability codes ERATO, MARS, PEST, NOVA-W and XTOR and for the global wave propagation codes LION and PENN. The two-dimensional MHD equilibrium (Grad-Shafranov) equation is solved in variational form. The discretization uses bicubic Hermite finite elements with continuous first order derivates for the poloidal flux function Ψ. The nonlinearity of the problem is handled by Picard iteration. The mapping to flux coordinates is carried out with a method which conserves the accuracy of the cubic finite elements. The code uses routines from the CRAY libsci.a program library. However, all these routines are included in the CHEASE package itself. If CHEASE computes equilibrium quantities for MARS with fast Fourier transforms, the NAG library is required. CHEASE is written in standard FORTRAN-77, except for the use of the input facility NAMELIST. CHEASE uses variable names with up to 8 characters, and therefore violates the ANSI standard. CHEASE transfers plot quantities through an external disk file to a plot program named PCHEASE using the UNIRAS or the NCAR plot package. (author) figs., tabs., 34 refs
Tearing Mode Stability of Evolving Toroidal Equilibria
Pletzer, A.; McCune, D.; Manickam, J.; Jardin, S. C.
2000-10-01
There are a number of toroidal equilibrium (such as JSOLVER, ESC, EFIT, and VMEC) and transport codes (such as TRANSP, BALDUR, and TSC) in our community that utilize differing equilibrium representations. There are also many heating and current drive (LSC and TORRAY), and stability (PEST1-3, GATO, NOVA, MARS, DCON, M3D) codes that require this equilibrium information. In an effort to provide seamless compatibility between the codes that produce and need these equilibria, we have developed two Fortran 90 modules, MEQ and XPLASMA, that serve as common interfaces between these two classes of codes. XPLASMA provides a common equilibrium representation for the heating and current drive applications while MEQ provides common equilibrium and associated metric information needed by MHD stability codes. We illustrate the utility of this approach by presenting results of PEST-3 tearing stability calculations of an NSTX discharge performed on profiles provided by the TRANSP code. Using the MEQ module, the TRANSP equilibrium data are stored in a Fortran 90 derived type and passed to PEST3 as a subroutine argument. All calculations are performed on the fly, as the profiles evolve.
Optimal equilibria of the best shot game
Dall'Asta, L; Ramezanpour, A
2010-01-01
We consider any network environment in which the "best shot game" is played. This is the case where the possible actions are only two for every node (0 and 1), and the best response for a node is 1 if and only if all her neighbors play 0. A natural application of the model is one in which the action 1 is the purchase of a good, which is locally a public good, in the sense that it will be available also to neighbors. This game typically exhibits a great multiplicity of equilibria. Imagine a social planner whose scope is to find an optimal equilibrium, i.e. one in which the number of nodes playing 1 is minimal. To find such an equilibrium is a very hard task for any non-trivial network architecture. We propose an implementable mechanism that, in the limit of infinite time, reaches an optimal equilibrium, even if this equilibrium and even the network structure is unknown to the social planner.
Grand Equilibrium: vapour-liquid equilibria by a new molecular simulation method
Vrabec, J
2009-01-01
A new molecular simulation method for the calculation of vapour-liquid equilibria of mixtures is presented. In this method, the independent thermodynamic variables are temperature and liquid composition. In the first step, one isobaric isothermal simulation for the liquid phase is performed, in which the chemical potentials of all components and their derivatives with respect to the pressure, i.e., the partial molar volumes, are calculated. From these results, first order Taylor series expansions for the chemical potentials as functions of the pressure $\\mu_i(p)$ at constant liquid composition are determined. That information is needed, as the specified pressure in the liquid will generally not be equal to the equilibrium pressure, which has to be found in the course of a vapour simulation. In the second step, one pseudo grand canonical simulation for the vapour phase is performed, where the chemical potentials are set according to the instantaneous pressure $p^v$ using the previously determined function $\\mu...
Applied chemical engineering thermodynamics
Tassios, Dimitrios P
1993-01-01
Applied Chemical Engineering Thermodynamics provides the undergraduate and graduate student of chemical engineering with the basic knowledge, the methodology and the references he needs to apply it in industrial practice. Thus, in addition to the classical topics of the laws of thermodynamics,pure component and mixture thermodynamic properties as well as phase and chemical equilibria the reader will find: - history of thermodynamics - energy conservation - internmolecular forces and molecular thermodynamics - cubic equations of state - statistical mechanics. A great number of calculated problems with solutions and an appendix with numerous tables of numbers of practical importance are extremely helpful for applied calculations. The computer programs on the included disk help the student to become familiar with the typical methods used in industry for volumetric and vapor-liquid equilibria calculations.
Phase equilibria in the uranium-chromium-carbon system
International Nuclear Information System (INIS)
The alloys for this study (40 different compositions) were prepared by melting a charge comprising appropriate amounts of the various components and a 'master' alloy under an argon atmosphere on a water-cooled copper tray in an arc furnace equipped with a tungsten electrode. The starting components were uranium of 99.7% purity, graphite with an 0.004% ash content and electrolytically prepared chromium. The alloys were analysed by X-ray spectroscopy, X-ray diffraction analysis and microstructural methods, and a selective chemical analysis was made. As a result of these studies, a new compound of composition 45 at.%Cr - 10 at.%U - 45 at.%C was found; it was subjected to X-ray diffraction analysis. The composition of the compound x(UCr2C3) was refined. The crystallization characteristics of the alloys were established over the entire composition range, a diagram of the non- and monovariant equilibria was drawn and the section for the sub-solidus temperature was constructed over the entire range of concentrations. The isothermal section at 1500-16000C was constructed for the UC2-UC-UCrC2 region; this is characterized by a broad region consisting of a homogeneous solid solution of chromium in the high-temperature (UC-β-UC2) solid solution, which the chromium stabilizes down to a lower temperature. The observed increase of the carbon content in the solid solution with increase in the content of iron can apparently explain the improvement of chromium-modified monocarbide nuclear fuel reported in the literature. The carbon content in uranium-based monocarbide fuel can be increased to approximately 55 at.% by the addition of approximately 7 at.% chromium without change in the crystal structure. The parameters of the tetragonal (UC-β-UC2) lattice were determined to be a=5.041 A and c=5.128 A
Numerical computation of FCT equilibria by inverse equilibrium method
International Nuclear Information System (INIS)
FCT (Flux Conserving Tokamak) equilibria were obtained numerically by the inverse equilibrium method. The high-beta tokamak ordering was used to get the explicit boundary conditions for FCT equilibria. The partial differential equation was reduced to the simultaneous quasi-linear ordinary differential equations by using the moment method. The regularity conditions for solutions at the singular point of the equations can be expressed correctly by this reduction and the problem to be solved becomes a tractable boundary value problem on the quasi-linear ordinary differential equations. This boundary value problem was solved by the method of quasi-linearization, one of the shooting methods. Test calculations show that this method provides high-beta tokamak equilibria with sufficiently high accuracy for MHD stability analysis. (author)
The mechanics of rocking stones: equilibria on separated scales
Domokos, Gábor; Szabó, Tímea
2011-01-01
Rocking stones, balanced in counter-intuitive positions have always intrigued geologists. In our paper we explain this phenomenon based on high-precision scans of pebbles which exhibit similar behavior. We construct their convex hull and the heteroclinic graph carrying their equilibrium points. By systematic simplification of the arising Morse-Smale complex in a one-parameter process we show that equilibria occur typically in highly localized groups (flocks), the number of the latter can be reliably observed and determined by hand experiments. Both local and global (micro and macro) equilibria can be either stable or unstable. Most commonly, rocks and pebbles are balanced on stable local equilibria belonging to stable flocks. However, it is possible to balance a convex body on a stable local equilibrium belonging to an unstable flock and this is the intriguing mechanical scenario corresponding to rocking stones. Since outside observers can only reliably perceive flocks, the last described situation will appea...
(Solid + liquid) equilibria predictions of ionic liquid containing systems using COSMO-RS
International Nuclear Information System (INIS)
Highlights: ► (Solid + liquid) equilibria (SLE) prediction on IL systems. ► Use of COSMO-RS model. ► Quantitative agreement with effect of temperature. - Abstract: (Solid + liquid) equilibria (SLE) prediction are an important phase equilibria property for ionic liquid (IL) mixtures especially when the IL exists as a solid. In this work, the SLE for the binary systems of (IL + thiophene) consisting of the ILs: n-butyl-4-methylpyridinium tosylate [BM4Py][TOS], n-butyl-3-methylpyridinium tosylate [BM3Py][TOS], n-hexyl-3-methylpyridinium tosylate [HM3Py][TOS], and 1,4-dimethylpyridinium tosylate [M1,4Py][TOS] are predicted using the quantum chemical based COSMO-RS (COnductor like Screening MOdel for Real Solvents) model. Initially, benchmarking studies are performed on binary mixtures which are known beforehand. The values of the predicted solubility are then compared with the experimental results by calculating the root mean square error (RMSE). The SLE predictions of the solubility of pyrene and dibenzothiophene in five different solvents were carried out giving an average RMSE of 4%. Further the applicability of COSMO-RS to binary systems consisting of (ionic liquid + alcohol) mixtures and (ionic liquid + hydrocarbons) are predicted. The ionic liquids concerned are n-butyl-3-methylpyridinium tosylate [BM3Py][TOS] while the alcohols and hydrocarbons are 1-butanol, 1-hexanol, 1-octanol, 1-decanol, and benzene, toluene, ethylbenzene, n-propylbenzene respectively. The experimental data for the ionic liquid [BM4Py][TOS] with thiophene gave the smallest deviation of 10.2%. The overall RMSE for IL–thiophene, IL–alcohol, and IL–hydrocarbons were 15%, 17.2% and 12.9% respectively. Thus the predicted solubility values were found to be in reasonable agreement with the experimental values.
Reaching Correlated Equilibria Through Multi-agent Learning
Cigler, Ludek; Faltings, Boi
2011-01-01
Many games have undesirable Nash equilibria. For exam- ple consider a resource allocation game in which two players compete for an exclusive access to a single resource. It has three Nash equilibria. The two pure-strategy NE are effi- cient, but not fair. The one mixed-strategy NE is fair, but not efficient. Aumann’s notion of correlated equilibrium fixes this problem: It assumes a correlation device which suggests each agent an action to take. However, such a “smart” coordination device migh...
Up-down asymmetric tokamak equilibria with parallel flows
International Nuclear Information System (INIS)
A class of exact axisymmetric tokamak equilibria with sheared flows parallel to the magnetic field is constructed, generalizing previous work on the subject (Kuiroukidis 2010 Plasma Phys. Control. Fusion 52 015002). The additional free parameters associated with new terms in the solution make it possible to construct up–down asymmetric configurations with a divertor X-point and desirable values of confinement figures of merit as the safety factor on the magnetic axis and plasma betas; in particular, we construct a number of ITER-pertinent equilibria. Their stability with respect to linear MHD perturbations is also examined by applying a sufficient condition.
Role of Exchange Equilibria in Structural Chemistry
International Nuclear Information System (INIS)
Although much of the past effort on the study of exchange reactions has been devoted to the scrambling of monofunctional substituents on a polyfunctional atom or moiety, complicated molecules may also undergo exchange of parts so as to give an equilibrium distribution of various molecular sizes and shapes. The use of high-resolution nuclear magnetic resonance (NMR) in investigating such equilibrated mixtures of compounds has been described in a number of 1964 and 1965 papers from the Monsanto Co. laboratory (see Refs [1-34] at the end of the abstracts). The systems thus studied include several new families of compounds; and the amounts and kinds of products resulting from the exchange reactions have been quantitatively described in terms of a small number of equilibrium constants. A new mathematical approach - that of stochastic graph theory [6] - has been employed to establish the form and the minimum number of equilibrium constants relating the non-cyclic structures and parts of molecular structures to each other. In addition, the equilibria between the cyclic and non-cyclic structures have been treated quantitatively. The emphasis in structural chemistry on the compounds of carbon (as evidenced by the division of descriptive chemistry into the organic and inorganic categories) is attributed to the fact that exchange reactions involving C-C bonds or bonds from carbon to any atom not exhibiting low-lying vacant bonding orbitals (e.g. Si, Ge, N, P, As. O, S, Se, F, Cl, Br) are exceedingly slow. On the other hand, there are vast areas of inorganic chemistry which have not previously been described because the molecules undergo such rapid exchange reactions that they cannot be separated. However, they can be identified and quantitatively assayed by means of physical methods (such as NMR) having short time constants, when the resulting data receive proper mathematical treatment - a procedure which is sufficiently involved to demand the use of a high-speed computer [6
Asset pricing puzzles explained by incomplete Brownian equilibria
DEFF Research Database (Denmark)
Christensen, Peter Ove; Larsen, Kasper
We examine a class of Brownian based models which produce tractable incomplete equilibria. The models are based on finitely many investors with heterogeneous exponential utilities over intermediate consumption who receive partially unspanned income. The investors can trade continuously on a finit...... markets. Consequently, our model can simultaneously help explaining the risk-free rate and equity premium puzzles....
Shallow-water vortex equilibria and their stability
International Nuclear Information System (INIS)
We first describe the equilibrium form and stability of steadily-rotating simply-connected vortex patches in the single-layer quasi-geostrophic model of geophysical fluid dynamics. This model, valid for rotating shallow-water flow in the limit of small Rossby and Froude numbers, has an intrinsic length scale LD called the 'Rossby deformation length' relating the strength of stratification to that of the background rotation rate. Specifically, LD = c/f where c=√gH is a characteristic gravity-wave speed, g is gravity (or 'reduced' gravity in a two-layer context where one layer is infinitely deep), H is the mean active layer depth, and f is the Coriolis frequency (here constant). We next introduce ageostrophic effects by using the full shallow-water model to generate what we call 'quasi-equilibria'. These equilibria are not strictly steady, but radiate such weak gravity waves that they are steady for all practical purposes. Through an artificial ramping procedure, we ramp up the potential vorticity anomaly of the fluid particles in our quasi-geostrophic equilibria to obtain shallow-water quasi-equilibria at finite Rossby number. We show a few examples of these states in this paper.
From Singularity Theory to Finiteness of Walrasian Equilibria
DEFF Research Database (Denmark)
Castro, Sofia B.S.D.; Dakhlia, Sami F.; Gothen, Peter
The paper establishes that for an open and dense subset of smooth exchange economies, the number of Walrasian equilibria is finite. In particular, our results extend to non-regular economies; it even holds when restricted to the subset of critical ones. The proof rests on concepts from singularity...... theory....
Computing Proper Equilibria of Zero-Sum Games
DEFF Research Database (Denmark)
Miltersen, Peter Bro; Sørensen, Troels Bjerre
We show that a proper equilibrium of a matrix game can be found in polynomial time by solving a linear (in the number of pure strategies of the two players) number of linear programs of roughly the same dimensions as the standard linear programs describing the Nash equilibria of the game....
Computation of Stackelberg Equilibria of Finite Sequential Games
DEFF Research Database (Denmark)
Bosanski, Branislav; Branzei, Simina; Hansen, Kristoffer Arnsfelt; Miltersen, Peter Bro; Sørensen, Troels Bjerre
The Stackelberg equilibrium is a solution concept that describes optimal strategies to commit to: Player~1 (the leader) first commits to a strategy that is publicly announced, then Player~2 (the follower) plays a best response to the leader's choice. We study Stackelberg equilibria in finite...
On Nash equilibria for noncooperative games governed by Burgers equation
Czech Academy of Sciences Publication Activity Database
Roubíček, Tomáš
2007-01-01
Roč. 132, č. 1 (2007), s. 41-50. ISSN 0022-3239 Grant ostatní: GA ČR(CZ) GA201/03/0934 Institutional research plan: CEZ:AV0Z10750506 Keywords : Nash equilibria * noncooperative games * Burgers equation Subject RIV: BA - General Mathematics Impact factor: 0.688, year: 2007
On Pure and (approximate) Strong Equilibria of Facility Location Games
Hansen, Thomas Dueholm
2008-01-01
We study social cost losses in Facility Location games, where n selfish agents install facilities over a network and connect to them, so as to forward their local demand (expressed by a non-negative weight per agent). Agents using the same facility share fairly its installation cost, but every agent pays individually a (weighted) connection cost to the chosen location. We study the Price of Stability (PoS) of pure Nash equilibria and the Price of Anarchy of strong equilibria (SPoA), that generalize pure equilibria by being resilient to coalitional deviations. A special case of recently studied network design games, Facility Location merits separate study as a classic model with numerous applications and individual characteristics: our analysis for unweighted agents on metric networks reveals constant upper and lower bounds for the PoS, while an O(ln n) upper bound implied by previous work is tight for non-metric networks. Strong equilibria do not always exist, even for the unweighted metric case. For this cas...
Schäfer, Harald
2013-01-01
Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and
Magnetoacoustic heating and FCT-equilibria in the belt pinch
International Nuclear Information System (INIS)
In the HECTOR belt pinch of high β plasma is produced by magnetic compression in a Tokamak geometry. After compresseion the initial β value can be varied between 0.2 and 0.8. During 5 μs the plasma is further heated by a fast magnetoacoustic wave with a frequency near the first harmonic of the ion cyclotronfrequency. For the first time the β-value of a pinch plasma could be increased further from 0.34 after compression to 0.46 at the end of the rf-heating cycle. By proper selection of the final β-value the region for resonance absorption of the heating wave can be shifted. Strong heating (200 MW) has been observed in the cases, where the resonance region has been located in the center of the plasma. In deuterium discharges an increase in ion temperature is observed during the heating process, whereas the electrons are energetically decoupled, showing no temperature increase. Strong plasma losses are found in the 200 MW range after the rf-heating process. The dominant mechanisms are charge exchange collisions with neutral gas atoms. During rf-heating and the subsequent cooling phase the magnetic flux is frozen due to the high conductivity of the plasma. The observed equilibria could be identified as flux conserving Tokamak (FCT) equilibria. Based on a two-dimensional code the time-evolution of the equilibria has been calculated. The q-profiles are time-independent, with increasing β the magnetic axis of the plasma is shifted towards the outer boundary of the torus, and finally the linear relation between β and βsub(pol), which is characteristic for low-β-equilibria, is no longer valid. Thus for the first time the existence of FCT-equilibria at high β has been demonstrated experimentally together with a qualitative agreement with FCT-theory. (orig./AH)
Phase equilibria, compatibility studies and thermal properties of beryllium systems
International Nuclear Information System (INIS)
The quality control of commercial beryllium, the examinations of the phase equilibria in beryllium systems as well as the broad field of incompatibility and the reaction kinetics of beryllium with other materials necessitate a sophisticated method for the analysis of this element in micrometer areas. A powerful tool is the wavelength dispersive X-ray microanalyser. Therefore, a commercial synthetic Mo-B4C multilayer X-ray diffracting device with 2 d = 22.2 nm periodicity was used to extend X-ray microanalysis to the ultra-light elements Be and B in an existing instrument. The spectrometer covers a wavelength range between 5.2 and 13 nm. The wavelength of the Be Kα emission line from elemental Be is λ = 11.35 nm and the full width at half maximum is ΔE = 7.2 eV. The optimum working voltage Uo is 10 kV for moderate X-ray mass absorption of the targets. The determination of Be in oxides is less favourable owing to the high mass absorption. Uo has to be reduced to 5 kV. The chemical shift of the Be Kα line in BeO is Δλ = + 0.3 nm relative to pure Be. Beryllium pebbles are foreseen as neutron multipliers in future fusion reactor blanket concepts. Industrial intermediate Be products which had been produced by a modified Kroll process and subsequent reduction of BeF2 using Mg were investigated by X-ray microanalysis. The following precipitates in the Be matrix of 2 mm pebbles partially annealed up to 790 C could be detected: (Mg, Zr, U) Be13, MgBe13, Mg2Si, Al2Mg3 and (Fe, Cr) alloys. The maximum solubility of selected metallic impurities in beryllium annealed at 800 C is: 0.06 mass % Fe, 0.03 mass % Al, 0.02 mass % Si, 5Fe2, Be2C and Cr-Fe-Si were observed in specimens annealed between 870 and 690 C. It is interesting that Al5Fe2 precipitates were observed; however, the phase AlFeBe4 that would have been expected according to the phase diagram of the ternary Al-Be-Fe system was not found. Probably the Fe/Al ratio is too low for AlFeBe4 formation. The high annealing
Vapor–Liquid Equilibrium Coupled with Chemical Reaction (Transesterification)
Czech Academy of Sciences Publication Activity Database
Wichterle, Ivan; Aim, Karel
- : -, 2005 - (Domanska-Zelazna, U.; Malanowski, S.), s.68-69 ISBN 83-920719-1-3. [European Symposium on Applied Thermodynamics ESAT 2005 /21./. Jurata (PL), 01.06.2005-05.06.2005] R&D Projects: GA ČR(CZ) GA203/03/1588 Institutional research plan: CEZ:AV0Z40720504 Keywords : phase equilibria * chemical equilibria * transesterification Subject RIV: CF - Physical ; Theoretical Chemistry
Zaghloul, Mofreh R
2015-01-01
We investigate the dissociation and ionization equilibria of deuterium fluid over a wide range of temperatures and densities. The partition functions for molecular and atomic species are evaluated, in a statistical-mechanically consistent way, implementing recent developments in the literature and taking high-density effects into account. A new chemical model (free energy function) is introduced in which the fluid is considered as a mixture of diatomic molecules, atoms, ions and free electrons. Intensive short range hard core repulsion is taken into account together with partial degeneracy of free electrons and Coulomb interactions among charged particles. Samples of computational results are presented as a set of isotherms for the degree of ionization, dissociated fraction of molecules, pressure, and specific internal energy for a wide range of densities and temperatures. Predictions from the present model calculations show an improved and sensible physical behavior compared to other results in the literatur...
Reactive extraction of lactic acid using alamine 336 in MIBK: equilibria and kinetics.
Wasewar, Kailas L; Heesink, A Bert M; Versteeg, Geert F; Pangarkar, Vishwas G
2002-07-17
Lactic acid is an important commercial product and extracting it out of aqueous solution is a growing requirement in fermentation based industries and recovery from waste streams. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid-amine (solvent) system used. Equilibria for lactic acid extraction by alamine 336 in methyl-iso-butyl-ketone (MIBK) as a diluent have been determined. The extent to which the organic phase (amine +MIBK) may be loaded with lactic acid is expressed as a loading ratio, z=[HL](o)/[B](i,o). Calculations based on the stoichiometry of the reactive extraction and the equilibria involved indicated that more lactic acid is transferred to the organic phase than would be expected from the (1:1) stoichiometry of the reaction. The extraction equilibrium was interpreted as a result of consecutive formation of two acid-amine species with stoichiometries of 1:1 and 2:1. Equilibrium complexation constant for (1:1) and (2:1) has been estimated. Kinetics of extraction of lactic acid by alamine 336 in MIBK has also been determined. In a first study of its kind, the theory of extraction accompanied by a chemical reaction has been used to obtain the kinetics of extraction of lactic acid by alamine 336 in MIBK. The reaction between lactic acid and alamine 336 in MIBK in a stirred cell falls in Regime 3, extraction accompanied by a fast chemical reaction occurring in the diffusion film. The reaction has been found to be zero order in alamine 336 and first order in lactic acid with a rate constant of 1.38 s(-1). These data will be useful in the design of extraction processes. PMID:12052683
Experimental measurements of vapor-liquid equilibria of the H2O + CO2 + CH4 ternary system
Qin, J.; Rosenbauer, R.J.; Duan, Zhenhao
2008-01-01
Reported are the experimental measurements on vapor-liquid equilibria in the H2O + CO2 + CH4 ternary system at temperatures from (324 to 375) K and pressures from (10 to 50) MPa. The results indicate that the CH4 solubility in the ternary mixture is about 10 % to 40 % more than that calculated by interpolation from the Henry's law constants of the binary system, H2O + CH4, and the solubility of CO2 is 6 % to 20 % more than what is calculated by the interpolation from the Henry's law constants of the binary mixture, H 2O + CO2. ?? 2008 American Chemical Society.
Solid-liquid equilibria in the systems ClF5-BF3 and BrF5-BF3
International Nuclear Information System (INIS)
The method of differential thermal analysis has been used to investigate solid-liquid equilibria in the systems ClF5-BF3 and BrF5-BF3 in the whole range of concent-- rations of components. No formation of chemical compounds is found. BrF5-BF3 system refers to the series of simple systems of the eutectic type and is characterized by eutectics depleted in bromine pentafluoride content (less than 5 mol. %) with the melting temperature close to melting temperature of pure boron trifluoride. In the ClF5-BF3 system components are mutually insoluble in both liquid and solid states
Phase diagrams and heterogeneous equilibria a practical introduction
Predel, Bruno; Pool, Monte
2004-01-01
This graduate-level textbook provides an introduction to the practical application of phase diagrams. It is intended for students and researchers in chemistry, metallurgy, mineralogy, and materials science as well as in engineering and physics. Heterogeneous equilibria are described by a minimum of theory illustrated by practical examples and realistic case discussions from the different fields of application. The treatment of the physical and energetic background of phase equilibria leads to the discussion of the thermodynamics of mixtures and the correlation between energetics and composition. Thus, tools for the prediction of energetic, structural, and physical quantities are provided. The authors treat the nucleation of phase transitions, the production and stability of technologically important metastable phases, and metallic glasses. Furthermore, the text also concisely presents the thermodynamics and composition of polymer systems.
Extended Group Contribution Model for Polyfunctional Phase Equilibria
DEFF Research Database (Denmark)
Abildskov, Jens
Material and energy balances and equilibrium data form the basis of most design calculations. While material and energy balances may be stated without much difficulty, the design engineer is left with a choice between a wide variety of models for describing phase equilibria in the design of...... physical separation processes. In a thermodynamic sense, design requires detailed knowledge of activity coefficients in the phases at equilibrium. The prediction of these quantities from a minimum of experimental data is the broad scope of this thesis. Adequate equations exist for predicting vapor......-liquid equilibria from data on binary mixtures, composed of structurally simple molecules with a single functional group. More complex is the situation with mixtures composed of structurally more complicated molecules or molecules with more than one functional group. The UNIFAC method is extended to handle...
Vlasov tokamak equilibria with shearad toroidal flow and anisotropic pressure
Throumoulopoulos, George; Kuiroukidis, Apostolos; Tasso, Henri
2015-11-01
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e. the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis. This work has received funding from (a) the National Programme for the Controlled Thermonuclear Fusion, Hellenic Republic, (b) Euratom research and training programme 2014-2018 under grant agreement No 633053.
On the extremum electric charge problem of steady electromagnetic equilibria
International Nuclear Information System (INIS)
The existence of steady electromagnetic equilibria has earlier been predicted in terms of an extended formulation of Maxwell's equation. In this connection of variational problem was formulated for finding extremum values of the total electric charge of such equilibria in the axisymmetric case. In this paper the variational procedure has been cast into a new form, in terms of a generating function F. This simplifies the variational procedure substantially, by incorporating the field equations of the electric and magnetic potentials into the integrals of the charge qo, the magnetic moment Mo, the mass mo and the angular momentum so of the system. As a result, the variational procedure reduces to finding extremum values of qo, by varying F under the constraints of a given asymptotic form of F at infinity, and of one quantum condition. At this stage it appears possible for a set of extremum values of qo to arise from such a procedure. (au)
Vlasov tokamak equilibria with shearad toroidal flow and anisotropic pressure
Kuiroukidis, Ap; Tasso, H
2015-01-01
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e. the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis.
Vlasov tokamak equilibria with sheared toroidal flow and anisotropic pressure
Energy Technology Data Exchange (ETDEWEB)
Kuiroukidis, Ap, E-mail: kouirouki@astro.auth.gr [Technological Education Institute of Serres, 62124 Serres (Greece); Throumoulopoulos, G. N., E-mail: gthroum@uoi.gr [Department of Physics, University of Ioannina, GR 451 10 Ioannina (Greece); Tasso, H., E-mail: het@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany)
2015-08-15
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e., the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions, these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis.
Bifurcation Analysis of Equilibria in Competitive Logistic Networks with Adaptation
Raimondi, A.; Tebaldi, C.
2008-04-01
A general n-node network is considered for which, in absence of interactions, each node is governed by a logistic equation. Interactions among the nodes take place in the form of competition, which also includes adaptive abilities through a (short term) memory effect. As a consequence the dynamics of the network is governed by a system of n2 nonlinear ordinary differential equations. As a first step, equilibria and their stability are investigated analytically for the general network in dependence of the relevant parameters, namely the strength of competition, the adaptation rate and the network size. The existence of classes of invariant subspaces, related to symmetries, allows the introduction of a reduced model, four dimensional, where n appears as a parameter, which give full account of existence and stability for the equilibria in the network.
Relative profit maximization in asymmetric oligopoly: Cournot and Bertrand equilibria
Satoh, Atsuhiro; Tanaka, Yasuhito
2014-01-01
We analyze Bertrand and Cournot equilibria in an asymmetric oligopoly with more than two firms in which the firms produce differentiated substitutable goods and seek to maximize their relative profits instead of their absolute profits. Assuming linear demand functions and constant marginal costs we show the following results. If the marginal cost of a firm is lower (higher) than the average marginal cost over the industry, its output at the Bertrand equilibrium is larger (smaller) than that a...
Low-aspect-ratio toroidal equilibria of electron clouds
International Nuclear Information System (INIS)
Toroidal electron clouds with a low aspect ratio (as small as 1.3) and lasting for thousands of poloidal rotation periods have been formed in the laboratory. Characteristic toroidal effects like a large inward shift of the minor axis of equipotential contours, elliptical and triangular deformations, etc., have been observed experimentally for the first time. The results of new analytic and numerical investigations of low-aspect-ratio electron cloud equilibria, which reproduce many of the observed features, are also presented
Cryptographically Blinded Games: Leveraging Players' Limitations for Equilibria and Profit
Pavel Hub\\xe1ek; Sunoo Park
2014-01-01
In this work we apply methods from cryptography to enable any number of mutually distrusting players to implement broad classes of mediated equilibria of strategic games without the need for trusted mediation. Our implementation makes use of a (standard) pre-play "cheap talk" phase, in which players engage in free and non-binding communication prior to playing in the original game. In our cheap talk phase, the players execute a secure multi-party computation protocol to sample an action profi...
Magnetic coordinates for equilibria with a continuous symmetry
International Nuclear Information System (INIS)
Magnetic coordinates for hydromagnetic equilibria are defined which treat toroidal and straight helical plasmas equivalently yet exploit the existence of a continuous symmetry to derive relations between various geometrical and physical quantities. This allows the number of equilibrium quantities which must be known to be reduced to a minimal, or primitive set. Practical formulae for various quantities required in hydromagnetic stability calculations (interchange, ballooning, and global) are given in terms of this primitive set
Settling the Complexity of Computing Two-Player Nash Equilibria
Chen, Xi; Deng, Xiaotie; Teng, Shang-Hua
2007-01-01
We settle a long-standing open question in algorithmic game theory. We prove that Bimatrix, the problem of finding a Nash equilibrium in a two-player game, is complete for the complexity class PPAD Polynomial Parity Argument, Directed version) introduced by Papadimitriou in 1991. This is the first of a series of results concerning the complexity of Nash equilibria. In particular, we prove the following theorems: Bimatrix does not have a fully polynomial-time approximation scheme unless every ...
What are the equilibria in linear public-good experiments?
Wolff, Irenaeus
2016-01-01
Most social-preference models have been tailored to yield only a full-defection equilibrium in one-shot linear public-good situations. This paper determines the Nash-equilibrium sets that result from experiment participants’ elicited preferences. The data show that multiple equilibria are relatively frequent even in a standard three-player setting. In this perspective, the common finding of close-toomnilateral defection at the end of repeated public-good games is surprising and raises the que...
Phase equilibria in alloys of Cr-Hf-N system
International Nuclear Information System (INIS)
Metallographic, X-ray phase and differential thermal analyses are used to study phase equilibria in alloys of the Cr-Hf-N system with nitrogen concentration less than 15% (at.). Isothermal section at 1150 deg C is plotted. The polythermal Cr-HfN section is stated to be quasibinary eutectic one. Maximal solubility of HfN in chromium is estimated by thermodynamic calculation
Exchange Equilibria on the Surface of Ionic Crystals
International Nuclear Information System (INIS)
New experimental data obtained by tracer techniques are presented and discussed. The number of exchanging cations and anions per unit area on the surface of BaSO4 and SrSO4 was measured for equivalent particles, cationic particles and anionic particles. Equivalent particles obtained by washing the precipitates thoroughly with water showed constant ratios of exchanging cations and anions per unit area of the surface. For cationic particles and anionic particles obtained by treatmeni of the precipitates with solutions containing barium ions or sulphate ions respectively, the ratio of the numbers of exchanging cations and anions was changed to higher values (cationic particles) or to lower values (anionic particles). From the values obtained the number of potential determining ions on the surface was determined. In the case of SrSO4 the numbers of exchanging cations and anions per unit area of the surface were measured as a function of temperature. They were found to decrease rapidly below 40°C in water solutions. This is explained by the immobilization of the water molecules on special points of the surface (in cracks for instance) proceeding gradually on approaching the freezing point. In agreement with this explanation the immobilization starts at lower temperatures for water-methanol mixtures. The exchange equilibria between different cations have been measured on the surface of the alkaline earth carbonates and sulphates and on the surface of the alkali tetraphenylborates. The equilibrium constants for these heterogeneous exchange reactions are discussed. In general these equilibria show the same trend as the solubilities. Barium ions, for instance, are enriched on the surface of strontium sulphate. The ratio of the solubilities, however, is no measure for these equilibria. The exchange equilibria on the surface of the alkaline earth sulphates show ''ideal'' behaviour; they are independent of the lattice parameters. (author)
Beltrami–Bernoulli equilibria in plasmas with degenerate electrons
Energy Technology Data Exchange (ETDEWEB)
Berezhiani, V. I., E-mail: vazhab@yahoo.com [Andronikashvili Institute of Physics, TSU, Tbilisi 0177, Georgia and School of Physics, Free University of Tbilisi, Tbilisi 0131, Georgia (United States); Shatashvili, N. L., E-mail: shatash@ictp.it [Andronikashvili Institute of Physics, TSU, Tbilisi 0177, Georgia and Department of Physics, Faculty of Exact and Natural Sciences, Ivane Javakhishvili Tbilisi State University (TSU), Tbilisi 0179, Georgia (United States); Mahajan, S. M., E-mail: mahajan@mail.utexas.edu [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)
2015-02-15
A new class of Double Beltrami–Bernoulli equilibria, sustained by electron degeneracy pressure, is investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami–Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars, etc.
Beltrami-Bernoulli Equilibria in Plasmas with Degenerate Electrons
Berezhiani, V I; Mahajan, S M
2014-01-01
A new class of Double Beltrami-Bernoulli equilibria, sustained by electron degeneracy pressure, are investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami-Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars etc.
Existence of equilibria in quantum Bertrand-Edgeworth duopoly game
Sekiguchi, Yohei; Sato, Takashi
2010-01-01
Both classical and quantum version of two models of price competition in duopoly market, the one is realistic and the other is idealized, are investigated. The pure strategy Nash equilibria of the realistic model exists under stricter condition than that of the idealized one in the classical form game. This is the problem known as Edgeworth paradox in economics. In the quantum form game, however, the former converges to the latter as the measure of entanglement goes to infinity.
Existence of equilibria in quantum Bertrand-Edgeworth duopoly game
Sekiguchi, Yohei; Sakahara, Kiri; Sato, Takashi
2012-12-01
Both classical and quantum version of two models of price competition in duopoly market, the one is realistic and the other is idealized, are investigated. The pure strategy Nash equilibria of the realistic model exists under stricter condition than that of the idealized one in the classical form game. This is the problem known as Edgeworth paradox in economics. In the quantum form game, however, the former converges to the latter as the measure of entanglement goes to infinity.
Consistent expectations equilibria and learning in a stock market
Sögner, Leopold; Mitlöhner, Johann
1999-01-01
In this article we investigate the question whether the highly demanding informative requirements of rational expectations models are necessary to derive equilibria within capital market models. In the analysis agents are only provided with publicly available information such as prices and dividends. Nevertheless, we require that agents should behave like econometricians. Additionally, we skip the assumption of rational expectations models that agents know the implied law of motion of the sys...
Long-term Nash equilibria in electricity markets
International Nuclear Information System (INIS)
In competitive electricity markets, companies simultaneously offer their productions to obtain the maximum profits on a daily basis. In the long run, the strategies utilized by the electric companies lead to various long-term equilibria that can be analyzed with the appropriate tools. We present a methodology to find plausible long-term Nash equilibria in pool-based electricity markets. The methodology is based on an iterative market Nash equilibrium model in which the companies can decide upon their offer strategies. An exponential smoothing of the bids submitted by the companies is applied to facilitate the convergence of the iterative procedure. In each iteration of the model the companies face residual demand curves that are accurately modeled by Hermite interpolating polynomials. We introduce the concept of meta-game equilibrium strategies to allow companies to have a range of offer strategies where several pure and mixed meta-game Nash equilibria are possible. With our model it is also possible to model uncertainty or to generate price scenarios for financial models that assess the value of a generating unit by real options analysis. The application of the proposed methodology is illustrated with several realistic case studies. (author)
(Liquid + liquid) equilibria of perfluorocarbons with fluorinated ionic liquids
International Nuclear Information System (INIS)
Highlights: • (Liquid + liquid) equilibria perfluorocarbons and fluorinated ionic liquids. • Non-Random Two Liquid model was successfully applied. • Thermodynamic functions that describe the solvation process were calculated. -- Abstract: In order to evaluate the feasibility of partially replace perfluorocarbons (PFCs) with fluorinated ionic liquids (FILs) in PFCs-in-water emulsions, usually used for biomedical purposes, herein the (liquid + liquid) phase equilibria of FILs containing fluorinated chains longer than four carbons with PFCs were carried out in a wide range of temperatures. With this goal in mind, two PFCs (perfluorooctane and perfluorodecalin) were selected and the (liquid + liquid) equilibria of the binary mixtures of these PFCs and FILs were studied at atmospheric pressure in a temperature range from T (293.15 to 343.15) K. For these studies, FILs containing ammonium, pyridinium and imidazolium cations and different anions with fluorocarbon alkyl chains between 4 and 8 were included. Additionally, Non-Random Two Liquid (NRTL) thermodynamic model was successfully applied to correlate the behaviour of the PFCs + FILs binary mixtures. Moreover, thermodynamic functions that describe the solvation process were calculated from the experimental data
Preference Games and Personalized Equilibria, with Applications to Fractional BGP
Poplawski, Laura J; Sundaram, Ravi; Teng, Shang-Hua
2008-01-01
We study the complexity of computing equilibria in two classes of network games based on flows - fractional BGP (Border Gateway Protocol) games and fractional BBC (Bounded Budget Connection) games. BGP is the glue that holds the Internet together and hence its stability, i.e. the equilibria of fractional BGP games (Haxell, Wilfong), is a matter of practical importance. BBC games (Laoutaris et al) follow in the tradition of the large body of work on network formation games and capture a variety of applications ranging from social networks and overlay networks to peer-to-peer networks. The central result of this paper is that there are no fully polynomial-time approximation schemes (unless PPAD is in FP) for computing equilibria in both fractional BGP games and fractional BBC games. We obtain this result by proving the hardness for a new and surprisingly simple game, the fractional preference game, which is reducible to both fractional BGP and BBC games. Generalizing both fractional BBC games and fractional BGP...
International Nuclear Information System (INIS)
Highlights: ► Aromatic/aliphatic hydrocarbons separation by ionic liquids. ► Cosmo-SAC thermodynamic model for prediction of LLE by quantum chemical calculations. ► Predictions successful for some ionic liquids. ► Correlation by single parameter for other ionic liquids. ► Preliminary screening of additional ionic liquids for aromatic/aliphatic separation. - Abstract: The extraction of aromatic hydrocarbons from aliphatic hydrocarbons is an important problem. This process can be used to enhance the capacity of ethylene crackers by prior removal of aromatics that cannot be cracked. Ionic liquids have been investigated extensively for liquid–liquid extraction of aromatics from aliphatics. The choice of a suitable ionic liquid may be made by measuring liquid−liquid equilibria. However, the large number of ionic liquids, formed by the various cation and anion combinations, makes the experimental measurements expensive and time consuming. Hence, a predictive thermodynamic model called Cosmo-SAC that uses quantum chemical calculations for calculating liquid−liquid equilibria has been evaluated. A priori predictions are accurate for some ionic liquids and inaccurate for some ionic liquids. However, it has been shown that even when a priori predictions are inaccurate, the data can be correlated using a single parameter that is characteristic of the ionic liquid and accurate predictions can be made for additional aromatic/aliphatic combinations for the same ionic liquid. A comparison with the NRTL and UNIQUAC models has also been carried out. In addition, a preliminary screening of ionic liquids for aromatic/aliphatic separations has been carried out using the Cosmo-SAC model. Finally, the “Cosmo” files for eight cations and sixteen anions corresponding to 128 potential ionic liquids have been provided for the use of the general scientific community to predict any thermodynamic equilibria involving ionic liquids without the use of any molecular modeling
Czech Academy of Sciences Publication Activity Database
Bernatová, Svatoslava; Aim, Karel; Wichterle, Ivan
2006-01-01
Roč. 247, 1-2 (2006) , s. 96-101. ISSN 0378-3812 R&D Projects: GA ČR(CZ) GA203/03/1588 Institutional research plan: CEZ:AV0Z40720504 Keywords : esterification * chemical equilibria * phase equilibria Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.680, year: 2006
Computation of thermodynamic equilibria of nuclear materials in multi-physics codes
International Nuclear Information System (INIS)
A new equilibrium thermodynamic solver is being developed with the primary impetus of direct integration into nuclear fuel performance and safety codes to provide improved predictions of fuel behavior. This solver is intended to provide boundary conditions and material properties for continuum transport calculations. There are several legitimate concerns with the use of existing commercial thermodynamic codes: 1) licensing entanglements associated with code distribution, 2) computational performance, and 3) limited capabilities of handling large multi-component systems of interest to the nuclear industry. The development of this solver is specifically aimed at addressing these concerns. In support of this goal, a new numerical algorithm for computing chemical equilibria is presented which is not based on the traditional steepest descent method or 'Gibbs energy minimization' technique. This new approach exploits fundamental principles of equilibrium thermodynamics, which simplifies the optimization equations. The chemical potentials of all species and phases in the system are constrained by the system chemical potentials, and the objective is to minimize the residuals of the mass balance equations. Several numerical advantages are achieved through this simplification, as described in this paper. (author)
Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria
Sverjensky, D.A.; Hemley, J.J.; d'Angelo, W. M.
