WorldWideScience

Sample records for model phase

  1. Modeling of liquid phases

    CERN Document Server

    Soustelle, Michel

    2015-01-01

    This book is part of a set of books which offers advanced students successive characterization tool phases, the study of all types of phase (liquid, gas and solid, pure or multi-component), process engineering, chemical and electrochemical equilibria, and the properties of surfaces and phases of small sizes. Macroscopic and microscopic models are in turn covered with a constant correlation between the two scales. Particular attention has been given to the rigor of mathematical developments. This second volume in the set is devoted to the study of liquid phases.

  2. Modeling of phased array transducers.

    Science.gov (United States)

    Ahmad, Rais; Kundu, Tribikram; Placko, Dominique

    2005-04-01

    Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.

  3. Phase Transition in Tensor Models

    CERN Document Server

    Delepouve, Thibault

    2015-01-01

    Generalizing matrix models, tensor models generate dynamical triangulations in any dimension and support a $1/N$ expansion. Using the intermediate field representation we explicitly rewrite a quartic tensor model as a field theory for a fluctuation field around a vacuum state corresponding to the resummation of the entire leading order in $1/N$ (a resummation of the melonic family). We then prove that the critical regime in which the continuum limit in the sense of dynamical triangulations is reached is precisely a phase transition in the field theory sense for the fluctuation field.

  4. Phase Computations and Phase Models for Discrete Molecular Oscillators.

    OpenAIRE

    Demir, Alper; Şuvak, Önder

    2012-01-01

    RESEARCH Open Access Phase computations and phase models for discrete molecular oscillators Onder Suvak* and Alper Demir Abstract Background: Biochemical oscillators perform crucial functions in cells, e.g., they set up circadian clocks. The dynamical behavior of oscillators is best described and analyzed in terms of the scalar quantity, phase. A rigorous and useful definition for phase is based on the so-called isochrons of oscillators. Phase computation techniques for ...

  5. Phase computations and phase models for discrete molecular oscillators

    Science.gov (United States)

    2012-01-01

    Background Biochemical oscillators perform crucial functions in cells, e.g., they set up circadian clocks. The dynamical behavior of oscillators is best described and analyzed in terms of the scalar quantity, phase. A rigorous and useful definition for phase is based on the so-called isochrons of oscillators. Phase computation techniques for continuous oscillators that are based on isochrons have been used for characterizing the behavior of various types of oscillators under the influence of perturbations such as noise. Results In this article, we extend the applicability of these phase computation methods to biochemical oscillators as discrete molecular systems, upon the information obtained from a continuous-state approximation of such oscillators. In particular, we describe techniques for computing the instantaneous phase of discrete, molecular oscillators for stochastic simulation algorithm generated sample paths. We comment on the accuracies and derive certain measures for assessing the feasibilities of the proposed phase computation methods. Phase computation experiments on the sample paths of well-known biological oscillators validate our analyses. Conclusions The impact of noise that arises from the discrete and random nature of the mechanisms that make up molecular oscillators can be characterized based on the phase computation techniques proposed in this article. The concept of isochrons is the natural choice upon which the phase notion of oscillators can be founded. The isochron-theoretic phase computation methods that we propose can be applied to discrete molecular oscillators of any dimension, provided that the oscillatory behavior observed in discrete-state does not vanish in a continuous-state approximation. Analysis of the full versatility of phase noise phenomena in molecular oscillators will be possible if a proper phase model theory is developed, without resorting to such approximations. PMID:22687330

  6. Phase Field Modeling Using PetIGA

    KAUST Repository

    Vignal, Philippe A.

    2013-06-01

    Phase field modeling has become a widely used framework in the computational material science community. Its ability to model different problems by defining appropriate phase field parameters and relating it to a free energy functional makes it highly versatile. Thermodynamically consistent partial differential equations can then be generated by assuming dissipative dynamics, and setting up the problem as one of minimizing this free energy. The equations are nonetheless challenging to solve, and having a highly efficient and parallel framework to solve them is necessary. In this work, a brief review on phase field models is given, followed by a short analysis of the Phase Field Crystal Model solved with Isogeometric Analysis us- ing PetIGA. We end with an introduction to a new modeling concept, where free energy functions are built with a periodic equilibrium structure in mind.

  7. Langley's CSI evolutionary model: Phase O

    Science.gov (United States)

    Belvin, W. Keith; Elliott, Kenny B.; Horta, Lucas G.; Bailey, Jim P.; Bruner, Anne M.; Sulla, Jeffrey L.; Won, John; Ugoletti, Roberto M.

    1991-01-01

    A testbed for the development of Controls Structures Interaction (CSI) technology to improve space science platform pointing is described. The evolutionary nature of the testbed will permit the study of global line-of-sight pointing in phases 0 and 1, whereas, multipayload pointing systems will be studied beginning with phase 2. The design, capabilities, and typical dynamic behavior of the phase 0 version of the CSI evolutionary model (CEM) is documented for investigator both internal and external to NASA. The model description includes line-of-sight pointing measurement, testbed structure, actuators, sensors, and real time computers, as well as finite element and state space models of major components.

  8. Phase diagram of a truncated tetrahedral model

    Science.gov (United States)

    Krcmar, Roman; Gendiar, Andrej; Nishino, Tomotoshi

    2016-08-01

    Phase diagram of a discrete counterpart of the classical Heisenberg model, the truncated tetrahedral model, is analyzed on the square lattice, when the interaction is ferromagnetic. Each spin is represented by a unit vector that can point to one of the 12 vertices of the truncated tetrahedron, which is a continuous interpolation between the tetrahedron and the octahedron. Phase diagram of the model is determined by means of the statistical analog of the entanglement entropy, which is numerically calculated by the corner transfer matrix renormalization group method. The obtained phase diagram consists of four different phases, which are separated by five transition lines. In the parameter region, where the octahedral anisotropy is dominant, a weak first-order phase transition is observed.

  9. Hybrid model for QCD deconfining phase boundary

    Science.gov (United States)

    Srivastava, P. K.; Singh, C. P.

    2012-06-01

    Intensive search for a proper and realistic equations of state (EOS) is still continued for studying the phase diagram existing between quark gluon plasma (QGP) and hadron gas (HG) phases. Lattice calculations provide such EOS for the strongly interacting matter at finite temperature (T) and vanishing baryon chemical potential (μB). These calculations are of limited use at finite μB due to the appearance of notorious sign problem. In the recent past, we had constructed a hybrid model description for the QGP as well as HG phases where we make use of a new excluded-volume model for HG and a thermodynamically-consistent quasiparticle model for the QGP phase and used them further to get QCD phase boundary and a critical point. Since then many lattice calculations have appeared showing various thermal and transport properties of QCD matter at finite T and μB=0. We test our hybrid model by reproducing the entire data for strongly interacting matter and predict our results at finite μB so that they can be tested in future. Finally we demonstrate the utility of the model in fixing the precise location, the order of the phase transition and the nature of CP existing on the QCD phase diagram. We thus emphasize the suitability of the hybrid model as formulated here in providing a realistic EOS for the strongly interacting matter.

  10. Phases and phase transitions in the algebraic microscopic shell model

    Directory of Open Access Journals (Sweden)

    Georgieva A. I.

    2016-01-01

    Full Text Available We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott’s SU(3 basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3 basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.

  11. PHASE CHAOS IN THE DISCRETE KURAMOTO MODEL

    DEFF Research Database (Denmark)

    Maistrenko, V.; Vasylenko, A.; Maistrenko, Y.;

    2010-01-01

    The paper describes the appearance of a novel, high-dimensional chaotic regime, called phase chaos, in a time-discrete Kuramoto model of globally coupled phase oscillators. This type of chaos is observed at small and intermediate values of the coupling strength. It arises from the nonlinear inter...

  12. The comfortable driving model revisited: Traffic phases and phase transitions

    CERN Document Server

    Knorr, Florian

    2013-01-01

    We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast it with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner's three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides `hard' rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow (F) to a wide moving jam (J) often involves an intermediate transition; first from free flow F to synchronized flow S and then from synchronized flow to a wide moving jam. This is supported by the fact that the so called F->S transition (from free flow to synchronized t...

  13. Modeling phase noise in multifunction subassemblies.

    Science.gov (United States)

    Driscoll, Michael

    2012-03-01

    Obtaining requisite phase noise performance in hardware containing multifunction circuitry requires accurate modeling of the phase noise characteristics of each signal path component, including both absolute (oscillator) and residual (non-oscillator) circuit contributors. This includes prediction of both static and vibration-induced phase noise. The model (usually in spreadsheet form) is refined as critical components are received and evaluated. Additive (KTBF) phase noise data can be reasonably estimated, based on device drive level and noise figure. However, accurate determination of component near-carrier (multiplicative) and vibration-induced noise usually must be determined via measurement. The model should also include the effects of noise introduced by IC voltage regulators and properly discriminate between common versus independent signal path residual noise contributors. The modeling can be easily implemented using a spreadsheet.

  14. Phase Transition in the Simplest Plasma Model

    CERN Document Server

    Iosilevskiy, Igor

    2009-01-01

    We have investigated the phase transition of the gas-liquid type, with an upper critical point, in a variant of the One Component Plasma model (OCP) that has a uniform but compressible compensating background. We have calculated the parameters of the critical and triple points, spinodals, and two-phase coexistence curves (binodals). We have analyzed the connection of this simplest plasma phase transition with anomalies in the spatial charge profiles of equilibrium non-uniform plasma in the local-density approximations of Thomas-Fermi or Poisson-Boltzmann-type.

  15. Preliminary Phase Field Computational Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yulan [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hu, Shenyang Y. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xu, Ke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Suter, Jonathan D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McCloy, John S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Bradley R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ramuhalli, Pradeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-12-15

    This interim report presents progress towards the development of meso-scale models of magnetic behavior that incorporate microstructural information. Modeling magnetic signatures in irradiated materials with complex microstructures (such as structural steels) is a significant challenge. The complexity is addressed incrementally, using the monocrystalline Fe (i.e., ferrite) film as model systems to develop and validate initial models, followed by polycrystalline Fe films, and by more complicated and representative alloys. In addition, the modeling incrementally addresses inclusion of other major phases (e.g., martensite, austenite), minor magnetic phases (e.g., carbides, FeCr precipitates), and minor nonmagnetic phases (e.g., Cu precipitates, voids). The focus of the magnetic modeling is on phase-field models. The models are based on the numerical solution to the Landau-Lifshitz-Gilbert equation. From the computational standpoint, phase-field modeling allows the simulation of large enough systems that relevant defect structures and their effects on functional properties like magnetism can be simulated. To date, two phase-field models have been generated in support of this work. First, a bulk iron model with periodic boundary conditions was generated as a proof-of-concept to investigate major loop effects of single versus polycrystalline bulk iron and effects of single non-magnetic defects. More recently, to support the experimental program herein using iron thin films, a new model was generated that uses finite boundary conditions representing surfaces and edges. This model has provided key insights into the domain structures observed in magnetic force microscopy (MFM) measurements. Simulation results for single crystal thin-film iron indicate the feasibility of the model for determining magnetic domain wall thickness and mobility in an externally applied field. Because the phase-field model dimensions are limited relative to the size of most specimens used in

  16. Phase Diagram of the Frustrated Hubbard Model

    Science.gov (United States)

    Zitzler, R.; Tong, N.-H.; Pruschke, Th.; Bulla, R.

    2004-07-01

    The Mott-Hubbard metal-insulator transition in the paramagnetic phase of the one-band Hubbard model has long been used to describe similar features in real materials like V2O3. In this Letter we investigate the antiferromagnetic phase of this model with frustration. At T=0 we find a first-order transition from a paramagnetic metal to an antiferromagnetic insulator. We show that even in the presence of strong magnetic frustration, the paramagnetic metal-insulator transition is hidden inside an extended antiferromagnetic region. This raises the question of whether the one-band Hubbard model with frustration is sufficient to describe the phase diagram of V2O3 or similar transition metal oxides even qualitatively.

  17. Pasta phases within the QMC model

    CERN Document Server

    Grams, Guilherme; Panda, Prafulla K; Providência, Constança; Menezes, Débora P

    2016-01-01

    In this work the low density regions of nuclear and neutron star matter are studied. The search for the existence of pasta phases in this region is performed within the context of the quark-meson coupling (QMC) model, which incorporates quark degrees of freedom. Fixed proton fractions are considered, as well as nuclear matter in beta equilibrium at zero temperature. We discuss the recent attempts to better understand the surface energy in the coexistence phases regime and we present results that show the existence of the pasta phases subject to some choices of the surface energy coefficient. We also analyze the influence of the nuclear pasta on some neutron star properties. The equation of state containing the pasta phase will be part of a complete grid for future use in supernova simulations.

  18. On Affine Fusion and the Phase Model

    Directory of Open Access Journals (Sweden)

    Mark A. Walton

    2012-11-01

    Full Text Available A brief review is given of the integrable realization of affine fusion discovered recently by Korff and Stroppel. They showed that the affine fusion of the su(n Wess-Zumino-Novikov-Witten (WZNW conformal field theories appears in a simple integrable system known as the phase model. The Yang-Baxter equation leads to the construction of commuting operators as Schur polynomials, with noncommuting hopping operators as arguments. The algebraic Bethe ansatz diagonalizes them, revealing a connection to the modular S matrix and fusion of the su(n WZNW model. The noncommutative Schur polynomials play roles similar to those of the primary field operators in the corresponding WZNW model. In particular, their 3-point functions are the su(n fusion multiplicities. We show here how the new phase model realization of affine fusion makes obvious the existence of threshold levels, and how it accommodates higher-genus fusion.

  19. Phase transitions in Thirring’s model

    Science.gov (United States)

    Campa, Alessandro; Casetti, Lapo; Latella, Ivan; Pérez-Madrid, Agustín; Ruffo, Stefano

    2016-07-01

    In his pioneering work on negative specific heat, Walter Thirring introduced a model that is solvable in the microcanonical ensemble. Here, we give a complete description of the phase-diagram of this model in both the microcanonical and the canonical ensemble, highlighting the main features of ensemble inequivalence. In both ensembles, we find a line of first-order phase transitions which ends in a critical point. However, neither the line nor the point have the same location in the phase-diagram of the two ensembles. We also show that the microcanonical and canonical critical points can be analytically related to each other using a Landau expansion of entropy and free energy, respectively, in analogy with what has been done in (Cohen and Mukamel 2012 J. Stat. Mech. P12017). Examples of systems with certain symmetries restricting the Landau expansion have been considered in this reference, while no such restrictions are present in Thirring’s model. This leads to a phase diagram that can be seen as a prototype for what happens in systems of particles with kinematic degrees of freedom dominated by long-range interactions.

  20. Theory and modelling of nanocarbon phase stability.

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, A. S.

    2006-01-01

    The transformation of nanodiamonds into carbon-onions (and vice versa) has been observed experimentally and has been modeled computationally at various levels of sophistication. Also, several analytical theories have been derived to describe the size, temperature and pressure dependence of this phase transition. However, in most cases a pure carbon-onion or nanodiamond is not the final product. More often than not an intermediary is formed, known as a bucky-diamond, with a diamond-like core encased in an onion-like shell. This has prompted a number of studies investigating the relative stability of nanodiamonds, bucky-diamonds, carbon-onions and fullerenes, in various size regimes. Presented here is a review outlining results of numerous theoretical studies examining the phase diagrams and phase stability of carbon nanoparticles, to clarify the complicated relationship between fullerenic and diamond structures at the nanoscale.

  1. CFD Modeling of Mixed-Phase Icing

    Science.gov (United States)

    Zhang, Lifen; Liu, Zhenxia; Zhang, Fei

    2016-12-01

    Ice crystal ingestion at high altitude has been reported to be a threat for safe operation of aero-engine in recently. Ice crystals do not accrete on external surface because of cold environment. But when they enter the core flow of aero-engine, ice crystals melt partially into droplets due to higher temperature. Air-droplets-ice crystal is the mixed-phase, which will give rise to ice accretion on static and rotating components in compressor. Subsequently, compressor surge and engine shutdowns may occur. To provide a numerical tool to analyze this in detail, a numerical method was developed in this study. The mixed phase flow was solved using Eulerian-Lagrangian method. The dispersed phase was represented by one-way coupling. A thermodynamic model that considers mass and energy balance with ice crystals and droplets was presented as well. The icing code was implemented by the user-defined function of Fluent. The method of ice accretion under mixed-phase conditions was validated by comparing the results simulated on a cylinder with experimental data derived from literature. The predicted ice shape and mass agree with these data, thereby confirming the validity of the numerical method developed in this research for mixed-phase conditions.

  2. High-performance phase-field modeling

    KAUST Repository

    Vignal, Philippe

    2015-04-27

    Many processes in engineering and sciences involve the evolution of interfaces. Among the mathematical frameworks developed to model these types of problems, the phase-field method has emerged as a possible solution. Phase-fields nonetheless lead to complex nonlinear, high-order partial differential equations, whose solution poses mathematical and computational challenges. Guaranteeing some of the physical properties of the equations has lead to the development of efficient algorithms and discretizations capable of recovering said properties by construction [2, 5]. This work builds-up on these ideas, and proposes novel discretization strategies that guarantee numerical energy dissipation for both conserved and non-conserved phase-field models. The temporal discretization is based on a novel method which relies on Taylor series and ensures strong energy stability. It is second-order accurate, and can also be rendered linear to speed-up the solution process [4]. The spatial discretization relies on Isogeometric Analysis, a finite element method that possesses the k-refinement technology and enables the generation of high-order, high-continuity basis functions. These basis functions are well suited to handle the high-order operators present in phase-field models. Two-dimensional and three dimensional results of the Allen-Cahn, Cahn-Hilliard, Swift-Hohenberg and phase-field crystal equation will be presented, which corroborate the theoretical findings, and illustrate the robustness of the method. Results related to more challenging examples, namely the Navier-Stokes Cahn-Hilliard and a diusion-reaction Cahn-Hilliard system, will also be presented. The implementation was done in PetIGA and PetIGA-MF, high-performance Isogeometric Analysis frameworks [1, 3], designed to handle non-linear, time-dependent problems.

  3. SEISMIC MODELING ENGINES PHASE 1 FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    BRUCE P. MARION

    2006-02-09

    Seismic modeling is a core component of petroleum exploration and production today. Potential applications include modeling the influence of dip on anisotropic migration; source/receiver placement in deviated-well three-dimensional surveys for vertical seismic profiling (VSP); and the generation of realistic data sets for testing contractor-supplied migration algorithms or for interpreting AVO (amplitude variation with offset) responses. This project was designed to extend the use of a finite-difference modeling package, developed at Lawrence Berkeley Laboratories, to the advanced applications needed by industry. The approach included a realistic, easy-to-use 2-D modeling package for the desktop of the practicing geophysicist. The feasibility of providing a wide-ranging set of seismic modeling engines was fully demonstrated in Phase I. The technical focus was on adding variable gridding in both the horizontal and vertical directions, incorporating attenuation, improving absorbing boundary conditions and adding the optional coefficient finite difference methods.

  4. Phase Fluctuations in the ABC Model

    Science.gov (United States)

    Bodineau, T.; Derrida, B.

    2011-11-01

    We analyze the fluctuations of the steady state profiles in the modulated phase of the ABC model. For a system of L sites, the steady state profiles move on a microscopic time scale of order L 3. The variance of their displacement is computed in terms of the macroscopic steady state profiles by using fluctuating hydrodynamics and large deviations. Our analytical prediction for this variance is confirmed by the results of numerical simulations.

  5. Phase transition in the ABC model

    Science.gov (United States)

    Clincy, M.; Derrida, B.; Evans, M. R.

    2003-06-01

    Recent studies have shown that one-dimensional driven systems can exhibit phase separation even if the dynamics is governed by local rules. The ABC model, which comprises three particle species that diffuse asymmetrically around a ring, shows anomalous coarsening into a phase separated steady state. In the limiting case in which the dynamics is symmetric and the parameter q describing the asymmetry tends to one, no phase separation occurs and the steady state of the system is disordered. In the present work, we consider the weak asymmetry regime q=exp(-β/N), where N is the system size, and study how the disordered state is approached. In the case of equal densities, we find that the system exhibits a second-order phase transition at some nonzero βc. The value of βc=2π(3) and the optimal profiles can be obtained by writing the exact large deviation functional. For nonequal densities, we write down mean-field equations and analyze some of their predictions.

  6. Phase Diagram for Ashkin-Teller Model on Bethe Lattice

    Institute of Scientific and Technical Information of China (English)

    LE Jian-Xin; YANG Zhan-Ru

    2005-01-01

    Using the recursion method, we study the phase transitions of the Ashkin-Teller model on the Bethe lattice,restricting ourselves to the case of ferromagnetic interactions. The isotropic Ashkin-Teller model and the anisotropic one are respectively investigated, and exact expressions for the free energy and the magnetization are obtained. It can be found that each of the three varieties of phase diagrams, for the anisotropic Ashkin-Teller model, consists of four phases, I.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases and , while the phase diagram, for the isotropic Ashkin-Teller model,contains three phases, I.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, and the partially ordered ferromagnetic phase .

  7. Phase diagram of a Schelling segregation model

    Science.gov (United States)

    Gauvin, L.; Vannimenus, J.; Nadal, J.-P.

    2009-07-01

    The collective behavior in a variant of Schelling’s segregation model is characterized with methods borrowed from statistical physics, in a context where their relevance was not conspicuous. A measure of segregation based on cluster geometry is defined and several quantities analogous to those used to describe physical lattice models at equilibrium are introduced. This physical approach allows to distinguish quantitatively several regimes and to characterize the transitions between them, leading to the building of a phase diagram. Some of the transitions evoke empirical sudden ethnic turnovers. We also establish links with ‘spin-1’ models in physics. Our approach provides generic tools to analyze the dynamics of other socio-economic systems.

  8. A MODEL FOR PREDICTING PHASE INVERSION IN OIL-WATER TWO-PHASE PIPE FLOW

    Institute of Scientific and Technical Information of China (English)

    GONG Jing; LI Qing-ping; YAO Hai-yuan; YU Da

    2006-01-01

    Experiments of phase inversion characteristics for horizontal oil-water two-phase flow in a stainless steel pipe loop (25.7 mm inner diameter,52 m long) are conducted. A new viewpoint is brought forward about the process of phase inversion in oil-water two-phase pipe flow. Using the relations between the total free energies of the pre-inversion and post-inversion dispersions, a model for predicting phase inversion in oil-water two-phase pipe flow has been developed that considers the characteristics of pipe flow. This model is compared against other models with relevant data of phase inversion in oil-water two-phase pipe flow. Results indicate that this model is better than other models in terms of calculation precision and applicability. The model is useful for guiding the design for optimal performance and safety in the operation of oil-water two-phase pipe flow in oil fields.

  9. Phase-field modeling of hydraulic fracture

    Science.gov (United States)

    Wilson, Zachary A.; Landis, Chad M.

    2016-11-01

    In this work a theoretical framework implementing the phase-field approach to fracture is used to couple the physics of flow through porous media and cracks with the mechanics of fracture. The main modeling challenge addressed in this work, which is a challenge for all diffuse crack representations, is on how to allow for the flow of fluid and the action of fluid pressure on the aggregate within the diffuse damage zone of the cracks. The theory is constructed by presenting the general physical balance laws and conducting a consistent thermodynamic analysis to constrain the constitutive relationships. Constitutive equations that reproduce the desired responses at the various limits of the phase-field parameter are proposed in order to capture Darcy-type flow in the intact porous medium and Stokes-type flow within open cracks. A finite element formulation for the solution of the governing model equations is presented and discussed. Finally, the theoretical and numerical model is shown to compare favorably to several important analytical solutions. More complex and interesting calculations are also presented to illustrate some of the advantageous features of the approach.

  10. Modeling the distinct phases of skill acquisition.

    Science.gov (United States)

    Tenison, Caitlin; Anderson, John R

    2016-05-01

    A focus of early mathematics education is to build fluency through practice. Several models of skill acquisition have sought to explain the increase in fluency because of practice by modeling both the learning mechanisms driving this speedup and the changes in cognitive processes involved in executing the skill (such as transitioning from calculation to retrieval). In the current study, we use hidden Markov modeling to identify transitions in the learning process. This method accounts for the gradual speedup in problem solving and also uncovers abrupt changes in reaction time, which reflect changes in the cognitive processes that participants are using to solve math problems. We find that as participants practice solving math problems they transition through 3 distinct learning states. Each learning state shows some speedup with practice, but the major speedups are produced by transitions between learning states. In examining and comparing the behavioral and neurological profiles of each of these states, we find parallels with the 3 phases of skill acquisition proposed by Fitts and Posner (1967): a cognitive, an associative, and an autonomous phase. (PsycINFO Database Record

  11. Molecular Modeling of Solid Fluid Phase Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Peter A. Monson

    2007-12-20

    This report gives a summary of the achievements under DOE contract No. DOE/ER/14150 during the period September 1, 1990 to December 31, 2007. This project was concerned with the molecular modeling of solid-fluid equilibrium. The focus was on understanding how solid-fluid and solid-solid phase behavior are related to molecular structure, and the research program made a seminal contribution in this area. The project led to 34 journal articles, including a comprehensive review article published in Advances in Chemical Physics. The DOE funding supported the work of 5 Ph.D. students, 2 M.S. students and 5 postdoctoral researchers.

  12. Preon model and cosmological quantum-hyperchromodynamic phase transition

    Science.gov (United States)

    Nishimura, H.; Hayashi, Y.

    1987-05-01

    From the cosmological viewpoint, we investigate whether or not recent preon models are compatible with the picture of the first-order phase transition from the preon phase to the composite quark-lepton phase. It is shown that the current models accepting the 't Hooft anomaly-matching condition together with quantum hyperchromodynamics are consistent with the cosmological first-order phase transition.

  13. Application of an analytical phase transformation model

    Institute of Scientific and Technical Information of China (English)

    LIU Feng; WANG Hai-feng; YANG Chang-lin; CHEN Zheng; YANG Wei; YANG Gen-cang

    2006-01-01

    Employing isothermal and isochronal differential scanning calorimetry, an analytical phase transformation model was used to study the kinetics of crystallization of amorphous Mg82.3Cu17.7 and Pd40Cu30P20Ni10 alloys. The analytical model comprised different combinations of various nucleation and growth mechanisms for a single transformation. Applying different combinations of nucleation and growth mechanisms, the nucleation and growth modes and the corresponding kinetic and thermodynamic parameters, have been determined. The influence of isothermal pre-annealing on subsequent isochronal crystallization kinetics with the increase of pre-annealing can be analyzed. The results show that the changes of the growth exponent, n, and the effective overall activation energy Q, occurring as function of the degree of transformation, do not necessarily imply a change of nucleation and growth mechanisms, i.e. such changes can occur while the transformation is isokinetic.

  14. Microgravity two-phase flow regime modeling

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.; Best, F.R.; Faget, N.

    1987-01-01

    A flow pattern or flow regime is the characteristics spatial distribution of the phases of fluid in a duct. Since heat transfer and pressure drop are dependent on the characteristic distribution of the phases, it is necessary to describe flow patterns in an appropriate manner so that a hydrodynamic or heat transfer theory applicable to that pattern can be chosen. The objective of the present analysis is to create a flow regime map based on physical modeling of vapor/liquid interaction phenomena in a microgravity environment. In the present work, four basic flow patterns are defined: dispersed flow, stratified flow, slug flow, and annular flow. Fluid properties, liquid and vapor flow rates, and pipe size were chosen as the principal parameters. It is assumed that a transition from one flow pattern to another will occur when there is a change in the dominant force which controls that flow pattern. The forces considered in this modeling are surface tension force, both force, inertial force, friction, and turbulent fluctuations.

  15. Dynamic Modeling of Phase Crossings in Two-Phase Flow

    DEFF Research Database (Denmark)

    Madsen, Søren; Veje, Christian; Willatzen, Morten

    2012-01-01

    of the variables and are usually very slow to evaluate. To overcome these challenges, we use an interpolation scheme with local refinement. The simulations show that the method handles crossing of the saturation lines for both liquid to two-phase and two-phase to gas regions. Furthermore, a novel result obtained...... in this work, the method is stable towards dynamic transitions of the inlet/outlet boundaries across the saturation lines. Results for these cases are presented along with a numerical demonstration of conservation of mass under dynamically varying boundary conditions. Finally we present results...

  16. The phase transition of Axelrod's model revisited

    CERN Document Server

    Reia, Sandro M

    2016-01-01

    Axelrod's model with $F=2$ cultural features, where each feature can assume $k$ states drawn from a Poisson distribution of parameter $q$, exhibits a continuous nonequilibrium phase transition in the square lattice. Here we use extensive Monte Carlo simulations and finite size scaling to study the critical behavior of the order parameter $\\rho$, which is the fraction of sites that belong to the largest domain of an absorbing configuration averaged over many runs. We find that it vanishes as $\\rho \\sim \\left (q_c^0 - q \\right)^\\beta$ with $\\beta \\approx 0.25$ at the critical point $q_c^0 \\approx 3.10$ and that the exponent that measures the width of the critical region is $\

  17. Model-based phase-shifting interferometer

    Science.gov (United States)

    Liu, Dong; Zhang, Lei; Shi, Tu; Yang, Yongying; Chong, Shiyao; Miao, Liang; Huang, Wei; Shen, Yibing; Bai, Jian

    2015-10-01

    A model-based phase-shifting interferometer (MPI) is developed, in which a novel calculation technique is proposed instead of the traditional complicated system structure, to achieve versatile, high precision and quantitative surface tests. In the MPI, the partial null lens (PNL) is employed to implement the non-null test. With some alternative PNLs, similar as the transmission spheres in ZYGO interferometers, the MPI provides a flexible test for general spherical and aspherical surfaces. Based on modern computer modeling technique, a reverse iterative optimizing construction (ROR) method is employed for the retrace error correction of non-null test, as well as figure error reconstruction. A self-compiled ray-tracing program is set up for the accurate system modeling and reverse ray tracing. The surface figure error then can be easily extracted from the wavefront data in forms of Zernike polynomials by the ROR method. Experiments of the spherical and aspherical tests are presented to validate the flexibility and accuracy. The test results are compared with those of Zygo interferometer (null tests), which demonstrates the high accuracy of the MPI. With such accuracy and flexibility, the MPI would possess large potential in modern optical shop testing.

  18. Numerical simulations of the phase separation properties for the thermal aged CDSS with Phase Field Model

    Energy Technology Data Exchange (ETDEWEB)

    Xue Fei [Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Wang Zhaoxi, E-mail: wangzx03@mails.tsinghua.edu.cn [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Applied Mechanics Laboratory, Tsinghua University, Beijing 100084 (China); Zhang Guodong [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); School of Mechanical and Power Engineering, Nanjing University of Technology, Nanjing 210009 (China); Qu Baoping; Shi Huiji [Applied Mechanics Laboratory, Tsinghua University, Beijing 100084 (China); Shu Guogang [Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Liu Wei [Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2011-07-15

    Highlights: > Thermal aging causes the Cr-rich phase precipitate and form clusters. > Phase field dynamic model is used for simulating the phase separation coarsening. > Damage initiated more easily in the ferrite matrix for the Cr clusters. - Abstract: Experiments and numerical simulations with Phase Field Model and Finite Element Analysis were carried out to investigate the phase separation dynamic properties and the corresponding thermal aging degradation mechanism. Experimental results from transmission electron microscopy and atomic force microscopy show that thermal aging causes the Cr-rich phase precipitate and form clusters. A phase field dynamic model was developed with constitutive relations and empirical potential functions to investigate the phase separation dynamics in the ferrite phase. Numerical results integrated with cell dynamical system method show clearly the micro structure morphology and the phase separation coarsening with aging time. The evolution process of the phase separation was quantitatively illustrated and reproduced macroscopically. The scattering pattern becomes clearer and the corresponding radius becomes smaller along with the increasing aging time. The average characteristic length increases firstly then decreases and enters a more stable stage. With the increment of the local Cr concentration, the evolution of the phase morphology was quite different. Finite Element Analysis simulation results with the Gurson-Tvergaard-Needleman void model show that the damage initiated more easily in the ferrite matrix for the Cr atoms forming clusters with increasing aging time. The phenomenological simulations with Phase Field Model and Finite Element Analysis were in remarkably good agreement with experimental results and analytical considerations.

  19. Spectral modeling of nebular-phase supernovae

    CERN Document Server

    Jerkstrand, Anders

    2011-01-01

    Massive stars live fast and die young. They shine furiously for a few million years, during which time they synthesize most of the heavy elements in the universe in their cores. They end by blowing themselves up in a powerful explosion known as a supernova. During this process, the core collapses to a neutron star or a black hole, while the outer layers are expelled with velocities of thousands of kilometers per second. The resulting fireworks often outshine the entire host galaxy for many weeks. The explosion energy is eventually radiated away, but powering of the newborn nebula continues by radioactive isotopes synthesized in the explosion. The ejecta are now quite transparent, and we can see the material produced in the deep interiors of the star. To interpret the observations, detailed spectral modeling is needed. This thesis aims to develop and apply state-of-the-art computational tools for interpreting and modeling supernova observations in the nebular phase. This requires calculation of the physical co...

  20. Wax Precipitation Modeled with Many Mixed Solid Phases

    DEFF Research Database (Denmark)

    Heidemann, Robert A.; Madsen, Jesper; Stenby, Erling Halfdan

    2005-01-01

    The behavior of the Coutinho UNIQUAC model for solid wax phases has been examined. The model can produce as many mixed solid phases as the number of waxy components. In binary mixtures, the solid rich in the lighter component contains little of the heavier component but the second phase shows sub...

  1. Thermal fluctuations and phase diagrams of the phase-field crystal model with pinning.

    Science.gov (United States)

    Ramos, J A P; Granato, E; Achim, C V; Ying, S C; Elder, K R; Ala-Nissila, T

    2008-09-01

    We study the influence of thermal fluctuations in the phase diagram of a recently introduced two-dimensional phase field crystal model with an external pinning potential. The model provides a continuum description of pinned lattice systems allowing for both elastic deformations and topological defects. We introduce a nonconserved version of the model and determine the ground-state phase diagram as a function of lattice mismatch and strength of the pinning potential. Monte Carlo simulations are used to determine the phase diagram as a function of temperature near commensurate phases. The results show a rich phase diagram with commensurate, incommensurate, and liquidlike phases with a topology strongly dependent on the type of ordered structure. A finite-size scaling analysis of the melting transition for the c(2x2) commensurate phase shows that the thermal correlation length exponent nu and specific heat behavior are consistent with the Ising universality class as expected from analytical arguments.

  2. Modeling Image Structure with Factorized Phase-Coupled Boltzmann Machines

    CERN Document Server

    Cadieu, Charles F

    2010-01-01

    We describe a model for capturing the statistical structure of local amplitude and local spatial phase in natural images. The model is based on a recently developed, factorized third-order Boltzmann machine that was shown to be effective at capturing higher-order structure in images by modeling dependencies among squared filter outputs (Ranzato and Hinton, 2010). Here, we extend this model to $L_p$-spherically symmetric subspaces. In order to model local amplitude and phase structure in images, we focus on the case of two dimensional subspaces, and the $L_2$-norm. When trained on natural images the model learns subspaces resembling quadrature-pair Gabor filters. We then introduce an additional set of hidden units that model the dependencies among subspace phases. These hidden units form a combinatorial mixture of phase coupling distributions, concentrated in the sum and difference of phase pairs. When adapted to natural images, these distributions capture local spatial phase structure in natural images.

  3. Phase field modeling and simulation of three-phase flow on solid surfaces

    Science.gov (United States)

    Zhang, Qian; Wang, Xiao-Ping

    2016-08-01

    Phase field models are widely used to describe the two-phase system. The evolution of the phase field variables is usually driven by the gradient flow of a total free energy functional. The generalization of the approach to an N phase (N ≥ 3) system requires some extra consistency conditions on the free energy functional in order for the model to give physically relevant results. A projection approach is proposed for the derivation of a consistent free energy functional for the three-phase Cahn-Hilliard equations. The system is then coupled with the Navier-Stokes equations to describe the three-phase flow on solid surfaces with moving contact line. An energy stable scheme is developed for the three-phase flow system. The discrete energy law of the numerical scheme is proved which ensures the stability of the scheme. We also show some numerical results for the dynamics of triple junctions and four phase contact lines.

  4. Modeling the phase diagram of carbon

    NARCIS (Netherlands)

    Ghiringhelli, L.M.; Los, J.H.; Meijer, E.J.; Fasolino, A.; Frenkel, D.

    2005-01-01

    We determined the phase diagram involving diamond, graphite, and liquid carbon using a recently developed semiempirical potential. Using accurate free-energy calculations, we computed the solid-solid and solid-liquid phase boundaries for pressures and temperatures up to 400 GPa and 12 000 K, respect

  5. A new atmospheric aerosol phase equilibrium model (UHAERO: organic systems

    Directory of Open Access Journals (Sweden)

    N. R. Amundson

    2007-09-01

    Full Text Available In atmospheric aerosols, water and volatile inorganic and organic species are distributed between the gas and aerosol phases in accordance with thermodynamic equilibrium. Within an atmospheric particle, liquid and solid phases can exist at equilibrium. Models exist for computation of phase equilibria for inorganic/water mixtures typical of atmospheric aerosols; when organic species are present, the phase equilibrium problem is complicated by organic/water interactions as well as the potentially large number of organic species. We present here an extension of the UHAERO inorganic thermodynamic model (Amundson et al., 2006c to organic/water systems. Phase diagrams for a number of model organic/water systems characteristic of both primary and secondary organic aerosols are computed. Also calculated are inorganic/organic/water phase diagrams that show the effect of organics on inorganic deliquescence behavior. The effect of the choice of activity coefficient model for organics on the computed phase equilibria is explored.

  6. A new atmospheric aerosol phase equilibrium model (UHAERO: organic systems

    Directory of Open Access Journals (Sweden)

    N. R. Amundson

    2007-06-01

    Full Text Available In atmospheric aerosols, water and volatile inorganic and organic species are distributed between the gas and aerosol phases in accordance with thermodynamic equilibrium. Within an atmospheric particle, liquid and solid phases can exist at equilibrium. Models exist for computation of phase equilibria for inorganic/water mixtures typical of atmospheric aerosols; when organic species are present, the phase equilibrium problem is complicated by organic/water interactions as well as the potentially large number of organic species. We present here an extension of the UHAERO inorganic thermodynamic model (Amundson et al., 2006c to organic/water systems. Phase diagrams for a number of model organic/water systems characteristic of both primary and secondary organic aerosols are computed. Also calculated are inorganic/organic/water phase diagrams that show the effect of organics on inorganic deliquescence behavior. The effect of the choice of activity coefficient model for organics on the computed phase equilibria is explored.

  7. Regularity of solutions of a phase field model

    KAUST Repository

    Amler, Thomas

    2013-01-01

    Phase field models are widely-used for modelling phase transition processes such as solidification, freezing or CO2 sequestration. In this paper, a phase field model proposed by G. Caginalp is considered. The existence and uniqueness of solutions are proved in the case of nonsmooth initial data. Continuity of solutions with respect to time is established. In particular, it is shown that the governing initial boundary value problem can be considered as a dynamical system. © 2013 International Press.

  8. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M

    1993-01-01

    Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  9. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175

    2009-01-01

    We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  10. Bioluminescence tomography based on the phase approximation model

    OpenAIRE

    Cong, W; Wang, G.

    2010-01-01

    A reconstruction method of bioluminescence sources is proposed based on a phase approximation model. Compared with the diffuse approximation, this phase approximation model more correctly predicts bioluminescence photon propagation in biological tissues, so that bioluminescence tomography can accurately locate and quantify the distribution of bioluminescence sources. The compressive sensing (CS) technique is applied to regularize the inverse source reconstruction to enhance numerical stabilit...

  11. Linear Sigma Models With Strongly Coupled Phases -- One Parameter Models

    CERN Document Server

    Hori, Kentaro

    2013-01-01

    We systematically construct a class of two-dimensional $(2,2)$ supersymmetric gauged linear sigma models with phases in which a continuous subgroup of the gauge group is totally unbroken. We study some of their properties by employing a recently developed technique. The focus of the present work is on models with one K\\"ahler parameter. The models include those corresponding to Calabi-Yau threefolds, extending three examples found earlier by a few more, as well as Calabi-Yau manifolds of other dimensions and non-Calabi-Yau manifolds. The construction leads to predictions of equivalences of D-brane categories, systematically extending earlier examples. There is another type of surprise. Two distinct superconformal field theories corresponding to Calabi-Yau threefolds with different Hodge numbers, $h^{2,1}=23$ versus $h^{2,1}=59$, have exactly the same quantum K\\"ahler moduli space. The strong-weak duality plays a crucial r\\^ole in confirming this, and also is useful in the actual computation of the metric on t...

  12. Anisotropy in wavelet-based phase field models

    KAUST Repository

    Korzec, Maciek

    2016-04-01

    When describing the anisotropic evolution of microstructures in solids using phase-field models, the anisotropy of the crystalline phases is usually introduced into the interfacial energy by directional dependencies of the gradient energy coefficients. We consider an alternative approach based on a wavelet analogue of the Laplace operator that is intrinsically anisotropic and linear. The paper focuses on the classical coupled temperature/Ginzburg--Landau type phase-field model for dendritic growth. For the model based on the wavelet analogue, existence, uniqueness and continuous dependence on initial data are proved for weak solutions. Numerical studies of the wavelet based phase-field model show dendritic growth similar to the results obtained for classical phase-field models.

  13. Phase noise and jitter modeling for fractional-N PLLs

    Directory of Open Access Journals (Sweden)

    S. A. Osmany

    2007-06-01

    Full Text Available We present an analytical phase noise model for fractional-N phase-locked loops (PLL with emphasis on integrated RF synthesizers in the GHz range. The noise of the crystal reference, the voltage-controlled oscillator (VCO, the loop filter, the charge pump, and the sigma-delta modulator (SDM is filtered by the PLL operation. We express the rms phase error (jitter in terms of phase noise of the reference, the VCO phase noise and the third-order loop filter parameters. In addition, we consider OFDM systems, where the PLL phase noise is reduced by digital signal processing after down-conversion of the RF signal to baseband. The rms phase error is discussed as a function of the loop parameters. Our model drastically simplifies the noise optimization of the PLL loop dynamics.

  14. Phase noise and jitter modeling for fractional-N PLLs

    Science.gov (United States)

    Osmany, S. A.; Herzel, F.; Schmalz, K.; Winkler, W.

    2007-06-01

    We present an analytical phase noise model for fractional-N phase-locked loops (PLL) with emphasis on integrated RF synthesizers in the GHz range. The noise of the crystal reference, the voltage-controlled oscillator (VCO), the loop filter, the charge pump, and the sigma-delta modulator (SDM) is filtered by the PLL operation. We express the rms phase error (jitter) in terms of phase noise of the reference, the VCO phase noise and the third-order loop filter parameters. In addition, we consider OFDM systems, where the PLL phase noise is reduced by digital signal processing after down-conversion of the RF signal to baseband. The rms phase error is discussed as a function of the loop parameters. Our model drastically simplifies the noise optimization of the PLL loop dynamics.

  15. A mechanical model for phase-separation in debris flow

    CERN Document Server

    Pudasaini, Shiva P

    2016-01-01

    Understanding the physics of phase-separation between solid and fluid phases as a mixture mass moves down slope is a long-standing challenge. Here, we propose an extension of the two phase mass flow model (Pudasaini, 2012) by including a new mechanism, called separation-flux, that leads to strong phase-separation in avalanche and debris flows while balancing the enhanced solid flux with the reduced fluid flux. The separation flux mechanism is capable of describing the dynamically evolving phase-separation and levee formation in a multi-phase, geometrically three-dimensional debris flow. These are often observed phenomena in natural debris flows and industrial processes that involve the transportation of particulate solid-fluid mixture material. The novel separation-flux model includes several dominant physical and mechanical aspects such as pressure gradients, volume fractions of solid and fluid phases and their gradients, shear-rates, flow depth, material friction, viscosity, material densities, topographic ...

  16. Phase noise and jitter modeling for fractional-N PLLs

    OpenAIRE

    S. A. Osmany; Herzel, F.; Schmalz, K; Winkler, W.

    2007-01-01

    We present an analytical phase noise model for fractional-N phase-locked loops (PLL) with emphasis on integrated RF synthesizers in the GHz range. The noise of the crystal reference, the voltage-controlled oscillator (VCO), the loop filter, the charge pump, and the sigma-delta modulator (SDM) is filtered by the PLL operation. We express the rms phase error (jitter) in terms of phase noise of the reference, the VCO phase noise and the third-order loop filter parameters. In addition, we conside...

  17. Modeling the competing phase transition pathways in nanoscale olivine electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Tang Ming, E-mail: tang25@llnl.go [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Carter, W. Craig [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Belak, James F. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Chiang, Yet-Ming [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2010-12-30

    Recent experimental developments reveal that nanoscale lithium iron phosphate (LiFePO{sub 4}) olivine particles exhibit very different phase transition behavior from the bulk olivine phase. A crystalline-to-amorphous phase transition has been observed in nanosized particles in competition with the equilibrium phase transition between the lithium-rich and lithium-poor olivine phases. Here we apply a diffuse-interface (phase-field) model to study the kinetics of the different phase transition pathways in nanosized LiFePO{sub 4} particles upon delithiation. We find that the nucleation and growth kinetics of the crystalline-to-crystalline and crystalline-to-amorphous phase transformations are sensitive to the applied electrical overpotential and particle size, which collectively determine the preferred phase transition pathway. While the crystalline-to-crystalline phase transition is favored by either faster nucleation or growth kinetics at low or high overpotentials, particle amorphization dominates at intermediate overpotentials. Decreasing particle size expands the overpotential region in which amorphization is preferred. The asymmetry in the nucleation energy barriers for amorphization and recrystallization results in a phase transition hysteresis that should promote the accumulation of the amorphous phase in electrodes after repeated electrochemical cycling. The predicted overpotential- and size-dependent phase transition behavior of nanoscale LiFePO{sub 4} particles is consistent with experimental observations.

  18. Modeling of Phase Equilibria Containing Associating Fluids

    DEFF Research Database (Denmark)

    Derawi, Samer; Kontogeorgis, Georgios

    glycol + heptane, methylcyclohexane, hexane, propylene glycol + heptane, diethylene glycol + heptane, triethylene glycol + heptane, and tetraethylene glycol + heptane. The data obtained were correlated with the NRTL model and two different versions of the UNIQUAC equation. The NRTL model and one...

  19. Simulation model for a seven-phase BLDCM drive system

    Science.gov (United States)

    Park, Sang-Hoon; Lee, Won-Cheol; Lee, Jung-Hyo; Yu, Jae-Sung; Kim, Gyu-Sik; Won, Chung-Yuen

    2007-12-01

    BLDC motors have many advantages over brushed DC motors and induction motors. So, BLDC motors extend their application to many industrial fields. In this paper, the digital simulation and modeling of a 7-phase brushless DC motor have been presented. The 14-switch inverter and a 7-phase brushless DC motor drive system are simulated using hysteresis current controller and logic of switching pattern with the Boolean¡s function. Through some simulations, we found that our modeling and analysis of a 7-phase BLDCM with PWM inverter would be helpful for the further studies of the multi-phase BLDCM drive systems.

  20. Dissecting the Phase Response of a Model Bursting Neuron

    CERN Document Server

    Sherwood, William Erik

    2009-01-01

    We investigate the phase response properties of the Hindmarsh-Rose model of neuronal bursting using burst phase response curves (BPRCs) computed with an infinitesimal perturbation approximation and by direct simulation of synaptic input. The resulting BPRCs have a significantly more complicated structure than the usual Type I and Type II PRCs of spiking neuronal models, and they exhibit highly timing-sensitive changes in the number of spikes per burst that lead to large magnitude phase responses. We use fast-slow dissection and isochron calculations to analyze the phase response dynamics in both weak and strong perturbation regimes.

  1. Revised Phase Diagram of the Gross-Neveu Model

    CERN Document Server

    Thies, M; Thies, Michael; Urlichs, Konrad

    2003-01-01

    We confirm earlier hints that the conventional phase diagram of the discrete chiral Gross-Neveu model in the large N limit is deficient at non-zero chemical potential. We present the corrected phase diagram constructed in mean field theory. It has three different phases, including a kink-antikink crystal phase. All transitions are second order. The driving mechanism for the new structure of baryonic matter in the Gross-Neveu model is an Overhauser type instability with gap formation at the Fermi surface.

  2. Phase field modelling of interfaces from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Pruessner, G [Mathematics Institute, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Sutton, A P [Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)], E-mail: g.pruessner@imperial.ac.uk, E-mail: a.sutton@imperial.ac.uk

    2008-01-15

    Phase field modelling is a technique in (computational) material science that utilises diffuse interface constructions to simulate the dynamics of microstructural evolution. To date, phase field modelling of crystalline interfaces has been guided mainly by phenomenology and symmetry considerations, rather than microscopic physics. The central equation of motion minimises a free energy with respect to the phase field, which is considered as a space and time dependent, coarse-grained, continuous degree of freedom of the system. However, it is neither clear how to interpret the phase field microscopically, nor how to derive the equation of motion from atomic interactions. Based on the (classical) density functional theory by Haymet and Oxtoby, we derive the phase field model by Allen and Cahn, which is commonly used for modelling crystalline interfaces. In the present article, we summarise the physical implications of the various observables and parameters as well as the underlying approximations.

  3. Phase Diagram Modelling: Nickel - Aluminum - Chromium System

    Science.gov (United States)

    1998-04-01

    conducted by Kaufman and co-workers and their lattice stabilities have formed the basis of phase diagram calculations to the present day.1 In...mol ( 0.74827 Ni + 0.73305E-01 Cr + 0.83609E-02 Al ( 1200.00 C, 1.0000 <—s -.Molten alloy <—s <—s) atm, L- NiCrAl , a=0.82994 ) 0.00000

  4. Lattice-Boltzmann-based two-phase thermal model for simulating phase change

    NARCIS (Netherlands)

    Kamali, M.R.; Gillissen, J.J.J.; Van den Akker, H.E.A.; Sundaresan, S.

    2013-01-01

    A lattice Boltzmann (LB) method is presented for solving the energy conservation equation in two phases when the phase change effects are included in the model. This approach employs multiple distribution functions, one for a pseudotemperature scalar variable and the rest for the various species. A

  5. Lattice-Boltzmann-based two-phase thermal model for simulating phase change

    NARCIS (Netherlands)

    Kamali, M.R.; Gillissen, J.J.J.; Van den Akker, H.E.A.; Sundaresan, S.

    2013-01-01

    A lattice Boltzmann (LB) method is presented for solving the energy conservation equation in two phases when the phase change effects are included in the model. This approach employs multiple distribution functions, one for a pseudotemperature scalar variable and the rest for the various species. A

  6. Employment, Production and Consumption model: Patterns of phase transitions

    Science.gov (United States)

    Lavička, H.; Lin, L.; Novotný, J.

    2010-04-01

    We have simulated the model of Employment, Production and Consumption (EPC) using Monte Carlo. The EPC model is an agent based model that mimics very basic rules of industrial economy. From the perspective of physics, the nature of the interactions in the EPC model represents multi-agent interactions where the relations among agents follow the key laws for circulation of capital and money. Monte Carlo simulations of the stochastic model reveal phase transition in the model economy. The two phases are the phase with full unemployment and the phase with nearly full employment. The economy switches between these two states suddenly as a reaction to a slight variation in the exogenous parameter, thus the system exhibits strong non-linear behavior as a response to the change of the exogenous parameters.

  7. Lattice-Boltzmann-based two-phase thermal model for simulating phase change

    OpenAIRE

    Kamali, M.R.; Gillissen, J.J.J.; Van den Akker, H.E.A.; Sundaresan, S.

    2013-01-01

    A lattice Boltzmann (LB) method is presented for solving the energy conservation equation in two phases when the phase change effects are included in the model. This approach employs multiple distribution functions, one for a pseudotemperature scalar variable and the rest for the various species. A nonideal equation of state (EOS) is introduced by using a pseudopotential LB model. The evolution equation for the pseudotemperature variable is constructed in such a manner that in the continuum l...

  8. Modeling Phase-Locked Loops Using Verilog

    Science.gov (United States)

    2007-11-01

    a charge pump, the phase detector has a tri-state output that can drive a opamp loop filter directly. This signal is conditioned by the charge pump...then it can directly drive an opamp based loop filter. Most loop filters are based upon an integrator loop. The integrator loop filter is advantageous...replaced with an accumulator. The opamp circuit can be replaced by a digital filter using Z-transform theory z=exp(jwT), where T is the sampling

  9. Phase Correlation Based Iris Image Registration Model

    Institute of Scientific and Technical Information of China (English)

    Jun-Zhou Huang; Tie-Niu Tan; Li Ma; Yun-Hong Wang

    2005-01-01

    Iris recognition is one of the most reliable personal identification methods. In iris recognition systems, image registration is an important component. Accurately registering iris images leads to higher recognition rate for an iris recognition system. This paper proposes a phase correlation based method for iris image registration with sub-pixel accuracy.Compared with existing methods, it is insensitive to image intensity and can compensate to a certain extent the non-linear iris deformation caused by pupil movement. Experimental results show that the proposed algorithm has an encouraging performance.

  10. Phase field modeling of dendrite growth

    Institute of Scientific and Technical Information of China (English)

    Yutuo ZHANG; Chengzhi WANG; Dianzhong LI; Yiyi LI

    2009-01-01

    Single dendrite and multi-dendrite growth for A1-2 mol pct Si alloy during isothermal solidification are simulated by phase field method. In the case of single equiaxed dendrite growth, the secondary and the necking phenomenon can be observed. For multi-dendrite growth, there exists the competitive growth among the dendrites dur-ing solidification. As solidification proceeds, growing and coarsening of the primary arms occurs, together with the branching and coarsening of the secondary arms.When the diffusion fields of dendrite tips come into contact with those of the branches growing from the neighboring dendrites, the dendrites stop growing and being to ripen and thicken.

