Two dimensional compass model with Heisenberg interactions
Pires, A. S. T.
2018-04-01
We consider a two dimensional compass model with a next and a next near Heisenberg term. The interactions are of two types: frustrated near neighbor compass interactions of amplitudes Jx and Jy, and next and next near neighbor Heisenberg interactions with exchanges J1 and J2 respectively. The Heisenberg interactions are isotropic in spin space, but the compass interactions depend on the bond direction. The ground state of the pure compass model is degenerated with a complex phase diagram. This degeneracy is removed by the Heisenberg terms leading to the arising of a magnetically ordered phase with a preferred direction. We calculate the phase diagrams at zero temperature for the case where, for J2 = 0, we have an antiferromagnetic ground state. We show that varying the value of J2, a magnetically disordered phase can be reached for small values of the compass interactions. We also calculate the critical temperature for a specified value of parameters.
International Nuclear Information System (INIS)
Rojas T, J.; Instituto Peruano de Energia Nuclear, Lima; Manrique C, E.; Torres T, E.
2002-01-01
Using monte Carlo simulation have been carried out an atomistic description of the structure and ordering processes in the system Cu-Au in a two-dimensional model. The ABV model of the alloy is a system of N atoms A and B, located in rigid lattice with some vacant sites. In the model we assume pair wise interactions between nearest neighbors with constant ordering energy J = 0,03 eV. The dynamics was introduced by means of a vacancy that exchanges of place with any atom of its neighbors. The simulations were carried out in a square lattice with 1024 and 4096 particles, using periodic boundary conditions to avoid border effects. We calculate the first two parameters of short range order of Warren-Cowley as function of the concentration and temperature. It was also studied the probabilities of formation of different atomic clusters that consist of 9 atoms as function of the concentration of the alloy and temperatures in a wide range of values. In some regions of temperature and concentration it was observed compositional and thermal polymorphism
Two-dimensional effects in nonlinear Kronig-Penney models
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim
1997-01-01
An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...
Polaron dynamics in a two-dimensional anharmonic Holstein model
DEFF Research Database (Denmark)
Zolotaryuk, Yaroslav; Christiansen, Peter Leth; Juul Rasmussen, Jens
1998-01-01
A generalized two-dimensional semiclassical :Holstein model with a realistic on-site potential that contains anharmonicity is studied. More precisely, the lattice subsystem of anharmonic on-site oscillators is supposed to have a restricting core. The core plays the role of an effective saturation...
Two-dimensional models in statistical mechanics and field theory
International Nuclear Information System (INIS)
Koberle, R.
1980-01-01
Several features of two-dimensional models in statistical mechanics and Field theory, such as, lattice quantum chromodynamics, Z(N), Gross-Neveu and CP N-1 are discussed. The problems of confinement and dynamical mass generation are also analyzed. (L.C.) [pt
Two dimensional analytical model for a reconfigurable field effect transistor
Ranjith, R.; Jayachandran, Remya; Suja, K. J.; Komaragiri, Rama S.
2018-02-01
This paper presents two-dimensional potential and current models for a reconfigurable field effect transistor (RFET). Two potential models which describe subthreshold and above-threshold channel potentials are developed by solving two-dimensional (2D) Poisson's equation. In the first potential model, 2D Poisson's equation is solved by considering constant/zero charge density in the channel region of the device to get the subthreshold potential characteristics. In the second model, accumulation charge density is considered to get above-threshold potential characteristics of the device. The proposed models are applicable for the device having lightly doped or intrinsic channel. While obtaining the mathematical model, whole body area is divided into two regions: gated region and un-gated region. The analytical models are compared with technology computer-aided design (TCAD) simulation results and are in complete agreement for different lengths of the gated regions as well as at various supply voltage levels.
Minimal quantization of two-dimensional models with chiral anomalies
International Nuclear Information System (INIS)
Ilieva, N.
1987-01-01
Two-dimensional gauge models with chiral anomalies - ''left-handed'' QED and the chiral Schwinger model, are quantized consistently in the frames of the minimal quantization method. The choice of the cone time as a physical time for system of quantization is motivated. The well-known mass spectrum is found but with a fixed value of the regularization parameter a=2. Such a unique solution is obtained due to the strong requirement of consistency of the minimal quantization that reflects in the physically motivated choice of the time axis
Two dimensional hydrodynamic modeling of a high latitude braided river
Humphries, E.; Pavelsky, T.; Bates, P. D.
2014-12-01
Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.
The emergence of geometry: a two-dimensional toy model
Alfaro, Jorge; Puigdomenech, Daniel
2010-01-01
We review the similarities between the effective chiral lagrangrian, relevant for low-energy strong interactions, and the Einstein-Hilbert action. We use these analogies to suggest a specific mechanism whereby gravitons would emerge as Goldstone bosons of a global SO(D) X GL(D) symmetry broken down to SO(D) by fermion condensation. We propose a two-dimensional toy model where a dynamical zwei-bein is generated from a topological theory without any pre-existing metric structure, the space being endowed only with an affine connection. A metric appears only after the symmetry breaking; thus the notion of distance is an induced effective one. In spite of several non-standard features this simple toy model appears to be renormalizable and at long distances is described by an effective lagrangian that corresponds to that of two-dimensional gravity (Liouville theory). The induced cosmological constant is related to the dynamical mass M acquired by the fermion fields in the breaking, which also acts as an infrared re...
Surface Ship Shock Modeling and Simulation: Two-Dimensional Analysis
Directory of Open Access Journals (Sweden)
Young S. Shin
1998-01-01
Full Text Available The modeling and simulation of the response of a surface ship system to underwater explosion requires an understanding of many different subject areas. These include the process of underwater explosion events, shock wave propagation, explosion gas bubble behavior and bubble-pulse loading, bulk and local cavitation, free surface effect, fluid-structure interaction, and structural dynamics. This paper investigates the effects of fluid-structure interaction and cavitation on the response of a surface ship using USA-NASTRAN-CFA code. First, the one-dimensional Bleich-Sandler model is used to validate the approach, and second, the underwater shock response of a two-dimensional mid-section model of a surface ship is predicted with a surrounding fluid model using a constitutive equation of a bilinear fluid which does not allow transmission of negative pressures.
A two-dimensional mathematical model of percutaneous drug absorption
Directory of Open Access Journals (Sweden)
Kubota K
2004-06-01
Full Text Available Abstract Background When a drug is applied on the skin surface, the concentration of the drug accumulated in the skin and the amount of the drug eliminated into the blood vessel depend on the value of a parameter, r. The values of r depend on the amount of diffusion and the normalized skin-capillary clearence. It is defined as the ratio of the steady-state drug concentration at the skin-capillary boundary to that at the skin-surface in one-dimensional models. The present paper studies the effect of the parameter values, when the region of contact of the skin with the drug, is a line segment on the skin surface. Methods Though a simple one-dimensional model is often useful to describe percutaneous drug absorption, it may be better represented by multi-dimensional models. A two-dimensional mathematical model is developed for percutaneous absorption of a drug, which may be used when the diffusion of the drug in the direction parallel to the skin surface must be examined, as well as in the direction into the skin, examined in one-dimensional models. This model consists of a linear second-order parabolic equation with appropriate initial conditions and boundary conditions. These boundary conditions are of Dirichlet type, Neumann type or Robin type. A finite-difference method which maintains second-order accuracy in space along the boundary, is developed to solve the parabolic equation. Extrapolation in time is applied to improve the accuracy in time. Solution of the parabolic equation gives the concentration of the drug in the skin at a given time. Results Simulation of the numerical methods described is carried out with various values of the parameter r. The illustrations are given in the form of figures. Conclusion Based on the values of r, conclusions are drawn about (1 the flow rate of the drug, (2 the flux and the cumulative amount of drug eliminated into the receptor cell, (3 the steady-state value of the flux, (4 the time to reach the steady
Classical symmetries of some two-dimensional models
International Nuclear Information System (INIS)
Schwarz, J.H.
1995-01-01
It is well-known that principal chiral models and symmetric space models in two-dimensional Minkowski space have an infinite-dimensional algebra of hidden symmetries. Because of the relevance of symmetric space models to duality symmetries in string theory, the hidden symmetries of these models are explored in some detail. The string theory application requires including coupling to gravity, supersymmetrization, and quantum effects. However, as a first step, this paper only considers classical bosonic theories in flat space-time. Even though the algebra of hidden symmetries of principal chiral models is confirmed to include a Kac-Moody algebra (or a current algebra on a circle), it is argued that a better interpretation is provided by a doubled current algebra on a semi-circle (or line segment). Neither the circle nor the semi-circle bears any apparent relationship to the physical space. For symmetric space models the line segment viewpoint is shown to be essential, and special boundary conditions need to be imposed at the ends. The algebra of hidden symmetries also includes Virasoro-like generators. For both principal chiral models and symmetric space models, the hidden symmetry stress tensor is singular at the ends of the line segment. (orig.)
Mathematical modeling of the neuron morphology using two dimensional images.
Rajković, Katarina; Marić, Dušica L; Milošević, Nebojša T; Jeremic, Sanja; Arsenijević, Valentina Arsić; Rajković, Nemanja
2016-02-07
In this study mathematical analyses such as the analysis of area and length, fractal analysis and modified Sholl analysis were applied on two dimensional (2D) images of neurons from adult human dentate nucleus (DN). Using mathematical analyses main morphological properties were obtained including the size of neuron and soma, the length of all dendrites, the density of dendritic arborization, the position of the maximum density and the irregularity of dendrites. Response surface methodology (RSM) was used for modeling the size of neurons and the length of all dendrites. However, the RSM model based on the second-order polynomial equation was only possible to apply to correlate changes in the size of the neuron with other properties of its morphology. Modeling data provided evidence that the size of DN neurons statistically depended on the size of the soma, the density of dendritic arborization and the irregularity of dendrites. The low value of mean relative percent deviation (MRPD) between the experimental data and the predicted neuron size obtained by RSM model showed that model was suitable for modeling the size of DN neurons. Therefore, RSM can be generally used for modeling neuron size from 2D images. Copyright © 2015 Elsevier Ltd. All rights reserved.
A two dimensional model of undertow current over mud bed
International Nuclear Information System (INIS)
Mir Hammadul Azam; Abdul Aziz Ibrahim; Noraieni Hj, Mokhtar
1996-01-01
Coastal wave-current dynamics often causes severe erosion and this activity is more prominent within the surf zone. Turbulence generated by breaking wave is a complex phenomena and the degree of complexity increases to a higher degree when it happens over mud bed. A better understanding on wave and current is necessary to enrich the engineering hand to facilitate any coastal development work. Since physical model has certain deficiencies, such as high cost and scaling problem, the need for developing numerical models in such cases is significant. A time averaged two dimensional model has been developed to simulate the undertow over mud bed. A turbulent energy model also included which considers only the vertical variation of mixing length. Production of turbulent kinetic energy in the surf zone has been calculated from an hydraulic jump analogy. The result obtained shows an insignificant vertical variation of current. Further research is needed involving laboratory and field works to get sufficient data for comparing the model results
Persistence in a Two-Dimensional Moving-Habitat Model.
Phillips, Austin; Kot, Mark
2015-11-01
Environmental changes are forcing many species to track suitable conditions or face extinction. In this study, we use a two-dimensional integrodifference equation to analyze whether a population can track a habitat that is moving due to climate change. We model habitat as a simple rectangle. Our model quickly leads to an eigenvalue problem that determines whether the population persists or declines. After surveying techniques to solve the eigenvalue problem, we highlight three findings that impact conservation efforts such as reserve design and species risk assessment. First, while other models focus on habitat length (parallel to the direction of habitat movement), we show that ignoring habitat width (perpendicular to habitat movement) can lead to overestimates of persistence. Dispersal barriers and hostile landscapes that constrain habitat width greatly decrease the population's ability to track its habitat. Second, for some long-distance dispersal kernels, increasing habitat length improves persistence without limit; for other kernels, increasing length is of limited help and has diminishing returns. Third, it is not always best to orient the long side of the habitat in the direction of climate change. Evidence suggests that the kurtosis of the dispersal kernel determines whether it is best to have a long, wide, or square habitat. In particular, populations with platykurtic dispersal benefit more from a wide habitat, while those with leptokurtic dispersal benefit more from a long habitat. We apply our model to the Rocky Mountain Apollo butterfly (Parnassius smintheus).
Two-dimensional modeling of conduction-mode laser welding
International Nuclear Information System (INIS)
Russo, A.J.
1984-01-01
WELD2D is a two-dimensional finite difference computer program suitable for modeling the conduction-mode welding process when the molten weld pool motion can be neglected. The code is currently structured to treat butt-welded geometries in a plane normal to the beam motion so that dissimilar materials may be considered. The surface heat transfer models used in the code include a Gaussian beam or uniform laser source, and a free electron theory reflectance calculation. Temperature-dependent material parameters are used in the reflectance calculation. Measured cold reflection data are used to include surface roughness or oxide effects until melt occurs, after which the surface is assumed to be smooth and clean. Blackbody reradiation and a simple natural convection model are also included in the upper surface boundary condition. Either an implicit or explicit finite-difference representation of the heat conduction equation in an enthalpy form is solved at each time step. This enables phase transition energies to be easily and accurately incorporated into the formulation. Temperature-dependent 9second-order polynominal dependence) thermal conductivities are used in the conduction calculations. Constant values of specific heat are used for each material phase. At present, material properties for six metals are included in the code. These are: aluminium, nickel, steel, molybdenum, copper and silicon
Chiral anomaly, fermionic determinant and two dimensional models
International Nuclear Information System (INIS)
Rego Monteiro, M.A. do.
1985-01-01
The chiral anomaly in random pair dimension is analysed. This anomaly is perturbatively calculated by dimensional regularization method. A new method for non-perturbative Jacobian calculation of a general chiral transformation, 1.e., finite and non-Abelian, is developed. This method is used for non-perturbative chiral anomaly calculation, as an alternative to bosonization of two-dimensional theories for massless fermions and to study the phenomenum of fermion number fractionalization. The fermionic determinant from two-dimensional quantum chromodynamics is also studied, and calculated, exactly, as in decoupling gauge as with out reference to a particular gauge. (M.C.K.) [pt
Discrete elastic model for two-dimensional melting
Lansac, Yves; Glaser, Matthew A.; Clark, Noel A.
2006-04-01
We present a network model for the study of melting and liquid structure in two dimensions, the first in which the presence and energy of topological defects (dislocations and disclinations) and of geometrical defects (elemental voids) can be independently controlled. Interparticle interaction is via harmonic springs and control is achieved by Monte Carlo moves which springs can either be orientationally “flipped” between particles to generate topological defects, or can be “popped” in force-free shape, to generate geometrical defects. With the geometrical defects suppressed the transition to the liquid phase occurs via disclination unbinding, as described by the Kosterlitz-Thouless-Halperin-Nelson-Young model and found in soft potential two-dimensional (2D) systems, such as the dipole-dipole potential [H. H. von Grünberg , Phys. Rev. Lett. 93, 255703 (2004)]. By contrast, with topological defects suppressed, a disordering transition, the Glaser-Clark condensation of geometrical defects [M. A. Glaser and N. A. Clark, Adv. Chem. Phys. 83, 543 (1993); M. A. Glaser , Springer Proceedings in Physics: Dynamics and Patterns in Complex Fluids (Springer-Verlag, Berlin, 1990), Vol. 52, p. 141], produces a state that accurately characterizes the local liquid structure and first-order melting observed in hard-potential 2D systems, such as hard disk and the Weeks-Chandler-Andersen (WCA) potentials (M. A. Glaser and co-workers, see above). Thus both the geometrical and topological defect systems play a role in melting. The present work introduces a system in which the relative roles of topological and geometrical defects and their interactions can be explored. We perform Monte Carlo simulations of this model in the isobaric-isothermal ensemble, and present the phase diagram as well as various thermodynamic, statistical, and structural quantities as a function of the relative populations of geometrical and topological defects. The model exhibits a rich phase behavior
Schimming, C. D.; Durian, D. J.
2017-09-01
For dry foams, the transport of gas from small high-pressure bubbles to large low-pressure bubbles is dominated by diffusion across the thin soap films separating neighboring bubbles. For wetter foams, the film areas become smaller as the Plateau borders and vertices inflate with liquid. So-called "border-blocking" models can explain some features of wet-foam coarsening based on the presumption that the inflated borders totally block the gas flux; however, this approximation dramatically fails in the wet or unjamming limit where the bubbles become close-packed spheres and coarsening proceeds even though there are no films. Here, we account for the ever-present border-crossing flux by a new length scale defined by the average gradient of gas concentration inside the borders. We compute that it is proportional to the geometric average of film and border thicknesses, and we verify this scaling by numerical solution of the diffusion equation. We similarly consider transport across inflated vertices and surface Plateau borders in quasi-two-dimensional foams. And we show how the d A /d t =K0(n -6 ) von Neumann law is modified by the appearance of terms that depend on bubble size and shape as well as the concentration gradient length scales. Finally, we use the modified von Neumann law to compute the growth rate of the average bubble area, which is not constant.
The two-dimensional Godunov scheme and what it means for macroscopic pedestrian flow models
Van Wageningen-Kessels, F.L.M.; Daamen, W.; Hoogendoorn, S.P.
2015-01-01
An efficient simulation method for two-dimensional continuum pedestrian flow models is introduced. It is a two-dimensional and multi-class extension of the Go-dunov scheme for one-dimensional road traffic flow models introduced in the mid 1990’s. The method can be applied to continuum pedestrian
Critical behavior of the two-dimensional icosahedron model
Ueda, Hiroshi; Okunishi, Kouichi; Krčmár, Roman; Gendiar, Andrej; Yunoki, Seiji; Nishino, Tomotoshi
2017-12-01
In the context of a discrete analog of the classical Heisenberg model, we investigate the critical behavior of the icosahedron model, where the interaction energy is defined as the inner product of neighboring vector spins of unit length pointing to the vertices of the icosahedron. The effective correlation length and magnetization of the model are calculated by means of the corner-transfer-matrix renormalization group (CTMRG) method. A scaling analysis with respect to the cutoff dimension m in CTMRG reveals a second-order phase transition characterized by the exponents ν =1.62 ±0.02 and β =0.12 ±0.01 . We also extract the central charge from the classical analog of entanglement entropy as c =1.90 ±0.02 , which cannot be explained by the minimal series of conformal field theory.
Eight-Vertex Model of Two-Dimensional Domain Walls
Rys, Franz S.
1983-09-01
A statistical model of interacting linear domain walls (occurring, e.g., in monolayer adsorbates) is solved on the square lattice with use of exact and numerical results of an equivalent eight-vertex model. For attractive walls a commensurate and an incommensurate phase are separated by a first-order line for stiff walls and by a fluid phase for flexible walls. The phase boundaries with the fluid phase are Ising-like. For repulsive stiff walls an intermediate striped phase with a nonuniversal boundary occurs which vanishes for higher flexibilities. Moreover, disorder lines are located.
Two - Dimensional Mathematical Model of Water Flow in Open ...
African Journals Online (AJOL)
The irrotational flow condition is used for simplification of the system of the governing shallow water equations and the final nonlinear differential equation is solved for the unknown energy head using the finite element method. A one - dimensional problem was solved with diffusion hydraulic model (DHM), energy diffusion ...
Two-dimensional hydrologic modeling to evaluate aquatic habitat conditions
Pamela Edwards; Frederica Wood; Michael Little; Peter Vila; Peter Vila
2006-01-01
We describe the modeling and mapping procedures used to examine aquatic habitat conditions and habitat suitability of a small river in north- central West Virginia where fish survival and reproduction in specific reaches are poor. The study includes: (1) surveying cross sections of streambed reaches and measuring discharges and corresponding water-surface elevations,...
Recent numerical results on the two dimensional Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Parola, A.; Sorella, S.; Baroni, S.; Car, R.; Parrinello, M.; Tosatti, E. (SISSA, Trieste (Italy))
1989-12-01
A new method for simulating strongly correlated fermionic systems, has been applied to the study of the ground state properties of the 2D Hubbard model at various fillings. Comparison has been made with exact diagonalizations in the 4 x 4 lattices where very good agreement has been verified in all the correlation functions which have been studied: charge, magnetization and momentum distribution. (orig.).
Efficient two-dimensional magnetotellurics modelling using implicitly ...
Indian Academy of Sciences (India)
integral equation methods, we have opted for the. Keywords. Finite difference; eigenmode method; multi-frequency approach. J. Earth Syst. Sci. 120, No. 4, August 2011, pp. 595–604. cO Indian Academy of Sciences. 595 ... (1984) used Singular Value Decomposition (SVD) for 2D forward modelling. However, the versatile.
Flow Modelling for partially Cavitating Two-dimensional Hydrofoils
DEFF Research Database (Denmark)
Krishnaswamy, Paddy
2001-01-01
The present work addresses te computational analysis of partial sheet hydrofoil cavitation in two dimensions. Particular attention is given to the method of simulating the flow at the end of the cavity. A fixed-length partially cavitating panel method is used to predict the height of the re...... of the model and comparing the present calculations with numerical results. The flow around the partially cavitating hydrofoil with a re-entrant jet has also been treated with a viscous/inviscid interactive method. The viscous flow model is based on boundary layer theory applied on the compound foil......, consisting of the union of the cavity and the hydrofoil surface. The change in the flow direction in the cavity closure region is seen to have a slightly adverse effect on the viscous pressure distribution. Otherwise, it is seen that the viscous re-entrant jet solution compares favourably with experimental...
Model and observed seismicity represented in a two dimensional space
Directory of Open Access Journals (Sweden)
M. Caputo
1976-06-01
Full Text Available In recent years theoretical seismology lias introduced
some formulae relating the magnitude and the seismic moment of earthquakes
to the size of the fault and the stress drop which generated the
earthquake.
In the present paper we introduce a model for the statistics of the
earthquakes based on these formulae. The model gives formulae which
show internal consistency and are also confirmed by observations.
For intermediate magnitudes the formulae reproduce also the trend
of linearity of the statistics of magnitude and moment observed in all the
seismic regions of the world. This linear trend changes into a curve with
increasing slope for large magnitudes and moment.
When a catalogue of the magnitudes and/or the seismic moment of
the earthquakes of a seismic region is available, the model allows to estimate
the maximum magnitude possible in the region.
Block Pickard Models for Two-Dimensional Constraints
DEFF Research Database (Denmark)
Forchhammer, Søren; Justesen, Jørn
2009-01-01
In Pickard random fields (PRF), the probabilities of finite configurations and the entropy of the field can be calculated explicitly, but only very simple structures can be incorporated into such a field. Given two Markov chains describing a boundary, an algorithm is presented which determines...... for the domino tiling constraint represented by a quaternary alphabet. PRF models are also presented for higher order constraints, including the no isolated bits (n.i.b.) constraint, and a minimum distance 3 constraint by defining super symbols on blocks of binary symbols....
On the renormalization group flow in two dimensional superconformal models
International Nuclear Information System (INIS)
Ahn, Changrim; Stanishkov, Marian
2014-01-01
We extend the results on the RG flow in the next to leading order to the case of the supersymmetric minimal models SM p for p≫1. We explain how to compute the NS and Ramond fields conformal blocks in the leading order in 1/p and follow the renormalization scheme proposed in [1]. As a result we obtained the anomalous dimensions of certain NS and Ramond fields. It turns out that the linear combination expressing the infrared limit of these fields in term of the IR theory SM p−2 is exactly the same as those of the nonsupersymmetric minimal theory
Mesh-free Hamiltonian implementation of two dimensional Darwin model
Siddi, Lorenzo; Lapenta, Giovanni; Gibbon, Paul
2017-08-01
A new approach to Darwin or magnetoinductive plasma simulation is presented, which combines a mesh-free field solver with a robust time-integration scheme avoiding numerical divergence errors in the solenoidal field components. The mesh-free formulation employs an efficient parallel Barnes-Hut tree algorithm to speed up the computation of fields summed directly from the particles, avoiding the necessity of divergence cleaning procedures typically required by particle-in-cell methods. The time-integration scheme employs a Hamiltonian formulation of the Lorentz force, circumventing the development of violent numerical instabilities associated with time differentiation of the vector potential. It is shown that a semi-implicit scheme converges rapidly and is robust to further numerical instabilities which can develop from a dominant contribution of the vector potential to the canonical momenta. The model is validated by various static and dynamic benchmark tests, including a simulation of the Weibel-like filamentation instability in beam-plasma interactions.
TWO-DIMENSIONAL MODELLING OF ACCIDENTAL FLOOD WAVES PROPAGATION
Directory of Open Access Journals (Sweden)
Lorand Catalin STOENESCU
2011-05-01
Full Text Available The study presented in this article describes a modern modeling methodology of the propagation of accidental flood waves in case a dam break; this methodology is applied in Romania for the first time for the pilot project „Breaking scenarios of Poiana Uzului dam”. The calculation programs used help us obtain a bidimensional calculation (2D of the propagation of flood waves, taking into consideration the diminishing of the flood wave on a normal direction to the main direction; this diminishing of the flood wave is important in the case of sinuous courses of water or with urban settlements very close to the minor river bed. In the case of Poiana Uzului dam, 2 scenarios were simulated with the help of Ph.D. Eng. Dan Stematiu, plausible scenarios but with very little chances of actually producing. The results were presented as animations with flooded surfaces at certain time steps successively.
International Nuclear Information System (INIS)
Getmanov, B.S.
1988-01-01
The results of classification of two-dimensional relativistic field models (1) spinor; (2) essentially-nonlinear scalar) possessing higher conservation laws using the system of symbolic computer calculations are presented shortly
On Regularity Criteria for the Two-Dimensional Generalized Liquid Crystal Model
Directory of Open Access Journals (Sweden)
Yanan Wang
2014-01-01
Full Text Available We establish the regularity criteria for the two-dimensional generalized liquid crystal model. It turns out that the global existence results satisfy our regularity criteria naturally.
Some issues in two-dimensional modeling of tritium transport
International Nuclear Information System (INIS)
Tam, S.W.
1991-01-01
Among the major processes leading to tritium transport through Li ceramic breeders the percolation of gaseous tritium species through the connected porosity remains the lest amenable to a satisfactory treatment. The combination of diffusion and reaction through the convoluted transport pathways prescribed by the system of pores poses a formidable challenge. The key issue is to make the fundamental connection between the tortuousity of the medium with the transport processes in terms of only basic parameters that are amenable to fundamental understanding and experimental determinations. This fundamental challenges is met within the following approaches. The technique that we have employed is a random network percolation model. Local transport in each individual pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the medium is accounted for via Monte Carlo methods. In this way the approach requires as inputs only physical-chemical parameters that are amenable to clear basic understanding and experimental determination. In the sense it provides predictive capability. The approach has been applied to an analysis of the concept of tritium residence time which is associated with the first passage time, a direct output of our analysis. In the next stage of our work the tool that we have developed would be employed to investigate the issues of vary large networks, realistic microstructural information and the effect of varying pressure gradient along the purge channels. We have demonstrated that the approach that has been adopted can be utilized to analyze in a very illuminating way the underlying issues of the concept of residence time. We believe that the present approach is ideally suited to tackle these very important yet difficult issues
Effects of Response Style on Polarity and Validity of Two-Dimensional Mood Models
1985-08-01
A. (1979) Affective space is bipolar. Journal of PersonalitY and Social Psychology, 37, 345-356. RUSSELL, J. A. (1980) A circumplex model of affect...Classification) (U) EFFECTS OF RESPONSE STYLE ON POLARITY AND VALIDITY OF TWO-DIMENSIONAL MOOD MODELS 12. PERSONAL AUTHOR(S) Vickers, Ross R. Jr., & Hervig, Linda...number) "’"T nipolar and bipolar two-dimensional models have been proposed to represent mood. This study showed that a given data set will produce both
Schiek, Richard [Albuquerque, NM
2006-06-20
A method of generating two-dimensional masks from a three-dimensional model comprises providing a three-dimensional model representing a micro-electro-mechanical structure for manufacture and a description of process mask requirements, reducing the three-dimensional model to a topological description of unique cross sections, and selecting candidate masks from the unique cross sections and the cross section topology. The method further can comprise reconciling the candidate masks based on the process mask requirements description to produce two-dimensional process masks.
The Wheeler-De Witt equation in two-dimensional dilaton gravity models
International Nuclear Information System (INIS)
Ahmed, M. A.
2000-01-01
In this paper it is studied the quantum theory of a model of two-dimensional dilaton gravity within the canonical framework. It is set up and solved the Wheeler-De Witt equation for the model and obtain its exact analytic solutions
A Model for the Two-dimensional no Isolated Bits Constraint
DEFF Research Database (Denmark)
Forchhammer, Søren; Laursen, Torben Vaarby
2006-01-01
A stationary model is presented for the two-dimensional (2-D) no isolated bits (n.i.b.) constraint over an extended alphabet defined by the elements within 1 by 2 blocks. This block-wise model is based on a set of sufficient conditions for a Pickard random field (PRF) over an m-ary alphabet...
DEFF Research Database (Denmark)
Sørensen, Paul Haase; Baungaard, Jens Rane
1996-01-01
A general model for a rotating homogenous flexible robot link is developed. The model describes two-dimensional transverse vibrations induced by the actuator due to misalignment of the actuator axis of rotation relative to the link symmetry axis and due to translational acceleration of the link...
Modeling of the financial market using the two-dimensional anisotropic Ising model
Lima, L. S.
2017-09-01
We have used the two-dimensional classical anisotropic Ising model in an external field and with an ion single anisotropy term as a mathematical model for the price dynamics of the financial market. The model presented allows us to test within the same framework the comparative explanatory power of rational agents versus irrational agents with respect to the facts of financial markets. We have obtained the mean price in terms of the strong of the site anisotropy term Δ which reinforces the sensitivity of the agent's sentiment to external news.
Two-dimensional black hole as a topological coset model of c = 1 string theory
International Nuclear Information System (INIS)
Mukhi, S.; Vafa, C.
1993-01-01
We show that a special superconformal coset (with c=3) is equivalent to c=1 matter coupled to two-dimensional gravity. This identification allows a direct computation of the correlation functions of the c=1 non-critical string to all genus, and at nonzero cosmological constant, directly from the continuum approach. The results agree with those of the matrix model. Moreover we connect our coset with a twisted version of a euclidean two-dimensional black hole, in which the ghost and matter systems are mixed. (orig.)
Transport in two-dimensional scattering stochastic media: Simulations and models
International Nuclear Information System (INIS)
Haran, O.; Shvarts, D.; Thieberger, R.
1999-01-01
Classical monoenergetic transport of neutral particles in a binary, scattering, two-dimensional stochastic media is discussed. The work focuses on the effective representation of the stochastic media, as obtained by averaging over an ensemble of random realizations of the media. Results of transport simulations in two-dimensional stochastic media are presented and compared against results from several models. Problems for which this work is relevant range from transport through cracked or porous concrete shields and transport through boiling coolant of a nuclear reactor, to transport through stochastic stellar atmospheres
Alignment dynamics of diffusive scalar gradient in a two-dimensional model flow
Gonzalez, M.
2018-04-01
The Lagrangian two-dimensional approach of scalar gradient kinematics is revisited accounting for molecular diffusion. Numerical simulations are performed in an analytic, parameterized model flow, which enables considering different regimes of scalar gradient dynamics. Attention is especially focused on the influence of molecular diffusion on Lagrangian statistical orientations and on the dynamics of scalar gradient alignment.
Two-dimensional quantum electrodynamics as a model in the constructive quantum field theory
International Nuclear Information System (INIS)
Ito, K.R.
1976-01-01
We investigate two-dimensional quantum electrodynamics((QED) 2 ) type models on the basis of the Hamiltonian formalism of a vector field. The transformation into a sine-Gordon equation is clarified as a generalized mass-shift transformation through canonical linear transformations. (auth.)
Stationary states of the two-dimensional nonlinear Schrödinger model with disorder
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Hendriksen, D.; Christiansen, Peter Leth
1998-01-01
Solitonlike excitations in the presence of disorder in the two-dimensional cubic nonlinear Schrodinger equation are analyzed. The continuum as well as the discrete problem are analyzed. In the continuum model, otherwise unstable excitations are stabilized in the presence of disorder...
Exploring a two-dimensional model of mentor teacher roles in mentoring dialogues
Dr. F.J.A.J. Crasborn; Dr. Paul Hennissen; Dr. Niels Brouwer; Prof. Dr. Fred Korthagen; Prof. Dr. Theo Bergen
2011-01-01
The extent to which mentor teachers are able to address mentees' individual needs is an important factor in the success of mentoring. A two-dimensional model of mentor teacher roles in mentoring dialogues, entitled MERID, is explored empirically. Data regarding five aspects of mentoring dialogues
DEFF Research Database (Denmark)
Christiansen, Peter Leth; Gaididei, Yuri Borisovich; Johansson, M.
1998-01-01
The dynamics of discrete two-dimensional nonlinear Schrodinger models with long-range dispersive interactions is investigated. In particular, we focus on the cases where the dispersion arises from a dipole-dipole interaction, assuming the dipole moments at each lattice site to be aligned either...
On two-dimensionalization of three-dimensional turbulence in shell models
DEFF Research Database (Denmark)
Chakraborty, Sagar; Jensen, Mogens Høgh; Sarkar, A.
2010-01-01
Applying a modified version of the Gledzer-Ohkitani-Yamada (GOY) shell model, the signatures of so-called two-dimensionalization effect of three-dimensional incompressible, homogeneous, isotropic fully developed unforced turbulence have been studied and reproduced. Within the framework of shell...
Proton transport in a membrane protein channel: two-dimensional infrared spectrum modeling.
Liang, C.; Knoester, J.; Jansen, T.L.Th.A.
2012-01-01
We model the two-dimensional infrared (2DIR) spectrum of a proton channel to investigate its applicability as a spectroscopy tool to study the proton transport process in biological systems. Proton transport processes in proton channels are involved in numerous fundamental biochemical reactions.
Two-dimensional and transient thermal model of the continuous tape laying process
Skandali, M.; Jansen, K.M.B.; Koussios, S.; Sinke, J.; Benedictus, R.
2015-01-01
The purpose of this study is to simulate the two-dimensional, transient and continuous heat transfer during the thermoset Automated Tape Laying (ATL) process. The heat transfer analysis is coupled with a cure kinetics model of the thermoset prepreg tapes used for the process. Unlike most studies,
Model of two-dimensional electron gas formation at ferroelectric interfaces
Energy Technology Data Exchange (ETDEWEB)
Aguado-Puente, P.; Bristowe, N. C.; Yin, B.; Shirasawa, R.; Ghosez, Philippe; Littlewood, P. B.; Artacho, Emilio
2015-07-01
The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here, we study under what circumstances similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms, a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO3/SrTiO3 heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first-principles simulations of free-standing slabs of PbTiO3. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a nonvolatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.
Effects of Response Style on the Polarity and Validity of Two-Dimensional Mood Models.
1985-08-01
bipolar. Journal of Personality and Social Psychology, 37, 345-356. Russell, J.A. (1980). A circumplex model of affect. Journal of Personality and Social...RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS- 19 6 3 A ’ EFFECTS OF RESPONSE STYLE ON THE POLARITY AND VALIDITY OF TWO-DIMENSIONAL MOOD MODELS -: N R...hypothesis requires appropriate measures of emotional state. Therefore, this study compared two alternative models for describing emotional states as
Two-dimensional model of laser alloying of binary alloy powder with interval of melting temperature
Knyzeva, A. G.; Sharkeev, Yu. P.
2017-10-01
The paper contains two-dimensional model of laser beam melting of powders from binary alloy. The model takes into consideration the melting of alloy in some temperature interval between solidus and liquidus temperatures. The external source corresponds to laser beam with energy density distributed by Gauss law. The source moves along the treated surface according to given trajectory. The model allows investigating the temperature distribution and thickness of powder layer depending on technological parameters.
Modelling floor heating systems using a validated two-dimensional ground coupled numerical model
DEFF Research Database (Denmark)
Weitzmann, Peter; Kragh, Jesper; Roots, Peter
2005-01-01
This paper presents a two-dimensional simulation model of the heat losses and tempera-tures in a slab on grade floor with floor heating which is able to dynamically model the floor heating system. The aim of this work is to be able to model, in detail, the influence from the floor construction...... the floor. This model can be used to design energy efficient houses with floor heating focusing on the heat loss through the floor construction and foundation. It is found that it is impor-tant to model the dynamics of the floor heating system to find the correct heat loss to the ground, and further......, that the foundation has a large impact on the energy consumption of buildings heated by floor heating. Consequently, this detail should be in focus when designing houses with floor heating....
A two-dimensional analytical model of laminar flame in lycopodium dust particles
Energy Technology Data Exchange (ETDEWEB)
Rahbari, Alireza [Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of); Shakibi, Ashkan [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Bidabadi, Mehdi [Combustion Research Laboratory, Narmak, Tehran (Iran, Islamic Republic of)
2015-09-15
A two-dimensional analytical model is presented to determine the flame speed and temperature distribution of micro-sized lycopodium dust particles. This model is based on the assumptions that the particle burning rate in the flame front is controlled by the process of oxygen diffusion and the flame structure consists of preheat, reaction and post flame zones. In the first step, the energy conservation equations for fuel-lean condition are expressed in two dimensions, and then these differential equations are solved using the required boundary condition and matching the temperature and heat flux at the interfacial boundaries. Consequently, the obtained flame temperature and flame speed distributions in terms of different particle diameters and equivalence ratio for lean mixture are compared with the corresponding experimental data for lycopodium dust particles. Consequently, it is shown that this two-dimensional model demonstrates better agreement with the experimental results compared to the previous models.
Numerical simulation of potato slices drying using a two-dimensional finite element model
Directory of Open Access Journals (Sweden)
Beigi Mohsen
2017-01-01
Full Text Available An experimental and numerical study was conducted to investigate the process of potato slices drying. For simulating the moisture transfer in the samples and predict the dehydration curves, a two-dimensional finite element model was developed and programmed in Compaq Visual Fortran, version 6.5. The model solved the Fick’s second law for slab in a shrinkage system to calculate the unsteady two-dimensional moisture transmission in rectangular coordinates (x,y. Moisture diffusivity and moisture transfer coefficient were determined by minimizing the sum squares of residuals between experimental and numerical predicted data. Shrinkage kinetics of the potato slices during dehydration was determined experimentally and found to be a linear function of removed moisture. The determined parameters were used in the mathematical model. The predicted moisture content values were compared to the experimental data and the validation results demonstrated that the dynamic drying curves were predicted by the methodology very well.
Rheological properties of the soft-disk model of two-dimensional foams
DEFF Research Database (Denmark)
Langlois, Vincent; Hutzler, Stefan; Weaire, Denis
2008-01-01
The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel-Bulkley re......The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel......-Bulkley relation, normal stress effects (dilatancy), and localization in the presence of wall drag. We show that even a model that incorporates only linear viscous effects at the local level gives rise to nonlinear (power-law) dependence of the limit stress on strain rate. With wall drag, shear localization...
String field theory in minimal model backgrounds and non-perturbative two-dimensional gravity
International Nuclear Information System (INIS)
Imbimbo, C.; Mukhi, S.
1991-01-01
The classical phase space of free closed-string field theory in the background of (p,q) minimal models is studied. It is shown that in the limit q→∞ for fixed p, this becomes the phase space of p-1 massless chiral bosons on a two-dimensional target space, twisted by Z p . It is argued that in the interacting theory, the bosons remain free and massless in the limit, but the non-linear gauge symmetries of string field theory require the imposition of W p -algebra conditions on the Hilbert space, allowing a single physical state. The wave function for this state is the KdV τ-function associated to non-perturbative two-dimensional gravity in the matrix-model approach. (orig.)
A Novel Machine Learning Strategy Based on Two-Dimensional Numerical Models in Financial Engineering
Directory of Open Access Journals (Sweden)
Qingzhen Xu
2013-01-01
Full Text Available Machine learning is the most commonly used technique to address larger and more complex tasks by analyzing the most relevant information already present in databases. In order to better predict the future trend of the index, this paper proposes a two-dimensional numerical model for machine learning to simulate major U.S. stock market index and uses a nonlinear implicit finite-difference method to find numerical solutions of the two-dimensional simulation model. The proposed machine learning method uses partial differential equations to predict the stock market and can be extensively used to accelerate large-scale data processing on the history database. The experimental results show that the proposed algorithm reduces the prediction error and improves forecasting precision.
A Discontinuous Galerkin Method for Two-Dimensional Shock Wave Modeling
Directory of Open Access Journals (Sweden)
W. Lai
2011-01-01
Full Text Available A numerical scheme based on discontinuous Galerkin method is proposed for the two-dimensional shallow water flows. The scheme is applied to model flows with shock waves. The form of shallow water equations that can eliminate numerical imbalance between flux term and source term and simplify computation is adopted here. The HLL approximate Riemann solver is employed to calculate the mass and momentum flux. A slope limiting procedure that is suitable for incompressible two-dimensional flows is presented. A simple method is adapted for flow over initially dry bed. A new formulation is introduced for modeling the net pressure force and gravity terms in discontinuous Galerkin method. To validate the scheme, numerical tests are performed to model steady and unsteady shock waves. Applications include circular dam break with shock, shock waves in channel contraction, and dam break in channel with 45∘ bend. Numerical results show that the scheme is accurate and efficient to model two-dimensional shallow water flows with shock waves.
International Nuclear Information System (INIS)
Kirillov, I.R.; Obukhov, D.M.
2005-01-01
One introduces a completely two-dimensional mathematical model to calculate characteristics of induction magnetohydrodynamic (MHD) machines with a cylindrical channel. On the basis of the numerical analysis one obtained a pattern of liquid metal flow in a electromagnetic pump at presence of the MHD-instability characterized by initiation of large-scale vortices propagating longitudinally and azimuthally. Comparison of the basic calculated characteristics of pump with the experiment shows their adequate qualitative and satisfactory quantitative coincidence [ru
Two Dimensional Modeling of III-V Heterojunction Gate All Around Tunnel Field Effect Transistor
Manjula Vijh; R.S. Gupta; Sujata Pandey
2017-01-01
Tunnel Field Effect Transistor is one of the extensively researched semiconductor devices, which has captured attention over the conventional Metal Oxide Semiconductor Field Effect Transistor. This device, due to its varied advantages, is considered in applications where devices are scaled down to deep sub-micron level. Like MOSFETs, many geometries of TFETs have been studied and analyzed in the past few years. This work, presents a two dimensional analytical model for a III-V Heterojunction ...
Two-Dimensional Model Test Study of New Western Breakwater Proposal for Port of Hanstholm
DEFF Research Database (Denmark)
Eldrup, Mads Røge; Andersen, Thomas Lykke
The present report presents results from a two-dimensional model test study carried out at Aalborg University in December 2016 with the proposed trunk section for the new western breakwater in Port of Hanstholm. The objectives of the model tests were to study the stability of the armour layer, to...... erosion, overtopping and transmission. The scale used for the model tests was 1:61.5. Unless otherwise specified all values given in this report are prototype values converted from the model to prototype according to the Froude model law....
Formulation and validation of a two-dimensional steady-state model of desiccant wheels
DEFF Research Database (Denmark)
Bellemo, Lorenzo; Elmegaard, Brian; Kærn, Martin R.
2015-01-01
systems. A steady-state two-dimensional model is formulated and implemented, aiming to obtain good accuracy and short computational times with the purpose of inclusion in complete system models. The model includes mass and energy balances and correlations for heat and mass transfer based on empirical...... relations from the scientific literature. Convective heat and mass transfer coefficients are computed locally accounting for the entrance length effects. Mass diffusion inside the desiccant material is neglected. Comparison with experimental data from the literature shows that the model reproduces...
S-matrix regularities of two-dimensional sigma-models of Stiefel manifolds
International Nuclear Information System (INIS)
Flume-Gorczyca, B.
1980-01-01
The S-matrices of the two-dimensional nonlinear O(n + m)/O(n) and O(n + m)/O(n) x O(m) sigma-models corresponding to Stiefel and Grassmann manifolds, respectively, are compared in leading order in 1/n. It is shown, that after averaging over O(m) labels of the incoming and outgoing particles, the S-matrices of both models become identical. This result explains why commonly expected regularities of the Grassmann models, in particular absence of particle production, are found, modulo an O(m) average, also in Stiefel models. (orig.)
International Nuclear Information System (INIS)
Choi, S. N.; Kim, H. N.; Jang, K. S.; Kim, H. J.
2000-01-01
The purpose of this paper is to determine a two dimensional axisymmetric model through a comparative study between a three dimensional and an axisymmetric finite element analysis of the reactor coolant piping nozzle subject to internal pressure. The finite element analysis results show that the stress adopting the axisymmetric model with the radius of equivalent spherical vessel are well agree with that adopting the three dimensional model. The radii of equivalent spherical vessel are 3.5 times and 7.3 times of the radius of the reactor coolant piping for the safety injection nozzle and for the residual heat removal nozzle, respectively
Two-dimensional modeling of apparent resistivity pseudosections in the Cerro Prieto region
Energy Technology Data Exchange (ETDEWEB)
Vega, R.; Martinez, M.
1981-01-01
Using a finite-difference program (Dey, 1976) for two-dimensional modeling of apparent resistivity pseudosections obtained by different measuring arrays, four apparent resistivity pseudosections obtained at Cerro Prieto with a Schlumberger array by CFE personnel were modeled (Razo, 1978). Using geologic (Puente and de la Pena, 1978) and lithologic (Diaz, et al., 1981) data from the geothermal region, models were obtained which show clearly that, for the actual resistivity present in the zone, the information contained in the measured pseudosections is primarily due to the near-surface structure and does not show either the presence of the geothermal reservoir or the granitic basement which underlies it.
Energy-landscape analysis of the two-dimensional nearest-neighbor φ⁴ model.
Mehta, Dhagash; Hauenstein, Jonathan D; Kastner, Michael
2012-06-01
The stationary points of the potential energy function of the φ⁴ model on a two-dimensional square lattice with nearest-neighbor interactions are studied by means of two numerical methods: a numerical homotopy continuation method and a globally convergent Newton-Raphson method. We analyze the properties of the stationary points, in particular with respect to a number of quantities that have been conjectured to display signatures of the thermodynamic phase transition of the model. Although no such signatures are found for the nearest-neighbor φ⁴ model, our study illustrates the strengths and weaknesses of the numerical methods employed.
Two-dimensional model of flows and interface instability in aluminum reduction cells
Zikanov, Oleg; Sun, Haijun; Ziegler, Donald
2003-11-01
We derive a two-dimensional model for the melt flows and interface instability in aluminum reduction cells. The model is based on the de St. Venant shallow water equations and incorporates the essential features of the system such as the magnetohydrodynamic instability mechanism and nonlinear coupling between the flows and interfacial waves. The model is applied to verify a recently proposed theory that explains the instability through the interaction between perturbations of horizontal electric currents in the aluminum layer and the imposed vertical magnetic field. We investigate the role of other factors, in particular, background melt flows and magnetic field perturbations.
Basic problems solving for two-dimensional discrete 3 × 4 order hidden markov model
International Nuclear Information System (INIS)
Wang, Guo-gang; Gan, Zong-liang; Tang, Gui-jin; Cui, Zi-guan; Zhu, Xiu-chang
2016-01-01
A novel model is proposed to overcome the shortages of the classical hypothesis of the two-dimensional discrete hidden Markov model. In the proposed model, the state transition probability depends on not only immediate horizontal and vertical states but also on immediate diagonal state, and the observation symbol probability depends on not only current state but also on immediate horizontal, vertical and diagonal states. This paper defines the structure of the model, and studies the three basic problems of the model, including probability calculation, path backtracking and parameters estimation. By exploiting the idea that the sequences of states on rows or columns of the model can be seen as states of a one-dimensional discrete 1 × 2 order hidden Markov model, several algorithms solving the three questions are theoretically derived. Simulation results further demonstrate the performance of the algorithms. Compared with the two-dimensional discrete hidden Markov model, there are more statistical characteristics in the structure of the proposed model, therefore the proposed model theoretically can more accurately describe some practical problems.
Energy Technology Data Exchange (ETDEWEB)
Contreras, Anthony Marshall [Univ. of California, Berkeley, CA (United States)
2006-05-20
In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.
Simple Screened Hydrogen Model of Excitons in Two-Dimensional Materials
DEFF Research Database (Denmark)
Olsen, Thomas; Latini, Simone; Rasmussen, Filip Anselm
2016-01-01
We present a generalized hydrogen model for the binding energies (EB) and radii of excitons in two-dimensional (2D) materials that sheds light on the fundamental differences between excitons in two and three dimensions. In contrast to the well-known hydrogen model of three-dimensional (3D) excitons......, the description of 2D excitons is complicated by the fact that the screening cannot be assumed to be local. We show that one can consistently define an effective 2D dielectric constant by averaging the screening over the extend of the exciton. For an ideal 2D semiconductor this leads to a simple expression for EB...
Hollow cathode modeling: I. A coupled plasma thermal two-dimensional model
Sary, Gaétan; Garrigues, Laurent; Boeuf, Jean-Pierre
2017-05-01
A two-dimensional axisymmetric quasi-neutral fluid model of an emissive hollow cathode that includes neutral xenon, single charge ions and electrons has been developed. The gas discharge is coupled with a thermal model of the cathode into a self-consistent generic model applicable to any hollow cathode design. An exhaustive description of the model assumptions and governing equations is given. Boundary conditions for both the gas discharge and thermal model are clearly specified as well. A new emissive sheath model that is valid for any emissive material and in both space charge and thermionic emission limited regimes is introduced. Then, setting the emitter temperature to an experimentally measured profile, we compare simulation results of the plasma model to measurements available in the literature for NASA NSTAR barium oxide cathode. Qualitative discrepancies between simulation results and measurements are noted in the cathode plume regarding the simulated plasma potential. Motivated by experimental evidence supporting the occurrence of ion acoustic instabilities in the cathode plume, an enhanced model of electron transport in the plume is presented and its consequences analyzed. Using the obtained plasma model, simulated quantities in the plume are qualitatively comparable with measurements. Inside the cathode, the simulated plasma density agrees well with measurements and is within the +/- 50 % experimental uncertainty associated with these measurements. A comparison of simulation results of the full coupled cathode model for the NASA NSTAR cathode with experimental measurements is presented in a companion paper, as well as a physical analysis of the cathode behavior and a parametric study of the influence of the operating point and key design choices.
Continued development and validation of the AER two-dimensional interactive model
Ko, M. K. W.; Sze, N. D.; Shia, R. L.; Mackay, M.; Weisenstein, D. K.; Zhou, S. T.
1996-01-01
Results from two-dimensional chemistry-transport models have been used to predict the future behavior of ozone in the stratosphere. Since the transport circulation, temperature, and aerosol surface area are fixed in these models, they cannot account for the effects of changes in these quantities, which could be modified because of ozone redistribution and/or other changes in the troposphere associated with climate changes. Interactive two-dimensional models, which calculate the transport circulation and temperature along with concentrations of the chemical species, could provide answers to complement the results from three-dimension model calculations. In this project, we performed the following tasks in pursuit of the respective goals: (1) We continued to refine the 2-D chemistry-transport model; (2) We developed a microphysics model to calculate the aerosol loading and its size distribution; (3) The treatment of physics in the AER 2-D interactive model were refined in the following areas--the heating rate in the troposphere, and wave-forcing from propagation of planetary waves.