1991-01-01
The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K2O- and Na2O-Al2O3-SiO2-H2O-HCl (e.g., K-fs - Ms - Qtz - K+ - H+). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies (Berman, 1988) with the properties of aqueous species calculated from a calibrated equation of state (Shock and Helgeson, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25??C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300??C and Psat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates (Berman, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 (??500) cal/mol to all the K- and Na-bearing silicates, respectively, in Berman (1988) are required. In all cases, the revised values are within ??0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from Helgeson et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600??C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance-derived dissociation
DEFF Research Database (Denmark)
Cismondi, Martin; Mollerup, Jørgen M.; Zabaloy, Marcelo S.
2010-01-01
available interaction parameters) in modern equations of state.In particular, the phase equilibria of binary mixtures containing CO2 and heavy n-alkanes have been studied by an important number of authors and using different types of models, achieving only partially accurate results and realizing the...... for the first time a quite successful complete description of asymmetric CO2+n-alkane binary systems, with n-alkane carbon number from 14 to 22....... a great diversity of mixtures. Nevertheless, the models for representing phase equilibria and physico-chemical properties of asymmetric systems may require more flexible mixing rules than the classical quadratic van der Waals (vdW) mixing rules or their equivalent (with regard to the number of...
Close pairs of relative equilibria for identical point vortices
DEFF Research Database (Denmark)
Dirksen, Tobias; Aref, Hassan
2011-01-01
Numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane reveals configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. New numerical solutions of this kind are found...... for 3n + 1 vortices, where n = 2, 3, ..., 30. A sufficient, although apparently not necessary, condition for this phenomenon of close solutions is that the "core" of the configuration is marginally stable, as occurs for a central vortex surrounded by an equilateral triangle. The open, regular heptagon...
Solitonlike solutions of magnetostatic equilibria: Plane-symmetric case
Yoshino, Hirotaka
2008-01-01
We present the plane-symmetric solitonlike solutions of magnetostatic equilibria by solving the nonlinear Grad-Shafranov (GS) equation numerically. The solutions have solitonlike and periodic structures in the $x$ and $y$ directions, respectively, and $z$ is the direction of plane symmetry. Although such solutions are unstable against the numerical iteration, we give the procedure to realize the sufficient convergence. Our result provides the definite answer for the existence of the solitonlike solutions that was questioned in recent years. The method developed in this paper will make it possible to study the axisymmetric solitonlike solutions of the nonlinear GS equation, which could model astrophysical jets with knotty structures.
Thermodynamic calculation of phase equilibria in Cr - V - N alloys
International Nuclear Information System (INIS)
PHase equilibria in the Cr-V-N system alloys using the thermodynamic calculation method are investigated. It is shown that Cr2N and V2N nitrides at the 1073 K temperature form a continuous series of solid solutions. Free energy of VNsub(0.42) nitride formation at the 1073 K temperature is determined to be equal - 44.4+-3 kJ/mol V. By the thermodynamic calculation method the isothermal cross section of the Cr-V-N phase diagram is plotted. The calculation results the limits of measurements error coincide with the experimental results
Analytical calculation of boozer magnetic coordinates for axisymmetric MHD equilibria
International Nuclear Information System (INIS)
A new analytical technique for extracting the Boozer magnetic coordinates in axisymmetric MHD equilibria is described. The method is based upon the correspondence between the expansion of the flux function in toroidal multipolar moments and the expansion in toroidal axisymmetric harmonics of the magnetic scalar potential χ0, which appears in the covariant representation B=∇χ0+β∇ψ-T of the magnetic field. An example of calculation of Boozer magnetic coordinates is given for an experimental highly shaped high β equilibrium of DIIID
Anomeric and tautomeric equilibria in D-2-glucosamine Schiff bases
Kołodziej, B.; Grech, E.; Schilf, W.; Kamieński, B.; Makowski, M.; Rozwadowski, Z.; Dziembowska, T.
2007-11-01
The structure of some glucosamine Schiff bases has been studied by means of ab initio RHF and DFT calculation and CP/MAS 13C and 15N NMR measurements. The anomeric and tautomeric equilibria in a DMSO solution have been studied by 1H, 13C and 15N NMR spectroscopy. The anomeric composition of D-2-glucosamine Schiff bases in the solid state and in DMSO solution has been shown to depends on the tautomeric form of Schiff bases and electronic properties of substituents on the aromatic ring.
Phase Equilibria Relationships of High-Tc Superconductors
International Nuclear Information System (INIS)
As an integral part of a R and D program partially supported by the Electricity Delivery and Energy Reliability Office of DOE, we have determined phase equilibria data and phase diagrams for the three generations of superconductor materials: 1st generation, (Bi,Pb)-Sr-Ca- Cu-O systems; 2nd generation, Ba-R-Cu-O systems (R=lanthanides and yttrium); and 3rd generation, MgB2 systems. Our studies involved bulk materials, single crystals and thin films. This report gives a summary of our accomplishments, a list of publications, and 15 selected journal publications.
The free energy of Maxwell-Vlasov equilibria
International Nuclear Information System (INIS)
A previously derived expression for the energy of arbitrary perturbations about arbitrary Vlasov-Maxwell equilibria is transformed into a very compact form. The new form is also obtained by a canonical transformation method for solving Vlasov's equation, which is based on Lie group theory. This method is simpler than the one used before and provides better physical insight. Finally a procedure is presented for determining the existence of negative-energy modes. In this context the question of why there is an accessibility constraint for the particles, but not for the fields, is discussed. 16 refs
Existence of Nash equilibria in sporting contests with capacity constraints
平井, 秀明; ヒライ, シュウメイ; HIRAI, SHUMEI
2014-01-01
The main purpose of this paper is to demonstrate the existence of pure-strategy Nash equilibria in an “n” team sporting contest. Since the seminal papers of Szymanski (2003, 2004) and Szymanski and Késenne (2004), the Nash equilibrium model has been used in the analysis of professional team sports. However, many papers have been restricted to a two-team league model (Chang and Sanders, 2009; Cyrenne, 2009; Dietl et al., 2009). Dietl et al. (2008) that is considered a more general n-team...
Phase equilibria in the In–Sb–Bi system at 300 ºC
Directory of Open Access Journals (Sweden)
DUSKO MINIC
2006-07-01
Full Text Available Binary thermodynamic data, successfully used for phase diagram calculations of the binary systems In–Sb, Bi–Sb and In–Bi, were used fort the prediction of phase equilibria in the ternary system In–Sb–Bi at 300 ºC. The predicted equilibria were compared with the results of SEM–EDX analysis.
Stability and bifurcations of relative equilibria of a pendulum suspended on the equator
Burov, A. A.; Kosenko, I. I.
2013-05-01
The problem of equilibria of a pendulum suspended at an equatorial point relative to the rotating Earth is considered. An altitude is determined at which the degree of instability of the inverted pendulum changes from two to unity. Relative equilibria are investigated that bifurcate from the radial one when its degree of instability changes. Their stability properties are studied.
The Structure of the Set of Equilibria for Two Person Multicriteria Games
Borm, P.E.M.; Vermeulen, D.; Voorneveld, M.
1998-01-01
In this paper the structure of the set of equilibria for two person multicriteria games is analysed. It turns out that the classical result for the set of equilibria for bimatrix games, that it is a finite union of polytopes, is only valid for multicriteria games if one of the players only has two p
International Nuclear Information System (INIS)
Highlights: • Experimental LLE data for water + acetic acid + toluene + NaCl or KCl were reported. • The salting-out effect was detected; indicating the stronger effect of NaCl. • The electrolyte-NRTL model was adequately used to correlate the phase equilibria. • A good agreement was observed between calculated and experimental tie-lines. - Abstract: The presence of salts can significantly alter the (liquid + liquid) equilibrium and extraction process. In this work, a study was conducted on the (liquid + liquid) equilibria of (water + acetic acid + toluene + sodium chloride or potassium chloride) at temperatures (288.2, 298.2 and 313.2) K. This chemical system, irrespective of salt, is frequently used in (liquid + liquid) extraction investigations. The selected salt concentrations in initial aqueous solutions were (0.9 and 1.7) mol · L−1. The results show that salting-out effect of the salts was significant, so that an enhancement in the acetic acid distribution coefficient was achieved within (15.6 to 66.8)% with NaCl and within (2.5 to 37.6)% with KCl. Meantime, high separation factors were found at low temperatures and low solute concentrations. The electrolyte-NRTL model was satisfactorily used to correlate the phase equilibria. In this regard for each salt, the temperature dependent binary interaction parameters between components were calculated. The predicted tie-line mole fractions give root-mean square deviation (RMSD) values of only 0.0038 and 0.0045 for the systems containing NaCl and KCl, respectively
Equilibria, Dynamics and Current Sheets Formation in Magnetically Confined Coronae
Rappazzo, A F
2015-01-01
The dynamics of magnetic fields in closed regions of solar and stellar coronae are investigated with a reduced magnetohydrodynamic (MHD) model in the framework of Parker scenario for coronal heating. A novel analysis of reduced MHD equilibria shows that their magnetic fields have an asymmetric structure in the axial direction with variation length-scale $z_\\ell \\sim \\ell B_0/b$, where $B_0$ is the intensity of the strong axial guide field, $b$ that of the orthogonal magnetic field component, and $\\ell$ the scale of $\\mathbf{b}$. Equilibria are then quasi-invariant along the axial direction for variation scales larger than approximatively the loop length $z_\\ell \\gtrsim L_z$, and increasingly more asymmetric for smaller variation scales $z_\\ell \\lesssim L_z$. The $critical$ $length$ $z_\\ell \\sim L_z$ corresponds to the magnetic field intensity threshold $b \\sim \\ell B_0/L_z$. Magnetic fields stressed by photospheric motions cannot develop strong axial asymmetries. Therefore fields with intensities below such t...
High temperature interdiffusion and phase equilibria in U-Mo
International Nuclear Information System (INIS)
Experimental data for interdiffusion and phase equilibria in the U-Mo system have been obtained over the temperature range 1400 to 1525 K as a fallout from compatibility experiments in which UO2 was decomposed by lithium in closed molybdenum capsules. Composition-position, x-ray diffraction and microstructural data from the interdiffusion zones indicate that the intermediate phase U2Mo is found in this temperature range, contrary to the currently accepted equilibrium U-Mo phase diagram. The U-Mo interdiffusion data are in good agreement with published values. Inclusion of the U2Mo phase in a theoretical correlation of interdiffusion and phase equilibria data using Darken's equation indicate that high temperature interdiffusion of uranium and molybdenum follows the usual thermodynamic rules. Significant changes in the value of the thermodynamic based Darken factor near the U2Mo phase boundary on the high uranium side are indicated from both the new and published interdiffusion data. 9 refs., 10 figs., 3 tabs
Self-consistent diverted tokamak equilibria with nonzero edge current
Institute of Scientific and Technical Information of China (English)
Shi Bing-Ren
2012-01-01
The semi-analytical method,previously used to construct model double-null and single-null diverted tokamak equilibria (Bingren Shi,Plasma Phys.Control Fusion 50 (2008) 085006,51 (2009) 105008,Nucl.Fusion 51 (2011) 023004),is extended to describe diverted tokamak equilibria with nonzero edge current,including the Pfirsch-Schlüter(PS) current.The PS current density is expressed in a way suitable to describe a diverted tokamak configuration in the near separatrix region.The model equilibrium is expressed by only two terms of the exact separable solutions of the GradShafranov equation,one of which is governed by a homogeneous ordinary differential equation,and the other by an inhomogeneous one.The particular merits of such a model configuration are that the internal region inside the separatrix and a suitable scrape-off layer can be simultaneously described by this exact solution.To investigate the physics in the region near the X-point,the magnetic surfaces can be satisfactorily described by approximate hyperbolic curves.
On Pure and (approximate) Strong Equilibria of Facility Location Games
DEFF Research Database (Denmark)
Hansen, Thomas Dueholm; Telelis, Orestis A.
2008-01-01
We study social cost losses in Facility Location games, where n selfish agents install facilities over a network and connect to them, so as to forward their local demand (expressed by a non-negative weight per agent). Agents using the same facility share fairly its installation cost, but every ag......-approximate (e = 2.718...) strong equilibria and an upper bound of O(ln W) on SPoA (W is the sum of agents’ weights), which becomes tight Θ(ln n) for unweighted agents. Center for Algorithmic Game Theory, funded by the Carlsberg Foundation, Denmark.......We study social cost losses in Facility Location games, where n selfish agents install facilities over a network and connect to them, so as to forward their local demand (expressed by a non-negative weight per agent). Agents using the same facility share fairly its installation cost, but every...... networks we prove upper and lower bounds on PoS, while an O(ln n) upper bound implied by previous work is tight for non-metric networks. We also prove a constant upper bound for the SPoA of metric networks when strong equilibria exist. For the weighted game on general networks we prove existence of e...
Stability of Hall equilibria in neutron star crusts
Energy Technology Data Exchange (ETDEWEB)
Marchant, Pablo; Reisenegger, Andreas [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul 7820436, Santiago (Chile); Valdivia, Juan Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile Casilla 653, Santiago (Chile); Hoyos, Jaime H., E-mail: pablo@astro.uni-bonn.de [Departamento de Ciencias Básicas, Universidad de Medellín Cra. 87 # 30-65, Medellín (Colombia)
2014-12-01
In the solid crusts of neutron stars, the advection of the magnetic field by the current-carrying electrons, an effect known as Hall drift, should play a very important role as the ions remain essentially fixed (as long as the solid does not break). Although Hall drift preserves the magnetic field energy, it has been argued that it may drive a turbulent cascade to scales at which ohmic dissipation becomes effective, allowing a much faster decay in objects with very strong fields. On the other hand, it has been found that there are 'Hall equilibria', i.e., field configurations that are unaffected by Hall drift. Here we address the crucial question of the stability of these equilibria through axially symmetric (two-dimensional (2D)) numerical simulations of Hall drift and ohmic diffusion, with the simplifying assumption of uniform electron density and conductivity. We demonstrate the 2D stability of a purely poloidal equilibrium, for which ohmic dissipation makes the field evolve toward an attractor state through adjacent stable configurations, around which damped oscillations occur. For this field, the decay scales with the ohmic timescale. We also study the case of an unstable equilibrium consisting of both poloidal and toroidal field components that are confined within the crust. This field evolves into a stable configuration, which undergoes damped oscillations superimposed on a slow evolution toward an attractor, just as the purely poloidal one.
Stability of Hall equilibria in neutron star crusts
Marchant, Pablo; Valdivia, Juan Alejandro; Hoyos, Jaime H
2014-01-01
In the solid crusts of neutron stars, the advection of the magnetic field by the current-carrying electrons, an effect known as Hall drift, should play a very important role as the ions remain essentially fixed (as long as the solid does not break). Although Hall drift preserves the magnetic field energy, it has been argued that it may drive a turbulent cascade to scales at which Ohmic dissipation becomes effective, allowing a much faster decay in objects with very strong fields. On the other hand, it has been found that there are "Hall equilibria", i.e., field configurations that are unaffected by Hall drift. Here, we address the crucial question of the stability of these equilibria through axially symmetric (2D) numerical simulations of Hall drift and Ohmic diffusion, with the simplifying assumption of uniform electron density and conductivity. We demonstrate the 2D-stability of a purely poloidal equilibrium, for which Ohmic dissipation makes the field evolve towards an attractor state through adjacent stab...
Stability of Hall equilibria in neutron star crusts
International Nuclear Information System (INIS)
In the solid crusts of neutron stars, the advection of the magnetic field by the current-carrying electrons, an effect known as Hall drift, should play a very important role as the ions remain essentially fixed (as long as the solid does not break). Although Hall drift preserves the magnetic field energy, it has been argued that it may drive a turbulent cascade to scales at which ohmic dissipation becomes effective, allowing a much faster decay in objects with very strong fields. On the other hand, it has been found that there are 'Hall equilibria', i.e., field configurations that are unaffected by Hall drift. Here we address the crucial question of the stability of these equilibria through axially symmetric (two-dimensional (2D)) numerical simulations of Hall drift and ohmic diffusion, with the simplifying assumption of uniform electron density and conductivity. We demonstrate the 2D stability of a purely poloidal equilibrium, for which ohmic dissipation makes the field evolve toward an attractor state through adjacent stable configurations, around which damped oscillations occur. For this field, the decay scales with the ohmic timescale. We also study the case of an unstable equilibrium consisting of both poloidal and toroidal field components that are confined within the crust. This field evolves into a stable configuration, which undergoes damped oscillations superimposed on a slow evolution toward an attractor, just as the purely poloidal one.
Axisymmetric equilibria with pressure anisotropy and plasma flow
Evangelias, A.; Throumoulopoulos, G. N.
2016-04-01
A generalised Grad-Shafranov equation that governs the equilibrium of an axisymmetric toroidal plasma with anisotropic pressure and incompressible flow of arbitrary direction is derived. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a plasma reaching the separatrix and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy and plasma flow on these equilibria are examined. It turns out that depending on the maximum value and the shape of an anisotropy function, the anisotropy can act either paramagnetically or diamagnetically. Also, in most of the cases considered both the anisotropy and the flow have stronger effects on NSTX equilibria than on ITER ones.
Electronic structure and phase equilibria in ternary substitutional alloys
International Nuclear Information System (INIS)
A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate abinitio calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr0.5(Ru, Pd)0.5
Axisymmetric equilibria with pressure anisotropy and plasma flow
Throumoulopoulos, George; Evangelias, Achilleas
2015-11-01
A generalised Grad-Shafranov equation that governs the equilibrium of an axisymmetric toroidal plasma with anisotropic pressure and incompressible flow of arbitrary direction is derived. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a free boundary and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy and plasma flow on these equilibria are examined. It turns out that depending on the maximum value and the shape of an anisotropy function, the anisotropy can act either paramagnetically or diamagnetically. Also, in most of the cases considered both the anisotropy and the flow have stronger effects on NSTX equilibria than on ITER ones. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from (a) the National Programme for the Controlled Thermonuclear Fusion, Hellenic Republic, (b) Euratom research and training programme 2014-2018.
Swarm dynamics and equilibria for a nonlocal aggregation model
International Nuclear Information System (INIS)
We consider the aggregation equation ρt − ∇ · (ρ∇K * ρ) = 0 in Rn, where the interaction potential K models short-range repulsion and long-range attraction. We study a family of interaction potentials for which the equilibria are of finite density and compact support. We show global well-posedness of solutions and investigate analytically and numerically the equilibria and their global stability. In particular, we consider a potential for which the corresponding equilibrium solutions are of uniform density inside a ball of Rn and zero outside. For such a potential, various explicit calculations can be carried out in detail. In one dimension we fully solve the temporal dynamics, and in two or higher dimensions we show the global stability of this steady state within the class of radially symmetric solutions. Finally, we solve the following restricted inverse problem: given a radially symmetric density ρ-bar that is zero outside some ball of radius R and is polynomial inside the ball, construct an interaction potential K for which ρ-bar is the steady-state solution of the corresponding aggregation equation. Throughout the paper, numerical simulations are used to motivate and validate the analytical results
Expansions of non-symmetric toroidal magnetohydrodynamic equilibria
Weitzner, Harold
2016-06-01
Expansions of non-symmetric toroidal ideal magnetohydrodynamic equilibria with nested flux surfaces are carried out for two cases. The first expansion is in a topological torus in three dimensions, in which physical quantities are periodic of period 2 π in y and z. Data is given on the flux surface x = 0. Despite the possibility of magnetic resonances the power series expansion can be carried to all orders in a parameter which measures the flux between x = 0 and the surface in question. Resonances are resolved by appropriate addition resonant fields, as by Weitzner, [Phys. Plasmas 21, 022515 (2014)]. The second expansion is about a circular magnetic axis in a true torus. It is also assumed that the cross section of a flux surface at constant toroidal angle is approximately circular. The expansion is in an analogous flux coordinate, and despite potential resonance singularities, may be carried to all orders. Non-analytic behavior occurs near the magnetic axis. Physical quantities have a finite number of derivatives there. The results, even though no convergence proofs are given, support the possibility of smooth, well-behaved non-symmetric toroidal equilibria.
An integrated chemical and stable-isotope model of the origin of Midocean Ridge Hot Spring Systems
Bowers, Teresa Suter; Taylor, Hugh P., Jr.
1985-01-01
Chemical and isotopic changes accompanying seawater-basalt interaction in axial midocean ridge hydrothermal systems are modeled with the aid of chemical equilibria and mass transfer computer programs, incorporating provision for addition and subtraction of a wide-range of reactant and product minerals, as well as cation and oxygen and hydrogen isotopic exchange equilibria. The models involve stepwise introduction of fresh basalt into progressively modified seawater at discrete temperature int...
Rickaby, R E M
2015-03-13
Life and the chemical environment are united in an inescapable feedback cycle. The periodic table of the elements essential for life has transformed over Earth's history, but, as today, evolved in tune with the elements available in abundance in the environment. The most revolutionary time in life's history was the advent and proliferation of oxygenic photosynthesis which forced the environment towards a greater degree of oxidation. Consideration of three inorganic chemical equilibria throughout this gradual oxygenation prescribes a phased release of trace metals to the environment, which appear to have coevolved with employment of these new chemicals by life. Evolution towards complexity was chemically constrained, and changes in availability of notably Fe, Zn and Cu paced the systematic development of complex organisms. Evolving life repeatedly catalysed its own chemical challenges via the unwitting release of new and initially toxic chemicals. Ultimately, the harnessing of these allowed life to advance to greater complexity, though the mechanism responsible for translating novel chemistry to heritable use remains elusive. Whether a chemical acts as a poison or a nutrient lies both in the dose and in its environmental history. PMID:25666070
International Nuclear Information System (INIS)
Phenol and cresol (o-, m-, and p-) were selected as the adsorbates with different dipole moment (cresol > phenol, methyl being electron-drawing group) and solubility (phenol > cresol, methyl being hydrophobic group). Macropore polymers (NDA-1800 and XAD-4), hypercrosslinked polymers (NDA-100), and chemically modified adsorbents (NDA-150 and NDA-99), were comparatively used to investigate the adsorption properties including equilibria, thermodynamics and kinetics. First, all of the results about equilibria show that the adsorption data fit well to the Freundlich model. The adsorption capacity of NDA-99 and NDA-150 especially for phenol is larger in a certain extent than other three types of polymers. The hydrophobic interaction from large specific surface was mainly occurred, while the polar groups containing oxygen and amine markedly enhance the adsorption process via hydrogen interaction. Furthermore, the adsorption amount for NDA-99 and XAD-4 decrease linearly with the solubility of solutes tested. Then, the negative values of enthalpy demonstrate the predominantly exothermic and physical solid-extraction processes. Finally, the relatively more rapid adsorption process could be found onto NDA-150 than NDA-99, with the reason of the double larger pore size of the former. In conclusion, solubility of solute, together with surface area, pore size and modified groups, extremely exerts influences to the adsorption performances
Dynamics near manifolds of equilibria of codimension one and bifurcation without parameters
Directory of Open Access Journals (Sweden)
Stefan Liebscher
2011-05-01
Full Text Available We investigate the breakdown of normal hyperbolicity of a manifold of equilibria of a flow. In contrast to classical bifurcation theory we assume the absence of any flow-invariant foliation at the singularity transverse to the manifold of equilibria. We call this setting bifurcation without parameters. We provide a description of general systems with a manifold of equilibria of codimension one as a first step towards a classification of bifurcations without parameters. This is done by relating the problem to singularity theory of maps.
Chess-Like Games May Have No Uniform Nash Equilibria Even in Mixed Strategies
Directory of Open Access Journals (Sweden)
Endre Boros
2013-01-01
Full Text Available Recently, it was shown that Chess-like games may have no uniform (subgame perfect Nash equilibria in pure positional strategies. Moreover, Nash equilibria may fail to exist already in two-person games in which all infinite plays are equivalent and ranked as the worst outcome by both players. In this paper, we extend this negative result further, providing examples that are uniform Nash equilibria free, even in mixed or independently mixed strategies. Additionally, in case of independently mixed strategies we consider two different definitions for effective payoff: the Markovian and the a priori realization.
Radionuclide equilibria between the aquatic environment and fish tissues
International Nuclear Information System (INIS)
Equilibrium conditions are often assumed in dose and risk calculations based on the simple linear concentration factor model, a commonly used model in the study of contaminant flow through ecosystems. It has been argued that by using a power function model to describe radionuclide retention in fish, equilibrium may never be achieved under natural conditions, thereby violating the equilibrium requirement in the concentration factor model. Our results demonstrate uranium-series radionuclide equilibria in a natural population of common white sucker (Catostomus commersoni). Concentration factors indicated that 226Ra, 232Th, 230Th, and 228Th preferentially deposited in bone over muscle. Although 226Ra had the highest concentration in bone, 228Th yielded the highest concentration factors for water-to-bone transfer. 232Th may not be in equilibrium because of a growth dilution effect. (Copyright (c) 1997 Elsevier Science B.V., Amsterdam. All rights reserved.)
Axisymmetric equilibria with pressure anisotropy and plasma flow
Evangelias, A
2016-01-01
A generalised Grad-Shafranov equation that governs the equilibrium of an axisymmetric toroidal plasma with anisotropic pressure and incompressible flow of arbitrary direction is derived. This equation includes six free surface functions and recovers known Grad-Shafranov-like equations in the literature as well as the usual static, isotropic one. The form of the generalised equation indicates that pressure anisotropy and flow act additively on equilibrium. In addition, two sets of analytical solutions, an extended Solovev one with a plasma reaching the separatrix and an extended Hernegger-Maschke one for a plasma surrounded by a fixed boundary possessing an X-point, are constructed, particularly in relevance to the ITER and NSTX tokamaks. Furthermore, the impacts both of pressure anisotropy and plasma flow on these equilibria are examined. It turns out that depending on the maximum value and the shape of an anisotropy function, the anisotropy can act either paramagnetically or diamagnetically. Also, in most of...
Navigable networks as Nash equilibria of navigation games
Gulyás, András; Bíró, József J.; Kőrösi, Attila; Rétvári, Gábor; Krioukov, Dmitri
2015-07-01
Common sense suggests that networks are not random mazes of purposeless connections, but that these connections are organized so that networks can perform their functions well. One function common to many networks is targeted transport or navigation. Here, using game theory, we show that minimalistic networks designed to maximize the navigation efficiency at minimal cost share basic structural properties with real networks. These idealistic networks are Nash equilibria of a network construction game whose purpose is to find an optimal trade-off between the network cost and navigability. We show that these skeletons are present in the Internet, metabolic, English word, US airport, Hungarian road networks, and in a structural network of the human brain. The knowledge of these skeletons allows one to identify the minimal number of edges, by altering which one can efficiently improve or paralyse navigation in the network.
Social Interactions under Incomplete Information: Games, Equilibria, and Expectations
Yang, Chao
My dissertation research investigates interactions of agents' behaviors through social networks when some information is not shared publicly, focusing on solutions to a series of challenging problems in empirical research, including heterogeneous expectations and multiple equilibria. The first chapter, "Social Interactions under Incomplete Information with Heterogeneous Expectations", extends the current literature in social interactions by devising econometric models and estimation tools with private information in not only the idiosyncratic shocks but also some exogenous covariates. For example, when analyzing peer effects in class performances, it was previously assumed that all control variables, including individual IQ and SAT scores, are known to the whole class, which is unrealistic. This chapter allows such exogenous variables to be private information and models agents' behaviors as outcomes of a Bayesian Nash Equilibrium in an incomplete information game. The distribution of equilibrium outcomes can be described by the equilibrium conditional expectations, which is unique when the parameters are within a reasonable range according to the contraction mapping theorem in function spaces. The equilibrium conditional expectations are heterogeneous in both exogenous characteristics and the private information, which makes estimation in this model more demanding than in previous ones. This problem is solved in a computationally efficient way by combining the quadrature method and the nested fixed point maximum likelihood estimation. In Monte Carlo experiments, if some exogenous characteristics are private information and the model is estimated under the mis-specified hypothesis that they are known to the public, estimates will be biased. Applying this model to municipal public spending in North Carolina, significant negative correlations between contiguous municipalities are found, showing free-riding effects. The Second chapter "A Tobit Model with Social
Settling the Complexity of Computing Two-Player Nash Equilibria
Chen, Xi; Teng, Shang-Hua
2007-01-01
We settle a long-standing open question in algorithmic game theory. We prove that Bimatrix, the problem of finding a Nash equilibrium in a two-player game, is complete for the complexity class PPAD Polynomial Parity Argument, Directed version) introduced by Papadimitriou in 1991. This is the first of a series of results concerning the complexity of Nash equilibria. In particular, we prove the following theorems: Bimatrix does not have a fully polynomial-time approximation scheme unless every problem in PPAD is solvable in polynomial time. The smoothed complexity of the classic Lemke-Howson algorithm and, in fact, of any algorithm for Bimatrix is not polynomial unless every problem in PPAD is solvable in randomized polynomial time. Our results demonstrate that, even in the simplest form of non-cooperative games, equilibrium computation and approximation are polynomial-time equivalent to fixed point computation. Our results also have two broad complexity implications in mathematical economics and operations res...
Three-dimensional equilibria in axially symmetric tokamaks.
Garabedian, Paul R
2006-12-19
The NSTAB and TRAN computer codes have been developed to study equilibrium, stability, and transport in fusion plasmas with three-dimensional (3D) geometry. The numerical method that is applied calculates islands in tokamaks like the Doublet III-D at General Atomic and the International Thermonuclear Experimental Reactor. When bifurcated 3D solutions are used in Monte Carlo computations of the energy confinement time, a realistic simulation of transport is obtained. The significance of finding many 3D magnetohydrodynamic equilibria in axially symmetric tokamaks needs attention because their cumulative effect may contribute to the prompt loss of alpha particles or to crashes and disruptions that are observed. The 3D theory predicts good performance for stellarators. PMID:17159158
Efficiently Finding Trends in Macroscopic MHD Stability Using Perturbed Equilibria
Comer, K. J.; Callen, J. D.; Hegna, C. C.; Turnbull, A. D.; Cowley, S. C.
2001-10-01
The effects of equilibrium shaping and profiles on long wavelength ideal MHD instabilities in toroidal plasmas are traditionally studied using numerical parameter scans. Previously, we introduced a new perturbative technique to explore these dependencies: assuming small equilibrium variations, new stability properties are found using a perturbation of the energy principle rather than with a traditional stability code. With this approach, stability dependencies can be efficiently examined without numerically generating complete MHD stability results for every set of parameters (which can be time-intensive for accurate representations of several configurations). Here, we briefly expand on previous successful perturbed stability analyses for screw pinch equilibria by discussing cases where the approach fails. Next, we extend the approach to toroidal geometry using the GATO and TOQ codes, and present cases that both validate the approach and suggest caution in its application.
Dynamic data evaluation for solid-liquid equilibria
DEFF Research Database (Denmark)
Cunico, Larissa; Ceriani, Roberta; Kang, Jeong Won;
The accuracy and reliability of the measured data sets to be used in regression of model parameters is an important issue related to modeling of phase equilibria. It is clear that good parameters for any model cannot be obtained from low quality data. A thermodynamic consistency test for solid......-liquid systems using a relation between the solid and liquid activity coefficients for systems containing metals [1], where the data from the two phases are given were proposed. However, as consistency tests based on the Gibbs–Duhem equation are not feasible, new consistency tests have been developed [2]. Some...... of the developed tests were based in the quality tests proposed for VLE data by Kang et al. [3] and a methodology that combines solute activity coefficients in the liquid phase at infinite dilution and a theoretically based term to account for the non-ideality in dilute solutions are discussed. In...
Phase equilibria in the Ni-Co-Ga alloy system
International Nuclear Information System (INIS)
Phase equilibria among the α (A1), α' (L12), β (B2), δ (Ni5Ga3) and ε (Ni13Ga9) phases at elevated temperatures and the existing composition region of the martensite phase at room temperature in the Ni-Co side of the Ni-Co-Ga system were examined by electron probe microanalysis (EPMA) using diffusion triples which were fabricated by two-step diffusion coupling. It was confirmed that single-phase regions of the α, α' and β phases at 700 and 1000 deg. C exist in a wide composition range parallel to Ni-Co section and that the existing region of the martensite phase at room temperature is also located over a wide range in the β phase along the β + α (or α') two-phase region
Multiple equilibria of cross-equatorial Inertial jets
Institute of Scientific and Technical Information of China (English)
CHAO JiPing; LIU Fei
2007-01-01
Based on the developed Anderson and Moore's theory about cross-equatorial inertial jets and a nonlinear equivalence shallow water model, new universal functions are determined by the characters of the vortical large-scale air flow (atmosphere) or ocean current (ocean) related to the jet, then the potential vorticity and energy conservation equations along the streamline in the cross-equatorial inertial jets can be obtained. Because the governing equations are nonlinear, some limited multiple equilibria of cross-equatorial inertial jets may exist. According to the character of large-scale air flow or ocean current outside the jets, the existent criterion for multiple eqnilibria in cross-equatorial inertial jets is discussed, and two examples for multiple equilibia of nonlinear governing equations are given.
Multiple equilibria of cross-equatorial Inertial jets
Institute of Scientific and Technical Information of China (English)
2007-01-01
Based on the developed Anderson and Moore’s theory about cross-equatorial inertial jets and a nonlinear equivalence shallow water model, new universal functions are determined by the characters of the vortical large-scale air flow (atmosphere) or ocean current (ocean) related to the jet, then the potential vorticity and energy conservation equations along the streamline in the cross-equatorial in-ertial jets can be obtained. Because the governing equations are nonlinear, some limited multiple equi-libria of cross-equatorial inertial jets may exist. According to the character of large-scale air flow or ocean current outside the jets, the existent criterion for multiple eqnilibria in cross-equatorial inertial jets is discussed, and two examples for multiple equilibia of nonlinear governing equations are given.
Complex Networks as Nash Equilibria of Navigation Games
Gulyás, András; Kőrösi, Attila; Rétvári, Gábor; Krioukov, Dmitri
2014-01-01
The common sense suggests that networks are not random mazes of purposeless connections, but that these connections are organised so that networks can perform their functions. One common function that many networks perform is targeted transport or navigation. Here with the help of game theory we show that minimalistic networks designed to maximise the navigation efficiency at minimal cost share basic structural properties of real networks. These idealistic networks are Nash equilibria of a network construction game whose purpose is to find an optimal trade-off between the network cost and navigability. They are navigation skeletons that we show are present in the Internet, {\\it E. coli} metabolic network, English word network, US airport network, and the Hungarian road network. The knowledge of these skeletons allows one to identify the minimal number of edges by altering which one can dramatically improve or paralyse the navigation in the network.
Bifurcated equilibria in two-dimensional MHD with diamagnetic effects
Energy Technology Data Exchange (ETDEWEB)
Ottaviani, M. [CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Tebaldi, C. [Lecce University (Italy). Dept. of Mathematics
1998-12-01
In this work we analyzed the sequence of bifurcated equilibria in two-dimensional reduced magnetohydrodynamics. Diamagnetic effects are studied under the assumption of a constant equilibrium pressure gradient, not altered by the formation of the magnetic island. The formation of an island when the symmetric equilibrium becomes unstable is studied as a function of the tearing mode stability parameter {Delta}` and of the diamagnetic frequency, by employing fixed-points numerical techniques and an initial value code. At larger values of {Delta}` a tangent bifurcation takes place, above which no small island solutions exist. This bifurcation persists up to fairly large values of the diamagnetic frequency (of the order of one tenth of the Alfven frequency). The implications of this phenomenology for the intermittent MHD dynamics observed in tokamaks is discussed. (authors) 20 refs.
Bifurcated equilibria in two-dimensional MHD with diamagnetic effects
International Nuclear Information System (INIS)
In this work we analyzed the sequence of bifurcated equilibria in two-dimensional reduced magnetohydrodynamics. Diamagnetic effects are studied under the assumption of a constant equilibrium pressure gradient, not altered by the formation of the magnetic island. The formation of an island when the symmetric equilibrium becomes unstable is studied as a function of the tearing mode stability parameter Δ' and of the diamagnetic frequency, by employing fixed-points numerical techniques and an initial value code. At larger values of Δ' a tangent bifurcation takes place, above which no small island solutions exist. This bifurcation persists up to fairly large values of the diamagnetic frequency (of the order of one tenth of the Alfven frequency). The implications of this phenomenology for the intermittent MHD dynamics observed in tokamaks is discussed. (authors)
Phase equilibria and molecular interaction studies on (naphthols + vanillin) systems
International Nuclear Information System (INIS)
Highlights: ► Phase equilibria of (naphthol + vanillin) systems have been studied for the first time. ► Eutectic type phase diagrams are obtained. ► Eutectic mixtures show nonideal behaviour. ► There is a weak molecular interaction between the components in the eutectic mixtures. ► α-Naphthol–vanillin eutectic is more stable as compared to β-naphthol–vanillin. - Abstract: Phase equilibria between (α-naphthol + vanillin) and (β-naphthol + vanillin) systems have been studied by thaw-melt method and the results show the formation of simple eutectic mixtures. Crystallization velocities of components and eutectic mixtures were determined at different stages under cooling. With the help of differential scanning calorimeter (DSC), the enthalpy of fusion of components and eutectic mixtures was determined and from the values excess thermodynamic functions viz., excess Gibbs free energy (GE), excess entropy (SE), excess enthalpy (HE) of hypo-, hyper- and eutectic mixtures were calculated. Flexural strength measurements were made in order to understand the non-ideal nature of eutectics. FT-IR spectral studies indicate the formation of hydrogen bond in the eutectic mixture. Anisotropic and isotropic microstructural studies of components, hypo-, hyper- and eutectic mixtures were made. Jackson’s roughness parameter was calculated and found to be greater than 2 suggesting the faceted morphology with irregular structures. The overall results have shown that there is a weak molecular interaction between the components in the eutectic mixtures and the (α-naphthol + vanillin) eutectic is more stable as compared to the (β-naphthol + vanillin) eutectic system.
Equilibria and stability in partially relaxed plasma-vacuum systems
International Nuclear Information System (INIS)
We develop a multiple interface variational model, comprising multiple Taylor-relaxed plasma regions separated by ideal MHD barriers. The magnetic field in each region is Beltrami, ∇ x B = μB, and the pressure constant. Between regions the pressure, field strength, and rotational transform may have step changes at the ideal barrier. A principle motivation is the development of a mathematically rigorous ideal MHD model to describe intrinsically 3D equilibria, with nonzero internal pressure, using robust KAM surfaces as the barriers. This article chiefly addresses whether the stability of two interface configurations with continuous rotational transform, but vanishing interface separation, is different from the stability of a single interface configuration with jump in the rotational transform. To make the problem analytically tractable, we derive the equilibria and stability of a multi-interface plasma in a periodic cylinder, generalizing the cylindrical treatment of Kaiser and Uecker (2004 Q. J. Mech. Appl. Math. 57 1-17). For two interfaces with no jump in rotational transform, we show that one eigenmode has in-phase interface displacements, and an eigenvalue that converges to the single barrier case in the limit of vanishing interface width. The complementary eigenmode is out-of-phase, and highly unstable. Physically, the unstable eigenmode is driven by the parallel current, and caused by the high shear required to match the different rotational transform on each interface. In the limit that the interface separation vanishes, the shear and parallel current density become infinite, and the parallel current between the interfaces nonzero. Surfaces with out-of-phase displacements will then collide, unless the amplitude goes to zero as the interface separation goes to zero. These results suggest the hypothesis that KAM barriers with different irrational rotational transform on either side may be allowable without violating nonlinear stability
Observation of equilibria with a double magnetic axis in LHD
International Nuclear Information System (INIS)
Plasma shape control is a major knob to investigate confinement as well as MHD characteristics of magnetically confined plasmas. LHD has a large flexibility to explore a configuration effect by using 6 independent coil systems. Elongation can be controlled by a quadrupole field. Experimental observation of moderate elongation has shown that confinement is degraded gradually in both prolate (vertically elongated) and oblate (horizontally elongated) configurations. Since the rotational transform is weaker in the core region than in the periphery in LHD, a theoretical analysis suggests that excess quadrupole field results in split of the magnetic axis. Then the internal separatrix like petals emerges. Further application of quadrupole field eventually realizes a doublet configuration with a double magnetic axis bounded by this separatrix. An analytics suggests that split of the magnetic axis starts beyond elongation κ of 1.6 in the prolate case. The role of separatrix is attracting interest in effect on confinement performance as well as physics of unstable manifold, which has motivated strong shaping experiment in LHD. Both shaping of prolate and oblate directions has been explored for NBI heated plasmas. In the strongly prolate case, the doublet image has been observed by a tangential soft X-ray camera. Available profile measurements of temperature and density have not provided the 2-dimensional profile, however, assumption of concentric surfaces with a single magnetic axis seems to contradict with experimental observations in the 1-dimensional measurements in the case with strong shaping. This suggests the existence of doublet magnetic surfaces. These complex equilibria cannot be treated by the numerical code, ex. VMEC, with an assumption of nested flux surfaces with a single magnetic axis. Characteristics of these eccentric equilibria have been investigated by the HINT code which does not assume existence of nested flux surfaces. Experimental and computational
Aluminum Deoxidation Equilibria in Liquid Iron: Part II. Thermodynamic Modeling
Paek, Min-Kyu; Pak, Jong-Jin; Kang, Youn-Bae
2015-10-01
Al deoxidation equilibria in liquid iron over the whole composition range from very low Al ([pct Al] = 0.0027) to almost pure liquid Al were thermodynamically modeled for the first time using the Modified Quasichemical Model in the pair approximation for the liquid phase. The present modeling is distinguished from previous approaches in many ways. First, very strong attractions between metallic components, Fe and Al, and non-metallic component, O, were taken into account explicitly in terms of Short-Range Ordering. Second, the present thermodynamic modeling does not distinguish solvent and solutes among metallic components, and the model calculation can be applied from pure liquid Fe to pure liquid Al. Therefore, this approach is thermodynamically self-consistent, contrary to the previous approaches using interaction parameter formalism. Third, the present thermodynamic modeling describes an integral Gibbs energy of the liquid alloy in the framework of CALPHAD; therefore, it can be further used to develop a multicomponent thermodynamic database for liquid steel. Fourth, only a small temperature-independent parameter for ternary liquid was enough to account for the Al deoxidation over wide concentration (0.0027 oxide saturation) were modeled, and relevant model parameters were optimized. By merging these Gibbs energy descriptions with that of Fe-Al binary liquid modeled by the same modeling approach, the Gibbs energy of ternary Fe-Al-O solution at metal-rich region was obtained along with one small ternary parameter. It was shown that the present model successfully reproduced all available experimental data for the Al deoxidation equilibria. Limit of previously used interaction parameter formalism at high Al concentration is discussed.