  11. Phase diagram of anisotropic boson t-J model

    OpenAIRE

    Boninsegni, M.; Prokof'ev, N. V.

    2007-01-01

    We have studied by Quantum Monte Carlo simulations the low temperature phase diagram of a mixture of isotopic, hard core bosons, described by the t-Jz-Jperp model, with Jperp=a Jz. Coexistence of superfluid hole-rich and insulating, antiferromagnetically ordered hole-free phases is observed at sufficiently low hole density, for any a < 1. A two-component checkerboard supersolid phase is not observed. The experimental relevance and possible broader implications of these findings are discussed.

  12. HYTEST Phase I Facility Commissioning and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Lee P. Shunn; Richard D. Boardman; Shane J. Cherry; Craig G. Rieger

    2009-09-01

    The purpose of this document is to report the first year accomplishments of two coordinated Laboratory Directed Research and Development (LDRD) projects that utilize a hybrid energy testing laboratory that couples various reactors to investigate system reactance behavior. This work is the first phase of a series of hybrid energy research and testing stations - referred to hereafter as HYTEST facilities – that are planned for construction and operation at the Idaho National Laboratory (INL). A HYTEST Phase I facility was set up and commissioned in Bay 9 of the Bonneville County Technology Center (BCTC). The purpose of this facility is to utilize the hydrogen and oxygen that is produced by the High Temperature Steam Electrolysis test reactors operating in Bay 9 to support the investigation of kinetic phenomena and transient response of integrated reactor components. This facility provides a convenient scale for conducting scoping tests of new reaction concepts, materials performance, new instruments, and real-time data collection and manipulation for advance process controls. An enclosed reactor module was assembled and connected to a new ventilation system equipped with a variable-speed exhaust blower to mitigate hazardous gas exposures, as well as contract with hot surfaces. The module was equipped with a hydrogen gas pump and receiver tank to supply high quality hydrogen to chemical reactors located in the hood.

  13. Dynamical phase transitions in the two-dimensional ANNNI model

    Energy Technology Data Exchange (ETDEWEB)

    Barber, M.N.; Derrida, B.

    1988-06-01

    We study the phase diagram of the two-dimensional anisotropic next-nearest neighbor Ising (ANNNI) model by comparing the time evolution of two distinct spin configurations submitted to the same thermal noise. We clearly se several dynamical transitions between ferromagnetic, paramagnetic, antiphase, and floating phases. These dynamical transitions seem to occur rather close to the transition lines determined previously in the literature.

  14. Instabilities near the QCD phase transition in the holographic models

    NARCIS (Netherlands)

    Gürsoy, U.; Lin, S.; Shuryak, E.

    2013-01-01

    This paper discusses phenomena close to the critical QCD temperature, using the holographic model. One issue studied is the overcooled high-T phase, in which we calculate quasinormal sound modes. We do not find instabilities associated with other first-order phase transitions, but nevertheless obser

  15. Equivalent-circuit modeling of a MEMS phase detector for phase-locked loop applications

    Science.gov (United States)

    Han, Juzheng; Liao, Xiaoping

    2016-05-01

    This paper presents an equivalent-circuit model of a MEMS phase detector and deals with its application in phase-locked loops (PLLs). Due to the dc voltage output of the MEMS phase detector, the low-pass filter which is essential in a conventional PLL can be omitted. Thus, the layout area can be miniaturized and the consumed power can be saved. The signal transmission inside the phase detector is realized in circuit model by waveguide modules while the electric-thermal-electric conversion is illustrated in circuit term based on analogies between thermal and electrical variables. Losses are taken into consideration in the modeling. Measurement verifications for the phase detector model are conducted at different input powers 11, 14 and 17 dBm at 10 GHz. The maximum discrepancies between the simulated and measured results are 0.14, 0.42 and 1.13 mV, respectively. A new structure of PLL is constructed by connecting the presented model directly to a VCO module in the simulation platform. It allows to model the transient behaviors of the PLL at both locked and out of lock conditions. The VCO output frequency is revealed to be synchronized with the reference frequency within the hold range. All the modeling and simulation are performed in Advanced Design System (ADS) software.

  16. Phase transitions in simplified models with long-range interactions

    Science.gov (United States)

    Rocha Filho, T. M.; Amato, M. A.; Mello, B. A.; Figueiredo, A.

    2011-10-01

    We study the origin of phase transitions in several simplified models with long-range interactions. For the self-gravitating ring model, we are unable to observe a possible phase transition predicted by Nardini and Casetti [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.80.060103 80, 060103R (2009).] from an energy landscape analysis. Instead we observe a sharp, although without any nonanalyticity, change from a core-halo to a core-only configuration in the spatial distribution functions for low energies. By introducing a different class of solvable simplified models without any critical points in the potential energy we show that a behavior similar to the thermodynamics of the ring model is obtained, with a first-order phase transition from an almost homogeneous high-energy phase to a clustered phase and the same core-halo to core configuration transition at lower energies. We discuss the origin of these features for the simplified models and show that the first-order phase transition comes from the maximization of the entropy of the system as a function of energy and an order parameter, as previously discussed by Hahn and Kastner [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.72.056134 72, 056134 (2005); Eur. Phys. J. BEPJBFY1434-602810.1140/epjb/e2006-00100-7 50, 311 (2006)], which seems to be the main mechanism causing phase transitions in long-range interacting systems.

  17. Characterization and Computational Modeling of Minor Phases in Alloy LSHR

    Science.gov (United States)

    Jou, Herng-Jeng; Olson, Gregory; Gabb, Timothy; Garg, Anita; Miller, Derek

    2012-01-01

    The minor phases of powder metallurgy disk superalloy LSHR were studied. Samples were consistently heat treated at three different temperatures for long times to approach equilibrium. Additional heat treatments were also performed for shorter times, to assess minor phase kinetics in non-equilibrium conditions. Minor phases including MC carbides, M23C6 carbides, M3B2 borides, and sigma were identified. Their average sizes and total area fractions were determined. CALPHAD thermodynamics databases and PrecipiCalc(TradeMark), a computational precipitation modeling tool, were employed with Ni-base thermodynamics and diffusion databases to model and simulate the phase microstructural evolution observed in the experiments with an objective to identify the model limitations and the directions of model enhancement.

  18. QCD Phase Transition in a new Hybrid Model Formulation

    CERN Document Server

    Srivastava, P K

    2013-01-01

    Search of a proper and realistic equations of state (EOS) for strongly interacting matter used in the study of QCD phase diagram still appears as a challenging task. Recently, we have constructed a hybrid model description for the quark gluon plasma (QGP) as well as hadron gas (HG) phases where we use a new excluded-volume model for HG and a thermodynamically-consistent quasiparticle model for the QGP phase. We attempt to use them to get a QCD phase boundary and a critical point. We test our hybrid model by reproducing the entire lattice QCD data for strongly interacting matter at zero baryon chemical potential ($\\mu_{B}$)and predict the results at finite $\\mu_{B}$ and $T$.

  19. Integrability and Quantum Phase Transitions in Interacting Boson Models

    CERN Document Server

    Dukelsky, J; García-Ramos, J E; Pittel, S

    2003-01-01

    The exact solution of the boson pairing hamiltonian given by Richardson in the sixties is used to study the phenomena of level crossings and quantum phase transitions in the integrable regions of the sd and sdg interacting boson models.

  20. Phase Transition Properties of 3D Potts Models

    CERN Document Server

    Bazavov, Alexei; Dubey, Santosh

    2008-01-01

    Using multicanonical Metropolis simulations we estimate phase transition properties of 3D Potts models for q=4 to 10: The transition temperatures, latent heats, entropy gaps, normalized entropies at the disordered and ordered endpoints, interfacial tensions, and spinodal endpoints.

  1. Modelling of phase diagrams of nanoalloys with complex metallic phases: application to Ni-Sn.

    Science.gov (United States)

    Kroupa, A; Káňa, T; Buršík, J; Zemanová, A; Šob, M

    2015-11-14

    A method for modelling of size-dependent phase diagrams was developed by combining the semiempirical CALPHAD method and ab initio calculations of surface stresses for intermetallic phases. A novel approach was devised for the calculation of surface energy, free of systematic errors from the selection of different parameters of the software (e.g. number of the k-points) and for handling layered structures and off-stoichiometric slabs. Our approach allows the determination of complex size-dependent phase diagrams of systems with intermetallic phases, which was not possible up to now. The method was verified for the modelling of the phase diagram of the Ni-Sn system and basic comparison with rare experimental results was shown. There is reasonable agreement between the calculated and experimental results. The modelling of size-dependent phase diagrams of real systems allows the prediction of phase equilibria existing in nanosystems and possible changes in material properties. There is a need for such knowledge and the existence of reliable data for simpler systems is crucial for further application of this approach. This should motivate future experimental work.

  2. Advanced Phase noise modeling techniques of nonlinear microwave devices

    OpenAIRE

    Prigent, M.; J. C. Nallatamby; R. Quere

    2004-01-01

    In this paper we present a coherent set of tools allowing an accurate and predictive design of low phase noise oscillators. Advanced phase noise modelling techniques in non linear microwave devices must be supported by a proven combination of the following : - Electrical modeling of low-frequency noise of semiconductor devices, oriented to circuit CAD . The local noise sources will be either cyclostationary noise sources or quasistationary noise sources. - Theoretic...

  3. A phase-space model for Pleistocene ice volume

    CERN Document Server

    Imbrie, John Z; Lisiecki, Lorraine E

    2011-01-01

    We present a phase-space model that simulates Pleistocene ice volume changes based on Earth's orbital parameters. Terminations in the model are triggered by a combination of ice volume and orbital forcing and agree well with age estimates for Late Pleistocene terminations. The average phase at which model terminations begin is approximately 90 +/- 90 degrees before the maxima in all three orbital cycles. The large variability in phase is likely caused by interactions between the three cycles and ice volume. Unlike previous ice volume models, this model produces an orbitally driven increase in 100-kyr power during the mid-Pleistocene transition without any change in model parameters. This supports the hypothesis that Pleistocene variations in the 100-kyr power of glacial cycles could be caused, at least in part, by changes in Earth's orbital parameters, such as amplitude modulation of the 100-kyr eccentricity cycle, rather than changes within the climate system.

  4. Phase field modeling of flexoelectricity in solid dielectrics

    Science.gov (United States)

    Chen, H. T.; Zhang, S. D.; Soh, A. K.; Yin, W. Y.

    2015-07-01

    A phase field model is developed to study the flexoelectricity in nanoscale solid dielectrics, which exhibit both structural and elastic inhomogeneity. The model is established for an elastic homogeneous system by taking into consideration all the important non-local interactions, such as electrostatic, elastic, polarization gradient, as well as flexoelectric terms. The model is then extended to simulate a two-phase system with strong elastic inhomogeneity. Both the microscopic domain structures and the macroscopic effective piezoelectricity are thoroughly studied using the proposed model. The results obtained show that the largest flexoelectric induced polarization exists at the interface between the matrix and the inclusion. The effective piezoelectricity is greatly influenced by the inclusion size, volume fraction, elastic stiffness, and the applied stress. The established model in the present study can provide a fundamental framework for computational study of flexoelectricity in nanoscale solid dielectrics, since various boundary conditions can be easily incorporated into the phase field model.

  5. A stochastic phase-field model determined from molecular dynamics

    KAUST Repository

    von Schwerin, Erik

    2010-03-17

    The dynamics of dendritic growth of a crystal in an undercooled melt is determined by macroscopic diffusion-convection of heat and by capillary forces acting on the nanometer scale of the solid-liquid interface width. Its modelling is useful for instance in processing techniques based on casting. The phase-field method is widely used to study evolution of such microstructural phase transformations on a continuum level; it couples the energy equation to a phenomenological Allen-Cahn/Ginzburg-Landau equation modelling the dynamics of an order parameter determining the solid and liquid phases, including also stochastic fluctuations to obtain the qualitatively correct result of dendritic side branching. This work presents a method to determine stochastic phase-field models from atomistic formulations by coarse-graining molecular dynamics. It has three steps: (1) a precise quantitative atomistic definition of the phase-field variable, based on the local potential energy; (2) derivation of its coarse-grained dynamics model, from microscopic Smoluchowski molecular dynamics (that is Brownian or over damped Langevin dynamics); and (3) numerical computation of the coarse-grained model functions. The coarse-grained model approximates Gibbs ensemble averages of the atomistic phase-field, by choosing coarse-grained drift and diffusion functions that minimize the approximation error of observables in this ensemble average. © EDP Sciences, SMAI, 2010.

  6. Full Phase Diagram of the Massive Gross-Neveu Model

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2006-01-01

    The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The scalar potential is given in terms of Jacobi elliptic functions. It contains three parameters which are determined by transcendental equations. Self-consistency of the scalar potential is proved. The phase diagram for non-zero bare quark mass is found to contain a kink-antikink crystal phase as well as a massive fermion gas phase featuring a cross-over from light to heavy effective fermion mass. For zero bare quark mass we recover the three known phases kink-antikink crystal, massless fermion gas, and massive fermion gas. All phase transitions are shown to be of second order. Equations for the phase boundaries are given and solved numerically. Implications on condensed matter physics are indicated where our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.

  7. Phase transitions in models of human cooperation

    Science.gov (United States)

    Perc, Matjaž

    2016-08-01

    If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.

  8. Lattice Boltzmann modeling of three-phase incompressible flows

    Science.gov (United States)

    Liang, H.; Shi, B. C.; Chai, Z. H.

    2016-01-01

    In this paper, based on multicomponent phase-field theory we intend to develop an efficient lattice Boltzmann (LB) model for simulating three-phase incompressible flows. In this model, two LB equations are used to capture the interfaces among three different fluids, and another LB equation is adopted to solve the flow field, where a new distribution function for the forcing term is delicately designed. Different from previous multiphase LB models, the interfacial force is not used in the computation of fluid velocity, which is more reasonable from the perspective of the multiscale analysis. As a result, the computation of fluid velocity can be much simpler. Through the Chapman-Enskog analysis, it is shown that the present model can recover exactly the physical formulations for the three-phase system. Numerical simulations of extensive examples including two circular interfaces, ternary spinodal decomposition, spreading of a liquid lens, and Kelvin-Helmholtz instability are conducted to test the model. It is found that the present model can capture accurate interfaces among three different fluids, which is attributed to its algebraical and dynamical consistency properties with the two-component model. Furthermore, the numerical results of three-phase flows agree well with the theoretical results or some available data, which demonstrates that the present LB model is a reliable and efficient method for simulating three-phase flow problems.

  9. Phase diagram of model anisotropic particles with octahedral symmetry

    OpenAIRE

    Noya, E. G.; Vega, C.; Doye, J. P. K.; Louis, A. A.

    2007-01-01

    We computed the phase diagram for a system of model anisotropic particles with six attractive patches in an octahedral arrangement. We chose to study this model for a relatively narrow value of the patch width where the lowest-energy configuration of the system is a simple cubic crystal. At this value of the patch width, there is no stable vapour-liquid phase separation, and there are three other crystalline phases in addition to the simple cubic crystal that is most stable at low pressure. F...

  10. Cellular automata modelling of phase-change memories

    Institute of Scientific and Technical Information of China (English)

    Wanhua Yu; David Wright

    2008-01-01

    A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton (CA) approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.

  11. On the Chiral Phase Transition in the Linear Sigma Model

    CERN Document Server

    Phat, T H; Hoa, L V; Phat, Tran Huu; Anh, Nguyen Tuan; Hoa, Le Viet

    2004-01-01

    The Cornwall-Jackiw-Tomboulis (CJT) effective action for composite operators at finite temperature is used to investigate the chiral phase transition within the framework of the linear sigma model as the low-energy effective model of quantum chromodynamics (QCD). A new renormalization prescription for the CJT effective action in the Hartree-Fock (HF) approximation is proposed. A numerical study, which incorporates both thermal and quantum effect, shows that in this approximation the phase transition is of first order. However, taking into account the higher-loop diagrams contribution the order of phase transition is unchanged.

  12. The KM phase in semi-realistic heterotic orbifold models

    Energy Technology Data Exchange (ETDEWEB)

    Giedt, Joel

    2000-07-05

    In string-inspired semi-realistic heterotic orbifolds models with an anomalous U(1){sub X},a nonzero Kobayashi-Masakawa (KM) phase is shown to arise generically from the expectation values of complex scalar fields, which appear in nonrenormalizable quark mass couplings. Modular covariant nonrenormalizable superpotential couplings are constructed. A toy Z{sub 3} orbifold model is analyzed in some detail. Modular symmetries and orbifold selection rules are taken into account and do not lead to a cancellation of the KM phase. We also discuss attempts to obtain the KM phase solely from renormalizable interactions.

  13. Phase transitions in the lattice model of intercalation

    Directory of Open Access Journals (Sweden)

    T.S. Mysakovych

    2008-12-01

    Full Text Available The lattice model which can be employed for the description of intercalation of ions in crystals is considered in this work. Pseudospin formalism is used in describing the interaction of electrons with ions. The possibility of hopping of intercalated ions between different positions is taken into account. The thermodynamics of the model is investigated in the mean field approximation. Phase diagrams are built. It is shown that at high values of the parameter of ion transfer, the phase transition to a modulated phase disappears.

  14. Cupola modeling research: Phase 2 (Year one), Final report

    Energy Technology Data Exchange (ETDEWEB)

    1991-11-20

    Objective was to develop a mathematical model of the cupola furnace (cast iron production) in on-line and off-line process control and optimization. In Phase I, the general structure of the heat transfer, fluid flow, and chemical models were laid out, providing reasonable descriptions of cupola behavior with a one-dimensional representation. Work was also initiated on a two-dimensional model. Phase II was focused on perfecting the one-dimensional model. The contributions include these from MIT, Michigan University, and GM.

  15. Modeling thermodynamics of Fe-N phases

    DEFF Research Database (Denmark)

    Pekelharing, Marjon I.; Böttger, Amarante; Somers, Marcel A. J.

    1999-01-01

    In the present work homogeneous epsilon-nitride powders prepared at 723 K, having nitrogen contents ranging from 26.1 at. % N (z=0.29) to 31.1 at.% N (z=0.10), were investigated with X-ray diffraction (XRD) and Mössbauer spectroscopy. A thermodynamic model accounting for the two possible configur......In the present work homogeneous epsilon-nitride powders prepared at 723 K, having nitrogen contents ranging from 26.1 at. % N (z=0.29) to 31.1 at.% N (z=0.10), were investigated with X-ray diffraction (XRD) and Mössbauer spectroscopy. A thermodynamic model accounting for the two possible...

  16. Comparative assessment of three-phase oil relative permeability models

    Science.gov (United States)

    Ranaee, Ehsan; Riva, Monica; Porta, Giovanni M.; Guadagnini, Alberto

    2016-07-01

    We assess the ability of 11 models to reproduce three-phase oil relative permeability (kro) laboratory data obtained in a water-wet sandstone sample. We do so by considering model performance when (i) solely two-phase data are employed to render predictions of kro and (ii) two and three-phase data are jointly used for model calibration. In the latter case, a Maximum Likelihood (ML) approach is used to estimate model parameters. The tested models are selected among (i) classical models routinely employed in practical applications and implemented in commercial reservoir software and (ii) relatively recent models which are considered to allow overcoming some drawbacks of the classical formulations. Among others, the latter set of models includes the formulation recently proposed by Ranaee et al., which has been shown to embed the critical effects of hysteresis, including the reproduction of oil remobilization induced by gas injection in water-wet media. We employ formal model discrimination criteria to rank models according to their skill to reproduce the observed data and use ML Bayesian model averaging to provide model-averaged estimates (and associated uncertainty bounds) of kro by taking advantage of the diverse interpretive abilities of all models analyzed. The occurrence of elliptic regions is also analyzed for selected models in the framework of the classical fractional flow theory of displacement. Our study confirms that model outcomes based on channel flow theory and classical saturation-weighted interpolation models do not generally yield accurate reproduction of kro data, especially in the regime associated with low oil saturations, where water alternating gas injection (WAG) techniques are usually employed for enhanced oil recovery. This negative feature is not observed in the model of Ranaee et al. (2015) due to its ability to embed key effects of pore-scale phase distributions, such as hysteresis effects and cycle dependency, for modeling kro observed

  17. Mathematical modeling of disperse two-phase flows

    CERN Document Server

    Morel, Christophe

    2015-01-01

    This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, a...

  18. Mathematical model of two-phase flow in accelerator channel

    Directory of Open Access Journals (Sweden)

    О.Ф. Нікулін

    2010-01-01

    Full Text Available  The problem of  two-phase flow composed of energy-carrier phase (Newtonian liquid and solid fine-dispersed phase (particles in counter jet mill accelerator channel is considered. The mathematical model bases goes on the supposition that the phases interact with each other like independent substances by means of aerodynamics’ forces in conditions of adiabatic flow. The mathematical model in the form of system of differential equations of order 11 is represented. Derivations of equations by base physical principles for cross-section-averaged quantity are produced. The mathematical model can be used for estimation of any kinematic and thermodynamic flow characteristics for purposely parameters optimization problem solving and transfer functions determination, that take place in  counter jet mill accelerator channel design.

  19. A novel three-phase model of brain tissue microstructure.

    Science.gov (United States)

    Gevertz, Jana L; Torquato, Salvatore

    2008-08-15

    We propose a novel biologically constrained three-phase model of the brain microstructure. Designing a realistic model is tantamount to a packing problem, and for this reason, a number of techniques from the theory of random heterogeneous materials can be brought to bear on this problem. Our analysis strongly suggests that previously developed two-phase models in which cells are packed in the extracellular space are insufficient representations of the brain microstructure. These models either do not preserve realistic geometric and topological features of brain tissue or preserve these properties while overestimating the brain's effective diffusivity, an average measure of the underlying microstructure. In light of the highly connected nature of three-dimensional space, which limits the minimum diffusivity of biologically constrained two-phase models, we explore the previously proposed hypothesis that the extracellular matrix is an important factor that contributes to the diffusivity of brain tissue. Using accurate first-passage-time techniques, we support this hypothesis by showing that the incorporation of the extracellular matrix as the third phase of a biologically constrained model gives the reduction in the diffusion coefficient necessary for the three-phase model to be a valid representation of the brain microstructure.

  20. A novel three-phase model of brain tissue microstructure.

    Directory of Open Access Journals (Sweden)

    Jana L Gevertz

    Full Text Available We propose a novel biologically constrained three-phase model of the brain microstructure. Designing a realistic model is tantamount to a packing problem, and for this reason, a number of techniques from the theory of random heterogeneous materials can be brought to bear on this problem. Our analysis strongly suggests that previously developed two-phase models in which cells are packed in the extracellular space are insufficient representations of the brain microstructure. These models either do not preserve realistic geometric and topological features of brain tissue or preserve these properties while overestimating the brain's effective diffusivity, an average measure of the underlying microstructure. In light of the highly connected nature of three-dimensional space, which limits the minimum diffusivity of biologically constrained two-phase models, we explore the previously proposed hypothesis that the extracellular matrix is an important factor that contributes to the diffusivity of brain tissue. Using accurate first-passage-time techniques, we support this hypothesis by showing that the incorporation of the extracellular matrix as the third phase of a biologically constrained model gives the reduction in the diffusion coefficient necessary for the three-phase model to be a valid representation of the brain microstructure.

  1. Non-equilibrium model of two-phase porous media flow with phase change

    Science.gov (United States)

    Cueto-Felgueroso, L.; Fu, X.; Juanes, R.

    2014-12-01

    The efficient simulation of multi-phase multi-component flow through geologic porous media is challenging and computationally intensive, yet quantitative modeling of these processes is essential in engineering and the geosciences. Multiphase flow with phase change and complex phase behavior arises in numerous applications, including enhanced oil recovery, steam injection in groundwater remediation, geologic CO2 storage and enhanced geothermal energy systems. A challenge of multiphase compositional simulation is that the number of existing phases varies with position and time, and thus the number of state variables in the saturation-based conservation laws is a function of space and time. The tasks of phase-state identification and determination of the composition of the different phases are performed assuming local thermodynamic equilibrium. Here we investigate a thermodynamically consistent formulation for non-isothermal two-phase flow, in systems where the hypothesis of instantaneous local equilibrium does not hold. Non-equilibrium effects are important in coarse-scale simulations where the assumption of complete mixing in each gridblock is not realistic. We apply our model to steam injection in water-saturated porous media.

  2. Use of piecewise polynomial phase modeling to compensate ionospheric phase contamination in skywave radar systems

    Institute of Scientific and Technical Information of China (English)

    Lu Kun; Liu Xingzhao

    2005-01-01

    Recognition and correction of ionospheric phase path contamination is a vital part of the global radar signal processing sequence. A number of model-based correction algorithms have been developed to deal with the radar performance degradation due to the ionospheric distortion and contamination. This paper addresses a novel parametric estimation and compensation method based on High-order Ambiguity Function (HAF) to solve the problem of phase path contamination of HF skywave radar signals. When signal-to-noise ratio and data sequence available satisfy the predefined conditions, the ionospheric phase path contamination may be modeled by a polynomial phase signal (PPS). As a new parametric tool for analyzing the PPS, HAF is introduced to estimate parameters of the polynomial-phase model and reconstruct the correction signal. Using the reconstructed correction signal, compensation can be performed before coherent integration so that the original echo spectrum can be restored. A piecewise scheme is proposed to track rapid variation of the phase contamination based on HAF method, and it can remove the Doppler spread effect caused by the ionos phere nonstationarity. Simulation and experimental results are given to demonstrate the efficiency of the proposed algorithm.

  3. COMMON PHASES OF COMPUTER FORENSICS INVESTIGATION MODELS

    Directory of Open Access Journals (Sweden)

    Yunus Yusoff

    2011-06-01

    Full Text Available The increasing criminal activities using digital information as the means or targets warrant for a structured manner in dealing with them. Since 1984 when a formalized process been introduced, a great number of new and improved computer forensic investigation processes have been developed. In this paper, we reviewed a few selected investigation processes that have been produced throughout the yearsand then identified the commonly shared processes. Hopefully, with the identification of the commonly shard process, it would make it easier for the new users to understand the processes and also to serve as the basic underlying concept for the development of a new set of processes. Based on the commonly shared processes, we proposed a generic computer forensics investigation model, known as GCFIM.

  4. A SPICE model for a phase-change memory cell based on the analytical conductivity model

    Science.gov (United States)

    Yiqun, Wei; Xinnan, Lin; Yuchao, Jia; Xiaole, Cui; Jin, He; Xing, Zhang

    2012-11-01

    By way of periphery circuit design of the phase-change memory, it is necessary to present an accurate compact model of a phase-change memory cell for the circuit simulation. Compared with the present model, the model presented in this work includes an analytical conductivity model, which is deduced by means of the carrier transport theory instead of the fitting model based on the measurement. In addition, this model includes an analytical temperature model based on the 1D heat-transfer equation and the phase-transition dynamic model based on the JMA equation to simulate the phase-change process. The above models for phase-change memory are integrated by using Verilog-A language, and results show that this model is able to simulate the I-V characteristics and the programming characteristics accurately.

  5. A Temperature-Dependent Phase-Field Model for Phase Separation and Damage

    Science.gov (United States)

    Heinemann, Christian; Kraus, Christiane; Rocca, Elisabetta; Rossi, Riccarda

    2017-07-01

    In this paper we study a model for phase separation and damage in thermoviscoelastic materials. The main novelty of the paper consists in the fact that, in contrast with previous works in the literature concerning phase separation and damage processes in elastic media, in our model we encompass thermal processes, nonlinearly coupled with the damage, concentration and displacement evolutions. More particularly, we prove the existence of "entropic weak solutions", resorting to a solvability concept first introduced in Feireisl (Comput Math Appl 53:461-490, 2007) in the framework of Fourier-Navier-Stokes systems and then recently employed in Feireisl et al. (Math Methods Appl Sci 32:1345-1369, 2009) and Rocca and Rossi (Math Models Methods Appl Sci 24:1265-1341, 2014) for the study of PDE systems for phase transition and damage. Our global-in-time existence result is obtained by passing to the limit in a carefully devised time-discretization scheme.

  6. EFFECTS OF PHASE CONTINUITY ON RHEOLOGY OF TWO-PHASE ROCKS:A CONTINUUM MECHANICL MODEL

    Institute of Scientific and Technical Information of China (English)

    JI Shao-cheng

    2001-01-01

    Based on continuum mechanics,we have developed a model for semi-quantitative estimating effects of phase continuity on flow strength of two-phase rocks including partially melted or crystallized rocks.Calculations of the bulk flow strength of composite rocks as functions of the volume fraction,geometrical shape and continuity of the constitutive phases involve in numerically solving two non-linear equations and thus are easy to be performed.The model has been justified by a good agreement between the predicted and measured results on diabase (64% clinopyroxene and 36% plagioclase) in the range of experimental temperatures and strain-rates.It is believed that the present model could provide an approximate estimate for the rheological evolution of magmatic rocks during their life cycle of melting-crystallization-deformation.

  7. An SPICE model for phase-change memory simulations

    Institute of Scientific and Technical Information of China (English)

    Li Xi; Song Zhitang; Cai Daolin; Chen Xiaogang; Chen Houpeng

    2011-01-01

    Along with a series of research works on the physical prototype and properties of the memory cell,an SPICE model for phase-change memory (PCM) simulations based on Verilog-A language is presented.By handling it with the heat distribution algorithm,threshold switching theory and the crystallization kinetic model,the proposed SPICE model can effectively reproduce the physical behaviors of the phase-change memory cell.In particular,it can emulate the cell's temperature curve and crystallinity profile during the programming process,which can enable us to clearly understand the PCM's working principle and program process.

  8. Cascade Failure in a Phase Model of Power Grids

    Science.gov (United States)

    Sakaguchi, Hidetsugu; Matsuo, Tatsuma

    2012-07-01

    We propose a phase model to study cascade failure in power grids composed of generators and loads. If the power demand is below a critical value, the model system of power grids maintains the standard frequency by feedback control. On the other hand, if the power demand exceeds the critical value, an electric failure occurs via step out (loss of synchronization) or voltage collapse. The two failures are incorporated as two removal rules of generator nodes and load nodes. We perform direct numerical simulation of the phase model on a square lattice and a scale-free network and compare the results with a mean-field approximation.

  9. Modeling quantitative phase image formation under tilted illuminations.

    Science.gov (United States)

    Bon, Pierre; Wattellier, Benoit; Monneret, Serge

    2012-05-15

    A generalized product-of-convolution model for simulation of quantitative phase microscopy of thick heterogeneous specimen under tilted plane-wave illumination is presented. Actual simulations are checked against a much more time-consuming commercial finite-difference time-domain method. Then modeled data are compared with experimental measurements that were made with a quadriwave lateral shearing interferometer.

  10. A mechanical erosion model for two-phase mass flows

    CERN Document Server

    Pudasaini, Shiva P

    2016-01-01

    Erosion, entrainment and deposition are complex and dominant, but yet poorly understood, mechanical processes in geophysical mass flows. Here, we propose a novel, process-based, two-phase, erosion-deposition model capable of adequately describing these complex phenomena commonly observed in landslides, avalanches, debris flows and bedload transport. The model is based on the jump in the momentum flux including changes of material and flow properties along the flow-bed interface and enhances an existing general two-phase mass flow model (Pudasaini, 2012). A two-phase variably saturated erodible basal morphology is introduced and allows for the evolution of erosion-deposition-depths, incorporating the inherent physical process including momentum and rheological changes of the flowing mixture. By rigorous derivation, we show that appropriate incorporation of the mass and momentum productions or losses in conservative model formulation is essential for the physically correct and mathematically consistent descript...

  11. Two kinds of Phase transitions in a Voting model

    CERN Document Server

    Hisakado, Masato

    2012-01-01

    In this paper, we discuss a voting model with two candidates, C_1 and C_2. We consider two types of voters--herders and independents. The voting of independents is based on their fundamental values; on the other hand, the voting of herders is based on the number of previous votes. We can identify two kinds of phase transitions. One is information cascade transition similar to a phase transition seen in Ising model. The other is a transition of super and normal diffusions. These phase transitions coexist together. We compared our results to the conclusions of experiments and identified the phase transitions in the upper t limit using analysis of human behavior obtained from experiments.

  12. Lifshitz Transitions in Magnetic Phases of the Periodic Anderson Model

    Science.gov (United States)

    Kubo, Katsunori

    2015-09-01

    We investigate the reconstruction of a Fermi surface, which is called a Lifshitz transition, in magnetically ordered phases of the periodic Anderson model on a square lattice with a finite Coulomb interaction between f electrons. We apply the variational Monte Carlo method to the model by using the Gutzwiller wavefunctions for the paramagnetic, antiferromagnetic, ferromagnetic, and charge-density-wave states. We find that an antiferromagnetic phase is realized around half-filling and a ferromagnetic phase is realized when the system is far away from half-filling. In both magnetic phases, Lifshitz transitions take place. By analyzing the electronic states, we conclude that the Lifshitz transitions to large ordered-moment states can be regarded as itinerant-localized transitions of the f electrons.

  13. Modeling and Simulation of Two-Phase Two-Component Flow with Disappearing Nonwetting Phase

    CERN Document Server

    Neumann, Rebecca; Ippisch, Olaf

    2012-01-01

    Carbon Capture and Storage (CCS) is a recently discussed new technology, aimed at allowing an ongoing use of fossil fuels while preventing the produced CO2 to be released to the atmosphere. CSS can be modeled with two components (water and CO2) in two phases (liquid and CO2). To simulate the process, a multiphase flow equation with equilibrium phase exchange is used. One of the big problems arising in two-phase two-component flow simulations is the disappearance of the nonwetting phase, which leads to a degeneration of the equations satisfied by the saturation. A standard choice of primary variables, which is the pressure of one phase and the saturation of the other phase, cannot be applied here. We developed a new approach using the pressure of the nonwetting phase and the capillary pressure as primary variables. One important advantage of this approach is the fact that we have only one set of primary variables that can be used for the biphasic as well as the monophasic case. We implemented this new choice o...

  14. KN Phase Shifts in Chiral SU(3) Quark Model

    Institute of Scientific and Technical Information of China (English)

    HUANGFei; ZHANGZong-Ye; YUYou-Wen

    2004-01-01

    The isospin I = 0 and I = 1 kaon-nucleon S and P partial waves phase shifts have been studied in the chiral SU(3) quark model by solving a resonating group method equation. When the parameters of the chiral fields are taken in a reasonable region, the numerical results of S-wave are in good agreement with the experimental data, and the P-wave phase shifts can also be explained qualitatively by the calculation of only central force considered.

  15. Advanced geothermal hydraulics model -- Phase 1 final report, Part 2

    Energy Technology Data Exchange (ETDEWEB)

    W. Zheng; J. Fu; W. C. Maurer

    1999-07-01

    An advanced geothermal well hydraulics model (GEODRIL) is being developed to accurately calculate bottom-hole conditions in these hot wells. In Phase 1, real-time monitoring and other improvements were added to GEODRIL. In Phase 2, GEODRIL will be integrated into Marconi's Intelligent Drilling Monitor (IDM) that will use artificial intelligence to detect lost circulation, fluid influxes and other circulation problems in geothermal wells. This software platform has potential for significantly reducing geothermal drilling costs.

  16. The rich phase structure of a mutator model

    Science.gov (United States)

    Saakian, David B.; Yakushkina, Tatiana; Hu, Chin-Kun

    2016-10-01

    We propose a modification of the Crow-Kimura and Eigen models of biological molecular evolution to include a mutator gene that causes both an increase in the mutation rate and a change in the fitness landscape. This mutator effect relates to a wide range of biomedical problems. There are three possible phases: mutator phase, mixed phase and non-selective phase. We calculate the phase structure, the mean fitness and the fraction of the mutator allele in the population, which can be applied to describe cancer development and RNA viruses. We find that depending on the genome length, either the normal or the mutator allele dominates in the mixed phase. We analytically solve the model for a general fitness function. We conclude that the random fitness landscape is an appropriate choice for describing the observed mutator phenomenon in the case of a small fraction of mutators. It is shown that the increase in the mutation rates in the regular and the mutator parts of the genome should be set independently; only some combinations of these increases can push the complex biomedical system to the non-selective phase, potentially related to the eradication of tumors.

  17. Model-based optimization of phased array ultrasonic testing

    Institute of Scientific and Technical Information of China (English)

    Sung-Jin; Song; Hak-Joon; Kim; Suk-Chull; Kang; Sung-Sik; Kang; Kyungcho; Kim; Myung-Ho; Song

    2010-01-01

    Simulation of phased array beams in dovetail and austenitic welds is conducted to optimize the setup of phased array ultrasonic testing(PAUT).To simulate the beam in such material with complex geometry or with characteristic of anisotropy and inhomogeneity, firstly,linear phased multi-Gaussian beam(LPMGB) models are introduced and discussed. Then,in the case of dovetail,wedge is designed to maximize the stable amplitude of the beam along the steering path;in the case of austenitic weld,modified focal law...

  18. Aharonov-Anandan Phases in Lipkin-Meskov-Glick Model

    Institute of Scientific and Technical Information of China (English)

    杨大宝; 陈景灵

    2011-01-01

    In the system of several interacting spins, geometric phases have been researched intensively. However, the studies are mainly focused on the adiabatic case (Berry phase), so it is necessary for us to study the non-adiabatic counterpart (Aharonov and Anandan phase). In this paper, we analyze both the non-degenerate and degenerate geometric phase of Lipkin-Meskov-Glick type model, which has many application in Bose-Einstein condensates and entanglement theory. Furthermore, in order to calculate degenerate geometric phases, the Floquet theorem and decomposition of operator are generalized. And the general formula is achieved.

  19. Two-phase relative permeability models in reservoir engineering calculations

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, S.; Hicks, P.J.; Ertekin, T.

    1999-01-15

    A comparison of ten two-phase relative permeability models is conducted using experimental, semianalytical and numerical approaches. Model predicted relative permeabilities are compared with data from 12 steady-state experiments on Berea and Brown sandstones using combinations of three white mineral oils and 2% CaCl1 brine. The model results are compared against the experimental data using three different criteria. The models are found to predict the relative permeability to oil, relative permeability to water and fractional flow of water with varying degrees of success. Relative permeability data from four of the experimental runs are used to predict the displacement performance under Buckley-Leverett conditions and the results are compared against those predicted by the models. Finally, waterflooding performances predicted by the models are analyzed at three different viscosity ratios using a two-dimensional, two-phase numerical reservoir simulator. (author)

  20. The Application of Phase Type Distributions for Modelling Queuing Systems

    Directory of Open Access Journals (Sweden)

    EIMUTIS VALAKEVICIUS

    2007-12-01

    Full Text Available Queuing models are important tools for studying the performance of complex systems, but despite the substantial queuing theory literature, it is often necessary to use approximations in the case the system is nonmarkovian. Phase type distribution is by now indispensable tool in creation of queuing system models. The purpose of this paper is to suggest a method and software for evaluating queuing approximations. A numerical queuing model with priorities is used to explore the behaviour of exponential phase-type approximation of service-time distribution. The performance of queuing systems described in the event language is used for generating the set of states and transition matrix between them. Two examples of numerical models are presented – a queuing system model with priorities and a queuing system model with quality control.

  1. Phase transition of p-adic Ising λ-model

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, Mutlay; Akın, Hasan [Department of Mathematics, Faculty of Education, Zirve University, Gaziantep, TR27260 (Turkey); Mukhamedov, Farrukh [Department of Computational & Theoretical Sciences Faculty of Science, International Islamic University Malaysia P.O. Box, 141, 25710, Kuantan Pahang (Malaysia)

    2015-09-18

    We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model.

  2. A MATLAB GUI to study Ising model phase transition

    Science.gov (United States)

    Thornton, Curtislee; Datta, Trinanjan

    We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.

  3. Microcanonical Phase Diagram of the BEG and Ising Models

    Institute of Scientific and Technical Information of China (English)

    李粮生; 郑宁; 史庆藩

    2012-01-01

    The density of states of long-range Blume-Emery-Criffiths (BEG) and short-range lsing models are obtained by using Wang-Landau sampling with adaptive windows in energy and magnetization space. With accurate density of states, we are able to calculate the mierocanonical specific heat of fixed magnetization introduced by Kastner et al. in the regions of positive and negative temperature. The microcanonical phase diagram of the Ising model shows a continuous phase transition at a negative temperature in energy and magnetization plane. However the phase diagram of the long-range model constructed by peaks of the microeanonieal specific heat looks obviously different from the Ising chart.

  4. A thermodynamically consistent phase-field model for two-phase flows with thermocapillary effects

    CERN Document Server

    Guo, Zhenlin

    2014-01-01

    In this paper, we develop a phase-field model for binary incompressible fluid with thermocapillary effects, which allows the different properties (densities, viscosities and heat conductivities) for each component and meanwhile maintains the thermodynamic consistency. The governing equations of the model including the Navier-Stokes equations, Cahn-Hilliard equations and energy balance equation are derived together within a thermodynamic framework based on the entropy generation, which guarantees the thermodynamic consistency. The sharp-interface limit analysis is carried out to show that the interfacial conditions of the classical sharp-interface models can be recovered from our phase-field model. Moreover, some numerical examples including thermocapillary migration of a bubble and thermocapillary convections in a two- layer fluid system are computed by using a continuous finite element method. The results are compared to the existing analytical solutions and theoretical predictions as validations for our mod...

  5. Phase separation coupled with damage processes analysis of phase field models in elastic media

    CERN Document Server

    Heinemann, Christian

    2014-01-01

    The authors explore a unifying model which couples phase separation and damage processes in a system of partial differential equations. The model has technological applications to solder materials where interactions of both phenomena have been observed and cannot be neglected for a realistic description. The equations are derived in a thermodynamically consistent framework and suitable weak formulations for various types of this coupled system are presented. In the main part, existence of weak solutions is proven and degenerate limits are investigated. Contents Modeling of Phase Separation and Damage Processes Notion of Weak Solutions Existence of Weak Solutions Degenerate Limit Target Groups Researchers, academics and scholars in the field of (applied) mathematics Material scientists in the field of modeling damaging processes The Authors Christian Heinemann earned his doctoral degree at the Humboldt-Universität zu Berlin under the supervision of Prof. Dr. Jürgen Sprekels and Dr. Christiane Kraus. He is a ...

  6. Phase diagram of a model of the protein amelogenin

    Science.gov (United States)

    Haaga, Jason; Pemberton, Elizabeth; Gunton, J. D.; Rickman, J. M.

    2016-08-01

    There has been considerable recent interest in the self-assembly and phase behavior of models of colloidal and protein particles with anisotropic interactions. One example of particular interest is amelogenin, an important protein involved in the formation of dental enamel. Amelogenin is primarily hydrophobic with a 25-residue charged C-terminus tail. This protein undergoes a hierarchical assembly process that is crucial to mineral deposition, and experimental work has demonstrated that the deletion of the C-terminus tail prevents this self-assembly. A simplified model of amelogenin has been proposed in which the protein is treated as a hydrophobic sphere, interacting via the Asakura-Oosawa (AO) potential, with a tethered point charge on its surface. In this paper, we examine the effect of the Coulomb interaction between the point charges in altering the phase diagram of the AO model. For the parameter case specific to amelogenin, we find that the previous in vitro experimental and model conditions correspond to the system being near the low-density edge of the metastable region of the phase diagram. Our study illustrates more generally the importance of understanding the phase diagram for proteins, in that the kinetic pathway for self-assembly and the resulting aggregate morphology depends on the location of the initial state in the phase diagram.

  7. A Hybrid Model for QCD Deconfining Phase Boundary

    CERN Document Server

    Srivastava, P K

    2012-01-01

    Intensive search for a proper and realistic equations of state (EOS) is still continued for studying the phase diagram existing between quark gluon plasma (QGP) and hadron gas (HG) phases. Lattice calculations provide such EOS for the strongly interacting matter at finite temperature ($T$) and vanishing baryon chemical potential ($\\mu_{B}$). These calculations are of limited use at finite $\\mu_{B}$ due to the appearance of notorious sign problem. In the recent past, we had constructed a hybrid model description for the QGP as well as HG phases where we make use of a new excluded-volume model for HG and a thermodynamically-consistent quasiparticle model for the QGP phase and used them further to get QCD phase boundary and a critical point. Since then many lattice calculations have appeared showing various thermal and transport properties of QCD matter at finite $T$ and $\\mu_{B}=0$. We test our hybrid model by reproducing the entire data for strongly interacting matter and predict our results at finite $\\mu_{B}...

  8. The electroweak phase transition in models with gauge singlets

    Energy Technology Data Exchange (ETDEWEB)

    Ahriche, A.

    2007-04-18

    A strong first order phase transition is needed for generating the baryon asymmetry; and also to save it during the electroweak phase transition (EWPT). However this condition is not fulfilled within the Standard Model (SM), but in its extensions. It is widely believed that the existence of singlet scalars in some Standard Model extensions can easily make the EWPT strongly first order. In this work, we will examine the strength of the EWPT in the simplest extension of the SM with a real gauge singlet using the sphaleron energy at the critical temperature. We find that the phase transition is stronger by adding a singlet; and also that the criterion for a strong phase transition {omega}(T{sub c})/T{sub c} >or similar 1, where {omega} = (v{sup 2} + (x - x{sub 0}){sup 2}){sup (}1)/(2) and x(x{sub 0}) is the singlet vacuum expectation value in the broken (symmetric) phase, is not valid for models containing singlets, even though often used in the literature. The usual condition v{sub c}/T{sub c} >or similar 1 is more meaningful, and it is satisfied for the major part of the parameter space for physically allowed Higgs masses. Then it is convenient to study the EWPT in models with singlets that couple only to the Higgs doublets, by replacing the singlets by their vevs. (orig.)

  9. Common world model for unmanned systems: Phase 2

    Science.gov (United States)

    Dean, Robert M. S.; Oh, Jean; Vinokurov, Jerry

    2014-06-01

    The Robotics Collaborative Technology Alliance (RCTA) seeks to provide adaptive robot capabilities which move beyond traditional metric algorithms to include cognitive capabilities. Key to this effort is the Common World Model, which moves beyond the state-of-the-art by representing the world using semantic and symbolic as well as metric information. It joins these layers of information to define objects in the world. These objects may be reasoned upon jointly using traditional geometric, symbolic cognitive algorithms and new computational nodes formed by the combination of these disciplines to address Symbol Grounding and Uncertainty. The Common World Model must understand how these objects relate to each other. It includes the concept of Self-Information about the robot. By encoding current capability, component status, task execution state, and their histories we track information which enables the robot to reason and adapt its performance using Meta-Cognition and Machine Learning principles. The world model also includes models of how entities in the environment behave which enable prediction of future world states. To manage complexity, we have adopted a phased implementation approach. Phase 1, published in these proceedings in 2013 [1], presented the approach for linking metric with symbolic information and interfaces for traditional planners and cognitive reasoning. Here we discuss the design of "Phase 2" of this world model, which extends the Phase 1 design API, data structures, and reviews the use of the Common World Model as part of a semantic navigation use case.

  10. On SU(3 Effective Models and Chiral Phase Transition

    Directory of Open Access Journals (Sweden)

    Abdel Nasser Tawfik

    2015-01-01

    Full Text Available Sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL model and Polyakov linear sigma-model (PLSM has been utilized in studying QCD phase-diagram. From quasi-particle model (QPM a gluonic sector is integrated into LSM. The hadron resonance gas (HRG model is used in calculating the thermal and dense dependence of quark-antiquark condensate. We review these four models with respect to their descriptions for the chiral phase transition. We analyze the chiral order parameter, normalized net-strange condensate, and chiral phase-diagram and compare the results with recent lattice calculations. We find that PLSM chiral boundary is located in upper band of the lattice QCD calculations and agree well with the freeze-out results deduced from various high-energy experiments and thermal models. Also, we find that the chiral temperature calculated from HRG is larger than that from PLSM. This is also larger than the freeze-out temperatures calculated in lattice QCD and deduced from experiments and thermal models. The corresponding temperature and chemical potential are very similar to that of PLSM. Although the results from PNJL and QLSM keep the same behavior, their chiral temperature is higher than that of PLSM and HRG. This might be interpreted due the very heavy quark masses implemented in both models.

  11. Phase-field modeling of shock-induced α- γ phase transformation of RDX

    Science.gov (United States)

    Rahul, -; de, Suvranu

    2015-06-01

    A thermodynamically consistent continuum phase field model has been developed to investigate the role of shock-induced α- γ phase transition in the sensitivity of RDX. Dislocations and phase transformations are distinguished and modeled within a crystal plasticity framework. The Landau potential is derived for the finite elastic deformation analysis. The response of the shock loaded RDX crystal is obtained by solving the continuum momentum equation along with phase evolution equation using a Helmholtz free energy functional, which consists of elastic potential energy and local interfacial energy that follows from the Cahn-Hilliard formalism. We observe that the orientations for which there is a resolved shear stress along the slip direction, the material absorbs large shear strain through plastic deformation, allowing it to be less sensitive as less mechanical work is available for temperature rise. Therefore, plastic slip should be associated with greater shear relaxation and, hence, decreased sensitivity. For elastic orientations, large shear stress arises from steric hindrance that may provides much more mechanical work to increase the temperature and hence more sensitive to detonation. Our simulations suggest that the α- γ phase transformation in RDX may be associated with the increased temperature rise and hence the shock sensitivity. The authors gratefully acknowledge the support of this work through Office of Naval Research (ONR) Grants N000140810462 and N000141210527 with Dr. Clifford Bedford as the cognizant Program Manager.

  12. A two-phase model for smoothly joining disparate growth phases in the macropodid Thylogale billardierii.

    Directory of Open Access Journals (Sweden)

    Clive R McMahon

    Full Text Available Generally, sigmoid curves are used to describe the growth of animals over their lifetime. However, because growth rates often differ over an animal's lifetime a single curve may not accurately capture the growth. Broken-stick models constrained to pass through a common point have been proposed to describe the different growth phases, but these are often unsatisfactory because essentially there are still two functions that describe the lifetime growth. To provide a single, converged model to age animals with disparate growth phases we developed a smoothly joining two-phase nonlinear function (SJ2P, tailored to provide a more accurate description of lifetime growth of the macropod, the Tasmanian pademelon Thylogale billardierii. The model consists of the Verhulst logistic function, which describes pouch-phase growth--joining smoothly to the Brody function, which describes post-pouch growth. Results from the model demonstrate that male pademelons grew faster and bigger than females. Our approach provides a practical means of ageing wild pademelons for life history studies but given the high variability of the data used to parametrise the second growth phase of the model, the accuracy of ageing of post-weaned animals is low: accuracy might be improved with collection of longitudinal growth data. This study provides a unique, first robust method that can be used to characterise growth over the lifespan of pademelons. The development of this method is relevant to collecting age-specific vital rates from commonly used wildlife management practices to provide crucial insights into the demographic behaviour of animal populations.

  13. Residual phase noise modeling of amplifiers using silicon bipolar transistors.

    Science.gov (United States)

    Theodoropoulos, Konstantinos; Everard, Jeremy

    2010-03-01

    In this paper, we describe the modeling of residual 1/f phase noise for Si bipolar amplifiers operating in the linear region. We propose that for Si bipolar amplifiers, the 1/f phase noise is largely caused by the base emitter recombination flicker noise. The up-conversion mechanism is described through linear approximation of the phase variation of the amplifier phase response by the variation of the device parameters (C(b)c, C(be), g(m), r(e)) caused by the recombination 1/f noise. The amplifier phase response describes the device over the whole frequency range of operation for which the influence of the poles and zeros is investigated. It is found that for a common emitter amplifier it is sufficient to only incorporate the effect of the device poles to describe the phase noise behavior over most of its operational frequency range. Simulations predict the measurements of others, including the flattening of the PM noise at frequencies beyond f(3dB), not predicted by previous models.

  14. Instabilities near the QCD phase transition in the holographic models

    CERN Document Server

    Gursoy, Umut; Shuryak, Edward

    2013-01-01

    The paper discusses phenomena close to the critical QCD temperature, using the holographic model. One issue studied is the overcooled high-T phase, in which we calculate quasi normal sound modes. We do not find instabilities associated with other first order phase transitions, but nevertheless observe drastic changes in sound propagation/dissipation. The rest of the paper considers a cluster of the high-T phase in the UV in coexistence with the low-T phase, in a simplified ansatz in which the wall separating them is positioned only in the holographic coordinate. This allows to find the force on the wall and classical motion of the cluster. When classical motion is forbidden, we evaluate tunneling probability through the remaining barrier.

  15. Dividing phases in two-phase flow and modeling of interfacial drag

    Energy Technology Data Exchange (ETDEWEB)

    Narumo, T.; Rajamaeki, M. [VTT Energy (Finland)

    1997-07-01

    Different models intended to describe one-dimensional two-phase flow are considered in this paper. The following models are introduced: conventional six-equation model, conventional model equipped with terms taking into account nonuniform transverse velocity distribution of the phases, several virtual mass models and a model in which the momentum equations have been derived by using the principles of Separation of the Flow According to Velocity (SFAV). The dynamics of the models have been tested by comparing their characteristic velocities to each other and against experimental data. The results show that the SFAV-model makes a hyperbolic system and predicts the propagation velocities of disturbances with the same order of accuracy as the best tested virtual mass models. Furthermore, the momentum interaction terms for the SFAV-model are considered. These consist of the wall friction terms and the interfacial friction term. The authors model wall friction with two independent terms describing the effect of each fluid on the wall separately. In the steady state, a relationship between the slip velocity and friction coefficients can be derived. Hence, the friction coefficients for the SFAV-model can be calculated from existing correlations, viz. from a drift-flux correlation and a wall friction correlation. The friction model was tested by searching steady-state distributions in a partial BWR fuel channel and comparing the relaxed values with the drift-flux correlation, which agreed very well with each other. In addition, response of the flow to a sine-wave disturbance in the water inlet flux was calculated as function of frequency. The results of the models differed from each other already with frequency of order 5 Hz, while the time constant for the relaxation, obtained from steady-state distribution calculation, would have implied significant differences appear not until with frequency of order 50 Hz.