Treatment of dynamical processes in two-dimensional models of the troposphere and stratosphere
International Nuclear Information System (INIS)
Wuebbles, D.J.
1980-07-01
The physical structure of the troposphere and stratosphere is the result of an intricate interplay among a large number of radiative, chemical, and dynamical processes. Because it is not possible to model the global environment in the laboratory, theoretical models must be relied on, subject to observational verification, to simulate atmospheric processes. Of particular concern in recent years has been the modeling of those processes affecting the structure of ozone and other trace species in the stratosphere and troposphere. Zonally averaged two-dimensional models with spatial resolution in the vertical and meridional directions can provide a much more realistic representation of tracer transport than one-dimensional models, yet are capable of the detailed representation of chemical and radiative processes contained in the one-dimensional models. The purpose of this study is to describe and analyze existing approaches to representing global atmospheric transport processes in two-dimensional models and to discuss possible alternatives to these approaches. A general description of the processes controlling the transport of trace constituents in the troposphere and stratosphere is given
Two-dimensional Heisenberg model with nonlinear interactions: 1/N corrections
International Nuclear Information System (INIS)
Caracciolo, Sergio; Mognetti, Bortolo Matteo; Pelissetto, Andrea
2005-01-01
We investigate a two-dimensional classical N-vector model with a generic nearest-neighbor interaction W(σi-bar σj) in the large-N limit, focusing on the finite-temperature transition point at which energy-energy correlations become critical. We show that this transition belongs to the Ising universality class. However, the width of the region in which Ising behavior is observed scales as 1/N3/2 along the magnetic direction and as 1/N in the thermal direction; outside a crossover to mean-field behavior occurs. This explains why only mean-field behavior is observed for N=∼
Kinetic theory model for the flow of a simple gas from a two-dimensional nozzle
Riley, B. R.; Scheller, K. W.
1989-01-01
A system of nonlinear integral equations equivalent to the Krook kinetic equation for the steady state is the mathematical basis used to develop a computer code to model the flowfields for low-thrust two-dimensional nozzles. The method of characteristics was used to solve numerically by an iteration process the approximated Boltzmann equation for the number density, temperature, and velocity profiles of a simple gas as it exhausts into a vacuum. Results predict backscatter and show the effect of the inside wall boundary layer on the flowfields external to the nozzle.
Properties of loop equations for the Hermitean matrix model and for two-dimensional quantum gravity
International Nuclear Information System (INIS)
Ambjoern, J.; Makeenko, Yu.M.
1990-05-01
We study properties of the loop equations for the NxN Hermitean matrix model with arbitrary (even) interaction as well as of their continuum limit, associated with the two-dimensional quantum gravity. We apply the general procedure of iterative solution proposed recently by David. We relate the specific heat to the singular behavior of the connected correlator of two loops. We solve the continuum equation to a few lower orders in the string coupling constant, obtaining results for macroscopic loops, including the case of a multicritical fixed point. (orig.)
Crossover scaling in the two-dimensional three-state Potts model
Directory of Open Access Journals (Sweden)
T. Nagai
2013-06-01
Full Text Available We apply simulated tempering and magnetizing (STM Monte Carlo simulations to the two-dimensional three-state Potts model in an external magnetic field in order to investigate the crossover scaling behaviour in the temperature-field plane at the Potts critical point and towards the Ising universality class for negative magnetic fields. Our data set has been generated by STM simulations of several square lattices with sizes up to 160x160 spins, supplemented by conventional canonical simulations of larger lattices at selected simulation points. We present careful scaling and finite-size scaling analyses of the crossover behaviour with respect to temperature, magnetic field and lattice size.
Eigenstate thermalization in the two-dimensional transverse field Ising model.
Mondaini, Rubem; Fratus, Keith R; Srednicki, Mark; Rigol, Marcos
2016-03-01
We study the onset of eigenstate thermalization in the two-dimensional transverse field Ising model (2D-TFIM) in the square lattice. We consider two nonequivalent Hamiltonians: the ferromagnetic 2D-TFIM and the antiferromagnetic 2D-TFIM in the presence of a uniform longitudinal field. We use full exact diagonalization to examine the behavior of quantum chaos indicators and of the diagonal matrix elements of operators of interest in the eigenstates of the Hamiltonian. An analysis of finite size effects reveals that quantum chaos and eigenstate thermalization occur in those systems whenever the fields are nonvanishing and not too large.
Ishiwata, Ryosuke; Sugiyama, Yuki
2015-12-01
The two-dimensional optimal velocity model has potential applications to pedestrian dynamics and the collective motion of animals. In this paper, we extend the linear stability analysis presented in a previous paper [A Nakayama et al., Phys. Rev. E. 77, 016105 (2008), 10.1103/PhysRevE.77.016105] and investigate the effects of particle configuration on the stability of several wave modes of collective oscillations of moving particles. We find that, when a particle moves without interacting with particles that are positioned in a diagonally forward or backward direction, the stable region of the particle flow is completely removed by the elliptically polarized mode.
Nonlinear kinetic modeling and simulations of Raman scattering in a two-dimensional geometry
Directory of Open Access Journals (Sweden)
Bénisti Didier
2013-11-01
Full Text Available In this paper, we present our nonlinear kinetic modeling of stimulated Raman scattering (SRS by the means of envelope equations, whose coefficients have been derived using a mixture of perturbative and adiabatic calculations. First examples of the numerical resolution of these envelope equations in a two-dimensional homogeneous plasma are given, and the results are compared against those of particle-in-cell (PIC simulations. These preliminary comparisons are encouraging since our envelope code provides threshold intensities consistent with those of PIC simulations while requiring computational resources reduced by 4 to 5 orders of magnitude compared to full-kinetic codes.
Dynamics of the two-dimensional directed Ising model in the paramagnetic phase
Godrèche, C.; Pleimling, M.
2014-05-01
We consider the nonconserved dynamics of the Ising model on the two-dimensional square lattice, where each spin is influenced preferentially by its east and north neighbours. The single-spin flip rates are such that the stationary state is Gibbsian with respect to the usual ferromagnetic Ising Hamiltonian. We show the existence, in the paramagnetic phase, of a dynamical transition between two regimes of violation of the fluctuation-dissipation theorem in the nonequilibrium stationary state: a regime of weak violation where the stationary fluctuation-dissipation ratio is finite, when the asymmetry parameter is less than a threshold value, and a regime of strong violation where this ratio vanishes asymptotically above the threshold. This study suggests that this novel kind of dynamical transition in nonequilibrium stationary states, already found for the directed Ising chain and the spherical model with asymmetric dynamics, might be quite general. In contrast with the latter models, the equal-time correlation function for the two-dimensional directed Ising model depends on the asymmetry.
An incompressible two-dimensional multiphase particle-in-cell model for dense particle flows
Energy Technology Data Exchange (ETDEWEB)
Snider, D.M. [SAIC, Albuquerque, NM (United States); O`Rourke, P.J. [Los Alamos National Lab., NM (United States); Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
1997-06-01
A two-dimensional, incompressible, multiphase particle-in-cell (MP-PIC) method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to a Eulerian grid and then mapping back computed stress tensors to particle positions. This approach utilizes the best of Eulerian/Eulerian continuum models and Eulerian/Lagrangian discrete models. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. The computational method is implicit with respect to pressure, velocity, and volume fraction in the continuum solution thus avoiding courant limits on computational time advancement. MP-PIC simulations are compared with one-dimensional problems that have analytical solutions and with two-dimensional problems for which there are experimental data.
Development and validation of a new two-dimensional wake model for wind turbine wakes
DEFF Research Database (Denmark)
Tian, Linlin; Zhu, Wei Jun; Shen, Wen Zhong
2015-01-01
, wind tunnel experiments, and results of an advanced k-ω turbulence model as well as large eddy simulations. From the comparisons, it is found that the proposed new wake model gives a good prediction in terms of both shape and velocity amplitude of the wake deficit, especially in the far wake which......A new two-dimensional (2D) wake model is developed and validated in this article to predict the velocity and turbulence distribution in the wake of a wind turbine. Based on the classical Jensen wake model, this model is further employing a cosine shape function to redistribute the spread...... of the wake deficit in the crosswind direction. Moreover, a variable wake decay rate is proposed to take into account both the ambient turbulence and the rotor generated turbulence, different from a constant wake decay rate used in the Jensen model. The obtained results are compared to field measurements...
Jesus, Danilo A; Iskander, D Robert
2015-12-01
Ray tracing is a powerful technique to understand the light behavior through an intricate optical system such as that of a human eye. The prediction of visual acuity can be achieved through characteristics of an optical system such as the geometrical point spread function. In general, its precision depends on the number of discrete rays and the accurate surface representation of each eye's components. Recently, a method that simplifies calculation of the geometrical point spread function has been proposed for circularly symmetric systems [Appl. Opt.53, 4784 (2014)]. An extension of this method to 2D noncircularly symmetric systems is proposed. In this method, a two-dimensional ray tracing procedure for an arbitrary number of surfaces and arbitrary surface shapes has been developed where surfaces, rays, and refractive indices are all represented in functional forms being approximated by Chebyshev polynomials. The Liou and Brennan anatomically accurate eye model has been adapted and used for evaluating the method. Further, real measurements of the anterior corneal surface of normal, astigmatic, and keratoconic eyes were substituted for the first surface in the model. The results have shown that performing ray tracing, utilizing the two-dimensional Chebyshev function approximation, is possible for noncircularly symmetric models, and that such calculation can be performed with a newly created Chebfun toolbox.
Maltha, J. Bacchetti, A.C. & Heijer, T.
1977-01-01
Two different computer programs have been developed for a two-dimensional and a three-dimensional crash victim model. In this study the three-dimensional model is tested in comparison with the two-dimensional model. A test run of the two-dimensional model is simulated with the SWOV-TNO
Wan, Weibing; Yuan, Lingfeng; Zhao, Qunfei; Fang, Tao
2018-01-01
Saliency detection has been applied to the target acquisition case. This paper proposes a two-dimensional hidden Markov model (2D-HMM) that exploits the hidden semantic information of an image to detect its salient regions. A spatial pyramid histogram of oriented gradient descriptors is used to extract features. After encoding the image by a learned dictionary, the 2D-Viterbi algorithm is applied to infer the saliency map. This model can predict fixation of the targets and further creates robust and effective depictions of the targets' change in posture and viewpoint. To validate the model with a human visual search mechanism, two eyetrack experiments are employed to train our model directly from eye movement data. The results show that our model achieves better performance than visual attention. Moreover, it indicates the plausibility of utilizing visual track data to identify targets.
Finite Element Model for Failure Study of Two-Dimensional Triaxially Braided Composite
Li, Xuetao; Binienda, Wieslaw K.; Goldberg, Robert K.
2010-01-01
A new three-dimensional finite element model of two-dimensional triaxially braided composites is presented in this paper. This meso-scale modeling technique is used to examine and predict the deformation and damage observed in tests of straight sided specimens. A unit cell based approach is used to take into account the braiding architecture as well as the mechanical properties of the fiber tows, the matrix and the fiber tow-matrix interface. A 0 deg / plus or minus 60 deg. braiding configuration has been investigated by conducting static finite element analyses. Failure initiation and progressive degradation has been simulated in the fiber tows by use of the Hashin failure criteria and a damage evolution law. The fiber tow-matrix interface was modeled by using a cohesive zone approach to capture any fiber-matrix debonding. By comparing the analytical results to those obtained experimentally, the applicability of the developed model was assessed and the failure process was investigated.
Two-dimensional finite elements model for selenium transport in saturated and unsaturated zones.
Tayfur, Gokmen; Tanji, Kenneth K; Baba, Alper
2010-10-01
A two-dimensional finite element model was developed to simulate species of selenium transport in two dimensions in both saturated and unsaturated soil zones. The model considers water, selenate, selenite, and selenomethionine uptake by plants. It also considers adsorption and desorption, oxidation and reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. In addition to simulating water flow, selenate, selenite, and selenomethionine transport, the model also simulates organic and gaseous selenium transport. The developed model was applied to simulate two different observed field data. The simulation of the observed data was satisfactory, with mean absolute error of 48.5 microg/l and mean relative error of 8.9%.
Energy Technology Data Exchange (ETDEWEB)
Sahraoui, Melik [Institut Preparatoire aux Etudes d' Ingenieurs de Tunis (IPEIT) (Tunisia); Kharrat, Chafik; Halouani, Kamel [UR: Micro-Electro-Thermal Systems (METS-ENIS), Industrial Energy Systems Group, Institut Preparatoire aux Etudes d' Ingenieurs de Sfax (IPEIS), University of Sfax, B.P: 1172, 3018 Sfax (Tunisia)
2009-04-15
A two-dimensional CFD model of PEM fuel cell is developed by taking into account the electrochemical, mass and heat transfer phenomena occurring in all of its regions simultaneously. The catalyst layers and membrane are each considered as distinct regions with finite thickness and calculated properties such as permeability, local protonic conductivity, and local dissolved water diffusion. This finite thickness model enables to model accurately the protonic current in these regions with higher accuracy than using an infinitesimal interface. In addition, this model takes into account the effect of osmotic drag in the membrane and catalyst layers. General boundary conditions are implemented in a way taking into consideration any given species concentration at the fuel cell inlet, such as water vapor which is a very important parameter in determining the efficiency of fuel cells. Other operating parameters such as temperature, pressure and porosity of the porous structure are also investigated to characterize their effect on the fuel cell efficiency. (author)
Two-dimensional models as testing ground for principles and concepts of local quantum physics
Schroer, Bert
2006-02-01
In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g., chiral models, factorizing models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work, I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff( S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL (2, Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular "Euclideanization" is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J.A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an "Encyclopedia of Mathematical Physics" contribution hep-th/0502125.
Two-dimensional models as testing ground for principles and concepts of local quantum physics
International Nuclear Information System (INIS)
Schroer, Bert
2005-04-01
In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g. chiral models, factoring models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff(S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL(2,Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular 'Euclideanization' is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J. A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an 'Encyclopedia of Mathematical Physics' contribution hep-th/0502125. (author)
Two-dimensional models as testing ground for principles and concepts of local quantum physics
International Nuclear Information System (INIS)
Schroer, Bert
2006-01-01
In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g., chiral models, factorizing models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work, I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff(S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL (2, Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular 'Euclideanization' is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J.A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an 'Encyclopedia of Mathematical Physics' contribution hep-th/0502125
Two-dimensional models as testing ground for principles and concepts of local quantum physics
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [FU Berlin (Germany). Institut fuer Theoretische Physik
2005-04-15
In the past two-dimensional models of QFT have served as theoretical laboratories for testing new concepts under mathematically controllable condition. In more recent times low-dimensional models (e.g. chiral models, factoring models) often have been treated by special recipes in a way which sometimes led to a loss of unity of QFT. In the present work I try to counteract this apartheid tendency by reviewing past results within the setting of the general principles of QFT. To this I add two new ideas: (1) a modular interpretation of the chiral model Diff(S)-covariance with a close connection to the recently formulated local covariance principle for QFT in curved spacetime and (2) a derivation of the chiral model temperature duality from a suitable operator formulation of the angular Wick rotation (in analogy to the Nelson-Symanzik duality in the Ostertwalder-Schrader setting) for rational chiral theories. The SL(2,Z) modular Verlinde relation is a special case of this thermal duality and (within the family of rational models) the matrix S appearing in the thermal duality relation becomes identified with the statistics character matrix S. The relevant angular 'Euclideanization' is done in the setting of the Tomita-Takesaki modular formalism of operator algebras. I find it appropriate to dedicate this work to the memory of J. A. Swieca with whom I shared the interest in two-dimensional models as a testing ground for QFT for more than one decade. This is a significantly extended version of an 'Encyclopedia of Mathematical Physics' contribution hep-th/0502125. (author)
Phase transitions in two-dimensional uniformly frustrated XY models. II. General scheme
International Nuclear Information System (INIS)
Korshunov, S.E.
1986-01-01
For two-dimensional uniformly frustrated XY models the group of symmetry spontaneously broken in the ground state is a cross product of the group of two-dimensional rotations by some discrete group of finite order. Different possibilities of phase transitions in such systems are investigated. The transition to the Coulomb gas with noninteger charges is widely used when analyzing the properties of relevant topological excitations. The number of these excitations includes not only domain walls and traditional (integer) vortices, but also vortices with a fractional number of circulation quanta which are to be localized at bends and intersections of domain walls. The types of possible phase transitions prove to be dependent on their relative sequence: in the case the vanishing of domain wall free energy occurs earlier (at increasing temperature) than the dissociation of pairs of ordinary vortices, the second phase transition is to be associated with dissociation of pairs of fractional vortices. The general statements are illustrated with a number of examples
Test of quantum thermalization in the two-dimensional transverse-field Ising model.
Blaß, Benjamin; Rieger, Heiko
2016-12-01
We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system thermalizes or not. We consider both interaction quenches in the paramagnetic phase and field quenches in the ferromagnetic phase and compare the time-averaged probability distributions of non-conserved quantities like magnetization and correlation functions to the thermal distributions according to the canonical Gibbs ensemble obtained with quantum Monte Carlo simulations at temperatures defined by the excess energy in the system. We find that the occurrence of thermalization crucially depends on the quench parameters: While after the interaction quenches in the paramagnetic phase thermalization can be observed, our results for the field quenches in the ferromagnetic phase show clear deviations from the thermal system. These deviations increase with the quench strength and become especially clear comparing the shape of the thermal and the time-averaged distributions, the latter ones indicating that the system does not completely lose the memory of its initial state even for strong quenches. We discuss our results with respect to a recently formulated theorem on generalized thermalization in quantum systems.
Urbic, Tomaz
2017-02-01
In this paper we applied an analytical theory for the two dimensional dimerising fluid. We applied Wertheims thermodynamic perturbation theory (TPT) and integral equation theory (IET) for associative liquids to the dimerising model with arbitrary position of dimerising points from center of the particles. The theory was used to study thermodynamical and structural properties. To check the accuracy of the theories we compared theoretical results with corresponding results obtained by Monte Carlo computer simulations. The theories are accurate for the different positions of patches of the model at all values of the temperature and density studied. IET correctly predicts the pair correlation function of the model. Both TPT and IET are in good agreement with the Monte Carlo values of the energy, pressure, chemical potential, compressibility and ratios of free and bonded particles.
Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator
DEFF Research Database (Denmark)
Petersen, Thomas Frank; Pryds, Nini; Smith, Anders
2008-01-01
and water as the heat transfer fluid. The results show that the AMR is able to obtain a no-load temperature span of 10.9 K in a 1 T magnetic field with a corresponding work input of 93.0 kJ m−3 of gadolinium per cycle. The model shows significant temperature differences between the regenerator and the heat......A time-dependent, two-dimensional mathematical model of a reciprocating Active Magnetic Regenerator (AMR) operating at room-temperature has been developed. The model geometry comprises a regenerator made of parallel plates separated by channels of a heat transfer fluid and a hot as well as a cold...
Semianalytical model of the contact resistance in two-dimensional semiconductors
Grassi, Roberto; Wu, Yanqing; Koester, Steven J.; Low, Tony
2017-10-01
Contact resistance is a severe performance bottleneck for electronic devices based on two-dimensional (2D) layered semiconductors, whose contacts are Schottky rather than Ohmic. Although there is a general consensus that the injection mechanism changes from thermionic to tunneling with gate biasing, existing models tend to oversimplify the transport problem, by neglecting the 2D transport nature and the modulation of the Schottky barrier height, the latter being of particular importance in back-gated devices. In this paper, we develop a semianalytical model based on Bardeen's transfer Hamiltonian approach to describe both effects. Remarkably, our model is able to reproduce several experimental observations of a metallic behavior in the contact resistance, i.e., a decreasing resistance with decreasing temperature, occurring at high gate voltages.
General Voltage Feedback Circuit Model in the Two-Dimensional Networked Resistive Sensor Array
Directory of Open Access Journals (Sweden)
JianFeng Wu
2015-01-01
Full Text Available To analyze the feature of the two-dimensional networked resistive sensor array, we firstly proposed a general model of voltage feedback circuits (VFCs such as the voltage feedback non-scanned-electrode circuit, the voltage feedback non-scanned-sampling-electrode circuit, and the voltage feedback non-scanned-sampling-electrode circuit. By analyzing the general model, we then gave a general mathematical expression of the effective equivalent resistor of the element being tested in VFCs. Finally, we evaluated the features of VFCs with simulation and test experiment. The results show that the expression is applicable to analyze the VFCs’ performance of parameters such as the multiplexers’ switch resistors, the nonscanned elements, and array size.
A Two-Dimensional Human Minilung System (Model for Respiratory Syncytial Virus Infections
Directory of Open Access Journals (Sweden)
Esmeralda Magro-Lopez
2017-12-01
Full Text Available Human respiratory syncytial virus (HRSV is a major cause of serious pediatric respiratory diseases that lacks effective vaccine or specific therapeutics. Although our understanding about HRSV biology has dramatically increased during the last decades, the need for adequate models of HRSV infection is compelling. We have generated a two-dimensional minilung from human embryonic stem cells (hESCs. The differentiation protocol yielded at least six types of lung and airway cells, although it is biased toward the generation of distal cells. We show evidence of HRSV replication in lung cells, and the induction of innate and proinflammatory responses, thus supporting its use as a model for the study of HRSV–host interactions.
Two-dimensional velocity models for paths from Pahute Mesa and Yucca Flat to Yucca Mountain
International Nuclear Information System (INIS)
Walck, M.C.; Phillips, J.S.
1990-11-01
Vertical acceleration recordings of 21 underground nuclear explosions recorded at stations at Yucca Mountain provide the data for development of three two-dimensional crystal velocity profiles for portions of the Nevada Test Site. Paths from Area 19, Area 20 (both Pahute Mesa), and Yucca Flat to Yucca Mountain have been modeled using asymptotic ray theory travel time and synthetic seismogram techniques. Significant travel time differences exist between the Yucca Flat and Pahute Mesa source areas; relative amplitude patterns at Yucca Mountain also shift with changing source azimuth. The three models, UNEPM1, UNEPM2, and UNEYF1, successfully predict the travel time and amplitude data for all three paths. 24 refs., 34 figs., 8 tabs
Multipetal vortex structures in two-dimensional models of geophysical fluid dynamics and plasma
International Nuclear Information System (INIS)
Goncharov, V.P.; Pavlov, V.I.
2001-01-01
A new class of strongly nonlinear steadily rotating vortices is found. The Hamiltonian contour dynamics is proposed as a new approach for their study in some models of geophysical fluid dynamics and plasma. Using the Euler description as a starting point, we present a systematic procedure to reduce the two-dimensional dynamics of constant-vorticity and constant-density patches to the Hamiltonian dynamics of their contours for various parametrizations of the contour. The special Dirac procedure is used to eliminate the constraints arising in the Hamiltonian formulations with the Lagrangian parametrization of the contour. Numerical estimations illustrating the physical significance of the results and the range of model parameters where these results can be applicable are presented. Possible generalizations of the approach based on the application of the Hamiltonian contour dynamics to nonplanar and 3D flows are discussed
Quantization of coset space σ-models coupled to two-dimensional gravity
International Nuclear Information System (INIS)
Korotkin, D.; Samtleben, H.
1996-07-01
The mathematical framework for an exact quantization of the two-dimensional coset space σ-models coupled to dilaton gravity, that arise from dimensional reduction of gravity and supergravity theories, is presented. The two-time Hamiltonian formulation is obtained, which describes the complete phase space of the model in the whole isomonodromic sector. The Dirac brackets arising from the coset constraints are calculated. Their quantization allows to relate exact solutions of the corresponding Wheeler-DeWitt equations to solutions of a modified (Coset) Knizhnik-Zamolodchikov system. On the classical level, a set of observables is identified, that is complete for essential sectors of the theory. Quantum counterparts of these observables and their algebraic structure are investigated. Their status in alternative quantization procedures is discussed, employing the link with Hamiltonian Chern-Simons theory. (orig.)
Directory of Open Access Journals (Sweden)
Kunal Pathak
2016-09-01
Full Text Available The calcium signaling plays a crucial role in expansion and contraction of cardiac myocytes. This calcium signaling is achieved by calcium diffusion, buffering mechanisms and influx in cardiac myocytes. The various calcium distribution patterns required for achieving calcium signaling in myocytes are still not well understood. In this paper an attempt has been made to develop a model of calcium distribution in myocytes incorporating diffusion of calcium, point source and excess buffer approximation. The model has been developed for a two dimensional unsteady state case. Appropriate boundary conditions and initial condition have been framed. The finite element method has been employed to obtain the solution. The numerical results have been used to study the effect of buffers and source amplitude on calcium distribution in myocytes.
Qin, X. P.; Zheng, B.; Zhou, N. J.
2012-03-01
With Monte Carlo methods, we investigate the universality class of the depinning transition in the two-dimensional Ising model with quenched random fields. Based on the short-time dynamic approach, we accurately determine the depinning transition field and both static and dynamic critical exponents. The critical exponents vary significantly with the form and strength of the random fields, but exhibit independence of the updating schemes of the Monte Carlo algorithm. From the roughness exponents ζ, ζloc and ζs, one may judge that the depinning transition of the random-field Ising model belongs to the new dynamic universality class with ζ ≠ ζloc ≠ ζs and ζloc ≠ 1. The crossover from the second-order phase transition to the first-order one is observed for the uniform distribution of the random fields, but it is not present for the Gaussian distribution.
Two-dimensional modeling of stepped planing hulls with open and pressurized air cavities
Directory of Open Access Journals (Sweden)
Konstantin I. Matveev
2012-06-01
Full Text Available A method of hydrodynamic discrete sources is applied for two-dimensional modeling of stepped planing surfaces. The water surface deformations, wetted hull lengths, and pressure distribution are calculated at given hull attitude and Froude number. Pressurized air cavities that improve hydrodynamic performance can also be modeled with the current method. Presented results include validation examples, parametric calculations of a single-step hull, effect of trim tabs, and performance of an infinite series of periodic stepped surfaces. It is shown that transverse steps can lead to higher lift-drag ratio, although at reduced lift capability, in comparison with a stepless hull. Performance of a multi-step configuration is sensitive to the wave pattern between hulls, which depends on Froude number and relative hull spacing.
Ordering in the quenched two-dimensional axial next-nearest-neighbor Ising model
International Nuclear Information System (INIS)
Hassold, G.N.; Srolovitz, D.J.
1988-01-01
Monte Carlo simulations of ordering in the two-dimensional axial next-nearest-neighbor Ising model following a quench were performed using nonconserved dynamics for a wide range of frustration parameters, κ, and temperatures. It was found that in quenches from T>>T/sub c/ to T 1 2 kinetics. Similar results are found for quenches at κ≥1, where the ordered structure is striped. However, for 0 phase (i.e., striped phase). Quenches to higher temperatures show the presence of a finite glass-transition temperature. Discontinuous changes in the value of the frustration parameter from the ferromagnetic to the -phase region of the phase diagram at low temperature yields a phase change which occurs via classical nucleation and growth. A simple energetic or growth model is proposed which accounts for all of the temperatures at which the ordering kinetics undergoes transitions
Non-perturbative effects in two-dimensional lattice O(N) models
International Nuclear Information System (INIS)
Ogilvie, M.C.; Maryland Univ., College Park
1981-01-01
Non-abelian analogues of Kosterlitz-Thouless vortices may have important effects in two-dimensional lattice spin systems with O(N) symmetries. Renormalization group equations which include these effects are developed in two ways. The first set of equations extends the renormalization group equations of Kosterlitz to 0(N) spin systems, in a form suggested by Cardy and Hamber. The second is derived from a Villain-type 0(N) model using Migdal's recursion relations. Using these equations, the part played by topological excitations int he crossover from weak to strong coupling behavior is studied. Another effect which influences crossover behavior is also discussed; irrelevant operators which occur naturally in lattice theories can make important contributions to the renormalization group flow in the crossover region. When combined with conventional perturbative results, these two effects may explain the observed crossover behavior of these models. (orig.)
Limitations to the use of two-dimensional thermal modeling of a nuclear waste repository
International Nuclear Information System (INIS)
Davis, B.W.
1979-01-01
Thermal modeling of a nuclear waste repository is basic to most waste management predictive models. It is important that the modeling techniques accurately determine the time-dependent temperature distribution of the waste emplacement media. Recent modeling studies show that the time-dependent temperature distribution can be accurately modeled in the far-field using a 2-dimensional (2-D) planar numerical model; however, the near-field cannot be modeled accurately enough by either 2-D axisymmetric or 2-D planar numerical models for repositories in salt. The accuracy limits of 2-D modeling were defined by comparing results from 3-dimensional (3-D) TRUMP modeling with results from both 2-D axisymmetric and 2-D planar. Both TRUMP and ADINAT were employed as modeling tools. Two-dimensional results from the finite element code, ADINAT were compared with 2-D results from the finite difference code, TRUMP; they showed almost perfect correspondence in the far-field. This result adds substantially to confidence in future use of ADINAT and its companion stress code ADINA for thermal stress analysis. ADINAT was found to be somewhat sensitive to time step and mesh aspect ratio. 13 figures, 4 tables
Scaling and asymptotic scaling in two-dimensional CPN-1 models
International Nuclear Information System (INIS)
Campostrini, M.; Rossi, P.; Vicari, E.
1993-01-01
Two-dimensional CP N-1 models are investigated by Monte Carlo methods on the lattice, for values of N ranging from 2 to 21. Scaling and rotation invariance are studied by comparing different definitions of correlation length ξ. Several lattice formulations are compared and shown to enjoy scaling for ξ as small as 2.5. Asymptotic scaling is investigated using as bare coupling constant both the usual β and β E (related to the internal energy); the latter is shown to improve asymptotic scaling properties. Studies of finite size effects show their N-dependence to be highly non-trivial, due to the increasing radius of the anti zz bound states at large N. (orig.)
High-velocity two-phase flow two-dimensional modeling
International Nuclear Information System (INIS)
Mathes, R.; Alemany, A.; Thilbault, J.P.
1995-01-01
The two-phase flow in the nozzle of a LMMHD (liquid metal magnetohydrodynamic) converter has been studied numerically and experimentally. A two-dimensional model for two-phase flow has been developed including the viscous terms (dragging and turbulence) and the interfacial mass, momentum and energy transfer between the phases. The numerical results were obtained by a finite volume method based on the SIMPLE algorithm. They have been verified by an experimental facility using air-water as a simulation pair and a phase Doppler particle analyzer for velocity and droplet size measurement. The numerical simulation of a lithium-cesium high-temperature pair showed that a nearly homogeneous and isothermal expansion of the two phases is possible with small pressure losses and high kinetic efficiencies. In the throat region a careful profiling is necessary to reduce the inertial effects on the liquid velocity field
Applications of neural networks to the studies of phase transitions of two-dimensional Potts models
Li, C.-D.; Tan, D.-R.; Jiang, F.-J.
2018-04-01
We study the phase transitions of two-dimensional (2D) Q-states Potts models on the square lattice, using the first principles Monte Carlo (MC) simulations as well as the techniques of neural networks (NN). We demonstrate that the ideas from NN can be adopted to study these considered phase transitions efficiently. In particular, even with a simple NN constructed in this investigation, we are able to obtain the relevant information of the nature of these phase transitions, namely whether they are first order or second order. Our results strengthen the potential applicability of machine learning in studying various states of matters. Subtlety of applying NN techniques to investigate many-body systems is briefly discussed as well.
Directory of Open Access Journals (Sweden)
Dongkyun Im
2011-12-01
Full Text Available River corridors, even if highly modified or degraded, still provide important habitats for numerous biological species, and carry high aesthetic and economic values. One of the keys to urban stream restoration is recovery and maintenance of ecological flows sufficient to sustain aquatic ecosystems. In this study, the Hongje Stream in the Seoul metropolitan area of Korea was selected for evaluating a physically-based habitat with and without habitat structures. The potential value of the aquatic habitat was evaluated by a weighted usable area (WUA using River2D, a two-dimensional hydraulic model. The habitat suitability for Zacco platypus in the Hongje Stream was simulated with and without habitat structures. The computed WUA values for the boulder, spur dike, and riffle increased by about 2%, 7%, and 131%, respectively, after their construction. Also, the three habitat structures, especially the riffle, can contribute to increasing hydraulic heterogeneity and enhancing habitat diversity.
Qamar, Shamsul; Uche, David U; Khan, Farman U; Seidel-Morgenstern, Andreas
2017-05-05
This work is concerned with the analytical solutions and moment analysis of a linear two-dimensional general rate model (2D-GRM) describing the transport of a solute through a chromatographic column of cylindrical geometry. Analytical solutions are derived through successive implementation of finite Hankel and Laplace transformations for two different sets of boundary conditions. The process is further analyzed by deriving analytical temporal moments from the Laplace domain solutions. Radial gradients are typically neglected in liquid chromatography studies which are particularly important in the case of non-perfect injections. Several test problems of single-solute transport are considered. The derived analytical results are validated against the numerical solutions of a high resolution finite volume scheme. The derived analytical results can play an important role in further development of liquid chromatography. Copyright © 2017 Elsevier B.V. All rights reserved.
A two-dimensional volatility basis set – Part 3: Prognostic modeling and NOx dependence
Directory of Open Access Journals (Sweden)
W. K. Chuang
2016-01-01
Full Text Available When NOx is introduced to organic emissions, aerosol production is sometimes, but not always, reduced. Under certain conditions, these interactions will instead increase aerosol concentrations. We expanded the two-dimensional volatility basis set (2D-VBS to include the effects of NOx on aerosol formation. This includes the formation of organonitrates, where the addition of a nitrate group contributes to a decrease of 2.5 orders of magnitude in volatility. With this refinement, we model outputs from experimental results, such as the atomic N : C ratio, organonitrate mass, and nitrate fragments in Aerosol Mass Spectrometer (AMS measurements. We also discuss the mathematical methods underlying the implementation of the 2D-VBS and provide the complete code in the Supplement. A developer version is available on Bitbucket, an online community repository.
Chen, Shanyan; Meng, Fanjun; Chen, Zhenzhou; Qu, Zhe; Cui, Jiankun; Gu, Zezong
2017-01-01
Pathological activation of gelatinases (matrix metalloproteinase-2 and -9; MMP-2/-9) has been shown to cause a number of detrimental outcomes in neurodegenerative diseases. In gel gelatin zymography is a highly sensitive methodology commonly used in revealing levels of gelatinase activity and in separating the proform and active form of gelatinases, based on their different molecular weights. However, this methodology is inadequate in resolving complex enzyme isoforms, because gelatinase expression and activity can be regulated at transcriptional and/or post-translational levels under in vivo conditions resulting in alternation of their isoelectric focusing (IEF) points. In this chapter, we describe an advanced methodology, termed two-dimensional zymography, combining IEF with zymographic electrophoresis under non-reducing conditions to achieve significant improvement in separation of the gelatinase isoforms in both cell-based and in vivo models for acute brain injuries and neuroinflammation.
Spin supercurrent and effect of quantum phase transition in the two-dimensional XY model
Lima, L. S.
2018-04-01
We have verified the influence of quantum phase transition on spin transport in the spin-1 two-dimensional XY model on the square lattice, with easy plane, single ion and exchange anisotropy. We analyze the effect of the phase transition from the Néel phase to the paramagnetic phase on the AC spin conductivity. Our results show a bit influence of the quantum phase transition on the conductivity. We also obtain a conventional spin transport for ω > 0 and an ideal spin transport in the limit of DC conductivity and therefore, a superfluid spin transport for the DC current in this limit. We have made the diagrammatic expansion for the Green-function with objective to include the effect exciton-exciton scattering on the results.
Rodriguez, Alvaro; Fernandez-Lozano, Carlos; Dorado, Julian; Rabuñal, Juan R
2014-06-01
Block-matching techniques have been widely used in the task of estimating displacement in medical images, and they represent the best approach in scenes with deformable structures such as tissues, fluids, and gels. In this article, a new iterative block-matching technique-based on successive deformation, search, fitting, filtering, and interpolation stages-is proposed to measure elastic displacements in two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) images. The proposed technique uses different deformation models in the task of correlating proteins in real 2D electrophoresis gel images, obtaining an accuracy of 96.6% and improving the results obtained with other techniques. This technique represents a general solution, being easy to adapt to different 2D deformable cases and providing an experimental reference for block-matching algorithms. Copyright © 2014 Elsevier Inc. All rights reserved.
Existence of several surface-reconstructed phases in a two-dimensional lattice model
Huckaby, Dale A.; Rys, Franz S.
1992-03-01
The zero-temperature phase diagram is rigorously obtained for a two-dimensional lattice model with four energy parameters. It is shown that the parameter space can be divided into regions, together with their boundaries, such that in each region the ground-state configurations are of one of seven different types. These types include one which is nondegenerate, four which are doubly degenerate, one which is infinitely degenerate but with no residual entropy, and one which is infinitely degenerate and has a nonzero residual entropy. The Pirogov-Sinai extension of the Peierls argument is used to establish the existence at low temperatures of four different types of ordered surface-reconstructed phases.
Friction phenomena in a two-dimensional Frenkel–Kontorova model
International Nuclear Information System (INIS)
Mai-Mai, Lin; Wen-Shan, Duan; Jian-Min, Chen
2010-01-01
By using the molecular dynamic simulation method with a fourth-order Runge–Kutta algorithm, a two-dimensional dc- and ac-driven Frenkel–Kontorova (FK) model with a square symmetry substrate potential for a square lattice layer has been investigated in this paper. For this system, the effects of many different parameters on the average velocity and the static friction force have been studied. It is found that not only the amplitude and frequency of ac-driven force, but also the direction of the external driving force and the misfit angle between two layers have some strong influences on the static friction force. It can be concluded that the superlubricity phenomenon appears easily with a larger ac amplitude and lower ac frequency for some special direction of the external force and misfit angle. (condensed matter: structure, thermal and mechanical properties)
Itinerant ferromagnetism in the two-dimensional t-t' Hubbard model
Arrachea, Liliana
2000-10-01
Using exact diagonalization techniques, the Hubbard model with hopping between nearest (t) and next-nearest neighbors (t') is studied in a two-dimensional cluster with 4×4 sites. Within a range of values of t'<0 and low densities, states with different total spin are degenerate in the noninteracting system. At a finite value of the Coulomb repulsion U, states with high spin are energetically favored and the ground state can be fully polarized. The behavior of the density of states differs from that obtained within the Hartree-Fock approximation. The low energy region of the density of states (DOS) for the majority spins remains weakly modified by U. Our results bring further support to the idea that itinerant ferromagnetism occurs in strongly correlated systems with high noninteracting DOS at the bottom of the band.
Ishola, Kehinde S; Nawawi, Mohd Nm; Abdullah, Khiruddin; Sabri, Ali Idriss Aboubakar; Adiat, Kola Abdulnafiu
2014-01-01
This study attempts to combine the results of geophysical images obtained from three commonly used electrode configurations using an image processing technique in order to assess their capabilities to reproduce two-dimensional (2-D) resistivity models. All the inverse resistivity models were processed using the PCI Geomatica software package commonly used for remote sensing data sets. Preprocessing of the 2-D inverse models was carried out to facilitate further processing and statistical analyses. Four Raster layers were created, three of these layers were used for the input images and the fourth layer was used as the output of the combined images. The data sets were merged using basic statistical approach. Interpreted results show that all images resolved and reconstructed the essential features of the models. An assessment of the accuracy of the images for the four geologic models was performed using four criteria: the mean absolute error and mean percentage absolute error, resistivity values of the reconstructed blocks and their displacements from the true models. Generally, the blocks of the images of maximum approach give the least estimated errors. Also, the displacement of the reconstructed blocks from the true blocks is the least and the reconstructed resistivities of the blocks are closer to the true blocks than any other combined used. Thus, it is corroborated that when inverse resistivity models are combined, most reliable and detailed information about the geologic models is obtained than using individual data sets.
Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers
International Nuclear Information System (INIS)
Maingi, R.
1992-08-01
The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles
A two-dimensional analytical model of vapor intrusion involving vertical heterogeneity
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M.
2017-05-01
In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz-Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
A two-dimensional analytical model of vapor intrusion involving vertical heterogeneity.
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M
2017-05-01
In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz-Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
Directory of Open Access Journals (Sweden)
Farideh Hosseini
2015-09-01
Full Text Available Introduction As a tumor grows, the demand for oxygen and nutrients increases and it grows further if acquires the ability to induce angiogenesis. In this study, we aimed to present a two-dimensional continuous mathematical model for avascular tumor growth, coupled with a discrete model of angiogenesis. Materials and Methods In the avascular growth model, tumor is considered as a single mass, which uptakes oxygen through diffusion and invades the extracellular matrix (ECM. After the tumor reaches its maximum size in the avascular growth phase, tumor cells may be in three different states (proliferative, quiescent and apoptotic, depending on oxygen availability. Quiescent cells are assumed to secrete tumor angiogenic factors, which diffuse into the surrounding tissue until reaching endothelial cells. The mathematical model for tumor angiogenesis is consisted of a five-point finite difference scheme to simulate the progression of endothelial cells in ECM and their penetration into the tumor. Results The morphology of produced networks was investigated, based on various ECM degradation patterns. The generated capillary networks involved the rules of microvascular branching and anastomosis. Model predictions were in qualitative agreement with experimental observations and might have implications as a supplementary model to facilitate mathematical analyses for anti-cancer therapies. Conclusion Our numerical simulations could facilitate the qualitative comparison between three layers of tumor cells, their TAF-producing abilities and subsequent penetration of micro-vessels in order to determine the dynamics of microvascular branching and anastomosis in ECM and three different parts of the tumor.
Two-dimensional lattice model for the surface states of topological insulators
Zhou, Yan-Feng; Jiang, Hua; Xie, X. C.; Sun, Qing-Feng
2017-06-01
The surface states in three-dimensional (3D) topological insulators can be described by a two-dimensional (2D) continuous Dirac Hamiltonian. However, there exists the fermion doubling problem when putting the continuous 2D Dirac equation into a lattice model. In this paper, we introduce a Wilson term with a zero bare mass into the 2D lattice model to overcome the difficulty. By comparing with a 3D Hamiltonian, we show that the modified 2D lattice model can faithfully describe the low-energy electrical and transport properties of surface states of 3D topological insulators. So this 2D lattice model provides a simple and cheap way to numerically simulate the surface states of 3D topological-insulator nanostructures. Based on the 2D lattice model, we also establish the wormhole effect in a topological-insulator nanowire by a magnetic field along the wire and show the surface states being robust against disorder. The proposed 2D lattice model can be extensively applied to study the various properties and effects, such as the transport properties, Hall effect, universal conductance fluctuations, localization effect, etc. So, it paves a way to study the surface states of the 3D topological insulators.
A two-dimensional CFD model of a refrigerated display case
Energy Technology Data Exchange (ETDEWEB)
Stribling, D.; Tassou, S.A. [Brunel Univ., Uxbridge (United Kingdom). Dept. of Mechanical Engineering; Marriott, D. [Safeway Stores plc, Middlesex (United Kingdom)
1997-12-31
The discomfort caused by the cold air overspill from vertical refrigerated display cases in supermarkets is widely accepted as being a problem to customers. This, together with the adverse effect on case performance caused by heat and moisture transfer across the air curtain, suggests that there may be room for improvement in the design and fundamental operation of these display fixtures. This paper presents a two-dimensional computational fluid dynamics (CFD) model of a vertical dairy display case that could be used in the design and optimization of such equipment. Comparisons are also made with experimentally obtained values of velocity and temperature measured around the case in order to assess the accuracy and viability of such a model. Parameters of the computer model, such as the size of the calculation grid, the turbulence model, and the discretization scheme, were also varied to determine their effect on the converged solution, and these results are presented. The CFD model showed good qualitative agreement with measured values and requires only fine tuning to make it quantitatively accurate.
Study of the two-dimensional Hubbard model at half-filling through constructive methods
International Nuclear Information System (INIS)
Afchain, St.
2005-02-01
The Hubbard model is the simplest model to describe the behaviour of fermions on a network, it takes into account only fermion scattering and only interactions with other fermions located on the same site. Half-filling means that the total number of fermions is equal to half the number of sites. In the first chapter we show how we can pass trough successive approximations from a very general Hamiltonian to the Hubbard Hamiltonian. The second chapter is dedicated to the passage from the Hamiltonian formalism to the Grassmanian functional formalism. The main idea is to show that the correlation functions of the Hamiltonian approach can be described through fermionic functional integrals which implies the possibility of speaking of the model in terms of field theory. The chapter 3 deals with the main constructive techniques that allow the strict and consistent construction of models inside the frame of field theory. We show by proving the violation of a condition concerning self-energy, that the two-dimensional Hubbard model at half-filling has not the behaviour of a Fermi liquid in the Landau's interpretation. (A.C.)
Global vertical mass transport by clouds - A two-dimensional model study
International Nuclear Information System (INIS)
Olofsson, Mats
1988-05-01
A two-dimensional global dispersion model, where vertical transport in the troposphere carried out by convective as well as by frontal cloud systems is explicitly treated, is developed from an existing diffusion model. A parameterization scheme for the cloud transport, based on global cloud statistics, is presented. The model has been tested by using Kr-85, Rn-222 and SO 2 as tracers. Comparisons have been made with observed distributions of these tracers, but also with model results without the cloud transport, using eddy diffusion as the primary means of vertical transport. The model results indicate that for trace species with a turnover time of days to weeks, the introduction of cloud-transport gives much more realistic simulations of their vertical distribution. Layers of increased mixing ratio with height, which can be found in real atmosphere, are reproduced in our cloud-transport model profiles, but can never be simulated with a pure eddy diffusion model. The horizontal transport in the model, by advection and eddy diffusion, gives a realistic distribution between the hemispheres of the more long-lived tracers (Kr-85). A combination of vertical transport by convective and frontal cloud systems is shown to improve the model simulations, compared to limiting it to convective transport only. The importance of including cumulus clouds in the convective transport scheme, in addition to the efficient transport by cumulonimbus clouds, is discussed. The model results are shown to be more sensitive to the vertical detrainment distribution profile than to the absolute magnitude of the vertical mass transport. The scavenging processes for SO 2 are parameterized without the introduction of detailed chemistry. An enhanced removal, due to the increased contact with droplets in the in-cloud lifting process, is introduced in the model. (author)
Spatiotemporal chaos and two-dimensional dissipative rogue waves in Lugiato-Lefever model
Panajotov, Krassimir; Clerc, Marcel G.; Tlidi, Mustapha
2017-06-01
Driven nonlinear optical cavities can exhibit complex spatiotemporal dynamics. We consider the paradigmatic Lugiato-Lefever model describing driven nonlinear optical resonator. This model is one of the most-studied nonlinear equations in optics. It describes a large spectrum of nonlinear phenomena from bistability, to periodic patterns, localized structures, self-pulsating localized structures and to a complex spatiotemporal behavior. The model is considered also as prototype model to describe several optical nonlinear devices such as Kerr media, liquid crystals, left handed materials, nonlinear fiber cavity, and frequency comb generation. We focus our analysis on a spatiotemporal chaotic dynamics in one-dimension. We identify a route to spatiotemporal chaos through an extended quasiperiodicity. We have estimated the Kaplan-Yorke dimension that provides a measure of the strange attractor complexity. Likewise, we show that the Lugiato-Leferver equation supports rogues waves in two-dimensional settings. We characterize rogue-wave formation by computing the probability distribution of the pulse height. Contribution to the Topical Issue "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.
International Nuclear Information System (INIS)
Milioli, F.E.
1985-01-01
In this research work a numerical model for the solution of two-dimensional natural convection problems in arbitrary cavities of a Boussinesq fluid is presented. The conservation equations are written in a general curvilinear coordinate system which matches the irregular boundaries of the domain. The nonorthogonal system is generated by a suitable system of elliptic equations. The momentum and continuity equations are transformed from the Cartesian system to the general curvilinear system keeping the Cartesian velocity components as the dependent variables in the transformed domain. Finite difference equations are obtained for the contravariant velocity components in the transformed domain. The numerical calculations are performed in a fixed rectangular domain and both the Cartesian and the contravariant velocity components take part in the solutiomn procedure. The dependent variables are arranged on the grid in a staggered manner. The numerical model is tested by solving the driven flow in a square cavity with a moving side using a nonorthogoanl grid. The natural convenction in a square cavity, using an orthogonal and a nonorthogonal grid, is also solved for the model test. Also, the solution for the buoyancy flow between a square cylinder placed inside a circular cylinder is presented. The results of the test problems are compared with those available in the specialized literature. Finally, in order to show the generality of the model, the natural convection problem inside a very irregular cavity is presented. (Author) [pt
Comparison of Three Different Parallel Computation Methods for a Two-Dimensional Dam-Break Model
Directory of Open Access Journals (Sweden)
Shanghong Zhang
2017-01-01
Full Text Available Three parallel methods (OpenMP, MPI, and OpenACC are evaluated for the computation of a two-dimensional dam-break model using the explicit finite volume method. A dam-break event in the Pangtoupao flood storage area in China is selected as a case study to demonstrate the key technologies for implementing parallel computation. The subsequent acceleration of the methods is also evaluated. The simulation results show that the OpenMP and MPI parallel methods achieve a speedup factor of 9.8× and 5.1×, respectively, on a 32-core computer, whereas the OpenACC parallel method achieves a speedup factor of 20.7× on NVIDIA Tesla K20c graphics card. The results show that if the memory required by the dam-break simulation does not exceed the memory capacity of a single computer, the OpenMP parallel method is a good choice. Moreover, if GPU acceleration is used, the acceleration of the OpenACC parallel method is the best. Finally, the MPI parallel method is suitable for a model that requires little data exchange and large-scale calculation. This study compares the efficiency and methodology of accelerating algorithms for a dam-break model and can also be used as a reference for selecting the best acceleration method for a similar hydrodynamic model.
Flocking with discrete symmetry: The two-dimensional active Ising model.
Solon, A P; Tailleur, J
2015-10-01
We study in detail the active Ising model, a stochastic lattice gas where collective motion emerges from the spontaneous breaking of a discrete symmetry. On a two-dimensional lattice, active particles undergo a diffusion biased in one of two possible directions (left and right) and align ferromagnetically their direction of motion, hence yielding a minimal flocking model with discrete rotational symmetry. We show that the transition to collective motion amounts in this model to a bona fide liquid-gas phase transition in the canonical ensemble. The phase diagram in the density-velocity parameter plane has a critical point at zero velocity which belongs to the Ising universality class. In the density-temperature "canonical" ensemble, the usual critical point of the equilibrium liquid-gas transition is sent to infinite density because the different symmetries between liquid and gas phases preclude a supercritical region. We build a continuum theory which reproduces qualitatively the behavior of the microscopic model. In particular, we predict analytically the shapes of the phase diagrams in the vicinity of the critical points, the binodal and spinodal densities at coexistence, and the speeds and shapes of the phase-separated profiles.