Energy Technology Data Exchange (ETDEWEB)
Guillon, E
2004-09-15
A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges with the external environment. By the utilization of a geochemical code associated to a thermodynamical database and coupled to a 3D transport model, this approach authorizes the study of all aggressive solution. The approach has been validated by the comparison of experimental observations to simulated degradations for three different environments (pure water, mineralized water, seawater) and on three different materials (CEM I Portland cement with 0.25, 0.4 and 0.5 water-to cement ratio). The microstructural approach permits also to have access to mechanical properties evolutions. During chemical aggressions, the cement matrix evolution is traduced in a microstructure evolution. This one is represented from 3D images similarly to the models developed at NIST (National Institute of Standards and Technology). A new finite-element model, validated on previous tests or models, evaluates the stiffness of the cement paste, using as a mesh these microstructures. Our approach identifies and quantifies the major influence of porosity and its spatial
AGGREGATION OF NANOPARTICLES IN POLYPHASE MIXTURES — IMPACT ON PHASE EQUILIBRIA
Hebabcha, Mustapha; Miltgen, Morgane; Modaressi, Ali; Magri, Pierre; Ait-kaci, A.; Rogalski, Marek
2013-01-01
In this work we were concerned with the inﬂuence of dispersed nanoarticles (Nps) on liquid—liquid and solid—liquid phase equilibria. The cryoscopic depression due to the presence of Nps of silver (d
Czech Academy of Sciences Publication Activity Database
Aim, Karel; Lísal, Martin
2002. s. 1. [European Conference on Applied Thermodynamics ESAT 2002 /19./. 06.09.2002-10.09.2002, Santorini] Institutional research plan: CEZ:AV0Z4072921 Keywords : Simulation * Phase equilibria Subject RIV: CC - Organic Chemistry
Multiple equilibria, soil conservation investments and the resilience of agricultural systems
Antle, J.M.; Stoorvogel, J.J.; Valdivia, R.O.
2006-01-01
This paper provides a new explanation for the persistent land degradation in some parts of the world, despite the availability of seemingly effective soil conservation technologies.We demonstrate that soil conservation technologies may induce agricultural systems to exhibit equilibria characterized by both low and high levels of soil degradation. These two equilibria are separated by a threshold level of soil degradation beyond which a conservation investment will not yield a positive return....
Bertrand and price-taking equilibria in markets with product differentiation
Coloma, Germán
2008-01-01
In this paper we show that a homogeneous-product market with multiple Bertrand equilibria becomes a market with a single Bertrand equilibrium when we introduce a small degree of product differentiation. When differentiation tends to zero, that Bertrand equilibrium converges to the unique price-taking equilibrium of the homogeneous-product market, which is in turn one of the multiple Bertrand equilibria for that market.
Export Restrictions and Multiple Spatial Price Equilibria: Export Quotas for Wheat in Ukraine
Götz, Linde; Qiu, Feng; Gervais, Jean-Philippe; Glauben, Thomas
2013-01-01
Relatively few models exist that allow for regime-dependent spatial price equilibria. This paper focuses on temporary export restrictions during international commodity price peaks. Theory suggests that export restrictions have price insulating effects and lead to multiple spatial equilibria between domestic and world market prices. Our analysis is unique in that it tests for linear versus non-linear cointegration within a smooth transition cointegration model. Applying this model to the whea...
On the Equilibria of the Extended Nematic Polymers under Elongational Flow
Directory of Open Access Journals (Sweden)
Hong Zhou
2007-01-01
Full Text Available We classify the equilibrium solutions of the Smoluchowski equation for dipolar (extended rigid nematic polymers under imposed elongational flow. The Smoluchowski equation couples the Maier-Saupe short-range interaction, dipole-dipole interaction, and an external elongational flow. We show that all stable equilibria of rigid, dipolar rod dispersions under imposed uniaxial elongational flow field are axisymmetric. This finding of axisymmetry significantly simplifies any procedure of obtaining experimentally observable equilibria.
Calculation of Binary Adsorption Equilibria: Hydrocarbons and Carbon Dioxide on Activated Carbon
DEFF Research Database (Denmark)
Marcussen, Lis; Krøll, A.
1999-01-01
Binary adsorption equilibria are calculated by means of a mathematical model for multicomponent mixtures combined with the SPD (Spreading Pressure Dependent) model for calculation of activity coefficients in the adsorbed phase. The model has been applied successfully for the adsorption of binary ...... mixtures of hydrocarbons and carbon dioxide on activated carbons. The model parameters have been determined, and the model has proven to be suited for prediction of adsorption equilibria in the investigated systems....
Multiple Equilibria and Interfirm Macro-Externality: An Analysis of Sluggish Real Adjustment
Yew-Kwang Ng; Ying Wu
2004-01-01
In an imperfectly competitive economy, a continuum of equilibria at the firm level exists under certain analytical conditions (Ng 1986). Extending the earlier analysis of a representative firm, this paper shows that even if the condition for a continuum of equilibria is not exactly satisfied, the factors of price-adjustment costs, interfirm heterogeneity, and macro-externality can cause the economy to be stuck at the quasi macroequilibria after aggregate demand experiences a contractionary sh...
Phase equilibria in the system MoCl5-MoF5
International Nuclear Information System (INIS)
Phase equilibria in system MoCl5-MoF5 are studied using the DTA and visual-polythermal methods, as well as roentgenography. The system is characterized by the formation of incongruent MoCl4F and congruent compounds MoCl3F2, MoCl2F3, MoClF4 and also by the presence of stable and metastable equilibria
Calculation of phase equilibria in ternary systems uranyl salt-water-organic solvent
International Nuclear Information System (INIS)
Experience in modeling extraction equilibria in systems with uranyl nitrate and halogen acetates with oxygen-containing organic solvents and tributylphosphate is presented. A method of calculating the equilibria on the basis of thermodynamic approach was suggested, phase diagrams for 12 extractive mixtures being calculated. Comparative analysis with the known experimental data was concluded, efficiency of the systems, that had not been previously considered by experiments, was predicted
New investigation of phase equilibria in the system Al–Cu–Si
Ponweiser, Norbert; Richter, Klaus W.
2012-01-01
The phase equilibria and invariant reactions in the system Al–Cu–Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °...
On the application of the NRTL method to ternary (liquid + liquid) equilibria
International Nuclear Information System (INIS)
The use of the NRTL method for correlating experimental data in ternary (liquid + liquid) equilibria is considered. It is concluded that parameters obtained by direct correlation techniques have not a direct physical meaning. Also, it is shown that the resulting values for these parameters depend on the number of experimental points considered and on the particular calculation method employed. Thus, it is very risky to employ such parameters in predicting equilibria of other ternary mixtures
The Structure of the Set of Equilibria for Two Person Multicriteria Games
Borm, P.E.M.; Vermeulen, D.; Voorneveld, M.
1998-01-01
In this paper the structure of the set of equilibria for two person multicriteria games is analysed. It turns out that the classical result for the set of equilibria for bimatrix games, that it is a finite union of polytopes, is only valid for multicriteria games if one of the players only has two pure strategies. A full polyhedral description of these polytopes can be derived when the player with an arbitrary number of pure strategies has one criterion.
Nie, Xiaobing; Zheng, Wei Xing
2016-03-01
This paper addresses the problem of coexistence and dynamical behaviors of multiple equilibria for competitive neural networks. First, a general class of discontinuous nonmonotonic piecewise linear activation functions is introduced for competitive neural networks. Then based on the fixed point theorem and theory of strict diagonal dominance matrix, it is shown that under some conditions, such n -neuron competitive neural networks can have 5(n) equilibria, among which 3(n) equilibria are locally stable and the others are unstable. More importantly, it is revealed that the neural networks with the discontinuous activation functions introduced in this paper can have both more total equilibria and locally stable equilibria than the ones with other activation functions, such as the continuous Mexican-hat-type activation function and discontinuous two-level activation function. Furthermore, the 3(n) locally stable equilibria given in this paper are located in not only saturated regions, but also unsaturated regions, which is different from the existing results on multistability of neural networks with multiple level activation functions. A simulation example is provided to illustrate and validate the theoretical findings. PMID:25826814
Anufriev, Mikhail; Bottazzi, Giulio; Pancotto, Francesca
2005-05-01
We consider a simple pure exchange economy with two assets, one riskless, yielding a constant return on investment, and one risky, paying a stochastic dividend. Trading takes place in discrete time and in each trading period the price of the risky asset is fixed through the market clearing condition. Individual demands are expressed as fractions of traders wealth and depend on traders forecasts about future price movement. Under these assumptions, we derive the stochastic dynamical system that describes the evolution of price and wealth. We study the cases in which one or two agents operate in the market, identifying the possible equilibria and discussing their stability conditions. The main novelty of this paper rests in the abstraction from the precise characterization of agents' beliefs and preferences. In this respect our results generalize several previous contributions in the field. In particular, we show that, irrespectively of agents' behavior, the system can only possess isolated generic equilibria where a single agent dominates the market and continuous manifolds of non-generic equilibria where heterogeneous agents hold finite shares of the aggregate wealth. Moreover, we show that all possible equilibria belong to a one dimensional "Equilibria Market Line". Finally we discuss the role of different parameters for the stability of equilibria and the selection principle governing market dynamics.
On the steady states of weakly reversible chemical reaction networks
Deng, Jian; Jones, Christopher; Feinberg, Martin; Nachman, Adrian
2011-01-01
A natural condition on the structure of the underlying chemical reaction network, namely weak reversibility, is shown to guarantee the existence of an equilibrium (steady state) in each positive stoichiometric compatibility class for the associated mass-action system. Furthermore, an index formula is given for the set of equilibria in a given stoichiometric compatibility class.
Bootstrap current for small aspect ratio TOKAMAK equilibria
International Nuclear Information System (INIS)
Full text. We present equilibrium features of the very small ratio tokamak, TBR-2 E, with the aspect ratio of 1.6, which is being designed in Brazil - a joint project with the participation of the University of Sao Paulo, the State University of Campinas, and the National Institute for Space Research. The equilibria have been studied by using the SELENE-J code developed at JAERI, Japan, by Tokuda et al. We have concentrated our study on the determination of the stability limit by using the critical pressure criterion for ballooning stability and Mercier criterion for other MHD modes. The β-limit values were calculated for the case of the non-inductive current and found that its maximum lies at elongation of 1.7. Increasing the triangularity, the β-limit values increase, but the maximum continues to stay at the same value of elongation. We have also studied the effect of the neo-classical transport properties by changing the plasma temperature (or β values). In particular, we have studied the trapped particles and bootstrap current. We have found that at temperatures as low as 600 eV the transport is already in banana regime and that the bootstrap current may account for a significant part of the total plasma current. (author)
Equilibria of idealized confined astral microtubules and coupled spindle poles.
Directory of Open Access Journals (Sweden)
Ivan V Maly
Full Text Available Positioning of the mitotic spindle through the interaction of astral microtubules with the cell boundary often determines whether the cell division will be symmetric or asymmetric. This process plays a crucial role in development. In this paper, a numerical model is presented that deals with the force exerted on the spindle by astral microtubules that are bent by virtue of their confinement within the cell boundary. It is found that depending on parameters, the symmetric position of the spindle can be stable or unstable. Asymmetric stable equilibria also exist, and two or more stable positions can exist simultaneously. The theory poses new types of questions for experimental research. Regarding the cases of symmetric spindle positioning, it is necessary to ask whether the microtubule parameters are controlled by the cell so that the bending mechanics favors symmetry. If they are not, then it is necessary to ask what forces external to the microtubule cytoskeleton counteract the bending effects sufficiently to actively establish symmetry. Conversely, regarding the cases with asymmetry, it is now necessary to investigate whether the cell controls the microtubule parameters so that the bending favors asymmetry apart from any forces that are external to the microtubule cytoskeleton.
Ion-exchange equilibria and diffusion in engineered backfill
International Nuclear Information System (INIS)
Engineered backfill can add confidence to confinement times of high-level nuclear waste stored in geologic media. This paper discusses the design and operation of a unique radial-flow diffusion cell to determine ion migration rates in backfill material under realistic repository conditions. New experimental results were reported for diffusion of CsCl in a background of NaCl into compacted bentonite and bentonite/quartz mixtures. Representation of the measured diffusion rates by the traditional, homogeneous porous-medium model significantly underestimates cesium penetration distances into the backfill. Surface diffusion is suggested as an additional mechanism by which cations transport in swollen montmorillonite; the surface diffusion coefficients for cesium is determined to be approximately 10-7 cm2/s. An electrostatic site-binding model is developed for ion-exchange equilibria on montmorillonite clay. The effect of pH, ionic strength, and specific adsorption are evaluated and compared favorably to new, experimental exchange isotherms measured on disaggregated clay. The electrostatic site-binding model permits a prediction of the influence of backfill compaction on K/sub d/ values. We find that for strongly adsorbing cations, compactions has little effect. However, anions exhibit significant Donnan exclusion with clay compaction. 40 references, 12 figures
Local gyrokinetic Vlasov simulations with realistic tokamak MHD equilibria
International Nuclear Information System (INIS)
A local gyrokinetic Vlasov simulation code GKV is extended to incorporate realistic tokamak equilibria including up-down asymmetry, which are produced by a free-boundary 2D Grad-Shafranov equation solver MEUDAS. By using a newly developed interface code IGS, two dimensional rectangular equilibrium data from MEUDAS is converted to straight-field-line flux coordinates such as Hamada, Boozer, and axisymmetric coordinates, which are useful for gyrokinetic micro-instability and turbulent transport analyses. The developed codes have been verified by a cross-code benchmark test using Cyclone-base-case like MHD equilibrium, where good agreement in the dispersion relation of ion temperature gradient (ITG) driven mode has been confirmed. The extended GKV is applied to two types of shaped plasmas expected in JT-60SA tokamak devices, i.e., ITER-like and highly-shaped plasmas, and ITG-mode stability and residual zonal-flow level are investigated. Through the detailed comparisons, more favorable stability properties against the ITG mode are revealed for the highly-shaped case, where the lower ITG-mode growth rate and higher residual zonal-flow levels compared to the ITER-like case are identified. (author)
Phase equilibria in the Ni-Fe-Ga alloy system
International Nuclear Information System (INIS)
The phase equilibria, A2/B2 and B2/L21 (or D03) order-disorder transitions and martensitic transformation on the Ni-Fe side of the Ni-Fe-Ga system were examined by electron probe microanalysis (EPMA) and differential scanning calorimetric (DSC) measurement. The equilibrium compositions of interrelations mainly among the α (A2), β (B2), β' (L21 or D03), γ (A1) and γ' (L12) phases were determined using diffusion triples which were fabricated by two-step diffusion coupling. It was confirmed that a bcc single-phase region composed of α, β and β' at 850-1000 deg. C exists in a wide composition range and that the critical temperature of the B2/L21 order-disorder transformation in the Fe3Ga-Ni3Ga pseudo-binary section gradually increases with increasing Ni content. The existing composition region of the martensite phase at room temperature was also determined by the diffusion triple method
Thermodynamically predicted oscillations in closed chemical systems
Zilbergleyt, B
2010-01-01
All known up to now models of chemical oscillations are based exclusively on kinetic considerations. The chemical gross-process equation is split usually by elementary steps, each step is supplied by an arrow and a differential equation, joint solution to such a construction under certain, often ad hoc chosen conditions and with ad hoc numerical coefficients leads to chemical oscillations. Kinetic perception of chemical oscillations reigns without exclusions. However, as it was recently shown by the author for the laser and for the electrochemical systems, chemical oscillations follow also from solutions to the basic expressions of discrete thermodynamics of chemical equilibria. Graphically those solutions are various fork bifurcation diagrams, and, in certain types of chemical systems, oscillations are well pronounced in the bistable bifurcation areas. In this work we describe a general thermodynamic approach to chemical oscillations as opposite to kinetic models, and depict some of their new features like s...
O'Hara, M. J.; Herzberg, C.
2002-06-01
The concentrations and ratios of the major elements determine the physical properties and the phase equilibria behavior of peridotites and basalts in response to the changing energy contents of the systems. The behavior of the trace elements and isotopic features are influenced in their turn by the phase equilibria, by the physical character of the partial melting and partial crystallization processes, and by the way in which a magma interacts with its wall rocks. Concentrating on the trace element and isotope contents of basalts to the exclusion of the field relations, petrology, major element data, and phase equilibria is as improvident as slaughtering the buffalo for the sake of its tongue. The crust is a cool boundary layer and a density filter, which impedes the upward transfer of hot, dense "primary" picritic and komatiitic liquids. Planetary crusts are sites of large-scale contamination and extensive partial crystallization of primitive melts striving to escape to the surface. Escape of truly unmodified primitive melts to the surface is a rare event, requiring the resolution of daunting problems in chemical and mechanical engineering. Primary status for volumetrically abundant basalts such as mid-ocean ridge basalt, ocean island basalt, and continental flood basalts is denied by their low-pressure cotectic character, first remarked upon on petrological grounds in 1928 and on experimental grounds in 1962. These basalt liquids are products of crystal-liquid separation at low pressure. Primary status for these common basalts is further denied by the phase equilibria of such compositions at elevated pressures, when the required residual mantle mineralogy (magnesian olivine and orthopyroxene) is not stable at the liquidus. It is also denied by the picritic or komatiitic nature of partial melts of candidate upper-mantle compositions at high pressures - a conclusion supported by calculation of the melt composition, which would need to be extracted in order to
Modelling of phase equilibria of glycol ethers mixtures using an association model
DEFF Research Database (Denmark)
Garrido, Nuno M.; Folas, Georgios; Kontogeorgis, Georgios
2008-01-01
Vapor-liquid and liquid-liquid equilibria of glycol ethers (surfactant) mixtures with hydrocarbons, polar compounds and water are calculated using an association model, the Cubic-Plus-Association Equation of State. Parameters are estimated for several non-ionic surfactants of the polyoxyethylene......, Kamlet-Taft parameters and, perhaps most importantly, mixture liquid-liquid equilibria data with alkanes are used for choosing optimum parameter sets is illustrated. Vapor-liquid, liquid-liquid equilibria and second virial coefficient data are used for model validation, including aqueous and other cross-associating...... mixtures. The influence on the results of the association schemes, type of data available, combining rules for cross-associating mixtures and interaction parameters are discussed also in connection to other cross-associating mixtures, previously studied with the model. Finally, the capabilities and...
Lagrangian relative equilibria for a gyrostat in the three-body problem: bifurcations and stability
Energy Technology Data Exchange (ETDEWEB)
Guirao, Juan L G; Vera, Juan A, E-mail: juan.garcia@upct.e, E-mail: juanantonio.vera@upct.e [Departamento de Matematica Aplicada y EstadIstica, Universidad Politecnica de Cartagena, Hospital de Marina, 30203 Cartagena, Region de Murcia (Spain)
2010-05-14
In this paper we consider the non-canonical Hamiltonian dynamics of a gyrostat in the frame of the three-body problem. Using geometric/mechanic methods we study the approximate dynamics of the truncated Legendre series representation of the potential of an arbitrary order. Working in the reduced problem, we study the existence of relative equilibria that we refer to as Lagrange type following the analogy with the standard techniques. We provide necessary and sufficient conditions for the linear stability of Lagrangian relative equilibria if the gyrostat morphology form is close to a sphere. Thus, we generalize the classical results on equilibria of the three-body problem and many results on them obtained by the classic approach for the case of rigid bodies.
MHD Stability Trends from Perturbed Equilibria: Possible Limitations with Toroidal Geometry
Comer, K. J.; Callen, J. D.; Hegna, C. C.; Turnbull, A. D.; Cowley, S.
2003-10-01
The effects of equilibrium changes on ideal MHD properties are usually studied using numerical parameter scans. Previously, we introduced a new technique to explore these dependencies: changes in the potential energy δ W due to equilibrium changes are found with an expansion of the energy principle, rather than an eigenvalue-solver code. Validation of the approach in toroidal geometry attempted to use GATO (an ideal MHD stability code) and DIII-D shot 87009. The approach should succeed with the global modes of 87009; however, ˜ 0.1% changes to qo predicted δ W rapidly increasing. Perturbing β of other toroidal equilibria resulted in similar behavior. We first review results for a cylindrical equilibrium and for 87009. Between the cylindrical case and 87009 lie several other equilibria, which should produce intermediate results. We examine several of these intermediate equilibria, starting with the cylindrical case and changing aspect ratio, shape and profiles until ending at 87009.
A note on relative equilibria in a rotating shallow water layer
Ait Abderrahmane, Hamid
2013-05-08
Relative equilibria of two and three satellite vortices in a rotating shallow water layer have been recorded via particle image velocimetry (PIV) and their autorotation speed was estimated. This study shows that these equilibria retain the fundamental characteristics of Kelvin\\'s equilibria, and could be adequately described by the classical idealized point vortex theory. The same conclusion can also be inferred using the experimental dataset of Bergmann etÂ al.Â (J.Â FluidÂ Mech., vol. 679, 2011, pp. 415-431; J. Fluid Mech., vol. 691, 2012, pp. 605-606) if the assigned field\\'s contribution to pattern rotation is included. © 2013 Cambridge University Press.
Bernardo, Mario di; Camlibel, Kanat
2005-01-01
This paper is concerned with the structural stability of boundary equilibria in a class of hybrid systems, that of piecewise linear continuous systems. Specifically, we study the structural stability under parameter variations of equilibria lying on discontinuity boundaries in phase space dividing r
Phase Equilibria for extraction processes with designer solvents
Lago García de Dios, Sara
2013-01-01
In recent years, there has been an increasing concern about the effects of toxic chemicals in the environment. In response to this concern, there is a growing impetus to develop chemical manufacturing processes which can reduce or eliminate the use or generation of hazardous substances. Within this aspect of green chemistry, in this Thesis, Ionic Liquids (ILs) and Deep Eutectic Solvents (DESs) have been tested as greener alternatives in different chemical processes. In a ...
Studies of the chemical equilibria in the solvent extraction of uranium
International Nuclear Information System (INIS)
Uranium was extracted with amines dissolved in diluents. Using alamine 336 as an extractant, dodecane as a diluent, and n-octanol as an additive for third phase inhibition, UO2++ extraction from H2SO4-Na2SO4 aqueous solutions was studied. When the extraction coefficient of uranium was plotted as a function of the initial Na2SO4 concentration at a constant sulfuric acid concentration, the typical initial spike type extraction curve was obtained in this case too. Thus, at low Na2SO4 concentrations, a reaction such as UO2SO4 + 2 (AlamineH)2SO4 reversible (AlamineH)4UO2(SO4)3...(1) is believed to take place, while at high Na2SO4 concentrations reaction (2) is thought to be occurring. UO2(SO4)34- + 2(R3NH)2SO4 reversible (R3NH)4UO2(SO4)3 = 2SO4-2...(2). The same result obtained with Na2SO4 as with H2SO4 is explained by the action of sulfate ions
Haubrock, J.; Raspe, M.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Hogendoorn, J.A.
2008-01-01
New experimental equilibrium data of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of MPC to diphenyl carbonate (DPC) are presented and interpreted in terms of the reaction equilibrium coefficien
Chemical speciation and equilibria of some nucleic acid compounds and their iron(III) complexes
Masoud, Mamdouh S.; Abd El-Kaway, Marwa Y.; Hindawy, Ahmed M.; Soayed, Amina A.
The pH effect on electronic absorption spectra of some biologically active nucleic acid constituents have been studied at room temperature and the mechanism of ionization was explained. These compounds are of two categories (pyrimidines: [barbital; 5,5'-diethyl-barbituric acid], [SBA; 4,6-dihydroxy-2-mercapto-pyrimidin], [NBA; 5-nitro-2,4,6(1H,3H,5H)-pyrimidine trione] and [TU; 2,3-dihydro-2-thioxo-pyrimidin-4(1H)-one]) and (purines: [adenine; 6-amino purine], its [Schiff bases derived from adenine-acetylacetone; (Z)-4-(7H-purin-6-ylimino)pentan-2-one) and adenine-salicylaldehyde; 2-((7H-purin-6-ylimino) methyl) phenol] and its [Azo derived from adenine-resorcinol; 4-((7H-purin-6-yl)-diazenyl) benzene-1,3-diol]. The phenomena of tautomerization assigned different tautomers. Different spectrophotometric methods are applied to evaluate the pK's values that explained with their molecular structures. The interaction of Fe3+ with some selected pyrimidines (barbital, NBA and SBA) was explained using familiar six spectrophotometric methods. The data typified the existence of different absorbing species with the different stoichiometries 1:1, 1:2, 1:3 and 2:3. The stability constant of the complexes was computed. More approach was deduced to assign the existence of different species applying the distribution diagrams.
Sasidevan, V
2015-01-01
The study of games and their equilibria is central to developing insights for understanding many socio-economic phenomena. Here we present a dynamical systems view of the equilibria of two-person, payoff-symmetric games. In particular, using this perspective, we discuss the differences between two solution concepts for such games - namely, those of Nash equilibrium and co-action equilibrium. For the Nash equilibrium, we show that the dynamical view can provide an equilibrium refinement, selecting one equilibrium among several possibilities, thereby solving the issue of multiple equilibria that appear in some games. We illustrate in detail this dynamical perspective by considering three well known 2-person games namely the Prisoner's Dilemma, game of Chicken and the Stag-Hunt. We find that in all of these cases, co-action equilibria tends to correspond to `nicer' strategies than those corresponding to Nash equilibria.
Experimental determination of phase equilibria in the Fe-Nb-V ternary system
International Nuclear Information System (INIS)
The phase equilibria in the Fe-Nb-V ternary system were investigated by means of optical microscopy, electron probe microanalysis and X-ray diffraction. Four isothermal sections in the Fe-Nb-V ternary system at 1000 deg. C, 1100 deg. C, 1200 deg. C and 1300 deg. C were firstly experimentally established. Present experimental results indicate that: (1) there is a large (Nb, V) continuous bcc solid solution; (2) there are the larger solubilities of V in the FeNb and Fe2Nb phases. The newly determined phase equilibria in this system will provide important support for the development of hydrogen storage materials and microalloyed steels.
Analytic high-beta tokamak equilibria with poloidal-sonic flow and their stability
International Nuclear Information System (INIS)
Full text: In magnetically confined plasmas, equilibrium flows may suppress instability and turbulent transport to give rise to the formation of transport barriers or pedestals. In axisymmetric toroidal systems like tokamaks, both of the poloidal and toroidal components of flow are important for these phenomena. The ideal magnetohydrodynamic (MHD) equations for equilibria with flow reduce to the so-called generalized Grad-Shafranov (GS) equation and the Bernoulli law with five free functions of the magnetic flux in axisymmetric systems. These systems of a nonlinear partial differential equation (PDE) and a nonlinear algebraic equation can be solved numerically by iteration schemes when the PDE is elliptic in the whole region. Recently, a new reduced set of equilibrium equations has been derived for high-beta tokamaks with flow in the order of the poloidal-sound velocity. This model includes the effect of poloidal flow on both the magnetic flux and the pressure in higher-order terms of asymptotic expansions in terms of the inverse aspect ratio. We have found analytical solutions for this reduced set of equations for linear profiles of the lowest order free functions and perform qualitative studies of equilibria with sub- and super-poloidal-sonic flow. Analytical representations of equilibria with flow may be useful for benchmarks and initial guesses of iteration as well as for qualitative studies of equilibrium flows and stability analyses. In this presentation, we will also discuss the stability of these analytical equilibria. Equilibrium flow brings non-Hermitian properties to linear perturbations. In contrast to the static equilibria, the variational formulation does not give necessary and sufficient conditions, and the growth and damping can be non-exponential where mode analysis does not work. Due to these reasons, stability analysis of equilibria with flow must be done more carefully than that of static equilibria. Based on the formalism of the reduced MHD
Exotic equilibria of Harary graphs and a new minimum degree lower bound for synchronization
Energy Technology Data Exchange (ETDEWEB)
Canale, Eduardo A., E-mail: ecanale@pol.una.py [Facultad Politénica, UNA, Asunción (Paraguay); Monzón, Pablo, E-mail: monzon@fing.edu.uy [School of Engineering, UDELAR, Montevideo 11300 (Uruguay)
2015-02-15
This work is concerned with stability of equilibria in the homogeneous (equal frequencies) Kuramoto model of weakly coupled oscillators. In 2012 [R. Taylor, J. Phys. A: Math. Theor. 45, 1–15 (2012)], a sufficient condition for almost global synchronization was found in terms of the minimum degree–order ratio of the graph. In this work, a new lower bound for this ratio is given. The improvement is achieved by a concrete infinite sequence of regular graphs. Besides, non standard unstable equilibria of the graphs studied in Wiley et al. [Chaos 16, 015103 (2006)] are shown to exist as conjectured in that work.
Exotic equilibria of Harary graphs and a new minimum degree lower bound for synchronization
Canale, Eduardo A.
2015-02-01
© 2015 AIP Publishing LLC. This work is concerned with stability of equilibria in the homogeneous (equal frequencies) Kuramoto model of weakly coupled oscillators. In 2012 [R. Taylor, J. Phys. A: Math. Theor. 45, 1-15 (2012)], a sufficient condition for almost global synchronization was found in terms of the minimum degree-order ratio of the graph. In this work, a new lower bound for this ratio is given. The improvement is achieved by a concrete infinite sequence of regular graphs. Besides, non standard unstable equilibria of the graphs studied in Wiley et al. [Chaos 16, 015103 (2006)] are shown to exist as conjectured in that work.
Theory of phase equilibria and critical mixing points in binary lipid bilayers
DEFF Research Database (Denmark)
Risbo, Jens; Sperotto, Maria Maddalena; Mouritsen, Ole G.
1995-01-01
energy necessary to derive phase equilibria is determined from the simulations using distribution functions and histogram techniques, and the nature of the phase equilibria is determined by a finite-size scaling analysis which also permits the interfacial tension to be derived. Results are also presented...... for the enthalpy and the compositional fluctuations. It is shown, in accordance with experiments, that the nonideal mixing of lipid species due to mismatch in the hydrophobic lengths leads to a progressively nonideal mixing behavior as the chain-length difference is increased. Moreover, indications...
Existence of three-dimensional ideal-magnetohydrodynamic equilibria with current sheets
Energy Technology Data Exchange (ETDEWEB)
Loizu, J. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany); Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543 (United States); Hudson, S. R.; Bhattacharjee, A.; Lazerson, S. [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543 (United States); Helander, P. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany)
2015-09-15
We consider the linear and nonlinear ideal plasma response to a boundary perturbation in a screw pinch. We demonstrate that three-dimensional, ideal-MHD equilibria with continuously nested flux-surfaces and with discontinuous rotational-transform across the resonant rational-surfaces are well defined and can be computed both perturbatively and using fully nonlinear equilibrium calculations. This rescues the possibility of constructing MHD equilibria with current sheets and continuous, smooth pressure profiles. The results predict that, even if the plasma acts as a perfectly conducting fluid, a resonant magnetic perturbation can penetrate all the way into the center of a tokamak without being shielded at the resonant surface.
TOWARD A THEORY OF SUSTAINABLE SYSTEMS. FLUID PHASE EQUILIBRIA: JOURNAL ARTICLE
NRMRL/STD JOURNAL NRMRL-CIN-1364 Cabezas*, H., and Fath**, B.D. Toward a Theory of Sustainable Systems. Fluid Phase Equilibria (Nakanishi, K., Yasukiko, A., Miyano, Y. (Ed.), Elsevier Science B.V.) 194-197:3-14 (2002). EPA/600/J-02/186, www.elsevier.com/locate/fluid. 03/2...
High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004)
DEFF Research Database (Denmark)
Dohrn, Ralf; Peper, Stephanie; Fonseca, José
2010-01-01
-vapor-liquid equilibria, critical points, the solubility of high-boiling substances in supercritical fluids, the solubility of gases in liquids and the solubility (sorption) of volatile components in polymers are included. For the systems investigated, the reference, the temperature and pressure range of the data, and...
Control Algorithms Along Relative Equilibria of Underactuated Lagrangian Systems on Lie Groups
DEFF Research Database (Denmark)
Nordkvist, Nikolaj; Bullo, F.
2008-01-01
We present novel algorithms to control underactuated mechanical systems. For a class of invariant systems on Lie groups, we design iterative small-amplitude control forces to accelerate along, decelerate along, and stabilize relative equilibria. The technical approach is based upon a perturbation...
Control algorithms along relative equilibria of underactuated Lagrangian systems on Lie groups
DEFF Research Database (Denmark)
Nordkvist, Nikolaj; Bullo, Francesco
We present novel algorithms to control underactuated mechanical systems. For a class of invariant systems on Lie groups, we design iterative small-amplitude control forces to accelerate along, decelerate along, and stabilize relative equilibria. The technical approach is based upon a perturbation...
On convergence to equilibria for the Keller-Segel chemotaxis model
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Laurencot, P.; Petzeltová, Hana
2007-01-01
Roč. 236, č. 2 (2007), s. 551-569. ISSN 0022-0396 R&D Projects: GA AV ČR(CZ) IAA100190606 Institutional research plan: CEZ:AV0Z10190503 Keywords : Keller-Segel chemotaxis model * convergence to equilibria * Łojasiewicz-Simon theory Subject RIV: BA - General Mathematics Impact factor: 1.097, year: 2007
Truth-telling and Nash equilibria in minimum cost spanning tree models
DEFF Research Database (Denmark)
Hougaard, Jens Leth; Tvede, Mich
2012-01-01
to the rules of the game. We characterize ways of allocating costs such that true announcements constitute Nash equilibria both in case of full and incomplete information. In particular, we find that the Shapley rule based on the irreducible cost matrix is consistent with truthful announcements while...
The Representation of Highly Non-Ideal Phase Equilibria Using Computer Graphics.
Charos, Georgios N.; And Others
1986-01-01
Previous work focused on use of computer graphics in teaching thermodynamic phase equilibria for classes I and II. Extends this work to include the considerably more non-ideal phase behavior shown by classes III, IV, and V. Student and instructor response has been overwhelmingly positive about the approach. (JN)
Vapor-Liquid Equilibria Using the Gibbs Energy and the Common Tangent Plane Criterion
Olaya, Maria del Mar; Reyes-Labarta, Juan A.; Serrano, Maria Dolores; Marcilla, Antonio
2010-01-01
Phase thermodynamics is often perceived as a difficult subject with which many students never become fully comfortable. The Gibbsian geometrical framework can help students to gain a better understanding of phase equilibria. An exercise to interpret the vapor-liquid equilibrium of a binary azeotropic mixture, using the equilibrium condition based…
Liquid-liquid equilibria for binary and ternary polymer solutions with PC-SAFT
DEFF Research Database (Denmark)
Lindvig, Thomas; Michelsen, Michael Locht; Kontogeorgis, Georgios
2004-01-01
Two algorithms for evaluating liquid-liquid equilibria (LLE) for binary and ternary polymer solutions are presented. The binary algorithm provides the temperature versus concentration cloud-point curve at fixed pressure, whereas the ternary algorithm provides component 1 versus component 2...... accuracy, even by using interaction parameters obtained from binary vapor-liquid equlibrium data....
Phase equilibria study of binary systems comprising an (ionic liquid + hydrocarbon)
International Nuclear Information System (INIS)
Highlights: • The (solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) study. • {[PMPyr][CF3SO3] + heptane, or benzene, or thiophene, or benzothiophene}. • {[BCN4Py][TCM] + heptane, or toluene, or 2-methylthiophene, or benzothiophene}. • Thermodynamic NRTL modelling. • Separation of sulfur compounds from alkanes and aromatics from aliphatics. - Abstract: In this study, the interaction of two ionic liquids with hydrocarbons has been investigated. With this aim, (solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) for binary systems of {1-methyl-1-propyl-pyrrolidinium triflate [PMPyr][CF3SO3] + heptane, or benzene, or thiophene, or benzothiophene} and {N-butyl-4-cyanopyridinium tricyanomethanide [BCN4Py][TCM] + heptane, or toluene, or 2-methylthiophene, or benzothiophene} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (T = 270 to 370) K. An upper critical solution temperature (UCST) was detected for all mutually immiscible systems. The immiscibility gap for [BCN4Py][TCM] in benzene and thiophene is larger than those for [PMPyr][CF3SO3]. Conversely, in heptane it is slightly larger for [PMPyr][CF3SO3]. The basic thermal properties of the pure ILs, i.e. melting and glass-transition temperatures as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). The well-known NRTL model has been used to correlate the experimental SLE data points
Peeling-Ballooning Mode Analysis in Shifted-Circle Tokamak Equilibria
Burke, B.; Kruger, S. E.; Hegna, C. C.; Snyder, P. B.; Sovinec, C. R.; Zhu, P.
2009-11-01
Progress in understanding edge localized modes (ELMs) has been made by investigating the stability properties of edge localized peeling-ballooning modes. We focus on the evolution of ideal MHD modes over a large spectrum in two shifted-circle tokamak equilibria, using the extended-MHD code NIMROD. The TOQ-generated equilibria model a H-mode plasma with a pedestal pressure profile and parallel edge currents. A vacuum region is prescribed by a resistivity profile that transitions from a small to very large value at a specified location. The vacuum model is benchmarked against the linear ideal MHD codes ELITE & GATO. We demonstrate vacuum effects on the stability by adjusting the vacuum location relative to the pedestal pressure region. Ballooning-like instabilities dominate distant vacuum cases, whereas peeling mode physics is expected to dominate as the vacuum approaches the pedestal. Numerical simulations of the early nonlinear stages of edge localized MHD instabilities are presented. Comparisons between equilibria that have ``ballooning'' dominated instabilities relative to equilibria that are ``peeling'' dominated are made.
Simulation of the high-pressure phase equilibria of hydrocarbon-water/brine systems
DEFF Research Database (Denmark)
Zuo, You-Xiang; Stenby, Erling Halfdan; Guo, Tian-Min
1996-01-01
The major objectives of this work are: (1) extend the modified Patel-Teja (MPT) equation of state proposed for aqueous electrolyte systems (Zuo and Guo, 1991) to describe the liquid-liquid and vapor-liquid-liquid equilibria of hydrocarbon-water/brine systems through introducing an unconventional ...
Coalition Formation under Uncertainty: Bargaining Equilibria and the Bayesian Core Stability Concept
Chalkiadakis, G.; Markakis, V.; Boutillier, C.; Durfee, E.H.; Yokoo, M.; Huhns, M.N.
2007-01-01
Coalition formation is a problem of great interest in AI, allowing groups of autonomous, rational agents to form stable teams. Fur- thermore, the study of coalitional stability concepts and their re- lation to equilibria that guide the strategic interactions of agents during bargaining has lately at
Force-free analytical threedimensional toroidal MHD-equilibria of arbitrary cross section
International Nuclear Information System (INIS)
The equation curl B = γB describing force-free MHD equilibria is solved in threedimensional rotational coordinates for a torus with arbitrary cross section. An analytical threedimensional and an axisymmetric twodimensional example is given for a torus of circular cross section. (Auth.)
Convergence to equilibria of solutions to a conserved phase-field system with memory
Czech Academy of Sciences Publication Activity Database
Aizicovici, S.; Petzeltová, Hana
2009-01-01
Roč. 2, č. 1 (2009), s. 1-16. ISSN 1937-1632 R&D Projects: GA AV ČR(CZ) IAA100190606 Institutional research plan: CEZ:AV0Z10190503 Keywords : conserved phase-field systems * memory effects * convergence to equilibria Subject RIV: BA - General Mathematics
A periodic point-based method for the analysis of Nash equilibria in 2 x 2 symmetric quantum games
International Nuclear Information System (INIS)
We present a novel method of looking at Nash equilibria in 2 x 2 quantum games. Our method is based on a mathematical connection between the problem of identifying Nash equilibria in game theory, and the topological problem of the periodic points in nonlinear maps. To adapt our method to the original protocol designed by Eisert et al (1999 Phys. Rev. Lett. 83 3077-80) to study quantum games, we are forced to extend the space of strategies from the initial proposal. We apply our method to the extended strategy space version of the quantum Prisoner's dilemma and find that a new set of Nash equilibria emerge in a natural way. Nash equilibria in this set are optimal as Eisert's solution of the quantum Prisoner's dilemma and include this solution as a limit case.