  16. Phase transition and surface sublimation of a mobile Potts model.

    Science.gov (United States)

    Bailly-Reyre, A; Diep, H T; Kaufman, M

    2015-10-01

    We study in this paper the phase transition in a mobile Potts model by the use of Monte Carlo simulation. The mobile Potts model is related to a diluted Potts model, which is also studied here by a mean-field approximation. We consider a lattice where each site is either vacant or occupied by a q-state Potts spin. The Potts spin can move from one site to a nearby vacant site. In order to study the surface sublimation, we consider a system of Potts spins contained in a recipient with a concentration c defined as the ratio of the number of Potts spins N(s) to the total number of lattice sites N(L)=N(x)×N(y)×N(z). Taking into account the attractive interaction between the nearest-neighboring Potts spins, we study the phase transitions as functions of various physical parameters such as the temperature, the shape of the recipient, and the spin concentration. We show that as the temperature increases, surface spins are detached from the solid phase to form a gas in the empty space. Surface order parameters indicate different behaviors depending on the distance to the surface. At high temperatures, if the concentration is high enough, the interior spins undergo a first-order phase transition to an orientationally disordered phase. The mean-field results are shown as functions of temperature, pressure, and chemical potential, which confirm in particular the first-order character of the transition.

  17. Characterization of topological phases in models of interacting fermions

    Energy Technology Data Exchange (ETDEWEB)

    Motruk, Johannes

    2016-05-25

    The concept of topology in condensed matter physics has led to the discovery of rich and exotic physics in recent years. Especially when strong correlations are included, phenomenons such as fractionalization and anyonic particle statistics can arise. In this thesis, we study several systems hosting topological phases of interacting fermions. In the first part, we consider one-dimensional systems of parafermions, which are generalizations of Majorana fermions, in the presence of a Z{sub N} charge symmetry. We classify the symmetry-protected topological (SPT) phases that can occur in these systems using the projective representations of the symmetries and find a finite number of distinct phases depending on the prime factorization of N. The different phases exhibit characteristic degeneracies in their entanglement spectrum (ES). Apart from these SPT phases, we report the occurrence of parafermion condensate phases for certain values of N. When including an additional Z{sub N} symmetry, we find a non-Abelian group structure under the addition of phases. In the second part of the thesis, we focus on two-dimensional lattice models of spinless fermions. First, we demonstrate the detection of a fractional Chern insulator (FCI) phase in the Haldane honeycomb model on an infinite cylinder by means of the density-matrix renormalization group (DMRG). We report the calculation of several quantities characterizing the topological order of the state, i.e., (i) the Hall conductivity, (ii) the spectral flow and level counting in the ES, (iii) the topological entanglement entropy, and (iv) the charge and topological spin of the quasiparticles. Since we have access to sufficiently large system sizes without band projection with DMRG, we are in addition able to investigate the transition from a metal to the FCI at small interactions which we find to be of first order. In a further study, we consider a time-reversal symmetric model on the honeycomb lattice where a Chern insulator (CI

  18. An Improved Electrical Switching and Phase-Transition Model for Scanning Probe Phase-Change Memory

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2016-01-01

    Full Text Available Scanning probe phase-change memory (SPPCM has been widely considered as one of the most promising candidates for next-generation data storage devices due to its fast switching time, low power consumption, and potential for ultra-high density. Development of a comprehensive model able to accurately describe all the physical processes involved in SPPCM operations is therefore vital to provide researchers with an effective route for device optimization. In this paper, we introduce a pseudo-three-dimensional model to simulate the electrothermal and phase-transition phenomena observed during the SPPCM writing process by simultaneously solving Laplace’s equation to model the electrical process, the classical heat transfer equation, and a rate equation to model phase transitions. The crystalline bit region of a typical probe system and the resulting current-voltage curve obtained from simulations of the writing process showed good agreement with experimental results obtained under an equivalent configuration, demonstrating the validity of the proposed model.

  19. Modeling Human Population Separation History Using Physically Phased Genomes

    Science.gov (United States)

    Song, Shiya; Sliwerska, Elzbieta; Emery, Sarah; Kidd, Jeffrey M.

    2017-01-01

    Phased haplotype sequences are a key component in many population genetic analyses since variation in haplotypes reflects the action of recombination, selection, and changes in population size. In humans, haplotypes are typically estimated from unphased sequence or genotyping data using statistical models applied to large reference panels. To assess the importance of correct haplotype phase on population history inference, we performed fosmid pool sequencing and resolved phased haplotypes of five individuals from diverse African populations (including Yoruba, Esan, Gambia, Maasai, and Mende). We physically phased 98% of heterozygous SNPs into haplotype-resolved blocks, obtaining a block N50 of 1 Mbp. We combined these data with additional phased genomes from San, Mbuti, Gujarati, and Centre de’Etude du Polymorphism Humain European populations and analyzed population size and separation history using the pairwise sequentially Markovian coalescent and multiple sequentially Markovian coalescent models. We find that statistically phased haplotypes yield a more recent split-time estimation compared with experimentally phased haplotypes. To better interpret patterns of cross-population coalescence, we implemented an approximate Bayesian computation approach to estimate population split times and migration rates by fitting the distribution of coalescent times inferred between two haplotypes, one from each population, to a standard isolation-with-migration model. We inferred that the separation between hunter-gatherer populations and other populations happened ∼120–140 KYA, with gene flow continuing until 30–40 KYA; separation between west-African and out-of-African populations happened ∼70–80 KYA; while the separation between Maasai and out-of-African populations happened ∼50 KYA. PMID:28049708

  20. Gas phase metal cluster model systems for heterogeneous catalysis.

    Science.gov (United States)

    Lang, Sandra M; Bernhardt, Thorsten M

    2012-07-14

    Since the advent of intense cluster sources, physical and chemical properties of isolated metal clusters are an active field of research. In particular, gas phase metal clusters represent ideal model systems to gain molecular level insight into the energetics and kinetics of metal-mediated catalytic reactions. Here we summarize experimental reactivity studies as well as investigations of thermal catalytic reaction cycles on small gas phase metal clusters, mostly in relation to the surprising catalytic activity of nanoscale gold particles. A particular emphasis is put on the importance of conceptual insights gained through the study of gas phase model systems. Based on these concepts future perspectives are formulated in terms of variation and optimization of catalytic materials e.g. by utilization of bimetals and metal oxides. Furthermore, the future potential of bio-inspired catalytic material systems are highlighted and technical developments are discussed.

  1. Dynamical phase transition in a simple model of competing shops

    CERN Document Server

    Lambert, Gaultier; Bertin, Eric

    2011-01-01

    We consider a simple model in which a set of agents randomly visit one of two competing shops selling the same perishable products (typically food). The satisfaction of agents with respect to a given store is related to the freshness of the previously bought products. Agents then choose with a higher probability the store they are most satisfied with. Studying the model both through numerical simulations and mean-field analytical methods, we find a rich behaviour with continuous and discontinuous phase transitions between a symmetric phase where both stores maintain the same level of activity, and a phase with broken symmetry where one of the two shops attracts more customers than the other.

  2. Modeling and simulation for phase coarsening: A comparison with experiment

    Science.gov (United States)

    Wang, K. G.; Glicksman, M. E.; Rajan, K.

    2004-06-01

    The phase coarsening of precipitates is modeled in the framework of Debye-Hückel theory. The interactions observed among a population of precipitates dispersed throughout a matrix can be described by diffusion screening. The relationship between the maximum particle radius and the volume fraction of the phases is established, and the rate of coarsening is related to the volume fraction and the self-similar particle size distribution. We simulated the dynamics of late-stage phase separation using multiparticle diffusion methods. Experimental measurements on the rates of coarsening of δ' ( Al3 Li) precipitates in binary Al-Li alloys are compared with our results using modeling and simulation. The theoretically predicted particle size distributions and the maximum radius expected for particles in the microstructure agree well with recent experimental results.

  3. The pasta phase within density dependent hadronic models

    CERN Document Server

    Avancini, S S; Marinelli, J R; Peres-Menezes, D; Watanabe de Moraes, M M; Providência, C; Santos, A M

    2008-01-01

    In the present paper we investigate the onset of the pasta phase with different parametrisations of the density dependent hadronic model and compare the results with one of the usual parametrisation of the non-linear Walecka model. The influence of the scalar-isovector virtual delta meson is shown. At zero temperature two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature only the coexistence phases method is used. npe matter with fixed proton fractions and in beta-equilibrium are studied. We compare our results with restrictions imposed on the the values of the density and pressure at the inner edge of the crust, obtained from observations of the Vela pulsar and recent isospin diffusion data from heavy-ion reactions, and with predictions from spinodal calculations.

  4. Quantitative phase-field modeling for wetting phenomena.

    Science.gov (United States)

    Badillo, Arnoldo

    2015-03-01

    A new phase-field model is developed for studying partial wetting. The introduction of a third phase representing a solid wall allows for the derivation of a new surface tension force that accounts for energy changes at the contact line. In contrast to other multi-phase-field formulations, the present model does not need the introduction of surface energies for the fluid-wall interactions. Instead, all wetting properties are included in a unique parameter known as the equilibrium contact angle θeq. The model requires the solution of a single elliptic phase-field equation, which, coupled to conservation laws for mass and linear momentum, admits the existence of steady and unsteady compact solutions (compactons). The representation of the wall by an additional phase field allows for the study of wetting phenomena on flat, rough, or patterned surfaces in a straightforward manner. The model contains only two free parameters, a measure of interface thickness W and β, which is used in the definition of the mixture viscosity μ=μlϕl+μvϕv+βμlϕw. The former controls the convergence towards the sharp interface limit and the latter the energy dissipation at the contact line. Simulations on rough surfaces show that by taking values for β higher than 1, the model can reproduce, on average, the effects of pinning events of the contact line during its dynamic motion. The model is able to capture, in good agreement with experimental observations, many physical phenomena fundamental to wetting science, such as the wetting transition on micro-structured surfaces and droplet dynamics on solid substrates.

  5. A two phase harmonic model for left ventricular function

    CERN Document Server

    Dubi, S; Dubi, Y

    2006-01-01

    A minimal model for mechanical motion of the left ventricle is proposed. The model assumes the left ventricle to be a harmonic oscillator with two distinct phases, simulating the systolic and diastolic phases, at which both the amplitude and the elastic constant of the oscillator are different. Taking into account the pressure within the left ventricle, the model shows qualitative agreement with functional parameters of the left ventricle. The model allows for a natural explanation of heart failure with preserved systolic left ventricular function, also termed diastolic heart failure. Specifically, the rise in left ventricular filling pressures following increased left-ventricular wall stiffness is attributed to a mechanism aimed at preserving heart rate and cardiac output.

  6. Energy-dissipation-model for metallurgical multi-phase-systems

    Energy Technology Data Exchange (ETDEWEB)

    Mavrommatis, K.T. [Rheinisch-Westfaelische Technische Hochschule Aachen, Aachen (Germany)

    1996-12-31

    Entropy production in real processes is directly associated with the dissipation of energy. Both are potential measures for the proceed of irreversible processes taking place in metallurgical systems. Many of these processes in multi-phase-systems could then be modelled on the basis of the energy-dissipation associated with. As this entity can often be estimated using very simple assumptions from first principles, the evolution of an overall measure of systems behaviour can be studied constructing an energy-dissipation -based model of the system. In this work a formulation of this concept, the Energy-Dissipation-Model (EDM), for metallurgical multi-phase-systems is given. Special examples are studied to illustrate the concept, and benefits as well as the range of validity are shown. This concept might be understood as complement to usual CFD-modelling of complex systems on a more abstract level but reproducing essential attributes of complex metallurgical systems. (author)

  7. Network Inoculation: Heteroclinics and phase transitions in an epidemic model

    CERN Document Server

    Yang, Hui; Gross, Thilo

    2016-01-01

    In epidemiological modelling, dynamics on networks, and in particular adaptive and heterogeneous networks have recently received much interest. Here we present a detailed analysis of a previously proposed model that combines heterogeneity in the individuals with adaptive rewiring of the network structure in response to a disease. We show that in this model qualitative changes in the dynamics occur in two phase transitions. In a macroscopic description one of these corresponds to a local bifurcation whereas the other one corresponds to a non-local heteroclinic bifurcation. This model thus provides a rare example of a system where a phase transition is caused by a non-local bifurcation, while both micro- and macro-level dynamics are accessible to mathematical analysis. The bifurcation points mark the onset of a behaviour that we call network inoculation. In the respective parameter region exposure of the system to a pathogen will lead to an outbreak that collapses, but leaves the network in a configuration wher...

  8. Snowflake growth in three dimensions using phase field modelling

    CERN Document Server

    Demange, G; Patte, R; Brunel, M

    2016-01-01

    Snowflake growth provides us with a fascinating example of spontaneous pattern formation in nature. Attempts to understand this phenomenon have led to important insights in non-equilibrium dynamics observed in various active scientific fields, ranging from pattern formation in physical and chemical systems, to self-assembly problems in biology. Yet, very few models currently succeed in reproducing the diversity of snowflake forms in three dimensions, and the link between model parameters and thermodynamic quantities is not established. Here, we report a modified phase field model that describes the subtlety of the ice vapour phase transition, through anisotropic water molecules attachment and condensation, surface diffusion, and strong anisotropic surface tension, that guarantee the anisotropy, faceting and dendritic growth of snowflakes. We demonstrate that this model reproduces the growth dynamics of the most challenging morphologies of snowflakes from the Nakaya diagram. We find that the growth dynamics of...

  9. Consistent regularization and renormalization in models with inhomogeneous phases

    CERN Document Server

    Adhikari, Prabal

    2016-01-01

    In many models in condensed matter physics and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different consistent ways of regularizing and renormalizing quantum fluctuations, focusing on a symmetric energy cutoff scheme and dimensional regularization. We apply these techniques calculating the vacuum energy in the NJL model in 1+1 dimensions in the large-$N_c$ limit and the 3+1 dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.

  10. Consistent regularization and renormalization in models with inhomogeneous phases

    Science.gov (United States)

    Adhikari, Prabal; Andersen, Jens O.

    2017-02-01

    In many models in condensed matter and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different ways of consistently regularizing and renormalizing quantum fluctuations, focusing on momentum cutoff, symmetric energy cutoff, and dimensional regularization. We apply these techniques calculating the vacuum energy in the Nambu-Jona-Lasinio model in 1 +1 dimensions in the large-Nc limit and in the 3 +1 dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.

  11. Odd q-state clock spin-glass models in three dimensions, asymmetric phase diagrams, and multiple algebraically ordered phases.

    Science.gov (United States)

    Ilker, Efe; Berker, A Nihat

    2014-12-01

    Distinctive orderings and phase diagram structures are found, from renormalization-group theory, for odd q-state clock spin-glass models in d=3 dimensions. These models exhibit asymmetric phase diagrams, as is also the case for quantum Heisenberg spin-glass models. No finite-temperature spin-glass phase occurs. For all odd q≥5, algebraically ordered antiferromagnetic phases occur. One such phase is dominant and occurs for all q≥5. Other such phases occupy small low-temperature portions of the phase diagrams and occur for 5≤q≤15. All algebraically ordered phases have the same structure, determined by an attractive finite-temperature sink fixed point where a dominant and a subdominant pair states have the only nonzero Boltzmann weights. The phase transition critical exponents quickly saturate to the high q value.

  12. Mechanism modeling for phase fraction measurement with ultrasound attenuation in oil–water two-phase flow

    Science.gov (United States)

    Su, Qian; Tan, Chao; Dong, Feng

    2017-03-01

    When measuring the phase fraction of oil–water two-phase flow with the ultrasound attenuation, the phase distribution and fraction have direct influence on the attenuation coefficient. Therefore, the ultrasound propagation at various phase fractions and distributions were investigated. Mechanism models describing phase fraction with the ultrasound attenuation coefficient were established by analyzing the interaction between ultrasound and two-phase flow by considering the scattering, absorption and diffusion effect. Experiments were performed to verify the theoretical analysis, and the test results gave good agreement with the theoretical analysis. When the dispersed phase fraction is low, the relationship between ultrasound attenuation coefficient and phase fraction is of monotonic linearity; at higher dispersed phase fraction, ultrasound attenuation coefficient presents an irregular response to the dispersed phase fraction. The presented mechanism models give reasonable explanations about the trend of ultrasound attenuation.

  13. PHASE STRUCTURE OF TWISTED EGUCHI-KAWAI MODEL.

    Energy Technology Data Exchange (ETDEWEB)

    ISHIKAWA,T.; AZEYANAGI, T.; HANADA, M.; HIRATA, T.

    2007-07-30

    We study the phase structure of the four-dimensional twisted Eguchi-Kawai model using numerical simulations. This model is an effective tool for studying SU(N) gauge theory in the large-N limit and provides a nonperturbative formulation of the gauge theory on noncommutative spaces. Recently it was found that its Z{sub n}{sup 4} symmetry, which is crucial for the validity of this model, can break spontaneously in the intermediate coupling region. We investigate in detail the symmetry breaking point from the weak coupling side. Our simulation results show that the continuum limit of this model cannot be taken.

  14. Phase transition in the Sznajd model with independence

    CERN Document Server

    Sznajd-Weron, K; Timpanaro, A M

    2011-01-01

    We propose a model of opinion dynamics which describes two major types of social influence -- conformity and independence. Conformity in our model is described by the so called outflow dynamics (known as Sznajd model). According to sociologists' suggestions, we introduce also a second type of social influence, known in social psychology as independence. Various social experiments have shown that the level of conformity depends on the society. We introduce this level as a parameter of the model and show that there is a continuous phase transition between conformity and independence.

  15. Modelling two-phase transport of 3H/3He

    NARCIS (Netherlands)

    Visser, A.; Schaap, J.D.; Leijnse, T.; Broers, H.P.; Bierkens, M.F.P.

    2008-01-01

    Degassing of groundwater by excess denitrification of agricultural pollution complicates the interpretation of 3H/3He data and hinders the estimation of travel times in nitrate pollution studies. In this study we used a two-phase flow and transport model (STOMP) to evaluate the method presented by

  16. Modelling two-phase transport of 3H/3He

    NARCIS (Netherlands)

    Visser, A.; Schaap, J.D.; Leijnse, T.; Broers, H.P.; Bierkens, M.F.P.

    2008-01-01

    Degassing of groundwater by excess denitrification of agricultural pollution complicates the interpretation of 3H/3He data and hinders the estimation of travel times in nitrate pollution studies. In this study we used a two-phase flow and transport model (STOMP) to evaluate the method presented by V

  17. Phase-field modeling of dry snow metamorphism.

    Science.gov (United States)

    Kaempfer, Thomas U; Plapp, Mathis

    2009-03-01

    Snow on the ground is a complex three-dimensional porous medium consisting of an ice matrix formed by sintered snow crystals and a pore space filled with air and water vapor. If a temperature gradient is imposed on the snow, a water vapor gradient in the pore space is induced and the snow microstructure changes due to diffusion, sublimation, and resublimation: the snow metamorphoses. The snow microstructure, in turn, determines macroscopic snow properties such as the thermal conductivity of a snowpack. We develop a phase-field model for snow metamorphism that operates on natural snow microstructures as observed by computed x-ray microtomography. The model takes into account heat and mass diffusion within the ice matrix and pore space, as well as phase changes at the ice-air interfaces. Its construction is inspired by phase-field models for alloy solidification, which allows us to relate the phase-field to a sharp-interface formulation of the problem without performing formal matched asymptotics. To overcome the computational difficulties created by the large difference between diffusional and interface-migration time scales, we introduce a method for accelerating the numerical simulations that formally amounts to reducing the heat- and mass-diffusion coefficients while maintaining the correct interface velocities. The model is validated by simulations for simple one- and two-dimensional test cases. Furthermore, we perform qualitative metamorphism simulations on natural snow structures to demonstrate the potential of the approach.

  18. Generic phase coexistence in the totally asymmetric kinetic Ising model

    Science.gov (United States)

    Godrèche, Claude; Luck, Jean-Marc

    2017-07-01

    The physical analysis of generic phase coexistence in the North-East-Center Toom model was originally given by Bennett and Grinstein. The gist of their argument relies on the dynamics of interfaces and droplets. We revisit the same question for a specific totally asymmetric kinetic Ising model on the square lattice. This nonequilibrium model possesses the remarkable property that its stationary-state measure in the absence of a magnetic field coincides with that of the usual ferromagnetic Ising model. We use both analytical arguments and numerical simulations in order to make progress in the quantitative understanding of the phenomenon of generic phase coexistence. At zero temperature a mapping onto the TASEP allows an exact determination of the time-dependent shape of the ballistic interface sweeping a large square minority droplet of up or down spins. At finite temperature, measuring the mean lifetime of such a droplet allows an accurate measurement of its shrinking velocity v, which depends on temperature T and magnetic field h. In the absence of a magnetic field, v vanishes with an exponent Δ_v≈2.5+/-0.2 as the critical temperature T c is approached. At fixed temperature in the ordered phase, v vanishes at the phase-boundary fields +/- h_b(T) which mark the limits of the coexistence region. The latter fields vanish with an exponent Δ_h≈3.2+/-0.3 as T c is approached.

  19. On SU(3) effective models and chiral phase-transition

    CERN Document Server

    Tawfik, Abdel Nasser

    2015-01-01

    The sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL) model as an effective theory of quark dynamics to chiral symmetry has been utilized in studying the QCD phase-diagram. Also, Poyakov linear sigma-model (PLSM), in which information about the confining glue sector of the theory was included through Polyakov-loop potential. Furthermore, from quasi-particle model (QPM), the gluonic sector of QPM is integrated to LSM in order to reproduce recent lattice calculations. We review PLSM, QLSM, PNJL and HRG with respect to their descriptions for the chiral phase-transition. We analyse chiral order-parameter M(T), normalized net-strange condensate Delta_{q,s}(T) and chiral phase-diagram and compare the results with lattice QCD. We conclude that PLSM works perfectly in reproducing M(T) and Delta_{q,s}(T). HRG model reproduces Delta_{q,s}(T), while PNJL and QLSM seem to fail. These differences are present in QCD chiral phase-diagram. PLSM chiral boundary is located in upper band of lattice QCD calculations and agree we...

  20. Typical Phases of Transformative Learning: A Practice-Based Model

    Science.gov (United States)

    Nohl, Arnd-Michael

    2015-01-01

    Empirical models of transformative learning offer important insights into the core characteristics of this concept. Whereas previous analyses were limited to specific social groups or topical terrains, this article empirically typifies the phases of transformative learning on the basis of a comparative analysis of various social groups and topical…

  1. Extended Quark Potential Model From Random Phase Approximation

    Institute of Scientific and Technical Information of China (English)

    DENGWei-Zhen; CHENXiao-Lin; 等

    2002-01-01

    The quark potential model is extended to include the sea quark excitation using the random phase approximation.The effective quark interaction preserves the important QCD properties-chiral symmetry and confinement simultaneously.A primary qualitative analysis shows that the π meson as a well-known typical Goldstone boson and the other mesons made up of valence qq quark pair such as the ρ meson can also be described in this extended quark potential model.

  2. Extended Quark Potential Model from Random Phase Approximation

    Institute of Scientific and Technical Information of China (English)

    DENG Wei-Zhen; CHEN Xiao-Lin; LU Da-Hai; YANG Li-Ming

    2002-01-01

    The quark potential model is extended to include the sea quark excitation using the random phase approx-imation. The effective quark interaction preserves the important QCD properties - chiral symmetry and confinementsimultaneously. A primary qualitative analysis shows that the π meson as a well-known typical Goldstone boson andthe other mesons made up of valence qq quark pair such as the ρ meson can also be described in this extended quarkpotential model.

  3. Superconducting phases of strange quark matter in the NJL model

    CERN Document Server

    Paulucci, L; Ferrer, E J; de la Incera, V

    2013-01-01

    We analyze the color-flavor-locked phase of strange quark matter modelled by the three-flavor Nambu-Jona-Lasinio (NJL) framework with and without magnetic field and discuss some additional constraints on the stability scenario when a high magnetic field is applied. We compare the results obtained by employing the MIT Bag Model and discuss the pairing gap behavior and its influence on the equation of state.

  4. Phase space analysis of some interacting Chaplygin gas models

    Energy Technology Data Exchange (ETDEWEB)

    Khurshudyan, M. [Academy of Sciences of Armenia, Institute for Physical Research, Ashtarak (Armenia); Tomsk State University of Control Systems and Radioelectronics, Laboratory for Theoretical Cosmology, Tomsk (Russian Federation); Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); Myrzakulov, R. [Eurasian National University, Eurasian International Center for Theoretical Physics, Astana (Kazakhstan)

    2017-02-15

    In this paper we discuss a phase space analysis of various interacting Chaplygin gas models in general relativity. Linear and nonlinear sign changeable interactions are considered. For each case appropriate late time attractors of field equations are found. The Chaplygin gas is one of the dark fluids actively considered in modern cosmology due to the fact that it is a joint model of dark energy and dark matter. (orig.)

  5. Frustrated phase in the Z/sub 2/ gauge model

    Energy Technology Data Exchange (ETDEWEB)

    Epele, L.N.; Fanchiotti, H.; Garcia Canal, C.A. (La Plata Univ. Nacional (Argentina). Lab. de Fisica Teorica)

    1982-12-11

    Our purpose in this letter is to discuss the frustrated phase in the Z/sub 2/ gauge model in 2+1 dimensions. This study is based on a previously proposed real-space renormalization group realization and takes profit of the dual properties of the Ising-like models. In particular, we present results for the relevant critical functions and exponents obtained analytically and simultaneously with the corresponding ferromagnetic ones.

  6. A unified model-free controller for switching minimum phase, non-minimum phase and time-delay systems

    CERN Document Server

    Michel, Loïc

    2012-01-01

    This preliminary work presents a simple derivation of the standard model-free control in order to control switching minimum phase, non-minimum phase and time-delay systems. The robustness of the proposed method is studied in simulation.

  7. A phase mixing model for the frequency-doubling illusion.

    Science.gov (United States)

    Wielaard, James; Smith, R Theodore

    2013-10-01

    We introduce a temporal phase mixing model for a description of the frequency-doubling illusion (FDI). The model is generic in the sense that it can be set to refer to retinal ganglion cells, lateral geniculate cells, as well as simple cells in the primary visual cortex (V1). Model parameters, however, strongly suggest that the FDI originates in the cortex. The model shows how noise in the response phases of cells in V1, or in further processing of these phases, easily produces observed behavior of FDI onset as a function of spatiotemporal frequencies. It also shows how this noise can accommodate physiologically plausible spatial delays in comparing neural signals over a distance. The model offers an explanation for the disappearance of the FDI at sufficiently high spatial frequencies via increasingly correlated coding of neighboring grating stripes. Further, when the FDI is equated to vanishing perceptual discrimination between asynchronous contrast-reversal gratings, the model proposes the possibility that the FDI shows a resonance behavior at sufficiently high spatial frequencies, by which it is alternately perceived and not perceived in sequential temporal frequency bands.

  8. Characterizing Phase Transitions in a Model of Neutral Evolutionary Dynamics

    Science.gov (United States)

    Scott, Adam; King, Dawn; Bahar, Sonya

    2013-03-01

    An evolutionary model was recently introduced for sympatric, phenotypic evolution over a variable fitness landscape with assortative mating (Dees & Bahar 2010). Organisms in the model are described by coordinates in a two-dimensional phenotype space, born at random coordinates with limited variation from their parents as determined by a mutation parameter, mutability. The model has been extended to include both neutral evolution and asexual reproduction in Scott et al (submitted). It has been demonstrated that a second order, non-equilibrium phase transition occurs for the temporal dynamics as the mutability is varied, for both the original model and for neutral conditions. This transition likely belongs to the directed percolation universality class. In contrast, the spatial dynamics of the model shows characteristics of an ordinary percolation phase transition. Here, we characterize the phase transitions exhibited by this model by determining critical exponents for the relaxation times, characteristic lengths, and cluster (species) mass distributions. Missouri Research Board; J.S. McDonnell Foundation

  9. Phase equilibria in model surfactants forming Langmuir monolayers.

    Science.gov (United States)

    Ramírez, E; Santana, A; Cruz, A; López, G E

    2007-12-14

    The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

  10. Prediction of Three-Phase Capillary Pressure using a Network Model Anchored to Two-Phase Data

    OpenAIRE

    Dale, Elisabeth Iren; Dijke, Marinus I. J. van; Skauge, Arne

    2008-01-01

    Three-phase capillary pressure is difficult to measure experimentally and therefore has to be estimated by other methods. In this work a network model was applied to generate a consistent set of two-phase and three-phase capillary pressure curves. Experimental data for two-phase, gas-oil and oil-water, capillary pressure from a North Sea reservoir was used in this study. The network model was anchored to the measured two-phase data, and three-phase capillary pressure was constr...

  11. Hydraulic model tests on modified Wave Dragon. Phase 3

    Energy Technology Data Exchange (ETDEWEB)

    Hald, T.; Lynggaard, J.

    2002-11-01

    The purpose of this report is to describe the model tests conducted with a new designed 2. generation WD model as well as obtained model test results. Tests are conducted as sequential reconstruction followed by physical model tests. All details concerning the reconstruction are found in Hald and Lynggaard (2001). Model tests and reconstruction are carried out during the phase 3 project: 'Wave Dragon. Reconstruction of an existing model in scale 1:50 and sequential tests of changes to the model geometry and mass distribution parameters' sponsored by the Danish Energy Agency (DEA) wave energy programme. The tests will establish a well documented basis for the development of a 1:4.5 scale prototype planned for testing Nissum Bredning, a sea inlet on the Danish West Coast. (au)

  12. Phase dynamics modeling of parallel stacks of Josephson junctions

    Science.gov (United States)

    Rahmonov, I. R.; Shukrinov, Yu. M.

    2014-11-01

    The phase dynamics of two parallel connected stacks of intrinsic Josephson junctions (JJs) in high temperature superconductors is numerically investigated. The calculations are based on the system of nonlinear differential equations obtained within the CCJJ + DC model, which allows one to determine the general current-voltage characteristic of the system, as well as each individual stack. The processes with increasing and decreasing base currents are studied. The features in the behavior of the current in each stack of the system due to the switching between the states with rotating and oscillating phases are analyzed.

  13. Sketch the migration of Dictyostelium discoideum using phase field model

    Science.gov (United States)

    Zhang, Yunsong; Camley, Brian; Rappel, Wouter-Jan; Levine, Herbert

    Cell migration plays an important role in a lot of biological processes, like chemotaxis, wound healing, and cancer metastasis. The fact it is highly integrated has brought great challenges, physical and mathematical, to the modeling efforts. Recently, a phase field model, which couples cellular reaction dynamics, intra-cellular hydrodynamics, cell-substrate adhesions and deformable cell boundaries, has successfully captured some characteristics of moving cells, including morphological change, cytosolic actin flow pattern, periodic migration and so on. Here we apply the phase field model to sketch the migration of Dictyostelium discoideum, which shows a completely different moving pattern from the cells (like fish keratocyte) in our previous attempts. And we will also compare our results with some experimental observations, not only on the cell morphology, but also on the traction force patterns on the substrate.

  14. Topological phase transition in the Scheidegger model of river networks

    Science.gov (United States)

    Oppenheim, Jacob N.; Magnasco, Marcelo O.

    2012-08-01

    Transport networks are found at the heart of myriad natural systems, yet are poorly understood, except for the case of river networks. The Scheidegger model, in which rivers are convergent random walks, has been studied only in the case of flat topography, ignoring the variety of curved geometries found in nature. Embedding this model on a cone, we find a convergent and a divergent phase, corresponding to few, long basins and many, short basins, respectively, separated by a singularity, indicating a phase transition. Quantifying basin shape using Hacks law l˜ah gives distinct values for h, providing a method of testing our hypotheses. The generality of our model suggests implications for vascular morphology, in particular, differing number and shapes of arterial and venous trees.

  15. Groundwater flow modelling of the excavation and operational phases - Laxemar

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Urban (Computer-aided Fluid Engineering AB, Lyckeby (Sweden)); Rhen, Ingvar (SWECO Environment AB, Falun (Sweden))

    2010-12-15

    As a part of the license application for a final repository for spent nuclear fuel at Forsmark, the Swedish Nuclear Fuel and Waste Management Company (SKB) has undertaken a series of groundwater flow modelling studies. These represent time periods with different hydraulic conditions and the simulations carried out contribute to the overall evaluation of the repository design and long-term radiological safety. The modelling study reported here presents calculated inflow rates, drawdown of the groundwater table and upconing of deep saline water for different levels of grouting efficiency during the excavation and operational phases of a final repository at Laxemar. The inflow calculations were accompanied by a sensitivity study, which among other matters handled the impact of different deposition hole rejection criteria. The report also presents tentative modelling results for the duration of the saturation phase, which starts once the used parts of the repository are being backfilled

  16. GPU accelerated numerical simulations of viscoelastic phase separation model.

    Science.gov (United States)

    Yang, Keda; Su, Jiaye; Guo, Hongxia

    2012-07-05

    We introduce a complete implementation of viscoelastic model for numerical simulations of the phase separation kinetics in dynamic asymmetry systems such as polymer blends and polymer solutions on a graphics processing unit (GPU) by CUDA language and discuss algorithms and optimizations in details. From studies of a polymer solution, we show that the GPU-based implementation can predict correctly the accepted results and provide about 190 times speedup over a single central processing unit (CPU). Further accuracy analysis demonstrates that both the single and the double precision calculations on the GPU are sufficient to produce high-quality results in numerical simulations of viscoelastic model. Therefore, the GPU-based viscoelastic model is very promising for studying many phase separation processes of experimental and theoretical interests that often take place on the large length and time scales and are not easily addressed by a conventional implementation running on a single CPU.

  17. Analysis of the phase structure in extended Higgs models

    Energy Technology Data Exchange (ETDEWEB)

    Seniuch, M.

    2006-07-07

    We study the generation of the baryon asymmetry in the context of electroweak baryogenesis in two different extensions of the Standard Model. First, we consider an effective theory, in which the Standard Model is augmented by an additional dimension-six Higgs operator. The effects of new physics beyond a cut-off scale are parameterized by this operator. The second model is the two-Higgs-doublet model, whose particle spectrum is extended by two further neutral and two charged heavy Higgs bosons. In both cases we focus on the properties of the electroweak phase transition, especially on its strength and the profile of the nucleating bubbles. After reviewing some general aspects of the electroweak phase transition and baryogenesis we derive the respective thermal effective potentials to one-loop order. We systematically study the parameter spaces, using numerical methods, and compute the strength of the phase transition and the wall thickness as a function of the Higgs masses. We find a strong first order transition for a light Higgs state with a mass up to about 200 GeV. In case of the dimension-six model the cut-off scale has to stay between 500 and 850 GeV, in the two-Higgs-doublet model one needs at least one heavy Higgs mass of 300 GeV. The wall thickness varies for both theories in the range roughly from two to fifteen, in units of the inverse critical temperature. We also estimate the size of the electron and neutron electric dipole moments, since new sources of CP violation give rise to them. In wide ranges of the parameter space we are not in conflict with the experimental bounds. Finally the baryon asymmetry, which is predicted by these models, is related to the Higgs mass and the other appropriate input parameters. In both models the measured baryon asymmetry can be achieved for natural values of the model parameters. (orig.)

  18. Phase field modeling of partially saturated deformable porous media

    Science.gov (United States)

    Sciarra, Giulio

    2016-09-01

    A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).

  19. Application of cyclic partial phase transformations for identifying kinetic transitions during solid-state phase transformations: Experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hao, E-mail: hao.chen@tudelft.nl [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands); Appolaire, Benoit [LEM, CNRS/ONERA, 29 Av. Division Leclerc, BP 72, F-92322 Chatillon Cedex (France); Zwaag, Sybrand van der [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

    2011-10-15

    A series of cyclic partial phase transformation experiments has been performed to investigate the growth kinetics of the austenite to ferrite phase transformation, and vice versa, in Fe-Mn-C alloys. Unlike the usual phase transformation experiments (100% parent phase {yields} 100% new phase), in the case of cyclic partial transformations two special stages are observed: a stagnant stage in which the degree of transformation does not vary while the temperature changes, and an inverse phase transformation stage, during which the phase transformation proceeds in a direction contradictory to the temperature change. The experimental results have been analyzed using paraequilibrium and local equilibrium diffusional growth models. Only the local equilibrium model was shown to predict the new features of the cyclic phase transformation kinetics. The stagnant stage was found to be due to Mn partitioning, while the inverse phase transformation is caused by non-equilibrium conditions when switching from cooling to heating and vice versa.

  20. A Topological Phase Transition in Models of River Networks

    Science.gov (United States)

    Oppenheim, Jacob; Magnasco, Marcelo

    2012-02-01

    The classical Scheidegger model of river network formation and evolution is investigated on non-Euclidean geometries, which model the effects of regions of convergent and divergent flows - as seen around lakes and drainage off mountains, respectively. These new models may be differentiated by the number of basins formed. Using the divergence as an order parameter, we see a phase transition in the number of distinct basins at the point of a flat landscape. This is a surprising property of the statistics of river networks and suggests significantly different properties for riverine networks in uneven topography and vascular networks of arteries versus those of veins among others.

  1. Modeling PSInSAR time series without phase unwrapping

    Science.gov (United States)

    Zhang, L.; Ding, X.; Lu, Zhiming

    2011-01-01

    In this paper, we propose a least-squares-based method for multitemporal synthetic aperture radar interferometry that allows one to estimate deformations without the need of phase unwrapping. The method utilizes a series of multimaster wrapped differential interferograms with short baselines and focuses on arcs at which there are no phase ambiguities. An outlier detector is used to identify and remove the arcs with phase ambiguities, and a pseudoinverse of the variancecovariance matrix is used as the weight matrix of the correlated observations. The deformation rates at coherent points are estimated with a least squares model constrained by reference points. The proposed approach is verified with a set of simulated data. ?? 2006 IEEE.

  2. The new JET phased ICRH array: first experiments and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Bures, M.; Bhatnagar, V.; Brown, T.; Fechner, B.; Gormezano, C.; Kaye, A.; Lennholm, M.; Righi, E.; Rimini, F.; Sibley, A.; Start, D.; Wade, T. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Goulding, R. [Oak Ridge National Lab., TN (United States); Lamalle, P. [Ecole Royale Militaire, Brussels (Belgium). Lab. de Physique des Plasmas; Nguyen, F. [CEA Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France)

    1994-07-01

    New ICRH antennas on JET were designed to couple to the new JET divertor plasma configurations and to improve the Fast Wave Current Drive (FWCD) capabilities. The A2 antenna consists of 4 straps whose currents can be phased at arbitrary angles. The real time automatic tuning acts on frequency, line length (line phase shifters) and stub length. Provision is made for the coupling resistance/plasma position feedback to accommodate the fast changes in antenna loading. The first coupling, tuning and heating results are reported in 0{pi}0{pi}, 0000 and 00{pi}{pi} phasing. A new antenna model is described, which was developed to simulate the measured antenna loading in terms of plasma parameters and to provide a starting point for the real time automatic tuning. 5 refs., 4 figs.

  3. Phase transition with an isospin dependent lattice gas model

    Energy Technology Data Exchange (ETDEWEB)

    Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Chomaz, Ph. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)

    1998-10-01

    The nuclear liquid-gas phase transition is studied within an isospin dependent Lattice Gas Model in the canonical ensemble. Finite size effects on thermodynamical variables are analyzed by a direct calculation of the partition function, and it is shown that phase coexistence and phase transition are relevant concepts even for systems of a few tens of particles. Critical exponents are extracted from the behaviour of the fragment production yield as a function of temperature by means of a finite size scaling. The result is that in a finite system well defined critical signals can be found at supercritical (Kertesz line) as well as subcritical densities. For isospin asymmetric systems it is shown that, besides the modification of the critical temperature, isotopic distributions can provide an extra observable to identify and characterize the transition. (author) 21 refs.

  4. Modeling the recovery phase of extreme geomagnetic storms

    CERN Document Server

    Cid, C; Saiz, E; Cerrato, Y; Aguado, J; Guerrero, A

    2014-01-01

    The recovery phase of the largest storms ever recorded has been studied. These events provide an extraordinary opportunity for two goals: (1) to validate the hyperbolic model by Aguado et al. [2010] for the recovery phase after disturbances as severe as the Carrington event, or that related to the Hydro-Quebec blackout in March 1989, and (2) to check whether the linear relationship between the recovery time and the intensity of the storm still complies. Our results reveal the high accuracy of the hyperbolic decay function to reproduce the recovery phase of the magnetosphere after an extreme storm. Moreover, the characteristic time that takes the magnetosphere to recover depends in an exponential way on the intensity of the storm, as indicated by the relationship between the two parameters involved in the hyperbolic decay. This exponential function can be approached by a linear function when the severity of the storm diminishes.

  5. Modeling the Phase Composition of Gas Condensate in Pipelines

    Science.gov (United States)

    Dudin, S. M.; Zemenkov, Yu D.; Shabarov, A. B.

    2016-10-01

    Gas condensate fields demonstrate a number of thermodynamic characteristics to be considered when they are developed, as well as when gas condensate is transported and processed. A complicated phase behavior of the gas condensate system, as well as the dependence of the extracted raw materials on the phase state of the deposit other conditions being equal, is a key aspect. Therefore, when designing gas condensate lines the crucial task is to select the most appropriate methods of calculating thermophysical properties and phase equilibrium of the transported gas condensate. The paper describes a physical-mathematical model of a gas-liquid flow in the gas condensate line. It was developed based on balance equations of conservation of mass, impulse and energy of the transported medium within the framework of a quasi-1D approach. Constitutive relationships are given separately, and practical recommendations on how to apply the research results are provided as well.

  6. Equivalence of two models in single-phase multicomponent flow simulations

    KAUST Repository

    Wu, Yuanqing

    2016-02-28

    In this work, two models to simulate the single-phase multicomponent flow in reservoirs are introduced: single-phase multicomponent flow model and two-phase compositional flow model. Because the single-phase multicomponent flow is a special case of the two-phase compositional flow, the two-phase compositional flow model can also simulate the case. We compare and analyze the two models when simulating the single-phase multicomponent flow, and then demonstrate the equivalence of the two models mathematically. An experiment is also carried out to verify the equivalence of the two models.

  7. Phase diagram of the half-filled ionic Hubbard model

    Science.gov (United States)

    Bag, Soumen; Garg, Arti; Krishnamurthy, H. R.

    2015-06-01

    We study the phase diagram of the ionic Hubbard model (IHM) at half filling on a Bethe lattice of infinite connectivity using dynamical mean-field theory (DMFT), with two impurity solvers, namely, iterated perturbation theory (IPT) and continuous time quantum Monte Carlo (CTQMC). The physics of the IHM is governed by the competition between the staggered ionic potential Δ and the on-site Hubbard U . We find that for a finite Δ and at zero temperature, long-range antiferromagnetic (AFM) order sets in beyond a threshold U =UA F via a first-order phase transition. For U smaller than UA F the system is a correlated band insulator. Both methods show a clear evidence for a quantum transition to a half-metal (HM) phase just after the AFM order is turned on, followed by the formation of an AFM insulator on further increasing U . We show that the results obtained within both methods have good qualitative and quantitative consistency in the intermediate-to-strong-coupling regime at zero temperature as well as at finite temperature. On increasing the temperature, the AFM order is lost via a first-order phase transition at a transition temperature TA F(U ,Δ ) [or, equivalently, on decreasing U below UA F(T ,Δ ) ], within both methods, for weak to intermediate values of U /t . In the strongly correlated regime, where the effective low-energy Hamiltonian is the Heisenberg model, IPT is unable to capture the thermal (Neel) transition from the AFM phase to the paramagnetic phase, but the CTQMC does. At a finite temperature T , DMFT +CTQMC shows a second phase transition (not seen within DMFT +IPT ) on increasing U beyond UA F. At UN>UA F , when the Neel temperature TN for the effective Heisenberg model becomes lower than T , the AFM order is lost via a second-order transition. For U ≫Δ , TN˜t2/U (1 -x2) , where x =2 Δ /U and thus TN increases with increase in Δ /U . In the three-dimensional parameter space of (U /t ,T /t ,andΔ /t ) , as T increases, the surface of first

  8. Probing spacetime around Sagittarius A* using modeled VLBI closure phases

    CERN Document Server

    Fraga-Encinas, R; Brinkerink, C; Falcke, H

    2016-01-01

    The emission region and black hole shadow of Sagittarius A*, the supermassive black hole at the Galactic Center, can be probed with millimeter Very Long Baseline Interferometry. Our goal is to probe the geometry of the emitting plasma around Sgr A* by using modeled mm-VLBI closure phase calculations at 1.3 mm and to constrain the observer's inclination angle and position angle of the black hole spin axis. We have simulated images for three different models of the emission of Sgr A*: an orbiting spot, a disk model, and a jet model. The orbiting spot model was used as a test case scenario, while the disk and jet models are physically driven scenarios based on standard three-dimensional general relativistic magnetohydrodynamic simulations of hot accretion flows. Our results are compared to currently available closure phase observational limits. Our results indicate that more models with closer to edge-on viewing angles are consistent with observational limits. In general, jet and disk geometries can reproduce si...

  9. A Model Study Of The Deconfining Phase Transition

    CERN Document Server

    Velytsky, A

    2004-01-01

    The study of the deconfining phase transition or crossover is important for the understanding of properties of nuclear matter and the quark gluon plasma. Heavy ion collisions experiments are capable of creating conditions necessary for deconfinement. The dynamics of this process and not only its equilibrium properties are of interest. In this dissertation non-equilibrium aspects of rapid heating and cooling of the QCD vacuum are studied in a model framework. The 3-D Potts model with an external magnetic field is an effective model of QCD (of pure SU(3) gauge theory, when the magnetic field is set to zero), which we study by means of Monte Carlo simulations. Other models are used to understand the influence of the strength of the phase transition. In our investigations these systems are temperature driven through a phase transition or a rapid crossover using updating procedures in the Glauber universality class. We study hysteresis cycles with different updating speeds and simulations of a quench. Qualitativel...

  10. Supporting universal prevention programs: a two-phased coaching model.

    Science.gov (United States)

    Becker, Kimberly D; Darney, Dana; Domitrovich, Celene; Keperling, Jennifer Pitchford; Ialongo, Nicholas S

    2013-06-01

    Schools are adopting evidence-based programs designed to enhance students' emotional and behavioral competencies at increasing rates (Hemmeter et al. in Early Child Res Q 26:96-109, 2011). At the same time, teachers express the need for increased support surrounding implementation of these evidence-based programs (Carter and Van Norman in Early Child Educ 38:279-288, 2010). Ongoing professional development in the form of coaching may enhance teacher skills and implementation (Noell et al. in School Psychol Rev 34:87-106, 2005; Stormont et al. 2012). There exists a need for a coaching model that can be applied to a variety of teacher skill levels and one that guides coach decision-making about how best to support teachers. This article provides a detailed account of a two-phased coaching model with empirical support developed and tested with coaches and teachers in urban schools (Becker et al. 2013). In the initial universal coaching phase, all teachers receive the same coaching elements regardless of their skill level. Then, in the tailored coaching phase, coaching varies according to the strengths and needs of each teacher. Specifically, more intensive coaching strategies are used only with teachers who need additional coaching supports, whereas other teachers receive just enough support to consolidate and maintain their strong implementation. Examples of how coaches used the two-phased coaching model when working with teachers who were implementing two universal prevention programs (i.e., the PATHS curriculum and PAX Good Behavior Game [PAX GBG]) provide illustrations of the application of this model. The potential reach of this coaching model extends to other school-based programs as well as other settings in which coaches partner with interventionists to implement evidence-based programs.

  11. On a phase field model for solid-liquid phase transitions

    CERN Document Server

    Benzoni-Gavage, Sylvie; Jamet, Didier; Vovelle, Julien

    2012-01-01

    A new phase field model is introduced, which can be viewed as nontrivial generalisation of what is known as the Caginalp model. It involves in particular nonlinear diffusion terms. By formal asymptotic analysis, it is shown that in the sharp interface limit it still yields a Stefan-like model with: 1) a (generalized) Gibbs-Thomson relation telling how much the interface temperature differs from the equilibrium temperature when the interface is moving or/and is curved with surface tension; 2) a jump condition for the heat flux, which turns out to depend on the latent heat and on the velocity of the interface with a new, nonlinear term compared to standard models. From the PDE analysis point of view, the initial-boundary value problem is proved to be locally well-posed in time (for smooth data).

  12. PhasePlot: A Software Program for Visualizing Phase Relations Computed Using Thermochemical Models and Databases

    Science.gov (United States)

    Ghiorso, M. S.

    2011-12-01

    A new software program has been developed for Macintosh computers that permits the visualization of phase relations calculated from thermodynamic data-model collections. The data-model collections of MELTS (Ghiorso and Sack, 1995, CMP 119, 197-212), pMELTS (Ghiorso et al., 2002, G-cubed 3, 10.1029/2001GC000217) and the deep mantle database of Stixrude and Lithgow-Bertelloni (2011, GJI 184, 1180-1213) are currently implemented. The software allows users to enter a system bulk composition and a range of reference conditions and then calculate a grid of phase relations. These relations may be visualized in a variety of ways including phase diagrams, phase proportion plots, and contour diagrams of phase compositions and abundances. Results may be exported into Excel or similar spreadsheet applications. Flexibility in stipulating reference conditions permit the construction of temperature-pressure, temperature-volume, entropy-pressure, or entropy-volume display grids. Calculations on the grid are performed for fixed bulk composition or in open systems governed by user specified constraints on component chemical potentials (e.g., specified oxygen fugacity buffers). The calculation engine for the software is optimized for multi-core compute architectures and is very fast, allowing a typical grid of 64 points to be calculated in under 10 seconds on a dual-core laptop/iMac. The underlying computational thermodynamic algorithms have been optimized for speed and robust behavior. Taken together, both of these advances facilitate in classroom demonstrations and permit novice users to work with the program effectively, focusing on problem specification and interpretation of results rather than on manipulation and mechanics of computation - a key feature of an effective instructional tool. The emphasis in this software package is graphical visualization, which aids in better comprehension of complex phase relations in multicomponent systems. Anecdotal experience in using Phase

  13. Phase field modeling of tetragonal to monoclinic phase transformation in zirconia

    Science.gov (United States)

    Mamivand, Mahmood

    Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for

  14. Modeling the Reactions of Energetic Materials in the Condensed Phase

    Energy Technology Data Exchange (ETDEWEB)

    Fried, L E; Manaa, M R; Lewis, J P

    2003-12-03

    High explosive (HE) materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. Although the history of HE materials is long, condensed-phase properties are poorly understood. Understanding the condensed-phase properties of HE materials is important for determining stability and performance. Information regarding HE material properties (for example, the physical, chemical, and mechanical behaviors of the constituents in plastic-bonded explosive, or PBX, formulations) is necessary in efficiently building the next generation of explosives as the quest for more powerful energetic materials (in terms of energy per volume) moves forward. In addition, understanding the reaction mechanisms has important ramifications in disposing of such materials safely and cheaply, as there exist vast stockpiles of HE materials with corresponding contamination of earth and groundwater at these sites, as well as a military testing sites The ability to model chemical reaction processes in condensed phase energetic materials is rapidly progressing. Chemical equilibrium modeling is a mature technique with some limitations. Progress in this area continues, but is hampered by a lack of knowledge of condensed phase reaction mechanisms and rates. Atomistic modeling is much more computationally intensive, and is currently limited to very short time scales. Nonetheless, this methodology promises to yield the first reliable insights into the condensed phase processes responsible for high explosive detonation. Further work is necessary to extend the timescales involved in atomistic simulations. Recent work in implementing thermostat methods appropriate to shocks may promise to overcome some of these difficulties. Most current work on energetic material reactivity assumes that electronically adiabatic processes dominate. The role of excited states is becoming clearer, however. These states are not accessible in perfect

  15. Thermodynamic Property Model of Wide-Fluid Phase Propane

    Directory of Open Access Journals (Sweden)

    I Made Astina

    2007-05-01

    Full Text Available A new thermodynamic property model for propane is expressed in form of the Helmholtz free energy function. It consists of eight terms of the ideal-gas part and eighteen terms of the residual part. Accurate experimental data of fluid properties and theoretical approach from the intermolecular potential were simultaneously considered in the development to insure accuracy and to improve reliability of the equation of state over wide range of pressures and temperatures. Based on the state range of experimental data used in the model development, the validity range is judged from the triple-point of 85.48 K to temperature of 450 K and pressure up to 60 MPa. The uncertainties with respect to different properties are estimated to be 0.03% in ideal-gas isobaric specific heat, 0.2% in liquid phase density, 0.3% in gaseous phase density 1% in specific heats, 0.1% in vapor-pressure except at very low temperatures, 0.05% in saturated-liquid density, 0.02% in speed of sound of the gaseous phase and 1% in speed of sound of the liquid phase.

  16. Mathematical modeling of a three-phase trickle bed reactor

    Directory of Open Access Journals (Sweden)

    J. D. Silva

    2012-09-01

    Full Text Available The transient behavior in a three-phase trickle bed reactor system (N2/H2O-KCl/activated carbon, 298 K, 1.01 bar was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 x 10-6 m³ s-1 and the liquid phase flow (Q L varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ s-1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.

  17. Lattice-Boltzmann-based two-phase thermal model for simulating phase change.

    Science.gov (United States)

    Kamali, M R; Gillissen, J J J; van den Akker, H E A; Sundaresan, Sankaran

    2013-09-01

    A lattice Boltzmann (LB) method is presented for solving the energy conservation equation in two phases when the phase change effects are included in the model. This approach employs multiple distribution functions, one for a pseudotemperature scalar variable and the rest for the various species. A nonideal equation of state (EOS) is introduced by using a pseudopotential LB model. The evolution equation for the pseudotemperature variable is constructed in such a manner that in the continuum limit one recovers the well known macroscopic energy conservation equation for the mixtures. Heats of reaction, the enthalpy change associated with the phase change, and the diffusive transport of enthalpy are all taken into account; but the dependence of enthalpy on pressure, which is usually a small effect in most nonisothermal flows encountered in chemical reaction systems, is ignored. The energy equation is coupled to the LB equations for species transport and pseudopotential interaction forces through the EOS by using the filtered local pseudotemperature field. The proposed scheme is validated against simple test problems for which analytical solutions can readily be obtained.