Bekhit, H. B.; Hassan, A. E.
2002-12-01
It has long been known that colloids can facilitate the transport of contaminants in groundwater systems by reducing the effective retardation factor. A significant effort has been devoted to study colloid-facilitated contaminant transport during the past decade. Most of the previous studies were restricted to one-dimensional analysis and comparison with finite column experiments. Little attention was paid to the interaction between colloids and contaminant plumes in multi-dimensional domains, which are more realistic than one-dimensional domains. The main objective of the present work is to develop a two-dimensional numerical model to investigate the effect of different interactions between colloids, contaminants and porous media under homogeneous conditions. The numerical formulation of the model is based on discretizing the mass balance equations and the reaction equations using finite differences with a third-order total variance-diminishing (TVD) scheme for the advection terms. This latter scheme significantly reduces numerical dispersion and leads to more accurate results as compared to the standard central differencing scheme. The model was tested against a number of analytical solutions under simplified conditions and the results were favorable. The model is used to investigate the impact of different reaction rates and parameter values on the movement of contaminant plumes in two dimensions. The results of these investigations will be discussed and the cases under which colloids may act as a movement-retarding agent as opposed movement-facilitating agent are investigated and discussed.
Sun, N; Elimelech, M; Sun, N Z; Ryan, J N
2001-06-01
A two-dimensional model for colloid transport in geochemically and physically heterogeneous porous media is presented. The model considers patchwise geochemical heterogeneity, which is suitable to describe the chemical variability of many surficial aquifers with ferric oxyhydroxide-coated porous matrix, as well as spatial variability of hydraulic conductivity, which results in heterogeneous flow field. The model is comprised of a transient fluid flow equation, a transient colloid transport equation, and an equation for the dynamics of colloid deposition and release. Numerical simulations were carried out with the model to investigate the colloid transport behavior in layered and randomly heterogeneous porous media. Results demonstrate that physical and geochemical heterogeneities markedly affect the colloid transport behavior. Layered physical or geochemical heterogeneity can result in distinct preferential flow paths of colloidal particles. Furthermore, the combined effect of layered physical and geochemical heterogeneity may result in enhanced or reduced preferential flow of colloids. Random distribution of physical heterogeneity (hydraulic conductivity) results in a random flow field and an irregularly distributed colloid concentration profile in the porous medium. Contrary to random physical heterogeneity, the effect of random patchwise geochemical heterogeneity on colloid transport behavior is not significant. It is mostly the mean value of geochemical heterogeneity rather than its distribution that governs the colloid transport behavior.
Two-dimensional models for the optical response of thin films
Li, Yilei; Heinz, Tony F.
2018-04-01
In this work, we present a systematic study of 2D optical models for the response of thin layers of material under excitation by normally incident light. The treatment, within the framework of classical optics, analyzes a thin film supported by a semi-infinite substrate, with both the thin layer and the substrate assumed to exhibit local, isotropic linear response. Starting from the conventional three-dimensional (3D) slab model of the system, we derive a two-dimensional (2D) sheet model for the thin film in which the optical response is described by a sheet optical conductivity. We develop criteria for the applicability of this 2D sheet model for a layer with an optical thickness far smaller than the wavelength of the light. We examine in detail atomically thin semi-metallic and semiconductor van-der-Waals layers and ultrathin metal films as representative examples. Excellent agreement of the 2D sheet model with the 3D slab model is demonstrated over a broad spectral range from the radio frequency limit to the near ultraviolet. A linearized version of system response for the 2D model is also presented for the case where the influence of the optically thin layer is sufficiently weak. Analytical expressions for the applicability and accuracy of the different optical models are derived, and the appropriateness of the linearized treatment for the materials is considered. We discuss the advantages, as well as limitations, of these models for the purpose of deducing the optical response function of the thin layer from experiment. We generalize the theory to take into account in-plane anisotropy, layered thin film structures, and more general substrates. Implications of the 2D model for the transmission of light by the thin film and for the implementation of half- and totally absorbing layers are discussed.
International Nuclear Information System (INIS)
Wong, K.-L.; Hsien, T.-L.; Hsiao, M.-C.; Chen, W.-L.; Lin, K.-C.
2008-01-01
This investigation is to show that two-dimensional steady state heat transfer problems of composite walls should not be solved by the conventionally one-dimensional parallel thermal resistance circuits (PTRC) model because the interface temperatures are not unique. Thus PTRC model cannot be used like its conventional recognized analogy, parallel electrical resistance circuits (PERC) model which has the unique node electric voltage. Two typical composite wall examples, solved by CFD software, are used to demonstrate the incorrectness. The numerical results are compared with those obtained by PTRC model, and very large differences are observed between their results. This proves that the application of conventional heat transfer PTRC model to two-dimensional composite walls, introduced in most heat transfer text book, is totally incorrect. An alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to the two-dimensional composite walls with isothermal boundaries. Results with acceptable accuracy can be obtained by the new model
International Nuclear Information System (INIS)
Wong, K.-L.; Hsien, T.-L.; Chen, W.-L.; Yu, S.-J.
2008-01-01
This study is to prove that two-dimensional steady state heat transfer problems of composite circular pipes cannot be appropriately solved by the conventional one-dimensional parallel thermal resistance circuits (PTRC) model because its interface temperatures are not unique. Thus, the PTRC model is definitely different from its conventional recognized analogy, parallel electrical resistance circuits (PERC) model, which has unique node electric voltages. Two typical composite circular pipe examples are solved by CFD software, and the numerical results are compared with those obtained by the PTRC model. This shows that the PTRC model generates large error. Thus, this conventional model, introduced in most heat transfer text books, cannot be applied to two-dimensional composite circular pipes. On the contrary, an alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to a two-dimensional composite circular pipe with isothermal boundaries, and acceptable results are returned
A plausible two-dimensional vertical model of the East Mesa Geothermal Field, California
Energy Technology Data Exchange (ETDEWEB)
Goyal, K. P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Kassoy, D. R. [Univ. of Colorado, Boulder, CO (United States). Mechanical Engineering Dept.
1981-11-10
For this study, a two-dimensional conceptual model of the East Mesa Geothermal system is developed on the basis of existing geological, geophysical, geochemical, heat flux, and borehole logging data. Hot water rising in a set of faults is assumed to charge the reservoir, which is overlaid by a clay-rich cap. The temperature-depth distribution observed at the site implies that the liquid is converting at a high Rayleigh number. In this approximation, liquid rises up the fault and spreads isothermally into the nearby sections of the reservoir. The cooling effect of the surface on the flow in the reservoir is confined to a thin layer adjacent to the cap-reservoir interface near the fault. This layer grows with the distance from the fault. Eventually, the entire depth of the reservoir is cooled by the surface. The mathematical model is based on the flow of liquid water in a saturated porous medium. Results are obtained for the velocities, pressures, and temperatures in the entire system consisting of fault zone, aquifer, and clay cap. Finally we compare the predicted surface heat flux to that measured at the site in shallow wells. We conclude that the model represents a plausible description of fault zone controlled systems like that at East Mesa.
Wang, Y.; Ramaswamy, V.; Saleh, F.
2017-12-01
Barnegat Bay located on the east coast of New Jersey, United States and is separated from the Atlantic Ocean by the narrow Barnegat Peninsula which acts as a barrier island. The bay is fed by several rivers which empty through small estuaries along the inner shore. In terms of vulnerability from flooding, the Barnegat Peninsula is under the influence of both coastal storm surge and riverine flooding. Barnegat Bay was hit by Hurricane Sandy causing flood damages with extensive cross-island flow at many streets perpendicular to the shoreline. The objective of this work is to identify and quantify the sources of flooding using a two dimensional inland hydrodynamic model. The hydrodynamic model was forced by three observed coastal boundary conditions, and one hydrologic boundary condition from United States Geological Survey (USGS). The model reliability was evaluated with both FEMA spatial flooding extend and USGS High water marks. Simulated flooding extent showed good agreement with the reanalysis spatial inundation extents. Results offered important perspectives on the flow of the water into the bay, the velocity and the depth of the inundated areas. Using such information can enable emergency managers and decision makers identify evacuation and deploy flood defenses.
Yuste, A.; Moreno-Cardoner, M.; Sanpera, A.
2017-05-01
Disordered quantum antiferromagnets in two-dimensional compounds have been a focus of interest in the last years due to their exotic properties. However, with very few exceptions, the ground states of the corresponding Hamiltonians are notoriously difficult to simulate making their characterization and detection very elusive, both theoretically and experimentally. Here we propose a method to signal quantum disordered antiferromagnets by doing exact diagonalization in small lattices using random boundary conditions and averaging the observables of interest over the different disorder realizations. We apply our method to study the Heisenberg spin-1/2 model in an anisotropic triangular lattice. In this model, the competition between frustration and quantum fluctuations might lead to some spin-liquid phases as predicted from different methods ranging from spin-wave mean-field theory to 2D-DMRG or PEPS. Our method accurately reproduces the ordered phases expected of the model and signals quantum disordered phases by the presence of a large number of quasidegenerate ground states together with an undefined local order parameter. The method presents a weak dependence on finite-size effects.
Two-dimensional model for current and heat transport in solid-armature railguns
Powell, John D.; Walbert, David J.; Zielinski, Alexander E.
1993-02-01
A numerical model is developed for solving the equations which predict current and heat transport in a solid-armature railgun. The model is two dimensional and fully time dependent. Some preliminary calculations are carried out for a 'U-shaped' armature similar to that currently under investigation in the ARDEC small and cannon-caliber railgun programs. The most extensive calculations are for a situation in which the projectile is started at rest and accelerated to about 500 m/s in a time of about 1 ms. Results of the calculations can be used to infer, for example, where melting in the armature is most likely to occur and where the electromagnetic fields are largest. For comparison, calculations are also presented for a situation in which the projectile is held fixed. Some discussion of future efforts is given, with particular emphasis on describing how the model might be used to guide the design of armatures, or provide input for other types of calculations relating to electromagnetic guns.
Two-dimensional model of photon recycling in direct gap semiconductor devices
Parks, Joseph W., Jr.; Brennan, Kevin F.; Smith, Arlynn W.
1997-10-01
The effects of photon recycling are examined in a general, fully numerical, two-dimensional model accounting for the detailed geometry of the device and the spectral content of the recombined excess carriers. The primary component of this model is a three-dimensional ray tracing algorithm which encompasses effects such as wavelength dependent absorption and index of refraction, the angular dependence of transmissivity between layers in a heterostructure device, and multiple reflections within a device. This ray tracing preprocessing step is used to map all of the possible trajectories and absorption of various wavelengths of emitted light from each originating node within the device. These data are integrated into a macroscopic device simulator to determine the spatial and temporal location of the reabsorbed radiation within the geometry of the device. By incorporating the ray tracer results with the total quantity and spectral content of recombined carriers at each node within the simulation, the recycled generation rate can be obtained. To demonstrate the use of this model, the effects of photon recycling on the carrier lifetime in an InP/InGaAs double heterostructure photodiode are presented. Good agreement between the experimentally measured lifetime and that predicted using photon recycling is obtained.
Experimental investigation of flow over two-dimensional multiple hill models.
Li, Qing'an; Maeda, Takao; Kamada, Yasunari; Yamada, Keisuke
2017-12-31
The aim of this study is to investigate the flow field characteristics in ABL (Atmospheric Boundary Layer) flow over multiple hills and valleys in two-dimensional models under neutral conditions. Active turbulence grids and boundary layer generation frame were used to simulate the natural winds in wind tunnel experiments. As a result, the mean wind velocity, the velocity vector diagram and turbulence intensity around the hills were investigated by using a PIV (Particle Image Velocimetry) system. From the measurement results, it was known that the average velocity was increased along the upstream slope of upside hill, and then separated at the top of the hills, the acceleration region of U/U ref >1 was generated at the downstream of the hill. Meanwhile, a large clockwise circulation flow was generated between the two hill models. Moreover, the turbulence intensity showed small value in the circulation flow regions. Compared to 1H model, the turbulence intensity in the mainstream direction showed larger value than that in the vertical direction. This paper provided a better understanding of the wind energy distribution on the terrain for proper selection of suitable sites for installing wind farms in the ABL. Copyright © 2017 Elsevier B.V. All rights reserved.
Verification of the two-dimensional hydrodynamic model based on remote sensing
Sazonov, Alexey; Mikhailukova, Polina; Krylenko, Inna; Frolova, Natalya; Kireeva, Mariya
2016-04-01
Mathematical modeling methods are used more and more actively to evaluate possible damage, identify potential flood zone and the influence of individual factors affecting the river during the passage of the flood. Calculations were performed by means of domestic software complex «STREAM-2D» which is based on the numerical solution of two-dimensional St. Venant equations. One of the major challenges in mathematical modeling is the verification of the model. This is usually made using data on water levels from hydrological stations: the smaller the difference of the actual level and the simulated one, the better the quality of the model used. Data from hydrological stations are not always available, so alternative sources of verification, such as remote sensing, are increasingly used. The aim of this work is to develop a method of verification of hydrodynamic model based on a comparison of actual flood zone area, which in turn is determined on the basis of the automated satellite image interpretation methods for different imaging systems and flooded area obtained in the course of the model. The study areas are Lena River, The North Dvina River, Amur River near Blagoveshchensk. We used satellite images made by optical and radar sensors: SPOT-5/HRG, Resurs-F, Radarsat-2. Flooded area were calculated using unsupervised classification (ISODATA and K-mean) for optical images and segmentation for Radarsat-2. Knowing the flow rate and the water level at a given date for the upper and lower limits of the model, respectively, it is possible to calculate flooded area by means of program STREAM-2D and GIS technology. All the existing vector layers with the boundaries of flooding are included in a GIS project for flood area calculation. This study was supported by the Russian Science Foundation, project no. 14-17-00155.
Gualtero, D F; Lafaurie, G I; Fontanilla, M R
2018-02-01
Epidemiological studies have established a clinical association between periodontal disease and atherosclerosis. Bacteremia and endotoxemia episodes in patients with periodontitis appear to link these two diseases by inducing a body-wide production of cardiovascular markers. The presence of oral bacteria in atherosclerotic lesions in patients with periodontitis suggests that bacteria, or their antigenic components, induce alterations in the endothelium associated with atherosclerosis. Therefore, a causal mechanism explaining the association between both diseases can be constructed using in vitro models. This review presents current experimental approaches based on in vitro cell models used to shed light on the mechanism by which periodontal pathogenic microorganisms, and their antigenic components, induce proatherosclerotic endothelial activity. Monolayer cultures of endothelial vascular or arterial cells have been used to assess periodontal pathogenic bacteria and their antigenic compounds and endothelial activation. However, these models are not capable of reflecting the physiological characteristics of the endothelium inside vascularized tissue. Therefore, the shift from two-dimensional (2D) cellular models toward three-dimensional (3D) models of endothelial cells resembling an environment close to the physiological environment of the endothelial cell within the endothelium is useful for evaluating the physiological relevance of results regarding the endothelial dysfunction induced by periodontopathogens that are currently obtained from 2D models. The use of in vitro 3D cellular models can also be relevant to the search for therapeutic agents for chronic inflammatory diseases such as atherosclerosis. Here, we present some strategies for the assembly of 3D cultures with endothelial cells, which is useful for the study of periodontopathogen-mediated disease. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Correction to scaling in the response function of the two-dimensional kinetic Ising model
Corberi, Federico; Lippiello, Eugenio; Zannetti, Marco
2005-11-01
The aging part Rag(t,s) of the impulsive response function of the two-dimensional ferromagnetic Ising model, quenched below the critical point, is studied numerically employing an algorithm without the imposition of the external field. We find that the simple scaling form Rag(t,s)=s-(1+a)f(t/s) , which is usually believed to hold in the aging regime, is not obeyed. We analyze the data assuming the existence of a correction to scaling. We find a=0.273±0.006 , in agreement with previous numerical results obtained from the zero field cooled magnetization. We investigate in detail also the scaling function f(t/s) and we compare the results with the predictions of analytical theories. We make an ansatz for the correction to scaling, deriving an analytical expression for Rag(t,s) . This gives a satisfactory qualitative agreement with the numerical data for Rag(t,s) and for the integrated response functions. With the analytical model we explore the overall behavior, extrapolating beyond the time regime accessible with the simulations. We explain why the data for the zero field cooled susceptibility are not too sensitive to the existence of the correction to scaling in Rag(t,s) , making this quantity the most convenient for the study of the asymptotic scaling properties.
Plasma kinetics of Ar/O2 magnetron discharge by two-dimensional multifluid modeling
International Nuclear Information System (INIS)
Costin, C.; Minea, T. M.; Popa, G.; Gousset, G.
2010-01-01
Multifluid two-dimensional model was developed to describe the plasma kinetics of the direct current Ar/O 2 magnetron, coupling two modules: charged particles and neutrals. The first module deals with three positive ions - Ar + , O 2 + , and O + - and two negative species - e - and O - - treated by the moments of Boltzmann's equation. The second one follows seven neutral species (Ar, O 2 , O, O 3 , and related metastables) by the multicomponent diffusion technique. The two modules are self-consistently coupled by the mass conservation and kinetic coefficients taking into account more than 100 volume reactions. The steady state is obtained when the overall convergence is achieved. Calculations for 10%O 2 in Ar/O 2 mixture at 2.67 and 4 Pa show that the oxygen excited species are mainly created by electron collisions in the negative glow of the discharge. Decreasing the pressure down to 0.67 Pa, the model reveals the nonlocal behavior of the reactive species. The density gradient of O 2 ground state is reversed with respect to all gradients of the other reactive species, since the latter ones originate from the molecular ground state of oxygen. It is also found that the wall reactions drastically modify the space gradient of neutral reactive species, at least as much as the pressure, even if the discharge operates in compound mode.
International Nuclear Information System (INIS)
Grizzi, Fabio; Russo, Carlo; Colombo, Piergiuseppe; Franceschini, Barbara; Frezza, Eldo E; Cobos, Everardo; Chiriva-Internati, Maurizio
2005-01-01
Modeling the complex development and growth of tumor angiogenesis using mathematics and biological data is a burgeoning area of cancer research. Architectural complexity is the main feature of every anatomical system, including organs, tissues, cells and sub-cellular entities. The vascular system is a complex network whose geometrical characteristics cannot be properly defined using the principles of Euclidean geometry, which is only capable of interpreting regular and smooth objects that are almost impossible to find in Nature. However, fractal geometry is a more powerful means of quantifying the spatial complexity of real objects. This paper introduces the surface fractal dimension (D s ) as a numerical index of the two-dimensional (2-D) geometrical complexity of tumor vascular networks, and their behavior during computer-simulated changes in vessel density and distribution. We show that D s significantly depends on the number of vessels and their pattern of distribution. This demonstrates that the quantitative evaluation of the 2-D geometrical complexity of tumor vascular systems can be useful not only to measure its complex architecture, but also to model its development and growth. Studying the fractal properties of neovascularity induces reflections upon the real significance of the complex form of branched anatomical structures, in an attempt to define more appropriate methods of describing them quantitatively. This knowledge can be used to predict the aggressiveness of malignant tumors and design compounds that can halt the process of angiogenesis and influence tumor growth
Q-deformed Grassmann field and the two-dimensional Ising model
International Nuclear Information System (INIS)
Bugrij, A.I.; Shadura, V.N.
1994-01-01
In this paper we construct the exact representation of the Ising partition function in form of the SL q (2,R)-invariant functional integral for the lattice free q-fermion field theory (q=-1). It is shown that the proposed method of q-fermionization allows one to re-express the partition function of the eight vertex model in external field through the functional integral with four-fermion interaction. For the construction of these representation we define a lattice (l,q,s)-deformed Grassmann bi spinor field and extend the Berezin integration rules for this field. At q = - 1, l = s 1 we obtain the lattice q-fermion field which allows to fermionize the two-dimensional Ising model. We show that Gaussian integral over (q,s)-Grassmann variables is expressed through the (q,s)-deformed Pfaffian which is equal to square root of the determinant of some matrix at q = ± 1, s = ±1. (author). 39 refs
Two-dimensional modeling of an aircraft engine structural bladed disk-casing modal interaction
Legrand, Mathias; Pierre, Christophe; Cartraud, Patrice; Lombard, Jean-Pierre
2009-01-01
In modern turbo machines such as aircraft jet engines, structural contacts between the casing and bladed disk may occur through a variety of mechanisms: coincidence of vibration modes, thermal deformation of the casing, rotor imbalance due to design uncertainties to name a few. These nonlinear interactions may result in severe damage to both structures and it is important to understand the physical circumstances under which they occur. In this study, we focus on a modal coincidence during which the vibrations of each structure take the form of a k-nodal diameter traveling wave characteristic of axi-symmetric geometries. A realistic two-dimensional model of the casing and bladed disk is introduced in order to predict the occurrence of this very specific interaction phenomenon versus the rotation speed of the engine. The equations of motion are solved using an explicit time integration scheme in conjunction with the Lagrange multiplier method where friction is accounted for. This model is validated from the comparison with an analytical solution. The numerical results show that the structures may experience different kinds of behaviors (namely damped, sustained and divergent motions) mainly depending on the rotational velocity of the bladed disk.
Two-dimensional modeling of contaminant transport in porous media in the presence of colloids
Bekhit, Hesham M.; Hassan, Ahmed E.
2005-12-01
It has long been known that colloids can facilitate the transport of contaminants in groundwater systems by reducing the effective retardation factor. A significant effort has been devoted to study colloid-facilitated contaminant transport during the past decade. Many of the previous studies were restricted to one-dimensional analyses and comparisons with finite-column experiments. In this work, a two-dimensional numerical model is developed and used to study the different interactions between colloids, contaminants, and porous media under homogeneous conditions. The numerical formulation of the model is based on discretizing mass balance equations and reaction equations using finite differences having a third-order, total variance-diminishing scheme for the advection terms. This scheme significantly reduces numerical dispersion and leads to greater accuracy compared to the standard central-differencing scheme. The model is tested against analytical solutions under simplified conditions as well as against experimental data, and the results are favorable. The model is used to investigate the impact of the various reaction rates and parameter values on the movement of contaminant plumes in two dimensions. The model is also used to investigate the hypothesis that colloids may increase the effective retardation factor of contaminant plumes. The analysis shows that assuming kinetic mass exchange between contaminant and colloids with constant reaction rate coefficients that are not related to the concentrations may lead to inaccurate results. These inaccurate results are exemplified in the finding that under the kinetic assumption the ratio of the initial concentration of colloids to the initial concentration of contaminant does not affect the amount of facilitation or retardation that occurs in the system. It is also found that colloids can increase the effective retardation factor for the contaminant under certain combinations of reaction rates and distribution
Modeling of a piezoelectric/piezomagnetic nano energy harvester based on two dimensional theory
Yan, Zhi
2018-01-01
This work presents a two dimensional theory for a piezoelectric/piezomagnetic bilayer nanoplate in coupled extensional and flexural vibrations with both flexoelectric and surface effects. The magneto-electro-elastic (MEE) coupling equations are derived from three-dimensional equations and Kirchhoff plate theory. Based on the developed theory, a piezoelectric/piezomagnetic nano energy harvester is proposed, which can generate electricity under time-harmonic applied magnetic field. The approximate solutions for the mechanical responses and voltage of the energy harvester are obtained using the weighted residual method. Results show that the properties of the proposed energy harvester are size-dependent due to the flexoelectric and surface effects, and such effects are more pronounced when the bilayer thickness is reduced to dozens of nanometers. It is also found that the magnetoelectric coupling coefficient and power density of the energy harvester are sensitive to the load resistance, the thickness fraction of the piezoelectric or the piezomagnetic layer and damping ratios. Moreover, results indicate that the flexoelectric effect could be made use to build a dielectric/piezomagnetic nano energy harvester. This work provides modeling techniques and numerical methods for investigating the size-dependent properties of MEE nanoplate-based energy harvester and could be helpful for designing nano energy harvesters using the principle of flexoelectricity.
Parallel Factor-Based Model for Two-Dimensional Direction Estimation
Directory of Open Access Journals (Sweden)
Nizar Tayem
2017-01-01
Full Text Available Two-dimensional (2D Direction-of-Arrivals (DOA estimation for elevation and azimuth angles assuming noncoherent, mixture of coherent and noncoherent, and coherent sources using extended three parallel uniform linear arrays (ULAs is proposed. Most of the existing schemes have drawbacks in estimating 2D DOA for multiple narrowband incident sources as follows: use of large number of snapshots, estimation failure problem for elevation and azimuth angles in the range of typical mobile communication, and estimation of coherent sources. Moreover, the DOA estimation for multiple sources requires complex pair-matching methods. The algorithm proposed in this paper is based on first-order data matrix to overcome these problems. The main contributions of the proposed method are as follows: (1 it avoids estimation failure problem using a new antenna configuration and estimates elevation and azimuth angles for coherent sources; (2 it reduces the estimation complexity by constructing Toeplitz data matrices, which are based on a single or few snapshots; (3 it derives parallel factor (PARAFAC model to avoid pair-matching problems between multiple sources. Simulation results demonstrate the effectiveness of the proposed algorithm.
Parametric analyses of DEMO Divertor using two dimensional transient thermal hydraulic modelling
Domalapally, Phani; Di Caro, Marco
2017-11-01
Among the options considered for cooling of the Plasma facing components of the DEMO reactor, water cooling is a conservative option because of its high heat removal capability. In this work a two-dimensional transient thermal hydraulic code is developed to support the design of the divertor for the projected DEMO reactor with water as a coolant. The mathematical model accounts for transient 2D heat conduction in the divertor section. Temperature-dependent properties are used for more accurate analysis. Correlations for single phase flow forced convection, partially developed subcooled nucleate boiling, fully developed subcooled nucleate boiling and film boiling are used to calculate the heat transfer coefficients on the channel side considering the swirl flow, wherein different correlations found in the literature are compared against each other. Correlation for the Critical Heat Flux is used to estimate its limit for a given flow conditions. This paper then investigates the results of the parametric analysis performed, whereby flow velocity, diameter of the coolant channel, thickness of the coolant pipe, thickness of the armor material, inlet temperature and operating pressure affect the behavior of the divertor under steady or transient heat fluxes. This code will help in understanding the basic parameterś effect on the behavior of the divertor, to achieve a better design from a thermal hydraulic point of view.
Dynamics of a two-dimensional discrete-time SIS model
Directory of Open Access Journals (Sweden)
Jaime H. Barrera
2012-04-01
Full Text Available We analyze a two-dimensional discrete-time SIS model with a non-constant total population. Our goal is to determine the interaction between the total population, the susceptible class and the infective class, and the implications this may have for the disease dynamics. Utilizing a constant recruitment rate in the susceptible class, it is possible to assume the existence of an asymptotic limiting equation, which enables us to reduce the system of, two-equations into a single, dynamically equivalent equation. In this case, we are able to demonstrate the global stability of the disease-free and the endemic equilibria when the basic reproductive number (Ro is less than one and greater than one, respectively. When we consider a non-constant recruitment rate, the total population bifurcates as we vary the birth rate and the death rate. Using computer simulations, we observe different behavior among the infective class and the total population, and possibly, the occurrence of a strange attractor.
A two-dimensional analytical model for tidal wave propagation in convergent estuaries
Cai, Huayang; Toffolon, Marco; Savenije, Hubert H. G.; Chua, Vivien P.
2015-04-01
A knowledge of tidal dynamics in large-scale semi-closed estuaries, such as the Bay of Fundy, the Gulf of California, the Adriatic Sea, is very important since it affects the estuarine environment and its potential use of water resource in many ways (e.g., navigation, coastal safety, ecology). To obtain insight into physical mechanisms on tidal wave propagation in such systems, analytical models are invaluable tools. It is well known that the analytical solutions for tidal dynamics in semi-closed estuaries can be obtained by Taylor's method, where a cooscillating tide can be described as a superposition of an incident Kelvin wave, a reflected Kelvin wave, and Poincare waves. However, the method is usually limited to special conditions, e.g., prismatic channel with uniform depth, negligible friction etc. In this study, we extend the one-dimensional linear solution for tidal wave propagation in convergent estuaries to the two-dimensional case, explicitly accounting for both the channel convergence (width and depth convergence) and friction.
Two-dimensional modeling of x-ray output from switched foil implosions on Procyon
Bowers, R. L.; Nakafuji, G.; Greene, A. E.; McLenithan, K. D.; Peterson, D. L.; Roderick, N. F.
1996-09-01
A series of two-dimensional radiation magnetohydrodynamic calculations are presented of a Z-pinch implosion using a plasma flow switch. Results from a recent experiment using the high explosive driven generator Procyon, which delivered 16.5 MA to a plasma flow switch and switched about 15 MA into a static load, are used to study the implosion of a 29 mg load foil [J. H. Goforth et al., ``Review of the Procyon Explosive Pulsed Power System,'' in Ninth IEEE Pulsed Power Conference, June 1993, Albuquerque, edited by K. R. Prestwich and W. L. Baker (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1993), p. 36]. The interaction of the switch with the load plasma and the effects of background plasma on the total radiation output is examined. Models which assume ideal switching are also included. Also included are the effects of perturbations in the load plasma which may be associated with initial vaporization of the load foil. If the background plasma density in the switch region and in the load region does not affect the dynamics, the pinch is predicted to produce a total radiation output of about 4 MJ. Including perturbations of the load plasma associated with switching and assuming a background plasma density after switching in excess of 10-7 g/cm3 results in a total output from the pinch of about 0.6 MJ.
Simulation and Experimental Studies of Jamming for Model Two-Dimensional Particles Under Flow
Guariguata, A.; Wu, D. T.; Koh, C. A.; Sum, A. K.; Sloan, E. D.
2009-06-01
Jamming and plugging of flowlines with gas hydrates is the most critical issue in the flow assurance of oil and gas production lines. Because solid hydrate particles are often suspended in a fluid, the pipeline jamming and flow constriction formed by hydrates depend not only on particle/wall properties, such as friction, binding forces and mechanical characteristics, but also on the concentration of particles upstream of the restriction, flow velocity, fluid viscosity, and forces between the particles. Therefore, to gain insight into the jamming phenomena, both experiments and computer simulations on two-dimensional model systems have been carried out to characterize the flow of particles in a channel, with the eventual goal of applying that knowledge to gas hydrates jamming. Using the simulation software PFC2d®, we studied the effect of restriction geometry and flow velocity on the jamming process of particles. Results from the simulations were compared to experimental measurements on polyethylene discs floating on water flowing in an open channel.
Morphology Development in Model Polyethylene via Two-Dimensional Correlation Analysis
Energy Technology Data Exchange (ETDEWEB)
D Smirnova; J Kornfield; D Lohse
2011-12-31
Two-dimensional (2D) correlation analysis is applied to synchrotron X-ray scattering data to characterize morphological regimes during nonisothermal crystallization of a model ethylene copolymer (hydrogenated polybutadiene, HPBD). The 2D correlation patterns highlight relationships among multiple characteristics of structure evolution, particularly the extent to which separate features change simultaneously versus sequentially. By visualizing these relationships during cooling, evidence is obtained for two separate physical processes occurring in what is known as 'irreversible crystallization' in random ethylene copolymers. Initial growth of primarily lamellae into unconstrained melt ('primary-irreversible crystallization') is distinguished from subsequent secondary lamellae formation in the constrained, noncrystalline regions between the primary lamellae ('secondary-irreversible crystallization'). At successively lower temperatures ('reversible crystallization'), growth of the crystalline reflections is found to occur simultaneously with the change in shape of the amorphous halo, which is inconsistent with the formation of an additional phase. Rather, the synchronous character supports the view that growth of frustrated crystals distorts the adjacent noncrystalline material. Furthermore, heterocorrelation analysis of small-angle and wide-angle X-ray scattering data from the reversible crystallization regime reveals that the size of new crystals is consistent with fringed-micellar structures (9 nm). Thus, 2D correlation analysis provides new insights into morphology development in polymeric systems.
Exact lattice supersymmetry: The two-dimensional N=2 Wess-Zumino model
International Nuclear Information System (INIS)
Catterall, Simon; Karamov, Sergey
2002-01-01
We study the two-dimensional Wess-Zumino model with extended N=2 supersymmetry on the lattice. The lattice prescription we choose has the merit of preserving exactly a single supersymmetric invariance at finite lattice spacing a. Furthermore, we construct three other transformations of the lattice fields under which the variation of the lattice action vanishes to O(ga 2 ) where g is a typical interaction coupling. These four transformations correspond to the two Majorana supercharges of the continuum theory. We also derive lattice Ward identities corresponding to these exact and approximate symmetries. We use dynamical fermion simulations to check the equality of the mass gaps in the boson and fermion sectors and to check the lattice Ward identities. At least for weak coupling we see no problems associated with a lack of reflection positivity in the lattice action and find good agreement with theory. At strong coupling we provide evidence that problems associated with a lack of reflection positivity are evaded for small enough lattice spacing
Application of Gaussian cubature to model two-dimensional population balances
Directory of Open Access Journals (Sweden)
Bałdyga Jerzy
2017-09-01
Full Text Available In many systems of engineering interest the moment transformation of population balance is applied. One of the methods to solve the transformed population balance equations is the quadrature method of moments. It is based on the approximation of the density function in the source term by the Gaussian quadrature so that it preserves the moments of the original distribution. In this work we propose another method to be applied to the multivariate population problem in chemical engineering, namely a Gaussian cubature (GC technique that applies linear programming for the approximation of the multivariate distribution. Examples of the application of the Gaussian cubature (GC are presented for four processes typical for chemical engineering applications. The first and second ones are devoted to crystallization modeling with direction-dependent two-dimensional and three-dimensional growth rates, the third one represents drop dispersion accompanied by mass transfer in liquid-liquid dispersions and finally the fourth case regards the aggregation and sintering of particle populations.
International Nuclear Information System (INIS)
Kinnison, D.E.; Wuebbles, D.J.; Johnston, H.S.
1992-02-01
This study tests the transport processes in the LLNL two-dimensional chemical-radiative-transport model using recently reanalyzed carbon-14 and strontium-90 data. These radioactive tracers were produced bythe atmospheric nuclear bomb tests of 1952--58 and 1961--62, and they were measured at a few latitudes up to 35 kilometers over the period 1955--1970. Selected horizontal and vertical eddy diffusion coefficients were varied in the model to test their sensitivity to short and long term transpose of carbon-14. A sharp transition of K zz and K yy through the tropopause, as opposed to a slow transition between the same limiting values, shows a distinct improvement in the calculated carbon-14 distributions, a distinct improvement in the calculated seasonal and latitudinal distribution of ozone columns (relative to TOMS observations), and a very large difference in the calculated ozone reduction by a possible fleet of High Speed Civil Transports. Calculated northern hemisphere carbon-14 is more sensitive to variation of K yy than are global ozone columns. Strontium-90 was used to test the LLNL tropopause height at four different latitudes. Starting with the 1960 background distribution of carbon-14, we calculate the input of carbon-14 as the sum of each nuclear test of the 1961--62 series, using two bomb-cloud rise models. With the Seitz bomb-rise formulation in the LLNL model, we find good agreement between calculated and observedcarbon-14 (with noticeable exceptions at the north polar tropopause and the short-term mid-latitude mid-stratosphere) between 1963 and 1970
Spin transport in the two-dimensional quantum disordered anisotropic Heisenberg model
Energy Technology Data Exchange (ETDEWEB)
Lima, L.S. [Departamento de Física e Matemática, Centro Federal de Educação Tecnológica de Minas Gerais, 30510-000 Belo Horizonte, MG (Brazil); Pires, A.S.T.; Costa, B.V. [Departamento de Física ICEx, UFMG, CP 702, 31270-901 Belo Horizonte, MG (Brazil)
2014-12-15
We use the self consistent harmonic approximation together with the Linear Response Theory to study the effect of nonmagnetic disorder on spin transport in the quantum diluted two-dimensional anisotropic Heisenberg model with spin S=1 in a square lattice. The model has a BKT transition at zero dilution. We calculate the regular part of the spin conductivity σ{sup reg}(ω) and the Drude weight D{sub S}(T) as a function of the non-magnetic concentration, x. Our calculations show that the spin conductivity drops abruptly to zero at x{sub c}{sup SCHA}≈0.5 indicating that the system changes from an ideal spin conductor state to an insulator. This value is far above the site percolation threshold x{sub c}{sup site}≈0.41. Although the SCHA fails in determining precisely the percolation threshold, both the spin conductivity and the Drude weight show a quite regular behavior inside 0≤x≤x{sub c}{sup SCHA} indicating that the transition stays in the same universality class all along the interval. - Highlights: • The site dilution generates a large influence on regular part of the spin conductivity, σ{sup reg}(ω), and in the Drude weight, D(T). • In a concentration of impurities about x≈0.5, the regular part of the spin conductivity and the Drude weight fall to zero. • In this point we have a change in the state of the system from an ideal spin conductor to a spin insulator.
Collapse arresting in an inhomogeneous two-dimensional nonlinear Schrodinger model
DEFF Research Database (Denmark)
Schjødt-Eriksen, Jens; Gaididei, Yuri Borisovich; Christiansen, Peter Leth
2001-01-01
Collapse of (2 + 1)-dimensional beams in the inhomogeneous two-dimensional cubic nonlinear Schrodinger equation is analyzed numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams that in a homogeneous medium would collapse may...
Schapers, T; Nitta, J; Heersche, HB; Takayanagi, H
The spin dependent conductance of a ferromagnet/two-dimensional electron gas ferromagnet structure is theoretically examined in the ballistic transport regime. It is shown that the spin signal can be improved considerably by making use of the spin filtering effect of a barrier at the ferromagnet
Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model
Sherman, A.
2018-05-01
The influence of spin and charge fluctuations on spectra of the two-dimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the ranges of Hubbard repulsions , temperatures and electron concentrations with t the intersite hopping constant. For all considered U the system exhibits a transition to the long-range antiferromagnetic order at . At the same time no indication of charge ordering is observed. Obtained solutions agree satisfactorily with results of other approaches and obey moments sum rules. In the considered region of the U-T plane, the curve separating metallic solutions passes from at the highest temperatures to U = 2t at for half-filling. If only short-range fluctuations are allowed for the remaining part of this region is occupied by insulating solutions. Taking into account long-range fluctuations leads to strengthening of maxima tails, which transform a part of insulating solutions into bad-metal states. For low T, obtained results allow us to trace the gradual transition from the regime of strong correlations with the pronounced four-band structure and well-defined Mott gap for to the Slater regime of weak correlations with the spectral intensity having a dip along the boundary of the magnetic Brillouin zone due to an antiferromagnetic ordering for . For and doping leads to the occurrence of a pseudogap near the Fermi level, which is a consequence of the splitting out of a narrow band from a Hubbard subband. Obtained spectra feature waterfalls and Fermi arcs, which are similar to those observed in hole-doped cuprates.
Morimoto, Hisao; Maekawa, Toru; Matsumoto, Yoichiro
2003-12-01
We investigate two-dimensional cluster structures composed of ferromagnetic colloidal particles, based on a flexible chain model, by the configurational-bias Monte Carlo method. We clarify the dependence of the probabilities of the creation of different types of clusters on the dipole-dipole interactive energy and the cluster size.
DEFF Research Database (Denmark)
Baykal, Cüneyt; Ergin, Ayşen; Güler, Işikhan
2014-01-01
This study presents an application of a two-dimensional beach evolution model to a shoreline change problem at the Kizilirmak River mouth, which has been facing severe coastal erosion problems for more than 20 years. The shoreline changes at the Kizilirmak River mouth have been thus far...
International Nuclear Information System (INIS)
Su, Chun; Wang, Xiaolin
2016-01-01
In practice, customers can decide whether to buy an extended warranty or not, at the time of item sale or at the end of the basic warranty. In this paper, by taking into account the moments of customers purchasing two-dimensional extended warranty, the optimization of imperfect preventive maintenance for repairable items is investigated from the manufacturer's perspective. A two-dimensional preventive maintenance strategy is proposed, under which the item is preventively maintained according to a specified age interval or usage interval, whichever occurs first. It is highlighted that when the extended warranty is purchased upon the expiration of the basic warranty, the manufacturer faces a two-stage preventive maintenance optimization problem. Moreover, in the second stage, the possibility of reducing the servicing cost over the extended warranty period is explored by classifying customers on the basis of their usage rates and then providing them with customized preventive maintenance programs. Numerical examples show that offering customized preventive maintenance programs can reduce the manufacturer's warranty cost, while a larger saving in warranty cost comes from encouraging customers to buy the extended warranty at the time of item sale. - Highlights: • A two-dimensional PM strategy is investigated. • Imperfect PM strategy is optimized by considering both two-dimensional BW and EW. • Customers are categorized based on their usage rates throughout the BW period. • Servicing cost of the EW is reduced by offering customized PM programs. • Customers buying the EW at the time of sale is preferred for the manufacturer.
Graphene as a Prototypical Model for Two-Dimensional Continuous Mechanics
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Philippe Lambin
2017-08-01
Full Text Available This paper reviews a few problems where continuous-medium theory specialized to two-dimensional media provides a qualitatively correct picture of the mechanical behavior of graphene. A critical analysis of the parameters involved is given. Among other results, a simple mathematical description of a folded graphene sheet is proposed. It is also shown how the graphene–graphene adhesion interaction is related to the cleavage energy of graphite and its C 33 bulk elastic constant.
A two-dimensional numerical model of two-phase heat transfer and fluid flow in a kettle reboiler
International Nuclear Information System (INIS)
Edwards, D.P.; Jensen, M.K.
1991-01-01
This paper reports on a numerical model that has been developed to predict the two-dimensional, two-phase flow in a kettle reboiler using a finite difference computer code. The effects of bundle-averaged heat flux, heat transfer mode, weir height, and reboiler size were examined. The recirculation flow rate in the kettle reboiler was found to be strongly dependent upon the bundle-averaged heat flux; the recirculating flow increased with increasing heat flux, reached a plateau, and then decreased with further increases in the heat flux. Differences between the constant wall heat flux and constant wall temperature modes of heat transfer were minimal. The model is an improvement over previous one- and two-dimensional models because; the location of the recirculation center could be predicted, the model included the horizontal flow components within the tube bundle, and the model employed a two-fluid rather than a homogeneous fluid model
Non-linear two-dimensional model of melt flows and interface instability in aluminum reduction cells
Sun, Haijun; Zikanov, Oleg; Ziegler, Donald P.
2004-10-01
We derive a new two-dimensional model for the melt flows and interface instability in aluminum reduction cells. The model is based on the de St. Venant shallow water equations and incorporates the essential features of the system such as the magnetohydrodynamic instability mechanism and non-linear coupling between the flows and interfacial waves. The model is applied to investigate the impact of background melt flows and magnetic field perturbations on the instability.
Basic problems and solution methods for two-dimensional continuous 3 × 3 order hidden Markov model
International Nuclear Information System (INIS)
Wang, Guo-gang; Tang, Gui-jin; Gan, Zong-liang; Cui, Zi-guan; Zhu, Xiu-chang
2016-01-01
A novel model referred to as two-dimensional continuous 3 × 3 order hidden Markov model is put forward to avoid the disadvantages of the classical hypothesis of two-dimensional continuous hidden Markov model. This paper presents three equivalent definitions of the model, in which the state transition probability relies on not only immediate horizontal and vertical states but also immediate diagonal state, and in which the probability density of the observation relies on not only current state but also immediate horizontal and vertical states. The paper focuses on the three basic problems of the model, namely probability density calculation, parameters estimation and path backtracking. Some algorithms solving the questions are theoretically derived, by exploiting the idea that the sequences of states on rows or columns of the model can be viewed as states of a one-dimensional continuous 1 × 2 order hidden Markov model. Simulation results further demonstrate the performance of the algorithms. Because there are more statistical characteristics in the structure of the proposed new model, it can more accurately describe some practical problems, as compared to two-dimensional continuous hidden Markov model.
International Nuclear Information System (INIS)
Korshunov, S.E.; Uimin, G.V.
1986-01-01
A most popular model in the family of two-dimensional uniformly-frustrated XY models is the antiferromagnetic model on a triangular lattice (AF XY(t) model). Its ground state is both continuously and twofold discretely degenerated. Different phase transitions possible in such systems are investigated. Relevant topological excitations are analyzed and a new class of such (vortices with a fractional number of circulation quanta) is discovered. Their role in determining the properties of the system proves itself essential. The characteristics of phase transitions related to breaking of discrete and continuous symmetries change. The phase diagram of the ''generalized'' AF XY(t) model is constructed. The results obtained are rederived in the representation of the Coulomb gas with half-interger charges, equivalent to the AF XY(t) model with the Berezinskii-Villain interaction
A discontinuous Galerkin method for two-dimensional PDE models of Asian options
Hozman, J.; Tichý, T.; Cvejnová, D.
2016-06-01
In our previous research we have focused on the problem of plain vanilla option valuation using discontinuous Galerkin method for numerical PDE solution. Here we extend a simple one-dimensional problem into two-dimensional one and design a scheme for valuation of Asian options, i.e. options with payoff depending on the average of prices collected over prespecified horizon. The algorithm is based on the approach combining the advantages of the finite element methods together with the piecewise polynomial generally discontinuous approximations. Finally, an illustrative example using DAX option market data is provided.
Numerical model for two-dimensional hydrodynamics and energy transport. [VECTRA code
Energy Technology Data Exchange (ETDEWEB)
Trent, D.S.
1973-06-01
The theoretical basis and computational procedure of the VECTRA computer program are presented. VECTRA (Vorticity-Energy Code for TRansport Analysis) is designed for applying numerical simulation to a broad range of intake/discharge flows in conjunction with power plant hydrological evaluation. The code computational procedure is based on finite-difference approximation of the vorticity-stream function partial differential equations which govern steady flow momentum transport of two-dimensional, incompressible, viscous fluids in conjunction with the transport of heat and other constituents.
Revealing strategies of quorum sensing in Azospirillum brasilense strains Ab-V5 and Ab-V6.
Fukami, Josiane; Abrantes, Julia Laura Fernandes; Del Cerro, Pablo; Nogueira, Marco Antonio; Ollero, Francisco Javier; Megías, Manuel; Hungria, Mariangela
2018-01-01
Azospirillum brasilense is an important plant-growth promoting bacterium (PGPB) that requires several critical steps for root colonization, including biofilm and exopolysaccharide (EPS) synthesis and cell motility. In several bacteria these mechanisms are mediated by quorum sensing (QS) systems that regulate the expression of specific genes mediated by the autoinducers N-acyl-homoserine lactones (AHLs). We investigated QS mechanisms in strains Ab-V5 and Ab-V6 of A. brasilense, which are broadly used in commercial inoculants in Brazil. Neither of these strains carries a luxI gene, but there are several luxR solos that might perceive AHL molecules. By adding external AHLs we verified that biofilm and EPS production and cell motility (swimming and swarming) were regulated via QS in Ab-V5, but not in Ab-V6. Differences were observed not only between strains, but also in the specificity of LuxR-type receptors to AHL molecules. However, Ab-V6 was outstanding in indole acetic acid (IAA) synthesis and this molecule might mimic AHL signals. We also applied the quorum quenching (QQ) strategy, obtaining transconjugants of Ab-V5 and Ab-V6 carrying a plasmid with acyl-homoserine lactonase. When maize (Zea mays L.) was inoculated with the wild-type and transconjugant strains, plant growth was decreased with the transconjugant of Ab-V5-confirming the importance of an AHL-mediated QS system-but did not affect plant growth promotion by Ab-V6.
FireStem2D A two-dimensional heat transfer model for simulating tree stem injury in fires
Efthalia K. Chatziefstratiou; Gil Bohrer; Anthony S. Bova; Ravishankar Subramanian; Renato P.M. Frasson; Amy Scherzer; Bret W. Butler; Matthew B. Dickinson
2013-01-01
FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by...
Two-dimensional sigma models: modelling non-perturbative effects of quantum chromodynamics
International Nuclear Information System (INIS)
Novikov, V.A.; Shifman, M.A.; Vainshtein, A.I.; Zakharov, V.I.
1984-01-01
The basic features of the O(N) sigma models are discussed. Some aspects of the Wilson opera,tor expansion (OPE) are considered: mathematical formulation of OPE, its physical meaning and non-perturbative vacuum expectations of local operators. It is concluded that OPE is well defined outside the perturabation theory. The anomaly in the trace of the energy-momentum tensor is studied. It is shown that the anomaly determines the masses of physical particles. Low-energy theorems which relate low-energy scattering amplitudes to non-perturbative vacuum expectation values of some operators are investigated
Dunlavy, M. J.; Venus, D.
2005-04-01
Power-law scaling of the relaxation time τ associated with critical slowing down has been experimentally measured in the dynamics of the magnetization of a bilayer of iron grown on top of a W(110) substrate using the complex magnetic ac susceptibility χ(T) . The observed value of the critical exponent for the slowing down above the Curie transition of this two-dimensional Ising ferromagnetic system is zν=2.09±0.06 (95% confidence), in agreement with most contemporary theories and simulations. Further analysis reveals that dynamical effects cause χ(T) to deviate from power-law scaling as the temperature is decreased towards Tc , whereas the saturation of the correlation length due to finite-size effects (on the order of 500 lattice spaces) limits the divergence of τ .
Hall MHD Modeling of Two-dimensional Reconnection: Application to MRX Experiment
International Nuclear Information System (INIS)
Lukin, V.S.; Jardin, S.C.
2003-01-01
Two-dimensional resistive Hall magnetohydrodynamics (MHD) code is used to investigate the dynamical evolution of driven reconnection in the Magnetic Reconnection Experiment (MRX). The initial conditions and dimensionless parameters of the simulation are set to be similar to the experimental values. We successfully reproduce many features of the time evolution of magnetic configurations for both co- and counter-helicity reconnection in MRX. The Hall effect is shown to be important during the early dynamic X-phase of MRX reconnection, while effectively negligible during the late ''steady-state'' Y-phase, when plasma heating takes place. Based on simple symmetry considerations, an experiment to directly measure the Hall effect in MRX configuration is proposed and numerical evidence for the expected outcome is given
Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.
Zhong, Jian-Qiang; Wang, Mengen; Akter, Nusnin; Kestell, John D; Boscoboinik, Alejandro M; Kim, Taejin; Stacchiola, Dario J; Lu, Deyu; Boscoboinik, J Anibal
2017-07-17
The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.
Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems
Zhong, Jian-Qiang; Wang, Mengen; Akter, Nusnin; Kestell, John D.; Boscoboinik, Alejandro M.; Kim, Taejin; Stacchiola, Dario J.; Lu, Deyu; Boscoboinik, J. Anibal
2017-07-01
The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.
The Dugdale model for a semi-infinite crack in a strip of two-dimensional decagonal quasicrystals
Ling-yun, Xie; Tian-you, Fan
2011-05-01
The problem of a semi-infinite crack in a strip is useful in materials science and engineering. The paper proposes a Dugdale model for the configuration of two-dimensional decagonal quasicrystals. Through the complex variable method, we obtain the exact solution of the problem. The plastic zone and the crack tip opening displacement and the most important physical quantity, stress intensity factor, can be expressed in quite a simple form.