Directory of Open Access Journals (Sweden)
Span Roland
2012-04-01
Full Text Available Gas-hydrates (clathrates are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS [A. Yokozeki, Fluid Phase Equil. 222–223 (2004] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.
Ginting, Rizqy Romadhona; Mustain, Asalil; Tetrisyanda, Rizki; Gunardi, Ignatius; Wibawa, Gede
2015-12-01
In this work, liquid-liquid equilibria data of dimethyl carbonate (DMC) + 2-propanol + water system were accurately determined at 303.15 and 313.15 K using stirred and jacketed equilibrium cell under atmospheric pressure. The reliabilities of the experimental data were confirmed using Bachman-Brown correlation giving r-squared value of 0.9993 and 0.9983 at 303.15 and 313.15 K, respectively. Experimental data obtained in this work exhibit Treybal's Type I ternary phase behavior. The selectivity and distribution coefficient of DMC increases with addition of DMC concentration in the organic phase. On the other hand, the effect of temperature to phase boundary was found to be not significant. The data were correlated well using the Non-Random Two Liquid (NRTL) and Universal Quasi-Chemical (UNIQUAC) activity coefficient models with root-mean-square deviation of 1.5% and 1.3%, respectively.
DEFF Research Database (Denmark)
Fonseca, José M.S.; von Solms, Nicolas
2012-01-01
A new apparatus for the study of high-pressure phase equilibria at low temperatures using an analytical method was designed, assembled and tested. The apparatus was specially developed for the study of multi-phase equilibria in systems containing hydrocarbons, water and hydrate inhibitors, at tem...... the study of the system methane+water. An equilibrium point for the quaternary system methane+n-hexane+methanol+water is also presented....
Institute of Scientific and Technical Information of China (English)
FU,Dong(付东); LU,Jiu-Fang(陆九芳); WU,Wei(吴畏); Li,Yi-Gui(李以圭)
2004-01-01
An equation of state (EOS) was established to study the osmotic pressure and liquid-liquid equilibria for micelle,colloid and microemulsion systems. The Carnahan-Starling equation was used for the hard sphere repulsion. The Yukawa potential was used to describe both the attractive dispersion and the double-layer repulsion. By using the established EOS, the osmotic pressures for charged colloid, uncharged micelle, uncharged and weakly charged microemuslion, the phase equilibria for uncharged micelle and charged colloid systems were studied.
Treiman, Allan H.
1995-01-01
A thermochemical model of the activities of species in carbonate-rich melts would be useful in quantifying chemical equilibria between carbonatite magmas and vapors and in extrapolating liquidus equilibria to unexplored PTX. A regular-solution model of Ca-rich carbonate melts is developed here, using the fact that they are ionic liquids, and can be treated (to a first approximation) as interpenetrating regular solutions of cations and of anions. Thermochemical data on systems of alkali metal cations with carbonate and other anions are drawn from the literature; data on systems with alkaline earth (and other) cations and carbonate (and other) anions are derived here from liquidus phase equilibria. The model is validated in that all available data (at 1 kbar) are consistent with single values for the melting temperature and heat of fusion for calcite, and all liquidi are consistent with the liquids acting as regular solutions. At 1 kbar, the metastable congruent melting temperature of calcite (CaCO3) is inferred to be 1596 K, with (Delta)bar-H(sub fus)(calcite) = 31.5 +/- 1 kJ/mol. Regular solution interaction parameters (W) for Ca(2+) and alkali metal cations are in the range -3 to -12 kJ/sq mol; W for Ca(2+)-Ba(2+) is approximately -11 kJ/sq mol; W for Ca(2+)-Mg(2+) is approximately -40 kJ/sq mol, and W for Ca(2+)-La(3+) is approximately +85 kJ/sq mol. Solutions of carbonate and most anions (including OH(-), F(-), and SO4(2-)) are nearly ideal, with W between 0(ideal) and -2.5 kJ/sq mol. The interaction of carbonate and phosphate ions is strongly nonideal, which is consistent with the suggestion of carbonate-phosphate liquid immiscibility. Interaction of carbonate and sulfide ions is also nonideal and suggestive of carbonate-sulfide liquid immiscibility. Solution of H2O, for all but the most H2O-rich compositions, can be modeled as a disproportionation to hydronium (H3O(+)) and hydroxyl (OH(-)) ions with W for Ca(2+)-H3O(+) (approximately) equals 33 kJ/sq mol. The
International Nuclear Information System (INIS)
The phase equilibria in the Co-rich corner of the Co-Mn-Ta system were investigated by means of optical microscopy, electron probe microanalysis and X-ray diffraction. Six isothermal sections in the Co-rich corner of the Co-Mn-Ta ternary system at 1300 C, 1200 C, 1100 C, 1000 C, 900 C, 800 C were experimentally determined. On the basis of previous and present experimental data of the phase equilibria, the thermodynamic assessments of the Mn-Ta binary and Co-Mn-Ta ternary systems were carried out by using CALPHAD. The thermodynamic parameters of the Mn-Ta binary and the Co-Mn-Ta ternary systems have been optimized for reproducing the experimental results in each system. An agreement between the calculated results and experimental data is obtained.
Simulating Phase Equilibria using Wang-Landau-Transition Matrix Monte Carlo
International Nuclear Information System (INIS)
We will examine the strengths and weaknesses of the Wang-Landau and transition matrix Monte Carlo methods for simulating phase equilibria of continuous molecular systems alone and as a combined Wang-Landautransition matrix Monte Carlo algorithm. Although a combined Wang-Landau transition matrix Monte Carlo algorithm has been previously reported in the literature, the details of the method and a discussion of its performance for phase equilibria simulations has not been presented. The hybrid method combines the rapid initial estimate of the density of states from the Wang-Landau algorithm with the continual improvement in convergence of transition matrix Monte Carlo. The hybrid Wang-Landau-transition matrix (WL-TM) algorithm is found to be more efficient and has much better convergence properties than the Wang-Landau algorithm and is more robust than the transition matrix algorithm, enabling the simulations to reach relatively low reduced temperatures with ease
Toward detailed prominence seismology - I. Computing accurate 2.5D magnetohydrodynamic equilibria
Blokland, J W S
2011-01-01
Context. Prominence seismology exploits our knowledge of the linear eigenoscillations for representative magnetohydro- dynamic models of filaments. To date, highly idealized models for prominences have been used, especially with respect to the overall magnetic configurations. Aims. We initiate a more systematic survey of filament wave modes, where we consider full multi-dimensional models with twisted magnetic fields representative of the surrounding magnetic flux rope. This requires the ability to compute accurate 2.5 dimensional magnetohydrodynamic equilibria that balance Lorentz forces, gravity, and pressure gradients, while containing density enhancements (static or in motion). Methods. The governing extended Grad-Shafranov equation is discussed, along with an analytic prediction for circular flux ropes for the Shafranov shift of the central magnetic axis due to gravity. Numerical equilibria are computed with a finite element-based code, demonstrating fourth order accuracy on an explicitly known, non-triv...
Equilibria and stability of an electron beam confined in a torus
International Nuclear Information System (INIS)
Relativistic, cylindrical, rigid-rotor equilibria for electrons are developed in the beam frame, and the corresponding laboratory frame equilibria are obtained by Lorentz transformation. Limitations of the two-mass approximation are thus illuminated. A toroidal equilibrium is developed that is based on the two-mass approximation and expansion in terms of the ratio of minor to major radius. The toroidal equilibrium is shown to have no unstable kink-modes or no Kruskal--Shafranov current limit as in a Tokamak. Small variations in the toroidal magnetic field around the torus result in trapped electrons if they are injected with sufficient transverse energy. The presence of both trapped and untrapped electrons leads to two-stream instabilities. Some comparisons are made with HIPAC experiments and the recent torus experiments at MLI
Edge stability and pedestal profile sensitivity of snowflake diverted equilibria in the TCV Tokamak
International Nuclear Information System (INIS)
A second order null divertor (snowflake) has been successfully created and controlled in the TCV tokamak[1] (F. Piras et al., Plasma Phys. Control. Fusion, 2009). The results of ideal MHD edge stability computations show an enhancement of the edge stability properties of the snowflake equilibria compared to standard x-point configurations[2] (S. Yu. Medvedev et al., 36th EPS Conference on Plasma Physics, 2009). However, a sensitivity study of the stability limits to variations of the pedestal profiles is essential for making conclusions about possibilities of ELM control in snowflake plasmas. Variations of the edge stability and beta limits for several types of snowflake equilibria, different values of triangularity and various pedestal profiles are investigated (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Energy Technology Data Exchange (ETDEWEB)
McNamara, B.
1984-04-01
Tandem and stellarator equilibria at high ..beta.. have proved hard to compute and the relaxation methods of Bauer et al., Chodura and Schluter, Hirshman, Strauss, and Pearlstein et al. have been slow to converge. This paper reports an extension of the low-..beta.. analytic method of Pearlstein, Kaiser, and Newcomb to arbitrary ..beta.. for tandem mirrors which converges in 10 to 20 iterations. Extensions of the method to stellarator equilibria are proposed and are very close to the analytic method of Johnson and Greene - the stellarator expansion. Most of the results of all these calculations can be adequately described by low-..beta.. approximations since the MHD stability limits occur at low ..beta... The tandem mirror, having weak curvature and a long central cell, allows finite Larmor radius effects to eliminate most ballooning modes and offers the possibility of really high average ..beta... This is the interest in developing such three-dimensional numerical algorithms.
Phase equilibria of the Cu-Nb-Ti system at 850 deg. C
International Nuclear Information System (INIS)
The phase equilibria of the Cu-Nb-Ti system at 850 deg. C were investigated by a high-efficiency diffusion couple approach. The samples were studied by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. At 850 deg. C, the phase TiCu2, the stability range of which is controversial in the literature, was observed. The solubilities of Nb in Ti2Cu, TiCu and Ti3Cu4 were determined to be 3.5, 3.1 and 4.6 at.%, respectively. The solubility of Nb in TiCu4 was negligibly small. The following three-phase equilibria were observed: Ti2Cu + TiCu + (Nb,Ti), TiCu + Ti3Cu4 + (Nb,Ti) and Ti3Cu4 + TiCu4 + (Nb,Ti)
International Nuclear Information System (INIS)
An apparatus based on a static-analytic method assembled in this work was utilized to perform high pressure (vapour + liquid) equilibria measurements with uncertainties estimated at 2 + 1-propanol), (CO2 + 2-methyl-1-propanol), (CO2 + 3-methyl-1-butanol), and (CO2 + 1-pentanol) binary systems at temperatures of (313, 323, and 333) K, and at pressure range of (2 to 12) MPa. For all the (CO2 + alcohol) systems, it was visually monitored to insure that there was no liquid immiscibility at the temperatures and pressures studied. The experimental results were correlated with the Peng-Robinson equation of state using the quadratic mixing rules of van der Waals with two adjustable parameters. The calculated (vapour + liquid) equilibria compositions were found to be in good agreement with the experimental values with deviations for the mol fractions <0.12 and <0.05 for the liquid and vapour phase, respectively.
The global stability of coexisting equilibria for three models of mutualism.
Georgescu, Paul; Zhang, Hong; Maxin, Daniel
2016-02-01
We analyze the dynamics of three models of mutualism, establishing the global stability of coexisting equilibria by means of Lyapunov's second method. This further establishes the usefulness of certain Lyapunov functionals of an abstract nature introduced in an earlier paper. As a consequence, it is seen that the use of higher order self-limiting terms cures the shortcomings of Lotka-Volterra mutualisms, preventing unbounded growth and promoting global stability. PMID:26776263
Dana, Rose-Anne; Le Van, Cuong
2010-01-01
The overlapping expectations and the collective absence of arbitrage conditions introduced in the economic literature to insure existence of Pareto optima and equilibria with short-selling when investors have a single belief about future returns, is reconsidered. Investors use measures of risk. The overlapping sets of priors and the Pareto equilibrium conditions introduced by Heath and Ku for coherent risk measures are respectively reinterpreted as a weak no-arbitrage and a weak collective ab...
Complete classification and stability of equilibria in a delayed ring network
Directory of Open Access Journals (Sweden)
Shangjiang Guo
2008-06-01
Full Text Available In this paper, we consider a neural network model consisting of four neurons with delayed self and nearest-neighbor connections. We provide a full classification of all equilibria and their stability in the connection weighter parameter space. Such a classification is essential for the description of spatio-temporal patterns of the model system and for the applications to dynamic memory storage and retrieval.
Complete classification and stability of equilibria in a delayed ring network
Shangjiang Guo; Xuwen Lu
2008-01-01
In this paper, we consider a neural network model consisting of four neurons with delayed self and nearest-neighbor connections. We provide a full classification of all equilibria and their stability in the connection weighter parameter space. Such a classification is essential for the description of spatio-temporal patterns of the model system and for the applications to dynamic memory storage and retrieval.
New investigation of phase equilibria in the system Al-Cu-Si
Energy Technology Data Exchange (ETDEWEB)
Ponweiser, Norbert [University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Waehringer Strasse 42, 1090 Wien (Austria); Richter, Klaus W., E-mail: klaus.richter@univie.ac.at [University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Waehringer Strasse 42, 1090 Wien (Austria)
2012-01-25
Highlights: Black-Right-Pointing-Pointer Isothermal sections at 500 and 700 Degree-Sign C investigated. Black-Right-Pointing-Pointer Vertical sections (partial at 10 at.% Si, complete at 40 at.% Si) determined. Black-Right-Pointing-Pointer Partial ternary reaction scheme (Scheil diagram) established. Black-Right-Pointing-Pointer New ternary compound identified. - Abstract: The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 Degree-Sign C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 Degree-Sign C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound {tau} was found in the region between (Al,Cu)-{gamma}{sub 1} and (Cu,Si)-{gamma} and its solubility range was determined. The solubility of Al in {kappa}-CuSi was found to be extremely high at 700 Degree-Sign C. In contrast, no ternary solubility in the {beta}-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.
International Nuclear Information System (INIS)
A method for determining nuclide activities in 4n + 2 uranium series using alpha spectrometry of thick sources is described. This method has been applied to several uranium ores, showing different states of radioactive equilibria. The spectra from samples prepared by cold compression show some anomalies, due to the evolution and later decay of 219Rn and daughters. This phenomenon must be taken in consideration when computing spectra line intensities. (author)
Correlation of Liquid-Liquid Equilibria in Ternary Systems Containing Ionic Liquids
Czech Academy of Sciences Publication Activity Database
Bendová, Magdalena; Aim, Karel; Klusoň, Petr; Sedláková, Zuzana; Černá, I.; Vašinová, J.
- : -, 2009, 41/21/. ISBN B. [Thermodynamics 2009. London (GB), 23.09.09-25.09.09] R&D Projects: GA ČR GA104/07/0444; GA ČR GP104/06/P066; GA AV ČR IAA400720710 Institutional research plan: CEZ:AV0Z40720504 Keywords : liquid-liquid equilibria * ionic liquids * correlation Subject RIV: CF - Physical ; Theoretical Chemistry
Solid-Liquid Equilibria in Systems [Cxmim][Tf2N] with Diethylamine
Czech Academy of Sciences Publication Activity Database
Rotrekl, Jan; Vrbka, P.; Sedláková, Zuzana; Wagner, Zdeněk; Jacquemin, J.; Bendová, Magdalena
2015-01-01
Roč. 87, č. 5 (2015), s. 453-460. ISSN 0033-4545. [International Symposium on Solubility Phenomena 2014. Karlsruhe , 20.07.2014-24.07.2014] R&D Projects: GA MŠk(CZ) LD14094; GA MŠk LG13060 Institutional support: RVO:67985858 Keywords : ionic liquids * solid-liquid equilibria * COSMO-RS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.492, year: 2014
Using Simple Donors to Drive the Equilibria of Glycosyltransferase-Catalyzed Reactions
Gantt, Richard W.; Peltier-Pain, Pauline; Cournoyer, William J.; Thorson, Jon S.
2011-01-01
We report the ability of simple glycoside donors to drastically shift the equilibria of glycosyltransferase-catalyzed reactions, transforming NDP-sugar formation from an endo- to an exothermic process. To demonstrate the utility of this thermodynamic adaptability, we highlight the glycosyltransferase-catalyzed synthesis of 22 sugar nucleotides from simple aromatic sugar donors as well as the corresponding in situ formation of sugar nucleotides as a driving force in context of glycosyltransfer...
Graphical Derivatives and Stability Analysis for Parameterized Equilibria with Conic Constraints
Czech Academy of Sciences Publication Activity Database
Mordukhovich, B. S.; Outrata, Jiří; Ramírez, H. C.
2015-01-01
Roč. 23, č. 4 (2015), s. 687-704. ISSN 1877-0533 R&D Projects: GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : Variational analysis and optimization * Parameterized equilibria * Conic constraints * Sensitivity and stability analysis * Solution maps * Graphical derivatives * Normal and tangent cones Subject RIV: BA - General Mathematics Impact factor: 1.379, year: 2014 http://library.utia.cas.cz/separaty/2015/MTR/outrata-0449259.pdf
Productive Signaling Equilibria and Over-Maintenance: An Application to Real Estate Markets
Danny Ben-Shahar
2004-01-01
When there is asymmetric information regarding the quality of a traded durable asset, the informed seller might signal asset quality to prospective uninformed buyers by investing in improvements and maintenance. In contrast to Spence (1973), however, this signal may be productive. We derive conditions of signal productivity under which signaling separating, signaling pooling, and no-signaling pooling equilibria persist. We examine welfare implications of the model and identify the over-invest...
The empirical content of models with multiple equilibria in economies with social interactions
Bisin, Alberto; Moro, Andrea; Topa, Giorgio
2011-01-01
We study a general class of models with social interactions that might display multiple equilibria. We propose an estimation procedure for these models and evaluate its efficiency and computational feasibility relative to different approaches taken to the curse of dimensionality implied by the multiplicity. Using data on smoking among teenagers, we implement the proposed estimation procedure to understand how group interactions affect health-related choices. We find that interaction effects a...
Stability and bifurcation of equilibria for the axisymmetric averaged mean curvature flow
LeCrone, Jeremy
2012-01-01
We study the averaged mean curvature flow, also called the volume preserving mean curvature flow, in the particular setting of axisymmetric surfaces embedded in R^3 satisfying periodic boundary conditions. We establish analytic well--posedness of the flow within the space of little-H\\"older continuous surfaces, given rough initial data. We also establish dynamic properties of equilibria, including stability, instability, and bifurcation behavior of cylinders, where the radius acts as a bifurc...
Isothermal Vapor–Liquid Equilibria in Diluted Polystyrene + Butanone-2 System
Czech Academy of Sciences Publication Activity Database
Pavlíček, Jan; Bogdanić, Grozdana; Wichterle, Ivan
Ozarow Mazowiecki : Nobell Compressing sp. z o.o, 2015 - (Kosinsky, K.; Urbanczyk, M.; Žerko, S.), s. 196 ISBN N. [European Symposium on Applied Thermodynamics ESAT 2015 /28./. Athens (GR), 11.06.2015-14.06.2015] R&D Projects: GA ČR GA15-19542S Institutional support: RVO:67985858 Keywords : polymer-solvent system * experimental data * vapour-liquid equilibria Subject RIV: CF - Physical ; Theoretical Chemistry
Multiple Equilibria in a Single-Column Model of the Tropical Atmosphere
Sobel, Adam H; Bacmeister, Julio T
2007-01-01
A single-column model run under the weak temperature gradient approximation, a parameterization of large-scale dynamics appropriate for the tropical atmosphere, is shown to have multiple stable equilibria. Under conditions permitting persistent deep convection, the model has a statistically steady state in which such convection occurs, as well as an extremely dry state in which convection does not occur. Which state is reached depends on the initial moisture profile.
NIRA-3: An improved MATLAB package for finding Nash equilibria in infinite games
Krawczyk, Jacek; Zuccollo, James
2006-01-01
A powerful method for computing Nash equilibria in constrained, multi-player games is created when the relaxation algorithm and the Nikaido-Isoda function are used together in a suite of MATLAB routines. This paper updates the MATLAB suite described in \\cite{Berridge97} by adapting them to MATLAB 7. The suite is now capable of solving both static and open-loop dynamic games. An example solving a coupled constraints game using the suite is provided.
Hommes, C.
2013-01-01
This discussion paper led to a publication in the 'Journal of Economic Methodology' , 20(4), 2013. We discuss recent work on bounded rationality and learning in relation to Soros' principle of reflexivity and stress the empirical importance of non-rational, almost self-fulfilling equilibria in positive feedback systems. As an empirical example, we discuss a behavioral asset pricing model with heterogeneous expectations. Bubble and crash dynamics is triggered by shocks to fundamentals and ampl...
Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro
2015-01-01
We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical si...
New investigation of phase equilibria in the system Al–Cu–Si
International Nuclear Information System (INIS)
Highlights: ► Isothermal sections at 500 and 700 °C investigated. ► Vertical sections (partial at 10 at.% Si, complete at 40 at.% Si) determined. ► Partial ternary reaction scheme (Scheil diagram) established. ► New ternary compound identified. - Abstract: The phase equilibria and invariant reactions in the system Al–Cu–Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ1 and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu–Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al–Cu and Cu–Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.
International Nuclear Information System (INIS)
In order to provide an efficient tool to design alloy chemistry and processing conditions for high-strength, lightweight steel, an investigation of the Fe–Al–C ternary system was carried out by experimental phase diagram measurement and a CALPHAD thermodynamic analysis. Discrepancies between previously available experimental results and thermodynamic calculations were identified. The Fe–Al sub-binary system was re-optimized in order to obtain an accurate description of the liquid phase, while Gibbs energies of solid phases were mainly taken from a previous thermodynamic modeling. Phase equilibria among face-centered cubic (fcc)/body-centered cubic (bcc)/graphite/κ-carbide/liquid phases in the Fe–Al–C system in the temperature range from 1000 to 1400 °C were obtained by chemical equilibration followed by quenching, and subsequent composition analysis using electron probe microanalysis/inductively coupled plasma spectroscopy. By merging the revised Fe–Al binary description with existing Fe–C and Al–C binary descriptions, a complete thermodynamic description of the Fe–Al–C system was obtained in the present study. The modified quasi-chemical model in the pair approximation was used to model the liquid phase, while solid solutions were modeled using compound energy formalism. A2/B2 order/disorder transition in the bcc phase was taken into account. Compared with previously known experiments/thermodynamic modeling, a better agreement was obtained in the present study, regarding the stable region of fcc and the solidification thermal peak of a ternary alloy near the liquidus temperature. The obtained thermodynamic description also reproduced various types of experimental data in the Fe–Al–C system such as isothermal sections, vertical sections, liquidus projection, etc. The solidification of various steel grades was predicted and discussed
Phase equilibria and surfactant behavior of fluorinated ionic liquids with water
International Nuclear Information System (INIS)
Highlights: • Phase equilibria of water and fluorinated ionic liquids. • Critical micelle concentrations of fluorinated ionic liquids. • Size of the aggregates using Dynamic Light Scattering. - Abstract: This work studies the phase equilibria and surfactant behavior of fluorinated ionic liquids (FILs) containing fluorinated chains equal to four carbons with water. The knowledge about the phase behavior is crucial for the applications of these novel FILs with tuneable properties. The phase equilibria of the binary mixtures FILs with water were studied at atmospheric pressure in a temperature range from (298.15 to 353.15) K. In this study, FILs containing ammonium, pyrrolidinium and imidazolium cations and the perfluorobutanesulfonate anion were included. The Non-Random Two Liquid (NRTL) thermodynamic model was successfully applied to rationalize the phase behavior of the binary (water + FILs) mixtures. Furthermore, the critical micelle concentrations (CMCs) of these FILs, which present cations and/or anions with surfactant properties were also performed at T = 298.15 K by measurements of the ionic conductivity. Finally, the Dynamic Light Scattering (DLS) was used with aim to determinate the size of the aggregates of these FILs in water
Development of the Transferable Potentials for Phase Equilibria Model for Hydrogen Sulfide.
Shah, Mansi S; Tsapatsis, Michael; Siepmann, J Ilja
2015-06-11
The transferable potentials for phase equilibria force field is extended to hydrogen sulfide. The pure-component and binary vapor-liquid equilibria with methane and carbon dioxide and the liquid-phase relative permittivity are used for the parametrization of the Lennard-Jones (LJ) and Coulomb interactions, and models with three and four interaction sites are considered. For the three-site models, partial point charges are placed on the sites representing the three atoms, while the negative partial charge is moved to an off-atom site for the four-site models. The effect of molecular shape is probed using either only a single LJ interaction site on the sulfur atom or adding sites also on the hydrogen atoms. This procedure results in four distinct models, but only those with three LJ sites can accurately reproduce all properties considered for the parametrization. These two are further assessed for predictions of the liquid-phase structure, the lattice parameters and relative permittivity for the face-centered-cubic solid, and the triple point. An effective balance between LJ interactions and the dipolar and quadrupolar terms of the first-order electrostatic interactions is struck in order to obtain a four-site model that describes the condensed-phase properties and the phase equilibria with high accuracy. PMID:25981731
Phase equilibria in the YbTe–Sb2Te3–Te system
International Nuclear Information System (INIS)
Highlights: • The phase diagram of the YbTe–Sb2Te3–Te sub-system relates to the invariant eutectic type. • The primary crystallization fields of phases, the character and temperatures of the invariant equilibria were determined. • The existence of the ternary compound YbSb2Te4 and YbSb2Te4 were not confirmed. - Abstract: The phase equilibria in the YbTe–Sb2Te3–Te system were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope with energy dispersive analysis (SEM-EDS) techniques. Two isopleth sections and liquidus surface projection were constructed. The primary crystallization fields of phases, the character and temperatures of the invariant and monovariant processes were determined. No new ternary compound was found in this system and moreover, known ternary compounds YbSb2Te4 and YbSb4Te7 were not confirmed. The newly determined phase equilibria in this sub-system will provide important information for the future construction of self-consistent phase diagram of the ternary Yb–Sb–Te system in the entire concentration range
International Nuclear Information System (INIS)
Highlights: • Ternary (liquid + liquid) equilibria for 3 ionic liquid + thiophene + heptane systems. • The influence of ionic liquid structure on phase diagrams is discussed. • Influence of IL structure on S and β for heptane/thiophene separation is discussed. - Abstract: Ternary (liquid + liquid) equilibria for 3 systems containing ionic liquids {(1-ethyl-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, 1-(2-hydroxyethyl)-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, ethyl-dimethyl-(2-methoxyethyl)ammonium trifluorotris(perfluoroethyl)phosphate) + thiophene + heptane} have been determined at T = 298.15 K. The selectivity and solute distribution ratio were calculated for investigated systems and compared with literature values obtained for other systems containing ionic liquids with [FAP]− anions and [emim]+ cations. In each system, high solubility of thiophene and low solubility of heptane in the ionic liquid are observed. The experimental results have been correlated using NRTL model. The influence of the structure of ionic liquid on phase equilibria, selectivity and solute distribution ratio is discussed
International Nuclear Information System (INIS)
Research highlights: → (Vapor + liquid) equilibria of three (CO2 + C5 alcohol) binary systems were measured. → Complementary data are reported at (313, 323 and 333) K and from (2 to 11) MPa. → No liquid immiscibility was observed at the temperatures and pressures studied. → Experimental data were correlated with the PR-EoS and the van de Waals mixing rules. → Correlation results showed relative deviations ≤8 % (liquid) and ≤2 % (vapor). - Abstract: Complementary isothermal (vapor + liquid) equilibria data are reported for the (CO2 + 3-methyl-2-butanol), (CO2 + 2-pentanol), and (CO2 + 3-pentanol) binary systems at temperatures of (313, 323, and 333) K, and at pressure range of (2 to 11) MPa. For all (CO2 + alcohol) systems, it was visually monitored that there was no liquid immiscibility at the temperatures and pressures studied. The experimental data were correlated with the Peng-Robinson equation of state using the quadratic mixing rules of van der Waals with two adjustable parameters. The calculated (vapor + liquid) equilibria compositions were found to be in good agreement with the experimental data with deviations for the mole fractions <8% and <2% for the liquid and vapor phase, respectively.
Natural equilibria and anthropic effects on sediment transport in big river systems: The Nile case
Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Vezzoli, Giovanni; Villa, Igor
2014-05-01
The Nile River flows for ~ 6700 km, from Burundi and Rwanda highlands south of the Equator to the Mediterranean Sea at northern subtropical latitudes. It is thus the longest natural laboratory on Earth, a unique setting in which we are carrying out a continuing research project to investigate changes in sediment composition associated with a variety of chemical and physical processes, including weathering in equatorial climate and hydraulic sorting during transport and deposition. Petrographic, mineralogical, chemical, and isotopic fingerprints of sand and mud have been monitored along all Nile branches, from the Kagera and White Nile draining Archean, Paleoproterozoic and Mesoproterozoic basements uplifted along the western branch of the East African rift, to the Blue Nile and Atbara Rivers sourced in Ethiopian volcanic highlands made of Oligocene basalt. Downstream of the Atbara confluence, the Nile receives no significant tributary water and hardly any rainfall across the Sahara. After construction of the Aswan High Dam in 1964, the Nile ceased to be an active conveyor-belt in Egypt, where the mighty river has been tamed to a water canal; transported sediments are thus chiefly reworked from older bed and levee deposits, with minor contributions from widyan sourced in the Red Sea Hills and wind-blown desert sand and dust. Extensive dam construction has determined a dramatic sediment deficit at the mouth, where deltaic cusps are undergoing ravaging erosion. Nile delta sediments are thus recycled under the effect of dominant waves from the northwest, the longest Mediterranean fetch direction. Nile sands, progressively enriched in more stable minerals such as quartz and amphiboles relative to volcanic rock fragments and pyroxene, thus undergo multistep transport by E- and NE-directed longshore currents all along the coast of Egypt and Palestine, and are carried as far as Akko Bay in northern Israel. Nile mud reaches the Iskenderun Gulf in southern Turkey. A full
Phase transitions and connectivity in three-dimensional vortex equilibria
Energy Technology Data Exchange (ETDEWEB)
Akao, J.H.
1994-05-01
The statistical mechanics of collections of closed self avoiding vortex loops on a lattice are studied. The system is related to the vortex form of the three dimensional XY model and to lattice vortex equilibrium models of turbulence. The system exhibits vortex connectivity and screening effects, and models in vorticity variables the superfluid transition. The equilibrium states of the system are simulated by a grand canonical Monte Carlo method. A set of geometric transformations for self-avoiding loops is developed. The numerical method employs histogram sampling techniques and utilizes a modification to the Metropolis flow which enhances efficiency. Results are given for a region in the temperature-chemical potential plane, where the chemical potential is related to the vortex fugacity. A line of second order transitions is identified at low temperature. The transition is shown to be a percolation threshold at which connected vortex loops of infinite size appear in the system. The nature of the transition supports the assumption that the lambda transition in bulk superfluid helium is driven by vortices. An asymptotic analysis is performed for the energy and entropy scaling of the system as functions of the system size and the lattice spacing. These estimates indicate that the infinite temperature line is a phase boundary between small scale fractal vortices and large scale smooth vortices. A suggestion is made that quantum vortices have uniform structure on the scale of the lattice spacing and lie in the positive temperature regime, while classical vortices have uniform structure on the scale of the domain and lie in the negative temperature regime.
High temperature phase equilibria in a solar-composition gas
International Nuclear Information System (INIS)
Using recent additions to thermochemical data on minerals and information on their solid solution behavior, new equilibrium phase diagrams have been computed in a system of solar gas composition (Si, Al, Mg, Ca, Fe, Ni, Ti, Na, K, C, H, O, S, N) in the pressure and temperature ranges of 1 to 10-6 bar and 1153 to 1773 K respectively. These calculations show that Fe-Ni alloy condenses before all silicates included here (except melilite) down to a pressure of 2 x 10-4 bar below which plagioclase and clinopyroxene condense first. Orthopyroxene condenses next followed by ilmenite. Pressure-temperature variation of the chemical composition of melilite, clinopyroxene, orthopyroxene, metal alloy and plagioclase may be used for cosmothermometry and cosmobarometry for equilibrium assemblages. The major transition from the refractory oxides and melilite (the meteorite 'inclusion assemblage') to an assemblage of Fe-Ni alloy, olivine, plagioclase and pyroxenes ('planet-forming') takes place within a narrow interval of pressure and temperature. Small fluctuations of either pressure or temperature across this narrow region result in drastic changes in types and modes of minerals, which may explain the wide mineralogical varieties of meteorites. (author)
Biogas generation in landfills. Equilibria, rates and yields
Energy Technology Data Exchange (ETDEWEB)
Aakesson, M.
1997-05-01
Landfilling in `cells` has become more common in recent years. Different waste streams are guided to different cells, among which the biocell is a landfill designed for biogas production. In this thesis, the dependence of biogas generation on waste composition was investigated. Six 8,000 m{sup 3} test cells, with contents ranging from mainly commercial waste to pure domestic waste and equipped with gas extraction systems and bottom plastic liners, were monitored for seven years. Great emphasis was given to the characterization of conversion processes and governing mechanism in the topics of bio-energetics, kinetics and capacities. A thermodynamic model, in which the oxidations of volatile fatty acids (VFA) (2
International Nuclear Information System (INIS)
Highlights: ► Phase equilibria for water + hydrocarbon ternary mixture were measured by flow method. ► Phase equilibrium measurements were performed in various feed compositions. ► Region of VLE is expanded by increasing feed compositions of heavy oil. ► Vapor + liquid + liquid equilibria were found at 573 K for this ternary system. -- Abstract: Phase equilibria for the [{water + 1-methylnaphthalene + p-xylene}] ternary system at T = (573, 623 and 653) K and (4.2 to 20.7) MPa were measured by a flow method. The phase equilibrium measurements were carried out with change of the feed mole fraction of 1-methylnaphthalene in pure water from 0.25 to 0.75. The two phase region of the vapour–liquid equilibria is expanded by increasing the feed mole fraction of 1-methylnaphthalene in pure water. The vapour–liquid–liquid equilibria were found at T = 573 K unlike the (water + p-xylene) binary system. It is found that the type of phase behaviour for the (water + 1-methylnaphthalene + p-xylene) ternary system measured in this work is similar to that for the (water + 1-methylnaphthalene) binary system rather than that for the (water + p-xylene) binary system
International Nuclear Information System (INIS)
Highlights: ► Phase equilibria for (water + hydrocarbon) mixtures were measured by flow method. ► Liquid–liquid slugs in microtube were used for the mixing. ► The phase equilibria can be measured in short residential time. ► (Water + decalin) forms the two phase regions larger than (water + p-xylene) mixture. -- Abstract: (Vapour + liquid) and (liquid + liquid) equilibria for (water + p-xylene) and (water + decalin) mixtures at T = (573 to 623) K were measured by a flow type apparatus with microfluidic system. The liquid–liquid slug flows in the microfluidic system were used for mixing of water and hydrocarbon due to high mass transfer between two liquid phases. The formations of the liquid–liquid slugs for (water + p-xylene) system were studied by changing the flow rate. The results of the liquid–liquid slug formations at hydrocarbon and water rich compositions were used for the measurements for (vapour + liquid) and (liquid + liquid) equilibria, respectively. It was found that the phase equilibria using the apparatus with the microfluidic system can be measured in a short residential time (1.6 to 3.2) min. The experimental results of the phase equilibria for (water + p-xylene) and (water + decalin) systems give that the regions of the (vapour + liquid) and (liquid + liquid) equilibria for both mixtures reduce with the increasing temperature. The mixture of (water + decalin) at T = (583 to 623) K forms the two phase regions of the (vapour + liquid) and (liquid + liquid) equilibria larger than those for (water + p-xylene) mixture. The experimental data of the phase equilibria obtained in this work were correlated with Peng–Robinson–Stryjek–Vera equation of state. The correlated results of the (liquid + liquid) equilibria for both systems represent the experimental data. For (vapour + liquid) equilibria, the results give the qualitative representations in the shape of the two phase region for both mixtures
International Nuclear Information System (INIS)
The study of biological cells in terms of mesoscopic, nonequilibrium, nonlinear, stochastic dynamics of open chemical systems provides a paradigm for other complex, self-organizing systems with ultra-fast stochastic fluctuations, short-time deterministic nonlinear dynamics, and long-time evolutionary behavior with exponentially distributed rare events, discrete jumps among punctuated equilibria, and catastrophe. (general)
Qian, Hong
2012-01-01
The study of biological cells in terms of mesoscopic, nonequilibrium, nonlinear, stochastic dynamics of open chemical systems provides a paradigm for other complex, self-organizing systems with ultra-fast stochastic fluctuations, short-time deterministic nonlinear dynamics, and long-time evolutionary behavior with exponentially distributed rare events, discrete jumps among punctuated equilibria, and catastrophe.
Phase equilibria of the Ni–Si–P system at 800 °C
International Nuclear Information System (INIS)
Highlights: •The isothermal section at 800 °C of the Ni–Si–P system was determined. •Nine ternary phases, including three new ternary phases denoted as τ1, τ2 and τ3, were found at 800 °C. •Twenty-three-phase equilibria were determined at 800 °C for the phosphorous content range of up to 75 at.%. -- Abstract: The phase equilibria in the Ni–Si–P ternary system at 800 °C were experimentally investigated using optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction on 34 equilibrated alloys. Twenty-three-phase equilibria were well determined at 800 °C for the phosphorous content range of up to 75 at.%. The solubilities of P in Ni3Si, Ni5Si2, LT-Ni2Si, Ni3Si2, NiSi2and Ni3Si2, and those of Si in Ni3P, Ni2P or NiP2 does not exceed 5 at.%. The solid solubility of Ni in SiP is too small to observe. The maximum solid solubility of P in NiSi is 17.5 at.%. On the other side of the system the solubility of Si in LT-Ni5P2, LT-Ni12P5, Ni5P4 and NiP3 were measured to be 15.1 at.%, 9.4 at.%, 8.7 at.% and 5.9 at.%, respectively. The obtained phase diagrams presents nine ternary intermetallic compounds (IMCs), including three new ternary phases τ1, τ2 and τ3
Phase equilibria of the Mg–La–Nd system at 500 °C
International Nuclear Information System (INIS)
Highlights: • Isothermal section at 500 °C of the Mg-La-Nd system was firstly well established. • Both Mg41La5 and Mg2La are stabilized with the addition of Nd at 500 °C. • 5 three-phase equilibria were well determined. • Solubility of Nd in Mg2La, Mg17La2 and Mg12La, and of La in Mg41Nd5 was measured. • The continuous solid solutions of Mg(La, Nd) and Mg3(La, Nd) forms. -- Abstract: The phase equilibria at 500 °C of the Mg–La–Nd system were investigated with four diffusion couples and 38 alloys, by means of X-ray diffraction technique, scanning electron microscopy and electron probe microanalyses. Five three-phase equilibria were accurately determined. The Mg2La phase, which is not stable at 500 °C in the Mg–La binary system, was found to be stabilized with the addition of Nd. The composition range of the ternary Mg2La phase was measured to be ∼0–12.6 at.% Nd at 500 °C. The Mg41La5 phase, which is not stable at 500 °C in the Mg–La binary system, is stabilized at 500 °C with the addition of Nd. The solubility of La in Mg41Nd5 was measured to be up to 7.4 at.% La. The solubility of Nd in Mg17La2 and in Mg12La was determined to be 1.4 at.% Nd and 5.1 at.% Nd, respectively. The continuous solid solutions Mg(La, Nd) and Mg3(La, Nd) form between MgLa and MgNd and between Mg3La and Mg3Nd, respectively. The isothermal section at 500 °C was constructed in the present work
Thermal analysis and prediction of phase equilibria in ternary Pb-Zn-Ag system
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Živković D.
2011-01-01
Full Text Available Ternary Pb-Zn-Ag system is typical for some physicochemical processes going on in refining phase in the extractive metallurgy of lead. Therefore, investigation of mentioned system is important from both theoretical and practical research of the phenomena occurring during the lead desilverizing process. The results of experimental investigation using differential thermal analysis (DTA and thermodynamic calculation of phase equilibria in Pb-Zn-Ag system according to CALPHAD method, in the sections with Zn:Ag mass ratio equal to 90:10, 70:30 and 50:50, are presented in this paper.
Hydrate phase equilibria of CO2+N2+aqueous solution of THF, TBAB or TBAF system
DEFF Research Database (Denmark)
Sfaxi, Imen Ben Attouche; Durand, Isabelle; Lugo, Rafael;
2014-01-01
We report hydrate dissociation conditions of CO2 (15 and 30mol%)+N2 (85 and 70mol%) in the presence of aqueous solutions of THF, TBAB or TBAF. The concentrations of TBAB and TBAF in the aqueous solutions are 5wt% and 9wt% while THF concentration in aqueous solution is 3mol%. Two different...... experimental techniques including isochoric pressure search method and a DSC method are used to measure the hydrate dissociation conditions. A comparison is finally made with the literature data. It is expected that this study provides better understanding of hydrate phase equilibria associated with CO2...... capture. © 2014 Elsevier Ltd....
Two Equilibria of (N-Methyl-3-pyridinium)chlorocarbene, a Cationic Carbene.