  18. The Phase Structure of the Polyakov--Quark-Meson Model

    CERN Document Server

    Schaefer, Bernd-Jochen; Wambach, Jochen

    2007-01-01

    The relation between the deconfinement and chiral phase transition is explored in the framework of an Polyakov-loop-extended two-flavor quark-meson (PQM) model. In this model the Polyakov loop dynamics is represented by a background temporal gauge field which also couples to the quarks. As a novelty an explicit quark chemical potential and N_f-dependence in the Polyakov loop potential is proposed by using renormalization group arguments. The behavior of the Polyakov loop as well as the chiral condensate as function of temperature and quark chemical potential is obtained by minimizing the grand canonical thermodynamic potential of the system. The effect of the Polyakov loop dynamics on the chiral phase diagram and on several thermodynamic bulk quantities is presented.

  19. Phase structure of the Polyakov-quark-meson model

    Science.gov (United States)

    Schaefer, B.-J.; Pawlowski, J. M.; Wambach, J.

    2007-10-01

    The relation between the deconfinement and chiral phase transition is explored in the framework of a Polyakov-loop-extended two-flavor quark-meson (PQM) model. In this model the Polyakov loop dynamics is represented by a background temporal gauge field which also couples to the quarks. As a novelty an explicit quark chemical potential and Nf-dependence in the Polyakov loop potential is proposed by using renormalization group arguments. The behavior of the Polyakov loop as well as the chiral condensate as function of temperature and quark chemical potential is obtained by minimizing the grand canonical thermodynamic potential of the system. The effect of the Polyakov loop dynamics on the chiral phase diagram and on several thermodynamic bulk quantities is presented.

  20. Excited-state quantum phase transition in the Rabi model

    Science.gov (United States)

    Puebla, Ricardo; Hwang, Myung-Joong; Plenio, Martin B.

    2016-08-01

    The Rabi model, a two-level atom coupled to a harmonic oscillator, can undergo a second-order quantum phase transition (QPT) [M.-J. Hwang et al., Phys. Rev. Lett. 115, 180404 (2015), 10.1103/PhysRevLett.115.180404]. Here we show that the Rabi QPT accompanies critical behavior in the higher-energy excited states, i.e., the excited-state QPT (ESQPT). We derive analytic expressions for the semiclassical density of states, which show a logarithmic divergence at a critical energy eigenvalue in the broken symmetry (superradiant) phase. Moreover, we find that the logarithmic singularities in the density of states lead to singularities in the relevant observables in the system such as photon number and atomic polarization. We corroborate our analytical semiclassical prediction of the ESQPT in the Rabi model with its numerically exact quantum mechanical solution.

  1. Phase transitions in the $sdg$ interacting boson model

    CERN Document Server

    Van Isacker, P; Zerguine, S

    2009-01-01

    A geometric analysis of the $sdg$ interacting boson model is performed. A coherent-state is used in terms of three types of deformation: axial quadrupole ($\\beta_2$), axial hexadecapole ($\\beta_4$) and triaxial ($\\gamma_2$). The phase-transitional structure is established for a schematic $sdg$ hamiltonian which is intermediate between four dynamical symmetries of U(15), namely the spherical ${\\rm U}(5)\\otimes{\\rm U}(9)$, the (prolate and oblate) deformed ${\\rm SU}_\\pm(3)$ and the $\\gamma_2$-soft SO(15) limits. For realistic choices of the hamiltonian parameters the resulting phase diagram has properties close to what is obtained in the $sd$ version of the model and, in particular, no transition towards a stable triaxial shape is found.

  2. Nonparaxial multi-Gaussian beam models and measurement models for phased array transducers.

    Science.gov (United States)

    Zhao, Xinyu; Gang, Tie

    2009-01-01

    A nonparaxial multi-Gaussian beam model is proposed in order to overcome the limitation that paraxial Gaussian beam models lose accuracy in simulating the beam steering behavior of phased array transducers. Using this nonparaxial multi-Gaussian beam model, the focusing and steering sound fields generated by an ultrasonic linear phased array transducer are calculated and compared with the corresponding results obtained by paraxial multi-Gaussian beam model and more exact Rayleigh-Sommerfeld integral model. In addition, with help of this novel nonparaxial method, an ultrasonic measurement model is provided to investigate the sensitivity of linear phased array transducers versus steering angles. Also the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided measurement model.

  3. A Computational Framework for Phase-field Modeling

    Science.gov (United States)

    2011-01-01

    twin embryo within an otherwise perfect single crystal (12). Analytical models based on free energy variations in the context of phase...transformations have been applied to describe twin nucleation (12, 13). Such approaches consider nucleation of a twin embryo of idealized geometry—an elliptical...Crystals, in preparation, 2011. 12. Christian , J. W.; Mahajan, S. Deformation Twinning. Prog. Mater. Sci. 1995, 39, 1–157. 13. Lee, J. K.; Yoo, M

  4. Electroweak Phase Transitions in left-right symmetric models

    CERN Document Server

    Barenboim, G; Barenboim, Gabriela; Rius, Nuria

    1998-01-01

    We study the finite-temperature effective potential of minimal left-right symmetric models containing a bidoublet and two triplets in the scalar sector. We perform a numerical analysis of the parameter space compatible We perform a numerical analysis of the parameter space compatible with the requirement that baryon asymmetry is not washed out by sphaleron processes after the electroweak phase transition. We find that the spectrum of scalar particles for these acceptable cases is consistent with present experimental bounds.

  5. Analytical results for a three-phase traffic model.

    Science.gov (United States)

    Huang, Ding-wei

    2003-10-01

    We study analytically a cellular automaton model, which is able to present three different traffic phases on a homogeneous highway. The characteristics displayed in the fundamental diagram can be well discerned by analyzing the evolution of density configurations. Analytical expressions for the traffic flow and shock speed are obtained. The synchronized flow in the intermediate-density region is the result of aggressive driving scheme and determined mainly by the stochastic noise.

  6. Elasto-viscoplastic phase field modelling of anisotropic cleavage fracture

    Science.gov (United States)

    Shanthraj, P.; Svendsen, B.; Sharma, L.; Roters, F.; Raabe, D.

    2017-02-01

    A finite-strain anisotropic phase field method is developed to model the localisation of damage on a defined family of crystallographic planes, characteristic of cleavage fracture in metals. The approach is based on the introduction of an undamaged configuration, and the inelastic deformation gradient mapping this configuration to a damaged configuration is microstructurally represented by the opening of a set of cleavage planes in the three fracture modes. Crack opening is modelled as a dissipative process, and its evolution is thermodynamically derived. To couple this approach with a physically-based phase field method for brittle fracture, a scalar measure of the overall local damage is introduced, whose evolution is determined by the crack opening rates, and weakly coupled with the non-local phase field energy representing the crack opening resistance in the classical sense of Griffith. A finite-element implementation of the proposed model is employed to simulate the crack propagation path in a laminate and a polycrystalline microstructure. As shown in this work, it is able to predict the localisation of damage on the set of pre-defined cleavage planes, as well as the kinking and branching of the crack resulting from the crystallographic misorientation across the laminate boundary and the grain boundaries respectively.

  7. Modelling Galaxies with a 3d Multi-Phase ISM

    CERN Document Server

    Harfst, S; Hensler, G; Harfst, Stefan; Theis, Christian; Hensler, Gerhard

    2005-01-01

    We present a new particle code for modelling the evolution of galaxies. The code is based on a multi-phase description for the interstellar medium (ISM). We included star formation (SF), stellar feedback by massive stars and planetary nebulae, phase transitions and interactions between gas clouds and ambient diffuse gas, namely condensation, evaporation, drag and energy dissipation. The latter is realised by radiative cooling and inelastic cloud-cloud collisions. We present new schemes for SF and stellar feedback. They include a consistent calculation of the star formation efficiency (SFE) based on ISM properties as well as a detailed redistribution of the feedback energy into the different ISM phases. As a first test example we show a model of the evolution of a present day Milky-Way-type galaxy. Though the model exhibits a quasi-stationary behaviour in global properties like mass fractions or surface densities, the evolution of the ISM is locally strongly variable depending on the local SF and stellar feedb...

  8. Homogeneous gas phase models of relaxation kinetics in neon afterglow

    Directory of Open Access Journals (Sweden)

    Marković Vidosav Lj.

    2007-01-01

    Full Text Available The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time td (τ (memory curve is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect, because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2 + and nitrogen ions N2 + (present as impurities and the approximate value of N2 + ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.

  9. Modeling the solid-liquid phase transition in saturated triglycerides

    Science.gov (United States)

    Pink, David A.; Hanna, Charles B.; Sandt, Christophe; MacDonald, Adam J.; MacEachern, Ronald; Corkery, Robert; Rousseau, Dérick

    2010-02-01

    We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h∗-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h∗ conformation in the liquid state at temperatures higher than the phase-transition temperature, T∗=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ΔH in reasonable agreement with the experiment. We then defined an alternative h-h∗ model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h∗ model gave a value of ΔH that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman

  10. Charge fluctuations in chiral models and the QCD phase transition

    CERN Document Server

    Skokov, V; Karsch, F; Redlich, K

    2011-01-01

    We consider the Polyakov loop-extended two flavor chiral quark--meson model and discuss critical phenomena related with the spontaneous breaking of the chiral symmetry. The model is explored beyond the mean-field approximation in the framework of the functional renormalisation group. We discuss properties of the net-quark number density fluctuations as well as their higher cumulants. We show that with the increasing net-quark number density, the higher order cumulants exhibit a strong sensitivity to the chiral crossover transition. We discuss their role as probes of the chiral phase transition in heavy-ion collisions at RHIC and LHC.

  11. Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

    Science.gov (United States)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

  12. Detailed behavioral modeling of bang-bang phase detectors

    DEFF Research Database (Denmark)

    Jiang, Chenhui; Andreani, Pietro; Keil, U. D.

    2006-01-01

    In this paper, the metastability of current-mode logic (CML) latches and flip-flops is studied in detail. Based on the results of this analysis, a behavioral model of bang-bang phase detectors (BBPDs) is proposed, which is able to reliably capture the critical deadzone effect. The impact of jitter...... and of process, voltage and temperature variations on the BBPD behavior is also investigated. The proposed model can be used with advantage in the high-level design and verification of e.g. clock and data recovery (CDR) circuits...

  13. In-phase and quadrature imbalance modeling, estimation, and compensation

    CERN Document Server

    Li, Yabo

    2013-01-01

    This book provides a unified IQ imbalance model and systematically reviews the existing estimation and compensation schemes. It covers the different assumptions and approaches that lead to many models of IQ imbalance. In wireless communication systems, the In-phase and Quadrature (IQ) modulator and demodulator are usually used as transmitter (TX) and receiver (RX), respectively. For Digital-to-Analog Converter (DAC) and Analog-to-Digital Converter (ADC) limited systems, such as multi-giga-hertz bandwidth millimeter-wave systems, using analog modulator and demodulator is still a low power and l

  14. Simple thermodynamic model for the hydrogen phase diagram

    Science.gov (United States)

    Magdǎu, Ioan B.; Marqués, Miriam; Borgulya, Balint; Ackland, Graeme J.

    2017-03-01

    We describe a classical thermodynamic model that reproduces the main features of the solid hydrogen phase diagram. In particular, we show how the general structure types, which are found by electronic structure calculations and the quantum nature of the protons, can also be understood from a classical viewpoint. The model provides a picture not only of crystal structure, but also for the anomalous melting curve and insights into isotope effects, liquid metallisation, and infrared activity. The existence of a classical picture for this most quantum of condensed matter systems provides a surprising extension of the correspondence principle of quantum mechanics, in particular the equivalent effects of classical and quantum uncertainty.

  15. Traffic model with an absorbing-state phase transition

    Science.gov (United States)

    Iannini, M. L. L.; Dickman, Ronald

    2017-02-01

    We consider a modified Nagel-Schreckenberg (NS) model in which drivers do not decelerate if their speed is smaller than the headway (number of empty sites to the car ahead). (In the original NS model, such a reduction in speed occurs with probability p , independent of the headway, as long as the current speed is greater than zero.) In the modified model the free-flow state (with all vehicles traveling at the maximum speed, vmax) is absorbing for densities ρ smaller than a critical value ρc=1 /(vmax+2 ) . The phase diagram in the ρ -p plane is reentrant: for densities in the range ρc ,<<ρ <ρc , both small and large values of p favor free flow, while for intermediate values, a nonzero fraction of vehicles have speeds phase transition in the original model. Our results suggest an unexpected connection between traffic models and stochastic sandpiles.

  16. Phase Transition in Conditional Curie-Weiss Model

    CERN Document Server

    Opoku, Alex A; Ansah, Richard

    2016-01-01

    This paper proposes a conditional Curie-Weiss model as a model for opinion formation in a society polarized along two opinions, say opinions 1 and 2. The model comes with interaction strength $\\beta>0$ and bais $h$. Here the population in question is divided into three main groups, namely: Group one consisting of individuals who have decided on opinion 1. Let the proportion of this group be given by $s$. Group two consisting of individauls who have chosen opinion 2. Let $r$ be their proportion. Group three consisting of individuals who are yet to decide and they will decide based on their environmental conditions. Let $1-s-r$ be the proportion of this group. We show that the specific magnetization of the associated conditional Curie-Weiss model has a first order phase transition (discontinuous jump in specific magnetization) at $\\beta^*=\\left(1-s-r\\right)^{-1}$. It is also shown that not all the discontinuous jumps in magnetization will result in phase change. We point out how an extention of this model could...

  17. Phase-field-crystal model for fcc ordering.

    Science.gov (United States)

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to and reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  18. Self-similarity of phase-space networks of frustrated spin models and lattice gas models

    Science.gov (United States)

    Peng, Yi; Wang, Feng; Han, Yilong

    2013-03-01

    We studied the self-similar properties of the phase-spaces of two frustrated spin models and two lattice gas models. The frustrated spin models included (1) the anti-ferromagnetic Ising model on a two-dimensional triangular lattice (1a) at the ground states and (1b) above the ground states and (2) the six-vertex model. The two lattice gas models were (3) the one-dimensional lattice gas model and (4) the two-dimensional lattice gas model. The phase spaces were mapped to networks so that the fractal analysis of complex networks could be applied, i.e. the box-covering method and the cluster-growth method. These phase spaces, in turn, establish new classes of networks with unique self-similar properties. Models 1a, 2, and 3 with long-range power-law correlations in real space exhibit fractal phase spaces, while models 1b and 4 with short-range exponential correlations in real space exhibit nonfractal phase spaces. This behavior agrees with one of untested assumptions in Tsallis nonextensive statistics. Hong Kong GRC grants 601208 and 601911

  19. A Systematic Modelling Framework for Phase Transfer Catalyst Systems

    DEFF Research Database (Denmark)

    Anantpinijwatna, Amata; Sales-Cruz, Mauricio; Hyung Kim, Sun

    2016-01-01

    in an aqueous phase. These reacting systems are receiving increased attention as novel organic synthesis options due to their flexible operation, higher product yields, and ability to avoid hazardous or expensive solvents. Major considerations in the design and analysis of PTC systems are physical and chemical...... equilibria, as well as kinetic mechanisms and rates. This paper presents a modelling framework for design and analysis of PTC systems that requires a minimum amount of experimental data to develop and employ the necessary thermodynamic and reaction models and embeds them into a reactor model for simulation....... The application of the framework is made to two cases in order to highlight the performance and issues of activity coefficient models for predicting design and operation and the effects when different organic solvents are employed....

  20. Transient thermohydraulic modeling of two-phase fluid systems

    Science.gov (United States)

    Blet, N.; Delalandre, N.; Ayel, V.; Bertin, Y.; Romestant, C.; Platel, V.

    2012-11-01

    This paper presents a transient thermohydraulic modeling, initially developed for a capillary pumped loop in gravitational applications, but also possibly suitable for all kinds of two-phase fluid systems. Using finite volumes method, it is based on Navier-Stokes equations for transcribing fluid mechanical aspects. The main feature of this 1D-model is based on a network representation by analogy with electrical. This paper also proposes a parametric study of a counterflow condenser following the sensitivity to inlet mass flow rate and cold source temperature. The comparison between modeling results and experimental data highlights a good numerical evaluation of temperatures. Furthermore, the model is able to represent a pretty good dynamic evolution of hydraulic variables.

  1. Modeling the Lukewarm Corino Phase - is L1527 unique?

    CERN Document Server

    Hassel, George E; Garrod, Robin T

    2008-01-01

    Sakai et al. have observed long-chain unsaturated hydrocarbons and cyanopolyynes in the low-mass star-forming region L1527, and have attributed this result to a gas-phase ion-molecule chemistry, termed ``Warm Carbon Chain Chemistry'', which occurs during and after the evaporation of methane from warming grains. The source L1527 is an envelope surrounding a Class 0/I protostar with regions that possess a slightly elevated temperature of ~30 K. The molecules detected by Sakai et al. are typically associated only with dark molecular clouds, and not with the more evolved hot corino phase. In order to determine if L1527 is chemically distinct from a dark cloud, we compute models including various degrees of heating. The results indicate that the composition of L1527 is somewhat more likely to be due to ``Warm Carbon Chain Chemistry'' than to be a remnant of a colder phase. If so, the molecular products provide a signature of a previously uncharacterized early phase of low mass star formation, which can be characte...

  2. Phase behaviors and membrane properties of model liposomes: Temperature effect

    Science.gov (United States)

    Wu, Hsing-Lun; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2014-09-01

    The phase behaviors and membrane properties of small unilamellar vesicles have been explored at different temperatures by dissipative particle dynamics simulations. The vesicles spontaneously formed by model lipids exhibit pre-transition from gel to ripple phase and main transition from ripple to liquid phase. The vesicle shape exhibits the faceted feature at low temperature, becomes more sphere-like with increasing temperature, but loses its sphericity at high temperature. As the temperature rises, the vesicle size grows but the membrane thickness declines. The main transition (Tm) can be identified by the inflection point. The membrane structural characteristics are analyzed. The inner and outer leaflets are asymmetric. The length of the lipid tail and area density of the lipid head in both leaflets decrease with increasing temperature. However, the mean lipid volume grows at low temperature but declines at high temperature. The membrane mechanical properties are also investigated. The water permeability grows exponentially with increasing T but the membrane tension peaks at Tm. Both the bending and stretching moduli have their minima near Tm. Those results are consistent with the experimental observations, indicating that the main signatures associated with phase transition are clearly observed in small unilamellar vesicles.

  3. Nonequilibrium stationary states and phase transitions in directed Ising models

    Science.gov (United States)

    Godrèche, Claude; Bray, Alan J.

    2009-12-01

    We study the nonequilibrium properties of directed Ising models with non-conserved dynamics, in which each spin is influenced by only a subset of its nearest neighbours. We treat the following models: (i) the one-dimensional chain; (ii) the two-dimensional square lattice; (iii) the two-dimensional triangular lattice and (iv) the three-dimensional cubic lattice. We raise and answer the question: (a) under what conditions is the stationary state described by the equilibrium Boltzmann-Gibbs distribution? We show that, for models (i), (ii) and (iii), in which each spin 'sees' only half of its neighbours, there is a unique set of transition rates, namely with exponential dependence in the local field, for which this is the case. For model (iv), we find that any rates satisfying the constraints required for the stationary measure to be Gibbsian should satisfy detailed balance, ruling out the possibility of directed dynamics. We finally show that directed models on lattices of coordination number z>=8 with exponential rates cannot accommodate a Gibbsian stationary state. We conjecture that this property extends to any form of the rates. We are thus led to the conclusion that directed models with Gibbsian stationary states only exist in dimensions one and two. We then raise the question: (b) do directed Ising models, augmented by Glauber dynamics, exhibit a phase transition to a ferromagnetic state? For the models considered above, the answers are open problems, with the exception of the simple cases (i) and (ii). For Cayley trees, where each spin sees only the spins further from the root, we show that there is a phase transition provided the branching ratio, q, satisfies q>=3.

  4. Phase-field model for the two-phase lithiation of silicon

    Science.gov (United States)

    Gao, Fangliang; Hong, Wei

    2016-09-01

    As an ideal anode material, silicon has the highest lithium-ion capacity in theory, but the broader application is limited by the huge volumetric strain caused by lithium insertion and extraction. To better understand the physical process and to resolve the related reliability issue, enormous efforts have been made. Recent experiments observed sharp reaction fronts in both crystalline and amorphous silicon during the first lithiation half-cycle. Such a concentration profile indicates that the process is likely to be reaction limited. Based on this postulation, a phase-field model is developed and implemented into a finite-element code to simulate the coupled large inelastic deformation and motion of the reaction front in a silicon electrode. In contrast to most existing models, the model treats both volumetric and deviatoric inelastic deformation in silicon as a direct consequence of the lithiation at the reaction front. The amount of deviatoric deformation is determined by using the recently developed kinetic model of stress-induced anisotropic reaction. By considering the role of stress in the lithiation process, this model successfully recovers the self-limiting phenomenon of silicon electrodes, and relates it to the local geometry of electrodes. The model is also used to evaluate the energy-release rate of the surface crack on a spherical electrode, and the result suggests a critical size of silicon nanoparticles to avert fracture. As examples, the morphology evolution of a silicon disk and a Si nanowire during lithiation are also investigated.

  5. Digital herders and phase transition in a voting model

    CERN Document Server

    Hisakado, Masato

    2011-01-01

    In this paper, we discuss a voting model with two candidates, $C_1$ and $C_2$. We set two types of voters--herders and independents. The voting of independent voters is based on their fundamental values; on the other hand, the voting of herders is based on the number of votes. Herders always select the majority of the previous $r$ votes, which is visible to them. We call them digital herders. We can accurately calculate the distribution of votes for special cases. When $r\\geq 3$, we find that a phase transition occurs at the upper limit of $t$, where $t$ is the discrete time (or number of votes). As the fraction of herders increases, the model features a phase transition beyond which a state where most voters make the correct choice coexists with one where most of them are wrong. On the other hand, when $r<3$, there is no phase transition. In this case, the herder's performance is the same as that of the independent voters. At last, from the simple experiments, we recognize the behavior of human beings.

  6. Model of flicker noise effects on phase noise in oscillators

    Science.gov (United States)

    Centurelli, Francesco; Ercolani, Alessandro; Tommasino, Pasquale; Trifiletti, Alessandro

    2003-05-01

    Phase noise models that describe the near-carrier spectrum in an accurate but insightful way are needed, to better optimize the oscillator design. In this paper we present a model to describe the effect of flicker noise sources on the phase noise of an oscillator, that can be applied both to linear oscillators and to nonlinear structures like relaxation and ring oscillators, so extending previous works that considered only the effect of the flicker noise superimposed to the control voltage of a VCO. In the phase noise of an oscillator we can separate the effect of high frequency noise sources, that can be described by a short-time-constant system, and the effect of low frequency noises (mostly flicker sources), described by a system with time constants much slower than the oscillation period. Flicker noise has been considered to cause a change in the circuit bias point; this bias point change can be mapped in a shift of the oscillation frequency by exploiting Barkhausen conditions (for linear oscillators) or obtaining this link by simulations. The power spectral density of the oscillator can then be obtained as the probability distribution of the oscillation frequency, starting from the flicker noise probability distribution. If the effect of high frequency noise sources is also taken into account, the overall oscillator spectrum can be obtained as a convolution of the spectrum due to flicker sources with the Lorentzian-shaped spectrum due to white noise sources, in analogy with the description of inhomogeneous broadening of laser linewidth.

  7. Floquet topological semimetal phases of an extended kicked Harper model

    Science.gov (United States)

    Bomantara, Raditya Weda; Raghava, Gudapati Naresh; Zhou, Longwen; Gong, Jiangbin

    2016-02-01

    Recent discoveries on topological characterization of gapless systems have attracted interest in both theoretical studies and experimental realizations. Examples of such gapless topological phases are Weyl semimetals, which exhibit three-dimensional (3D) Dirac cones (Weyl points), and nodal line semimetals, which are characterized by line nodes (two bands touching along a line). Inspired by our previous discoveries that the kicked Harper model exhibits many fascinating features of Floquet topological phases, in this paper we consider a generalization of the model, where two additional periodic system parameters are introduced into the Hamiltonian to serve as artificial dimensions, so as to simulate a 3 D periodically driven system. We observe that by increasing the hopping strength and the kicking strength of the system, many new Floquet band touching points at Floquet quasienergies 0 and π will start to appear. Some of them are Weyl points, while the others form line nodes in the parameter space. By taking open boundary conditions along the physical dimension, edge states analogous to Fermi arcs in static Weyl semimetal systems are observed. Finally, by designing an adiabatic pumping scheme, the chirality of the Floquet-band Weyl points and the π Berry phase around Floquet-band line nodes can be manifested.

  8. A traffic model with an absorbing-state phase transition

    CERN Document Server

    Iannini, M L L

    2016-01-01

    We consider a modified Nagel-Schreckenberg (NS) model in which drivers do not decelerate if their speed is smaller than the headway (number of empty sites to the car ahead). (In the original NS model, such a reduction in speed occurs with probability $p$, independent of the headway, as long as the current speed is greater than zero.) In the modified model the free-flow state (with all vehicles traveling at the maximum speed, $v_{max}$) is {\\it absorbing} for densities $\\rho$ smaller than a critical value $\\rho_c = 1/(v_{max} + 2)$. The phase diagram in the $\\rho - p$ plane is reentrant: for densities in the range $\\rho_{c,<} < \\rho < \\rho_c$, both small and large values of $p$ favor free flow, while for intermediate values, a nonzero fraction of vehicles have speeds $< v_{max}$. In addition to representing a more realistic description of driving behavior, this change leads to a better understanding of the phase transition in the original model. Our results suggest an unexpected connection between ...

  9. Phase Characterization of Cucumber Growth: A Chemical Gel Model

    Directory of Open Access Journals (Sweden)

    Bo Li

    2016-01-01

    Full Text Available Cucumber grows with complex phenomena by changing its volume and shape, which is not fully investigated and challenges agriculture and food safety industry. In order to understand the mechanism and to characterize the growth process, the cucumber is modeled as a hydrogel in swelling and its development is studied in both preharvest and postharvest stages. Based on thermodynamics, constitutive equations, incorporating biological quantities, are established. The growth behavior of cucumber follows the classic theory of continuous or discontinuous phase transition. The mechanism of bulged tail in cucumber is interpreted by phase coexistence and characterized by critical conditions. Conclusions are given for advances in food engineering and novel fabrication techniques in mechanical biology.

  10. Characteristics of the chiral phase transition in nonlocal quark models

    CERN Document Server

    Dumm, D G

    2004-01-01

    The characteristics of the chiral phase transition are analyzed within the framework of chiral quark models with nonlocal interactions in the mean field approximation (MFA). In the chiral limit, we show that there is a region of low values of the chemical potential in which the transition is a second order one. In that region, it is possible to perform a Landau expansion and determine the critical exponents which, as expected, turn out to be the MFA ones. Our analysis also allows to obtain semi-analytical expressions for the transition curve and the location of the tricritical point. For the case of finite current quark masses, we study the behavior of various thermodynamical and chiral response functions across the phase transition.

  11. The electroweak phase transition in minimal supergravity models

    CERN Document Server

    Nanopoulos, Dimitri V

    1994-01-01

    We have explored the electroweak phase transition in minimal supergravity models by extending previous analysis of the one-loop Higgs potential to include finite temperature effects. Minimal supergravity is characterized by two higgs doublets at the electroweak scale, gauge coupling unification, and universal soft-SUSY breaking at the unification scale. We have searched for the allowed parameter space that avoids washout of baryon number via unsuppressed anomalous Electroweak sphaleron processes after the phase transition. This requirement imposes strong constraints on the Higgs sector. With respect to weak scale baryogenesis, we find that the generic MSSM is {\\it not} phenomenologically acceptable, and show that the additional experimental and consistency constraints of minimal supergravity restricts the mass of the lightest CP-even Higgs even further to $m_h\\lsim 32\\GeV$ (at one loop), also in conflict with experiment. Thus, if supergravity is to allow for baryogenesis via any other mechanism above the weak...

  12. Modeling Non-aqueous Phase Liquid Displacement Process

    Institute of Scientific and Technical Information of China (English)

    Yang Zhenqing; Shao Changjin; Zhou Guanggang; Qiu Chao

    2007-01-01

    A pore-network model physically based on pore level multiphase flow was used to study the water-non-aqueous phase liquid (NAPL) displacement process, especially the effects of wettability, water-NAPL interfacial tension, the fraction of NAPL-wet pores, and initial water saturation on the displacement. The computed data show that with the wettability of the mineral surfaces changing from strongly water-wet to NAPL-wet, capillary pressure and the NAPL relative permeability gradually decrease, while water-NAPL interfacial tension has little effect on water relative permeability, but initial water saturation has a strong effect on water and NAPL relative permeabilities. The analytical results may help to understand the micro-structure displacement process of non-aqueous phase liquid and to provide the theoretical basis for controlling NAPL migration.

  13. Solutions for a hyperbolic model of multi-phase flow

    Directory of Open Access Journals (Sweden)

    Amadori Debora

    2013-07-01

    Full Text Available We discuss a model for the flow of an inviscid fluid admitting liquid and vapor phases, as well as a mixture of them. The flow is modeled in one spatial dimension; the state variables are the specific volume, the velocity and the mass density fraction λ of vapor in the fluid. The equation governing the time evolution of λ contains a source term, which enables metastable states and drives the fluid towards stable pure phases. We first discuss, for the homogeneous system, the BV stability of Riemann solutions generated by large initial data and check the validity of several sufficient conditions that are known in the literature. Then, we review some recent results about the existence of solutions, which are globally defined in time, for λ close either to 0 or to 1 (corresponding to almost pure phases. These solutions possibly contain large shocks. Finally, in the relaxation limit, solutions are proved to satisfy a reduced system and the related entropy condition. On discute un modèle pour l’écoulement d’un fluide non visqueux admettant phases liquides et de vapeur, ainsi qu’un mélange d’entre eux. L’écoulement est modélisé dans une dimension spatiale ; les variables d’état sont le volume spécifique, la vitesse et la fraction de densité de masse λ de la vapeur dans le liquide. L’équation régissant l’évolution temporelle de λ contient un terme de source, ce qui permet des états métastables et conduit le fluide vers de phases stables pures. Nous discutons d’abord, pour le système homogène, la stabilité BV des solutions de Riemann générés par des grandes données initiales et vérifions la validité de plusieurs conditions suffisantes qui sont connues dans la littérature. Ensuite, nous passons en revue quelques résultats récents sur l’existence de solutions, qui sont definies pour tous les temps, pour λ soit près de 0 ou de 1 (correspondant à des phases presque pures. Ces solutions sont susceptibles

  14. Supersolidus Liquid Phase Sintering Modeling of Inconel 718 Superalloy

    Science.gov (United States)

    Levasseur, David; Brochu, Mathieu

    2016-02-01

    Powder metallurgy of Inconel 718 superalloy is advantageous as a near-net shape process for complex parts to reduce the buy-to-fly ratio and machining cost. However, sintering Inconel 718 requires the assistance of supersolidus liquid formation to achieve near full density and involves the risk of distortion at high temperatures. The present work is focused on modeling the onset of sintering and distortion as a function of temperature, grain size, and part geometry for Inconel 718. Using experimental sintering results and data available in the literature, the supersolidus liquid phase sintering of Inconel 718 was modeled. The model was used to define a processing window where part distortion would be avoided.

  15. Phase Model with Feedback Control for Power Grids

    CERN Document Server

    Matsuo, Tatsuma

    2013-01-01

    A phase model with feedback control is studied as a dynamical model of power grids. As an example, we study a model network corresponding to the power grid in the Kyushu region. The standard frequency is maintained by the mutual synchronization and the feedback control. Electric failures are induced by an overload. We propose a local feedback method in which the strength of feedback control is proportional to the magnitude of generators. We find that the electric failures do not occur until the utilization ratio is close to 1 under this feedback control. We also find that the temporal response for the time-varying input power is suppressed under this feedback control. We explain the mechanisms using the corresponding global feedback method.

  16. Phase Model with Feedback Control for Power Grids

    Science.gov (United States)

    Matsuo, Tatsuma; Sakaguchi, Hidetsugu

    2013-09-01

    A phase model with feedback control is studied as a dynamical model of power grids. As an example, we study a model network corresponding to the power grid in the Kyushu region. The standard frequency is maintained by the mutual synchronization and the feedback control. Electric failures are induced by an overload. We propose a local feedback method in which the strength of feedback control is proportional to the magnitude of generators. We find that the electric failures do not occur until the utilization ratio is close to 1 under this feedback control. We also find that the temporal response for the time-varying input power is suppressed under this feedback control. We explain the mechanisms using the corresponding global feedback method.

  17. Models and correlations of the DEBRIS Late-Phase Melt Progression Model

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, R.C.; Gasser, R.D. [Sandia National Labs., Albuquerque, NM (United States). Reactor Safety Experiments Dept.

    1997-09-01

    The DEBRIS Late Phase Melt Progression Model is an assembly of models, embodied in a computer code, which is designed to treat late-phase melt progression in dry rubble (or debris) regions that can form as a consequence of a severe core uncover accident in a commercial light water nuclear reactor. The approach is fully two-dimensional, and incorporates a porous medium modeling framework together with conservation and constitutive relationships to simulate the time-dependent evolution of such regions as various physical processes act upon the materials. The objective of the code is to accurately model these processes so that the late-phase melt progression that would occur in different hypothetical severe nuclear reactor accidents can be better understood and characterized. In this report the models and correlations incorporated and used within the current version of DEBRIS are described. These include the global conservation equations solved, heat transfer and fission heating models, melting and refreezing models (including material interactions), liquid and solid relocation models, gas flow and pressure field models, and the temperature and compositionally dependent material properties employed. The specific models described here have been used in the experiment design analysis of the Phebus FPT-4 debris-bed fission-product release experiment. An earlier DEBRIS code version was used to analyze the MP-1 and MP-2 late-phase melt progression experiments conducted at Sandia National Laboratories for the US Nuclear Regulatory Commission.

  18. Mesoscale Phase Field Modeling of Glass Strengthening Under Triaxial Compression

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yulan; Sun, Xin

    2016-09-30

    Recent hydraulic bomb and confined sleeve tests on transparent armor glass materials such as borosilicate glass and soda-lime glass showed that the glass strength was a function of confinement pressure. The measured stress-strain relation is not a straight line as most brittle materials behave under little or no confinement. Moreover, borosilicate glass exhibited a stronger compressive strength when compared to soda-lime glass, even though soda-lime has higher bulk and shear moduli as well as apparent yield strength. To better understand these experimental findings, a mesoscale phase field model is developed to simulate the nonlinear stress versus strain behaviors under confinement by considering heterogeneity formation under triaxial compression and the energy barrier of a micro shear banding event (referred to as pseudo-slip hereafter) in the amorphous glass. With calibrated modeling parameters, the simulation results demonstrate that the developed phase field model can quantitatively predict the pressure-dependent strength, and it can also explain the difference between the two types of glasses from the perspective of energy barrier associated with a pseudo-slip event.

  19. Groundwater flow modelling of the excavation and operational phases - Forsmark

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Urban (Computer-aided Fluid Engineering AB, Lyckeby (Sweden)); Follin, Sven (SF GeoLogic AB, Taeby (Sweden))

    2010-07-15

    As a part of the license application for a final repository for spent nuclear fuel at Forsmark, the Swedish Nuclear Fuel and Waste Management Company (SKB) has undertaken a series of groundwater flow modelling studies. These represent time periods with different climate conditions and the simulations carried out contribute to the overall evaluation of the repository design and long-term radiological safety. The modelling study reported here presents calculated inflow rates, drawdown of the groundwater table and upconing of deep saline water for different levels of grouting efficiency during the excavation and operational phases of a final repository at Forsmark. The inflow calculations are accompanied by a sensitivity study, which among other matters handles the impact of parameter heterogeneity, different deposition hole rejection criteria, and the SFR facility (the repository for short-lived radioactive waste located approximately 1 km to the north of the investigated candidate area for a final repository at Forsmark). The report also presents tentative modelling results for the duration of the saturation phase, which starts once the used parts of the repository are being backfilled.

  20. Computational studies of competing phases in model Hamiltonians

    Science.gov (United States)

    Jiang, Mi

    Model Hamiltonians play an important role in our understanding of both quantum and classical systems, such as strongly correlated unconventional superconductivity, quantum magnetism, non-fermi liquid heavy fermion materials and classical magnetic phase transitions. The central problem is how models with many degrees of freedom choose between competing ground states, e.g. magnetic, superconducting, metallic, insulating as the degree of thermal and quantum fluctuations is varied. This dissertation focuses on the numerical investigation of several important model Hamiltonians. Specifically, we used the determinant Quantum Monte Carlo (DQMC) to study three Hubbard-like models: the Fermi-Hubbard model with two regions of different interaction strength, the Fermi-Hubbard model with a spin-dependent band structure, and the related periodic Anderson model (PAM). The first model used was to explore inter-penetration of metallic and Mott insulator physics across a Metal-Mott Insulator interface by computing the magnetic properties and spectral functions. As a minimal model of a half metallic magnet, the second model was used to explore the impact of on-site Hubbard interaction U, finite temperature, and an external (Zeeman) magnetic field on a bilayer tight-binding model with spin-dependent hybridization. We use PAM to study the Knight shift anomaly in heavy fermion materials found in Nuclear magnetic resonance (NMR) experiments and confirm several predictions of the two-fluid theory accounting for the anomaly. Another application of the Hubbard model described in this dissertation is the investigation on the effects of spin-dependent disorder on s-wave superconductors based on the attractive Hubbard model. Here we used the Bogoliubov-de Gennes (BdG) self-consistent approach instead of quantum simulations. The spin-dependent random potential was shown to induce distinct transitions at which the energy gap and average order parameter vanish, generating an intermediate gapless

  1. Phase field modeling of dendritic coarsening during isothermal

    Directory of Open Access Journals (Sweden)

    Zhang Yutuo

    2011-08-01

    Full Text Available Dendritic coarsening in Al-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy: (a melting of small dendrite arms; (b coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.

  2. Kinetic Relations for a Lattice Model of Phase Transitions

    Science.gov (United States)

    Schwetlick, Hartmut; Zimmer, Johannes

    2012-11-01

    The aim of this article is to analyse travelling waves for a lattice model of phase transitions, specifically the Fermi-Pasta-Ulam chain with piecewise quadratic interaction potential. First, for fixed, sufficiently large subsonic wave speeds, we rigorously prove the existence of a family of travelling wave solutions. Second, it is shown that this family of solutions gives rise to a kinetic relation which depends on the jump in the oscillatory energy in the solution tails. Third, our constructive approach provides a very good approximate travelling wave solution.

  3. Dynamical Phase Transition in a Model for Evolution with Migration

    Science.gov (United States)

    Waclaw, Bartłomiej; Allen, Rosalind J.; Evans, Martin R.

    2010-12-01

    We study a simple quasispecies model for evolution in two different habitats, with different fitness landscapes, coupled through one-way migration. Our key finding is a dynamical phase transition at a critical value of the migration rate, at which the time to reach the steady state diverges. The genetic composition of the population is qualitatively different above and below the transition. Using results from localization theory, we show that the critical migration rate may be very small—demonstrating that evolutionary outcomes can be very sensitive to even a small amount of migration.

  4. A motivic approach to phase transitions in Potts models

    Science.gov (United States)

    Aluffi, Paolo; Marcolli, Matilde

    2013-01-01

    We describe an approach to the study of phase transitions in Potts models based on an estimate of the complexity of the locus of real zeros of the partition function, computed in terms of the classes in the Grothendieck ring of the affine algebraic varieties defined by the vanishing of the multivariate Tutte polynomial. We give completely explicit calculations for the examples of the chains of linked polygons and of the graphs obtained by replacing the polygons with their dual graphs. These are based on a deletion-contraction formula for the Grothendieck classes and on generating functions for splitting and doubling edges.

  5. Final model independent result of DAMA/LIBRA-phase1

    Energy Technology Data Exchange (ETDEWEB)

    Bernabei, R.; D' Angelo, S.; Di Marco, A. [Universita di Roma ' ' Tor Vergata' ' , Dipartimento di Fisica, Rome (Italy); INFN, sez. Roma ' ' Tor Vergata' ' , Rome (Italy); Belli, P. [INFN, sez. Roma ' ' Tor Vergata' ' , Rome (Italy); Cappella, F.; D' Angelo, A.; Prosperi, D. [Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); INFN, sez. Roma, Rome (Italy); Caracciolo, V.; Castellano, S.; Cerulli, R. [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Dai, C.J.; He, H.L.; Kuang, H.H.; Ma, X.H.; Sheng, X.D.; Wang, R.G. [Chinese Academy, IHEP, Beijing (China); Incicchitti, A. [INFN, sez. Roma, Rome (Italy); Montecchia, F. [INFN, sez. Roma ' ' Tor Vergata' ' , Rome (Italy); Universita di Roma ' ' Tor Vergata' ' , Dipartimento di Ingegneria Civile e Ingegneria Informatica, Rome (Italy); Ye, Z.P. [Chinese Academy, IHEP, Beijing (China); University of Jing Gangshan, Jiangxi (China)

    2013-12-15

    The results obtained with the total exposure of 1.04 ton x yr collected by DAMA/LIBRA-phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles (i.e. adding a further 0.17 ton x yr exposure) are presented. The DAMA/LIBRA-phase1 data give evidence for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target, at 7.5{sigma} C.L. Including also the first generation DAMA/NaI experiment (cumulative exposure 1.33 ton x yr, corresponding to 14 annual cycles), the C.L. is 9.3{sigma} and the modulation amplitude of the single-hit events in the (2-6) keV energy interval is: (0.0112{+-}0.0012) cpd/kg/keV; the measured phase is (144{+-}7) days and the measured period is (0.998{+-}0.002) yr, values well in agreement with those expected for DM particles. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. (orig.)

  6. Phase Field Models for Thin Elastic Structures with Topological Constraint

    Science.gov (United States)

    Dondl, Patrick W.; Lemenant, Antoine; Wojtowytsch, Stephan

    2017-02-01

    This article is concerned with the problem of minimising the Willmore energy in the class of connected surfaces with prescribed area which are confined to a small container. We propose a phase field approximation based on De Giorgi's diffuse Willmore functional to this variational problem. Our main contribution is a penalisation term which ensures connectedness in the sharp interface limit. The penalisation of disconnectedness is based on a geodesic distance chosen to be small between two points that lie on the same connected component of the transition layer of the phase field. We prove that in two dimensions, sequences of phase fields with uniformly bounded diffuse Willmore energy and diffuse area converge uniformly to the zeros of a double-well potential away from the support of a limiting measure. In three dimensions, we show that they converge H^1-almost everywhere on curves. This enables us to show {Γ}-convergence to a sharp interface problem that only allows for connected structures. The results also imply Hausdorff convergence of the level sets in two dimensions and a similar result in three dimensions. Furthermore, we present numerical evidence of the effectiveness of our model. The implementation relies on a coupling of Dijkstra's algorithm in order to compute the topological penalty to a finite element approach for the Willmore term.

  7. ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Goodarz Ahmadi

    2004-10-01

    In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established.

  8. The Harari Shupe preon model and nonrelativistic quantum phase space

    Science.gov (United States)

    Żenczykowski, P.

    2008-03-01

    We propose that the whole algebraic structure of the Harari-Shupe rishon model originates via a Dirac-like linearization of quadratic form x2 +p2, with position and momentum satisfying standard commutation relations. The scheme does not invoke the concept of preons as spin-1/2 subparticles, thus evading the problem of preon confinement, while fully explaining all symmetries emboded in the Harari-Shupe model. Furthermore, the concept of quark colour is naturally linked to the ordering of rishons. Our scheme leads to group U (1) ⊗ SU (3) combined with SU (2), with two of the SU (2) generators not commuting with reflections. An interpretation of intra-generation quark-lepton transformations in terms of genuine rotations and reflections in phase space is proposed.

  9. Theory and Modeling of Phase Transformations under Stress in Steel

    Institute of Scientific and Technical Information of China (English)

    T.Y. Hsu (XU Zu-yao)

    2004-01-01

    Thermodynamic prediction of the increment of the formation temperature of proeutectoid ferrite by applied stress is nearly consistent with the experimental data. Kinetics models for ferrite, pearlite and bainite transformations can be shown as modified Johnson-Mehl-Avrami equation in which parameter b(σ) varies with the level of applied stress.The effects of tensile and compressive stresses on enhancement of the ferrite/pearlite and bainite transformations are discussed. The necessity and approach of modification of additivity hypothesis are introduced and the results from modified equation in which some parameters are obtained by regression of two experimental results or taken from TTT and CCT diagrams of a certain steel are superior than that from Scheil's equation. Thermodynamic calculation of Ms and nucleation kinetics equations of martensitic transformation under stress are suggested. Modeling of phase transformations under stress in ferrous alloys is briefly described.

  10. Models for the propagation phase of reinforcement corrosion - an overview

    Energy Technology Data Exchange (ETDEWEB)

    Raupach, M. [Institute for Building Materials Research of Aachen University (ibac), Schinkelstr. 3, 52062 Aachen (Germany)

    2006-08-15

    The deterioration of a concrete structure by reinforcement corrosion proceeds in two phases: the initiation stage and the propagation stage. The first stage describes the time to onset of corrosion due to carbonation of the concrete or chloride ingress. The second stage is the actual deterioration stage. Most methods for life time assessments refer only to the first stage, what is on the safe side with respect to design of structures, but also a model for the second stage can be of interest, e.g. if the remaining life time of an existing structure has to be estimated. This paper presents and discusses the state-of-the-art of models for the propagation stage with regard to their different approaches. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  11. Quad-phased data mining modeling for dementia diagnosis.

    Science.gov (United States)

    Bang, Sunjoo; Son, Sangjoon; Roh, Hyunwoong; Lee, Jihye; Bae, Sungyun; Lee, Kyungwon; Hong, Changhyung; Shin, Hyunjung

    2017-05-18

    The number of people with dementia is increasing along with people's ageing trend worldwide. Therefore, there are various researches to improve a dementia diagnosis process in the field of computer-aided diagnosis (CAD) technology. The most significant issue is that the evaluation processes by physician which is based on medical information for patients and questionnaire from their guardians are time consuming, subjective and prone to error. This problem can be solved by an overall data mining modeling, which subsidizes an intuitive decision of clinicians. Therefore, in this paper we propose a quad-phased data mining modeling consisting of 4 modules. In Proposer Module, significant diagnostic criteria are selected that are effective for diagnostics. Then in Predictor Module, a model is constructed to predict and diagnose dementia based on a machine learning algorism. To help clinical physicians understand results of the predictive model better, in Descriptor Module, we interpret causes of diagnostics by profiling patient groups. Lastly, in Visualization Module, we provide visualization to effectively explore characteristics of patient groups. The proposed model is applied for CREDOS study which contains clinical data collected from 37 university-affiliated hospitals in republic of Korea from year 2005 to 2013. This research is an intelligent system enabling intuitive collaboration between CAD system and physicians. And also, improved evaluation process is able to effectively reduce time and cost consuming for clinicians and patients.

  12. Mathematical Simulating Model of Phased-Array Antenna in Multifunction Array Radar

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.

  13. Phase-separation models for swimming enhancement in complex fluids

    CERN Document Server

    Man, Yi

    2015-01-01

    Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that micro-structured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensiona...

  14. Nahoon: Time-dependent gas-phase chemical model

    Science.gov (United States)

    Wakelam, V.

    2014-09-01

    Nahoon is a gas-phase chemical model that computes the chemical evolution in a 1D temperature and density structure. It uses chemical networks downloaded from the KInetic Database for Astrochemistry (KIDA) but the model can be adapted to any network. The program is written in Fortran 90 and uses the DLSODES (double precision) solver from the ODEPACK package to solve the coupled stiff differential equations. The solver computes the chemical evolution of gas-phase species at a fixed temperature and density and can be used in one dimension (1D) if a grid of temperature, density, and visual extinction is provided. Grains, both neutral and negatively charged, and electrons are considered as chemical species and their concentrations are computed at the same time as those of the other species. Nahoon contains a test to check the temperature range of the validity of the rate coefficients and avoid extrapolations outside this range. A test is also included to check for duplication of chemical reactions, defined over complementary ranges of temperature.

  15. Simulation and modeling of two-phase bubbly flows

    Energy Technology Data Exchange (ETDEWEB)

    Sylvain L Pigny; Pierre F Coste [DEN/DER/SSTH, CEA/Grenoble, 38054 Grenoble Cedex 9 (France)

    2005-07-01

    Full text of publication follows: Phenomena related to bubbles in two-phase recirculating flows are investigated, via the computational code SIMMER, concerning an experiment in which air is injected in the lower part of a tank filled of water and initially at rest. Averaged mass and momentum transport equations are solved for air and water. Close to the injector, the formation of individual large bubbles is represented in the calculations, via direct simulation. Small scale phenomena, related to small bubbles behavior or turbulence in the liquid continuous phase, are modeled, in a statistical way, via classical closure laws. In a first calculation, the splitting of large bubbles is not represented. It is shown that this phenomenon, the space scale of which is close to the cell size, cannot be simulated, in view of the present computational resources. Nevertheless, relatively fine meshes are used, for an accurate description of hydrodynamical phenomena, and the splitting phenomenon is too large to be modeled via closure laws. A specific approach for the intermediate scales is therefore developed to represent it. (authors)

  16. SINGLE PHASE ANALYTICAL MODELS FOR TERRY TURBINE NOZZLE

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Haihua; Zhang, Hongbin; Zou, Ling; O' Brien, James

    2016-11-01

    benchmarked with CFD simulations. The analytical models generally agree well with the experimental data and CFD simulations. The analytical models are suitable for implementation into a reactor system analysis code or severe accident code as part of mechanistic and dynamical models to understand the RCIC behaviors. The cases with two-phase flow at the turbine inlet will be pursued in future work.

  17. Dynamic phase transitions and dynamic phase diagrams of the Ising model on the Shastry-Sutherland lattice

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Şeyma Akkaya, E-mail: sadeviren@nevsehir.edu.tr [Department of Science Education, Education Faculty, Nevsehir Hacı Bektaş Veli University, 50300 Nevşehir (Turkey); Deviren, Bayram [Department of Physics, Nevsehir Hacı Bektaş Veli University, 50300 Nevsehir (Turkey)

    2016-03-15

    The dynamic phase transitions and dynamic phase diagrams are studied, within a mean-field approach, in the kinetic Ising model on the Shastry-Sutherland lattice under the presence of a time varying (sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. The time-dependence behavior of order parameters and the behavior of average order parameters in a period, which is also called the dynamic order parameters, as a function of temperature, are investigated. Temperature dependence of the dynamic magnetizations, hysteresis loop areas and correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic phase transitions as well as to obtain the dynamic phase transition temperatures. We present the dynamic phase diagrams in the magnetic field amplitude and temperature plane. The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena. The phase diagrams also contain paramagnetic (P), Néel (N), Collinear (C) phases, two coexistence or mixed regions, (N+C) and (N+P), which strongly depend on interaction parameters. - Highlights: • Dynamic magnetization properties of spin-1/2 Ising model on SSL are investigated. • Dynamic magnetization, hysteresis loop area, and correlation have been calculated. • The dynamic phase diagrams are constructed in (T/|J|, h/|J|) plane. • The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena.

  18. Phase equilibrium measurements and modelling for separation process design

    Energy Technology Data Exchange (ETDEWEB)

    Dell' Era, C.

    2012-07-01

    the thermodynamic representation of the equilibrium between phases. For this purpose an extensive experimental work was performed, comprising of vapour-liquid, gas-liquid and solid-liquid equilibrium measurements. Vapour liquid equilibrium of binary mixtures of butane + alcohols was measured with a static total pressure apparatus due to the importance of hydrocarbon and alcohol mixtures in the production of biofuels. The same equipment was used to measure binary systems of diethyl sulphide + C4 - hydrocarbons of importance in refinery applications. The activity coefficients of these systems were modelled with activity coefficients models. The absorption of carbon dioxide in alkanolamine solutions is the leading technology for the removal of carbon dioxide during refining of gas and oil. In recent years, this technology has gained importance also for carbon capture from large point sources. The scarcity of experimental data for some alkanolamine systems affected the accuracy of thermodynamic models. Several experimental techniques were developed to supply new experimental data for aqueous solutions of diisopropanolamine (DIPA) and methyldiethanolamine (MDEA). The solubility of carbon dioxide in solutions of these amines was measured with a static total pressure apparatus for gas solubility, and with a bubbling apparatus. The density of carbonated aqueous DIPA was also measured and modelled. The vapour-liquid equilibrium of water + DIPA and water + MDEA was measured with a static total pressure apparatus. The solid-liquid equilibrium of the same systems was measured with a visual method and a Differential Scanning Calorimeter. The activity coefficients of aqueous DIPA and MDEA solutions were modelled using NRTL, thus providing the first model of this sort for DIPA. A new model of the Henry's law constant of carbon dioxide in binary and ternary aqueous solutions of alkanolamines was developed at temperatures up to 393 K. (orig.)

  19. Phase-separated charge-density-wave phase in the two-species extended Bose-Hubbard model

    NARCIS (Netherlands)

    Mishra, Tapan; Sahoo, B. K.; Pai, Ramesh V.

    We study the quantum phase transitions in a two component Bose mixture in a one-dimensional optical lattice. The calculations have been performed in the framework of the extended Bose-Hubbard model using the finite size density matrix renormalization group method. We obtain different phase

  20. Partitioning of Nanoparticles into Organic Phases and Model Cells

    Energy Technology Data Exchange (ETDEWEB)

    Posner, J.D.; Westerhoff, P.; Hou, W-C.