A NetCDF version of the two-dimensional energy balance model based on the full multigrid algorithm
Directory of Open Access Journals (Sweden)
Kelin Zhuang
2017-01-01
Full Text Available A NetCDF version of the two-dimensional energy balance model based on the full multigrid method in Fortran is introduced for both pedagogical and research purposes. Based on the land–sea–ice distribution, orbital elements, greenhouse gases concentration, and albedo, the code calculates the global seasonal surface temperature. A step-by-step guide with examples is provided for practice.
An, Taeyang; Cha, Min-Chul
2013-03-01
We study the superfluid-insulator quantum phase transition in a disordered two-dimensional quantum rotor model with random on-site interactions in the presence of particle-hole symmetry. Via worm-algorithm Monte Carlo calculations of superfluid density and compressibility, we find the dynamical critical exponent z ~ 1 . 13 (2) and the correlation length critical exponent 1 / ν ~ 1 . 1 (1) . These exponents suggest that the insulating phase is a incompressible Mott glass rather than a Bose glass.
DEFF Research Database (Denmark)
Eldrup, Mads Røge; Andersen, Thomas Lykke
The present report presents results from a two-dimensional model test study carried out at Aalborg University in December 2017 with the proposed trunk section for the new cubipod armoured western breakwater in Port of Hanstholm as proposed by the contractor Aarsleff and their consultant Cowi....... The objectives of the model tests were to study the stability of the armour layer, toe erosion, overtopping and transmission. The scale used for the model tests was 1:44.6. Initially the model was created on a scale 1:47, but model was adapted to 1:44.6 due to a mismatch in density of rented cupipods. Unless...
Ludwig, Alon; Leviatan, Yehuda
2003-08-01
We introduce a solution based on the source-model technique for periodic structures for the problem of electromagnetic scattering by a two-dimensional photonic bandgap crystal slab illuminated by a transverse-magnetic plane wave. The proposed technique takes advantage of the periodicity of the slab by solving the problem within the unit cell of the periodic structure. The results imply the existence of a frequency bandgap and provide a valuable insight into the relationship between the dimensions of a finite periodic structure and its frequency bandgap characteristics. A comparison shows a discrepancy between the frequency bandgap obtained for a very thick slab and the bandgap obtained by solving the corresponding two-dimensionally infinite periodic structure. The final part of the paper is devoted to explaining in detail this apparent discrepancy.
DNA sequencing by two-dimensional materials: As theoretical modeling meets experiments.
Liang, Lijun; Shen, Jia-Wei; Zhang, Zhisen; Wang, Qi
2017-03-15
Owing to their extraordinary electrical, chemical, optical, mechanical and structural properties, two-dimensional (2D) materials (mainly including graphene, boron nitride, MoS 2 etc.) have stimulated exploding interests in sensor applications. 2D-material based nanoscale DNA sequencing is a single-molecule technique with revolutionary potential. In this paper, we review the methodology of DNA sequencing based on the measurements of ionic current, force peak, and transverse electrical currents etc. by 2D materials. The advantages and disadvantages of DNA sequencing by 2D materials are discussed. Besides the recent development of experiments, we will focus on the theoretical calculations of DNA sequencing, which have been played a critical role in the development of this field. Special emphasis will focus on the disagreements between experiments and theoretical calculations, and the explanations for the discrepancy will be highlighted. Finally, some new plausible sequencing methods from computational studies will be discussed, which may be applied in the realistic DNA sequencing experiments in future. Copyright © 2015 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Eylenceoğlu, E.; Rafatov, I., E-mail: rafatov@metu.edu.tr [Department of Physics, Middle East Technical University, Ankara (Turkey); Kudryavtsev, A. A. [Saint Petersburg State University, St.Petersburg (Russian Federation)
2015-01-15
Two-dimensional hybrid Monte Carlo–fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model.
Chuang, Mo-Hsiung; Hung, Chi-Tung; -Yen Lin, Wen; Ma, Kuo-chen
2017-04-01
In recent years, cities and industries in the vicinity of the estuarine region have developed rapidly, resulting in a sharp increase in the population concerned. The increasing demand for human activities, agriculture irrigation, and aquaculture relies on massive pumping of water in estuarine area. Since the 1950s, numerous studies have focused on the effects of tidal fluctuations on groundwater flow in the estuarine area. Tide-induced head fluctuation in a two-dimensional estuarine aquifer system is complicated and rather important in dealing with many groundwater management or remediation problems. The conceptual model of the aquifer system considered is multi-layered with estuarine bank and the leaky aquifer extend finite distance under the estuary. The solution of the model describing the groundwater head distribution in such an estuarine aquifer system and subject to the tidal fluctuation effects from estuarine river is developed based on the method of separation of variables along with river boundary. The solutions by Sun (Sun H. A two-dimensional analytical solution of groundwater response to tidal loading in an estuary, Water Resour. Res. 1997; 33:1429-35) as well as Tang and Jiao (Tang Z. and J. J. Jiao, A two-dimensional analytical solution for groundwater flow in a leaky confined aquifer system near open tidal water, Hydrological Processes, 2001; 15: 573-585) can be shown to be special cases of the present solution. On the basis of the analytical solution, the groundwater head distribution in response to estuarine boundary is examined and the influences of leakage, hydraulic parameters, and loading effect on the groundwater head fluctuation due to tide are investigated and discussed. KEYWORDS: analytical model, estuarine river, groundwater fluctuation, leaky aquifer.
Guo, Yangyu; Wang, Moran
2017-10-01
The single mode relaxation time approximation has been demonstrated to greatly underestimate the lattice thermal conductivity of two-dimensional materials due to the collective effect of phonon normal scattering. Callaway's dual relaxation model represents a good approximation to the otherwise ab initio solution of the phonon Boltzmann equation. In this work we develop a discrete-ordinate-method (DOM) scheme for the numerical solution of the phonon Boltzmann equation under Callaway's model. Heat transport in a graphene ribbon with different geometries is modeled by our scheme, which produces results quite consistent with the available molecular dynamics, Monte Carlo simulations, and experimental measurements. Callaway's lattice thermal conductivity model with empirical boundary scattering rates is examined and shown to overestimate or underestimate the direct DOM solution. The length convergence of the lattice thermal conductivity of a rectangular graphene ribbon is explored and found to depend appreciably on the ribbon width, with a semiquantitative correlation provided between the convergence length and the width. Finally, we predict the existence of a phonon Knudsen minimum in a graphene ribbon only at a low system temperature and isotope concentration so that the average normal scattering rate is two orders of magnitude stronger than the intrinsic resistive one. The present work will promote not only the methodology for the solution of the phonon Boltzmann equation but also the theoretical modeling and experimental detection of hydrodynamic phonon transport in two-dimensional materials.
Holmquist, Jeffrey G.; Waddle, Terry J.
2013-01-01
We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.
Underdown, Ruth; Redfern, Jonathan
2008-01-01
The Ghadames Basin contains important oil- and gas-producing reservoirs distributed across Algeria, Tunisia, and Libya. Regional two-dimensional (2-D) modeling, using data from more than 30 wells, has been undertaken to assess the timing and distribution of hydrocarbon generation in the basin. Four potential petroleum systems have been identified: (1) a Middle-Upper Devonian (Frasnian) and Triassic (Triassic Argilo Gréseux Inférieur [TAG-I]) system in the central-western basin; (2) a Lower Si...
Critical behavior of the Higgs- and Goldstone-mass gaps for the two-dimensional S=1 XY model
Directory of Open Access Journals (Sweden)
Yoshihiro Nishiyama
2015-08-01
Full Text Available Spectral properties for the two-dimensional quantum S=1 XY model were investigated with the exact diagonalization method. In the symmetry-broken phase, there appear the massive Higgs and massless Goldstone excitations, which correspond to the longitudinal and transverse modes of the spontaneous magnetic moment, respectively. The former excitation branch is embedded in the continuum of the latter, and little attention has been paid to the details, particularly, in proximity to the critical point. The finite-size-scaling behavior is improved by extending the interaction parameters. An analysis of the critical amplitude ratio for these mass gaps is made.
Miao, Zheng; He, Ya-Ling; Li, Xiang-Lin; Zou, Jin-Qiang
A two-dimensional two-phase mass transport model for liquid-feed direct methanol fuel cells (DMFCs) is presented in this paper. The fluid flow and mass transport across the membrane electrode assembly (MEA) is formulated based on the classical multiphase flow theory in the porous media. The modeling of mass transport in the catalyst layers (CLs) and membrane is given more attentions. The effect of the two-dimensional migration of protons in the electrolyte phase on the liquid flow behavior is considered. Water and methanol crossovers through the membrane are implicitly calculated in the governing equations of momentum and methanol concentration. A modified agglomerate model is developed to characterize the microstructure of the CLs. A self-written computer code is used to solve the inherently coupled differential governing equations. Then this model is applied to investigate the mechanisms of species transport and the distributions of the species concentrations, overpotential and the electrochemical reaction rates in CLs. The effects of radius and overlapping angle of agglomerates on cell performance are also explored in this work.
Microwave Analysis for Two-Dimensional C-V and Noise Model of AlGaN/GaN MODFET
Directory of Open Access Journals (Sweden)
Ramnish Kumar
2014-01-01
Full Text Available A new two-dimensional analytical model for the capacitance-voltage and noise characteristics of a AlGaN/GaN MODFET is developed. The two-dimensional electron gas density is calculated as a function of device dimensions. The model includes the spontaneous and polarization effects. The contribution of various capacitances to the performance of the device is shown. The model further predicts the transconductance, drain conductance, and frequency of operation. A high transconductance of 160 mS/mm and a cut-off frequency of 11.6 GHz are obtained for a device of 50 nm gate length. The effect of gate length on the gate length behaviour of the noise coefficients P, R, and C is also studied. The effect of parasitic source and gate resistance has also been studied to evaluate the minimum noise figure. The excellent agreement with the previously simulated results confirms the validity of the proposed model to optimize the device performance at high frequencies.
International Nuclear Information System (INIS)
Chan, T.; Nakka, B.W.
1994-12-01
A two-dimensional analytical well model has been developed to describe steady groundwater flow in an idealized, confined aquifer intersected by a withdrawal well. The aquifer comprises a low-dipping fracture zone. The model is useful for making simple quantitative estimates of the transport of contaminants along groundwater pathways in the fracture zone to the well from an underground source that intercepts the fracture zone. This report documents the mathematical development of the analytical well model. It outlines the assumptions and method used to derive an exact analytical solution, which is verified by two other methods. It presents expressions for calculating quantities such as streamlines (groundwater flow paths), fractional volumetric flow rates, contaminant concentration in well water and minimum convective travel time to the well. In addition, this report presents the results of applying the analytical model to a site-specific conceptual model of the Whiteshell Research Area in southeastern Manitoba, Canada. This hydrogeological model includes the presence of a 20-m-thick, low-dipping (18 deg) fracture zone (LD1) that intercepts the horizon of a hypothetical disposal vault located at a depth of 500 m. A withdrawal well intercepts LD1 between the vault level and the ground surface. Predictions based on parameters and boundary conditions specific to LD1 are presented graphically. The analytical model has specific applications in the SYVAC geosphere model (GEONET) to calculate the fraction of a plume of contaminants moving up the fracture zone that is captured by the well, and to describe the drawdown in the hydraulic head in the fracture zone caused by the withdrawal well. (author). 16 refs., 6 tabs., 35 figs
Lai, Ruixun; Wang, Min; Yang, Ming; Zhang, Chao
2018-02-01
The accuracy of the widely-used two-dimensional hydrodynamic numerical model depends on the quality of the river terrain model, particularly in the main channel. However, in most cases, the bathymetry of the river channel is difficult or expensive to obtain in the field, and there is a lack of available data to describe the geometry of the river channel. We introduce a method that originates from the grid generation with the elliptic equation to generate streamlines of the river channel. The streamlines are numerically solved with the Laplace equations. In the process, streamlines in the physical domain are first computed in a computational domain, and then transformed back to the physical domain. The interpolated streamlines are integrated with the surrounding topography to reconstruct the entire river terrain model. The approach was applied to a meandering reach in the Qinhe River, which is a tributary in the middle of the Yellow River, China. Cross-sectional validation and the two-dimensional shallow-water equations are used to test the performance of the river terrain generated. The results show that the approach can reconstruct the river terrain using the data from measured cross-sections. Furthermore, the created river terrain can maintain a geometrical shape consistent with the measurements, while generating a smooth main channel. Finally, several limitations and opportunities for future research are discussed.
A new model for two-dimensional numerical simulation of pseudo-2D gas-solids fluidized beds
Energy Technology Data Exchange (ETDEWEB)
Li, Tingwen; Zhang, Yongmin
2013-10-11
Pseudo-two dimensional (pseudo-2D) fluidized beds, for which the thickness of the system is much smaller than the other two dimensions, is widely used to perform fundamental studies on bubble behavior, solids mixing, or clustering phenomenon in different gas-solids fluidization systems. The abundant data from such experimental systems are very useful for numerical model development and validation. However, it has been reported that two-dimensional (2D) computational fluid dynamic (CFD) simulations of pseudo-2D gas-solids fluidized beds usually predict poor quantitative agreement with the experimental data, especially for the solids velocity field. In this paper, a new model is proposed to improve the 2D numerical simulations of pseudo-2D gas-solids fluidized beds by properly accounting for the frictional effect of the front and back walls. Two previously reported pseudo-2D experimental systems were simulated with this model. Compared to the traditional 2D simulations, significant improvements in the numerical predictions have been observed and the predicted results are in better agreement with the available experimental data.
Degenerate ground states and multiple bifurcations in a two-dimensional q-state quantum Potts model.
Dai, Yan-Wei; Cho, Sam Young; Batchelor, Murray T; Zhou, Huan-Qiang
2014-06-01
We numerically investigate the two-dimensional q-state quantum Potts model on the infinite square lattice by using the infinite projected entangled-pair state (iPEPS) algorithm. We show that the quantum fidelity, defined as an overlap measurement between an arbitrary reference state and the iPEPS ground state of the system, can detect q-fold degenerate ground states for the Z_{q} broken-symmetry phase. Accordingly, a multiple bifurcation of the quantum ground-state fidelity is shown to occur as the transverse magnetic field varies from the symmetry phase to the broken-symmetry phase, which means that a multiple-bifurcation point corresponds to a critical point. A (dis)continuous behavior of quantum fidelity at phase transition points characterizes a (dis)continuous phase transition. Similar to the characteristic behavior of the quantum fidelity, the magnetizations, as order parameters, obtained from the degenerate ground states exhibit multiple bifurcation at critical points. Each order parameter is also explicitly demonstrated to transform under the Z_{q} subgroup of the symmetry group of the Hamiltonian. We find that the q-state quantum Potts model on the square lattice undergoes a discontinuous (first-order) phase transition for q=3 and q=4 and a continuous phase transition for q=2 (the two-dimensional quantum transverse Ising model).
Choi, Haecheon; Park, Hyungmin; Choi, Jin; Jeon, Woo-Pyung
2004-11-01
A wind-tunnel experiment is performed to control flow behind a two-dimensional model vehicle, which has a fixed separation point, with a newly proposed passive device, wake disrupter. The wake disrupter is a small-size rectangular body attached to the upper and lower trailing edges, designed to perturb an essentially two-dimensional nature of wake. The effect of the wake disrupter on the base pressure of the model vehicle is tested for various configurations by varying its size and spanwise spacing. The experiments are conducted at the Reynolds numbers of 20000, 40000 and 80000 based on the free stream velocity and model height. The optimal configuration of wake disrupter produces 33% increase in the base pressure, whose amount is much larger than that by single optimal pair(22%). A hot-wire measurement is also carried out to examine the characteristics of turbulent flow disturbed by the wake disrupter. It shows that the wake disrupter significantly increases the length and width of vortex formation along the entire spanwise direction, which is closely related to the pressure recovery at the base surface.
A comparison study of one-and two-dimensional hydraulic models for river environments.
2017-05-01
Computer models are used every day to analyze river systems for a wide variety of reasons vital to : the public interest. For decades most hydraulic engineers have been limited to models that simplify the fluid : mechanics to the unidirectional case....
Two-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (2DFATMIC) Model
This model simulates subsurface flow, fate, and transport of contaminants that are undergoing chemical or biological transformations. This model is applicable to transient conditions in both saturated and unsaturated zones.
Group theoretical construction of two-dimensional models with infinite sets of conservation laws
International Nuclear Information System (INIS)
D'Auria, R.; Regge, T.; Sciuto, S.
1980-01-01
We explicitly construct some classes of field theoretical 2-dimensional models associated with symmetric spaces G/H according to a general scheme proposed in an earlier paper. We treat the SO(n + 1)/SO(n) and SU(n + 1)/U(n) case, giving their relationship with the O(n) sigma-models and the CP(n) models. Moreover, we present a new class of models associated to the SU(n)/SO(n) case. All these models are shown to possess an infinite set of local conservation laws. (orig.)
International Nuclear Information System (INIS)
Krapchev, V.
1976-01-01
In the framework of the two-dimensional scalar quantum theory of the bag model of Chodos et al a definition of the physical field and a general scheme for constructing a physical state are given. Some of the difficulties associated with such an approach are exposed. Expressions for the physical current and the elastic form factor are given. The calculation of the latter is restricted at first to the approximation in which the mapping from a bag of changing shape to a fixed domain is realized only by a term which is a diagonal, bilinear function of the creation and annihilation operators. This is done for the case of a one-mode and an infinite-mode bag theory. By computing the form factor in an exact one-mode bag model it is shown that the logarithmic falloff of the asymptotic term is the same as the one in the approximation. On the basis of this a form for the asymptotic behavior of the form factor is suggested which may be correct for the general two-dimensional scalar bag theory
Urbic, Tomaz
2017-07-01
In this paper we applied analytical theories for the two dimensional chain-forming fluid. Wertheims thermodynamic perturbation theory (TPT) and integral equation theory (IET) for associative liquids were used to study thermodynamical and structural properties of the chain-forming model. The model has polymerizing points at arbitrary position from center of the particles. Calculated analytical results were tested against corresponding results obtained by Monte Carlo computer simulations to check the accuracy of the theories. The theories are accurate for the different positions of patches of the model at all values of the temperature and density studied. The IET's pair correlation functions of the model agree well with computer simulations. Both TPT and IET are in good agreement with the Monte Carlo values of the energy, chemical potential and ratios of free, once and twice bonded particles.
Directory of Open Access Journals (Sweden)
Adam Formánek
2013-12-01
Full Text Available The objective of this study was to present a sophisticated method of developing supporting material for flood control implementation in DKI Jakarta. High flow rates in the Ciliwung River flowing through Jakarta regularly causes extensive flooding in the rainy season. The affected area comprises highly densely populated villages. For developing an efficient early warning system in view of decreasing the vulnerability of the locations a flood index map has to be available. This study analyses the development of a flood risk map of the inundation area based on a two-dimensional modeling using FESWMS. The reference event used for the model was the most recent significant flood in 2007. The resulting solution represents flood characteristics such as inundation area, inundation depth and flow velocity. Model verification was performed by confrontation of the results with survey data. The model solution was overlaid with a street map of Jakarta. Finally, alternatives for flood mitigation measures are discussed.
A Two-Dimensional Analytic Thermal Model for a High-Speed PMSM Magnet
CSIR Research Space (South Africa)
Grobler, AJ
2015-11-01
Full Text Available . The temperature-dependent properties of permanent magnets necessitate high-detail thermal models. This paper presents a 2-D analytical model for a HS PMSM magnet. The diffusion equation is solved where three of the PM boundaries experience convection heat flow...
A Two-Dimensional Model of Intergroup Leadership: The Case of National Diversity
Pittinsky, Todd L.
2010-01-01
The model presented argues that leadership involves bringing together not only diverse individuals but also the subgroups to which they belong. The model further argues that this does not require replacing people's subgroup identities with a superordinate group identity (turning "us" and "them" into "we"); bringing together diverse individuals and…
DEFF Research Database (Denmark)
Swierczynski, Maciej Jozef; Stroe, Daniel Loan; Knap, Vaclav
2016-01-01
Thermal modeling of lithium-ion batteries is gaining its importance together with increasing power density and compact design of the modern battery systems in order to assure battery safety and long lifetime. Thermal models of lithium-ion batteries are usually either expensive to develop and accu...
Two-Dimensional Model Test Study of the New Caisson Breakwater at Playa Blanca, Lanzarote
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Garborg, Karsten; Stagsted, Esben Rubech
This report present the results of 2-D physical model tests (length scale 1:42.5) carried out in a wave flume at Department of Civil Engineering, Aalborg University (AAU) on behalf of SENER Ingenera y Sistemas S.A. Associate Prof. Thomas Lykke Andersen was in charge of the model tests, assisted b...
International Nuclear Information System (INIS)
Laval, Jean Philippe
1999-01-01
We developed a turbulent model based on asymptotic development of the Navier-Stokes equations within the hypothesis of non-local interactions at small scales. This model provides expressions of the turbulent Reynolds sub-grid stresses via estimates of the sub-grid velocities rather than velocities correlations as is usually done. The model involves the coupling of two dynamical equations: one for the resolved scales of motions, which depends upon the Reynolds stresses generated by the sub-grid motions, and one for the sub-grid scales of motions, which can be used to compute the sub-grid Reynolds stresses. The non-locality of interaction at sub-grid scales allows to model their evolution with a linear inhomogeneous equation where the forcing occurs via the energy cascade from resolved to sub-grid scales. This model was solved using a decomposition of sub-grid scales on Gabor's modes and implemented numerically in 2D with periodic boundary conditions. A particles method (PIC) was used to compute the sub-grid scales. The results were compared with results of direct simulations for several typical flows. The model was also applied to plane parallel flows. An analytical study of the equations allows a description of mean velocity profiles in agreement with experimental results and theoretical results based on the symmetries of the Navier-Stokes equation. Possible applications and improvements of the model are discussed in the conclusion. (author) [fr
Conservation Laws and Nonlocally Related Systems of Two-Dimensional Boundary Layer Models
Naz, R.; Cheviakov, A. F.
2017-10-01
Local conservation laws, potential systems, and nonlocal conservation laws are systematically computed for three-equilibrium two-component boundary layer models that describe different physical situations: a plate flow, a flow parallel to the axis of a circular cylinder, and a radial jet striking a planar wall. First, local conservation laws of each model are computed using the direct method. For each of the three boundary layer models, two local conservation laws are found. The corresponding potential variables are introduced, and nonlocally related potential systems and subsystems are formed. Then nonlocal conservation laws are sought, arising as local conservation laws of nonlocally related systems. For each of the three physical models, similar nonlocal conservation laws arise. Further nonlocal variables that lead to further potential systems are considered. Trees of nonlocally related systems are constructed; their structure coincides for all three models. The three boundary layer models considered in this work provide rich and interesting examples of the construction of trees of nonlocally related systems. In particular, the trees involve spectral potential systems depending on a parameter; these spectral potential systems lead to nonlocal conservation laws. Moreover, potential variables that are not locally related on solution sets of some potential systems become local functions of each other on solution sets of other systems. The point symmetry analysis shows that the plate and radial jet flow models possess infinite-dimensional Lie algebras of point symmetries, whereas the Lie algebra of point symmetries for the cylinder flow model is three-dimensional. The computation of nonlocal symmetries reveals none that arise for the original model equations, which is common for partial differential equations (PDE) systems without constitutive parameters or functions, but does reveal nonlocal symmetries for some nonlocally related PDE systems.
Directory of Open Access Journals (Sweden)
Rosa Ana Salas
2013-11-01
Full Text Available We propose a modeling procedure specifically designed for a ferrite inductor excited by a waveform in time domain. We estimate the loss resistance in the core (parameter of the electrical model of the inductor by means of a Finite Element Method in 2D which leads to significant computational advantages over the 3D model. The methodology is validated for an RM (rectangular modulus ferrite core working in the linear and the saturation regions. Excellent agreement is found between the experimental data and the computational results.
A two-dimensional model of intergroup leadership: the case of national diversity.
Pittinsky, Todd L
2010-04-01
The model presented argues that leadership involves bringing together not only diverse individuals but also the subgroups to which they belong. The model further argues that this does not require replacing people's subgroup identities with a superordinate group identity (turning "us" and "them" into "we"); bringing together diverse individuals and their subgroups can be accomplished by promoting positive relations among subgroups, even as their distinctive identities (their senses of "us" and "them") remain. The model conceptualizes positive and negative intergroup attitudes as two independent dimensions of intergroup relations, each with distinct antecedents and distinct associated outcomes. Leaders seeking to create a collective from diverse subgroups must therefore (a) reduce negative intergroup attitudes and (b) increase positive intergroup attitudes. The author applies the model to organizational contexts of national diversity, but it can be applied to leadership across other forms of diversity. (PsycINFO Database Record (c) 2010 APA, all rights reserved).
Large Deviations for Stochastic Models of Two-Dimensional Second Grade Fluids
Energy Technology Data Exchange (ETDEWEB)
Zhai, Jianliang, E-mail: zhaijl@ustc.edu.cn [University of Science and Technology of China, School of Mathematical Sciences (China); Zhang, Tusheng, E-mail: Tusheng.Zhang@manchester.ac.uk [University of Manchester, School of Mathematics (United Kingdom)
2017-06-15
In this paper, we establish a large deviation principle for stochastic models of incompressible second grade fluids. The weak convergence method introduced by Budhiraja and Dupuis (Probab Math Statist 20:39–61, 2000) plays an important role.
National Research Council Canada - National Science Library
Holmes, Kenneth
2002-01-01
.... This thesis studies the effects of AIGaN/GaN HEMTs' polarization, piezoelectric (PZ) and spontaneous, properties utilizing the TM commercially available Silvaco Atlas software for modeling and simulation...
A nonlinear vertex-based model for animation of two-dimensional dry foam
DEFF Research Database (Denmark)
Kelager, Micky; Erleben, Kenny
2010-01-01
Foam is the natural phenomenon of bubbles that arise due to nucleation of gas in liquids. The current state of art in Computer Graphics rarely includes foam effects on large scales. In this paper we introduce a vertexbased, quasi-static equilibrium model from the field of Computational Physics as...... simulations with free dynamic boundary conditions. The presented model is interesting and well suited for 2D graphics applications like video games and procedural or animated textures....
DEFF Research Database (Denmark)
Shaikh, Danish; Kjær Schmidt, Michael
2017-01-01
Three-dimensional acoustic localisation is relevant in personal and social robot platforms. Conventional approaches extract interaural time difference cues via impractically large stationary two-dimensional multi-microphone grids with at least four microphones or spectral cues via head-related tr......Three-dimensional acoustic localisation is relevant in personal and social robot platforms. Conventional approaches extract interaural time difference cues via impractically large stationary two-dimensional multi-microphone grids with at least four microphones or spectral cues via head......-related transfer functions of stationary KEMAR dummy heads equipped with two microphones. We present a preliminary approach using two sound sensors, whose directed movements resolve the location of a stationary acoustic target in three dimensions. A model of the peripheral auditory system of lizards provides sound...... direction information in a single plane which by itself is insufficient to localise the acoustic target in three dimensions. Two spatial orientations of this plane by rotating the sound sensors by -45 deg. and +45 deg. along the sagittal axis generate a pair of measurements, each encoding the location...
Lefkoff, L.J.; Gorelick, S.M.
1987-01-01
A FORTRAN-77 computer program code that helps solve a variety of aquifer management problems involving the control of groundwater hydraulics. It is intended for use with any standard mathematical programming package that uses Mathematical Programming System input format. The computer program creates the input files to be used by the optimization program. These files contain all the hydrologic information and management objectives needed to solve the management problem. Used in conjunction with a mathematical programming code, the computer program identifies the pumping or recharge strategy that achieves a user 's management objective while maintaining groundwater hydraulic conditions within desired limits. The objective may be linear or quadratic, and may involve the minimization of pumping and recharge rates or of variable pumping costs. The problem may contain constraints on groundwater heads, gradients, and velocities for a complex, transient hydrologic system. Linear superposition of solutions to the transient, two-dimensional groundwater flow equation is used by the computer program in conjunction with the response matrix optimization method. A unit stress is applied at each decision well and transient responses at all control locations are computed using a modified version of the U.S. Geological Survey two dimensional aquifer simulation model. The program also computes discounted cost coefficients for the objective function and accounts for transient aquifer conditions. (Author 's abstract)
Two-dimensional time dependent hurricane overwash and erosion modeling at Santa Rosa Island
McCall, R.T.; Van Theil de Vries, J. S. M.; Plant, N.G.; Van Dongeren, A. R.; Roelvink, J.A.; Thompson, D.M.; Reniers, A.J.H.M.
2010-01-01
A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias - 0.21 m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response.
Exactly solvable models of two-dimensional dilaton cosmology with quantum backreaction
International Nuclear Information System (INIS)
Zaslavskii, O B
2003-01-01
We consider a general approach to exactly solvable 2D dilaton cosmology with one-loop backreaction from conformal fields taken into account. It includes as particular cases previous models discussed in the literature. We list different types of solutions and investigate their properties for simple models, typical for string theory. We find a rather rich class of everywhere-regular solutions, which exist practically in every type of analysed solution. They exhibit different kinds of asymptotic behaviour in the past and future, including inflation, superinflation, deflation, power expansion or contraction. In particular, for some models the dS spacetime with a time-dependent dilaton field is the exact solution of the field equations. For some kinds of solution the weak-energy condition is violated independently of a specific model. We also find the solutions with a singularity which is situated in an infinite past (or future), so at any finite moment of a comoving time the universe is singularity-free. It is pointed out that for some models the spacetime may be everywhere regular even in spite of infinitely large quantum backreaction in an infinite past
International Nuclear Information System (INIS)
Anon.
1991-01-01
This chapter addresses the extension of previous work in one-dimensional (linear) error theory to two-dimensional error analysis. The topics of the chapter include the definition of two-dimensional error, the probability ellipse, the probability circle, elliptical (circular) error evaluation, the application to position accuracy, and the use of control systems (points) in measurements
Functional techniques in quantum field theory and two-dimensional models
International Nuclear Information System (INIS)
Souza, C. Farina de.
1985-03-01
Functional methods applied to Quantum Field Theory are studied. It is shown how to construct the Generating Functional using three of the most important methods existent in the literature, due to Feynman, Symanzik and Schwinger. The Axial Anomaly is discussed in the usual way, and a non perturbative method due to Fujikawa to obtain this anomaly in the path integral formalism is presented. The ''Roskies-Shaposnik-Fujikawa's method'', which makes use of Fujikawa's original idea to solve bidimensional models, is introduced in the Schwinger's model, which, in turn, is applied to obtain the exact solution of the axial model. It is discussed briefly how different regularization procedures can affect the theory in question. (author)
Thermodynamic model of social influence on two-dimensional square lattice: Case for two features
Genzor, Jozef; Bužek, Vladimír; Gendiar, Andrej
2015-02-01
We propose a thermodynamic multi-state spin model in order to describe equilibrial behavior of a society. Our model is inspired by the Axelrod model used in social network studies. In the framework of the statistical mechanics language, we analyze phase transitions of our model, in which the spin interaction J is interpreted as a mutual communication among individuals forming a society. The thermal fluctuations introduce a noise T into the communication, which suppresses long-range correlations. Below a certain phase transition point Tt, large-scale clusters of the individuals, who share a specific dominant property, are formed. The measure of the cluster sizes is an order parameter after spontaneous symmetry breaking. By means of the Corner transfer matrix renormalization group algorithm, we treat our model in the thermodynamic limit and classify the phase transitions with respect to inherent degrees of freedom. Each individual is chosen to possess two independent features f = 2 and each feature can assume one of q traits (e.g. interests). Hence, each individual is described by q2 degrees of freedom. A single first-order phase transition is detected in our model if q > 2, whereas two distinct continuous phase transitions are found if q = 2 only. Evaluating the free energy, order parameters, specific heat, and the entanglement von Neumann entropy, we classify the phase transitions Tt(q) in detail. The permanent existence of the ordered phase (the large-scale cluster formation with a non-zero order parameter) is conjectured below a non-zero transition point Tt(q) ≈ 0.5 in the asymptotic regime q → ∞.
Nogawa, Tomoaki
2011-12-05
The evaporation-condensation transition of the Potts model on a square lattice is numerically investigated by the Wang-Landau sampling method. An intrinsically system-size-dependent discrete transition between supersaturation state and phase-separation state is observed in the microcanonical ensemble by changing constrained internal energy. We calculate the microcanonical temperature, as a derivative of microcanonical entropy, and condensation ratio, and perform a finite-size scaling of them to indicate the clear tendency of numerical data to converge to the infinite-size limit predicted by phenomenological theory for the isotherm lattice gas model. © 2011 American Physical Society.
Goyal, Mukesh; Chakravarty, Anindya; Atrey, M. D.
2017-03-01
Experimental investigations are carried out using a specially developed three-layer plate fin heat exchanger (PFHE), with helium as the working fluid cooled to cryogenic temperatures using liquid nitrogen (LN2) as a coolant. These results are used for validation of an already proposed and reported numerical model based on finite volume analysis for multistream (MS) plate fin heat exchangers (PFHE) for cryogenic applications (Goyal et al., 2014). The results from the experiments are presented and a reasonable agreement is observed with the already reported numerical model.
Chen, Huili; Liang, Zhongyao; Liu, Yong; Liang, Qiuhua; Xie, Shuguang
2017-10-01
The projected frequent occurrences of extreme flood events will cause significant losses to crops and will threaten food security. To reduce the potential risk and provide support for agricultural flood management, prevention, and mitigation, it is important to account for flood damage to crop production and to understand the relationship between flood characteristics and crop losses. A quantitative and effective evaluation tool is therefore essential to explore what and how flood characteristics will affect the associated crop loss, based on accurately understanding the spatiotemporal dynamics of flood evolution and crop growth. Current evaluation methods are generally integrally or qualitatively based on statistic data or ex-post survey with less diagnosis into the process and dynamics of historical flood events. Therefore, a quantitative and spatial evaluation framework is presented in this study that integrates remote sensing imagery and hydraulic model simulation to facilitate the identification of historical flood characteristics that influence crop losses. Remote sensing imagery can capture the spatial variation of crop yields and yield losses from floods on a grid scale over large areas; however, it is incapable of providing spatial information regarding flood progress. Two-dimensional hydraulic model can simulate the dynamics of surface runoff and accomplish spatial and temporal quantification of flood characteristics on a grid scale over watersheds, i.e., flow velocity and flood duration. The methodological framework developed herein includes the following: (a) Vegetation indices for the critical period of crop growth from mid-high temporal and spatial remote sensing imagery in association with agricultural statistics data were used to develop empirical models to monitor the crop yield and evaluate yield losses from flood; (b) The two-dimensional hydraulic model coupled with the SCS-CN hydrologic model was employed to simulate the flood evolution process
Is there a delocalization transition in a two-dimensional model for quantum percolation
International Nuclear Information System (INIS)
Dasgupta, I.; Saha, T.; Mookerjee, A.; Chakrabarti, B.K.
1992-01-01
In this paper, the authors estimate the transmittance of the quantum percolation model of Eggarter and Kirkpatrick on the square lattice of various sizes using the vector recursion method. The authors note from finite size scaling that there is no delocalization transition for any degree of disorder in two dimensions
Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model
Reid, Daniel A. P.; Hildenbrandt, H.; Hemelrijk, C. K.; Padding, J.T.
2012-01-01
The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed
Temporomandibular Joint and its Two-Dimensional and Three-Dimensional Modelling
Czech Academy of Sciences Publication Activity Database
Hliňáková, P.; Dostálová, T.; Daněk, Josef; Nedoma, Jiří; Hlaváček, Ivan
2010-01-01
Roč. 80, č. 6 (2010), s. 1256-1268 ISSN 0378-4754 Grant - others:GA MZd(CZ) NS9902 Institutional research plan: CEZ:AV0Z10300504; CEZ:AV0Z10190503 Keywords : dentistry * temporomandibular joint * mathematical modelling * contact problem * finite element method Subject RIV: FF - HEENT, Dentistry Impact factor: 0.812, year: 2010
Breakup of a Stoner model for the two-dimensional ferromagnetic quantum critical point
Dzero, M.; Gor'kov, L. P.
2004-03-01
Generalization of the results by A. V. Chubukov et al. [Phys. Rev. Lett. 90, 077002 (2003)] leads to the conclusion that the ferromagnetic quantum critical point cannot be described by a Stoner model because of a strong interplay between the paramagnetic fluctuations and the Cooper channel, at least in two dimensions.
Geothermal modeling along a two-dimensional crustal profile in Southern Portugal
Czech Academy of Sciences Publication Activity Database
Correia, A.; Šafanda, Jan
2002-01-01
Roč. 34, č. 1 (2002), s. 47-61 ISSN 0264-3707. [Geothermics at the turn of the century. Evora, 03.04.2000-07.04.2000] Institutional research plan: CEZ:AV0Z3012916 Keywords : geothermal modeling * Southern Portugal * surface heat flow * crustal profile Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.058, year: 2002
On impossibility of limit cycles in certain two-dimensional countinuous-time growth models
Czech Academy of Sciences Publication Activity Database
Slobodyan, Sergey
2001-01-01
Roč. 5, č. 1 (2001), s. 33-40 ISSN 1081-1826 Institutional research plan: CEZ:AV0Z7085904 Keywords : growth model Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.150, year: 2001
On the geometry of two-dimensional anisotropic non-linear Sigma-models
International Nuclear Information System (INIS)
Franco, D.H.; Negrao, M.G.; Helayel Neto, J.A.; Pereira, A.R.
1997-12-01
One discusses here the connection between α-model gauge anomalies and the existence of a connection with torsion that does not flatten the Ricci tensor of the target manifold. The influence of an eventual anisotropy along a certain internal direction is also contemplated. (author)
John F. Hunt; Hongmei Gu
2006-01-01
The anisotropy of wood complicates solution of heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment, earlywood/latewood differences, or...
DEFF Research Database (Denmark)
Friis, Lars; Ohlrich, Mogens
2008-01-01
is considered as one or more fuzzy substructures that are known in some statistical sense only. Experiments have shown that such fuzzy substructures often introduce a damping in the master which is much higher than the structural losses account for. A special method for modeling fuzzy substructures with a one...
A nonlinear vertex-based model for animation of two-dimensional dry foam
DEFF Research Database (Denmark)
Kelager, Micky; Erleben, Kenny
2010-01-01
Foam is the natural phenomenon of bubbles that arise due to nucleation of gas in liquids. The current state of art in Computer Graphics rarely includes foam effects on large scales. In this paper we introduce a vertexbased, quasi-static equilibrium model from the field of Computational Physics...
Matsui, H.; Mahowald, N.
2017-08-01
Global aerosol simulations are conducted by using the Community Atmosphere Model version 5 with the Aerosol Two-dimensional bin module for foRmation and Aging Simulation version 2 (CAM5-chem/ATRAS2) which was developed in part 1. The model uses a two-dimensional (2-D) section representation with 12 size bins from 1 nm to 10 μm and 8 black carbon (BC) mixing state bins, and it can calculate detailed aerosol processes and their interactions with radiation and clouds. The simulations have similar or better agreement with aerosol observations (e.g., aerosol optical depth, absorption aerosol optical depth (AAOD), aerosol number concentrations, mass concentrations of each species) compared with the simulations using the Modal Aerosol Model with three modes. Sensitivity simulations show that global mean AAOD is reduced by 15% by resolving BC mixing state as a result of two competing effects (optical and lifetime effects). AAOD is reduced by 10-50% at low and midlatitudes in the 2-D sectional simulation because BC absorption enhancement by coating species is reduced by resolving pure BC, thinly coated BC, and BC-free particles in the model (optical effect). In contrast, AAOD is enhanced by 5-30% at high-latitudes because BC concentrations are enhanced by 40-200% over the regions by resolving less CCN active particles (lifetime effect). The simulations also suggest a model which resolves more than 3 BC categories (including BC-free particles) is desirable to calculate the optical and lifetime effects accurately. The complexity of aerosol representation is shown to be especially important for simulations of BC and CCN concentrations and AAOD.
Current-voltage characteristics of two-dimensional vortex-glass models
Energy Technology Data Exchange (ETDEWEB)
Hyman, R.A. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States); Wallin, M. [Department of Theoretical Physics, Royal Institute of Technology, S-100 44 Stockholm (Sweden); Fisher, M.P.A. [Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Girvin, S.M. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States); Young, A.P. [Department of Physics, University of California, Santa Cruz, California 95064 (United States)
1995-06-01
We have performed Monte Carlo simulations to determine current-voltage characteristics of two vortex-glass models in two dimensions. Our results confirm earlier studies which concluded that there is a zero-temperature transition. Additionally we find that, as the temperature approaches zero, the linear resistance vanishes exponentially, and the current scale {ital J}{sub {ital n}{ital l}} where nonlinearities appear in the current-voltage characteristics, varies roughly as {ital T}{sup 3}. This result is quite different from the prediction of conventional flux creep theory in which {ital J}{sub {ital n}{ital l}}{similar_to}{ital T}. The results for the two models agree quite well with each other, and also agree fairly well with recent experiments on very thin films of Y-Ba-Cu-O.
Crop growth and two dimensional modeling of soil water transport in drip irrigated potatoes
DEFF Research Database (Denmark)
Plauborg, Finn; Iversen, Bo Vangsø; Mollerup, Mikkel
2009-01-01
Drip irrigation can be an effective way to improve water and nitrogen use efficiency in soil and hence to reduce the environmental pollution. In the EU project SAFIR ( http://www.safir4eu.org/ ) a potato experiment was carried out in lysimeters on three different soil types: coarse sand, loamy sand...... and sandy loam. An automatic roof was used to exclude the lysimeters from natural precipitation. The potatoes were drip irrigated following different strategies: Fully irrigated (FI), deficit irrigation (65% FI), and partial root zone drying (PRD). Gas exchange measurements were carried as well as sampling...... of abscisic acid (ABA). Model outputs from the mechanistic simulation model Daisy, in SAFIR developed to include 2D soil processes and gas exchange processes based on Ball et al. and Farquhar were compared with measured crop dynamics, final DM yield and volumetric water content in the soil measured by TDR...
Two-Dimensional FCT Model of Low-Altitude Nuclear Effects.
1980-10-16
medium, and preliminary height-of-burst ( HoB ) calculations. A. Reflecting Shock in a Reactive Medium Under a Navy-supported program to study combustion...hydrodynamics, LCP has developed a simple numerical treatment of coinustion processes based on 12 the induction time hypothesis. This model represents...the chemistry through a composite process, in which reactants begin to combine into combustion products only after a finite " induction " time has
DEFF Research Database (Denmark)
Græsbøll, Rune; Nielsen, Nikoline Juul; Christensen, Jan H.
2014-01-01
A method for choosing orthogonal columns for a specific sample set in on-line comprehensive two-dimensional liquid chromatography (LC×LC) was developed on the basis of the hydrophobic subtraction model. The method takes into account the properties of the sample analytes by estimating new F......-weights for the prediction of orthogonality. We compared sets of F-weights and used these F-weights to predict orthogonal column combinations: (1) the standard F-weights determined by Gilroy et al. [1], (2) F-weights determined from the retention of sample analytes, and the same procedure of calculation as described...... neutral and 4 acidic oxygenated polycyclic aromatic compounds (PACs) and 3 nitrogen-containing PAC bases was measured isocratically on 12 columns. The isocratic runs were used to determine the hydrophobic subtraction model analyte parameters, and these were used to estimate new F-weights and predict...
Funamoto, Kenichi; Hayase, Toshiyuki; Shirai, Atsushi
Simplified two-dimensional flow analysis is performed in order to simulate frictional characteristics measurement of red blood cells moving on a glass plate in a medium with an inclined centrifuge microscope. Computation under various conditions reveals the influences of parameters on lift, drag, and moment acting on a red blood cell. Among these forces, lift appears only when the cell is longitudinally asymmetric. By considering the balance of forces, the frictional characteristics of the red blood cell are modeled as the sum of Coulomb friction and viscous drag. The model describes the possibility that the red blood cell deforms to expand in the front side in response to the inclined centrifugal force. When velocity exceeds some critical value, the lift overcomes the normal centrifugal force component, and the thickness of the plasma layer between the cell and the glass plate increases from the initial value of the plasma protein thickness.
Stordal, F.; Isaksen, I. S. A.; Horntveth, K.
1985-01-01
Numerous studies have been concerned with the possibility of a reduction of the stratospheric ozone layer. Such a reduction could lead to an enhanced penetration of ultraviolet (UV) radiation to the ground, and, as a result, to damage in the case of several biological processes. It is pointed out that the distributions of many trace gases, such as ozone, are governed in part by transport processes. The present investigation presents a two-dimensional photochemistry-transport model using the residual circulation. The global distribution of both ozone and components with ground sources computed in this model is in good agreement with the observations even though slow diffusion is adopted. The agreement is particularly good in the Northern Hemisphere. The results provide additional support for the idea that tracer transport in the stratosphere is mainly of advective nature.
Energy Technology Data Exchange (ETDEWEB)
Kim, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Petersson, N. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rodgers, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-10-25
Acoustic waveform modeling is a computationally intensive task and full three-dimensional simulations are often impractical for some geophysical applications such as long-range wave propagation and high-frequency sound simulation. In this study, we develop a two-dimensional high-order accurate finite-difference code for acoustic wave modeling. We solve the linearized Euler equations by discretizing them with the sixth order accurate finite difference stencils away from the boundary and the third order summation-by-parts (SBP) closure near the boundary. Non-planar topographic boundary is resolved by formulating the governing equation in curvilinear coordinates following the interface. We verify the implementation of the algorithm by numerical examples and demonstrate the capability of the proposed method for practical acoustic wave propagation problems in the atmosphere.
Khodel, V A
2001-01-01
Spectral functions of strongly correlated two-dimensional electron systems in solids are studied on the assumption that these systems undergo as phase transition, called fermion condensation, whose characteristic feature is flattening of the electron spectrum epsilon (p). Unlike the previous models in the present study, the decay of single-particle states is properly taken into account. Results of calculations are shown to be in qualitative agreement with ARPES data. The universal behavior of the ration Im EPSILON(p, epsilon, T)/T as a function of x = epsilon/T are found to be reproduced reasonably well. However, in the present model this behavior is destroyed in vicinities of the van Hove points where the fermion condensate resides
Iliev, Oleg P.
2013-05-15
Paper production is a problem with significant importance for society; it is also a challenging topic for scientific investigation. This study is concerned with the simulation of the pressing section of a paper machine. A two-dimensional model is developed to account for the water flow within the pressing zone. A Richards-type equation is used to describe the flow in the unsaturated zone. The dynamic capillary pressure-saturation relation is adopted for the paper production process. The mathematical model accounts for the coexistence of saturated and unsaturated zones in a multilayer computational domain. The discretization is performed by the MPFA-O method. Numerical experiments are carried out for parameters that are typical of the production process. The static and dynamic capillary pressure-saturation relations are tested to evaluate the influence of the dynamic capillary effect. © 2013 Springer Science+Business Media Dordrecht.
DEFF Research Database (Denmark)
Yang, H.; Chemia, Zurab; Artemieva, Irina
The Baikal Rift zone (BRZ) is a narrow ( 10 km) active intra-continental basin, located at the boundary between the Amurian and Eurasian Plates. Although the BRZ is one of the major tectonically active rift zones in the world andit has been a subject of numerous geological...... on topography,basin depth, the structure of the crust, lithosphere thickness, and the location of major tectonic faults. Our goal is to determine the physical models that reproduce reasonably well the ob-served deformation patterns of the BRZ.We perform a systematic analysis of the pa-rameter space in order...
Two-dimensional computational modeling of high-speed transient flow in gun tunnel
Mohsen, A. M.; Yusoff, M. Z.; Hasini, H.; Al-Falahi, A.
2018-03-01
In this work, an axisymmetric numerical model was developed to investigate the transient flow inside a 7-meter-long free piston gun tunnel. The numerical solution of the gun tunnel was carried out using the commercial solver Fluent. The governing equations of mass, momentum, and energy were discretized using the finite volume method. The dynamic zone of the piston was modeled as a rigid body, and its motion was coupled with the hydrodynamic forces from the flow solution based on the six-degree-of-freedom solver. A comparison of the numerical data with the theoretical calculations and experimental measurements of a ground-based gun tunnel facility showed good agreement. The effects of parameters such as working gases and initial pressure ratio on the test conditions in the facility were examined. The pressure ratio ranged from 10 to 50, and gas combinations of air-air, helium-air, air-nitrogen, and air-CO2 were used. The results showed that steady nozzle reservoir conditions can be maintained for a longer duration when the initial conditions across the diaphragm are adjusted. It was also found that the gas combination of helium-air yielded the highest shock wave strength and speed, but a longer test time was achieved in the test section when using the CO2 test gas.
Numerical simulation of a theta-pinch: two-dimensional hybrid model
International Nuclear Information System (INIS)
Zenum, C.S.S.
1987-01-01
A numerical code based on a 2D-hybrid model, were the electrons are considered as a fluid of zero mass and the ions as discrete particles, was elaborated. The magnetic field responsable by ion acceleration was obtained from equation of motion of the electrons and Maxwell equations. The ions are randomly distributed in a space phase of five dimensions (Vr, Vo, Vz, r, z), according to the Maxwellian. The equation of motion is solved for each ion, and the distribution functions of ion is obtained by the technique of particle into the box. The resistivity was classically and phenomenologically treated. The model was applied to theta-pinch to study: the plasma physical behaviour during the phase of implosion; the effect of reflected ions by magnetic piston; and the effect of magnetic field line reconnection 3D graphics of magnetic field, electric field current density, particle, and pressure densities, electron temperature, ion temperature is presented space phase of ion velocity in function of the position is also shown. The obtained results allow to characterized the obtained phenomena which occur during the phase of implosion. (M.C.K.) [pt
Two-dimensional modeling of water spray cooling in superheated steam
Directory of Open Access Journals (Sweden)
Ebrahimian Vahid
2008-01-01
Full Text Available Spray cooling of the superheated steam occurs with the interaction of many complex physical processes, such as initial droplet formation, collision, coalescence, secondary break up, evaporation, turbulence generation, and modulation, as well as turbulent mixing, heat, mass and momentum transfer in a highly non-uniform two-phase environment. While it is extremely difficult to systematically study particular effects in this complex interaction in a well defined physical experiment, the interaction is well suited for numerical studies based on advanced detailed models of all the processes involved. This paper presents results of such a numerical experiment. Cooling of the superheated steam can be applied in order to decrease the temperature of superheated steam in power plants. By spraying the cooling water into the superheated steam, the temperature of the superheated steam can be controlled. In this work, water spray cooling was modeled to investigate the influences of the droplet size, injected velocity, the pressure and velocity of the superheated steam on the evaporation of the cooling water. The results show that by increasing the diameter of the droplets, the pressure and velocity of the superheated steam, the amount of evaporation of cooling water increases. .
Development of a two-dimensional finite element plasma edge model
International Nuclear Information System (INIS)
Vesey, R.A.