Cang, Hui; Moss, Robert A; Krogh-Jespersen, Karsten
2016-02-11
Equilibrium constants and the associated thermodynamic parameters are reported for the equilibria established between the cationic carbene (N-methyl-3-pyridinium)chlorocarbene tetrafluoroborate (MePyr(+)CCl BF4(-), 3) and 1,3,5-trimethoxybenzene (TMB) to form a carbene-TMB complex, as well as between carbene 3 and chloride ion to form the zwitterion, N-methyl-3-pyridinium dichloromethide (10). These equilibrium constants and thermodynamic parameters are contrasted with analogous data for several related carbenes, and the influence of the pyridinium unit in carbene 3 is thereby highlighted. Computational studies augment and elucidate the experimental results. PMID:26830199
Representing Strategic Games and Their Equilibria in Many-Valued Logics
Czech Academy of Sciences Publication Activity Database
Běhounek, Libor; Cintula, Petr; Fermüller, C.; Kroupa, Tomáš
2016-01-01
Roč. 24, č. 3 (2016), s. 238-267. ISSN 1367-0751 R&D Projects: GA ČR GAP402/12/1309; GA MŠk 7AMB13AT014; GA ČR(CZ) GF15-34650L Grant ostatní: Austrian Science Fund(AT) P25417-G15; Austrian Science Fund(AT) I1897-N25 Institutional support: RVO:67985807 ; RVO:67985556 Keywords : strategic games * many-valued logics * Nash equilibria * Lukasiewicz games Subject RIV: BA - General Mathematics Impact factor: 0.461, year: 2014
Phase equilibria of didecyldimethylammonium nitrate ionic liquid with water and organic solvents
International Nuclear Information System (INIS)
The phase diagrams for binary mixtures of an ammonium ionic liquid, didecyldimethylammonium nitrate, [DDA][NO3], with: alcohols (propan-1-ol, butan-1-ol, octan-1-ol, and decan-1-ol): hydrocarbons (toluene, propylbenzene, hexane, and hexadecane) and with water were determined in our laboratory. The phase equilibria were measured by a dynamic method from T 220 K to either the melting point of the ionic liquid, or to the boiling point of the solvent. A simple liquidus curve in a eutectic system was observed for [DDA][NO3] with: alcohols (propan-1-ol, butan-1-ol, and octan-1-ol); aromatic hydrocarbons (toluene and propylbenzene) and with water. (Solid + liquid) equilibria with immiscibility in the liquid phase were detected with the aliphatic hydrocarbons heptane and hexadecane and with decan-1-ol. (Liquid + liquid) equilibria for the system [DDA][NO3] with hexadecane was observed for the whole mole fraction range of the ionic liquid. The observation of the upper critical solution temperature in binary mixtures of ([DDA][NO3] + decan-1-ol, heptane, or hexadecane) was limited by the boiling temperature of the solvent. Characterisation and purity of the compounds were determined by elemental analysis, water content (Fisher method) and differential scanning microcalorimetry (d.s.c.) analysis. The d.s.c. method of analysis was used to determine melting temperatures and enthalpies of fusion. The thermal stability of the ionic liquid was resolved by the thermogravimetric technique-differential thermal analysis (TG-DTA) technique over a wide temperature range from (200 to 780) K. The thermal decomposition temperature of 50% of the sample was greater than 500 K. The (solid + liquid) phase equilibria, curves were correlated by means of different G Ex models utilizing parameters derived from the (solid + liquid) equilibrium. The root-mean-square deviations of the solubility temperatures for all calculated data are dependent upon the particular system and the particular equation
International Nuclear Information System (INIS)
A stabilization problem of the equilibrium of stochastically forced nonlinear discrete-time system with incomplete information is considered. Our approach uses a regulator which synthesizes the required stochastic sensitivity of the equilibrium. Mathematically, this problem is reduced to the solution of some quadratic matrix equations. A description of attainability sets and algorithms for regulators design is given. The general results are applied to the suppression of unwanted large-amplitude oscillations around the equilibria of the stochastically forced Verhulst model with noisy observations
Peptide Conformational Equilibria Computed via a Single-Stage Shifting Protocol
Ytreberg, F M; Zuckerman, Daniel M.
2004-01-01
We study the conformational equilibria of two peptides using a novel statistical mechanics approach designed for calculating free energy differences between highly dis-similar conformational states. Our results elucidate the contrasting roles of entropy in implicitly solvated leucine dipeptide and decaglycine. The method extends earlier work by Voter, and overcomes the notorious "overlap" problem in free energy computations by constructing a mathematically equivalent calculation with high conformational similarity. The approach requires only equilibrium simulations of the two states of interest, without the need for sampling transition states. We discuss extensions of the approach to binding affinity estimation and explicitly solvated systems, as well as possible optimizations.
Ion, Anca Veronica
2010-01-01
The paper is devoted to the study of stability of equilibrium solutions of a delay differential equation that models leukemia. The equation was previously studied in [5] and [6], where the emphasis is put on the numerical study of periodic solutions. Some stability results for the equilibria are also presented in these works, but they are incomplete and contain some errors. Our work aims to complete and to bring corrections to those results. Both Lyapunov first order approximation method and second Lyapunov method are used.
Nitride phase equilibria in the Fe-Cr-Mn-N system at 1273 and 1073 K
International Nuclear Information System (INIS)
Phase equilibria between the fcc matrix and the hcp nitride phase were installed by long-time heat treatment at 1273 and 1073 K, respectively, in different Fe-Cr-Mn-N alloys. The composition of the phases was determined applying wavelength-dispersive X-ray microanalysis. The results are compared with thermodynamic calculations using published data describing the fcc and the hcp phases in the system Fe-Cr-Mn-N. The agreement is satisfactory at medium concentrations at 1273 K but there are considerable differences at 1073 K. (orig.)
Computation of zero β three-dimensional equilibria with magnetic islands
International Nuclear Information System (INIS)
A Picard iteration scheme has been implemented for the computation of toroidal, fully three-dimensional, zero β equilibria with islands and stochastic regions. Representation of the variables in appropriate coordinate systems has been found to be a key to making the scheme work well. In particular, different coordinate systems are used for solving magnetic differential equations and Ampere's law. The current profile is adjusted when islands and stochastic regions appear. An underrelaxation of the current profile modifications is generally needed for stable iteration of the algorithm. Some examples of equilibrium calculations are presented. 16 refs., 6 figs., 1 tab
Evolution of generalized two-dimensional magnetotail equilibria in ideal and resistive MHD
Merkin, V. G.; Sitnov, M. I.; Lyon, J. G.
2015-03-01
We present results of two-dimensional (2-D) magnetohydrodynamic (MHD) simulations of the terrestrial magnetotail. A regional adaptation of the Lyon-Fedder-Mobarry global MHD model is used. As initial conditions, we employ a class of asymptotic magnetotail equilibria with and without an accumulation of magnetic flux at the tailward end (a Bz hump). The former have been recently shown by full particle simulations to be unstable to a kinetic mode with formal properties of ion tearing. Thus, our goal here is to investigate the evolution of the same equilibria in the MHD approximation and assist in the physical interpretation of the kinetic simulations. This is additionally motivated by the energy principle considerations which suggest that if the system is unstable kinetically, it may also be unstable ideally. To seek dynamical MHD regimes similar to those observed in kinetic simulations, we implement two sets of boundary conditions (velocity balanced, VB, and momentum balanced, MB), one allowing plasma flows through the boundaries and the other inhibiting such flows. The use of more reflecting MB boundary conditions results in suppression of any significant dynamics, and we see no substantial changes beyond initial equilibrium relaxation. On the other hand, VB boundary conditions allow a more efficient relaxation of initial equilibrium and absorb subsequently generated plasma flows. With these boundary conditions we find the equilibrium without a flux accumulation (i.e., with constant magnetic field component normal to the current sheet) to develop an apparently resistive mode accompanied by tailward plasma flows. At the same time, the equilibria with a Bz hump of sufficiently large amplitude develop a different, ideal, mode characterized by spontaneous generation of earthward plasma flows and an exponential growth of the corresponding electric field. This growth is qualitatively similar to the corresponding fully kinetic simulations although no explosive growth of
Sunspot Equilibria in a Production Economy: Do Rational Animal Spirits Cause Overproduction?
Kajii, Atsushi
2008-01-01
We study a standard two period economy with one nominal bond and one firm. The input of the firm is done in the first period and financed with the nominal bond, and its profits are distributed to the shareholders in the second period. We show that a sunspot equilibrium exists around each efficient equilibrium. The interest rate is lower than optimal and there is over production in sunspot equilibria, under some conditions. But a sunspot equilibrium does not exist if the profit share can be tr...
The Existence and Stability Analysis of the Equilibria in Dengue Disease Infection Model
Anggriani, N.; Supriatna, A. K.; Soewono, E.
2015-06-01
In this paper we formulate an SIR (Susceptible - Infective - Recovered) model of Dengue fever transmission with constant recruitment. We found a threshold parameter K0, known as the Basic Reproduction Number (BRN). This model has two equilibria, disease-free equilibrium and endemic equilibrium. By constructing suitable Lyapunov function, we show that the disease- free equilibrium is globally asymptotic stable whenever BRN is less than one and when it is greater than one, the endemic equilibrium is globally asymptotic stable. Numerical result shows the dynamic of each compartment together with effect of multiple bio-agent intervention as a control to the dengue transmission.
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Lu-Chuan Ceng
2014-01-01
Full Text Available We first introduce and analyze one multistep iterative algorithm by hybrid shrinking projection method for finding a solution of the system of generalized equilibria with constraints of several problems: the generalized mixed equilibrium problem, finitely many variational inclusions, the minimization problem for a convex and continuously Fréchet differentiable functional, and the fixed-point problem of an asymptotically strict pseudocontractive mapping in the intermediate sense in a real Hilbert space. We prove strong convergence theorem for the iterative algorithm under suitable conditions. On the other hand, we also propose another multistep iterative algorithm involving no shrinking projection method and derive its weak convergence under mild assumptions.
Energy Technology Data Exchange (ETDEWEB)
Bruschi, M; Calogero, F [Dipartimento di Fisica, Universita di Roma ' La Sapienza' , 00185 Roma (Italy); Droghei, R [Dipartimento di Fisica, Universita Roma Tre (Italy)], E-mail: mario.bruschi@roma1.infn.it, E-mail: francesco.calogero@roma1.infn.it, E-mail: francesco.calogero@uniroma1.it, E-mail: droghei@fis.uniroma3.it
2009-11-27
An isochronous system is introduced by modifying the Nth ODE of the stationary Burgers hierarchy, and then, by investigating its behaviour near its equilibria, neat Diophantine relations are identified, involving (well-known) polynomials of arbitrary degree having integer zeros, or equivalently matrices the determinants of which yield such polynomials. The basic idea to arrive at such relations is not new, but the specific application reported in this paper is new, and it is likely to open the way to several analogous new findings.
Vrabec, J.; Kedia, G. K.; Buchhauser, U.; Meyer-Pittroff, R.; Hasse, H.
2009-01-01
For the design and optimization of CO2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry's law constants, are proposed for the ternary mixture N2+O2+CO2. Pure substance parameters of the Peng-Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to exper...
Adsorption equilibria of butyl- and amylbenzene on monolithic silica-based columns.
Cavazzini, Alberto; Bardin, Gregory; Kaczmarski, Krzystof; Szabelski, Paweł; Al-Bokari, Majed; Guiochon, Georges
2002-05-31
The adsorption isotherms of butyl- and amylbenzene on silica monolithic columns were measured by frontal analysis. The external, internal and total porosities of these columns were determined by inverse size-exclusion chromatography. The adsorption isotherms are concave upward in the entire concentration range investigated. They were fitted to the anti-Langmuir model, an unusual model in liquid-solid and liquid-liquid phase equilibria. Band profiles under overloaded conditions were recorded. They were in good agreement with the profiles calculated using th,e lumped pore diffusion model of chromatography and these adsorption isotherms. PMID:12113336
Phase equilibria in BaS-Cu2S-Gd2S3 system
International Nuclear Information System (INIS)
Phase equilibria in BaS-Cu2S-Gd2S3 system are studied along isothermal (800 K) and polythermal sections CuGdS2-BaS, Cu2S-BaGdCuS3, BaGdCuS3-Gd2S3, BaGdCuS3-BaGd2S4. Complex sulfide BaGdCuS3 with orthorhombic lattice is formed, lattice parameters are determined. Compositions of eutectics forming in the system are determined
Stability of Negative Image Equilibria in Spike-Timing Dependent Plasticity
Williams, A; Leen, T K; Williams, Alan; Roberts, Patrick D.; Leen, Todd K.
2003-01-01
We investigate the stability of negative image equilibria in mean synaptic weight dynamics governed by spike-timing dependent plasticity (STDP). The neural architecture of the model is based on the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of external electric fields. We derive a necessary and sufficient condition for stability, for arbitrary postsynaptic potential functions and arbitrary learning rules. We then apply the general result to several examples of biological interest.
Liquid-liquid and solid-liquid equilibria of 2-isopropoxyethanol-H{sub 2}O-NaCl mixtures
Energy Technology Data Exchange (ETDEWEB)
Zijlema, T.G.; Witkamp, G.J.; Rosmalen, G.M. van
1999-12-01
Liquid-liquid equilibria experiments demonstrated that mixtures of 2-isopropoxyethanol and water saturated with NaCl are partially miscible. The lower critical solution temperature was estimated to be 29.2 C at a 2-isopropoxyethanol concentration of 0.399 (m{sub IPE}/(m{sub IPE} + m{sub H{sub 2}O})). Solid-liquid equilibria experiments showed that the solubility of NaCl in water is reduced significantly by the presence of 2-isopropoxyethanol. As in pure water, the NaCl solubility in 2-isopropoxyethanol-H{sub 2}O mixtures increases weakly with temperature.
Investigations of (acid+base) equilibria in systems modelling interactions occurring in biomolecules
International Nuclear Information System (INIS)
By using the potentiometric microtitration method, acidity constants, Ka, anionic, KAHA-, and cationic, KBHB+, homoconjugation constants, as well as molecular heteroconjugation, KBHA, constants have been determined in (acid+base) systems formed by the following compounds: acetic acid, phenol, n-butylamine, imidazole, and 4(5)-methylimidazole. These compounds constitute fragments of the side chains of amino acids capable of proton exchange in active sites of enzymes. The (acid+base) equilibria were studied in five polar solvents of different properties, namely in aprotic protophobic acetonitrile, acetone and propylene carbonate, in aprotic protophilic dimethyl sulfoxide and in amphiprotic methanol. The lowest values of the acidity constants of the molecular and cationic acids have been found in aprotic protophobic polar solvents - acetonitrile, propylene carbonate and acetone. Their acid strength have been found to depend on solvent basicity expressed as donor numbers, DN. These media, in particular acetonitrile and acetone, are also favourable for establishing molecular homo- and heteroconjugation equilibria. The most stable homocomplexes are formed in the case of acetic acid (KAHA- values range from 2.26 to 3.56 in these media, being more than an order of magnitude higher than those for the remaining compounds). The magnitudes of lgKBHA reveal that the most stable heterocomplexes are formed by n-butylamine and acetic acid that are characterized by the smallest differences in pKa values
Experimental vapor-liquid equilibria data for binary mixtures of xylene isomers
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W.L. Rodrigues
2005-09-01
Full Text Available Separation of aromatic C8 compounds by distillation is a difficult task due to the low relative volatilities of the compounds and to the high degree of purity required of the final commercial products. For rigorous simulation and optimization of this separation, the use of a model capable of describing vapor-liquid equilibria accurately is necessary. Nevertheless, experimental data are not available for all binaries at atmospheric pressure. Vapor-liquid equilibria data for binary mixtures were isobarically obtained with a modified Fischer cell at 100.65 kPa. The vapor and liquid phase compositions were analyzed with a gas chromatograph. The methodology was initially tested for cyclo-hexane+n-heptane data; results obtained are similar to other data in the literature. Data for xylene binary mixtures were then obtained, and after testing, were considered to be thermodynamically consistent. Experimental data were regressed with Aspen Plus® 10.1 and binary interaction parameters were reported for the most frequently used activity coefficient models and for the classic mixing rules of two cubic equations of state.
Water/oil/[P6,6,6,14][NTf2] phase equilibria
International Nuclear Information System (INIS)
Highlights: • [P6,6,6,14][NTf2] forms a triphasic system when mixing with dodecane and water. • The water composition in the intermediate phase is very low. • The increase of temperature slightly increases oil content of this phase. • [P6,6,6,14][NTf2] shows a minor surfactant character than [P6,6,6,14]Cl. - Abstract: Phase equilibria data for complex systems (more than three components or two phases, high pressures, complex fluids…) are needed to develop thermodynamic models capable of correlating and predicting their behaviour. Along these lines, systems composed of water, oil and surfactant exhibit an interesting conduct. In this work, the (liquid + liquid) equilibria of a ternary system comprising water, n-dodecane and a surfactant ionic liquid, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, have been determined at temperatures (298.15 or 348.15) K and atmospheric pressure. Winsor type III systems have been found without the need of adding any co-surfactant. The stability of the triphasic system with temperature has been tested. Some physical properties (density, viscosity and interfacial tension) for phases involved have been also determined. As expected, a minor surfactant character has been found for this ionic liquid rather than for the homologous with the chloride anion
Experimental investigation of phase equilibria in the Co–Hf system
International Nuclear Information System (INIS)
Highlights: • Phase equilibria in the Co–Hf binary system were experimentally determined. • The reported Co7Hf phase was replaced with an orthorhombic compound of Co11Hf2. • Eutectic composition for the reaction L ↔ CoHf2 + (βHf) was modified. • Invariant reaction temperatures were experimentally determined. • Composition ranges of intermetallic compounds were experimentally measured. - Abstract: Phase equilibria in the Co–Hf binary system were investigated based on the experimental results from X-ray diffraction, transmission electron microscopy, scanning electron microscopy, electron probe microanalysis and differential scanning calorimetry on annealed and as-cast alloys. A new orthorhombic compound Co11Hf2 with a stability range from ∼650 to 1273 °C was observed instead of Co7Hf reported in literature. Another stoichiometric phase Co7Hf2 proposed in literature was not observed in the present work. The reaction type for the formation of CoHf2 was confirmed to be peritectic, but the eutectic composition for the reaction L ↔ CoHf2 + (βHf) was modified to be ∼71.5 at.% Hf. Homogeneity ranges of different intermetallic compounds and solution phases at 700 and 1100 °C as well as the invariant reaction temperatures were experimentally determined. The newly constructed phase diagram shall provide accurate information for further thermodynamic modeling of the Co–Hf binary system
Stable equilibria for bootstrap-current-driven low aspect ratio tokamaks
International Nuclear Information System (INIS)
Low aspect ratio tokamaks (LATs) can potentially provide a high ratio of plasma pressure to magnetic pressure β and high plasma current I at a modest size. This opens up the possibility of a high-power density compact fusion power plant. For the concept to be economically feasible, bootstrap current must be a major component of the plasma current, which requires operating at high βp. A high value of the Troyon factor βN and strong shaping is required to allow simultaneous operation at a high-β and high bootstrap fraction. Ideal magnetohydrodynamic stability of a range of equilibria at aspect ratio 1.4 is systematically explored by varying the pressure profile and shape. The pressure and current profiles are constrained in such a way as to assure complete bootstrap current alignment. Both βN and β are defined in terms of the vacuum toroidal field. Equilibria with βN≥8 and β∼35%endash 55% exist that are stable to n=∞ ballooning modes. The highest β case is shown to be stable to n=0,1,2,3 kink modes with a conducting wall. copyright 1997 American Institute of Physics
International Nuclear Information System (INIS)
One of the most effective applications of radioisotopes in physical chemistry is the study of two-phase equilibria; our own studies for a number of years have been concentrated on ion exchange reactions with commercial organic and with new types of non-siliceous inorganic exchangers. With the former, the studies were carried out in depth, covering at times most elements in the periodic table, the objective being comparison of functional relationships of many systems rather than the detailed study of a few. With the inorganic exchangers, the objective was also broad coverage of many systems, particularly comparison of large numbers of adsorbents. Since these studies required hundreds of thousands of analyses, they would have been almost impossible with conventional analytical techniques. The feasibility of such studies can therefore be considered a direct outgrowth of the ready availability of radioactive tracers, and the steady increase in precision and convenience of counting techniques. More recently, packed-column techniques have been developed which, with radioactive tracers and relatively simple equipment, permit ready extension of studies of two-phase equilibria and of the kinetics of interfaces to higher temperatures (at present up to 200o C). Sampling and continuous monitoring techniques were used. Through adsorption and solubility studies, information on enthalpy and entropy changes of adsorption and ion-exchange reactions is reported as well as information on heats of solution, activity coefficients in concentrated electrolyte mixtures, and on complexing reactions in high-temperature aqueous systems. (author)
Experimental determination of phase equilibria in the Co–V–Mo ternary system
International Nuclear Information System (INIS)
Highlights: ► Four isothermal sections of the Co–V–Mo system were experimentally determined. ► The solubility of Mo in the σ-Co2V3 phase increases with an increase in temperature region from 800 to 1200 °C. ► A large region of (V, Mo) continuous bcc solid solution was determined. -- Abstract: The phase equilibria in the Co–V–Mo ternary system were investigated by means of optical microscopy, electron probe microanalyzer and X-ray diffraction. Four isothermal sections of the Co–V–Mo ternary system at 800, 1000, 1100 and 1200 °C were experimentally established, and no ternary compound was found in this system. Experimental results show that the solubility of Mo in the σ-Co2V3 phase increases with an increase in temperature region from 800 to 1200 °C. The newly determined phase equilibria in this system will provide important information for the development of Co-based alloys
Experimental investigation of phase equilibria in the Fe–Nb–Si ternary system
International Nuclear Information System (INIS)
Highlights: • Three isothermal sections of the Fe–Nb–Si system were experimentally determined. • Some different phase relationships are confirmed in this work. • The solubility of Si in the εNbFe2 phase is about 27.5 at.%, remaining unchanged with the temperature range from 1200 °C to 1000 °C. • The solubility of Si in the μFeNb phase decreases from 14.7 at.% to 10.0 at.% with decrease of temperature from 1200 °C to 1000 °C. - Abstract: The phase equilibria of the Fe–Nb–Si ternary system were investigated by electron probe microanalyzer (EPMA), back scattered electron (BSE), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) on the equilibrated alloys. In this study, three isothermal sections of the Fe–Nb–Si ternary system at 1200 °C, 1100 °C and 1000 °C were respectively determined and six ternary compounds were confirmed. The obtained experimental results show that there are large solubilities of Si in the εNbFe2 and μFeNb phases. The newly determined phase equilibria of the Fe–Nb–Si system will provide useful information for silicon steels development
Phases and phase equilibria in the quaternary system Ti-Cu-Al-N at 850 C
Energy Technology Data Exchange (ETDEWEB)
Durlu, N. [Vienna Univ. (Austria); Gruber, U. [Vienna Univ. (Austria); Pietzka, M.A. [Vienna Univ. (Austria); Schmidt, H. [Vienna Univ. (Austria); Schuster, J.C. [Vienna Univ. (Austria)
1997-05-01
Phase equilibria in the quaternary system Ti-Cu-Al-N are investigated using XRD, metallography and EDX, yielding the observation of 18 four phase spaces of the 850 C isotherm. In the ternary boundary systems Ti-Cu-Al and Ti-Al-N, all previously reported phases are confirmed, but several tielines are newly determined. In the system Ti-N, the new ternary phase Ti{sub 3}CuN dominates most phase fields. Based on thermochemical data of the binary boundary systems and the newly investigated or re-investigated phase equilibria of the ternary boundary systems, a set of Gibbs energies for the solid phases occuring in the quaternary system is derived, which is used in combination with the quaternary experimental data to derive a large section of the isotherm for Ti-Cu-Al-N at 850 C. The quaternary {eta}-phase (Ti, Cu, Al){sub 6}N having the composition Ti{sub 3}Cu{sub 2}Al{sub 1}N{sub 0.8} is found to be the only stable quaternary phase of this system. Several {eta}-phases isotypic to Ti{sub 3}Cu{sub 2}Al{sub 1}N{sub 0.8} are synthesized to explore the crystal chemistry effects of substitutions on different crystallographic sites. (orig.)
Behaviour of magnetic islands in 3D MHD equilibria of helical devices
International Nuclear Information System (INIS)
Magnetic island formation in 3D finite-β equilibria in the H-1 Heliac is studied by using the HINT code. It is found that the size of a dangerous island should increase with β but that destruction of the equilibrium at low β is avoided because the rotational transform evolves to exclude the rational surface concerned. At higher β there is evidence of near-resonant flux surface deformations which may lead to an equilibrium limit. A reconnected equilibrium at still higher β exhibits a double island structure which is similar to homoclinic phase portraits which have been observed after separatrix reconnection in Hamiltonian systems. The physical mechanisms of island formation in finite-β helical equilibria have been investigated. The HINT code predicts that the global effect to the Pfirsch-Schlueter currents can lead to self-healing of magnetic islands independent of whether or not the plasma is stable to resistive interchange modes. This result has been compared with the predictions of a boundary-layer analysis which has been extended to consider configurations with islands in the vacuum magnetic field. (author). 5 refs, 1 fig
A Hierarchy of Dynamic Equilibria and a View of a Fly's Equilibrium Reflex
Wang, Z. Jane
Understanding structures within a structure is a topic that has fascinated Leo throughout his life, and we are now benefiting from his fundamental insights when we think about living organisms. A living organism is far from statistical equilibrium and it does not have a single critical parameter. Nevertheless, each organism has a hierarchical structure within itself. Recently, asking how often a fly must sense its orientation in order to balance in air has led us to suggest one of the fly's 17 steering muscles, the first basalar muscle, is responsible for maintaining flight stability. Here I suggest that the chain of events associated with flight equilibrium reflex can be viewed as a succession of local linear transformation about a set of dynamic equilibria. Each of the functionally different parts, the sensors, motor neurons, muscles, wing-hinges, flapping wings, and the thorax, operates near its own dynamic equilibrium, often close to the boundary between stability and instability. Locomotion rises as an organism responds to a small perturbation from these equilibria. Kadanoff session.
High-beta equilibria in tokamaks with pressure anisotropy and toroidal flow
Layden, B.; Hole, M. J.; Ridden-Harper, R.
2015-12-01
We extend previous analytical calculations of 2D high-β equilibria in order-unity aspect ratio tokamaks with toroidal flow to include pressure anisotropy, assuming guiding-center theory for a bi-Maxwellian plasma and the ideal MHD Ohm's law. Equilibrium solutions are obtained in the core region (which fills most of the plasma volume) and the boundary layer. We find that pressure anisotropy with p∥>p⊥ ( p∥Ωmin ) were previously found to suppress the field-free region (diamagnetic hole) that exists in static isotropic high-β equilibria. We find that all equilibrium solutions with pressure anisotropy suppress the diamagnetic hole. For the static case with a volume-averaged toroidal beta of 70%, plasmas with max (p∥/p⊥)>α1=1.07 have equilibrium solutions. We find that α1 decreases with increasing toroidal flow speed, and above the flow threshold Ωmin we find α1=1 , so that all p∥>p⊥ plasmas have equilibrium solutions. On the other hand, for p∥p⊥ , while the converse is true for p∥
Energy Technology Data Exchange (ETDEWEB)
Rossilhol, N.
1995-12-01
In this work we discuss phase equilibria of mixtures similar to those formed during natural gas treatment (transportation and purification). The mixtures can contain light hydrocarbons (methane, ethane, propane, etc), acid gases (hydrogen sulfide, carbon dioxide), methanol (solvent, inhibitor) and (water). We present a low temperature phase equilibrium equipment to obtain two and three phase equilibrium data of light hydrocarbon-methanol-water mixtures. The realisation of the equipment, the measuring procedure and some determination of binary, ternary and quaternary systems are described. The range of application is - 100 deg. C to 0 deg. C in temperature and between 0 and 100 bar in pressure. The binary subsystems of the systems mentioned above are calculated in order to study the possibilities of the MHV2 and Wong and Sandler methods to represent simultaneously their vapor-liquid and liquid-liquid equilibria. According to the formalism proposed by the two methods, the cubic Soave-Redlich-Kwong equation of state is systematically combined with the NRTL excess Gibbs energy model. (authors). 72 refs., 47 figs., 38 tabs.
NIMROD studies of RWM stability and non-linear evolution for NSTX equilibria
Becerra, A. L.; Hegna, C. C.; Sovinec, C. R.; Kruger, S. E.; King, J. R.; Sabbagh, S. A.
2015-11-01
We make use of the generalized thin resistive wall boundary condition recently implemented in NIMROD to study the linear and nonlinear RWM stability properties of a series of reconstructed NSTX equilibria. The boundary condition operates by matching the magnetic field inside the computational domain with external fields found using the Green's function method in the GRIN vacuum-field solver at the wall, and is valid for toroidal geometries with poloidal asymmetry as well as for cylindrical geometries. Time series of NSTX equilibrium reconstructions from two shots whose normalized betas span the no-wall limit are studied. The critical beta for RWM onset found by NIMROD is compared with the stability limit predicted by ideal MHD code DCON. Scans with varying wall parameters are also performed to demonstrate the approximately linear relationship between growth rate and wall resistivity, and to test the performance limits of the boundary condition. The stability of these equilibria for n>1 is also examined, with both linear and non-linear runs in preparation for examining the non-linear effects due to toroidal rotation. Research supported by U. S. DoE under grant no. DE-FG02-86ER53218.
F-OH exchange equilibria between mica-amphibole mineral pairs
Westrich, Henry R.
1982-01-01
Fluoride-hydroxyl exchange equilibria between phlogopite-pargasite and phlogopite-tremolite mineral pairs were experimentally determined at 1,173 K, 500 bars and 1,073 1,173 K, 500 bars respectively. The distribution of fluorine between phlogopite and pargasite was found to favor phlogopite slightly, Δ G {ex/.}(1,173 K)=-1.71 kJ anion-1, while in the case of phlogopite-tremolite, fluorine was preferentially incorporated in the mica, Δ G {ex/.}(1,073)=- 5.67 kJ anion-1 and Δ G {ex/.}(1,173K)=-5.84 kJ anion-1. These results have yielded new values of entropy and Gibbs energy of formation for fluortremolite, Δ S {f/∘}=-2,293.4±16.0JK-1 mol-1 and Δ G {f/∘}= -11,779.3±25.0 kJ mol-1, respectively. In addition, F-OH mineral exchange equilibria support a recent molten oxide calorimetric value for the Gibbs energy of fluorphlogopite, Δ G {f/∘}=-6,014.0±7.0 kJ mol-1, which is approximately 40 kJ mol-1 more exothermic than the tabulated value.
Phase equilibria of the Co-Ta-Ti system at 950 deg. C
International Nuclear Information System (INIS)
The phase equilibria of the Co-Ta-Ti system at 950 deg. C were investigated via a combination of diffusion couples and equilibrated alloys. The samples were examined by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The experimental results showed the existence of no ternary compounds at 950 deg. C. Two continuous series of solid solutions form between γ-TaCo2 and TiCo2 (h), and between β-TaCo2 and TiCo2 (c), respectively. The 950 deg. C isothermal section consists of 10 single-phase regions, 15 binary phase regions and 6 ternary phase regions. The following six three-phase equilibria at 950 deg. C were well determined: (1) (Co) + TiCo3 + Ta2Co7, (2) TiCo3 + Ta2Co7 + (Ta,Ti)Co2 (h), (3) (Ta,Ti)Co2 (c) + TiCo + TaCo, (4) TiCo + TaCo + Ta2Co, (5) TiCo + Ta2Co + (Ta,Ti) and (6) TiCo + Ti2Co + (Ta,Ti).
Phase equilibria of the Co-Ni-Ta system at 1100 deg. C
International Nuclear Information System (INIS)
The phase equilibria of the Co-Ni-Ta system at 1100 deg. C are investigated using diffusion couples and five equilibrated alloys. The samples are examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. The experimental results show no existence of ternary compounds at 1100 deg. C. The following 4 three-phase equilibria are observed: (1) Ta(Co, Ni) + β-TaCo2 + TaNi3; (2) Ta(Co, Ni) + TaNi2 + TaNi3; (3) β-TaCo2 + TaNi3 + (Co, Ni); and (4) TaNi3 + TaNi8 + (Co, Ni). The compounds Ta2Co and Ta2Ni form continuous solid solutions. It is also the case for TaCo and TaNi. The solubilities of Co in TaNi3, and Ni in β-TaCo2 were determined to be up to 70 at.% Co and 30 at.% Ni, respectively
High-temperature interdiffusion and phase equilibria in U-Mo
International Nuclear Information System (INIS)
Experimental data for interdiffusion and phase equilibria in the U-Mo system have been obtained over the temperature range 1400 to 1525 K from analysis of compatibility experiments in which UO2 was decomposed by lithium in closed molybdenum capsules. Composition-position, X-ray diffraction, and microstructural data from the interdiffusion zones indicate that the intermediate phase U2Mo is formed in the temperature range, contrary to prediction from the currently accepted equilibrium U-Mo phase diagram. The U-Mo interdiffusion data generally agree with published values. Inclusion of the U2Mo phase in a theoretical correlation of interdiffusion and phase equilibria data using Darken's equation indicates that high-temperature interdiffusion of uranium and molybdenium proceeds under conditions of local thermodynamic equilibrium. Significant changes in the value of the thermodynamic-based Darken factor near the U2Mo phase boundary on the high uranium side are indicated from both the new and published interdiffusion data. (orig.)
Phase equilibria of the Co-Mo-Ti system at 950 deg. C
International Nuclear Information System (INIS)
The phase equilibria at 950 deg. C of the Co-Mo-Ti system was investigated by a combination of a diffusion couple technique and equilibrated alloys. The samples were examined by means of optical microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis. The isothermal section of the Co-Mo-Ti system at 950 deg. C consists of 7 three-phase fields and 15 two-phase fields. The following five three-phase equilibria were well determined: (1) TiCo2 (h) + MoCo3 + Mo6Co7, (2) TiCo2 (c) + TiCo2 (h) + TiCo, (3) TiCo2 (h) + TiCo + Mo6Co7, (4) TiCo + Ti2Co + (Mo,Ti), and (5) TiCo + Mo6Co7 + (Mo,Ti). The solubility of Ti in Mo6Co7 was determined to be 23.1 at.% Ti. The solubilities of Mo in TiCo2 (h), TiCo2 (c), and TiCo were measured to be 11.4, 4.7, and 5.4 at.% Mo, respectively. The solubility of Mo in Ti2Co is about 0.3 at.% Mo. The two-phase region of TiCo3 + MoCo3 was found to be very narrow and close to the TiCo3 side
Chemical Principls Exemplified
Plumb, Robert C.
1973-01-01
Two topics are discussed: (1) Stomach Upset Caused by Aspirin, illustrating principles of acid-base equilibrium and solubility; (2) Physical Chemistry of the Drinking Duck, illustrating principles of phase equilibria and thermodynamics. (DF)
DEFF Research Database (Denmark)
Tsivintzelis, Ioannis; Kontogeorgis, Georgios; Michelsen, Michael Locht; Stenby, Erling Halfdan
2011-01-01
In Part I of this series of articles, the study of H2S mixtures has been presented with CPA. In this study the phase behavior of CO2 containing mixtures is modeled. Binary mixtures with water, alcohols, glycols and hydrocarbons are investigated. Both phase equilibria (vapor–liquid and liquid...
DEFF Research Database (Denmark)
Tybjerg, Peter Chr. V.; Kontogeorgis, Georgios; Michelsen, Michael Locht;
2010-01-01
Proper representation at various conditions of phase equilibria of methanol-containing mixtures (with hydrocarbons, water, etc.) is Important for oil flow assurance purposes In this work two association equations of state. CPA and sPC-SAFT, are applied to methanol-containing mixtures The purpose of...
Czech Academy of Sciences Publication Activity Database
Kroupa, Aleš; Buršík, Jiří; Svoboda, Milan; Chen, J. K.; Weatherly, G. C.
2002-01-01
Roč. 18, č. 1 (2002), s. 13-20. ISSN 0267-0836 R&D Projects: GA ČR GA106/00/0174 Institutional research plan: CEZ:AV0Z2041904 Keywords : Ti,V alloys * thermodynamic s * phase equilibria Subject RIV: JG - Metallurgy Impact factor: 0.686, year: 2002
Thermodynamic Modeling of Multi-phase Solid–Liquid Equilibria in Industrial-Grade Oils and Fats
DEFF Research Database (Denmark)
Hjorth, Jeppe Lindegaard; Miller, Rasmus L.; Woodley, John M.;
2015-01-01
Compositional thermodynamic phase separation is investigated for industrial-grade vegetable oils with complex compositions. Solid–liquid equilibria have been calculated by utilizing the Margules 2-suffix activity-coefficient model in combination with minimization of the Gibb’s free energy...
Gridchin, S. N.; Shekhanov, R. F.; Pyreu, D. F.
2015-02-01
Enthalpies of the neutralization and protonation of taurine (HL) are measured by direct calorimetry at 298.15 K and ionic strengths of 0.3, 0.5, and 1.0 (KNO3). The standard thermodynamic characteristics of HL protolytic equilibria are calculated.
DEFF Research Database (Denmark)
Fettouhi, André; Thomsen, Kaj
2010-01-01
A systematic investigation of the CPA model's performance within solid-liquid equilibria (SLE) in binary mixtures (methane + ethane, methane + heptane, methane + benzene, methane + CO2, ethane + heptane, ethane + CO2, 1-propanol + 1,4-dioxane, ethanol + water, 2-propanol + water) is presented. Th...
Lesnov, A. E.; Golovkina, A. V.; Kudryashova, O. S.; Denisova, S. A.
2016-08-01
Phase equilibria in layering systems of water, polyethyleneglycol ethers of monoethanolamides of synthetic fatty acids (SFAs) (synthamide-5), and ammonium chloride are studied. The possibility of using such systems for the liquid extraction of metal ions is evaluated. The effect the nature of salting-out agents has on the processes of segregation of the systems has been considered.
Clathrate hydrate equilibria in mixed monoethylene glycol and electrolyte aqueous solutions
International Nuclear Information System (INIS)
Highlights: ► New water activity of mixed salt(s) and MEG aqueous solutions were measured. ► New 3-phase H–Lw–V data for methane and a natural gas in equilibrium with MEG and NaCl solutions are reported. ► The CPA-EoS combined with a modified Debye Hückel electrostatic term is employed to model the phase equilibria. ► Water activity data were used to adjust parameters of the modified Debye Hückel electrostatic term. ► The modified model was independently validated using hydrate data. - Abstract: Monoethylene glycol (MEG) is commonly added in the formulation of hydraulic and drilling fluids and injected into pipelines to prevent the formation of gas hydrates. It is therefore necessary to establish the effect of a combination of salts and thermodynamic inhibitors on gas hydrate equilibria. In this communication, water activity of five ternary solutions (MEG–H2O–NaCl, MEG–H2O–CaCl2, MEG–H2O–MgCl2, MEG–H2O–KCl and MEG–H2O–NaBr) and four multicomponent solutions have been measured by a reliable resistive electrolytic humidity sensor. We also report new experimental measurements of the locus of incipient hydrate-liquid water–vapour curve for systems containing methane or natural gas with aqueous solution of ethylene glycol and NaCl over a wide range of concentrations, pressures and temperatures. A thermodynamic approach in which the Cubic-Plus-Association equation of state is combined with a modified Debye Hückel electrostatic term is employed to model the phase equilibria. These new data have been used to optimise binary interaction parameters between salts and MEG implemented in the modified Debye Hückel electrostatic term. The model developed has been evaluated using the new generated hydrate data and literature data. Good agreement between predictions of the modified model and experimental data is observed, supporting the reliability of the developed model.
When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...
QUIL: a chemical equilibrium code. [HTGR
Energy Technology Data Exchange (ETDEWEB)
Lunsford, J.L.
1977-02-01
A chemical equilibrium code QUIL is described, along with two support codes FENG and SURF. QUIL is designed to allow calculations on a wide range of chemical environments, which may include surface phases. QUIL was written specifically to calculate distributions associated with complex equilibria involving fission products in the primary coolant loop of the high-temperature gas-cooled reactor. QUIL depends upon an energy-data library called ELIB. This library is maintained by FENG and SURF. FENG enters into the library all reactions having standard free energies of reaction that are independent of concentration. SURF enters all surface reactions into ELIB. All three codes are interactive codes written to be used from a remote terminal, with paging control provided. Plotted output is also available.
The Alfven wave spectrum of analytic high-beta tokamak equilibria
International Nuclear Information System (INIS)
This thesis addresses a number of problems regarding the equilibrium and stability of a tokamak plasma under fusion conditions. To get insight into the geometric effects on the behaviour of the most prominent global modes, a spectral study was carried out on a class of analytic, noncircular plasma equilibria. Parallel to this work, extending a previous high-beta energy principle a variational principle is developed for the numerical determination of the Alfven spectrum of a high-beta tokamak with arbitrary cross-section. Based on the Lagrangian formalism, representations were derived for the potential and kinetic energy in terms of arbitrary, non-orthogonal flux coordinates, which can be readily implemented in a numerical programme. The method is then tested by using the analytic equilibrium as input. 85 refs.; 32 figs.; 2 tabs
Liquid-Liquid equilibria of the water-acetic acid-butyl acetate system
Directory of Open Access Journals (Sweden)
E. Ince
2002-04-01
Full Text Available Experimental liquid-liquid equilibria of the water-acetic acid-butyl acetate system were studied at temperatures of 298.15± 0.20, 303.15± 0.20 and 308.15± 0.20 K. Complete phase diagrams were obtained by determining solubility and tie-line data. The reliability of the experimental tie-line data was ascertained by using the Othmer and Tobias correlation. The UNIFAC group contribution method was used to predict the observed ternary liquid-liquid equilibrium (LLE data. It was found that UNIFAC group interaction parameters used for LLE did not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region.