    2011-08-25

    There is a recognized need to understand and predict the fate, transport and bioavailability of engineered nanoparticles (ENPs) in aquatic and soil ecosystems. Recent research focuses on either collection of empirical data (e.g., removal of a specific NP through water or soil matrices under variable experimental conditions) or precise NP characterization (e.g. size, degree of aggregation, morphology, zeta potential, purity, surface chemistry, and stability). However, it is almost impossible to transition from these precise measurements to models suitable to assess the NP behavior in the environment with complex and heterogeneous matrices. For decades, the USEPA has developed and applies basic partitioning parameters (e.g., octanol-water partition coefficients) and models (e.g., EPI Suite, ECOSAR) to predict the environmental fate, bioavailability, and toxicity of organic pollutants (e.g., pesticides, hydrocarbons, etc.). In this project we have investigated the hypothesis that NP partition coefficients between water and organic phases (octanol or lipid bilayer) is highly dependent on their physiochemical properties, aggregation, and presence of natural constituents in aquatic environments (salts, natural organic matter), which may impact their partitioning into biological matrices (bioaccumulation) and human exposure (bioavailability) as well as the eventual usage in modeling the fate and bioavailability of ENPs. In this report, we use the terminology "partitioning" to operationally define the fraction of ENPs distributed among different phases. The mechanisms leading to this partitioning probably involve both chemical force interactions (hydrophobic association, hydrogen bonding, ligand exchange, etc.) and physical forces that bring the ENPs in close contact with the phase interfaces (diffusion, electrostatic interactions, mixing turbulence, etc.). Our work focuses on partitioning, but also provides insight into the relative behavior of ENPs as either "more like

  1. Partitioning of Nanoparticles into Organic Phases and Model Cells

    Energy Technology Data Exchange (ETDEWEB)

    Posner, J.D.; Westerhoff, P.; Hou, W-C.

    2011-08-25

    There is a recognized need to understand and predict the fate, transport and bioavailability of engineered nanoparticles (ENPs) in aquatic and soil ecosystems. Recent research focuses on either collection of empirical data (e.g., removal of a specific NP through water or soil matrices under variable experimental conditions) or precise NP characterization (e.g. size, degree of aggregation, morphology, zeta potential, purity, surface chemistry, and stability). However, it is almost impossible to transition from these precise measurements to models suitable to assess the NP behavior in the environment with complex and heterogeneous matrices. For decades, the USEPA has developed and applies basic partitioning parameters (e.g., octanol-water partition coefficients) and models (e.g., EPI Suite, ECOSAR) to predict the environmental fate, bioavailability, and toxicity of organic pollutants (e.g., pesticides, hydrocarbons, etc.). In this project we have investigated the hypothesis that NP partition coefficients between water and organic phases (octanol or lipid bilayer) is highly dependent on their physiochemical properties, aggregation, and presence of natural constituents in aquatic environments (salts, natural organic matter), which may impact their partitioning into biological matrices (bioaccumulation) and human exposure (bioavailability) as well as the eventual usage in modeling the fate and bioavailability of ENPs. In this report, we use the terminology "partitioning" to operationally define the fraction of ENPs distributed among different phases. The mechanisms leading to this partitioning probably involve both chemical force interactions (hydrophobic association, hydrogen bonding, ligand exchange, etc.) and physical forces that bring the ENPs in close contact with the phase interfaces (diffusion, electrostatic interactions, mixing turbulence, etc.). Our work focuses on partitioning, but also provides insight into the relative behavior of ENPs as either "more like

  2. Disorder induced phase transition in an opinion dynamics model: results in 2 and 3 dimensions

    CERN Document Server

    Mukherjee, Sudip

    2016-01-01

    We study a model of continuous opinion dynamics with both positive and negative mutual interaction. The model shows a continuous phase transition between a phase with consensus (order) and a phase having no consensus (disorder). The mean field version of the model was already studied. Using extensive numerical simulations, we study the same model in $2$ and $3$ dimensions. The critical points of the phase transitions for various cases and the associated critical exponents have been estimated. The universality class of the phase transitions in the model is found to be same as Ising model in the respective dimensions.

  3. Modeling the radiation of ultrasonic phased-array transducers with Gaussian beams.

    Science.gov (United States)

    Huang, Ruiju; Schmerr, Lester W; Sedov, Alexander

    2008-12-01

    A new transducer beam model, called a multi-Gaussian array beam model, is developed to simulate the wave fields radiated by ultrasonic phased-array transducers. This new model overcomes the restrictions on using ordinary multi-Gaussian beam models developed for large single-element transducers in phased-array applications. It is demonstrated that this new beam model can effectively model the steered and focused beams of a linear phased-array transducer.

  4. Global phase diagram of a doped Kitaev-Heisenberg model

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Satoshi [ORNL

    2013-01-01

    The global phase diagram of a doped Kitaev-Heisenberg model is studied using an $SU(2)$ slave-boson mean-field method. Near the Kitaev limit, $p$-wave superconducting states which break the time-reversal symmetry are stabilized as reported by You {\\it et al.} [Phys. Rev. B {\\bf 86}, 085145 (2012)] irrespective of the sign of the Kitaev interaction. By further doping, a $d$-wave superconducting state appears when the Kitaev interaction is antiferromagnetic, while another $p$-wave superconducting state appears when the Kitaev interaction is ferromagnetic. This $p$-wave superconducting state does not break the time-reversal symmetry as reported by Hyart {\\it et al.} [Phys. Rev. B {\\bf 85}, 140510 (2012)], and such a superconducting state also appears when the antiferromagnetic Kitaev interaction and the ferromagnetic Heisenberg interaction compete. This work, thus, demonstrates the clear difference between the antiferromagnetic Kitaev model and the ferromagnetic Kitaev model when carriers are doped while these models are equivalent in the undoped limit, and how novel superconducting states emerge when the Kitaev interaction and the Heisenberg interaction compete.

  5. Analysis of free-surface flows through energy considerations: Single-phase versus two-phase modeling.

    Science.gov (United States)

    Marrone, Salvatore; Colagrossi, Andrea; Di Mascio, Andrea; Le Touzé, David

    2016-05-01

    The study of energetic free-surface flows is challenging because of the large range of interface scales involved due to multiple fragmentations and reconnections of the air-water interface with the formation of drops and bubbles. Because of their complexity the investigation of such phenomena through numerical simulation largely increased during recent years. Actually, in the last decades different numerical models have been developed to study these flows, especially in the context of particle methods. In the latter a single-phase approximation is usually adopted to reduce the computational costs and the model complexity. While it is well known that the role of air largely affects the local flow evolution, it is still not clear whether this single-phase approximation is able to predict global flow features like the evolution of the global mechanical energy dissipation. The present work is dedicated to this topic through the study of a selected problem simulated with both single-phase and two-phase models. It is shown that, interestingly, even though flow evolutions are different, energy evolutions can be similar when including or not the presence of air. This is remarkable since, in the problem considered, with the two-phase model about half of the energy is lost in the air phase while in the one-phase model the energy is mainly dissipated by cavity collapses.

  6. 2013 CEF RUN - PHASE 1 DATA ANALYSIS AND MODEL VALIDATION

    Energy Technology Data Exchange (ETDEWEB)

    Choi, A.

    2014-05-08

    Phase 1 of the 2013 Cold cap Evaluation Furnace (CEF) test was completed on June 3, 2013 after a 5-day round-the-clock feeding and pouring operation. The main goal of the test was to characterize the CEF off-gas produced from a nitric-formic acid flowsheet feed and confirm whether the CEF platform is capable of producing scalable off-gas data necessary for the revision of the DWPF melter off-gas flammability model; the revised model will be used to define new safety controls on the key operating parameters for the nitric-glycolic acid flowsheet feeds including total organic carbon (TOC). Whether the CEF off-gas data were scalable for the purpose of predicting the potential flammability of the DWPF melter exhaust was determined by comparing the predicted H{sub 2} and CO concentrations using the current DWPF melter off-gas flammability model to those measured during Phase 1; data were deemed scalable if the calculated fractional conversions of TOC-to-H{sub 2} and TOC-to-CO at varying melter vapor space temperatures were found to trend and further bound the respective measured data with some margin of safety. Being scalable thus means that for a given feed chemistry the instantaneous flow rates of H{sub 2} and CO in the DWPF melter exhaust can be estimated with some degree of conservatism by multiplying those of the respective gases from a pilot-scale melter by the feed rate ratio. This report documents the results of the Phase 1 data analysis and the necessary calculations performed to determine the scalability of the CEF off-gas data. A total of six steady state runs were made during Phase 1 under non-bubbled conditions by varying the CEF vapor space temperature from near 700 to below 300°C, as measured in a thermowell (T{sub tw}). At each steady state temperature, the off-gas composition was monitored continuously for two hours using MS, GC, and FTIR in order to track mainly H{sub 2}, CO, CO{sub 2}, NO{sub x}, and organic gases such as CH{sub 4}. The standard

  7. 2013 CEF RUN - PHASE 1 DATA ANALYSIS AND MODEL VALIDATION

    Energy Technology Data Exchange (ETDEWEB)

    Choi, A.

    2014-05-08

    Phase 1 of the 2013 Cold cap Evaluation Furnace (CEF) test was completed on June 3, 2013 after a 5-day round-the-clock feeding and pouring operation. The main goal of the test was to characterize the CEF off-gas produced from a nitric-formic acid flowsheet feed and confirm whether the CEF platform is capable of producing scalable off-gas data necessary for the revision of the DWPF melter off-gas flammability model; the revised model will be used to define new safety controls on the key operating parameters for the nitric-glycolic acid flowsheet feeds including total organic carbon (TOC). Whether the CEF off-gas data were scalable for the purpose of predicting the potential flammability of the DWPF melter exhaust was determined by comparing the predicted H{sub 2} and CO concentrations using the current DWPF melter off-gas flammability model to those measured during Phase 1; data were deemed scalable if the calculated fractional conversions of TOC-to-H{sub 2} and TOC-to-CO at varying melter vapor space temperatures were found to trend and further bound the respective measured data with some margin of safety. Being scalable thus means that for a given feed chemistry the instantaneous flow rates of H{sub 2} and CO in the DWPF melter exhaust can be estimated with some degree of conservatism by multiplying those of the respective gases from a pilot-scale melter by the feed rate ratio. This report documents the results of the Phase 1 data analysis and the necessary calculations performed to determine the scalability of the CEF off-gas data. A total of six steady state runs were made during Phase 1 under non-bubbled conditions by varying the CEF vapor space temperature from near 700 to below 300°C, as measured in a thermowell (T{sub tw}). At each steady state temperature, the off-gas composition was monitored continuously for two hours using MS, GC, and FTIR in order to track mainly H{sub 2}, CO, CO{sub 2}, NO{sub x}, and organic gases such as CH{sub 4}. The standard

  8. Approaches to myosin modelling in a two-phase flow model for cell motility

    Science.gov (United States)

    Kimpton, L. S.; Whiteley, J. P.; Waters, S. L.; Oliver, J. M.

    2016-04-01

    A wide range of biological processes rely on the ability of cells to move through their environment. Mathematical models have been developed to improve our understanding of how cells achieve motion. Here we develop models that explicitly track the cell's distribution of myosin within a two-phase flow framework. Myosin is a small motor protein which is important for contracting the cell's actin cytoskeleton and enabling cell motion. The two phases represent the actin network and the cytosol in the cell. We start from a fairly general description of myosin kinetics, advection and diffusion in the two-phase flow framework, then identify a number of sub-limits of the model that may be relevant in practice, two of which we investigate further via linear stability analyses and numerical simulations. We demonstrate that myosin-driven contraction of the actin network destabilizes a stationary steady state leading to cell motion, but that rapid diffusion of myosin and rapid unbinding of myosin from the actin network are stabilizing. We use numerical simulation to investigate travelling-wave solutions relevant to a steadily gliding cell and we consider a reduction of the model in which the cell adheres strongly to the substrate on which it is crawling. This work demonstrates that a number of existing models for the effect of myosin on cell motility can be understood as different sub-limits of our two-phase flow model.

  9. Phase response curves for models of earthquake fault dynamics

    CERN Document Server

    Franović, Igor; Perc, Matjaz; Klinshov, Vladimir; Nekorkin, Vladimir; Kurths, Jürgen

    2016-01-01

    We systematically study effects of external perturbations on models describing earthquake fault dynamics. The latter are based on the framework of the Burridge-Knopoff spring-block system, including the cases of a simple mono-block fault, as well as the paradigmatic complex faults made up of two identical or distinct blocks. The blocks exhibit relaxation oscillations, which are representative for the stick-slip behavior typical for earthquake dynamics. Our analysis is carried out by determining the phase response curves of first and second order. For a mono-block fault, we consider the impact of a single and two successive pulse perturbations, further demonstrating how the profile of phase response curves depends on the fault parameters. For a homogeneous two-block fault, our focus is on the scenario where each of the blocks is influenced by a single pulse, whereas for heterogeneous faults, we analyze how the response of the system depends on whether the stimulus is applied to the block having a shorter or a ...

  10. Phase response curves for models of earthquake fault dynamics

    Science.gov (United States)

    Franović, Igor; Kostić, Srdjan; Perc, Matjaž; Klinshov, Vladimir; Nekorkin, Vladimir; Kurths, Jürgen

    2016-06-01

    We systematically study effects of external perturbations on models describing earthquake fault dynamics. The latter are based on the framework of the Burridge-Knopoff spring-block system, including the cases of a simple mono-block fault, as well as the paradigmatic complex faults made up of two identical or distinct blocks. The blocks exhibit relaxation oscillations, which are representative for the stick-slip behavior typical for earthquake dynamics. Our analysis is carried out by determining the phase response curves of first and second order. For a mono-block fault, we consider the impact of a single and two successive pulse perturbations, further demonstrating how the profile of phase response curves depends on the fault parameters. For a homogeneous two-block fault, our focus is on the scenario where each of the blocks is influenced by a single pulse, whereas for heterogeneous faults, we analyze how the response of the system depends on whether the stimulus is applied to the block having a shorter or a longer oscillation period.

  11. Phase transitions and relaxation dynamics of Ising models exchanging particles

    Science.gov (United States)

    Goh, Segun; Fortin, Jean-Yves; Choi, M. Y.

    2017-01-01

    A variety of systems in nature and in society are open and subject to exchanging their constituents with other systems (e.g., environments). For instance, in biological systems, cells collect necessary energy and material by exchange of molecules or ions. Similarly, countries, cities or research institutes evolve as their constituents move in or out. To probe the corresponding particle exchange dynamics in such systems, we consider two Ising models exchanging particles and establish a master equation describing the equilibrium phases as well as the non-equilibrium dynamics of the system. It is found that an additional stable phase emerges as a consequence of the particle exchange process. Furthermore, we formulate the Ginzburg-Landau theory which allows to probe correlation effects. Accordingly, critical slowing down is manifested and the associated dynamic exponent is computed in the linear relaxation regime. In particular, this approach is relevant for investigating the grand canonical description of the system plus environment, with particle exchange and state transitions taken into account explicitly.

  12. Phase transitions in community detection: A solvable toy model

    Science.gov (United States)

    Ver Steeg, Greg; Moore, Cristopher; Galstyan, Aram; Allahverdyan, Armen

    2014-05-01

    Recently, it was shown that there is a phase transition in the community detection problem. This transition was first computed using the cavity method, and has been proved rigorously in the case of q = 2 groups. However, analytic calculations using the cavity method are challenging since they require us to understand probability distributions of messages. We study analogous transitions in the so-called “zero-temperature inference” model, where this distribution is supported only on the most likely messages. Furthermore, whenever several messages are equally likely, we break the tie by choosing among them with equal probability, corresponding to an infinitesimal random external field. While the resulting analysis overestimates the thresholds, it reproduces some of the qualitative features of the system. It predicts a first-order detectability transition whenever q > 2 (as opposed to q > 4 according to the finite-temperature cavity method). It also has a regime analogous to the “hard but detectable” phase, where the community structure can be recovered, but only when the initial messages are sufficiently accurate. Finally, we study a semisupervised setting where we are given the correct labels for a fraction ρ of the nodes. For q > 2, we find a regime where the accuracy jumps discontinuously at a critical value of ρ.

  13. Phase transitions in diluted negative-weight percolation models.

    Science.gov (United States)

    Apolo, L; Melchert, O; Hartmann, A K

    2009-03-01

    We investigate the geometric properties of loops on two-dimensional lattice graphs, where edge weights are drawn from a distribution that allows for positive and negative weights. We are interested in the appearance of spanning loops of total negative weight. The resulting percolation problem is fundamentally different from conventional percolation, as we have seen in a previous study of this model for the undiluted case. Here, we investigate how the percolation transition is affected by additional dilution. We consider two types of dilution: either a certain fraction of edges exhibits zero weight, or a fraction of edges is even absent. We study these systems numerically using exact combinatorial optimization techniques based on suitable transformations of the graphs and applying matching algorithms. We perform a finite-size scaling analysis to obtain the phase diagram and determine the critical properties of the phase boundary. We find that the first type of dilution does not change the universality class compared to the undiluted case whereas the second type of dilution leads to a change in the universality class.

  14. Phase interface effects in the total enthalpy-based lattice Boltzmann model for solid-liquid phase change

    Science.gov (United States)

    Huang, Rongzong; Wu, Huiying

    2015-08-01

    In this paper, phase interface effects, including the differences in thermophysical properties between solid and liquid phases and the numerical diffusion across phase interface, are investigated for the recently developed total enthalpy-based lattice Boltzmann model for solid-liquid phase change, which has high computational efficiency by avoiding iteration procedure and linear equation system solving. For the differences in thermophysical properties (thermal conductivity and specific heat) between solid and liquid phases, a novel reference specific heat is introduced to improve the total enthalpy-based lattice Boltzmann model, which makes the thermal conductivity and specific heat decoupled. Therefore, the differences in thermal conductivity and specific heat can be handled by the dimensionless relaxation time and equilibrium distribution function, respectively. As for the numerical diffusion across phase interface, it is revealed for the first time and found to be induced by solid-liquid phase change. To reduce such numerical diffusion, multiple-relaxation-time collision scheme is exploited, and a special value (one fourth) for the so-called "magic" parameter, a combination of two relaxation parameters, is found. Numerical tests show that the differences in thermophysical properties can be correctly handled and the numerical diffusion across phase interface can be dramatically reduced. Finally, theoretical analyses are carried out to offer insights into the roles of the reference specific heat and "magic" parameter in the treatments of phase interface effects.

  15. Comparative simulation study of gas-phase propylene polymerization in fluidized bed reactors using aspen polymers and two phase models

    Directory of Open Access Journals (Sweden)

    Shamiria Ahmad

    2013-01-01

    Full Text Available A comparative study describing gas-phase propylene polymerization in fluidized-bed reactors using Ziegler-Natta catalyst is presented. The reactor behavior was explained using a two-phase model (which is based on principles of fluidization as well as simulation using the Aspen Polymers process simulator. The two-phase reactor model accounts for the emulsion and bubble phases which contain different portions of catalysts with the polymerization occurring in both phases. Both models predict production rate, molecular weight, polydispersity index (PDI and melt flow index (MFI of the polymer. We used both models to investigate the effect of important polymerization parameters, namely catalyst feed rate and hydrogen concentration, on the product polypropylene properties, such as production rate, molecular weight, PDI and MFI. Both the two-phase model and Aspen Polymers simulator showed good agreement in terms of production rate. However, the models differed in their predictions for weight-average molecular weight, PDI and MFI. Based on these results, we propose incorporating the missing hydrodynamic effects into Aspen Polymers to provide a more realistic understanding of the phenomena encountered in fluidized bed reactors for polyolefin production.

  16. The Impact of Consumer Phase Models in Microbial Risk Analysis

    DEFF Research Database (Denmark)

    Nauta, Maarten; Christensen, Bjarke Bak

    2011-01-01

    In quantitative microbiological risk assessment (QMRA), the consumer phase model (CPM) describes the part of the food chain between purchase of the food product at retail and exposure. Construction of a CPM is complicated by the large variation in consumer food handling practices and a limited...... availability of data. Therefore, several subjective (simplifying) assumptions have to be made when a CPM is constructed, but with a single CPM their impact on the QMRA results is unclear. We therefore compared the performance of eight published CPMs for Campylobacter in broiler meat in an example of a QMRA......, where all the CPMs were analyzed using one single input distribution of concentrations at retail, and the same dose-response relationship. It was found that, between CPMs, there may be a considerable difference in the estimated probability of illness per serving. However, the estimated relative risk...

  17. Improved quark coalescence for a multi-phase transport model

    Science.gov (United States)

    He, Yuncun; Lin, Zi-Wei

    2017-07-01

    The string melting version of a multi-phase transport model is often applied to high-energy heavy-ion collisions since the dense matter thus formed is expected to be in parton degrees of freedom. In this work we improve its quark coalescence component, which describes the hadronization of the partonic matter to a hadronic matter. We removed the previous constraint that forced the numbers of mesons, baryons, and antibaryons in an event to be separately conserved through the quark coalescence process. A quark now could form either a meson or a baryon depending on the distance to its coalescence partner(s). We then compare results from the improved model with the experimental data on hadron d N /d y ,pT spectra, and v2 in heavy-ion collisions from √{s NN}=62.4 GeV to 5.02 TeV. We show that, besides being able to describe these observables for low-pTpions and kaons, the improved model also better describes the low-p T baryon observables in general, especially the baryon p T spectra and antibaryon-to-baryon ratios for multistrange baryons.

  18. Dynamic dielectrophoresis model of multi-phase ionic fluids.

    Directory of Open Access Journals (Sweden)

    Ying Yan

    Full Text Available Ionic-based dielectrophoretic microchips have attracted significant attention due to their wide-ranging applications in electro kinetic and biological experiments. In this work, a numerical method is used to simulate the dynamic behaviors of ionic droplets in a microchannel under the effect of dielectrophoresis. When a discrete liquid dielectric is encompassed within a continuous fluid dielectric placed in an electric field, an electric force is produced due to the dielectrophoresis effect. If either or both of the fluids are ionic liquids, the magnitude and even the direction of the force will be changed because the net ionic charge induced by an electric field can affect the polarization degree of the dielectrics. However, using a dielectrophoresis model, assuming ideal dielectrics, results in significant errors. To avoid the inaccuracy caused by the model, this work incorporates the electrode kinetic equation and defines a relationship between the polarization charge and the net ionic charge. According to the simulation conditions presented herein, the electric force obtained in this work has an error exceeding 70% of the actual value if the false effect of net ionic charge is not accounted for, which would result in significant issues in the design and optimization of experimental parameters. Therefore, there is a clear motivation for developing a model adapted to ionic liquids to provide precise control for the dielectrophoresis of multi-phase ionic liquids.

  19. Non-equilibrium dynamical phases of the two-atom Dicke model

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacherjee, Aranya B.

    2014-09-12

    In this paper, we investigate the non-equilibrium dynamical phases of the two-atom Dicke model, which can be realized in a two species Bose–Einstein condensate interacting with a single light mode in an optical cavity. Apart from the usual non-equilibrium normal and inverted phases, a non-equilibrium mixed phase is possible which is a combination of normal and inverted phase. A new kind of dynamical phase transition is predicted from non-superradiant mixed phase to the superradiant phase which can be achieved by tuning the two different atom–photon couplings. We also show that a dynamical phase transition from the non-superradiant mixed phase to the superradiant phase is forbidden for certain values of the two atom–photon coupling strengths. - Highlights: • We investigate the non-equilibrium dynamical phases of the two-atom Dicke model. • The dynamical phase diagram reveals a new kind of non-equilibrium mixed phase. • A new kind of dynamical phase transition is predicted from mixed phase to the superradiant phase. • In the dynamical phase diagram of the mixed phase, there are regions where the superradiant phase cannot exist.

  20. Mathematical models for two-phase stratified pipe flow

    Energy Technology Data Exchange (ETDEWEB)

    Biberg, Dag

    2005-06-01

    The simultaneous transport of oil, gas and water in a single multiphase flow pipe line has for economical and practical reasons become common practice in the gas and oil fields operated by the oil industry. The optimal design and safe operation of these pipe lines require reliable estimates of liquid inventory, pressure drop and flow regime. Computer simulations of multiphase pipe flow have thus become an important design tool for field developments. Computer simulations yielding on-line monitoring and look ahead predictions are invaluable in day-to-day field management. Inaccurate predictions may have large consequences. The accuracy and reliability of multiphase pipe flow models are thus important issues. Simulating events in large pipelines or pipeline systems is relatively computer intensive. Pipe-lines carrying e.g. gas and liquefied gas (condensate) may cover distances of several hundred km in which transient phenomena may go on for months. The evaluation times associated with contemporary 3-D CFD models are thus not compatible with field applications. Multiphase flow lines are therefore normally simulated using specially dedicated 1-D models. The closure relations of multiphase pipe flow models are mainly based on lab data. The maximum pipe inner diameter, pressure and temperature in a multiphase pipe flow lab is limited to approximately 0.3 m, 90 bar and 60{sup o}C respectively. The corresponding field values are, however, much higher i.e.: 1 m, 1000 bar and 200{sup o}C respectively. Lab data does thus not cover the actual field conditions. Field predictions are consequently frequently based on model extrapolation. Applying field data or establishing more advanced labs will not solve this problem. It is in fact not practically possible to acquire sufficient data to cover all aspects of multiphase pipe flow. The parameter range involved is simply too large. Liquid levels and pressure drop in three-phase flow are e.g. determined by 13 dimensionless parameters

  1. Phase field modeling of the defect evolution and failure

    Science.gov (United States)

    Xie, Yuesong

    The plastic recovery processes in ultrafine and nano grained metals and the yield criteria and failure mechanisms in polymer matrix composite are the two major topics in this work. In the first part of the work, a phase field dislocation dynamics (PFDD) approach is introduced, which tracks the evolution of the dislocations in ultrafine and nano grained metals and takes into account the elastic interaction between dislocations, obstacles and the applied resolved shear stress on a single slip plane. Two phenomena, the reverse plastic strain during cyclic loading and plastic strain recovery upon unloading, are studied. One major finding of our simulations is that these two plastic recovery processes are related to the formation of dislocation structures during loading, and additional grain size inhomogeneity will increase the amount of plastic strain recovered. In the second part of the work, a phase field damage model (PFDM) is presented to study the onset of yielding and crack propagation in polymer matrix composite. The effect of two damage parameters, the fracture toughness Gc and crack length scale parameter l0, are first investigated. The former is shown to determine the energy needed during crack propagation and the latter is observed to control the crack nucleation process. Moreover, two asymmetric damage models are compared regarding their yield surfaces and it is found that the model of Miehe et al. leads to a linear pressure modified von Mises relation. Next, the PFDM reveals that the yield criterion in amorphous polymers should be described in terms of local stress and strains fields and cannot be extended directly from applied stress field values. Furthermore, it is demonstrated that the same damage model can be used to study the failure under shear yielding and crazing conditions. And if local defects in the samples such as voids are included explicitly in the simulations, the PFDM is able to explain the breakdown of the pressure modified von Mises

  2. Thermodynamic Model Formulations for Inhomogeneous Solids with Application to Non-isothermal Phase Field Modelling

    Science.gov (United States)

    Gladkov, Svyatoslav; Kochmann, Julian; Reese, Stefanie; Hütter, Markus; Svendsen, Bob

    2016-04-01

    The purpose of the current work is the comparison of thermodynamic model formulations for chemically and structurally inhomogeneous solids at finite deformation based on "standard" non-equilibrium thermodynamics [SNET: e. g. S. de Groot and P. Mazur, Non-equilibrium Thermodynamics, North Holland, 1962] and the general equation for non-equilibrium reversible-irreversible coupling (GENERIC) [H. C. Öttinger, Beyond Equilibrium Thermodynamics, Wiley Interscience, 2005]. In the process, non-isothermal generalizations of standard isothermal conservative [e. g. J. W. Cahn and J. E. Hilliard, Free energy of a non-uniform system. I. Interfacial energy. J. Chem. Phys. 28 (1958), 258-267] and non-conservative [e. g. S. M. Allen and J. W. Cahn, A macroscopic theory for antiphase boundary motion and its application to antiphase domain coarsening. Acta Metall. 27 (1979), 1085-1095; A. G. Khachaturyan, Theory of Structural Transformations in Solids, Wiley, New York, 1983] diffuse interface or "phase-field" models [e. g. P. C. Hohenberg and B. I. Halperin, Theory of dynamic critical phenomena, Rev. Modern Phys. 49 (1977), 435-479; N. Provatas and K. Elder, Phase Field Methods in Material Science and Engineering, Wiley-VCH, 2010.] for solids are obtained. The current treatment is consistent with, and includes, previous works [e. g. O. Penrose and P. C. Fife, Thermodynamically consistent models of phase-field type for the kinetics of phase transitions, Phys. D 43 (1990), 44-62; O. Penrose and P. C. Fife, On the relation between the standard phase-field model and a "thermodynamically consistent" phase-field model. Phys. D 69 (1993), 107-113] on non-isothermal systems as a special case. In the context of no-flux boundary conditions, the SNET- and GENERIC-based approaches are shown to be completely consistent with each other and result in equivalent temperature evolution relations.

  3. Retention models for ionizable compounds in reversed-phase liquid chromatography: effect of variation of mobile phase composition and temperature.

    Science.gov (United States)

    Rosés, Martí; Subirats, Xavier; Bosch, Elisabeth

    2009-03-06

    General models in reversed-phase liquid chromatography that have been extended to relate retention of ionizable compounds to mobile phase composition, pH and/or temperature are reviewed. In particular, the fundamentals and applications of the solvation parameter model, the polarity parameter model and several classical models based on empirical equations are presented and compared. A main parameter in all these models is the degree of ionization of the acid-base compound, which depends on both the pH of the mobile phase and the acid-base constant of the compound. Thus, on one hand, the different procedures for pH measurement in the mobile phase and their influence on the performance of the models are outlined. On the other hand, equations that relate the variation of the pH of the buffer and the pK(a) of the compound with the mobile phase composition and/or temperature are reviewed and their applicability to the retention models critically discussed.

  4. Phase diagram of the bosonic Kondo-Hubbard model

    Energy Technology Data Exchange (ETDEWEB)

    Foss-Feig, Michael; Rey, Ana Maria [JILA, National Institute of Standards and Technology, and University of Colorado, Boulder, Colorado 80309 (United States)

    2011-11-15

    We study a bosonic version of the Kondo lattice model with an onsite repulsion in the conduction band, implemented with alkali-metal atoms in two bands of an optical lattice. Using both weak- and strong-coupling perturbation theory, we find that at unit filling of the conduction bosons the superfluid-to-Mott-insulator transition should be accompanied by a magnetic transition from a ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator). Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that quantum spin fluctuations induced by the Kondo exchange cause the otherwise continuous superfluid-to-Mott-insulator phase transition to be first order. We show that lattice separability imposes a serious constraint on proposals to exploit excited bands for quantum simulations, and discuss a way to overcome this constraint in the context of our model by using an experimentally realized nonseparable lattice. A method to probe the first-order nature of the transition based on collapses and revivals of the matter-wave field is also discussed.

  5. MARMOT Phase-Field Model for the U-Si System

    Energy Technology Data Exchange (ETDEWEB)

    Aagesen, Larry Kenneth [Idaho National Laboratory; Schwen, Daniel [Idaho National Laboratory

    2016-09-01

    A phase-field model for the U-Si system has been implemented in MARMOT. The free energies for the phases relevant to accident-tolerant fuel applications (U3Si2, USi, U3Si, and liquid) were implemented as free energy materials within MARMOT. A new three-phase phase-field model based on the concepts of the Kim-Kim-Suzuki two-phase model was developed and implemented in the MOOSE phase-field module. Key features of this model are that two-phase interfaces are stable with respect to formation of the third phase, and that arbitrary phase free energies can be used. The model was validated using a simplified three-phase system and the U-Si system. In the U-Si system, the model correctly reproduced three-phase coexistence in a U3Si2-liquid-USi system at the eutectic temperature, solidification of a three-phase mixture below the eutectic temperature, and complete melting of a three-phase mixture above the eutectic temperature.

  6. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissila, T.

    2010-01-01

    We present a derivation of the recently proposed eighth order phase field crystal model [Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase field crystal models. We find that among the phase field crystal models...

  7. An original combined multiphase model of the steam-explosion premixing phase

    OpenAIRE

    Leskovar, Matjaž; Mavko, Borut

    2015-01-01

    In multiphase flow, different distributions can occur that cannot be adequately modeled with just free-surface models or with just multiphase models. Such a distribution of phases occurs for example, in isothermal steam-explosion premixing experiments, where dispersed spheres penetrate the water and the water-air surface remains sharp. A common practice when modeling isothermal premixing experiments is to treat all three phases involved - the water, the air and the spheres phase - equally, wi...

  8. Competition between the s-wave and p-wave superconductivity phases in a holographic model

    CERN Document Server

    Nie, Zhang-Yu; Gao, Xin; Zeng, Hui

    2013-01-01

    We build a holographic superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. In this model, the s-wave and p-wave condensates can be consistently realized. We find that there are totally four phases in this model, namely, the normal phase without any condensate, s-wave phase, p-wave phase and the s+p coexisting phase. By calculating Gibbs free energy, the s+p coexisting phase turns out to be thermodynamically favored once it can appear. The phase diagram with the dimension of the scalar operator and temperature is drawn. The temperature range for the s+p coexisting phase is very narrow, which shows the competition between the s-wave and p-wave orders in the superconductor model.

  9. Phase structure of hadronic and Polyakov-loop extended NJL model at finite isospin density

    CERN Document Server

    Cavagnoli, Rafael; Providência, Constança

    2013-01-01

    It is believed that there exists a rich phase structure of quantum chromodynamics (QCD) at finite temperature and baryon density, namely, the deconfinement process from hadron gas to quark-gluon plasma, the transition from chiral symmetry breaking phase to the symmetry restoration phase, and the color superconductivity at low temperature and high baryon density. In the present work we study the hadron-quark phase transition by investigating the binodal surface and extending it to finite temperature in order to mimic the QCD phase diagram. In order to obtain these conditions we use different models for the two possible phases, namely the quark and hadron phases. The phase separation boundary (binodal) is determined by the Gibbs criteria for phase equilibrium. The boundaries of the mixed phase and the related critical points for symmetric and asymmetric matter are obtained. Isospin effects appear to be rather significant. The critical endpoint (CEP) and the phase structure are also studied in the Polyakov-loop ...

  10. Phase transition in matrix model with logarithmic action: Toy-model for gluons in baryons

    CERN Document Server

    Krishnaswami, G S

    2006-01-01

    We study the competing effects of gluon self-coupling and their interactions with quarks in a baryon, using the very simple setting of a hermitian 1-matrix model with action tr A^4 - log det(nu + A^2). The logarithmic term comes from integrating out N quarks. The model is a caricature of 2d QCD coupled to adjoint scalars, which are the transversely polarized gluons in a dimensional reduction. nu is a dimensionless ratio of quark mass to coupling constant. The model interpolates between gluons in the vacuum (nu=infinity), gluons weakly coupled to heavy quarks (large nu) and strongly coupled to light quarks in a baryon (nu to 0). It's solution in the large-N limit exhibits a phase transition from a weakly coupled 1-cut phase to a strongly coupled 2-cut phase as nu is decreased below nu_c = 0.27. Free energy and correlation functions are discontinuous in their third and second derivatives at nu_c. The transition to a two-cut phase forces eigenvalues of A away from zero, making glue-ring correlations grow as nu i...

  11. Chiral Phase Transition at Finite Isospin Density in Linear Sigma Model

    Institute of Scientific and Technical Information of China (English)

    SHU Song; LI Jia-Rong

    2005-01-01

    Using the linear sigma model, we have introduced the pion isospin chemical potential. The chiral phase transition is studied at finite temperatures and finite isospin densities. We have studied the μ - T phase diagram for the chiral phase transition and found the transition cannot happen below a certain low temperature because of the BoseEinstein condensation in this system. Above that temperature, the chiral phase transition is studied by the isotherms of pressure versus density. We indicate that the transition, in the chiral limit, is a first-order transition from a low-density phase to a high-density phase like a gas-liquid phase transition.

  12. Energy spectrum and phase diagrams of two-sublattice hard-core boson model

    Directory of Open Access Journals (Sweden)

    I.V. Stasyuk

    2013-06-01

    Full Text Available The energy spectrum, spectral density and phase diagrams have been obtained for two-sublattice hard-core boson model in frames of random phase approximation approach. Reconstruction of boson spectrum at the change of temperature, chemical potential and energy difference between local positions in sublattices is studied. The phase diagrams illustrating the regions of existence of a normal phase which can be close to Mott-insulator (MI or charge-density (CDW phase diagrams as well as the phase with the Bose-Einstein condensate (SF phase are built.

  13. High-response piezoelectricity modeled quantitatively near a phase boundary

    Science.gov (United States)

    Newns, Dennis M.; Kuroda, Marcelo A.; Cipcigan, Flaviu S.; Crain, Jason; Martyna, Glenn J.

    2017-01-01

    Interconversion of mechanical and electrical energy via the piezoelectric effect is fundamental to a wide range of technologies. The discovery in the 1990s of giant piezoelectric responses in certain materials has therefore opened new application spaces, but the origin of these properties remains a challenge to our understanding. A key role is played by the presence of a structural instability in these materials at compositions near the "morphotropic phase boundary" (MPB) where the crystal structure changes abruptly and the electromechanical responses are maximal. Here we formulate a simple, unified theoretical description which accounts for extreme piezoelectric response, its observation at compositions near the MPB, accompanied by ultrahigh dielectric constant and mechanical compliances with rather large anisotropies. The resulting model, based upon a Landau free energy expression, is capable of treating the important domain engineered materials and is found to be predictive while maintaining simplicity. It therefore offers a general and powerful means of accounting for the full set of signature characteristics in these functional materials including volume conserving sum rules and strong substrate clamping effects.

  14. Diagnosing Traffic Anomalies Using a Two-Phase Model

    Institute of Scientific and Technical Information of China (English)

    Bin Zhang; Jia-Hai Yang; Jian-Ping Wu; Ying-Wu Zhu

    2012-01-01

    Network traffic anomalies are unusual changes in a network,so diagnosing anomalies is important for network management.Feature-based anomaly detection models (ab)normal network traffic behavior by analyzing packet header features. PCA-subspace method (Principal Component Analysis) has been verified as an efficient feature-based way in network-wide anomaly detection.Despite the powerful ability of PCA-subspace method for network-wide traffic detection,it cannot be effectively used for detection on a single link.In this paper,different from most works focusing on detection on flow-level traffic,based on observations of six traffc features for packet-level traffic,we propose a new approach B6SVM to detect anomalies for packet-level traffic on a single link.The basic idea of B6-SVM is to diagnose anomalies in a multi-dimensional view of traffic features using Support Vector Machine (SVM).Through two-phase classification,B6-SVM can detect anomalies with high detection rate and low false alarm rate.The test results demonstrate the effectiveness and potential of our technique in diagnosing anomalies.Further,compared to previous feature-based anomaly detection approaches,B6-SVM provides a framework to automatically identify possible anomalous types.The framework of B6-SVM is generic and therefore,we expect the derived insights will be helpful for similar future research efforts.

  15. f(R,T) Dark Energy Models in Phase Space

    CERN Document Server

    Shabani, Hamid

    2013-01-01

    We investigate cosmological solutions of f(R,T) modified theories of gravity for a perfect fluid in a spatially homogeneous and isotropic background through phase space analysis, where R is Ricci scalar and T denotes trace of energy-momentum tensor of matter content. The theory is explored for minimal case f(R,T)=g(R)+h(T), pure non-minimal case f(R,T)=g(R)h(T), and f(R,T)=g(R)+g(R)h(T). For first case, the acceptable cosmological solutions which contain long enough matter dominated era followed by a late-time accelerated expansion are found. We classify solutions in six classes which demonstrate more acceptable solutions than the f(R) gravity. In background of f(R,T) gravity, cosmological behavior of some function g(R) is explored theoretically and is shown that the models $aR^{-\\beta}$ for $-1.43\\leq\\beta0$, $R [\\log{(\\alpha R)}]^{q}$ for two values $q=\\pm1$ with $\\alpha>0$, $R^{p}\\exp{(qR)}$ for $p\\rightarrow 1^{+}$ with $q>0$, $R+\\alpha R^{-n}$ for $n\\rightarrow-1^{+}$ with $\\alpha0$ and $R^{p}\\exp{(q/R)}...

  16. Phase transition in a spatial Lotka-Volterra model

    Energy Technology Data Exchange (ETDEWEB)

    Szabo, Gyorgy; Czaran, Tamas

    2001-06-01

    Spatial evolution is investigated in a simulated system of nine competing and mutating bacterium strains, which mimics the biochemical war among bacteria capable of producing two different bacteriocins (toxins) at most. Random sequential dynamics on a square lattice is governed by very symmetrical transition rules for neighborhood invasions of sensitive strains by killers, killers by resistants, and resistants by sensitives. The community of the nine possible toxicity/resistance types undergoes a critical phase transition as the uniform transmutation rates between the types decreases below a critical value P{sub c} above that all the nine types of strains coexist with equal frequencies. Passing the critical mutation rate from above, the system collapses into one of three topologically identical (degenerated) states, each consisting of three strain types. Of the three possible final states each accrues with equal probability and all three maintain themselves in a self-organizing polydomain structure via cyclic invasions. Our Monte Carlo simulations support that this symmetry-breaking transition belongs to the universality class of the three-state Potts model.

  17. Anisotropic distributions in a multi-phase transport model

    CERN Document Server

    Zhou, You; Feng, Zhao; Liu, Feng; Snellings, Raimond

    2015-01-01

    With A Multi-Phase Transport (AMPT) model we investigate the relation between the magnitude, fluctuations and correlations of the initial state spatial anisotropy $\\varepsilon_{n}$ and the final state anisotropic flow coefficients $v_{n}$ in Au+Au collisions at $\\sqrt{s_{_{\\rm NN}}}=$ 200 GeV. It is found that the relative eccentricity fluctuations in AMPT account for the observed elliptic flow fluctuations, in agreement with measurements of the STAR collaboration. In addition, the studies based on 2- and multi-particle correlations and event-by-event distributions of the anisotropies suggest that the Elliptic-Power function is a promising candidate of the underlying probability density function of the event-by-event distributions of $\\varepsilon_{n}$ as well as $v_{n}$. Furthermore, the correlations between different order symmetry planes and harmonics in the initial coordinate space and final state momentum space are presented. Non-zero values of these correlations have been observed. The comparison between...

  18. Semiphenomenological model for gas-liquid phase transitions.

    Science.gov (United States)

    Benilov, E S; Benilov, M S

    2016-03-01

    We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets.

  19. Phase transition in a spatial Lotka-Volterra model.

    Science.gov (United States)

    Szabó, G; Czárán, T

    2001-06-01

    Spatial evolution is investigated in a simulated system of nine competing and mutating bacterium strains, which mimics the biochemical war among bacteria capable of producing two different bacteriocins (toxins) at most. Random sequential dynamics on a square lattice is governed by very symmetrical transition rules for neighborhood invasions of sensitive strains by killers, killers by resistants, and resistants by sensitives. The community of the nine possible toxicity/resistance types undergoes a critical phase transition as the uniform transmutation rates between the types decreases below a critical value P(c) above that all the nine types of strains coexist with equal frequencies. Passing the critical mutation rate from above, the system collapses into one of three topologically identical (degenerated) states, each consisting of three strain types. Of the three possible final states each accrues with equal probability and all three maintain themselves in a self-organizing polydomain structure via cyclic invasions. Our Monte Carlo simulations support that this symmetry-breaking transition belongs to the universality class of the three-state Potts model.

  20. Phase lagging model of brain response to external stimuli - modeling of single action potential

    CERN Document Server

    Seetharaman, Karthik; Kulish, Vladimir V

    2012-01-01

    In this paper we detail a phase lagging model of brain response to external stimuli. The model is derived using the basic laws of physics like conservation of energy law. This model eliminates the paradox of instantaneous propagation of the action potential in the brain. The solution of this model is then presented. The model is further applied in the case of a single neuron and is verified by simulating a single action potential. The results of this modeling are useful not only for the fundamental understanding of single action potential generation, but also they can be applied in case of neuronal interactions where the results can be verified against the real EEG signal.

  1. Phase Structure in a Quark Mass Density-and-Temperature-Dependent Model

    Institute of Scientific and Technical Information of China (English)

    WEN Xin-Jian; PENG Guang-Xiong; SHEN Peng-Nian

    2007-01-01

    The phase diagram of bulk quark matter in equilibrium with a finite hadronic gas is studied. Different from previous investigations, we treat the quark phase with the quark rnass density-and-temperature-dependent model to take the strong quark interaction into account, while the hadron phase is treated by hard core repulsion factor. It is found that the phase diagram in this model is, in several aspects, different from those in the conventional MIT bag model, especially at high temperature. The new phase diagram also has strong effects on the mass-radius relation of compact hybrid stars.

  2. Sample-dependent phase transitions in disordered exclusion models

    Science.gov (United States)

    Enaud, C.; Derrida, B.

    2004-04-01

    We give numerical evidence that the location of the first-order phase transition between the low- and the high-density phases of the one-dimensional asymmetric simple exclusion process with open boundaries becomes sample dependent when quenched disorder is introduced for the hopping rates.

  3. Investigation of binary solid phases by calorimetry and kinetic modelling

    NARCIS (Netherlands)

    Matovic, M.

    2007-01-01

    The traditional methods for the determination of liquid-solid phase diagrams are based on the assumption that the overall equilibrium is established between the phases. However, the result of the crystallization of a liquid mixture will typically be a non-equilibrium or metastable state of the solid

  4. Multi-phase SPH modelling of violent hydrodynamics on GPUs

    Science.gov (United States)

    Mokos, Athanasios; Rogers, Benedict D.; Stansby, Peter K.; Domínguez, José M.

    2015-11-01

    This paper presents the acceleration of multi-phase smoothed particle hydrodynamics (SPH) using a graphics processing unit (GPU) enabling large numbers of particles (10-20 million) to be simulated on just a single GPU card. With novel hardware architectures such as a GPU, the optimum approach to implement a multi-phase scheme presents some new challenges. Many more particles must be included in the calculation and there are very different speeds of sound in each phase with the largest speed of sound determining the time step. This requires efficient computation. To take full advantage of the hardware acceleration provided by a single GPU for a multi-phase simulation, four different algorithms are investigated: conditional statements, binary operators, separate particle lists and an intermediate global function. Runtime results show that the optimum approach needs to employ separate cell and neighbour lists for each phase. The profiler shows that this approach leads to a reduction in both memory transactions and arithmetic operations giving significant runtime gains. The four different algorithms are compared to the efficiency of the optimised single-phase GPU code, DualSPHysics, for 2-D and 3-D simulations which indicate that the multi-phase functionality has a significant computational overhead. A comparison with an optimised CPU code shows a speed up of an order of magnitude over an OpenMP simulation with 8 threads and two orders of magnitude over a single thread simulation. A demonstration of the multi-phase SPH GPU code is provided by a 3-D dam break case impacting an obstacle. This shows better agreement with experimental results than an equivalent single-phase code. The multi-phase GPU code enables a convergence study to be undertaken on a single GPU with a large number of particles that otherwise would have required large high performance computing resources.

  5. Phase Error Modeling and Its Impact on Precise Orbit Determination of GRACE Satellites

    Directory of Open Access Journals (Sweden)

    Jia Tu

    2012-01-01

    Full Text Available Limiting factors for the precise orbit determination (POD of low-earth orbit (LEO satellite using dual-frequency GPS are nowadays mainly encountered with the in-flight phase error modeling. The phase error is modeled as a systematic and a random component each depending on the direction of GPS signal reception. The systematic part and standard deviation of random part in phase error model are, respectively, estimated by bin-wise mean and standard deviation values of phase postfit residuals computed by orbit determination. By removing the systematic component and adjusting the weight of phase observation data according to standard deviation of random component, the orbit can be further improved by POD approach. The GRACE data of 1–31 January 2006 are processed, and three types of orbit solutions, POD without phase error model correction, POD with mean value correction of phase error model, and POD with phase error model correction, are obtained. The three-dimensional (3D orbit improvements derived from phase error model correction are 0.0153 m for GRACE A and 0.0131 m for GRACE B, and the 3D influences arisen from random part of phase error model are 0.0068 m and 0.0075 m for GRACE A and GRACE B, respectively. Thus the random part of phase error model cannot be neglected for POD. It is also demonstrated by phase postfit residual analysis, orbit comparison with JPL precise science orbit, and orbit validation with KBR data that the results derived from POD with phase error model correction are better than another two types of orbit solutions generated in this paper.

  6. Sterol structure determines the separation of phases and the curvature of the liquid-ordered phase in model membranes.

    Science.gov (United States)

    Bacia, Kirsten; Schwille, Petra; Kurzchalia, Teymuras

    2005-03-01

    The existence of lipid rafts in biological membranes in vivo is still debated. In contrast, the formation of domains in model systems has been well documented. In giant unilamellar vesicles (GUVs) prepared from ternary mixtures of dioleoyl-phosphatidylcholine/sphingomyelin/cholesterol, a clear separation of liquid-disordered and sphingomyelin-enriched, liquid-ordered phases could be observed. This phase separation can lead to the fission of the liquid-ordered phase from the vesicle. Here we show that in cholesterol-containing GUVs, the phase separation can involve dynamic redistribution of lipids from one phase into another as a result of a cross-linking perturbation. We found that the molecular structure of a sterol used for the preparation of GUVs determines (i) its ability to induce phase separation and (ii) the curvature (positive or negative) of the formed liquid-ordered phase. As a consequence, the latter can pinch off to the outside or inside of the vesicle. Remarkably, some mixtures of sterols induce liquid-ordered domains exhibiting both positive and negative curvature, which can lead to a new type of budding behavior in GUVs. Our findings could have implications for the role of sterols in various cell-biological processes such as budding of secretory vesicles, endocytosis, or formation of multivesicular bodies.

  7. Maximum likelihood estimation of the parameters of nonminimum phase and noncausal ARMA models

    DEFF Research Database (Denmark)

    Rasmussen, Klaus Bolding

    1994-01-01

    The well-known prediction-error-based maximum likelihood (PEML) method can only handle minimum phase ARMA models. This paper presents a new method known as the back-filtering-based maximum likelihood (BFML) method, which can handle nonminimum phase and noncausal ARMA models. The BFML method is id...... is identical to the PEML method in the case of a minimum phase ARMA model, and it turns out that the BFML method incorporates a noncausal ARMA filter with poles outside the unit circle for estimation of the parameters of a causal, nonminimum phase ARMA model...

  8. MODELLING OF SINGLE PHASE UPFC WITHOUT DC CAPACITOR

    Directory of Open Access Journals (Sweden)

    Dr. Arvind Kumar Singh,

    2011-05-01

    Full Text Available The main focus of this paper is Flexible AC Transmission System (FACTS device known as the Unified Power Flow Controller (UPFC. We know that Unified Power Flow Controller (UPFC has uniquecapability to control simultaneously real and reactive power flows on a transmission line as well as to regulate voltage at the bus where it is connected, this class of Flexible AC Transmission System (FACTS device creates a tremendous quality impact on power system stability. These features become even more significant knowingthat the UPFC can allow loading of the transmission lines close to their thermal limits, forcing the power to flow through the desired paths. This will give the power system operators much needed flexibility in order to satisfy the demands that the deregulated power system will impose. The most cost-effective way to estimate the effect the Unified Power Flow Controller (UPFC has on a specific power system operation is to simulate that system together with the UPFC by using one of the existing simulations packages. Specifically, the objective of this paper is to develop a single phase Unified Power Flow Controller (UPFC model that can be incorporated into existing MATLAB. As it is known that UPFC has two parts one is in shunt and other is in series with the transmission line, but in conventional UPFC these two parts are connected and designed to install in one corner of power grid. An attempt, in this paper had made to separate or extend the series part and shunt part of UnifiedPower Flow Controller (UPFC. This gives the possibility to installed series and shunt part of UPFC at different required locations. Finally the responses of two modified DC link UPFC is compared.

  9. Model for resistance evolution in shape memory alloys including R-phase

    Science.gov (United States)

    Brammajyosula, Ravindra; Buravalla, Vidyashankar; Khandelwal, Ashish

    2011-03-01

    The electrical resistance behavior of a shape memory alloy (SMA) wire can be used for sensing the state of an SMA device. Hence, this study investigates the resistance evolution in SMAs. A lumped parameter model with cosine kinetics to capture the resistance variation during the phase transformation is developed. Several SMA materials show the presence of trigonal or rhombohedral (R) phase as an intermediate phase, apart from the commonly recognized austenite and martensite phases. Most of the SMA models ignore the R-phase effect in their prediction of thermomechanical response. This may be acceptable since the changes in thermomechanical response associated with the R-phase are relatively less. However, the resistivity related effects are pronounced in the presence of the R-phase and its appearance introduces non-monotonicity in the resistivity evolution. This leads to additional complexities in the use of resistance signal for sensing and control. Hence, a lumped model is developed here for resistance evolution including the R-phase effects. A phase-diagram-based model is proposed for predicting electro-thermomechanical response. Both steady state hysteretic response and transient response are modeled. The model predictions are compared with the available test data. Numerical studies have shown that the model is able to capture all the essential features of the resistance evolution in SMAs in the presence of the R-phase.