1992-01-01
The fluid equations modeling plasma transport in the tokamak scrape-off region are discretized via optimal upwind finite element methods developed for convection-dominated problems. These methods allow the non-orthogonal geometry of the edge region to be represented accurately, while applying the necessary boundary conditions. Newton's method with mesh sequencing is used to arrive at a converged solution to the resulting nonlinear algebraic system of equations. Preliminary results are presented for a 20x20 finite element discretization of the ASDEX edge region, with some simplifications. General agreement between the finite element solution and the Braams code B2 is observed. The code will be extended to allow equilibrium-based meshes and arbitrary boundary geometries
A Two-Dimensional Multiphase Model of Biofilm Formation in Microfluidic Chambers.
Whidden, Mark; Cogan, Nick; Donahue, Matt; Navarrete, Fernando; De La Fuente, Leonardo
2015-12-01
The bacterial pathogen Xylella fastidiosa is the causal agent of many pathological conditions of economically important agricultural crops. There is no known cure for X. fastidiosa diseases, and management of the problem is based solely in controlling the population of insect vectors, which is somewhat effective. The bacterium causes disease by forming biofilms inside the vascular system of the plant, a process that is poorly understood. In microfluidic chambers, used as artificial xylem vessels, this bacterium has been observed to reproducibly cluster into a distinct, regular pattern of aggregates, spatially separated by channels of non-biofilm components. We develop a multiphase model in two dimensions, which recapitulates this spatial patterning, suggesting that bacterial growth and attachment/detachment processes are strongly influential modulators of these patterns. This indicates plausible strategies, such as the addition of metals and chelators, for mitigating the severity of diseases induced by this bacterial pathogen.
Uncovering wind turbine properties through two-dimensional stochastic modeling of wind dynamics.
Raischel, Frank; Scholz, Teresa; Lopes, Vitor V; Lind, Pedro G
2013-10-01
Using a method for stochastic data analysis borrowed from statistical physics, we analyze synthetic data from a Markov chain model that reproduces measurements of wind speed and power production in a wind park in Portugal. We show that our analysis retrieves indeed the power performance curve, which yields the relationship between wind speed and power production, and we discuss how this procedure can be extended for extracting unknown functional relationships between pairs of physical variables in general. We also show how specific features, such as the rated speed of the wind turbine or the descriptive wind speed statistics, can be related to the equations describing the evolution of power production and wind speed at single wind turbines.
d-wave superconductivity in the frustrated two-dimensional periodic Anderson model
Directory of Open Access Journals (Sweden)
Wei Wu
2015-02-01
Full Text Available Superconductivity in heavy-fermion materials can sometimes appear in the incoherent regime and in proximity to an antiferromagnetic quantum critical point. Here, we study these phenomena using large-scale determinant quantum Monte Carlo simulations and the dynamical cluster approximation with various impurity solvers for the periodic Anderson model with frustrated hybridization. We obtain solid evidence for a d_{x^{2}−y^{2}} superconducting phase arising from an incoherent normal state in the vicinity of an antiferromagnetic quantum critical point. There is a coexistence region, and the width of the superconducting dome increases with frustration. Through a study of the pairing dynamics, we find that the retarded spin fluctuations give the main contribution to the pairing glue. These results are relevant for unconventional superconductivity in the Ce-115 family of heavy fermions.
Two-dimensional modeling of water and heat fluxes in green roof substrates
Suarez, F. I.; Sandoval, V. P.
2016-12-01
Due to public concern towards sustainable development, greenhouse gas emissions and energy efficiency, green roofs have become popular in the last years. Green roofs integrate vegetation into infrastructures to reach additional benefits that minimize negative impacts of the urbanization. A properly designed green roof can reduce environmental pollution, noise levels, energetic requirements or surface runoff. The correct performance of green roofs depends on site-specific conditions and on each component of the roof. The substrate and the vegetation layers strongly influence water and heat fluxes on a green roof. The substrate is an artificial media that has an improved performance compared to natural soils as it provides critical resources for vegetation survival: water, nutrients, and a growing media. Hence, it is important to study the effects of substrate properties on green roof performance. The objective of this work is to investigate how the thermal and hydraulic properties affect the behavior of a green roof through numerical modeling. The substrates that were investigated are composed by: crushed bricks and organic soil (S1); peat with perlite (S2); crushed bricks (S3); mineral soil with tree leaves (S4); and a mixture of topsoil and mineral soil (S5). The numerical model utilizes summer-arid meteorological information to evaluate the performance of each substrate. Results show that the area below the water retention curve helps to define the substrate that retains more water. In addition, the non-linearity of the water retention curve can increment the water needed to irrigate the roof. The heat propagation through the roof depends strongly on the hydraulic behavior, meaning that a combination of a substrate with low thermal conductivity and more porosity can reduce the heat fluxes across the roof. Therefore, it can minimize the energy consumed of an air-conditioner system.
Bragança, Helena; Sakai, Shiro; Aguiar, M. C. O.; Civelli, Marcello
2018-02-01
We study the relationship between the pseudogap and Fermi-surface topology in the two-dimensional Hubbard model by means of the cellular dynamical mean-field theory. We find two possible mean-field metallic solutions on a broad range of interactions, doping, and frustration: a conventional renormalized metal and an unconventional pseudogap metal. At half filling, the conventional metal is more stable and displays an interaction-driven Mott metal-insulator transition. However, for large interactions and small doping, a region that is relevant for cuprates, the pseudogap phase becomes the ground state. By increasing doping, we show that a first-order transition from the pseudogap to the conventional metal is tied to a change of the Fermi surface from hole- to electronlike, unveiling a correlation-driven mechanism for a Lifshitz transition. This explains the puzzling link between the pseudogap phase and Fermi surface topology that has been pointed out in recent experiments.
The effect of ac-driven force on superlubricity in a two-dimensional Frenkel-Kontorova model
International Nuclear Information System (INIS)
Lin Maimai
2010-01-01
By using the molecular dynamic simulation method with a fourth-order Runge-Kutta algorithm, a two-dimensional dc- and ac-driven Frenkel-Kontorova model with a square symmetry substrate potential for a square lattice layer has been investigated in this paper. For this system, the effects of many different parameters on the static friction force have been studied in detail. It was found that not only the amplitude and frequency of the ac-driven force, but also the direction of dc- and ac-driven forces and the misfit angle between two layers have a strong influence on the static friction force. This indicated that the phenomenon of superlubricity appears easily with larger ac amplitude and smaller ac frequency for some special direction of the external driving force and misfit angle.
Mondaini, Rubem; Rigol, Marcos
2017-07-01
We study the matrix elements of few-body observables, focusing on the off-diagonal ones, in the eigenstates of the two-dimensional transverse field Ising model. By resolving all symmetries, we relate the onset of quantum chaos to the structure of the matrix elements. In particular, we show that a general result of the theory of random matrices, namely, the value 2 of the ratio of variances (diagonal to off-diagonal) of the matrix elements of Hermitian operators, occurs in the quantum chaotic regime. Furthermore, we explore the behavior of the off-diagonal matrix elements of observables as a function of the eigenstate energy differences and show that it is in accordance with the eigenstate thermalization hypothesis ansatz.
International Nuclear Information System (INIS)
Hua-Bing, Li; Li, Jin; Bing, Qiu
2008-01-01
To study two-dimensional red blood cells deforming in a shear Bow with the membrane nonuniform on the rigidity and mass, the membrane is discretized into equilength segments. The fluid inside and outside the red blood cell is simulated by the D2Q9 lattice Boltzmann model and the hydrodynamic forces exerted on the membrane from the inner and outer of the red blood cell are calculated by a stress-integration method. Through the global deviation from the curvature of uniform-membrane, we find that when the membrane is nonuniform on the rigidity, the deviation first decreases with the time increases and implies that the terminal profile of the red blood cell is static. To a red blood cell with the mass nonuniform on the membrane, the deviation becomes more large, and the mass distribution affects the profile of the two sides of the flattened red blood cell in a shear flow. (fundamental areas of phenomenology(including applications))
A two-dimensional model study of the QBO signal in SAGE II NO2 and O3
Chipperfield, M. P.; Gray, L. J.; Kinnersley, J. S.; Zawodny, J.
1994-01-01
Calculations of the quasi biennial oscillation (QBO) signal in Stratospheric Aerosol and Gas Experiment (SAGE) II O3 and NO2 data between 1984 and 1991 are presented and have been investigated by using a two-dimensional model. The isentropic 2D model is a fully interactive radiative-dynamical-chemical model in which the eddy fluxes of chemical species are calculated in a consistent manner. The QBO in the model has been forced by relaxing the equatorial zonal wind toward the observations at Singapore allowing the comparison of the model with observations from specific years. The model reproduces the observed vertical structure of the equatorial ozone anomaly with the well-known transition from dynamical to photochemical control at around 28km. The model also reproduces the observed vertical structure of the SAGE II observed NO2 anomaly. The model studies have shown that it is the QBO modulation of NO2 which the main cause of QBO signal in O3 above 30 km. The model also reproduces the observed latitudinal structure of the QBO signals in O3 and NO2. Due to the differing horizontal distribution of O3 and NO(y) the ozone signal shows a distinct phase change in the subtropics whereas the NO2 anomaly gives a broader signal.
Evaluation of subgrid-scale models in large-eddy simulation of flow past a two-dimensional block
International Nuclear Information System (INIS)
Cheng, Wai-Chi; Porté-Agel, Fernando
2013-01-01
Highlights: • Large-eddy simulations of flow past a 2D block were performed. • Four subgrid-scale models were evaluated against wind tunnel experimental data. • The recently-developed modulated gradient model (MGM) shows the best overall results. • This study is the first time to validate the MGM in recirculating flows. • Analysis of TKE budget in the flow shows strong TKE production above the block. -- Abstract: Large-eddy simulations of flow past a two-dimensional (2D) block were performed to evaluate four subgrid-scale (SGS) models: (i) the traditional Smagorinsky model, (ii) the Lagrangian dynamic model, (iii) the Lagrangian scale-dependent dynamic model, and (iv) the modulated gradient model. An immersed boundary method was employed to simulate the 2D block boundaries on a uniform Cartesian grid. The sensitivity of the simulation results to grid refinement was investigated by using four different grid resolutions. The velocity streamlines and the vertical profiles of the mean velocities and variances were compared with experimental results. The modulated gradient model shows the best overall agreement with the experimental results among the four SGS models. In particular, the flow recirculation, the reattachment position and the vertical profiles are accurately reproduced with a relative coarse grid resolution of (N x × N y × N z =) 160 × 40 × 160 (n x × n z = 13 × 16 covering the block). Besides the modulated gradient model, the Lagrangian scale-dependent dynamic model is also able to give reasonable prediction of the flow statistics with some discrepancies compared with the experimental results. Relatively poor performance by the Lagrangian dynamic model and the Smagorinsky model is observed, with simulated recirculating patterns that differ from the measured ones. Analysis of the turbulence kinetic energy (TKE) budget in this flow shows evidence of a strong production of TKE in the shear layer that forms as the flow is deflected around the
Duddu, Ravindra
2009-05-01
We present a two-dimensional biofilm growth model in a continuum framework using an Eulerian description. A computational technique based on the eXtended Finite Element Method (XFEM) and the level set method is used to simulate the growth of the biofilm. The model considers fluid flow around the biofilm surface, the advection-diffusion and reaction of substrate, variable biomass volume fraction and erosion due to the interfacial shear stress at the biofilm-fluid interface. The key assumptions of the model and the governing equations of transport, biofilm kinetics and biofilm mechanics are presented. Our 2D biofilm growth results are in good agreement with those obtained by Picioreanu et al. (Biotechnol Bioeng 69(5):504-515, 2000). Detachment due to erosion is modeled using two continuous speed functions based on: (a) interfacial shear stress and (b) biofilm height. A relation between the two detachment models in the case of a 1D biofilm is established and simulated biofilm results with detachment in 2D are presented. The stress in the biofilm due to fluid flow is evaluated and higher stresses are observed close to the substratum where the biofilm is attached. © 2008 Wiley Periodicals, Inc.
FTOM-2D: a two-dimensional approach to model the detailed thermal behavior of nonplanar surfaces
Bartos, B.; Stein, K.
2015-10-01
The Fraunhofer thermal object model (FTOM) predicts the temperature of an object as a function of the environmental conditions. The model has an outer layer exchanging radiation and heat with the environment and a stack of layers beyond modifying the thermal behavior. The innermost layer is at a constant or variable temperature called core temperature. The properties of the model (6 parameters) are fitted to minimize the difference between the prediction and a time series of measured temperatures. The model can be used for very different objects like backgrounds (e.g. meadow, forest, stone, or sand) or objects like vehicles. The two dimensional enhancement was developed to model more complex objects with non-planar surfaces and heat conduction between adjacent regions. In this model we call the small thermal homogenous interacting regions thermal pixels. For each thermal pixel the orientation and the identities of the adjacent pixels are stored in an array. In this version 7 parameters have to be fitted. The model is limited to a convex geometry to reduce the complexity of the heat exchange and allow for a higher number of thermal pixels. For the test of the model time series of thermal images of a test object (CUBI) were analyzed. The square sides of the cubes were modeled as 25 thermal pixels (5 × 5). In the time series of thermal images small areas in the size of the thermal pixels were analyzed to generate data files that can easily be read by the model. The program was developed with MATLAB and the final version in C++ using the OpenMP multiprocessor library. The differential equation for the heat transfer is the time consuming part in the computation and was programmed in C. The comparison show a good agreement of the fitted and not fitted thermal pixels with the measured temperatures. This indicates the ability of the model to predict the temperatures of the whole object.
Directory of Open Access Journals (Sweden)
Jingwei Shen
2017-02-01
Full Text Available Determining the spatial relations between objects is a primary function of a geographic information system (GIS. One important aspect of spatial relations is topological relations, which remain constant under topological transformations. Describing the geometry of a spatial object using the OpenGIS Simple Features Specification requires only simple features: the interior, boundary and exterior of a spatial object are defined. This paper proposes a comprehensive model, the 27-intersection model (27IM, which considers both the dimensions and the number of intersections. Some propositions are presented to exclude relations that the 27IM cannot implement. The 27IM describes six groups of topological relations: point/point, point/line, point/region, line/line, line/region and region/region. The formalism of the 27IM and the corresponding geometric interpretations between spatial objects are illustrated and then compared to the topological relations represented by the existing models, the nine-intersection model (9IM, the dimensionally-extended nine-intersection matrix (DE-9IM and the separation number extended nine-intersection matrix (SNE-9IM. The results show that (1 the 27IM can represent the topological relations between two-dimensional spatial objects, (2 the 27IM can distinguish more topological relations than can the 9IM, DE-9IM or the SNE-9IM and that (3 the interoperability of the 27IM with the 9IM, DE-9IM and SNE-9IM is good.
Energy Technology Data Exchange (ETDEWEB)
Caselle, M.; Grinza, P. [Dipartimento di Fisica Teorica dell' Universita di Torino and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Torino (Italy)]. E-mails: caselle@to.infn.it; grinza@to.infn.it; Magnoli, N. [Dipartimento di Fisica, Universita di Genova and Istituto Nazionale di Fisica Nucleare, Sezione di Genova, Genova (Italy)]. E-mail: magnoli@ge.infn.it
2001-10-26
We investigate the presence of irrelevant operators in the two-dimensional Ising model perturbed by a magnetic field, by studying the corrections induced by these operators in the spin-spin correlator of the model. To this end we perform a set of high-precision simulations for the correlator both along the axes and along the diagonal of the lattice. By comparing the numerical results with the predictions of a perturbative expansion around the critical point we find unambiguous evidence of the presence of such irrelevant operators. It turns out that among the irrelevant operators the one which gives the largest correction is the spin-4 operator T{sup 2}+T-bar{sup 2}, which accounts for the breaking of the rotational invariance due to the lattice. This result agrees with what was already known for the correlator evaluated exactly at the critical point and also with recent results obtained in the case of the thermal perturbation of the model. (author)
Waters, Thomas R; Garg, Arun
2010-01-01
Youth and adolescents are routinely engaged in manual material handling (MMH) tasks that may exceed their strength capability to perform the task and may place them at excessive risk for musculoskeletal disorders. This paper reports on a two-dimensional biomechanical model that was developed to assess MMH tasks performed by youth 3-21 years of age. The model uses age, gender, posture of the youth performing the MMH activity, and weight of the load handled as input, and provides an estimate of the strength demands of the task and spinal disc compression and shear force resulting from the activity as output. The model can be used to assess whether a specific MMH task exceeds the strength demands for youth of certain ages or genders, which of the internal muscle strengths are most affected, and provides information about the estimated spinal disc compression and shear forces on the spine as a result of the specified MMH task. These results would be helpful in deciding whether a task is appropriate for a youth to perform or whether a certain task modification may be sufficient in reducing the physical demands to a level acceptable for a youth of certain age and gender.
Stock, Eduardo Velasco; da Silva, Roberto; Fernandes, H. A.
2017-07-01
In this paper, we propose a stochastic model which describes two species of particles moving in counterflow. The model generalizes the theoretical framework that describes the transport in random systems by taking into account two different scenarios: particles can work as mobile obstacles, whereas particles of one species move in the opposite direction to the particles of the other species, or particles of a given species work as fixed obstacles remaining in their places during the time evolution. We conduct a detailed study about the statistics concerning the crossing time of particles, as well as the effects of the lateral transitions on the time required to the system reaches a state of complete geographic separation of species. The spatial effects of jamming are also studied by looking into the deformation of the concentration of particles in the two-dimensional corridor. Finally, we observe in our study the formation of patterns of lanes which reach the steady state regardless of the initial conditions used for the evolution. A similar result is also observed in real experiments involving charged colloids motion and simulations of pedestrian dynamics based on Langevin equations, when periodic boundary conditions are considered (particles counterflow in a ring symmetry). The results obtained through Monte Carlo simulations and numerical integrations are in good agreement with each other. However, differently from previous studies, the dynamics considered in this work is not Newton-based, and therefore, even artificial situations of self-propelled objects should be studied in this first-principles modeling.
Johnson, R.H.; Poeter, E.P.
2005-01-01
Ground-penetrating radar (GPR) is used to track a dense non-aqueous phase liquid (DNAPL) injection in a laboratory sand tank. Before modeling, the GPR data provide a qualitative image of DNAPL saturation and movement. One-dimensional (1D) GPR modeling provides a quantitative interpretation of DNAPL volume within a given thickness during and after the injection. DNAPL saturation in sublayers of a specified thickness could not be quantified because calibration of the 1D GPR model is nonunique when both permittivity and depth of multiple layers are unknown. One-dimensional GPR modeling of the sand tank indicates geometric interferences in a small portion of the tank. These influences are removed from the interpretation using an alternate matching target. Two-dimensional (2D) GPR modeling provides a qualitative interpretation of the DNAPL distribution through pattern matching and tests for possible 2D influences that are not accounted for in the 1D GPR modeling. Accurate quantitative interpretation of DNAPL volumes using GPR modeling requires (1) identification of a suitable target that produces a strong reflection and is not subject to any geometric interference; (2) knowledge of the exact depth of that target; and (3) use of two-way radar-wave travel times through the medium to the target to determine the permittivity of the intervening material, which eliminates reliance on signal amplitude. With geologic conditions that are suitable for GPR surveys (i.e., shallow depths, low electrical conductivities, and a known reflective target), the procedures in this laboratory study can be adapted to a field site to delineate shallow DNAPL source zones.
Zakynthinaki, Maria S.; Stirling, James R.; Cordente Martínez, Carlos A.; Díaz de Durana, Alfonso López; Quintana, Manuel Sillero; Romo, Gabriel Rodríguez; Molinuevo, Javier Sampedro
2010-03-01
We present a method of modeling the basin of attraction as a three-dimensional function describing a two-dimensional manifold on which the dynamics of the system evolves from experimental time series data. Our method is based on the density of the data set and uses numerical optimization and data modeling tools. We also show how to obtain analytic curves that describe both the contours and the boundary of the basin. Our method is applied to the problem of regaining balance after perturbation from quiet vertical stance using data of an elite athlete. Our method goes beyond the statistical description of the experimental data, providing a function that describes the shape of the basin of attraction. To test its robustness, our method has also been applied to two different data sets of a second subject and no significant differences were found between the contours of the calculated basin of attraction for the different data sets. The proposed method has many uses in a wide variety of areas, not just human balance for which there are many applications in medicine, rehabilitation, and sport.
Surzhikov, S. T.
2017-08-01
The drift-diffusion model of a Penning discharge in molecular hydrogen under pressures of about 1 Torr with regard to the external electric circuit has been proposed. A two-dimensional axially symmetric discharge geometry with a cylindrical anode and flat cathodes perpendicular to the symmetry axis has been investigated. An external magnetic field of about 0.1 T is applied in the axial direction. Using the developed drift-diffusion model, the electrodynamic structure of a Penning discharge in the pressure range of 0.5-5 Torr at a current source voltage of 200-500 V is numerically simulated. The evolution of the discharge electrodynamic structure upon pressure variations in zero magnetic field (the classical glow discharge mode) and in the axial magnetic field (Penning discharge) has been studied using numerical experiments. The theoretical predictions of the existence of an averaged electron and ion motion in a Penning discharge both in the axial and radial directions and in the azimuthal direction have been confirmed by the calculations.
Legleiter, C. J.; McDonald, R.; Kyriakidis, P. C.; Nelson, J. M.
2009-12-01
Numerical models of flow and sediment transport increasingly are used to inform studies of aquatic habitat and river morphodynamics. Accurate topographic information is required to parameterize such models, but this fundamental input is typically subject to considerable uncertainty, which can propagate through a model to produce uncertain predictions of flow hydraulics. In this study, we examined the effects of uncertain topographic input on the output from FaSTMECH, a two-dimensional, finite difference flow model implemented on a regular, channel-centered grid; the model was applied to a simple, restored gravel-bed river. We adopted a spatially explicit stochastic simulation approach because elevation differences (i.e., perturbations) at one node of the computational grid influenced model predictions at nearby nodes, due to the strong coupling between proximal locations dictated by the governing equations of fluid flow. Geostatistical techniques provided an appropriate framework for examining the impacts of topographic uncertainty by generating many, equally likely realizations, each consistent with a statistical model summarizing the variability and spatial structure of channel morphology. By applying the model to each realization in turn, a distribution of model outputs was generated for each grid node. One set of realizations, conditioned to the available survey data and progressively thinned versions thereof, was used to quantify the effects of sampling strategy on topographic uncertainty and hence the uncertainty of model predictions. This analysis indicated that as the spacing between surveyed cross-sections increased, the reach-averaged ensemble standard deviation of water surface elevation, depth, velocity, and boundary shear stress increased as well, for both baseflow conditions and for a discharge of ~75% bankfull. A second set of realizations was generated by retaining randomly selected subsets of the original survey data and used to investigate the
Sawada, A.; Koga, T.
2017-02-01
We have developed a method to calculate the weak localization and antilocalization corrections based on the real-space simulation, where we provide 147 885 predetermined return orbitals of quasi-two-dimensional electrons with up to 5000 scattering events that are repeatedly used. Our model subsumes that of Golub [L. E. Golub, Phys. Rev. B 71, 235310 (2005), 10.1103/PhysRevB.71.235310] when the Rashba spin-orbit interaction (SOI) is assumed. Our computation is very simple, fast, and versatile, where the numerical results, obtained all at once, cover wide ranges of the magnetic field under various one-electron interactions H' exactly. Thus, it has straightforward extensibility to incorporate interactions other than the Rashba SOI, such as the linear and cubic Dresselhaus SOIs, Zeeman effect, and even interactions relevant to the valley and pseudo spin degrees of freedom, which should provide a unique tool to study new classes of materials like emerging 2D materials. Using our computation, we also demonstrate the robustness of a persistent spin helix state against the cubic Dresselhaus SOI.
Directory of Open Access Journals (Sweden)
2015-12-01
Full Text Available Numerical results for ground-state and excited-state properties (energies, double occupancies, and Matsubara-axis self-energies of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary-field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed-node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock methods. Comparison of results obtained by different methods allows for the identification of uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic-limit values is emphasized. Cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.
Directory of Open Access Journals (Sweden)
P. Martini
2004-01-01
Full Text Available The paper presents a numerical model for the simulation of flood waves and suspended sediment transport in a lowland river basin of North Eastern Italy. The two dimensional depth integrated momentum and continuity equations are modified to take into account the bottom irregularities that strongly affect the hydrodynamics in partially dry areas, as for example, in the first stages of an inundation process or in tidal flow. The set of equations are solved with a standard Galerkin finite element method using a semi-implicit numerical scheme where the effects of both the small channel network and the regulation devices on the flood wave propagation are accounted for. Transport of suspended sediment and bed evolution are coupled with the hydrodynamics using an appropriate form of the advection-dispersion equation and Exner's equation. Applications to a case study are presented in which the effects of extreme flooding on the Brenta River (Italy are examined. Urban and rural flood risk areas are identified and the effects of a alleviating action based on a diversion channel flowing into Venice Lagoon are simulated. The results show that this solution strongly reduces the flood risk in the downstream areas and can provide an important source of sediment for the Venice Lagoon. Finally, preliminary results of the sediment dispersion due to currents and waves in the Venice Lagoon are presented.
Integrable two dimensional supersystems
International Nuclear Information System (INIS)
Tripathy, K.C.; Tripathy, L.K.
1988-08-01
The integrability of two dimensional time-dependent classical systems is examined in N=2 superspace using Dirac's second class constraints. The invariants involving quadratic powers in velocities for super harmonic oscillator and super Kepler potentials have been derived. (author). 5 refs
Aouad, Patrick; Saikali, Melody; Abdel-Samad, Rana; Fostok, Sabreen; El-Houjeiri, Leeanna; Pisano, Claudio; Talhouk, Rabih; Darwiche, Nadine
2017-08-01
Despite recent advances in chemotherapy, aggressive and metastatic breast cancers remain refractory to targeted therapy and the development of novel drugs is urgently needed. Retinoids are crucial regulators of cellular proliferation, differentiation, and cell death, and have shown potent chemotherapeutic and chemopreventive properties. The major drawback of the use of all-trans retinoic acid (ATRA) in cancer therapy is disease relapse. Therefore, synthetic retinoids, specifically ST1926, have emerged as potent anticancer agents. Given the importance of the microenvironment in modulating the response of cancer cells to chemotherapeutic drugs, we investigated the antitumor activities of ST1926 in two-dimensional (2D) and different three-dimensional (3D) human breast cancer models and compared them with ATRA. We have shown that in 2D cell culture models, ATRA-resistant MCF-7 and MDA-MB-231 cells were sensitive to ST1926 at submicromolar concentrations that spared the 'normal-like' breast epithelial cells. ST1926 induced apoptosis and S-phase arrest, caused DNA damage, and downregulated the Wnt/β-catenin pathway in breast cancer cells in 2D and 3D cell culture models. ST1926-mediated growth inhibition was independent of the retinoid receptor-signaling pathway. Long-term treatments with low submicromolar ST1926 concentrations reduced the anchorage-independent growth and decreased the sphere-forming ability of breast cancer progenitor cells in the sphere formation assay. Furthermore, ST1926 potently induced cell death of breast cancer cells under 3D conditions and spared the lumen-forming ability of normal-like breast epithelial cells. In tested 3D models, ATRA had minimal effects on the growth of breast cancer cells compared with ST1926. In summary, our results highlight the therapeutic potential of ST1926 in breast cancer and warrant its further clinical development.
Shamalta, M.; Metrikine, A.V.
2002-01-01
In this paper, the steady-state response of an embedded track to the axle loading of a moving train is studied theoretically using two models. The first and the second models are one-dimensional (1D) and two-dimensional (2D), respectively, and differ by the fact that the latter model accounts for
Directory of Open Access Journals (Sweden)
Yanjuan Wang
2017-10-01
Full Text Available Abstract: In this paper, the endothermic methanol decomposition reaction is used to obtain syngas by transforming middle and low temperature solar energy into chemical energy. A two-dimensional multiphysics coupling model of a middle and low temperature of 150~300 °C solar receiver/reactor was developed, which couples momentum equation in porous catalyst bed, the governing mass conservation with chemical reaction, and energy conservation incorporating conduction/convection/radiation heat transfer. The complex thermochemical conversion process of the middle and low temperature solar receiver/reactor (MLTSRR system was analyzed. The numerical finite element method (FEM model was validated by comparing it with the experimental data and a good agreement was obtained, revealing that the numerical FEM model is reliable. The characteristics of chemical reaction, coupled heat transfer, the components of reaction products, and the temperature fields in the receiver/reactor were also revealed and discussed. The effects of the annulus vacuum space and the glass tube on the performance of the solar receiver/reactor were further studied. It was revealed that when the direct normal irradiation increases from 200 W/m2 to 800 W/m2, the theoretical efficiency of solar energy transformed into chemical energy can reach 0.14–0.75. When the methanol feeding rate is 13 kg/h, the solar flux increases from 500 W/m2 to 1000 W/m2, methanol conversion can fall by 6.8–8.9% with air in the annulus, and methanol conversion can decrease by 21.8–28.9% when the glass is removed from the receiver/reactor.
Waddell, R.K.
1982-01-01
A two-dimensional, steady-state model of ground-water flow beneath the Nevada Test Site and vicinity has been developed using inverse techniques. The area is underlain by clastic and carbonate rocks of Precambrian and Paleozoic age and by volcanic rocks and alluvium of Tertiary and Quaternary age that have been juxtaposed by normal and strike-slip faulting. Aquifers are composed of carbonate and volcanic rocks and alluvium. Characteristics of the flow system are determined by distribution of low-conductivity rocks (barriers); by recharge originating in the Spring Mountains, Pahranagat, Timpahute, and Sheep Ranges, and in Pahute Mesa; and by underflow beneath Pahute Mesa from Gold Flat and Kawich Valley. Discharge areas (Ash Meadows, Oasis Valley, Alkali Flat, and Furnace Creek Ranch) are upgradient from barriers. Sensitivities of simulated hydraulic heads and fluxes to variations in model parameters were calculated to guide field studies and to help estimate errors in predictions from transport modeling. Hydraulic heads and fluxes are very sensitive to variations in the greater magnitude recharge/discharge terms. Transmissivity at a location may not be the most important transmissivity for determining flux there. Transmissivities and geometries of large barriers that impede flow from Pahute Mesa have major effects on fluxes elsewhere; as their transmissivities are decreased, flux beneath western Jackass Flats and Yucca Mountains is increased as water is diverted around the barriers. Fortymile Canyon is underlain by highly transmissive rocks that cause potentiometric contours to vee upgradient; increasing their transmissivity increases flow through them, and decreases it beneath Yucca Mountain. (USGS)
Huth, Tobias; Schroeder, Indra; Hansen, Ulf-Peter
2006-01-01
Two-dimensional (2D) dwell-time analysis of time series of single-channel patch-clamp current was improved by employing a Hinkley detector for jump detection, introducing a genetic fit algorithm, replacing maximum likelihood by a least square criterion, averaging over a field of 9 or 25 bins in the 2D plane and normalizing per measuring time, not per events. Using simulated time series for the generation of the "theoretical" 2D histograms from assumed Markov models enabled the incorporation of the measured filter response and noise. The effects of these improvements were tested with respect to the temporal resolution, accuracy of the determination of the rate constants of the Markov model, sensitivity to noise and requirement of open time and length of the time series. The 2D fit was better than the classical hidden Markov model (HMM) fit in all tested fields. The temporal resolution of the two most efficient algorithms, the 2D fit and the subsequent HMM/beta fit, enabled the determination of rate constants 10 times faster than the corner frequency of the low-pass filter. The 2D fit was much less sensitive to noise. The requirement of computing time is a problem of the 2D fit (100 times that of the HMM fit) but can now be handled by personal computers. The studies revealed a fringe benefit of 2D analysis: it can reveal the "true" single-channel current when the filter has reduced the apparent current level by averaging over undetected fast gating.
Kim, Sung-Jin; Reidy, Shaelah M; Block, Bruce P; Wise, Kensall D; Zellers, Edward T; Kurabayashi, Katsuo
2010-07-07
In comprehensive two-dimensional gas chromatography (GC x GC), a modulator is placed at the juncture between two separation columns to focus and re-inject eluting mixture components, thereby enhancing the resolution and the selectivity of analytes. As part of an effort to develop a microGC x microGC prototype, in this report we present the design, fabrication, thermal operation, and initial testing of a two-stage microscale thermal modulator (microTM). The microTM contains two sequential serpentine Pyrex-on-Si microchannels (stages) that cryogenically trap analytes eluting from the first-dimension column and thermally inject them into the second-dimension column in a rapid, programmable manner. For each modulation cycle (typically 5 s for cooling with refrigeration work of 200 J and 100 ms for heating at 10 W), the microTM is kept approximately at -50 degrees C by a solid-state thermoelectric cooling unit placed within a few tens of micrometres of the device, and heated to 250 degrees C at 2800 degrees C s(-1) by integrated resistive microheaters and then cooled back to -50 degrees C at 250 degrees C s(-1). Thermal crosstalk between the two stages is less than 9%. A lumped heat transfer model is used to analyze the device design with respect to the rates of heating and cooling, power dissipation, and inter-stage thermal crosstalk as a function of Pyrex-membrane thickness, air-gap depth, and stage separation distance. Experimental results are in agreement with trends predicted by the model. Preliminary tests using a conventional capillary column interfaced to the microTM demonstrate the capability for enhanced sensitivity and resolution as well as the modulation of a mixture of alkanes.
Energy Technology Data Exchange (ETDEWEB)
Carriger, John F. [U.S. Environmental Protection Agency, Office of Research and Development, Gulf Ecology Division, Gulf Breeze, FL, 32561 (United States); Martin, Todd M. [U.S. Environmental Protection Agency, Office of Research and Development, Sustainable Technology Division, Cincinnati, OH, 45220 (United States); Barron, Mace G., E-mail: barron.mace@epa.gov [U.S. Environmental Protection Agency, Office of Research and Development, Gulf Ecology Division, Gulf Breeze, FL, 32561 (United States)
2016-11-15
Highlights: • A Bayesian network was developed to classify chemical mode of action (MoA). • The network was based on the aquatic toxicity MoA for over 1000 chemicals. • A Markov blanket algorithm selected a subset of theoretical molecular descriptors. • Sensitivity analyses found influential descriptors for classifying the MoAs. • Overall precision of the Bayesian MoA classification model was 80%. - Abstract: The mode of toxic action (MoA) has been recognized as a key determinant of chemical toxicity, but development of predictive MoA classification models in aquatic toxicology has been limited. We developed a Bayesian network model to classify aquatic toxicity MoA using a recently published dataset containing over one thousand chemicals with MoA assignments for aquatic animal toxicity. Two dimensional theoretical chemical descriptors were generated for each chemical using the Toxicity Estimation Software Tool. The model was developed through augmented Markov blanket discovery from the dataset of 1098 chemicals with the MoA broad classifications as a target node. From cross validation, the overall precision for the model was 80.2%. The best precision was for the AChEI MoA (93.5%) where 257 chemicals out of 275 were correctly classified. Model precision was poorest for the reactivity MoA (48.5%) where 48 out of 99 reactive chemicals were correctly classified. Narcosis represented the largest class within the MoA dataset and had a precision and reliability of 80.0%, reflecting the global precision across all of the MoAs. False negatives for narcosis most often fell into electron transport inhibition, neurotoxicity or reactivity MoAs. False negatives for all other MoAs were most often narcosis. A probabilistic sensitivity analysis was undertaken for each MoA to examine the sensitivity to individual and multiple descriptor findings. The results show that the Markov blanket of a structurally complex dataset can simplify analysis and interpretation by
Lu, S.; Hwang, Y.; Shao, X.; Hamann, H.
2015-12-01
Previously, we reported the application of a "weather situation" dependent multi-model blending approach to improve the forecast accuracy of solar irradiance and other atmospheric parameters. The approach uses machine-learning techniques to classify "weather situations" by a set of atmospheric parameters. The "weather situation" classification is location-dependent and each "weather situation" has characteristic forecast errors from a set of individual input numerical weather prediction (NWP) models. The input models are thus corrected or combined differently for different "weather situations" to minimize the overall forecast error. While the original implementation of the model-blending is applicable to only point-like locations having historical data of both measurements and forecasts, here we extend the approach to provide two-dimensional (2D) gridded forecasts. An experimental 2D forecasting system has been set up to provide gridded forecasts of solar irradiance (global horizontal irradiance), temperature, wind speed, and humidity for the contiguous United States (CONUS). Validation results show around 30% enhancement of 0 to 48 hour ahead solar irradiance forecast accuracy compared to the best input NWP model. The forecasting system may be leveraged by other site- or region-specific solar energy forecast products. To enable the 2D forecasting system, historical solar irradiance measurements from around 1,600 selected sites of the remote automated weather stations (RAWS) network have been employed. The CONUS was divided into smaller sub-regions, each containing a group of 10 to 20 RAWS sites. A group of sites, as classified by statistical analysis, have similar "weather patterns", i.e. the NWPs have similar "weather situation" dependent forecast errors for all sites in a group. The model-blending trained by the historical data from a group of sites is then applied for all locations in the corresponding sub-region. We discuss some key techniques developed for
Ritsema, C.J.; Oostindie, K.; Stolte, J.
1996-01-01
On four hill-slopes in the loess region of the Netherlands pressure heads were monitored during rain events with time intervals of five minutes. Water flow through these hill-slopes during erosive rain events in summer and winter was simulated two-dimensionally. These simulations showed that
International Nuclear Information System (INIS)
Sun Jiaxiang; Tang Yahang; Gao Weiling; Chen Hengliang; Pang Jingshun
1998-01-01
Osteoporosis (OP) is a disease characterized by reduced bone mineral, lowered density, weakened strength, etc. A great deal of the illness appeared in the old people, especially old women. The article will deal mainly with two questions: traditional chinese medicine care OP and the usage of two dimensional bone densimeter in the therapeutic effect observation
Ferentinos, Panagiotis; Fountoulakis, Konstantinos N; Lewis, Cathryn M; Porichi, Evgenia; Dikeos, Dimitris; Papageorgiou, Charalambos; Douzenis, Athanassios
2017-08-01
The literature on DSM-5's 'Major Depressive Disorder with lifetime mixed features' (MDD-MF) is limited. This study investigated MDD-MF's potential inclusion into a bipolar spectrum. We recruited 287 patients with Bipolar I disorder (BD-I), BD-II, MDD-MF or 'MDD without lifetime mixed features' (MDD-noMF); most (N=280) were stabilized for at least one year on medication. Sixteen validators (clinical features, psychiatric family history, temperament, stabilizing treatment) were compared across groups and subjected to trend analyses. Two discriminant function analyses (DFA; primary and secondary), excluding or including, respectively, treatment-related predictors, explored latent dimensions maximizing between-group discrimination; mahalanobis distances between group 'centroids' were calculated. Eleven validators differed significantly across groups; nine varied monotonically along a bipolar diathesis gradient with significant linear trends; two peaked at MDD-MF and displayed significant quadratic trends. In the primary DFA, apart from a classic bipolarity dimension, correlating with hospitalizations, early age at onset, lifetime psychosis and lower anxious temperament scores, on which groups ranked along a bipolar propensity gradient, a second dimension was also significant, peaking at BD-II and MDD-MF (challenging the classic bipolar ranking), which correlated with lifetime psychiatric comorbidities, suicidality, lower lifetime psychosis rates, female gender, higher cyclothymic and lower depressive temperament scores; MDD-MF was equipoised amidst BD-II and MDD-noMF. After including treatment-related predictors (secondary DFA), discrimination improved overall but BD-II and MDD-MF were closest than any other pair, suggesting similar treatment patterns for these two groups at this naturalistic setting. To our knowledge, this is the first time a two-dimensional bipolar spectrum based on classic external validators is proposed, fitting the data better than a
Cheraghalizadeh, J.; Najafi, M. N.; Dashti-Naserabadi, H.; Mohammadzadeh, H.
2017-11-01
The self-organized criticality on the random fractal networks has many motivations, like the movement pattern of fluid in the porous media. In addition to the randomness, introducing correlation between the neighboring portions of the porous media has some nontrivial effects. In this paper, we consider the Ising-like interactions between the active sites as the simplest method to bring correlations in the porous media, and we investigate the statistics of the BTW model in it. These correlations are controlled by the artificial "temperature" T and the sign of the Ising coupling. Based on our numerical results, we propose that at the Ising critical temperature Tc the model is compatible with the universality class of two-dimensional (2D) self-avoiding walk (SAW). Especially the fractal dimension of the loops, which are defined as the external frontier of the avalanches, is very close to DfSAW=4/3 . Also, the corresponding open curves has conformal invariance with the root-mean-square distance Rrms˜t3 /4 (t being the parametrization of the curve) in accordance with the 2D SAW. In the finite-size study, we observe that at T =Tc the model has some aspects compatible with the 2D BTW model (e.g., the 1 /log(L ) -dependence of the exponents of the distribution functions) and some in accordance with the Ising model (e.g., the 1 /L -dependence of the fractal dimensions). The finite-size scaling theory is tested and shown to be fulfilled for all statistical observables in T =Tc . In the off-critical temperatures in the close vicinity of Tc the exponents show some additional power-law behaviors in terms of T -Tc with some exponents that are reported in the text. The spanning cluster probability at the critical temperature also scales with L1/2, which is different from the regular 2D BTW model.
Type Ia Supernovae as Sites of the p-process: Two-dimensional Models Coupled to Nucleosynthesis
Travaglio, C.; Röpke, F. K.; Gallino, R.; Hillebrandt, W.
2011-10-01
Beyond Fe, there is a class of 35 proton-rich nuclides, between 74Se and 196Hg, called p-nuclei. They are bypassed by the s and r neutron capture processes and are typically 10-1000 times less abundant than the s- and/or r-isotopes in the solar system. The bulk of p-isotopes is created in the "gamma processes" by sequences of photodisintegrations and beta decays in explosive conditions in both core collapse supernovae (SNe II) and in Type Ia supernovae (SNe Ia). SNe II contribute to the production of p-nuclei through explosive neon and oxygen burning. However, the major problem in SN II ejecta is a general underproduction of the light p-nuclei for A explosive nucleosynthesis with a detailed nuclear reaction network for all isotopes up to 209Bi. We select tracers within the typical temperature range for p-process production, (1.5-3.7) × 109 K, and analyze in detail their behavior, exploring the influence of different s-process distributions on the p-process nucleosynthesis. In addition, we discuss the sensitivity of p-process production to parameters of the explosion mechanism, taking into account the consequences on Fe and alpha elements. We find that SNe Ia can produce a large amount of p-nuclei, both the light p-nuclei below A = 120 and the heavy-p nuclei, at quite flat average production factors, tightly related to the s-process seed distribution. For the first time, we find a stellar source able to produce both light and heavy p-nuclei almost at the same level as 56Fe, including the debated neutron magic 92, 94Mo and 96, 98Ru. We also find that there is an important contribution from the p-process nucleosynthesis to the s-only nuclei 80Kr, 86Sr, to the neutron magic 90Zr, and to the neutron-rich 96Zr. Finally, we investigate the metallicity effect on p-process production in our models. Starting with different s-process seed distributions for two metallicities Z = 0.02 and Z = 0.001, running two-dimensional SN Ia models with different initial composition, we
Two-dimensional critical phenomena
International Nuclear Information System (INIS)
Saleur, H.
1987-09-01
Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr
Eslamizadeh, H.
2016-02-01
A stochastic approach based on one- and two-dimensional Langevin equations is applied to calculate the pre-scission neutron multiplicity, fission probability, anisotropy of fission fragment angular distribution, fission cross section and the evaporation cross section for the compound nuclei 188Pt, 227Pa and 251Es in an intermediate range of excitation energies. The chaos weighted wall and window friction formula are used in the Langevin equations. The elongation parameter, c, is used as the first dimension and projection of the total spin of the compound nucleus onto the symmetry axis, K, considered as the second dimension in Langevin dynamical calculations. A constant dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, is used in two-dimensional calculations to reproduce the above mentioned experimental data. Comparison of the theoretical results of the pre-scission neutron multiplicity, fission probability, fission cross section and the evaporation cross section with the experimental data shows that the results of two-dimensional calculations are in better agreement with the experimental data. Furthermore, it is shown that the two-dimensional Langevin equations together with a dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, can satisfactorily reproduce the anisotropy of fission fragment angular distribution for the heavy compound nucleus 251Es. However, a larger value of γK = 0.250(MeV zs)-1/2 is needed to reproduce the anisotropy of fission fragment angular distribution for the lighter compound nucleus 227Pa.
Osserman, Robert
2011-01-01
The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o
Two-dimensional ferroelectrics
Energy Technology Data Exchange (ETDEWEB)
Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)
2000-03-31
The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)
Energy Technology Data Exchange (ETDEWEB)
Filho, J. F. P. [Institute de Matematica, Estatistica e Fisica, Universidade Federal do Rio Grande, Av. Italia, s/n, 96203-900 Rio Grande, RS (Brazil); Barichello, L. B. [Institute de Matematica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves, 9500, 91509-900 Porto Alegre, RS (Brazil)
2013-07-01
In this work, an analytical discrete ordinates method is used to solve a nodal formulation of a neutron transport problem in x, y-geometry. The proposed approach leads to an important reduction in the order of the associated eigenvalue systems, when combined with the classical level symmetric quadrature scheme. Auxiliary equations are proposed, as usually required for nodal methods, to express the unknown fluxes at the boundary introduced as additional unknowns in the integrated equations. Numerical results, for the problem defined by a two-dimensional region with a spatially constant and isotropically emitting source, are presented and compared with those available in the literature. (authors)
International Nuclear Information System (INIS)
Petrov, A.V.; Samsonova, L.M.; Vasil'kova, N.A.; Zinin, A.I.; Zinina, G.A.
1994-06-01
Methodological aspects of the numerical modeling of the groundwater contaminant transport for the Lake Karachay area are discussed. Main features of conditions of the task are the high grade of non-uniformity of the aquifer in the fractured rock massif and the high density of the waste solutions, and also the high volume of the input data: both on the part of parameters of the aquifer (number of pump tests) and on the part of observations of functions of processes (long-time observations by the monitoring well grid). The modeling process for constructing the two dimensional regional model is described, and this model is presented as the basic model for subsequent full three-dimensional modeling in sub-areas of interest. Original powerful mathematical apparatus and computer codes for finite-difference numerical modeling are used
Kalscheuer, Thomas; Juhojuntti, Niklas; Vaittinen, Katri
2017-12-01
A combination of magnetotelluric (MT) measurements on the surface and in boreholes (without metal casing) can be expected to enhance resolution and reduce the ambiguity in models of electrical resistivity derived from MT surface measurements alone. In order to quantify potential improvement in inversion models and to aid design of electromagnetic (EM) borehole sensors, we considered two synthetic 2D models containing ore bodies down to 3000 m depth (the first with two dipping conductors in resistive crystalline host rock and the second with three mineralisation zones in a sedimentary succession exhibiting only moderate resistivity contrasts). We computed 2D inversion models from the forward responses based on combinations of surface impedance measurements and borehole measurements such as (1) skin-effect transfer functions relating horizontal magnetic fields at depth to those on the surface, (2) vertical magnetic transfer functions relating vertical magnetic fields at depth to horizontal magnetic fields on the surface and (3) vertical electric transfer functions relating vertical electric fields at depth to horizontal magnetic fields on the surface. Whereas skin-effect transfer functions are sensitive to the resistivity of the background medium and 2D anomalies, the vertical magnetic and electric field transfer functions have the disadvantage that they are comparatively insensitive to the resistivity of the layered background medium. This insensitivity introduces convergence problems in the inversion of data from structures with strong 2D resistivity contrasts. Hence, we adjusted the inversion approach to a three-step procedure, where (1) an initial inversion model is computed from surface impedance measurements, (2) this inversion model from surface impedances is used as the initial model for a joint inversion of surface impedances and skin-effect transfer functions and (3) the joint inversion model derived from the surface impedances and skin-effect transfer
Directory of Open Access Journals (Sweden)
Daigo Ohki
2018-03-01
Full Text Available The optical conductivity in the charge order phase is calculated in the two-dimensional extended Hubbard model describing an organic Dirac electron system α -(BEDT-TTF 2 I 3 using the mean field theory and the Nakano-Kubo formula. Because the interband excitation is characteristic in a two-dimensional Dirac electron system, a peak structure is found above the charge order gap. It is shown that the peak structure originates from the Van Hove singularities of the conduction and valence bands, where those singularities are located at a saddle point between two Dirac cones in momentum space. The frequency of the peak structure exhibits drastic change in the vicinity of the charge order transition.
Ludwig, Alon; Leviatan, Yehuda
2008-02-01
We introduce a time-domain source-model technique for analysis of two-dimensional, transverse-magnetic, plane-wave scattering by a photonic crystal slab composed of a finite number of identical layers, each comprising a linear periodic array of dielectric cylinders. The proposed technique takes advantage of the periodicity of the slab by solving the problem within a unit cell of the periodic structure. A spectral analysis of the temporal behavior of the fields scattered by the slab shows a clear agreement between frequency bands where the spectral density of the transmitted energy is low and the bandgaps of the corresponding two-dimensionally infinite periodic structure. The effect of the bandwidth of the incident pulse and its center frequency on the manner it is transmitted through and reflected by the slab is studied via numerical examples.
International Nuclear Information System (INIS)
Pigarov, A. Yu.; Krasheninnikov, S. I.; Rognlien, T. D.
2011-01-01
A new approach is proposed to simulate intermittent, non-diffusive plasma transport (via blobs and filaments of edge localized modes (ELMs)) observed in the tokamak edge region within the framework of two-dimensional transport codes. This approach combines the inherently three-dimensional filamentary structures associated with an ensemble of blobs into a macro-blob in the two-dimensional poloidal cross-section and advects the macro-blob ballistically across the magnetic field, B. Intermittent transport is represented as a sequence of macro-blobs appropriately seeded in the edge plasma according to experimental statistics. In this case, the code is capable of reproducing both the long-scale temporal evolution of the background plasma and the fast spatiotemporal dynamics of blobs. We report the results from a two-dimensional edge plasma code modeling of a single macro-blob dynamics, and its interaction with initially stationary background plasma as well as with material surfaces. The mechanisms of edge plasma particle and energy losses from macro-blobs are analyzed. The effects of macro-blob sizes and advection velocity on edge plasma profiles are studied. The macro-blob impact on power loading and sputtering rates on the chamber wall and on inner and outer divertor plates is discussed. Temporal evolution of particle inventory of the edge plasma perturbed by macro-blobs is analyzed. Application of macro-blobs to ELM modeling is highlighted.
Rasmussen, J.; Skalbeck, J.; Stewart, E.