The phase equilibria in the Au–In–Ga ternary system
International Nuclear Information System (INIS)
Highlights: • The Au–In–Ga ternary phase diagram was experimentally investigated. • XRD, DTA, SEM and EDS techniques and a CALPHAD prediction were implemented. • A previously unknown ternary phase was identified. • Using DTA results, a number of key reactions were identified and discussed. -- Abstract: The phase equilibria of the Au–In–Ga system were investigated for the first time using Differential Thermal Analysis (DTA), X-Ray Diffractometry (XRD), Energy Dispersive X-ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM). A new ternary phase (Au2InGa2) with the hexagonal structure (P63/mmc) was discovered which melts incongruently at 394 °C. From the experimental results, several invariant reactions have been identified and discussed
Influence of somatic cell count on mineral content and salt equilibria of milk
Directory of Open Access Journals (Sweden)
Primo Mariani
2010-01-01
Full Text Available Aim of this research was to study the effect of somatic cell count on mineral content and salt equilibria at the level of quarter milk samples. Ten Italian Friesian cows, in which two homologous quarters (front quarters in 1 cow, rear quarters in 6 cows and both rear and front quarters in 3 cows were characterised by a milk SCC400,000 cells/mL (HC-milk, respectively, were selected. Cows were milked at quarter level during the morning milking and a single sample was collected from each selected quarter, thus, 26 quarter milk samples were collected. Compared to LC-milk, HC-milk was characterised by a lower content of phosphorus and potassium and by a higher content of both sodium and chloride. The equilibrium of calcium, phosphorus and magnesium between the colloidal and soluble phase of milk and the mineralisation degree of the casein micelles, were not different between HC and LC milk.
Prediction of phase equilibria in the In–Sb–Pb system
Directory of Open Access Journals (Sweden)
DUSKO MINIC
2008-03-01
Full Text Available Binary thermodynamic data, successfully used for phase diagram calculations of the binary systems In–Sb, Pb–Sb and In–Pb, were used for the prediction of the phase equilibria in the ternary In–Sb–Pb system. The predicted equilibrium phase diagram of the vertical Pb–InSb section was compared with the results of differential thermal analysis DTA and optical microscopy. The calculated phase diagram of the isothermal section at 300 °C was compared with the experimentally (SEM, EDX determined composition of phases in the chosen alloys after annealing. Very good agreement between the binary-based thermodynamic prediction and the experimental data was found in all cases. The calculated liquidus projection of the ternary In–Sb–Pb system is also presented.
Formation and 'self-healing' of magnetic islands in finite-β Helias equilibria
International Nuclear Information System (INIS)
The behavior of finite-pressure-induced magnetic islands is numerically analyzed for three-dimensional magnetohydrostatic equilibria of the Helias configuration by using a three- dimensional equilibrium code. It is found that an island chain is generated on the 5/6 rational surface, when such a surface appears in the plasma region of the finite-β equilibrium. The island chain, however, is not so dangerous as to destroy the plasma confinement even if it appears in a vanishingly small shear region. Thus, a high β equilibrium with clear magnetic surfaces can be realized. Moreover, it is definitely confirmed that the finite pressure effect sometimes exhibits an unexpectedly good aspect, namely, that the vacuum islands are removed as β increases, which can be called 'self-healing' of islands. This property can be explained by the numerically discovered fact that the phases of islands induced by the finite-pressure effect are always locked in the same phase regardless of β
International Nuclear Information System (INIS)
Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy
Yasutake, Nobutoshi; Yamada, Shoichi
2016-01-01
We have developed a new formulation to obtain self-gravitating, axisymmetric configurations in permanent rotation. The formulation is based on the Lagrangian variational principle with a triangulated mesh. It treats not only barotropic but also baroclinic equations of state. We compare the various stellar equilibria obtained by our new scheme with those by Hachisu's self-consistent field scheme for the barotropic case, and those by Fujisawa's self-consistent field scheme for the baroclinic case. Included in these rotational configurations are those with shellular-type rotations, which are commonly assumed in the evolution calculation of rotating stars. Although radiation processes, convections and meridional flows have not been taken into account in this study, we have in mind the application of this method to the two-dimensional evolution calculations of rotating stars, for which the Lagrangian formulation is best suited.
Local equilibria and state transfer of charged classical particles on a helix in an electric field
Plettenberg, J; Zampetaki, A V; Schmelcher, P
2016-01-01
We explore the effects of a homogeneous external electric field on the static properties and dynamical behavior of two charged particles confined to a helix. In contrast to the field-free setup which provides a separation of the center-of-mass and relative motion, the existence of an external force perpendicular to the helix axis couples the center-of-mass to the relative degree of freedom leading to equilibria with a localized center of mass. By tuning the external field various fixed points are created and/or annihilated through different bifurcation scenarios. We provide a detailed analysis of these bifurcations based on which we demonstrate a robust state transfer between essentially arbitrary equilibrium configurations of the two charges that can be induced by making the external force time-dependent.
Aspect ratio scaling of toroidal plasma equilibria and the tokamak bootstrap effect
International Nuclear Information System (INIS)
The aspect ratio scaling of toroidal plasma equilibria is examined using a parametrization of an exact Solov close-quote ev solution to the Grad endash Shafranov equation in Boozer coordinates. The equilibrium analysis suggests that simultaneous enhancements in magnetohydrodynamic (MHD) stability and the bootstrap effect are possible in tight aspect ratio (A→1) tokamaks. The fundamental physical mechanism causing the enhancements is shown to be the natural increase of the MHD safety factor q in tight aspect ratio toroidal geometries. The results of the scaling model suggest that the lowest bootstrap current fractions are obtained in tokamaks with aspect ratios A∼3. It is also shown that a tight aspect ratio bootstrapped tokamak can be a weakly paramagnetic device. copyright 1997 American Institute of Physics
Experimental study of ternary M-Zn-Se (M=W, Au, In, Ti) phase equilibria
International Nuclear Information System (INIS)
Ternary phase equilibria in the systems M-Zn-Se (M=W, Au, In, Ti) are studied by X-ray diffraction on samples annealed in silica capsules and quenched. Four isothermal phase diagram sections are presented and discussed. Only in the In-Zn-Se system a ternary compound is present (ZnIn2Se4). The metals W, Au and In are in equilibrium with the II-VI semiconductor ZnSe, whereas Ti and ZnSe are not in equilibrium. The particular feature of the large Zn-solubility in solid (Au) does not modify the (Au)-ZnSe equilibrium, in contrast to the related Au-Cd-Te system. Possible reactions at the metal/ZnSe interface in an open or closed environment are discussed based on the phase diagrams, and potential contact materials are indicated. (orig.)
MHD equilibria in a straight system with a non-planar magnetic axis
International Nuclear Information System (INIS)
Numerical investigations of equilibria with free boundary are made in the straight syste m with a three dimensional magnetic axis. Grad-Shafranov equation is solved by both iterative SOR method and direct method on the basis of LU matrix decomposition. From the standpoint of CPU time, SOR method is better than direct method, when number of outer iterations is executed. A part of the ''Self-Stabilization Effect'' due to the increase of plasma pressure is successfully simulated. On the parameter space where the relation between the rotational transform due to the plasma current and that due to the torsion of helical magnetic axis is subtractive, the convergence region is very small. (author)
Optical trapping by Laguerre-Gaussian beams: Symmetries, stability and equilibria
Kiselev, Alexei D
2016-01-01
We use the T-matrix formalism in combination with the method of far-field matching to evaluate the optical force exerted by Laguerre-Gaussian (LG) light beams on a spherical (Mie) particle. For both non-vortex and optical vortex LG beams, the theoretical results are used to analyze the optical-force-induced dynamics of the scatterer near the trapping points represented by the equilibrium (zero-force) positions. The regimes of linearized dynamics are described in terms of the stiffness matrix spectrum and the damping constant of the ambient medium. For the purely azimuthal LG beams, the dynamics is found to be locally non-conservative and is characterized by the presence of conditionally stable equilibria (unstable zero-force points that can be stabilized by the ambient damping). The effects related to the Mie resonances that under certain conditions manifest themselves as the points changing the trapping properties of the particles are discussed.
High-pressure Phase Equilibria for Binary Ethanol System Containing Supercriticai CO2
Institute of Scientific and Technical Information of China (English)
朱虎刚; 田宜灵; 陈丽; 秦颖; 冯季军
2001-01-01
High-pressure phase behavior of supercritical (SC) CO2+ethanol system was investigated at 333.2 K,348.2K, 353.2K, 368.2K, 413.2K and 453.2K and pressure from 2.0MPa to 14.3MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.
The Swelling Equilibria of N－isopropylacrylamide Based Hydrogel in Aqueous Solution of Ethanol
Institute of Scientific and Technical Information of China (English)
许小平; HUETHERAndreas; MAURERGerd
2003-01-01
N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the "free-volume" contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture.
On the scarcity of solutions of the equations of magnetohydrodynamic equilibria with flow
Energy Technology Data Exchange (ETDEWEB)
Nunez, Manuel [Departamento de Analisis Matematico, Universidad de Valladolid, 47005 Valladolid (Spain)], E-mail: mnjmhd@am.uva.es
2008-06-16
While particular analytic solutions to the equations of axisymmetric MHD equilibria with flow are known, it is not clear what possible choosing of the free parameters of the equation of the magnetic flux will yield a solution. The most important of these is the poloidal stream function. We show that for a given flow to be able to yield an equilibrium, the flow itself must satisfy an analogous equation to the generalized Grad-Shafranov one. The problem therefore turns out to be how common are solutions to this type of equations. It is shown that in a natural space of functions, the set of these solutions is contained within a manifold of infinite codimension: extremely small by any criteria. Hence the class of flows for which an equilibrium, even defined only locally and irrespective of boundary conditions, may be found, is highly constrained.
Proteolytic Equilibria of Vanillic Acid in the Ground and Excited States
Vusovich, O. V.; Tchaikovskaya, O. N.; Sokolova, I. V.; Vasil‧eva, N. Yu.
2016-03-01
Proteolytic equilibria of vanillic acid in aqueous solutions were studied using electronic spectroscopy. The pH ranges for anionic, dianionic, cationic, and neutral forms of vanillic acid in the ground and excited states were determined. The electron density distribution on atoms in the proteolytic forms was determined using quantum-chemistry methods. The anion formed as a result of dissociation of the carboxylic acid. The dianion formed in the presence of two and more equivalents of alkali as a result of proton loss from the phenol and carboxylic acid. The vanillic acid cation formed via protonation of the carbonyl oxygen. Differences in spectral features of the proteolytic forms in the ground and excited states were observed.
ECOM: a fast and accurate solver for toroidal axisymmetric MHD equilibria
Lee, Jungpyo
2014-01-01
We present ECOM (Equilibrium solver via COnformal Mapping), a fast and accurate fixed boundary solver for toroidally axisymmetric magnetohydrodynamic equilibria with or without a toroidal flow. ECOM combines conformal mapping and Fourier and integral equation methods on the unit disk to achieve exponential convergence for the poloidal flux function as well as its first and second partial derivatives. As a consequence of its high order accuracy, for dense grids and tokamak-like elongations ECOM computes key quantities such as the safety factor and the magnetic shear with higher accuracy than the finite element based code CHEASE [H. L\\"utjens \\textit{et al.}, Computer physics communications 97, 219 (1996)] at equal run time. ECOM has been developed to provide equilibrium quantities and details of the flux contour geometry as inputs to stability, wave propagation and transport codes.
A new geometrical approach to Nash equilibria organization in Eisert's quantum games
International Nuclear Information System (INIS)
We extend the periodic point-based method for Eisert's quantum games (Schneider 2011 J. Phys. A: Math. Theor. 44 095301) to games not previously analyzed. From the comparison of different cases, we observe that games sharing the same classical features (as for instance the symmetrized Battle of the Sexes and the Chicken game) can have different characteristics after the quantization, and conversely, games with different classical behaviors (the Chicken game and the Prisoner's dilemma), are completely equivalent within Eisert's protocol. This fact is reflected in the structure of the map that the periodic point-procedure associates to the quantum game (from which the Nash equilibria are deduced). In order to understand how these unexpected outcomes are generated, we give a geometrical description of our observations in terms of bifurcation theory for maps. (paper)
Learning Stationary Correlated Equilibria in Constrained General-Sum Stochastic Games.
Hakami, Vesal; Dehghan, Mehdi
2016-07-01
We study constrained general-sum stochastic games with unknown Markovian dynamics. A distributed constrained no-regret Q -learning scheme (CNR Q ) is presented to guarantee convergence to the set of stationary correlated equilibria of the game. Prior art addresses the unconstrained case only, is structured with nested control loops, and has no convergence result. CNR Q is cast as a single-loop three-timescale asynchronous stochastic approximation algorithm with set-valued update increments. A rigorous convergence analysis with differential inclusion arguments is given which draws on recent extensions of the theory of stochastic approximation to the case of asynchronous recursive inclusions with set-valued mean fields. Numerical results are given for the exemplary application of CNR Q to decentralized resource control in heterogeneous wireless networks. PMID:26259228
Kinetic simulations of the lowest-order unstable mode of relativistic magnetostatic equilibria
Nalewajko, Krzysztof; Yuan, Yajie; East, William E; Blandford, Roger D
2016-01-01
We present the results of particle-in-cell numerical pair plasma simulations of relativistic 2D magnetostatic equilibria known as the 'ABC' fields. In particular, we focus on the lowest-order unstable configuration consisting of two minima and two maxima of the magnetic vector potential. Breaking of the initial symmetry leads to exponential growth of the electric energy and to the formation of two current layers, which is consistent with the picture of 'X-point collapse' first described by Syrovatskii. Magnetic reconnection within the layers heats a fraction of particles to very high energies. After the saturation of the linear instability, the current layers are disrupted and the system evolves chaotically, diffusing the particle energies in a stochastic second-order Fermi process leading to the formation of power-law energy distributions. The power-law slopes harden with the increasing mean magnetization, but they are significantly softer than those produced in simulations initiated from Harris-type layers....
On the scarcity of solutions of the equations of magnetohydrodynamic equilibria with flow
International Nuclear Information System (INIS)
While particular analytic solutions to the equations of axisymmetric MHD equilibria with flow are known, it is not clear what possible choosing of the free parameters of the equation of the magnetic flux will yield a solution. The most important of these is the poloidal stream function. We show that for a given flow to be able to yield an equilibrium, the flow itself must satisfy an analogous equation to the generalized Grad-Shafranov one. The problem therefore turns out to be how common are solutions to this type of equations. It is shown that in a natural space of functions, the set of these solutions is contained within a manifold of infinite codimension: extremely small by any criteria. Hence the class of flows for which an equilibrium, even defined only locally and irrespective of boundary conditions, may be found, is highly constrained
Hyperviscosity and statistical equilibria of Euler turbulence on the torus and the sphere
Qi, Wanming
2013-01-01
Coherent structures such as jets and vortices appear in two-dimensional (2D) high-Reynolds-number turbulence. To gain insight into both numerical simulation (NS) and equilibrium statistical mechanical descriptions of 2D Euler flows, the Euler equation with added hyperviscosity is integrated forward in time on the square torus and on the sphere. Coherent structures that form are compared against a hierarchy of truncated Miller-Robert-Sommeria equilibria. The energy-circulation-enstrophy MRS-2 description produces a complete condensation of energy to the largest scales, and in the absence of rotation correctly predicts the number and polarity of coherent vortices. Perturbative imposition of the quartic Casimir constraint improves agreement with NS by sharpening the cores and transferring some energy to smaller-scale modes. MRS-2 cannot explain qualitative changes due to rotation, but descriptions that conserve higher Casimirs beyond enstrophy have the potential to do so. The result is in agreement with the some...
EFFECT OF PROFILES AND SHAPE ON IDEAL STABILITY OF ADVANCED TOKAMAK EQUILIBRIA
Energy Technology Data Exchange (ETDEWEB)
MAKOWSKI,MA; CASPER,TA; FERRON,JR; TAYLOR,TS; TURNBULL,AD
2003-08-01
OAK-B135 The pressure profile and plasma shape, parameterized by elongation ({kappa}), triangularity ({delta}), and squareness ({zeta}), strongly influence stability. In this study, ideal stability of single null and symmetric, double-null, advanced tokamak (AT) configurations is examined. All the various shapes are bounded by a common envelope and can be realized in the DIII-D tokamak. The calculated AT equilibria are characterized by P{sub 0}/
{approx} 2.0-4.5, weak negative central shear, high q{sub min} (> 2.0), high bootstrap fraction, an H-mode pedestal, and varying shape parameters. The pressure profile is modeled by various polynomials together with a hyperbolic tangent pedestal, consistent with experimental observations. Stability is calculated with the DCON code and the resulting stability boundary is corroborated by GATO runs.
Effect of Profiles and Space on Ideal Stability of Advanced Tokamak Equilibria
Energy Technology Data Exchange (ETDEWEB)
Makowski, M A; Casper, T A; Ferron, J R; Taylor, T S; Turnbull, A D
2003-07-07
The pressure profile and plasma shape, parameterized by elongation ({kappa}), triangularity ({delta}), and squareness ({zeta}), strongly influence stability. In this study, ideal stability of single null and symmetric, double-null, advanced tokamak (AT) configurations is examined. All the various shapes are bounded by a common envelope and can be realized in the DIII-D tokamak. The calculated AT equilibria are characterized by P{sub 0}/{l_angle}P{r_brace} {approx} 2.0-4.5, weak negative central shear, high q{sub min} (>2.0), high bootstrap fraction, an H-mode pedestal, and varying shape parameters. The pressure profile is modeled by various polynomials together with a hyperbolic tangent pedestal, consistent with experimental observations. Stability is calculated with the DCON code and the resulting stability boundary is corroborated by GATO runs.
Thermodynamic modelling of phase equilibria in Al–Ga–P–As system
Indian Academy of Sciences (India)
S Acharya; J P Hajra
2005-04-01
A generalized thermodynamic expression of the liquid Al–Ga–P–As alloys is used in conjunction with the solid solution model in determining the solid–liquid equilibria at 1173 K and 1273 K. The liquid solution model contains thirtyseven parameters. Twentyfour of them pertain to those of the six constituent binaries, twelve refer to the specific ternary interactions. Additionally the liquid solution model also contains a specific quaternary interaction parameter. The latter has been evaluated here based on the experimental data available in the literature. The present research shows an excellent agreement between the derived and experimental values at 1173 K and 1273 K for the system. The article also presents a comparison between the evaluated values with those based on the regular solution model for the liquid alloys.
Semistability of Nonlinear Systems Having a Continuum of Equilibria and Time-Varying Delays
Hui, Qing
2010-01-01
In this paper, we develop a semistability analysis framework for nonlinear systems with time-varying delays with applications to stability analysis of multiagent dynamic networks with consensus protocols in the presence of unknown heterogeneous time-varying delays along the communication links. We show that for such a nonlinear system having a continuum of equilibria, if the system asymptotically converges to a constant time-delay system and this new system is semistable, then the original time-varying delay system is semistable, provided that the delays are just bounded, not necessarily differentiable. In proving our results, we extend the limiting equation approach to the time-varying delay systems and also develop some new convergence results for functional differential equations.
On the question of phase equilibria in the succinonitrile-(D)camphor system
Witusiewicz, V. T.; Hecht, U.; Rex, S.
2013-07-01
Alloys from the succinonitrile-(D)camphor (SCN-DC) system are widely used as model alloys for the in situ investigation of solidification using light optical microscopy, but literature on the binary phase diagram is contradictory with respect to the solubility limit of DC in (SCN). Phase equilibria of the system were therefore revisited experimentally and critically assessed in the present work. The results prove that the maximum solubility of DC in the succinonitrile solid solution (SCN) is far less 1 wt% and the volume fraction of the (DC) phase in the eutectic solid is 23.3%. On this basis and on recently reported experimental data the CALPHAD description of the SCN-DC system was re-optimized.
International Nuclear Information System (INIS)
Using the recently developed multiregion, relaxed MHD (MRxMHD) theory, which bridges the gap between Taylor's relaxation theory and ideal MHD, we provide a thorough analytical and numerical proof of the formation of singular currents at rational surfaces in non-axisymmetric ideal MHD equilibria. These include the force-free singular current density represented by a Dirac δ-function, which presumably prevents the formation of islands, and the Pfirsch-Schlüter 1/x singular current, which arises as a result of finite pressure gradient. An analytical model based on linearized MRxMHD is derived that can accurately (1) describe the formation of magnetic islands at resonant rational surfaces, (2) retrieve the ideal MHD limit where magnetic islands are shielded, and (3) compute the subsequent formation of singular currents. The analytical results are benchmarked against numerical simulations carried out with a fully nonlinear implementation of MRxMHD
Prediction of phase equilibria and thermal analysis in the Bi-Cu-Pb ternary system
International Nuclear Information System (INIS)
The knowledge about phase diagram of the Bi-Cu-Pb ternary system is of importance in development of copper-lead based bearing materials, soldering and in refining of copper and lead. In this work, the phase diagram of the Bi-Cu-Pb ternary system was calculated by the CALPHAD method using binary thermodynamic parameters included in the COST 531 database. The results include liquidus projection, invariant equilibria and three vertical sections with molar ratio Cu:Pb = 1, Cu:Pb = 1:3 and Bi:Cu = 1. Alloys, with compositions along three predicted vertical sections, were measured using differential scanning calorimetry (DSC). The experimentally determined phase transition temperatures were compared with calculated results and good mutual agreement was noticed.
Solid—Liquid Equilibria of Several Binary and Ternary Systems Containing Meleic Anhydride
Institute of Scientific and Technical Information of China (English)
MAPeisheng; CHENMingming; 等
2002-01-01
Solid-liquid equilibria(SLE) of three binary systems and seven ternary systems containing maleic anhydride(MA) are measured by visual method. The experimental data are compared with the calculated ones with modified universal quasichemical functional group activity coefficient(UNIFAC) method in which the interaction parameters between groups come from two sources,dortmund data bank (DDB), if there′s any,and correlations based on our former presented experimental SLE data of twenty binary systems.New groups of MA,ACCOO group,COO group,>C=O group and cy-CH2 group are defined and the SLE data of maleic anhydride in isopropyl acetate in literature are cited in order to assess the new interaction parameters,correlated with Wilson equation and the λh equation.The modified UNIFAC method with these new regressed interaction parameters is also used to predict other three binary systems containing maleic anhydride.
Sokkalingam, Nandhini; Kamath, Ganesh; Coscione, Maria; Potoff, Jeffrey J
2009-07-30
The transferable potentials for phase equilibria force field is extended to dimethylmethylphosphonate (DMMP), sarin, and soman by introducing a new interaction site representing the phosphorus atom. Parameters for the phosphorus atom are optimized to reproduce the liquid densities at 303 and 373 K and the normal boiling point of DMMP. Calculations for sarin and soman are performed in predictive mode, without further parameter optimization. Vapor-liquid coexistence curves, critical properties, vapor pressures and heats of vaporization are predicted over a wide range of temperatures with histogram reweighting Monte Carlo simulations in the grand canonical ensemble. Excellent agreement with experiment is achieved for all compounds, with unsigned errors of less than 1% for vapor pressures and normal boiling points and under 5% for heats of vaporization and liquid densities at ambient conditions. PMID:19719285
From one-dimensional fields to Vlasov equilibria: Theory and application of Hermite polynomials
Allanson, O; Troscheit, S; Wilson, F
2016-01-01
We consider the theory and application of a solution method for the inverse problem in collisionless equilibria, namely that of calculating a Vlasov-Maxwell equilibrium for a given macroscopic (fluid) equilibrium. Using Jeans' Theorem, the equilibrium distribution functions are expressed as functions of the constants of motion, in the form of a Maxwellian multiplied by an unknown function of the canonical momenta. In this case it is possible to reduce the inverse problem to inverting Weierstrass transforms, which we achieve by using expansions over Hermite polynomials. A sufficient condition on the pressure tensor is found which guarantees the convergence and the boundedness of the candidate solution, when satisfied. This condition is obtained by elementary means, and it is clear how to put it into practice. We also argue that for a given pressure tensor for which our method applies, there always exists a positive distribution function solution for a sufficiently magnetised plasma. Illustrative examples of th...
Directory of Open Access Journals (Sweden)
Lu-Chuan Ceng
2014-01-01
Full Text Available We first introduce and analyze one iterative algorithm by using the composite shrinking projection method for finding a solution of the system of generalized equilibria with constraints of several problems: a generalized mixed equilibrium problem, finitely many variational inequalities, and the common fixed point problem of an asymptotically strict pseudocontractive mapping in the intermediate sense and infinitely many nonexpansive mappings in a real Hilbert space. We prove a strong convergence theorem for the iterative algorithm under suitable conditions. On the other hand, we also propose another iterative algorithm involving no shrinking projection method and derive its weak convergence under mild assumptions. Our results improve and extend the corresponding results in the earlier and recent literature.
Accelerated convergence of the steepest-descent method for magnetohydrodynamic equilibria
International Nuclear Information System (INIS)
Iterative schemes based on the method of steepest descent have recently been used to obtain magnetohydrodynamic (MHD) equilibria. Such schemes generate asymptotic geometric vector sequences whose convergence rate can be improved through the use of the epsilon-algorithm. The application of this nonlinear recursive technique to stiff systems is discussed. In principle, the epsilon-algorithm is capable of yielding quadratic convergence and therefore represents an attractive alternative to other quadratic convergence schemes requiring Jacobian matrix inversion. Because the damped MHD equations have eigenvalues with negative real parts (in the neighborhood of a stable equilibrium), the epsilon-algorithm will generally be stable. Concern for residual monotonic sequences leads to consideration of alternative methods for implementing the algorithm
Simulated annealing for three-dimensional low-beta reduced MHD equilibria in cylindrical geometry
Furukawa, M
2016-01-01
Simulated annealing (SA) is applied for three-dimensional (3D) equilibrium calculation of ideal, low-beta reduced MHD in cylindrical geometry. The SA is based on the theory of Hamiltonian mechanics. The dynamical equation of the original system, low-beta reduced MHD in this study, is modified so that the energy changes monotonically while preserving the Casimir invariants in the artificial dynamics. An equilibrium of the system is given by an extremum of the energy, therefore SA can be used as a method for calculating ideal MHD equilibrium. Previous studies demonstrated that the SA succeeds to lead to various MHD equilibria in two dimensional rectangular domain. In this paper, the theory is applied to 3D equilibrium of ideal, low-beta reduced MHD. An example of equilibrium with magnetic islands, obtained as a lower energy state, is shown. Several versions of the artificial dynamics are developed that can effect smoothing.
Hydrothermal phase equilibria in Ln2O3-H2O systems
International Nuclear Information System (INIS)
Hydrothermal phase equilibria studies have been carried out in the Ln2O3-H2O systems (Ln= La, Pr, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and the stability fields of the phases Ln(OH)3 LnOOH and Ln2O3-C have been established in the pressure-temperature range of 25000 psi and 900deg C. The sequioxides Ln2O3-C are stable only in the last four systems of Er to Lu along with the Ln(OH)3 and LnOOH. The systems from Nd to Ho have only Ln(OH)3 and LnOOH as stable phases and those from La to Pr have only Ln(OH)3 as the stable phase. The unit cell parameters of trihydroxides deviate from the values reported in the literature and this is attributed to the contamination of CO2 in the starting material. (author)
Free-boundary ideal MHD stability of W7-X divertor equilibria
Nührenberg, C.
2016-07-01
Plasma configurations describing the stellarator experiment Wendelstein 7-X (W7-X) are computationally established taking into account the geometry of the test-divertor unit and the high-heat-flux divertor which will be installed in the vacuum chamber of the device (Gasparotto et al 2014 Fusion Eng. Des. 89 2121). These plasma equilibria are computationally studied for their global ideal magnetohydrodynamic (MHD) stability properties. Results from the ideal MHD stability code cas3d (Nührenberg 1996 Phys. Plasmas 3 2401), stability limits, spatial structures and growth rates are presented for free-boundary perturbations. The work focusses on the exploration of MHD unstable regions of the W7-X configuration space, thereby providing information for future experiments in W7-X aiming at an assessment of the role of ideal MHD in stellarator confinement.
Phase equilibria of the Al–Mn–Zn system at 600 °C
International Nuclear Information System (INIS)
Highlights: ► The isothermal section at 600 °C of the Al–Mn–Zn system was determined. ► Five ternary phases, denoted as T1, T2, T3, T4 and γ3, were found at 600 °C. ► Four of the ternary phases, T1, T2, T3 and T4, are assumed to be the newly found ternary phases. -- Abstract: The phase equilibria at 600 °C of the Al–Mn–Zn system were investigated with 38 alloys, by means of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and electron probe microanalysis. Five ternary phases, denoted as T1, T2, T3, T4 and γ3, were found at 600 °C. T1 extends approximately at a constant Mn content and has a composition range from 73.6 to 79.8 at.% Al. T3 and T4 have composition ranges from about 67.1 to 70.1 at.% Al and from about 61.5 to 67.6 at.% Al, respectively. Three ternary compounds of τ1 (Mn5ZnAl24), τ2 (Mn2ZnAl9) and τ3 (Mn3Zn2Al11), which had been reported in the literature, were not detected in the present work. An extensive homogeneity range of the γ3 phase was observed at 600 °C. This phase is isomorphic to the binary Mn5Zn21 compound, which is stable only below 420 °C, and is stabilized by the Al addition in the ternary system. The sixteen three-phase equilibria were determined and the isothermal section was constructed at 600 °C
Experimental investigation of phase equilibria in the Co–Hf system
Energy Technology Data Exchange (ETDEWEB)
Lu, Xingxu, E-mail: xingxulu@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Cheng, Kaiming, E-mail: chengkaimingtry@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Liu, Shuhong, E-mail: shhliu@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Sino-German Cooperation Group “Microstructure in Al alloys”, Central South University, Changsha, Hunan 410083 (China); Li, Kai, E-mail: leking137joey@gmail.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Zheng, Feng, E-mail: fzheng@mail.csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Du, Yong, E-mail: yong-du@mail.csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Sino-German Cooperation Group “Microstructure in Al alloys”, Central South University, Changsha, Hunan 410083 (China)
2015-04-05
Highlights: • Phase equilibria in the Co–Hf binary system were experimentally determined. • The reported Co{sub 7}Hf phase was replaced with an orthorhombic compound of Co{sub 11}Hf{sub 2}. • Eutectic composition for the reaction L ↔ CoHf{sub 2} + (βHf) was modified. • Invariant reaction temperatures were experimentally determined. • Composition ranges of intermetallic compounds were experimentally measured. - Abstract: Phase equilibria in the Co–Hf binary system were investigated based on the experimental results from X-ray diffraction, transmission electron microscopy, scanning electron microscopy, electron probe microanalysis and differential scanning calorimetry on annealed and as-cast alloys. A new orthorhombic compound Co{sub 11}Hf{sub 2} with a stability range from ∼650 to 1273 °C was observed instead of Co{sub 7}Hf reported in literature. Another stoichiometric phase Co{sub 7}Hf{sub 2} proposed in literature was not observed in the present work. The reaction type for the formation of CoHf{sub 2} was confirmed to be peritectic, but the eutectic composition for the reaction L ↔ CoHf{sub 2} + (βHf) was modified to be ∼71.5 at.% Hf. Homogeneity ranges of different intermetallic compounds and solution phases at 700 and 1100 °C as well as the invariant reaction temperatures were experimentally determined. The newly constructed phase diagram shall provide accurate information for further thermodynamic modeling of the Co–Hf binary system.
Spectroscopic studies on U(VI)-salicylate complex formation with multiple equilibria
Energy Technology Data Exchange (ETDEWEB)
Cha, W.; Cho, H.R.; Jung, E.C.; Park, K.K.; Kim, W.H.; Song, K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Nuclear Chemistry Research Div.
2012-07-01
This study investigates multiple equilibria related to the formation of the U(VI)-salicylate complex in a pH range of 3.0-5.5 using UV-Vis absorption and fluorescence measurement techniques. The absorbance changes at the characteristic charge-transfer bands of the complex were monitored, and the results indicated the presence of multiple equilibria and the formation of both 1:1 and 1:2 (U(VI):salicylate) complexes possessing bi-dentate chelate structures. The determined step-wise formation constants (log K{sub 1:1} and log K{sub 1:2}) are as follows: 12.5 {+-} 0.1 and 11.4 {+-} 0.2 for salicylate, 11.2 {+-} 0.1 and 10.1 {+-} 0.2 for 5-sulfosalicylate, and 12.4 {+-} 0.1 and 11.4 {+-} 0.1 for 2,6-dihydroxybenzoate, respectively. The molar absorptivities of the complexes are also provided. Furthermore, time-resolved laser-induced luminescence spectra of U(VI) species demonstrate the presence of both a dynamic and static quenching process upon the addition of a salicylate ligand. Particularly for the luminescent hydroxouranyl species, a strong static quenching effect is observed. The results suggest that both the UO{sub 2}(HSal){sup +} and the U(VI)-Sal chelate complexes serve as ground-state complexes that induce static quenching. The Stern-Volmer parameters were derived based on the measured luminescent intensity and lifetime data. The static quenching constants (log K{sub S}) obtained are 3.3 {+-} 0.1, 4.9 {+-} 0.1, and 4.4 {+-} 0.1 for UO{sub 2}{sup 2+}, (UO{sub 2}){sub 2}(OH){sub 2}{sup 2+} and (UO{sub 2}){sub 3}(OH){sub 5}{sup +}, respectively. (orig.)
Evolution of flux-conserving tokamak equilibria with preprogrammed cross sections
International Nuclear Information System (INIS)
The evolution of MHD equilibria toward high β is modeled by magnetic flux conservation with a given q(psi) and by single fluid particle and energy balances which determine p(psi, t). These one-dimensional flux surface averaged equations, written with magnetic flux psi as the independent varianle, are coupled to the two-dimensional MHD equilibrium equation through psi, p(psi, t), and q(psi). The location an evolution of the plasma cross section boundary are precisely specified through the use of a fixed boundary equilibrium technique. In moving boundary studies (e.g., plasma compression) the resulting system of equations is advanced in time from an inital state by a procedure which utilizes two nested predictor-corrector loops together with an implicit time-stepping technique. The inner predictor-corrector loop advances the transport equations subject to a given equilibrium configuration while the outer loop evolves the equilibrium. For fixed plasma boundaries this procedure is modified for greater computational speed. These techniques provide satisfactory numerical convergence together with complete consistency between the coupled one-dimensional system of equations and the two-dimensional equilibrium. This method can be applied to the study of equilibrium evolution involving dramatic changes of plasma position, shape, an profiles while prescribing the evolution of the plasma boundary. As such, it can serve as a useful tool in the design of poloidal field systems or as a source of equilibria in high-β MHD stability studies. As an example, the compressional scaling laws of Furth and Yoshikawa are found to be modified for small aspect ratio
International Nuclear Information System (INIS)
Although this book contains a very good review of computation methods applicable to equilibrium systems, most of the book is dedicated to the description and evaluation of computer programs available for doing such calculations. As stated in the preface, the authors (two computniks and a user of graphical and computer methods) have joined forces in order to present the reader with the points of view of both the creator and user of modern computer program tools available for the study of solution equilibria. The successful presentation of such a complicated amalgamation of concepts is greatly aided by the structure of the book, which begins with a brief but thorough discussion of equilibrium concepts in general, followed by an equally brief discussion of experimental methods used to study equilibria with potentiometric, extraction, and spectroscopic methods. These sections would not be sufficient to teach these topics to the beginner but offer an informative presentation of concepts in relation to one another to those already familiar with basic equilibrium concepts. The importance of evaluating and analyzing the suitability of data for further analysis is then presented before an in depth (by a chemist's standards) look at the individual parts that make up a detailed equilibrium analysis program. The next one-third of the book is an examination of specific equilibrium problems and the programs available to study them. These are divided into chapters devoted to potentiometric, extraction, and spectroscopic methods. The format is to discuss a variety of programs, one at a time, including the parts of the program, the types of problems to which it has been applied, and the program's limitations. A number of problems are then presented, which are representative of the type of questions that are normally addressed by research projects in the area
Experimental determination of the phase equilibria of the Mg–Nd–Zn system at 320 °C
International Nuclear Information System (INIS)
Highlights: • The 320 °C isothermal section of the Mg–Nd–Zn system was well established. • Eight ternary phases (τ1–τ7 and T-NdMg12) were found at 320 °C. • T-NdMg12 is the Nd-stabilized NdMg12 phase. • T-NdMg12 and τ5–τ7 can be regarded as the newly found ternary phases. - Abstract: The phase equilibria of the Mg–Nd–Zn system at 320 °C were investigated with an Mg–Nd–Zn diffusion couple and 34 equilibrated alloys, by means of X-ray diffraction technique and electron probe microanalyses. Eight ternary phases, denoted as τ–τ7 and T-NdMg12, respectively, were found at 320 °C. It was revealed that the T-NdMg12 phase is based on the metastable NdMg12 compound and stabilized by the substitution of Zn for Mg. The τ1 phase with a C-centered orthorhombic crystal structure was determined to have a composition range of 7.4–7.7 at.% Nd and 25.8–40.1 at.% Zn. The τ2 phase with a hexagonal crystal structure was measured to have a composition range of 6.3–7.8 at.% Nd and 61.0–64.0 at.% Zn. The crystal structures of the five ternary phases τ3–τ7 are still unknown. Four ternary phases, viz. T-NdMg12 and τ5 to τ7, can be regarded as the newly found ternary phases in the present work. According to the present work, the τ3, τ4 and τ5 phases have the Zn composition ranges of 61.6–64.6 at.% Zn, 54.4–67.9 at.% Zn and 59.5–64.5 at.% Zn, and have the approximate Nd contents of 10.4, 13.5 and 17.2 at.% Nd, respectively. The τ6 phase has a approximate chemical composition of Nd15.7Mg8.4Zn75.9 while the τ7 phase has a composition range of 58.0–60.2 at.% Zn at about 21.3 at.% Nd
Wai, C. M.; Hutchinson, S. G.
1989-01-01
Discusses the calculation of free energy in reactions between silicon dioxide and carbon. Describes several computer programs for calculating the free energy minimization and their uses in chemistry classrooms. Lists 16 references. (YP)
Al-Radhawi, M. Ali; Angeli, David
2014-01-01
Piecewise-Linear in Rates (PWLR) Lyapunov functions are introduced for a class of Chemical Reaction Networks (CRNs). In addition to their simple structure, these functions are robust with respect to arbitrary monotone reaction rates, of which mass-action is a special case. The existence of such functions ensures the convergence of trajectories towards equilibria, and guarantee their asymptotic stability with respect to the corresponding stoichiometric compatibility class. We give the definiti...
International Nuclear Information System (INIS)
Highlights: •We have constructed the isothermal section of the system Bi2O3–Fe2O3–Sb2Ox. •Ternary compound formation is limited to pyrochlore, which forms a solid solution region. •The phase diagram points out that 7–25% of Bi-positions are occupied with Fe3+. •The Mossbauer data confirmed that Fe3+ ions enter the Bi-positions. •Magnetic measurements revealed spin-glass magnetic transition at 9 K. -- Abstract: The subsolidus phase equilibria of the Bi2O3–Fe2O3–Sb2Ox system have been investigated by X-ray powder diffraction. The isothermal section of the system at 775–800 °C has been constructed. It can be represented by 9 phase assemblage triangles. Ternary compound formation is limited to pyrochlore which forms a substantial solid solution region of Bi-deficient compositions relative to Bi2FeSbO7. As follows from the phase diagram, approximately 7–25% of Bi positions in pyrochlore may be occupied with Fe3+ ions that was confirmed by Mossbauer data. Magnetic measurements were carried out on the pyrochlore specimen of quasi-chemical formula (Bi1.8Fe0.2)(FeSb)O7. The existence of the strong short-range antiferromagnetic superexchange interactions and spin-glass magnetic transition at around 9 K were revealed
Semenov, V.; Korneev, I.; Arinushkin, P.; Strelkova, G.; Vadivasova, T.; Anishchenko, V.
2015-07-01
The intrinsic features of systems with a line of equilibria are analyzed by studying of memristor-based Chua's oscillator. The analog modeling of the system is carried out together with its numerical simulation. The characteristics of stochastic oscillations in the system under study are explored in the presence of noise. The issues concerning the physical realization of a system with a line of equilibria are also considered.
von Nessi, G T
2012-01-01
A new method, based on Bayesian analysis, is presented which unifies the inference of plasma equilibria parameters in a Tokamak with the ability to quantify differences between inferred equilibria and Grad-Shafranov force-balance solutions. At the heart of this technique is the new method of observation splitting, which allows multiple forward models to be associated with a single diagnostic observation. This new idea subsequently provides a means by which the the space of GS solutions can be efficiently characterised via a prior distribution. Moreover, by folding force-balance directly into one set of forward models and utilising simple Biot-Savart responses in another, the Bayesian inference of the plasma parameters itself produces an evidence (a normalisation constant of the inferred posterior distribution) which is sensitive to the relative consistency between both sets of models. This evidence can then be used to help determine the relative accuracy of the tested force-balance model across several discha...
Isotropic-nematic phase equilibria of hard-sphere chain fluids-Pure components and binary mixtures.
Oyarzún, Bernardo; van Westen, Thijs; Vlugt, Thijs J H
2015-02-14
The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components. PMID:25681939
Mariani, P.; P. Vecchia; A. Tambini; M. Pecorari; Franceschi, P.; A. Summer; M. Malacarne; P. Formaggioni
2010-01-01
The “maturation” of milk for Parmigiano-Reggiano cheese is characterised by natural creaming process: the full cream milk is placed in large flat vats, for about 10-12 hours, to obtain the gravity separation of milk fat. The modifications of mineral equilibria and technological properties of milk during the “maturation” phase, were studied. To this aim 24 full cream (FC) milk samples and the corresponding partially skimmed (PS) milk, by natural creaming, were analysed....