  10. Preliminary Two-Phase Terry Turbine Nozzle Models for RCIC Off-Design Operation Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Haihua [Idaho National Lab. (INL), Idaho Falls, ID (United States); O' Brien, James [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-06-12

    This report presents the effort to extend the single-phase analytical Terry turbine model to cover two-phase off-design conditions. The work includes: (1) adding well-established two-phase choking models – the Isentropic Homogenous Equilibrium Model (IHEM) and Moody’s model, and (2) theoretical development and implementation of a two-phase nozzle expansion model. The two choking models provide bounding cases for the two-phase choking mass flow rate. The new two-phase Terry turbine model uses the choking models to calculate the mass flow rate, the critical pressure at the nozzle throat, and steam quality. In the divergent stage, we only consider the vapor phase with a similar model for the single-phase case by assuming that the liquid phase would slip along the wall with a much slower speed and will not contribute the impulse on the rotor. We also modify the stagnation conditions according to two-phase choking conditions at the throat and the cross-section areas for steam flow at the nozzle throat and at the nozzle exit. The new two-phase Terry turbine model was benchmarked with the same steam nozzle test as for the single-phase model. Better agreement with the experimental data is observed than from the single-phase model. We also repeated the Terry turbine nozzle benchmark work against the Sandia CFD simulation results with the two-phase model for the pure steam inlet nozzle case. The RCIC start-up tests were simulated and compared with the single-phase model. Similar results are obtained. Finally, we designed a new RCIC system test case to simulate the self-regulated Terry turbine behavior observed in Fukushima accidents. In this test, a period inlet condition for the steam quality varying from 1 to 0 is applied. For the high quality inlet period, the RCIC system behaves just like the normal operation condition with a high pump injection flow rate and a nominal steam release rate through the turbine, with the net addition of water to the primary system; for

  11. Dark energy and dust matter phases from an exact f(R)-cosmology model

    Energy Technology Data Exchange (ETDEWEB)

    Capozziello, S. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' and INFN Sezioze di Napoli, Complesso Universitario di Monte S. Angelo, Ed. N, Via Cinthia, I-80126 Napoli (Italy)], E-mail: capozziello@na.infn.it; Martin-Moruno, P. [Colina de los Chopos, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Rubano, C. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' and INFN Sezioze di Napoli, Complesso Universitario di Monte S. Angelo, Ed. N, Via Cinthia, I-80126 Napoli (Italy)

    2008-06-12

    We show that dust matter-dark energy combined phases can be achieved by the exact solution derived from a power law f(R) cosmological model. This example answers the query by which a dust-dominated decelerated phase, before dark-energy accelerated phase, is needed in order to form large scale structures.

  12. The Collins Model and the Eutectic-Type and the Peritectic-Type Phase Diagrams

    Institute of Scientific and Technical Information of China (English)

    XIE Chuan-Mei; CHEN Li-Rong

    2003-01-01

    From the Gibbs free energy and the equations of two-phase equilibrium curves of the two-dimensionalbinary system which has the Lennard-Jones potential, using the Collins model, the eutectic-type phase diagram and theperitectic-type phase diagram of the binary system are obtained, whose results are quite similar to the behavior of thethree-dimensional (3D) substances.

  13. Numerical modeling of two-phase high speed jet with non-equilibrium solid phase crystallization

    Science.gov (United States)

    Molchanov, A. M.; Yanyshev, D. S.; Bykov, L. V.

    2016-11-01

    The main purpose of the paper is to demonstrate that the Euler approach is fully applicable to the multiphase flows with discrete phase undergoing phase transitions. It is carried out using the example of a jet flow with aluminium oxide particles non-equilibrium crystallization. The jet is strongly underexpanded. The non-equilibrium molecular effects are being taken into account. The obtained results of the simulations are in good agreement with the works of the other authors. The developed Euler approach proved itself to be the most robust in flows with complex flow geometry.

  14. [Modeling and simulation of responses from ultrasonic linear phased array].

    Science.gov (United States)

    He, Wenjing; Zhu, Yuanzhong; Wang, Yufeng; He, Lingli; Lai, Siyu

    2012-10-01

    Phased array transducers are very attractive because the beam generated by the arrays can be electronically focused and steered. The present work characterizes far-field 2D properties of phased array system by functions that are deduced from rectangle source, rectangle line array and phased array based on point source. Results are presented for the distribution of ultrasound intensity on plane xoz and on x-axis by simulation using numerical calculation. It is shown that the shape of response of rectangle line array is modulated by the single array element. It is also demonstrated that the delay time of phased array is the key to steer the beam, sacrificing the value of main lobe and increasing the number of side lobes.

  15. TWO PHASE FLOW SPLIT MODEL FOR PARALLEL CHANNELS

    African Journals Online (AJOL)

    Ifeanyichukwu Onwuka

    The equations are solved using the Broyden'smethod ... channel system subjected to a two-phase flow transient, and the results have been very .... system pressure, the heat addition rates inside ... three dimensional flows in the LP.

  16. Phase structure of the $O(2)$ ghost model with higher-order gradient term

    CERN Document Server

    Péli, Z; Sailer, K

    2016-01-01

    The phase structure and the infrared behaviour of the Euclidean 3-dimensional $O(2)$ symmetric ghost scalar field model with higher-order derivative term has been investigated in Wegner and Houghton's renormalization group framework. The symmetric phase in which no ghost condensation occurs and the phase with restored symmetry but with a transient presence of a ghost condensate have been identified. Finiteness of the correlation length at the phase boundary hints to a phase transition of first order. The results are compared with those for the ordinary $O(2)$ symmetric scalar field model.

  17. Phase diagram and criticality of the two-dimensional prisoner's dilemma model

    Science.gov (United States)

    Santos, M.; Ferreira, A. L.; Figueiredo, W.

    2017-07-01

    The stationary states of the prisoner's dilemma model are studied on a square lattice taking into account the role of a noise parameter in the decision-making process. Only first neighboring players—defectors and cooperators—are considered in each step of the game. Through Monte Carlo simulations we determined the phase diagrams of the model in the plane noise versus the temptation to defect for a large range of values of the noise parameter. We observed three phases: cooperators and defectors absorbing phases, and a coexistence phase between them. The phase transitions as well as the critical exponents associated with them were determined using both static and dynamical scaling laws.

  18. Phase Field Modeling of Twinning in Indentation of Transparent Crystals

    Science.gov (United States)

    2011-09-01

    twin boundaries . Equilibrium configurations of deformed and twinned crystals are attained via direct energy minimization. The theory is framed in the...phases: (i) the original crystal (the parent) and (ii) the twin. Interfaces between phases are twin boundaries . Order parameter η generally exhibits the...following values: η(X, •) = 0∀X ∈ parent, = 1∀X ∈ twin, ∈ (0, 1)∀X ∈ twin boundaries . (1) In linear elasticity, kinematic field variables are

  19. Exact ground-state phase diagrams for the spin-3/2 Blume Emery Griffiths model

    Science.gov (United States)

    Canko, Osman; Deviren, Bayram; Keskin, Mustafa

    2008-05-01

    We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and Jnon-uniform phases. We have also constructed the exact ground-state phase diagrams of the model on the triangular lattice and found 20 and 59 fundamental phase diagrams for J>0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found.

  20. Thermal behavior for a nanoscale two ferromagnetic phase system based on random anisotropy model

    Energy Technology Data Exchange (ETDEWEB)

    Muraca, D., E-mail: diego.muraca@gmail.co [INTECIN - Instituto de Tecnologia y Ciencias de la Ingenieria ' Hilario Fernandez Long' (UBA-CONICET), Facultad de Ingenieria, Paseo Colon 850, (1063), Buenos Aires (Argentina); Sanchez, F.H. [Departamento de Fisica-Instituto de Fisica de La Plata, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C. C. 69, (1900), La Plata (Argentina); Pampillo, L.G.; Saccone, F.D. [INTECIN - Instituto de Tecnologia y Ciencias de la Ingenieria ' Hilario Fernandez Long' (UBA-CONICET), Facultad de Ingenieria, Paseo Colon 850, (1063), Buenos Aires (Argentina)

    2010-03-15

    Advances in theory that explain the magnetic behavior as function of temperature for two phase nanocrystalline soft magnetic materials are presented. The theory developed is based on the well known random anisotropy model, which includes the crystalline exchange stiffness and anisotropy energies in both amorphous and crystalline phases. The phenomenological behavior of the coercivity was obtained in the temperature range between the amorphous phase Curie temperature and the crystalline phase one.

  1. A two-phase model for chronic disease processes under intermittent inspection.

    Science.gov (United States)

    Wu, Ying; Cook, Richard J

    2017-06-15

    A model is developed for chronic diseases with an indolent phase that is followed by a phase with more active disease resulting in progression and damage. The time scales for the intensity functions for the active phase are more naturally based on the time since the start of the active phase, corresponding to a semi-Markov formulation. This two-phase model enables one to fit a separate regression model for the duration of the indolent phase and intensity-based models for the more active second phase. In cohort studies for which the disease status is only known at a series of clinical assessment times, transition times are interval-censored, which means the time origin for phase II is interval-censored. Weakly parametric models with piecewise constant baseline hazard and rate functions are specified, and an expectation-maximization algorithm is described for model fitting. Simulation studies examining the performance of the proposed model show good performance under maximum likelihood and two-stage estimation. An application to data from the motivating study of disease progression in psoriatic arthritis illustrates the procedure and identifies new human leukocyte antigens associated with the duration of the indolent phase. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  2. Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects

    Science.gov (United States)

    Gotfryd, Dorota; Rusnačko, Juraj; Wohlfeld, Krzysztof; Jackeli, George; Chaloupka, Jiří; Oleś, Andrzej M.

    2017-01-01

    We explore the phase diagram of the Kitaev-Heisenberg model with nearest neighbor interactions on the honeycomb lattice using the exact diagonalization of finite systems combined with the cluster mean field approximation, and supplemented by the insights from analytic approaches: the linear spin-wave and second-order perturbation theories. This study confirms that by varying the balance between the Heisenberg and Kitaev term, frustrated exchange interactions stabilize in this model either one of four phases with magnetic long range order: Néel phase, ferromagnetic phase, and two other phases with coexisting antiferromagnetic and ferromagnetic bonds, zigzag and stripy phase, or one of two distinct spin-liquid phases. Out of these latter disordered phases, the one with ferromagnetic Kitaev interactions has a substantially broader range of stability as the neighboring competing ordered phases, ferromagnetic and stripy, have very weak quantum fluctuations. Focusing on the quantum spin-liquid phases, we study spatial spin correlations and dynamic spin structure factor of the model by the exact diagonalization technique, and discuss the evolution of gapped low-energy spin response across the quantum phase transitions between the disordered spin liquid and phases with long range magnetic order.

  3. Research Note: Full-waveform inversion of the unwrapped phase of a model

    KAUST Repository

    Alkhalifah, Tariq Ali

    2013-12-06

    Reflections in seismic data induce serious non-linearity in the objective function of full- waveform inversion. Thus, without a good initial velocity model that can produce reflections within a half cycle of the frequency used in the inversion, convergence to a solution becomes difficult. As a result, we tend to invert for refracted events and damp reflections in data. Reflection induced non-linearity stems from cycle skipping between the imprint of the true model in observed data and the predicted model in synthesized data. Inverting for the phase of the model allows us to address this problem by avoiding the source of non-linearity, the phase wrapping phenomena. Most of the information related to the location (or depths) of interfaces is embedded in the phase component of a model, mainly influenced by the background model, while the velocity-contrast information (responsible for the reflection energy) is mainly embedded in the amplitude component. In combination with unwrapping the phase of data, which mitigates the non-linearity introduced by the source function, I develop a framework to invert for the unwrapped phase of a model, represented by the instantaneous depth, using the unwrapped phase of the data. The resulting gradient function provides a mechanism to non-linearly update the velocity model by applying mainly phase shifts to the model. In using the instantaneous depth as a model parameter, we keep track of the model properties unfazed by the wrapping phenomena. © 2013 European Association of Geoscientists & Engineers.

  4. Modeling of gamma/gamma-prime phase equilibrium in the nickel-aluminum system

    Science.gov (United States)

    Sanchez, J. M.; Barefoot, J. R.; Jarrett, R. N.; Tien, J. K.

    1984-01-01

    A theoretical model is proposed for the determination of phase equilibrium in alloys, taking into consideration dissimilar lattice parameters. Volume-dependent pair interactions are introduced by means of phenomenological Lennard-Jones potentials and the configurational entropy of the system is treated in the tetrahedron approximation of the cluster variation method. The model is applied to the superalloy-relevant, nickel-rich, gamma/gamma-prime phase region of the Ni-Al phase diagram. The model predicts reasonable values for the lattice parameters and the enthalpy of formation as a function of composition, and the calculated phase diagram closely approximates the experimental diagram.

  5. Application of New Electrolyte Model to Phase Transfer Catalyst (PTC) Systems

    DEFF Research Database (Denmark)

    2015-01-01

    Abstract Phase transfer catalyst (PTC) is used to transfer the desirable active form of an anion from the aqueous phase to organic phase where the reaction occurs. One of major challenges for process design of the PTC system is to establish a reliable thermodynamic model capable of describing phase...... in PTC systems, thereby, extending the application range of the PTC-system model. The solubility of PTC in organic solvents, which is a key factor for strategy of PTC and solvent selection, has been calculated using the e-NRTL-SAC model....

  6. Gas-liquid phase transition in modified pseudopotential and “shelf Coulomb” ultracold plasma models

    Science.gov (United States)

    Butlitsky, M. A.; Zelener, B. B.; Zelener, B. V.

    2016-11-01

    Phase diagrams for the “shelf Coulomb” and the modified pseudopotential plasma models developed in our previous works are compared. Qualitative agreement is observed between gas-liquid phase transition region of “shelf Coulomb” model and liquid-gas structure region of modified pseudopotential one. The possibility of experimental finding of the phase transition in nonequilibrium ultracold Rydberg plasma is considered. Parameters (density, temperature, levels of Rydberg atoms) for such a transition are estimated. Conclusion is made that “shelf Coulomb” model phase transition is practically impossible to observe in equilibrium strongly coupled plasmas due to high neutral atoms density at low temperatures: T crit ≈ 0.076.

  7. Generalized Ginzburg–Landau approach to inhomogeneous phases in nonlocal chiral quark models

    Energy Technology Data Exchange (ETDEWEB)

    Carlomagno, J.P. [IFLP, CONICET – Dpto. de Física, FCE, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata (Argentina); CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Gómez Dumm, D., E-mail: dumm@fisica.unlp.edu.ar [IFLP, CONICET – Dpto. de Física, FCE, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata (Argentina); CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Scoccola, N.N. [CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Physics Department, Comisión Nacional de Energía Atómica, Av. Libertador 8250, 1429 Buenos Aires (Argentina); Universidad Favaloro, Solís 453, 1078 Buenos Aires (Argentina)

    2015-05-18

    We analyze the presence of inhomogeneous phases in the QCD phase diagram within the framework of nonlocal chiral quark models. We concentrate in particular in the positions of the tricritical (TCP) and Lifshitz (LP) points, which are studied in a general context using a generalized Ginzburg–Landau approach. We find that for all the phenomenologically acceptable model parametrizations considered the TCP is located at a higher temperature and a lower chemical potential in comparison with the LP. Consequently, these models seem to favor a scenario in which the onset of the first order transition between homogeneous phases is not covered by an inhomogeneous, energetically favored phase.

  8. Towards a phase field model of the microstructural evolution of duplex steel with experimental verification

    DEFF Research Database (Denmark)

    Poulsen, Stefan Othmar; Voorhees, P.W.; Lauridsen, Erik Mejdal

    2012-01-01

    A phase field model to study the microstructural evolution of a polycrystalline dual-phase material with conserved phase fraction has been implemented, and 2D simulations have been performed. For 2D simulations, the model predicts the cubic growth well-known for diffusion-controlled systems. Some...... interphase boundaries are found to show a persistent non-constant curvature, which seems to be a feature of multi-phase materials. Finally, it is briefly outlined how this model is to be applied to investigate microstructural evolution in duplex steel. © (2012) Trans Tech Publications, Switzerland....

  9. Phase transitions and topology in 2+k XY mean-field models.

    Science.gov (United States)

    Angelani, L; Ruocco, G

    2007-11-01

    The thermodynamics and topology of mean-field models with 2+k body interaction terms (generalizing XY model) are derived. Focusing on two particular cases (2+4 and 2+6 body interaction terms), a comparison between thermodynamic (phase transition energy, thermodynamically forbidden energy regions) and topological (singularity and curvature of saddle entropy) properties is performed. We find that (i) a topological change is present at the phase transition energy; however, (ii) only one topological change occurs, also for those models exhibiting two phase transitions; (iii) the order of a phase transition is not completely signaled by the curvature of topological quantities.

  10. The Pliocene Model Intercomparison Project (PlioMIP) Phase 2: Scientific objectives and experimental design

    Science.gov (United States)

    Haywood, Alan M.; Dowsett, Harry J.; Dolan, Aisling M.; Rowley, David; Abe-Ouchi, Ayako; Otto-Bliesner, Bette; Chandler, Mark A.; Hunter, Stephen J.; Lunt, Daniel J.; Pound, Matthew; Salzmann, Ulrich

    2016-01-01

    The Pliocene Model Intercomparison Project (PlioMIP) is a co-ordinated international climate modelling initiative to study and understand climate and environments of the Late Pliocene, as well as their potential relevance in the context of future climate change. PlioMIP examines the consistency of model predictions in simulating Pliocene climate and their ability to reproduce climate signals preserved by geological climate archives. Here we provide a description of the aim and objectives of the next phase of the model intercomparison project (PlioMIP Phase 2), and we present the experimental design and boundary conditions that will be utilized for climate model experiments in Phase 2. 

  11. Deconfinement Phase Transition with External Magnetic Field in the Friedberg—Lee Model

    Science.gov (United States)

    Mao, Shi-Jun

    2016-11-01

    The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. In the frame of functional renormalization group, we extend the often used potential expansion method for continuous phase transitions to the first-order phase transition in the model. By solving the flow equations we find that, the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement in hot and dense medium.

  12. Liquid-Gas Phase Transition for Asymmetric Nuclear Matter in the Zimanyi-Moszkowski Model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xu-Ming; QIAN Wei-Liang; SU Ru-Keng

    2004-01-01

    By using the improved Zimanyi-Moszkowski (ZM) model including the freedom of nucleons, σ mesons, ω mesons and ρ mesons, we investigate the liquid-gas phase transition for asymmetric nuclear matter. It is found that the phase transition for asymmetric nuclear matter in the improved ZM model with the isospin vector ρ meson degree of freedom is well defined. The binodal surface, which is essential in the study of the phase transition process, is addressed.

  13. Deconfinement Phase Transition with External Magnetic Field in Friedberg-Lee Model

    CERN Document Server

    Mao, Shijun

    2015-01-01

    The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. In the frame of functional renormalization group, we extend the often used potential expansion method for continuous phase transitions to the first-order phase transition in the model. By solving the flow equations we find that, the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement in hot and dense medium.

  14. Interface Propagation and Microstructure Evolution in Phase Field Models of Stress-Induced Martensitic Phase Transformations

    Science.gov (United States)

    2010-01-01

    between phase transformation and thermoelasticity equations has important computational con- sequences: finite element thermoelasticity codes can be...combination of four herring bone types of micro- structure is developed (Fig. 10). At some stage, the equivalence of both variants is violated-units...preceding analysis . At these high driving forces the interface motion is governed by the phonon (and at lower temperatures, by the electron) drag

  15. Induction generator model in phase coordinates for fault ride-through capability studies of wind turbines

    DEFF Research Database (Denmark)

    Ruano, Luis Alberto Fajardo; Iov, Florin; Medina Reos, J. Aurelio

    2007-01-01

    A phase coordinates induction generator model with time varying electrical parameters as influenced by magnetic saturation and rotor deep bar effects, is presented in this paper. The model exhibits a per-phase formulation, uses standard data sheet for characterization of the electrical parameters...

  16. Aerothermal modeling program, Phase 2, Element C: Fuel injector-air swirl characterization

    Science.gov (United States)

    Mostafa, A. A.; Mongia, H. C.; Mcdonnel, V. G.; Samuelsen, G. S.

    1987-01-01

    The main objectives of the NASA sponsored Aerothermal Modeling Program, Phase 2, Element C, are to collect benchmark quality data to quantify the fuel spray interaction with the turbulent swirling flows and to validate current and advanced two phase flow models. The technical tasks involved in this effort are discussed.

  17. PRELIMINARY PROGRESS IN THE DEVELOPMENT OF DUCTILE-PHASE TOUGHENED TUNGSTEN FOR PLASMA-FACING MATERIALS: DUAL-PHASE FINITE ELEMENT DAMAGE MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.

    2016-09-30

    The objective of this study is to develop a finite element continuum damage model suitable for modeling deformation, cracking, and crack bridging for W-Cu, W-Ni-Fe, and other ductile phase toughened W-composites, or more generally, any multi-phase composite structure where two or more phases undergo cooperative deformation in a composite system.

  18. Computation of reduced energy input current stimuli for neuron phase models.

    Science.gov (United States)

    Anyalebechi, Jason; Koelling, Melinda E; Miller, Damon A

    2014-01-01

    A regularly spiking neuron can be studied using a phase model. The effect of an input stimulus current on the phase time derivative is captured by a phase response curve. This paper adapts a technique that was previously applied to conductance-based models to discover optimal input stimulus currents for phase models. First, the neuron phase response θ(t) due to an input stimulus current i(t) is computed using a phase model. The resulting θ(t) is taken to be a reference phase r(t). Second, an optimal input stimulus current i(*)(t) is computed to minimize a weighted sum of the square-integral `energy' of i(*)(t) and the tracking error between the reference phase r(t) and the phase response due to i(*)(t). The balance between the conflicting requirements of energy and tracking error minimization is controlled by a single parameter. The generated optimal current i(*)t) is then compared to the input current i(t) which was used to generate the reference phase r(t). This technique was applied to two neuron phase models; in each case, the current i(*)(t) generates a phase response similar to the reference phase r(t), and the optimal current i(*)(t) has a lower `energy' than the square-integral of i(t). For constant i(t), the optimal current i(*)(t) need not be constant in time. In fact, i(*)(t) is large (possibly even larger than i(t)) for regions where the phase response curve indicates a stronger sensitivity to the input stimulus current, and smaller in regions of reduced sensitivity.

  19. Phase field model for the study of boiling; Modele de champ de phase pour l'etude de l'ebullition

    Energy Technology Data Exchange (ETDEWEB)

    Ruyer, P

    2006-07-15

    This study concerns both the modeling and the numerical simulation of boiling flows. First we propose a review concerning nucleate boiling at high wall heat flux and focus more particularly on the current understanding of the boiling crisis. From this analysis we deduce a motivation for the numerical simulation of bubble growth dynamics. The main and remaining part of this study is then devoted to the development and analyze of a phase field model for the liquid-vapor flows with phase change. We propose a thermodynamic quasi-compressible formulation whose properties match the one required for the numerical study envisaged. The system of governing equations is a thermodynamically consistent regularization of the sharp interface model, that is the advantage of the di use interface models. We show that the thickness of the interface transition layer can be defined independently from the thermodynamic description of the bulk phases, a property that is numerically attractive. We derive the kinetic relation that allows to analyze the consequences of the phase field formulation on the model of the dissipative mechanisms. Finally we study the numerical resolution of the model with the help of simulations of phase transition in simple configurations as well as of isothermal bubble dynamics. (author)

  20. Basic simulation models of phase tracking devices using Matlab

    CERN Document Server

    Tranter, William

    2010-01-01

    The Phase-Locked Loop (PLL), and many of the devices used for frequency and phase tracking, carrier and symbol synchronization, demodulation, and frequency synthesis, are fundamental building blocks in today's complex communications systems. It is therefore essential for both students and practicing communications engineers interested in the design and implementation of modern communication systems to understand and have insight into the behavior of these important and ubiquitous devices. Since the PLL behaves as a nonlinear device (at least during acquisition), computer simulation can be used

  1. Vienna Soil-Organic-Matter Modeler--Generating condensed-phase models of humic substances.

    Science.gov (United States)

    Sündermann, Axel; Solc, Roland; Tunega, Daniel; Haberhauer, Georg; Gerzabek, Martin H; Oostenbrink, Chris

    2015-11-01

    Humic substances are ubiquitous in the environment and have manifold functions. While their composition is well known, information on the chemical structure and three-dimensional conformation is scarce. Here we describe the Vienna Soil-Organic-Matter Modeler, which is an online tool to generate condensed phase computer models of humic substances (http://somm.boku.ac.at). Many different models can be created that reflect the diversity in composition and conformations of the constituting molecules. To exemplify the modeler, 18 different models are generated based on two experimentally determined compositions, to explicitly study the effect of varying e.g. the amount of water molecules in the models or the pH. Molecular dynamics simulations were performed on the models, which were subsequently analyzed in terms of structure, interactions and dynamics, linking macroscopic observables to the microscopic composition of the systems. We are convinced that this new tool opens the way for a wide range of in silico studies on soil organic matter.

  2. Discontinuous phase transition in a multi-state majority-vote model

    CERN Document Server

    Li, Guofeng; Huang, Feng; Shen, Chuansheng

    2016-01-01

    In this paper, we generalize the original majority-vote (MV) model with noise from two states to arbitrary $q$ states, where $q$ is an integer no less than two. The main emphasis is paid to the comparison on the nature of phase transitions between the two-state MV (MV2) model and the three-state MV (MV3) model. By extensive Monte Carlo simulation and mean-field analysis, we find that the MV3 model undergoes a discontinuous order-disorder phase transition, in contrast to a continuous phase transition in the MV2 model. A central feature of such a discontinuous transition is a strong hysteresis behavior as noise intensity goes forward and backward. Within the hysteresis region, the disordered phase and ordered phase are coexisting.

  3. Microemulsion phases in one and two dimensional magnetic models with long-range interactions

    Science.gov (United States)

    Nielsen, Erik; Bhatt, R. N.; Huse, David

    2007-03-01

    Spivak and Kivelson have proposed that the first order phase transition between the Wigner crystal and Fermi liquid phases of the interacting electron gas in two dimensions is pre-empted by a series of microemulsion phases characterized by phase separation on the mesoscopic scale, which may be responsible for the anomalous conductivity. We have studied analogous classical magnetic models in one and two dimensions. In particular, we present an exact analytical solution of a one dimensional classical ferromagnetic Ising spin chain frustrated by a long range antiferromagnetic interaction, which clearly exhibits such phase separation in which the mesoscale varies continuously with applied magnetic field. We describe these phases in the 1D model and consider extensions to stripe and bubble phases in two dimensions. B. Spivak and S. A.Kivelson, Physical Review B, 70 155114 (2004) K. Ng and D. Vanderbilt, Physical Review B, 52 2177 (1995)

  4. Spiral magnetic phases on the Kondo Lattice Model: A Hartree-Fock approach

    Science.gov (United States)

    Costa, N. C.; Lima, J. P.; dos Santos, Raimundo R.

    2017-02-01

    We study the Kondo Lattice Model (KLM) on a square lattice through a Hartree-Fock approximation in which the local spins are treated semi-classically, in the sense that their average values are modulated by a magnetic wavevector Q while they couple with the conduction electrons through fermion operators. In this way, we obtain a ground state phase diagram in which spiral magnetic phases (in which the wavevector depends on the coupling constants and on the density) interpolate between the low-density ferromagnetic phase and the antiferromagnetic phase at half filling; within small regions of the phase diagram commensurate magnetic phases can coexist with Kondo screening. We have also obtained 'Doniach-like' diagrams, showing the effect of temperature on the ground state phases, and established that for some ranges of the model parameters (the exchange coupling and conduction electron density) the magnetic wavevector changes with temperature, either continuously or abruptly (e.g., from spiral to ferromagnetic).

  5. A Four-Phase Multidisciplinary Faculty Development Model in Aging.

    Science.gov (United States)

    Batsche, Catherine N.; Monoson, Patricia

    1993-01-01

    A faculty development program combining social services, human performance, psychology, nutrition, audiology, and nursing had four phases: study of gerontology theories, practical experience, course development, and test of curriculum materials. Ten faculty developed 50 instructional units; 300 undergraduate students demonstrated significant gains…

  6. Modelling and simulation of multi-phase effects on X-ray elasticity constants

    Energy Technology Data Exchange (ETDEWEB)

    Freour, S.; Gloaguen, D.; Guillen, R. [Laboratoire d' Applications des Materiaux a la Mecanique (L.A.M.M.), L.A.M.M.-C.R.T.T., Boulevard de L' Universite, BP 406, 44602 Saint Nazaire Cedex (France); Francois, M. [Laboratoire des Systemes Mecaniques et d' Ingenierie Simultanee (L.A.S.M.I.S.), Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes (France)

    2003-10-01

    This paper deals with the calculation of X-ray Elasticity Constants (XEC) of phases embedded in multi-phase polycrystals. A three scales (macroscopic, pseudo-macroscopic, mesoscopic) model based on the classical self-consistent formalism is developed in order to analyse multi-phase effects on XEC values. Simulations are performed for cubic or hexagonal crystallographic structure phases embedded in several two-phases materials. In fact, it is demonstrated that XEC vary with the macroscopic stiffness of the whole polycrystal. In consequence, the constants of one particular phase depend on the elastic behaviour and the volume fraction of all the phases constituting the material. Now, XEC play a leading role in pseudo-macroscopic stresses determination by X-Ray Diffraction (XRD) methods. In this work, a quantitative analysis of the multi-phase effects on stresses determination by XRD methods was performed. Numerical results will be compared and discussed. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  7. Peculiar Quantum Phase Transitions and Hidden Supersymmetry in a Lipkin-Meshkov-Glick Model

    Institute of Scientific and Technical Information of China (English)

    CHEN Gang; LIANG Jiu-Qing

    2009-01-01

    In this paper we theoretically report an unconventional quantum phase transition of a simple Lipkin-Meshkov-Glick model: an interacting collective spin system without external magnetic field. It is shown that this model with integer-spin can exhibit a first-order quantum phase transition between different disordered phases, and more intriguingly, possesses a hidden supersymmetry at the critical point. However, for half-integer spin we predict another first-order quantum phase transition between two different long-range-ordered phases with a vanishing energy gap, which is induced by the destructive topological quantum interference between the intanton and anti-instanton tunneling paths and accompanies spontaneously breaking of supersymmetry at the same critical point. We also show that, when the total spin-value varies from half-integer to integer this model can exhibit an abrupt variation of Berry phase from π to zero.

  8. Predictive Modelling of Phase-Transfer Catalyst Systems for Improved and Innovative Design

    DEFF Research Database (Denmark)

    Anantpinijwatna, Amata; Hyung Kim, Sun; Sales-Cruz, Mauricio

    2016-01-01

    increasing attention as a novel organic synthesis option due to its flexible and easier operation, higher production yield, and ability to eliminate expensive solvents, although, not eliminating the use of solvents. New mathematical models of the PTC system, which includes physical and chemical equilibrium......Phase-transfer catalyst (PTC) systems contain two immiscible liquid phases with a heterogeneous PTC transferring active ion from one phase to the other for converting the reactant to the desired product, and in the process generating the inactive ion. This type of reacting systems is receiving......, reaction mechanism and unit operation has been developed. In the developed model, the PTC system is divided into four sub-systems of aqueous-organic solvent partition, inorganic salt in aqueous phase, PTC in aqueous phase, and PTC in aqueous phase. Each subsystem requires an appropriate thermodynamic model...

  9. Comparing predictive validity of four ballistic swing phase models of human walking.

    Science.gov (United States)

    Selles, R W; Bussmann, J B; Wagenaar, R C; Stam, H J

    2001-09-01

    It is unclear to what extent ballistic walking models can be used to qualitatively predict the swing phase at comfortable walking speed. Different study findings regarding the accuracy of the predictions of the swing phase kinematics may have been caused by differences in (1) kinematic input, (2) model characteristics (e.g. the number of segments), and (3) evaluation criteria. In the present study, the predictive validity of four ballistic swing phase models was evaluated and compared, that is, (1) the ballistic walking model as originally introduced by Mochon and McMahon, (2) an extended version of this model in which heel-off of the stance leg is added, (3) a double pendulum model, consisting of a two-segment swing leg with a prescribed hip trajectory, and (4) a shank pendulum model consisting of a shank and rigidly attached foot with a prescribed knee trajectory. The predictive validity was evaluated by comparing the outcome of the model simulations with experimentally derived swing phase kinematics of six healthy subjects. In all models, statistically significant differences were found between model output and experimental data. All models underestimated swing time and step length. In addition, statistically significant differences were found between the output of the different models. The present study shows that although qualitative similarities exist between the ballistic models and normal gait at comfortable walking speed, these models cannot adequately predict swing phase kinematics.

  10. Model-order reduction of nonlinear models of electromagnetic phased-array hyperthermia.

    Science.gov (United States)

    Kowalski, Marc E; Jin, Jian-Ming

    2003-11-01

    A method based on the Karhunen-Loéve (KL) transform is proposed for the reduction of large-scale, nonlinear ordinary differential equations such as those arising from the finite difference modeling of biological heat transfer. The method of snapshots is used to expedite computation of the required quantities in the KL procedure. Guidelines are presented and validated for snapshot selection and resultant basis series truncation, emphasizing the special physical features of the electromagnetic phased-array heat transfer physics. Applications to fast temperature prediction are presented.

  11. Modelling elliptical galaxies phase-space constraints on two-component (gamma1,gamma2) models

    CERN Document Server

    Ciotti, L

    1999-01-01

    In the context of the study of the properties of the mutual mass distribution of the bright and dark matter in elliptical galaxies, present a family of two-component, spherical, self-consistent galaxy models, where one density distribution follows a gamma_1 profile, and the other a gamma_2 profile [(gamma_1,gamma_2) models], with different total masses and ``core'' radii. A variable amount of Osipkov-Merritt (radial) orbital anisotropy is allowed in both components. For these models, I derive analytically the necessary and sufficient conditions that the model parameters must satisfy in order to correspond to a physical system. Moreover, the possibility of adding a black hole at the center of radially anisotropic gamma models is discussed, determining analytically a lower limit of the anisotropy radius as a function of gamma. The analytical phase-space distribution function for (1,0) models is presented, together with the solution of the Jeans equations and the quantities entering the scalar virial theorem. It...

  12. On phase transitions of the Potts model with three competing interactions on Cayley tree

    Directory of Open Access Journals (Sweden)

    S. Temir

    2011-06-01

    Full Text Available In the present paper we study a phase transition problem for the Potts model with three competing interactions, the nearest neighbors, the second neighbors and triples of neighbors and non-zero external field on Cayley tree of order two. We prove that for some parameter values of the model there is phase transition. We reduce the problem of describing by limiting Gibbs measures to the problem of solving a system of nonlinear functional equations. We extend the results obtained by Ganikhodjaev and Rozikov [Math. Phys. Anal. Geom., 2009, vol. 12, No. 2, 141-156] on phase transition for the Ising model to the Potts model setting.

  13. Universal limiting pressure for a three-flavor color superconducting PNJL model phase diagram

    CERN Document Server

    Ayriyan, A; Blaschke, D; Lastowiecki, R

    2016-01-01

    The phase diagram of a three-flavor Polyakov-loop Nambu-Jona-Lasinio model is analyzed for the case of isospin symmetric matter with color superconducting phases. The coexistence of chiral symmetry breaking and two-flavor color superconductivity (2SC phase) and a thermodynamic instability due to the implementation of a color neutrality constraint is observed. It is suggested to use a universal hadronization pressure to estimate the phase border between hadronic and quark-gluon plasma phases. Trajectories of constant entropy per baryon are analyzed for conditions appropriate for heavy-ion collisions in the NICA-FAIR energy range.

  14. Cloud radiative effects and changes simulated by the Coupled Model Intercomparison Project Phase 5 models

    Science.gov (United States)

    Shin, Sun-Hee; Kim, Ok-Yeon; Kim, Dongmin; Lee, Myong-In

    2017-07-01

    Using 32 CMIP5 (Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects (CREs) in the historical run driven by observed external radiative forcing for 1850-2005, and their future changes in the RCP (Representative Concentration Pathway) 4.5 scenario runs for 2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics, four models—ACCESS1.0, ACCESS1.3, HadGEM2-CC, and HadGEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average. All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about -0.99% K-1 and net radiative warming of 0.46 W m-2 K-1, suggesting a role of positive feedback to global warming.

  15. Parameter estimation for LLDPE gas-phase reactor models

    Directory of Open Access Journals (Sweden)

    G. A. Neumann

    2007-06-01

    Full Text Available Product development and advanced control applications require models with good predictive capability. However, in some cases it is not possible to obtain good quality phenomenological models due to the lack of data or the presence of important unmeasured effects. The use of empirical models requires less investment in modeling, but implies the need for larger amounts of experimental data to generate models with good predictive capability. In this work, nonlinear phenomenological and empirical models were compared with respect to their capability to predict the melt index and polymer yield of a low-density polyethylene production process consisting of two fluidized bed reactors connected in series. To adjust the phenomenological model, the optimization algorithms based on the flexible polyhedron method of Nelder and Mead showed the best efficiency. To adjust the empirical model, the PLS model was more appropriate for polymer yield, and the melt index needed more nonlinearity like the QPLS models. In the comparison between these two types of models better results were obtained for the empirical models.

  16. Distinct Topological Crystalline Phases in Models for the Strongly Correlated Topological Insulator SmB_{6}.

    Science.gov (United States)

    Baruselli, Pier Paolo; Vojta, Matthias

    2015-10-09

    SmB_{6} was recently proposed to be both a strong topological insulator and a topological crystalline insulator. For this and related cubic topological Kondo insulators, we prove the existence of four different topological phases, distinguished by the sign of mirror Chern numbers. We characterize these phases in terms of simple observables, and we provide concrete tight-binding models for each phase. Based on theoretical and experimental results for SmB_{6} we conclude that it realizes the phase with C_{k_{z}=0}^{+}=+2, C_{k_{z}=π}^{+}=+1, C_{k_{x}=k_{y}}^{+}=-1, and we propose a corresponding minimal model.

  17. Energy landscape and phase transitions in the self-gravitating ring model.

    Science.gov (United States)

    Nardini, Cesare; Casetti, Lapo

    2009-12-01

    We apply a recently proposed criterion for the existence of phase transitions, which is based on the properties of the saddles of the energy landscape, to a simplified model of a system with gravitational interactions referred to as the self-gravitating ring model. We show analytically that the criterion correctly singles out the phase transition between a homogeneous and a clustered phase and also suggests the presence of another phase transition not previously known. On the basis of the properties of the energy landscape we conjecture on the nature of the latter transition.

  18. Phase Diagram of the Gross-Neveu Model: Exact Results and Condensed Matter Precursors

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2004-01-01

    Recently the revised phase diagram of the (large N) Gross-Neveu model in 1+1 dimensions with discrete chiral symmetry has been determined numerically. It features three phases, a massless and a massive Fermi gas and a kink-antikink crystal. Here we investigate the phase diagram by analytical means, mapping the Dirac-Hartree-Fock equation onto the non-relativistic Schroedinger equation with the (single gap) Lame potential. It is pointed out that mathematically identical phase diagrams appeared in the condensed matter literature some time ago in the context of the Peierls-Froehlich model and ferromagnetic superconductors.

  19. Geometrical Models of the Phase Space Structures Governing Reaction Dynamics

    CERN Document Server

    Waalkens, Holger

    2009-01-01

    Hamiltonian dynamical systems possessing equilibria of ${saddle} \\times {centre} \\times...\\times {centre}$ stability type display \\emph{reaction-type dynamics} for energies close to the energy of such equilibria; entrance and exit from certain regions of the phase space is only possible via narrow \\emph{bottlenecks} created by the influence of the equilibrium points. In this paper we provide a thorough pedagogical description of the phase space structures that are responsible for controlling transport in these problems. Of central importance is the existence of a \\emph{Normally Hyperbolic Invariant Manifold (NHIM)}, whose \\emph{stable and unstable manifolds} have sufficient dimensionality to act as separatrices, partitioning energy surfaces into regions of qualitatively distinct behavior. This NHIM forms the natural (dynamical) equator of a (spherical) \\emph{dividing surface} which locally divides an energy surface into two components (`reactants' and `products'), one on either side of the bottleneck. This di...

  20. Nonequilibrium phase transition in a driven Potts model with friction.

    Science.gov (United States)

    Iglói, Ferenc; Pleimling, Michel; Turban, Loïc

    2011-04-01

    We consider magnetic friction between two systems of q-state Potts spins which are moving along their boundaries with a relative constant velocity ν. Due to the interaction between the surface spins there is a permanent energy flow and the system is in a steady state, which is far from equilibrium. The problem is treated analytically in the limit ν=∞ (in one dimension, as well as in two dimensions for large-q values) and for v and q finite by Monte Carlo simulations in two dimensions. Exotic nonequilibrium phase transitions take place, the properties of which depend on the type of phase transition in equilibrium. When this latter transition is of first order, a sequence of second- and first-order nonequilibrium transitions can be observed when the interaction is varied. ©2011 American Physical Society

  1. Phase Field Modeling of Directional Fracture in Anisotropic Polycrystals

    Science.gov (United States)

    2015-02-01

    the Army position unless so designated by other authorized documents. Citation of manufacturer’s or trade names does not constitute an official...consider preferential fracture on cleavage planes of multiple discrete orientations requires introduction of additional order parameter(s) for...trends for elastically compliant grain boundary phases are in general agreement with experiment [6]. As will be examined in more detail in Section 4.2

  2. Symmetry-enriched string nets: Exactly solvable models for SET phases

    Science.gov (United States)

    Heinrich, Chris; Burnell, Fiona; Fidkowski, Lukasz; Levin, Michael

    2016-12-01

    We construct exactly solvable models for a wide class of symmetry-enriched topological (SET) phases. Our construction applies to two-dimensional (2D) bosonic SET phases with finite unitary on-site symmetry group G and we conjecture that our models realize every phase in this class that can be described by a commuting projector Hamiltonian. Our models are designed so that they have a special property: If we couple them to a dynamical lattice gauge field with gauge group G , the resulting gauge theories are equivalent to string-net models. This property is what allows us to analyze our models in generality. As an example, we present a model for a phase with the same anyon excitations as the toric code and with a Z2 symmetry which exchanges the e and m type anyons. We further illustrate our construction with a number of additional examples.

  3. Improving Mixed-phase Cloud Parameterization in Climate Model with the ACRF Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhien [Univ. of Wyoming, Laramie, WY (United States)

    2016-12-13

    Mixed-phase cloud microphysical and dynamical processes are still poorly understood, and their representation in GCMs is a major source of uncertainties in overall cloud feedback in GCMs. Thus improving mixed-phase cloud parameterizations in climate models is critical to reducing the climate forecast uncertainties. This study aims at providing improved knowledge of mixed-phase cloud properties from the long-term ACRF observations and improving mixed-phase clouds simulations in the NCAR Community Atmosphere Model version 5 (CAM5). The key accomplishments are: 1) An improved retrieval algorithm was developed to provide liquid droplet concentration for drizzling or mixed-phase stratiform clouds. 2) A new ice concentration retrieval algorithm for stratiform mixed-phase clouds was developed. 3) A strong seasonal aerosol impact on ice generation in Arctic mixed-phase clouds was identified, which is mainly attributed to the high dust occurrence during the spring season. 4) A suite of multi-senor algorithms was applied to long-term ARM observations at the Barrow site to provide a complete dataset (LWC and effective radius profile for liquid phase, and IWC, Dge profiles and ice concentration for ice phase) to characterize Arctic stratiform mixed-phase clouds. This multi-year stratiform mixed-phase cloud dataset provides necessary information to study related processes, evaluate model stratiform mixed-phase cloud simulations, and improve model stratiform mixed-phase cloud parameterization. 5). A new in situ data analysis method was developed to quantify liquid mass partition in convective mixed-phase clouds. For the first time, we reliably compared liquid mass partitions in stratiform and convective mixed-phase clouds. Due to the different dynamics in stratiform and convective mixed-phase clouds, the temperature dependencies of liquid mass partitions are significantly different due to much higher ice concentrations in convective mixed phase clouds. 6) Systematic evaluations

  4. Modeling and online recognition of surgical phases using Hidden Markov Models.

    Science.gov (United States)

    Blum, Tobias; Padoy, Nicolas; Feussner, Hubertus; Navab, Nassir

    2008-01-01

    The amount of signals that can be recorded during a surgery, like tracking data or state of instruments, is constantly growing. These signals can be used to better understand surgical workflow and to build surgical assist systems that are aware of the current state of a surgery. This is a crucial issue for designing future systems that provide context-sensitive information and user interfaces. In this paper, Hidden Markov Models (HMM) are used to model a laparoscopic cholecystectomy. Seventeen signals, representing tool usage, from twelve surgeries are used to train the model. The use of a model merging approach is proposed to build the HMM topology and compared to other methods of initializing a HMM. The merging method allows building a model at a very fine level of detail that also reveals the workflow of a surgery in a human-understandable way. Results for detecting the current phase of a surgery and for predicting the remaining time of the procedure are presented.

  5. Fourth order phase-field model for local max-ent approximants applied to crack propagation

    OpenAIRE

    Amiri, Fatemeh; Millán, Daniel; Arroyo Balaguer, Marino; Silani, Mohammad; Rabczuk, Timon

    2016-01-01

    We apply a fourth order phase-field model for fracture based on local maximum entropy (LME) approximants. The higher order continuity of the meshfree LME approximants allows to directly solve the fourth order phase-field equations without splitting the fourth order differential equation into two second order differential equations. We will first show that the crack surface can be captured more accurately in the fourth order model. Furthermore, less nodes are needed for the fourth order model ...

  6. Morphological modelling of three-phase microstructures of anode layers using SEM images.

    Science.gov (United States)

    Abdallah, Bassam; Willot, François; Jeulin, Dominique

    2016-07-01

    A general method is proposed to model 3D microstructures representative of three-phases anode layers used in fuel cells. The models are based on SEM images of cells with varying morphologies. The materials are first characterized using three morphological measurements: (cross-)covariances, granulometry and linear erosion. They are measured on segmented SEM images, for each of the three phases. Second, a generic model for three-phases materials is proposed. The model is based on two independent underlying random sets which are otherwise arbitrary. The validity of this model is verified using the cross-covariance functions of the various phases. In a third step, several types of Boolean random sets and plurigaussian models are considered for the unknown underlying random sets. Overall, good agreement is found between the SEM images and three-phases models based on plurigaussian random sets, for all morphological measurements considered in the present work: covariances, granulometry and linear erosion. The spatial distribution and shapes of the phases produced by the plurigaussian model are visually very close to the real material. Furthermore, the proposed models require no numerical optimization and are straightforward to generate using the covariance functions measured on the SEM images.

  7. Thermodynamic modelling of phase equilibrium for water + poly(Ethylene glycol + salt aqueous two-phase systems

    Directory of Open Access Journals (Sweden)

    R.A.G. Sé

    2002-04-01

    Full Text Available The NRTL (nonrandom, two-liquid model, expressed in mass fraction instead of mole fraction, was used to correlate liquid-liquid equilibria for aqueous two-phase polymer-salt solutions. New interaction energy parameters for this model were determined using reported data on the water + poly(ethylene glycol + salt systems, with different molecular masses for PEG and the salts potassium phosphate, sodium sulfate, sodium carbonate and magnesium sulfate. The correlation of liquid-liquid equilibrium is quite satisfactory.

  8. Gibbs measures and phase transitions in one-dimensional models

    OpenAIRE

    Mallak, Saed

    2000-01-01

    Ankara : Department of Mathematics and the Institute of Engineering and Sciences of Bilkent University, 2000. Thesis (Ph.D.) -- Bilkent University, 2000. Includes bibliographical references leaves 63-64 In this thesis we study the problem of limit Gibbs measures in one-dimensional models. VVe investigate uniqueness conditions for the limit Gibbs measures for one-dimensional models. VVe construct a one-dimensional model disproving a uniqueness conjecture formulated before for...

  9. Modeling of Incubation Time for Austenite to Ferrite Phase Transformation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiao-guang; LIU Zhen-yu; WU Di; WANG Wei; JIAO Si-hai

    2006-01-01

    On the basis of the classical nucleation theory, a new model of incubation time for austenite to ferrite transformation has been developed, in which the effect of deformation on austenite has been taken into consideration. To prove the precision of modeling, ferrite transformation starting temperature (Ar3) has been calculated using the Scheil′s additivity rule, and the Ar3 values were measured using a Gleeble 1500 thermomechanical simulator. The Ar3 values provided by the modeling method coincide with the measured ones, indicating that the model is precise in predicting the incubation time for austenite to ferrite transformation in hot deformed steels.

  10. Towards Complete Phase Diagrams of a Holographic P-wave Superconductor Model

    CERN Document Server

    Cai, Rong-Gen; Li, Li-Fang; Yang, Run-Qiu

    2014-01-01

    We study in detail the phase structure of a holographic p-wave superconductor model in a five dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. To construct complete phase diagrams of the model, we consider both the soliton and black hole backgrounds. In both two cases, there exist second order, first order and zeroth order phase transitions, and the so-called "retrograde condensation" also happens. In particular, in the soliton case with the mass of the vector field being beyond a certain critical value, we find a series of phase transitions happen such as "insulator/superconductor/insulator/superconductor", as the chemical potential continuously increases. We construct complete phase diagrams in terms of temperature and chemical potential and find some new phase boundaries.

  11. Numerical modeling of coupled heat transfer and phase transformation for solidification of the gray cast iron

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Hosseinzadeh, Azin

    2013-01-01

    In the present study the numerical model in 2D is used to study the solidification bahavior of the gray cast iron. The conventional heat transfer is coupled with the proposed micro-model to predict the amount of different phases, i.e. total austenite (c) phase, graphite (G) and cementite (C......), in gray cast iron based on the cooling rate (R). The results of phase amount are evaluated to find the proper correlation in respect to cooling rate. The semi-empirical formulas are proposed to find a good correlation between mechanical property (hardness Brinell) and different phase amounts...... and the cooling rate. Results show that the hardness of the gray cast iron decreases as the amount of graphite phase increases. It also increases by increased amount of the cementite and the cooling rate. These formulas were developed to correlate the phase fractions to hardness. Results are compared whit...

  12. It's Only a Phase: Applying the 5 Phases of Clinical Trials to the NSCR Model Improvement Process

    Science.gov (United States)

    Elgart, S. R.; Milder, C. M.; Chappell, L. J.; Semones, E. J.

    2017-01-01

    NASA limits astronaut radiation exposures to a 3% risk of exposure-induced death from cancer (REID) at the upper 95% confidence level. Since astronauts approach this limit, it is important that the estimate of REID be as accurate as possible. The NASA Space Cancer Risk 2012 (NSCR-2012) model has been the standard for NASA's space radiation protection guidelines since its publication in 2013. The model incorporates elements from U.S. baseline statistics, Japanese atomic bomb survivor research, animal models, cellular studies, and radiation transport to calculate astronaut baseline risk of cancer and REID. The NSCR model is under constant revision to ensure emerging research is incorporated into radiation protection standards. It is important to develop guidelines, however, to determine what new research is appropriate for integration. Certain standards of transparency are necessary in order to assess data quality, statistical quality, and analytical quality. To this effect, all original source code and any raw data used to develop the code are required to confirm there are no errors which significantly change reported outcomes. It is possible to apply a clinical trials approach to select and assess the improvement concepts that will be incorporated into future iterations of NSCR. This poster describes the five phases of clinical trials research, pre-clinical research, and clinical research phases I-IV, explaining how each step can be translated into an appropriate NSCR model selection guideline.

  13. Modeling spatially localized photonic nanojets from phase diffraction gratings

    Energy Technology Data Exchange (ETDEWEB)

    Geints, Yu. E., E-mail: ygeints@iao.ru [V.E. Zuev Institute of Atmospheric Optics SB RAS (IAO SB RAS), 1, Academician Zuev Square, Tomsk 634055 (Russian Federation); Tomsk State University, 36, Lenina Avenue, Tomsk 634050 (Russian Federation); Zemlyanov, A. A. [V.E. Zuev Institute of Atmospheric Optics SB RAS (IAO SB RAS), 1, Academician Zuev Square, Tomsk 634055 (Russian Federation)

    2016-04-21

    We investigated numerically the specific spatially localized intense optical structure, a photonic nanojet (PNJ), formed in the near-field scattering of optical radiation at phase diffraction gratings. The finite-difference time-domain technique was employed to study the PNJ key parameters (length, width, focal distance, and intensity) produced by diffraction gratings with the saw-tooth, rectangle, and hemispheric line profiles. Our analysis showed that each type of diffraction gratings produces a photonic jet with unique characteristics. Based on the numerical calculations, we demonstrate that the PNJ could be manipulated in a wide range through the variation of period, duty cycle, and shape of diffraction grating rulings.

  14. Global dust model intercomparison in AeroCom phase I

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2011-08-01

    Full Text Available This study presents the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations related to desert dust aerosols, their direct radiative effect, and their impact on the biogeochemical cycle, i.e., aerosol optical depth (AOD and dust deposition. Additional comparisons to Angström exponent (AE, coarse mode AOD and dust surface concentrations are included to extend the assessment of model performance and to identify common biases present in models. These data comprise a benchmark dataset that is proposed for model inspection and future dust model development. There are large differences among the global models that simulate the dust cycle and its impact on climate. In general, models simulate the climatology of vertically integrated parameters (AOD and AE within a factor of two whereas the total deposition and surface concentration are reproduced within a factor of 10. In addition, smaller mean normalized bias and root mean square errors are obtained for the climatology of AOD and AE than for total deposition and surface concentration. Characteristics of the datasets used and their uncertainties may influence these differences. Large uncertainties still exist with respect to the deposition fluxes in the southern oceans. Further measurements and model studies are necessary to assess the general model performance to reproduce dust deposition in ocean regions sensible to iron contributions. Models overestimate the wet deposition in regions dominated by dry deposition. They generally simulate more realistic surface concentration at stations downwind of the main sources than at remote ones. Most models simulate the gradient in AOD and AE between the different dusty regions. However the seasonality and magnitude of both variables is better simulated at African stations than Middle East ones. The models simulate the offshore transport of West Africa throughout the year

  15. Scaling of geometric phase versus band structure in cluster-Ising models

    Science.gov (United States)

    Nie, Wei; Mei, Feng; Amico, Luigi; Kwek, Leong Chuan

    2017-08-01

    We study the phase diagram of a class of models in which a generalized cluster interaction can be quenched by an Ising exchange interaction and external magnetic field. The various phases are studied through winding numbers. They may be ordinary phases with local order parameters or exotic ones, known as symmetry protected topologically ordered phases. Quantum phase transitions with dynamical critical exponents z =1 or z =2 are found. In particular, the criticality is analyzed through finite-size scaling of the geometric phase accumulated when the spins of the lattice perform an adiabatic precession. With this study, we quantify the scaling behavior of the geometric phase in relation to the topology and low-energy properties of the band structure of the system.