2017-12-01
The deep sandstone and dolomite aquifer of Wisconsin is the primary source of water in the central, southern, and western portions of the state, as well as a supplier for many high-capacity wells in the eastern portion. This prominent groundwater system is highly impacted by the underlying Precambrian basement, which includes the doubly plunging Baraboo Syncline in Columbia and Sauk Counties. This project is a continuation of previous work done in Dodge and Fond du Lac Counties by the University of Wisconsin-Parkside (UW-P) and the Wisconsin Geological & Natural History Survey (WGNHS). The goal of this project was to produce of an updated Precambrian topographic map of southern Wisconsin, by adding Gravity and Aeromagnetic data to the existing map which is based mainly on sparse outcrop and well data. Gravity and Aeromagnetic data from the United States Geological Survey (USGS) was processed using GM-SYS 3D modeling software in Geosoft Oasis Montaj. Grids of subsurface layers were created from the data and constrained by well and drilling records. The Columbia County basement structure is a complex network of Precambrian granites and rhyolites which is non-conformably overlain by quartzite, slate, and a layer of iron rich sedimentary material. Results from previously collected cores as well as drilling done in neighboring Dodge County, show that the iron rich layer was draped over much of the Baraboo area before being subject to the multitude of folding and faulting events that happened in the region during the late Precambrian. This layer provides telltale signatures that aided in construction of the model due to having an average density of 3.7 g/cm3 and a magnetic susceptibility of 8000 x 10-6 cgs, compared to the average density and susceptibility of the rest of the bedrock being 2.8 g/cm3 and 1500 x 10-6 cgs, respectively. The research done on the Columbia County basement is one part of a larger project aimed at improving groundwater management efforts of the
The water desalination complex based on ABV-type reactor plant
International Nuclear Information System (INIS)
Panov, Yu.K.; Fadeev, Yu.P.; Vorobiev, V.M.; Baranaev, Yu.D.
1997-01-01
A floating nuclear desalination complex with two barges, one for ABV type reactor plant, with twin reactor 2 x 6 MW(e), and one for reverse osmosis desalination plant, was described. The principal specifications of the ABV type reactor plant and desalination barge were given. The ABV type reactor has a traditional two-circuit layout using an integral type reactor vessel with all mode natural convection of primary coolant. The desalted water cost was estimated to be around US $0.86 per cubic meter. R and D work has been performed and preparations for commercial production are under way. (author)
Energy Technology Data Exchange (ETDEWEB)
Golatta, Michael, E-mail: Michael.Golatta@med.uni-heidelberg.de; Franz, Dorothea; Harcos, Aba; Junkermann, Hans; Rauch, Geraldine; Scharf, Alexander; Schuetz, Florian; Sohn, Christof; Heil, Joerg
2013-08-15
Objectives: Handheld breast ultrasound (HHUS) lacks standardization and reproducibility. The automated breast volume scanner (ABVS) could overcome this limitation. To analyze the interobserver reliability of ABVS and the agreement with HHUS, mammography and pathology is the aim of this study. Methods: All 42 study participants (=84 breasts) received an ABVS examination in addition to the conventional breast diagnostic work-up. 25 breasts (30%) showed at least one lesion. The scans were interpreted by six breast diagnostic specialists blinded to results of breast imaging and medical history. 32 lesions received histological work-up: 20 cancers were detected. We used kappa statistics to interpret agreement between examiners and diagnostic instruments. Results: On the basis of the Breast Imaging Reporting and Data System (BI-RADS) classification of the 84 breasts an agreement (defined as ≥4 of 6 examiners) was achieved in 63 cases (75%) (mk = 0.35) and even improved when dichotomizing the interpretation in benign (BI-RADS 1, 2) and suspicious (BI-RADS 4, 5) to 98% (mk = 0.52). Agreement of ABVS examination to HHUS, mammography and pathology was fair to substantial depending on the specific analysis. Conclusions: The development of an ABVS seems to be a promising diagnostic method with a good interobserver reliability, as well as a comparable good test criteria as HHUS.
International Nuclear Information System (INIS)
Truong, Nguyen-Vu; Wang, Liuping; Wong, Peter K.C.
2008-01-01
Power demand forecasting is of vital importance to the management and planning of power system operations which include generation, transmission, distribution, as well as system's security analysis and economic pricing processes. This paper concerns the modeling and short-term forecast of daily peak power demand in the state of Victoria, Australia. In this study, a two-dimensional wavelet based state dependent parameter (SDP) modelling approach is used to produce a compact mathematical model for this complex nonlinear dynamic system. In this approach, a nonlinear system is expressed by a set of linear regressive input and output terms (state variables) multiplied by the respective state dependent parameters that carry the nonlinearities in the form of 2-D wavelet series expansions. This model is identified based on historical data, descriptively representing the relationship and interaction between various components which affect the peak power demand of a certain day. The identified model has been used to forecast daily peak power demand in the state of Victoria, Australia in the time period from the 9th of August 2007 to the 24th of August 2007. With a MAPE (mean absolute prediction error) of 1.9%, it has clearly implied the effectiveness of the identified model. (author)
Energy Technology Data Exchange (ETDEWEB)
Afchain, St
2005-02-15
The Hubbard model is the simplest model to describe the behaviour of fermions on a network, it takes into account only fermion scattering and only interactions with other fermions located on the same site. Half-filling means that the total number of fermions is equal to half the number of sites. In the first chapter we show how we can pass trough successive approximations from a very general Hamiltonian to the Hubbard Hamiltonian. The second chapter is dedicated to the passage from the Hamiltonian formalism to the Grassmanian functional formalism. The main idea is to show that the correlation functions of the Hamiltonian approach can be described through fermionic functional integrals which implies the possibility of speaking of the model in terms of field theory. The chapter 3 deals with the main constructive techniques that allow the strict and consistent construction of models inside the frame of field theory. We show by proving the violation of a condition concerning self-energy, that the two-dimensional Hubbard model at half-filling has not the behaviour of a Fermi liquid in the Landau's interpretation. (A.C.)
Orski, Sara V; Kundu, Santanu; Gross, Richard; Beers, Kathryn L
2013-02-11
A two-dimensional model of a solid-supported enzyme catalyst bead is fabricated on a quartz crystal microbalance with dissipation monitoring (QCM-D) sensor to measure in situ interfacial stability and mechanical properties of Candida antarctica Lipase B (CAL B) under varied conditions relating to ring-opening polymerization. The model was fabricated using a dual photochemical approach, where poly(methyl methacrylate) (PMMA) thin films were cross-linked by a photoactive benzophenone monolayer and blended cross-linking agent. This process produces two-dimensional, homogeneous, rigid PMMA layers, which mimic commercial acrylic resins in a QCM-D experiment. Adsorption of CAL B to PMMA in QCM-D under varied buffer ionic strengths produces a viscoelastic enzyme surface that becomes more rigid as ionic strength increases. The rigid CAL B/PMMA interface demonstrates up to 20% desorption of enzyme with increasing trace water content. Increased polycaprolactone (PCL) binding at the enzyme surface was also observed, indicating greater PCL affinity for a more hydrated enzyme surface. The enzyme layer destabilized with increasing temperature, yielding near complete reversible catalyst desorption in the model.
McCue, Justin T; Cecchini, Douglas; Chu, Cathy; Liu, Wei-Han; Spann, Andrew
2007-03-23
A two-dimensional model was formulated to describe the pressure-flow behavior of compressible stationary phases for protein chromatography at different temperatures and column scales. The model was based on the assumption of elastic deformation of the solid phase and steady-state Darcy flow. Using a single fitted value for the empirical modulus parameters, the model was applied to describe the pressure-flow behavior of several adsorbents packed using both fluid flow and mechanical compression. Simulations were in agreement with experimental data and accurately predicted the pressure-flow and compression behavior of three adsorbents over a range of column scales and operating temperatures. Use of the described theoretical model potentially improves the accuracy of the column scale-up process, allowing the use of limited laboratory scale data to predict column performance in large scale applications.
Xu, Hui Fang; Gui Guan, Bang
2017-05-01
A two-dimensional analytical model for hetero-junction double-gate tunnel FETs (DG TFETs) with a stacked gate-oxide structure is proposed in this paper. The effects of both the channel mobile charges and source/drain depletion regions on the channel potential profile are considered for the higher accuracy of the proposed model. Poisson’s equation is solved using the superposition principle and Fourier series solution to model the channel potential. The band-to-band tunneling generation rate is expressed as a function of the channel electric field derived from the channel potential and then integrated analytically to derive the drain current of the hetero-junction DG TFETs with a stacked gate-oxide structure using the shortest tunneling path. The effects of device parameters on the channel potential, drain current, and transconductance are investigated. Very good agreements are observed between the model calculations and the simulated results.
Jackman, Charles H.; Douglass, Anne R.; Chandra, Sushil; Stolarski, Richard S.; Rosenfield, Joan E.; Kaye, Jack A.
1991-01-01
Values of the monthly mean heating rates and the residual circulation characteristics were calculated using NMC data for temperature and the solar backscattered UV ozone for the period between 1979 and 1986. The results were used in a two-dimensional photochemical model in order to examine the effects of temperature and residual circulation on the interannual variability of ozone. It was found that the calculated total ozone was more sensitive to variations in interannual residual circulation than in the interannual temperature. The magnitude of the modeled ozone variability was found to be similar to the observed variability, but the observed and modeled year-to-year deviations were, for the most part, uncorrelated, due to the fact that the model did not account for most of the QBO forcing and for some of the observed tropospheric changes.
Directory of Open Access Journals (Sweden)
Haigen Yang
2016-11-01
Full Text Available The hysteresis characteristics resulted from piezoelectric actuators (PAs and the residual vibration in the rapid positioning of a two-dimensional piezo-driven micro-displacement scanning platform (2D-PDMDSP will greatly affect the positioning accuracy and speed. In this paper, in order to improve the accuracy and speed of the positioning and restrain the residual vibration of 2D-PDMDSP, firstly, Utilizing an online hysteresis observer based on the asymmetrical Bouc-Wen model, the PA with the hysteresis characteristics is feedforward linearized and can be used as a linear actuator; secondly, zero vibration and derivative shaping (ZVDS technique is used to eliminate the residual vibration of the 2D-PDMDSP; lastly, the robust model reference adaptive (RMRA control for the 2D-PDMDSP is proposed and explored. The rapid control prototype of the RMRA controller combining the proposed feedforward linearization and ZVDS control for the 2D-PDMDSP with rapid control prototyping technique based on the real-time simulation system is established and experimentally tested, and the corresponding controlled results are compared with those by the PID control method. The experimental results show that the proposed RMRA control method can significantly improve the accuracy and speed of the positioning and restrain the residual vibration of 2D-PDMDSP.
Retta, Moges; Ho, Quang Tri; Yin, Xinyou; Verboven, Pieter; Berghuijs, Herman N.C.; Struik, Paul C.; Nicolaï, Bart M.
2016-01-01
CO_{2} exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C_{4} photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C_{4} plants, the model
International Nuclear Information System (INIS)
Erdogan, E.
2007-01-01
In earth investigation done by using the direct current resistivity technique, impact of the change in the examined surface topography on determining the resistivity distrubition in the earth has been a frequently faced question. In order to get more fruitful results and make more correct interpretetions in earth surveying carried on the areas where topographical changes occur, modelling should be done by taking the change in surface topography into account and topography effect should be included into inversion. In this study impact of topography to the direct current resistivity method has been analysed. For this purpose, 2-D forward modeling algorithm has been developed by using finite element method. In this algorithm impact of topography can be incorporate into the model. Also the pseudo sections which is produced from the program can be imaged with topography. By using this algorithm response of models under different surface topography has been analysed and compared with the straight topography of same models
TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION
International Nuclear Information System (INIS)
Wang, Yougang; Xu, Yidong; Chen, Xuelei; Park, Changbom; Kim, Juhan
2015-01-01
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array
International Nuclear Information System (INIS)
Boyd, J; Buick, J; Cosgrove, J A; Stansell, P
2005-01-01
The lattice Boltzmann model is used to observe changes in the velocity flow and shear stress in a carotid artery model during a simulated stenosis growth. Near wall shear stress in the unstenosed artery is found to agree with literature values. The model also shows regions of low velocity, rotational flow and low near wall shear stress along parts of the walls of the carotid artery that have been identified as being prone to atherosclerosis. These regions persist during the simulated stenosis growth, suggesting that atherosclerotic plaque build-up creates regions of flow with properties that favour atherosclerotic progression
International Nuclear Information System (INIS)
Chaujar, Rishu; Kaur, Ravneet; Gupta, Mridula; Gupta, R S; Saxena, Manoj
2009-01-01
This paper discusses a threshold voltage model for novel device structure: gate electrode work function engineered recessed channel (GEWE-RC) nanoscale MOSFET, which combines the advantages of both RC and GEWE structures. In part I, the model accurately predicts (a) surface potential, (b) threshold voltage and (c) sub-threshold slope for single material gate recessed channel (SMG-RC) and GEWE-RC structures. Part II focuses on the development of compact analytical drain current model taking into account the transition regimes from sub-threshold to saturation. Furthermore, the drain conductance evaluation has also been obtained, reflecting relevance of the proposed device for analogue design. The analysis takes into account the effect of gate length and groove depth in order to develop a compact model suitable for device design. The analytical results predicted by the model confirm well with the simulated results. Results in part I also provide valuable design insights in the performance of nanoscale GEWE-RC MOSFET with optimum threshold voltage and negative junction depth (NJD), and hence serves as a tool to optimize important device and technological parameters for 40 nm technology
International Nuclear Information System (INIS)
Mudry, Christopher; Wen Xiaogang
1999-01-01
Effective theories for random critical points are usually non-unitary, and thus may contain relevant operators with negative scaling dimensions. To study the consequences of the existence of negative-dimensional operators, we consider the random-bond XY model. It has been argued that the XY model on a square lattice, when weakly perturbed by random phases, has a quasi-long-range ordered phase (the random spin wave phase) at sufficiently low temperatures. We show that infinitely many relevant perturbations to the proposed critical action for the random spin wave phase were omitted in all previous treatments. The physical origin of these perturbations is intimately related to the existence of broadly distributed correlation functions. We find that those relevant perturbations do enter the Renormalization Group equations, and affect critical behavior. This raises the possibility that the random XY model has no quasi-long-range ordered phase and no Kosterlitz-Thouless (KT) phase transition
Lee, A. A.; Crosato, A.; Omer, A. Y. A.; Bregoli, F.
2017-12-01
The need for accurate and robust predictive methods of assessing fluvial ecosystems is highlighted by the accelerating practice of dam removal. Dam removal can be a restorative measure, but the sudden release of impounded sediment and change in flow regime may negatively impact aquatic biota and their habitat. This study assesses the performance of a quasi-three-dimensional morphodynamic numerical model, coupled with habitat suitability indices, to predict short-term impacts to Chinook salmon (Oncorhynchus tshawytscha) spawning habitat from dam removal. The 2007 removal of Marmot Dam on the Sandy River (Oregon, U.S.A.) is used as a case study. Delft3D-FLOW is employed to simulate changes in river channel topography, sediment composition and hydrodynamic conditions for a 20-kilometer reach of the Sandy River. The transport of non-uniform sediment and three-dimensional flow effects are included in the model. Output parameters such as flow depth, velocity and substrate are processed to evaluate habitat quality in the year following the Marmot Dam removal. Impacts are evaluated across four life-stages of Chinook salmon. As a hindcast analysis, the morphodynamic model sufficiently reproduces the evolution of river morphology at the reach-scale while requiring only a low level of calibration. The model performs well in predicting impacts to fish passage, but carries more uncertainty for developing life stages. By coupling flow-sediment-biota interactions, this method shows strong potential for habitat assessment in unsteady and non-uniform environments. Computation time is a primary constraint, as it limits grid-cell resolution, modelling of suspended sediment and capacity to characterize the sediment grain size distribution. Research on the effects of suspended sediment on habitat quality is ongoing, and further research is recommended for modelling reservoir erosion processes numerically.
International Nuclear Information System (INIS)
Schroer, B.
1975-07-01
The quasiclassical aspects of the D = 2 Lenz-Ising model are sketched which are similar to those of the A 4 -theory, in particular the conclusion that there are new coherent states - which appear to be Majorana fermions-similar to the A 4 -theory. An explicit construction for the scale invariant limit is given and shown that its most simple field theoretical description can be given in terms of a free D = 2 Majorana field. The relation of the Thirring-model to the Sine Gordon equation is discussed. (BJ) [de
Vasilyev, V.; Ludwig, H.-G.; Freytag, B.; Lemasle, B.; Marconi, M.
2018-03-01
Context. Standard spectroscopic analyses of variable stars are based on hydrostatic 1D model atmospheres. This quasi-static approach has not been theoretically validated. Aim. We aim at investigating the validity of the quasi-static approximation for Cepheid variables. We focus on the spectroscopic determination of the effective temperature Teff, surface gravity log g, microturbulent velocity ξt, and a generic metal abundance log A, here taken as iron. Methods: We calculated a grid of 1D hydrostatic plane-parallel models covering the ranges in effective temperature and gravity that are encountered during the evolution of a 2D time-dependent envelope model of a Cepheid computed with the radiation-hydrodynamics code CO5BOLD. We performed 1D spectral syntheses for artificial iron lines in local thermodynamic equilibrium by varying the microturbulent velocity and abundance. We fit the resulting equivalent widths to corresponding values obtained from our dynamical model for 150 instances in time, covering six pulsational cycles. In addition, we considered 99 instances during the initial non-pulsating stage of the temporal evolution of the 2D model. In the most general case, we treated Teff, log g, ξt, and log A as free parameters, and in two more limited cases, we fixed Teff and log g by independent constraints. We argue analytically that our approach of fitting equivalent widths is closely related to current standard procedures focusing on line-by-line abundances. Results: For the four-parametric case, the stellar parameters are typically underestimated and exhibit a bias in the iron abundance of ≈-0.2 dex. To avoid biases of this type, it is favorable to restrict the spectroscopic analysis to photometric phases ϕph ≈ 0.3…0.65 using additional information to fix the effective temperature and surface gravity. Conclusions: Hydrostatic 1D model atmospheres can provide unbiased estimates of stellar parameters and abundances of Cepheid variables for particular
Zamorano, J.; Sánchez de Miguel, A.; Ocaña, F.; Pila-Díez, B.; Gómez Castaño, J.; Pascual, S.; Tapia, C.; Gallego, J.; Fernández, A.; Nievas, M.
2016-09-01
We present a study of the night sky brightness around the extended metropolitan area of Madrid using Sky Quality Meter (SQM) photometers. The map is the first to cover the spatial distribution of the sky brightness in the centre of the Iberian peninsula. These surveys are necessary to test the light pollution models that predict night sky brightness as a function of the location and brightness of the sources of light pollution and the scattering of light in the atmosphere. We describe the data-retrieval methodology, which includes an automated procedure to measure from a moving vehicle in order to speed up the data collection, providing a denser and wider survey than previous works with similar time frames. We compare the night sky brightness map to the nocturnal radiance measured from space by the DMSP satellite. We find that (i) a single source model is not enough to explain the radial evolution of the night sky brightness, despite the predominance of Madrid in size and population and (ii) that the orography of the region should be taken into account when deriving geo-specific models from general first-principles models. We show the tight relationship between these two luminance measures. This finding sets up an alternative roadmap to extended studies over the globe that will not require the local deployment of photometers or trained personnel.
DEFF Research Database (Denmark)
Gaididei, Yu. B.; Christiansen, Peter Leth
2008-01-01
We study a parametrically driven Ginzburg-Landau equation model with nonlinear management. The system is made of laterally coupled long active waveguides placed along a circumference. Stationary solutions of three kinds are found: periodic Ising states and two types of Bloch states, staggered and...
Rohan Benjankar; Daniele Tonina; James McKean
2014-01-01
Studies of the effects of hydrodynamic model dimensionality on simulated flow properties and derived quantities such as aquatic habitat quality are limited. It is important to close this knowledge gap especially now that entire river networks can be mapped at the microhabitat scale due to the advent of point-cloud techniques. This study compares flow properties, such...
Directory of Open Access Journals (Sweden)
BRAHIM BENAISSA
2014-12-01
Full Text Available In this study the proper orthogonal decomposition method is utilised as a model reduction technique in crack size estimation in a cracked plate under traction problem. The idea is to create a reduced model based on the results issued from finite element method, thus the crack size parameter is directly related to the boundary displacement obtained from the boundary nodes considered as sensor points. The inverse investigation is run using a genetic algorithm to minimization the error function expressed as the difference between data caused by the crack proposed by genetic algorithm in every individual and the one measured at the actual crack identity. The reduced model is validated by comparing the estimated structural response with the corresponding results from the finite element model. The effectiveness of the approach related to the used number of sensors is presented. Finally the stability of the method against uncertainty is tested by introducing different levels of white noise to the reference data.
Hongmei Gu; John F. Hunt
2007-01-01
The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models for softwood use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment or...
Mills, Kyle; Tamblyn, Isaac
2018-03-01
We demonstrate the capability of a convolutional deep neural network in predicting the nearest-neighbor energy of the 4 ×4 Ising model. Using its success at this task, we motivate the study of the larger 8 ×8 Ising model, showing that the deep neural network can learn the nearest-neighbor Ising Hamiltonian after only seeing a vanishingly small fraction of configuration space. Additionally, we show that the neural network has learned both the energy and magnetization operators with sufficient accuracy to replicate the low-temperature Ising phase transition. We then demonstrate the ability of the neural network to learn other spin models, teaching the convolutional deep neural network to accurately predict the long-range interaction of a screened Coulomb Hamiltonian, a sinusoidally attenuated screened Coulomb Hamiltonian, and a modified Potts model Hamiltonian. In the case of the long-range interaction, we demonstrate the ability of the neural network to recover the phase transition with equivalent accuracy to the numerically exact method. Furthermore, in the case of the long-range interaction, the benefits of the neural network become apparent; it is able to make predictions with a high degree of accuracy, and do so 1600 times faster than a CUDA-optimized exact calculation. Additionally, we demonstrate how the neural network succeeds at these tasks by looking at the weights learned in a simplified demonstration.
Directory of Open Access Journals (Sweden)
Jian Zhou
2016-09-01
Full Text Available Hydraulic fracturing is a useful tool for enhancing rock mass permeability for shale gas development, enhanced geothermal systems, and geological carbon sequestration by the high-pressure injection of a fracturing fluid into tight reservoir rocks. Although significant advances have been made in hydraulic fracturing theory, experiments, and numerical modeling, when it comes to the complexity of geological conditions knowledge is still limited. Mechanisms of fluid injection-induced fracture initiation and propagation should be better understood to take full advantage of hydraulic fracturing. This paper presents the development and application of discrete particle modeling based on two-dimensional particle flow code (PFC2D. Firstly, it is shown that the modeled value of the breakdown pressure for the hydraulic fracturing process is approximately equal to analytically calculated values under varied in situ stress conditions. Furthermore, a series of simulations for hydraulic fracturing in competent rock was performed to examine the influence of the in situ stress ratio, fluid injection rate, and fluid viscosity on the borehole pressure history, the geometry of hydraulic fractures, and the pore-pressure field, respectively. It was found that the hydraulic fractures in an isotropic medium always propagate parallel to the orientation of the maximum principal stress. When a high fluid injection rate is used, higher breakdown pressure is needed for fracture propagation and complex geometries of fractures can develop. When a low viscosity fluid is used, fluid can more easily penetrate from the borehole into the surrounding rock, which causes a reduction of the effective stress and leads to a lower breakdown pressure. Moreover, the geometry of the fractures is not particularly sensitive to the fluid viscosity in the approximate isotropic model.
Energy Technology Data Exchange (ETDEWEB)
Prinja, A.K.
1998-09-01
In this work, it has been shown that, for the given sets of parameters (transport coefficients), the Tangent-Predictor (TP) continuation method, which was used in the coarsest grid, works remarkably well. The problems in finding an initial guess that resides well within Newton`s method radius of convergence are alleviated by correcting the initial guess by the predictor step of the TP method. The TP method works well also in neutral gas puffing and impurity simulations. The neutral gas puffing simulation is performed by systematically increasing the fraction of puffing rate according to the TP method until it reaches a desired condition. Similarly, the impurity simulation characterized by using the fraction of impurity density as the continuation parameter, is carried out in line with the TP method. Both methods show, as expected, a better performance than the classical embedding (CE) method. The convergence criteria {epsilon} is set to be 10{sup {minus}9} based on the fact that lower value of {epsilon} does not alter the solution significantly. Correspondingly, the number of Newton`s iterations in the corrector step of the TP method decrease substantially, an extra point in terms of code speed. The success of the TP method enlarges the possibility of including other sets of parameters (operations and physics). With the availability of the converged coarsest grid solution, the next forward step to the multigrid cycle becomes possible. The multigrid method shows that the memory storage problems that plagued the application of Newton`s method on fine grids, are of no concern. An important result that needs to be noted here is the performance of the FFCD model. The FFCD model is relatively simple and is based on the overall results the model has shown to predict different divertor plasma parameters. The FFCD model treats exactly the implementation of the deep penetration of energetic neutrals emerging from the divertor plate. The resulting ionization profiles are
International Nuclear Information System (INIS)
Prinja, A.K.
1998-01-01
In this work, it has been shown that, for the given sets of parameters (transport coefficients), the Tangent-Predictor (TP) continuation method, which was used in the coarsest grid, works remarkably well. The problems in finding an initial guess that resides well within Newton's method radius of convergence are alleviated by correcting the initial guess by the predictor step of the TP method. The TP method works well also in neutral gas puffing and impurity simulations. The neutral gas puffing simulation is performed by systematically increasing the fraction of puffing rate according to the TP method until it reaches a desired condition. Similarly, the impurity simulation characterized by using the fraction of impurity density as the continuation parameter, is carried out in line with the TP method. Both methods show, as expected, a better performance than the classical embedding (CE) method. The convergence criteria ε is set to be 10 -9 based on the fact that lower value of ε does not alter the solution significantly. Correspondingly, the number of Newton's iterations in the corrector step of the TP method decrease substantially, an extra point in terms of code speed. The success of the TP method enlarges the possibility of including other sets of parameters (operations and physics). With the availability of the converged coarsest grid solution, the next forward step to the multigrid cycle becomes possible. The multigrid method shows that the memory storage problems that plagued the application of Newton's method on fine grids, are of no concern. An important result that needs to be noted here is the performance of the FFCD model. The FFCD model is relatively simple and is based on the overall results the model has shown to predict different divertor plasma parameters. The FFCD model treats exactly the implementation of the deep penetration of energetic neutrals emerging from the divertor plate. The resulting ionization profiles are relatively smooth as a
International Nuclear Information System (INIS)
Moraes, Manoel; Diaz, Marcos
2009-01-01
The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Hα, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10 -4 M sun is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.
International Nuclear Information System (INIS)
Grant, K.E.; Ellingson, R.G.; Wuebbles, D.J.
1988-08-01
Radiative processes strongly effect equilibrium trace gas concentrations both directly, through photolysis reactions, and indirectly through temperature and transport processes. As part of our continuing radiative submodel development and validation, we have used the LLNL 2-D chemical-radiative-transport (CRT) model to investigate the net sensitivity of equilibrium ozone concentrations to several changes in radiative forcing. Doubling CO 2 from 300 ppmv to 600 ppmv resulted in a temperature decrease of 5 K to 8 K in the middle stratosphere along with an 8% to 16% increase in ozone in the same region. Replacing our usual shortwave scattering algorithms with a simplified Rayleigh algorithm led to a 1% to 2% increase in ozone in the lower stratosphere. Finally, modifying our normal CO 2 cooling rates by corrections derived from line-by-line calculations resulted in several regions of heating and cooling. We observed temperature changes on the order of 1 K to 1.5 K with corresponding changes of 0.5% to 1.5% in O 3 . Our results for doubled CO 2 compare favorably with those by other authors. Results for our two perturbation scenarios stress the need for accurately modeling radiative processes while confirming the general validity of current 2-D CRT models. 15 refs., 5 figs
International Nuclear Information System (INIS)
Qian Tianwei; Li, Shushen; Ding Qingwei; Wu Guibin; Zhao Dongye
2009-01-01
90 Sr is a fission byproduct of uranium and plutonium, and it presents a major health problem in the environment. A field test on the transport of various radionuclides including 90 Sr in an unsaturated Chinese loess was conducted under artificial rain conditions from July 1997 to August 2000. The vertical concentration distribution of 90 Sr displayed an unusual profile of double concentration peaks, which were separated by a thin (0.7 cm) source layer. In order to interpret the double-peak concentration profile, the transport of 3 H and 90 Sr in the unsaturated Chinese loess under artificial sprinkling conditions was simulated using WATERM, a numerical code for simulating flow field, and NESOR, also a numerical code but for simulating nuclide migration. The models were able to adequately simulate the double-peak concentration profile. The observation suggested that the fine arenaceous quartz layer, though 0.7 cm thick, formed a capillary barrier together with the local loess, which prevented water from penetrating. A significant discrepancy was observed between the model-fitted distribution coefficient (K d ) of 90 Sr and that determined from independent laboratory experiments, which can be attributed to a number of factors such as the capillary barrier effect, solution-to-solid ratio and soil water content. Therefore, when the model is used for predictive purposes where K d is used as an input parameter, K d must be determined under well controlled conditions by taking into account these factors as well as the heterogeneity in the field.
Parashar, R.; Pickman, L. H.; Reeves, M. D.
2015-12-01
The Continuous Time Random Walk (CTRW) method provides a framework for modeling non-Fickian transport behavior through heterogeneous media by employing probability distributions to generate particle jump lengths and residence times spanning multiple orders of magnitude. In this work, we seek to formulate and parameterize a 2D CTRW directly from attributes of fracture networks with complex geometry. A Discrete Fracture Network (DFN) model is used to produce data on plume evolution over multiple spatial scales by synthetically generating a fracture network based on known fracture characteristics and conducting flow and particle tracking simulations under steady-state boundary conditions and flux-weighted particle migration. DFN Fracture segments, defined as the linear distance between two fracture intersections, are analyzed to define the distribution of jump lengths. The time for particles to migrate along these segments is recorded by the DFN model and is used to define a distribution of waiting times. These distributions provide a basis on which to formulate a CTRW to predict the migration of inert particles on a continuum of scales. The performance of the CTRW in simulating transport at multiple spatial scales is obtained by comparing spatial moments of the DFN plumes with CTRW solutions.
Goel, Ekta; Kumar, Sanjay; Singh, Balraj; Singh, Kunal; Jit, Satyabrata
2017-06-01
The subthreshold performance of graded-channel dual-material double-gate (GCDMDG) MOSFETs is examined through two-dimensional (2D) analytical modeling of subthreshold-current (SC) and subthreshold-swing (SS). The potential function obtained by using the parabolic approach to solve the 2D Poisson's equation, has been used to formulate SC and SS characteristics of the device. The variations of SS against different device parameters have been obtained with the help of effective conduction path parameter. The SC and SS characteristics of the GCDMDG MOS transistor have been compared with those of the dual-material double-gate (DMDG) and simple graded-channel double-gate (GCDG) MOS structures to show its better subthreshold characteristics over the latter two devices. The results of the developed model are well-agreed with the commercially available SILVACO ATLAS™ simulator data.
Török, János; Kertész, János
1996-02-01
We carried out computer simulations to study the green wave model (GWM), the parallel updating version of the two-dimensional traffic model of Biham et al. The better convergence properties of the GWM together with a multi-spin coding technique enabled us to extrapolate to the infinite system size which indicates a nonzero density transition from the free flow to the congested state (jamming transition). In spite of the sudden change in the symmetry of the correlation function at the transition point, finite size scaling and temporal scaling seems to hold, at least above the threshold density. There is a second transition point at a density deep in the congested phase where the geometry of the cluster of jammed cars changes from linear to branched: Just at this transition point this cluster has fractal geometry with dimension 1.58. The jamming transition is also described within the mean field approach.
Coupled two-dimensional edge-plasma and neutral gas modelling of the DIII-D scrape-off-layer
International Nuclear Information System (INIS)
Maingi, R.; Gilligan, J.; Hankins, O.; Rensink, M.; Owen, L.; Klepper, C.; Mioduszewski, P.
1992-01-01
This paper reports that in order to do consistent scrape-off-layer plasma and neutral transport calculations, the 2-D fluid code, B2 has been externally coupled to the neutral transport code, DEGAS, for Dlll-D. The coupling procedure is similar to recent simulations done for TFTR, Tore Supra, and ClT. An averaged source approach is utilized to allow convergence between the two codes. Initial comparison of plasma quantities between the coupled code set and the B2 code alone shows that a colder, denser plasma may exist at the divertor targets than predicted by the B2 code with its internal recycling model
The costs of no – a two-dimensional issue-voting model of voter behavior in EU referendums
DEFF Research Database (Denmark)
Beach, Derek
of evaluation is voter satisfaction with the economic and political performance of the incumbent government (Franklin, Marsh, and Wlezien 1994; Franklin 2002). Or do voters undertake a utility calculation of the costs and benefits of the issue before them (whether the country should ratify an EU treaty...... in understanding the issues. However, in contrast to existing issue-voting arguments, I argue that the calculation of the utility of voting yes/no by voters has two distinct dimensions. Existing models are based upon the idea that voters undertake a utility calculation of the benefits of ratifying an EU treaty (or...
Espejo, Elio; Winkler, Michael
2018-04-01
The interplay of chemotaxis, convection and reaction terms is studied in the particular framework of a refined model for coral broadcast spawning, consisting of three equations describing the population densities of unfertilized sperms and eggs and the concentration of a chemical released by the latter, coupled to the incompressible Navier-Stokes equations. Under mild assumptions on the initial data, global existence of classical solutions to an associated initial-boundary value problem in bounded planar domains is established. Moreover, all these solutions are shown to approach a spatially homogeneous equilibrium in the large time limit.
Loxley, P N
2017-10-01
The two-dimensional Gabor function is adapted to natural image statistics, leading to a tractable probabilistic generative model that can be used to model simple cell receptive field profiles, or generate basis functions for sparse coding applications. Learning is found to be most pronounced in three Gabor function parameters representing the size and spatial frequency of the two-dimensional Gabor function and characterized by a nonuniform probability distribution with heavy tails. All three parameters are found to be strongly correlated, resulting in a basis of multiscale Gabor functions with similar aspect ratios and size-dependent spatial frequencies. A key finding is that the distribution of receptive-field sizes is scale invariant over a wide range of values, so there is no characteristic receptive field size selected by natural image statistics. The Gabor function aspect ratio is found to be approximately conserved by the learning rules and is therefore not well determined by natural image statistics. This allows for three distinct solutions: a basis of Gabor functions with sharp orientation resolution at the expense of spatial-frequency resolution, a basis of Gabor functions with sharp spatial-frequency resolution at the expense of orientation resolution, or a basis with unit aspect ratio. Arbitrary mixtures of all three cases are also possible. Two parameters controlling the shape of the marginal distributions in a probabilistic generative model fully account for all three solutions. The best-performing probabilistic generative model for sparse coding applications is found to be a gaussian copula with Pareto marginal probability density functions.
Liu, Lei; Guo, Rui; Chen, Liang; Cao, Yu; Yang, Yongliang; Zhao, Bobo
2016-12-01
Underwater shock wave focusing by ellipsoidal reflector is an important method for medical treatment, detection, and acoustic warfare. However, its pressure field is difficult to predict due to complicated physics. In this study, the pressure by focusing is modeled based on theories of shock wave propagation, nonlinear reflection, and nonlinear focusing, and the calculation domain is determined by approximate equations of wave fronts and lines. The pressure field during the whole process is described by combining direct and focusing pressures in the time and space domains. On this basis, the focusing behavior is simulated, and obtained pressure profiles are compared with experimental results, and the influence of reflector length on focusing performance is also discussed. The results indicate that although there are some rough assumptions, this model can simulate the underwater focusing in some detail and does a good job of predicting the pressure distribution, especially for the positive peak pressure, with an error below 10%; as the reflector length increases, the dynamic focus tends to move linearly forward to the other geometric focus, and the pressure gain increases continuously but the growth rate decreases.
Khan, Farman U; Qamar, Shamsul
2017-05-01
A set of analytical solutions are presented for a model describing the transport of a solute in a fixed-bed reactor of cylindrical geometry subjected to the first (Dirichlet) and third (Danckwerts) type inlet boundary conditions. Linear sorption kinetic process and first-order decay are considered. Cylindrical geometry allows the use of large columns to investigate dispersion, adsorption/desorption and reaction kinetic mechanisms. The finite Hankel and Laplace transform techniques are adopted to solve the model equations. For further analysis, statistical temporal moments are derived from the Laplace-transformed solutions. The developed analytical solutions are compared with the numerical solutions of high-resolution finite volume scheme. Different case studies are presented and discussed for a series of numerical values corresponding to a wide range of mass transfer and reaction kinetics. A good agreement was observed in the analytical and numerical concentration profiles and moments. The developed solutions are efficient tools for analyzing numerical algorithms, sensitivity analysis and simultaneous determination of the longitudinal and transverse dispersion coefficients from a laboratory-scale radial column experiment. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
DEFF Research Database (Denmark)
Mouritsen, Ole G.; Praestgaard, Eigil
1988-01-01
obeys dynamical scaling and the shape of the dynamical scaling function pertaining to the structure factor is found to depend on P. Specifically, this function is described by a Porod-law behavior, q-ω, where ω increases with the wall softness. The kinetic exponent, which describes how the linear domain...... infinite to zero temperature as well as to nonzero temperatures below the ordering transition. The continuous nature of the spin variables causes the domain walls to be ‘‘soft’’ and characterized by a finite thickness. The steady-state thickness of the walls can be varied by a model parameter, P. At zero...... size varies with time, R(t)∼tn, is for both models at zero temperature determined to be n≃0.25, independent of P. At finite temperatures, the growth kinetics is found to cross over to the Lifshitz-Allen-Cahn law characterized by n≃0.50. The results support the idea of two separate zero...
Directory of Open Access Journals (Sweden)
R. Daud
2013-06-01
Full Text Available Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b > a. Crack interaction factors are evaluated based on stress intensity factors (SIFs for Mode I SIFs using a displacement extrapolation technique. Parametric studies involved a wide range of crack-to-width (0.05 ≤ a/W ≤ 0.5 and crack interval ratios (b/a > 1. For validation, crack interaction factors are compared with single edge crack SIFs as a state of zero interaction. Within the considered range of parameters, the proposed numerical evaluation used to predict the crack interaction factor reduces the error of existing analytical solution from 1.92% to 0.97% at higher a/W. In reference to FFS codes, the small discrepancy in the prediction of the crack interaction factor validates the reliability of the numerical model to predict crack interaction limits under shielding interaction effects. In conclusion, the numerical model gave a successful prediction in estimating the crack interaction limit, which can be used as a reference for the shielding orientation of other cracks.
Gravity dual of two-dimensional N = (2, 2)∗ supersymmetric Yang-Mills theory and integrable models
Nian, Jun
2018-03-01
The 2D N = (2, 2)∗ supersymmetric Yang-Mills theory can be obtained from the 2D N = (4, 4) theory with a twisted mass deformation. In this paper we construct the gravity dual theory of the 2D N = (2, 2)∗ supersymmetric U( N ) Yang-Mills theory at the large N and large 't Hooft coupling limit using the 5D gauged supergravity. In the UV regime, this construction also provides the gravity dual of the 2D N = (2 , 2)∗ U( N ) topological Yang-Mills-Higgs theory. We propose a triality in the UV regime among integrable model, gauge theory and gravity, and we make some checks of this relation at classical level.
International Nuclear Information System (INIS)
Sherman, A.; Schreiber, M.
1995-01-01
We use the Eliashberg formalism for calculating T c in a model of cuprate perovskites with pairing mediated by both magnons and apex-oxygen vibrations. The influence of strong correlations on the energy spectrum is taken into account in the spin-wave approximation. It is shown that the hole-magnon interaction alone cannot yield high T c . But together with a moderate hole-phonon interaction it does lead to d-wave superconductivity at temperatures and hole concentrations observed in cuprates. High T c are connected with a large density of states due to extended Van Hove singularities, a conformity of the two interactions for the d symmetry, and high phonon frequencies
Suenaga, Nobuaki; Yoshioka, Shoichi; Matsumoto, Takumi; Ji, Yingfeng
2018-01-01
In Hyuga-nada, southern Kyushu in southwest Japan, afterslip events were found in association with the two large interplate earthquakes, which occurred on October 19 and December 3, 1996. In Kyushu, low-frequency earthquakes (LFEs) and tectonic tremors are not common, but a considerable concentration of tectonic tremors is observed beneath the Pacific coast of the Miyazaki prefecture. To investigate the generation mechanisms of these seismic events, we performed 2-D box-type time-dependent thermal modeling in southern Kyushu. As a result, the temperature range of the upper surface of the subducting Philippine Sea (PHS) plate, where the afterslip occurred, reached approximately 300 to 350 °C. The temperatures where the tectonic tremors occurred ranged from 450 to 650 °C in the mantle wedge corner. We also estimated the spatial distribution of water content within the subducting PHS plate, using phase diagrams of hydrous mid-ocean ridge basalt (MORB) and ultramafic rock. Then, we found that no characteristic phase transformations accompany the dehydration of the subducting PHS plate in the afterslip region, but phase transformation from lawsonite blueschist to lawsonite eclogite is expected within the oceanic crust of the PHS plate just below the active region of the tectonic tremors. Our estimated water content distribution is consistent with the VP/VS ratio calculated from the seismic tomography. Therefore, we conclude that the occurrence of the afterslip is controlled by the temperature condition at the plate boundary, and occurs near the down-dip limit of the seismogenic zone. On the other hand, determining the major factors leading to the occurrence of the tectonic tremors is difficult, we estimated the temperature in the mantle wedge is ranging from 450 °C to 650 °C, and dehydration of 1.0 wt% would be expected from the subducting PHS plate near the active region of the tectonic tremors.
A two-dimensional iterative panel method and boundary layer model for bio-inspired multi-body wings
Blower, Christopher J.; Dhruv, Akash; Wickenheiser, Adam M.
2014-03-01
The increased use of Unmanned Aerial Vehicles (UAVs) has created a continuous demand for improved flight capabilities and range of use. During the last decade, engineers have turned to bio-inspiration for new and innovative flow control methods for gust alleviation, maneuverability, and stability improvement using morphing aircraft wings. The bio-inspired wing design considered in this study mimics the flow manipulation techniques performed by birds to extend the operating envelope of UAVs through the installation of an array of feather-like panels across the airfoil's upper and lower surfaces while replacing the trailing edge flap. Each flap has the ability to deflect into both the airfoil and the inbound airflow using hinge points with a single degree-of-freedom, situated at 20%, 40%, 60% and 80% of the chord. The installation of the surface flaps offers configurations that enable advantageous maneuvers while alleviating gust disturbances. Due to the number of possible permutations available for the flap configurations, an iterative constant-strength doublet/source panel method has been developed with an integrated boundary layer model to calculate the pressure distribution and viscous drag over the wing's surface. As a result, the lift, drag and moment coefficients for each airfoil configuration can be calculated. The flight coefficients of this numerical method are validated using experimental data from a low speed suction wind tunnel operating at a Reynolds Number 300,000. This method enables the aerodynamic assessment of a morphing wing profile to be performed accurately and efficiently in comparison to Computational Fluid Dynamics methods and experiments as discussed herein.
DEFF Research Database (Denmark)
Nielsen, Morten; Miao, Ling; Ipsen, John Hjorth
1996-01-01
In this work we concentrate on phase equilibria in two-dimensional condensed systems of particles where both translational and internal degrees of freedom are present and coupled through microscopic interactions, with a focus on the manner of the macroscopic coupling between the two types...... spin-spin interactions that may have spatial dependence. The fluctuating number of nearest neighbors and the possible spatial dependence of the spin-spin interactions couple microscopically the spin degrees of freedom to the translational degrees of freedom. The first model (I) is a random......-disorder singularity can be of first order throughout the phase diagram. It is found that this first-order singularity can be either coupled to or decoupled from the lattice-melting singularity, depending on the strength of the microscopic coupling. The calculated phase diagram and the associated thermodynamic...
Tietz, D
1991-01-01
This report presents the stand-alone computer application ELPHOFIT, a software package for the analysis of gel electrophoretic data based on Ferguson plots. Either conventional one-dimensional gels or two-dimensional agarose gels (Serwer-type) can be evaluated. Special emphasis is on the latter gel type, which has been applied previously for the separation of DNA, intact viruses and polydisperse meningitis vaccines. ELPHOFIT is designed for Macintosh PCs and for the IBM XT, AT, PS/2 and compatibles. The program operates interactively with the user, who determines the course of evaluation. Data input is in the format of files providing values of gel electrophoretic migration distances or particle mobility (absolute or relative). Data processing involves a simultaneous least-square curve fitting algorithm (Newton-Gauss, Marquardt-Levenberg) which uses equations derived from the extended Ogston model. Functions are fit to the database by adjusting their variables, representing physical parameters of the gel and the electrophoresed particle. The program output consists of tables and graphics accompanied by an explanatory text providing the following information: (i) radius and free mobility of the electrophoresed particle, (ii) fiber radius, length and volume, mean or median pore radius of the gel, (iii) linear Ferguson plots, (iv) iso-free-mobility/iso-size nomogram for two-dimensional gels, (v) confidence ellipses, (vi) required parameters for image processing program GELFIT and (vii) goodness-of-fit and other statistical parameters, such as standard errors, dependency values, root-mean-square (RMS) error and determination coefficient. Other features of the program are (i) simulation of Serwer-type two-dimensional electrophoresis, (ii) standardization according to size, or size and free mobility, (iii) the conversion of particle radii to molecular (or particle) weight and vice versa, (iv) interconversion of DNA size specifications, i.e. the number of base pairs and
Guo, Zhiqiang; Wang, Huaiqing; Yang, Jie; Miller, David J
2015-01-01
In this paper, we propose and implement a hybrid model combining two-directional two-dimensional principal component analysis ((2D)2PCA) and a Radial Basis Function Neural Network (RBFNN) to forecast stock market behavior. First, 36 stock market technical variables are selected as the input features, and a sliding window is used to obtain the input data of the model. Next, (2D)2PCA is utilized to reduce the dimension of the data and extract its intrinsic features. Finally, an RBFNN accepts the data processed by (2D)2PCA to forecast the next day's stock price or movement. The proposed model is used on the Shanghai stock market index, and the experiments show that the model achieves a good level of fitness. The proposed model is then compared with one that uses the traditional dimension reduction method principal component analysis (PCA) and independent component analysis (ICA). The empirical results show that the proposed model outperforms the PCA-based model, as well as alternative models based on ICA and on the multilayer perceptron.
Gisplana two dimensional flow model
International Nuclear Information System (INIS)
Payeras Socias, J.; Montero Ramos, M.; Pablo Sanmartin, M.A. de; Diaz Teijeiro, M.
1996-01-01
The Environmental Radiological Monitoring Network (R.V.R.A.) includes a set of 90 sampling points chosen from the major spanish river basins. The R.V.R.A.'s database is an structured system providing quantitative radiological information of radioactivity levels in spanish continental waters. (Author)
International Nuclear Information System (INIS)
Colombo, V; Ghedini, E; Gherardi, M; Sanibondi, P; Shigeta, M
2012-01-01
Nano-particle synthesis by means of inductively coupled plasma torches is a material process of large technological interest. Numerous parameters are involved in the optimization of this process; hence the development of numerical models for the prediction of thermal and magneto-fluid dynamics fields, precursor powder trajectories and thermal history, as well as nano-particle formation and growth, is necessary for the up-scaling of these devices from laboratory batch production to an industrial continuous process. In this work, a two-dimensional (2D) discrete-type model (nodal model) for the analysis of nano-powder nucleation and growth is presented, taking into account convection, diffusion and turbulent effects on particle formation. Discrete-type models feature high precision and reveal a great deal of information useful for clarifying the nano-particle formation process. Using Si as the precursor material, 2D simulations of a nano-particle synthesis RF plasma apparatus with a reaction chamber are carried out. Good agreement is found when comparing results obtained with this model with those coming from a well-established nucleation-coupled moment method. Moreover, the extended amount of obtainable information that characterizes the nodal model is underlined. (paper)
Quasi-two-dimensional holography
International Nuclear Information System (INIS)
Kutzner, J.; Erhard, A.; Wuestenberg, H.; Zimpfer, J.
1980-01-01
The acoustical holography with numerical reconstruction by area scanning is memory- and time-intensive. With the experiences by the linear holography we tried to derive a scanning for the evaluating of the two-dimensional flaw-sizes. In most practical cases it is sufficient to determine the exact depth extension of a flaw, whereas the accuracy of the length extension is less critical. For this reason the applicability of the so-called quasi-two-dimensional holography is appropriate. The used sound field given by special probes is divergent in the inclined plane and light focussed in the perpendicular plane using cylindrical lenses. (orig.) [de
Figueiredo, T. P.; Rocha, J. C. S.; Costa, B. V.
2017-12-01
Although the topological Berezinskii-Kosterlitz-Thouless transition was for the first time described by 40 years ago, it is still a matter of discussion. It has been used to explain several experiments in the most diverse physical systems. In contrast with the ordinary continuous phase transitions the BKT-transition does not break any symmetry. However, in some contexts it can easily be confused with other continuous transitions, in general due to an insufficient data analysis. The two-dimensional XY (or sometimes called planar rotator) spin model is the fruit fly model describing the BKT transition. As demonstrated by Bramwell and Holdsworth (1993) the finite-size effects are more important in two-dimensions than in others due to the logarithmic system size dependence of the properties of the system. Closely related is the anisotropic two dimensional Heisenberg model (AH). Although they have the same Hamiltonian the spin variable in the former has only two degrees of freedom while the AH has three. Many works treat the AH model as undergoing a transition in the same universality class as the XY model. However, its characterization as being in the BKT class of universality deserve some investigation. This paper has two goals. First, we describe an analytical evidence showing that the AH model is in the BKT class of universality. Second, we make an extensive simulation, using the numerical Replica Exchange Wang-Landau method that corroborate our analytical calculations. From our simulation we obtain the BKT transition temperature as TBKT = 0 . 6980(10) by monitoring the susceptibility, the two point correlation function and the helicity modulus. We discuss the misuse of the fourth order Binder's cumulant to locate the transition temperature. The specific heat is shown to have a non-critical behavior as expected in the BKT transition. An analysis of the two point correlation function at low temperature, C(r) ∝r - η(T), shows that the exponent, η, is consistent
Witt, Emitt C.
2015-01-01
Growing use of two-dimensional (2-D) hydraulic models has created a need for high resolution data to support flood volume estimates, floodplain specific engineering data, and accurate flood inundation scenarios. Elevation data are a critical input to these models that guide the flood-wave across the landscape allowing the computation of valuable engineering specific data that provides a better understanding of flooding impacts on structures, debris movement, bed scour, and direction. High resolution elevation data are becoming publicly available that can benefit the 2-D flood modeling community. Comparison of these newly available data with legacy data suggests that better modeling outcomes are achieved by using 3D Elevation Program (3DEP) lidar point data and the derived 1 m Digital Elevation Model (DEM) product relative to the legacy 3 m, 10 m, or 30 m products currently available in the U.S. Geological Survey (USGS) National Elevation Dataset. Within the low topographic relief of a coastal floodplain, the newer 3DEP data better resolved elevations within the forested and swampy areas achieving simulations that compared well with a historic flooding event. Results show that the 1 m DEM derived from 3DEP lidar source provides a more conservative estimate of specific energy, static pressure, and impact pressure for grid elements at maximum flow relative to the legacy DEM data. Better flood simulations are critically important in coastal floodplains where climate change driven storm frequency and sea level rise will contribute to more frequent flooding events.