Energy Technology Data Exchange (ETDEWEB)
Alvarez, Victor H. [School of Chemical Engineering, University of Campinas (UNICAMP), Av. Albert Einstein 500, 13083-852 Campinas, SP (Brazil); Mattedi, Silvana [Chemical Engineering Department, Polytechnic School, Federal University of Bahia (UFBA), R. Aristides Novis 2, 40210-630 Salvador, BA (Brazil); Aznar, Martin, E-mail: maznar@feq.unicamp.b [School of Chemical Engineering, University of Campinas (UNICAMP), Av. Albert Einstein 500, 13083-852 Campinas, SP (Brazil)
2011-06-15
Research highlights: We report density, refraction index, and VLE for (propionaldehyde or valeraldehyde) + [emim][EtSO{sub 4}]. The Peng-Robinson + Wong-Sandler + COSMO-SAC model was used to predict density and VLE. The densities were predicted with deviations below than 2.3%. The experimental VLE was predicted with deviations below than 1.6%. - Abstract: This paper reports the density, refraction index, and (vapor + liquid) equilibria (VLE) for binary systems {l_brace}aldehyde + 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO{sub 4}]){r_brace}: {l_brace}propionaldehyde + [emim][EtSO{sub 4}]{r_brace} and {l_brace}valeraldehyde + [emim][EtSO{sub 4}]{r_brace}. The uncertainties for the temperature, pressure, and compositions measurements for the phase equilibria are {+-}0.1 K, {+-}0.01 kPa and {+-}0.0004, respectively. A qualitative analysis of the variation of the properties with changes in solvent and temperature was performed. The Peng-Robinson equation of state (PR EoS), coupled with the Wong-Sandler mixing rule (WS), is used to describe the experimental data. To calculate activity coefficients we used three different models: NRTL, UNIQUAC, and COSMO-SAC. Since the predictive liquid activity coefficient model COSMO-SAC is used in the Wong-Sandler mixing rule, the resulting thermodynamic model is a completely predictive one. The prediction results for the density and for the (vapor + liquid) equilibria have a deviation lower than 2.3% and 1.6%, respectively. The (vapor + liquid) equilibria predictions show a good description for the propionaldehyde system and only a qualitative description for the valeraldehyde system.
DEFF Research Database (Denmark)
Pedersen, Kim Vestergaard; Christensen, Henrik; Shim, Irene;
2004-01-01
Trichlorothioacetyl chloride 1, tetrachlorothiirane 2, and trichloroethenesulfenyl chloride 3 and the equilibria between them have been investigated by ab initio Hartree-Fock (HF), Møller-Plesset second order perturbation (MP2) calculations, and by Gaussian-3 theory, G3(MP2). The transition state...... of the isomerization reactions have been identified. Also investigated were possible reactions leading to the isomers and their possible decomposition products. The results show that the unobserved isomerization reactions are feasible....
Basu, Kaushik; Amanda J Felkey
2008-01-01
This paper uses efficiency wage theory and the existence of community-based sharing to hypothesize that labor markets in developing countries have multiple equilibria - the same economy can be stuck at different levels of unemployment with different levels of wages. The model is meant for developing economies where wage-productivity links are discernible and income-sharing among the poor is prevalent. It seems reasonable to posit that in such an economy more unemployment leads to more income ...
Gotz, Linde; Qiu, Feng; Gervais, Jean-Philippe; Glauben, Thomas
2012-01-01
Only few models exist which allow for a regime-dependent spatial price equilibrium. This paper focuses on the price insulating effects of export restrictions. The theory of a Walrasian equilibrium and the spatial price equilibrium theory suggest that export restrictions lead to multiple spatial equilibria between the domestic and the world market price. Our analysis is unique in testing for linear versus non-linear cointegration within a smooth transition cointegration model. The application ...
Phase equilibria at 773 K and microwave absorbing properties of Er–Fe–Cr alloys
International Nuclear Information System (INIS)
Highlights: • The phase equilibria of Er–Fe–Cr system at 773 K were investigated experimentally. • The isothermal section consists of 8 single-phase regions, 14 two-phase regions and 7 three-phase regions. • The solid solubilities of Cr in ErFe2, ErFe3, Er6Fe23, Er2Fe17, and Fe at 773 K are determined by experimental method. • The intermetallic compounds in Er–Fe–Cr system exhibit good microwave absorbing property in the X–band (8–12 GHz). - Abstract: The phase equilibria of Er–Fe–Cr system at 773 K were investigated by X-ray powder diffraction (XRD), differential thermal analysis (DTA), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The isothermal section consists of 8 single-phase regions, 14 two-phase regions and 7 three-phase regions. The homogeneity range of the ternary compound ErFe12−xCrx was determined to be x = 1.6–3.0. The maximum solid solubilities of Cr in ErFe2, ErFe3, Er6Fe23, Er2Fe17, and Fe are about 8.2, 1.2, 15.6, 9.6 and 13.8 at.% Cr, respectively, and the solubility limit of Fe in Cr is about 13.3 at.% Fe. The microwave absorbing properties of the intermetallic compounds in Er–Fe–Cr system were determined. All the samples exhibited good absorbing property in the X-band (8–12 GHz). With a coating thickness of d = 2.0 mm, the minimum return loss at the absorption peak frequency of the ErFe2, ErFe3, Er6Fe23, Er2Fe17 and ErFe10Cr2 are −19.66 dB at 9.6 GHz, −29.57 dB at 8.16 GHz, −35.04 dB at 12.72 GHz, −22.72 dB at 9.76 GHz and −13.51 dB at 11.2 GHz, respectively
Effect of Resonant Magnetic Perturbations on 3D equilibria in the MST RFP
Munaretto, Stefano
2015-11-01
The orientation of 3D, stellarator-like equilibria in the MST RFP can now be controlled with application of an m = 1 RMP. This has led to greatly improved diagnosis, revealing enhancements in both the central electron temperature and density. Coupled to a recent advance in the V3FIT code, reconstructions of the 3D equilibria have also been dramatically improved. The RMP also inhibits the generation of high-energy >20 keV electrons that is otherwise common with the 3D state. This state occurs when the normally broad spectrum of core-resonant m = 1 tearing modes condenses, with the innermost resonant mode growing to large amplitude, reaching ~ 8% of the axisymmetric field strength. This occurs in plasmas of sufficiently large Lundquist number ~ IpTe3/2, and the duration of the state is maximized with zero applied Bt (infinite toroidal beta). As the dominant mode grows, eddy current in MST's conducting shell slows the mode's rotation. This leads to locking of the 3D structure, but with an orientation that varies randomly shot to shot, making diagnosis difficult. An m = 1 RMP can now be applied with an array of saddle coils at the vertical insulated cut in the shell. With an amplitude br/B ~ 10% and a tailored temporal waveform, the RMP can force the 3D structure into any desired orientation relative to MST's diagnostics. A recent advance in V3FIT allows calculation of the substantial helical image current flowing in MST's shell, which has in turn allowed self-consistent utilization of both external and internal (Faraday rotation) measurements of the magnetic field. The ORBIT code predicts reduced stochasticity and improved confinement of high-energy electrons within the 3D structure. The suppression of these electrons by the m = 1 RMP may reflect a change to the central magnetic topology. The generation of these electrons is unaffected by non-resonant perturbations, such as m = 3. Supported by the US DOE.
Institute of Scientific and Technical Information of China (English)
ZHAO Nan; DING Yi-hui; Masaaki Takahashi; SHEN Xin-yong
2006-01-01
Multiple equilibria and their stability in tropical atmosphere are investigated through β -plane barotropic models with consideration of heating and dissipation. We have derived the solutions of the model equations corresponding to the multiple equilibria or the steady flows first, and then establish the criteria for the stability of steady flow by use of the Liapunov direct Method. When these criteria are applied to the solutions of equilibria obtained, stable flows, which are closely related to the different patterns of quasi-stationary circulation in the tropical region, are found. The configurations of these stable flows and the shift between two of them as season changes provide quite reasonable explanations to many fundamental problems of tropical circulation features such as the catastrophe mechanism of the onset and the break-active cycle of the Asian summer monsoon. It follows that the onset or the abrupt transition of the Asian summer monsoon could be attributed to the multiple equilibrium property of the tropical circulation resulted from the advective nonlinearity, which provide another explanation among others.
Semenov, K. N.; Charykov, N. A.; Postnov, V. N.; Sharoyko, V. V.; Murin, I. V.
2016-01-01
This review is the first attempt to integrate the available data on all types of phase equilibria (solubility, extraction and sorption) in systems containing light fullerenes (C60 and C70). In the case of solubility diagrams, the following types of phase equilibria are considered: individual fullerene (C60 or C70)-solvent under polythermal and polybaric conditions; C60-C70-solvent, individual fullerene-solvent(1)-solvent(2), as well as multicomponent systems comprising a single fullerene or an industrial mixture of fullerenes and vegetable oils, animal fats or essential oils under polythermal conditions. All published experimental data on the extraction equilibria in C60-C70-liquid phase(1)-liquid phase(2) systems are described systematically and the sorption characteristics of various materials towards light fullerenes are estimated. The possibility of application of these experimental data for development of pre-chromatographic and chromatographic methods for separation of fullerene mixtures and application of fullerenes as nanomodifiers are described. The bibliography includes 87 references.
Phase equilibria in the YbTe–Sb{sub 2}Te{sub 3}–Te system
Energy Technology Data Exchange (ETDEWEB)
Aliev, Ziya S., E-mail: ziyasaliev@gmail.com [Baku State University, General and Inorganic Chemistry Department, Baku (Azerbaijan); Institute of Physics, Azerbaijan National Academy of Science, Baku (Azerbaijan); Ibadova, Gulnara I. [Baku State University, General and Inorganic Chemistry Department, Baku (Azerbaijan); Tedenac, Jean-Claude [University of Montpellier II, ICGM UMR 5253, Montpellier (France); Babanly, Mahammad B. [Baku State University, General and Inorganic Chemistry Department, Baku (Azerbaijan); Institute of Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Science, Baku (Azerbaijan)
2015-01-05
Highlights: • The phase diagram of the YbTe–Sb{sub 2}Te{sub 3}–Te sub-system relates to the invariant eutectic type. • The primary crystallization fields of phases, the character and temperatures of the invariant equilibria were determined. • The existence of the ternary compound YbSb{sub 2}Te{sub 4} and YbSb{sub 2}Te{sub 4} were not confirmed. - Abstract: The phase equilibria in the YbTe–Sb{sub 2}Te{sub 3}–Te system were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope with energy dispersive analysis (SEM-EDS) techniques. Two isopleth sections and liquidus surface projection were constructed. The primary crystallization fields of phases, the character and temperatures of the invariant and monovariant processes were determined. No new ternary compound was found in this system and moreover, known ternary compounds YbSb{sub 2}Te{sub 4} and YbSb{sub 4}Te{sub 7} were not confirmed. The newly determined phase equilibria in this sub-system will provide important information for the future construction of self-consistent phase diagram of the ternary Yb–Sb–Te system in the entire concentration range.
Energy Technology Data Exchange (ETDEWEB)
Gutierrez, Jorge E.; Bejarano, Arturo [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Fuente, Juan C. de la, E-mail: juan.delafuente@usm.c [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Centro Regional de Estudios en Alimentos Saludables, Blanco 1623, Valparaiso (Chile)
2010-05-15
An apparatus based on a static-analytic method assembled in this work was utilized to perform high pressure (vapour + liquid) equilibria measurements with uncertainties estimated at <5%. Complementary isothermal (vapour + liquid) equilibria results are reported for the (CO{sub 2} + 1-propanol), (CO{sub 2} + 2-methyl-1-propanol), (CO{sub 2} + 3-methyl-1-butanol), and (CO{sub 2} + 1-pentanol) binary systems at temperatures of (313, 323, and 333) K, and at pressure range of (2 to 12) MPa. For all the (CO{sub 2} + alcohol) systems, it was visually monitored to insure that there was no liquid immiscibility at the temperatures and pressures studied. The experimental results were correlated with the Peng-Robinson equation of state using the quadratic mixing rules of van der Waals with two adjustable parameters. The calculated (vapour + liquid) equilibria compositions were found to be in good agreement with the experimental values with deviations for the mol fractions <0.12 and <0.05 for the liquid and vapour phase, respectively.
Energy Technology Data Exchange (ETDEWEB)
Bejarano, Arturo; Gutierrez, Jorge E. [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Araus, Karina A. [Departamento de Ingenieria Quimica y Bioprocesos, Pontificia Universidad Catolica de Chile, Avda. Vicuna Mackenna 4860, Macul, Santiago (Chile); Fuente, Juan C. de la, E-mail: juan.delafuente@usm.c [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Centro Regional de Estudios en Alimentos Saludables, Blanco 1623, Valparaiso (Chile)
2011-05-15
Research highlights: (Vapor + liquid) equilibria of three (CO{sub 2} + C{sub 5} alcohol) binary systems were measured. Complementary data are reported at (313, 323 and 333) K and from (2 to 11) MPa. No liquid immiscibility was observed at the temperatures and pressures studied. Experimental data were correlated with the PR-EoS and the van de Waals mixing rules. Correlation results showed relative deviations {<=}8 % (liquid) and {<=}2 % (vapor). - Abstract: Complementary isothermal (vapor + liquid) equilibria data are reported for the (CO{sub 2} + 3-methyl-2-butanol), (CO{sub 2} + 2-pentanol), and (CO{sub 2} + 3-pentanol) binary systems at temperatures of (313, 323, and 333) K, and at pressure range of (2 to 11) MPa. For all (CO{sub 2} + alcohol) systems, it was visually monitored that there was no liquid immiscibility at the temperatures and pressures studied. The experimental data were correlated with the Peng-Robinson equation of state using the quadratic mixing rules of van der Waals with two adjustable parameters. The calculated (vapor + liquid) equilibria compositions were found to be in good agreement with the experimental data with deviations for the mole fractions <8% and <2% for the liquid and vapor phase, respectively.
Experimental investigation of phase equilibria in the Co–Si–Zr ternary system
International Nuclear Information System (INIS)
Highlights: •Two isothermal sections of the Co–Si–Zr system were experimentally determined. •The compositions of two ternary compounds (Zr5Co8Si9 and Zr4Co4Si7) were confirmed. •The solubility of Si in the Co23Zr6 phase at 1273 K is large (about 27.5 at.%). -- Abstract: The phase equilibria in the Co–Si–Zr ternary system were investigated by means of back-scattered electron (BSE), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Two isothermal sections of the Co–Si–Zr ternary system at 1273 and 1373 K were experimentally established, and the compositions of the two ternary compounds (Zr5Co8Si9 and Zr4Co4Si7) were confirmed. The isothermal sections of the system at 1273 and 1373 K respectively consist of 29 and 30 three-phase regions, and also six ternary compounds was found in both two isothermal sections. The solubility of Zr in the intermediate and solution phases (i.e. αCo2Si, αCoSi, CoSi2, αCo and εCo) at the Co–Si side is extremely small, whereas the situation of Si in the Co-rich corner (especially for Co23Zr6 and Co2Zr phases) is reverse
Phase equilibria of the Sn–Si–Ti system at 900 and 1200 °C
Energy Technology Data Exchange (ETDEWEB)
Liu, Ya; Dong, Zhen; Peng, Haoping; Wu, Changjun; Wang, Jianhua; Su, Xuping, E-mail: sxping@cczu.edu.cn
2015-09-05
Highlights: • The isothermal sections of the Sn–Si–Ti system at 900 and 1200 °C were determined. • Ternary intermediate phase τ, with a tetragonal W{sub 5}Si{sub 3}-type structure, can be stable up to at least 1200 °C. • Eleven three-phase equilibria were determined at each temperature. - Abstract: Phase relations in the ternary Sn–Si–Ti system were established for the whole composition range for two temperatures, 900 and 1200 °C, by X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopic. The results indicate that the previously reported compound τ is the only ternary intermediate phase, which can be stable up to at least 1200 °C and remains a tetragonal W{sub 5}Si{sub 3}-type structure. No Si solubility was found in Ti{sub 6}Sn{sub 5} phase, and no Sn solubility was found in the Si–Ti binary phases except for Ti{sub 5}Si{sub 3} at either temperature.
Complex equilibria, speciation, and heteroprotein coacervation of lactoferrin and β-lactoglobulin.
Flanagan, Sean E; Malanowski, Alexander J; Kizilay, Ebru; Seeman, Daniel; Dubin, Paul L; Donato-Capel, Laurence; Bovetto, Lionel; Schmitt, Christophe
2015-02-10
There has been a resurgence of interest in complex coacervation, a form of liquid-liquid phase separation (LLPS) in systems of oppositely charged macroions, but very few reports describe the somewhat anomalous coacervation between acidic and basic proteins, which occurs under very narrow ranges of conditions. We sought to identify the roles of equilibrium interprotein complexes during the coacervation of β-lactoglobulin dimer (BLG2) with lactoferrin (LF) and found that this LLPS arises specifically from LF(BLG2)2. We followed the progress of complexation and coacervation as a function of r, the LF/BLG molar ratio, using turbidity to monitor the degree of coacervation and proton release and dynamic light scattering (DLS) to assess the stoichiometry and abundance of complexes. Isothermal titration calorimetry (ITC) showed that initial complex formation is endothermic, but a large exotherm related to coacervate formation obscured other regions. On the basis of turbidimetry, proton release, and DLS, we propose a speciation diagram that presents the abundance of various complexes as a function of r. Although multiple species could be simultaneously present, distinct regions could be identified corresponding to equilibria among particular protein pairs. PMID:25565379
Experimental investigation of the phase equilibria in the Co-Fe-Ti ternary system
International Nuclear Information System (INIS)
Phase equilibria in the Co-Fe-Ti ternary system were investigated by means of the equilibrated alloy method with X-ray powder diffraction and electron probe microanalysis. No ternary compounds were found. The experimental results indicated the existence of seven two-phase and one three-phase regions at 600 C, five two-phase and two three-phase regions at 800 C, and six two-phase and two three-phase regions at 950 C. The solubility of Co in TiFe2 was determined to be larger than 54 at.% at all investigated temperatures, and the solubilities of Fe in TiCo3 and Ti2Co showed an appreciable increase with increasing temperature. The three-phase equilibrium in the Ti-rich corner at 800 C was revealed to be ((β-Ti) + Ti(Fe, Co) + Ti2Co) rather than ((α-Ti) + Ti(Fe, Co) + Ti2Co) reported in previous investigations. Based on the experimental data obtained in the present work, three isothermal sections at 600, 800 and 950 C were established.
Energy Technology Data Exchange (ETDEWEB)
Li, J.; Guo, Y.H. [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Yang, S.Y.; Shi, Z.; Wang, C.P. [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005 (China); Liu, X.J., E-mail: lxj@xmu.edu.cn [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005 (China)
2015-09-05
Highlights: • The sections of Nb–Si–Zr system at 1373, 1473 and 1573 K were determined. • Large solubilities of Nb in αZr{sub 5}Si{sub 4}, Zr{sub 3}Si{sub 2} and Zr{sub 2}Si phases were observed. • The thermodynamic assessment of Nb–Si–Zr ternary system was carried out. - Abstract: In this study, the phase equilibria of Nb–Si–Zr at 1373 K, 1473 K and 1573 K were experimentally determined by means of back-scattered electron (BSE), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that there were five three-phase regions and sixteen two-phase regions in the studied isothermal sections, and no any ternary compounds were found. The solubility of Si in the Nb–Zr side is very small. Large solubilities of Nb in αZr{sub 5}Si{sub 4}, Zr{sub 3}Si{sub 2} and Zr{sub 2}Si phases were observed, otherwise the solubilities of Nb in ZrSi{sub 2}, αZrSi and Zr{sub 3}Si phases are relatively small. Based on the present experimental results, the thermodynamic assessment of Nb–Si–Zr system was carried out using the CALPHAD (Calculation of Phase Diagrams) method. The current calculated phase diagrams are in reasonable agreement with the present experimental data.
International Nuclear Information System (INIS)
Highlights: • The sections of Nb–Si–Zr system at 1373, 1473 and 1573 K were determined. • Large solubilities of Nb in αZr5Si4, Zr3Si2 and Zr2Si phases were observed. • The thermodynamic assessment of Nb–Si–Zr ternary system was carried out. - Abstract: In this study, the phase equilibria of Nb–Si–Zr at 1373 K, 1473 K and 1573 K were experimentally determined by means of back-scattered electron (BSE), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that there were five three-phase regions and sixteen two-phase regions in the studied isothermal sections, and no any ternary compounds were found. The solubility of Si in the Nb–Zr side is very small. Large solubilities of Nb in αZr5Si4, Zr3Si2 and Zr2Si phases were observed, otherwise the solubilities of Nb in ZrSi2, αZrSi and Zr3Si phases are relatively small. Based on the present experimental results, the thermodynamic assessment of Nb–Si–Zr system was carried out using the CALPHAD (Calculation of Phase Diagrams) method. The current calculated phase diagrams are in reasonable agreement with the present experimental data
Phase equilibria of the Sn–Si–Ti system at 900 and 1200 °C
International Nuclear Information System (INIS)
Highlights: • The isothermal sections of the Sn–Si–Ti system at 900 and 1200 °C were determined. • Ternary intermediate phase τ, with a tetragonal W5Si3-type structure, can be stable up to at least 1200 °C. • Eleven three-phase equilibria were determined at each temperature. - Abstract: Phase relations in the ternary Sn–Si–Ti system were established for the whole composition range for two temperatures, 900 and 1200 °C, by X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopic. The results indicate that the previously reported compound τ is the only ternary intermediate phase, which can be stable up to at least 1200 °C and remains a tetragonal W5Si3-type structure. No Si solubility was found in Ti6Sn5 phase, and no Sn solubility was found in the Si–Ti binary phases except for Ti5Si3 at either temperature
Experimental determination of the phase equilibria in the Co–Cr–Ta ternary system
International Nuclear Information System (INIS)
Highlights: • Three isothermal sections at 800, 1000, and 1100 °C were established. • A large solubility of Cr is identified in the Co6Ta7 phase. • The high–temperature phase (Co,Cr)2Ta(HT) was found to be stabilized at low temperatures. - Abstract: The phase equilibria in the Co–Cr–Ta ternary system were experimentally investigated by using backscattered electron (BSE), wavelength dispersive X-ray analyzer (WDX) and X-ray diffraction (XRD). Three isothermal sections of the Co–Cr–Ta ternary system at 800 °C, 900 °C and 1100 °C were experimentally determined. The experimental results show that: (1) No ternary compound is found in this system; (2) A large solubility of Cr is identified in the Co6Ta7 phase; (3) The (Co, Cr)2Ta(HT) phase is stabilized at temperatures below it stability limits in Co–Ta and Cr–Ta binary systems in the range of Cr concentrations from 4 to 61 at.% and from 24 to 41 at.% Ta
The Zr-Ti-Cr system. Equilibria at 900 and 1100 C degrees
International Nuclear Information System (INIS)
Main contributions to the knowledge of the ternary system Zr-Ti-Cr were published in the sixties. Stability domains of phases at temperatures between 500 and 1400 C degrees were there presented. Here, results related to the phase diagram at 900 and 1100 C degrees are informed. Three alloys with 40 at.% Cr and different Zr/Ti ratios and one more, richer in Cr, were elaborated. Specimens of the alloys were heat treated 1000 and 800 h at 900 and 1100 C degrees respectively. Phase characterizations were performed by optic metallography and X-ray diffraction analysis. Compositions were determined by microprobe. Alloys with 40 at.% Cr at both temperatures have biphasic equilibria between the intermetallic Laves phase AB2 and the body-centered cubic solid solution containing principally zirconium and titanium. The Cr-rich alloy presents equilibrium of the AB2 compound and the Cr-rich solid solution. Results of the present and previous works are used in order to propose new isothermal sections at 900 and 1100 C degrees. (author)
Experimental investigation of the phase equilibria in the Co-Fe-Ti ternary system
Energy Technology Data Exchange (ETDEWEB)
Yuan, Chaohui; Chen, Chong; Peng, Yingbiao; Du, Yong; Li, Kun [Central South Univ., State Key of Powder Metallurgy, Changsha (China); Lu, Xingxu [Central South Univ., State Key of Powder Metallurgy, Changsha (China); Central South Univ., School of Materials Science and Engineering, Changsha (China)
2015-08-15
Phase equilibria in the Co-Fe-Ti ternary system were investigated by means of the equilibrated alloy method with X-ray powder diffraction and electron probe microanalysis. No ternary compounds were found. The experimental results indicated the existence of seven two-phase and one three-phase regions at 600 C, five two-phase and two three-phase regions at 800 C, and six two-phase and two three-phase regions at 950 C. The solubility of Co in TiFe{sub 2} was determined to be larger than 54 at.% at all investigated temperatures, and the solubilities of Fe in TiCo{sub 3} and Ti{sub 2}Co showed an appreciable increase with increasing temperature. The three-phase equilibrium in the Ti-rich corner at 800 C was revealed to be ((β-Ti) + Ti(Fe, Co) + Ti{sub 2}Co) rather than ((α-Ti) + Ti(Fe, Co) + Ti{sub 2}Co) reported in previous investigations. Based on the experimental data obtained in the present work, three isothermal sections at 600, 800 and 950 C were established.
Stability of relativistic laminar flow equilibria for electrons drifting in crossed fields
International Nuclear Information System (INIS)
The stability of the electron flow in magnetically insulated transmission lines and diodes, and in microwave devices is an important issue. Presented in this paper are the results of an electromagnetic, linear stability analysis of transverse magnetic waves propagating along the direction of electron drift in a planar system described by a relativistic laminar flow equilibrium. In general, this equilibrium features cold electrons executing E x B drifts in self-consistently calculated electromagnetic fields. For this paper, a class of laminar flow equilibria in which the relativistic plasma and cyclotron frequencies are multiples of one another was chosen, and the electrons were taken to be confined to a layer placed in a vacuum gap between two conductors. This configuration is driven unstable by two separate mechanisms which tap the free energy associated with the sheared velocity field of the layer. At long wavelengths, the interaction of positive and negative energy surface waves results in the diocotron instability. At shorter wavelengths, the interaction of surface waves and sheets of electrons resonant at the local Doppler-shifted cyclotron frequencies leads to a pair of unstable branches of the dispersion relation which are referred to collectively as the magnetron instability. The scaling of the growth rates with equilibrium parameters and the relative importance of the two instabilities are discussed
DETERMINATION OF SOLID-LIQUID EQUILIBRIA DATA FOR MIXTURES OF HEAVY HYDROCARBONS IN A LIGHT SOLVENT
Energy Technology Data Exchange (ETDEWEB)
F.V. Hanson; J.V. Fletcher; Karthik R.
2003-06-01
A methodology was developed using an FT-IR spectroscopic technique to obtain solid-liquid equilibria (SLE) data for mixtures of heavy hydrocarbons in significantly lighter hydrocarbon diluents. SLE was examined in multiple Model Oils that were assembled to simulate waxes. The various Model oils were comprised of C-30 to C-44 hydrocarbons in decane. The FT-IR technique was used to identify the wax precipitation temperature (WPT). The DSC technique was also used in the identification of the onset of the two-phase equilibrium in this work. An additional Model oil made up of C-20 to C-30 hydrocarbons in decane was studied using the DSC experiment. The weight percent solid below the WPT was calculated using the FT-IR experimental results. The WPT and the weight percent solid below the WPT were predicted using an activity coefficient based thermodynamic model. The FT-IR spectroscopy method is found to successfully provide SLE data and also has several advantages over other laboratory-based methods.
International Nuclear Information System (INIS)
A thermodynamic equilibrium between aluminum and oxygen along with the inclusion morphology in Fe-16%Cr stainless steel was investigated to understand the fundamentals of aluminum deoxidation technology for ferritic stainless steels. Further, the effects of calcium addition on the changes in chemistry and morphology of inclusions were discussed. The measured results for aluminum-oxygen equilibria exhibit relatively good agreement with the calculated values, indicating that the introduction of the first- and second-order interaction parameters, recently reported, is reasonable to numerically express aluminum deoxidation equilibrium in a ferritic stainless steel. In the composition of dissolved aluminum content greater than about 60 ppm, pure alumina particles were observed, while the alumino-manganese silicates containing Cr2O3 were appeared at less than 20 mass ppm of dissolved aluminum. The formation of calcium aluminate inclusions after Ca treatment could be discussed based on the thermodynamic equilibrium with calcium, aluminum, and oxygen in the steel melts. In the composition of steel melt with relatively high content of calcium and low aluminum, the log(XCaO/XAl2O3) of inclusions linearly increases with increasing the log [aCa/aAl2·aO2] with the slope close to unity. However, the slope of the line is significantly lower than the expected value in the composition of steel melt with relatively low calcium and high aluminum contents
Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C
Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen
2016-07-01
The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.
Energy Technology Data Exchange (ETDEWEB)
Alonso, Victor; Garcia, Mario [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Gonzalez, Juan Antonio, E-mail: jagl@termo.uva.es [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Garcia De La Fuente, Isaias; Cobos, Jose Carlos [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain)
2011-07-10
Highlights: {yields} LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. {yields} UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. {yields} For the latter mixtures, UCST increases with the size of the alkyl group attached. {yields} Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.
Vrabec, J; Buchhauser, U; Meyer-Pittroff, R; Hasse, H
2009-01-01
For the design and optimization of CO2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry's law constants, are proposed for the ternary mixture N2+O2+CO2. Pure substance parameters of the Peng-Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to experimental binary VLE data. The Peng-Robinson EOS describes both binary and ternary experimental data well, except at high pressures approaching the critical region. A molecular model is validated by simulation using binary and ternary experimental VLE data. On the basis of this model, the Henry's law constants of N2 and O2 in CO2 are predicted by molecular simulation. An easy-to-use thermodynamic model, based on those Henry's law constants, is developed to reliably describe the VLE in the CO2-rich region.
Calculation of α/γ equilibria in SA508 grade 3 steels for intercritical heat treatment
International Nuclear Information System (INIS)
An attempt has been made to suggest an optimum temperature for intercritical heat treatment of an SA508 grade 3 steel for nuclear pressure vessels, based on thermodynamic calculation of the α/γ phase equilibria. A thermodynamic database constructed for the Fe-Mn-Ni-Mo-Cr-Si-V-Al-C-N ten-component system and an empirical criterion that the amount of reformed austenite should be around 40 pct were used for thermodynamic calculation and derivation of the optimum heat-treatment temperature, respectively. The calculated optimum temperature, 720 C, was in good agreement with an experimentally determined temperature of 725 C obtained through an independent experimental investigation of the same steel. The agreement between the calculated and measured fraction of reformed austenite during the intercritical heat treatment was also confirmed. Based on the agreement between calculation and experiment, it could be concluded that thermodynamic calculations can be successfully applied to the materials and/or process design as an additive tool to the already established technology, and that the currently constructed thermodynamic database for steel systems shows an accuracy that makes such applications possible
International Nuclear Information System (INIS)
Highlights: ► A ternary system (water + dodecane + propylene glycol n-propyl ether) was chosen. ► LLE data for this ternary system were determined at T = (288.15, 298.15, and 308.15) K. ► The system exists one three-liquid-phase-coexisting tie triangle at T = 298.15 K. ► The NRTL model was applied to correlate the experimental data. - Abstract: The (liquid + liquid) equilibria of a ternary system (water + dodecane + propylene glycol n-propyl ether) were measured at T = (288.15, 298.15, and 308.15) K under atmospheric pressure. At T = 298.15 K, the system exhibits one three-liquid-phase-coexisting tie triangle and three two-liquid-phase-coexisting envelopes in the triangle phase diagram. There is only one two-liquid-phase-coexisting envelope in the triangle phase diagram at T = (288.15 and 308.15) K. The experimental data were further correlated with the NRTL model.
Phase equilibria and thermodynamic functions for Ag–Hg and Cu–Hg binary systems
International Nuclear Information System (INIS)
Highlights: ► The thermodynamic properties of Ag–Hg and Cu–Hg are explored in order to facilitate dental materials design. ► A self-consistent set of thermodynamic parameters is obtained. ► The experimental information can be well reproduced by the optimized thermodynamic data. - Abstract: In order to facilitate the computational design of new amalgams for novel dental alloys, the phase equilibria, phase diagrams and thermodynamic functions for Ag–Hg and Cu–Hg binary systems are explored in this work, based on the CALPHAD framework and experimental characterizations. The Gibbs free energies of the solution phases as well as the stoichiometric phases are calculated, with the aid of enthalpies of mixing, activities, enthalpies of formation, and phase equilibrium data. The thermodynamic descriptions provided in this work enable the stabilities of each phase at various temperatures and compositions to be well described, which contribute to the establishment of a general database to design novel metallic dental materials.
Kinetic Simulations of the Lowest-order Unstable Mode of Relativistic Magnetostatic Equilibria
Nalewajko, Krzysztof; Zrake, Jonathan; Yuan, Yajie; East, William E.; Blandford, Roger D.
2016-08-01
We present the results of particle-in-cell numerical pair plasma simulations of relativistic two-dimensional magnetostatic equilibria known as the “Arnold–Beltrami–Childress” fields. In particular, we focus on the lowest-order unstable configuration consisting of two minima and two maxima of the magnetic vector potential. Breaking of the initial symmetry leads to exponential growth of the electric energy and to the formation of two current layers, which is consistent with the picture of “X-point collapse” first described by Syrovatskii. Magnetic reconnection within the layers heats a fraction of particles to very high energies. After the saturation of the linear instability, the current layers are disrupted and the system evolves chaotically, diffusing the particle energies in a stochastic second-order Fermi process, leading to the formation of power-law energy distributions. The power-law slopes harden with the increasing mean magnetization, but they are significantly softer than those produced in simulations initiated from Harris-type layers. The maximum particle energy is proportional to the mean magnetization, which is attributed partly to the increase of the effective electric field and partly to the increase of the acceleration timescale. We describe in detail the evolving structure of the dynamical current layers and report on the conservation of magnetic helicity. These results can be applied to highly magnetized astrophysical environments, where ideal plasma instabilities trigger rapid magnetic dissipation with efficient particle acceleration and flares of high-energy radiation.
Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions.
Domańska, Urszula; Marciniak, Andrzej; Królikowski, Marek
2008-01-31
Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated. PMID:18179194
Global gyrokinetic models for energetic particle driven Alfvén instabilities in 3D equilibria
Spong, Don; Holod, Ihor
2015-11-01
The GTC global gyrokinetic PIC model has been adapted to 3D VMEC equilibria and provides a new method for the analysis of Alfvénic instabilities in stellarators, 3D tokamaks, and helical RFP states. The gyrokinetic orderings (k||/k⊥ applicable to a range of energetic particle driven instabilities that have been observed in 3D configurations. Applications of this model to stellarators have indicated that a variety of different Alfvén instabilities can be excited, depending on the toroidal mode number, fast ion average energy and fast ion density profile. Both an LHD discharge where bursting n = 1 Alfvén activity in the TAE gap was observed and a W7-X case have been examined. TAE,/EAE/GAE modes have been found in the simulations, depending on the mode family and fast ion profiles used. The dynamical evolution of the instabilities shows the field period coupling between n and n + Nfp expected for a stellarator. The development of gyrofluid reduced models that can capture relevant physics aspects of the gyrokinetic models will also be discussed. Research sponsored by the U.S. Department of Energy under Contract DE-AC05-00OR22725 with UT-Battelle, LLC and the GSEP SciDAC Center.
Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro
2015-10-01
We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.
International Nuclear Information System (INIS)
Highlights: → LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. → UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. → For the latter mixtures, UCST increases with the size of the alkyl group attached. → Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.
Fusion burn equilibria sensitive to the ratio between energy and helium transport
International Nuclear Information System (INIS)
An analysis of the burn equilibria of fusion reactors of the tokamak family is presented. The global (zero-dimensional) analysis is self-consistent in that it takes into account the dependence of the energy confinement on the variables of the burning plasma, such as temperature and density. Universal burn contours are presented for a selection of commonly used scaling laws for energy confinement. It is shown that the output power of a fusion reactor is to good approximation inversely proportional to the particle confinement time, due to the choking effect of the accumulation of helium, the ash of the fusion reaction. It is further shown that, whereas a fusion reactor requires a minimum energy confinement time to ignite, the output power reaches a maximum for an energy confinement that lies about 30% above this minimum. Further improvement of confinement will lower the output, although in some cases the β limit will be the limiting factor. Given that for maximum performance density the confinement and fuel mix are best chosen to be optimal, the particle confinement is proposed as an attractive parameter for burn control. (letter)
Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation
International Nuclear Information System (INIS)
Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings. (paper)
Solvent isotope effects on tautomerization equilibria of papain and model thiolamines
International Nuclear Information System (INIS)
The state of ionization of the active site sulfhydryl group of papain at the pH-optimum of activity (pH approximately 6.5) remains a controversial issue. An alternative approach to the problem is reported here which utilizes the difference between the isotopic fractionation factor of the S-H bond (phi approximately equal to 0.4) and the N-H bond (phi = 0.97). In principle, the tautomerization equilibrium should be subject to an inverse solvent deuterium isotope effect in which the non-ionised form is more stable relative to the ionised form in D2O compared to H2O (K(H2O)/K(D2O) = phisub(SH)/phisub(MH) approximately equal to 0.4). This priniciple has been successfully tested on the tautomerization equilibria of cysteine and β-mercaptoethylamine from spectrophotometric titrations. To the extent that these simple thiolamines model the spectral properties of the tautomeric species envisioned in the active site of papain, the tautomerization equilibrium constant for papain is estimated (K(H2O) approximately equal to 2) from a comparison of the effect of solvent D2O on the mercaptide ion spectra of the thiolamines and the mercaptide ion-like difference absorption spectrum of papain. (Auth.)
Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation
Denton, Alan R.; Schmidt, Michael P.
2013-03-01
Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings.
Phase equilibria in the Co–Ti–V system at 873 K
International Nuclear Information System (INIS)
Highlights: • The 873 K isothermal section of Co–Ti–V ternary system is determined. • Nine three-phase equilibria are experimentally measured. • All of Co–V and Co–Ti binary phases show large ternary solubility. • The maximum solid solubility of Ti, Co, V in binary phases is determined. - Abstract: The isothermal section of the Co–Ti–V ternary system at 873 K has been investigated by means of diffusion triple together with electron probe microanalysis technique. Series of tie lines and tie-triangles have been determined and the isothermal section at 873 K has been established, and nine three-phase fields have been figured out. It is found that VCo3, VCo, TiCo3, TiCo2(h), TiCo2(c) and TiCo have range of homogeneity at 873 K, and the V3Co and Ti2Co are line compounds. The solid solubility of Ti in VCo3, VCo and V3Co is about 5.2 at.% Ti, 8.8 at.% Ti and 6.9 at.% Ti, and that of V in TiCo3, TiCo2(h), TiCo2(c), TiCo and Ti2Co is about 6.1 at.% V, 3.7 at.% V, 3.0 at.% V, 9.3 at.% V and 6.6 at.% V, respectively
Experimental investigation of phase equilibria in the Cu–Ni–Si ternary system
International Nuclear Information System (INIS)
Highlights: •Three isothermal sections of the Cu–Ni–Si system have been investigated. •The ternary compound τ1 and the liquid phase are confirmed at 1073 K. •The γ (Cu5Si) and θ (Ni2Si) phases can be stabilized at higher or lower temperatures. -- Abstract: The phase equilibria in the Cu–Ni–Si ternary system have been investigated experimentally by means of electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis on equilibrated ternary alloys. Three isothermal sections at 1073, 1173 and 1273 K are determined in the whole composition range. The existence of liquid phase and the ternary compound τ1 is confirmed at 1073 K. The binary γ (Cu5Si), γ (Ni31Si12), δ (Ni2Si) and θ (Ni2Si) phases exhibit a considerable solubility of a third element. In addition, the γ (Cu5Si) and θ (Ni2Si) phases can be stabilized by the addition of Ni and Cu, respectively
The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O
Anovitz, Lawrence M.; Treiman, A.H.; Essene, E.J.; Hemingway, B.S.; Westrum, E.F., Jr.; Wall, V.J.; Burriel, R.; Bohlen, S.R.
1985-01-01
Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO3) from 5 to 1000 K. These measurements yield S2980 = 108.9 J/(mol ?? K). Calculations from published experimental data on the reduction of ilmenite yield ??2980(I1) = -1153.9 kJ/(mol ?? K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of f{hook}O2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookitess and hematite-ilmenitess. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling. ?? 1985.
Directory of Open Access Journals (Sweden)
MIRJANA P. VOJIC
2005-02-01
Full Text Available The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25 ºC at a constant ionic strength of 0.1M(NaCl. The acidity constant Ka1 was determined by potentiometric (pKa1 3.20 and spectrophotometric (pKa1 3.26 methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.