  16. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissilä, Tapio

    2010-01-01

    We present a derivation of the recently proposed eighth-order phase-field crystal model [A. Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two-dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase-field crystal models. We find that among the phase-field crystal mod...

  17. Traveling waves for models of phase transitions of solids driven by configurational forces

    CERN Document Server

    Kawashima, Shuichi

    2009-01-01

    This article is concerned with the existence of traveling wave solutions, including standing waves, to some models based on configurational forces, describing respectively the diffusionless phase transformations of solid materials, e.g., Steel, and phase transitions due to interface motion by interface diffusion, e.g., Sintering. These models are recently proposed by Alber and Zhu. We consider both the order-parameter-conserved case and the non-conserved one, under suitable assumptions. Also we compare our results with the corresponding ones for the Allen-Cahn and the Cahn-Hilliard equations coupled with linear elasticity, which are models for diffusion-dominated phase transformations in elastic solids.

  18. Power Loss Calculation and Thermal Modelling for a Three Phase Inverter Drive System

    Directory of Open Access Journals (Sweden)

    Z. Zhou

    2005-12-01

    Full Text Available Power losses calculation and thermal modelling for a three-phase inverter power system is presented in this paper. Aiming a long real time thermal simulation, an accurate average power losses calculation based on PWM reconstruction technique is proposed. For carrying out the thermal simulation, a compact thermal model for a three-phase inverter power module is built. The thermal interference of adjacent heat sources is analysed using 3D thermal simulation. The proposed model can provide accurate power losses with a large simulation time-step and suitable for a long real time thermal simulation for a three phase inverter drive system for hybrid vehicle applications.

  19. Global dust model intercomparison in AeroCom phase I

    NARCIS (Netherlands)

    Huneeus, N.; Schulz, M.; Balkanski, Y.; Griesfeller, J.; Krol, M.C.

    2011-01-01

    This study presents the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations related to desert dust aerosols, their direct radiative effect, and their impact on the biogeochemical cycle, i.e., aerosol optical dep

  20. Modeling the Thermodynamic and Transport Properties of Decahydronaphthalene/Propane Mixtures: Phase Equilibria, Density, and Viscosity

    Science.gov (United States)

    2011-01-01

    Modeling the Thermodynamic and Transport Properties of Decahydronaphthalene/Propane Mixtures: Phase Equilibria , Density, and Viscosity Nathaniel...Decahydronaphthalene/Propane Mixtures: Phase Equilibria , Density, And Viscosity 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Keywords: phase equilibria ; modified Sanchez-Lacombe equation of state

  1. MODELING OF SYMMETRIC THREE-PHASE ASYNCHRONOUS ELECTRIC MOTOR IN ASYMMETRIC CONNECTION TO NETWORK

    Directory of Open Access Journals (Sweden)

    V. I. Lukovnikov

    2005-01-01

    Full Text Available The paper shows how to solve the problem concerning reveal of changes in mathematical models and electric parameters of symmetric three-phase short-circuited asynchronous electric motors in case of their connection to single- or two-phase network in comparison with their connection to three-phase network. The uniform methodological approach permitting to generalize the known data and receive new results is offered in the paper.

  2. Supersolid Phase in One-Dimensional Hard-Core Boson Hubbard Model with a Superlattice Potential

    Institute of Scientific and Technical Information of China (English)

    GUO Huai-Ming; LIANG Ying

    2008-01-01

    The ground state of the one-dimensional hard-core boson Hubbard model with a superlattice potential is studied by quantum Monte Carlo methods. We demonstrate that besides the CDW phase and the Mort insulator phase, the supersolid phase emerges due to the presence of the superlattice potential, which reflects the competition with the hopping term. We also study the densities of sublattices and have a clear idea about the distribution of the bosons on the lattice.

  3. Matrix model approximations of fuzzy scalar field theories and their phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Tekel, Juraj [Department of Theoretical Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska Dolina, Bratislava, 842 48 (Slovakia)

    2015-12-29

    We present an analysis of two different approximations to the scalar field theory on the fuzzy sphere, a nonperturbative and a perturbative one, which are both multitrace matrix models. We show that the former reproduces a phase diagram with correct features in a qualitative agreement with the previous numerical studies and that the latter gives a phase diagram with features not expected in the phase diagram of the field theory.

  4. MODELING TWO-PHASE FLOW IN PULSED FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Dayou Liu; Guodong Jin

    2003-01-01

    Mathematical models for pulsed fluidization are systematically discussed. Several undetermined constitutive relationships are included in the General Two-Fluid Model (GTFM), the adjustable parameters of which are always chosen at will to some extent. Although there are no adjustable parameters in the Basic Two-Fluid Model (BTFM), its eigenvalues are complex numbers and it is ill-posed for initial-value problems. The Local Equilibrium Model (LEM), a further simplification of BTFM, is discussed at length. Although the model is very simple, it is highly capable of simulating complex processes in pulsed fluidization over a broad range of operating parameters, and its numerical results well fit experimental results in both the variation of bed height and the distribution of particle concentration as fluidizing velocity varies.

  5. Finite size effects on the phase diagram of the thermodynamical cluster model

    CERN Document Server

    Mallik, S; Chaudhuri, G

    2016-01-01

    The thermodynamical cluster model is known to present a first-order liquid-gas phase transition in the idealized case of an uncharged, infinitely extended medium. However, in most practical applications of this model, the system is finite and charged. In this paper we study how the phase diagram is modified by finite size and Coulomb effects. We show that the thermodynamic anomalies which are associated to the finite system counterpart of first order phase transitions, are correctly reproduced by this effective model. However, approximations in the calculation of the grandcanonical partition sum prevent obtaining the exact mapping between statistical ensembles which should be associated to finite systems. The ensemble inequivalence associated to the transition persists in the presence of Coulomb, but the phase diagram is deeply modified with respect to the simple liquid-gas phase transition characteristic of the neutral system.

  6. Crystal Level Continuum Modeling of Phase Transformations: The (alpha) <--> (epsilon) Transformation in Iron

    Energy Technology Data Exchange (ETDEWEB)

    Barton, N R; Benson, D J; Becker, R; Bykov, Y; Caplan, M

    2004-10-18

    We present a crystal level model for thermo-mechanical deformation with phase transformation capabilities. The model is formulated to allow for large pressures (on the order of the elastic moduli) and makes use of a multiplicative decomposition of the deformation gradient. Elastic and thermal lattice distortions are combined into a single lattice stretch to allow the model to be used in conjunction with general equation of state relationships. Phase transformations change the mass fractions of the material constituents. The driving force for phase transformations includes terms arising from mechanical work, from the temperature dependent chemical free energy change on transformation, and from interaction energy among the constituents. Deformation results from both these phase transformations and elasto-viscoplastic deformation of the constituents themselves. Simulation results are given for the {alpha} to {epsilon} phase transformation in iron. Results include simulations of shock induced transformation in single crystals and of compression of polycrystals. Results are compared to available experimental data.

  7. Phase field modelling of stressed grain growth: Analytical study and the effect of microstructural length scale

    Energy Technology Data Exchange (ETDEWEB)

    Jamshidian, M., E-mail: mostafa.jamshidian@gmail.com [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Rabczuk, T., E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); School of Civil, Environmental and Architectural Engineering, Korea University, Seoul (Korea, Republic of)

    2014-03-15

    We establish the correlation between the diffuse interface and sharp interface descriptions for stressed grain boundary migration by presenting analytical solutions for stressed migration of a circular grain boundary in a bicrystalline phase field domain. The validity and accuracy of the phase field model is investigated by comparing the phase field simulation results against analytical solutions. The phase field model can reproduce precise boundary kinetics and stress evolution provided that a thermodynamically consistent theory and proper expressions for model parameters in terms of physical material properties are employed. Quantitative phase field simulations are then employed to investigate the effect of microstructural length scale on microstructure and texture evolution by stressed grain growth in an elastically deformed polycrystalline aggregate. The simulation results reveal a transitional behaviour from normal to abnormal grain growth by increasing the microstructural length scale.

  8. Phase structure of the massive chiral Gross-Neveu model from Hartree-Fock

    CERN Document Server

    Boehmer, Christian; Kraus, Sebastian; Thies, Michael

    2008-01-01

    The phase diagram of the massive chiral Gross-Neveu model (the massive Nambu-Jona-Lasinio model in 1+1 dimensions) is constructed. In the large N limit, the Hartree-Fock approach can be used. We find numerically a chiral crystal phase separated from a massive Fermi gas phase by a 1st order transition. Using perturbation theory, we also construct the critical sheet where the homogeneous phase becomes unstable in a 2nd order transition. A tricritical curve is located. The phase diagram is mapped out as a function of fermion mass, chemical potential and temperature and compared with the one of the discrete chiral Gross-Neveu model. As a by-product, we illustrate the crystal structure of matter at zero temperature for various densities and fermion masses.

  9. Liquid-gas phase transition in strange hadronic matter with relativistic models

    CERN Document Server

    Torres, James R; Menezes, Débora P

    2015-01-01

    Background: The advent of new dedicated experimental programs on hyperon physics is rapidly boosting the field, and the possibility of synthetizing multiple strange hypernuclei requires the addition of the strangeness degree of freedom to the models dedicated to nuclear structure and nuclear matter studies at low energy. Purpose: We want to settle the influence of strangeness on the nuclear liquid-gas phase transition. Because of the large uncertainties concerning the hyperon sector, we do not aim at a quantitative estimation of the phase diagram but rather at a qualitative description of the phenomenology, as model independent as possible. Method: We analyze the phase diagram of low density matter composed of neutrons, protons and $\\Lambda$ hyperons using a Relativistic Mean Field (RMF) model. We largely explore the parameter space to pin down generic features of the phase transition, and compare the results to ab-initio quantum Monte Carlo calculations. Results: We show that the liquid-gas phase transition ...

  10. Thermodynamical modeling of nuclear glasses: coexistence of amorphous phases; Modelisation thermodynamique des verres nucleaires: coexistence entre phases amorphes

    Energy Technology Data Exchange (ETDEWEB)

    Adjanor, G

    2007-11-15

    Investigating the stability of borosilicate glasses used in the nuclear industry with respect to phase separation requires to estimate the Gibbs free energies of the various phases appearing in the material. In simulation, using current computational resources, a direct state-sampling of a glassy system with respect to its ensemble statistics is not ergodic and the estimated ensemble averages are not reliable. Our approach consists in generating, at a given cooling rate, a series of quenches, or paths connecting states of the liquid to states of the glass, and then in taking into account the probability to generate the paths leading to the different glassy states in ensembles averages. In this way, we introduce a path ensemble formalism and calculate a Landau free energy associated to a glassy meta-basin. This method was validated by accurately mapping the free energy landscape of a 38-atom glassy cluster. We then applied this approach to the calculation of the Gibbs free energies of binary amorphous Lennard-Jones alloys, and checked the correlation between the observed tendencies to order or to phase separate and the computed Gibbs free energies. We finally computed the driving force to phase separation in a simplified three-oxide nuclear glass modeled by a Born-Mayer-Huggins potential that includes a three-body term, and we compared the estimated quantities to the available experimental data. (author)

  11. Modeling the effects of systemic mediators on the inflammatory phase of wound healing.

    Science.gov (United States)

    Cooper, Racheal L; Segal, Rebecca A; Diegelmann, Robert F; Reynolds, Angela M

    2015-02-21

    The normal wound healing response is characterized by a progression from clot formation, to an inflammatory phase, to a repair phase, and finally, to remodeling. In many chronic wounds there is an extended inflammatory phase that stops this progression. In order to understand the inflammatory phase in more detail, we developed an ordinary differential equation model that accounts for two systemic mediators that are known to modulate this phase, estrogen (a protective hormone during wound healing) and cortisol (a hormone elevated after trauma that slows healing). This model describes the interactions in the wound between wound debris, pathogens, neutrophils and macrophages and the modulation of these interactions by estrogen and cortisol. A collection of parameter sets, which qualitatively match published data on the dynamics of wound healing, was chosen using Latin Hypercube Sampling. This collection of parameter sets represents normal healing in the population as a whole better than one single parameter set. Including the effects of estrogen and cortisol is a necessary step to creating a patient specific model that accounts for gender and trauma. Utilization of math modeling techniques to better understand the wound healing inflammatory phase could lead to new therapeutic strategies for the treatment of chronic wounds. This inflammatory phase model will later become the inflammatory subsystem of our full wound healing model, which includes fibroblast activity, collagen accumulation and remodeling.

  12. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    Energy Technology Data Exchange (ETDEWEB)

    Butlitsky, M. A.; Zelener, B. V. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Zelener, B. B. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Moscow Engineering Physics Institute, 115409, Russia, Moscow, Kashirskoe sh. 31 (Russian Federation)

    2014-07-14

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ε parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ε and γ = βe{sup 2}n{sup 1/3} (where β = 1/k{sub B}T, n is the particle's density, k{sub B} is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ε and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ε{sub crit}≈13(T{sub crit}{sup *}≈0.076),γ{sub crit}≈1.8(v{sub crit}{sup *}≈0.17),P{sub crit}{sup *}≈0.39, where specific volume v* = 1/γ{sup 3} and reduced temperature T{sup *} = ε{sup −1}.

  13. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    Science.gov (United States)

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1).

  14. One-dimensional frustrated plaquette compass model: Nematic phase and spontaneous multimerization

    Science.gov (United States)

    Brzezicki, Wojciech; Oleś, Andrzej M.

    2016-06-01

    We introduce a one-dimensional (1D) pseudospin model on a ladder where the Ising interactions along the legs and along the rungs alternate between XiXi +1 and ZiZi +1 for even/odd bond (rung). We include also the next-nearest-neighbor Ising interactions on plaquettes' diagonals that alternate in such a way that a model where only leg interactions are switched on is equivalent to the one when only the diagonal ones are present. Thus in the absence of rung interactions the model can interpolate between two 1D compass models. The model possesses local symmetries which are the parities within each 2 ×2 cell (plaquette) of the ladder. We find that for different values of the interaction it can realize ground states that differ by the patterns formed by these local parities. By exact diagonalization we derive detailed phase diagrams for small systems of L =4 , 6, and 8 plaquettes, and use next L =12 to identify generic phases that appear in larger systems as well. Among them we find a nematic phase with macroscopic degeneracy when the leg and diagonal interactions are equal and the rung interactions are larger than a critical value. By performing a perturbative expansion around this phase we find indeed a very complex competition around the nematic phase which has to do with releasing frustration in this range of parameters. The nematic phase is similar to the one found in the two-dimensional compass model. For particular parameters the low-energy sector of the present plaquette model reduces to a 1D compass model with spins S =1 which suggests that it realizes peculiar crossovers within the class of compass models. Finally, we show that the model can realize phases with broken translation invariance which can be either dimerized, trimerized, etc., or completely disordered and highly entangled in a well identified window of the phase diagram.

  15. Compositional modeling of three-phase flow with gravity using higher-order finite element methods

    Science.gov (United States)

    Moortgat, Joachim; Sun, Shuyu; Firoozabadi, Abbas

    2011-05-01

    A wide range of applications in subsurface flow involve water, a nonaqueous phase liquid (NAPL) or oil, and a gas phase, such as air or CO2. The numerical simulation of such processes is computationally challenging and requires accurate compositional modeling of three-phase flow in porous media. In this work, we simulate for the first time three-phase compositional flow using higher-order finite element methods. Gravity poses complications in modeling multiphase processes because it drives countercurrent flow among phases. To resolve this issue, we propose a new method for the upwinding of three-phase mobilities. Numerical examples, related to enhanced oil recovery and carbon sequestration, are presented to illustrate the capabilities of the proposed algorithm. We pay special attention to challenges associated with gravitational instabilities and take into account compressibility and various phase behavior effects, including swelling, viscosity changes, and vaporization. We find that the proposed higher-order method can capture sharp solution discontinuities, yielding accurate predictions of phase boundaries arising in computational three-phase flow. This work sets the stage for a broad extension of the higher-order methods for numerical simulation of three-phase flow for complex geometries and processes.

  16. Compositional modeling of three-phase flow with gravity using higher-order finite element methods

    KAUST Repository

    Moortgat, Joachim

    2011-05-11

    A wide range of applications in subsurface flow involve water, a nonaqueous phase liquid (NAPL) or oil, and a gas phase, such as air or CO2. The numerical simulation of such processes is computationally challenging and requires accurate compositional modeling of three-phase flow in porous media. In this work, we simulate for the first time three-phase compositional flow using higher-order finite element methods. Gravity poses complications in modeling multiphase processes because it drives countercurrent flow among phases. To resolve this issue, we propose a new method for the upwinding of three-phase mobilities. Numerical examples, related to enhanced oil recovery and carbon sequestration, are presented to illustrate the capabilities of the proposed algorithm. We pay special attention to challenges associated with gravitational instabilities and take into account compressibility and various phase behavior effects, including swelling, viscosity changes, and vaporization. We find that the proposed higher-order method can capture sharp solution discontinuities, yielding accurate predictions of phase boundaries arising in computational three-phase flow. This work sets the stage for a broad extension of the higher-order methods for numerical simulation of three-phase flow for complex geometries and processes.

  17. Phase Transitions of a Dilute O(n) Model

    Institute of Scientific and Technical Information of China (English)

    GUO Wen-An; Henk W.J. Blote; LIU Yuan-Yuan

    2004-01-01

    We investigate tricritical behavior of the O(n) model in two dimensions by means of transfer-matrix and finite-size scaling methods. For this purpose we consider an O(n) symmetric spin model on the honeycomb lattice with vacancies; the tricritical behavior is associated with the percolation threshold of the vacancies. The vacancies are represented by face variables on the elementary hexagons of thelattice. We apply a mapping of the spin degrees of freedom model on a non-intersecting-loop model, in which the number n of spin components assumes the role of a continuously variable parameter. This loop model serves as a suitable basis for the construction of the transfer matrix.Our results reveal the existence of a tricritical line, parametrized by n, which connects the known universality classes of the tricritical Ising model and the theta point describing the collapse of a polymer. On the other side of theIsing point,the tricritical line extends to the n = 2 point describing a tricritical O(2) model.

  18. Electroweak phase transition in the economical 3-3-1 model

    CERN Document Server

    Phong, Vo Quoc; Van, Vo Thanh; Minh, Le Hoang

    2014-01-01

    Following our approach to the electroweak phase transition (EWPT), we consider the phase transitions in framework of the economical 3-3-1 model (E331). Structure of phase transition in this model is divided into two periods. The first period is the phase transition $SU(3) \\rightarrow SU(2)$ at TeV scale and the second one is $SU(2) \\rightarrow U(1)$, which is like the Standard Model (SM) electroweak phase transition. Two periods are the first-order phase transitions if the masses of heavy bosons is equal to few TeVs and the mass of second neutral Higgs is, $0phase transition period is $1<\\omega<5$ TeV. In addition, we also derived conditions of the self interaction parameters in the Higgs potential. Therefore, new bosons are the triggers of the first-order electroweak phase transition with significant implications for the viability of electroweak baryogenesis scenarios in this model.

  19. Dynamic Characterization and Impulse Response Modeling of Amplitude and Phase Response of Silicon Nanowires

    DEFF Research Database (Denmark)

    Cleary, Ciaran S.; Ji, Hua; Dailey, James M.

    2013-01-01

    Amplitude and phase dynamics of silicon nanowires were measured using time-resolved spectroscopy. Time shifts of the maximum phase change and minimum amplitude as a function of pump power due to saturation of the free-carrier density were observed. A phenomenological impulse response model used...

  20. Phase-field modeling of microstructural pattern formation in alloys and geological veins

    OpenAIRE

    Ankit, Kumar

    2016-01-01

    With the advent of high performance computing, the application areas of the phase-field method, traditionally used to numerically model the phase transformation in metals and alloys, have now spanned into geoscience. A systematic investigation of the two distinct scientific problems in consideration suggest a strong influence of interfacial energy on the natural and induced pattern formation in diffusion-controlled regime.

  1. Finite-Temperature Phase Structure in the Chiral σ-ω Model with Dilatons

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-Bing ZHANG Xiao-Bing; LI Xue-Qian; NING Ping-Zhi

    2000-01-01

    We investigate the finite-temperature phase structure in a scaled chiral model which includes the dilaton (glueball) field. It is shown that hot nuclear matter undergoes a discontinuous transition in the mean field of scalar mesons as well as the Lee-Wick abnormal transition. The corresponding behavior of the gluon condensate during the chiral phase transition is also studied.

  2. Multi-phase flow modeling of soil contamination and soil remediation.

    NARCIS (Netherlands)

    Dijke, van M.I.J.

    1997-01-01

    In this thesis multi-phase flow models are used to study the flow behavior of liquid contaminants in aquifers and of gases that are injected below the groundwater table for remediation purposes. Considered problems are redistribution of a lens of light nonaqueous phase liquid(LNAPL)on a hor

  3. Two-phase flow experimental studies in micro-models (Utrecht Studies in Earth Sciences 034)

    NARCIS (Netherlands)

    Karadimitriou, N.K.

    2013-01-01

    The aim of this research project was to put more physics into theories of two-phase flow. The significance of including interfacial area as a separate variable in two-phase flow and transport models was investigated. In order to investigate experimentally the significance of the inclusion of interfa

  4. Model description of bactrial 3-methylcatechol production in one- and two-phase systems

    NARCIS (Netherlands)

    Husken, L.E.; Hoogakker, J.; Bont, de J.A.M.; Tramper, J.; Beeftink, H.H.

    2003-01-01

    Pseudomonas putida MC2 produces 3-methylcatechol from toluene in aqueous medium. A second phase of 1-octanol may improve total product accumulation. To optimise the design of such a biphasic process, a process model was developed, both for one- and two-phase applications. The insights obtained by th

  5. Phase transitions in a holographic s + p model with back-reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Zhang-Yu [Kunming University of Science and Technology, Kunming (China); Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Shanghai Jiao Tong University, INPAC, Department of Physics, and Shanghai Key Laboratory of Particle Physics and Cosmology, Shanghai (China); Cai, Rong-Gen [Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Gao, Xin [Virginia Tech, Department of Physics, Blacksburg, VA (United States); Li, Li [University of Crete, Department of Physics, Crete Center for Theoretical Physics, Heraklion (Greece); Zeng, Hui [Kunming University of Science and Technology, Kunming (China); Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China)

    2015-11-15

    In a previous paper (Nie et al. in JHEP 1311:087, arXiv:1309.2204 [hep-th], 2013), we presented a holographic s + p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. We also study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back-reaction. The model shows a rich phase structure and various condensate behaviors such as the ''n-type'' and ''u-type'' ones, which are also known as reentrant phase transitions in condensed matter physics. The phase transitions to the p-wave phase or s + p coexisting phase become first order in strong back-reaction cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s + p solution can also play an important role. The phase diagrams of this model are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back-reaction parameter, which show that the region for the s + p coexisting phase is enlarged with a small or medium back-reaction parameter but is reduced in the strong back-reaction cases. (orig.)

  6. IMPROVED SUBGRID SCALE MODEL FOR DENSE TURBULENT SOLID-LIQUID TWO-PHASE FLOWS

    Institute of Scientific and Technical Information of China (English)

    TANG Xuelin; QIAN Zhongdong; WU Yulin

    2004-01-01

    The dense solid-phase governing equations for two-phase flows are obtained by using the kinetic theory of gas molecules. Assuming that the solid-phase velocity distributions obey the Maxwell equations, the collision term for particles under dense two-phase flow conditions is also derived.In comparison with the governing equations of a dilute two-phase flow, the solid-particle's governing equations are developed for a dense turbulent solid-liquid flow by adopting some relevant terms from the dilute two-phase governing equations. Based on Cauchy-Helmholtz theorem and Smagorinsky model,a second-order dynamic sub-grid-scale (SGS) model, in which the sub-grid-scale stress is a function of both the strain-rate tensor and the rotation-rate tensor, is proposed to model the two-phase governing equations by applying dimension analyses. Applying the SIMPLEC algorithm and staggering grid system to the two-phase discretized governing equations and employing the slip boundary conditions on the walls, the velocity and pressure fields, and the volumetric concentration are calculated. The simulation results are in a fairly good agreement with experimental data in two operating cases in a conduit with a rectangular cross-section and these comparisons imply that these models are practical.

  7. The phase diagram of the massive Gross-Neveu model, revisited

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2005-01-01

    The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The phase diagram features a kink-antikink crystal phase which was missed in previous works. Translated into the framework of condensed matter physics our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.

  8. Multicritical phase diagrams of the Blume-Emery-Griffiths model with repulsive biquadratic coupling including metastable phases

    Science.gov (United States)

    Ekiz, Cesur; Keskin, Mustafa

    2002-08-01

    We investigate the thermal variations of the spin-1 Blume-Emergy-Griffiths model with the repulsive biquadratic interaction by using the lowest approximation of the cluster-variation method. Besides the stable branches of the order parameters, we obtain the metastable and unstable parts of these curves and also find phase transitions of the metastable branches of the order parameters. The classification of the stable, metastable, and unstable states is made by comparing the free-energy values of these states. We also study the dynamics of the model by the path probability method in order to make sure that we find and define the metastable and unstable branches of the order parameters completely and correctly. This is done by studying the relaxation of the order parameters and as well as expressing the solution of the dynamic equations by means of the flow diagrams. Finally, we present the metastable phase diagrams in addition to the equilibrium phase diagrams in (kT/J,D/J) and (kT/J,K/J) planes.

  9. Underground Test Area Subproject Phase I Data Analysis Task. Volume VII - Tritium Transport Model Documentation Package

    Energy Technology Data Exchange (ETDEWEB)

    None

    1996-12-01

    Volume VII of the documentation for the Phase I Data Analysis Task performed in support of the current Regional Flow Model, Transport Model, and Risk Assessment for the Nevada Test Site Underground Test Area Subproject contains the tritium transport model documentation. Because of the size and complexity of the model area, a considerable quantity of data was collected and analyzed in support of the modeling efforts. The data analysis task was consequently broken into eight subtasks, and descriptions of each subtask's activities are contained in one of the eight volumes that comprise the Phase I Data Analysis Documentation.

  10. Underground Test Area Subproject Phase I Data Analysis Task. Volume VI - Groundwater Flow Model Documentation Package

    Energy Technology Data Exchange (ETDEWEB)

    None

    1996-11-01

    Volume VI of the documentation for the Phase I Data Analysis Task performed in support of the current Regional Flow Model, Transport Model, and Risk Assessment for the Nevada Test Site Underground Test Area Subproject contains the groundwater flow model data. Because of the size and complexity of the model area, a considerable quantity of data was collected and analyzed in support of the modeling efforts. The data analysis task was consequently broken into eight subtasks, and descriptions of each subtask's activities are contained in one of the eight volumes that comprise the Phase I Data Analysis Documentation.

  11. Interactive Model-Centric Systems Engineering (IMCSE) Phase Two

    Science.gov (United States)

    2015-02-28

    implementation uses a 8 MongoDB/Express/Node.js stack to provide remote model execution and services to store and query model results. Front - end user...the design is on the Pareto Front , across all epochs. 105 Smaling, R., “ Fuzzy Pareto Frontiers in Multidisciplinary System Architecture Analysis...Comparison of benefit versus cost tradespaces with compromise, promising, and fuzzy joint designs indicated

  12. Interactive Model-Centric Systems Engineering (IMCSE) Phase 1

    Science.gov (United States)

    2014-09-30

    engineering design and analysis processes. They state that sensemaking evolved from naturalistic decision making research, as published by Klein et al...2012 16 Klein , G.A., A Recognition-Primed Decision (RPD) Model of Rapid Decision Making, Decision making in action: Models and methods, vol 5, no...psychology to probe human abilities to ‘affectively forecast’—that is, to make accurate projections about their future wants, desires, and emotional

  13. Ultrasonic measurement models for imaging with phased arrays

    Science.gov (United States)

    Schmerr, Lester W., Jr.; Engle, Brady J.; Sedov, Alexander; Li, Xiongbing

    2014-02-01

    Ultrasonic imaging measurement models (IMMs) are developed that generate images of flaws by inversion of ultrasonic measurement models. These IMMs are generalizations of the synthetic aperture focusing technique (SAFT) and the total focusing method (TFM). A special case when the flaw is small is shown to generalize physical optics far field inverse scattering (POFFIS) images. The ultrasonic IMMs provide a rational basis for generating and understanding the ultrasonic images produced by delay-and-sum imaging methods.

  14. Global dust model intercomparison in AeroCom phase I

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2010-10-01

    Full Text Available Desert dust plays an important role in the climate system through its impact on Earth's radiative budget and its role in the biogeochemical cycle as a source of iron in high-nutrient-low-chlorophyll regions. A large degree of diversity exists between the many global models that simulate the dust cycle to estimate its impact on climate. We present the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations focusing on variables responsible for the uncertainties in estimating the direct radiative effect and the dust impact on the biogeochemical cycle, i.e., aerosol optical depth (AOD and dust deposition. Additional comparisons to Angström Exponent (AE, coarse mode AOD and dust surface concentration are included to extend the assessment of model performance. These datasets form a benchmark data set which is proposed for model inspection and future dust model developments. In general, models perform better in simulating climatology of vertically averaged integrated parameters (AOD and AE in dusty sites than they do with total deposition and surface concentration. Almost all models overestimate deposition fluxes over Europe, the Indian Ocean, the Atlantic Ocean and ice core data. Differences among the models arise when simulating deposition at remote sites with low fluxes over the Pacific and the Southern Atlantic Ocean. This study also highlights important differences in models ability to reproduce the deposition flux over Antarctica. The cause of this discrepancy could not be identified but different dust regimes at each site and issues with data quality should be considered. Models generally simulate better surface concentration at stations downwind of the main sources than at remote ones. Likewise, they simulate better surface concentration at stations affected by Saharan dust than at stations affected by Asian dust. Most models simulate the gradient in AOD and

  15. The Pliocene Model Intercomparison Project (PlioMIP) Phase 2: scientific objectives and experimental design

    Science.gov (United States)

    Haywood, Alan M.; Dowsett, Harry J.; Dolan, Aisling M.; Rowley, David; Abe-Ouchi, Ayako; Otto-Bliesner, Bette; Chandler, Mark A.; Hunter, Stephen J.; Lunt, Daniel J.; Pound, Matthew; Salzmann, Ulrich

    2016-03-01

    The Pliocene Model Intercomparison Project (PlioMIP) is a co-ordinated international climate modelling initiative to study and understand climate and environments of the Late Pliocene, as well as their potential relevance in the context of future climate change. PlioMIP examines the consistency of model predictions in simulating Pliocene climate and their ability to reproduce climate signals preserved by geological climate archives. Here we provide a description of the aim and objectives of the next phase of the model intercomparison project (PlioMIP Phase 2), and we present the experimental design and boundary conditions that will be utilized for climate model experiments in Phase 2. Following on from PlioMIP Phase 1, Phase 2 will continue to be a mechanism for sampling structural uncertainty within climate models. However, Phase 1 demonstrated the requirement to better understand boundary condition uncertainties as well as uncertainty in the methodologies used for data-model comparison. Therefore, our strategy for Phase 2 is to utilize state-of-the-art boundary conditions that have emerged over the last 5 years. These include a new palaeogeographic reconstruction, detailing ocean bathymetry and land-ice surface topography. The ice surface topography is built upon the lessons learned from offline ice sheet modelling studies. Land surface cover has been enhanced by recent additions of Pliocene soils and lakes. Atmospheric reconstructions of palaeo-CO2 are emerging on orbital timescales, and these are also incorporated into PlioMIP Phase 2. New records of surface and sea surface temperature change are being produced that will be more temporally consistent with the boundary conditions and forcings used within models. Finally we have designed a suite of prioritized experiments that tackle issues surrounding the basic understanding of the Pliocene and its relevance in the context of future climate change in a discrete way.

  16. The Pliocene Model Intercomparison Project (PlioMIP) Phase 2: Scientific Objectives and Experimental Design

    Science.gov (United States)

    Haywood, Alan M.; Dowsett, Harry J.; Dolan, Aisling M.; Rowley, David; Abe-Ouchi, Ayako; Otto-Bliesner, Bette; Chandler, Mark A.; Hunter, Stephen J.; Lunt, Daniel J.; Pound, Matthew; Salzmann, Ulrich

    2016-01-01

    The Pliocene Model Intercomparison Project (PlioMIP) is a co-ordinated international climate modelling initiative to study and understand climate and environments of the Late Pliocene, as well as their potential relevance in the context of future climate change. PlioMIP examines the consistency of model predictions in simulating Pliocene climate and their ability to reproduce climate signals preserved by geological climate archives. Here we provide a description of the aim and objectives of the next phase of the model intercomparison project (PlioMIP Phase 2), and we present the experimental design and boundary conditions that will be utilized for climate model experiments in Phase 2. Following on from PlioMIP Phase 1, Phase 2 will continue to be a mechanism for sampling structural uncertainty within climate models. However, Phase 1 demonstrated the requirement to better understand boundary condition uncertainties as well as uncertainty in the methodologies used for data-model comparison. Therefore, our strategy for Phase 2 is to utilize state-of-the-art boundary conditions that have emerged over the last 5 years. These include a new palaeogeographic reconstruction, detailing ocean bathymetry and land-ice surface topography. The ice surface topography is built upon the lessons learned from offline ice sheet modelling studies. Land surface cover has been enhanced by recent additions of Pliocene soils and lakes. Atmospheric reconstructions of palaeo-CO2 are emerging on orbital timescales, and these are also incorporated into PlioMIP Phase 2. New records of surface and sea surface temperature change are being produced that will be more temporally consistent with the boundary conditions and forcings used within models. Finally we have designed a suite of prioritized experiments that tackle issues surrounding the basic understanding of the Pliocene and its relevance in the context of future climate change in a discrete way.

  17. Magnetic model for a horse-spleen ferritin with a three-phase core structure

    Energy Technology Data Exchange (ETDEWEB)

    Jung, J.H.; Eom, T.W. [Quantum Photonic Science Research Center, Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 133-791 (Korea, Republic of); Lee, Y.P., E-mail: yplee@hanyang.ac.kr [Quantum Photonic Science Research Center, Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 133-791 (Korea, Republic of); Rhee, J.Y. [Department of Physics, Sungkyunkwan University, Suwon (Korea, Republic of); Choi, E.H. [Kwangwoon University, Seoul (Korea, Republic of)

    2011-12-15

    The increasing interests in magnetic nanoparticles has prompted research on ferritin, which is naturally a well-defined iron-storage protein in most living organisms. However, the exact magnetic behavior of ferritin is not well understood, because the crystal structures of ferritin and ferrihydrite, its major component, are not fully understood. Briefly, we discuss the previous magnetization models of ferritin and ferrihydrite and we present a new model ({Sigma}3L) of the initial magnetization of ferritin, considering its different phases. The new model includes three Langevin-function terms, which represent three different magnetic moments provided by the likely hydroxide and oxide mineral phases in ferritin. Compared to previous models, our simple model fits the experimental data 12 times better in terms of the sum of least squares. The magnetic independence of each component supports the multi-phase compositional model of the mineral core of horse-spleen ferritin. This {Sigma}3L model gives a quantization of the amounts of the different phases within horse-spleen ferritins that matches other published experimental data: 60-80% ferrihydrite, 15-25% maghemite/magnetite, and 1-10% hematite. - Highlights: > We present a new model ({Sigma}3L) of the initial magnetization of ferritin, considering its different phases. > New model includes three Langevin-function terms, which represent three different magnetic moments provided by ferritin phases. > Compared to previous models, our simple model fits the experimental data 12 times better in terms of the sum of least square. > The magnetic independence of each component supports that ferritin and ferrihydrite are composed of different phases.

  18. A state-of-the-art report on two-phase critical flow modelling

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Jae Joon; Jang, Won Pyo; Kim, Dong Soo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1993-09-01

    This report reviews and analyses two-phase, critical flow models. The purposes of the report are (1) to make a knowledge base for the full understanding and best-estimate of two-phase, critical flow, (2) to analyse the model development trend and to derive the direction of further studies. A wide range of critical flow models are reviewed. Each model, in general, predicts critical flow well only within specified conditions. The critical flow models of best-estimate codes are special process model included in the hydrodynamic model. The results of calculations depend on the nodalization, discharge coefficient, and other user`s options. The following topics are recommended for continuing studies: improvement of two-fluid model, development of multidimensional model, data base setup and model error evaluation, and generalization of discharge coefficients. 24 figs., 5 tabs., 80 refs. (Author).

  19. Two-phase SPH modelling of waves caused by dam break over a movable bed

    Institute of Scientific and Technical Information of China (English)

    Seyedeh Leila RAZAVITOOSI; Seyed Ali AYYOUBZADEH; Alireza VALIZADEH

    2014-01-01

    This paper describes the application of the Smoothed Particle Hydrodynamics (SPH) method for modeling two dimensional waves caused by dam break over a movable bed in two dimensions. The two phase SPH method is developed to solve the Navier-Stokes equations. Both fluid and sediment phases are described by particles as weakly compressible fluids and the incompressibility is achieved by the equation of state. The sediment phase is modeled as a non-Newtonian fluid using three alternative approaches of artificial viscosity and Bingham Model. In this paper, the new formulations for two-phase flows are proposed. The numerical results obtained from the developed SPH model show acceptable accuracy with comparison to experimental data.

  20. Signals of the QGP phase transition - a view from microscopic transport models

    CERN Document Server

    Bratkovskaya, E L

    2007-01-01

    In this contribution the results from various transport models on different observables - considered as possible signals of the phase transition from hadronic matter to the quark-gluon plasma (QGP) - are briefly reviewed.

  1. IDC Re-Engineering Phase 2 Data Model to IDC Schema Mapping.

    Energy Technology Data Exchange (ETDEWEB)

    Hamlet, Benjamin R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Montoya, Mark Sinclair [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandoval, Rudy Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vickers, James Wallace [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    This initial draft document contains formative data model content for select areas of Re-Engineering Phase 2 IDC System. The purpose of this document is to facilitate discussion among the stakeholders. It is not intended as a definitive proposal.

  2. Analysis of Data on Xanthan Fermentation in Stationary Phase Using Black Box and Metabolic Network Models

    Institute of Scientific and Technical Information of China (English)

    马红武; 赵学明; 唐寅杰

    1999-01-01

    The xanthan fermentation data in the stationary phase was analyzed using the black box and the metabolic network models. The data consistency ls checked through the elemental balance in the black box model. In the metabolic network model, the metabolic flux distribution in the cell is calculated using the metabolic flux analysis method, then the maintenance coefficients is calculated.

  3. Brittle fracture phase-field modeling of a short-rod specimen

    Energy Technology Data Exchange (ETDEWEB)

    Escobar, Ivana [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tupek, Michael R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bishop, Joseph E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Predictive simulation capabilities for modeling fracture evolution provide further insight into quantities of interest in comparison to experimental testing. Based on the variational approach to fracture, the advent of phase-field modeling achieves the goal to robustly model fracture for brittle materials and captures complex crack topologies in three dimensions.

  4. Modeling of soft impingement effect during solid-state partitioning phase transformations in binary alloys

    NARCIS (Netherlands)

    Chen, H.; Van der Zwaag, S.

    2010-01-01

    The soft impingement effect at the later stage of partitioning phase transformations has been modeled both for the diffusion-controlled growth model and for the mixed-mode model. Instead of the linear and exponential approximations for the concentration gradient in front of the interface used in the

  5. Procedural Modeling for Rapid-Prototyping of Multiple Building Phases

    Science.gov (United States)

    Saldana, M.; Johanson, C.

    2013-02-01

    RomeLab is a multidisciplinary working group at UCLA that uses the city of Rome as a laboratory for the exploration of research approaches and dissemination practices centered on the intersection of space and time in antiquity. In this paper we present a multiplatform workflow for the rapid-prototyping of historical cityscapes through the use of geographic information systems, procedural modeling, and interactive game development. Our workflow begins by aggregating archaeological data in a GIS database. Next, 3D building models are generated from the ArcMap shapefiles in Esri CityEngine using procedural modeling techniques. A GIS-based terrain model is also adjusted in CityEngine to fit the building elevations. Finally, the terrain and city models are combined in Unity, a game engine which we used to produce web-based interactive environments which are linked to the GIS data using keyhole markup language (KML). The goal of our workflow is to demonstrate that knowledge generated within a first-person virtual world experience can inform the evaluation of data derived from textual and archaeological sources, and vice versa.

  6. IAEA CRP on HTGR Uncertainties in Modeling: Assessment of Phase I Lattice to Core Model Uncertainties

    Energy Technology Data Exchange (ETDEWEB)

    Rouxelin, Pascal Nicolas [Idaho National Lab. (INL), Idaho Falls, ID (United States); Strydom, Gerhard [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-09-01

    Best-estimate plus uncertainty analysis of reactors is replacing the traditional conservative (stacked uncertainty) method for safety and licensing analysis. To facilitate uncertainty analysis applications, a comprehensive approach and methodology must be developed and applied. High temperature gas cooled reactors (HTGRs) have several features that require techniques not used in light-water reactor analysis (e.g., coated-particle design and large graphite quantities at high temperatures). The International Atomic Energy Agency has therefore launched the Coordinated Research Project on HTGR Uncertainty Analysis in Modeling to study uncertainty propagation in the HTGR analysis chain. The benchmark problem defined for the prismatic design is represented by the General Atomics Modular HTGR 350. The main focus of this report is the compilation and discussion of the results obtained for various permutations of Exercise I 2c and the use of the cross section data in Exercise II 1a of the prismatic benchmark, which is defined as the last and first steps of the lattice and core simulation phases, respectively. The report summarizes the Idaho National Laboratory (INL) best estimate results obtained for Exercise I 2a (fresh single-fuel block), Exercise I 2b (depleted single-fuel block), and Exercise I 2c (super cell) in addition to the first results of an investigation into the cross section generation effects for the super-cell problem. The two dimensional deterministic code known as the New ESC based Weighting Transport (NEWT) included in the Standardized Computer Analyses for Licensing Evaluation (SCALE) 6.1.2 package was used for the cross section evaluation, and the results obtained were compared to the three dimensional stochastic SCALE module KENO VI. The NEWT cross section libraries were generated for several permutations of the current benchmark super-cell geometry and were then provided as input to the Phase II core calculation of the stand alone neutronics Exercise

  7. Model investigation of non-thermal phase transition in high energy collisions

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The non-thermal phase transition in high energy collisions is studied in detail in the framework of random cascade model. The relation between the characteristic parameter λq of phase transition and the rank q of moment is obtained using Monte Carlo simulation, and the existence of two phases in self-similar cascading multiparticle systems is shown. The relation between the critical point qc of phase transition on the fluctuation parameter α is obtained and compared with the experimental results from NA22. The same study is carried out also by analytical calculation under central limit approximation. The range of validity of the central limit approximation is discussed.

  8. Finite Element Modeling of Five Phase Permanent Magnet BLDC Motor for High Power Density Application

    Directory of Open Access Journals (Sweden)

    Kiran George

    2013-12-01

    Full Text Available Fault-tolerant capability of electrical motor drives is an essential feature in applications such as automotive, aeronautic, and many others. A multi-phase permanent-magnet BLDC motor exhibits a high fault tolerant capability hence increasing the reliability, as it can be designed to reduce the fault occurrence as well as to operate indefinitely in the presence of fault. With multi independent phases, in the event of failure of one or more, the remaining healthy phases let the motor to operate properly. This paper presents finite element modeling and results of a five-phase permanent magnet brushless motor designed for high power density application .

  9. Estimation of flow velocity for a debris flow via the two-phase fluid model

    Directory of Open Access Journals (Sweden)

    S. Guo

    2014-06-01

    Full Text Available The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

  10. Locally self-similar phase diagram of the disordered Potts model on the hierarchical lattice.

    Science.gov (United States)

    Anglès d'Auriac, J-Ch; Iglói, Ferenc

    2013-02-01

    We study the critical behavior of the random q-state Potts model in the large-q limit on the diamond hierarchical lattice with an effective dimensionality d(eff)>2. By varying the temperature and the strength of the frustration the system has a phase transition line between the paramagnetic and the ferromagnetic phases which is controlled by four different fixed points. According to our renormalization group study the phase boundary in the vicinity of the multicritical point is self-similar; it is well represented by a logarithmic spiral. We expect an infinite number of reentrances in the thermodynamic limit; consequently one cannot define standard thermodynamic phases in this region.

  11. Ground-State Phase Diagram of Transverse Spin-2 Ising Model with Longitudinal Crystal-Field

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The transverse spin-2 Ising ferromagnetic model with a longitudinal crystal-field is studied within the mean-field theory based on Bogoliubov inequality for the Gibbs free energy. The ground-state phase diagram and the tricritical point are obtained in the transverse field Ω/z J-longitudinal crystal D/zJ field plane. We find that there are the first order-order phase transitions in a very smallrange of D/zJ besides the usual first order-disorder phase transitions and the second order-disorder phase transitions.

  12. Model Based Control of Single-Phase Marine Cooling Systems

    DEFF Research Database (Denmark)

    Hansen, Michael

    2014-01-01

    ”, it is shown that the part of the proposed model relating to the thermodynamics is dynamically accurate and with relatively small steady state deviations. The same is shown for a linear version of the part of the model governing the hydraulics of the cooling system. On the subject of control, the main focus...... in this work is on the development of a nonlinear robust control design. The design is based on principles from feedback. linearization to compensate for nonlinearities as well as transport delays by including a delay estimate in the feedback law. To deal with the uncertainties that emerged from the feedback...

  13. A kinetic model for the burst phase of processive cellulases

    DEFF Research Database (Denmark)

    Præstgaard, Eigil; Olsen, Jens Elmerdahl; Murphy, Leigh;

    2011-01-01

    of the model, which can be solved analytically, shows that the burst and slowdown can be explained by the relative rates of the sequential reactions in the hydrolysis process and the occurrence of obstacles for the processive movement along the cellulose strand. More specifically, the maximum enzyme activity...... reflects a balance between a rapid processive movement, on the one hand, and a slow release of enzyme which is stalled by obstacles, on the other. This model only partially accounts for the experimental data, and we therefore also test a modified version that takes into account random enzyme inactivation...

  14. On the stable discretization of strongly anisotropic phase field models with applications to crystal growth

    CERN Document Server

    Barrett, John W; Nürnberg, Robert

    2012-01-01

    We introduce unconditionally stable finite element approximations for anisotropic Allen--Cahn and Cahn--Hilliard equations. These equations frequently feature in phase field models that appear in materials science. On introducing the novel fully practical finite element approximations we prove their stability and demonstrate their applicability with some numerical results. We dedicate this article to the memory of our colleague and friend Christof Eck (1968--2011) in recognition of his fundamental contributions to phase field models.

  15. A WEAKLY NONLINEAR WATER WAVE MODEL TAKING INTO ACCOUNT DISPERSION OF WAVE PHASE VELOCITY

    Institute of Scientific and Technical Information of China (English)

    李瑞杰; 李东永

    2002-01-01

    This paper presents a weakly nonlinear water wave model using a mild slope equation and a new explicit formulation which takes into account dispersion of wave phase velocity, approximates Hedges' (1987) nonlinear dispersion relationship, and accords well with the original empirical formula. Comparison of the calculating results with those obtained from the experimental data and those obtained from linear wave theory showed that the present water wave model considering the dispersion of phase velocity is rational and in good agreement with experiment data.

  16. Striped periodic minimizers of a two-dimensional model for martensitic phase transitions

    CERN Document Server

    Giuliani, Alessandro

    2010-01-01

    In this paper we consider a simplified two-dimensional scalar model for the formation of mesoscopic domain patterns in martensitic shape-memory alloys at the interface between a region occupied by the parent (austenite) phase and a region occupied by the product (martensite) phase, which can occur in two variants (twins). The model, first proposed by Kohn and Mueller, is defined by the following functional:

  17. Quantum phase transitions in the bosonic single-impurity Anderson model

    Science.gov (United States)

    Lee, H.-J.; Bulla, R.

    2007-04-01

    We consider a quantum impurity model in which a bosonic impurity level is coupled to a non-interacting bosonic bath, with the bosons at the impurity site subject to a local Coulomb repulsion U. Numerical renormalization group calculations for this bosonic single-impurity Anderson model reveal a zero-temperature phase diagram where Mott phases with reduced charge fluctuations are separated from a Bose-Einstein condensed phase by lines of quantum critical points. We discuss possible realizations of this model, such as atomic quantum dots in optical lattices. Furthermore, the bosonic single-impurity Anderson model appears as an effective impurity model in a dynamical mean-field theory of the Bose-Hubbard model.

  18. Modeling of phase equilibria with CPA using the homomorph approach

    DEFF Research Database (Denmark)

    Breil, Martin Peter; Tsivintzelis, Ioannis; Kontogeorgis, Georgios

    2011-01-01

    For association models, like CPA and SAFT, a classical approach is often used for estimating pure-compound and mixture parameters. According to this approach, the pure-compound parameters are estimated from vapor pressure and liquid density data. Then, the binary interaction parameters, kij, are ...

  19. Model validation studies of solar systems, Phase III. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lantz, L.J.; Winn, C.B.

    1978-12-01

    Results obtained from a validation study of the TRNSYS, SIMSHAC, and SOLCOST solar system simulation and design are presented. Also included are comparisons between the FCHART and SOLCOST solar system design programs and some changes that were made to the SOLCOST program. Finally, results obtained from the analysis of several solar radiation models are presented. Separate abstracts were prepared for ten papers.

  20. Mathematical modelling of ultrasound propagation in multi-phase flow

    DEFF Research Database (Denmark)

    Simurda, Matej

    2017-01-01

    . Acoustic media are modelled by setting the shear modulus to zero. Spatial derivatives are approximated by a Fourier collocation method allowing the use of the Fast Fourier transform while the time integration is realized by the explicit fourth order Runge-Kutta finite difference scheme. The method...

  1. Building information modeling in the architectural design phases

    DEFF Research Database (Denmark)

    Hermund, Anders

    2009-01-01

    with an architectural quality? In Denmark the implementation of the digital working methods related to BIM has been introduced by government law in 2007. Will the important role of the architect as designer change in accordance with these new methods, and does the idea of one big integrated model represent a paradox...... in relation to designing? The BIM mindset requires changes on many levels....

  2. Phase transitions in a spinless, extended Falicov-Kimball model on the triangular lattice

    Science.gov (United States)

    Yadav, Umesh K.; Maitra, T.; Singh, Ishwar

    2013-06-01

    A numerical diagonalization technique with canonical Monte-Carlo simulation algorithm is used to study the phase transitions from low temperature (ordered) phase to high temperature (disordered) phase of spinless Falicov-Kimball model on a triangular lattice with correlated hopping (t'). It is observed that the low temperature ordered phases (i.e. regular, bounded and segregated) persist up to a finite critical temperature (Tc). In addition, we observe that the critical temperature decreases with increasing the correlated hopping in regular and bounded phases whereas it increases in the segregated phase. Single and multi peak patterns seen in the temperature dependence of specific heat (Cv) and charge susceptibility (χ) for different values of parameters like on-site Coulomb correlation strength (U), correlated hopping (t') and filling of localized electrons (nf) are also discussed.

  3. The fluctuational region on the phase diagram of lattice Weinberg - Salam model

    CERN Document Server

    Zubkov, M A

    2009-01-01

    The lattice Weinberg - Salam model without fermions is investigated numerically for the realistic choice of bare coupling constants correspondent to the value of the Weinberg angle $\\theta_W \\sim 30^o$, and the fine structure constant $\\alpha \\sim {1/100}$. On the phase diagram there exists the vicinity of the phase transition between the physical Higgs phase and the unphysical symmetric phase, where the fluctuations of the scalar field become strong. The classical Nambu monopole can be considered as an embryo of the unphysical symmetric phase within the physical phase. In the fluctuational region quantum Nambu monopoles are dense and, therefore, the perturbation expansion around trivial vacuum cannot be applied. The maximal value of the cutoff at the given values of coupling constants calculated using the lattices of sizes $8^3\\times 16$ and $12^3\\times 16$ is $\\Lambda_c \\sim 1.4 \\pm 0.2$ Tev.

  4. RCS estimation of linear and planar dipole phased arrays approximate model

    CERN Document Server

    Singh, Hema; Jha, Rakesh Mohan

    2016-01-01

    In this book, the RCS of a parallel-fed linear and planar dipole array is derived using an approximate method. The signal propagation within the phased array system determines the radar cross section (RCS) of phased array. The reflection and transmission coefficients for a signal at different levels of the phased-in scattering array system depend on the impedance mismatch and the design parameters. Moreover the mutual coupling effect in between the antenna elements is an important factor. A phased array system comprises of radiating elements followed by phase shifters, couplers, and terminating load impedance. These components lead to respective impedances towards the incoming signal that travels through them before reaching receive port of the array system. In this book, the RCS is approximated in terms of array factor, neglecting the phase terms. The mutual coupling effect is taken into account. The dependence of the RCS pattern on the design parameters is analyzed. The approximate model is established as a...

  5. Phase diagram determination and thermodynamic modeling of the Cu-Mg-Si system

    Directory of Open Access Journals (Sweden)

    Zhao J.

    2016-01-01

    Full Text Available 13 ternary Cu-Mg-Si alloys were prepared by means of the powder metallurgy method. Phase equilibria at 500 and 700 oC of the Cu-Mg-Si system were determined using X-ray diffraction analysis (XRD. The existence of 3 ternary compounds in this system was verified: CuMgSi_Sigma (Cu16Mg6Si7, Tau (Cu3Mg2Si, and Laves ((Cu0.8Si0.22(Mg0.88Cu0.12. A thermodynamic modeling for the Cu-Mg-Si system was then conducted on the basis of the experimental data obtained in this work and those critically reviewed from the literature. The complex phase relationship between Laves phase and other phases has been successfully modeled in this work. Comparisons between the calculated and the measured phase diagrams show that most of the experimental data can be reproduced by the presently obtained thermodynamic parameters.