AUTHOR|(CDS)2080070; Hebbeker, Thomas
2017-07-07
The discovery of a new particle consistent with the standard model Higgs boson at the Large Hadron Collider in 2012 completed the standard model of particle physics (SM). Despite its remarkable success many questions remain unexplained. Numerous theoretical models, predicting the existence of new heavy particles, provide answers to these unresolved questions and are tested at high energy experiments such as the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). In this thesis a model independent search method for new particles in two-dimensional mass space in events with missing transverse energy is presented using 19.7 $\\mbox{fb}^{-1}$ of proton-proton collision data recorded by the CMS detector at a centre of mass energy $\\sqrt{s}$ = 8 TeV at the LHC. The analysis searches for signatures of pair-produced new heavy particles $\\mbox{T}^\\prime$ which decay further into unknown heavy particles $\\mbox{W}^\\prime$ and SM quarks $q$ ($\\mbox{T}^\\prime\\overline{\\mbox{T}^\\prime} \\rightarrow {...
Wei, Ying-Jie; Jing, Li-Jun; Zhan, Yang; Sun, E; Jia, Xiao-Bin
2014-05-01
To break through the restrictions of the evaluation model and the quantity of compounds by using the two-dimensional zebrafish model combined with chromatographic techniques, and establish a new method for the high-throughput screening of active anti-osteoporosis components. According to the research group-related studies and relevant foreign literatures, on the basis of the fact that the zebrafish osteoporosis model could efficiently evaluate the activity, the zebrafish metabolism model could efficiently enrich metabolites and the chromatographic techniques could efficiently separate and analyze components of traditional Chinese medicines, we proposed that the inherent combination of the three methods is expected to efficiently decode in vivo and in vitro efficacious anti-osteoporosis materials of traditional Chinese medicines. The method makes it simple and efficient in the enrichment, separation and analysis on components of traditional Chinese medicines, particularly micro-components and metabolites and the screening anti-osteoporosis activity, fully reflects that efficacious materials of traditional Chinese medicines contain original components and metabolites, with characteristic of "multi-components, multi-targets and integral effect", which provides new ideas and methods for the early and rapid discovery of active anti-osteoporosis components of traditional Chinese medicines.
Two dimensional plasma simulation code
International Nuclear Information System (INIS)
Hazak, G.; Boneh, Y.; Goshen, Sh.; Oreg, J.
1977-03-01
An electrostatic two-dimensional particle code for plasma simulation is described. Boundary conditions which take into account the finiteness of the system are presented. An analytic solution for the case of crossed fields plasma acceleration is derived. This solution serves as a check on a computer test run
Geitner, Robert; Götz, Stefan; Stach, Robert; Siegmann, Michael; Krebs, Patrick; Zechel, Stefan; Schreyer, Kristin; Winter, Andreas; Hager, Martin D; Schubert, Ulrich S; Gräfe, Stefanie; Dietzek, Benjamin; Mizaikoff, Boris; Schmitt, Michael; Popp, Jürgen
2018-03-15
The presented study reports the synthesis and the vibrational spectroscopic characterization of different matrix-embedded model photocatalysts. The goal of the study is to investigate the interaction of a polymer matrix with photosensitizing dyes and metal complexes for potential future photocatalytic applications. The synthesis focuses on a new rhodamine B derivate and a Pt(II) terpyridine complex, which both contain a polymerizable methacrylate moiety and an acid labile acylhydrazone group. The methacrylate moieties are afterward utilized to synthesize functional model hydrogels mainly consisting of poly(ethylene glycol) methacrylate units. The pH-dependent and temperature-dependent behavior of the hydrogels is investigated by means of Raman and IR spectroscopy assisted by density functional theory calculations and two-dimensional correlation spectroscopy. The spectroscopic results reveal that the Pt(II) terpyridine complex can be released from the polymer matrix by cleaving the C═N bond in an acid environment. The same behavior could not be observed in the case of the rhodamine B dye although it features a comparable C═N bond. The temperature-dependent study shows that the water evaporation has a significant influence neither on the molecular structure of the hydrogel nor on the model photocatalytic moieties.
Ertaş, Mehmet
2015-09-01
Keskin and Ertaş (2009) presented a study of the magnetic properties of a mixed spin (2, 5/2) ferrimagnetic Ising model within an oscillating magnetic field. They employed dynamic mean-field calculations to find the dynamic phase transition temperatures, the dynamic compensation points of the model and to present the dynamic phase diagrams. In this work, we extend the study and investigate the dynamic hysteresis behaviors for the two-dimensional (2D) mixed spin (2, 5/2) ferrimagnetic Ising model on a hexagonal lattice in an oscillating magnetic field within the framework of dynamic mean-field calculations. The dynamic hysteresis curves are obtained for both the ferromagnetic and antiferromagnetic interactions and the effects of the Hamiltonian parameters on the dynamic hysteresis behaviors are discussed in detail. The thermal behaviors of the coercivity and remanent magnetizations are also investigated. The results are compared with some theoretical and experimental works and a qualitatively good agreement is found. Finally, the dynamic phase diagrams depending on the frequency of an oscillating magnetic field in the plane of the reduced temperature versus magnetic field amplitude is examined and it is found that the dynamic phase diagrams display richer dynamic critical behavior for higher values of frequency than for lower values.
Carlotti, Massimo; Brizzi, Gabriele; Papandrea, Enzo; Prevedelli, Marco; Ridolfi, Marco; Dinelli, Bianca Maria; Magnani, Luca
2006-02-01
We present a new retrieval model designed to analyze the observations of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which is on board the ENVironmental SATellite (ENVISAT). The new geo-fit multitarget retrieval model (GMTR) implements the geo-fit two-dimensional inversion for the simultaneous retrieval of several targets including a set of atmospheric constituents that are not considered by the ground processor of the MIPAS experiment. We describe the innovative solutions adopted in the inversion algorithm and the main functionalities of the corresponding computer code. The performance of GMTR is compared with that of the MIPAS ground processor in terms of accuracy of the retrieval products. Furthermore, we show the capability of GMTR to resolve the horizontal structures of the atmosphere. The new retrieval model is implemented in an optimized computer code that is distributed by the European Space Agency as "open source" in a package that includes a full set of auxiliary data for the retrieval of 28 atmospheric targets.
Spegazzini, Nicolas; Siesler, Heinz W; Ozaki, Yukihiro
2012-10-02
A sequential identification approach by two-dimensional (2D) correlation analysis for the identification of a chemical reaction model, activation, and thermodynamic parameters is presented in this paper. The identification task is decomposed into a sequence of subproblems. The first step is the construction of a reaction model with the suggested information by model-free 2D correlation analysis using a novel technique called derivative double 2D correlation spectroscopy (DD2DCOS), which enables one to analyze intensities with nonlinear behavior and overlapped bands. The second step is a model-based 2D correlation analysis where the activation and thermodynamic parameters are estimated by an indirect implicit calibration or a calibration-free approach. In this way, a minimization process for the spectral information by sample-sample 2D correlation spectroscopy and kinetic hard modeling (using ordinary differential equations) of the chemical reaction model is carried out. The sequential identification by 2D correlation analysis is illustrated with reference to the isomeric structure of diphenylurethane synthesized from phenylisocyanate and phenol. The reaction was investigated by FT-IR spectroscopy. The activation and thermodynamic parameters of the isomeric structures of diphenylurethane linked through a hydrogen bonding equilibrium were studied by means of an integration of model-free and model-based 2D correlation analysis called a sequential identification approach. The study determined the enthalpy (ΔH = 15.25 kJ/mol) and entropy (TΔS = 13.20 kJ/mol) of C═O···H hydrogen bonding of diphenylurethane through direct calculation from the differences in the kinetic parameters (δΔ(‡)H, -TδΔ(‡)S) at equilibrium in the chemical reaction system.
International Nuclear Information System (INIS)
Auluck, S K H
2014-01-01
Dense plasma focus (DPF) is known to produce highly energetic ions, electrons and plasma environment which can be used for breeding short-lived isotopes, plasma nanotechnology and other material processing applications. Commercial utilization of DPF in such areas would need a design tool that can be deployed in an automatic search for the best possible device configuration for a given application. The recently revisited (Auluck 2013 Phys. Plasmas 20 112501) Gratton–Vargas (GV) two-dimensional analytical snowplow model of plasma focus provides a numerical formula for dynamic inductance of a Mather-type plasma focus fitted to thousands of automated computations, which enables the construction of such a design tool. This inductance formula is utilized in the present work to explore global optimization, based on first-principles optimality criteria, in a four-dimensional parameter-subspace of the zero-resistance GV model. The optimization process is shown to reproduce the empirically observed constancy of the drive parameter over eight decades in capacitor bank energy. The optimized geometry of plasma focus normalized to the anode radius is shown to be independent of voltage, while the optimized anode radius is shown to be related to capacitor bank inductance. (paper)
International Nuclear Information System (INIS)
Helling, C.; Dunger, V.
1998-01-01
Uranium mill tailings were deposited in a section of the Kaitzbach valley which was closed by tow dams. The Kaitzbach creek was cased in the area. After the uranium ore processing was finish the dump was used as a municipal waste deposit. The water balance of the IAA Dresden-Coschuetz/Gittersee was only estimated in former works. In this case a modeling of the water balance is very useful in regard to a process orientated quantification of the contaminant transport within the dump as well as into the underground. Simplified and rough estimating methods such as the runoff coefficient concept or rating curves are less suited because of the complexity of the processes. That's why we tried to get a runoff and seepage water balance by means of a two-dimensional water balance model for waste heaps called BOWAHALD. The tailings site IAA Dresden-Coschuetz/Gittersee was divited into several hydrotopes (areas with similar hydrological characteristics). Different exposition and slopes as well as different soils and vegetation were taken into account. The parameter verification is possible due to comparison with available data such hydrochemical and isotopic analysis of seepage water and groundwater. (orig.)
Hosseiny, S. M. H.; Smith, V. B.; Zarzar, C.
2016-12-01
Darby Creek, in metro-Philadelphia, PA, has been subject hydrologic engineering since the late 17th century. Today, this urbanized creek is considered one of the most flood-prone in the U.S. [Philadelphia Inquirer, 2012]. The creek channel and floodplain are predominately composed of alluvial sediments. During flood events sediment transport increases, geomorphically altering the channel and floodplain. However, most flood inundation mapping does not consider water-sediment interaction and the geomorphic implications. To address the potential uncertainty embedded in neglecting geomorphic processes, this study aims to analyze flood inundation maps through describing the flow velocity field and sediment transport. This study uses LiDAR and bathymetric data in the International River Interface Cooperative software (iRIC) with FaSTMECH (a two-dimensional quasi unsteady flow solver) to calculate sediment transport relative to hydraulic characteristics of the flow. A flood event April 30th, 2014 is modeled and tested based on stage and discharge data from an upstream USGS gage. For model validation the boundary conditions were set using the USGS gage in combination with two NOAA stream gages on the Delaware River near the outlet of Darby Creek. The results from this study demonstrate how to incorporate sediment transport in flood inundation maps and can ultimately be used to gain a deeper understanding of sediment transport and sediment storage in the floodplain.
Auluck, S. K. H.
2014-12-01
Dense plasma focus (DPF) is known to produce highly energetic ions, electrons and plasma environment which can be used for breeding short-lived isotopes, plasma nanotechnology and other material processing applications. Commercial utilization of DPF in such areas would need a design tool that can be deployed in an automatic search for the best possible device configuration for a given application. The recently revisited (Auluck 2013 Phys. Plasmas 20 112501) Gratton-Vargas (GV) two-dimensional analytical snowplow model of plasma focus provides a numerical formula for dynamic inductance of a Mather-type plasma focus fitted to thousands of automated computations, which enables the construction of such a design tool. This inductance formula is utilized in the present work to explore global optimization, based on first-principles optimality criteria, in a four-dimensional parameter-subspace of the zero-resistance GV model. The optimization process is shown to reproduce the empirically observed constancy of the drive parameter over eight decades in capacitor bank energy. The optimized geometry of plasma focus normalized to the anode radius is shown to be independent of voltage, while the optimized anode radius is shown to be related to capacitor bank inductance.
Czuba, Christiana; Czuba, Jonathan A.; Gendaszek, Andrew S.; Magirl, Christopher S.
2010-01-01
The Cedar River in Washington State originates on the western slope of the Cascade Range and provides the City of Seattle with most of its drinking water, while also supporting a productive salmon habitat. Water-resource managers require detailed information on how best to manage high-flow releases from Chester Morse Lake, a large reservoir on the Cedar River, during periods of heavy precipitation to minimize flooding, while mitigating negative effects on fish populations. Instream flow-management practices include provisions for adaptive management to promote and maintain healthy aquatic habitat in the river system. The current study is designed to understand the linkages between peak flow characteristics, geomorphic processes, riverine habitat, and biological responses. Specifically, two-dimensional hydrodynamic modeling is used to simulate and quantify the effects of the peak-flow magnitude, duration, and frequency on the channel morphology and salmon-spawning habitat. Two study reaches, representative of the typical geomorphic and ecologic characteristics of the Cedar River, were selected for the modeling. Detailed bathymetric data, collected with a real-time kinematic global positioning system and an acoustic Doppler current profiler, were combined with a LiDAR-derived digital elevation model in the overbank area to develop a computational mesh. The model is used to simulate water velocity, benthic shear stress, flood inundation, and morphologic changes in the gravel-bedded river under the current and alternative flood-release strategies. Simulations of morphologic change and salmon-redd scour by floods of differing magnitude and duration enable water-resource managers to incorporate model simulation results into adaptive management of peak flows in the Cedar River. PDF version of a presentation on hydrodynamic modelling in the Cedar River in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.
Two dimensional image correlation processor
Yao, Shi-Kai
1992-06-01
Two dimensional images are converted into a very long 1-dimensional data stream by means of raster scan. It is shown that the 1-dimensional correlation function of such long data streams is equivalent to the raster scan converted data of 2-dimensional correlation function of images. Real time correlation of high resolution two-dimensional images has been demonstrated using commercially available components. The advantages of this approach includes programmable electronics reference images, easy interface to objects of interest using conventional image collection optics, real time operation with high resolution images using off-the shelf components, and usefulness in the form of either black and white or full colored images. Such system would be versatile enough for robotics vision, optical inspection, and other pattern recognition and identification applications.
Two-dimensional topological photonics
Khanikaev, Alexander B.; Shvets, Gennady
2017-12-01
Originating from the studies of two-dimensional condensed-matter states, the concept of topological order has recently been expanded to other fields of physics and engineering, particularly optics and photonics. Topological photonic structures have already overturned some of the traditional views on wave propagation and manipulation. The application of topological concepts to guided wave propagation has enabled novel photonic devices, such as reflection-free sharply bent waveguides, robust delay lines, spin-polarized switches and non-reciprocal devices. Discrete degrees of freedom, widely used in condensed-matter physics, such as spin and valley, are now entering the realm of photonics. In this Review, we summarize the latest advances in this highly dynamic field, with special emphasis on the experimental work on two-dimensional photonic topological structures.
Yarnell, S.; Lind, A.; Kupferberg, S.
2007-12-01
We used a freely available two-dimensional model, River2D, to evaluate changes in habitat suitability and availability for Foothill yellow-legged frog egg masses and tadpoles during pulsed flow events. Two study sites in Northern California, one on the unregulated South Fork Eel River and the other on the regulated North Fork Feather River, were selected for modeling. Simulated depths and velocities agreed well with measured field values. When coupled with a definition of breeding habitat suitability that encompassed the variability of field- measured values and the range of error within the model output, the model accurately predicted suitable breeding locations throughout the survey reach. Using data on percentages of egg mass and tadpole loss associated with increased velocities, we assessed several scenarios of how pulsed flows affected habitat availability and suitability. In a seasonal (spring) pulse scenario, lower discharges provided the greatest weighted usable area for breeding, but higher initial discharges provided the greatest buffering capacity against lethal increases in velocity. In an aseasonal (summer) pulse scenario, only 20-30% of the suitable tadpole habitat in the unregulated site and regulated site remained suitable during the pulse regardless of initial flow level. In both scenarios, the unregulated study site provided 2-3 times the buffering capacity of the regulated site. This was likely due to differences in channel morphology; the regulated site had an entrenched channel with steep banks, while the unregulated site had an asymmetric cross-sectional shape where shallow overbank areas provided refuge from high velocities as flows fluctuated. This type of model-based methodology that can evaluate effects from flow fluctuation on individuals and local habitat conditions for multiple life stages would be useful for managing Foothill yellow-legged frog or similar aquatic species in regulated river systems.
Kumari, Babita; Adlakha, Neeru
2015-02-01
Thermoregulation is a complex mechanism regulating heat production within the body (chemical thermoregulation) and heat exchange between the body and the environment (physical thermoregulation) in such a way that the heat exchange is balanced and deep body temperatures are relatively stable. The external heat transfer mechanisms are radiation, conduction, convection and evaporation. The physical activity causes thermal stress and poses challenges for this thermoregulation. In this paper, a model has been developed to study temperature distribution in SST regions of human limbs immediately after physical exercise under cold climate. It is assumed that the subject is doing exercise initially and comes to rest at time t = 0. The human limb is assumed to be of cylindrical shape. The peripheral region of limb is divided into three natural components namely epidermis, dermis and subdermal tissues (SST). Appropriate boundary conditions have been framed based on the physical conditions of the problem. Finite difference has been employed for time, radial and angular variables. The numerical results have been used to obtain temperature profiles in the SST region immediately after continuous exercise for a two-dimensional unsteady state case. The results have been used to analyze the thermal stress in relation to light, moderate and vigorous intensity exercise.
Levashov, V A; Stepanov, M G
2016-01-01
Considerations of local atomic-level stresses associated with each atom represent a particular approach to address structures of disordered materials at the atomic level. We studied structural correlations in a two-dimensional model liquid using molecular dynamics simulations in the following way. We diagonalized the atomic-level stress tensor of every atom and investigated correlations between the eigenvalues and orientations of the eigenvectors of different atoms as a function of distance between them. It is demonstrated that the suggested approach can be used to characterize structural correlations in disordered materials. In particular, we found that changes in the stress correlation functions on decrease of temperature are the most pronounced for the pairs of atoms with separation distance that corresponds to the first minimum in the pair density function. We also show that the angular dependencies of the stress correlation functions previously reported by Wu et al. [Phys. Rev. E 91, 032301 (2015)10.1103/PhysRevE.91.032301] do not represent the anisotropic Eshelby's stress fields, as it is suggested, but originate in the rotational properties of the stress tensors.
Directory of Open Access Journals (Sweden)
Sara-Jane Dunn
Full Text Available The role of the basement membrane is vital in maintaining the integrity and structure of an epithelial layer, acting as both a mechanical support and forming the physical interface between epithelial cells and the surrounding connective tissue. The function of this membrane is explored here in the context of the epithelial monolayer that lines the colonic crypt, test-tube shaped invaginations that punctuate the lining of the intestine and coordinate a regular turnover of cells to replenish the epithelial layer every few days. To investigate the consequence of genetic mutations that perturb the system dynamics and can lead to colorectal cancer, it must be possible to track the emerging tissue level changes that arise in the crypt. To that end, a theoretical crypt model with a realistic, deformable geometry is required. A new discrete crypt model is presented, which focuses on the interaction between cell- and tissue-level behaviour, while incorporating key subcellular components. The model contains a novel description of the role of the surrounding tissue and musculature, based upon experimental observations of the tissue structure of the crypt, which are also reported. A two-dimensional (2D cross-sectional geometry is considered, and the shape of the crypt is allowed to evolve and deform. Simulation results reveal how the shape of the crypt may contribute mechanically to the asymmetric division events typically associated with the stem cells at the base. The model predicts that epithelial cell migration may arise due to feedback between cell loss at the crypt collar and density-dependent cell division, an hypothesis which can be investigated in a wet lab. This work forms the basis for investigation of the deformation of the crypt structure that can occur due to proliferation of cells exhibiting mutant phenotypes, experiments that would not be possible in vivo or in vitro.
International Nuclear Information System (INIS)
Raisee, M.; Hejazi, S.H.
2007-01-01
This paper presents comparisons between heat transfer predictions and measurements for developing turbulent flow through straight rectangular channels with sudden contractions at the mid-channel section. The present numerical results were obtained using a two-dimensional finite-volume code which solves the governing equations in a vertical plane located at the lateral mid-point of the channel. The pressure field is obtained with the well-known SIMPLE algorithm. The hybrid scheme was employed for the discretization of convection in all transport equations. For modeling of the turbulence, a zonal low-Reynolds number k-ε model and the linear and non-linear low-Reynolds number k-ε models with the 'Yap' and 'NYP' length-scale correction terms have been employed. The main objective of present study is to examine the ability of the above turbulence models in the prediction of convective heat transfer in channels with sudden contraction at a mid-channel section. The results of this study show that a sudden contraction creates a relatively small recirculation bubble immediately downstream of the channel contraction. This separation bubble influences the distribution of local heat transfer coefficient and increases the heat transfer levels by a factor of three. Computational results indicate that all the turbulence models employed produce similar flow fields. The zonal k-ε model produces the wrong Nusselt number distribution by underpredicting heat transfer levels in the recirculation bubble and overpredicting them in the developing region. The linear low-Re k-ε model, on the other hand, returns the correct Nusselt number distribution in the recirculation region, although it somewhat overpredicts heat transfer levels in the developing region downstream of the separation bubble. The replacement of the 'Yap' term with the 'NYP' term in the linear low-Re k-ε model results in a more accurate local Nusselt number distribution. Moreover, the application of the non-linear k
García-Peñarrubia, Pilar; Gálvez, Juan J; Gálvez, Jesús
2014-09-01
Cell signalling processes involve receptor trafficking through highly connected networks of interacting components. The binding of surface receptors to their specific ligands is a key factor for the control and triggering of signalling pathways. But the binding process still presents many enigmas and, by analogy with surface catalytic reactions, two different mechanisms can be conceived: the first mechanism is related to the Eley-Rideal (ER) mechanism, i.e. the bulk-dissolved ligand interacts directly by pure three-dimensional (3D) diffusion with the specific surface receptor; the second mechanism is similar to the Langmuir-Hinshelwood (LH) process, i.e. 3D diffusion of the ligand to the cell surface followed by reversible ligand adsorption and subsequent two-dimensional (2D) surface diffusion to the receptor. A situation where both mechanisms simultaneously contribute to the signalling process could also occur. The aim of this paper is to perform a computational study of the behavior of the signalling response when these different mechanisms for ligand-receptor interactions are integrated into a model for signal transduction and ligand transport. To this end, partial differential equations have been used to develop spatio-temporal models that show trafficking dynamics of ligands, cell surface components, and intracellular signalling molecules through the different domains of the system. The mathematical modeling developed for these mechanisms has been applied to the study of two situations frequently found in cell systems: (a) dependence of the signal response on cell density; and (b) enhancement of the signalling response in a synaptic environment.
Pellerin, Louise; Schmidt, Jeanine M.; Hoversten, G. Michael
2003-01-01
As part of an integrated geological and geophysical study to assess the mineral potential in the Amphitheater Mountains of south-central Alaska, USA, two magnetotelluric (MT) profiles were acquired during the summer of 2002. The two parallel MT lines, along with helicopter electromagnetic (HEM) and magnetic data acquired by the State of Alaska Division of Geological and Geophysical Surveys and new detailed U.S. Geological Survey gravity data, are being used to investigate a feeder system to a Late Triassic flood basalt, the Nikolai Greenstone. The platinum-group-element-bearing, layered, and mafic-ultramafic sills of the Fish Lake and Tangle complexes and the geophysical responses suggest the presence of a substantial root of ultramafic material below the Amphitheater synform and several conductive, dense, magnetic, and possibly sulfide-bearing lenses within the surrounding Tangle Formation. The Amphitheater synform was defined by a prominent magnetic anomaly and the repetition of geologic units. Data from the HEM survey were used to assess and correct static shifts in the MT data. A striking conductivity anomaly was observable in the MT apparent resistivity data at sites on each line. Two-dimensional (2-D) inversion was used to model the geometry of the synform structure, electrical properties related to possible mineralization in the top few kilometers, and a feeder root to the magmatic system substantiated with potential field and geological models. The synform plunges to the west with the highly conductive zone ranging from depths of roughly 1.5 to 3.5 km where sampled. Two sensitivity analyses were performed to aid in assessment decisions. First, 2-D models were evaluated from several algorithms, including the rapid-relaxation inversion, the conjugate-gradient method, and Occam?s inversion with the use of different combinations of the apparent resistivity and phase for the transverse electric and magnetic modes. Second, a three-dimensional forward model
Wu, Wei-Chun; Ma, Hong; Xie, Rong-Ai; Gao, Li-Jian; Tang, Yue; Wang, Hao
2016-04-01
This study evaluated the role of two-dimensional speckle tracking echocardiography (2DSTE) for predicting left ventricular (LV) diastolic dysfunction in pacing-induced canine heart failure. Pacing systems were implanted in 8 adult mongrel dogs, and continuous rapid right ventricular pacing (RVP, 240 beats/min) was maintained for 2 weeks. The obtained measurements from 2DSTE included global strain rate during early diastole (SRe) and during late diastole (SRa) in the longitudinal (L-SRe, L-SRa), circumferential (C-SRe, C-SRa), and radial directions (R-SRe, R-SRa). Changes in heart morphology were observed by light microscopy and transmission electron microscopy at 2 weeks. The onset of LV diastolic dysfunction with early systolic dysfunction occurred 3 days after RVP initiation. Most of the strain rate imaging indices were altered at 1 or 3 days after RVP onset and continued to worsen until heart failure developed. Light and transmission electron microscopy showed myocardial vacuolar degeneration and mitochondrial swelling in the left ventricular at 2 weeks after RVP onset. Pearson's correlation analysis revealed that parameters of conventional echocardiography and 2DSTE showed moderate correlation with LV pressure parameters, including E/Esep' (r = 0.58, P echocardiography and strain rate imaging could effectively predict LV diastolic dysfunction (area under the curve: E/Esep' 0.78; L-SRe 0.84; E/L-SRe 0.80; R-SRe 0.80). 2DSTE was a sensitive and accurate technique that could be used for predicting LV diastolic dysfunction in canine heart failure model. © 2015, Wiley Periodicals, Inc.
Two-dimensional sensitivity calculation code: SENSETWO
International Nuclear Information System (INIS)
Yamauchi, Michinori; Nakayama, Mitsuo; Minami, Kazuyoshi; Seki, Yasushi; Iida, Hiromasa.
1979-05-01
A SENSETWO code for the calculation of cross section sensitivities with a two-dimensional model has been developed, on the basis of first order perturbation theory. It uses forward neutron and/or gamma-ray fluxes and adjoint fluxes obtained by two-dimensional discrete ordinates code TWOTRAN-II. The data and informations of cross sections, geometry, nuclide density, response functions, etc. are transmitted to SENSETWO by the dump magnetic tape made in TWOTRAN calculations. The required input for SENSETWO calculations is thus very simple. The SENSETWO yields as printed output the cross section sensitivities for each coarse mesh zone and for each energy group, as well as the plotted output of sensitivity profiles specified by the input. A special feature of the code is that it also calculates the reaction rate with the response function used as the adjoint source in TWOTRAN adjoint calculation and the calculated forward flux from the TWOTRAN forward calculation. (author)
Two-dimensional capillary origami
International Nuclear Information System (INIS)
Brubaker, N.D.; Lega, J.
2016-01-01
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.
Two-dimensional capillary origami
Energy Technology Data Exchange (ETDEWEB)
Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu
2016-01-08
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.
Shan, Feng; Close, David A; Camarco, Daniel P; Johnston, Paul A
2018-01-01
High cancer drug development attrition rates have provoked considerable debate about whether the two-dimensional tumor growth inhibition high-throughput screening assays used in pre-clinical lead discovery adequately reflect solid tumor complexity. We used automated high-content screening image acquisition and analysis methods to compare fluorescent drug uptake, accumulation, and distribution in Cal33 and FaDu head and neck cancer (HNC) monolayer and multicellular tumor spheroid (MCTS) models. Ellipticine, idarubicin, daunorubicin, and doxorubicin were studied because of their fluorescent properties and broad anti-tumor activities. HNC MCTSs were generated in 384-well ultra-low attachment plates where compound exposure, image acquisition, and analysis could be performed in situ. Fluorescent drug accumulation in Cal33 monolayer and MCTS cultures was linear with respect to concentration, and appeared to achieve steady-state levels within 10-15 min of drug exposure, which were maintained through 30-45 min. Drug accumulation in monolayers was independent of cell number and/or density, and every cell achieved uniform drug concentrations. In MCTSs, however, drug accumulation increased as the number of cells and sizes of the MCTSs became bigger. Drugs exhibited restricted penetration and distribution gradients, accumulating preferentially in cells in the outer layers of MCTSs relative to those in the inner cores. Cal33 monolayers were 6-, 20-, 10-, and 16-fold more sensitive than MCTSs to growth inhibition by ellipticine, idarubicin, daunorubicin, and doxorubicin, respectively. In Cal33 MCTSs exposed to ellipticine or doxorubicin for 24 h, MCTSs were smaller and although they still exhibited drug penetration and distribution gradients, the fluorescent intensity difference between outer and inner cells was reduced. After a 24 h exposure, both drugs had penetrated throughout FaDu MCTSs, consistent with drug-induced death of peripheral cell layers enhancing drug
Agnaou, Mehrez; Lasseux, Didier; Ahmadi, Azita
2017-10-01
Inertial flow in porous media occurs in many situations of practical relevance among which one can cite flows in column reactors, in filters, in aquifers, or near wells for hydrocarbon recovery. It is characterized by a deviation from Darcy's law that leads to a nonlinear relationship between the pressure drop and the filtration velocity. In this work, this deviation, also known as the nonlinear, inertial, correction to Darcy's law, which is subject to controversy upon its origin and dependence on the filtration velocity, is studied through numerical simulations. First, the microscopic flow problem was solved computationally for a wide range of Reynolds numbers up to the limit of steady flow within ordered and disordered porous structures. In a second step, the macroscopic characteristics of the porous medium and flow (permeability and inertial correction tensors) that appear in the macroscale model were computed. From these results, different flow regimes were identified: (1) the weak inertia regime where the inertial correction has a cubic dependence on the filtration velocity and (2) the strong inertia (Forchheimer) regime where the inertial correction depends on the square of the filtration velocity. However, the existence and origin of those regimes, which depend also on the microstructure and flow orientation, are still not well understood in terms of their physical interpretations, as many causes have been conjectured in the literature. In the present study, we provide an in-depth analysis of the flow structure to identify the origin of the deviation from Darcy's law. For accuracy and clarity purposes, this is carried out on two-dimensional structures. Unlike the previous studies reported in the literature, where the origin of inertial effects is often identified on a heuristic basis, a theoretical justification is presented in this work. Indeed, a decomposition of the convective inertial term into two components is carried out formally allowing the
Two-dimensional Quantum Gravity
Rolf, Juri
1998-10-01
This Ph.D. thesis pursues two goals: The study of the geometrical structure of two-dimensional quantum gravity and in particular its fractal nature. To address these questions we review the continuum formalism of quantum gravity with special focus on the scaling properties of the theory. We discuss several concepts of fractal dimensions which characterize the extrinsic and intrinsic geometry of quantum gravity. This work is partly based on work done in collaboration with Jan Ambjørn, Dimitrij Boulatov, Jakob L. Nielsen and Yoshiyuki Watabiki (1997). The other goal is the discussion of the discretization of quantum gravity and to address the so called quantum failure of Regge calculus. We review dynamical triangulations and show that it agrees with the continuum theory in two dimensions. Then we discuss Regge calculus and prove that a continuum limit cannot be taken in a sensible way and that it does not reproduce continuum results. This work is partly based on work done in collaboration with Jan Ambjørn, Jakob L. Nielsen and George Savvidy (1997).
Binding energy of two-dimensional biexcitons
DEFF Research Database (Denmark)
Singh, Jai; Birkedal, Dan; Vadim, Lyssenko
1996-01-01
Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....
Mukhartova, Yulia; Krupenko, Alexandr; Levashova, Natalia; Olchev, Alexandr
2017-04-01
Within the framework of the study a two dimensional hydrodynamic model of turbulent transfer of greenhouse gases was developed and applied for calculating the CO2 and H2O turbulent fluxes within the atmospheric surface layer over the heterogeneous land surface with mosaic vegetation and complex topography. The vegetation cover in the model is represented as the two-phase medium containing the elements of vegetation and the air. The model is based on solving the system of averaged Navier-Stokes and continuity equations for the wind velocity components (⃗V = {V1,V2}), using the 1.5-order closure scheme (Wilcox 1998, Wyngaard 2010). The system of the main equations includes also the diffusion and advection equations for turbulent transfer of sensible heat, CO2 concentration (Cs) and specific humidity (q) at soil - vegetation -atmosphere interface (Sogachev, Panferov 2006, Mukhartova et al. 2015, Mamkin et al. 2016): ( ) { ( )} ∂Vi+ ⃗V,∇ V = -1ṡ-∂-δP -∂- 2δ ¯e- K ṡ ∂Vi-+ ∂Vj- +gṡδTv+F , i,j = 1,2, ∂t i ρ0 ∂xi ∂xj 3 ij ∂xj ∂xi T0 i div⃗V = 0, ∂T ( ) Tv γa ∂T 1 ( ) H ∂t-+ ⃗V ,∇ T+ γaṡT-ṡV2 = div (KT ṡ∇T )+ T-ṡKT ṡ∂x-+ρ-c- ⃗V,∇ δP -ρ-c-, 0 0 2 0 p 0 p ∂Cs- (⃗ ) ∂q- (⃗ ) E- ∂t + V ,∇ Cs = div(KC ṡ∇Cs )+FC, ∂t+ V ,∇ q = div(Kv ṡ∇q )+ ρ , where x1,x2 - horizontal and vertical coordinates respectively, ρ0 - the density of dry air, δP - the deviation of mean air pressure from the hydrostatic distribution, ¯e - the turbulent kinetic energy, T - the temperature of the air, δTv = T ṡ(1+ 0.61q) -T0 - the deviation of virtual temperature from the adiabatic temperature T0(x2) for dry air, Fi - the components of the viscous drag forces induced by the presence of vegetation, K,KT,KC,Kv - turbulent exchange coefficients for momentum, sensible heat, CO2and H2O respectively, γa = g/ cp, cp - the specific heat of the air at constant atmospheric pressure, FC - the sources/sinks of CO2in
Partition function of the two-dimensional nearest neighbour Ising ...
Indian Academy of Sciences (India)
Abstract. The partition function for two-dimensional nearest neighbour Ising model in a non-zero magnetic field have been derived for a finite square lattice of 16, 25, 36 and 64 sites with the help of ...
Flow transitions in two-dimensional foams.
Gilbreth, Christopher; Sullivan, Scott; Dennin, Michael
2006-11-01
For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional foam. Recent work in three-dimensional foam has identified three distinct regimes of flow [S. Rodts, J. C. Baudez, and P. Coussot, Europhys. Lett. 69, 636 (2005)]. Two of these regimes are identified with continuum behavior (full flow and shear banding), and the third regime is identified as a discrete regime exhibiting extreme localization. In this paper, the discrete regime is studied in more detail using a model two-dimensional foam: a bubble raft. We characterize the behavior of the bubble raft subjected to a constant rate of strain as a function of time, system size, and applied rate of strain. We observe localized flow that is consistent with the coexistence of a power-law fluid with rigid-body rotation. As a function of applied rate of strain, there is a transition from a continuum description of the flow to discrete flow when the thickness of the flow region is approximately ten bubbles. This occurs at an applied rotation rate of approximately 0.07 s-1.
Jielile, Jiasharete; Jialili, Ainuer; Sabirhazi, Gulnur; Shawutali, Nuerai; Redati, Darebai; Chen, Jiangtao; Tang, Bin; Bai, Jingping; Aldyarhan, Kayrat
2011-10-01
Postoperative early kinesitherapy has been advocated as an optimal method for treating Achilles tendon rupture. However, an insight into the rationale of how early kinesitherapy contributes to healing of Achilles tendon remains to be achieved, and research in the area of proteomic analysis of Achilles tendon has so far been lacking. Forty-two rabbits were randomized into control group, immobilization group, and early motion group, and received postoperative cast immobilization and early motion treatments. Achilles tendon samples were prepared 21 days following microsurgery, and the proteins were separated with two-dimensional polyacrylamide gel electrophoresis. Differentially expressed proteins were first recognized by PDQuest software, and then identified using peptide mass fingerprinting, tandem mass spectrometry, and database searching. A total of 463 ± 12, 511 ± 39, and 513 ± 80 protein spots were successfully detected in the two-dimensional polyacrylamide gels for the Achilles tendon samples of rabbits in the control group, immobilization group, and early motion group, respectively. There were 15, 8, and 9 unique proteins in these three groups, respectively, and some differentially expressed proteins were also identified in each group. It was indicated that some of the differentially expressed proteins were involved in various metabolism pathways and may play an important role in healing of Achilles tendon rupture. Postoperative early kinesitherapy resulted in differentially expressed proteins in ruptured Achilles tendon compared with those treated with postoperative cast immobilization. These differentially expressed proteins may contribute to healing of Achilles tendon rupture through a mechanobiological mechanism due to the application of postoperative early kinesitherapy.
The theory of critical phenomena in two-dimensional systems
International Nuclear Information System (INIS)
Olvera de la C, M.
1981-01-01
An exposition of the theory of critical phenomena in two-dimensional physical systems is presented. The first six chapters deal with the mean field theory of critical phenomena, scale invariance of the thermodynamic functions, Kadanoff's spin block construction, Wilson's renormalization group treatment of critical phenomena in configuration space, and the two-dimensional Ising model on a triangular lattice. The second part of this work is made of four chapters devoted to the application of the ideas expounded in the first part to the discussion of critical phenomena in superfluid films, two-dimensional crystals and the two-dimensional XY model of magnetic systems. Chapters seven to ten are devoted to the following subjects: analysis of long range order in one, two, and three-dimensional physical systems. Topological defects in the XY model, in superfluid films and in two-dimensional crystals. The Thouless-Kosterlitz iterated mean field theory of the dipole gas. The renormalization group treatment of the XY model, superfluid films and two-dimensional crystal. (author)
Modified black holes in two dimensional gravity
International Nuclear Information System (INIS)
Mohammedi, N.
1991-11-01
The SL(2,R)/U(1) gauged WZWN model is modified by a topological term and the accompanying change in the geometry of the two dimensional target space is determined. The possibility of this additional term arises from a symmetry in the general formalism of gauging an isometry subgroup of a non-linear sigma model with an antisymmetric tensor. It is shown, in particular, that the space-time exhibits some general singularities for which the recently found black hole is just a special case. From a conformal field theory point of view and for special values of the unitary representation of SL(2,R), this topological term can be interpreted as a small perturbation by a (1,1) conformal operator of the gauged WZWN action. (author). 26 refs
Structures of two-dimensional three-body systems
International Nuclear Information System (INIS)
Ruan, W.Y.; Liu, Y.Y.; Bao, C.G.
1996-01-01
Features of the structure of L = 0 states of a two-dimensional three-body model system have been investigated. Three types of permutation symmetry of the spatial part, namely symmetric, antisymmetric, and mixed, have been considered. A comparison has been made between the two-dimensional system and the corresponding three-dimensional one. The effect of symmetry on microscopic structures is emphasized. (author)
Energy Technology Data Exchange (ETDEWEB)
Chang, Jiwon [SEMATECH, 257 Fuller Rd #2200, Albany, New York 12203 (United States)
2015-06-07
Ballistic transport characteristics of metal-oxide semiconductor field effect transistors (MOSFETs) based on anisotropic two-dimensional materials monolayer HfS{sub 2} and phosphorene are explored through quantum transport simulations. We focus on the effects of the channel crystal orientation and the channel length scaling on device performances. Especially, the role of degenerate conduction band (CB) valleys in monolayer HfS{sub 2} is comprehensively analyzed. Benchmarking monolayer HfS{sub 2} with phosphorene MOSFETs, we predict that the effect of channel orientation on device performances is much weaker in monolayer HfS{sub 2} than in phosphorene due to the degenerate CB valleys of monolayer HfS{sub 2}. Our simulations also reveal that at 10 nm channel length scale, phosphorene MOSFETs outperform monolayer HfS{sub 2} MOSFETs in terms of the on-state current. However, it is observed that monolayer HfS{sub 2} MOSFETs may offer comparable, but a little bit degraded, device performances as compared with phosphorene MOSFETs at 5 nm channel length.
Miyamoto, Yoshiyuki; Zhang, Hong; Cheng, Xinlu; Rubio, Angel
2017-09-01
We use time-dependent density functional theory to study laser-pulse induced decomposition of H2O molecules above the two-dimensional (2D) materials graphene, hexagonal boron nitride, and graphitic carbon nitride. We examine femtosecond-laser pulses with a full width at half maximum of 10 or 20 fs for laser-field intensity and wavelengths of 800 or 400 nm by varying the intensity of the laser field from 5 to 9 V/Å, with the corresponding range of fluence per pulse up to 10.7 J /cm2 . For a H2O molecule above the graphitic sheets, the threshold for laser-field H2O decomposition is reduced by more than 20% compared with that of an isolated H2O molecule. We also show that hole doping enhances the water adsorption energy above graphene. The present results indicate that the graphitic materials should support laser-induced chemistry and that other 2D materials that can enhance laser-induced H2O decomposition should be investigated.
Le Texier, H.; Solomon, S.; Thomas, R. J.; Garcia, R. R.
1989-01-01
Seasonal variations of the OH-asterisk (7-5) mesospheric hydroxyl emission at 1.89 microns observed by the SME near-IR spectrometer are compared with the theoretical predictions of a two-dimensional dynamical/chemical model. The good agreement found at low latitudes for both dayglow and nightglow provides support for the model assumption that breaking gravity waves induce seasonal and latitudinal variations in diffusion. The seasonal behavior of atomic hydrogen in the upper mesosphere (related to vertical transport) and/or uncertainties in the OH Meinel band parameters are proposed as possible explanations for the discrepancy noted between model and observational data for the middle latitudes.
Ward identities in two-dimensional gravity
International Nuclear Information System (INIS)
Polchinski, J.
1991-01-01
We study the decoupling of null states in two-dimensional gravity, using methods of critical string theory. We identify a family of null states which fail to decouple due to curvature and boundary terms. This gives relations involving amplitudes at different genus. At genus zero, these determine certain operator product coefficients. At genus one, they determine the partition function. At higher genus, we obtain a relation similar in form to the Painleve equation, but due to an incomplete understanding of a certain ghost/curvature term we do not have a closed relation for the partition function. Our results appear to correspond to the L 0 and L 1 equations in the topological and matrix model approaches. (orig.)
Topology optimization of two-dimensional waveguides
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard; Sigmund, Ole
2003-01-01
In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....
Parchevsky, V. M.; Guryanova, V. V.
2017-01-01
A computational and experimental procedure for construction of the two-dimensional separation curve (TDSC) for a horizontal steam generator (SG) at a nuclear power station (NPS) with VVER-reactors. In contrast to the conventional one-dimensional curve describing the wetness of saturated steam generated in SG as a function of the boiler water level at one, usually rated, load, TDSC is a function of two variables, which are the level and the load of SGB that enables TDSC to be used for wetness control in a wide load range. The procedure is based on two types of experimental data obtained during rated load operation: the nonuniformity factor of the steam load at the outlet from the submerged perforated sheet (SPS) and the dependence of the mass water level in the vicinity of the "hot" header on the water level the "cold" end of SG. The TDSC prediction procedure is presented in the form of an algorithm using SG characteristics, such as steam load and water level as the input and giving the calculated steam wetness at the output. The zoneby-zone calculation method is used. The result is presented in an analytical form (as an empirical correlation) suitable for uploading into controllers or other controls. The predicted TDSC can be used during real-time operation for implementation of different wetness control scenarios (for example, if the effectiveness is a priority, then the minimum water level, minimum wetness, and maximum turbine efficiency should be maintained; if safety is a priority, then the maximum level at the allowable wetness and the maximum water inventory should be kept), for operation of NPS in controlling the frequency and power in a power system, at the design phase (as a part of the simulation complex for verification of design solutions), during construction and erection (in developing software for personnel training simulators), during commissioning tests (to reduce the duration and labor-intensity of experimental activities), and for training.
Two-dimensional multifractal cross-correlation analysis
International Nuclear Information System (INIS)
Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong
2017-01-01
Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.
International Nuclear Information System (INIS)
Brard, D.
1982-11-01
In the aim of studying the climatic variations related to the reversal of the geomagnetic field, an analysis has been made of the effects of precipitations of galactic and solar protons, on oxide of nitrogen (NOsub(x) and NO) and ozone. Modifications are introduced into the one- and two-dimensional models which take into account the structure of the magnetic field. In situ measurements after the solar event of August 1972 enable changes due to the solar cycles to be introduced and the use of a 2D model to be justified [fr
Two-dimensional signal analysis
Garello, René
2010-01-01
This title sets out to show that 2-D signal analysis has its own role to play alongside signal processing and image processing.Concentrating its coverage on those 2-D signals coming from physical sensors (such as radars and sonars), the discussion explores a 2-D spectral approach but develops the modeling of 2-D signals and proposes several data-oriented analysis techniques for dealing with them. Coverage is also given to potential future developments in this area.
Two-dimensional topological photonic systems
Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng
2017-09-01
The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.
Energy Technology Data Exchange (ETDEWEB)
Girometti, Rossano; Zanotel, Martina; Londero, Viviana; Bazzocchi, Massimo; Zuiani, Chiara [University of Udine, Azienda Ospedaliero-Universitaria, ' S. Maria della Misericordia' , Institute of Diagnostic Radiology, Department of Medical and Biological Sciences, Udine (Italy)
2017-09-15
To evaluate the agreement between automated breast volume scanner (ABVS) and conventional ultrasound (US) as a second-look (SL) tool for assessing additional findings found on MRI. Over a 7-month period, we prospectively assigned to SL-US and SL-ABVS all patients undergoing 1.5 T breast MRI in whom additional findings were found. Five experienced breast radiologists independently interpreted SL-US and SL-ABVS in blinded sessions to evaluate the detection rate of MRI findings and assign them to BI-RADS categories. We calculated the agreement between the two methods in assessing MRI findings as significant (BI-RADS 3-5) versus not significant (BI-RADS 1-2), as well as their cancer detection rate. In a population of 131 patients, SL-ABVS and SL-US showed a comparable detection rate of MRI findings (69.3 vs. 71.5%) (p > 0.05; McNemar test), with an almost perfect agreement in assessing them as significant or not (k = 0.94). This translated into a comparably high cancer detection rate (83.8% for SL-ABVS vs. 87.0% for SL-US). Only 1/31 cancers was missed by SL-ABVS. SL-ABVS and SL-US are nearly equivalent in assessing the significance of MRI findings, leading to a comparable cancer detection rate. SL-ABVS has the potential to replace SL-US in the SL scenario. (orig.)
Development of Two-Dimensional NMR
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 11. Development of Two-Dimensional NMR: Strucure Determination of Biomolecules in Solution. Anil Kumar. General Article Volume 20 Issue 11 November 2015 pp 995-1002 ...
Conoscopic holography: two-dimensional numerical reconstructions.
Mugnier, L M; Sirat, G Y; Charlot, D
1993-01-01
Conoscopic holography is an incoherent light holographic technique based on the properties of crystal optics. We present experimental results of the numerical reconstruction of a two-dimensional object from its conoscopic hologram.
Stress distribution in two-dimensional silos
Blanco-Rodríguez, Rodolfo; Pérez-Ángel, Gabriel
2018-01-01
Simulations of a polydispersed two-dimensional silo were performed using molecular dynamics, with different numbers of grains reaching up to 64 000, verifying numerically the model derived by Janssen and also the main assumption that the walls carry part of the weight due to the static friction between grains with themselves and those with the silo's walls. We vary the friction coefficient, the radii dispersity, the silo width, and the size of grains. We find that the Janssen's model becomes less relevant as the the silo width increases since the behavior of the stresses becomes more hydrostatic. Likewise, we get the normal and tangential stress distribution on the walls evidencing the existence of points of maximum stress. We also obtained the stress matrix with which we observe zones of concentration of load, located always at a height around two thirds of the granular columns. Finally, we observe that the size of the grains affects the distribution of stresses, increasing the weight on the bottom and reducing the normal stress on the walls, as the grains are made smaller (for the same total mass of the granulate), giving again a more hydrostatic and therefore less Janssen-type behavior for the weight of the column.
Two-dimensional bipolar junction transistors
Gharekhanlou, Behnaz; Khorasani, Sina; Sarvari, Reza
2014-03-01
Recent development in fabrication technology of planar two-dimensional (2D) materials has introduced the possibility of numerous novel applications. Our recent analysis has revealed that by definition of p-n junctions through appropriate patterned doping of 2D semiconductors, ideal exponential I-V characteristics may be expected. However, the theory of 2D junctions turns out to be very different to that of standard bulk junctions. Based on this theory of 2D diodes, we construct for the first time a model to describe 2D bipolar junction transistors (2D-BJTs). We derive the small-signal equivalent model, and estimate the performance of a 2D-BJT device based on graphone as the example material. A current gain of about 138 and maximum threshold frequency of 77 GHz, together with a power-delay product of only 4 fJ per 1 μm lateral width is expected at an operating voltage of 5 V. In addition, we derive the necessary formulae and a new approximate solution for the continuity equation in the 2D configuration, which have been verified against numerical solutions.
Hobley, Daniel E. J.; Adams, Jordan M.; Nudurupati, Sai Siddhartha; Hutton, Eric W. H.; Gasparini, Nicole M.; Istanbulluoglu, Erkan; Tucker, Gregory E.
2017-01-01
The ability to model surface processes and to couple them to both subsurface and atmospheric regimes has proven invaluable to research in the Earth and planetary sciences. However, creating a new model typically demands a very large investment of time, and modifying an existing model to address a new problem typically means the new work is constrained to its detriment by model adaptations for a different problem. Landlab is an open-source software framework explicitly designed to accelerate the development of new process models by providing (1) a set of tools and existing grid structures - including both regular and irregular grids - to make it faster and easier to develop new process components, or numerical implementations of physical processes; (2) a suite of stable, modular, and interoperable process components that can be combined to create an integrated model; and (3) a set of tools for data input, output, manipulation, and visualization. A set of example models built with these components is also provided. Landlab's structure makes it ideal not only for fully developed modelling applications but also for model prototyping and classroom use. Because of its modular nature, it can also act as a platform for model intercomparison and epistemic uncertainty and sensitivity analyses. Landlab exposes a standardized model interoperability interface, and is able to couple to third-party models and software. Landlab also offers tools to allow the creation of cellular automata, and allows native coupling of such models to more traditional continuous differential equation-based modules. We illustrate the principles of component coupling in Landlab using a model of landform evolution, a cellular ecohydrologic model, and a flood-wave routing model.