Chemical Sciences Division annual report, 1990
International Nuclear Information System (INIS)
This report contains sections on the following topics: photochemistry of materials in the stratosphere, energy transfer and structural studies of molecules on surfaces, crossed molecular beams, molecular interactions, theory of atomic and molecular collision processes, selective photochemistry, photodissociation of free radicals, physical chemistry with emphasis on thermodynamic properties, chemical physics at the high photon energies, high-energy atomic physics, atomic physics, high-energy oxidizers and delocalized-electron solids, catalytic hydrogenation of CO, transition metal-catalyzed conversion of CO, NO, H2, and organic molecules to fuels and petrochemicals, formation of oxyacids of sulfur from SO2, potentially catalytic and conducting polyorganometallics, actinide chemistry, and molecular thermodynamics for phase equilibria in mixtures
Chemical Sciences Division annual report, 1990
Energy Technology Data Exchange (ETDEWEB)
1991-08-01
This report contains sections on the following topics: photochemistry of materials in the stratosphere, energy transfer and structural studies of molecules on surfaces, crossed molecular beams, molecular interactions, theory of atomic and molecular collision processes, selective photochemistry, photodissociation of free radicals, physical chemistry with emphasis on thermodynamic properties, chemical physics at the high photon energies, high-energy atomic physics, atomic physics, high-energy oxidizers and delocalized-electron solids, catalytic hydrogenation of CO, transition metal-catalyzed conversion of CO, NO, H{sub 2}, and organic molecules to fuels and petrochemicals, formation of oxyacids of sulfur from SO{sub 2}, potentially catalytic and conducting polyorganometallics, actinide chemistry, and molecular thermodynamics for phase equilibria in mixtures.
International Nuclear Information System (INIS)
Phase equilibria of the CaO–Al2O3–CaS and the CaO–SiO2–CaS systems were experimentally investigated using equilibration and quenching techniques. Equilibrium phases were analyzed by means of electron probe X-ray microanalysis, X-ray diffraction analysis and differential thermal analysis. Solubility limits of all solid phases in these liquid oxysulfide phases were successfully constructed in the temperature range investigated in the present study (1500–1600 °C). In order to supplement understanding the phase equilibria, a thermodynamic modeling of these liquid oxysulfides was conducted by taking into account strong chemical short-range ordering (SRO) in the framework of the modified quasichemical model in the quadruplet approximation. As for the solubility of CaS in the liquid oxysulfides, the solubility increases with increase in CaO in the case of the CaO–Al2O3–CaS system, whereas it decreases with increase in CaO in the case of the CaO–SiO2–CaS system. Such opposite behavior is explained by differences in the effect of the SRO in different liquid phases. It is shown that consideration for the SRO in the thermodynamic modeling is essential in order to properly describe the Gibbs energy of the liquid oxysulfide phase. Using the thermodynamic model and the database developed in the present study, liquidus projections of these oxysulfide systems are proposed for the first time.
Dolejs, David
The progressive enrichment in volatiles and light incompatible elements observed during upper-crustal differentiation of granitic and rhyolitic magmas leads to significant changes in melt physical-chemical properties and has important implications for ore deposition and volcanic devolatization. Thermodynamic calculations and experimental studies of melting equilibria in the Na 2O-K2O-Al2O3-SiO2-F 2O-1-H2O system are used to evaluate mineral stabilities, fluid compositions, the extent of fluoride-silicate liquid-liquid immiscibility, fluorine and water solubility limits and differentiation paths of natural fluorine-bearing silicic magmas. The interaction of fluorine with rock-forming aluminosilicates corresponds to progressive fluorination by the thermodynamic component F2O-1. Formation of fluorine-bearing minerals first occurs in peralkaline and silica-undersaturated systems that buffer fluorine concentrations at very low levels (villiaumite, fluorite). The highest concentrations of fluorine are achieved in peraluminous silica-oversaturated systems, saturated with fluorite or topaz. Thermodynamic models of fluorosilicate melts indicate clustering of silicate tetrahedra in the Na2O-SiO 2-F2O-1 system, whereas initial NaAl-F short-range order evolves into partial O-F disorder in the albite-cryolite system. Experiments performed at 520-1100°C and 0.1-100 MPa completely describe liquidus relations and differentiation paths of fluorine-bearing felsic magmas. Coordination differences and short-range order effects between [NaAl]-F, Na-F vs. Si-O lead to the fluoride-silicate liquid immiscibility, which extends from the silica-cryolite binary through the peralkaline albite-silica-cryolite ternary and closes in multicomponent, topaz-bearing systems owing to the destabilizing effect of increasing peraluminosity. Liquidus relations indicate that fluoride-silicate liquid-liquid immiscibility is inaccessible to quartz-feldspar-saturated granitic melts. Differentiation paths of
US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...
Chemical speciation code CHEMSPEC and its applications
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The adsorption and migration behavior of a radionuclide in geological media heavily depends on its chemical forms in a given chemical environment.In order to predict the temporal and spatial distribution of radionuclides around a disposal site when its canister is damaged,it is necessary to develop coupled chemical speciation-solute transport models and relevant software.For that reason,we wrote a new chemical speciation program CHEMSPEC.In this paper,the principles and structure of CHEMSPEC are briefly described,and the strategy and algorithms that were used in this code are interpreted in some detail,such as the measures adopted to prevent divergence in iteratively solving the mass balance equations,the "predictor-corrector" algorithm for calculation of the number and quantities of solid species formed,and the alternate use of "freezing" and "defreezing" oxidation states in handling of co-existent redox and precipitation equilibria.Four examples are given to illustrate CHEMSPEC’s features and capabilities.
Rauh, R. David (Inventor)
1990-01-01
A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.
Phase equilibria in the Ni–Al–Ga system at 700 °C
International Nuclear Information System (INIS)
Graphical abstract: - Highlights: • We study phase equilibria in ternary Ni–Al–Ga in the whole concentration range. • Ni(Al,Ga), Ni2(Al,Ga)3, Ni5(Al,Ga)3 extended solid solutions exist in this system. • Isothermal section (700 °C) of the Ni–Al–Ga system has been constructed. • Small additions of Ga increase compressive strength of Ni3(Al,Ga) solid solution. - Abstract: Phase relations in the ternary Ni–Al–Ga system at 700 °C have been established by the X-ray powder diffraction methods. In addition to already known Ni3(Al,Ga) continuous solid solution, Ni(Al,Ga) continuous solid solution as well as Ni2(Al,Ga)3 and Ni5(Al,Ga)3 extended solid solutions were found to exist in this system. It was shown that the ternary Ni2(Al,Ga)3 and Ni5(Al,Ga)3 compounds do not belong to the continuous solid solutions because of two-phase gaps on the Ni2Al3–Ni2Ga3 (∼30–50 at.% Ga) and Ni5Al3–Ni5Ga3 (∼12–25 at.% Ga) isolines at 700 °C. Some crystal structure peculiarities such as atomic ordering–disordering and presence of structural vacancies have been revealed for all solid solutions existing in the Ni–Al–Ga system. It was found that the compressive strength of the Ni3(Al,Ga) solid solution increases with small additions of gallium (about 2.5 at.%). The isothermal section (700 °C) of the ternary Ni–Al–Ga system including four extended solid solutions (Ni3(Al,Ga), Ni5(Al,Ga)3, Ni(Al,Ga) and Ni2(Al,Ga)3) has been constructed and plotted
Multi-Equilibria Regulation Agent-Based Model of Opinion Dynamics in Social Networks
Directory of Open Access Journals (Sweden)
Andreas Koulouris
2013-01-01
Full Text Available This article investigates the Multiple Equilibria Regulation (MER model, i.e., an agent-based simulation model, to represent opinion dynamics in social networks. It relies on a small set of micro-prerequisites (intra-individual balance and confidence bound, leading to emergence of (nonstationary macro-outcomes. These outcomes may refer to consensus, polarization or fragmentation of opinions about taxation (e.g., congestion pricing or other policy measures, according to the way communication is structured. In contrast with other models of opinion dynamics, it allows for the impact of both the regulation of intra-personal discrepancy and the interpersonal variability of opinions on social learning and network dynamics. Several simulation experiments are presented to demonstrate, through the MER model, the role of different network structures (complete, star, cellular automata, small-world and random graphs on opinion formation dynamics and the overall evolution of the system. The findings can help to identify specific topological characteristics, such as density, number of neighbourhoods and critical nodes-agents, that affect the stability and system dynamics. This knowledge can be used to better organize the information diffusion and learning in the community, enhance the predictability of outcomes and manage possible conflicts. It is shown that a small-world organization, which depicts more realistic aspects of real-life and virtual social systems, provides increased predictability and stability towards a less fragmented and more manageable grouping of opinions, compared to random networks. Such macro-level organizations may be enhanced with use of web-based technologies to increase the density of communication and public acceptability of policy measures.
Calculation of continuum damping of Alfvén eigenmodes in tokamak and stellarator equilibria
International Nuclear Information System (INIS)
In an ideal magnetohydrodynamic (MHD) plasma, shear Alfvén eigenmodes may experience dissipationless damping due to resonant interaction with the shear Alfvén continuum. This continuum damping can make a significant contribution to the overall growth/decay rate of shear Alfvén eigenmodes, with consequent implications for fast ion transport. One method for calculating continuum damping is to solve the MHD eigenvalue problem over a suitable contour in the complex plane, thereby satisfying the causality condition. Such an approach can be implemented in three-dimensional ideal MHD codes which use the Galerkin method. Analytic functions can be fitted to numerical data for equilibrium quantities in order to determine the value of these quantities along the complex contour. This approach requires less resolution than the established technique of calculating damping as resistivity vanishes and is thus more computationally efficient. The complex contour method has been applied to the three-dimensional finite element ideal MHD Code for Kinetic Alfvén waves. In this paper, we discuss the application of the complex contour technique to calculate the continuum damping of global modes in tokamak as well as torsatron, W7-X and H-1NF stellarator cases. To the authors' knowledge, these stellarator calculations represent the first calculation of continuum damping for eigenmodes in fully three-dimensional equilibria. The continuum damping of global modes in W7-X and H-1NF stellarator configurations investigated is found to depend sensitively on coupling to numerous poloidal and toroidal harmonics
Calculation of continuum damping of Alfvén eigenmodes in tokamak and stellarator equilibria
Bowden, G. W.; Hole, M. J.; Könies, A.
2015-09-01
In an ideal magnetohydrodynamic (MHD) plasma, shear Alfvén eigenmodes may experience dissipationless damping due to resonant interaction with the shear Alfvén continuum. This continuum damping can make a significant contribution to the overall growth/decay rate of shear Alfvén eigenmodes, with consequent implications for fast ion transport. One method for calculating continuum damping is to solve the MHD eigenvalue problem over a suitable contour in the complex plane, thereby satisfying the causality condition. Such an approach can be implemented in three-dimensional ideal MHD codes which use the Galerkin method. Analytic functions can be fitted to numerical data for equilibrium quantities in order to determine the value of these quantities along the complex contour. This approach requires less resolution than the established technique of calculating damping as resistivity vanishes and is thus more computationally efficient. The complex contour method has been applied to the three-dimensional finite element ideal MHD Code for Kinetic Alfvén waves. In this paper, we discuss the application of the complex contour technique to calculate the continuum damping of global modes in tokamak as well as torsatron, W7-X and H-1NF stellarator cases. To the authors' knowledge, these stellarator calculations represent the first calculation of continuum damping for eigenmodes in fully three-dimensional equilibria. The continuum damping of global modes in W7-X and H-1NF stellarator configurations investigated is found to depend sensitively on coupling to numerous poloidal and toroidal harmonics.
Phase equilibria of the Cu-Ni-Si system at 700 deg. C
International Nuclear Information System (INIS)
Highlights: → The phase diagram of the Cu-Ni-Si system at 700 deg. C was measured for the first time. → The existence of the ternary compound τ1 reported in literature was confirmed. → A new compound τ2-Cu45.8Ni25Si29.2 with no solubility was observed for the first time. → The Ni2SiH compound was found to be stable at 700 deg. C in the ternary system by dissolving Cu. - Abstract: The phase equilibria at the isothermal section of the Cu-Ni-Si system at 700 deg. C were experimentally investigated. Thirty Cu-Ni-Si alloys were prepared by arc melting and annealed at 700 deg. C for 30 or 80 days, and examined with optical microscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and electron probe microanalysis. Twelve three-phase regions were determined. The existence of the ternary compound τ1-Cu56.8-63Ni10.4-16.1Si26.6-27.3 reported in literature was confirmed and a new compound τ2-Cu45.8Ni25Si29.2 with nearly no homogeneity range was observed. The θ-Ni2Si compound, which exists above 820 deg. C in the binary Ni-Si system, was found to be stable at 700 deg. C and the composition range of Cu is 12.7-20.6 at.% Cu. The ternary solubilities of binary compounds were measured and noticeably the Cu56Si11 compound can dissolve Ni up to 21.9 at.%.
Calculation of continuum damping of Alfvén eigenmodes in tokamak and stellarator equilibria
Energy Technology Data Exchange (ETDEWEB)
Bowden, G. W.; Hole, M. J. [Plasma Theory and Modelling, Research School of Physics and Engineering, Australian National University, Acton 2601, Australian Capital Territory (Australia); Könies, A. [Max-Planck-Institut für Plasmaphysik, EURATOM-Association, D-17491 Greifswald (Germany)
2015-09-15
In an ideal magnetohydrodynamic (MHD) plasma, shear Alfvén eigenmodes may experience dissipationless damping due to resonant interaction with the shear Alfvén continuum. This continuum damping can make a significant contribution to the overall growth/decay rate of shear Alfvén eigenmodes, with consequent implications for fast ion transport. One method for calculating continuum damping is to solve the MHD eigenvalue problem over a suitable contour in the complex plane, thereby satisfying the causality condition. Such an approach can be implemented in three-dimensional ideal MHD codes which use the Galerkin method. Analytic functions can be fitted to numerical data for equilibrium quantities in order to determine the value of these quantities along the complex contour. This approach requires less resolution than the established technique of calculating damping as resistivity vanishes and is thus more computationally efficient. The complex contour method has been applied to the three-dimensional finite element ideal MHD Code for Kinetic Alfvén waves. In this paper, we discuss the application of the complex contour technique to calculate the continuum damping of global modes in tokamak as well as torsatron, W7-X and H-1NF stellarator cases. To the authors' knowledge, these stellarator calculations represent the first calculation of continuum damping for eigenmodes in fully three-dimensional equilibria. The continuum damping of global modes in W7-X and H-1NF stellarator configurations investigated is found to depend sensitively on coupling to numerous poloidal and toroidal harmonics.
Chemical reaction network approaches to Biochemical Systems Theory.
Arceo, Carlene Perpetua P; Jose, Editha C; Marin-Sanguino, Alberto; Mendoza, Eduardo R
2015-11-01
This paper provides a framework to represent a Biochemical Systems Theory (BST) model (in either GMA or S-system form) as a chemical reaction network with power law kinetics. Using this representation, some basic properties and the application of recent results of Chemical Reaction Network Theory regarding steady states of such systems are shown. In particular, Injectivity Theory, including network concordance [36] and the Jacobian Determinant Criterion [43], a "Lifting Theorem" for steady states [26] and the comprehensive results of Müller and Regensburger [31] on complex balanced equilibria are discussed. A partial extension of a recent Emulation Theorem of Cardelli for mass action systems [3] is derived for a subclass of power law kinetic systems. However, it is also shown that the GMA and S-system models of human purine metabolism [10] do not display the reactant-determined kinetics assumed by Müller and Regensburger and hence only a subset of BST models can be handled with their approach. Moreover, since the reaction networks underlying many BST models are not weakly reversible, results for non-complex balanced equilibria are also needed. PMID:26363083
Directory of Open Access Journals (Sweden)
A. Yardimeden
2007-08-01
Full Text Available Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and machined materials. Advantages and disadvantages of the chemical machining are mentioned.Design/methodology/approach: In this study, chemical machining process was described its importance as nontraditional machining process. The steps of process were discussed in detail. The tolerances of machined parts were examined.Findings: Paper describes the chemical machining process, industrial applications, applied chemical etchants and machined materials.Practical implications: The machining operation should be carried out carefully to produce a desired geometry. Environmental laws have important effects when chemical machining is used.Originality/value: The importance of nontraditional machining processes is very high.
Bonamonte, Domenico; Vestita, Michelangelo; Romita, Paolo; Filoni, Angela; Foti, Caterina; Angelini, Gianni
2016-01-01
Chemical leukoderma, often clinically mimicking idiopathic vitiligo and other congenital and acquired hypopigmentation, is an acquired form of cutaneous pigment loss caused by exposure to a variety of chemicals that act through selective melanocytotoxicity. Most of these chemicals are phenols and aromatic or aliphatic catechols derivatives. These chemicals, however, are harmful for melanocytes in individuals with an individual susceptibility. Nowadays, chemical leukoderma is fairly common, caused by common domestic products. The presence of numerous acquired confetti- or pea-sized macules is clinically characteristic of chemical leukoderma, albeit not diagnostic. Other relevant diagnostic elements are a history of repeated exposure to a known or suspected depigmenting agent at the sites of onset and a macules distribution corresponding to sites of chemical exposure. Spontaneous repigmentation has been reported when the causative agent is avoided; the repigmentation process is perifollicular and gradual, taking place for a variable period of weeks to months. PMID:27172302
International Nuclear Information System (INIS)
The role of singular currents in three-dimensional toroidal equilibria and their resolution by magnetic island formation is discussed from both analytical and computational points of view. Earlier analytical results are extended to include small vacuum islands, which may, in general, have different phases with respect to pressure-induced islands. In currentless stellarators, the formation of islands is shown to depend on the resistive parameter DR, as well as the integrated effect of global Pfirsch--Schlueter currents. It is demonstrated that the pressure-induced ''self-healing'' effect, recently discovered computationally, is also predicted by analytical theory
Energy Technology Data Exchange (ETDEWEB)
Mekki, Ahmed [Ecole Militaire Polytechnique EMP, BP 17 Bordj-El-Bahri, Alger (Algeria); Khimeche, Kamel, E-mail: kamel.khimeche@yahoo.f [Ecole Militaire Polytechnique EMP, BP 17 Bordj-El-Bahri, Alger (Algeria); Dahmani, Abdallah [Laboratoire de thermodynamique et modelisation moleculaire, Faculte de chimie, USTHB, BP. 32 El-Alia, 1611 Bab-Ezzouar, Alger (Algeria)
2010-08-15
A differential scanning calorimetry (d.s.c.) was used to determine binary (solid + liquid) phase equilibria (SLE) for four binary mixtures, viz. (n-nitrosodiphenylamine + diphenylamine), (2-nitrodiphenylamine + ethyl centralite), (2,4-dinitro-N-ethylaniline + methyl centralite), and (2,4-diphenylamine + 4,4'-dinitroethylcentralite). These compounds are used as stabilizers in gun powders and propellants. Results obtained with this technique are compared with those correlated by NRTL and ideal models. It was found out that all the systems are simple eutectic systems and deviations between experimental and predicted SLE results were observed.
DEFF Research Database (Denmark)
Oliveira, Mariana B.; Freire, Mara G.; Marrucho, Isabel M.;
2007-01-01
-plus-association equation of state (CPA EoS) has been extended to binary mixtures of water with several linear, cyclic, aromatic, and substituted fluorocarbons. The CPA EoS was successfully used to model the liquid-liquid equilibria of aqueous mixtures that contain FCs, while also being able to describe the cross...... dioxide, making them interesting for several biomedical applications. In most of these applications, water or aqueous systems are present for which the knowledge of the mutual solubilities between the fluorocarbons and the aqueous phases is important. In this work, the application of the cubic...
Czech Academy of Sciences Publication Activity Database
Bogdanić, Grozdana; Pavlíček, Jan; Wichterle, Ivan
Praha : Česká společnost chemického inženýrství, 2015, s. 155. ISBN N. [Konference chemického a procesního inženýrství - CHISA 2015 /62./. hotel Jezerka, přehrada Seč (CZ), 09.11.2015-12.11.2015] R&D Projects: GA ČR GA15-19542S Institutional support: RVO:67985858 Keywords : experimental data * vapour-liquid equilibria * systems Subject RIV: CF - Physical ; Theoretical Chemistry
Cooke, Darren; McSweeney, Paul
2014-01-01
The mineral equilibria of milk can have a major influence on the properties of rennet milk gels. The influence of increased Mg, Ca, and Sr concentrations on milk and rennet milk gels was investigated. Reconstituted skim milk was supplemented with MgCl2, CaCl2, or SrCl2 at levels from 2.5–10 mmol.L−1 and adjusted to pH 6.6. Dynamic rheological properties of the renneted milks at 32 °C were investigated during 6-h time sweeps and by frequency sweeps. Whey was separated from rennet gels by centr...
(Liquid plus liquid) equilibria of binary polymer solutions using a free-volume UNIQUAC-NRF model
DEFF Research Database (Denmark)
Radfarnia, H.R.; Ghotbi, C.; Taghikhani, V.;
2006-01-01
+ liquid) equilibria (LLE) for a number of binary polymer solutions at various temperatures. The values for the binary characteristic energy parameters for the proposed model and the FV-UNIQUAC model along with their average relative deviations from the experimental data were reported. It should be stated...... that the binary polymer solutions studied in this work were considered as monodisperse. The results obtained from the FV-UNIQUAC-NRF model were compared with those obtained from the FV-UNIQUAC model. The results of the proposed model show that the FV-UNIQUAC-NRF model can accurately correlate the...... capability in predicting the LCST for binary polymer solutions....
DEFF Research Database (Denmark)
Tsivintzelis, Ioannis; Kontogeorgis, Georgios
2009-01-01
The vapor–liquid equilibria of binary polymer–solvent systems was modeled using the Non-Random Hydrogen Bonding (NRHB) model. Mixtures of poly(ethylene glycol), poly(propylene glycol), poly(vinyl alcohol) and poly(vinyl acetate) with various solvents were investigated, while emphasis was put on...... hydrogen bonding systems, in which functional groups of the polymer chain can self-associate or cross-associate with the solvent molecules. Effort has been made to explicitly account for all hydrogen bonding interactions. The results reveal that the NRHB model offers a flexible approach to account for...
Energy Technology Data Exchange (ETDEWEB)
Gonzalez, E.; Ortega, J. [Univ. of Las Palmas de Gran Canaria (Spain)
1996-01-01
Densities of 298.15 K and the vapor-liquid equilibria for 1-butanol + butyl methanoate, + butyl ethanoate, + butyl propanoate, and + butyl butanoate have been measured at 101.32 kPa in small capacity ebulliometer. All results were found to be thermodynamically consistent with a point-to-point test. The mixtures containing butyl methanoate and butyl ethanoate show azeotropes at T = 379.14 K, x = 0.871 and T = 389.64 K, x = 0.222, respectively. Different group-contribution methods were applied to these mixtures.
DEFF Research Database (Denmark)
Fettouhi, André; Thomsen, Kaj
In the creation of liquefied natural gas the formation of solids play a substantial role, hence detailed knowledge is needed about solid-liquid equilibria (SLE). In this abstract we shortly summarize the work we have carried out at CERE over the past year with SLE for many-component mixtures usin...... the Cubic-Plus-Association (CPA) equation of state. Components used in this work are highly relevant to the oil and gas industry and include light and heavy hydrocarbons, alcohols, water and carbon dioxide....
International Nuclear Information System (INIS)
In this work a comparison between the 226 Ra concentration and its decay products (214 Pb and 214 Bi) in soil samples is presented before and after that the decay mentioned products reach the equilibria with the radium. Moreover, the obtained daughter/father ratio is presented; and the correction factor for the calculus of the 214 Pb and 214 Bi quantification without being necessary to wait until that the secular equilibria has been established. For the quantification of the concentration of the three radionuclides the gamma spectrometry technique was used. (Author)
A General Form of Hybrid Equilibria in Job-Market Signaling Games%工作市场信号博弈混同均衡通式
Institute of Scientific and Technical Information of China (English)
黄怡胜
2001-01-01
提出双混同均衡的概念，作为对混同均衡的推广.基于该概念，给出了工作市场信号博弈混同均衡的一般形式，因而，普通的混同均衡都是它的特例.%The idea of bi-hybrid equilibrium is presented. With this generalized definition of hybrid equilibrium,a general form of hybrid equilibria in job-market signaling games is obstained.Both usual hybrid equilibria are special cases of this form.
Calogero, Francesco
2013-01-01
Some properties of a solvable N-body problem featuring several free parameters ("coupling constants") are investigated. Restrictions on its parameters are reported which guarantee that all its solutions are completely periodic with a fixed period independent of the initial data (isochrony). The restrictions on its parameters which guarantee the existence of equilibria are also identified. In this connection a remarkable second-order ODE—generally not of hypergeometric type, hence not reducible to those characterizing the classical polynomials—is studied: if its parameters satisfy a Diophantine condition, its general solution is a polynomial of degree N, the N zeros of which identify the equilibria of the N-body system.
Thi Wing-Fai
2015-01-01
This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One o...
Directory of Open Access Journals (Sweden)
Lozano, L. J.
2005-10-01
Full Text Available This work focuses on general guidelines to be considered for application of least-squares routines and artificial neural networks (ANN in the estimation of metal distribution equilibria in liquid-liquid extraction process. The goal of the procedure in the statistical method is to find the values of the equilibrium constants (K_{j} for the reactions involved in the metal extraction which minimizes the differences between experimental distribution coefficient (D_{exp} and theoretical distribution coefficients according to the mechanism proposed (D_{theor}- In the first part of the article, results obtained with the most frequently routine reported in the bibliography are compared with those obtained using the algorithms previously discussed. In the second part, the main features of a single back-propagation neural network for the same purpose are discussed, and the results obtained are compared with those obtained with the classical methods.
El trabajo presenta las líneas generales a considerar para la estimación del equilibrio de distribución de metales en procesos de extracción líquido-líquido, según dos métodos: algoritmo clásico de mínimos cuadrados y redes neuronales artificiales. El objetivo del procedimiento, en el caso del método estadístico, es encontrar los valores de las constantes de equilibrio (K_{j} para las reacciones involucradas en la extracción del metal, que minimizan las diferencias entre el coeficiente de distribución experimental y el coeficiente de distribución teórico, de acuerdo al mecanismo propuesto. En la primera parte del artículo se comparan los resultados obtenidos a partir de los algoritmos usados más habitualmente en la bibliografía, con los datos obtenidos mediante el algoritmo previamente descrito. En la segunda parte, se presentan las características fundamentales para aplicar una red neuronal sencilla con algoritmo back-propagation y los
Statistical equilibria of the coupled barotropic flow and shallow water flow on a rotating sphere
Ding, Xueru
The motivation of this research is to build equilibrium statistical models that can apply to explain two enigmatic phenomena in the atmospheres of the solar system's planets: (1) the super-rotation of the atmospheres of slowly-rotating terrestrial planets---namely Venus and Titan, and (2) the persistent anticyclonic large vortex storms on the gas giants, such as the Great Red Spot (GRS) on Jupiter. My thesis is composed of two main parts: the first part focuses on the statistical equilibrium of the coupled barotropic vorticity flow (non-divergent) on a rotating sphere; the other one has to do with the divergent shallow water flow rotating sphere system. The statistical equilibria of these two systems are simulated in a wide range of parameter space by Monte Carlo methods based on recent energy-relative enstrophy theory and extended energy-relative enstrophy theory. These kind of models remove the low temperatures defect in the old classical doubly canonical energy-enstrophy theory which cannot support any phase transitions. The other big difference of our research from previous work is that we work on the coupled fluid-sphere system, which consists of a rotating high density rigid sphere, enveloped by a thin shell of fluid. The sphere is considered to have infinite mass and angular momentum; therefore, it can serve as a reservoir of angular momentum. Unlike the fluid sphere system itself, the coupled fluid sphere system allows for the exchange of angular momentum between the atmosphere and the solid planet. This exchange is the key point in any model that is expected to capture coherent structures such as the super-rotation and GRS-like vortices problems in planetary atmospheres. We discovered that slowly-rotating planets can have super-rotation at high energy state. All known slowly-rotating cases in the solar system---Venus and Titan---have super-rotation. Moreover, we showed that the anticyclonicity in the GRS-like structures is closely associated with the
Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12
Anovitz, Lawrence M.; Essene, E.J.; Metz, G.W.; Bohlen, S.R.; Westrum, E.F., Jr.; Hemingway, B.S.
1993-01-01
The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.
International Nuclear Information System (INIS)
Highlights: • The LLE for n-alkanes and aromatic hydrocarbons in [C8iQuin][SCN] have been determined. • The NRTL equation was used to correlate experimental data. • The influence of the ionic liquid structure on mutual solubility was discussed. -- Abstract: Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C8iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed
International Nuclear Information System (INIS)
FLAPW total energy electronic structure calculations are combined with cluster variation method in order to perform first-principles investigation of phase equilibria for three kinds of Fe-based binary alloy systems, Fe-Ni, Fe-Pd, and Fe-Pt. A particular focus of the present investigation is placed on L10-disorder phase equilibria. The lattice vibration effects are incorporated within the quasi-harmonic approximation via Debye-Gruneisen model. The ground state analysis revealed that magnetism plays a crucial role in the phase stability of each system. The calculated transition temperatures for Fe-Pd and Fe-Pt systems are in close agreement with experimental ones. The lattice vibration effects further improves the accuracy, and it is found that magnetic fine structure also affects the resultant transition temperature in Fe-Pt system. Although L10-ordered phase does not appear as a stable ordered phase in a conventional phase diagram of Fe-Ni system, the present first-principles calculation suggests the possibility of the stabilization of this phase. The effect of the second nearest neighbor pair interactions as well as multibody interactions are investigated
Phase Equilibria of the Ternary Sn-Zn-Co System at 250°C and 500°C
Wang, Chao-hong; Huang, Sheng-en; Huang, Po-yen
2015-12-01
The isothermal sections of the ternary Sn-Zn-Co system (IMCs) are very limited. For the phase equilibria at 250°C, two ternary IMCs, T1 and T2, were found, whose compositions were Sn-25 at.%Zn-25 at.%Co and Sn-15 at.%Zn-41 at.%Co, respectively. For the phase equilibria at 500°C, in addition to the T2 phase, another ternary IMC, namely T3 (Sn-18 at.%Zn-37 at.%Co), was also found. Moreover, the phase stability of the T1 and T3 phases was investigated at temperatures of 260°C to 400°C in detail. The equilibrium phase was the T1 phase below 300°C, and changed to the T3 phase at 400°C. The crystal structures of these three ternary IMCs were also studied. The T1 phase has a cubic structure ( Pm3m), and the T2 and T3 phases are orthorhombic in space group Cmcm and Pnma, respectively.
Kılıç, H.
2010-02-01
The UV-vis spectra of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one, ( I), and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione, ( II) were studied in aqueous methanol (5%, v/v methanol). The nature of the electronic transitions and the roles of carbonyl oxygen of I and thiocarbonyl sulfur of II on the behavior of UV-vis spectra were discussed. Acid-base equilibria of the compounds against varying pH and p Ka values related equilibria were determined at an ionic strength of 0.10 M by using the Henderson-Haselbalch equation. The mean acidity constants for the protonated forms of the compounds were determined as p Ka1 = 5.121, p Ka2 = 7.929 and p Ka3 = 11.130 for I and p Ka1 = 4.684, p Ka2 = 7.245 and p Ka3 = 10.630 for II. The preferred dissociation mechanisms were discussed based on UV-vis data and a mechanism was proposed for each compound.
Experimental study of the phase equilibria in the Mg–Zn–Ag ternary system at 300 °C
International Nuclear Information System (INIS)
Highlights: • The phase equilibria of Mg–Zn–Ag system at 300 °C were determined. • A bcc continuous ternary solid solution forms between MgAg (bcc-B2) and AgZn (bcc-A2) was determined. • The extended solid solubilities of the sub-binary compounds were also determined. - Abstract: The phase equilibria in the Mg–Zn–Ag ternary system at 300 °C were investigated using three diffusion couples and 35 key samples. Scanning electron microscopy (SEM) equipped with energy-dispersive spectroscope (EDS) and X-ray diffraction (XRD) techniques were used for homogeneity ranges and crystal structure determination. Large solid solubility limits, due to substitution among Mg, Zn and Ag atoms in Mg3Ag and MgZn2 phases, were observed in the present work. Solid solubility limits of Ag and Zn in the hcp (Mg) phase were found to be less than 1 at.%. The extended solid solubilities of the Mg12Zn13, Mg2Zn3, MgZn2 (C14), Mg2Zn11, Ag5Zn8 and hcp (AgZn3) sub-binary compounds were also determined in the Mg–Zn–Ag ternary system. In addition, a bcc continuous ternary solid solution forms between MgAg (bcc-B2) and AgZn (bcc-A2) at 300 °C
Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper
Hidayat, Taufiq; Henao, Hector M.; Hayes, Peter C.; Jak, Evgueni
2012-10-01
Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373 K and 1673 K (1100 °C and 1400 °C) and (2) with metallic copper at temperatures between 1373 K and 1573 K (1100 °C and 1300 °C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of "Cu2O"-"Fe2O3"-SiO2 ternary sections. The relationships between the activity of CuO0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.
First-principles calculation of phase equilibria and phase separation of the Fe-Ni alloy system
Institute of Scientific and Technical Information of China (English)
Ying Chen; Shuichi Iwata; Tetsuo Mohri
2006-01-01
Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calculations have proved the stabilization of the L12 phase at 1:3 stoichiometry, which is in agreement with the experimental result,and predicted the existence of L10 as a stable phase below 550 K; this L10 phase has been missing in the conventional phasediagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L10 and L12 order-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion (CTE) is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye-Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed.
Ferraro, N. M.; Jardin, S. C.; Lao, L. L.; Shephard, M. S.; Zhang, F.
2016-05-01
Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.
Zhang, Fan; Hu, Biao; Xu, Honghui; Liu, Shuhong; Zhou, Tao; Jin, Zhanpeng
2015-10-01
The phase equilibria of the Mg-Gd-Mn system at 773 K (500 °C) were investigated with sixteen alloys, by means of X-ray diffraction technique and electron probe microanalyses. Eight three-phase equilibria were accurately determined. No ternary compound was observed at 773 K (500 °C). The solubility of the third elements in the binary phases was measured. The isothermal section of the Mg-Gd-Mn system at 773 K (500 °C) was firstly established. It is worth mentioning that the three-phase field GdMg3-GdMg5-( αMn) was experimentally observed and is different from the three-phase field GdMg3-GdMg5-GdMn12 predicted using only the binary interaction parameters. Using the CALPHAD method, a thermodynamic modeling of the Mg-Gd-Mn system has been carried out in order to reasonably describe the experimental observations. The substitutional solution and sublattice models were used to describe the solution phases and intermediate phases. Comprehensive comparison between the calculated and measured isothermal sections shows that the experimental information is satisfactorily accounted for by the present thermodynamic modeling.
Chemical compatibility between lithium oxide and transition metals
International Nuclear Information System (INIS)
The chemical reactions between Li2O and transition metals (Ti, V, Cr, Mn, Fe, Ni), particularly 316 steel, have been studied up to 1273 K in sealed systems under argon and also under vacuum. Pure Li2O is inherently inert towards transition metals except when such equilibria as 4Li2O + Fe = Li5FeO4 + 3Li 2Li2O + Cr = LiCrO2 + 3Li are disturbed by removal of Li by vacuum or chemical means. The results are rationalised with the known thermodynamics. LiOH impurity has a deleterious effect on the metals and accounts for some of the supposed reactivity of LI2O. It may be possible to inhibit the corrosive reaction of LiOH and LiOT towards steel, and facilitate the release of T2, by introducing metallic lithium. (orig.)
NATO Advanced Study Institute on Advances in Chemical Reaction Dynamics
Capellos, Christos
1986-01-01
This book contains the formal lectures and contributed papers presented at the NATO Advanced Study Institute on. the Advances in Chemical Reaction Dynamics. The meeting convened at the city of Iraklion, Crete, Greece on 25 August 1985 and continued to 7 September 1985. The material presented describes the fundamental and recent advances in experimental and theoretical aspects of, reaction dynamics. A large section is devoted to electronically excited states, ionic species, and free radicals, relevant to chemical sys tems. In addition recent advances in gas phase polymerization, formation of clusters, and energy release processes in energetic materials were presented. Selected papers deal with topics such as the dynamics of electric field effects in low polar solutions, high electric field perturbations and relaxation of dipole equilibria, correlation in picosecond/laser pulse scattering, and applications to fast reaction dynamics. Picosecond transient Raman spectroscopy which has been used for the elucidati...
A. Yardimeden; T. Ozben; O. Cakir
2007-01-01
Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and mac...
Directory of Open Access Journals (Sweden)
S. N. Upadhyay
2005-10-01
Full Text Available Protection of biological systems against radiation damage is of paramount importance during accidental and unavoidable exposure to radiation. Several physico-chemical and biological factors collectively contribute to the damage caused by radiation and are, therefore, targets for developing radioprotectors. Work on the development of chemicals capable of protecting biological systemsfrom radiation damage was initiated nearly six decades ago with cysteine being the first molecule to be reported. Chemicals capable of scavenging free radicals, inducing oxygen depletion,antioxidants and modulators of immune response have been some of the radioprotectors extensively investigated with limited success. Mechanism of action of some chemical radioprotectors and their combinations have been elucidated, while further understanding is required in many instances. The present review elaborates on structure-activity relationship of some of the chemical radioprotectors, their evaluation, and assessment, limitation, and future prospects.
DEFF Research Database (Denmark)
Wilczura-Wachnik, H.; Jonsdottir, Svava Osk
2006-01-01
This paper presents the vapor-liquid (VLE) and liquid-liquid (LLE) phase equilibria predictions for polystyrene in two theta solvents: cyclohexane and methylcyclohexane. VLE calculations were performed with the Elbro free volume method and a modified version of the PC-SAFT method, as well as with...
Tellinghuisen, Joel
2010-01-01
Liquid-vapor, solid-vapor, and solid-liquid-vapor equilibria are studied for the pure substance water, using modern equipment that includes specially fabricated glass cells. Samples are evaporatively frozen initially, during which they typically supercool to -5 to -10 [degrees]C before spontaneously freezing. Vacuum pumping lowers the temperature…
DEFF Research Database (Denmark)
Weber, Roy E.; Bonaventura, J.; Sullivan, B.;
1978-01-01
Oxygen equilibria, ligand-binding kinetics and some other physicochemical properties are reported for erythrocruorins of two intertidal polychaetes:Marphysa sanguinea, which inhabits simple, relatively stagnant burrows, andDiopatra cuprea, which inhabits impermeable, parchment-like tubes that are...
Energy Technology Data Exchange (ETDEWEB)
Hyeong, Seonghoon; Jang, Sunghyun; Kim, Hwayong [Seoul National University, Seoul (Korea, Republic of)
2015-02-15
Isothermal vapor liquid equilibria for the binary system of 3-methylpentane with ethylene glycol monopropyl ether (C{sub 3}E{sub 1}) and ethylene glycol isopropyl ether (iC{sub 3}E{sub 1}) were measured at 303.15, 318.15, and 333.15K. In our previous work, phase equilibria for the binary system of C{sub 3}E{sub 1} mixtures were investigated according to the chain length of alkane, alcohol or those isomer. But in this study, we discussed the different effect of C{sub 3}E{sub 1} and its isomer, iC{sub 3}E{sub 1}, on the phase equilibria. The measured systems were correlated with a Peng-Robinson equation of state (PR EOS) combined with Wong-Sandler mixing rule for the vapor phase, and NRTL, UNIQUAC, and Wilson activity coefficient models for the liquid phase. All the measured systems showed good agreement with the correlation results. And it was found that the phase equilibria showed very little difference between the iC{sub 3}E{sub 1} mixture system and the C{sub 3}E{sub 1} mixture system.
International Nuclear Information System (INIS)
Isothermal vapor liquid equilibria for the binary system of 3-methylpentane with ethylene glycol monopropyl ether (C3E1) and ethylene glycol isopropyl ether (iC3E1) were measured at 303.15, 318.15, and 333.15K. In our previous work, phase equilibria for the binary system of C3E1 mixtures were investigated according to the chain length of alkane, alcohol or those isomer. But in this study, we discussed the different effect of C3E1 and its isomer, iC3E1, on the phase equilibria. The measured systems were correlated with a Peng-Robinson equation of state (PR EOS) combined with Wong-Sandler mixing rule for the vapor phase, and NRTL, UNIQUAC, and Wilson activity coefficient models for the liquid phase. All the measured systems showed good agreement with the correlation results. And it was found that the phase equilibria showed very little difference between the iC3E1 mixture system and the C3E1 mixture system
Czech Academy of Sciences Publication Activity Database
Teodorescu, M.; Barhala, A.; Wichterle, Ivan
2005-01-01
Roč. 49, č. 11 (2005), s. 927-934. ISSN 0035-3930 R&D Projects: GA ČR(CZ) GA104/03/1555; GA AV ČR(CZ) IAA4072102 Institutional research plan: CEZ:AV0Z40720504 Keywords : vapor liquid equilibria * description Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.226, year: 2005
Czech Academy of Sciences Publication Activity Database
Pavlíček, Jan; Bogdanić, Grozdana; Wichterle, Ivan
- : -, 2013. ID-089. ISBN N. [International Conference on Properties and Phase Equilibria for Products and Process Design /13./. 26.05.213-30.05.2013, Iguazu Falls] Institutional support: RVO:67985858 Keywords : polymer * water * activity Subject RIV: CF - Physical ; Theoretical Chemistry http://www.ppeppd2013.plapiqui.edu.ar/openconf.php
Rodriguez-Rodriguez, Cristina; Amigo, Jose Manuel; Coello, Jordi; Maspoch, Santiago
2007-01-01
A spectrophotometric study of the acid-base equilibria of 8-hydroxyquinoline-5-sulfonic acid to describe the multivariate curve resolution-alternating least squares algorithm (MCR-ALS) is described. The algorithm provides a lot of information and hence is of great importance for the chemometrics research.
Energy Technology Data Exchange (ETDEWEB)
Liu, Rui; Cheng, Shuang; Baker, Erin Shammel; Smith, Richard D.; Zeng, Xiao Cheng; Gong, Bing
2016-01-28
Oligoamide 1, consisting of two H-bonding units linked by a trimethylene linker, was previously found to form a very stable, folded dimer. In this work, replacing the side chains and end groups of 1 led to derivatives that show the surprising impact of end groups on the folding and dimer-chain equilibria of the resultant molecules.