  6. Numerical simulation of the two-phase flows in a hydraulic coupling by solving VOF model

    Science.gov (United States)

    Luo, Y.; Zuo, Z. G.; Liu, S. H.; Fan, H. G.; Zhuge, W. L.

    2013-12-01

    The flow in a partially filled hydraulic coupling is essentially a gas-liquid two-phase flow, in which the distribution of two phases has significant influence on its characteristics. The interfaces between the air and the liquid, and the circulating flows inside the hydraulic coupling can be simulated by solving the VOF two-phase model. In this paper, PISO algorithm and RNG k-ɛ turbulence model were employed to simulate the phase distribution and the flow field in a hydraulic coupling with 80% liquid fill. The results indicate that the flow forms a circulating movement on the torus section with decreasing speed ratio. In the pump impeller, the air phase mostly accumulates on the suction side of the blades, while liquid on the pressure side; in turbine runner, air locates in the middle of the flow passage. Flow separations appear near the blades and the enclosing boundaries of the hydraulic coupling.

  7. Phase Diagram of the Frustrated Square-Lattice Hubbard Model: Variational Cluster Approach

    Science.gov (United States)

    Misumi, Kazuma; Kaneko, Tatsuya; Ohta, Yukinori

    2016-06-01

    The variational cluster approximation is used to study the frustrated Hubbard model at half filling defined on the two-dimensional square lattice with anisotropic next-nearest-neighbor hopping parameters. We calculate the ground-state phase diagrams of the model in a wide parameter space for a variety of lattice geometries, including square, crossed-square, and triangular lattices. We examine the Mott metal-insulator transition and show that, in the Mott insulating phase, magnetic phases with Néel, collinear, and spiral orders appear in relevant parameter regions, and in an intermediate region between these phases, a nonmagnetic insulating phase caused by the quantum fluctuations in the geometrically frustrated spin degrees of freedom emerges.

  8. A new two-phase erosion-deposition model for mass flows

    Science.gov (United States)

    Pudasaini, Shiva P.; Fischer, Jan-Thomas

    2016-04-01

    Erosion, entrainment and deposition are complex and dominant, but yet poorly understood, mechanical processes in geophysical mass flows. Here, we propose a novel, two-phase, erosion-deposition model capable of adequately describing these complex phenomena commonly observed in landslides, avalanches, debris flows and bedload transports. The model enhances an existing general two-phase mass flow model (Pudasaini, 2012) by introducing a two-phase variably saturated erodible basal morphology. The adaptive basal morphology allows for the evolution of erosion-deposition-depths, incorporating the inherent physical process and rheological changes of the flowing mixture. With rigorous derivation, we show that appropriate incorporation of the mass and momentum productions and losses in conservative model formulation is essential for the physically correct and mathematically consistent description of erosion-entrainment-deposition processes. Simulation indicates a sharp erosion-front and steady-state-rear erosion depth. The model appropriately captures the emergence and propagation of complex frontal surge dynamics associated with the frontal ambient-drag which is a new hypothesis associated with erosion. The novel enhanced real two-phase model also allows for simulating fluid-run-off during the deposition process. The model resembles laboratory experiments for particle-fluid mixture flows and reveals some major aspects of the mechanics associated with erosion, entrainment and deposition. Reference: Shiva P. Pudasaini (2012): A general two-phase debris flow model. J. Geophys. Res., 117, F03010, doi: 10.1029/2011JF002186.

  9. Characteristics of QCD phase transitions in an extended Skyrme model on S$^{3}$

    CERN Document Server

    Kim, J H; Lee, H K; Kim, Joon Ha; Yee, Sooman; Lee, Hyun Kyu

    1994-01-01

    We study the characteristics of the QCD phase transitions in dense hadronic matter using the Skyrme model constructed on S^3. We find numerically the localized solutions on S^3 using the extended Skyrme model which implements correctly the scale symmetry of QCD. The transition from the localized phase to the delocalized phase is found to be of first order at the critical radius of the hypersphere, L_c. The chiral restoration and the gluon decondensation also take place at the same critical size.

  10. Finite-size scaling analysis of a nonequilibrium phase transition in the naming game model

    Science.gov (United States)

    Brigatti, E.; Hernández, A.

    2016-11-01

    We realize an extensive numerical study of the naming game model with a noise term which accounts for perturbations. This model displays a nonequilibrium phase transition between an absorbing ordered consensus state, which occurs for small noise, and a disordered phase with fragmented clusters characterized by heterogeneous memories, which emerges at strong noise levels. The nature of the phase transition is studied by means of a finite-size scaling analysis of the moments. We observe a scaling behavior typical of a discontinuous transition and we are able to estimate the thermodynamic limit. The scaling behavior of the clusters size seems also compatible with this kind of transition.

  11. Finite size scaling analysis of a nonequilibrium phase transition in the naming game model

    CERN Document Server

    Brigatti, E

    2016-01-01

    We realize an extensive numerical study of the Naming Game model with a noise term which accounts for perturbations. This model displays a non-equilibrium phase transition between an absorbing ordered consensus state, which occurs for small noise, and a disordered phase with fragmented clusters characterized by heterogeneous memories, which emerges at strong noise levels. The nature of the phase transition is studied by means of a finite-size scaling analysis of the moments. We observe a scaling behavior typical of a discontinuous transition and we are able to estimate the thermodynamic limit. The scaling behavior of the clusters size seems also compatible with this kind of transition.

  12. Experimentally enhanced model-based deconvolution of propagation-based phase-contrast data

    Science.gov (United States)

    Pichotka, M.; Palma, K.; Hasn, S.; Jakubek, J.; Vavrik, D.

    2016-12-01

    In recent years phase-contrast has become a much investigated modality in radiographic imaging. The radiographic setups employed in phase-contrast imaging are typically rather costly and complex, e.g. high performance Talbot-Laue interferometers operated at synchrotron light sources. In-line phase-contrast imaging states the most pedestrian approach towards phase-contrast enhancement. Utilizing small angle deflection within the imaged sample and the entailed interference of the deflected and un-deflected beam during spatial propagation, in-line phase-contrast imaging only requires a well collimated X-ray source with a high contrast & high resolution detector. Employing high magnification the above conditions are intrinsically fulfilled in cone-beam micro-tomography. As opposed of 2D imaging, where contrast enhancement is generally considered beneficial, in tomographic modalities the in-line phase-contrast effect can be quite a nuisance since it renders the inverse problem posed by tomographic reconstruction inconsistent, thus causing reconstruction artifacts. We present an experimentally enhanced model-based approach to disentangle absorption and in-line phase-contrast. The approach employs comparison of transmission data to a system model computed iteratively on-line. By comparison of the forward model to absorption data acquired in continuous rotation strong local deviations of the data residual are successively identified as likely candidates for in-line phase-contrast. By inducing minimal vibrations (few mrad) to the sample around the peaks of such deviations the transmission signal can be decomposed into a constant absorptive fraction and an oscillating signal caused by phase-contrast which again allows to generate separate maps for absorption and phase-contrast. The contributions of phase-contrast and the corresponding artifacts are subsequently removed from the tomographic dataset. In principle, if a 3D handling of the sample is available, this method also

  13. Modeling acoustic attenuation of soft tissue with a minimum-phase filter.

    Science.gov (United States)

    Kuc, R

    1984-01-01

    Soft biological tissue has been observed to exhibit an acoustic attenuation log-magnitude characteristic which increases as an approximately linear function of frequency. This paper describes the implementation of a finite-impulse-response (FIR) digital filter model for simulating this behavior on a digital computer. To insure that the filter is causal, the minimum-phase constraint is imposed. For minimum-phase filters, the log-magnitude and phase characteristics form a Hilbert Transform pair. The discrete-time Hilbert Transform of the linear log-magnitude characteristic was evaluated to determine the phase of the filter. The inverse Fourier Transform of the resulting real and imaginary components of the frequency transform produces the finite-duration unit-sample response of the digital filter model. Experimental results using plexiglas material, which has a linear-with-frequency loss characteristic, indicate that the minimum-phase model is more accurate than the linear-phase model, resulting in a rms error between predicted and observed time waveforms that is 3 times smaller. The effects of varying the sampling period and the size of the FIR filter are discussed. A FORTRAN program to calculate the minimum-phase unit-sample response from the slope of the log-magnitude characteristic is included in the Appendix.

  14. Detecting Gait Phases from RGB-D Images Based on Hidden Markov Model.

    Science.gov (United States)

    Heravi, Hamed; Ebrahimi, Afshin; Olyaee, Ehsan

    2016-01-01

    Gait contains important information about the status of the human body and physiological signs. In many medical applications, it is important to monitor and accurately analyze the gait of the patient. Since walking shows the reproducibility signs in several phases, separating these phases can be used for the gait analysis. In this study, a method based on image processing for extracting phases of human gait from RGB-Depth images is presented. The sequence of depth images from the front view has been processed to extract the lower body depth profile and distance features. Feature vector extracted from image is the same as observation vector of hidden Markov model, and the phases of gait are considered as hidden states of the model. After training the model using the images which are randomly selected as training samples, the phase estimation of gait becomes possible using the model. The results confirm the rate of 60-40% of two major phases of the gait and also the mid-stance phase is recognized with 85% precision.

  15. Asymptotic formation and orbital stability of phase-locked states for the Kuramoto model

    Science.gov (United States)

    Choi, Young-Pil; Ha, Seung-Yeal; Jung, Sungeun; Kim, Yongduck

    2012-04-01

    We discuss the asymptotic formation and nonlinear orbital stability of phase-locked states arising from the ensemble of non-identical Kuramoto oscillators. We provide an explicit lower bound for a coupling strength on the formation of phase-locked states, which only depends on the diameters of natural frequencies and initial phase configurations. We show that, when the phases of non-identical oscillators are distributed over the half circle and the coupling strength is sufficiently large, the dynamics of Kuramoto oscillators exhibits two stages (transition and relaxation stages). In a transition stage, initial configurations shrink to configurations whose diameters are strictly less than {π}/{2} in a finite-time, and then the configurations tend to phase-locked states asymptotically. This improves previous results on the formation of phase-locked states by Chopra-Spong (2009) [26] and Ha-Ha-Kim (2010) [27] where their attention were focused only on the latter relaxation stage. We also show that the Kuramoto model is ℓ1-contractive in the sense that the ℓ1-distance along two smooth Kuramoto flows is less than or equal to that of initial configurations. In particular, when two initial configurations have the same averaged phases, the ℓ1-distance between them decays to zero exponentially fast. For the configurations with different phase averages, we use the method of average adjustment and translation-invariant of the Kuramoto model to show that one solution converges to the translation of the other solution exponentially fast. This establishes the orbital stability of the phase-locked states. Our stability analysis does not employ any standard linearization technique around the given phase-locked states, but instead, we use a robust ℓ1-metric functional as a Lyapunov functional. In the formation process of phase-locked states, we estimate the number of collisions between oscillators, and lower-upper bounds of the transversal phase differences.

  16. Phase Equilibria of Water/CO2 and Water/n-Alkane Mixtures from Polarizable Models.

    Science.gov (United States)

    Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2017-02-16

    Phase equilibria of water/CO2 and water/n-alkane mixtures over a range of temperatures and pressures were obtained from Monte Carlo simulations in the Gibbs ensemble. Three sets of Drude-type polarizable models for water, namely the BK3, GCP, and HBP models, were combined with a polarizable Gaussian charge CO2 (PGC) model to represent the water/CO2 mixture. The HBP water model describes hydrogen bonds between water and CO2 explicitly. All models underestimate CO2 solubility in water if standard combining rules are used for the dispersion interactions between water and CO2. With the dispersion parameters optimized to phase compositions, the BK3 and GCP models were able to represent the CO2 solubility in water, however, the water composition in CO2-rich phase is systematically underestimated. Accurate representation of compositions for both water- and CO2-rich phases cannot be achieved even after optimizing the cross interaction parameters. By contrast, accurate compositions for both water- and CO2-rich phases were obtained with hydrogen bonding parameters determined from the second virial coefficient for water/CO2. Phase equilibria of water/n-alkane mixtures were also studied using the HBP water and an exponenial-6 united-atom n-alkanes model. The dispersion interactions between water and n-alkanes were optimized to Henry's constants of methane and ethane in water. The HBP water and united-atom n-alkane models underestimate water content in the n-alkane-rich phase; this underestimation is likely due to the neglect of electrostatic and induction energies in the united-atom model.

  17. Modelling of two-phase flow based on separation of the flow according to velocity

    Energy Technology Data Exchange (ETDEWEB)

    Narumo, T. [VTT Energy, Espoo (Finland). Nuclear Energy

    1997-12-31

    The thesis concentrates on the development work of a physical one-dimensional two-fluid model that is based on Separation of the Flow According to Velocity (SFAV). The conventional way to model one-dimensional two-phase flow is to derive conservation equations for mass, momentum and energy over the regions occupied by the phases. In the SFAV approach, the two-phase mixture is divided into two subflows, with as distinct average velocities as possible, and momentum conservation equations are derived over their domains. Mass and energy conservation are treated equally with the conventional model because they are distributed very accurately according to the phases, but momentum fluctuations follow better the flow velocity. Submodels for non-uniform transverse profile of velocity and density, slip between the phases within each subflow and turbulence between the subflows have been derived. The model system is hyperbolic in any sensible flow conditions over the whole range of void fraction. Thus, it can be solved with accurate numerical methods utilizing the characteristics. The characteristics agree well with the used experimental data on two-phase flow wave phenomena Furthermore, the characteristics of the SFAV model are as well in accordance with their physical counterparts as of the best virtual-mass models that are typically optimized for special flow regimes like bubbly flow. The SFAV model has proved to be applicable in describing two-phase flow physically correctly because both the dynamics and steady-state behaviour of the model has been considered and found to agree well with experimental data This makes the SFAV model especially suitable for the calculation of fast transients, taking place in versatile form e.g. in nuclear reactors. 45 refs. The thesis includes also five previous publications by author.

  18. Extended Group Contribution Model for Polyfunctional Phase Equilibria

    DEFF Research Database (Denmark)

    Abildskov, Jens

    -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...... polyfunctional group situations, based on additional information on molecular structure. The extension involves the addition of second-order correction terms to the existing equation. In this way the current first-order formulation is retained. The second-order concept is developed for mixture properties based....... In chapter 4 parameters are estimated for the first-order UNIFAC model, based on which parameters are estimated for one of the second-order models described in chapter 3. The parameter estimation is based on measured binary data on around 4000 systems, covering 11 C-, H- and O-containing functional groups...

  19. Collins Model and Phase Diagram of 2D Ternary System

    Institute of Scientific and Technical Information of China (English)

    XIE Chuan-Mei; CHEN Li-Rong

    2004-01-01

    The Collins model is introduced into the two-dimensional (2D) alternative ternary system having the Lennard-Jones (L-J) potential. The Gibbs free energy of this ternary system is calculated, and according to thermodynamic theory, a group of equations that determine the solid-liquid diagram of ternary system are derived, some isothermal sectional diagrams of the 2D ternary system are obtained. The results are quite similar to the behavior of three-dimensional substances.

  20. 2014 Enhanced LAW Glass Property-Composition Models, Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Muller, Isabelle [The Catholic Univ. of America, Washington, DC (United States); Pegg, Ian L. [The Catholic Univ. of America, Washington, DC (United States); Joseph, Innocent [Energy Solutions, Salt Lake City, UT (United States); Gilbo, Konstantin [The Catholic Univ. of America, Washington, DC (United States)

    2015-10-28

    This report describes the results of testing specified by the Enhanced LAW Glass Property-Composition Models, VSL-13T3050-1, Rev. 0 Test Plan. The work was performed in compliance with the quality assurance requirements specified in the Test Plan. Results required by the Test Plan are reported. The te4st results and this report have been reviewed for correctness, technical adequacy, completeness, and accuracy.

  1. Multi-Phase Modeling of Rainbird Water Injection

    Science.gov (United States)

    Vu, Bruce T.; Moss, Nicholas; Sampson, Zoe

    2014-01-01

    This paper describes the use of a Volume of Fluid (VOF) multiphase model to simulate the water injected from a rainbird nozzle used in the sound suppression system during launch. The simulations help determine the projectile motion for different water flow rates employed at the pad, as it is critical to know if water will splash on the first-stage rocket engine during liftoff.

  2. Zero phase sequence impedance and tank heating model for three phase three leg core type power transformers coupling magnetic field and electric circuit equations in finite element software

    Energy Technology Data Exchange (ETDEWEB)

    Ngnegueu, T.; Mailhot, M.; Munar, A. [Jeumont Schneider Transformateurs, Lyon (France); Sacotte, M. [France-Transfo. Voie romaine, Mezieres-Les-Metz (France)

    1995-05-01

    In this paper, the authors present a finite element model for the calculation of zero phase sequence reactance for three phase three leg core type power transformers. An axisymmetrical approximation is assumed. A simplified model is used to assess the tank`s hottest spot temperature.

  3. Phase-Field and Korteweg-Type Models for the Time-Dependent Flow of Compressible Two-Phase Fluids

    Science.gov (United States)

    Freistühler, Heinrich; Kotschote, Matthias

    2016-11-01

    Various versions of the Navier-Stokes-Allen-Cahn (NSAC), the Navier-Stokes-Cahn-Hilliard (NSCH), and the Navier-Stokes-Korteweg (NSK) equations have been used in the literature to model the dynamics of two-phase fluids. One main purpose of this paper consists in (re-)deriving NSAC, NSCH and NSK from first principles, in the spirit of rational mechanics, for fluids of very general constitutive laws. For NSAC, this deduction confirms and extends a proposal of Blesgen. Regarding NSCH, it continues work of Lowengrub and Truskinovsky and provides the apparently first justified formulation in the non-isothermal case. For NSK, it yields a most natural correction to the formulation by Dunn and Serrin. The paper uniformly recovers as examples various classes of fluids, distinguished according to whether none, one, or both of the phases are compressible, and according to the nature of their co-existence. The latter is captured not only by the mixing energy, but also by a `mixing rule'—a constitutive law that characterizes the type of the mixing. A second main purpose of the paper is to communicate the apparently new observation that in the case of two immiscible incompressible phases of different temperature-independent specific volumes, NSAC reduces literally to NSK. This finding may be considered as an independent justification of NSK. An analogous fact is shown for NSCH, which under the same assumption reduces to a new non-local version of NSK.

  4. Thermodynamics and phase structure of the Polyakov-Quark-Meson model

    Energy Technology Data Exchange (ETDEWEB)

    Braun, Jens [Institut fuer Kernphysik (Theoriezentrum), Technische Universitaet Darmstadt (Germany); ExtreMe Matter Institute EMMI, GSI (Germany); Fraga, Eduardo S. [Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil); Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt (Germany); Haas, Lisa M.; Pawlowski, Jan M. [Institut fuer Theoretische Physik, Universitaet Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI (Germany); Herbst, Tina K.; Stiele, Rainer [Institut fuer Theoretische Physik, Universitaet Heidelberg (Germany); Mintz, Bruno W.; Ramos, Rudnei O. [Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro (Brazil); Mitter, Mario [Institut fuer Theoretische Physik, Universitaet Heidelberg (Germany); Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt (Germany); Schaefer, Bernd-Jochen [Institut fuer Theoretische Physik, Justus-Liebig-Universitaet Giessen (Germany); Institut fuer Physik, Karl-Franzens-Universitaet Graz (Austria); Schaffner-Bielich, Juergen [Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt (Germany)

    2014-07-01

    Polyakov-loop extended chiral effective models are important tools to describe the phase structure and thermodynamics of strongly interacting matter. We show that taking into account the backreaction of quarks onto the gauge sector is crucial in such models to achieve results for the order parameters and thermodynamics that are in line with lattice calculations. Achieving a good description of lattice data at zero density, we test the reliability of those models in systems containing other control parameters besides the temperature by confronting its results with lattice data at nonzero isospin. Furthermore, we investigate the phase structure of the three-dimensional T-μ{sub isospin}-μ{sub quark} phase diagram and calculate the surface tension of the first order phase transition at small temperatures and large quark densities.

  5. A 3-phase model for mixed columnar-equiaxed solidification in DC casting of bronze

    Science.gov (United States)

    Hao, J.; Grasser, M.; Wu, M.; Ludwig, A.; Riedle, J.; Eberle, R.

    2012-01-01

    A three-phase Eulerian approach is used to model the columnar-to-equiaxed transition (CET) during solidification in DC casting of technical bronze. The three phases are the melt, the solidifying columnar dendrites and the equiaxed grains. They are considered as spatially interpenetrating and interacting continua by solving the conservation equations of mass, momentum, species and enthalpy for all three phases. The so defined solidification model is applied to a binary CuSn6 DC casting process as a benchmark to demonstrate the model potentials. Two cases are studied: one considering only feeding flow and one including both feeding flow and equiaxed sedimentation. The simulated results of mixed columnar and equiaxed solidification are presented and discussed including the occurrence of CET, phase distribution, feeding flow, equiaxed sedimentation and their influence on macrosegregation.

  6. Numerical model of phase transformation of steel C80U during hardening

    Directory of Open Access Journals (Sweden)

    T. Domański

    2007-12-01

    Full Text Available The article concerns numerical modelling of the phase transformations in solid state hardening of tool steel C80U. The transformations were assumed: initial structure – austenite, austenite – perlite, bainite and austenite – martensite. Model for evaluation of fractions of phases and their kinetics based on continuous heating diagram (CHT and continuous cooling diagram (CCT. The dilatometric tests on the simulator of thermal cycles were performed. The results of dilatometric tests were compared with the results of the test numerical simulations. In this way the derived models for evaluating phase content and kinetics of transformations in heating and cooling processes were verified. The results of numerical simulations confirm correctness of the algorithm that were worked out. In the numerical example the simulated estimation of the phase fraction in the hardened axisimmetrical element was performed.

  7. Modelling production system architectures in the early phases of product development

    DEFF Research Database (Denmark)

    Guðlaugsson, Tómas Vignir; Martin Ravn, Poul; Mortensen, Niels Henrik;

    2016-01-01

    on – leading to an improved basis for prioritizing activities in the project. Requirements for the contents of the framework are presented, and literature on production and system models is reviewed. The production system architecture modelling framework is founded on methods and approaches in literature......This article suggests a framework for modelling a production system architecture in the early phases of product development.The challenge in these phases is that the products to be produced are not completely defined and yet decisions need to be made early in the process on what investments...... and adjusted to fit the modelling requirements of a production system architecture at an early phase of development. The production system architecture models capture and describe the structure, capabilities and expansions of the production system architecture underdevelopment. The production system...

  8. A Unified Impedance Model of Voltage-Source Converters with Phase-Locked Loop Effect

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Harnefors, Lennart; Blaabjerg, Frede

    2016-01-01

    This paper proposes a unified impedance model for analyzing the effect of Phase-Locked Loop (PLL) on the stability of grid-connected voltage-source converters. In the approach, the dq-frame impedance model is transformed into the stationary αβ-frame by means of complex transfer functions and comp......This paper proposes a unified impedance model for analyzing the effect of Phase-Locked Loop (PLL) on the stability of grid-connected voltage-source converters. In the approach, the dq-frame impedance model is transformed into the stationary αβ-frame by means of complex transfer functions...... and complex space vectors, which not only predicts the stability impact of the PLL, but reveals also its frequency coupling effect in the phase domain. Thus, the impedance models previously developed in the different domains can be unified. Moreover, the impedance shaping effects of PLL are structurally...

  9. Modulated Phase of a Potts Model with Competing Binary Interactions on a Cayley Tree

    Science.gov (United States)

    Ganikhodjaev, N.; Temir, S.; Akin, H.

    2009-11-01

    We study the phase diagram for Potts model on a Cayley tree with competing nearest-neighbor interactions J 1, prolonged next-nearest-neighbor interactions J p and one-level next-nearest-neighbor interactions J o . Vannimenus proved that the phase diagram of Ising model with J o =0 contains a modulated phase, as found for similar models on periodic lattices, but the multicritical Lifshitz point is at zero temperature. Later Mariz et al. generalized this result for Ising model with J o ≠0 and recently Ganikhodjaev et al. proved similar result for the three-state Potts model with J o =0. We consider Potts model with J o ≠0 and show that for some values of J o the multicritical Lifshitz point be at non-zero temperature. We also prove that as soon as the same-level interaction J o is nonzero, the paramagnetic phase found at high temperatures for J o =0 disappears, while Ising model does not obtain such property. To perform this study, an iterative scheme similar to that appearing in real space renormalization group frameworks is established; it recovers, as particular case, previous work by Ganikhodjaev et al. for J o =0. At vanishing temperature, the phase diagram is fully determined for all values and signs of J 1, J p and J o . At finite temperatures several interesting features are exhibited for typical values of J o / J 1.

  10. Extended soft-wall model for the QCD phase diagram

    CERN Document Server

    Zöllner, Rico; Kampfer, Burkhard

    2016-01-01

    The soft-wall model, emerging as bottom-up holographic scenario anchored in the AdS/CFT correspondence, displays the disappearance of normalisable modes referring to vector mesons at a temperature $T_{\\dis}$ depending on the chemical potential $\\mu$, $T_{\\dis}(\\mu)$. We explore options for making $T_{\\dis}(\\mu)$ consistent with the freeze-out curve $T_{\\rm f.o.}(\\mu)$ from relativistic heavy-ion collisions and the cross-over curve $T_{\\rm c}(\\mu)$ from QCD at small values of $\\mu$.

  11. Berezinskii-Kosterlitz-Thouless phase transitions in two-dimensional non-Abelian spin models.

    Science.gov (United States)

    Borisenko, Oleg; Chelnokov, Volodymyr; Cuteri, Francesca; Papa, Alessandro

    2016-07-01

    It is argued that two-dimensional U(N) spin models for any N undergo a Berezinskii-Kosterlitz-Thouless (BKT)-like phase transition, similarly to the famous XY model. This conclusion follows from the Berezinskii-like calculation of the two-point correlation function in U(N) models, approximate renormalization group analysis, and numerical investigations of the U(2) model. It is shown, via Monte Carlo simulations, that the universality class of the U(2) model coincides with that of the XY model. Moreover, preliminary numerical results point out that two-dimensional SU(N) spin models with the fundamental and adjoint terms and N>4 exhibit two phase transitions of BKT type, similarly to Z(N) vector models.

  12. Exotic phase diagram of a cluster charging model of bosons on the kagome lattice

    Science.gov (United States)

    Isakov, Sergei V.; Paramekanti, Arun; Kim, Yong Baek

    2007-12-01

    We study a model of hard-core bosons on the kagome lattice with short-range hopping (t) and repulsive interactions (V) . This model directly maps onto an easy-axis S=1/2 XXZ model on the kagome lattice and is also related, at large V/t , to a quantum dimer model on the triangular lattice. Using quantum Monte Carlo numerics, we map out the phase diagram of this model at half-filling. At T=0 , we show that this model exhibits a superfluid phase at small V/t and an insulating phase at large V/t , separated by a continuous quantum phase transition at Vc/t≈19.8 . The insulating phase at T=0 appears to have no conventional broken symmetries, and is thus a uniform Mott insulator (a “spin liquid” in magnetic language). We characterize this insulating phase as a uniform Z2 fractionalized insulator from the topological order in the ground state and estimate its vison gap. Consistent with this identification, there is no apparent thermal phase transition upon heating the insulator. The insulating phase instead smoothly crosses over into the high temperature paramagnet via an intermediate cooperative paramagnetic regime. We also study the superfluid-to-normal thermal transition for V

  13. Superimposed folding and thrusting by two phases of mutually orthogonal or oblique shortening in analogue models

    Science.gov (United States)

    Deng, Hongling; Koyi, Hemin A.; Nilfouroushan, Faramarz

    2016-02-01

    Orogens may suffer more than one phase shortening resulting in superposition of structures of different generations. Superimposition of orthogonal or oblique shortening is studied using sandbox and centrifuge modelling. Results of sand models show that in orthogonal superimposition, the two resulting structural trends are approximately orthogonal to each other. In oblique superimposition, structures trend obliquely to each other in the relatively thin areas of the model (foreland), and mutually orthogonal in areas where the model is thickened during the first phase of shortening (i.e. the hinterland). Thrusts formed during the first shortening phase may be reactivated during the later shortening phase. Spacing of the later phase structures is not as wide as expected, considering they across the pre-existing thickened wedge. Superposition of structures results in formation of type 1 fold interference pattern. Bedding is curved outwards both in the dome and basin structures. Folded layers are dipping and plunging outwards in a dome, while they are dipping and plunging inwards in a basin. In the areas between two adjacent domes or basins (i.e. where an anticline is superimposed by a syncline or a syncline is superimposed by an anticline), bedding is curved inwards, and the anticlines plunge inwards and the synclines outwards. The latter feature could be helpful to determine the age relationship for type 2 fold interference pattern. In tectonic regions where multiple phases of shortening have occurred, the orogenic-scale dome-and-basin and arrowhead-shaped interference patterns are commonly formed, as in the models. However, in some areas, the fold interference pattern might be modified by a later phase of thrusting. Similar to models results, superimposition of two and/or even more deformation phases may not be recorded by structures all over the tectonic area.

  14. Transient ejection phase modeling of a Plasma Synthetic Jet actuator

    Science.gov (United States)

    Laurendeau, F.; Chedevergne, F.; Casalis, G.

    2014-12-01

    For several years, a promising Plasma Synthetic Jet actuator for high-speed flow control has been under development at ONERA. So far, its confined geometry and small space-time scales at play have prevented its full experimental characterization. Complementary accurate numerical simulations are then considered in this study in order to provide a complete aerothermodynamic description of the actuator. Two major obstacles have to be overcome with this approach: the modeling of the energy deposited by the electric arc and the accurate computation of the transient response of the cavity generating the pulsed jet. To solve the first problem, an Euler solver coupled with an electric circuit model was used to evaluate the energy deposition in the cavity. Such a coupling is performed by considering the electric field between the two electrodes. The second issue was then addressed by injecting these source terms in large Eddy simulations of the entire actuator. Aerodynamic results were finally compared with Schlieren visualizations. Using the proposed methodology, the temporal evolution of the jet front is remarkably well predicted.

  15. Phase-noise-induced resonance in arrays of coupled excitable neural models.

    Science.gov (United States)

    Xiaoming Liang; Liang Zhao

    2013-08-01

    Recently, it is observed that, in a single neural model, phase noise (time-varying signal phase) arising from an external stimulating signal can induce regular spiking activities even if the signal is subthreshold. In addition, it is also uncovered that there exists an optimal phase noise intensity at which the spiking rhythm coincides with the frequency of the subthreshold signal, resulting in a phase-noise-induced resonance phenomenon. However, neurons usually do not work alone, but are connected in the form of arrays or blocks. Therefore, we study the spiking activity induced by phase noise in arrays of globally and locally coupled excitable neural models. We find that there also exists an optimal phase noise intensity for generating large neural response and such an optimal value is significantly decreased compared to an isolated single neuron case, which means the detectability in response to the subthreshold signal of neurons is sharply improved because of the coupling. In addition, we reveal two new resonance behaviors in the neuron ensemble with the presence of phase noise: there exist optimal values of both coupling strength and system size, where the coupled neurons generate regular spikes under subthreshold stimulations, which are called as coupling strength and system size resonance, respectively. Finally, the dependence of phase-noise-induced resonance on signal frequency is also examined.

  16. Groundwater cleanup by in-situ sparging. IX. Air channeling model for nonaqueous phase liquid removal

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, D.J.; Norris, R.D.; Clarke, A.N. [Eckenfelder, Inc., Nashville, TN (United States)

    1996-04-01

    A mathematical model is developed to simulate the removal of dissolved and nonaqueous phase liquid (NAPL) volatile organic compounds (VOCs) from contaminated aquifers by sparging. The model assumes that the sparging air moves through the aquifer in persistent channels and that NAPL must dissolve and move to these channels by diffusion and dispersion processes. The dependence of the model results on model parameters is explored, and practical implications for sparging well operation are discussed.

  17. Phase chemistry in process models for cement clinker and lime production

    OpenAIRE

    2014-01-01

    The goal of the thesis is to evaluate if developed phase chemical process models for cement clinker and lime production processes are reliable to use as predictive tools in understanding the changes when introducing sustainability measures. The thesis describes the development of process simulation models in the application of sustainability measures as well as the evaluation of these models. The motivation for developing these types of models arises from the need to predict the chemical and ...

  18. Study of phase separation using liquid-gas model of lattice-gas cellular automata

    Energy Technology Data Exchange (ETDEWEB)

    Ebihara, Kenichi; Watanabe, Tadashi; Kaburaki, Hideo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-07-01

    This report describes the study of phase separation by the liquid gas model of lattice gas cellular automata. The lattice gas cellular automaton is one model for simulating fluid phenomena which was proposed by Frisch, Hasslacher and Pomeau in 1986. In 1990, Appert and Zaleski added a new long-range interaction to lattice gas cellular automata to construct a model, the liquid-gas model, which could simulate phase separation using lattice-gas cellular automata. Gerits et al formulated the liquid-gas model mathematically using the theory of statistical dynamics in 1993 and explained the mechanism of phase separation in the liquid-gas model using the equation of state. At first this report explains the FHP model of lattice gas cellular automata and derives fluid dynamics equations such as the equation of continuity and the Navier-Stokes equation. Then the equation of state for the liquid-gas model which was derived by Gerits et al is modified by adding the interactions which were proposed by Appert but not considered by Gerits et al. The modified equation of state is verified by the computer simulation using the liquid gas model. The relation between phase separation and the equation of state is discussed. (author)

  19. Zigzag order and phase competition in expanded Kitaev–Heisenberg model on honeycomb lattice

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Xiaoyan, E-mail: yaoxiaoyan@gmail.com

    2015-07-17

    Highlights: • Expanded Kitaev–Heisenberg model on honeycomb lattice is investigated. • Kitaev interactions between the first or second nearest neighbors are considered. • Phase competition is discussed by energy calculation and Monte Carlo simulation. • Zigzag phase shows a symmetric behavior to the stripy phase. • Zigzag order is extended to the whole parameter range by more interactions. - Abstract: The Kitaev–Heisenberg model on the honeycomb lattice is investigated in two cases: (I) with the Kitaev interaction between the nearest neighbors, and (II) with the Kitaev interaction between the next nearest neighbors. In the full parameter range, the ground states are searched by Monte Carlo simulation and identified by evaluating the correlation functions. The energies of different phases are calculated and compared with the simulated result to show the phase competition. It is observed from both energy calculation and the density of states that the zigzag order shows a symmetric behavior to the stripy phase in the pure Kitaev–Heisenberg model. By considering more interactions in both cases, the energy of zigzag order can be reduced lower than the energies of other states. Thus the zigzag phase may be stabilized in more parameter region and even extended to the whole parameter range.

  20. Quantum correlation and quantum phase transition in the one-dimensional extended Ising model

    Science.gov (United States)

    Zhang, Xi-Zheng; Guo, Jin-Liang

    2017-09-01

    Quantum phase transitions can be understood in terms of Landau's symmetry-breaking theory. Following the discovery of the quantum Hall effect, a new kind of quantum phase can be classified according to topological rather than local order parameters. Both phases coexist for a class of exactly solvable quantum Ising models, for which the ground state energy density corresponds to a loop in a two-dimensional auxiliary space. Motivated by this we study quantum correlations, measured by entanglement and quantum discord, and critical behavior seen in the one-dimensional extended Ising model with short-range interaction. We show that the quantum discord exhibits distinctive behaviors when the system experiences different topological quantum phases denoted by different topological numbers. Quantum discords capability to detect a topological quantum phase transition is more reliable than that of entanglement at both zero and finite temperatures. In addition, by analyzing the divergent behaviors of quantum discord at the critical points, we find that the quantum phase transitions driven by different parameters of the model can also display distinctive critical behaviors, which provides a scheme to detect the topological quantum phase transition in practice.

  1. Phase transitions in a holographic s+p model with backreaction

    CERN Document Server

    Nie, Zhang-Yu; Gao, Xin; Li, Li; Zeng, Hui

    2015-01-01

    In a previous paper (arXiv:1309.2204, JHEP 1311 (2013) 087), we present a holographic s+p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk and study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back reaction. The model shows a rich phase structure and various condensate behaviors such as the "n-type" and "u-type" ones. The phase transitions to the p-wave phase or s+p coexisting phase become first order in strongly back reacted cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s+p solution can also play an important role. The phase diagrams of this system are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back reaction parameter, which show that the region for the s+p coexisting phase is enlarged with a small or medium b...

  2. Limited by sensing - A minimal stochastic model of the lag-phase during diauxic growth.

    Science.gov (United States)

    Chu, Dominique

    2017-02-07

    Many microbes when grown on a mixture of two carbon sources utilise first and exclusively the preferred sugar, before switching to the less preferred carbon source. This results in two distinct exponential growth phases, often interrupted by a lag-phase of reduced growth termed the lag-phase. While the lag-phase appears to be an evolved feature, it is not clear what drives its evolution, as it comes with a substantial up-front fitness penalty due to lost growth. In this article a minimal mathematical model based on a master-equation approach is proposed. This model can explain many empirically observed phenomena. It suggests that the lag-phase can be understood as a manifestation of the trade-off between switching speed and switching efficiency. Moreover, the model predicts heterogeneity of the population during the lag-phase. Finally, it is shown that the switch from one carbon source to another one is a sensing problem and the lag-phase is a manifestation of known fundamental limitations of biological sensors.

  3. Plaquette ordered phase and quantum phase diagram in the spin-1/2 J(1)-J(2) square Heisenberg model.

    Science.gov (United States)

    Gong, Shou-Shu; Zhu, Wei; Sheng, D N; Motrunich, Olexei I; Fisher, Matthew P A

    2014-07-11

    We study the spin-1/2 Heisenberg model on the square lattice with first- and second-neighbor antiferromagnetic interactions J(1) and J(2), which possesses a nonmagnetic region that has been debated for many years and might realize the interesting Z(2) spin liquid. We use the density matrix renormalization group approach with explicit implementation of SU(2) spin rotation symmetry and study the model accurately on open cylinders with different boundary conditions. With increasing J(2), we find a Néel phase and a plaquette valence-bond (PVB) phase with a finite spin gap. From the finite-size scaling of the magnetic order parameter, we estimate that the Néel order vanishes at J(2)/J(1)≃0.44. For 0.5

  4. A theoretical model of phase transitions in the human brain.

    Science.gov (United States)

    Jirsa, V K; Friedrich, R; Haken, H; Kelso, J A

    1994-01-01

    An experiment using a multisensor SQUID (superconducting quantum interference device) array was performed by Kelso and colleagues (1992) which combined information from three different sources: perception, motor response, and brain signals. When an acoustic stimulus frequency is changed systematically, a spontaneous transition in coordination occurs at a critical frequency in both motor behavior and brain signals. Qualitatively analogous transitions are known for physical and biological systems such as changes in the coordination of human hand movements (Kelso 1981, 1984). In this paper we develop a theoretical model based on methods from the interdisciplinary field of synergetics (Haken 1983, 1987) and nonlinear oscillator theory that reproduces the main experimental features very well and suggests a formulation of a fundamental biophysical coupling.

  5. Phase transition in kinetic exchange opinion models with independence

    CERN Document Server

    Crokidakis, Nuno

    2014-01-01

    In this work we study the critical behavior of a three-state ($+1$, $-1$, $0$) opinion model with independence. Each agent has a probability $q$ to act as independent, i.e., he/she can choose his/her opinion independently of the opinions of the other agents. On the other hand, with the complementary probability $1-q$ the agent interacts with a randomly chosen individual through a kinetic exchange. Our analytical and numerical results show that the independence mechanism acts as a noise that induce an order-disorder transition at critical points $q_{c}$ that depend on the individuals' flexibility. For a special value of this flexibility the system undergoes a transition to an absorbing state with all opinions $0$.

  6. Phase diagram of the Kondo-Heisenberg model on honeycomb lattice with geometrical frustration

    Science.gov (United States)

    Li, Huan; Song, Hai-Feng; Liu, Yu

    2016-11-01

    We calculated the phase diagram of the Kondo-Heisenberg model on a two-dimensional honeycomb lattice with both nearest-neighbor and next-nearest-neighbor antiferromagnetic spin exchanges, to investigate the interplay between RKKY and Kondo interactions in the presence of magnetic frustration. Within a mean-field decoupling technology in slave-fermion representation, we derived the zero-temperature phase diagram as a function of Kondo coupling J k and frustration strength Q. The geometrical frustration can destroy the magnetic order, driving the original antiferromagnetic (AF) phase to non-magnetic valence bond solids (VBS). In addition, we found two distinct VBS. As J k is increased, a phase transition from AF to Kondo paramagnetic (KP) phase occurs, without the intermediate phase coexisting AF order with Kondo screening found in square lattice systems. In the KP phase, the enhancement of frustration weakens the Kondo screening effect, resulting in a phase transition from KP to VBS. We also found a process to recover the AF order from VBS by increasing J k in a wide range of frustration strength. Our work may provide predictions for future experimental observation of new processes of quantum phase transitions in frustrated heavy-fermion compounds.

  7. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in

  8. Thermodynamically Consistent Algorithms for the Solution of Phase-Field Models

    KAUST Repository

    Vignal, Philippe

    2016-02-11

    Phase-field models are emerging as a promising strategy to simulate interfacial phenomena. Rather than tracking interfaces explicitly as done in sharp interface descriptions, these models use a diffuse order parameter to monitor interfaces implicitly. This implicit description, as well as solid physical and mathematical footings, allow phase-field models to overcome problems found by predecessors. Nonetheless, the method has significant drawbacks. The phase-field framework relies on the solution of high-order, nonlinear partial differential equations. Solving these equations entails a considerable computational cost, so finding efficient strategies to handle them is important. Also, standard discretization strategies can many times lead to incorrect solutions. This happens because, for numerical solutions to phase-field equations to be valid, physical conditions such as mass conservation and free energy monotonicity need to be guaranteed. In this work, we focus on the development of thermodynamically consistent algorithms for time integration of phase-field models. The first part of this thesis focuses on an energy-stable numerical strategy developed for the phase-field crystal equation. This model was put forward to model microstructure evolution. The algorithm developed conserves, guarantees energy stability and is second order accurate in time. The second part of the thesis presents two numerical schemes that generalize literature regarding energy-stable methods for conserved and non-conserved phase-field models. The time discretization strategies can conserve mass if needed, are energy-stable, and second order accurate in time. We also develop an adaptive time-stepping strategy, which can be applied to any second-order accurate scheme. This time-adaptive strategy relies on a backward approximation to give an accurate error estimator. The spatial discretization, in both parts, relies on a mixed finite element formulation and isogeometric analysis. The codes are

  9. a Radiative Transfer Equation/phase Function Approach to Vegetation Canopy Reflectance Modeling

    Science.gov (United States)

    Randolph, Marion Herbert

    Vegetation canopy reflectance models currently in use differ considerably in their treatment of the radiation scattering problem, and it is this fundamental difference which stimulated this investigation of the radiative transfer equation/phase function approach. The primary objective of this thesis is the development of vegetation canopy phase functions which describe the probability of radiation scattering within a canopy in terms of its biological and physical characteristics. In this thesis a technique based upon quadrature formulae is used to numerically generate a variety of vegetation canopy phase functions. Based upon leaf inclination distribution functions, phase functions are generated for plagiophile, extremophile, erectophile, spherical, planophile, blue grama (Bouteloua gracilis), and soybean canopies. The vegetation canopy phase functions generated are symmetric with respect to the incident and exitant angles, and hence satisfy the principle of reciprocity. The remaining terms in the radiative transfer equation are also derived in terms of canopy geometry and optical properties to complete the development of the radiative transfer equation/phase function description for vegetation canopy reflectance modeling. In order to test the radiative transfer equation/phase function approach the iterative discrete ordinates method for solving the radiative transfer equation is implemented. In comparison with field data, the approach tends to underestimate the visible reflectance and overestimate infrared reflectance. The approach does compare well, however, with other extant canopy reflectance models; for example, it agrees to within ten to fifteen percent of the Suits model (Suits, 1972). Sensitivity analysis indicates that canopy geometry may influence reflectance as much as 100 percent for a given wavelength. Optical thickness produces little change in reflectance after a depth of 2.5 (Leaf area index of 4.0) is reached, and reflectance generally increases

  10. Comparative analysis of CFD models for jetting fluidized beds: Effect of particle-phase viscosity

    Institute of Scientific and Technical Information of China (English)

    Pei Pei; Kai Zhang; Gang Xu; Yongping Yang; Dongsheng Wen

    2012-01-01

    Under the Eulerian-Eulerian framework of simulating gas-solid two-phase flow,the accuracy of the hydrodynamic prediction is strongly affected by the selection of rheology of the particulate phase,for which a detailed assessment is still absent.Using a jetting fluidized bed as an example,this work investigates the influence of solid theology on the hydrodynamic behavior by employing different particle-phase viscosity models.Both constant particle-phase viscosity model (CVM) with different viscosity values and a simple two-fluid model without particle-phase viscosity (NVM) are incorporated into the classical twofluid model and compared with the experimental measurements.Qualitative and quantitative results show that the jet penetration depth,jet frequency and averaged bed pressure drop are not a strong function of the particle-phase viscosity.Compared to CVM,the NVM exhibits better predictions on the jet behaviors,which is more suitable for investigating the hydrodynamics of gas-solid fluidized bed with a central jet.

  11. Phase-field lattice Boltzmann modeling of boiling using a sharp-interface energy solver

    Science.gov (United States)

    Mohammadi-Shad, Mahmood; Lee, Taehun

    2017-07-01

    The main objective of this paper is to extend an isothermal incompressible two-phase lattice Boltzmann equation method to model liquid-vapor phase change problems using a sharp-interface energy solver. Two discrete particle distribution functions, one for the continuity equation and the other for the pressure evolution and momentum equations, are considered in the current model. The sharp-interface macroscopic internal energy equation is discretized with an isotropic finite difference method to find temperature distribution in the system. The mass flow generated at liquid-vapor phase interface is embedded in the pressure evolution equation. The sharp-interface treatment of internal energy equation helps to find the interfacial mass flow rate accurately where no free parameter is needed in the calculations. The proposed model is verified against available theoretical solutions of the two-phase Stefan problem and the two-phase sucking interface problem, with which our simulation results are in good agreement. The liquid droplet evaporation in a superheated vapor, the vapor bubble growth in a superheated liquid, and the vapor bubble rising in a superheated liquid are analyzed and underlying physical characteristics are discussed in detail. The model is successfully tested for the liquid-vapor phase change with large density ratio up to 1000.

  12. Liquid-gas phase transition in strange hadronic matter with relativistic models

    Science.gov (United States)

    Torres, James R.; Gulminelli, F.; Menezes, Débora P.

    2016-02-01

    Background: The advent of new dedicated experimental programs on hyperon physics is rapidly boosting the field, and the possibility of synthesizing multiple strange hypernuclei requires the addition of the strangeness degree of freedom to the models dedicated to nuclear structure and nuclear matter studies at low energy. Purpose: We want to settle the influence of strangeness on the nuclear liquid-gas phase transition. Because of the large uncertainties concerning the hyperon sector, we do not aim at a quantitative estimation of the phase diagram but rather at a qualitative description of the phenomenology, as model independent as possible. Method: We analyze the phase diagram of low-density matter composed of neutrons, protons, and Λ hyperons using a relativistic mean field (RMF) model. We largely explore the parameter space to pin down generic features of the phase transition, and compare the results to ab initio quantum Monte Carlo calculations. Results: We show that the liquid-gas phase transition is only slightly quenched by the addition of hyperons. Strangeness is seen to be an order parameter of the phase transition, meaning that dilute strange matter is expected to be unstable with respect to the formation of hyperclusters. Conclusions: More quantitative results within the RMF model need improved functionals at low density, possibly fitted to ab initio calculations of nuclear and Λ matter.

  13. Modeling Patterns of Precipitation Phase in the Central Sierra Nevada

    Science.gov (United States)

    Strikas, O.; Pavelsky, T.

    2013-12-01

    Snowpack provides 75% of summer hydrologic flow in the western United States. This summer flow is vitally important in California, the country's leading producer of agriculture, with $43.5 billion dollars in cash receipts in 2011. Snowpack in the California Sierra Nevada has declined by approximately half from 1900 to 1990. In this study, we use the Weather Research and Forecasting (WRF) regional climate model at a 3km resolution to understand the critical temperature window at which both snow and rain fall for the Central Sierra Nevada during the 2002 water year. Results suggest that temperature and snow fraction [snowfall / (snowfall + rainfall)] share a logistic relationship with the snow fraction being 1 until approximately 272 K, then the snow fraction decreases by approximately 22%/K leveling at 0 snow fraction at 276.5 K. We further examine the spatial patterns of temperatures, precipitation amounts, and precipitation types in the Sierra Nevada to determine the areas of greatest potential snow to rain transition under a future warmer climate. Preliminary results suggest that the high risk areas are at the low to mid elevations. This research provides evidence that even a minor increase in temperature (+0.5 K) will yield changes in spring and summer hydrographs for the region. The spatial variability of IPCC temperature regime change for 2050 and 2100 will be downscaled for a higher resolution prediction of precipitation. It is currently under investigation how the proposed IPCC (A1 and B2) predictions of climate change for the region by 2050 (+2.7 K; +1.6 K ) and 2100 (+4.4 K; +2.7 K) will alter the corresponding annual river hydrographs. Given the complex topography of the Sierra Nevada, several spatial interpolations using GIS and statistical algorithms will be executed to render this high resolution (3km) output. Other future work with collaborators intends to model the agricultural risk associated with our predicted changes. This plot demonstrates the

  14. Fermionic Symmetry-Protected Topological Phase in a Two-Dimensional Hubbard Model

    Science.gov (United States)

    Chen, Cheng-Chien; Muechler, Lukas; Car, Roberto; Neupert, Titus; Maciejko, Joseph

    2016-08-01

    We study the two-dimensional (2D) Hubbard model using exact diagonalization for spin-1 /2 fermions on the triangular and honeycomb lattices decorated with a single hexagon per site. In certain parameter ranges, the Hubbard model maps to a quantum compass model on those lattices. On the triangular lattice, the compass model exhibits collinear stripe antiferromagnetism, implying d -density wave charge order in the original Hubbard model. On the honeycomb lattice, the compass model has a unique, quantum disordered ground state that transforms nontrivially under lattice reflection. The ground state of the Hubbard model on the decorated honeycomb lattice is thus a 2D fermionic symmetry-protected topological phase. This state—protected by time-reversal and reflection symmetries—cannot be connected adiabatically to a free-fermion topological phase.

  15. A phenomenological model of two-phase (air/fuel droplet developing and breakup

    Directory of Open Access Journals (Sweden)

    Pavlović Radomir R.

    2013-01-01

    Full Text Available Effervescent atomization namely the air-filled liquid atomization comprehends certain complex two-phase phenomenon that are difficult to be modeled. Just a few researchers have found the mathematical expressions for description of the complex atomization model of the two-phase mixture air/diesel fuel. In the following review, developing model of twophase (air/fuel droplet of Cummins spray pump-injector is shown. The assumption of the same diameters of the droplet and the opening of the atomizer is made, while the air/fuel mass ratio inside the droplet varies.

  16. Design-oriented analytic model of phase and frequency modulated optical links

    Science.gov (United States)

    Monsurrò, Pietro; Saitto, Antonio; Tommasino, Pasquale; Trifiletti, Alessandro; Vannucci, Antonello; Cimmino, Rosario F.

    2016-07-01

    An analytic design-oriented model of phase and frequency modulated microwave optical links has been developed. The models are suitable for design of broadband high dynamic range optical links for antenna remoting and optical beamforming, where noise and linearity of the subsystems are a concern Digital filter design techniques have been applied to the design of optical filters working as frequency discriminator, that are the bottleneck in terms of linearity for these systems. The models of frequency modulated, phase modulated, and coherent I/Q link have been used to compare performance of the different architectures in terms of linearity and SFDR.

  17. Regularization dependence on phase diagram in Nambu-Jona-Lasinio model

    CERN Document Server

    Inagaki, T; Kohyama, H

    2015-01-01

    We study the regularization dependence on meson properties and the phase diagram of quark matter by using the two flavor Nambu-Jona-Lasinio model. We find that the meson properties and the phase structure do not show drastically difference depending the regularization procedures. We also find that the location or the existence of the critical end point highly depends on the regularization methods and the model parameters. Then we think that regularization and parameters are carefully considered when one investigates the QCD critical end point in the effective model studies.

  18. First Order Electroweak Phase Transition from (Non)Conformal Extensions of the Standard Model

    DEFF Research Database (Denmark)

    Sannino, Francesco; Virkajärvi, Jussi

    2015-01-01

    We analyse and compare the finite-temperature electroweak phase transition properties of classically (non)conformal extensions of the Standard Model. In the classically conformal scenarios the breaking of the electroweak symmetry is generated radiatively. The models feature new scalars coupled...... conformally to the Higgs sector as well as new fermions. We uncover the parameter space leading to a first order phase transition with(out) the Veltman conditions. We also discuss dark (matter) aspects of some of the models and compare with existing literature when appropriate. We observe that to accommodate...

  19. Quantum phase diagrams of the Jaynes–Cummings Hubbard models in non-rectangular lattices

    Science.gov (United States)

    Zhang, Jun; Jiang, Ying

    2017-03-01

    In this paper, we investigate systematically the quantum phase transition between the Mott-insulator and superfluid states of the Jaynes–Cummings Hubbard model in triangular, square, honeycomb and kagomé lattices. With the help of Green’s function method, by treating the hopping term in the Jaynes–Cummings Hubbard model as perturbation, we calculate the phase boundaries of Jaynes–Cummings Hubbard models on different geometrical lattices analytically up to second order for both detuning Δ =0 and Δ \

  20. Advanced induction machine model in phase coordinates for wind turbine applications

    DEFF Research Database (Denmark)

    Fajardo, L.A.; Iov, F.; Hansen, Anca Daniela

    2007-01-01

    In this paper an advanced phase coordinates squirrel cage induction machine model with time varying electrical parameters affected by magnetic saturation and rotor deep bar effects, is presented. The model uses standard data sheet for characterization of the electrical parameters, it is developed...