A nonperturbative treatment of two-dimensional quantum gravity
International Nuclear Information System (INIS)
Gross, D.J.; Migdal, A.A.
1990-01-01
We propose a nonperturbative definition of two-dimensional quantum gravity, based on a double scaling limit of the random matrix model. We develop an operator formalism for utilizing the method of orthogonal polynomials that allows us to solve the matrix models to all orders in the genus expansion. Using this formalism we derive an exact differential equation for the partition function of two-dimensional gravity as a function of the string coupling constant that governs the genus expansion of two-dimensional surfaces, and discuss its properties and consequences. We construct and discuss the correlation functions of an infinite set of pointlike and loop operators to all orders in the genus expansion. (orig.)
Ye, Swe Soe; Ng, Yan Cheng; Tan, Justin; Leo, Hwa Liang; Kim, Sangho
2014-05-13
Computational modeling of Red Blood Cell (RBC) flow contributes to the fundamental understanding of microhemodynamics and microcirculation. In order to construct theoretical RBC models, experimental studies on single RBC mechanics have presented a material description for RBC membranes based on their membrane shear, bending and area moduli. These properties have been directly employed in 3D continuum models of RBCs but practical flow analysis with 3D models have been limited by their computationally expensive nature. As such, various researchers have employed 2D models to efficiently and qualitatively study microvessel flows. Currently, the representation of RBC dynamics using 2D models is a limited methodology that breaks down at high shear rates due to excessive and unrealistic stretching. We propose a localized scaling of the 2D elastic moduli such that it increases with RBC local membrane strain, thereby accounting for effects such as the Poisson effect and membrane local area incompressibility lost in the 2D simplification. Validation of our 2D Large Deformation (2D-LD) RBC model was achieved by comparing the predicted RBC deformation against the 3D model from literature for the case of a single RBC in simple shear flow under various shear rates (dimensionless shear rate G = 0.05, 0.1, 0.2, 0.5). The multi-cell flow of RBCs (38% Hematocrit) in a 20 μm width microchannel under varying shear rates (50, 150, 150 s-1) was then simulated with our proposed model and the popularly-employed 2D neo-Hookean model in order to evaluate the efficacy of our proposed 2D-LD model. The validation set indicated similar RBC deformation for both the 2D-LD and the 3D models across the studied shear rates, highlighting the robustness of our model. The multi-cell simulation indicated that the 2D neo-Hookean model predicts noodle-like RBC shapes at high shear rates (G = 0.5) whereas our 2D-LD model maintains sensible RBC deformations. The ability of the 2D-LD model to
Energy Technology Data Exchange (ETDEWEB)
Chang, Semyong [Kunsan National Univ., Gunsan (Korea, Republic of); Kim, Hyoung Tae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-05-15
To limit the subcooling for the avoidance of dryout condition in a CANDU reactor, a suitable experiment should be proposed such as Ref. In this study, we simulated this experiment in 2-D with COMSOL Multi physics. A benchmark experiment model based on the Calandria moderator system of the CANDU reactor has been reduced to an ideal concentric 2-D computational model. A plastic deformation model is introduced, based on the creeping model in CATHENA code. The result shows a sudden inflation and contact of PT and CT in a very short time of milliseconds.
Rosas-Carbajal, M.; Linde, N.; Kalscheuer, T.; Vrugt, J.A.
2014-01-01
Probabilistic inversion methods based on Markov chain Monte Carlo (MCMC) simulation are well suited to quantify parameter and model uncertainty of nonlinear inverse problems. Yet, application of such methods to CPU-intensive forward models can be a daunting task, particularly if the parameter space
Energy Technology Data Exchange (ETDEWEB)
Bessenasse, M. [Universite SAAD Dahleb (Blida), Lab. de Recherche des Sciences de l' Eau LRS EAU ENP, Alger (Algeria); Kettab, A. [Ecole Nationale Polytechnique, LRS-EAU, Alger (Algeria); Paquier, A. [Cemagref de Lyon, Unite de Recherche Hydrologie-Hydraulique, 69 (France)
2004-07-01
The method to build a numerical model intended to predict the formation and the change of sediment deposits upstream from a dam is presented. From information about the inputs of water and sediments coming from the catchment supported by a QdF type hydrological analysis, a horizontal 2-D hydraulic model which couples shallow water equations and one equation for advection and diffusion of sediment concentration is used. Applying this model to Zardezas reservoir in Skikda (Algeria) region shows, on the one hand, the practical difficulties met on such case and, on the other hand, the potentialities of such a method for the management of Algerian reservoirs. (authors)
International Nuclear Information System (INIS)
Mao Wei; She Wei-Bo; Zhang Chao; Zhang Jin-Cheng; Zhang Jin-Feng; Liu Hong-Xia; Yang Lin-An; Zhang Kai; Zhao Sheng-Lei; Chen Yong-He; Zheng Xue-Feng; Hao Yue; Yang Cui; Ma Xiao-Hua
2014-01-01
In this paper, we present a two-dimensional (2D) fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor (FP-HEMT) on the basis of 2D Poisson's solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, AlGaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco—Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Hamiltonian formalism of two-dimensional Vlasov kinetic equation.
Pavlov, Maxim V
2014-12-08
In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.
Control Operator for the Two-Dimensional Energized Wave Equation
Directory of Open Access Journals (Sweden)
Sunday Augustus REJU
2006-07-01
Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.
Agatz, Annika; Brown, Colin D
2017-05-15
Mathematical models of pesticide fate and behaviour in soils have been developed over the last 30years. Most models simulate fate of pesticides in a 1-dimensional system successfully, supporting a range of applications where the prediction target is either bulk residues in soil or receiving compartments outside of the soil zone. Nevertheless, it has been argued that the 1-dimensional approach is limiting the application of knowledge on pesticide fate under specific pesticide placement strategies, such as seed, furrow and band applications to control pests and weeds. We report a new model (2-DROPS; 2-Dimensional ROots and Pesticide Simulation) parameterised for maize and we present simulations investigating the impact of pesticide properties (thiamethoxam, chlorpyrifos, clothianidin and tefluthrin), pesticide placement strategies (seed treatment, furrow, band and broadcast applications), and soil properties (two silty clay loam and two loam top soils with either silty clay loam, silt loam, sandy loam or unconsolidated bedrock in the lower horizons) on microscale pesticide distribution in the soil profile. 2-DROPS is to our knowledge the first model that simulates temporally- and spatially-explicit water and pesticide transport in the soil profile under the influence of explicit and stochastic development of root segments. This allows the model to describe microscale movement of pesticide in relation to root segments, and constitutes an important addition relative to existing models. The example runs demonstrate that the pesticide moves locally towards root segments due to water extraction for plant transpiration, that the water holding capacity of the top soil determines pesticide transport towards the soil surface in response to soil evaporation, and that the soil type influences the pesticide distribution zone in all directions. 2-DROPS offers more detailed information on microscale root and pesticide appearance compared to existing models and provides the
Critical Behaviour of a Two-Dimensional Random Antiferromagnet
DEFF Research Database (Denmark)
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1976-01-01
A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphous...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....
Two dimensional nonlinear spectral estimation techniques for breast cancer localization
International Nuclear Information System (INIS)
Stathaki, P.T.; Constantinides, A.G.
1994-01-01
In this paper the problem of image texture analysis in the presence of noise is examined from a higher-order statistical perspective. The approach taken involves the use of two dimensional second order Volterra filters where the filter weights are derived from third order cumulants of the two dimensional signal. The specific application contained in this contribution is in mammography, an area in which it is difficult to discern the appropriate features. The paper describes the fundamental issues of the various components of the approach. The results of the entire texture modelling, classification and segmentation scheme contained in this paper are very encouraging
Directory of Open Access Journals (Sweden)
Woochul Nam
Full Text Available Kinesins are molecular motors which walk along microtubules by moving their heads to different binding sites. The motion of kinesin is realized by a conformational change in the structure of the kinesin molecule and by a diffusion of one of its two heads. In this study, a novel model is developed to account for the 2D diffusion of kinesin heads to several neighboring binding sites (near the surface of microtubules. To determine the direction of the next step of a kinesin molecule, this model considers the extension in the neck linkers of kinesin and the dynamic behavior of the coiled-coil structure of the kinesin neck. Also, the mechanical interference between kinesins and obstacles anchored on the microtubules is characterized. The model predicts that both the kinesin velocity and run length (i.e., the walking distance before detaching from the microtubule are reduced by static obstacles. The run length is decreased more significantly by static obstacles than the velocity. Moreover, our model is able to predict the motion of kinesin when other (several motors also move along the same microtubule. Furthermore, it suggests that the effect of mechanical interaction/interference between motors is much weaker than the effect of static obstacles. Our newly developed model can be used to address unanswered questions regarding degraded transport caused by the presence of excessive tau proteins on microtubules.
Tropin, D. A.; Fedorov, A. V.; Fomin, P. A.
2017-10-01
The paper deals with the problem of the 1D and 2D structures of detonation waves (DW) in the silane-air mixture within the framework of mathematical model of a nonequilibrium gas dynamics. Detailed kinetics scheme of silane oxidation as well as the newly developed reduced kinetic model of detonation combustion of silane are used. On its basis the DW structure in stoichiometric silane - air mixture and dependences of Chapman-Jouguet parameters of mixture on stoichiometric ratio between the fuel (silane) and an oxidizer (air) were obtained. It was revealed that in the reaction zone, in the structure of DW, the heat release in the model with detailed kinetics is non-monotonic.
International Nuclear Information System (INIS)
Luescher, M.; Pohlmeyer, K.
1977-09-01
Finite energy solutions of the field equations of the non-linear sigma-model are shown to decay asymptotically into massless lumps. By means of a linear eigenvalue problem connected with the field equations we then find an infinite set of dynamical conserved charges. They, however, do not provide sufficient information to decode the complicated scattering of lumps. (orig.) [de
International Nuclear Information System (INIS)
Luescher, M.
1977-12-01
Conserved non-local charges are shown to exist in the quantum non-linear sigma-model by a non-perturbative method. They imply the absence of particle production and the 'factorization equations' for the two particle S-matrix, which can then be calculated explicitly. (Auth.)
Yaghini, N.; Iedema, P.D.
2015-01-01
A full extensive 2-dimensional (2D) model of low-density Polyethylene chain length/branching distribution is provided in this paper. 2D Population Balance Equations are solved by the Galerkinfinite element method to obtain the distributions, accounting for 2D 'topological scission'; a manner to
Dirac cones in two-dimensional borane
Martinez-Canales, Miguel; Galeev, Timur R.; Boldyrev, Alexander I.; Pickard, Chris J.
2017-11-01
We introduce two-dimensional borane, a single-layered material of BH stoichiometry, with promising electronic properties. We show that, according to density functional theory calculations, two-dimensional borane is semimetallic, with two symmetry-related Dirac cones meeting right at the Fermi energy Ef. The curvature of the cones is lower than in graphene, thus closer to the ideal linear dispersion. Its structure, formed by a puckered trigonal boron network with hydrogen atoms connected to each boron atom, can be understood as distorted, hydrogenated borophene [Mannix et al., Science 350, 1513 (2015), 10.1126/science.aad1080]. Chemical bonding analysis reveals the boron layer in the network being bound by delocalized four-center two-electron σ bonds. Finally, we suggest high pressure could be a feasible route to synthesize two-dimensional borane.
Spagnol, S.; Wolanski, E.; Deleersnijder, E.; Brinkman, R.; McAllister, F.; Cushman-Roisin, B.; Hanert, E.
2002-01-01
The flushing time of reef lagoons estimated over recent years by 2-dimensional Lagrangian algorithms may have been significantly overestimated. This is due to a numerical artefact, leading to spurious accumulation of particles in regions where the water depth or the diffusivity is smallest. The nature of this numerical problem has remained largely unknown in the coral reef modelling community, although it was described, along with an efficient remedy, in several studies which are about a deca...
International Nuclear Information System (INIS)
Manousakis, E.; Salvador, R.
1989-01-01
We study the spin-1/2 quantum ferromagnetic and antiferromagnetic Heisenberg model using Handscomb's Monte Carlo (MC) method on square lattices of various sizes. As the temperature is lowered the calculated correlation length in the antiferromagnetic case grows more rapidly than in the ferromagnetic case. We also obtain the correlation length in the leading order of the high-temperature series expansion which, at high temperatures, agrees very well with the MC results. The correlation length obtained from the MC calculation for the ferromagnetic and antiferromagnetic case is compared with existing theories. Taking the average value for the antiferromagnetic coupling between the values suggested by neutron- and Raman-scattering experiments done on La 2 CuO 4 , we compare our results for the correlation length with those observed by the neutron-scattering experiments. We find that our results for the correlation lengths away from the three-dimensional (3D) Neel temperature T/sub N/∼200 K are consistent with the experimental findings. In order to obtain agreement close to the Neel temperature, however, we need to introduce an interlayer coupling between the CuO 2 planes. The effect on a 3D coupling is only discussed in the framework of the quantum mechanical nonlinear σ model in three space dimensions. For the case of La 2 CuO 4 we find that close to T/sub N/ the σ model in 3+1 dimensions reduces to the classical 3D Heisenberg model whose critical properties are known and fit the neutron-scattering data for T∼T/sub N/
1986-08-01
project operation, limnology , and aquatic biology. Decisions made throughout a model application may require knowledge in these areas. Within Part...1974 Asterionella formosa 0.4 Margalef 1961 Bacteriastrum hyalinum 0.39-1.27 Smayda and Boleyn 1966 Chaetoceros didymus 0.85 Eppley, Holmes, and...Strickland 1967b --. Chaetoceros lauderi 0.46-1.54 Smayda and Boleyn 1966 Chaetoceros spp. 0.25 Margalef 1961 Chaetoceros spp. 4.0 Allen 1932 Coscinodiscus
Two-dimensional x-ray diffraction
He, Bob B
2009-01-01
Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea
Two-dimensional hazard estimation for longevity analysis
DEFF Research Database (Denmark)
Fledelius, Peter; Guillen, M.; Nielsen, J.P.
2004-01-01
We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface i...... for analysis of economic implications arising from mortality changes....
Seismically constrained two-dimensional crustal thermal structure of ...
Indian Academy of Sciences (India)
The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to ...
A very useful experiment of two dimensional po- tential mapping ...
Indian Academy of Sciences (India)
A very useful experiment of two dimensional po- tential mapping, namely electrolytic tank model, for graduate and post graduate level physics stu- dents is given here. Laplace's equation is solved for the above and the results are compared with the experiment. The agreement· is so good that this is extended to complex ...
Trobo, Marta L; Albano, Ezequiel V; Binder, Kurt
2014-08-01
We present a study of the critical behavior of the Blume-Capel model with three spin states (S=±1,0) confined between parallel walls separated by a distance L where competitive surface magnetic fields act. By properly choosing the crystal field (D), which regulates the density of nonmagnetic species (S=0), such that those impurities are excluded from the bulk (where D=-∞) except in the middle of the sample [where D(M)(L/2)≠-∞], we are able to control the presence of a defect line in the middle of the sample and study its influence on the interface between domains of different spin orientations. So essentially we study an Ising model with a defect line but, unlike previous work where defect lines in Ising models were defined via weakened bonds, in the present case the defect line is due to mobile vacancies and hence involves additional entropy. In this way, by drawing phase diagrams, i.e., plots of the wetting critical temperature (T(w)) versus the magnitude of the crystal field at the middle of the sample (D(M)), we observe curves of (first-) second-order wetting transitions for (small) high values of D(M). Theses lines meet in tricritical wetting points, i.e., (T(w)(tc),D(M)(tc)), which also depend on the magnitude of the surface magnetic fields. It is found that second-order wetting transitions satisfy the scaling theory for short-range interactions, while first-order ones do not exhibit hysteresis, provided that small samples are used, since fluctuations wash out hysteretic effects. Since hysteresis is observed in large samples, we performed extensive thermodynamic integrations in order to accurately locate the first-order transition points, and a rather good agreement is found by comparing such results with those obtained just by observing the jump of the order parameter in small samples.
International Nuclear Information System (INIS)
1983-04-01
VISCOT is a non-linear, transient, thermal-stress finite-element code designed to determine the viscoelastic, fiscoplastic, or elastoplastic deformation of a rock mass due to mechanical and thermal loading. The numerical solution of the nonlinear incremental equilibrium equations within VISCOT is performed by using an explicit Euler time-stepping scheme. The rock mass may be modeled as a viscoplastic or viscoelastic material. The viscoplastic material model can be described by a Tresca, von Mises, Drucker-Prager or Mohr-Coulomb yield criteria (with or without strain hardening) with an associated flow rule which can be a power or an exponential law. The viscoelastic material model within VISCOT is a temperature- and stress-dependent law which has been developed specifically for salt rock masses by Pfeifle, Mellegard and Senseny in ONWI-314 topical report (1981). Site specific parameters for this creep law at the Richton, Permian, Paradox and Vacherie salt sites have been calculated and are given in ONWI-314 topical report (1981). A major application of VISCOT (in conjunction with a SCEPTER heat transfer code such as DOT) is the thermomechanical analysis of a rock mass such as salt in which significant time-dependent nonlinear deformations are expected to occur. Such problems include room- and canister-scale studies during the excavation, operation, and long-term post-closure stages in a salt repository. In Section 1.5 of this document the code custodianship and control is described along with the status of verification, validation and peer review of this report
Llovel, W.; Cazenave, A.; Rogel, P.; Lombard, A.; Nguyen, M. B.
2009-01-01
ISI Document Delivery No.: 464XM Times Cited: 19 Cited Reference Count: 32 Cited References: Alvera-Azcarate A, 2005, OCEAN MODEL, V9, P325, DOI 10.1016/j.ocemod.2004.08.001 Berge-Nguyen M, 2008, GLOBAL PLANET CHANGE, V62, P1, DOI 10.1016/j.gloplacha.2007.11.007 Bindoff NL, 2007, CLIMATE CHANGE 2007: THE PHYSICAL SCIENCE BASIS, P385 Cabanes C, 2001, SCIENCE, V294, P840, DOI 10.1126/science.1063556 CAZENAVE A, 2004, REV GEOPHYS, V42, DOI DOI 10.1029/2003RG000139 Chambers DP, 2002, PHYS CHEM EA...
Dynamics of two-dimensional bubbles
Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón
2015-06-01
The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.
Mamin, R. F.; Shaposhnikova, T. S.; Kabanov, V. V.
2018-03-01
We have considered the model of the phase transition of the second order for the Coulomb frustrated 2D charged system. The coupling of the order parameter with the charge was considered as the local temperature. We have found that in such a system, an appearance of the phase-separated state is possible. By numerical simulation, we have obtained different types ("stripes," "rings," "snakes") of phase-separated states and determined the parameter ranges for these states. Thus the system undergoes a series of phase transitions when the temperature decreases. First, the system moves from the homogeneous state with a zero order parameter to the phase-separated state with two phases in one of which the order parameter is zero and, in the other, it is nonzero (τ >0 ). Then a first-order transition occurs to another phase-separated state, in which both phases have different and nonzero values of the order parameter (for τ <0 ). Only a further decrease of temperature leads to a transition to a homogeneous ordered state.
Directory of Open Access Journals (Sweden)
Vanderley de Vasconcelos
1997-12-01
Full Text Available Na formação de aglomerados, partículas pequenas tendem a se agregar, reduzindo a energia livre total do sistema. Mesmo quando as partículas primárias têm forma esférica e tamanhos uniformes, dependendo do tipo do processamento e das forças envolvidas, os aglomerados podem apresentar orientações preferenciais de partículas. Este trabalho utiliza técnica de processamento digital de imagens para a obtenção das distribuições de orientação de partículas em aglomerados bidimensionais simulados. As simulações foram realizadas em um ambiente de computação gráfica com recursos de modelagem de sólidos. A escolha de modelos bidimensionais para representar casos tridimensionais é um artifício muito empregado para reduzir os altos tempos de processamento computacional envolvidos no estudo de processos complexos.Apesar de simples, em príncipio, muitas conclusões importante podem ser extraídas dos modelos bidimensionais e muitos de seus resultados aplicados diretamente aos casos reais.In the formation of agglomerates, small particles tend to aggregate in order to reduce the total free energy of the system. Even when the individual particles can be treated as spheres of uniform size, depending on the process and involved forces the agglomerates can show some kind of particle orientation. This paper uses digital image processing techniques for obtaining particle orientation distribution of two-dimensional simulated agglomerates. These simulations were carried out using a computer graphics environment with solid modeling extension. The use of two-dimensional models instead of three-dimensional ones is an alternative to reduce the long computacional times involved in the analysis of complex real systems. Despite being simple, in principle, very important information can be obtained from two-dimensional systems and directly applied to real three-dimensional cases.
Dipolar vortices in two-dimensional flows
DEFF Research Database (Denmark)
Juul Rasmussen, J.; Hesthaven, J.S.; Lynov, Jens-Peter
1996-01-01
The dynamics of dipolar vortex solutions to the two-dimensional Euler equations is studied. A new type of nonlinear dipole is found and its dynamics in a slightly viscous system is compared with the dynamics of the Lamb dipole. The evolution of dipolar structures from an initial turbulent patch...
Analytical simulation of two dimensional advection dispersion ...
African Journals Online (AJOL)
The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would migrate ...
Analytical Simulation of Two Dimensional Advection Dispersion ...
African Journals Online (AJOL)
ADOWIE PERE
ABSTRACT: The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would ...
Two-dimensional position sensitive neutron detector
Indian Academy of Sciences (India)
A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons.
Stability of two-dimensional vorticity filaments
International Nuclear Information System (INIS)
Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.
2004-01-01
We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability
Two-dimensional membranes in motion
Davidovikj, D.
2018-01-01
This thesis revolves around nanomechanical membranes made of suspended two - dimensional materials. Chapters 1-3 give an introduction to the field of 2D-based nanomechanical devices together with an overview of the underlying physics and the measurementtools used in subsequent chapters. The research
Piezoelectricity in Two-Dimensional Materials
Wu, Tao
2015-02-25
Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.
Sums of two-dimensional spectral triples
DEFF Research Database (Denmark)
Christensen, Erik; Ivan, Cristina
2007-01-01
We study countable sums of two dimensional modules for the continuous complex functions on a compact metric space and show that it is possible to construct a spectral triple which gives the original metric back. This spectral triple will be finitely summable for any positive parameter. We also co...
A novel two dimensional particle velocity sensor
Pjetri, O.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.
2013-01-01
In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to
Two-dimensional microstrip detector for neutrons
Energy Technology Data Exchange (ETDEWEB)
Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1997-04-01
Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.
CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION
Directory of Open Access Journals (Sweden)
Toth Reka
2010-12-01
Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.
Recombination in one- and two-dimensional fitness landscapes.
Avetisyan, Zh; Saakian, David B
2010-05-01
We consider many-site mutation-recombination models of molecular evolution, where fitness is a function of a Hamming distance from one (one-dimensional case) or two (two-dimensional case) sequences. For the one-dimensional case, we calculate the population distribution dynamics for a model with zero fitness and an arbitrary symmetric initial distribution and find an error threshold transition point in the single-peak fitness model for a given initial symmetric distribution. We calculate the recombination period in the case of a single-peak fitness function, when the original population is located at one sequence, at some Hamming distance from the peak configuration. Steady-state fitness is calculated with finite genome length corrections. We derive analytical equations for the two-dimensional mutation-recombination model.
Two-dimensional ranking of Wikipedia articles
Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.
2010-10-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Two-dimensional confinement of heavy fermions
International Nuclear Information System (INIS)
Shishido, Hiroaki; Shibauchi, Takasada; Matsuda, Yuji; Terashima, Takahito
2010-01-01
Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons is enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Here we report on the first realization of a two-dimensional heavy-fermion system, where the dimensionality is adjusted in a controllable fashion by fabricating heterostructures using molecular beam epitaxy. The two-dimensional heavy fermion system displays striking deviations from the standard Fermi liquid low-temperature electronic properties. (author)
Toward two-dimensional search engines
International Nuclear Information System (INIS)
Ermann, L; Shepelyansky, D L; Chepelianskii, A D
2012-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank–CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed. (paper)
Plasmonics with two-dimensional conductors
Yoon, Hosang; Yeung, Kitty Y. M.; Kim, Philip; Ham, Donhee
2014-01-01
A wealth of effort in photonics has been dedicated to the study and engineering of surface plasmonic waves in the skin of three-dimensional bulk metals, owing largely to their trait of subwavelength confinement. Plasmonic waves in two-dimensional conductors, such as semiconductor heterojunction and graphene, contrast the surface plasmonic waves on bulk metals, as the former emerge at gigahertz to terahertz and infrared frequencies well below the photonics regime and can exhibit far stronger subwavelength confinement. This review elucidates the machinery behind the unique behaviours of the two-dimensional plasmonic waves and discusses how they can be engineered to create ultra-subwavelength plasmonic circuits and metamaterials for infrared and gigahertz to terahertz integrated electronics. PMID:24567472
Two-dimensional Kagome photonic bandgap waveguide
DEFF Research Database (Denmark)
Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou
2000-01-01
The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....
Superintegrability on the two dimensional hyperboloid
International Nuclear Information System (INIS)
Akopyan, E.; Pogosyan, G.S.; Kalnins, E.G.; Miller, W. Jr
1998-01-01
This work is devoted to the investigation of the quantum mechanical systems on the two dimensional hyperboloid which admit separation of variables in at least two coordinate systems. Here we consider two potentials introduced in a paper of C.P.Boyer, E.G.Kalnins and P.Winternitz, which haven't been studied yet. An example of an interbasis expansion is given and the structure of the quadratic algebra generated by the integrals of motion is carried out
Two-dimensional silica opens new perspectives
Büchner, Christin; Heyde, Markus
2017-12-01
In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science
Two-dimensional weak pseudomanifolds on eight vertices
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
whose 2-simplices are abv, acv, bcv, xyv, yzv, xzv and those of M other than τ1 and τ2. Observe that we get P33 from P2 and P39 from T1 by this process. From these definitions one gets the following: PROPOSITION 3.3. Let ˜M be obtained from M by identifying two vertices u and v. (a) If M is a (weak) pseudomanifold, then ...
Duality-invariant class of two-dimensional field theories
Sfetsos, K
1999-01-01
We construct a new class of two-dimensional field theories with target spaces that are finite multiparameter deformations of the usual coset G/H-spaces. They arise naturally, when certain models, related by Poisson-Lie T-duality, develop a local gauge invariance at specific points of their classical moduli space. We show that canonical equivalences in this context can be formulated in loop space in terms of parafermionic-type algebras with a central extension. We find that the corresponding generating functionals are non-polynomial in the derivatives of the fields with respect to the space-like variable. After constructing models with three- and two-dimensional targets, we study renormalization group flows in this context. In the ultraviolet, in some cases, the target space of the theory reduces to a coset space or there is a fixed point where the theory becomes free.
Linear negative magnetoresistance in two-dimensional Lorentz gases
Schluck, J.; Hund, M.; Heckenthaler, T.; Heinzel, T.; Siboni, N. H.; Horbach, J.; Pierz, K.; Schumacher, H. W.; Kazazis, D.; Gennser, U.; Mailly, D.
2018-03-01
Two-dimensional Lorentz gases formed by obstacles in the shape of circles, squares, and retroreflectors are reported to show a pronounced linear negative magnetoresistance at small magnetic fields. For circular obstacles at low number densities, our results agree with the predictions of a model based on classical retroreflection. In extension to the existing theoretical models, we find that the normalized magnetoresistance slope depends on the obstacle shape and increases as the number density of the obstacles is increased. The peaks are furthermore suppressed by in-plane magnetic fields as well as by elevated temperatures. These results suggest that classical retroreflection can form a significant contribution to the magnetoresistivity of two-dimensional Lorentz gases, while contributions from weak localization cannot be excluded, in particular for large obstacle densities.
Topological field theories and two-dimensional instantons
International Nuclear Information System (INIS)
Schaposnik, F.A.
1990-01-01
In this paper, the author discusses some topics related to the recently developed Topological Field Theories (TFTs). The first part is devoted to a discussion on how a TFT can be quantized using techniques which are well-known from the study of gauge theories. Then the author describes the results that we have obtained in collaboration with George Thompson in the study of a two-dimensional TFT related to the Abelian Higgs model
Pseudospectral reduction of incompressible two-dimensional turbulence
Bowman, John C.; Roberts, Malcolm
2012-05-01
Spectral reduction was originally formulated entirely in the wavenumber domain as a coarse-grained wavenumber convolution in which bins of modes interact with enhanced coupling coefficients. A Liouville theorem leads to inviscid equipartition solutions when each bin contains the same number of modes. A pseudospectral implementation of spectral reduction which enjoys the efficiency of the fast Fourier transform is described. The model compares well with full pseudospectral simulations of the two-dimensional forced-dissipative energy and enstrophy cascades.
Stability theory for a two-dimensional channel
Troshkin, O. V.
2017-08-01
A scheme for deriving conditions for the nonlinear stability of an ideal or viscous incompressible steady flow in a two-dimensional channel that is periodic in one direction is described. A lower bound for the main factor ensuring the stability of the Reynolds-Kolmogorov sinusoidal flow with no-slip conditions (short wavelength stability) is improved. A condition for the stability of a vortex strip modeling Richtmyer-Meshkov fluid vortices (long wavelength stability) is presented.
On the Initial Singularity Problem in Two Dimensional Quantum Cosmology
Gamboa, J.
1995-01-01
The problem of how to put interactions in two-dimensional quantum gravity in the strong coupling regime is studied. It shows that the most general interaction consistent with this symmetry is a Liouville term that contain two parameters $(\\alpha, \\beta)$ satisfying the algebraic relation $2\\beta - \\alpha =2$ in order to assure the closure of the diffeomorphism algebra. The model is classically soluble and it contains as general solution the temporal singularity. The theory is quantized and we...
Spontaneous spiral formation in two-dimensional oscillatory media
Kettunen, Petteri; Amemiya, Takashi; Ohmori, Takao; Yamaguchi, Tomohiko
1999-08-01
Computational studies of pattern formation in a modified Oregonator model of the Belousov-Zhabotinsky reaction is described. Initially inactive two-dimensional reaction media with an immobilized catalyst is connected to a reservoir of fresh reactants through a set of discrete points distributed randomly over the interphase surface. It is shown that the diffusion of reactants combined with oscillatory reaction kinetics can give rise to spontaneous spiral formation and phase waves.
Gyroscope with two-dimensional optomechanical mirror
Davuluri, Sankar; Li, Kai; Li, Yong
2017-11-01
We propose an application of two-dimensional optomechanical oscillator as a gyroscope by detecting the Coriolis force which is modulated at the natural frequency of the optomechanical oscillator. Dependence of gyroscope's sensitivity on shot noise, back-action noise, thermal noise, and input laser power is studied. At optimal input laser power, the gyroscope's sensitivity can be improved by increasing the mass or by decreasing the temperature and decay rate of the mechanical oscillator. When the mechanical oscillator's thermal occupation number, n th, is zero, sensitivity improves with decrease in frequency of the mechanical oscillator. For {n}{{th}}\\gg 1, the sensitivity is independent of the mechanical oscillator's frequency.
Versatile two-dimensional transition metal dichalcogenides
DEFF Research Database (Denmark)
Canulescu, Stela; Affannoukoué, Kévin; Döbeli, Max
Two-dimensional transition metal dichalcogenides (2D-TMDCs), such as MoS2, have emerged as a new class of semiconducting materials with distinct optical and electrical properties. The availability of 2D-TMDCs with distinct band gaps allows for unlimited combinations of TMDC monolayers (MLs...... vacancies. We have found that the absorption spectra of the MoS2 films exhibit distinct excitonic peaks at ~1.8 and ~2 eV when grown in the presence of a sulfur evaporation beam as compared to those deposited in vacuum. The structure of the PLD-grown MoS2 films will be further discussed based Raman...
Tuning spin transport across two-dimensional organometallic junctions
Liu, Shuanglong; Wang, Yun-Peng; Li, Xiangguo; Fry, James N.; Cheng, Hai-Ping
2018-01-01
We study via first-principles modeling and simulation two-dimensional spintronic junctions made of metal-organic frameworks consisting of two Mn-phthalocyanine ferromagnetic metal leads and semiconducting Ni-phthalocyanine channels of various lengths. These systems exhibit a large tunneling magnetoresistance ratio; the transmission functions of such junctions can be tuned using gate voltage by three orders of magnitude. We find that the origin of this drastic change lies in the orbital alignment and hybridization between the leads and the center electronic states. With physical insight into the observed on-off phenomenon, we predict a gate-controlled spin current switch based on two-dimensional crystallines and offer general guidelines for designing spin junctions using 2D materials.
Folding two dimensional crystals by swift heavy ion irradiation
International Nuclear Information System (INIS)
Ochedowski, Oliver; Bukowska, Hanna; Freire Soler, Victor M.; Brökers, Lara; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika
2014-01-01
Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS 2 and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS 2 does not
Folding two dimensional crystals by swift heavy ion irradiation
Energy Technology Data Exchange (ETDEWEB)
Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)
2014-12-01
Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.
Wang, Yuzhe; Zhang, Tong; Ren, Jiawen; Qin, Xiang; Liu, Yushuo; Sun, Weijun; Chen, Jizu; Ding, Minghu; Du, Wentao; Qin, Dahe
2018-03-01
By combining in situ measurements and a two-dimensional thermomechanically coupled ice flow model, we investigate the thermomechanical features of the largest valley glacier (Laohugou Glacier No. 12; LHG12) on Qilian Shan located in the arid region of western China. Our model results suggest that LHG12, previously considered as fully cold, is probably polythermal, with a lower temperate ice layer overlain by an upper layer of cold ice over a large region of the ablation area. Modelled ice surface velocities match well with the in situ observations in the east branch (main branch) but clearly underestimate those near the glacier terminus, possibly because the convergent flow is ignored and the basal sliding beneath the confluence area is underestimated. The modelled ice temperatures are in very good agreement with the in situ measurements from a deep borehole (110 m deep) in the upper ablation area. The model results are sensitive to surface thermal boundary conditions, for example surface air temperature and near-surface ice temperature. In this study, we use a Dirichlet surface thermal condition constrained by 20 m borehole temperatures and annual surface air temperatures. Like many other alpine glaciers, strain heating is important in controlling the englacial thermal structure of LHG12. Our transient simulations indicate that the accumulation zone becomes colder during the last two decades as a response to the elevated equilibrium line altitude and the rising summer air temperatures. We suggest that the extent of accumulation basin (the amount of refreezing latent heat from meltwater) of LHG12 has a considerable impact on the englacial thermal status.
Parallel comprehensive two-dimensional gas chromatography.
Yan, DanDan; Tedone, Laura; Koutoulis, Anthony; Whittock, Simon P; Shellie, Robert A
2017-11-17
We introduce an information rich analytical approach called parallel comprehensive two-dimensional gas chromatography (2GC×2GC). This parallel chromatography approach splits injected samples into two independent two-dimensional column ensembles and provides two GC×GC separations by using contra-directional thermal modulation. The first-dimension ( 1 D) and second-dimension ( 2 D) columns are connected using planar three-port microchannel devices, which are supplied with supplementary flow via two pressure controller modules. Precise carrier gas flow control at the junction of the 1 D and 2 D columns permits independent control of flow conditions in each separation column. The 2GC×2GC approach provides two entirely independent GC×GC separations for each injection. Analysis of hop (Humulus lupulus L.) essential oils is used to demonstrate the capability of the approach. The analytical performance of each GC×GC separation in the 2GC×2GC experiment is comparable to individual GC×GC separation with matching column configurations. The peak capacity of 2GC×2GC is about 2 times than that of single GC×GC system. The dual 2D chromatograms produced by this single detector system provide complementary separations and additional identification information by harnessing different selectivity provided by the four separation columns. Copyright © 2017 Elsevier B.V. All rights reserved.
Two-dimensional Lagrangian simulation of suspended sediment
Schoellhamer, David H.
1988-01-01
A two-dimensional laterally averaged model for suspended sediment transport in steady gradually varied flow that is based on the Lagrangian reference frame is presented. The layered Lagrangian transport model (LLTM) for suspended sediment performs laterally averaged concentration. The elevations of nearly horizontal streamlines and the simulation time step are selected to optimize model stability and efficiency. The computational elements are parcels of water that are moved along the streamlines in the Lagrangian sense and are mixed with neighboring parcels. Three applications show that the LLTM can accurately simulate theoretical and empirical nonequilibrium suspended sediment distributions and slug injections of suspended sediment in a laboratory flume.
Two dimensional NMR studies of polysaccharides
International Nuclear Information System (INIS)
Byrd, R.A.; Egan, W.; Summers, M.F.
1987-01-01
Polysaccharides are very important components in the immune response system. Capsular polysaccharides and lipopolysaccharides occupy cell surface sites of bacteria, play key roles in recognition and some have been used to develop vaccines. Consequently, the ability to determine chemical structures of these systems is vital to an understanding of their immunogenic action. The authors have been utilizing recently developed two-dimensional homonuclear and heteronuclear correlation spectroscopy for unambiguous assignment and structure determination of a number of polysaccharides. In particular, the 1 H-detected heteronuclear correlation experiments are essential to the rapid and sensitive determination of these structures. Linkage sites are determined by independent polarization transfer experiments and multiple quantum correlation experiments. These methods permit the complete structure determination on very small amounts of the polysaccharides. They present the results of a number of structural determinations and discuss the limits of these experiments in terms of their applications to polysaccharides
Two-dimensional fourier transform spectrometer
DeFlores, Lauren; Tokmakoff, Andrei
2013-09-03
The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.
Two-dimensional materials for ultrafast lasers
International Nuclear Information System (INIS)
Wang Fengqiu
2017-01-01
As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out. (paper)
Two dimensional generalizations of the Newcomb equation
International Nuclear Information System (INIS)
Dewar, R.L.; Pletzer, A.
1989-11-01
The Bineau reduction to scalar form of the equation governing ideal, zero frequency linearized displacements from a hydromagnetic equilibrium possessing a continuous symmetry is performed in 'universal coordinates', applicable to both the toroidal and helical cases. The resulting generalized Newcomb equation (GNE) has in general a more complicated form than the corresponding one dimensional equation obtained by Newcomb in the case of circular cylindrical symmetry, but in this cylindrical case , the equation can be transformed to that of Newcomb. In the two dimensional case there is a transformation which leaves the form of the GNE invariant and simplifies the Frobenius expansion about a rational surface, especially in the limit of zero pressure gradient. The Frobenius expansions about a mode rational surface is developed and the connection with Hamiltonian transformation theory is shown. 17 refs
Strategies for Interpreting Two Dimensional Microwave Spectra
Martin-Drumel, Marie-Aline; Crabtree, Kyle N.; Buchanan, Zachary
2017-06-01
Microwave spectroscopy can uniquely identify molecules because their rotational energy levels are sensitive to the three principal moments of inertia. However, a priori predictions of a molecule's structure have traditionally been required to enable efficient assignment of the rotational spectrum. Recently, automated microwave double resonance spectroscopy (AMDOR) has been employed to rapidly generate two dimensional spectra based on transitions that share a common rotational level, which may enable automated extraction of rotational constants without any prior estimates of molecular structure. Algorithms used to date for AMDOR have relied on making several initial assumptions about the nature of a subset of the linked transitions, followed by testing possible assignments by "brute force." In this talk, we will discuss new strategies for interpreting AMDOR spectra, using eugenol as a test case, as well as prospects for library-free, automated identification of the molecules in a volatile mixture.
Thermal properties of two-dimensional materials
International Nuclear Information System (INIS)
Zhang Gang; Zhang Yong-Wei
2017-01-01
Two-dimensional (2D) materials, such as graphene, phosphorene, and transition metal dichalcogenides (e.g., MoS 2 and WS 2 ), have attracted a great deal of attention recently due to their extraordinary structural, mechanical, and physical properties. In particular, 2D materials have shown great potential for thermal management and thermoelectric energy generation. In this article, we review the recent advances in the study of thermal properties of 2D materials. We first review some important aspects in thermal conductivity of graphene and discuss the possibility to enhance the ultra-high thermal conductivity of graphene. Next, we discuss thermal conductivity of MoS 2 and the new strategy for thermal management of MoS 2 device. Subsequently, we discuss the anisotropic thermal properties of phosphorene. Finally, we review the application of 2D materials in thermal devices, including thermal rectifier and thermal modulator. (topical reviews)
Two-dimensional heterostructures for energy storage
Energy Technology Data Exchange (ETDEWEB)
Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States); Pomerantseva, Ekaterina [Drexel Univ., Philadelphia, PA (United States)
2017-06-12
Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. As a result, we also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.
Two-dimensional electroacoustic waves in silicene
Zhukov, Alexander V.; Bouffanais, Roland; Konobeeva, Natalia N.; Belonenko, Mikhail B.
2018-01-01
In this letter, we investigate the propagation of two-dimensional electromagnetic waves in a piezoelectric medium built upon silicene. Ultrashort optical pulses of Gaussian form are considered to probe this medium. On the basis of Maxwell's equations supplemented with the wave equation for the medium's displacement vector, we obtain the effective governing equation for the vector potential associated with the electromagnetic field, as well as the component of the displacement vector. The dependence of the pulse shape on the bandgap in silicene and the piezoelectric coefficient of the medium was analyzed, thereby revealing a nontrivial triadic interplay between the characteristics of the pulse dynamics, the electronic properties of silicene, and the electrically induced mechanical vibrations of the medium. In particular, we uncovered the possibility for an amplification of the pulse amplitude through the tuning of the piezoelectric coefficient. This property could potentially offer promising prospects for the development of amplification devices for the optoelectronics industry.
Equivalency of two-dimensional algebras
International Nuclear Information System (INIS)
Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S.
2011-01-01
Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)
Shimahara, Hiroshi; Ito, Kazuhiro
2014-11-01
We examine a two-dimensional (2D) coupled antiferromagnetic (AF) Heisenberg model that consists of two subsystems: an isotropic S = 1/2 spin subsystem with strong AF exchange interactions (main system), and a uniaxial S = 5/2 spin subsystem with weak exchange interactions. This model is an example in which additional semiclassical degrees of freedom affect a quantum system; it also describes a possible stabilization mechanism of AF long-range order (LRO) in the 2D organic compound λ-(BETS)2FeCl4, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. Previous experimental studies have revealed that 3d spins on FeCl4 anions passively follow the AF LRO of the π-electron system in the BETS layers, although the AF LRO is stabilized by the 3d spins themselves. To explain this paradoxical behavior, we examine a scenario in which the uniaxial anisotropy of the 3d spins stabilizes the AF LRO on an isotropic 2D π-spin system. We extend Green's function theory, called the Tyablikov approximation, to the present system, which describes spin-wave excitations and is consistent with the Mermin-Wagner theorem. It is shown that even extremely weak interactions with the uniaxial subsystem efficiently stabilize the AF LRO in the main system, even in the absence of AF exchange interactions in the uniaxial subsystem. The AF LRO is triggered by the uniaxial subsystem, but the sublattice magnetization remains smaller than that of the main system in the high-temperature region. These results are consistent with experimental data for λ-(BETS)2FeCl4 and λ-(BETS)2GaCl4; the latter does not have the 3d spins and does not exhibit the AF LRO.
International Nuclear Information System (INIS)
Eschke, Andy
2015-01-01
Examination object of the present thesis was the determination of local distributions of crystallographic texture and mechanical (eigen-)stresses in submicro-/nan0crystalline many-phase gradient materials. For this at the one hand experimental methods of the two-dimensional X-ray diffraction were applied as well as at the other hand theoretical calculations performed by means of analytical and numerical modeling approaches. The interest for the material is founded on the fact that ultrafine-granular materials because of their mechanical propertier (for instance hardness, ductility) ar to be stressed for advanced engineering application purposes. Furthermore the application of many-phase gradient materials makes to some extent possible a manufacture for measure concerning physical properties and by this a manifold of application potentials as well as a tuning of the material properties to the differential requirements in the application fields. This measure tailoring is related both to the degree of gradiation and to the special composition of the composite materials by the chosen starting materials. The work performed in the framework of the excellence cluster ''European Centre for Emerging Materials and Processes Dresden (ECEMP)'' of the Saxonian excellence initiative aimed especially to the analysis of an especially processed, ultrafine-granular Ti/Al composite, which was and is research object of the partial ECEMP project ''High strength metallic composites'' (HSMetComp). Thereby were process as well as materials in the focus of the above mentioned (indirect) examination methods. which were adapted and further developed for these purposes. The results of the experimental as well as theoretical studies could contribute to an increased understanding of the technological process as well as the material behaviour and can by this also used for hints concerning process- and/or material-sided optimizations. Altogether they
Radiation effects on two-dimensional materials
Energy Technology Data Exchange (ETDEWEB)
Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)
2016-12-15
The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Photodetectors based on two dimensional materials
Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen
2016-09-01
Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.
Two-dimensional atomic crystals beyond graphene
Kaul, Anupama B.
2014-06-01
Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology over the past decade after monolayers of this material were experimentally isolated in 2004. The recent emergence of other classes of 2D graphene-like layered materials has added yet more exciting dimensions for research in exploring the diverse properties and applications arising from these 2D material systems. For example, hexagonal-BN, a layered material closest in structure to graphene, is an insulator, while NbSe2, a transition metal di-chalcogenide, is metallic and monolayers of other transition metal di-chalcogenides such as MoS2 are direct band-gap semiconductors. The rich spectrum of properties that 2D layered material systems offer can potentially be engineered ondemand, and creates exciting prospects for using such materials in applications ranging from electronics, sensing, photonics, energy harvesting and flexible electronics over the coming years.
Seismic isolation of two dimensional periodic foundations
Energy Technology Data Exchange (ETDEWEB)
Yan, Y.; Mo, Y. L., E-mail: yilungmo@central.uh.edu [University of Houston, Houston, Texas 77004 (United States); Laskar, A. [Indian Institute of Technology Bombay, Powai, Mumbai (India); Cheng, Z.; Shi, Z. [Beijing Jiaotong University, Beijing (China); Menq, F. [University of Texas, Austin, Texas 78712 (United States); Tang, Y. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2014-07-28
Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5 Hz to 50 Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.
Comparative Two-Dimensional Fluorescence Gel Electrophoresis.
Ackermann, Doreen; König, Simone
2018-01-01
Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.
Asymptotics for Two-dimensional Atoms
DEFF Research Database (Denmark)
Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip
2012-01-01
We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....
Network patterns in exponentially growing two-dimensional biofilms
Zachreson, Cameron; Yap, Xinhui; Gloag, Erin S.; Shimoni, Raz; Whitchurch, Cynthia B.; Toth, Milos
2017-10-01
Anisotropic collective patterns occur frequently in the morphogenesis of two-dimensional biofilms. These patterns are often attributed to growth regulation mechanisms and differentiation based on gradients of diffusing nutrients and signaling molecules. Here, we employ a model of bacterial growth dynamics to show that even in the absence of growth regulation or differentiation, confinement by an enclosing medium such as agar can itself lead to stable pattern formation over time scales that are employed in experiments. The underlying mechanism relies on path formation through physical deformation of the enclosing environment.
Two-dimensional N = 2 Super-Yang-Mills Theory
Directory of Open Access Journals (Sweden)
August Daniel
2018-01-01
Full Text Available Supersymmetry is one of the possible scenarios for physics beyond the standard model. The building blocks of this scenario are supersymmetric gauge theories. In our work we study the N = 1 Super-Yang-Mills (SYM theory with gauge group SU(2 dimensionally reduced to two-dimensional N = 2 SYM theory. In our lattice formulation we break supersymmetry and chiral symmetry explicitly while preserving R symmetry. By fine tuning the bar-mass of the fermions in the Lagrangian we construct a supersymmetric continuum theory. To this aim we carefully investigate mass spectra and Ward identities, which both show a clear signal of supersymmetry restoration in the continuum limit.
Stable corrugated state of the two-dimensional electron gas
International Nuclear Information System (INIS)
Mendez-Moreno, R.M.; Moreno, M.; Ortiz, M.A.
1991-01-01
A corrugated and stable ground state is found for the two-dimensional electron gas in both the normal paramagnetic and the fully polarized phases. The self-consistent Hartree-Fock method is used with a modulated set of trial wave functions within the deformable jellium model. The results for high metallic densities reproduce the usual noncorrugated ferromagnetic electron-gas behavior. A transition to a paramagnetic corrugated state for values of r s ∼6.5 is predicted. At lower densities r s ∼30, a second transition to a corrugated ferromagnetic phase is suggested
Two-dimensional fermionic correlations in topologically nontrivial backgrounds
Energy Technology Data Exchange (ETDEWEB)
Manias, M.V.; Naon, C.M.; Trobo, M.L. (Departamento de Fisica, Universidad Nacional de La Plata, Casilla de Correo No. 67, 1900 La Plata, Buenos Aires (Argentina))
1993-04-15
By using a path-integral approach to the study of two-dimensional massless fermionic models in nontrivial sectors, we compute certain special correlation functions which are nonvanishing only when nontrivial topology is taken into account. In particular, we derive the first explicit expression for the so-called nonminimal Green's function. We introduce one specific topological charge distribution for which this correlation function takes a simple form. We also comment on the application of our results to the analysis of massive fermions in topological backgrounds.
Energy Technology Data Exchange (ETDEWEB)
Moreira Bastos, Patricia; Haglund, Peter [Umeaa Univ. (Sweden). Dept. of Chemistry
2012-08-15
Purpose: This article aims to investigate the use and benefits of using comprehensive two-dimensional gas chromatography (GC x GC) and structure-activity relationship modeling for screening and prioritization of organic contaminants in complex matrices. The benefit of applying comprehensive screening techniques to samples with high organic contaminant content is primarily that compounds with diverse physicochemical properties can be analyzed simultaneously. Here, a heavily contaminated industrial area was surveyed for organic pollutants by analyzing soil, sediment, and surface water samples. The hazard of the pollutants were ranked using SARs. Material and methods: The water samples were liquid-liquid extracted using dichloromethane and directly analyzed by GC x GC-time-of-flight mass spectrometry (GC x GC-TofMS). Soil and sediment samples were extracted with dichloromethane in an ultrasonic bath and subjected to gel permeation chromatography to eliminate lipids and humic matter. The low molecular weight fraction was then analyzed with GC x GC-TofMS. Results and discussion: More than 10,000 components were found in each sample, of which ca. 300 individual compounds were unambiguously identified using the National Institute of Standards and Technology mass spectra library and authentic reference standards. Alkanes, polycyclic aromatic hydrocarbons, and phthalates were generally the most abundant and were found in all matrices. In contrast, chlorinated compounds such as chlorophenols, biphenyls, and chlorinated pesticides were only detected in samples from a few hotspot regions. The toxicities of the most frequently detected compounds and of the compounds detected at the highest concentrations in samples from hotspot regions were estimated by ecological structure-activity relationships. The ratio of the measured concentration to the predicted toxicity level was then calculated for each compound and used for an initial risk assessment in order to prioritize compounds
Interaction of two-dimensional magnetoexcitons
Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.
2017-04-01
We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .